Image Forum Festival

Image Forum Festival is Japan's largest art film festival, and the largest dedicated to the screening of new experimental films, both in Japan and around the world. It began in 1987 in Tokyo, and includes space for video installations and live performance. It is now held in Tokyo, Kyoto and Yokohama annually, and often includes other cities across Japan. As well as featuring modern domestic and international films, it includes a selection of historical masterpieces.
The festival is run by Image Forum, a school and cinemathéque that preserves and promotes the production of experimental film, and fosters the next generation of filmmakers. Its affiliate company, Dagurreo Press, Inc. publishes books on filmmaking and video software.
Awards.
Image Forum won the 1988 Japan Movie Pen Club Award.


Hybrid input-output algorithm

Hybrid input-output (HIO) algorithm for phase retrieval is a modification of the error reduction algorithm for retrieving the phases in coherent diffraction imaging. Determining the phases of a diffraction pattern is crucial since the diffraction pattern of an object is its Fourier transform and in order to properly invert transform the diffraction pattern the phases must be known. Only the amplitude however, can be measured from the intensity of the diffraction pattern and can thus be known experimentally. This fact together with some kind of support constraint can be used in order to iteratively calculate the phases. The HIO algorithm uses negative feedback in Fourier space in order to progressively force the solution to conform to the Fourier domain constraints (support). Unlike the error reduction algorithm which alternately applies Fourier and object constraints the HIO "skips" the object domain step and replaces it with negative feedback acting upon the previous solution.
Although it has been shown that the method of error reduction converges to a limit (but usually not to the correct or optimal solution)
there is no limit to how long this process can take. Moreover, the error reduction algorithm will almost certainly find a local minimum instead of the global solution. The HIO differs from error reduction only in one step but this is enough to reduce this problem significantly. Whereas the error reduction approach iteratively improves solutions over time the HIO remodels the previous solution in Fourier space applying negative feedback. By minimizing the mean square error in Fourier space from the previous solution, the HIO provides a better candidate solution for inverse transforming. Although it is both faster and more powerful than error reduction, the HIO algorithm does have a uniqueness problem.
Depending on how strong the negative feedback is there can often be more than one solution for any set of diffraction data. Although a problem, it has been shown that many of these possible solutions stem from the fact that HIO allows for mirror images taken in any plane to arise as solutions. In crystallography, the scientist is seldom interested in the atomic coordinates relative to any other reference than the molecule itself and is therefore more than happy with a solution that is upside-down of flipped from the actual image. A downside is that HIO has a tendency to escape both global and local maxima. This problem also depends on the strength of the feedback parameter, and a good solution to this problem is to switch algorithm when the error reaches its minimum. Other methods of phasing a coherent diffraction pattern include difference map algorithm and "relaxed averaged alternating reflections" or RAAR.


Throat microphone

A throat microphone, also called a laryngophone, is a type of contact microphone that absorbs vibrations directly from the wearer's throat by way of single or dual sensors worn against the neck. The sensors, called transducers, can pick up speech even in extremely noisy or windy environments, such as on a motorcycle or in a nightclub. Other types of microphones do not function well under these conditions because of high levels of background noise. Advanced laryngophones are able to pick up whispers, and therefore perform well in environments where communicating with others at a distance in silence is required, such as during covert military or law enforcement operations. Throat microphones are also very useful when helmets or respiratory protection is required. Many full-face SCBA, CABA, SAR Respirator, Elastomeric Respirator, N95 Respirator PAPR, or re-breather masks do not have a provision for a microphone inside the mask. The throat microphone can be used safely, as it is positioned outside the mask's face seal and as such does not compromise the respiratory protection provided by the mask, nor does it violate mask approvals and certification.
History.
World War I – first throat mics.
Charles Edmond Prince lead the development of throat microphones for the British during World War I for use in the noisy and windy environment of aircraft cockpits. Over a 3 year period from 1915-1918 they went through a series of prototype and production handheld "airplane telephones" before arriving at a hands free throat mic incorporated into a leather flying helmet
World War II – full body suits.
During World War II, German Luftwaffe pilots and panzer crews used throat microphones. Soon after, they were adopted by the Allied air forces—the USAAF with the T-20 and T-30 and the RAF with the Mark II. Later, Soviet pilots relied on LA-3 and LA-5 models.
Scientific studies.
Starting in the 1970s, researchers explored the use of throat microphones in speech therapy,
Current use.
Throat microphones have maintained their presence in the military, law enforcement, and emergency services. Newer single-transducer designs are available that make the throat microphone much more comfortable to wear than earlier units and also better balance transmission quality. Additionally, this next generation of throat microphones provides varying outputs and frequency responses to accommodate a wide variety of professional communication devices such as digital and analog portable radios and Terrestrial Trunked Radio (TETRA) and P25 systems.
Several throat microphones including wireless throat mics now exist for mobile devices. Mobile device apps are starting to allow further customisation for end-user applications. Consumer uses such as for airsoft competitions and motorcycle riding are increasingly more popular. With the advent of COVID-19 and higher rate of face mask usage throat mics for general use is becoming more common to facilitate communications.


Susan Halabi

Susan Halabi is a professor of biostatistics and bioinformatics at Duke University, known for her research on prostate cancer.
As a member of the data safety monitoring board for a study of the anti-prostate cancer effects of abiraterone acetate (Zytiga), she argued that stopping the study early had prevented the study from accurately determining the effectiveness of the drug, and possibly made it appear to be more effective than it actually was. She also took part in a study showing that, when prostate cancer has reached the point of spreading to other parts of the body, the parts that it spreads to can be used to predict the survival rate from the disease.
Halabi earned her Ph.D. in biometry from the University of Texas Health Science Center at Houston in 1994, and joined the Duke faculty in 1996. She up in a family of engineers in Lebanon, where she was one of the first students in the undergraduate biostatistics program at the American University of Beirut. She was named a fellow of the Society for Clinical Trials in 2014, "for her outstanding leadership in cancer clinical trials and prognostic development, ... educational activities, and for dedicated service on national review committees, DSMBs and scientific advisory committees and for the SCT".
She was elected as a Fellow of the American Statistical Association in 2015.


Guitar tunings

Guitar tunings are the assignment of pitches to the open strings of guitars, including acoustic guitars, electric guitars, and classical guitars. Tunings are described by the particular pitches that are made by notes in Western music. By convention, the notes are ordered and arranged from the lowest-pitched string (i.e., the deepest bass sounding note) to the highest-pitched string (i.e.the highest sounding note), or the thickest string to thinnest, or the lowest frequency to the highest. This sometimes confuses beginner guitarists, since the highest-pitched string is referred to as the 1st string, and the lowest-pitched is the 6th string.
Standard tuning defines the string pitches as E, A, D, G, B, and E, from the lowest pitch (low E2) to the highest pitch (high E4). Standard tuning is used by most guitarists, and frequently used tunings can be understood as variations on standard tuning. To aid in memorising these notes, mnemonics are used, for example, Eddy Ate Dynamite, Good Bye Eddy.
The term "guitar tunings" may refer to pitch sets other than standard tuning, also called "nonstandard", "alternative", or "alternate". There are hundreds of these tunings, often with small variants of established tunings. Communities of guitarists who share a common musical tradition often use the same or similar tuning styles.
Standard and alternatives.
Standard.
Standard tuning is the tuning most frequently used on a six-string guitar and musicians assume this tuning by default if a specific alternate (or scordatura) is not mentioned. In scientific pitch notation, the guitar's standard tuning consists of the following notes:
The guitar is a transposing instrument; that is, music for guitars is notated one octave higher than the true pitch. This is to reduce the need for ledger lines in music written for the instrument, and thus simplify the reading of notes when playing the guitar.
Standard tuning provides reasonably simple fingering (fret-hand movement) for playing standard scales and basic chords in all major and minor keys. Separation of the first (high E) and second (B) string, as well as the separation between the third (G), fourth (D), fifth (A), and sixth (low E) strings by a five-semitone interval (a perfect fourth) allows the guitarist to play a chromatic scale with each of the four fingers of the fretting hand controlling one of the first four frets (index finger on fret 1, little finger on fret 4, etc.) only when the hand is in the first position.
The open notes of the second (B) and third (G) strings are separated by four semitones (a major third). This tuning pattern of (low) fourths, one major third, and one fourth was inherited by the guitar from its predecessor instrument, the viol. The irregular major third breaks the fingering patterns of scales and chords, so that guitarists have to memorize multiple chord-shapes for each chord. Scales and chords are simplified by major thirds tuning and all-fourths tuning, which are regular tunings maintaining the same musical interval between consecutive open-string notes.
Alternative.
Alternative ("alternate") tuning refers to any open-string note arrangement other than standard tuning. These offer different kinds of deep or ringing sounds, chord voicings, and fingerings on the guitar. Alternative tunings are common in folk music where the guitar may be called upon to produce a sustained note or chord known as a drone. This often gives folk music its haunting and lamenting ambience due to the atmosphere and mood that the notes make. Alternative tunings change the fingering of common chords when playing the guitar, and this can ease the playing of certain chords while simultaneously increase the difficulty of playing other chords.
Some tunings are used for particular songs, and may be named after the song's title. There are hundreds of these tunings, although many are slight variations of other alternate tunings. Several alternative tunings are used regularly by communities of guitarists who share a common musical tradition, such as American folk or Celtic folk music.
The various alternative tunings have been grouped into the following categories:
Joni Mitchell is known for developing a shorthand descriptive method of noting guitar tuning where the first letter documents the note of the lowest string, and is followed by the relative fret (half-step) offsets required to obtain the pitch of the next (higher) string. This scheme highlights pitch relationships and simplifies the process of comparing different tuning schemes.
String gauges.
String gauge refers to the thickness and diameter of a guitar string, which influences the overall sound and pitch of the guitar depending on the guitar string used. Some alternative tunings are difficult or even impossible to achieve with conventional guitars due to the sets of guitar strings, which have gauges optimized for standard tuning. With conventional sets of guitar strings, some higher tunings increase the string-tension until playing the guitar requires significantly more finger-strength and stamina, or even until a string snaps or the guitar is warped. However, with lower tunings, the sets of guitar strings may be loose and buzz. The tone of the guitar strings is also negatively affected by using unsuitable string gauges on the guitar.
Generally, alternative tunings benefit from re-stringing of the guitar with string gauges purposefully chosen to optimize particular tunings by using lighter strings for higher-pitched notes (to lower the tension of the strings) and heavier strings for lower-pitched notes (to prevent string buzz and vibration).
Dropped tunings.
A dropped tuning is one of the categories of alternative tunings and the process starts with standard tuning and typically lowers the pitch of ("drops") only a single string, almost always the lowest-pitched (E) string on the guitar.
The drop D tuning is common in electric guitar and heavy metal music. The low E string is tuned down one whole step (to D) and the rest of the strings remain in standard tuning. This creates an "open power chord" (three-note fifth) with the low three strings (DAD).
There also exists Double-drop D tuning, in which both E strings are down-tuned a whole step (to D). The rest of the strings keep their original pitch.
Open tunings.
An open tuning allows the guitarist to play a chord by strumming the open strings (no strings fretted).
Open tunings may be "chordal" or "modal". In chordal open tunings, the open chord consists of at least three different pitch classes. In a given key, these are the root note, its 3rd and its 5th, and may include all the strings or a subset. The tuning is named for the base chord when played open, typically a major chord, and all similar chords in the chromatic scale are played by barring all strings across a single fret. Open tunings are common in blues and folk music. These tunings are frequently used in the playing of slide and lap-slide ("Hawaiian") guitars, and Hawaiian slack key music. A musician who is well-known for using open tuning in his music is Ry Cooder, who uses open tunings when playing the slide guitar.
Most modern music uses equal temperament because it facilitates the ability to play the guitar in any key—as compared to just intonation, which favors certain keys, and makes the other keys sound less in tune.
Repetitive open-tunings are used for two classical non-Spanish guitars. For the English guitar, the open chord is C major (C–E–G–C–E–G); for the Russian guitar, which has seven strings, it is G major (D–G–B–D–G–B–D).
When the open strings constitute a minor chord, the open tuning may sometimes be called a "cross-note" tuning.
Major key tunings.
Major open-tunings give a major chord with the open strings.
Open tunings often tune the lowest open note to C, D, or E and they often tune the highest open note to D or E; tuning down the open string from E to D or C avoids the risk of breaking strings, which is associated with tuning up strings.
Open D.
The open D tuning (D–A–D–F–A–D), also called "Vestopol" tuning, is a common open tuning used by European and American/Western guitarists working with alternative tunings. The Allman Brothers instrumental "Little Martha" used an open-D tuning raised one half step, giving an open E♭ tuning with the same intervalic relationships as open D.
Open C.
The English guitar used a repetitive open-C tuning (with distinct open notes C–E–G–C–E–G) that approximated a major-thirds tuning. This tuning is evident in William Ackerman's song "Townsend Shuffle", as well as by John Fahey for his tribute to Mississippi John Hurt.
The C–C–G–C–E–G tuning uses some of the harmonic sequence (overtones) of the note C. This overtone-series tuning was modified by Mick Ralphs, who used a high C note rather than the high G note for "Can't Get Enough" on "Bad Company". Ralphs said, "It needs the open C to have that ring," and "it never really sounds right in standard tuning".
Open G.
Mick Ralphs' open-C tuning was originally an open-G tuning, which listed the initial six overtones of the G note, namely G–G–D–G–B–D; Ralphs used this open-G tuning for "Hey Hey" and while writing the demo of "Can't Get Enough".
Open-G tuning usually refers to D–G–D–G–B–D.
The open G tuning variant G–G–D–G–B–D was used by Joni Mitchell for "Electricity", "For the Roses" and "Hunter (The Good Samaritan)". Truncating this tuning to G–D–G–B–D for his five-string guitar, Keith Richards uses this overtones-tuning on The Rolling Stones's "Honky Tonk Women", "Brown Sugar" and "Start Me Up".
The seven-string Russian guitar uses the open-G tuning D–G–B–D–G–B–D, which contains mostly major and minor thirds.
Creating any kind of open tuning.
Any kind of chordal tuning can be achieved, simply by using the notes in the chord and tuning the strings to those notes. For example, Asus4 has the notes A, D, E. By tuning the strings to only those notes, it creates a chordal Asus4 tuning.
Bass players may omit the last two strings.
Minor or "cross-note" tunings.
Cross-note tunings include a minor third, so giving a minor chord with open strings. Fretting the minor-third string at the first fret produces a major-third, so allowing a one-finger fretting of a major chord. By contrast, it is more difficult to fret a minor chord using an open major-chord tuning.
Bukka White and Skip James are well-known for using cross-note E-minor in their music.
Other open chordal tunings.
Some guitarists choose open tunings that use more complex chords, which gives them more available intervals on the open strings. C6, E6, E7, E6/9 and other such tunings are common among lap-steel players such as Hawaiian slack-key guitarists and country guitarists, and are also sometimes applied to the regular guitar by bottleneck (a slide repurposed from a glass bottle) players striving to emulate these styles. A common C6 tuning, for example, is C–E–G–A–C–E, which provides open major and minor thirds, open major and minor sixths, fifths, and octaves. By contrast, most open major or open minor tunings provide only octaves, fifths, and either a major third/sixth or a minor third/sixth—but not both. Don Helms of Hank Williams band favored C6 tuning; slack-key artist Henry Kaleialoha Allen uses a modified C6/7 (C6 tuning with a B on the bottom); Harmon Davis favored E7 tuning; David Gilmour has used an open G6 tuning.
Modal tunings.
Modal tunings are open tunings in which the open strings of the guitar do not produce a tertian (i.e., major or minor, or variants thereof) chord. The strings may be tuned to exclusively present a single interval (all fourths; all fifths; etc.) or they may be tuned to a non-tertian chord (unresolved suspensions such as E–A–B–E–A–E, for example). Modal open tunings may use only one or two pitch classes across all strings (as, for example, some metal guitarists who tune each string to either E or B, forming "power chords" of ambiguous major/minor tonality).
Popular modal tunings include D Modal (D-G-D-G-B-E) and C Modal (C-G-D-G-B-D).
Lowered (standard).
Derived from standard EADGBE, all the strings are tuned lower by the same interval, thus providing the same chord positions transposed to a lower key. Lower tunings are popular among rock and heavy metal bands. The reason for tuning down below the standard pitch is usually either to accommodate a singer's vocal range or to get a deeper/heavier sound or pitch. Common examples include:
E♭ tuning.
Rock guitarists (such as Jimi Hendrix on the songs Voodoo Child (Slight Return) and Little Wing) occasionally tune all their strings down by one semitone to obtain "E♭ tuning". This makes the strings easier to bend when playing and with standard fingering results in a lower key.
D tuning.
D Tuning, also called One Step Lower, Whole Step Down, Full Step or D Standard, is another alternative. Each string is lowered by a whole tone (two semitones) resulting in D-G-C-F-A-D. It is used mostly by heavy metal bands to achieve a heavier, deeper sound, and by blues guitarists, who use it to accommodate string bending and by 12-string guitar players to reduce the mechanical load on their instrument. Among musicians, Elliott Smith was known to use D tuning as his main tuning for his music. It was also used for several songs on The Velvet Underground's album The Velvet Underground & Nico.
Regular tunings.
In standard tuning, there is an interval of a major third between the second and third strings, and all the other intervals are fourths. The irregularity has a price. Chords cannot be shifted around the fretboard in the standard tuning E–A–D–G–B–E, which requires four chord-shapes for the major chords. There are separate chord-forms for chords having their root note on the third, fourth, fifth, and sixth strings. These are called inversions.
In contrast, regular tunings have equal intervals between the strings, and so they have symmetrical scales all along the fretboard. This makes it simpler to translate chords. For the regular tunings, chords may be moved diagonally around the fretboard. The diagonal movement of chords is especially simple for the regular tunings that are repetitive, in which case chords can be moved vertically: Chords can be moved three strings up (or down) in major-thirds tuning, and chords can be moved two strings up (or down) in augmented-fourths tuning. Regular tunings thus appeal to new guitarists and also to jazz-guitarists, whose improvisation is simplified by regular intervals.
On the other hand, five- and six-string open chords ("cowboy chords") are more difficult to play in a regular tuning than in standard tuning. Instructional literature uses standard tuning. Traditionally a course begins with the hand in first position, that is, with the left-hand covering frets 1–4. Beginning players first learn open chords belonging to the major keys C, G, and D. Guitarists who play mainly open chords in these three major-keys and their relative minor-keys (Am, Em, Bm) may prefer standard tuning over many regular tunings, On the other hand, minor-thirds tuning features many barre chords with repeated notes, properties that appeal to acoustic-guitarists and beginners.
Major thirds and perfect fourths.
Standard tuning mixes a major third (M3) with its perfect fourths. Regular tunings that are based on either major thirds or perfect fourths are used, for example, in jazz.
All fourths tuning E2–A2–D3–G3–C4–F4 keeps the lowest four strings of standard tuning, changing the major third to a perfect fourth. Jazz musician Stanley Jordan stated that all-fourths tuning "simplifies the fingerboard, making it logical".
Major-thirds tuning (M3 tuning) is a regular tuning in which the musical intervals between successive strings are each major thirds, for example E2–G2–C3–E3–G3–C4. Unlike all-fourths and all-fifths tuning, M3 tuning repeats its octave after three strings, which simplifies the learning of chords and improvisation. This repetition provides the guitarist with many possibilities for fingering chords. With six strings, major-thirds tuning has a smaller range than standard tuning; with seven strings, the major-thirds tuning covers the range of standard tuning on six strings.
Major-thirds tunings require less hand-stretching than other tunings, because each M3 tuning packs the octave's twelve notes into four consecutive frets. The major-third intervals let the guitarist play major chords and minor chords with two–three consecutive fingers on two consecutive frets.
Chord inversion is especially simple in major-thirds tuning. The guitarist can invert chords by raising one or two notes on three strings—playing the raised notes with the same finger as the original notes. In contrast, inverting triads in standard and all-fourths tuning requires three fingers on a span of four frets. In standard tuning, the shape of an inversion depends on involvement of the major-third between the 2nd and 3rd strings.
All fifths and "new standard tuning".
All-fifths tuning is a tuning in intervals of perfect fifths like that of a mandolin or a violin; other names include "perfect fifths" and "fifths". It has a wide range. Its implementation has been impossible with nylon strings and has been difficult with conventional steel strings. The high B makes the first string very taut, and consequently a conventionally gauged string easily breaks.
Jazz guitarist Carl Kress used a variation of all-fifths tuning—with the bottom four strings in fifths, and the top two strings in thirds, resulting in B1–F2–C3–G3–B3–D4. This facilitated tenor banjo chord shapes on the bottom four strings and plectrum banjo chord shapes on the top four strings. Contemporary New York jazz-guitarist Marty Grosz uses this tuning.
All-fifths tuning has been approximated by the so-called "New Standard Tuning" (NST) of King Crimson's Robert Fripp, which NST replaces all-fifths' high B4 with a high G4. To build chords, Fripp uses "perfect intervals in fourths, fifths and octaves", so avoiding minor thirds and especially major thirds, which are slightly sharp in equal temperament tuning (in comparison to thirds in just intonation). It is a challenge to adapt conventional guitar-chords to new standard tuning, which is based on all-fifths tuning. Some closely voiced jazz chords become impractical in NST and all-fifths tuning.
Instrumental tunings.
These are tunings in which some or all strings are retuned to emulate the standard tuning of some other instrument, such as a lute, banjo, cittern, mandolin, etc. Many of these tunings overlap other categories, especially open and modal tunings.
Miscellaneous or "special" tunings.
This category includes everything that does not fit into any of the other categories, for example (but not limited to): tunings designated only for a particular piece; non-western intervals and modes; micro- or macro-tones(half sharps/flats, etc.); and "hybrid tunings" combining features of major alternate tuning categories – most commonly an open tuning with the lowest string dropped.


Chi-squared test

A chi-squared test, also written as test, is a statistical hypothesis test that is valid to perform when the test statistic is chi-squared distributed under the null hypothesis, specifically Pearson's chi-squared test and variants thereof. Pearson's chi-squared test is used to determine whether there is a statistically significant difference between the expected frequencies and the observed frequencies in one or more categories of a contingency table.
In the standard applications of this test, the observations are classified into mutually exclusive classes. If the null hypothesis that there are no differences between the classes in the population is true, the test statistic computed from the observations follows a frequency distribution. The purpose of the test is to evaluate how likely the observed frequencies would be assuming the null hypothesis is true.
Test statistics that follow a distribution occur when the observations are independent and normally distributed, which are assumptions often justified under the central limit theorem. There are also tests for testing the null hypothesis of independence of a pair of random variables based on observations of the pairs.
Chi-squared tests often refers to tests for which the distribution of the test statistic approaches the distribution asymptotically, meaning that the sampling distribution (if the null hypothesis is true) of the test statistic approximates a chi-squared distribution more and more closely as sample sizes increase.
History.
In the 19th century, statistical analytical methods were mainly applied in biological data analysis and it was customary for researchers to assume that observations followed a normal distribution, such as Sir George Airy and Professor Merriman, whose works were criticized by Karl Pearson in his 1900 paper.
At the end of the 19th century, Pearson noticed the existence of significant skewness within some biological observations. In order to model the observations regardless of being normal or skewed, Pearson, in a series of articles published from 1893 to 1916, devised the Pearson distribution, a family of continuous probability distributions, which includes the normal distribution and many skewed distributions, and proposed a method of statistical analysis consisting of using the Pearson distribution to model the observation and performing a test of goodness of fit to determine how well the model really fits to the observations.
Pearson's chi-squared test.
In 1900, Pearson published a paper on the test which is considered to be one of the foundations of modern statistics. In this paper, Pearson investigated a test of goodness of fit.
Suppose that observations in a random sample from a population are classified into mutually exclusive classes with respective observed numbers (for ), and a null hypothesis gives the probability that an observation falls into the th class. So we have the expected numbers for all , where
Pearson proposed that, under the circumstance of the null hypothesis being correct, as the limiting distribution of the quantity given below is the distribution.
Pearson dealt first with the case in which the expected numbers are large enough known numbers in all cells assuming every may be taken as normally distributed, and reached the result that, in the limit as becomes large, follows the distribution with degrees of freedom.
However, Pearson next considered the case in which the expected numbers depended on the parameters that had to be estimated from the sample, and suggested that, with the notation of being the true expected numbers and being the estimated expected numbers, the difference
will usually be positive and small enough to be omitted. In a conclusion, Pearson argued that if we regarded as also distributed as distribution with degrees of freedom, the error in this approximation would not affect practical decisions. This conclusion caused some controversy in practical applications and was not settled for 20 years until Fisher's 1922 and 1924 papers.
Other examples of chi-squared tests.
One test statistic that follows a chi-squared distribution exactly is the test that the variance of a normally distributed population has a given value based on a sample variance. Such tests are uncommon in practice because the true variance of the population is usually unknown. However, there are several statistical tests where the chi-squared distribution is approximately valid:
Fisher's exact test.
For an exact test used in place of the 2 x 2 chi-squared test for independence, see Fisher's exact test.
Binomial test.
For an exact test used in place of the 2 x 1 chi-squared test for goodness of fit, see Binomial test.
Yates's correction for continuity.
Using the chi-squared distribution to interpret Pearson's chi-squared statistic requires one to assume that the discrete probability of observed binomial frequencies in the table can be approximated by the continuous chi-squared distribution. This assumption is not quite correct and introduces some error.
To reduce the error in approximation, Frank Yates suggested a correction for continuity that adjusts the formula for Pearson's chi-squared test by subtracting 0.5 from the absolute difference between each observed value and its expected value in a contingency table. This reduces the chi-squared value obtained and thus increases its "p"-value.
Chi-squared test for variance in a normal population.
If a sample of size is taken from a population having a normal distribution, then there is a result (see distribution of the sample variance) which allows a test to be made of whether the variance of the population has a pre-determined value. For example, a manufacturing process might have been in stable condition for a long period, allowing a value for the variance to be determined essentially without error. Suppose that a variant of the process is being tested, giving rise to a small sample of product items whose variation is to be tested. The test statistic in this instance could be set to be the sum of squares about the sample mean, divided by the nominal value for the variance (i.e. the value to be tested as holding). Then has a chi-squared distribution with degrees of freedom. For example, if the sample size is 21, the acceptance region for with a significance level of 5% is between 9.59 and 34.17.
Example chi-squared test for categorical data.
Suppose there is a city of 1,000,000 residents with four neighborhoods: , , , and . A random sample of 650 residents of the city is taken and their occupation is recorded as "white collar", "blue collar", or "no collar". The null hypothesis is that each person's neighborhood of residence is independent of the person's occupational classification. The data are tabulated as:
Let us take the sample living in neighborhood , 150, to estimate what proportion of the whole 1,000,000 live in neighborhood . Similarly we take to estimate what proportion of the 1,000,000 are white-collar workers. By the assumption of independence under the hypothesis we should "expect" the number of white-collar workers in neighborhood to be
Then in that "cell" of the table, we have
The sum of these quantities over all of the cells is the test statistic; in this case, formula_6. Under the null hypothesis, this sum has approximately a chi-squared distribution whose number of degrees of freedom is
If the test statistic is improbably large according to that chi-squared distribution, then one rejects the null hypothesis of independence.
A related issue is a test of homogeneity. Suppose that instead of giving every resident of each of the four neighborhoods an equal chance of inclusion in the sample, we decide in advance how many residents of each neighborhood to include. Then each resident has the same chance of being chosen as do all residents of the same neighborhood, but residents of different neighborhoods would have different probabilities of being chosen if the four sample sizes are not proportional to the populations of the four neighborhoods. In such a case, we would be testing "homogeneity" rather than "independence". The question is whether the proportions of blue-collar, white-collar, and no-collar workers in the four neighborhoods are the same. However, the test is done in the same way.
Applications.
In cryptanalysis, the chi-squared test is used to compare the distribution of plaintext and (possibly) decrypted ciphertext. The lowest value of the test means that the decryption was successful with high probability. This method can be generalized for solving modern cryptographic problems.
In bioinformatics, chi-squared test is used to compare the distribution of certain properties of genes (e.g., genomic content, mutation rate, interaction network clustering, etc.) belonging to different categories (e.g., disease genes, essential genes, genes on a certain chromosome etc.).


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2659 Millis


Flack parameter

In X-ray crystallography, the Flack parameter is a factor used to estimate the absolute configuration of a structural model determined by single-crystal structure analysis.
In this approach, one determines the absolute structure of a noncentrosymmetric crystal. The processes used to decide the absolute structure use the anomalous dispersion effect. If atomic scattering factors did not have imaginary parts, the Friedel pairs would have exactly the same amplitudes (i.e., the scattering intensity formula_1 from crystal plane (h k l) is equal to formula_2). However, atomic scattering factors have imaginary parts due to the anomalous dispersion effect, and Friedel's law is broken by this effect.
There are several ways to determine the absolute structure by X-ray crystallography. For example, a comparison of the intensities of Bijvoet pairs or of the R-factors for the two possible structures can suggest the correct absolute structure. One of the more powerful and simple approaches is using the Flack parameter, because this single parameter clearly indicates the absolute structure.
The Flack parameter is calculated during the structural refinement using the equation given below:
where "x" is the Flack parameter, "I" is the square of the scaled observed structure factor and "F" is the calculated structure factor.
By determining "x" for all data, "x" is usually found to be between 0 and 1. If the value is near 0, with a small standard uncertainty, the absolute structure given by the structure refinement is likely correct, and if the value is near 1, then the inverted structure is likely correct. If the value is near 0.5, the crystal may be racemic or twinned. The technique is most effective when the crystal contains both lighter and heavier atoms. Light atoms usually show only a small anomalous dispersion effect. In this case, the Flack parameter can refine to a physically unrealistic value (less than 0 or greater than 1) and has no meaning.
This parameter, introduced by H. D. Flack
became one of a standard set of values being checked for structures with noncentrosymmetric space groups.


Document-based question

In American Advanced Placement exams, a document-based question (DBQ), also known as data-based question, is an essay or series of short-answer questions that is constructed by students using one's own knowledge combined with support from several provided sources. Usually, it is employed on timed history tests.
In the United States.
The document based question was first used for the 1973 AP United States History Exam published by the College Board, created as a joint effort between Development Committee members Reverend Giles Hayes and Stephen Klein. Both were unhappy with student performance on free-response essays, and often found that students were "groping for half-remembered information" and "parroted factual information with little historical analysis or argument" when they wrote their essays. The goal of the Document Based Question was for students to be "less concerned with the recall of previously learned information" and more engaged in deeper historical inquiry. Hayes, in particular, hoped students would "become junior historians and play the role of historians for that hour" as they engaged in the DBQ.
A typical DBQ is a packet of several original sources (anywhere from three to sixteen), labeled by letters (beginning with "Document A" or "Source A") or numbers. Usually all but one or two source(s) are textual, with the other source(s) being graphic (usually a political cartoon, map, or poster if primary and a chart or graph if secondary). In most cases, the sources are selected to provide different perspectives or views on the events or movements being analyzed.
On the Advanced Placement (AP) exams, only primary sources are provided; on the International Baccalaureate (IB) exams, both primary and secondary sources are provided. AP exams also require students to construct and defend a thesis based on one prompt, while IB exams focus on a series of questions, with at least one asking students to assess the "value and limitations" of a source, usually "with reference to the documents' origin or purpose."
The documents contained in the document-based questions are rarely familiar texts (for example, the Emancipation Proclamation and Declaration of Independence are not likely to be on a U.S. history test), though the documents' authors may be major historical figures. The documents vary in length and format.
On some tests students are not permitted to begin responding to the question or questions in the essay packet until after a mandatory reading time ("planning period"), usually around 10 to 15 minutes. During this time, students read the passage and, if desired, make notes or markings. After this period, students are permitted to respond, usually for around 45 minutes to an hour.


PLIDA

PLIDA, or Progetto Lingua Italiana Dante Alighieri (Dante Alighieri Society Diplomas), are language diplomas issued by Dante Alighieri Society certifying the holder's proficiency in Italian language as a foreign language. The diplomas could only be obtained after passing a standardised language test. The Rome Branch of the Dante Alighieri Society is the official centre of examination for the issuing of PLIDA Certification.
Recognition.
The PLIDA certificate is officially recognised by the Ministry of Foreign Affairs, the Ministry of Labour and Welfare and the Ministry of Education, University and Research of Italy.
According to the Decree of the Ministry of the Interior of 4 June 2010, any foreigners should be able to demonstrate proficiency in the Italian language, if they want to obtain the long-term residence permit. Holders of A2 PLIDA certificate could be exempted from the test held by the Prefectures.
With the certificate (B2 or C1 level, depending on university and subject), students can be enrolled into universities or schools without taking the mandatory Italian language examinations.
Eligibility.
PLIDA tests can be taken only by those who are not native speakers of Italian. All candidates can take the test at the level they prefer, and it is not a pre-requisite that they have passed the tests at lower levels.
Test.
The Dante Alighieri Society is the organiser of PLIDA tests, with the academic approval from the Sapienza University of Rome. The Certification test is designed on the principles of the communicative approach, based on real-life tasks so as to test the ability in four areas: listening, reading, writing and speaking. The examination lasts for a minimum of 100 minutes to a maximum of 190 minutes, depending on the level.
There are tests of six levels, A1 to C2, set according to the levels in the Common European Framework of Reference for Languages.
Results.
Tests are marked in terms of a maximum of thirty points. To pass the examination, the candidate has to obtain a minimum of 18/30 in every tested areas, namely, listening, reading, writing and speaking. A candidate who passes at least three of the four areas obtains a credit in the areas passed, and these three credits may be used in the next attempt in the failed area.


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Graphoscope

A graphoscope was a 19th-century device used in parlors in order to enhance the viewing of photographs and text. The graphoscope is supposed to be based on a 1864 patent of Charles John Rowsell.
These novelty items consisted of a single magnifying glass, often in a wooden frame, in an overall construction that could collapse into a compact rectangular form. A photo/card holder was usually also included. A KOMBI camera often had included its design a graphoscope for better film viewing. Many devices combined a Stereoscope and Graphoscope.


Isomeric shift

The isomeric shift (also called isomer shift) is the shift on atomic spectral lines and gamma spectral lines, which occurs as a consequence of replacement of one nuclear isomer by another. It is usually called isomeric shift on atomic spectral lines and Mössbauer isomeric shift respectively. If the spectra also have hyperfine structure the shift refers to the center of gravity of the spectra. The isomeric shift provides important information about the nuclear structure and the physical, chemical or biological environment of atoms. More recently the effect has also been proposed as a tool in the search for the time variation of fundamental constants of nature.
Isomeric shift on atomic spectral lines.
The isomeric shift on atomic spectral lines is the energy or frequency shift in atomic spectra, which occurs when one replaces one nuclear isomer by another. The effect was predicted by Richard M. Weiner in 1956, whose calculations showed that it should be measurable by atomic (optical) spectroscopy (see also). It was observed experimentally for the first time in 1958. The theory of the atomic isomeric shift is also used in the interpretation of the Mössbauer isomeric shift.
Terminology.
The notion of isomer also appears in other fields such as chemistry and meteorology. Therefore, in the first publications devoted to this effect the name "nuclear isomeric shift on spectral lines" was used. Before the discovery of the Mössbauer effect, the isomeric shift referred exclusively to atomic spectra; this explains the absence of the word "atomic" in the initial definition of the effect. Subsequently, the isomeric shift was also observed in gamma spectroscopy through the Mössbauer effect and was called Mössbauer isomeric shift. For further details on the history of the isomeric shift and the terminology used, see.
Isotopic versus isomeric shift on atomic spectral lines.
Atomic spectral lines are due to transitions of electrons between different atomic energy levels "E", followed by emission of photons. Atomic levels are a manifestation of the electromagnetic interaction between electrons and nuclei. The energy levels of two atoms, the nuclei of which are different isotopes of the same element, are shifted one with respect to the other, despite the fact that the electric charges "Z" of the two isotopes are identical. This is so because isotopes differ by the number of neutrons, and therefore the masses and volumes of two isotopes are different; these differences give rise to the isotopic shift on atomic spectral lines.
In the case of two nuclear isomers, the number of protons and the number of neutrons are identical, but the quantum states and in particular the energy levels of the two nuclear isomers differ. This difference induces a difference in the electric charge distributions of two isomers and thus a difference δφ in the corresponding electrostatic nuclear potentials φ, which ultimately leads to a difference Δ"E" in the atomic energy levels. The isomeric shift on atomic spectral lines is then given by
where ψ is the wave function of the electron involved in the transition, "e" its electric charge, and the integration is performed over the electron coordinates.
The isotopic and the isomeric shift are similar in the sense that both are effects in which the finite size of the nucleus manifests itself and both are due to a difference in the electromagnetic interaction energy between the electrons and the nucleus of the atom. The isotopic shift had been known decades before the isomeric shift and provided useful but limited information about atomic nuclei. Unlike the isomeric shift, the isotopic shift was at first discovered in experiment and then interpreted theoretically (see also ). While in the case of the isotopic shift the determination of the interaction energy between electrons and nuclei is a relatively simple electromagnetic problem, for isomers the problem is more involved, since it is the strong interaction, which accounts for the isomeric excitation of the nucleus and thus for the difference of charge distributions of the two isomeric states. This circumstance explains in part why the nuclear isomeric shift was not discovered earlier: the appropriate nuclear theory and in particular the nuclear shell model were developed only in the late 1940s and early 1950s. As to the experimental observation of this shift, it also had to await the development of a new technique, that permitted spectroscopy with isomers, which are metastable nuclei. This too happened only in the 1950s.
While the isomeric shift is sensitive to the internal structure of the nucleus, the isotopic shift is (in a good approximation) not. Therefore, the nuclear physics information that can be obtained from the investigation of the isomeric shift, is superior to what can be obtained from isotopic-shift studies. The measurements through the isomeric shift of e.g. the difference of nuclear radii of the excited and ground state constitute one of the most sensitive tests of nuclear models. Moreover, combined with the Mössbauer effect, the isomeric shift constitutes at present a unique tool in many other fields besides physics.
The nuclear shell model.
According to the nuclear shell model, there exists a class of isomers, for which, in a first approximation, it is sufficient to consider one single nucleon, called the "optical" nucleon, to get an estimate of the difference between the charge distributions of the two isomer states, the rest of the nucleons being "filtered out". This applies in particular for isomers in odd-proton–even-neutron nuclei, with nearly closed shells. Indium-115, for which the effect was calculated, is such an example. The result of the calculation was that the isomeric shift on atomic spectral lines, although rather small, turned out to be two orders of magnitude bigger than a typical natural line width, which constitutes the limit of optical measurability.
The shift measured three years later in Hg-197 was quite close to that calculated for In-115, although in Hg-197, unlike in In-115, the optical nucleon is a neutron instead of a proton, and the electron–free-neutron interaction is much smaller than the electron—free-proton interaction. This is a consequence of the fact that the optical nucleons are not free, but bound particles. Thus the results could be explained within the theory by associating with the odd optical neutron an effective electric charge of "Z"/"A".
The Mössbauer isomeric shift.
The Mössbauer isomeric shift is the shift seen in gamma-ray spectroscopy when one compares two different nuclear isomeric states in two different physical, chemical or biological environments, and is due to the combined effect of the recoil-free Mössbauer transition between the two nuclear isomeric states and the transition between two atomic states in those two environments.
The isomeric shift on atomic spectral lines depends on the electron wave function ψ and on the difference δφ of electrostatic potentials φ of the two isomeric states.
For a given nuclear isomer in two different physical or chemical environments (different physical phases or different chemical combinations), the electron wave functions are also different. Therefore, on top of the isomeric shift on atomic spectral lines, which is due to the difference of the two nuclear isomer states, there will be a shift between the two environments (because of the experimental arrangement, these are called source (s) and absorber (a)). This combined shift is the Mössbauer isomeric shift, and it is described mathematically by the same formalism as the nuclear isomeric shift on atomic spectral lines, except that instead of one electron wave function, that in the source ψs, one deals with the difference between the electron wave function in the source ψs and the electron wave function in the absorber ψa:
The first measurement of the isomeric shift in gamma spectroscopy with the help of the Mössbauer effect was reported in 1960, two years after its first experimental observation in atomic spectroscopy. By measuring this shift, one obtains important and extremely precise information, both about the nuclear isomer states and about the physical, chemical or biological environment of the atoms, represented by the electronic wave functions.
Under its Mössbauer variant, the isomeric shift has found important applications in domains as different as atomic physics, solid-state physics, nuclear physics, chemistry, biology, metallurgy, mineralogy, geology, and lunar research. For further literature, see also.
The nuclear isomeric shift has also been observed in muonic atoms, that is, atoms in which a muon is captured by the excited nucleus and makes a transition from an atomic excited state to the atomic ground state in a time shorter than the lifetime of the excited isomeric nuclear state.


Local regression

Local regression or local polynomial regression, also known as moving regression, is a generalization of moving average and polynomial regression.
Its most common methods, initially developed for scatterplot smoothing, are LOESS (locally estimated scatterplot smoothing) and LOWESS (locally weighted scatterplot smoothing), both pronounced . They are two strongly related non-parametric regression methods that combine multiple regression models in a "k"-nearest-neighbor-based meta-model.
Outside econometrics, LOESS is known and commonly referred to as Savitzky–Golay filter (proposed 15 years before LOESS).
LOESS and LOWESS thus build on "classical" methods, such as linear and nonlinear least squares regression. They address situations in which the classical procedures do not perform well or cannot be effectively applied without undue labor. LOESS combines much of the simplicity of linear least squares regression with the flexibility of nonlinear regression. It does this by fitting simple models to localized subsets of the data to build up a function that describes the deterministic part of the variation in the data, point by point. In fact, one of the chief attractions of this method is that the data analyst is not required to specify a global function of any form to fit a model to the data, only to fit segments of the data.
The trade-off for these features is increased computation. Because it is so computationally intensive, LOESS would have been practically impossible to use in the era when least squares regression was being developed. Most other modern methods for process modeling are similar to LOESS in this respect. These methods have been consciously designed to use our current computational ability to the fullest possible advantage to achieve goals not easily achieved by traditional approaches.
A smooth curve through a set of data points obtained with this statistical technique is called a loess curve, particularly when each smoothed value is given by a weighted quadratic least squares regression over the span of values of the "y"-axis scattergram criterion variable. When each smoothed value is given by a weighted linear least squares regression over the span, this is known as a lowess curve; however, some authorities treat lowess and loess as synonyms.
Model definition.
In 1964, Savitsky and Golay proposed a method equivalent to LOESS, which is commonly referred to as Savitzky–Golay filter.
William S. Cleveland rediscovered the method in 1979 and gave it a distinct name. The method was further developed by Cleveland and Susan J. Devlin (1988). LOWESS is also known as locally weighted polynomial regression.
At each point in the range of the data set a low-degree polynomial is fitted to a subset of the data, with explanatory variable values near the point whose response is being estimated. The polynomial is fitted using weighted least squares, giving more weight to points near the point whose response is being estimated and less weight to points further away. The value of the regression function for the point is then obtained by evaluating the local polynomial using the explanatory variable values for that data point. The LOESS fit is complete after regression function values have been computed for each of the formula_1 data points. Many of the details of this method, such as the degree of the polynomial model and the weights, are flexible. The range of choices for each part of the method and typical defaults are briefly discussed next.
Localized subsets of data.
The subsets of data used for each weighted least squares fit in LOESS are determined by a nearest neighbors algorithm. A user-specified input to the procedure called the "bandwidth" or "smoothing parameter" determines how much of the data is used to fit each local polynomial. The smoothing parameter, formula_2, is the fraction of the total number "n" of data points that are used in each local fit. The subset of data used in each weighted least squares fit thus comprises the formula_3 points (rounded to the next largest integer) whose explanatory variables' values are closest to the point at which the response is being estimated.
Since a polynomial of degree "k" requires at least "k" + 1 points for a fit, the smoothing parameter formula_2 must be between formula_5 and 1, with formula_6 denoting the degree of the local polynomial.
formula_2 is called the smoothing parameter because it controls the flexibility of the LOESS regression function. Large values of formula_2 produce the smoothest functions that wiggle the least in response to fluctuations in the data. The smaller formula_2 is, the closer the regression function will conform to the data. Using too small a value of the smoothing parameter is not desirable, however, since the regression function will eventually start to capture the random error in the data.
Degree of local polynomials.
The local polynomials fit to each subset of the data are almost always of first or second degree; that is, either locally linear (in the straight line sense) or locally quadratic. Using a zero degree polynomial turns LOESS into a weighted moving average. Higher-degree polynomials would work in theory, but yield models that are not really in the spirit of LOESS. LOESS is based on the ideas that any function can be well approximated in a small neighborhood by a low-order polynomial and that simple models can be fit to data easily. High-degree polynomials would tend to overfit the data in each subset and are numerically unstable, making accurate computations difficult.
Weight function.
As mentioned above, the weight function gives the most weight to the data points nearest the point of estimation and the least weight to the data points that are furthest away. The use of the weights is based on the idea that points near each other in the explanatory variable space are more likely to be related to each other in a simple way than points that are further apart. Following this logic, points that are likely to follow the local model best influence the local model parameter estimates the most. Points that are less likely to actually conform to the local model have less influence on the local model parameter estimates.
The traditional weight function used for LOESS is the tri-cube weight function,
where "d" is the distance of a given data point from the point on the curve being fitted, scaled to lie in the range from 0 to 1.
However, any other weight function that satisfies the properties listed in Cleveland (1979) could also be used. The weight for a specific point in any localized subset of data is obtained by evaluating the weight function at the distance between that point and the point of estimation, after scaling the distance so that the maximum absolute distance over all of the points in the subset of data is exactly one.
Consider the following generalisation of the linear regression model with a metric formula_11 on the target space formula_12 that depends on two parameters, formula_13. Assume that the linear hypothesis is based on formula_1 input parameters and that, as customary in these cases, we embed the input space formula_15 into formula_16 as formula_17, and consider the following "loss function"
Here, formula_19 is an formula_20 real matrix of coefficients, formula_21 and the subscript "i" enumerates input and output vectors from a training set. Since formula_22 is a metric, it is a symmetric, positive-definite matrix and, as such, there is another symmetric matrix formula_23 such that formula_24. The above loss function can be rearranged into a trace by observing that formula_25. By arranging the vectors formula_26 and formula_27 into the columns of a formula_28 matrix formula_29 and an formula_30 matrix formula_31 respectively, the above loss function can then be written as
where formula_33 is the square diagonal formula_34 matrix whose entries are the formula_35s. Differentiating with respect to formula_19 and setting the result equal to 0 one finds the extremal matrix equation
Assuming further that the square matrix formula_38 is non-singular, the loss function formula_39 attains its minimum at
A typical choice for formula_11 is the Gaussian weight
Advantages.
As discussed above, the biggest advantage LOESS has over many other methods is the process of fitting a model to the sample data does not begin with the specification of a function. Instead the analyst only has to provide a smoothing parameter value and the degree of the local polynomial. In addition, LOESS is very flexible, making it ideal for modeling complex processes for which no theoretical models exist. These two advantages, combined with the simplicity of the method, make LOESS one of the most attractive of the modern regression methods for applications that fit the general framework of least squares regression but which have a complex deterministic structure.
Although it is less obvious than for some of the other methods related to linear least squares regression, LOESS also accrues most of the benefits typically shared by those procedures. The most important of those is the theory for computing uncertainties for prediction and calibration. Many other tests and procedures used for validation of least squares models can also be extended to LOESS models .
Disadvantages.
LOESS makes less efficient use of data than other least squares methods. It requires fairly large, densely sampled data sets in order to produce good models. This is because LOESS relies on the local data structure when performing the local fitting. Thus, LOESS provides less complex data analysis in exchange for greater experimental costs.
Another disadvantage of LOESS is the fact that it does not produce a regression function that is easily represented by a mathematical formula. This can make it difficult to transfer the results of an analysis to other people. In order to transfer the regression function to another person, they would need the data set and software for LOESS calculations. In nonlinear regression, on the other hand, it is only necessary to write down a functional form in order to provide estimates of the unknown parameters and the estimated uncertainty. Depending on the application, this could be either a major or a minor drawback to using LOESS. In particular, the simple form of LOESS can not be used for mechanistic modelling where fitted parameters specify particular physical properties of a system.
Finally, as discussed above, LOESS is a computationally intensive method (with the exception of evenly spaced data, where the regression can then be phrased as a non-causal finite impulse response filter). LOESS is also prone to the effects of outliers in the data set, like other least squares methods. There is an iterative, robust version of LOESS [Cleveland (1979)] that can be used to reduce LOESS' sensitivity to outliers, but too many extreme outliers can still overcome even the robust method.


Micromanipulator

A micromanipulator is a device which is used to physically interact with a sample under a microscope, where a level of precision of movement is necessary that cannot be achieved by the unaided human hand. It may typically consist of an input joystick, a mechanism for reducing the range of movement and an output section with the means of holding a microtool to hold, inject, cut or otherwise manipulate the object as required. The mechanism for reducing the movement usually requires the movement to be free of backlash. This is achieved by the use of kinematic constraints to allow each part of the mechanism to move only in one or more chosen degrees of freedom, which achieves a high precision and repeatability of movement, usually at the expense of some absolute accuracy.
Movement.
Movement reduction can be performed by mechanical levers, hydraulically using pistons of different diameters connected by tubing containing non-compressible fluid, electronically using stepper motors or linear actuators, or combinations of techniques in one instrument. Mechanisms with different ranges of movement or variable reduction ratio may be incorporated in one instrument to allow coarse and fine positioning.
Depending on the application, users may require different scales of movement resolution, movement speed, range and accuracy. These are the critical variables integrated into manipulator design by manufacturers, which are typically presented to suit particular applications.
Microscope integration.
Micromanipulators are usually used in conjunction with microscopes. Depending on the application, one or more micromanipulators may be fitted to a microscope stage or rigidly mounted to a bench next to a microscope. A typical application of micromanipulation is human intracytoplasmic sperm injection. Here, a spermatozoon measuring some 3 to 5 micrometres across is injected into an oocyte of approximately 100 micrometres in diameter, under the direct manual control of an embryologist. A disposable glass micropipette is fitted to a toolholder mounted on the output of the manipulator. The toolholder can be adjusted for different sized tools as well as the angle at which the tool is held.
Microelectronics.
Micromanipulators are also used in applications such as microelectronics to position test probes onto small to medium scale integrated circuits and hybrid devices, and patch clamp experiments in biological research.


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Mirau interferometer

A Mirau interferometer works on the same basic principle as a Michelson interferometer. The difference between the two is in the physical location of the reference arm. The reference arm of a Mirau interferometer is located within a microscope objective assembly.
It is named after André Henri Mirau, who filed a patent on the concept in 1949.
A schematic of a Mirau interferometer is shown on the right. At the beam splitter the source light is split into a reference path (reflected) and a sampling path (transmitted onto the sample). On the comparison face there is a mirrored circle in the middle. The two paths recombine to form an interference image. By changing the z position of the sample, interference images are acquired at a sequence of path (phase) differences: 0, λ/4, λ/2, and 3λ/4. These interference maps are functions of background intensity, fringe modulation, and phase. Three such images provide enough information to solve for the topographic image of a sample.
This orientation is often used in optical profilometers due to the increase in stability between the sample and reference path lengths.
Immersion Mirau Interferometer.
An immersion Mirau interferometer is a modification of a Mirau interferometer, in which the light path is immersed in a liquid medium. One application of an immersion Mirau interferometer is to image cells with medium. Since the index of refraction of the medium is substantially different from that of the neighboring air, each millimeter of medium would introduce a path length difference from the reference wave, and ideal interference conditions are lost. Filling the microscope optics with medium restores the ideal interference conditions.
Simultaneous Immersion Mirau Interferometer.
In immersion Mirau interferometry, the interference patterns needed to reproduce the image are acquired at different times and vibrations, if they exist, prevent maintaining the desirable phase shifts between consecutive frames. Thus immersion Mirau interferometry is very sensitive to vibrations. One solution is to acquire all interference images at the same time. This is known as a simultaneous immersion Mirau interferometer.


Cyanidin-3,5-O-diglucoside

Cyanidin-3,5-"O"-diglucoside, also known as cyanin, is an anthocyanin. It is the 3,5-"O"-diglucoside of cyanidin.
Natural occurrences.
Cyanin can be found in species of the genus "Rhaponticum" (Asteraceae).
In food.
Cyanin can be found in red wine as well as pomegranate juice according to a study done by Graça Miguel, Susana Dandlen, Dulce Antunes, Alcinda Neves, and Denise Martins in the winter of 2004. Pomegranate juice extracted through centrifugal seed separation has higher amounts of cyanidin-3,5-"O"-diglucoside than juice extracted by squeezing fruit halves with an electric lemon squeezer.


Proximity sensor

A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact.
A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive proximity sensor or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target.
Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between the sensor and the sensed object.
Proximity sensors are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings.
A proximity sensor adjusted to a very short range is often used as a touch switch.
Use with smartphones and tablet computers.
Proximity sensors are commonly used on mobile devices. When the target is within nominal range, the device lock screen user interface will appear, thus emerging from what is known as sleep mode. Once the device has awoken from sleep mode, if the proximity sensor's target is still for an extended period of time, the sensor will then ignore it, and the device will eventually revert into sleep mode. For example, during a telephone call, proximity sensors play a role in detecting (and skipping) accidental touchscreen taps when mobiles are held to the ear.
Proximity sensors can be used to recognise air gestures and hover-manipulations. An array of proximity sensing elements can replace vision-camera or depth camera based solutions for hand gesture detection.


Western Vinyl

Western Vinyl is an independent record label founded in 1998 and based in Austin, Texas. The imprint was formed by Brian Sampson and Ryan Murphy originally to release their lo-fi indie rock projects as Win Foster and Havergal.


Caroline Herzenberg

Caroline Stuart Littlejohn Herzenberg (born March 25, 1932) is an American physicist.
Biography.
Caroline Herzenberg was born Caroline Stuart Littlejohn to Caroline Dorothea Schulze and Charles Frederick Littlejohn on March 25, 1932 in East Orange, New Jersey. In the aftermath of the Great Depression, her parents decided to move to Oklahoma City Oklahoma to join his sister, Hilda Littlejohn Will and her family. Herzenberg grew up and attended public school in Oklahoma City. In 1961 she married Leonardo Herzenberg and is the mother of two grown children, Karen Ann Herzenberg and Catherine Stuart Herzenberg Larson. She lives in Hyde Park, Chicago.
After winning the Westinghouse Science Talent Search in high school, Herzenberg attended Massachusetts Institute of Technology. She was one of very few women students at M.I.T. at that time. She was awarded a bachelor's degree by M.I.T. in 1953.
For graduate study she went on to the University of Chicago. She took a class with Enrico Fermi and subsequently conducted some calculations for him. She went on to receive her master's degree from the University of Chicago in 1955. For doctoral work she turned to Samuel K. Allison, who became her thesis advisor. Her thesis research, in experimental physics, was in low energy nuclear physics, and was conducted on the 3 Mev Van de Graaff accelerator in the Research Institutes. She was awarded a PhD in 1958 by the University of Chicago.
Herzenberg continued at the University of Chicago for another year as a postdoctoral fellow and a research associate at the Enrico Fermi Institute for Nuclear Studies at the University of Chicago. She then went on to become a research associate in the Physics Division of Argonne National Laboratory in Illinois. In 1961 Herzenberg became an assistant professor of physics at Illinois Institute of Technology in Chicago, where she worked for 5 years as Director of the High Voltage Laboratory and the Van de Graaff accelerator, and directed experimental nuclear physics and Mössbauer research programs, supervising MS and PhD theses and undergraduate and graduate physics instruction.
After being denied tenure at Illinois Institute of Technology, she worked at IIT Research Institute from 1967 to 1971 as a research physicist and then as a senior physicist. At IIT Research Institute, she conducted her work as a principal investigator in the NASA Apollo returned lunar sample analysis program, and continued applications of Mössbauer spectrometry. Subsequently she held a position as a visiting associate professor of physics at the University of Illinois at the Medical Center from 1971 to 1974. She was responsible for organization, instruction, and planning for the College of Pharmacy, and she supervised graduate laboratory instruction in radioisotope utilization and applications for the University of Illinois at the Medical Center. From 1975 to 1976 she spent an academic year in California at California State University, Fresno, where she was a lecturer in physics, and was involved in general physics curriculum organization and instruction and presented lectures on electromagnetic theory.
Herzenberg returned to Argonne National Laboratory in 1977, and worked there until her retirement in 2001. At Argonne during this period of time, she was engaged primarily in applied work. This involved applications of physics in engineering and in specific areas such as radiation safety. In particular, her work included engineering research relative to fossil energy utilization, as well as radioactive waste disposal, technology for arms control verification, and radiological emergency preparedness and also chemical warfare agent emergency preparedness.
Initially, in 1977, Herzenberg joined a project for developing instrumentation for process control for a new generation of coal conversion and combustion plants. Development proceeded on non-invasive techniques for measuring the composition and flow rate of coal slurries and pulverized coal in pneumatic transport in pipes. For the analysis of the composition of coal, she worked on the application of neutron-induced gamma spectrometry; while measurement of slurry flow was based on using short lived radioactivity induced in the slurry. She later worked in technology assessment and evaluation of programs in areas that included fossil energy utilization, arms control verification, and radioactive waste disposal. She also worked in emergency preparedness and response for technological hazards, mainly in radiological emergency preparedness for nuclear power plants and emergency preparedness for chemical demilitarization.
Herzenberg was the first scientist to be inducted into the Chicago Women's Hall of Fame. She was awarded an honorary Sc.D. degree by the State University of New York, Plattsburgh in 1991. As a result of her work, Herzenberg was elected a fellow of the American Association for the Advancement of Science, the American Physical Society, and the Association for Women in Science, and served as the president of the Association for Women in Science from 1988 to 1990.
Research in the History of Science.
Herzenberg has contributed to our knowledge of the history of women in science. She published a number of articles and chapters in books on this topic. In 1986 she authored a book titled "Women Scientists from Antiquity to the Present" and later in 1999 with Ruth Howes coauthored another book titled "". As a result of her work Herzenberg was elected a fellow of the American Association for the Advancement of Science and the American Physical Society, and served as president of the Association for Women in Science from 1988 to 1990.
Research in Physics and Related Fields.
Following Caroline Herzenberg's doctoral research in experimental low energy nuclear physics with Samuel K. Allison as thesis advisor, her research continued at the University of Chicago during her year of postdoctoral work when she measured the products of nuclear reactions between lithium isotopes and those of beryllium and boron; research which laid foundations for future heavy ion investigation. Subsequently her work focused on Mössbauer spectroscopy; she was engaged in pioneering research on the Mössbauer effect and was part of the team which succeeded in verifying the Mössbauer effect. She later established Mössbauer-effect research facilities at Illinois Institute of Technology and at IIT Research Institute. Turning her focus to geological applications of the effect, Herzenberg concluded that it would be possible to analyze rocks and minerals retrieved from the Moon using Mössbauer spectrometry; and she was awarded a grant from NASA to carry out Mössbauer spectrometry during the Apollo program. She served as a principal investigator in the NASA Apollo Returned Lunar Sample Analysis Program, and analyzed some of the first returned lunar samples as well as material from subsequent sample returns.
Herzenberg has authored or coauthored hundreds of scientific and technical papers, and has written a number of chapters in books dealing with scientific and technical topics.
Further Activities.
Caroline Herzenberg has had a longstanding interest in certain societal issues, largely centering on peace and justice and human rights issues, but also including related concerns.
Already when she was an undergraduate at M.I.T., she participated in student group support of M.I.T. mathematics professor Dirk Jan Struik when he had drawn the unwelcome attention of Senator Joseph McCarthy after the advent of McCarthyism.
Throughout much of her adult life, she has worked very extensively and successfully on women's issues, especially issues relating to women in science, notably with the Association for Women in Science.
In conjunction with concerns about ethical issues, she developed some recognized guidelines on ethical issues in physics.
A foray into politics, seeking a position as an alderman in Freeport, Illinois, was unsuccessful, but the experience guided her efforts in related activities.
While in Freeport, she developed and presented a television series on science, "Camera on Science".
National attention was directed at her when in 1986 she conducted independent research and published a short paper showing that Strategic Defense Initiative (SDI) weapons under development for use in defense would also be able to be used offensively.
Following her retirement, Herzenberg has been active as a citizen in a variety of ways, including engaging in demonstrations and vigils in support of peace and justice and human rights and related endeavors. She has participated with the American Friends Service Committee, the 8th Day Center for Justice, Jewish Voice for Peace and a number of other groups. She occasionally writes popular material, including correspondence to newspapers.
In her leisure time, Herzenberg enjoys bird watching, usually in nearby Jackson Park (Chicago).


2973 Paola


OneSync

OneSync is a free and open-source sync tool developed by CodeDroids team. It maximizes lightweight synchronization experience and provides both offline synchronization through thumb drive and online synchronization through Dropbox.


Test of English Proficiency (South Korea)

The Test of English Proficiency developed by Seoul National University or TEPS is an English proficiency test created by Seoul National University's Language Education Institute to evaluate South Korean test takers' English language skills. TEPS has been administered nationwide since January 1999. It consists of 200 questions which are divided into four sections: Listening (60 questions, 55 minutes), Grammar (50 questions, 25 minutes), Vocabulary (50 questions, 15 minutes), and Reading (40 questions, 45 minutes). TEPS scores are divided into the ten ratings ranging from 1 + to 5. It is designed to test applicants' communicative English skills and to minimize test-taker reliance on certain strategies such as rote memorization. A study of the test indicated that it is valid and fair.
TEPS score is valid to be converted into TOEFL score and this conversion is used throughout many universities in the United States.
Test structure.
TEPS consists of four sections: Listening Comprehension, Grammar, Vocabulary, and Reading Comprehension. The test has a total of 135 questions and takes approximately 1 hours and 45 minutes to administer. Scores are assigned on a scale of 0 points to 600 points total and incorporate Item Response Theory, which is also called the IRT.
The new revised version of the test was introduced in May 2018, which includes four section. The listening section divided in to five parts with total 240 points and 40 minutes test time. Vocabulary and grammar section each have 60 points, with 25 minute test time and divided into further 2 and 3 parts respectively. The comprehensive reading section complete in 40 minutes and 240 points with 4 parts. The overall new test have 14 parts, 135 questions, 105 minute test duration and 0 to 600 points.


Solar electric propulsion

Solar electric propulsion (SEP) refers to the combination of solar cells and electric thrusters to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft by the European Space Agency (ESA), the JAXA (Japanese Space Agency), Indian Space Research Organisation (ISRO) and NASA. SEP has a significantly higher specific impulse than normal chemical rockets, thus requiring less propellant mass to be launched with a spacecraft and it has been evaluated for missions to Mars.
Overview.
Solar electric propulsion combines solar panels on spacecraft and one or more electric thrusters, used in tandem. There are many different types of electric thrusters, including a so-called ion thruster, a term that is often incorrectly used to describe all types of electric thrusters.
It is also possible to generate electricity from the Sun without using photovoltaic panels, such as with solar concentrators and a Stirling engine.
A 50 kilowatt SEP system was studied in the 2010s for a mission to an asteroid. In February 2012, NASA awarded a contract for a Solar Electric Propulsion Flight System.
An example of work on this type of technology is Advanced Electric Propulsion System.
The NASA Solar Technology Application Readiness (NSTAR) ion engine has been used with photovoltaic solar panels, which was tested on the Deep Space 1 mission along with Solar Concentrator Arrays (Launched in 1998 as part of the New Millennium Program).
SEP has been studied as a technology for a mission to Mars. In particular the high specific impulse of the ion engines could lower overall mass and avoid having to use nuclear technology for power when coupled with solar panels. A 1998 study for SEP for a human mission suggest that a human-sized spacecraft would need 600 to 800 kilowatts of electrical power coupled with ion engines with a specific impulse of 2000 to 2500 seconds.


Solar neutrino unit

The solar neutrino unit (SNU) is a unit of Solar neutrino flux widely used in neutrino astronomy and radiochemical neutrino experiments. It is equal to the neutrino flux producing 10−36 captures per target atom per second. It is convenient given the very low event rates in radiochemical experiments. Typical rate is expected to be from tens SNU to hundred SNU.
There are two ways of detecting solar neutrinos: radiochemical and real time experiments. The principle of radiochemical experiments is the reaction of the form
formula_1.
The daughter nucleus's decay is used in the detection. Production rate of the daughter nucleus is given by
formula_2,
where
With typical neutrino flux of 1010 cm−2 s−1 and a typical interaction cross section of about 10−45 cm2, about 1030 target atoms are required to produce one event per day. Taking into account that 1 mole is equal to 6.022 atoms, this number corresponds to ktons of the target substances, whereas present neutrino detectors operate at much lower quantities of those.


Gon (angle)


G-strain

In EPR spectroscopy, g-strain refers to broadening of g-values owing to small sample inhomogeneity owing to slight variations in the orientation of the paramagnetic centers. The phenomenon is indicated by broadening of the g-values that depends on the frequency of the spectrometer, such as X- or Q-band. If the line width were determined only by hyperfine coupling (which are field-independent), then the line widths would also be field independent, but they often are not. In iron-sulfur proteins, some other metalloproteins, as well as some solids, g-strain can be substantial.


Just minor tone


Wide Range Achievement Test

The Wide Range Achievement Test 4 (WRAT4) is an achievement test which measures an individual's ability to read words, comprehend sentences, spell, and compute solutions to math problems. The test currently is in its fourth revision. A fifth version has been released.
The test was developed in 1941 by psychologists Sidney W. Bijou and Joseph Jastak.
The test is appropriate for individuals ages 5–94 years. The WRAT4 provides two equivalent forms (Blue and Green), which enables retesting within short periods of time without potential practice effects that occur from repeating the same items. The alternate forms also may be administered together in a single examination.
The Wide Range Achievement Test 4 (WRAT4) is the latest offering in a test series first published in 1946. The various editions of the Wide Range Achievement Test (WRAT) have enjoyed widespread use in a variety of settings as a measure of the basic academic skills necessary for effective learning, communication, and thinking: reading and spelling words and performing basic mathematical calculations.
An added feature in the WRAT4 is a Reading Composite Score.
Previous versions of the WRAT4 included WRAT III.
Description.
The Wide Range Achievement Test (WRAT) is a brief achievement test measuring reading recognition, spelling, and arithmetic computation. There are two levels; level I is normed for children ages 0–5 to 6-11; level II is normed for children aged 12 through their adult age 94.
Scoring.
Norms provided for the 1978 edition include standard scores with a mean of 100 and a standard deviation of 15, percentile scores, and grade levels. The standard scores are scaled based on the norm group; the grade levels are arbitrarily assigned and can be interpreted only as rough references to achievement level. Only standard scores should be used for comparisons among scores.
Reliability.
The manual reports split-half reliabilities of .98 for Reading at both levels, .94 for Arithmetic at both levels, .96 for Spelling I, and .97 for Spelling II. During the norming study, both levels of the WRAT were administered to children ages 9 through 14. Since there is overlap in skills tested between the high end of level I and the low end of level II, this provides another estimate of the reliability of both. On Reading and Spelling, split-half reliabilities ranged from .88 to .94 for different age groups; on Arithmetic they ranged from .79 to .89. These results indicate that overall the reliability of the WRAT is excellent.
Validity.
The test most similar to the WRAT is the Peabody Individual Achievement Test (PIAT), another short, individually administered test which covers comparable material. In general the WRAT correlates very highly with the PIAT. The WRAT correlates moderately with various IQ tests, in the range of .40 to .70 for most groups and most tests.
Norms.
The 1978 WRAT norms are based on 15,200 subjects for seven states. According to the manual, no attempt was made to make the sample representative of national characteristics. The manual states that minorities were represented, but gives no data on their representation. The sample was stratified by age, sex, and approximately by ability.
Suggested uses.
Recommended uses for the test described in the manual include comparing achievement of one person to another, determining learning ability or learning disability, comparing codes with comprehension in order to prescribe remedial programs, and informally assessing error patterns to plan instructional programs.


ASTRO (satellite)

Autonomous Space Transport Robotic Operations (ASTRO), is an American technology demonstration satellite which was operated as part of the Orbital Express program. It was used to demonstrate autonomous servicing and refuelling operations in orbit, performing tests on the NEXTSat satellite which was launched with ASTRO for that purpose. Launched in March 2007, it was operated for four months, and then deactivated in orbit.
ASTRO was launched by United Launch Alliance on an Atlas V 401 rocket; serial number AV-013. The launch occurred at 03:10 UTC on 9 March 2007, from Space Launch Complex 41 at the Cape Canaveral Air Force Station. The launch was contracted by the Space Test Program to launch the STPSat-1 spacecraft, and was named STP-1. It also deployed NEXTSat; as well as FalconSAT-3, CFESat and MidSTAR-1. The launch marked the first time United Launch Alliance had launched an Atlas V, the type having previously been operated by International Launch Services.
ASTRO was a spacecraft, which was built by Boeing. It was operated in low Earth orbit. On 9 March 2007, it had a perigee of , an apogee of , 46.0 degrees of inclination, and an orbital period of 94.49 minutes. After completing operations, the ASTRO and NEXTSat spacecraft were separated, and ASTRO performed a separation burn. On 21 July 2007, ASTRO was deactivated. It re-entered on October 25, 2013 (UTC).


Giant lock

In operating systems, a giant lock, also known as a big-lock or kernel-lock, is a lock that may be used in the kernel to provide concurrency control required by symmetric multiprocessing (SMP) systems.
A giant lock is a solitary global lock that is held whenever a thread enters kernel space and released when the thread returns to user space; a system call is the archetypal example. In this model, threads in user space can run concurrently on any available processors or processor cores, but no more than one thread can run in kernel space; any other threads that try to enter kernel space are forced to wait. In other words, the giant lock eliminates all concurrency in kernel space.
By isolating the kernel from concurrency, many parts of the kernel no longer need to be modified to support SMP. However, as in giant-lock SMP systems only one processor can run the kernel code at a time, performance for applications spending significant amounts of time in the kernel is not much improved. Accordingly, the giant-lock approach is commonly seen as a preliminary means of bringing SMP support to an operating system, yielding benefits only in user space. Most modern operating systems use a fine-grained locking approach.
Linux.
The Linux kernel had a big kernel lock (BKL) since the introduction of SMP, until Arnd Bergmann removed it in 2011 in kernel version 2.6.39, with the remaining uses of the big lock removed or replaced by finer-grained locking. Linux distributions at or above CentOS 7, Debian 7 (Wheezy) and Ubuntu 11.10 are therefore not using BKL.
BSD.
, OpenBSD and NetBSD are still using the spl (Unix) family of primitives to facilitate synchronisation of critical sections within the kernel, meaning that many system calls may inhibit SMP capabilities of the system, and, according to Matthew Dillon, the SMP capabilities of these two systems cannot be considered modern.
FreeBSD still has support for "the Giant mutex", which provides semantics akin to the old spl interface, but performance-critical core components have long been converted to use finer-grained locking.
It is claimed by Matthew Dillon that out of the open-source software general-purpose operating systems, only Linux, DragonFly BSD and FreeBSD have modern SMP support, with OpenBSD and NetBSD falling behind.
The NetBSD Foundation views modern SMP support as vital to the direction of The NetBSD Project, and has offered grants to developers willing to work on SMP improvements; NPF (firewall) was one of the projects that arose as a result of these financial incentives, but further improvements to the core networking stack may still be necessary.


BEBC


5294 Onnetoh


Graphite furnace atomic absorption

Graphite furnace atomic absorption spectroscopy (GFAAS) (also known as Electrothermal Atomic absorption spectroscopy (ETAAS)) is a type of spectrometry that uses a graphite-coated furnace to vaporize the sample. Briefly, the technique is based on the fact that free atoms will absorb light at frequencies or wavelengths characteristic of the element of interest (hence the name atomic absorption spectrometry). Within certain limits, the amount of light absorbed can be linearly correlated to the concentration of analyte present. Free atoms of most elements can be produced from samples by the application of high temperatures. In GFAAS, samples are deposited in a small graphite or pyrolytic carbon coated graphite tube, which can then be heated to vaporize and atomize the analyte. The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. Applying the Beer-Lambert law directly in AA spectroscopy is difficult due to variations in the atomization efficiency from the sample matrix, and nonuniformity of concentration and path length of analyte atoms (in graphite furnace AA). Concentration measurements are usually determined from a working curve after calibrating the instrument with standards of known concentration.
The main advantages of the graphite furnace comparing to aspiration atomic absorption are the following:
System Components.
GFAA spectrometry instruments have the following basic features: 1. a source of light (lamp) that emits resonance line radiation; 2. an atomization chamber (graphite tube) in which the sample is vaporized; 3. a monochromator for selecting only one of the characteristic wavelengths (visible or ultraviolet) of the element of interest; 4. a detector, generally a photomultiplier tube (light detectors that are useful in low-intensity applications), that measures the amount of absorption; 5. a signal processor-computer system (strip chart recorder, digital display, meter, or printer).
Mode of Operation.
Most currently available GFAAs are fully controlled from a personal computer that has Windows-compatible software. The software easily optimizes run parameters, such as ramping cycles or calibration dilutions. Aqueous samples should be acidified (typically with nitric acid, HNO3) to a pH of 2.0 or less. GFAAs are more sensitive than flame atomic absorption spectrometers, and have a smaller dynamic range. This makes it necessary to dilute aqueous samples into the dynamic range of the specific analyte. GFAAS with automatic software can also pre-dilute samples before analysis.
After the instrument has warmed up and been calibrated, a small aliquot (usually less than 100 microliters (µL) and typically 20 µL) is placed, either manually or through an automated sampler, into the opening in the graphite tube. The sample is vaporized in the heated graphite tube; the amount of light energy absorbed in the vapor is proportional to atomic concentrations. Analysis of each sample takes from 1 to 5 minutes, and the results for a sample is the average of triplicate analysis.


Margaret Gurney

Margaret Gurney (October 28, 1908 – March 19, 2002) was an American mathematician, statistician, and computer programmer. Originally trained in the mathematical study of partial differential equations at Swarthmore College, Brown University, and the University of Göttingen, she came to work for the United States Census Bureau. There, she became known for her expertise in sampling, stratified sampling, and survey methodology. At the Census Bureau she also worked as an early programmer of the UNIVAC I computer. Later, she became an international consultant, teaching statistical methods in developing countries. She won the Department of Commerce Silver Medal and was recognized as a Fellow of the American Statistical Association.
Early life and education.
Gurney's parents, Anna Elizabeth Pickett and Dayton Alvin Gurney, both studied at Michigan State University, then called the State Agricultural College. Her father became a civilian engineer for the military (later the chief engineer of the Ordnance Department), and she and her two siblings were born in Washington, DC. She attended Central High School there, and then went to Swarthmore College with the support of a White scholarship. At Swarthmore, she completed a bachelor's degree in mathematics, physics, and astronomy in 1930, with highest honors.
She began graduate study at Brown University in 1930 and earned a master's degree there in 1931. From 1932 to 1933 she traveled on a fellowship to the University of Göttingen in Germany; she returned to Brown, and completed her Ph.D. there in 1934. Her dissertation, on the mathematical analysis of hyperbolic partial differential equations, was "Some General Existence Theorems for Partial Differential Equations of Hyperbolic Type"; her doctoral advisor was Jacob Tamarkin.
Career.
Gurney began her work with the US Government in 1938, working for the Budget Bureau first as a statistical consultant and then beginning in 1940 as an economist. She moved to the United States Census Bureau in 1944, and retired from the census in 1973.
At the Census Bureau, Gurney helped plan sampling-based surveys, and implemented her statistical methods on the UNIVAC I, the first commercial computer in the United States.
Beginning in 1961, and continuing past her retirement, Gurney also worked as an international statistical consultant, teaching statistical methodology and agricultural statistics in developing parts of the world in association with the Bureau of Labor Statistics of the United States Department of Labor. She began this work in Puerto Rico and later continued this work in Central and South America, Africa, and Southeast Asia.
She lived with her sister Ruth Park in Quilcene, Washington after her retirement and died there on March 19, 2002.
Recognition.
Gurney was awarded the Department of Commerce Silver Medal in 1966, "for her continuous contributions to the theory and application of sample survey methods over a long period". In 1968, Gurney was elected as a Fellow of the American Statistical Association in honor of her "distinguished contributions to the theory of recurrent sample surveys, to the measurement of nonsampling errors, and to training programs of foreign statisticians in sample surveys of their own countries".