Geocentric orbit

A geocentric orbit or Earth orbit involves any object orbiting the Earth, such as the Moon or artificial satellites. In 1997 NASA estimated there were approximately 2,465 artificial satellite payloads orbiting the Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. Over 16,291 previously launched objects have decayed into the Earth's atmosphere.
A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity. For a low Earth orbit, this velocity is about ; by contrast, the fastest manned airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was in 1967 by the North American X-15. The energy required to reach Earth orbital velocity at an altitude of is about 36 MJ/kg, which is six times the energy needed merely to climb to the corresponding altitude.
Spacecraft with a perigee below about are subject to drag from the Earth's atmosphere, which decreases the orbital altitude. The rate of orbital decay depends on the satellite's cross-sectional area and mass, as well as variations in the air density of the upper atmosphere. Below about , decay becomes more rapid with lifetimes measured in days. Once a satellite descends to , it has only hours before it vaporizes in the atmosphere. The escape velocity required to pull free of Earth's gravitational field altogether and move into interplanetary space is about .
Geocentric orbit types.
The following is a list of different geocentric orbit classifications.


LExan Bubble Chamber

The construction of the LExan Bubble Chamber, LEBC, was approved by the CERN Research Board on 16 November 1978.
Bubble chambers are similar to cloud chambers, both in application and in basic principle. A chamber is normally made by filling a large cylinder with a liquid heated to just below its boiling point. As particles enter the chamber, a piston suddenly decreases its pressure, and the liquid enters into a superheated, metastable phase. Charged particles create an ionization track, around which the liquid vaporizes, forming microscopic bubbles. Bubble density around a track is proportional to a particle's energy loss. Bubbles grow in size as the chamber expands, until they are large enough to be seen or photographed. Several cameras are mounted around it, allowing a three-dimensional image of an event to be captured.
LEBC was 20 centimetres in diameter and contained one litre of liquid hydrogen. It was designed to look for charmed particles, a type of particles that are so unstable that they usually decay too quickly to be detected in big bubble chambers. The bubbles in a small chamber like LEBC were about ten times smaller compared to the bubbles in the large chambers. Hence, LEBC had a higher probability of detecting short tracks.<ref name="No. 10/80"></ref>
LEBC was used for several CERN experiments in Geneva, among others NA13, NA16 and NA27, before it was transported to Fermilab outside Chicago where it was used for experiment E743.
The NA13 experiment was performed by exposing LEBC without any down-stream particle spectrometer. While for the NA16 experiment, LEBC was placed at the vertex position of the European Hybrid Spectrometer (EHS) that provided momentum analysis, particle identification and gamma detection for secondaries emerging from the hydrogen interactions.


Mass interconnect

Mass interconnect systems act as the connector interface between test instruments (PXI, VXI, LXI, GPIB, SCXI, & PCI) and devices/units under test (D/UUT) and are most often used in defense, aerospace, automotive, manufacturing, and other applications. By mating a receiver on the tester side with an interchangeable test adapter (ITA) on the UUT, a mass interconnect enables the entire system to mate together at one time. Mass interconnect systems are available in multiple sizes and configurations to accommodate virtually any testing requirement.
Companies that manufacture mass interconnects include VPC and MAC Panel Company.


AI Phoenicis

AI Phoenicis is a variable star in the constellation of Phoenix. An Algol-type eclipsing binary, its apparent magnitude is constant at 8.58 for most of the time, sharply dropping to 9.35 during primary eclipse and to 8.89 during secondary eclipse. The system's variability was discovered by W. Strohmeier in 1972. From parallax measurements by the Gaia spacecraft, the system is located at a distance of from Earth, in agreement with earlier estimates based on its luminosity (173 ± 11 parsecs).
The primary star is a K-type subgiant with a spectral type of K0IV and an effective temperature of 5,000 K, while the secondary is an F-type main sequence star with a spectral type of F7V and a temperature of 6,300 K. The primary component, while visually fainter, is slightly more luminous than the secondary due to its higher infrared output. The primary is at the end of its main sequence life and is likely in the short contraction phase known as a hook, where core hydrogen fusion has ceased but shell burning has not yet started, before ascending towards the red giant branch. Photometric and spectroscopic observations have allowed the direct determination of the parameters of the stars with extreme precision, and this system is frequently used to test stellar evolution models. The masses of the stars, 1.247 for the primary and 1.197 for the secondary, are known to a precision of just 0.3%, while the radii of 2.91 and 1.84 have uncertainties of 0.8% and 0.5% respectively. Stellar evolution models show the stars have a common age of about 4.4 billion years.
The orbit of AI Phoenicis has a period of 24.59248 days and a moderate eccentricity of 0.1821 ± 0.0051. The observation of eclipses is allowed by its 88.5° inclination to the plane of the sky. Times of minimum light show the orbital period of the system is not constant, which can be caused by a third star in the system. An analysis of the alignment of the system by the Rossiter–McLaughlin effect suggests that the secondary star rotation axis is not aligned with the orbital axis, with an angle of 87 ± 17° between them, which also indicates interactions with a third star.
Investigations continue with the TESS observatory in 2020. See Arxiv astro-ph.SR/
2003.09295


RF resistance architecture

RF resistance architecture is a feature found on microphones designed to protect the sensitive circuitry from outside radio frequency interference. The name is a trade mark from Astatic Corporation in Solon, Ohio. Certifications from the European Union have been established to certify products with this feature.


List of tests

The following is an alphabetized and categorized list of notable tests.


4256 Kagamigawa


RCA Type 77-DX microphone

The RCA Type 77-DX microphone is a poly-directional ribbon microphone, or pressure-gradient microphone, introduced by the RCA Corporation in 1954. It was preceded by the Type 77-D introduced in 1948. Its popularity and classic design has resulted in the 77-DX becoming an iconic microphone, used by broadcasters and media personalities such as Edward R. Murrow, David Letterman and Larry King.
Controls.
The directionality of the 77-DX is variable. A rotating backshutter on the acoustic labyrinth, controlled by a screwdriver-operated slot at the rear of the microphone, allows the user to vary the microphone's pattern from omnidirectional in the fully closed position, to cardioid, to figure-8 (bidirectional) in the fully open position. A 3-position switch at the bottom end of the microphone allows the user to control the desired amount of low-frequency rolloff.
Response and output characteristics.
At 1 kHz, the 77-DX has an output of -50 to -56dbm, depending on the pattern selection. The output impedance is user-selectable; factory preset at 250 ohms, and changeable to 30 or 150 ohms. The microphone has a fairly flat response. In the cardioid (unidirectional) pattern, it is level from approximately 150 Hz to 2 kHz, with a slight rise peaking at just under 5 kHz, then dropping approximately 3dB/octave to 20 kHz.
User techniques.
The 77-DX has been used on countless vocal recordings by Bing Crosby, Kate Smith, Frank Sinatra, Elvis Presley, Johnny Cash, Al Green, and many others. It is still sought after today for use in recording brass instruments.
The foil ribbon element in a 77-DX will respond to gravitational force as the microphone is positioned or tilted. Audio engineers experienced with the 77-DX typically suspend, hang or position the microphone at various angles to achieve a variety of desired frequency response characteristics. For example, with the microphone suspended, a slight tilt on the horizontal axis will cause the ribbon to 'sag' slightly, resulting in a noticeable boost in the lower-midrange frequencies.
The ribbon is positioned inside the housing in such a way that fricatives may cause popping sounds, due to the explosion of air directly into the ribbon. A common solution to this problem has been to attach a pencil vertically across the front of the microphone. The pencil deflects a vocalist's breath as it reaches the microphone, and prevents it from hitting the ribbon directly.


Hidden Shoal Recordings

Hidden Shoal is an independent record label and music publisher based in Perth, Western Australia.
Launched in 2006 by Cameron Merton, Stuart Medley and Malcolm Riddoch, Hidden Shoal is home to more than 40 international artists and an eclectic catalogue of music from across indie, experimental, post-rock, electronic and ambient music. Hidden Shoal's publishing arm licenses music for use in film, TV, games, web, compilations and other media.


Trinity College London ESOL

Trinity College London ESOL is an international English Language examinations board delivering assessments in English language learning and teaching and has been offering English language examinations since 1938. Trinity College London's exams are taken by over 850,000 candidates in over 60 countries each year.
Language certificates offered include English for Speakers of Other Languages (ESOL) for non-native speakers of English (learning), and Teaching English for Speakers of Other Languages (TESOL) for teachers of non-native speakers of English (teaching). Trinity College London provides the following examinations:
Secure English Language Test (SELT).
Secure English Language Tests (SELTs) are provided at ten Trinity SELT centres in the UK only. The tests are approved for applications to UK Visas and Immigration (UKVI) for visas, British Citizenship and Leave to Remain (LTR). The approved SELTs are Graded Examinations in Spoken English (GESE) at CEFR A1, A2 and B1 levels; Integrated Skills in English (ISE) at B1, B2 and C1 levels.
Graded Examinations in Spoken English (GESE).
The Graded Examinations in Spoken English (GESE) test candidates' ability in listening and speaking.
There are four Stages with three Grades at each Stage:
Integrated Skills in English (ISE).
Integrated Skills in English examinations (ISE) assess all four language skills - Speaking, Writing, Listening and Reading – interacting with each other as they do in the real world making them suitable assessments for many business and academic organisations. There are five ISE levels – ISE 0, ISE I, ISE II, ISE III, ISE IV.
ISE is accepted by academic institutions in the UK as evidence of English language proficiency for International students.
Learners can choose to take ISE exams on their own or combine them with the spoken grades (GESE) as they progress in their English language abilities.
UK ESOL Examinations.
These certificates are for ESOL learners in England, Wales and Northern Ireland, designed in accordance with the UK Adult ESOL Core Curriculum.
ESOL Skills for Life certificates<br>
These assessments are offered in Speaking and Listening, Reading and Writing and are available from Entry 1 to Level 2 in the Regulated Qualifications Framework (RQF). Trinity is the only examinations board to also offer pre-RQF assessments (non-accredited) in Speaking and Listening – ESOL Step 1 and Step 2.
ESOL Skills for Life is externally assessed by a Trinity examiner.
Teaching Qualifications (TESOL/TEFL).
Trinity College London also offers TESOL (Teaching of English to Speakers of Other Languages) qualifications - this is also known sometimes as TEFL or TESL qualifications. Trinity's TESOL qualifications are widely recognised by employers and authorities around the world.
Qualifications range from those starting out in a teaching career to senior teaching and management posts.
Trinity also offers Further Education (FE) qualifications, accredited by Standards Verification UK (formerly FENTO):
Inquirers should check that course providers listed as validated as of July 2006 are still validated by Trinity College London.
Academic Recognition.
Trinity ESOL qualifications are accredited by the UK Qualifications and Curriculum Authority QCA, and its respective partners in Wales and Northern Ireland. They are listed in the UK's UCAS (University and Colleges Admissions Services) guide to qualifications acceptable as evidence of English language competency.
UCAS considers an English language competency equivalent to NQF Levels 1 or 2 as appropriate for entry to UK Higher Education. The UCAS guides list the following Trinity ESOL qualifications acceptable as evidence of proficiency in English.
Comparison table for Trinity ESOL, Cambridge English Language Assessment and IELTS examinations
Worldwide accreditation varies from country to country.
Link to Common European Framework of Reference (CEFR).
The Trinity suite of exams are linked to the Common European Framework of Reference for Languages(CEFR). This framework sets standards in foreign language learning/teaching across Europe, by categorising learners into six levels of ability. The
Trinity ESOL exams fit into this framework as shown in the table


Brillouin spectroscopy

Brillouin spectroscopy is an empirical spectroscopy technique which allows the determination of elastic moduli of materials. The technique uses inelastic scattering of light when it encounters acoustic phonons in a crystal, a process known as Brillouin scattering, to determine phonon energies and therefore interatomic potentials of a material. The scattering occurs when an electromagnetic wave interacts with a density wave, photon-phonon scattering.
This technique is commonly used to determine the elastic properties of materials in mineral physics and material science. Brillouin spectroscopy can be used to determine the complete elastic tensor of a given material which is required in order to understand the bulk elastic properties.
Comparison with Raman spectroscopy.
Brillouin spectroscopy is similar to Raman spectroscopy in many ways; in fact the physical scattering processes involved are identical. However, the type of information gained is significantly different. The process observed in Raman spectroscopy, Raman scattering, primarily involves high frequency molecular vibrational modes. Information relating to modes of vibration, such as the six normal modes of vibration of the carbonate ion, (CO3)2−, can be obtained through a Raman spectroscopy study shedding light on structure and chemical composition, whereas Brillouin scattering involves the scattering of photons by low frequency phonons providing information regarding elastic properties. Optical phonons and molecular vibrations measured in Raman spectroscopy typically have wavenumbers between 10 and 4000 cm−1, while phonons involved in Brillouin scattering are on the order of 0.1–6 cm−1. This roughly two order of magnitude difference becomes obvious when attempting to perform Raman spectroscopy vs. Brillouin spectroscopy experiments.
In Brillouin scattering, and similarly Raman scattering, both energy and momentum are conserved in the relations:
Where and are the angular frequency and wavevector of the photon, respectively. While the phonon angular frequency and wavevector are and . The subscripts and denote the incident and scattered waves. The first equation is the result of the application of the conservation of energy to the system of the incident photon, the scattered photon, and the interacting phonon. Applying conservation of energy also sheds light upon the frequency regime in which Brillouin scattering occurs. The energy imparted on an incident photon from a phonon is relatively small, generally around 5-10% that of the photon's energy. Given an approximate frequency of visible light, ~1014 GHz, it is easy to see that Brillouin scattering generally lies in the GHz regime.
The second equation describes the application of conservation of momentum to the system. The phonon, which is either generated or annihilated, has a wavevector which is a linear combination of the incident and scattered wavevectors. This orientation will become more apparent and important when the orientation of the experimental setup is discussed.
The equations describe both the constructive (Stokes) and destructive (anti-Stokes) interactions between a photon and phonon. Stokes scattering describes the interaction scenario in which the material absorbs the photon, creating a phonon, inelastically emitting a photon with a lower energy than that of the absorbed photon. Anti-Stokes scattering describes the interaction scenario in which the incoming photon absorbs a phonon, phonon annihilation, and a photon with a higher energy than that of absorbed photon is emitted. The figure illustrates the differences between Raman scattering and Brillouin scattering along with Stokes and anti-Stokes interactions as is seen in experimental data.
The figure depicts three important details. The first is the Rayleigh line, the peak which has been suppressed at 0 cm−1. This peak is a result of Rayleigh scattering, a form of elastic scattering from the incident photons and the sample. Rayleigh scattering occurs when the induced polarization of the atoms, resulting from the incident photons, does not couple with possible vibrational modes of the atoms. The resulting emitted radiation has the same energy as the incident radiation, meaning no frequency shift is observed. This peak is generally quite intense and is not of direct interest for Brillouin spectroscopy. In an experiment, the incident light is most often a high power laser. This results in a very intense Rayleigh peak which has the ability to wash out the Brillouin peaks of interest. In order to adjust for this, most spectrum are plotted with the Rayleigh peak either filtered out or suppressed.
The second noteworthy aspect of the figure is the distinction between Brillouin and Raman peaks. As previously mentioned, Brillouin peaks range from 0.1 cm−1 to approximately 6 cm−1 while Raman scattering wavenumbers ranges from 10–10000 cm−1. As Brillouin and Raman spectroscopy probe two fundamentally different interaction regimes this is not too large of an inconvenience. The fact that Brillouin interactions are such low frequency however creates technical challenges when performing experiments for which a Fabry-Perot interferometer are usually used in order to overcome. A Raman spectroscopy system is generally less technically complicated and can be performed with a diffraction grating–based spectrometer. In some cases a single grating–based spectrometer has been used to collect both Brillouin and Raman spectra from a sample.
The figure also highlights the difference between Stokes and anti-Stokes scattering. Stokes scattering, positive photon creation, is displayed as a positive shift in wavenumber. Anti-Stokes scattering, negative photon annihilation, is displayed as a negative shift in wavenumber. The locations of peaks are symmetric about the Rayleigh line because they correspond to the same energy level transition but of a different sign.
In practice, six Brillouin lines of interest are generally seen in a Brillouin spectrum. Acoustic waves have three polarization directions one longitudinal and two transverse directions each being orthogonal to the others. Solids can be considered nearly incompressible, within an appropriate pressure regime, as a result, longitudinal waves, which are transmitted via compression parallel to the propagation direction, can transmit their energy through the material easily and thus travel quickly. The motion of transverse waves, on the other hand, is perpendicular to the propagation direction and is thus less easily propagated through the medium. As a result, longitudinal waves travel more quickly through solids than transverse waves. An example of this can be seen in quartz with an approximate acoustic longitudinal wave velocity of 5965 m/s and transverse wave velocity of 3750 m/s. Fluids cannot support transverse waves. As a result, transverse wave signals are not found in Brillouin spectra of fluids. The equation shows the relationship between acoustic wave velocity, , angular frequency , and phonon wavenumber, .
According to the equation, acoustic waves with varying speeds will appear on the Brillouin spectra with varying wavenumbers: faster waves with higher magnitude wavenumbers and slower waves with smaller wavenumbers. Therefore, three distinct Brillouin lines will be observable. In isotropic solids, the two transverse waves will be degenerate, as they will be traveling along elastically identical crystallographic planes. In non-isotropic solids the two transverse waves will be distinguishable from one another, but not distinguishable as being horizontally or vertically polarized without a deeper understanding of the material being studied. They are then generically labeled transverse 1 and transverse 2.
Applications.
Brillouin spectroscopy is a valuable tool for determining the complete elastic tensor, formula_4, of solids. The elastic tensor is an 81 component 3x3x3x3 matrix which, through Hooke's Law, relates stress and strain within a given material. The number of independent elastic constants found within the elastic tensor can be reduced through symmetry operations and depends on the symmetry of a given material ranging from 2 for non-crystalline substances or 3 for cubic crystals to 21 for systems with triclinic symmetry. The tensor is unique to given materials and thus must be independently determined for each material in order to understand their elastic properties. The elastic tensor is especially important to mineral physicist and seismologists looking to understand the bulk, polycrystalline, properties of deep Earth minerals. It is possible to determine elastic properties of materials such as the adiabatic bulk modulus, formula_5, without first finding the complete elastic tensor through techniques such as the determination of an equation of state through a compression study. Elastic properties found in this way, however, do not scale well to bulk systems such as those found within rock assemblages in the Earth's mantle. In order to calculate the elastic properties of bulk material with randomly oriented crystals the elastic tensor is needed.
Using Equation 3, it is possible to determine the sound velocity through a material. In order to obtain the elastic tensor the Christoffel Equation needs to be applied:
formula_6
The Christoffel Equation is essentially an eigenvalue problem which relates the elastic tensor, formula_4, to the crystal orientation and the orientation of the incident light, formula_8, to a matrix, formula_9, whose eigenvalues are equal to ρV2, where ρ is density and V is acoustic velocity. The polarization matrix, formula_10, contains the corresponding polarizations of the propagating waves.
Using the equation, where formula_8 and formula_12 are known from the experimental setup and is determined from the Brillouin spectra, it is possible to determine formula_4, given the density of the material.
For specific symmetries the relationship between a specific combination of elastic constants, , and acoustic wave velocities, ρV2, have been determined and tabulated. For example, in a cubic system formula_4 reduces to 3 independent components. Equation 5 shows the complete elastic tensor for a cubic material. The relations between the elastic constants and can be found in Table 1.
In a cubic material it is possible to determine the complete elastic tensor from pure longitudinal and pure transverse phonon velocities.
In order make the above calculations the phonon wavevector, , must be pre-determined from the geometry of the experiment. There are three main Brillouin spectroscopy geometries: 90 degree scattering, backscattering, and platelet geometry.
Frequency shift.
The frequency shift of the incident laser light due to Brillouin scattering is given by
where formula_16 is the angular frequency of the light, formula_17 is the velocity of acoustic waves (speed of sound in the medium), formula_18 is the index of refraction, formula_19 is the vacuum speed of light, and formula_20 is the angle of incidence of the light.


Werckmeister temperament

Werckmeister temperaments are the tuning systems described by Andreas Werckmeister in his writings. The tuning systems are numbered in two different ways: the first refers to the order in which they were presented as "good temperaments" in Werckmeister's 1691 treatise, the second to their labelling on his monochord. The monochord labels start from III since just intonation is labelled I and quarter-comma meantone is labelled II.
The tunings I (III), II (IV) and III (V) were presented graphically by a cycle of fifths and a list of major thirds, giving the temperament of each in fractions of a comma. Werckmeister used the organbuilder's notation of ^ for a downwards tempered or narrowed interval and v for an upward tempered or widened one. (This appears counterintuitive - it is based on the use of a conical tuning tool which would reshape the ends of the pipes.) A pure fifth is simply a dash. Werckmeister was not explicit about whether the syntonic comma or Pythagorean comma was meant: the difference between them, the so-called schisma, is almost inaudible and he stated that it could be divided up among the fifths.
The last "Septenarius" tuning was not conceived in terms of fractions of a comma, despite some modern authors' attempts to approximate it by some such method. Instead, Werckmeister gave the string lengths on the monochord directly, and from that calculated how each fifth ought to be tempered.
Werckmeister I (III): "correct temperament" based on 1/4 comma divisions.
This tuning uses mostly pure (perfect) fifths, as in Pythagorean tuning, but each of the fifths C-G, G-D, D-A and B-F is made smaller, i.e. tempered by 1/4 of the comma. No matter if the Pythagorean comma or the syntonic comma is used, the resulting tempered fifths are for all practical purposes the same as meantone temperament fifths. All major thirds are reasonably close to 400 cents and, because not all fifths are tempered, there is no wolf fifth and all 12 notes can be used as the tonic.
Werckmeister designated this tuning as particularly suited for playing chromatic music ("ficte"), which may have led to its popularity as a tuning for J.S. Bach's music in recent years.
Because a quarter of the Pythagorean comma is formula_1, or formula_2, it is possible to calculate exact mathematical values for the frequency relationships and intervals:
Werckmeister II (IV): another temperament included in the Orgelprobe, divided up through 1/3 comma.
In Werckmeister II the fifths C-G, D-A, E-B, F-C, and B-F are tempered narrow by 1/3 comma, and the fifths G-D and E-B are widened by 1/3 comma. The other fifths are pure. Werckmeister designed this tuning for playing mainly diatonic music (i.e. rarely using the "black notes"). Most of its intervals are close to sixth-comma meantone. Werckmeister also gave a table of monochord lengths for this tuning, setting C=120 units, a practical approximation to the exact theoretical values. Following the monochord numbers the G and D are somewhat lower than their theoretical values but other notes are somewhat higher.
Werckmeister III (V): an additional temperament divided up through 1/4 comma.
In Werckmeister III the fifths D-A, A-E, F-C, C-G, and F-C are narrowed by 1/4, and the fifth G-D is widened by 1/4 comma. The other fifths are pure. This temperament is closer to equal temperament than the previous two.
Werckmeister IV (VI): the Septenarius tunings.
This tuning is based on a division of the monochord length into formula_3 parts. The various notes are then defined by which 196-division one should place the bridge on in order to produce their pitches. The resulting scale has rational frequency relationships, so it is mathematically distinct from the irrational tempered values above; however in practice, both involve pure and impure sounding fifths. Werckmeister also gave a version where the total length is divided into 147 parts, which is simply a transposition of the intervals of the 196-tuning. He described the Septenarius as "an additional temperament which has nothing at all to do with the divisions of the comma, nevertheless in practice so correct that one can be really satisfied with it".
One apparent problem with these tunings is the value given to D (or A in the transposed version): Werckmeister writes it as 176. However this produces a musically bad effect because the fifth G-D would then be very flat (more than half a comma); the third B-D would be pure, but D-F would be more than a comma too sharp - all of which contradict the rest of Werckmeister's writings on temperament. In the illustration of the monochord division, the number "176" is written one place too far to the right, where 175 should be. Therefore it is conceivable that the number 176 is a mistake for 175, which gives a musically much more consistent result. Both values are given in the table below.
In the tuning with D=175, the fifths C-G, G-D, D-A, B-F, F-C, and B-F are tempered narrow, while the fifth G-D is tempered wider than pure; the other fifths are pure.


Alfred Msezane

Alfred Z. Msezane is Professor in the Department of Physics at Clark Atlanta University, and Founding Director of the Center for Theoretical Studies of Physical Systems. His research is primarily in Atomic and Molecular Physics Theory and Condensed Matter Theory. He also carries out research in mathematical physics, and image processing.
Education and Career.
Msezane was born in South Africa on December 31, 1938. He obtained his B. Sc and B. Sc (Hons) from the University of South Africa in 1962 and 1964, respectively, studying Physics and Applied Mathematics, and his M. Sc in physics at University of Saskatchewan in 1968. He did research for a year at the Nuclear Physics Research Unit of the Witwatersrand University . He obtained his Ph. D in physics at the University of Western Ontario in 1973.
After spending a year at the University of Western Ontario learning and implementing Modular Teaching to physics students, Msezane moved to Georgia State University in 1974 for his postdoctoral research. He became a college instructor and researcher at the University of New Brunswick in 1976. He served as a visiting professor at Louisiana State University from 1978 to 1980, and joined the faculty of Morehouse College as an assistant professor of physics in 1980.
In 1983 Msezane became professor and served as chair of the physics department from 1986 to 1989 at Atlanta University, which was merged with Clark College in 1988 to become Clark Atlanta University.
Research.
Msezane has published more than 400 physics research papers and given more than 380 presentations at national and international conferences.
He carries out research in theoretical atomic and molecular physics, mathematical physics, condensed matter physics, and image processing.
Msezane developed a fundamental theory to better understand negative ion formation in complex heavy systems and applied it to negative ion catalysis.
He is the founding director of the Center for Theoretical Studies of Physical Systems (CTSPS) at Clark Atlanta University, which was established in 1991 through an approximately 5 million dollar grant by the NSF which was further renewed at the same funding level in 1996.
Awards and honors.
Msezane's awards and honors include:


870 Manto

870 Manto ("prov. designation": "or" ) is a stony background asteroid and slow rotator from the inner region of the asteroid belt. It was discovered on 12 May 1917, by astronomer Max Wolf at the Heidelberg Observatory in southwest Germany. The likely heavily elongated S-type asteroid has a long rotation period of 122.3 hours and measures approximately in diameter. It was named after Manto, a prophetess in Greek mythology.
Orbit and classification.
"Manto" is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the inner asteroid belt at a distance of 1.7–2.9 AU once every 3 years and 6 months (1,293 days; semi-major axis of 2.32 AU). Its orbit has an eccentricity of 0.27 and an inclination of 6° with respect to the ecliptic. The asteroid was first observed as () at Taunton Observatory on 11 October 1907, and again as () at the Simeiz Observatory on 16 October 1914. The body's observation arc begins with its official discovery observation at Heidelberg Observatory on 12 May 1917.
Naming.
This minor planet was named after Manto from Greek mythology. She was the daughter of Teresias Thebanus and a famous soothsayer, who erected of a temple of Apollo (Apollo Clarius) in Claros. The was also mentioned in "The Names of the Minor Planets" by Paul Herget in 1955 ().
Physical characteristics.
"Manto" is a common stony S-type asteroid in the Bus–Binzel SMASS classification, and in both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2).
Rotation period.
In September 2013, a rotational lightcurve of "Manto" was obtained from photometric observations by Frederick Pilcher at the Organ Mesa Observatory , New Mexico, in collaboration with Eduardo Manuel Alvarez, Andrea Ferrero, Daniel Klinglesmith and Julian Oey Lightcurve analysis gave an exceptionally long rotation period of hours with a notably high brightness amplitude of magnitude, indicative of an elongated shape (). With a period above 100 hours, the asteroid is a slow rotator. The result supersedes observations by Alain W. Harris from July 1981, and by astronomers at the Intermediate Palomar Transient Factory in California ().
In 2016, a modeled lightcurve gave a concurring sidereal period of hours using data from a large collaboration of individual observers (such as above). The study also determined two spin axes of (96.0°, 30.0°) and (283.0°, 35.0°) in ecliptic coordinates (λ, β).
Diameter and albedo.
According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), "Manto" measures () and () kilometers in diameter and its surface has an albedo of () and (), respectively. The "Collaborative Asteroid Lightcurve Link" assumes a standard albedo for a stony asteroid of 0.20 and calculates a diameter of 13.71 kilometers based on an absolute magnitude of 11.68. The WISE team also published an alternative mean-diameter measurement of () with a corresponding albedo of ().


Quint Neck Guitar

The Quint Neck Guitar (also known as a five neck guitar) consists of 5 guitar necks, hardware and pick-ups in one oversized body, used by Rick Nielsen from the rock band Cheap Trick.
History.
The guitar's birth was first conceived on ruled note book paper by musician Rick Nielsen during one of his frequent scribble sessions. He brought the idea to his manufacturer (Hamer Guitars) to build. The original design sought by Rick was a circular guitar allowing him to spin the guitar from neck to neck. This design was scrapped by Hamer due to weight and logistical issues.
Rick Nielsen and Bobby Demonic both have employed several five necks over the years. Nielsen's original "orange Quint neck" with dove tail jointed necks, was retired in the mid-1990s after the top neck snapped off after years of abuse. It was replaced by a black and white with 1/2 inch checkers (Rick's unofficial trademark).
References.
Hamer News


Symbols per second


Summer time in Europe

Summer time in Europe is the variation of standard clock time that is applied in most European countries (apart from Iceland, Belarus, Turkey, Georgia and Russia) in the period between spring and autumn, during which clocks are advanced by one hour from the time observed in the rest of the year, with a view to making the most efficient use of seasonal daylight. It corresponds to the notion and practice of daylight saving time (DST) to be found in many other parts of the world.
In all locations in Europe where summer time is observed (the EU, EFTA and associated countries), European Summer Time begins at 01:00 UTC/WET (02:00 CET, 03:00 EET) on the last Sunday in March and ends at 01:00 UTC (02:00 WEST, 03:00 CEST, 04:00 EEST) on the last Sunday in October each year; i.e. the change is made at the same absolute time across all time zones. European Union Directive 2000/84/EC makes the observance of summer time mandatory for EU member states (except overseas territories), though a proposal to repeal this directive and require that member states observe their own choice year-round is currently going through the legislative process .
Summer time lasts 30 weeks in years when the last Sunday in March is after the 28th; otherwise, it is 31 weeks.
History.
Summer Time was first introduced during the First World War. However, most countries discontinued the practice after the war. It was then restarted in various countries during the Second World War and its immediate aftermath. Again it was widely cancelled by the 1950s, but reintroduced in isolated cases until the late 1960s, when the energy crisis of the late 1960s and early 1970s began to prompt policymakers to reintroduce Summer Time across the continent. It has remained in place in most European countries since then.
Historically the countries of Europe had different practices for observing Summer Time, but this hindered coordination of transport, communications, and movements. Starting in 1981 the European Commission began issuing directives requiring member states to legislate harmonised start and end dates for Summer Time.
Since 1981 each directive has specified a transition time of 01:00 UTC and a start date of the last Sunday in March, but the end dates have differed. Successive Directives laid down two dates for the end: one on the last Sunday in September applied by the continental Member States, and the other on the fourth Sunday in October for the United Kingdom and Ireland. In 1996 the end date was changed to the fourth Sunday in October for all countries. In 1998 the end date was changed to the last Sunday in October; this happened to be the same as the previous rule for 1996 and 1997. The ninth directive, Directive 2000/84/EC, currently (2018) in force, specifies this rule.
Future.
There were proposals in 2015 and 2016 from members of the European Parliament to abolish summer time observance, but the European Commission did not at that time put forward proposals to be considered, saying it had not found conclusive evidence in favour of a change, and member states were divided. It did however note that a cost would be incurred if harmonisation between member states' summer time rules was lost. In 2017 the Finnish and Lithuanian parliaments both voted in favour of proposals calling on the EU to reconsider daylight saving, with similar criticism from Poland and Sweden. The European Commission at the time was reviewing the practice.
On 8 February 2018, the European Parliament voted to ask the European Commission to re-evaluate DST in Europe. After a web survey, in which 4.6 million European citizens participated, showed high support for not switching clocks twice annually, on 12 September 2018 the European Commission decided to propose that an end be put to seasonal clock changes (repealing Directive 2000/84/EC). In order for this to be valid, the standard European Union legislative procedure must be followed, including that the Council of the European Union and the European Parliament must both approve the proposal.
Under the proposal, member countries were expected to decide by 31 March 2019 which time they would observe year round. This was however considered a fairly tight timescale by many. The Internet Assigned Numbers Authority, which coordinates changes to the time zone database used by most computers and smartphones, notes that "With less than a year's notice there is a good chance that some computer-based clocks will operate incorrectly after the change, due to delays in propagating updates to software and data." The airline industry points out the complexity of revising all airline schedules, particularly in terms of ensuring slot availability on flights outside the EU, and recommends keeping the status quo or deferring the change until at least 2021. An informal meeting of EU transport ministers on 29 October 2018 suggested that many member states would not support the "unrealistic" timetable and that implementation could be pushed back to 2021.
Discussions have shown support for year-round "winter time" in e.g. Denmark, the Netherlands (), and Finland () while permanent summer time was supported in Portugal (), Poland (), and Cyprus (). Spanish opinion is split on the matter; the mainland largely favours shifting to UTC, while the Balearic Islands would prefer to remain on and the Canary Islands on .
On 4 March 2019, the European Parliament Transport and Tourism Committee approved the Commission's proposal by 23 votes to 11. The start date will however be postponed until 2021 at the earliest, to ensure a smooth transition, and the Commission must ensure that countries' decisions to retain winter or summer time are coordinated and do not disrupt the internal market. This decision was confirmed by the full European Parliament on 26 March; it must now be approved by the Council of Ministers. As at July 2020, this approval has not yet been obtained. Under the draft directive, member states would be able to choose whether to remain on their current summer time, in which case the last transition would be on the last Sunday of March 2021, or their current winter time, which would take permanent effect from the last Sunday of October 2021.
A consultation by the Irish government found that 80% of those surveyed would not support any measure that resulted in different time zones between Northern Ireland and the Republic. In July 2019, Ireland announced its opposition to the proposed directive and intends to lobby other EU states on the issue. A qualified majority of 55% of member states representing at least 65% of the European population is required for the Council of Ministers to implement a directive. In the UK, the House of Lords launched a new inquiry in July 2019 to consider the implications of the European changes, explore the preparations that should be made and the factors that should inform the UK's response. The United Kingdom left the EU on 31 January 2020, before any reform became effective; EU rules continued to apply during the transition period (up until 31 December 2020) but thereafter the UK could choose to make its own arrangements. If the UK were thus to continue observing summer/winter time, Northern Ireland would have a one-hour time difference for 30 or 31 weeks of the year either with the rest of Ireland or with the rest of the UK. In September 2018, the UK Government said that it "has no plans" to end daylight saving.
, the decision has not been confirmed by the Council of the European Union. The Council has asked the Commission to produce a detailed impact assessment, but the Commission considers that the onus is on the Member States to find a common position in Council. As a result, progress on the issue is effectively blocked.
Table of transition dates for European Summer Time.
European Summer Time begins (clocks go forward) at 01:00 UTC on the last Sunday in March, and ends (clocks go back) at 01:00 UTC on the last Sunday in October:
Double Summer Time.
"Double Summer Time" (two hours ahead of local winter time) has been observed on some occasions, notably in 1921, 1941–45, and 1947. See:
Countries not switching to and from summer time.
There are four countries that do not use summer time, but keep the same time all year.
Some may be thought of as using "permanent" summer time, since they use time zones allocated to regions further east than themselves. Belarus explicitly decided to stay permanently on (what it formerly called) summer time after 2011.
Spain, France, Belgium, and the Netherlands may also be thought of as observing "summer time" throughout the winter, and "double-summer time" during summer, because of their positions to the west of the central European time zone.
Local observations.
In most of Europe, the word "Summer" is added to the name of each European time zone during this period: thus, in the time zone, Central European Time becomes Central European Summer Time ().
Austria.
Austria used summer time in 1916–1918, 1920, 1940–1948 (as part of Nazi Germany between 1940–1945), and since 1980.
Austria-Hungary.
Austria-Hungary used summer time during World War I in 1916, 1917, and 1918, in line with the German Empire.
Bulgaria.
Summer time was introduced in Bulgaria in 1979 by a regulation of the Bulgarian Council of Ministers. Bulgaria observes the European Union rules for summer time.
Croatia.
Croatia was a part of Yugoslavia as summer time was introduced in 1983. Yugoslavia was the last country in Europe introducing summer time. After gaining independence in the Croatian War of Independence in 1992, Croatia followed the Central European way to change the time on the last Sunday of March and on the last Sunday of October, respectively on the last Sunday of September till 1995.
Czech Republic.
In the Kingdom of Bohemia summer time was used for three seasons during World War I, from 1916 to 1918, while part of the Austro-Hungarian Empire.
During World War II, when the Protectorate of Bohemia and Moravia became a de facto part of Nazi Germany, summer time was used from 1940. In 1940/1941 and 1941/1942, the summer time was kept continuously even during the winter.
Czech Republic continued to use summer time after the dissolution of Czechoslovakia in 1993.
Czechoslovakia.
Czechoslovakia used summer time from 1945 to 1949 and from 1979 to 1992. In winter 1946/1947 (from 1 December to 23 February), winter time (CET+01:00) was used.
Denmark.
Summer time has been observed in Denmark since 1980. A national association against summer time (Landsforeningen mod Sommertid) exists, which celebrated the EU commission preliminary decision in August 2018.
Faroe Islands.
The Faroe Islands has observed summer time since 1981. The islands have never been part of the EU, so the decision to observe summer time was its own.
Greenland.
Part of the Kingdom of Denmark, Greenland observes Summer Time simultaneously with Europe. Summer Time thus begins at 00:00 East Greenland Time on Sunday, and 22:00 West Greenland Time on Saturday, and ends at 01:00 EGST on Sunday and 23:00 WGST on Saturday. It was introduced in 1980 when Greenland was legally a part of Denmark without local rule. The most other EU Overseas countries and territories do not observe summer time. Exceptions, based on company decisions, are the northeastern coast around Danmarkshavn (UTC year-round) for Thule Air Base (which follows Atlantic Time and observes in accordance with US and Canadian rules).
Estonia.
In Estonia summer time was not used in 1990–1996 and 2000–2001. It was used under Soviet rule in 1981–1989.
Finland.
In Finland, summer time has been used on a regular basis since 1981.
A citizens' initiative to abolish daylight saving time was signed by 70,000 Finnish citizens. It was presented to the Finnish parliament in June 2017.
France and Monaco.
France and Monaco follow Central European Time and Central European Summer Time. They apply EU rules regarding the start and end times and dates for summer time.
From 1923 until the Second World War, France and Monaco observed summer time from the last Saturday in March until the first Saturday in October. During the Second World War France also observed summer time. However, after the war the practice was abandoned (since the country changed time zones instituting "de facto" permanent summer time). In 1976, summer time was reimplemented because of the oil crisis.
Since is France's "natural" time zone (extreme points correspond to UTC-0:20 to UTC+0:38), its use of in winter could be seen as a form of daylight saving time, while its use of Central European Summer Time () in summer can be seen as a form of "double summer time".
Germany.
Summer time was first introduced during World War I by the German Empire from 1916 to 1918. After the end of the war and the proclamation of the Weimar Republic in November 1918, summer time ceased to be observed. Summer time was reintroduced in 1940, during World War II, to try to save energy for the war economy. After the defeat of Germany, summer time was retained by the occupation powers. In 1945, Berlin and the Soviet Occupation Zone even observed Central European Midsummer Time ("Mitteleuropäische Hochsommerzeit", "MEHSZ"; GMT+03:00): in 1947, all of Germany switched to midsummer time from 11 May to 29 June. After the Federal Republic (West Germany) and the German Democratic Republic (East Germany) were established in 1949, summer time again ceased to be observed in 1950.
In 1978, West Germany decided to reintroduce summer time, following the example set by several neighbouring states in the aftermath of the 1973 oil crisis. However, it only came into effect in 1980, after West and East Germany reached an agreement to observe summer time simultaneously from the last Sunday in March (02:00 CET) to the last Sunday in September (03:00 CEST). Thus both German states observed the same time until the German reunification in 1990, after which the reunified Germany retained the laws and thus also the Time Act ("Zeitgesetz") of West Germany.
After 1980, West and East Germany; since 1991 reunified Germany: Central European Summer Time.
Büsingen am Hochrhein, a small exclave of Germany entirely surrounded by Swiss territory, did not implement summer time in 1980 but observed the same time as Switzerland; thus there was a one-hour time difference between this village and the rest of Germany. For the tz database, the zone Europe/Busingen was created in its 2013a release, because since the Unix time epoch in 1970, Büsingen am Hochrhein has shared clocks with Zurich, but not with Germany every year.
Germany follows the EU rules regarding the start and end times and dates for summer time.
Greece.
Summer time was first introduced in Greece in 1932, from July 6 to September 1, but the idea was then quickly abandoned.
In the early 1970s and in the aftermath of the 1973 energy crisis that led many European states to implement summer time in order to save energy, Greece reintroduced summer time in 1975 for the period March–September.
Since 1997 Greece follows the EU rules regarding the start and end times and dates for summer time.
Hungary.
Summer time was first introduced in Hungary in 1916, and it was observed until 1919. After that, summer time was in use between 1941–1949 and 1954–1957. Summer time has been in use again since 1980 and follows EU rules.
Iceland.
Iceland uses but has not used summer time since April 1968. From 1908 to 1968 Iceland used GMT−01:00. Summer time was used in 1917–1919, 1921 and 1939–1967.
The European Union Directive 2000/84/EC is valid also in the European Economic Area, but Iceland has a special exception from it.
Ireland.
In the Republic of Ireland, Irish Standard Time (IST) (UTC+01, Western European Summer Time) is observed during Summer (March to October). IST is sometimes mistaken for "Irish Summer Time", though this is incorrect. Winter Time (UTC+00, WET is observed in the rest of the year.
(Northern Ireland, as part of the United Kingdom of Great Britain and Northern Ireland, observes UK time. , this is the same as the rest of Ireland).
Italy, San Marino, and Vatican City.
Summer time is known as "ora legale" (literally "legal hour", referencing the fact that it is mandated by law) in Italy, and it has been adopted and abolished several times: it was observed from 1916 to 1920 and between 1944 and 1948. A law was approved in 1965 that took effect the following year, and made the application of summer time mandatory in the whole country. Since 1996, it has been coordinated with the European Union. San Marino and Vatican City State share land borders solely with Italy and observe the same time as in Italy.
Netherlands.
In 1940 the German occupants forced the Netherlands to observe CEST, Germany's Daylight Saving Time, effectively advancing its time by one hour and 40 minutes. This time stayed in effect year round until 1942, when the normal clock followed the German DST switches.
The use of DST was abandoned directly after the war, and not observed again until 1977, when summer time was observed again, which it currently still is.
Norway.
In Norway, summer time was observed in 1916, 1940–45, and 1959–65. The arrangement was controversial, and in 1965 the Norwegian parliament (Stortinget) voted to discontinue the practice. Their neighbour, Sweden, did not use it.
However, in 1980 summer time was reintroduced (together with Sweden and Denmark), and since at least 2002 Norway has followed the European Union in this matter.
Poland.
In Poland, "the summer time" was observed in the following years:
In the years 1979–1995 the last day of summer time was the last Sunday of September. In 1996 it was changed to the last Sunday of October, to synchronise with other countries of the EU.
Portugal.
Most of Portugal operates Western European Time and Western European Summer Time.
Summer time (locally known by "Hora de Verão") was introduced in 1916. In the years 1922, 1923, 1925, 1930, 1933 and from 1966 to 1976 summer time was not applied.
For many years, the official time in Madeira was one hour behind that in Lisbon, and the Azores were two hours behind. Today in Madeira, the official time is the same as that of Lisbon and, in the Azores, it is one hour behind Lisbon. The start and end dates for summer time in Portugal follow the pattern in the rest of the EU.
Romania.
Summer time in Romania (locally known by "Ora de Vară") was originally introduced in 1932 (between 22 May and 2 October). Between 1933 and 1940 summer time started on the first Sunday in April and ended on the first Sunday in October. Summer time was abandoned in 1941 and reintroduced in 1979. Until 1996, with few exceptions, summer time in Romania follows European Union rules.
Russia.
A decree of the Russian Provisional Government introduced summer time () in Russia on 1 July 1917, and clocks moved one hour forward. A decree of the Soviet government led to the abandonment of this system six months later: clocks moved one hour back again on 28 December.
From 1930, Decree time had the effect of imposing year-round time-zone advances in the Soviet Union.
A decision of the Council of Ministers of the USSR reintroduced summer time in the USSR (Moscow Summer Time, for example) on 1 April 1981, and its practice continued into post-Soviet times until 2011. The changeover dates in Russia were the same as for other European countries, but clocks were moved forward or back at 02:00 local time in all zones. Thus in Moscow (local time = in winter, in summer), summer time commenced at 02:00 UTC on the day before the last Sunday in March, and ended at 03:00 UTC on the day before the last Sunday in October. (Note that "day before the last Sunday" is not the same as "the last Saturday" in a month where the last day is a Saturday.)
On 8 February 2011, Russian President Dmitry Medvedev announced cancellation of biannual clock changes in Russia in favor of a permanent switch to summer time. An hour was added in March 2011 for the last time, and clocks did not move back again. At the same time some of Russia's time zones were consolidated. After this reform many Russian cities had a "standard time" two hours more than would be suggested by their "astronomical time" (because the original standard time was already ahead of astronomical time in many areas).
During his 2012 election campaign, Vladimir Putin proposed re-introducing summer time, as some workers had complained about not seeing any daylight during the winter, since the sun had not risen when they went to work. According to a report in the "International Herald Tribune", Russian citizens remembered the winter of 2011-12 as the "darkest winter on record" as a result of the time change. However, Putin later said it would be up to then Prime Minister Medvedev's cabinet to decide how to proceed with a seasonal time shift, and it decided to stay with the 2011 policy.
On 26 October 2014, Russia permanently returned to "winter" time.
Slovakia.
Slovakia used summer time (locally known as "Letný čas") in 1916, 1917, and 1918 (as part of the Austro-Hungarian Empire), then again in the early 1940s (as the Slovak Republic (1939–1945), a client-state of Nazi Germany).
In 1979, Slovakia, as part of Czechoslovakia, established that summer time begins annually in the first weekend of April (moved to the last weekend in March in 1981) and ends in the last weekend of September.
After the dissolution of Czechoslovakia in 1993, independent Slovakia continued to use summer time. From 1996, Slovakia has prolonged summer time by about one month so it lasts until the last weekend in October, in accordance with European Union rules.
Slovenia.
Summer time in Slovenia (locally known as "Poletni čas") was introduced on 16 November 1982 to be practised from 1983 on. At that time, Slovenia was one of the Yugoslav republics. The same law was valid until 1996 when the end of summer time was changed from the first Sunday in October to the last Sunday in October. In 2006, the European Union standard was adopted and is still used today.
Spain.
Spain including the Canary Islands has summer time, applying EU rules regarding the start and end times and dates.
In 1918, Spain observed summer time for the first time, and then introduced and abolished several times. It was abolished autumn 1949, and then reintroduced 1974 and has been used since. Spain used GMT+00:00 before 1940 and GMT+01:00 from 1940 as standard time. The Canary Islands used GMT-01:00 before 1946 and GMT+00:00 since 1946 as standard time.
Since is Spain's "natural" time zone (extreme points, except Canary Islands, correspond to UTC-0:37 to UTC+0:17), its use of in winter could be seen as a form of daylight saving time, while its use of Central European Summer Time () in summer can be seen as a form of "double summer time".
Sweden.
In Sweden summer time was originally introduced on 15 May 1916. It proved unpopular, and on 30 September in the same year, Sweden returned to year-round standard time. This continued for more than half a century.
On 6 April 1980, Sweden again introduced summer time, and since then summer time has been observed every summer in Sweden. Except for the introduction year 1980, summer time has always started on the last Sunday in March. It ended on the last Sunday in September during the years 1980–1995, and has ended on the last Sunday in October since 1996, following a unification of start/end dates of summer time within the EU as well as in several European countries then outside the EU.
The transit authority Västtrafik changes its clocks at 04:00, so that the last tram that leaves around 03:30 actually goes 02:30 on the last weekend of October for those who have changed their clocks at the legal time. The public transport company SL changes their clocks at the legal time, and runs extra departures during the October transition hour.
Switzerland and Liechtenstein.
The second last country in Europe (only before Yugoslavia ) to adopt summer time, in 1981, was Switzerland, even though summer time had been rejected by 52.1% of voters in a federal referendum in 1978.
Since 1996, Swiss summer time has followed EU regulations. It had formerly been in use in 1941 and 1942. Liechtenstein observes the same time as Switzerland. The German village of Büsingen am Hochrhein, a small exclave entirely surrounded by Swiss territory, also observes the same time as in Switzerland. It did not implement summer time in 1980 and observed the same time as Switzerland, so that in 1980, there was a time difference of one hour during the implementation of summer time in Germany between Büsingen am Hochrhein and the rest of West Germany.
Turkey.
Summer time was introduced in Turkey in 1947, but suspended from 1965 to 1972. Since 1974, Turkey follows European Summer Time.
In 2008, the Turkish Ministry of Energy proposed that Turkey should abolish summer time while at the same time switching to , originally from 2009 onwards, but when this appeared infeasible, to start in 2011, the plan has not been heard of since.
For the year 2011, Turkey switched to European Summer Time at 3:00 am (03:00) on Monday 28 March, one day later than the rest of Europe, to avoid disrupting the national university entrance examinations held on 27 March.
Once again, for the year 2014, Turkey switched to European Summer Time at 3:00 am (03:00) on Monday 31 March, one day later than the rest of Europe, to avoid disrupting the local elections held on 30 March.
In 2015, Turkey delayed the switch from European Summer Time by 2 weeks, to 4:00 am (04:00) on Sunday 8 November, two weeks later than the rest of Europe, due to the calling of a snap general election on Sunday, 1 November.
In 2016, Turkey scrapped winter time, by permanently staying in daylight saving time zone passed Thursday 8 September.
Ukraine.
Summer time was introduced in Ukraine in the early 1980s; from 1981 till 1989 this was Moscow Summer Time; since 1992 Eastern European Summer Time has been used.
On 20 September 2011 the Verkhovna Rada (Ukrainian parliament) voted not to return from Eastern European Summer Time to Eastern European Time. This change would have had the effect of moving Ukraine into the Further-eastern European Time zone along with Belarus and western Russia (which do not observe summer time). However, on 18 October 2011 the Parliament canceled these plans and the country returned to Eastern European Time as scheduled. 295 MPs voted in favour out of 349 registered MPs.
On 3 March 2021 the Verkhovna Rada voted on bill №4201 «Draft Law on time observation in Ukraine» which, if accepted in the second reading in March 2021, will abandon transitioning to summer time and establish year-round standard time () on whole territory of Ukraine. Bill received 277 out of 226 required votes from 370 present MPs during the first reading. On March 19 bill was rejected in second reading with 212 out of 226 required votes and was sent to additional second reading instead.
Crimea and regions of eastern Ukraine under the control of pro-Russian separatists observe Further-eastern European Time.
United Kingdom.
In the United Kingdom, local time during this period is known as
British Summer Time (BST) (, WEST) while local time during the rest of the year is normally referred to as Greenwich Mean Time (GMT), (, WET).
Legislation: Summer Time Act 1916; Summer Time Act 1922; Time (Ireland) Act, 1916; Summer Time Act, 1925; Emergency Powers (Defence) Act, 1939; The Summer Time Order 1964; The Summer Time Order 1967; Summer Time Act 1972; The Summer Time Order 1997; The Summer Time Order 2002.
The UK was, until 23:00 GMT on 31 January 2020, a member state of the European Union. Since 1996, all clocks in the European Union have changed to summer or winter time on the same dates and at the same moment, at 01:00 UTC+00:00 (Thus summer time ends at 01:59:59 ).
Guernsey, Jersey, and the Isle of Man observe the same time as the UK. Gibraltar uses the same time as Spain.
, it appears that the UK government intends to continue to operate winter and summer time on these dates, irrespective of any EU decision on the matter. This may have the effect that Northern Ireland will have a different time zone from the Republic of Ireland.


French submarine Y

The French submarine "Y" was a single-hull experimental submarine designed by Louis-Émile Bertin for the French Navy. She was launched in July 1905 but was never commissioned and remained in experimental status. A planned refit, which included adding an electric motor for underwater propulsion in 1907 was cancelled. "Y" was disarmed and stricken on 1 March 1909.
Design.
"Y" was long, with a beam of and a draught of . The submarine had a surfaced displacement of and a submerged displacement of . The submarine was powered by a diesel engine for both surface and submerged running. She had a maximum speed of on the surface and while submerged. She had a complement of 15 men.
Her armament comprised two bow torpedo tubes, two Drzewiecki drop collar torpedo launchers and one external cradle aft .
Construction and career.
"Y" was laid down in the Arsenal de Toulon, launched on 24 July 1905 and completed in 1906. "Y" was a single-hull diesel design by Louis-Émile Bertin. "Y" received the pennant number Q 37 and cost F924,300.
"Y" was used for trials and experiments and never commissioned into the French "Marine Nationale". In 1907, a reconstruction was proposed to install an electric motor and batteries for submerged running, but eventually the idea was abandoned. "Y" was disarmed and stricken in May 1909.


Richter-tuned harmonica

The Richter-tuned harmonica, or 10-hole harmonica (in Asia) or blues harp (in America), is the most widely known type of harmonica. It is a variety of diatonic harmonica, with ten holes which offer the player 19 notes (10 holes times a draw and a blow for each hole minus one repeated note) in a three-octave range.
The standard diatonic harmonica is designed to allow a player to play chords and melody in a single key. Because they are only designed to be played in a single key at a time, diatonic harmonicas are available in all keys. Harps labeled G through B start (on hole 1 blow) below middle C, while Harps labeled D through F start above middle C (C4). Here is the layout for a standard diatonic harmonica, labeled C, starting on middle C (C4).
Although there are three octaves between 1 and 10 "blow", there is only one full major scale available on the harmonica, between holes 4 and 7. The lower holes are designed around the tonic (C major) and dominant (G major) chords, allowing a player to play these chords underneath a melody by blocking or unblocking the lower holes with the tongue. The most important notes (the tonic triad C–E–G) are given the blow, and the secondary notes (B–D–F–A), the draw.
Overview /Valved diatonics.
The valved diatonic is one of the most common ways of playing chromatic scales on diatonic harmonicas. While chromatic is available, valved diatonic is also common, and there are reasons to use a valved diatonic rather than chromatics. It does not have a slide assembly (so that it has less air leakage), and it has a wider tonal range and dynamic. As well, it has a smaller size and is much more suitable to use with microphone, and it is still cheaper than chromatic, even for a premade one like Hohner's "Auto Valve" or Suzuki's "Promaster MR-350v".
Valved diatonics are made by fitting windsavers on draw holes 1–6 and blow holes 7–10; this way, all reeds can be bent down a semitone at least, although most players can easily bend down a whole tone. Alternatively, one can simply buy a factory-made valved diatonic such as the Suzuki "Promaster Valved".
The disadvantage of the valved diatonic is that it does not require one to develop proper embouchure in order to bend the notes accurately. Also, many of the notes reached by bending are nearer just intonation, and the slightly lower equal tempered pitches preferred by western classical music are unattainable. This limits the number of chromatic notes available when playing classical repertoire when compared with that of jazz or blues. Another thing worth noting is that, due to the valved bends being one-reed bends, the sound is less full than traditional bends, and may seem dull, making it less dynamic. One way to address this is by having an additional reed that activates when one bends a note; this is the philosophy of Hohner's "XB-40" and Suzuki's "SUB30 Ultrabend".
Development/Playing in different keys.
Aside from bending, Richter-tuned harmonicas are modal.
Playing the harmonica in the key to which it is tuned is known as "straight harp" or "first position" playing. For example, playing music in the key of C on a C-tuned harmonica.
More common (especially in blues and rock) is "crossharp" or "second position" playing which involves playing in the key which is a perfect fourth below the key of the harmonica (for example, on a C tuned harmonica, a second position blues would be in G—resulting in the instrument playing in mixolydian mode). This is because the notes of the G pentatonic scale (a commonly used scale in blues and rock) are more easily accessible on a C-tuned harmonica. The lower notes of harps in the lower keys (G through C) are easier to bend, but take more wind. Since much of crossharp is played on the inhalation, every opportunity for exhalation must be capitalized upon—by heavily exhaling on every exhaled note and during every pause. Crossharp lends itself to seventh and ninth chords (particularly G7 and G9) as well as blue notes (particularly on D chords, where the harmonica is tuned to play D minor while the other instruments play D major).
Another method is to play in the key one whole tone above that of the harmonica. On a C-tuned harmonica, this would mean playing in the key of D. This is known as "slant harp" or "third position" playing, and results in the harmonica playing in dorian mode. This is much less intuitive as it requires the ability to bend notes completely accurately, and there are fewer useful chords available than in first or second-position playing. The technique offers many notes that are not achievable in the other positions without overblows, such as the blue note on the third degree, which may or may not be favorable depending on the circumstance. The bends available at the lower end of the instrument also make playing melodies in a D major scale relatively easy for those who have any semblance of proficiency at the bending technique, though most of the notes (all but the second and fourth, E and G) in the scale are on the draw, requiring great skill and strategy in exhaling, even more so than in crossharp.
Continuing along the circle of fifths, fourth position, fifth position, sixth position and zeroth positions can be played, with the scales played in those positions indicated as follows:
Note that using blue notes, any of the seven positions can be used over music in its corresponding major scale if only the notes in the corresponding pentatonic scale are played.
Specially tuned instruments.
Some players prefer specially tuned variants of the diatonic harmonica. Several manufacturers, for instance Lee Oskar Harmonicas, make a variety of harmonicas to help players used to a "cross-harp" style to play in other styles. Cross-harp players usually base their play around a mixolydian scale starting on 2 draw and ending a 6 blow (with a bend needed to get the second tone of the scale; a full scale can be played from 6 blow to 9 blow). Lee Oskar specially tunes harmonicas to allow players to play a natural minor or major scale from 2 draw to 6 blow, or a harmonic minor scale from 4 blow to 7 blow. Below are some sample layouts (the key labels describe the scale from 2 draw to 6 blow, whereas traditional harmonicas are labelled according to the scale between 4 and 8 blow).
It is also possible for harp players to tune the harmonica themselves. By making small scratches in a reed, the note played can be changed. It is possible to either get a higher or a lower note. Some harp players make extensive use of these modifications. One of the most famous examples is the harp solo on "On the Road Again" by Canned Heat, on which the harmonicist, Alan "Blind Owl" Wilson, gets the minor third crossharp on the sixth drawn reed, which is normally the major second crossharp. There are books, toolkits and guides to tuning and harp customization available on the Internet; anyone interested in trying their hand at tuning should be prepared to sacrifice a few harmonicas during the learning process.
12-hole and 14-hole diatonic.
Hohner had made a few non-standard harmonicas. All of them have more than 10 holes and are labeled "grosse richter". For 12 holes, Hohner makes the "M364 Marine Band", as well as the "M36460 Marine Band Soloist". The "Marine Band Soloist" is solo tuned, with 3 full diatonic octaves with all notes of the major scale of the key of C. Since it can bend notes in the same way as a regular diatonic harmonica in the middle octave, some players use this for blues (and even jazz) instead of the more well-known solo-tuned harmonica, the chromatic harmonica, since the bent notes sound very different from true semi-tones. (For layout, see below at Chromatic harmonica, key out) In this configuration, blues players usually play in the third position, the D-minor blue scale.
In addition to the M364 models with 12 holes, there is also the Hohner "Marine Band M365" 14-hole harmonica. The general dimensions of the 12- and 14- hole Hohner harmonicas are a bit bigger than regular diatonic harmonicas. The M36401 and M36501 harmonicas (in the key of C) are pitched one octave lower than the standard 10-hole C diatonic. Thus, hole-4 blow is the same pitch as hole-1 on a regular diatonic harmonica in the key of C. The "Marine Band M36408" and M36508 (in G) are similar to a usual G diatonic, having the higher end expanded.
Holes 1 through 4 and 6 are draw-bendable, and holes 8 through 14 are blow-bendable. Note the extra holes 11–14 which in theory extend the bending capabilities a lot (from A down to E in hole-14, for example), although in practice these are quite limited.
There is also the "Steve Baker Special" (M3658) manufactured by Hohner, a special tuned 14-hole diatonic. Below, the layout of the "Steve Baker Special" in the key of C:
They come in five keys:
This harmonica offers many interesting possibilities, especially for blues harmonica, like extended tongue-block octave playing, the possibility to play exactly the same second-position riffs in two octaves, etc.
Extra-reed harmonicas.
Two harmonica models have been released with altered designs that allow for increased bending abilities, and in effect, chromatic playing on a diatonic harmonica. They are often referred to as "extra-reed" harmonicas, because they carry more than the usual 20 reeds of a diatonic harp.
The Hohner XB-40, invented by Rick Epping, features an entirely new body design, though in practice, it is still a Richter-tuned (diatonic) harmonica. Here the blow reeds and the draw reeds are sealed off one from another with valves, effectively creating two separate cells in the comb for each hole in the mouthpiece: one for blow and another for draw. A second reed is then placed in this cell at a zero-offset (no gapping) so that it does not sound under normal playing. However, it is placed on the opposite side of the reed-plate from the speaking reed and tuned so that it responds when the player “bends” the note downwards in pitch. This allows for every note on the XB-40 to be bent downwards a whole-tone or more, whereas on standard diatonics only certain notes (the higher-pitched in the cell) will bend at all.
Blues harp player.
Sonny Boy Williamson I created basics of blues harp play style. He was killed during a robbery. After that Rice Miller, better known as Sonny Boy Williamson II, is one of the most important harmonicists of this era. Using a full blues band, he became one of the most popular acts in the South due to his daily broadcasts on the 'King Biscuit Hour', originating live from Helena, Arkansas. He also helped make popular the cross-harp technique, opening the possibilities of harp playing to new heights. This technique has now become one of the most important blues harmonica methods. Sonny Boy Williamson II used hand effects to give a very talkative feel to his harp playing. A number of his compositions have also become standards in the blues world. Williamson had a powerful sound and extended his influence on the young British white blues rockers in the 1960s, recording with Eric Clapton and The Yardbirds and appearing on live British television.
But Williamson was not the only innovator of his time. A young harmonicist by the name of Marion "Little Walter" Jacobs would completely revolutionize the instrument. He had new idea of playing the harmonica near a microphone. Big Walter Horton, Carey Bell, Sonny Terry(1911 - 1986), Junior Wells (1934 - 1998), James Cotton, Sugar Blue, Snooky Pryor, and Little Sonny were blues harp players also. Blues guitarist Jimmy Reed (1925 - 1976) sometimes played blues harp.


69230 Hermes

69230 Hermes is a sub-kilometer sized asteroid and binary system on an eccentric orbit, classified as a potentially hazardous asteroid and near-Earth object of the Apollo group, that passed Earth at approximately twice the distance of the Moon on 30 October 1937. The asteroid was named after Hermes from Greek mythology. It is noted for having been the last remaining named lost asteroid, rediscovered in 2003. The S-type asteroid has a rotation period of 13.9 hours. Its synchronous companion was discovered in 2003. The primary and secondary are similar in size; they measure approximately and in diameter, respectively.
Discovery.
"Hermes" was discovered by German astronomer Karl Reinmuth in images taken at Heidelberg Observatory on 28 October 1937. Only four days of observations could be made before it became too faint to be seen in the telescopes of the day. This was not enough to calculate an orbit, and "Hermes" became a lost asteroid. It thus did not receive a number, but Reinmuth nevertheless named it after the Greek god Hermes. It was the third unnumbered but named asteroid, having only the provisional designation . The two others long lost were (1862) Apollo, discovered in 1932 and numbered 1973, and (2101) Adonis, discovered in 1936 and numbered 1977.
On 15 October 2003, Brian A. Skiff of the LONEOS project made an asteroid observation that, when the orbit was calculated backwards in time (by Timothy B. Spahr, Steven Chesley and Paul Chodas), turned out to be a rediscovery of Hermes. It has been assigned sequential number 69230. Additional precovery observations were published by the Minor Planet Center, the earliest being found by an amateur astronomer on images taken serendipitously by the MPG/ESO 2.2-m La Silla telescope on 16 September 2000.
Naming.
This minor planet was named after the Greek god Hermes, who is the messenger of the gods and son of Zeus and Maia "(also see and )". Recovered and numbered in late 2003, "Hermes" was originally named by the Astronomical Calculation Institute as early as 1937. The official naming citation was published by the Minor Planet Center on 9 November 2003 ().
Orbit and classification.
"Hermes" is an Apollo asteroid, a subgroup of near-Earth asteroids that cross the orbit of Earth. It orbits the Sun at a distance of 0.6–2.7 AU once every 2 years and 2 months (778 days; semi-major axis of 1.66 AU). Its orbit has an eccentricity of 0.62 and an inclination of 6° with respect to the ecliptic. Due to its eccentricity, "Hermes" is also a Mars- and Venus-crosser. Frequent close approaches to both Earth and Venus make it unusually challenging to forecast its orbit more than a century in advance, though there is no impact risk within that timeframe.
Close approaches.
The asteroid has an Earth minimum orbital intersection distance of which translates into 1.6 LD. On 30 October 1937, "Hermes" passed from Earth, and on 26 April 1942, from Earth. In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7 lunar distances; the second pass was unobserved at the height of the Second World War. For decades, "Hermes" was known to have made the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach (by 4581 Asclepius) observed. At closest approach, "Hermes" was moving 5° per hour across the sky and reached 8th magnitude.
Physical characteristics.
Spectral type.
"Hermes" is a stony S-type asteroid, as reported by Andy Rivkin and Richard Binzel. It has been characterized as a Sq-subtype using the SpeX instrument at NASA Infrared Telescope Facility. Sq-types transition to the Q-type asteroid.
Lightcurves.
Three rotational lightcurves of "Hermes" were obtained from photometric observations in October 2003. Lightcurve analysis gave a well-defined rotation period between 13.892 and 13.894 hours with a brightness variation between and 0.06 and 0.08 magnitude, which indicates that the body has a nearly spherical shape ().
Binary system.
Radar observations led by Jean-Luc Margot at Arecibo Observatory and Goldstone in October and November 2003 showed Hermes to be a binary asteroid. The primary and secondary components have nearly identical radii of and , respectively, and their orbital separation is only 1,200 metres, much smaller than the Hill radius of 35 km.
The two components are in double synchronous rotation (similar to the trans-Neptunian system Pluto and Charon). Hermes is one of only four systems of that kind known in the near-Earth object population. The other three are , , and .
In popular culture.
In the 1978 novel "The Hermes Fall" by John Baxter, the asteroid endangers the Earth in 1980.


Portland Documentary and Experimental Film Festival

The Portland Documentary and eXperimental Film Festival, or PDX Fest, is a five-day event that showcases non-narrative film and video from Portland, Oregon, United States and around the world. The film festival was started in 2001 by filmmaker Matt McCormick and has since been credited with helping turn Portland into a hotbed of experimental film and new media production.
The Portland Documentary and eXperimental Film Festival is also home of the Peripheral Produce Invitational which every year crowns the world champion of experimental film.


Frames per second


Time-resolved spectroscopy

In physics and physical chemistry, time-resolved spectroscopy is the study of dynamic processes in materials or chemical compounds by means of spectroscopic techniques. Most often, processes are studied after the illumination of a material occurs, but in principle, the technique can be applied to any process that leads to a change in properties of a material. With the help of pulsed lasers, it is possible to study processes that occur on time scales as short as 10−16 seconds.
Transient-absorption spectroscopy.
Transient-absorption spectroscopy (TAS), also known as flash photolysis, is an extension of absorption spectroscopy. Ultrafast transient absorption spectroscopy, an example of non-linear spectroscopy, measures changes in the absorbance/transmittance in the sample. Here, the absorbance at a particular wavelength or range of wavelengths of a sample is measured as a function of time after excitation by a flash of light. In a typical experiment, both the light for excitation ('pump') and the light for measuring the absorbance ('probe') are generated by a pulsed laser. If the process under study is slow, then the time resolution can be obtained with a continuous (i.e., not pulsed) probe beam and repeated conventional spectrophotometric techniques.
Time-resolved absorption spectroscopy relies on our ability to resolve two physical actions in real time. The shorter the detection time, the better the resolution. This leads to the idea that femtosecond laser based spectroscopy offers better resolution than nano-second laser based spectroscopy.
In a typical experimental set up, a pump pulse excites the sample and later, a delayed probe pulse strikes the sample. In order to maintain the maximum spectral distribution, two pulses are derived from the same source. The impact of the probe pulse on the sample is recorded and analyzed with wavelength/ time to study the dynamics of the excited state.
Absorbance (after pump)-Absorbance (before pump)= Δ Absorbance
Δ Absorbance records any change in the absorption spectrum as a function of time and wavelength. As a matter of fact, it reflects ground state bleaching (-ΔA), further excitation of the excited electrons to higher excited states(+ΔA), stimulated emission(-ΔA) or product absorption(+ΔA). Bleaching of ground state refers to depletion of the ground state carriers to excited states. Stimulated emission follows the fluorescence spectrum of the molecule and is Stokes shifted relative to and often still overlaps with the bleach signal. This is a lasing effect (coherent emission) of the excited dye molecules under the strong probe light. This emission signal cannot be distinguished from the absorption signal and often gives false negative Δ absorbance peaks in the final spectra that can be decoupled via approximations. Product absorption refers to any absorption changes caused due to formation of intermediate reaction products. TA measurements can also be used to predict non emissive states and dark states unlike time resolved photoluminescence.
Transient absorption can be measured as a function of wavelength or time.
The TA curve along wavelength provides information regarding evolution/decay of various intermediate species involved in chemical reaction at different wavelengths.
The transient absorption decay curve against time contains information regarding the number of decay processes involved at a given wavelength, how fast or slow the decay processes are. It can provide evidences with respect to inter-system crossing, intermediate unstable electronic states, trap states, surface states etc.
Conditions.
TA measurements are highly sensitive to laser repetition rate, pulse duration, emission wavelength, polarization, intensity, sample chemistry, solvents, concentration and temperature. The excitation density (no. of photons per unit area per second) must be kept low otherwise sample annihilation, saturation and orientational saturation may come into play.
Application.
Transient absorption spectroscopy helps study the mechanistic and kinetic details of chemical processes occurring on the time scales of few picoseconds to femto-seconds. These chemical events are initiated by an ultrafast laser pulse and are further probed by a probe pulse.
With the help of TA measurements, one can look into non-radiative relaxation of higher electronic states (~femtoseconds), vibrational relaxations (~picoseconds) and radiative relaxation of excited singlet state (occurs typically on nanoseconds time scale).
Transient absorption spectroscopy can be used to trace the intermediate states in a photo-chemical reaction; energy, charge or electron transfer process; conformational changes, thermal relaxation, fluorescence or phosphorescence processes, optical gain spectroscopy of semiconductor laser materials. etc. With the availability of UV-Vis-NIR ultrafast lasers, one can selectively excite a portion of any large molecule to desired excited states to study the specific molecular dynamics.
Transient absorption spectroscopy has become an important tool for characterizing various electronic states and energy transfer processes in nanoparticles, to locate trap states and further helps in characterizing the efficient passivation strategies.
Other multiple-pulse techniques.
Transient spectroscopy as discussed above is a technique that involves two pulses. There are many more techniques that employ two or more pulses, such as:
The interpretation of experimental data from these techniques is usually much more complicated than in transient-absorption spectroscopy.
Nuclear magnetic resonance and electron spin resonance are often implemented with multiple-pulse techniques, though with radio waves and micro waves instead of visible light.
Time-resolved infrared spectroscopy.
Time-resolved infrared (TRIR) spectroscopy also employs a two-pulse, "pump-probe" methodology. The pump pulse is typically in the UV region and is often generated by a high-powered , whereas the probe beam is in the infrared region. This technique currently operates down to the picosecond time regime and surpasses transient absorption and emission spectroscopy by providing "structural" information on the excited-state kinetics of both dark and emissive states.
Time-resolved fluorescence spectroscopy.
Time-resolved fluorescence spectroscopy is an extension of fluorescence spectroscopy. Here, the fluorescence of a sample is monitored as a function of time after excitation by a flash of light. The time resolution can be obtained in a number of ways, depending on the required sensitivity and time resolution:
This technique uses convolution integral to calculate a lifetime from a fluorescence decay.
Time-resolved photoemission spectroscopy and 2PPE.
Time-resolved photoemission spectroscopy and two-photon photoelectron spectroscopy (2PPE) are important extensions to photoemission spectroscopy. These methods employ a pump-probe setup. In most cases the pump and probe are both generated by a pulsed laser and in the UV region. The pump excites the atom or molecule of interest, and the probe ionizes it. The electrons or positive ions resulting from this event are then detected. As the time delay between the pump and the probe are changed, the change in the energy (and sometimes emission direction) of the photo-products is observed. In some cases multiple photons of a lower energy are used as the ionizing probe.


Serializing tokens

In computer science, serializing tokens are a concept in concurrency control arising from the ongoing development of DragonFly BSD. According to Matthew Dillon, they are most akin to SPLs, except a token works across multiple CPUs while SPLs only work within a single CPU's domain.
Serializing tokens allow programmers to write multiprocessor-safe code without themselves or the lower level subsystems needing to be aware of every single entity that may also be holding the same token.
Comparison with mutual exclusion (mutex).
Tokens and mutual exclusion (mutex) mechanisms are locks. Unlike mutexes, tokens do not exclude other threads from accessing the resource while they are blocked or asleep. A thread sharing resources with other threads can be stopped and started for a variety of reasons:
The following table summarizes the properties of tokens and mutexes.
Issues such as deadlock and priority inversion can be very difficult to avoid, and require coordination at many levels of the kernel. Because locking with tokens does not deadlock and acquired tokens need not be atomic when later operations block, it allow much simpler code than mutexes.
Example.
The following pseudocode and explanations illustrate how serializing tokens work.
Prior art in the Darwin kernel.
Mac OS X's Darwin kernel uses a similar technique (called a funnel) to serialize access to the BSD portion of the kernel.


Ditonic scale

A ditonic scale is a musical scale or mode with two notes per octave. This is in contrast to a heptatonic (seven-note) scale such as the major scale and minor scale, or a dodecatonic (chromatic 12-note ) scale, both common in modern Western music. Ethnomusicologist Bruno Nettl noted that ditonic scales were common in many parts of the world but often limited to specific music types, such as children's songs, with the exception of some tribal societies.
Distribution.
Russia.
The Cheremis (Mari people) of Russia employ ditonic scales in children's songs, generally with the two notes a minor third apart. Nettl theorised that these ditonic songs may be a remnant of a more archaic form of music.
Peru.
The Shipibo people of Amazonian Peru used ditonic scales in approximately 2.5% of their music. The ditonic was found "almost exclusively in the complex ostinato songs."
Vietnam.
The "ca dao" folk poetry of Vietnam is sometimes sung in ditonic scales.
North America.
Several ditonic scales were noted about the Modoc and Klamath tribes of the North American West Coast, and are also found in the Great Plains in the rituals of the 1800s Ghost Dance religion. The scale was also used in the music of the Shawnee.
India.
The ditonic scale type is recognised in Indian music, and termed the "Dvisvara" ("two tone"), but ditonic scales are not recognised as raga scales.
Nigeria.
The ditonic is among the scale types employed in traditional Nigerian music.
Maori.
In a study carried out in 1969, Mervyn McLean noted that among the Maori tribes he surveyed, ditonic scales comprised 17% of the scales used.