Magnetism

Magnetism is a class of physical attributes that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomenon of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron, cobalt and nickel and their alloys. The prefix "" refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4.
All substances exhibit some type of magnetism. Magnetic materials are classified according to their bulk susceptibility. Ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, but there are actually several types of magnetism. Paramagnetic substances, such as aluminum and oxygen, are weakly attracted to an applied magnetic field; diamagnetic substances, such as copper and carbon, are weakly repelled; while antiferromagnetic materials, such as chromium and spin glasses, have a more complex relationship with a magnetic field. The force of a magnet on paramagnetic, diamagnetic, and antiferromagnetic materials is usually too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic.
The magnetic state (or magnetic phase) of a material depends on temperature, pressure, and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change.
The strength of a magnetic field almost always decreases with distance, though the exact mathematical relationship between strength and distance varies. Different configurations of magnetic moments and electric currents can result in complicated magnetic fields.
Only magnetic dipoles have been observed, although some theories predict the existence of magnetic monopoles.
History.
Magnetism was first discovered in the ancient world, when people noticed that lodestones, naturally magnetized pieces of the mineral magnetite, could attract iron. The word "magnet" comes from the Greek term μαγνῆτις λίθος "magnētis lithos", "the Magnesian stone, lodestone." In ancient Greece, Aristotle attributed the first of what could be called a scientific discussion of magnetism to the philosopher Thales of Miletus, who lived from about 625 BC to about 545 BC. The ancient Indian medical text "Sushruta Samhita" describes using magnetite to remove arrows embedded in a person's body.
In ancient China, the earliest literary reference to magnetism lies in a 4th-century BC book named after its author, "Guiguzi".
The 2nd-century BC annals, "Lüshi Chunqiu", also notes:
"The lodestone makes iron approach; some (force) is attracting it."
The earliest mention of the attraction of a needle is in a 1st-century work "Lunheng" ("Balanced Inquiries"): "A lodestone attracts a needle."
The 11th-century Chinese scientist Shen Kuo was the first person to write—in the "Dream Pool Essays"—of the magnetic needle compass and that it improved the accuracy of navigation by employing the astronomical concept of true north.
By the 12th century, the Chinese were known to use the lodestone compass for navigation. They sculpted a directional spoon from lodestone in such a way that the handle of the spoon always pointed south.
Alexander Neckam, by 1187, was the first in Europe to describe the compass and its use for navigation. In 1269, Peter Peregrinus de Maricourt wrote the "Epistola de magnete", the first extant treatise describing the properties of magnets. In 1282, the properties of magnets and the dry compasses were discussed by Al-Ashraf, a Yemeni physicist, astronomer, and geographer.
Leonardo Garzoni's only extant work, the "Due trattati sopra la natura, e le qualità della calamita", is the first known example of a modern treatment of magnetic phenomena. Written in years near 1580 and never published, the treatise had a wide diffusion. In particular, Garzoni is referred to as an expert in magnetism by Niccolò Cabeo, whose Philosophia Magnetica (1629) is just a re-adjustment of Garzoni's work. Garzoni's treatise was known also to Giovanni Battista Della Porta and William Gilbert.
In 1600, William Gilbert published his "De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure" ("On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth"). In this work he describes many of his experiments with his model earth called the terrella. From his experiments, he concluded that the Earth was itself magnetic and that this was the reason compasses pointed north (previously, some believed that it was the pole star (Polaris) or a large magnetic island on the north pole that attracted the compass).
An understanding of the relationship between electricity and magnetism began in 1819 with work by Hans Christian Ørsted, a professor at the University of Copenhagen, who discovered by the accidental twitching of a compass needle near a wire that an electric current could create a magnetic field. This landmark experiment is known as Ørsted's Experiment. Several other experiments followed, with André-Marie Ampère, who in 1820 discovered that the magnetic field circulating in a closed-path was related to the current flowing through a surface enclosed by the path; Carl Friedrich Gauss; Jean-Baptiste Biot and Félix Savart, both of whom in 1820 came up with the Biot–Savart law giving an equation for the magnetic field from a current-carrying wire; Michael Faraday, who in 1831 found that a time-varying magnetic flux through a loop of wire induced a voltage, and others finding further links between magnetism and electricity. James Clerk Maxwell synthesized and expanded these insights into Maxwell's equations, unifying electricity, magnetism, and optics into the field of electromagnetism. In 1905, Albert Einstein used these laws in motivating his theory of special relativity, requiring that the laws held true in all inertial reference frames.
Electromagnetism has continued to develop into the 21st century, being incorporated into the more fundamental theories of gauge theory, quantum electrodynamics, electroweak theory, and finally the standard model.
Sources.
Magnetism, at its root, arises from two sources:
The magnetic properties of materials are mainly due to the magnetic moments of their atoms' orbiting electrons. The magnetic moments of the nuclei of atoms are typically thousands of times smaller than the electrons' magnetic moments, so they are negligible in the context of the magnetization of materials. Nuclear magnetic moments are nevertheless very important in other contexts, particularly in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI).
Ordinarily, the enormous number of electrons in a material are arranged such that their magnetic moments (both orbital and intrinsic) cancel out. This is due, to some extent, to electrons combining into pairs with opposite intrinsic magnetic moments as a result of the Pauli exclusion principle (see "electron configuration"), and combining into filled subshells with zero net orbital motion. In both cases, the electrons preferentially adopt arrangements in which the magnetic moment of each electron is canceled by the opposite moment of another electron. Moreover, even when the electron configuration "is" such that there are unpaired electrons and/or non-filled subshells, it is often the case that the various electrons in the solid will contribute magnetic moments that point in different, random directions so that the material will not be magnetic.
Sometimes, either spontaneously, or owing to an applied external magnetic field—each of the electron magnetic moments will be, on average, lined up. A suitable material can then produce a strong net magnetic field.
The magnetic behavior of a material depends on its structure, particularly its electron configuration, for the reasons mentioned above, and also on the temperature. At high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment.
Types of magnetism.
Diamagnetism.
Diamagnetism appears in all materials and is the tendency of a material to oppose an applied magnetic field, and therefore, to be repelled by a magnetic field. However, in a material with paramagnetic properties (that is, with a tendency to enhance an external magnetic field), the paramagnetic behavior dominates. Thus, despite its universal occurrence, diamagnetic behavior is observed only in a purely diamagnetic material. In a diamagnetic material, there are no unpaired electrons, so the intrinsic electron magnetic moments cannot produce any bulk effect. In these cases, the magnetization arises from the electrons' orbital motions, which can be understood classically as follows:
This description is meant only as a heuristic; the Bohr–Van Leeuwen theorem shows that diamagnetism is impossible according to classical physics, and that a proper understanding requires a quantum-mechanical description.
All materials undergo this orbital response. However, in paramagnetic and ferromagnetic substances, the diamagnetic effect is overwhelmed by the much stronger effects caused by the unpaired electrons.
Paramagnetism.
In a paramagnetic material there are "unpaired electrons"; i.e., atomic or molecular orbitals with exactly one electron in them. While paired electrons are required by the Pauli exclusion principle to have their intrinsic ('spin') magnetic moments pointing in opposite directions, causing their magnetic fields to cancel out, an unpaired electron is free to align its magnetic moment in any direction. When an external magnetic field is applied, these magnetic moments will tend to align themselves in the same direction as the applied field, thus reinforcing it.
Ferromagnetism.
A ferromagnet, like a paramagnetic substance, has unpaired electrons. However, in addition to the electrons' intrinsic magnetic moment's tendency to be parallel to an applied field, there is also in these materials a tendency for these magnetic moments to orient parallel to each other to maintain a lowered-energy state. Thus, even in the absence of an applied field, the magnetic moments of the electrons in the material spontaneously line up parallel to one another.
Every ferromagnetic substance has its own individual temperature, called the Curie temperature, or Curie point, above which it loses its ferromagnetic properties. This is because the thermal tendency to disorder overwhelms the energy-lowering due to ferromagnetic order.
Ferromagnetism only occurs in a few substances; common ones are iron, nickel, cobalt, their alloys, and some alloys of rare-earth metals.
Magnetic domains.
The magnetic moments of atoms in a ferromagnetic material cause them to behave something like tiny permanent magnets. They stick together and align themselves into small regions of more or less uniform alignment called magnetic domains or Weiss domains. Magnetic domains can be observed with a magnetic force microscope to reveal magnetic domain boundaries that resemble white lines in the sketch. There are many scientific experiments that can physically show magnetic fields.
When a domain contains too many molecules, it becomes unstable and divides into two domains aligned in opposite directions, so that they stick together more stably, as shown at the right.
When exposed to a magnetic field, the domain boundaries move, so that the domains aligned with the magnetic field grow and dominate the structure (dotted yellow area), as shown at the left. When the magnetizing field is removed, the domains may not return to an unmagnetized state. This results in the ferromagnetic material's being magnetized, forming a permanent magnet.
When magnetized strongly enough that the prevailing domain overruns all others to result in only one single domain, the material is magnetically saturated. When a magnetized ferromagnetic material is heated to the Curie point temperature, the molecules are agitated to the point that the magnetic domains lose the organization, and the magnetic properties they cause cease. When the material is cooled, this domain alignment structure spontaneously returns, in a manner roughly analogous to how a liquid can freeze into a crystalline solid.
Antiferromagnetism.
In an antiferromagnet, unlike a ferromagnet, there is a tendency for the intrinsic magnetic moments of neighboring valence electrons to point in "opposite" directions. When all atoms are arranged in a substance so that each neighbor is anti-parallel, the substance is antiferromagnetic. Antiferromagnets have a zero net magnetic moment, meaning that no field is produced by them. Antiferromagnets are less common compared to the other types of behaviors and are mostly observed at low temperatures. In varying temperatures, antiferromagnets can be seen to exhibit diamagnetic and ferromagnetic properties.
In some materials, neighboring electrons prefer to point in opposite directions, but there is no geometrical arrangement in which "each" pair of neighbors is anti-aligned. This is called a spin glass and is an example of geometrical frustration.
Ferrimagnetism.
Like ferromagnetism, ferrimagnets retain their magnetization in the absence of a field. However, like antiferromagnets, neighboring pairs of electron spins tend to point in opposite directions. These two properties are not contradictory, because in the optimal geometrical arrangement, there is more magnetic moment from the sublattice of electrons that point in one direction, than from the sublattice that points in the opposite direction.
Most ferrites are ferrimagnetic. The first discovered magnetic substance, magnetite, is a ferrite and was originally believed to be a ferromagnet; Louis Néel disproved this, however, after discovering ferrimagnetism.
Superparamagnetism.
When a ferromagnet or ferrimagnet is sufficiently small, it acts like a single magnetic spin that is subject to Brownian motion. Its response to a magnetic field is qualitatively similar to the response of a paramagnet, but much larger.
Electromagnet.
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of a large number of closely spaced turns of wire that create the magnetic field. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet.
The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.
Electromagnets are widely used as components of other electrical devices, such as motors, generators, relays, solenoids, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment. Electromagnets are also employed in industry for picking up and moving heavy iron objects such as scrap iron and steel. Electromagnetism was discovered in 1820.
Magnetism, electricity, and special relativity.
As a consequence of Einstein's theory of special relativity, electricity and magnetism are fundamentally interlinked. Both magnetism lacking electricity, and electricity without magnetism, are inconsistent with special relativity, due to such effects as length contraction, time dilation, and the fact that the magnetic force is velocity-dependent. However, when both electricity and magnetism are taken into account, the resulting theory (electromagnetism) is fully consistent with special relativity. In particular, a phenomenon that appears purely electric or purely magnetic to one observer may be a mix of both to another, or more generally the relative contributions of electricity and magnetism are dependent on the frame of reference. Thus, special relativity "mixes" electricity and magnetism into a single, inseparable phenomenon called electromagnetism, analogous to how relativity "mixes" space and time into spacetime.
All observations on electromagnetism apply to what might be considered to be primarily magnetism, e.g. perturbations in the magnetic field are necessarily accompanied by a nonzero electric field, and propagate at the speed of light.
Magnetic fields in a material.
In a vacuum,
where is the vacuum permeability.
In a material,
The quantity is called "magnetic polarization".
If the field is small, the response of the magnetization in a diamagnet or paramagnet is approximately linear:
the constant of proportionality being called the magnetic susceptibility. If so,
In a hard magnet such as a ferromagnet, is not proportional to the field and is generally nonzero even when is zero (see Remanence).
Magnetic force.
The phenomenon of magnetism is "mediated" by the magnetic field. An electric current or magnetic dipole creates a magnetic field, and that field, in turn, imparts magnetic forces on other particles that are in the fields.
Maxwell's equations, which simplify to the Biot–Savart law in the case of steady currents, describe the origin and behavior of the fields that govern these forces. Therefore, magnetism is seen whenever electrically charged particles are in motion—for example, from movement of electrons in an electric current, or in certain cases from the orbital motion of electrons around an atom's nucleus. They also arise from "intrinsic" magnetic dipoles arising from quantum-mechanical spin.
The same situations that create magnetic fields—charge moving in a current or in an atom, and intrinsic magnetic dipoles—are also the situations in which a magnetic field has an effect, creating a force. Following is the formula for moving charge; for the forces on an intrinsic dipole, see magnetic dipole.
When a charged particle moves through a magnetic field B, it feels a Lorentz force F given by the cross product:
where
Because this is a cross product, the force is perpendicular to both the motion of the particle and the magnetic field. It follows that the magnetic force does no work on the particle; it may change the direction of the particle's movement, but it cannot cause it to speed up or slow down. The magnitude of the force is
where formula_8 is the angle between v and B.
One tool for determining the direction of the velocity vector of a moving charge, the magnetic field, and the force exerted is labeling the index finger "V", the middle finger "B", and the thumb "F" with your right hand. When making a gun-like configuration, with the middle finger crossing under the index finger, the fingers represent the velocity vector, magnetic field vector, and force vector, respectively. See also right-hand rule.
Magnetic dipoles.
A very common source of magnetic field found in nature is a dipole, with a "South pole" and a "North pole", terms dating back to the use of magnets as compasses, interacting with the Earth's magnetic field to indicate North and South on the globe. Since opposite ends of magnets are attracted, the north pole of a magnet is attracted to the south pole of another magnet. The Earth's North Magnetic Pole (currently in the Arctic Ocean, north of Canada) is physically a south pole, as it attracts the north pole of a compass.
A magnetic field contains energy, and physical systems move toward configurations with lower energy. When diamagnetic material is placed in a magnetic field, a "magnetic dipole" tends to align itself in opposed polarity to that field, thereby lowering the net field strength. When ferromagnetic material is placed within a magnetic field, the magnetic dipoles align to the applied field, thus expanding the domain walls of the magnetic domains.
Magnetic monopoles.
Since a bar magnet gets its ferromagnetism from electrons distributed evenly throughout the bar, when a bar magnet is cut in half, each of the resulting pieces is a smaller bar magnet. Even though a magnet is said to have a north pole and a south pole, these two poles cannot be separated from each other. A monopole—if such a thing exists—would be a new and fundamentally different kind of magnetic object. It would act as an isolated north pole, not attached to a south pole, or vice versa. Monopoles would carry "magnetic charge" analogous to electric charge. Despite systematic searches since 1931, , they have never been observed, and could very well not exist.
Nevertheless, some theoretical physics models predict the existence of these magnetic monopoles. Paul Dirac observed in 1931 that, because electricity and magnetism show a certain symmetry, just as quantum theory predicts that individual positive or negative electric charges can be observed without the opposing charge, isolated South or North magnetic poles should be observable. Using quantum theory Dirac showed that if magnetic monopoles exist, then one could explain the quantization of electric charge—that is, why the observed elementary particles carry charges that are multiples of the charge of the electron.
Certain grand unified theories predict the existence of monopoles which, unlike elementary particles, are solitons (localized energy packets). The initial results of using these models to estimate the number of monopoles created in the Big Bang contradicted cosmological observations—the monopoles would have been so plentiful and massive that they would have long since halted the expansion of the universe. However, the idea of inflation (for which this problem served as a partial motivation) was successful in solving this problem, creating models in which monopoles existed but were rare enough to be consistent with current observations.
Living things.
Some organisms can detect magnetic fields, a phenomenon known as magnetoception. Some materials in living things are ferromagnetic, though it is unclear if the magnetic properties serve a special function or are merely a byproduct of containing iron. For instance, chitons, a type of marine mollusk, produce magnetite to harden their teeth, and even humans produce magnetite in bodily tissue. Magnetobiology studies the effects of magnetic fields on living organisms; fields naturally produced by an organism are known as biomagnetism. Many biological organisms are mostly made of water, and because water is diamagnetic, extremely strong magnetic fields can repel these living things.
Quantum-mechanical origin of magnetism.
While heuristic explanations based on classical physics can be formulated, diamagnetism, paramagnetism and ferromagnetism can be fully explained only using quantum theory.
A successful model was developed already in 1927, by Walter Heitler and Fritz London, who derived, quantum-mechanically, how hydrogen molecules are formed from hydrogen atoms, i.e. from the atomic hydrogen orbitals formula_9 and formula_10 centered at the nuclei "A" and "B", see below. That this leads to magnetism is not at all obvious, but will be explained in the following.
According to the Heitler–London theory, so-called two-body molecular formula_11-orbitals are formed, namely the resulting orbital is:
Here the last product means that a first electron, r1, is in an atomic hydrogen-orbital centered at the second nucleus, whereas the second electron runs around the first nucleus. This "exchange" phenomenon is an expression for the quantum-mechanical property that particles with identical properties cannot be distinguished. It is specific not only for the formation of chemical bonds, but also for magnetism. That is, in this connection the term exchange interaction arises, a term which is essential for the origin of magnetism, and which is stronger, roughly by factors 100 and even by 1000, than the energies arising from the electrodynamic dipole-dipole interaction.
As for the "spin function" formula_13, which is responsible for the magnetism, we have the already mentioned Pauli's principle, namely that a symmetric orbital (i.e. with the + sign as above) must be multiplied with an antisymmetric spin function (i.e. with a − sign), and "vice versa". Thus:
I.e., not only formula_15 and formula_10 must be substituted by "α" and "β", respectively (the first entity means "spin up", the second one "spin down"), but also the sign + by the − sign, and finally ri by the discrete values "s"i (= ±½); thereby we have formula_17 and formula_18. The "singlet state", i.e. the − sign, means: the spins are "antiparallel", i.e. for the solid we have antiferromagnetism, and for two-atomic molecules one has diamagnetism. The tendency to form a (homoeopolar) chemical bond (this means: the formation of a "symmetric" molecular orbital, i.e. with the + sign) results through the Pauli principle automatically in an "antisymmetric" spin state (i.e. with the − sign). In contrast, the Coulomb repulsion of the electrons, i.e. the tendency that they try to avoid each other by this repulsion, would lead to an "antisymmetric" orbital function (i.e. with the − sign) of these two particles, and complementary to a "symmetric" spin function (i.e. with the + sign, one of the so-called "triplet functions"). Thus, now the spins would be "parallel" (ferromagnetism in a solid, paramagnetism in two-atomic gases).
The last-mentioned tendency dominates in the metals iron, cobalt and nickel, and in some rare earths, which are "ferromagnetic". Most of the other metals, where the first-mentioned tendency dominates, are "nonmagnetic" (e.g. sodium, aluminium, and magnesium) or "antiferromagnetic" (e.g. manganese). Diatomic gases are also almost exclusively diamagnetic, and not paramagnetic. However, the oxygen molecule, because of the involvement of π-orbitals, is an exception important for the life-sciences.
The Heitler-London considerations can be generalized to the Heisenberg model of magnetism (Heisenberg 1928).
The explanation of the phenomena is thus essentially based on all subtleties of quantum mechanics, whereas the electrodynamics covers mainly the phenomenology.


Roller coaster wheel assembly

Today's modern roller coasters, both wooden and steel, have the same basic design of wheel assembly. Each wheel assembly has three wheels: underfriction, or up-stop, wheels; tractor, or running, wheels; and side friction wheels. All of these help the train move safely and smoothly.
All modern roller coasters have up-stop wheels that hug the bottom of the rail. As their name implies, they prevent the train from coming up off the track. Side friction wheels hug the sides of the rail, either the outside or inside, depending on the track manufacturer. These wheels help the train stay in the center of the two rails to keep the train from derailing. The last wheel set are called tractor wheels, or running wheels. Tractor wheels have a simple but important purpose. These wheels bear the weight of the train on the track, keeping the train running on the track. Tractor wheels may lift off the track in when the vertical g-force is zero or negative, but the up-stop wheels keep the train from coming completely off the rails.
Steel roller coaster wheels are made with polyurethane which increase ride efficiency and have no chemical bond to the rail. Steel roller coaster wheel assemblies can change slightly with different manufacturers. A good example of this is the difference between B&M's track style and Arrow's. On B&M's coasters, the trains have their side friction wheels on the outside of the track, allowing the rails to connect from their inner edges. On Arrow coasters, the train has side friction wheels on the inside of the track, so the rail connectors must "wrap around" the outside of the rail and under the train.


CTI Electronics Corporation

CTI Electronics Corporation is a manufacturer of industrial computer peripherals such as rugged keyboards, pointing devices, motion controllers, analog joysticks, USB keypads and many other industrial, military, medical, or aerospace grade input devices. CTI Electronics Corporation products are made in the United States and it is a well-known supplier of input devices to some of the most notable private defense contractors in the world, including Lockheed Martin, DRS Technologies, Computer Sciences Corporation, General Dynamics, BAE Systems, L3 Communications, AAI, Northrop Grumman, Raytheon, Boeing, Thales Group and many more companies that provide security and defense around the world. CTI also supplies Homeland Security and United States Department of Defense supporting their efforts in protecting and serving the country and military personnel of the United States.
Background.
CTI Electronics Corporation was started in 1986 and is currently located in Stratford, Connecticut.
Industries.
CTI's products are used all over the world in a variety of industries and specialize in highly reliable industrial-grade input devices for use harsh environments. Its products are currently being used in the control systems of UAVs, UUVs, and UGVs. CTI has also donated industrial joysticks to students of UW-Madison to for research into the Standing Paraplegic Omni-directional Transport (SPOT)
These products are not only used for military but are also used in the medical, industrial, and aerospace industries all over the world.


Bates Haunt

Bates Haunt, an annual Halloween display in Taylorsville, Utah, is the first and longest running video projection mapping show on a building. The first show was on October 31, 2002. It continues to hold performances each October.
History.
The first performance was on October 31, 2002 using a borrowed 1200 lumen projector projecting from the home across the street. Each year additional elements were added. In 2005 a quartet of leaf bag pumpkins were added singing an original song. The haunt drew the attention of one of the first DIY haunter's conventions HauntX in 2006. There the haunt was awarded two awards: "Best Home Haunt" and "Halloween Enthusiast of the Year". The next year the haunt was featured on Comcast's new digital TV channel Fearnet. Since then the show has continued to grow adding additional original songs and content. It was featured in 2013 on Good Morning America's website in the top 10 Outrageous Halloween Homes Across America as well as various local media outlets.
Technology.
Bates Haunt pioneered a technique which used a common drawing program Adobe Photoshop to trace 3D objects using a projector. The resulting image is then brought into a video program and used to precisely align video elements to the projection surface. The show is a single 30 minute video running in a seamless loop.


Heteroclinic bifurcation


Text box

<inputbox>
type=search
placeholder=An example text box, which can be used to search the English Wikipedia.
</inputbox>
A text box, text field or text entry box is a control element of a graphical user interface, that should enable the user to input text information to be used by a program.
Human Interface Guidelines recommend a single-line text box when only one line of input is required, and a multi-line text box only if more than one line of input may be required. Non-editable text boxes can serve the purpose of simply displaying text.
A typical text box is a rectangle of any size, possibly with a border that separates the text box from the rest of the interface. Text boxes may contain zero, one, or two scrollbars. Text boxes usually display a text cursor (commonly a blinking vertical line), indicating the current region of text being edited. It is common for the mouse cursor to change its shape when it hovers over a text box.
Standard functionality.
Typical implementations allow a user to do the following:
The keys indicated relate to the text box widgets in Microsoft Windows and Mac OS X; similar if not identical keyboard bindings exist under the X Window System and other systems, and typically follow the same scheme as Windows.


FlashPath

FlashPath (FlashPath Floppy Disk Adapter) were a series of devices produced by SmartDisk that allowed a variety of memory cards to be used in a 3.5" Floppy disk drive. The initial version introduced in May 1998 allowed SmartMedia cards to be used with a floppy drive. Later, Memory Stick and Secure Digital/Multi Media Card versions were made as well. FlashPath adapters were sold both branded by SmartDisk, and as OEM devices under other brand names.
FlashPath is hardware compatible with all standard 3.5" High-Density Floppy disk drives, but is not a drop-in replacement for real floppy disks. A special software device driver must be installed on the computer that is to access data via FlashPath. Thus, FlashPath is only usable with computers and operating systems for which such a driver exists and can be installed.
SmartDisk was sued by PC Connector Solutions, LLC over alleged U.S. patent infringement by SmartDisk's Smarty and FlashPath products in 2000. However, the court ruled in favor of SmartDisk; a final ruling was made in 2005.
In 2007, SmartDisk sold its intellectual property assets to Verbatim, creating the patent holding company SMDK Corp. The holding company issued a new set of patent infringement lawsuits in 2008, some of which are still in process as of early 2010. However, since the product has become obsolete, most computer users are not affected by this lawsuit.


Marlin Levermatic

The Marlin Levermatic was a family of lever-action rifles created by Marlin Firearms in the 1950s. The Levermatic differed from the traditional lever-action rifles, such as the Marlin 39A, in that it employed a cam-and-roller system giving it an extremely smooth and short lever motion to reload a new cartridge.
This cam-and-roller system was originally invented by Kessler Arms Company for their "Lever-Matic" shotgun. Following Kessler's dissolution, Marlin licensed the idea and began producing rifles using a similar design.
Models.
The Levermatic system was used in the following rifle models:
Planned models.
Marlin had also planned to produce the Levermatic in .357 Magnum and .22 Remington Jet offered in the Marlin model 62. Both cartridges are related to the .256 Magnum which shared the same .357 Magnum parent case, but these options never materialized.


Modal window

In user interface design for computer applications, a modal window is a graphical control element subordinate to an application's main window.
A modal window creates a mode that disables the main window but keeps it visible, with the modal window as a child window in front of it. Users "must" interact with the modal window before they can return to the parent application. This avoids interrupting the workflow on the main window. Modal windows are sometimes called heavy windows or modal dialogs because they often display a dialog box.
User interfaces typically use modal windows to command user awareness and to display emergency states, though interaction designers argue they are ineffective for that use. Modal windows are prone to mode errors.
On the Web, they often show images in detail, such as those implemented by Lightbox library, or are used for hover ads.
The opposite of modal is modeless. Modeless windows don't block the main window, so the user can switch their focus between them, treating them as palette windows.
Relevance and usage.
Use cases.
Frequent uses of modal windows include:
Modal sheets in Mac OS X.
Many features that would typically be represented by modal windows are implemented as modal transient panels called "Sheets" on Mac OS X. Transient windows behave similarly to modal windowsthey are always on top of the parent window and are not shown in the window list, but they do not disable the use of other windows in the application. Sheets slide out of the window's title bar, and usually must be dismissed before the user can continue to work in the window, but the rest of the application stays usable. Thus they create a mode inside the window that contains them, but are modeless with respect to the rest of the application.
Control of interaction flow.
Modal windows are common in GUI toolkits for guiding user workflow. Alan Cooper contends that the importance of requiring the user to attend to important issues justifies restricting the user's freedom and that the alternative would increase user frustration.
Unexpected interruptions.
Unexpected alert dialogs are particular culprits of mode errors with potentially severe consequences. Usability practitioners prescribe that dangerous actions should be undoable wherever possible; an alert box that appears unexpectedly or is dismissed by habituation doesn't protect from the dangerous action. A modeless infobar is increasingly seen as preferable to a dialog box because it does not interrupt the user's activities, but rather allows the user to read extra information in their own time.
One proposed approach is to design every input element as a self-contained, task-oriented interaction, guided by its own specific requirements rather than by the global state of the entire application. For example, required elements might be preceded with an asterisk, elements with invalid data might acquire a red border, and so on. With this approach, users actually benefit from seeing many input elements at once — they can enter data in a way that makes sense to them, instead of having all the other unrelated elements blocked until a predefined data-entry sequence is completed.
Problems.
A modal window blocks all other workflows in the top-level program until the modal window is closed, as opposed to modeless dialogs that allow users to operate with other windows. Modal windows are intended to grab the user's full attention. Users may not recognize that a modal window requires their attention, leading to confusion about the main window being non-responsive, or causing loss of the user's data input intended for the main window (see Mode error). In severe cases, the modal window appears behind another window controlled by the same program, potentially rendering the entire program unresponsive until the modal window can be located manually.
However, many interface designers have recently taken steps to make modal windows more obvious and user friendly by darkening the background behind the window or allowing any mouse click outside of the modal window to force the window to close – a design called a Lightbox – thus alleviating those problems. Jakob Nielsen states as an advantage of modal dialogs that it improves user awareness: "When something does need fixing, it's better to make sure that the user knows about it." For this goal, the Lightbox design provides strong visual contrast of the dialog over the rest of the visuals. The Lightbox technique is now a common tool in website design.
Modal windows are commonly implemented in ways that block the possibility to move, minimize, iconify, or push that window back, and they grab input focus, which often prevents use of a system's cut, copy, and paste facilities. This can interfere with the use of their parent applications by blocking access to other windows and data within the same application, particularly in cases where the modal window is requiring the user to input information only available in one of the windows it's covering.
For users using virtual work areas larger than their actual screens, modal windows can cause further undesirable behavior, including creating the modal on a portion of the virtual screen not currently on the display, or abruptly switching the display from what the user was working on to an entirely different section.
Modal windows tend to create an abrupt diversion of text input, especially typed input intended for other programs, into themselves. Further, modals usually interpret actuation of the enter key (or in rare cases the presence of a newline in pasted input) as a cue to accept the input and process it—or, in rare cases, may intercept a mouse click intended for a different application that has suddenly been covered. Such interception, called focus stealing (or stealing focus) can compromise privacy and security practices, as well as capture inappropriate, out-of-context input that can cause undefined, arbitrary results in the program that generated the modal window.
Depending on the specifics of implementation, modal windows can violate the principle of least surprise.
Recommendations.
Modal dialogs are part of a task flow, and recommendations are given to place them where the focus is in that flow. For example, the window could be placed near the graphical control element that triggers its activation.
Using a semi-transparent dark background can obscure information in the main window, so it is best used only when that information would be distracting. A semi-transparent background can be made less intrusive by having the whole background area function as a close button: this is standard on most mobile operating systems, avoids making the user feel trapped, and makes modal windows feel less like malicious pop-ups.
Design should follow common practices in the platform the program is running on. Microsoft Windows uses standard controls for modal window dialogs, with affirmative action buttons at the lower right of the panel. Mac OS X uses modal sheets with affirmative action buttons being the right-most command.


Representation theory of SU(2)

In the study of the representation theory of Lie groups, the study of representations of SU(2) is fundamental to the study of representations of semisimple Lie groups. It is the first case of a Lie group that is both a compact group and a non-abelian group. The first condition implies the representation theory is discrete: representations are direct sums of a collection of basic irreducible representations (governed by the Peter–Weyl theorem). The second means that there will be irreducible representations in dimensions greater than 1.
SU(2) is the universal covering group of SO(3), and so its representation theory includes that of the latter, by dint of a surjective homomorphism to it. This underlies the significance of SU(2) for the description of non-relativistic spin in theoretical physics; see below for other physical and historical context.
As shown below, the finite-dimensional irreducible representations of SU(2) are indexed by a non-negative integer formula_1 and have dimension formula_2. In the physics literature, the representations are labeled by the quantity formula_3, where formula_4 is then either an integer or a half-integer, and the dimension is formula_5.
Lie algebra representations.
The representations of the group are found by considering representations of su(2), the Lie algebra of SU(2). Since the group SU(2) is simply connected, every representation of its Lie algebra can be integrated to a group representation; we will give an explicit construction of the representations at the group level below. A reference for this material is Section 4.6 of .
Real and complexified Lie algebras.
The real Lie algebra su(2) has a basis given by
(These basis matrices are related to the Pauli matrices by formula_7 and formula_8)
The matrices are a representation of the quaternions:
where is the conventional 2×2 identity matrix:formula_12
Consequently, the commutator brackets of the matrices satisfy
It is then convenient to pass to the complexified Lie algebra
(Skew self-adjoint matrices with trace zero plus self-adjoint matrices with trace zero gives all matrices with trace zero.) As long as we are working with representations over formula_15 this passage from real to complexified Lie algebra is harmless. The reason for passing to the complexification is that it allows us to construct a nice basis of a type that does not exist in the real Lie algebra su(2).
The complexified Lie algebra is spanned by three elements formula_16, formula_17, and formula_18, given by
or, explicitly,
These satisfy the commutation relations
Up to a factor of 2, the elements formula_18, formula_16 and formula_17 may be identified with the angular momentum operators formula_25, formula_26, and formula_27, respectively. The factor of 2 is a discrepancy between conventions in math and physics; we will attempt to mention both conventions in the results that follow.
Weights and the structure of the representation.
In this setting, the eigenvalues for formula_18 are referred to as the weights of the representation. The following elementary result is a key step in the analysis. Suppose that formula_29 is an eigenvector for formula_18 with eigenvalue formula_31, that is, that formula_32. Then
In other words, formula_34 is either the zero vector or an eigenvector for formula_18 with eigenvalue formula_36 and formula_37 is either zero or an eigenvector for formula_18 with eigenvalue formula_39. Thus, the operator formula_16 acts as a raising operator, increasing the weight by 2, while formula_17 acts as a lowering operator.
Suppose now that formula_42 is an irreducible, finite-dimensional representation of the complexified Lie algebra. Then formula_18 can have only finitely many eigenvalues. In particular, there must be an eigenvalue formula_44 with the property that formula_45 is not an eigenvalue. Let formula_46 be an eigenvector for formula_18 with eigenvalue formula_48:
Then we must have
or else the above identity would tell us that formula_51 is an eigenvector with eigenvalue formula_52.
Now define a "chain" of vectors formula_53 by
A simple argument by induction then shows that
for all formula_56. Now, if formula_57 is not the zero vector, it is an eigenvector for formula_18 with eigenvalue formula_59. Since, again, formula_18 has only finitely many eigenvectors, we conclude that formula_61 must be zero for some formula_4 (and then formula_63 for all formula_64).
Let formula_65 be the last nonzero vector in the chain; that is, formula_66 but formula_67. Then of course formula_68 and by the above identity with formula_69, we have
Since formula_2 is at least one and formula_66, we conclude that formula_48 "must be equal to the non-negative integer" formula_1.
We thus obtain a chain of formula_2 vectors formula_76 such that formula_17 acts as
and formula_16 acts as
and formula_18 acts as
(We have replaced formula_48 with its currently known value of formula_1 in the above formulas.)
Since the vectors formula_57 are eigenvectors for formula_18 with distinct eigenvalues, they must be linearly independent. Furthermore, the span of formula_87 is clearly invariant under the action of the complexified Lie algebra. Since formula_42 is assumed irreducible, this span must be all of formula_42. We thus obtain a complete description of what an irreducible representation must look like; that is, a basis for the space and a complete description of how the generators of the Lie algebra act. Conversely, for any formula_90 we can construct a representation by simply using the above formulas and checking that the commutation relations hold. This representation can then be shown to be irreducible.
Conclusion: For each non-negative integer formula_1, there is a unique irreducible representation with highest weight formula_1. Each irreducible representation is equivalent to one of these. The representation with highest weight formula_1 has dimension formula_2 with weights formula_95, each having multiplicity one.
The Casimir element.
We now introduce the (quadratic) Casimir element, formula_96 given by
We can view formula_96 as an element of the universal enveloping algebra or as an operator in each irreducible representation. Viewing formula_96 as an operator on the representation with highest weight formula_1, we may easily compute that formula_96 commutes with each formula_102. Thus, by Schur's lemma, formula_96 acts as a scalar multiple formula_104 of the identity for each formula_1. We can write formula_96 in terms of the formula_107 basis as follows:
which simplifies to
The eigenvalue of formula_96 in the representation with highest weight formula_1 can be computed by applying formula_96 to the highest weight vector, which is annihilated by formula_16. Thus, we get
In the physics literature, the Casimir is normalized as formula_115. Labeling things in terms of formula_3, the eigenvalue formula_117 of formula_118 is then computed as
The group representations.
Action on polynomials.
Since SU(2) is simply connected, a general result shows that every representation of its (complexified) Lie algebra gives rise to a representation of SU(2) itself. It is desirable, however, to give an explicit realization of the representations at the group level. The group representations can be realized on spaces of polynomials in two complex variables. That is, for each non-negative integer formula_1, we let formula_121 denote the space of homogeneous polynomials of degree formula_1 in two complex variables. Then the dimension of formula_121 is formula_2. There is a natural action of SU(2) on each formula_121, given by
The associated Lie algebra representation is simply the one described in the previous section. (See here for an explicit formula for the action of the Lie algebra on the space of polynomials.)
The characters.
The character of a representation formula_127 is the function formula_128 given by
Characters plays an important role in the representation theory of compact groups. The character is easily seen to be a class function, that is, invariant under conjugation.
In the SU(2) case, the fact that the character is a class function means it is determined by its value on the maximal torus formula_130 consisting of the diagonal matrices in SU(2). Since the irreducible representation with highest weight formula_1 has weights formula_95, it is easy to see that the associated character satisfies
This expression is a finite geometric series that can be simplified to
This last expression is just the statement of the Weyl character formula for the SU(2) case.
Actually, following Weyl's original analysis of the representation theory of compact groups, one can classify the representations entirely from the group perspective, without using Lie algebra representations at all. In this approach, the Weyl character formula plays an essential part in the classification, along with the Peter–Weyl theorem. The SU(2) case of this story is described here.
Relation to the representations of SO(3).
Note that either all of the weights of the representation are even (if formula_1 is even) or all of the weights are odd (if formula_1 is odd). In physical terms, this distinction is important: The representations with even weights correspond to ordinary representations of the rotation group SO(3). By contrast, the representations with odd weights correspond to double-valued (spinorial) representation of SO(3), also known as projective representations.
In the physics conventions, formula_1 being even corresponds to formula_4 being an integer while formula_1 being odd corresponds to formula_4 being a half-integer. These two cases are described as integer spin and half-integer spin, respectively. The representations with odd, positive values of formula_1 are faithful representations of SU(2), while the representations of SU(2) with non-negative, even formula_1 are not faithful.
Another approach.
See under the example for Borel–Weil–Bott theorem.
Most important irreducible representations and their applications.
Representations of SU(2) describe non-relativistic spin, due to being a double covering of the rotation group of Euclidean 3-space. Relativistic spin is described by the representation theory of SL2(C), a supergroup of SU(2), which in a similar way covers SO+(1;3), the relativistic version of the rotation group. SU(2) symmetry also supports concepts of isobaric spin and weak isospin, collectively known as "isospin".
The representation with formula_143 (i.e., formula_144 in the physics convention) is the 2 representation, the fundamental representation of SU(2). When an element of SU(2) is written as a complex matrix, it is simply a multiplication of column 2-vectors. It is known in physics as the spin-½ and, historically, as the multiplication of quaternions (more precisely, multiplication by a unit quaternion). This representation can also be viewed as a double-valued projective representation of the rotation group SO(3).
The representation with formula_145 (i.e., formula_146) is the 3 representation, the adjoint representation. It describes 3-d rotations, the standard representation of SO(3), so real numbers are sufficient for it. Physicists use it for the description of massive spin-1 particles, such as vector mesons, but its importance for spin theory is much higher because it anchors spin states to the geometry of the physical 3-space. This representation emerged simultaneously with the 2 when William Rowan Hamilton introduced versors, his term for elements of SU(2). Note that Hamilton did not use standard group theory terminology since his work preceded Lie group developments.
The formula_147 (i.e. formula_148) representation is used in particle physics for certain baryons, such as the Δ.


Splash screen

A splash screen is a graphical control element consisting of a window containing an image, a logo, and the current version of the software. A splash screen can appear while a game or program is launching. A splash page is an introduction page on a website. A splash screen may cover the entire screen or web page; or may simply be a rectangle near the center of the screen or page. The splash screens of operating systems and some applications that expect to be run in full screen usually cover the entire screen.
Purpose.
Splash screens are typically used by particularly large applications to notify the user that the program is in the process of loading. They provide feedback that a lengthy process is underway. Occasionally, a progress bar within the splash screen indicates the loading progress. A splash screen disappears when the application's main window appears. Splash screens may be added for a period of time and then replaced anew.
Splash screens typically serve to enhance the look and feel of an application or web site, hence they are often visually appealing. They may also have animations, graphics, and sound.
The Java programming language has a specific class for creating splash screens, called java.awt.SplashScreen that handles standard splash screen functions, e.g. display an image centered on screen that disappears when the first program window opens.
On the Web, a splash screen is a page of a web site that acts as a front page prior to displaying the home page. Designers may use splash pages:
An early use of the splash screen on a Flash website was to enable the site developer to launch the site in a JavaScript-controlled new window without browser elements such as scroll-bars or an address bar, and in the exact size of the Flash movie. This has gone out of style with the predominance of pop-up blockers. Instead many starting Flash web pages now allow their audience to choose to go to full screen viewing.
Since splash screens often increase the wait for the desired content and may take a long time to load, they are not liked by all users. Web splash screens are especially inconvenient for users with slow internet connections as the first page may take longer to load. Moreover, if the user has turned off rich content, such as images, Flash, or Shockwave, the splash page may not load at all. Splash pages and any associated main pages created in Flash often cannot be accessed by search engines or handled by text readers for the blind.
Splash screens can also be created in HTML and CSS if they are designed for a purpose other than as a loading screen. Instead, they are used for other purposes such as giving the option to pick the language.


F.T. Barney (schooner)

The F.T. Barney was a 19th-century American schooner that sank in 1868. Her wreck in Lake Huron near Rogers City, Michigan, was listed on the National Register of Historic Places in 1991.
"F.T. Barney" was built in 1856 by William Cherry of Vermilion, Ohio, and was owned by Lewis Wells, also of Vermillion. In late 1857, she ran aground near Goderich, Ontario, but was successfully towed to Detroit, Michigan, for repairs.
Just after midnight on October 23, 1868, "F.T. Barney" was traveling from Cleveland to Milwaukee with a load of coal. In Lake Huron near Rogers City, Michigan, the "F.T. Barney" collided with the schooner "T.J. Bronson". "F.T. Barney" sank in less than two minutes, but no lives were lost. Later investigation determined that both vessels were equally at fault.
The wreck remained undiscovered until 1987. It is in 160 feet (48.8 meters) of water, and is one of the most complete wrecks of a schooner of its era. The masts and deck equipment are still in place.


Severn Division Electrical Engineers


ArmaLite AR-7

The ArmaLite AR-7 Explorer is a semi-automatic firearm in .22 Long Rifle caliber, developed in 1959 from the AR-5 that was adopted by the U.S. Air Force as a pilot and aircrew survival weapon. The AR-7 was adopted and modified by the Israeli Air Force as an aircrew survival weapon in the 1980s.
The AR-7 was designed by American firearms designer Eugene Stoner, who is most associated with the development of the ArmaLite AR-15 rifle that was adopted by the US military as the M16. The civilian AR-7's intended markets today are backpackers and other recreational users as a takedown utility rifle. The AR-7 is often recommended for use by outdoor users of recreational vehicles (automobile, airplane or boat) who might have need for a weapon for foraging or defense in a wilderness emergency.
History and design.
The prototype of what would become the AR-7 was designed by Eugene Stoner at ArmaLite Inc., a division of Fairchild Aircraft. The rifle shares some of the features of the bolt-action AR-5, another takedown rifle designed by Stoner for ArmaLite and adopted by the United States Air Force in 1956 as the MA-1. The MA-1 was intended to replace the M4 Survival Rifle and the M6 Aircrew Survival Weapon which was a superposed ("over-under") twin-barrel rifle/shotgun chambered in .22 Hornet and .410 bore, using a break-open action. The AR-5 had the advantage of repeat fire over the then-standard M6, using the same .22 Hornet cartridge. When the AR-5 was adopted as the MA-1 but was not placed in issue due to the numbers of usable M4 and M6 survival weapons in USAF inventory, ArmaLite used the research and tooling for the AR-5 in developing the AR-7 for the civilian market.
The AR-7 uses a blowback semi-automatic action in .22 Long Rifle but retains the AR-5/MA-1 feature of storing the disassembled parts within the hollow stock, which is filled with plastic foam and capable of floating. Like the bolt-action AR-5, the AR-7 was designed as a survival rifle for foraging small game for food. The AR-7 is constructed primarily of aluminum, with plastic for the stock, buttcap, and recoil spring guide. The bolt is steel. The original barrel was aluminum using a rifled steel liner; barrels of some production models have used all steel barrels, others have used barrels made of composite materials. The AR-7 measures 35 inches overall when assembled. It disassembles to four sections (barrel, action, stock, and magazine), with three parts storing inside the plastic stock, measuring 16 inches long. The rifle weighs 2.5 pounds, light enough for convenient backpacking. The rear sight is a peep sight, which comes on a flat metal blade with an aperture (in later production two different size apertures available by removing and flipping the rear sight), and is adjustable for elevation (up-down). The front sight is adjustable for windage (side-to-side). Accuracy is sufficient for hunting small game at ranges to 50 yards.
Performance.
Reliability of the AR-7 is highly dependent on the condition of the magazine and on the ammunition used, perhaps more so than with other models of semi-automatic .22 caliber rifles. The feed ramp is part of the magazine and subject to damage from mishandling. Flat-nosed bullets tend to jam on the edge of the chamber of the barrel. The transition of cartridge from magazine to barrel can be smoothed by minor beveling of the chamber of the barrel, by using round-nosed as opposed to flat-nosed bullets and by paying attention to condition of the feed lips and feed ramp of the magazine. Later production magazines include an external wire spring to align the cartridge; earlier magazines used two pinch marks at the top of the magazine body, which in use could become sprung open or worn.
All iterations of the AR-7 from the ArmaLite to the Henry U.S. Survival rifle use a bolt and dual recoil springs that are heavy compared to most other .22 semiautomatics. The AR-7 requires high velocity ammunition for reliable functioning. The manufacturers recommend use of 40 grain round nose bullets in high velocity loadings. It is possible to manually load a single round into the firing chamber, allowing use of flat nosed bullets or low velocity or subsonic ammunition.
The barrel takedown nut tends to loosen during firing and may need hand-tightening to maintain both accuracy and reliability.
ArmaLite sold the design to Charter Arms in 1973. According to some accounts posted by enthusiasts, this is when quality began to deteriorate. Barrels were said to have a tendency to warp. Other sources state that the first production at Charter had problems which were corrected in later production runs.
Production history.
"(Summary of information available in The Blue Book of Gun Values)"
AR-7 variants.
ArmaLite AR-7 Explorer.
Original ArmaLite barrels had a steel liner in an aluminum shell. The stock was a foam filled plastic shell with internal recesses for the receiver, barrel and one magazine and did not accept the receiver with a magazine in place. The original ArmaLite stock retained buoyancy longer than some later stocks by other makers. The receiver did not provide for a scope mount. The rear sight was a peep aperture, adjustable for elevation. The front sight was drift-adjustable for windage.
Argentine variant.
The AR-7 was also manufactured in Argentina as the "Sistema de Armas .22 LR Fire de Brenta". It came with various barrel lengths, shrouds and fixed rifle stocks as well as pistol grips with retractable stocks.
Herter's Outdoor Supply.
Herter's, Hy Hunter and American International Distributors marketed .22 replicas of the Broomhandle Mauser (as "Bolomauser"), Thompson submachine gun (as "T-62 Civilian Defense Model") and M1 Carbine made on AR-7 receivers and barrels.
Charter Arms AR-7 Explorer.
The Charter Arms AR-7 Explorer rifle replicated the ArmaLite AR-7 Explorer with variations in finish.
Charter Arms Explorer II pistol.
Explorer II was a pistol version of the AR-7. It resembled a Broomhandle Mauser. The receiver had a built-in pistol grip with no provision for the rifle stock (the internal parts are interchangeable between rifle and pistol). The rear sight of the pistol was an open notch adjustable for windage and elevation. The Explorer II front sight was integral with the barrel shell and was not adjustable. The magazine well in front of the trigger guard would accept any magazine designed for the rifle. A spare 8-round magazine could be carried inside the grip. The most common barrel was six inches. Optional barrel lengths included eight and ten inches.
Legal note.
Because the U.S. 1934 NFA regulations set the minimum rifle barrel length at 16 inches, Charter Arms made the barrels of the Explorer I rifle and Explorer II pistol non-interchangeable to prevent installing the pistol barrel on the rifle. The AR-7 barrel has an alignment lug that mates a notch in the receiver. The rifle receiver notch and barrel lug are on top; the pistol notch and lug are broader and on the bottom. If a Charter Arms factory-made pistol barrel were installed on a rifle, the extractor on the bolt would be opposite the extractor slot in the barrel, preventing the bolt from closing (plus the front sight would be upside down). Modifying the pistol barrel to fit the rifle, or modifying the rifle receiver to accept the pistol barrel, would be "making a short barrel rifle" legally requiring federal registration on an ATF Form 1 with payment of a $200.00 tax.
Conversely, after the Supreme Court ruling in "United States v. Thompson/Center Arms Co.", modifying the pistol to accept the rifle barrel and/or stock, or modifying the rifle barrel or stock to fit the pistol is legal so long as you do not have the rifle stock attached at the same time as the pistol barrel. It is legal (as a pistol) to have the rifle barrel attached with the pistol grip; there is no federal maximum pistol barrel length.
In the United Kingdom this rifle is a section 1 firearm requiring a FAC
AR-7 Industries.
AR-7 Industries made solid steel barrels much heavier than the AR-7 barrels by ArmaLite, Charter or Henry.
Henry Survival Rifle.
In 1980, the design and production rights passed on to Henry Repeating Arms and the compact rifle was slightly revised, resulting in improved reliability and durability. The AR-7 is now (2018) known as the Henry U.S. Survival AR-7 rifle. An ABS material replaced the original stock plastic, which was prone to cracking and failure. The receiver recess in the Henry stock allows storage of receiver with a magazine in place and the rifle is normally sold with two magazines. The latest versions of the Henry allow for storage of three magazines total, with two in the stock recess, and one in the receiver. The modern Henry U.S. Survival Rifle floats on water for a while either assembled or stored, although it is not entirely waterproof and will sink eventually. The rifles now include a full Teflon coating on the outer surface. Henry added a 3/8 inch Dovetail rail (aka Weaver .22 Tip-Off Mount rail) on the top of the receiver for attaching a wide variety of optics.
Israeli pilot's survival rifle.
Another variant was made by ArmaLite and sold to the Israeli Military for use as pilot/aircrew survival weapons. The Israelis further modified these rifles, adding a telescoping stock, a pistol grip from a FAL-type rifle, shortening the barrel (to 13.5 inches), and adding a front sight based on the K98k Mauser.
After Israeli service, some of these rifles were re-imported into the U.S. by Bricklee Trading Company (the barrels are marked with the BTC identification as required by U.S. laws on imported guns) for sale on the civilian market, and command a premium among collectors. In order to comply with U.S. Federal law, a 3-inch muzzle brake had to be permanently attached in order to meet the minimum 16-inch-barrel requirement.
Operation.
The AR-7 functions as a simple or plain blowback semi-automatic. The AR-7 is a light firearm with heavy bolt and twin recoil springs.
Aftermarket modifications.
The fact that both the barrel and stock are detachable has led to a plethora of after-market accessories, similar to those available for the Ruger 10/22. Barrels, stocks, and grips, of varying finishes and utility, can be added to the rifle. These include collapsible stocks, wire-framed stocks, pistol grips, flash suppressors, shrouded barrels, high-capacity magazines, telescopic sights, reflex 'red dot' sights and other occasionally fanciful-looking hardware, some at a cost greater than the rifle itself. Such accessories often make it impossible to use the original floating stock for storage of modified parts.
The current Henry U.S. Survival AR-7 has a 3/8" scope sight rail integral with the receiver to accept standard Weaver-style "Tip-Off" rings. For earlier makes, B Square supplied the Charter Arms AR-7 Explorer Scope Mount Base, an accessory bracket with a 3/8" rail. The base attached by the receiver side plate screw (the Charter Arms side plate screw is longer than that of the ArmaLite). This base can be used on the ArmaLite and the Charter Arms Explorer rifles and the Charter Arms Explorer II pistol. However, with the base in place, the rifle receiver will no longer fit the recess in the stock for storage. (The base is not needed on the Henry version and will not fit the Henry receiver.)
Apart from the highly modified AR-7 Israeli survival rifles, most AR-7 models lack provision for a carry sling. AR-7 owners have adapted slings designed for use on guns without modification, such as universal shotgun slings designed to cup the shotgun buttstock at the rear and clamp to the barrel or magazine tube at the front. Given the light weight of the AR-7, 2.5 pounds, a proper length of parachute cord with a slip knot at either end can be used as a sling or lanyard.


Wz. 35 anti-tank rifle

The Model 35 antitank rifle ("Karabin przeciwpancerny wzór 35", abbreviated "kb ppanc wz. 35") was a Polish 7.9 mm anti-tank rifle used by the Polish Army during the 1939 Invasion of Poland. It was designated model 35 for its design year, 1935: It was also known by its codename "Uruguay", after that country ("kb Urugwaj"; or "kb Ur") and by the name of its designer, Józef Maroszek().
Secrecy.
The weapon was initially a top secret project of the Polish Army, and was also known by various codenames. Until mobilization in 1939, the combat-ready rifles were held in closed crates marked: "Do not open! Surveillance equipment!". Another of the rifle's cover names was "Uruguay" (Polish: "Urugwaj", hence "Ur"), the country to which the "surveillance equipment" was supposedly being exported.
After the fall of Poland, the German army captured large numbers of the "kb ppanc wz.35" and renamed it ""Panzerbüchse 35 (polnisch)" (abbreviated "PzB 35(p)"). The Italian army later received 800 of the captured weapons, renaming them "fucile controcarro 35(P)"." Both names translate roughly as "anti-tank rifle model 1935 (Polish)."
In early 1940, one of the rifles, its stock and barrel sawed off, was smuggled out of Poland across the Tatra Mountains into Hungary for the Allies by Krystyna Skarbek and fellow Polish couriers. The rifle never saw service with the Allies, however. The drawings and specifications had been destroyed by the Poles during the invasion of Poland.
Description.
It resembled a rifle with a longer-than-normal barrel supported by a bipod at the front of the wooden stock. It was a Mauser style, bolt-action rifle, fed from a 4-round box magazine. The barrel had a muzzle brake to limit recoil. It absorbed about 65% of the shot energy, and the recoil was comparable to a standard Mauser rifle, even though the cartridge carried more than twice the amount of propellant. It had iron sights fixed for a 300-meter range.
Unlike contemporary anti-tank rifles, it lacked a pistol grip and fired a bullet with a lead core rather than an armour-piercing round with a hard core. The full metal jacket bullet weighed 14.579 g and, due to a high muzzle velocity, was effective even under shallow angles, as instead of ricocheting, the bullet would "stick" to the armour and punch a roughly 20 mm diameter hole. Calculated kinetic energy, by shot, before brake was about 11,850 J. The high energy was due to the relatively long barrel, and nitro powder giving a muzzle velocity of 1,275 m/s.
History.
Ammunition.
In the late 1920s the Polish General Staff started the development of a light anti-tank weapon for the Polish infantry. In 1931 Lt. Colonel Tadeusz Felsztyn from the Institute of Armament Technology in Warsaw started the first tests of various low-calibre cartridges. After the tests of German-made Hagler bullets proved the possibilities of that type ammunition in perforating steel plate, the National Ammunition Factory in Skarżysko-Kamienna was ordered to develop its own 7.92 mm cartridge with a muzzle velocity of over 1,000 meters per second. After a series of tests, the new "DS" cartridge was proposed.
The "DS" ammunition was originated from the standard 7.92×57mm cartridge as used by both the Mauser rifle 1898 (wz.98) and its Polish variant the Karabinek wz.29. The length of the cartridge was extended to and the overall weight was . After an additional series of tests the copper cartridge case was replaced with a case made of brass (67% copper/ 23% zinc).
The round's armor-defeating properties were not through penetration, i.e. by punching the core through the armor like a typical penetrator, but through the impact of the bullet flattening against the plate, transferring kinetic energy to the metal. The result was that the bullet would cause spalling on the interior of the armor plate, ideally ejecting an approximately 20mm diameter fragment from the interior surface of the armour at high speed, which would then ricochet around the interior, hopefully killing crew and/or damaging equipment or engines (this is similar in concept to modern HESH anti-tank rounds, albeit less potent). Due to the physics of spalling, the size of this spall was larger than the actual rifle caliber, and could theoretically do more damage ricocheting around inside the vehicle than the bullet itself would if it penetrated. The downside was that since the bullet itself was not designed to penetrate, it could not be filled with an incendiary component and used to ignite fuel tanks, or filled with tear gas (as used by the similar German 7.92×94mm Patronen anti-tank rifle cartridge), which was intended to force the crew to evacuate, or at least greatly reduce their combat effectiveness, even if no-one was hit by the bullet itself.
The Soviet PTRD 14.5×114mm anti-tank rifle also used a bolt based on the Mauser Gewehr 98 rifle, as this design is legendary for its strength and simplicity and has become the most widely adopted and copied designs of all time. The Wz. 35 is itself inspired by the 13.2mm TuF anti-tank rifle, also a scaled-up G98 rifle. The main difference is that while the TuF and PTRD were chambered in a large-caliber round, the Wz. 35 used an oversized cartridge case mated to a rifle-caliber 8mm bullet, giving very high velocity at the expense of hitting power. The Panzerbüchse 39 also used an 8mm bullet, but with an out-sized 8mm Mauser cartridge case known as the 7.92x94mm Patronen, and a special tool-steel cored bullet.
Rifle.
Simultaneous to the development of the ammunition, a young graduate of the Warsaw University of Technology, Józef Maroszek, was ordered to design an anti-tank rifle. On August 1, 1935, the Committee of Equipment and Armament officially ordered the rifle and in October the first tests of the new weapon commenced.
The rifle was based on the Mauser Gewehr 98, with the action modified to sustain the higher pressure and length of the new cartridge and the barrel lengthened significantly. The first tests carried out in Brześć and Pionki showed that the new weapon was capable of penetrating a 15 mm steel plate at a distance of 300 metres with similar results against angled steel plate. Initially the barrel could withstand only about 30 shots, after which it had to be replaced with a new one. However, this drawback was soon corrected and the final prototype could fire approximately 300 shots. The committee accepted the new design on November 25, 1935, and in December the Ministry of Military Affairs ordered the delivery of 5 rifles, 5000 cartridges and a set of spare barrels for further tests.
After the tests carried out by the Centre of Infantry Training in Rembertów proved the effectiveness and reliability of "kbk ppanc wz.35", the Ministry ordered 7610 rifles to be delivered to the Polish Army by the end of 1939. It is uncertain how many rifles were actually produced, but it is estimated that there were more than 6,500 delivered by September 1939.
Use.
The rifle was the main anti-tank weapon of an infantry platoon. Each infantry company and cavalry squadron was to be equipped with three rifles, each operated by a team of two soldiers. Additional anti-tank teams were to be created at a later stage. Although the weapon was successively introduced to the units, it remained a top secret. The rifles were kept in closed wooden crates, each marked with a number and a notice "do not open; surveillance equipment". The teams were trained in secret military facilities just before the war, beginning in July 1939, and had to swear to preserve the secret.
The rifle was carried by the leader of the two-man rifle team on a carrying strap. The other member of the squad was his aide and provided him with cover while he was reloading. The weapon was usually fired from prone supported position with the bipod attached to the barrel. However, it could be also used in other positions, like prone unsupported and crouch. The effective range was 300 metres and the weapon was effective against any German tank of the period, including Panzer III and Panzer IV. It could penetrate all lightly armored vehicles in any range. It could penetrate 15 mm of armor, sloped at 30° at 300 m distance, or 33 mm of armor at 100 m.
Panzerbüchse 35(p).
The "Karabin przeciwpancerny wz.35" was extensively used during the Invasion of Poland of 1939 by most Polish units. After Poland was overrun by Germany and the Soviet Union, large numbers of the weapon were captured. By 1940, Germany had pressed 800 into service as "Panzerbüchse 35 (polnisch)" (PzB 35(p)) and later PzB 770(p), and sped up work on their own simplified, one-shot anti-tank rifle "Panzerbüchse 39" (PzB 39). Germany replaced some of the captured Polish DS ammunition with their own 7.92 mm hardened-steel-core bullets.
Hungary confiscated some of these guns from Polish forces withdrawn into the Magyar land. Finland bought 30 of them in March 1940 but they arrived after the end of the Winter War. They performed poorly during the Continuation War and were used for training.
In 1941, Germany transferred "PzB 35 (p)" to the Italian armed forces, which used them in combat under the designation "Fucile Controcarro 35(P)" until the end of World War II. The German Army recaptured some of these rifles after the Italian armistice and designated them as "PzB 770 (i)".
Survivors.
There are at least three in the United Kingdom. One is on exhibit in Poland, at Warsaw's Polish Army Museum; another is located in Armament Museum in Poznań Citadel, another is in Museum of the Second World War in Gdańsk, and one is in Australian War Memorial in Canberra. The Norwegian Armed Forces Museum holds several specimens of the Wz. 35.


Gnome-Pie

Gnome-Pie is a circular application launcher for Linux created by Simon Schneegans.
It is made of several pies, each consisting of multiple slices. The user presses a key stroke which opens the desired pie. By activating one of its slices, applications may be launched, key presses may be simulated or files can be opened. The user does not need to remember the name of an application – just the direction has to be remembered.
License change.
Version 0.7.1 and earlier was published under the GPL.


Riha Adagio

RIHA Adagio is a Dutch electronic organ with built-in Leslie speaker and fine wood finish. Similar to other RIHA organs, the Adagio was made by Benelux Musical Instruments, The Hague, the Netherlands. A fine member of those line of all-transistor Dutch organs that featured eight models in three console finishes - walnut, teak, and rosewood. All of them have standard features, including, but not limited to, pedal volume control, brilliance control, and reverberation. The Adagio is one of the once popular RIHA models, along with the Festivo, the Andante, and the Allegro.
Keyboards and pedalboard.
The RIHA Adagio has two manuals, a pedalboard, and an expression pedal. Both manuals have four octaves (49 notes).
The organ comes with a bass pedalboard, so that the organist can play bass lines with his feet. However, the pedal keyboard has just one octave (13 notes) which is much shorter than that of larger organs.
The balance of keyboards volumes is adjustable with a potentiometer. Pedalboard volume can be set separately.
Tabs.
The RIHA Adagio organ has 19 tabs for the upper keyboard, 11 tabs for the lower keyboard, and 4 tabs for the pedalboard.
Effects.
The RIHA Adagio offers a wide variety of keyboard, pedalboard, and special effects.
The effect of the Leslie speaker is not the only feature of the organ that is similar to the ones found in Hammond organs. The organist can use the harmonic percussion effect whose stop, time, repeat, and volume can be set separately.
A reverberation effect is also available, as well as the V-speed, V-depth, V-cancel, and V-delay. There is a SUSTAIN effect for the pedalboard.
Notable performers.
RIHA organs are far less well-known than other electronic organs, such as Hammond, but there are some famous organists who played RIHA organs (not necessarily the Adagio). Some examples are
Brian Sharp: B# Past & Present (CD) [CDGRS 1333], Organ Fiesta Volume 2 (Tape) [VFM VCA082]
Han Meyer: 23 Instruments In One Organ (LP) [B.M.I. 113 503]


Leica S-System

The Leica S-System is a medium format digital single lens reflect camera system introduced by Leica Camera in 1996. Beginning with the Leica S1, a prototype top-end studio digital camera unveiled at Photokina 1996. It went into production at the end of 1997.
Leica S lenses.
A series of new Leica lenses is manufactured specifically for the S2 and Leica claims they offer unsurpassed resolution and contrast at all apertures and focusing distances, even exceeding the sensor's capabilities. Lenses offered for the S2 include Summarit-S in normal (70 mm), wideangle (35 mm), and macro (120 mm) varieties, and Tele-Elmar (180 mm) portrait-length telephotos; these are available in versions that feature integrated multi-leaf blade shutters ("Central Shutter", or CS), in addition to the focal-plane shutter in the camera body, to enable higher flash sync speeds.


MCM pistol

The Margolin or (MCM pistol) Practice Shooting Pistol () is a .22 LR pistol primarily used for competitive target shooting in 25m Standard Pistol class under the rules of the International Shooting Sport Federation for bullseye round-target shooting at 25 m. The Margolin has been used since the 1950s, and complies with all international competition standards.
History.
The pistol was designed by Mikhail Vladimirovich Margolin (1906-1975). It was produced since 1948 and made its international debut at the 36th World Shooting Championships held in 1954 at Caracas, Venezuela.
A very accurate, reliable and economically priced pistol of functional and simple design.
The designer himself was blind - he was fighting in the Red Army against the "bandits" (anti-communist rebels) in the aftermath of the Russian Civil War and in 1924 (at the age of 18) had head injury resulting in total loss of vision.
There is some criticism of the pistol's elevated plane of sight, blaming it on an incorrect notion that the designer could not aim his pistol. However, Margolin's raised plane of sight is a deliberate design feature that increased the accuracy of the pistol. The bridge that made the rear sight stationary combined with the unusually high sights allows the shooter to hold the pistol lower and aligns barrel with the shoulder, giving the shooter an improvement in control in rapid fire competition. The high line of sight is a design feature that the Margolin's designs had in common with the famous AK-47. The AK-47, designed between 1946 and 1948, like the Margolin, had high sights which lowered the barrel, put it more in line with the shoulder, reducing muzzle climb.
The barrel, being comparatively light-weight, can be equipped with an under barrel weight for added steadiness.
Variants.
There were also a limited quantity made by the Norinco in China called "PS-01". Compared with the original, the Chinese version has some subtle differences, include the fully adjustable rear sight system and non-adjustable front sight blade and threaded muzzle.


Howa Type 89

The , referred to as the , is a Japanese assault rifle used by the Japan Self-Defense Forces, the Japan Coast Guard's Special Security Team units, and the Special Assault Team. It has never been exported outside Japan due to its strict anti-hardware export policy. It is known in JGSDF service as Buddy.
The Type 89 was introduced to replace the Howa Type 64 battle rifle in frontline units, entering service in 1989. It has remained Japan's principal service rifle since then. Limited numbers of the Type 89's replacement, the Howa Type 20, were purchased in 2020.
History.
Like most other nations, Japan began the Cold War with a battle rifle – the 7.62×51mm NATO Howa Type 64. However, over time, especially during the Vietnam War, the battle rifle's shortcomings became apparent, and ultimately, battles rifles began to be replaced with assault rifles, which fired intermediate cartridges, though they had a weaker effective range compared to battle rifles. The 5.56×45mm round (SS109), first used in the M16 rifle, eventually became the standard of ammunition type for all NATO member assault rifles. In accordance with this, the Defense Agency began development on their next generation assault rifle to replace the 7.62×51mm Type 64 battle rifle after its 25-year span of service.
Development was handled primarily by Howa since it was already licensed to produce the AR-180 version of the Armalite AR-18 rifle for commercial purposes, and some of the Type 89's internal workings are the same as those of the AR-18 - the Type 89 uses the same short-stroke gas piston system with a rotating bolt as the AR-18, but not its dual recoil springs. In order to determine suitability of the rifle, it was issued in limited numbers to the Japan Self-Defense Forces for field testing purposes. After the data collected from the field testing stage of the AR-18 was examined, formal development of the next-generation assault rifle began with its designation as the HR-16 (HR1604). The HR-15 was the first version of the experimental rifle that would eventually become the Type 89, but was developed concurrently with the HR-10, HR-11 and HR-13 by 1989.
On December 6, 2019, the Japanese Ministry of Defense announced that plans have started to eventually change the Type 89 to a new 5.56-based assault rifle. In 2020, the Howa Type 20 was developed, and is planned to replace the Type 89 as Japan's service rifle.
Design.
One of the most advantageous features of the Type 89 rifle over the Type 64 was the ability to ease the load on the individual soldier in relation to the amount of ammunition that he could carry. Also, due to the use of aluminum and thermoset plastic as opposed to the steel and wood construction of the Type 64 rifle, the speed with which a soldier could react to a threat was increased. The fixed stock version of the rifle contains a storage space covered by a rubberized cap that may be accessed by pulling the cap away from the body for the rifle and rotating it in either direction. Although the typical issue model is equipped with a fixed stock, a small number of the steel tubing folding stock version were produced for AFV crews and paratroopers.
Fit and finish of the Type 89 was improved greatly over the Type 64 due to the use of forged aluminum, molded thermoset plastics and stamped steel manufacturing methods pioneered by the processes used to produce the AR-18 and Heckler & Koch G3 series rifle.
Cost.
The Type 89 was designed with simplified operation and minimal number of parts due to the understanding that the complex structure and large number of parts were responsible for the often defective operation of the Type 64 rifle. Because of this, the cost of the Type 89 rifle was roughly half that of the 870,000 yen Type 64 rifle in 1989. According to the Defense Agency, the unit cost of the Type 89 rifle was reduced to about 340,000 yen by fiscal year 2005.
Despite this, it is still considered too expensive for general issue as the ideal price required by the Japanese Government for general production is between 10,000 and 100,000 yen per unit. This is further complicated because the procurement method for the weapon is limited to single fiscal year accounting and further reductions in manufacturing process costs are currently non existent.
Magazine.
The Type 89 can accept magazines designed for the M16 series of rifles. However, the magazine produced specifically for the Type-89 uses a follower that has a special shape to hold the bolt open after the final round is spent. If an M16 series magazine is used, the bolt will not lock back after the final round is expended. The magazine designed for the Type 89 also differs from ones produced for the M16 because it has holes in the sides of the body to indicate if it has been loaded with 30 or 20 rounds of ammunition. However, this comes with the hidden cost of allowing sand and other foreign bodies to enter the magazine easily and cause malfunctions in the operation of the weapon.
Unlike the M16, the magazine well of the Type 89 is not beveled or tapered because the lower receiver is only slightly wider than that of the magazine body, which makes reloading the rifle more difficult.
Ammo.
Type 89 rifle ammunition is interchangeable with the 5.56×45mm SS109/M855 round used by the U.S. military and NATO. Along with the 7.62×51mm round used in the Type 64 rifle, this allows for interchangeability with ammunition stockpiles of U.S. forces stationed in Japan. Since the ammunition developed for the Type 89 rifle is produced in Japan, it is head stamped with the sakura mark of the Self Defense Forces instead of the typical NATO circle-cross used on the SS109/M855 round.
The selector switch is located on the right side of the lower receiver and is often referred to as the "Atare 3," (アタレサン "Ataresan" アタレ(Atare) means "hit it") referencing the different selection positions. The markings and associated feature are as follows in functional order:
Accessories.
The bayonet manufactured specifically for the Type 89 rifle can be used as a wire cutter by connecting it to a lug on the scabbard. Furthermore, the end of the bayonet scabbard can be used as a bottle opener. The US Military M9 bayonet may also be affixed to the rifle.
The Type 89 rifle is equipped with an integrated bipod to facilitate accuracy, which was also on the Type 64. However, unlike the bipod on the Type 64, the version on the Type 89 is easily removed as it is clamped onto the barrel behind the bayonet lug with a clothes-pin style spring mechanism and retained with a lever-like lock. Also, the Type 89's handguard is molded with inlets along its lower edges in order to accommodate the legs of the bipod if they are folded inwards for storage.
The Type 06 rifle grenade is designed for the Type 89. The attachment of the M203 grenade launcher is possible with the proper adapter.
Special forces units of the Japan Ground Self-Defense Force are additionally issued a pressure switch activated targeting laser and flashlight which are mounted on the barrel end of the weapon ahead of the front sight assembly. Regular members of the Self-Defense Forces may also obtain these, but must pay for them out of their own funds.
Recent improvements.
A number of recent modifications have been made to the Type 89 due to the recent armed deployment to Iraq of JSDF members as well as an overall concern over counter-terrorist and possible future combat deployments.
In accordance with the "Iraq Revival Support Law on Special Measures on Land for the U.S. Military" (イラク復興支援特措法) or the "Self-Defense Forces Iraq Dispatch Law," a selector switch has been manufactured and installed on the left hand side of the lower receiver for ambidextrous use for rifles issued to JSDF members in Iraq. However, this is only a temporary modification and the rifle must be returned to its original state (with the selector switch on the right side only) when it is returned to Japan.
In 2004, JSDF elements that had the possibility of seeing combat were issued an optic (an unmagnified red dot sight) with their Type 89 along with a mounting bracket in order to decrease target acquisition time. However, since the use of the sight is still in its provisional stage, individual JSDF members are expected to purchase their own commercially available model for use in a possible combat theater. Among the commonly used optics include the MD-33 manufactured by Tasco Optics Japan under license.
During the initial deployment in Iraq, JSDF elements that had the possibility of seeing combat (for example the Western Army Infantry Regiment) were issued a removable foregrip and a 25 mm Weaver rail was installed under the front handguards of their Type 89s to accommodate it. Shortly afterwards, the restriction was lifted and all units began to receive foregrips despite common complaints about damage to the handguards that were caused by the mount. However, the JGSDF prohibited the attachment of foregrips due to concerns of damage.
A three-point sling was issued to JSDF elements that had the possibility of seeing combat due to the positive testimonials of various international military and police forces. The issued three-point sling is in black color (unlike the olive-drab for standard sling), with a buckle similar to the one for the ALICE LC-2 belt. Individual JSDF members were also allowed to purchase their own commercially available models for their own use if they wished.
Variants.
Type 89-F.
The only variant of the Type 89 is the Type 89-F rifle, also known as the Type 89 Para, which has a folding stock compared to the fixed stock of the standard Type 89. The Type 89 Para is issued to airborne soldiers, tankers, recon soldiers, and armored infantry soldiers. The stock folds to the left side in order to not cover the safety selector on the right side.
ACIES carbine.
As part of the development of the JSDF's Advanced Combat Infantry Equipment System (先進個人装備)—which is the approximate equivalent of the American Future Soldier program—some Type 89 Rifles have been modified to a carbine format with an overall length of about 800 millimeters, a four-sided rail system, a polymer retractable stock, and a shorter barrel.
Publicity photographs taken at exhibitions hosted by the Technical Research and Development Institute of the Japanese Ministry of Defense (TRDI) also show that the third generation of the prototyping process for ACIES has now produced a full size version of this modified Type 89 with a retractable stock and rail system.
That variant has a full-length barrel and an overall length of about 940 millimeters. An underbarrel digital interface switch connected to a foregrip has also been developed, along with an unusually large top-mounted sighting system. The sighting system incorporates a ranging device and a video camera so that, at least under shooting range conditions, it is possible to hold the rifle at a distance from the body to train and fire it around corners—much like analogous foreign systems. There was also some evidence of evaluation of other assault rifles as possible replacements for the Type 89, but this may no longer be the case.


Retransition


Hydrodynamic voltammetry

Hydrodynamic voltammetry is a form of voltammetry in which the analyte solution flows relative to a working electrode. In many voltammetry techniques, the solution is intentionally left still to allow diffusion controlled mass transfer. When a solution is made to flow, through stirring or some other physical mechanism, it is very important to the technique to achieve a very controlled flux or mass transfer in order to obtain predictable results. These methods are types of electrochemical studies which use potentiostats to investigate reaction mechanisms related to redox chemistry among other chemical phenomenon.
Structure.
Most experiments involve a three electrode setup but the setup configuration varies widely. All cell configurations create a laminar flow of solution across the working electrode(s) producing a steady-state current determined by solution flow rather than diffusion. The resulting current can be mathematically predicted and modeled. Among the most common hydrodynamic setup involves the working electrodes rotating to create a laminar flow of solution across the electrode surface. Both rotating disk electrodes (RDE) and rotating ring-disk electrodes (RRDE) are examples where the working electrode rotates. Other configurations, such as flow cells, use pumps to direct solution at or across the working electrode(s).
Distinction.
Hydrodynamic techniques are distinct from still and unstirred experiments such as cyclic voltammetry where the steady-state current is limited by the diffusion of substrate. Experiments are not however limited to linear sweep voltammetry. The configuration of many cells takes the substrate from one working electrode across another, RRDE for example. The potential of one electrode can be varied as the other is held constant or varied. The flow rate can also be varied to adjust the temporal gap the substrates experiences between working electrodes.


Apple Daisy Wheel Printer

The Apple Daisy Wheel Printer is a daisy wheel printer manufactured by Qume and sold by Apple Computer, Inc. in the 1980s. It utilized the ASCII character set and used continuous form paper, or with an optional feeder, cut sheet paper. The printer included several different 130-character "daisy" print wheels (e.g., Courier, Prestige Elite, Gothic, Executive) in English, French, German, and other languages. These 130 character print wheels are unique to the Apple DWP; the standard Qume printwheel has 96 characters.
It could be used with the Lisa system, Apple III system, and Apple IIe or Apple II Plus system if the Super Serial Interface Card was installed.
When used with the Lisa, the printer could produce simple graphics by microstepping the print head and using the period, pipe ( | ), and slash characters. The period is reinforced with brass to prevent it wearing out.
This printer is also referred to as the Apple Letter Quality printer.


Flat ride cymbal

A flat ride cymbal or flat top ride (or often just flat ride) is a ride cymbal without a bell, originally developed by Paiste in collaboration with jazz drummer Joe Morello as part of their Formula 602 series in the 1960s. The most common size is 20" followed by 18", but larger examples exist.
A flat ride cymbal produces the tightest, driest, most controlled stick sound of all ride cymbals, but with an airy wash. The lack of bell makes this cymbal quieter and most suitable for jazz. Roy Haynes was one of the first drummers to use a flat ride which can be heard on Chick Corea's album "Now He Sings, Now He Sobs" made in 1968.