Electrons flowing in a conductor constitute an electric current.

The number of electrons associated with the nucleus of an atom is equal to the atomic number of the substance.

A flow of electrical current consi that are in a given material, the greater its electrical conductance (or equivalently, the lower its resistance).

Electrons are the primary charge carriers in electric currents.

All atoms have electrons arranged around a nucleus and an electron may be positive (positron), but as the term is generally used, it refers to the negative form (negatron).

Variations in voltage can be noted between the areas that the wires touch.

In cryoelectron microscopy, the freezing of the sample is done in ethane slush to produce vitreous, or non-crystalline, ice. The frozen sample grid is then kept at liquid nitrogen temperature in the electron microscope and digital micrographs are collected with a camera.

The advantages of cryo-EM over traditional EM techniques include the preservation of the sample in a near-native hydrated state without the distortions from stains or fixatives needed for traditional EM. With image processing and averaging of multiple images, cyroelectron microscopy provides high resolution information (below 10 angstroms).

An angstrom is a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation.

The free electrons then free others in the same manner, etc.

The electron beam of the super-microscope has become a basic tool in the research of diseases.

The gas may be ionized; or a current may flow whose magnetic field focuses the electron beam on the target.

A klystron is an evacuated electron-beam tube in which an initial velocity modulation imparted to electrons in the beam results subsequently in density modulation of the beam. A klystron is used either as an amplifier in the microwave region or as an oscillator.

A dielectric-coated optical grating on the tape is bombarded with 10-keV electrons to induce momentary conductivity.

This causes electrons to flow fro the dielectric to the metal base of the tape.

Elemental areas on the surface of the tape lose charge in proportion to light from corresponding elemental areas of the image being stored.

Certain compounds entering the chamber have an affinity for these electrons, and this decrease in electrons is recorded for component identification.

The mass number is unchanged, but the atomic number is decreased by one and this process is accompanied by the emission of a neutrino.

Often the resulting nucleus is unstable and achieves stability by giving off a gamma ray.

As the electrons are transferred from one electron carrier to another carrier, their energy level decreases, and energy is released.

Negatively charged electrons are attracted to a positively charged nucleus to form an atom or an ion.

The electron stream passing between electrodes in one circuit transfers energy to electrodes in the other circuit.

Ions formed in the first chamber drift into the second chamber, where they become charged.

A whistler is defined as an effect that occurs when a plasma disturbance, caused by a lightning discharge, travels out along lines of magnetic force of the earth's field and is reflected back to its origin from a magnetic point on the earth's surface.

Electron diffraction refers to the bending of electromagnetic waves as they pass around corners or through holes smaller than the wavelengths of the waves themselves.

The occurrence or the technique of producing electron diffractions through the incidence of electrons on matter.

The bending of an electron stream which occurs when the electron diffraction travels through a medium; such as, very thin metal foil.

It is a reducing agent which, because of its donating electrons, is itself oxidized in the process.

It may be caused by an electric field, light, heat, or impact chemical disintegration.

Since all substances consist of atoms and since all atoms contain electrons, any substance may emit electrons; usually, however, the term refers to the emission of electrons from the surface of a solid.

Electron energies are functions of each particular atomic species.

The direction of electron flow is opposite to that of the current.

It is used for electrons in electron irradiation and for neutrons in connection with the effects of nuclear radiation on electronic components.

Each electron goes to form the communal "electron gas" which is responsible for the high electrical and thermal conductivity of the metallic state.

Electron guns are also used in oil refining and various other industries.

The source of the electron beam is the cathode, a flat metal support covered with oxides of barium and strontium.

When they are heated by a coil behind the support, these oxides produce electrons, that are drawn toward a positively charged sleeve (first anode) which is contoured to allow the electron beam to flow within the inside diameter.

The beam is then electrostatically constricted and collimated by a metal disk with a hole (the

It serves as a positive charge carrier, allowing electrons deeper in the band to move into the vacated area.

A valence is the combining power of atoms or groups measured by the number of electrons the atom or group will receive, give up, or share in forming a compound.

The electron density in a cross section of the stream is at each point proportional to the brightness of the corresponding point in an optical image.

The electron beam carries the images through an array of lenses and an enlarged electron image is used to stimulate a fluorescent screen that is photographed by a camera system.

A nondestructive analysis of the specimen can then be made by measuring the back-scattered electrons, the specimen current, the resulting X-radiation, or any other resulting process.

By using this technique, it is possible to obtain quantitative data on, for example, the calcium concentration in different parts of a cell; however, it is necessary to use ultra thin frozen sections.

It provides much greater plowers of magnification than an optical microscope; that is, up to 1,000,000 times actual size without loss of sharpness and degree of contrast in the image.

The specimen is stained with electron-opaque dyes and with its high magnification power, it creates an image that can be photographed or viewed on a florescent screen.

Since electrons carry waves of much smaller wavelengths than light waves, correspondingly greater magnifications can be obtained.

The electron microscope will resolve details from 1,000 to 10,000 times finer than the optical microscope and images can be studied on a fluorescent screen or recorded photographically.

It is used in multiplier phototubes and some types of television camera tubes.

An electron beam containing the desired signal is reflected from the surfaces of each of a series of dynodes (electrodes whose primary function is the secondary emission of electrons), and at each reflection an impinging electron releases two or more secondary electrons, so that the beam builds up in strength.

Electrons from the original current strike an anode, producing secondary electrons that are directed to the next anode in a multistage process until the desired level of current is obtained.

The electron stream from the photocathode is reflected off each dynode in sequence, with a secondary emission adding electrons to the stream at each reflection.

The term electron-optics is often used erroneously as a synonym for optoelectronic.

It arises because of the tendency of a magnetic field to orient the electronic magnetic moments parallel to itself.

A magnetic moment refers to a vector associated with a magnet, current loop, particle, etc., whose cross product with the magnetic induction (or alternatively, the magnetic field strength) of a magnetic field is equal to the torque exerted on the system by the field.

It is performed with an electron microscope fitted with an x-ray spectrometer, in a scanning or transmission mode.

It is used in radio receivers to indicate the accuracy of tuning and as a modulation indicator in some tape recorders.

To form a display, or image, on the screen, the electron beam is deflected in the vertical and horizontal directions either by the electrostatic effect of electrodes within the tube or by magnetic fields produced by coils located around the neck of the tube.

The display is usually like an "eye" with a keyhole in the middle, and the maximum recording level corresponds to the closing-up of a slot at the bottom of the keyhole which is superseded by meters in current-model recorders.

The beam is moved in a point-to-point manner over the surface of the specimen and these electrons are deflected collected, accelerated, and directed against a scintillator.

The large number of photons that are created are converted into an electric signal which, in turn, modulates the beam scanning the surface of the specimen.

Those with the least energy are in the shell closest to the nucleus, traditionally called the K shell, which can hold no more than two electrons.

The Q shell, farthest from the nucleus, can hold 98 electrons, but it is never completely filled.

It is used to investigate atomic, molecular, or solid-state structure, and in chemical analysis.

Spin is one of the permanent and basic properties of the electron.

This includes the ratio of the average stream current through the electrode to the stream current approaching the electrode.

The electron beam is allowed to strike an internal target, producing high-energy gamma rays which are used outside the machine.

The resulting electron image is enlarged by electron lenses and made visible by a fluorescent screen.

Such time is extremely important in tubes designed for ultrahigh frequencies.

It occurs in respiratory metabolism and in some types of fermentation.

It is also involved in the light reaction of photosynthesis.

They are composed of a series of oxidizing agents arranged in an order of increasing strength and terminating in oxygen.

Erasability is achieved by using a higher infrared level than that which is used in reading.

It is used to generate, to amplify, and to rectify electric oscillations and alternating currents.

A tube can perform rectification, amplification, modulation, demodulation, oscillation, limiting, and a variety of other activities.

Examples include cathode-ray tubes, gas tubes, phototubes, and vacuum tubes.

Such tools may be either gas filled, or partially or fully evacuated; such as,vacuums.

Common tubes include vacuum tubes, cathode-ray tubes, phototubes, mercury vapor tubes, thyratrons, and microwave tubes.

Thyratrons are gas-filled hot-cathode tubes which are used as electronic switches or relays in which signals applied to the control grids initiates anode currents but does not limit them and cannot interrupt, the flow of electrons.

It is equal to the energy gained by an electron when it moves from one point to a point higher in potential by one volt and it is a unit of energy or work, not of voltage.

The square of the function's modulus gives the probability per unit volume of finding electrons at a given position.

Electron beam evaporation is a commonly used process for coating lenses and filters with anti-reflection, scratch-resistant or other specialized coatings.

The process is also commonly used for coating insulating and resistor films on electronic components.

It consists of an emitting cathode and an anode, with an aperture for passage of some of the electrons.

Usually the beam is made to strike a fluorescent screen so the deflection can be observed.

The resulting laser output beam moves correspondingly, to provide high-speed scanning for data retrieval and imaging applications.

The beam can be electronically blanked, unblanked, or modulated with analog video signals for the projection of picture or other graphic data.

After exposure, the film is removed from the vacuum chamber for conventional development and other production processes.

Heat is produced by a focused and controlled electron beam at a sufficiently high temperature to volatilize and so to remove metal in a specified manner.

Drilling and cutting are examples of specific applications.

It's used principally for refining metals to a higher degree of purity than is possible with conventional vacuum-melting techniques.

Its chief advantage is the ability to control the temperature of the molten material and the time it remains melted because both affect the degree of volatilization of impurities.

Volatilization is the conversion of a chemical substance from a liquid or solid state to a gaseous or vapor state by the application of heat, by reducing pressure, or by a combination of these processes. It is also known as vaporization.

Heat is produced by a focused electron beam that can produce welds having depth-to-width ratios of up to twenty to one.

Applications include welding of thin metal foils to thicker metal without burning, sealing of metal cans containing uranium fuel elements for reactors, and direct fusion welding of ceramic objects.

The semiconductor target is a pair of silicon diodes, each consisting of two metallic electrodes with a pn (positive-negative) junction under the top contact.

A pn junction or a diode (one way valve) is a pn junction with p-type (positive-type) on one side and n-type (negative-type) on the other side.

When a positive voltage is applied to the p-type side (forward bias), it shrinks and overcomes the depletion zone, causing the current to flow from the p-type to the n-type side. When a negative voltage is applied to the p-type of the diode (reverse bias), it increases the depletion zone and prevents current from flowing.

The amplifier operation is based on the fact that a modulated electron beam can control the current in a reverse-based semiconductor junction.

It is characterized by a circuitry that feeds a portion of the generated energy back into the system to sustain its operation, and by an electron stream that is coupled between the screen and the plate to reduce the effects of the load.

The anode-circuit load is coupled to the oscillator through the electron stream.

Such an object will appear as a dark area on the viewing screen and photographic prints.

The map is calculated using a Fourier synthesis, a summation of waves of known phase, frequency, and amplitude.

A diffraction is the bending or spreading out of waves; such as, of sound or light, as they pass around the edge of an obstacle or through a narrow opening as when light passes sharp edges or goes through narrow slits and the rays are deflected and produce fringes of light and dark bands.

A cylindrical film placed around a specimen and which records the electrons that might be scattered or diffracted by it.

It is used to form holes with different shapes in materials that have poor machine operations.

The study of the distribution of energy that is lost by scattered electrons when a substance is bombarded with monochromatic electrons.

It is associated with a liquid-gas phase transition of the charge carriers, and consists of regions of conducting electron-hole Fermi liquid coexisting with regions of insulating exciton gas.

This is opposed to a nuclear magnetic moment.

A dynode is an electrode whose primary function is the secondary emission of electrons which are used in multiplier phototubes and some types of television camera tubes.

An electron-optical lens focuses the highly accelerated electrons into a tiny spot.

The emerging electrons are focused and directed by a second lens onto a fluorescent screen.

The magnified image which is produced is 1000 times greater than that produced by an optic microscope and well resolved, but it is two-dimensional because of the thinness of the specimen.

Such electrons are exchanged or shared in chemical reactions.