A. Glossary of the key notions in Bionics and beyond
10. G
G protein-coupled receptor → A member of the family of
transmembrane receptors, which are characterised by 7 transmembrane regions and coupled to intracellular signal transducers called G-proteins.
Galvanic cell → a cell that derives electrical energy
from chemical reactions inside the cell
Galvanic isolation → The signal is transformed into a
non-electric signal, then we percieve it and then it is transformed back into an non-electric signal. This can be done by transformator or optocoupler.
Galvanic skin response (GSR) → A change in the ability of the skin to conduct electricity.
Galvanometer → ~ is an instrument for detecting and
measuring electric current. The first device was invented by Johann Schweiger (1779-1857) in 1820.
Gamma EEG band → EEG rhythm above 25-30 Hz.
Gamma knife → ~ makes possible noninvasive brain
surgery by focusing large series of low intensity gamma radiation beams to one single point in the brain causing lesion of the tumor or malformation.
Gamma-aminobutyric acid (GABA) → A chemical substance, the major inhibitory neurotransmitter in the central nervous system.
Gamow → Georgy Antonovich Gamow (1904–
1968), Russian-born American nuclear physicist and cosmologist who was one of the foremost advocates of the big-bang theory.
Gantry → Cylindrical scanner assembly in the
bore of which the response of bodies or tissues to some specific exposure can be detected for 3D-imaging.
Gap junction → ~ or nexus is a specialized intercellular connection between cells. It connects directly the cytoplasm of two cells, through which molecules and ions can freely travel. Gap junctions are used in the electric synapse connecting two neurons via several connexin-built channels.
Gas → Gases are composed of particles that
are not associated with each other and are moving rapidly. Gases have no definite volume or shape.
Gate array → Gate arrays are the basic elements of
digital circuits. They are logical machines having inputs and outputs. Inputs are the independent logical variables, while the outputs are logical variables depending on the logical state of the inputs.
Gate level netlist → HDL contains only connecting wire
descriptions and gates, IP blocks
Gauche effect → 1. The stabilization of the gauche
(synclinal) conformation in a two carbon unit bonded vicinally to electronegative elements e.g. 1,2-difluoroethane. 2. The destabilization of the gauche (synclinal) conformation in a two carbon unit bonded vicinally to large, soft and polarizable elements such as sulfur and bromine.
Gauss → Johann Carl Friedrich Gauss (Gauß,
Carolus Fridericus Gauss) (1777–1855) was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics.Sometimes referred to as the Princeps mathematicorum (Prince of Mathematicians/the foremost of mathematicians)
Gauss law → ~ is a law relating the distribution of
electric charge to the resulting electric field. Gauss‘s law states that the electric flux through any closed surface is proportional to the enclosed electric charge.
Gaussian function → The normal (or Gaussian)
distribution is a continuous probability distribution that is often used as a first approximation to describe real-valued random variables that tend to cluster around a single mean value. The graph of a Gaussian is a characteristic symmetric ―bell curve‖ shape that quickly falls off towards plus/minus infinity and is known as the Gaussian function. One parameter is the height of the curve‘s peak, another is the position of the centre of the peak, and the third controls the width of the ―bell‖.
Gel electrophoresis → A laboratory method to separate
charged (biological) macromolecules in a gel matrix by electric force.
Gene → A segment of the DNA molecule that
encodes the information required for the synthesis of a gene product (protein or RNA).
Gene expression → Production of different types of
RNAs or proteins from the information coding sequence of the genetic material.
General purpose graphical processing unit (GPU)+A960 → A special type of GPU which is able to solve arbitrary tasks specified in a special programming language.
General purpose processor → A processor to solve various
different problem, with huge instruction set
Generalised orthogonal coordinates → Orthogonal coordinates are defined as a set of coordinates in which the coordinate surfaces all meet at right angles. A coordinate surface for a particular coordinate is the curve, surface, or hypersurface on which the particular coordinate is a constant.
Generalization capability → Ability to learn
Generalized coordinates → In the study of multibody systems, ~
are a set of coordinates used to describe the configuration of a system relative to some reference configuration.
A restriction for a set of coordinates to serve as generalized coordinates is that they should uniquely define any possible configuration of the system relative to the reference configuration. Frequently the ~ are chosen to be
independent of one another. The number of independent ~ is defined by the number of degrees of freedom of the system. The adjective ―generalized‖ is a holdover from a period when Cartesian coordinates were the standard.
Apart from practical reasons, any set of ~ is as good as another. The physics of the system is independent of the choice. However, there are more and less practical choices, that is, coordinates that are more or less optimally adapted to the system and make the solution of its equations of motion easier or more difficult.
Generalized dystonia → ~ affects most of the body,
frequently involving the legs and back
Generalized hebbian algorithm → An iterative learning algorithm named after Donald O. Hebb which can perform the estimation of the weights without the knowledge of the correlation matrix
Generalized velocities → The ~ are the time derivatives of the
generalized coordinates of the system.
Genetic code table → A table that shows the codon - amino
acid encoding
Genome → All the genetic information encoded
in the DNA or RNA of an organism.
Geometric isomerism (also known as cis-trans isomerism) → ~ is a stereoisomerism of olefins or cycloalkanes (or hetero-analogues) which differ in the positions of atoms (or groups) relative to a reference plane: in the cis-isomer the atoms are on the same side, in the trans-isomer they are on opposite sides.
Geometrical optics → ~, or ray optics, describes light
propagation in terms of ―rays‖. The ray in geometric optics is an abstraction, which can be used to approximately model how light will propagate. Light rays are defined to propagate in a rectilinear path as far as they travel in a homogeneous medium. This is a significant simplification of optics that fails to account for optical effects such as diffraction and interference. It is an excellent approximation, however, when the wavelength is very small compared with the size of structures with which the light interacts. Geometric optics can be used to describe the geometrical aspects of imaging.
G-glutamyl cycle → The entry of an amino acid (AA) into
a cell is catalyzed by a transferase enzyme. The AA reacts with glutathione, and in the cell AA is released.
Glutathione, hydrolyzed is resinthesized in a cycle.
Gibbs free energy (G) or free enthalpy → A state function. Mathematically G=H-TS, where G is the free enthalpy, H is the enthalpy, S is the entropy and T is the temperature. The equilibrium of a system at constant temperature and pressure is characterized by the minimum of the Helmholtz free energy.
Gibbs phenomena → A convergence phenomenon
occurring when a function with a discontinuity is approximated by a finite number of terms from a Fourier series
Gibbs-Duhem equation → ∑ni dκi=0 where ni is the number of moles of the i‘th component of a solution and dκi is the change of the chemical potential of the i‘th component of that solution.
Glass membrane → ~ are made of an ion-exchange type
of silicate or chalcogenide glass.
Global alignment → Determines the measure of similarity
from end to end
Global Positioning System (GPS)+A981 → It is a satelitte based radio navigation system that allows land, sea, and airborne users to determine their exact location and velocity anywhere (presicily any outdoors locations) in the world.
Glucogenic amino acids → Amino acids with carbon skeleton that can be used in glucose synthesis during gluconeogenesis (e.g. alanine, aspartate)
Gluconeogenesis → Synthesis of glucose from
non-carbohydrate precursors
Gluon → Gluons (English glue) or gauge
bosons are elementary particles. They mediate strong interactions of quarks in quantum chromodynamics (QCD). Unlike the electrically neutral photon of quantum electrodynamics (QED), ~ themselves carry color charge and therefore participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than QED.
Glutamate → The main excitatory neurotransmitter
in the central nervous system.
Glutamic acid decarboxylase (GAD) → The enzyme, which catalyses the decarboxylation of glutamate to GABA and carbon dioxide.
Glycerol → A trimer alcohol.
Glycine → An inhibitory neurotransmitter
primarily in the spinal cord, but it also facilitates the NMDA receptor-mediated excitation.
Glycogen storage diseases → Inherited disorders characterized by abnormal quantity or type of glycogen in tissues
Glycogenolysis → Intracellular decomposition of
glycogen
Glycolysis → Anaerobic degradation of glucose to
lactate
Glycoprotein → Proteins containing carbohydrate
groups
Glycosylation → Post-translational modification of
proteins through which a sugar chain is covalently attached to the polypeptide.
Golgi tendon spindle → ~ is a proprioceptive sensory
receptor organ located at the juction of the insertion of skeletal muscle fibers and tendons of skeletal muscle
Gradient amplifier → A ~ supplies power to a set of
gradient coils, providing the variation in magnetic field strength required to obtain images and perform localization. MRI systems therefore require three gradient amplifiers, one for each set of gradient coils: x, y, and z. A ~ may use large amount of power and frequently require cooling with chilled water or forced air flow.
Gradient coils → Current carrying coils designed to
produce a desired magnetic field gradient (so that the magnetic field will be stronger in some locations than others). Proper design of the size and configuration of the coils is necessary to produce a controlled and uniform gradient.
Gradient descent → ~ is a first-order optimization
algorithm that finds a local minimum of a function.
Gradient, grad → ~ of a scalar field is a vector field
that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change.
Gradient-echo pulse sequence → A pulse sequence that relies on gradient reversal to rephrase the transverse magnetization. Gradient-echo pulse sequences permit small flip-angle excitations, which preserve most of the longitudinal magnetization and therefore reduce or eliminate the time required for recovery of longitudinal magnetization before repeating the pulse sequence. Gradient echo
pulse sequences have gained common use in 2DFT (planar) and 3DFT (volume) imaging, flow imaging, magnetic susceptibility imaging, and BOLD imaging.
Gravity → ~ is a natural phenomenon by which
physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass. It is the weakest of the four fundamental forces
Gray code → The speciality of ~ is that only one
number changes every time, so it is great to characterize rotations and displacements.
Ground fault circuit interrupter (GFCI) → Is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor.
Ground state → An atom, molecule or nucleus is in
the ~ have no more energy than the absolute minimum. The ~ of an atom having the atom‘s electrons in the lowest possible orbit.
Grounding → Ground or earth may be the reference
point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth.
GUARD → Connection to avoid the influence of
the current leakage of the surface.
Gunn → John Battiscombe Gunn (1928–
2008), was a British physicist, who spent most of his career in the United States.
Gunn effect → In some materials (III-V
compounds), after an electric field in the material reaches a threshold level, the mobility of electrons decrease as the electric field is increased, thereby producing negative resistance. A two-terminal device made from such a material can produce microwave oscillations, the frequency of which is primarily determined by the characteristics of the specimen of the material and not by any external circuit.
Gyromagnetic ratio → The ratio of the magnetic moment to
the angular momentum of a particle. This is a constant for a given nucleus.
Gyrus → A ridge on the cerebral cortex.