A. Glossary of the key notions in Bionics and beyond
11. H
Haemodynamic response function (HRF) → The change in MR signal on T2*
images following local neuronal activity as a function of time. The haemodynamic response results from a decrease in the amount of deoxygenated haemoglobin present within a voxel.
Hamilton → Sir William Rowan Hamilton (1805–
1865) was an Irish physicist, astronomer, and mathematician, who made important contributions to classical mechanics, optics, and algebra. His greatest contribution is perhaps the reformulation of Newtonian mechanics, now called Hamiltonian mechanics.
Hamilton equations → The Hamilton(–Jacobi) equation is a
reformulation of classical mechanics and, thus, equivalent to other formulations such as Newton‘s laws of motion, Lagrangian mechanics and Hamiltonian mechanics. The Hamilton(–Jacobi) equation is particularly useful in identifying conserved quantities for mechanical systems, which may be possible even when the mechanical problem itself cannot be solved completely.
Hamilton‟s principle → ~ states that the dynamics of a
physical system is determined by a variational problem for a functional based on a single function, the Lagrangian, which contains all physical information concerning the system and the forces acting on it.
Hamiltonian cycle → B1650 visits every vertex in a graph
exactly once
Hamiltonian operator → Mathematically, it is an operator which describes the energy of a particle.
Hamming distance → Number of positions differ in two
sequences
Hammond principle (Hammond postulate) → The transition state is similar to the intermediate, thus if some-thing is stabilizing the intermediate, it is stabilizing the transi-tion state, too. On the other side, if something is destabilizing the intermediate, it is destabilizing the transition state.
Hantzsch–Widman name → Hantzsch–Widman name is a name
for a heteromonocyclic parent hydride having no more than ten ring members formed by the citation of ‗a‘
prefixes denoting the heteroatoms followed by an ending (the ‗stem‘) defining the size of the ring.
Harm activity → ~ is due to the mechanical injury of
the muscle fibers when the needle electrode is inserted or moved.
Harmonic oscillator → Its a model of the harmonic
vibrational motion. In the ~, the potential energy of the system is proportional to the square of the displacement from its equilibrium point.
Hartree–Fock (HF) method → The ~ is an approximate method for the determination of the ground-state wave function and ground-state energy of a quantum many-body system.
The ~ assumes that the exact, N-body wave function of the system can be approximated by a single Slater determinant (in the case where the particles are fermions) or by a single permanent (in the case of bosons) of N spin-orbitals. The ~ finds its typical application in the solution of the electronic Schrödinger equation of atoms, molecules.
HDL (Hardware description language) → ~ is any language from a class of computerlanguages for formal description of digital electronic circuits, for example, verilog, VHDL
Hearing aid → A ~ or traditional hearing aid is an
electroacoustic device designed to amplify the sound in frequency ranges, where the hearing loss is the greatest.
It is usually used to help people with conductive and sensorineural hearing loss.
Heart rate control → Generator: a small computer and an
incorporated battery of many years of life.electrodes: special-coated wires connecting the heart muscles and the generator.The pacemaker - which is the size of a pocket watch - is usually placed under the skin layers in the recess of the shoulder, the clavicle and the large pectoral muscle. The electrodes are led through the blood vessels and fixed in the heart chambers, or in the case of open surgery, they are fixed to the outer surface of the heart. The generator has a small pouch under the skin. The device can also have programs that adapt to the functioning of the heart, or to physical activity. The more advanced devices allow for full and active life, even a regular sport.
Heat capacity → C=δq/dT, where C is the ~, δq is the
heat absorbed by the system and dT is the change of the temperature of the system. It characterizes the ability of the system to absorb heat without temperature change.
Heat of combustion → The ~ (or the heat of the reaction) when 1 mole of a substance reacts with an excess of gaseous oxygen to convert all carbon atoms to carbon dioxide and all hydrogen atoms to water, at a constant pressure.
Hebbian learning → Hebbian theory describes a basic
mechanism for synaptic plasticity where an increase in synaptic efficacy arises from the presynaptic cell‘s repeated and persistent stimulation of the postsynaptic cell.
Hebb‟s rule → The ~ describes a basic mechanism
for synaptic plasticity wherein an increase in synaptic efficacy arises from the presynaptic cell‘s repeated and persistent stimulation of the postsynaptic cell.
Heisenberg → Werner Heisenberg (1901–1976) was
a German theoretical physicist who made foundational contributions to quantum mechanics and is best known
for asserting the uncertainty principle of quantum theory. In addition, he made important contributions to nuclear physics, quantum field theory, and particle physics.
Heisenberg‟s uncertainty principle → The ~ states by precise inequalities that certain pairs of physical properties, such as position and momentum, cannot be simultaneously known to arbitrarily high precision. That is, the more precisely one property is measured, the less precisely the other can be measured.
Helix → A geometrical space curve described
by a simultaneous rotating and translation.
Helmholtz free energy (F) → A state function. Mathematically F=U-TS, where F is the free energy, U is the internal energy, S is the entropy and T is the temperature. The equilibrium of a system at constant temperature and volume is characterized by the minimum of the ~.
Hemidystonia → Affects an arm and a leg on the same
side of the body
Henneman‟s size principle → Small motor units activate at first when some movement is carried out and by increasing the voluntary effort, more and bigger motor units will be activated.
Henry‟s law → p2=x2 K2 where p2 is the vapour
pressure, x2 is the mole fraction of the solute and K2 is an empirical constant of pressure dimension.
Hermite polynomials → They are polynomials which satisfy
the Hn(x)=(-1)n exp(x2) dn/dxn exp(-x2) differential equation. They appears in the wave function of a harmonic oscillator.
Hertz → Heinrich Rudolf Hertz (1857–1894)
was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell.
Hertz dipole → ~ (elementary doublet) is the ideal
(cannot be physically constructed because the current needs somewhere to come from and somewhere to go to) concept which represents the basis of the theory about antennas. It is a small length of conductor (small compared to the wavelength) carrying an alternating current
Heteroaromatic compounds: → ~ are cyclic compounds having the characteristics of an aromatic compound whilst having at least one non-carbon atom in the ring
Heteroatom → ~ is an atom in an organic compound
other than carbon and hydrogen.
Heterocyclic compounds → ~ are cyclic compounds having as
ring members atoms of at least two different elements.
Heterosynaptic depression → A persistent activity-dependent
decrease in synaptic efficacy between neurons, that involves interactions between synapses.
Heuristic model → Heuristic (Εύρίζθω, find/discover)
refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a good enough solution, where an exhaustive search is impractical.
Hexadecimal code → The ~ contains 16 code words, hence
its name. Its 4 bits in a binary code, it contains all 16 possible combinations. After 9, the number series is continued with the letters of the alphabet.
Hidden Markov model → Statistical Markov model in which
the system being modeled is assumed to be a Markov process with unobserved (hidden) states
Hierarchical clastering → It groups the instances into embedded groups
Hierarchy of experimental frames → A scheme for deriving experimental frame specifications for carrying out simulation experiments with hierarchical, modular models: the distributed architecture facilitates attachments of frame components to model simulators at different levels of the model hierarchy.
Hierarchy of models → Hierarchy (Greek εραρτία, derived
from ερός ~ sacred, and ρτω ~ rule) is a system of ranking and organizing things, where each element of the system (except for the top element) is subordinate to a single other element.
High pass filter → It is a filter that passes high
frequencies well but attenuates signals with frequencies lower than the cutoff frequency.
High temperature radiating → Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation.
High-frequency ECG (HFECG) → Additional information in the 150-250 Hz band.
High-frequency TMS (rapid-rate TMS) → Repetition rate above 1 Hz.
High-pass filter → A ~ is a device that passes high
frequencies well but attenuates frequencies lower than the filter‘s cutoff frequency. Also called low-cut filter.
Highpass filter → It allows high frequencies to pass
through and blocks low frequencies.
Hill equation → λ=(n·Ka·[A]x)/(1+n·Ka·[A]x) where n
is the number of binding sites, Ka is the association constant and x is the cooperativity
Hill plot → A quasi linear plot helping us to
obtain the cooperativity, x.
His-Bundle Electrogram (HBE) → Intracardiac electrogram from near the right atrioventricular valve.
Hodgkin-Huxley model → The ~ describes the behavior of
voltage-gated channels, and explains how action potentials in neurons are initiated and propagated. It is a set of nonlinear ordinary differential equations that approximates the electrical characteristics of neurons and other electrically excitable cells.
electron at a position where one could exist in an atom (an electron is excited into a higher state it leaves a hole in its old state) or atomic lattice (band structure calculations lead to an effective mass for the charge carriers, which can be negative).
Holter ECG → This system records all heartbeats for
24 hours, and a computer system evaluates it. Thus, at any time during the day, an arrhythmia can be detected.
HOMO Highest (energy) occupied molecular orbital → The highest energy molecular orbital of a given ground state molecule where electron can be found. The next energy level orbital is empty.
The HOMO - LUMO energy gap is descriptive of the excitability of themolecule.
Homocyclic compounds → ~ are cyclic compounds having as ring members atoms of the same element only, e.g. benzene, pentazole, cyclohexasilane.
Homogeneous → ~ (όκός meaning ‗same‘) usually
means describing a system that has the same properties at every point of the space; in other words, uniform without irregularities, or do not vary with position.
Homologous series → A ~ is a series of organic compounds
with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and shows a gradation in physical properties as a result of increase in molecular size and mass. Any two neighboring members of the series differ by a CH2 group from each other.
Homology → The quality of being similar or
corresponding in position or value or structure or function. In evolutionary biology, ~ refers to any similarity between characteristics of organisms that is due to their shared ancestry.
Homosynaptic depression → A persistent activity-dependent
decrease in synaptic efficacy between neurons, that does not involve interactions between synapses. It typically occurs following repeated low-frequency afferent stimulation, but it can be induced by other methods.
Homunculus → Proportional depiction of the body
parts in a ―little human‖ according to their representation in certain parts of the brain.
Hopf bifurcation → A ~ in which a fixed point of a
dynamical system loses stability as a pair of complex conjugate eigenvalues of the linearization around the fixed point cross the imaginary axis of the complex plane.
Hopfield Neural Network → A well known recurrent neural
network, which has only feedback connections.
Horizontal plane → A ~ is parallel to the ground (in
standard Descartes coordinate system the XY plnae can be drawn as that).
Hormone → A molecule which carries signal
from one cell to another trough the bloodstream or the extracellular space.
HSAB theory → Theory of hard and soft acids and
bases
Humerus → The bone of the upper arm.
Hückel-Möbius rule (Hückel (4n + 2) rule) → Monocyclic planar (or almost planar) systems of trigonally (or sometimes digonally) hybridized atoms that contain (4n + 2) π-electrons (where n is a non-negative integer) will exhibit aromatic character. The rule is generally limited to n = 0–5. This rule is derived from the Hückel MO calculation on planar monocyclic conjugated hydrocarbons (CH)m where m is an integer equal to or greater than 3 according to which (4n + 2) π-electrons are contained in a closed-shell system.
Hybrid Brain-computer interface → A hybrid BCI is composed of one BCI and another system (which might be another BCI), and must achieve specific goals better than a conventional system.
Hybridization → ~ is the linear combination of atomic
orbitals on an atom. Hybrid orbitals are often used in organic chemistry to describe the bonding molecules containing tetrahedral (sp 3), trigonal (sp 2) and digonal (sp) atoms.
Hydration (Solvation) → Any stabilizing interaction of a
solute (or solute moiety) and the solvent or a similar interaction of solvent with groups of an insoluble material (i.e. the ionic groups of an ion-exchange resin). Such interactions generally involve electrostatic forces and van der Waals forces, as well as chemically more specific effects such as hydrogen bond formation.
Hydrocarbons → ~ are compounds consisting of
carbon and hydrogen only.
Hydrogen bond → An intermolecular attractive force between a hydrogen atom in a bond, and a highly electronegative atom
Hydrogen-bridge → ~ is an interaction formed between
two electronegative elements where a hydrogen atom serves as a bridge. A hydrogen atom is bonded to an electronegative atom by a conventional covalent bond, and is loosely bonded to the second electronegative element by electrostatic (dipole–dipole) forces. The second electronegative atom withdraws electrons from the covalently bonded hydrogen atom attached to it, which results in a partial positive character of the hydrogen atom attracts electrons from the donating electronegative element.
Hydrolase → Enzyme catalyzing hydrolysis
reactions.
Hydrophilic → Hydrophilicity refers to a physical
property of a molecule that can transiently bond with water through hydrogen bonding. It is arising from the combining of Greek words ‗hydro‘ (water) and ‗philia‘ (bonding).
Hydrophobic → Hydrophobicity is the physical
property of a molecule (known as a hydrophobe) that is repelled from a mass of water. It is arising from the combining of Greek words ‗hydro‘ (water) and ‗phobos‘ (fear).
Hydrophobic interaction → The tendency of hydrocarbons (or of
lipophilic hydrocarbon-like groups in solutes) to form intermolecular aggregates in an aqueous medium, and analogous intramolecular interactions. The name arises from the attribution of the phenomenon to the apparent repulsion between water and hydrocarbons. However, the phenomenon ought to be attributed to the effect of the hydrocarbon-like groups on the water-water interaction.
Hydroxy carboxylic acids → ~ having the general formula
RCH(OH)C(=O)OH, formally derived from an aldose by oxidation the terminal carbon atom to carboxyl group.
Hydroxylation → A reaction typically catalyzed by
cytochrome P450 containing enzyme in which one of the atoms of molecular oxygen is inserted in a substrate molecule in the form of hydroxylic group. The reaction requires a reducing equivalent in the form of NADPH.
Hyperalgesia → Exaggerated pain in response to
noxious stimuli.
Hyperchromic shift → ~ is the increase in the intensity of a
spectral band due to substituents or interactions with the molecular environment.
Hyperconjugation → ~ is the interaction of ζ-bonds (e.g.
C–H, C–C, etc.) with a π network.
Hyperlipidemia → ~ is increased concentration of lipids
in the blood
Hyperplane → Arbitrary dimensioned plane
Hypochromic shift → ~ is the decrease in the intensity of a
spectral band due to substituents or interactions with the molecular environment.
Hypsochromic shift → ~ is a shift of a spectral band to higher frequency or shorter wavelength upon substitution or change in medium.
Hysteresis → In a system with ~ the output
depends in part on the internal state of system and not only on its input. There is no way to predict the system‘s output without looking at the history of the input. For example the afterhyperpolarization directly after removing a depolarizing input is a ~.