Glossary of the key notions in Bionics and beyond

Slope conductance → The derivative of the membrane current as function of membrane potential. Indicates how fast the net current changes.

Slow cortical potentials → Low frequency cortical potentials recorded from the surface of the brain that are associated with various cognitive or sensory-motor events.

Slow-wave sleep (SWS) → A phase of deep sleep, when large delta waves are recorded in the EEG.

Small scale fading → ~ refers to the dramatic changes in signal amplitude and phase that can be experienced as a result of small changes (as small as half wavelength) in the spatial position between transmitter and receiver.

Smart Dust → The engineering goal of the ~ project is to demonstrate that a complete sensor/communication system can be integrated into a cubic millimeter package. On the other hand it is a hypothetical system of many tiny MEMS that i) can sense their own environment; ii) are usually networked wirelessly; and iii) are distributed over some area to perform tasks (sensing and actuating).

SMILES (simplified molecular input line entry specification) → ~ is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings.

Snell → Willebrord Snellius/Willebrord Snel van Royen (1580–1626) was a Dutch astronomer and mathematician.

Snell’s Law → Refraction is described by ~, which states that the sine of the angle of incidence is related to the sine of the angle of refraction the same way as the wave velocities in the respective media, and the refractive indices. The form what is known as Snell’s law was actually published by Descartes as the Law of Sines. Snell did discover the relationship but articulated it in a different way. Snell and Descartes realized that when light went from one medium to another, the angles and refractive indices of the media determined the path that the light followed. The relationship is a function of the sine of the angles.

Sodium → ~ is a metallic element with a symbol Na and atomic number 11.

Sodium-potassium pump → Membrane protein that uses energy released by hydrolysis of ATP to actively transport sodium out and potassium into the cell

Software Defined Radio (SDR) → A radio in which the RF parameters including, but not limited to, frequency range, modulation type, or output power can be set or altered by software, and/or the technique by which this is achieved

Solid-state → Solid is one of the major states of matter. It is characterized by structural rigidity and resistance to changes of shape or volume.

Solution → A homogeneous mixture of two or more components.

Solvent effect → Solvent effects is the group of effects that a solvent has on chemical reactivity. Solvents can have an effect on solubility, stability and reaction rates and choosing the appropriate solvent allows for thermodynamic and kinetic control over a chemical reaction.

Somatic motor system → ~ is one part of the peripheral nervous system.Its main task is the voluntary control of body movements by using skeletal muscles

Somatosensory evoked potential (SEP) → Response of the brain to a somatosensory stimulus.

Somatostatin → A hypophyseotrophic hormone regulating GH secretion, as well as a synaptic modulator in the central nervous system.

Sommerfeld → Arnold Johannes Wilhelm Sommerfeld (1868–1951) was a German theoretical physicist who pioneered developments in atomic and quantum physics.

Sommerfeld model → A model of a metal in which the free electrons, that is, those giving rise to the conductivity, are regarded as moving in a potential which is approximated as constant everywhere inside the metal. Also known as ~.

Source localization → Neuroelectromagnetic source imaging which is often referred to as ‘source localization’ is the scientific field devoted to modeling and estimating the spatiotemporal dynamics of neuronal currents throughout the brain that generate the electric potentials and magnetic fields measured with noninvasive or invasive electromagnetic recording technologies. Unlike the images produced by fMRI , which are only indirectly related to neuroelectrical activity through neurovascular coupling (e.g., the BOLD signal), the current source density or activity images that ~ techniques generate are direct estimates of electrical activity in neuronal populations.

Space and time invariant (bionics) → The values of the A and B template is the same for each time instant and for each neuron in the array

Space charge effect → Space charge is a concept in which excess electric charge is treated as a continuum of charge distributed over a region of space rather than distinct point-like charges. This model typically applies when charge carriers have been emitted from some region of a solid - the cloud of emitted carriers can form a space charge region if they are sufficiently spread out, or the charged atoms or molecules left behind in the solid can form a space charge region. Space charge usually only occurs in dielectric media (including vacuum) because in a conductive medium the charge tends to be rapidly neutralized.

Space clamped → A small piece (e. g. of membrane) isolated in space.

Space clamp → A measuring technique that tries to achieve isopotentiality over a region of axon by threading a wire along its interior to short-circuit the longitudinal resistance of the axoplasm. (The whole space inside the membrane is clamped to a fixed value.)

Spasticity → ~ is a feature of altered skeletal muscle performance occurring in disorders of the central nervous system (CNS) impacting the upper motor neuron in the form of a lesion

Spatial resolution → The smallest distance between two points in the object that can be distinguished as separate details in the image, generally indicated as a length or a number of black and white line pairs per mm. The specific criterion for resolution to be used depends on the type of test used (e.g., bar pattern or contrast-detail phantom). As the ability to separate or detect objects depends on their contrast and the noise, and the different MR parameters of objects will affect image contrast differently for different imaging techniques, care must be taken in comparing the results of resolution phantom tests of different machines and no single simple measure of resolution can be specified. The resolution may be anisotropic. The resolution may be larger than the size corresponding to the discrete image element (pixel), although it cannot be smaller.

Special relativity → ~ is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein (after the considerable and independent contributions of Hendrik Lorentz, Henri Poincaré and others). It generalizes Galileo’s principle of relativity - that all uniform motion is relative, and that there is no absolute and well-defined state of rest (no privileged reference frames) - from mechanics to all the laws of physics, including both the laws of mechanics and of electrodynamics, whatever they may be. ~ incorporates the principle that the speed of light is the same for all inertial observers regardless of the state of motion of the source.

Specific absorption rate (SAR) (W/kg) → Time varying electromagnetic fields can deposit energy in tissues. This energy is deposited mostly in the form of heat which is considered the primary mechanism of biological effect. The ~ is defined as the energy dissipated in tissue (watts) per kilogram of tissue mass. Inhomogeneity of the RF fields leads to a local exposure where most of the power that is absorbed is applied to one body region rather than the entire person, leading to the concept of a local SAR. Averaging over the whole body leads to the global ~.

Specific purpose processor → A processor to solve one specific problem efficiently

Specificity (medical) → Measures the proportion of negatives which are correctly identified (e.g. the percentage of healthy people who are correctly identified as not having the condition). The formula for specificity is Sp = TrueNegatives / (TrueNegatives + FalsePositives).

Spectral Efficiency (SE) → It is measured in bit/s/Hz. It refers to the information rate that can be transmitted over a given bandwidth in a specific communication system.

Spectral lines → A ~ is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies. ~ are the result of interaction between a quantum system (atoms, molecules or atomic nuclei) and a single photon, either an emission line or an absorption line will be produced.

Spectrometer → A spectrometer/spectrograph/spectroscope is used in spectroscopy (to measure properties of light over a specific portion of the electromagnetic spectrum) for producing spectral lines and measuring their wavelengths and intensities. The variable measured is most often the light’s intensity but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a unit directly proportional to the photon energy, such as wavenumber or electron volts, which has a reciprocal relationship to wavelength.

Spectroscopy → ~ is the study of the interaction between matter and radiated energy, any interaction with radiative energy as a function of its wavelength or frequency. Spectroscopic data is often represented by a spectrum, a plot of the response of interest as a function of wavelength or frequency.

Spectrum → The electromagnetic ~ is the range of all possible frequencies of electromagnetic radiation. The “electromagnetic spectrum” of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. The electromagnetic ~ extends from low frequencies to gamma radiation at the short-wavelength end. The long wavelength limit is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length, although in principle the spectrum is infinite and continuous.

Speech processing strategies → ~ are methods which use different processing algorithms and different features of the sound waves to generate electrical stimulation patterns.

Spherical coordinates → A ~ system is a coordinate system for three-dimensional space where the position of a point is specified by three numbers: the radial distance of that point from a fixed origin, its inclination angle measured from a fixed zenith direction, and the azimuth angle of its orthogonal projection on a reference plane that passes through the origin and is orthogonal to the zenith, measured from a fixed reference direction on that plane.

Spherically symmetric → The ~ potential energy function depends only on the distance of the electron from the proton, not on the direction of the position vector. The dynamics of a particle in a ~ potential has a Hamiltonian. Due to the spherical symmetry of the system it is useful to use spherical coordinates. When this is done, the time-independent Schrödinger equation for the system is separable.

Sphygmomanometer → ~ is a device used to measure blood pressure, comprising an inflatable cuff to restrict blood flow, and a mercury or mechanical manometer to measure the pressure.

SPICE (Simulation Program with Integrated Circuit Emphasis) → SPICE (, the most known electronic simulator type

Spike → Detected action potential of a single neuron.

Spike-and-wave complex → Pathological EEG pattern that contains a spike followed by a slow wave.

Spike-timing-dependent plasticity (STPD) → ~ is a biological process that adjusts the strength of connections between neurons in the brain. The process adjusts the connection strengths based on the relative timing of a particular neuron’s output and input action potentials (or spikes).

Spin → In quantum mechanics and particle physics ~ is a fundamental characteristic property of elementary particles, composite particles (hadrons), and atomic nuclei. ~ was originally conceived as the rotation of a particle around some axis, it is a type of angular momentum. The “spin quantum number” is always dimensionless, and may take on integer or half-integer values.

Spin casting → Centrifugal force and heating is used to produce castings from a dissolved liquid on a substrate.

Spin coupling → ~ arises due to the direct interaction between two particles with non-zero spin. The magnitude of this coupling is proportional to the inverse third power of the distance between particles and to the product of their gyromagnetic ratios. Magnitude of coupling also has an orientation dependence on the cosine of the angle between the vector connecting the interacting particles and direction of the magnetic field.

Spin Echo (SE) → The RF pulse sequence where a 90° excitation pulse is followed by a 180° refocusing pulse to eliminate field inhomogeneity and chemical shift effects at the echo. RF spin echo would be a more appropriate name.

Spin quantum number → It is one of four quantum numbers (the principal quantum number, the azimuthal quantum number, the magnetic quantum number, and the ~) which describes the unique quantum state of a given particle. If the particle is an electron, it describes the spin orientation of an electron relative to an external magnetic field.

Spinal cord → The thick longitudinal cord of nervous tissue that in vertebrates is enclosed in the vertebral canal, it is continuous anteriorly with the medulla oblongata

Spinal nerve → Nerve composed by the ventral and dorsal root fibers of the spinal segment

Spinning top → Spinning top/spintop can be spun on an axis, balancing on a point. The action of a top relies on the gyroscopic effect for its operation. After spinning upright for an extended period, the angular momentum, and therefore the gyroscopic effect will gradually lessen, leading to ever increasing precession, finally causing the top to topple in a frequently violent last thrash.

Spin-spin splitting → ~ is the splitting of an NMR signal into a multiplet because of an interaction between nearby magnetic nuclei whose spins are coupled. The magnitude is given by the coupling constant, J.

Splicing → A process through which some segments called exons are cleaved from the prematured messenger RNAs.

Split levels → If several atoms are brought together into a molecule, their atomic orbitals split. This produces a number of molecular orbitals proportional to the number of atoms. There is an overlap of the electron wavefunctions occupying adjacent atoms, it leads to a splitting of the energy levels consistent with the Pauli exclusion principle.

Splitting → Energy level ~ occurs when the degenerate energy levels of two or more states are split because of external fields or other effects. The term is most commonly used in quantum theory in reference to the electron configuration in atoms or molecules.

Spontaneous activity → Electrical activity originating during rest either in muscle or nerve fibers.

Spontaneous emission → ~ is the process by which a light source such as an atom, molecule, nanocrystal or nucleus in an excited state undergoes a transition to a state with a lower energy, e.g., the ground state and emits a photon.

Spotted array → It is used to compare two biological samples and therefore applies two different dyes

SRE (Sterol Response Element) → ~, a DNA sequence in the regulatory region of genes which acts as a binding site for a transcription factor available in cholesterol-depleted state of the cell

SREBP (sterol regulatory element-binding proteins) → ~ is a protein in the membrane of the endoplasmic reticulum part of which is a transcription factor released following proteolysis in cholesterol-depleted state of the cell.

Stability analysis → The process of analyzing trajectories of dynamical systems under small perturbations of initial conditions.

Stable → A fixed point is (asymptotically) ~ if the system moves back towards the fixed point after being slightly displaced from it.

Stack → Part of the memory of the computer, in which the processor saves the memory addresses where it returns after completing certain procedures. The ~ is a data structure from which we can first read the last saved data.

Stack pointer → It appoints the top element of the stack.

Standard → It is an established norm or requirement about technical systems. (the IEEE develops global standards in a broad range of wireless communication systems)

Standard cell library → A collection of standardized sized logic gates.

Standard deviation → The average of the squared differences from the Mean. It is the square root of the variance.

Standards (units) → A properly defined unit allows quantities of the same kind to be compared

Standing wave/stationary wave → A vibration of a system in which some particular points remain fixed while others between them vibrate with the maximum amplitude. Such waves result from the interaction of similar waves traveling in opposite directions as when reflected waves meet advancing waves.

Stapes → The ~ is a stirrup-shaped small bone in the middle ear which is attached to the incus and to the oval window of the inner ear. It transmits sound vibrations from the incus to the oval window.

State function → They are functions of thermodynamic variables, the value of which depends only the state at which the system stays. They have an extremum at the equilibrium of the system. Such functions are: internal energy (U), enthalpy (H), entropy (S), Helmholtz free energy (A), Gibbs free energy (G)

State variable → A ~ is one of the set of variables that describe the “state” of a dynamical system. Intuitively, the state of a system describes enough about the system to determine its future behaviour. Models that consist of coupled first-order differential equations are said to be in state-variable form.

Static → ~ means that do not vary with time (freqneuency of 0 Hz).

Static (Leakage) power → The static consumption does not depend on the operation speed

Static capacity → Maximum number of orthogonal patterns, with the network steady points are statically stable

Static timing analysis → The STA checks the elements signal arrival and stability conditions by propagating the interleaved logic paths and interconnect delays

Stationary → ~ field which does not change during the time interval under consideration. Parameters such as the mean and variance, if they exist, also do not change over time or position.

Statistical dynamic capacity → Maximum number of quasy orthogonal patterns, with the network steady points are dynamically stable

Statistical physics → Statistical mechanics is a branch of physics that applies probability theory, which contains mathematical tools for dealing with large populations, to the study of the thermodynamic behavior of systems composed of a large number of particles. It provides a framework for relating the microscopic properties of individual atoms and molecules to the macroscopic bulk properties of materials that can be observed

Statistical thermodynamics → A discipline which attempts to explain the thermodynamic relationships based on the probability distributions of the different properties of particles, for example velocity.

Steady state → A system in a ~ has numerous properties that are unchanging in time. This implies that for any property of the system, the partial derivative with respect to time is zero.

Steady state approximation → A method for gaining the rate law which assumes that the concentration of an intermediate can be considered constant through a wide range of time.

Steady state approximation (chemistry) → ~ (or pseudo-rate law) is the simplified rate law observed when the concentration of a species appearing in the rate equation is present in large excess. The concentration of this compound can be considered as a constant, and thus the observed rate equation does not reflect its involvement. This kind of behavior can be observed when the solvent is involved in a reaction.

Steady State Visual Evoked Potential → This is a type of ERP often used in BCIs. The subject attends to a flickering light with a given repetition rate while neglecting other flickering lights. The ERP elicited by the attended flickering light increases and this is used for control.

Steady-state current → The current that would flow through the cell membrane after a very long (infinite) time if the membrane potential remained clamped to a given voltage.

Steady-state space constant → Characteristic length for the spatial attenuation of stationary (DC) inputs in a cable; denoted by lambda (λ). In an infinite cable, steady-state voltage will have decayed to 1/e times the original value at a distance of λ.

Stefan–Boltzmann’s law → It states that the total energy radiated per unit surface area of a black body per unit time is directly proportional to the fourth power of the black body’s thermodynamic temperature/absolute temperature.

Step function → a function on the real numbers is called a ~ (or staircase function) if it can be written as a finite linear combination of indicator functions of intervals. Informally speaking, a ~ is a piecewise constant function having only finitely many pieces.

Stepping reflex → Rhythmic stepping movements inducable in supported toddlers by touching the feet to the ground (well before they learn standing or walking).

Stereoisomers → Compounds possess the same general formula and connectivity, they differ in the spatial arrangement of their atoms/groups. (2D structures are different)

Stereospecific reactions → A reaction is termed stereospecific if starting materials differing only in their configuration are converted into stereoisomeric products. According to this definition, a stereospecific process is necessarily stereoselective but not all stereoselective processes are stereospecific. Stereospecificity may be total (100%) or partial. The term is also applied to situations where reaction can be performed with only one stereoisomer.

Stereotactic head holder → Frame for precisely directing the tip of a delicate instrument (as a needle) or orienting imaging volume in three planes using coordinates provided by standard anatomic atlases

Stereotaxic apparatus → ~ consists of a metal frame that serves for rigid fixation of the head of the subject in reference to the coordinate system. The frame also serves as the base for the manipulation of the positioners or electrode holders in the three dimensional coordinate system.

Stereotaxic atlas → An atlas of the brain, or parts of the brain, mapped out in serial sections and typically providing both pictures of brain tissue and schematic representations of it. The atlas gives the coordinates of the different structures.