Manifestation Of Such Effects Research Articles

Measuring the magnetization of a permanent magnet

The effect of an external magnetic field B on magnetic materials is a subject of immense importance. The simplest and oldest manifestation of such effects is the behavior of the magnetic compass. Magnetization M plays a key role in studying the response of magnetic materials to B. In this paper, an experimental technique for the determination of M of a permanent magnet will be presented. The proposed method discusses the effect of B (produced by a pair of Helmholtz coils) on a permanent magnet, suspended by two strings and allowed to oscillate under the influence of the torque that the magnetic field exerts on the magnet. The arrangement used Newton's second law for rotational motion to measure M via graphical analysis.

The radical-pair mechanism as a paradigm for the emerging science of quantum biology

The radical-pair mechanism (RPM) was introduced in the 1960s to explain anomalously large EPR and NMR signals in chemical reactions of organic molecules. It has evolved to the cornerstone of spin chemistry, the study of the effect electron and nuclear spins have on chemical reactions, with the avian magnetic compass mechanism and the photosynthetic reaction center dynamics being prominent biophysical manifestations of such effects. In recent years the RPM was shown to be an ideal biological system where the conceptual tools of quantum-information science can be fruitfully applied. We will here review recent work making the case that RPM is indeed a major driving force of the emerging field of quantum biology.

Peculiarities of hydrodynamic drag in a rotating fluid

Rapid rotation of a fluid media may lead to a considerable increase in the effective hydrodynamic drag coefficient in the direction of the rotational axis. This is demonstrated using some simple examples of perturbations caused by the forces applied to an incompressible fluid. Hydrodynamic drag in a rotating medium may increase upon a decrease in viscosity. Possible manifestations of such effects in intense atmospheric vortices are discussed.

Effects due to backscattering and pseudogap features in graphene nanoribbons with single vacancies

We present a systematic study of electron backscattering phenomena during conduction for graphene nanoribbons with single-vacancy scatterers and dimensions within the capabilities of modern lithographic techniques. Our analysis builds upon an \textit{ab initio} parameterized semiempirical model that breaks electron-hole symmetry and nonequilibrium Green's function methods for the calculation of the conductance distribution $g$. The underlying mechanism is based on wavefunction localizations and perturbations that in the case of the first $\pi-\pi{}^*$ plateau can give rise to impurity-like pseudogaps with both donor and acceptor characteristics. Confinement and geometry are crucial for the manifestation of such effects. Self-consistent quantum transport calculations characterize vacancies as local charging centers that can induce electrostatic inhomogeneities on the ribbon topology.

An account of spatial effects in describing the resolution function of a neutron powder diffractometer with a planar monochromator

This paper continues the series of papers devoted to the description of the resolution function of neutron powder diffractometers with focusing monochromators, where a mathematically correct approach for taking into account spatial effects has been developed. The manifestation of such effects is clearly demonstrated for instruments with plane monochromators. The validity of the formulas commonly used to describe these instruments is estimated. A comparison with the results obtained via a numerical simulation based on the Monte Carlo method is performed.

Preliminary results of TEC measurements in Guwahati, India

A dual frequency GPS receiver was installed in Guwahati, India (latitude 26.2°N, longitude 91.75°E, dip +35°) in January 2006 in the framework of an Indian–Russian project of seismo-ionospheric effects searching and investigation. It is quite clear that manifestations of such effects should be strongly dependent (among others) on regional features of ionosphere. In our case formation of the equatorial anomaly will affect the results. So, the data of half a year of observations were analyzed to establish the behavior of Total Electron Content (TEC) in a region of Northern crest of the equatorial anomaly in quiet helio-geophysical conditions as a background for detecting the impact of effects from below.

Lattice dynamics and magneto-elastic coupling in Kondo-insulator YbB12

Lattice dynamics and magneto-elastic coupling effects have been studied in the Kondo insulator YbB12 by means of inelastic neutron scattering. The analysis of the phonon density of states, dispersion, and symmetry properties is presented in connection with a possible magneto-elastic coupling. Manifestation of such effects was found for the phonons corresponding to the vibrations of Yb atoms.

Immune Mechanisms in Pain Control

Immune Mechanisms in Pain Control

Speculations on Difference between Tricyclic and Selective Serotonin Reuptake Inhibitor Antidepressants on Their Cardiac Effects. Is There Any?

The cardiovascular effects and toxicity of tricyclic antidepressants (TCAs) have been well documented in medical literature. The most common manifestation of such effects is slowing of intraventricular conduction, manifested by prolonged PR, QRS and QT intervals on the standard electrocardiogram (ECG) and postural hypotension. In contrast to TCAs, selective serotonin reuptake inhibitors (SSRIs), including fluoxetine and citalopram, are considered to cause less effect on cardiac impulse conduction. In addition, these compounds induced significantly less anticholinergic, antihistaminergic and cardiotoxic side-effects than TCAs. However, there is an increasing number of case reports on dysrhythmias, like atrial fibrillation or bradycardia and syncope associated with fluoxetine and another SSRI treatment and overdose. Although such reports have not been common, they do raise concerns. In cardiac tissues isolated from canine, rabbit, rat and guinea pig hearts we have found that fluoxetine and citalopram inhibited cardiac Na+ and Ca2+ channels. These direct cardiac electrophysiological effects were similar to those of observed for tricyclic antidepressants clomipramine and imipramine. The inhibition of cardiac Ca2+ and Na+ channels by fluoxetine may explain most cardiac side-effects observed occasionally with the drug and mild but significant bradycardia reported during chronic treatment. Our results suggest that fluoxetine and citalopram may have antiarrhythmic (class I + IV type), as well as proarrhythmic properties (due to impairment of atrioventricular or intraventricular conduction and shortening of repolarization). Taking all these into consideration, in depressed patients having also severe cardiac disorders, ECG control may be suggested during fluoxetine and probable another SSRI therapy. The primary goal of this review is to compare these direct cardiac effects of fluoxetine and citalopram to those of previously reported for TCAs. This paper also summarizes the recently observed effects of fluoxetine apparently not related to the blockage of 5-HT transporter based on literature.

The influence of thermal activation on measured critical currents in HTC and conventional weak links

A simple model for thermally activated phase slippage has been used to determine the effect of thermal fluctuations on critical current measurements in HTC, conventional BCS, and HTC/BCS superconducting junctions. The most important manifestation of such effects is a decrease in the measured critical current, below the intrinsic critical current of the junction. This also leads to a depression of the measured critical temperature of the junction, below that of the superconducting materials forming the junction. It is shown that such effects are significant for HTC superconductors with junctions, whether fabricated or naturally occurring between grains, with intrinsic low temperature critical currents <3 mA. This is almost always the case for intergranular ceramic or thin film material. Measurements of the critical temperature as a function of junction strength for both Nb/Nb and YBCO/YBCO junctions are shown to be consistent with the predicted depression due to thermal fluctuations.

Theory of cellular solidification of binary alloys with applications to succinonitrile-salol

This paper offers a nonlocal equilibrium model for stable cell formation as an alternative to the standard but unsuccessful local equilibrium models. Recognizing from the observations that the morphology in steady state cellular solidification of alloy single crystals belongs to the family of Widmanstätten figures, a Zener-Hillert type model has been developed and applied to our experiments on succinonitrile-salol. In the inverse Widmanstätten pattern generated and observed under controlled boundary conditions the interface curvature is such that strong capillarity effects appear only at the trailing roots of the cells. Since the roots have dimensions ⪡ 1 μm the temperature-composition diagram possesses a sharp low temperature jog towards higher compositions. Thus, since neither the temperature nor liquid diffusion profiles can sustain a matching singularity, the liquid-solid interface cannot everywhere exist in local equilibrium. Concomitantly, there must exist stabilizing effects associated with crystallographic or kinetic anisotropy acting at the cell walls if these liquid-solid Widmanstätten figures are to be sustained. Manifestations of such effects are commonly observed. The liquid solute diffusion equation has accordingly been solved rigorously subject to the boundary conditions: (a) local equilibrium at the cell tip; (b) local equilibrium at the root modified by capillarity; (c) local mass balance over the entire interface, including the necessary effect of solid state diffusion behind the cell root (equivalent to diffusion in advance of a Widmanstätten tip): (d) average solid interface composition equal to the alloy composition X 0; (e) a parametric elliptic conic shape as an experimental constraint which compensates in large part for the lack of knowledge of the nonequilibrium interface states lying between the roots and tips. This solution algorithm automatically generates nonlocal equilibrium interface states lying between the roots and tips and yields a free boundary problem with two degrees of freedom which may be characterized by the cell length and cell spacing as order parameters. Alternative optimizations of the degenerate solutions via a minimum in the dissipation, a minimum in tip undercooling or a minimum in root radius yield quantitatively similar predictions. This is because all of these parameters are related in an approximately monotone fashion to the degree of liquid solute segregation from the tips to the roots of the cells. The theory together with optimization gives satisfactory predictions of experiments on two-dimensional cells including cell length, spacing and the critical supersaturation for onset of stable cells. This paper offers for the first time systematic observations on cell length and comparison with a theory which predicts this quantity.

Anisotropic size effects in semiconductors and semimetals

Large differences between the characteristic times of various electronic relaxation processes (momentum relaxation, energy relaxation, intervalley relaxation, electron-hole recombination) make it possible to divide carriers into groups between which relaxation is relatively slow. Each of the "long" relaxation times can be matched by a characteristic diffusion length which is much greater than the usual mean free path. Transport coefficients of such groups are generally anisotropic even in cubic crystals and the anisotropy varies from group to group (this anisotropy may be natural or it may be induced by pressure, magnetic field, etc.). Therefore, the passage of a current produces nonequilibrium carrier densities in such groups. The density gradients are oriented at right-angles to the current and they decay over distances of the order of the diffusion length. The effects associated with the formation of nonequilibrium carriers and the influence of their diffusion on the transport coefficients are referred to in the paper as the anisotropic size effects. The paper reviews experimental and theoretical investigations of various manifestations of such effects. An analysis is made of the size dependences of the electrical conductivity and magnetoresistance manifested in "thick" samples (thickness of the order of the diffusion length). Other topics considered include nonlinearity of the electrical conductivity in relatively weak fields, redistribution of carriers in "strong" fields (accompanied by giant changes in the total number of carriers and by formation of domains, depletion layers, and accumulation layers), influence of the anisotropic size effects on the skin effect (which changes the surface impedance of semimetals by an order of magnitude), and electromagnetic excitation of sound in semimetals.