Effects Of Reorientation Research Articles

Solving Foreign Trade Puzzles in Post-Communist Transition

This article deals with the foreign trade of East-Central European countries in post-communist transition. It is primarily concerned with explaining certain early transition developments, unexpected and often neglected by policy makers and experts alike. The contribution of foreign trade to the generally unexpected steep output fall registered by each of these countries is discussed, stressing the inevitability of the disappearance of distorted demand patterns with the fall of communism and explaining why distorted demand was bound to affect not only the level of domestic output but also imports associated with the distorted demand. Exports to other former CMEA countries therefore fell precipitously. Other issues analysed in the article concern causes and beneficial effects of the rapid Westward reorientation of foreign trade, as well as the disappearance of another legacy of the communist past, East-Central European Countries', that is dual export structure.

Finite element analysis of cracks in ferroelectric ceramic materials

A constitutive law governing the behavior of ferroelectric ceramics is presented. The constitutive law includes the effects of ferroelectric and ferroelastic polarization reorientation. It is both multiaxial and non-proportional. This material model is implemented in a finite element code developed for this work. The material model determines changes of remanent strain and remanent polarization induced by the stress and electric field. The finite element code is used to analyze the effect of an elliptical hole in a ferroelectric plate. The effects of aspect ratio and ratio of the permittivity of the hole interior to that of the plate material are determined. As the ellipse shrinks to a crack, the electric field and stress concentrations increase. As the permittivity of the ellipse interior approaches that of the ferroelectric material, the electric field concentration diminishes. Ferroelectric and ferroelastic switching are shown to have a large effect on the magnitude of the field concentrations.

Effective drift velocities and effective diffusivities of swimming microorganisms in external flows.

In this note we calculate the effective drift velocities and the effective diffusivities of swimming microorganisms in an external flow field. It is shown that if the ambient velocity field is incompressible then the effects of reorientation of the cells can under certain circumstances enhance the effective drift velocity along the preferred direction.

Investigation of multiaxial molecular dynamics by [formula omitted] MAS NMR spectroscopy

The technique of 2 H MAS NMR spectroscopy is presented for the investigation of multiaxial molecular dynamics. To evaluate the effects of discrete random reorientation a Lie algebraic formalism based on the stochastic Liouville–von Neumann equation is developed. The solution to the stochastic Liouville–von Neumann equation is obtained both in the presence and absence of rf irradiation. This allows effects of molecular dynamics to be evaluated during rf pulses and extends the applicability of the formalism to arbitrary multiple pulse experiments. Theoretical methods are presented for the description of multiaxial dynamics with particular emphasis on the application of vector parameters to represent molecular rotations. Numerical time and powder integration algorithms are presented that are both efficient and easy to implement computationally. The applicability of 2 H MAS NMR spectroscopy for investigating molecular dynamics is evaluated from theoretical spectra. To demonstrate the potential of the technique the dynamics of thiourea– 2 H 4 is investigated experimentally. From a series of variable temperature MAS and quadrupole echo spectra it has been found that the dynamics can be described by composite rotation about the CS and CN bonds. Both experiments are sensitive to the fast CS rotation which is shown to be described by the Arrhenius parameters E CS=46.4±2.3 kJ mol −1 and ln( A CS)=32.6±0.9. The MAS experiment represents a significant improvement by simultaneously allowing the dynamics of the slow CN rotation to be fully characterized in terms of E CN=56.3±3.4 kJ mol −1 and ln( A CN)=25.3±1.1.

Effects of reorientation of molecules in a nonlinear-optical photoconducting polymer on formation of an antiguide structure

When the poled nonlinear-optical photoconducting polymer is irradiated by the pump light, the generated space charges screen the poling electric field and induce reorientation of the nonlinear-optical molecules. It results in reduction of refractive indices and of a nonlinear-optical coefficient of the polymer. Due to the former reduction, the antiguide structure is so made as to confine the leaky lightwaves. We confirmed the reduction by observing the second-harmonic generation from the pump-irradiated polymer and compared the self enhancement of the Cerenkov-radiation type second-harmonic power generated from a thin-film waveguide.

Spin dynamics calculations of electron and nuclear spin relaxation times in paramagnetic solutions

Spin dynamics (SD) methods have been developed to compute NMR paramagnetic relaxation enhancements (NMR-PRE) produced by solutes with electron spin S⩾1 in solution. The spin dynamics algorithms, which are implemented as the computer program SpinDyn.f, are similar in spirit to molecular dynamics calculations in statistical mechanics, except that the spin motion is propagated numerically in time using quantum mechanical equations of motion of the spin operators, rather than Newtonian equations of motion of the molecular degrees of freedom as in MD simulations. SD simulations as implemented in SpinDyn.f provide accurate, flexible, and rapid calculations of NMR-PRE phenomena with few of the assumptions or limitations of previous analytical theories. The program calculates inter- and intramolecular NMR-PRE phenomena for both integer and half-integer spin systems processing under arbitrary Zeeman and zfs Hamiltonians in the presence of Brownian reorientation. Isotropic Brownian reorientation is simulated by means of a finite-step algorithm with adjustable step size. Simulations computed by SpinDyn.f have been used in a systematic study aimed at better understanding the influence of Brownian reorientation on the NMR-PRE of an S=1 ion in a non-Zeeman-limit physical situation. Conditions required for the validity of zfs-limit analytical theory are given. SpinDyn.f has also been used to assess quantitatively the effects of molecular reorientation on a prior analysis of NMR-PRE data for the model S=2 complex ion [tris-(acetylacetonato)manganese(III)] in acetone solution; this system was found to be well described by zfs-limit analytical theory.

Effect of axial ligand plane reorientation on electronic and electrochemical properties observed in the A67V mutant of rat cytochrome b5.

Mutational studies directed at evaluating the effect of the axial ligand plane orientation on electrochemical properties of cytochrome b5 have been performed. As described in the previous paper, structural consequences of one of these mutations, the A67V mutation, have been evaluated using NMR solution methods. The lack of large shifts relative to the wild-type protein in both the imidazole Ndelta nitrogen and proton resonances of the H63 imidazole ring indicates that the hydrogen bond between the carbonyl of F58 and the imidazole ring of H63 remains intact in this mutant. Effects of the imidazole plane reorientation on the Fe d-orbitals were evaluated on the basis of interpretation of EPR spectra, near-infrared bands associated with ligand-to-metal charge transfer transitions, reorientation of the anisotropy of the paramagnetic center determined by calculation of pseudocontact shifts, and the temperature dependence of the contact-shifted resonances. The dominant effect of the imidazole reorientation appears to have been a destabilization of the d(xz) orbital energy and a reorientation of the d(pi) orbitals. This is surprising in light of the -20 mV shift in the reduction potential of the mutant relative to the wild-type protein and indicates that a destabilization of d(yz)-orbital energy level of the reduced state dictates the observed change in reduction potential. Measured values for the reorganizational energy and heterogeneous electron transfer rates were indistinguishable for wild-type and mutant proteins. This is perhaps surprising, given significant differences in the pattern of electron delocalization into the porphyrin ring observed as significantly altered contact shift patterns. Mutational studies perturbing the H39 imidazole were also performed but with more limited success.

Solvent and nuclear dynamic effects on intermolecular electron transfer

An ultrafast intermolecular electron transfer (ET) from electron donating solvent to an excited dye molecule was found. A temperature-dependent non-exponential time dependence was observed in aniline, and a temperature-independent single exponential process for Nile blue (160 fs) and oxazine 1 (260 fs) was observed in N,N-dimethylaniline. The solvation times of solvent anilines were obtained by dynamic Stokes shift measurements. The rate of ET in some systems was observed to be much greater than the solvation time of anilines. The dynamic behavior was simulated by the 2-dimensional potential energy surface for reaction, taking into account of the effects of both solvent reorientation and nuclear motion of reactants.

Solvent and nuclear dynamics in ultrafast intermolecular electron transfer in a diffusionless, weakly polar system

Femtosecond intermolecular electron (ET) transfer dynamics were studied by time-resolved fluorescence up-conversion technique in contact systems of oxazine dyes in electron-donating solvents. Clearly non-exponential ET time dependence was observed in aniline and explained by the effects of both solvent reorientation and nuclear motion of the reactants. Single exponential processes were measured for nile blue (⩽160 fs) and oxazine 1 (⩽280 fs) in N,N-dimethylaniline. The rate of ET is explained to be limited only by ultrafast nuclear relaxation.

Experimental results on phase transitions in betaine compounds

Abstract Phase transitions in betaine compounds are reviewed. Some topics are selected for detailed presentation: Effects of reorientation and frustration in the (BA - DBA)-system and the (BA - BP)-system are touched. The (p, T)-phase diagram of BCCD and its relation to the ANNNI- model is discussed at some length. Recent ESR- and NMR- experiments in BCCD are also mentioned.

Elasto-Plastic Behavior of K0-Consolidated Clay in Torsion Shear Tests

A series of torsion shear tests was performed along various stress-paths on hollow cylinder specimens of K 0 -consolidated clay to investigate the influence of rotation of principal stresses on the stress-strain and strength characteristics. The effects of stress-paths and reorientation of principal stresses were mainly observed in the prefailure stress-strain behavior. The experimentally obtained failure surface from torsion shear tests could practically be modeled by an isotropic failure criterion. Coupling effects between stresses and strains were observed when torsion shear and vertical normal stresses were applied. The work-space for torsion shear tests was illustrated, and the relation between stresses and strain increments was also studied in the work-space.

High-field magnetic properties of hot compacted extruded REFeB magnets

Magnetic properties of hot compacted extruded (Nd,Dy) 15Fe 79B 6 magnets were investigated between 4.2 and 273 K, in fields up to 90 kOe. The effects of the spin reorientation were much more pronounced in extruded REFeB than in the conventional sintered magnets. A model, based on a two-dimensional isotropic magnetization, is proposed to explain the magnetic behavior above and below the spin reorientation temperature, T sr .

Spin reorientation in melt-spun neodymium-iron-boron ribbons

Effects of the spin reorientation in Nd2Fe14B below Ts =135 K on the hard magnetic properties of melt-spun Nd-Fe-B ribbons are reported. As the ribbons are cooled from room temperature, the shape of the second quadrant demagnetization curve is maintained down to 150 K, with an intrinsic coercivity Hci which increases steadily from 14 to 24 kOe. As the magnetic structure of Nd2 Fe14 B changes from easy axis to easy cone below 135 K, however, demagnetization occurs in two steps, with a large decrease in magnetization at low reverse field followed by a second sharp drop at higher field. The size of the initial drop correlates well with the canting angle of the cone and is consistent with having little or no resistance to rotation of the magnetization along the cone. This effect artificially suppresses Hci , which decreases to 23 kOe at 5 K. Magnetization reversal from one easy cone to the opposite cone remains a hard process, and its effective coercivity is estimated to be 42 kOe at 5 K. The first quadrant magnetization is much closer to full saturation at low fields due to the improved net alignment of the moments. In thermomagnetic scans this appears as a large increase in magnetization as the sample cools through Ts at constant field. The observed behavior agrees with that predicted by the known easy cone structure of Nd2 Fe14 B below Ts .

Finite Deformation and Nonlinear Elastic Behavior of Flexible Composites

The flexible composites discussed in this paper are composed of continuous fibers in an elastomeric matrix. The usable range of deformation of these composites is much larger than that of conventional rigid composites. Due to the material as well as geometric factors, the stress-strain relations for these composites are generally nonlinear under finite deformations. A constitutive model has been developed based upon the Eulerian description. The material nonlinear stress-strain relation is derived by using the stress energy density referring to the deformed volume. The stretching-shear coupling and the effects of the in-plane reorientation of fibers are also considered in the theoretical analysis. Comparisons are made between predictions of the present theory and experimental data for tirecord/rubber and Kevlar/silicone-elastomer flexible composite laminae; very good correlations have been found.

Angular Dependence of Blue Phase Selective Reflection in the Electric Field

Abstract The angular dependence of the selective reflection peaks has been investigated for BP1 and BP2 as well as for non-cubic BP-structures occurring in the electric field. Although at normal light incidence the ratios of the wavelengths of reflection bands are known to fit in a Bragg condition, we found that the angular dependence behaves non-Bragg-like, i.e. certain reflection peaks are shifted to longer wavelengths with increasing angle of reflection. The angular dependence can be used to distinguish between the effects of deformation, reorientation and phase transitions occurring under the influence of the electric field.

Electrosorption from multicomponent liquid systems with particular regard to ternary solutions—I. The influence of ionic co-adsorption and the effects of reorientation of adsorbate

A theory is presented to describe the electrosorption from a three component system Mathematical formalism can be easily extended to describe electrosorption from a multicomponent system. The theory allows us also to describe the problem of reorientation of adsorbate inside of the double layer. The influence of reorientation equilibrium constant onto electrosorption isotherm has been demonstrated. Besides, sampled investigations of the effects of molecular size and particle-particle interactions have been performed. The possibilities of a phase separation and a phase transition inside of the double layer have been tentatively indicated. The role of the electrochemical free energy of mixing of surface solution has been briefly discussed.

Helicoidal orientation of cellulose microfibrils in Nitella opaca internode cells: ultrastructure and computed theoretical effects of strain reorientation during wall growth

The ultrastructure of the mature internode cell wall of Nitella opaca is described. It is interpreted in terms of a helicoidal array of cellulose microfibrils set in a matrix. A helicoid is a multiple 'plywood' made up of layers of parallel microfibrils. There is a progressive change in direction from ply to ply, giving rise to characteristic arced patterns in oblique sections. A critical tilting test, using an electron microscope fitted with a goniometric stage, showed the expected reversal of direction of the arced pattern. Nitella cell wall is thus more regularly structured than previous studies have shown. From a survey of the cell-wall literature, we show that such arced patterns are common. This indicates that the helicoidal structure may be more widespread than is generally realised, although numerous other cell walls show no signs of it. Nevertheless, there are examples in most major plant taxa, and in several types of cells, including wood tracheids. Most of the examples, however, need confirmation by tilting evidence. There are possible implications for wall morphogenesis. Helicoidal cell walls might arise by selfassembly via a liquid crystalline phase, since it is known that the cholesteric state is itself helicoidal. A computer graphics programme has been developed to plot the expected effects of growth strain on the patterns in oblique sections of helicoids with various original angles between consecutive layers. Herringbone patterns typical of crossed polylamellate texture can be generated in this way, indicating a possible mode of their formation.

A systematic semi-microscopic analysis of the scattering of oxygen isotopes

A semi-microscopic theory for the scattering of nuclei near closed shells is discussed in detail and applied to the bulk of the presently available experimental data. The results generally indicate that the single-folding model can be used to extrapolate the effective interactions for heavy-ion scattering away from closed-shell systems. We particularly discuss the importance of the imaginary part of the valence interaction and the effects of higher-order reorientation and two-step transfer processes.

2-(Aminomethyl)phenols, a new class of saluretic agents. 3. Effects of functional group reorientation and modification.

A series of modified 2-(aminomethyl)phenols was synthesized and tested orally in rats for saluretic and diuretic effects. Intravenous dog data are included as supplementary material to show that the diuretic responses, or lack thereof, may be obtained in a second species. Reorientation of the 2-(aminomethyl) group either meta or para to the hydroxyl substituent resulted in loss of diuretic effects. Similarly, replacement of either the phenolic hydroxyl or the aminomethyl group with other functional moieties substantially diminished saluretic effects.

Electroreflectance in SbSI

The electroreflectance (ER) of SbSI has been measured in a wide temperature range between 1.6 and 3.3 eV with linearly polarized light. The technique of transverse ER was used and the first and second harmonics of ER were measured simultaneously. The effects of domain reorientation, complementary light illumination, the specimen damping and electric field vector rotation on the sample surface are investigated. It is shown: (a) that the induced reflectivity change is not caused by purely Kern-Harbeke-effect, but depends on the piezoelectric strain; (b) that separated from the deformation component, the ER spectrum is close to the λ-modulation spectrum and may be interpreted in a similar way.