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Outline of a variational formulation of zone-plate theory

Transmission zone plates composed of materials describable by the complex index of refraction n^[n^=(1-δ)+ik] modulate both the amplitude and the phase of the light passing through them. In this paper, a general variational approach to the design of zone-plate profiles that maximize system transfer functions, such as…

Structure, spectra, and stability of solid bismuth carbonates

A previously unreported basic bismuth carbonate, (Bi0)4(0H)2C03, has been identified as an intermediate product in the interconversion of a-BiZ03 and synthetic bismutite, (BiO)?CO,, in aqueous carbonate solutions. It has a narrow stability field, between C 0 2 partial pressures of 10-55".0 Pa and IO-' .""' Pa, in the…

Photosensitive Dihydroazulenes with Chromogenic Properties

Even daylight effects the rearrangement of dihydroazulene 1 into 8-vinylheptafulvene 2; thermally, the reaction proceeds in the reverse direction. The behavior of 1 is largely determined by the residue R. The reaction cycle could find application in the storage of information.

The pi-Cell: A Fast Liquid-Crystal Optical-Switching Device

A new approach is given for obtaining fast electro-optical response and good angular-viewing characteristics in a liquid-crystal variable-retardation device. The improved characteristics make the new device well suited for use in field-sequential color systems.

Continuum Theory for Strain‐Softening

In heterogeneous materials such as concretes or rocks, failure occurs by progressive distributed damage during which the material exhibits strain‐softening, i.e., a gradual decline of stress at increasing strain. It is shown that strain‐softening which is stable within finite‐size regions and leads to a nonzero energy…

Anharmonicity of phonons in crystalline naphthalene

Neutron inelastic scattering experiments have been carried out to measure the phonon energies of deuterated naphthalene C 10 D 8 for the lowest 12 dispersion branches along ( xi 00) and (00 xi ) directions at various temperatures ranging from 6 to 300K. Using measured mode Gruneisen parameters the quasiharmonic shifts…

Collision integral for elastic scattering of electrons and phonons

The form of the collision integral describing elastic scattering of electrons and phonons by crystal defects is discussed once again. It is shown that in the absence of detailed balance for the transition probability (Wkk' ≠ Wk'k), the collision integral does not contain Fermi or Bose factors (1nk) contrary to the poi…

Structural Disorder and Mechanochemical Reactions in Solids

The present review is devoted to an analysis of the relationship between the changes in the structure and reactivity of solids, brought about by the development of a deformation. It has been shown that the principal regular features of mechanochemical transformations are determined by the extent of the structural diso…

Dynamics of supercooled liquids and the glass transition

Closed nonlinear equations are derived for a self-consistent treatment of density propagation, self-diffusion and current relaxation in a classical monatomic fluid. The solution for a hard-sphere model system brings out a phase transition to a glass at the packing fraction 0.516. Approaching the transition from the gl…

Nematic-Smectic-A-Smectic-CMulticritical Point in a Single-Component System

The first observation of the nematic-smectic-$A$-smectic-$C$ multicritical point in a single-component liquid-crystal system is reported. High-resolution pressure-temperature data are presented, which support the view that the phase diagram is universal near the nematic-smectic-$A$-smectic-$C$ point.

Shear Modulus and Specific Heat of the Liquid-Crystal Blue Phases

We report high-precision measurements of the shear modulus, viscosity, and specific heat of cholesteryl nonanoate through its blue phases (BPI-BPIII). For BPI and BPII we find a shear modulus which remains finite as the frequency approaches zero, indicating that they are viscoelastic solids. We find that the cholester…

Pattern Selection in Dendritic Solidification

We show that the dynamically selected velocity and tip radius of dendrites in the boundary-layer model of solidification have the special values which permit the existence of steady-state needle-crystal solutions. This result, in conjunction with considerations of stability, provides new insight concerning the validit…

Jump-like deformation and stability of the hardened and structural states of zinc single crystals with forest dislocations in the temperature range 293 to 4.2 K

Plastic deformation and stability are investigated of the hardened and structural states of zinc single crystals with forest dislocations in the system {1122} 〈1123〉 by shearing in the slip system (0001) [2110]. It is found that at 293 and 77 K plastic deformation in such single crystals has a pronounced jump-like nat…

Bragg-Laue diffraction in inclined geometry

On the basis of the dynamical theory a new geometry of X-ray diffraction is suggested and analyzed in detail. Diffraction scattering occurs from the planes deviated by several degrees from the surface normal, the incident and diffracted beams forming small glancing angles with the surface. It is shown that the asymmet…

Pure and Nd3+-doped Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 single crystals, their structure, optical, spectral luminescence, electromechanical properties, and stimulated emission

Structure peculiarities and disorderness of trigonal Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 crystals are considered. Absorption and luminescence characteristics and stimulated emission parameters of Nd3+ ions in said compounds are investigated. The luminescence intensity parameters of the activator are analyzed and the cross-s…

Transverse magnetoresistance and thermopower in metals

The transport equation is solved for a quantum-mechanical system in a transverse magnetic field. The solution gives the linear transport coefficients for electrostatic fields and temperature gradients for electrons in metals. In term of a small expansion parameter, the solution to lowest order confirms the existing se…

On continuous distributions of dislocations in nonlocal elasticity

A linear, nonlocal continuum theory of dislocations is developed. The field equations are given for the dislocation density and the stress field due to continuous distribution of dislocations. Green’s functions are obtained for two- and three-dimensional media and an integral formula is given for line distribution of…

Effect of temperature-dependent energy-level shifts on a semiconductor's Peltier heat

The Peltier heat of a charge carrier in a semiconductor is calculated for the situation in which the electronic energy levels are temperature dependent. The temperature dependences of the electronic energy levels, generally observed optically, arise from their dependences on the vibrational energy of the lattice (e.g.…

Structural and magnetic properties of a copper–amino acid salt: Copper (II) bis (α-amino isobutyrato)

The copper salt of the amino acid α-amino isobutyric acid was synthesized and the crystal structure was determined by x-ray techniques. The crystals are monoclinic, space group P21/c (Z=2) with a=10.470(3) Å, b=5.335(1) Å, c=10.201(3) Å, and β=115.6(2)°. The magnetic susceptibility, measured between 1.4 and 12 K, show…