Electromechanical properties of Pb<Subscript>3</Subscript>Ga<Subscript>2</Subscript>Ge<Subscript>4</Subscript>O<Subscript>14</Subscript> piezoelectric crystals grown from solution in a melt

Single crystals of lead gallium germanate Pb₃Ga₂Ge₄O₁₄ are grown from their own solution melts. The propagation of bulk acoustic waves is investigated, and the elastic, piezoelectric, and dielectric constants are calculated. The temperature dependences of the dielectric constants of this compound are analyzed.     

Plasmon-induced terahertz absorption and photoconductivity in a grid-gated double-quantum-well structure

The terahertz absorption spectra of plasmon modes in a grid-gated double-quantum-well field-effect transistor structure is analyzed theoretically and numerically using the scattering matrix approach and is shown to faithfully reproduce strong resonant features of recent experimental observations of terahertz photo-conductivity in such a structure.     

The structure and phase composition of stabilized zirconia-based nanosystems exposed to shock-wave treatment

The special features of the structure and phase composition of nanocrystalline zirconia-based powders subjected to shock-wave treatment are studied. The investigations show that zirconia with small amounts of yttria and/or alumina is in nanocrystalline and quasi-amorphous states representing a nonequilibrium solid solution of ZrO2 (Y, Al) and that an increase in the monoclinic phase abundance is associated with a reduction in the critical size of tetragonal crystallites due to an accumulation of lattice microdistortions. The monoclinic phase in powders with yttria and alumina additions is not formed even with shock compression at pressures up to 20 GPa. This is attributed to the fact that the resultant lattice microdistortion level is inadequate to destabilize the nanocrystalline tetragonal phase. Relaxation of microdistortions on annealing causes the critical size of tetragonal crystallites to increase. As this takes place, the monoclinic phase is converted into the tetragonal one.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 61–70, September, 2004.     

Physical Interpretation of the Motion of a Laser Pulse within the Framework of the Four-Oscillator Model

A physical multidimensional local model of the propagation process of a laser pulse in air having no analogy to famous models in laser physics is constructed. It is based on the representations of classical wave mechanics characteristic of the theory of scalar wave fields.     

On the transmission rate of classical information through quantum communication channels

The coding of quantum communication channels in real time is considered as applied to the situation when information is coded into continuous quantum degrees of freedom (into the shape of the amplitude of quantum states with an arbitrary number of photons). It is shown that the nonlocalizability of states in quantum field theory requires that the identity of particles should be taken into account. This, together with the finiteness of the limit speed of propagation, leads to the fact that the formulas for the transmission rate of nonrelativistic communication channels have an asymptotic character; i.e., these formulas are formally valid only when the separation between messages is infinite (when the identity of particles can be neglected) and, hence, when the transmission rate in [bit/message s] is infinitely small. A real-time information capacity of a sequential relativistic quantum communication channel is obtained that takes into account the identity of particles for pure signal states with an arbitrary number of photons. An explicit analytic expression is obtained for the transmission rate of a quantum channel of finite bandwidth for one-photon input states.     

Investigation of clustering in light nuclei by means of relativistic-multifragmentation processes

New results concerning the topology of the fragmentation of relativistic nuclei ⁷Li and ¹⁰B are presented. A program is proposed for studying the cluster structure of stable and radioactive nuclei. The use of emulsions in the investigation of nuclear clustering in the fragmentation of light nuclei at energies are in excess of 1 GeV per nucleon is discussed.     

Photoinitiators with functional groups. VII. Covalently bonded camphorquinone—amines

Camphorquinone (CQ), a widely used photoinitiator (PI) in dental applications, was covalently bonded to aromatic amines to enhance the rate of electron and proton transfer effect due to the close vicinity of the diketone and the amine group. 10‐bromocamphorquinone and 10‐bromomethylcamphorquinone were selected as suitable precursors for esterification with the carboxyl group containing aromatic amines based on 4‐dimethylaminobenzoic acid. Properties of the new photoinitiating systems were investigated by UV spectroscopy and differential scanning photocalorimetry in lauryl acrylate. Compared to physical mixtures, in all cases similar or even better performance was obtained. Surprisingly, 10‐acetyl derivatives 7 – 9 and 18 especially, were found to be highly reactive. Compared to CQ/ethyl 4‐dimethylaminobenzoate, the rate of photopolymerization was increased by a factor of up to 2. Intramolecular reaction was confirmed by photo‐differential scanning calorimetry experiments with varying PI concentrations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4948–4963, 2004     

Atom transfer radical polymerization of methyl methacrylate by copper(I)‐pyridine‐2‐carboximidate catalysts

Pyridine‐2‐carboximidates [methyl ( 1a ), ethyl ( 1b ), isopropyl ( 1c ), cyclopentyl ( 1d ), cyclohexyl ( 1e ), n‐octyl ( 1f ), and benzyl ( 1g )] were prepared from the reaction of 2‐cyanopyridine with the corresponding alcohols. Cyclopentyl‐substituted 1d was found to be a highly effective ligand for copper‐catalyzed atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). For example, the observed rate constant for a CuBr/ 1d catalytic system was found to be nearly twice as high as the cyclohexyl‐substituted CuBr/ 1e catalytic system [k_obs = (1.19 vs 0.56) × 10^?4 s^?1). The effects of the solvents, temperature, catalyst/initiator, and solvent/monomer ratio on the ATRP of MMA were studied systematically for the CuBr/ 1d catalytic system. The optimum condition for the ATRP of MMA was found to be a 1:2:1:400 [CuBr]_o/[ 1d ]_o/[ethyl 2‐bromoisobutyrate]_o/[MMA]_o ratio at 60 °C in veratrole solution, which yielded well‐defined poly(MMA) with a narrow molecular weight distribution of 1.14. The catalytically active copper complex 2d was isolated from the reaction of CuBr with 1d . Narrow molecular weight distributions as low as 1.06 were achieved for the CuBr/ 1d catalytic system by employing 10% of the deactivator CuBr₂. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2747–2755, 2004     

Completely biodegradable composites of poly(propylene carbonate) and short,lignocellulose fiber Hildegardia populifolia

The composites of biodegradable poly(propylene carbonate) (PPC) reinforced with short Hildegardia populifolia natural fiber were prepared by melt mixing followed by compression molding. The mechanical properties, thermal properties, and morphologies of the composites were studied via static and dynamic mechanical measurements, thermogravimetric analysis, and scanning electron microscopy (SEM) techniques, respectively. Static tensile tests showed that the stiffness and tensile strength of the composites increased with an increasing fiber content. However, the elongation at break and the energy to break decreased dramatically with the addition of short fiber. The relationship between the experimental results and the compatibility or interaction between the PPC matrix and fiber was correlated. SEM observations indicated good interfacial contact between the short fiber and PPC matrix. Thermogravimetric analysis revealed that the introduction of short Hildegardia populifolia fiber led to a slightly improved thermooxidative stability of PPC. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 666–675, 2004