70 research outputs found
Mesoscopic Phase Fluctuations: General Phenomenon in Condensed Matter
General conditions for the occurrence of mesoscopic phase fluctuations in
condensed matter are considered. The description of different thermodynamic
phases, which coexist as a mixture of mesoscopically separated regions, is
based on the {\it theory of heterophase fluctuations}. The spaces of states,
typical of the related phases, are characterized by {\it weighted Hilbert
spaces}. Several models illustrate the main features of heterophase condensed
matter.Comment: 23 pages, Latex, no figure
Mesoscopic Phase Separation in Anisotropic Superconductors
General properties of anisotropic superconductors with mesoscopic phase
separation are analysed. The main conclusions are as follows: Mesoscopic phase
separation can be thermodynamically stable only in the presence of repulsive
Coulomb interactions. Phase separation enables the appearance of
superconductivity in a heterophase sample even if it were impossible in
pure-phase matter. Phase separation is crucial for the occurrence of
superconductivity in bad conductors. Critical temperature for a mixture of
pairing symmetries is higher than the critical temperature related to any pure
gap-wave symmetry of this mixture. In bad conductors, the critical temperature
as a function of the superconductivity fraction has a bell shape. Phase
separation makes the single-particle energy dispersion softer. For planar
structures phase separation suppresses d-wave superconductivity and enhances
s-wave superconductivity. These features are in agreement with experiments for
cuprates.Comment: Revtex file, 25 pages, 2 figure
Heavy and light roles: myosin in the morphogenesis of the heart
Myosin is an essential component of cardiac muscle, from the onset of cardiogenesis through to the adult heart. Although traditionally known for its role in energy transduction and force development, recent studies
suggest that both myosin heavy-chain and myosin lightchain
proteins are required for a correctly formed heart.
Myosins are structural proteins that are not only expressed
from early stages of heart development, but when mutated
in humans they may give rise to congenital heart defects.
This review will discuss the roles of myosin, specifically
with regards to the developing heart. The expression of
each myosin protein will be described, and the effects that
altering expression has on the heart in embryogenesis in
different animal models will be discussed. The human
molecular genetics of the myosins will also be reviewed
Basics of Bose-Einstein Condensation
The review is devoted to the elucidation of the basic problems arising in the
theoretical investigation of systems with Bose-Einstein condensate.
Understanding these challenging problems is necessary for the correct
description of Bose-condensed systems. The principal problems considered in the
review are as follows: (i) What is the relation between Bose-Einstein
condensation and global gauge symmetry breaking? (ii) How to resolve the
Hohenberg-Martin dilemma of conserving versus gapless theories? (iii) How to
describe Bose-condensed systems in strong spatially random potentials? (iv)
Whether thermodynamically anomalous fluctuations in Bose systems are
admissible? (v) How to create nonground-state condensates? Detailed answers to
these questions are given in the review. As examples of nonequilibrium
condensates, three cases are described: coherent modes, turbulent superfluids,
and heterophase fluids.Comment: Review articl
Kinetics of laser-induced low-temperature crystallization of amorphous silicon
A brief report on experimental and theoretical studies of the kinetics of the laser-induced crystallization (LIC) in undoped amorphous hydrogenated silicon is presented. It is shown that the LIC occurs at a substantially lower temperature and occurs at this temperature much faster compared to the thermal crystallization in a furnace. A nanoscopic kinetic electron-related model of the LIC is presented. The model explains the experimental observations as the integral effect of a huge amount of nanoscale picosecond atomic and electronic reconstructions leading to more stable material states which are generated by electron-assisted short-lived (picosecond) large energy fluctuations in nanometer material regions. (C) 2002 American Institute of Physics
Low Temperature Nanoscopic Kinetics of Hydrogen Plasma-Enhanced Crystallization of a-Si:H Films
A nanoscopic kinetic model of controlled plasma-assisted microcrystallite formation (PAmuCF) of Si in pre deposited a-Si:H films at low temperatures is proposed. The model suggests mechanisms for enhancement of the Si crystallization in a-Si:H films at low temperatures by treatment of the films in plasma. The model reveals certain kinetic advantages of hydrogen plasmas for the formation of Si crystalline nuclei in a-Si:H compared to other plasmas (Ar plasma, etc.). These advantages make the hydrogen plasma substantially more efficient in the PAmuCF of Si in a-Si:H films. The proposed mechanism for PAmuCF of Si is associated with the formation on the surface of the a-Si:H film and in the adjacent nanometer material layer of nanoscale (picosecond) short-lived hot spots of high energy density (or effective temperature). The hot spots are generated in the material by energetic plasma ions of energy epsilon(is)=20-100 eV accelerated by the electrical field in the thin plasma layer near the solid surface. The hot spots promote Si crystallization in a-Si:H. It is shown how the plasma composition, energy, mass, and fluxes of the plasma ions impinging on the surface of the a-Si:H film determine the Si nucleation rate and density of Si microcrystallization. (C) 2003 American Institute of Physics
Kinetics of CW laser-induced low temperature crystallization of amorphous silicon
A brief report on experimental and theoretical studies of the kinetics of the laser-induced crystallization (LIC) in undoped amorphous hydrogenated silicon is presented. It is shown that the LIC occurs at a substantially lower temperature and occurs at this temperature much faster compared to the thermal crystallization in a furnace. A nanoscopic kinetic electron-related model of the LIC is presented. The model explains the experimental observations as the integral effect of a huge amount of nanoscale picosecond atomic and electronic reconstructions leading to more stable material states which are generated by electron-assisted short-lived (picosecond) large energy fluctuations in nanometer material regions. (C) 2002 American Institute of Physics
Comparison between the crystallization processes by laser and furnace annealing of pure and doped a-Si:H
A comparison between the annealing processes is made for undoped hydrogenated amorphous Si (a-Si:H), boron and phosphorus doped amorphous silicon. It is found that in all cases the crystallization onset in the furnace always occurs at higher temperature than for the laser-annealed material. The free-carrier phonon interaction shows up in furnace-annealed doped a-Si but is not seen in laser-annealed doped a-Si which has not been melted. The laser annealing crystallization before melting is never perfect, the size of microcrystals depends on the nature of the doping. The physical model which explains the experimental results is based on the existence of electron-assisted short-lived large energy fluctuations of Si atoms jumping from unstable positions in a-Si:H to more stable ones in crystalline materials. (C) 2002 Elsevier Science B.V. All rights reserved
Plants' ability to sense and respond to airborne sound is likely to be adaptive: reply to comment by Pyke et al.
- …