44,423 research outputs found
Optical studies of carrier and phonon dynamics in Ga_{1-x}Mn_{x}As
We present a time-resolved optical study of the dynamics of carriers and
phonons in Ga_{1-x}Mn_{x}As layers for a series of Mn and hole concentrations.
While band filling is the dominant effect in transient optical absorption in
low-temperature-grown (LT) GaAs, band gap renormalization effects become
important with increasing Mn concentration in Ga_{1-x}Mn_{x}As, as inferred
from the sign of the absorption change. We also report direct observation on
lattice vibrations in Ga1-xMnxAs layers via reflective electro-optic sampling
technique. The data show increasingly fast dephasing of LO phonon oscillations
for samples with increasing Mn and hole concentration, which can be understood
in term of phonon scattering by the holes.Comment: 13 pages, 3 figures replaced Fig.1 after finding a mistake in
previous versio
Self-organizing, two-temperature Ising model describing human segregation
A two-temperature Ising-Schelling model is introduced and studied for
describing human segregation. The self-organized Ising model with Glauber
kinetics simulated by M\"uller et al. exhibits a phase transition between
segregated and mixed phases mimicking the change of tolerance (local
temperature) of individuals. The effect of external noise is considered here as
a second temperature added to the decision of individuals who consider change
of accommodation. A numerical evidence is presented for a discontinuous phase
transition of the magnetization.Comment: 5 pages, 4 page
Molecular factors in human implantation: adhesion molecules, proteases and cytokines
Successful human reproduction remains an enigma, but this is slowly changing in the current era of expanding scientific knowledge. The discovery of various molecular factors such as adhesion molecules, proteases and cytokines have in recent years been at the forefront of medical research. The growing importance of immunology in particular has led to novel new immuno-modulatory therapies and increasing research into this new aspect of reproductive immunology may well prove to be the most important breakthrough in understanding the fundamentals of human reproduction. Implantation represents the first step in the complex interactions and processes involved in foetal-maternal interaction, which continues throughout pregnancy gestation and culminates in the birth of an infant. It is therefore vital that we understand the myriad processes controlling implantation in order to build a firm foundation for exploring reproductive immunology research in the new millennium. This review brings together and presents an overview of the potential roles of currently known molecular factors such as adhesion molecules, proteases, cytokines and its interaction with the maternal immune response, incorporating the findings of previous published research performed by the author on cytokines and reproductive immunology
Enhancement of plasticity in Ti-based metallic glass matrix composites by controlling characteristic and volume fraction of primary phase
In this study, Ti-based metallic glass matrix composites with high plasticity have been developed by controlling characteristic and volume fraction of primary phase embedded in the glass matrix. By careful alloy design procedure, the compositions of ß/glass phases, which are in metastable equilibrium have been properly selected, therefore the mechanical properties can be tailored by selecting the alloy compositions between the composition of ß and glass phases. The relation between the compressive yield strength and volume fraction of ß phase is well described using the rule of mixtures
Vibrations of closed-shell Lennard-Jones icosahedral and cuboctahedral clusters and their effect on the cluster ground state energy
Vibrational spectra of closed shell Lennard-Jones icosahedral and
cuboctahedral clusters are calculated for shell numbers between 2 and 9.
Evolution of the vibrational density of states with the cluster shell number is
examined and differences between icosahedral and cuboctahedral clusters
described. This enabled a quantum calculation of quantum ground state energies
of the clusters in the quasiharmonic approximation and a comparison of the
differences between the two types of clusters. It is demonstrated that in the
quantum treatment, the closed shell icosahedral clusters binding energies
differ from those of cuboctahedral clusters more than is the case in classical
treatment
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