94 research outputs found
Dark Matter Halo Mergers I: Dependence on Environment & Redshift Evolution
This paper presents a study of the specific merger rate as a function of
group membership, local environment, and redshift in a very large, , cosmological N-body simulation, the \textit{Millennium Simulation}. The
goal is to provide environmental diagnostics of major merger populations in
order to test simulations against observations and provide further constraints
on major merger driven galaxy evolution scenarios. A halo sample is defined
using the maximum circular velocity, which is both well defined for subhalos
and closely correlated with galaxy luminosity. Subhalos, including the
precursors of major mergers, are severely tidally stripped. Major mergers
between subhalos are therefore extremely rare. Tidal stripping also suppresses
dynamical friction, resulting in long major merger time scales when the more
massive halo does not host other subhalos. In contrast, when other subhalos are
present major merger time scales are several times shorter. This enhancement is
likely due to inelastic unbound collisions between subhalos. Following these
results, we predict that major mergers in group environments are dominated by
mergers involving the central galaxy, that the specific merger rate is
suppressed in groups, and that the frequency of fainter companions is enhanced
for mergers and their remnants. We also observe an `assembly bias' in the major
merger rate in that mergers of galaxy-like halos are slightly suppressed in
overdense environments while mergers of group-like halos are slightly enhanced.
A dynamical explanation for this trend is advanced which calls on both tidal
effects and interactions between bound halos beyond the virial radii of locally
dynamically dominant halos.Comment: 44 pages, 8 figures, Preprint Submitted to Ap
Spectral and Transport Properties of d-Wave Superconductors With Strong Impurities
One of the remarkable features of disordered d-wave superconductors is strong
sensitivity of long range properties to the microscopic realization of the
disorder potential. Particularly rich phenomenology is observed for the --
experimentally relevant -- case of dilute distributions of isolated impurity
centers. Building on earlier diagrammatic analyses, the present paper derives
and analyses a low energy effective field theory of this system. Specifically,
the results of previous diagrammatic T-matrix approaches are extended into the
perturbatively inaccessible low energy regimes, and the long range (thermal)
transport behaviour of the system is discussed. It turns out that in the
extreme case of a half-filled tight binding band and infinitely strong
impurities (impurities at the unitary limit), the system is in a delocalized
phase.Comment: 14 pages, two figures include
Transition from localized to extended eigenstates in the ensemble of power-law random banded matrices
We study statistical properties of the ensemble of large random
matrices whose entries decrease in a power-law fashion
. Mapping the problem onto a nonlinear
model with non-local interaction, we find a transition from localized
to extended states at . At this critical value of the system
exhibits multifractality and spectral statistics intermediate between the
Wigner-Dyson and Poisson one. These features are reminiscent of those typical
for the mobility edge of disordered conductors. We find a continuous set of
critical theories at , parametrized by the value of the coupling
constant of the model. At all states are expected to be
localized with integrable power-law tails. At the same time, for
the wave packet spreading at short time scale is superdiffusive: , which leads to a modification of the
Altshuler-Shklovskii behavior of the spectral correlation function. At
the statistical properties of eigenstates are similar to those
in a metallic sample in dimensions. Finally, the region
is equivalent to the corresponding Gaussian ensemble of random
matrices . The theoretical predictions are compared with results of
numerical simulations.Comment: 19 pages REVTEX, 4 figure
The evolution of substructure II: linking dynamics to environment
We present results from a series of high-resolution N-body simulations that
focus on the formation and evolution of eight dark matter halos, each of order
a million particles within the virial radius. We follow the time evolution of
hundreds of satellite galaxies with unprecedented time resolution, relating
their physical properties to the differing halo environmental conditions. The
self-consistent cosmological framework in which our analysis was undertaken
allows us to explore satellite disruption within live host potentials, a
natural complement to earlier work conducted within static potentials. Our host
halos were chosen to sample a variety of formation histories, ages, and
triaxialities; despite their obvious differences, we find striking similarities
within the associated substructure populations. Namely, all satellite orbits
follow nearly the same eccentricity distribution with a correlation between
eccentricity and pericentre. We also find that the destruction rate of the
substructure population is nearly independent of the mass, age, and triaxiality
of the host halo. There are, however, subtle differences in the velocity
anisotropy of the satellite distribution. We find that the local velocity bias
at all radii is greater than unity for all halos and this increases as we move
closer to the halo centre, where it varies from 1.1 to 1.4. For the global
velocity bias we find a small but slightly positive bias, although when we
restrict the global velocity bias calculation to satellites that have had at
least one orbit, the bias is essentially removed.Comment: 14 pages, 14 figures, MNRAS in pres
Diffusion in a Random Velocity Field: Spectral Properties of a Non-Hermitian Fokker-Planck Operator
We study spectral properties of the Fokker-Planck operator that describes
particles diffusing in a quenched random velocity field. This random operator
is non-Hermitian and has eigenvalues occupying a finite area in the complex
plane. We calculate the eigenvalue density and averaged one-particle Green's
function, for weak disorder and dimension d>2. We relate our results to the
time-evolution of particle density, and compare them with numerical
simulations.Comment: 4 pages, 2 figure
Random Dirac Fermions and Non-Hermitian Quantum Mechanics
We study the influence of a strong imaginary vector potential on the quantum
mechanics of particles confined to a two-dimensional plane and propagating in a
random impurity potential. We show that the wavefunctions of the non-Hermitian
operator can be obtained as the solution to a two-dimensional Dirac equation in
the presence of a random gauge field. Consequences for the localization
properties and the critical nature of the states are discussed.Comment: 5 pages, Latex, 1 figure, version published in PR
Freezing of dynamical exponents in low dimensional random media
A particle in a random potential with logarithmic correlations in dimensions
is shown to undergo a dynamical transition at . In
exact results demonstrate that , the static glass transition
temperature, and that the dynamical exponent changes from at high temperature to in the glass phase. The same
formulae are argued to hold in . Dynamical freezing is also predicted in
the 2D random gauge XY model and related systems. In a mapping between
dynamics and statics is unveiled and freezing involves barriers as well as
valleys. Anomalous scaling occurs in the creep dynamics.Comment: 5 pages, 2 figures, RevTe
Statistics of delay times in mesoscopic systems as a manifestation of eigenfunction fluctuations
We reveal a general explicit relation between the statistics of delay times
in one-channel reflection from a mesoscopic sample of any spatial dimension and
the statistics of the eigenfunction intensities in its closed counterpart. This
opens a possibility to use experimentally measurable delay times as a sensitive
probe of eigenfunction fluctuations. For the particular case of quasi-one
dimensional geometry of the sample we use an alternative technique to derive
the probability density of partial delay times for any number of open channels.Comment: 12 pages; published version with updated reference
Approaches to Educational Programs Modeling, Design and Implementation for Continuous Training of Various Experts
This article describes an approach to model, construct and implement multilevel system of continuous educational programs. The training content is determined by the system of generalized professional competencies. The educational levels correspond to the competency levels. The multilevel system includes five educational levels: primary professional training programs (perhaps at high school), secondary vocational programs (which are transformed into applied bachelor programs), bachelor programs, master programs, and postgraduate programs. This multi-level educational system may be implemented effectively using the fractal model of regional educational structures. The fractal model is based on self-similarity, self-organization and self-development. This implemented educational system makes possible to use individual learning tracks both in one educational program and during the transition between educational levels.
DOI: 10.5901/mjss.2015.v6n2s3p14
Association of the HTR2A T102C SNP with Weight Gain and Changes in Biochemical Markers in Patients Receiving Antipsychotics
The purpose of our research was to study the association of the HTR2A T102C (rs6313) SNP with anthropometric and biochemical markers in patients treated with typical and atypical antipsychotics in monotherapy mode.
Materials and methods: One hundred and seventeen white inpatients (95 men and 22 women) with F2 disorders (ICD-10, 1995) were enrolled in the study. All patients were divided into two groups by the antipsychotic class with which they were treated (Group 1 included 40 patients treated with typical antipsychotics; Group 2 included 77 patients treated with atypical antipsychotics) and two subgroups by weight change criteria during the study (Subgroup 1 included patients with weight change >6%; Subgroup 2 included patients with weight change <6%). The following examinations were performed: physical examination, anthropometric measurements (BMI. WC, TC), clinical examination, blood test (ALT, AST, FPG, VLDL-C, LDL-C, HDL-C, total cholesterol, triglycerides, total protein, albumin, creatinine, uric acid, carbamide), and genotyping for the HTR2A T102C (rs6313) SNP.
Results: There were no statistically significant differences in the distribution of genotypes of the HTR2A T102C (rs6313) SNP between Group 1 and Group 2 (P>0.05). Kruskal-Wallis one-way analysis of variance between subgroups showed statistically significant differences between carbamide levels in the second visit in Group 2 (P=0.02). A Dunn post hoc test with Bonferroni adjustment showed statistically significant differences between TT and CT genotypes of the HTR2A T102C SNP: carbamide level was greater in TT carriers (P=0.02). The strength of associations and risks between alleles of the HTR2A T102C SNP and antipsychotic-induced weight change were as follows: ORC=0.49; CIC [0.25; 0.95]; RRC=0.58 CIC [0.35; 0.97]; ORT=2.03; CIT [1.05; 3.94]; RRT=1.7 CIT [1.02; 2.81].
Conclusion: Our results of the pilot pharmacogenetic studies show an association of the T allele carriage of the HTR2A T102C SNP with risk of antipsychotic-induced weight gain. The continuation of this study and an increase in the sample size will allow establishing valid pharmacogenetic markers for the risk of antipsychotic-induced weight gain
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