1,937 research outputs found
Rotational Corrections to in the NJL Model and Charge Conjugation
We show that the rotational corrections to , derived using the
semiclassical quantization scheme in the NJL model, possess correct properties
under charge conjugation.Comment: 4 pages, revtex, no figures, final version published in
Phys.Rev.C52(1995)42
Conformational effects on the Circular Dichroism of Human Carbonic Anhydrase II: a multilevel computational study
Circular Dichroism (CD) spectroscopy is a powerful method for investigating conformational changes in proteins and therefore has numerous applications in structural and molecular biology. Here a computational investigation of the CD spectrum of the Human Carbonic Anhydrase II (HCAII), with main focus on the near-UV CD spectra of the wild-type enzyme and it seven tryptophan mutant forms, is presented and compared to experimental studies. Multilevel computational methods (Molecular Dynamics, Semiempirical Quantum Mechanics, Time-Dependent Density Functional Theory) were applied in order to gain insight into the mechanisms of interaction between the aromatic chromophores within the protein environment and understand how the conformational flexibility of the protein influences these mechanisms. The analysis suggests that combining CD semi empirical calculations, crystal structures and molecular dynamics (MD) could help in achieving a better agreement between the computed and experimental protein spectra and provide some unique insight into the dynamic nature of the mechanisms of chromophore interactions
RECURRENCES OF ТYPHUS FEVER
During recent years in our country а sharp decrease is observed in the incidence rаtе of typhus fever, typhoid fever, malaria, diphtheria, anthrax, etc. We аге now about to eradicate typhus fever as an infectious disease in our countгy. Thanks to the incessant and rapid improvement of the economic and cultural standard of our people and the continuous improvement of the medical services, there exists the actual possibility to eradicate this disease in the next few years.For these reasons for the present there are а number of particularities in the epidemiology and the clinical picture of typhus fever: sporadic nature of the disease; lack of louse infestation in the focus of infection and in the patient; difficulties in the detection of the source of infection; lack of seasonal determination; а milder clinical course of the disease and very low mortality гates; involvement almost exclusively of adults; difficulties in detection of Rickettsia Prowazeki in the patient's blооd
Thermodynamics of Coherent Structures near Phase Transitions
Phase transitions within large-scale systems may be modeled by nonlinear stochastic partial differential equations in which system dynamics are captured by appropriate potentials. Coherent structures in these systems evolve randomly through time; thus, statistical behavior of these fields is of greater interest than particular system realizations. The ability to simulate and predict phase transition behavior has many applications, from material behaviors (e.g., crystallographic phase transformations and coherent movement of granular materials) to traffic congestion. Past research focused on deriving solutions to the system probability density function (PDF), which is the ground-state wave function squared. Until recently, the extent to which these solutions could be verified was limited by computing power. Utilizing advanced computational resources, this work focused on verifying solutions for PDFs of sixth-order and tenth-order potentials and determining their respective autocorrelation functions. Large-scale MATLAB simulations utilizing first-order Euler discretization methods were used to model the evolution of fields at certain system “temperatures”, for which statistical PDFs and correlation functions were computed. It is anticipated that these PDF results will match the behavior predicted by analytical solutions for each system. This approach, once validated, will enable a better understanding of successive phase transitions in complex materials. In the future, it would be of interest to develop higher-order and more efficient numerical methods for simulating these system dynamics. It would also be of interest to evaluate field dynamics of higher-order potentials outside of the material science context (e.g., traffic flow) to better understand the behavior of stochastic processes in large-scale systems
Quantum trajectory perspective of atom-field interaction in attosecond time scale
Here the ionization and high harmonic generation in Hydrogen and Helium by
using quantum (hydrodynamic) trajectories is analyzed theoretically. The
quantum trajectories allow a self-contained treatment of the electron exchange
and correlation effects without introducing ad hoc potentials into the
Schrodinger equation. Our approach predicts the correct high harmonic spectra
and the attosecond pulses generated by the Helium atom beyond the single active
electron approximation. It can be used to study complex multi-electron systems
and their interaction with laser field of both high and low intensity.Comment: 8 pages, 4 figure
Weak electricity of the Nucleon in the Chiral Quark-Soliton Model
The induced pseudotensor constant (weak electricity) of the nucleon is
calculated in the framework of the chiral quark soliton model. This quantity
originates from the G-parity violation and hence is proportional to .
We obtain for a value of .Comment: The final version. Accepted for publication in Phys. Rev.
Stretching and folding versus cutting and shuffling: An illustrated perspective on mixing and deformations of continua
We compare and contrast two types of deformations inspired by mixing
applications -- one from the mixing of fluids (stretching and folding), the
other from the mixing of granular matter (cutting and shuffling). The
connection between mechanics and dynamical systems is discussed in the context
of the kinematics of deformation, emphasizing the equivalence between stretches
and Lyapunov exponents. The stretching and folding motion exemplified by the
baker's map is shown to give rise to a dynamical system with a positive
Lyapunov exponent, the hallmark of chaotic mixing. On the other hand, cutting
and shuffling does not stretch. When an interval exchange transformation is
used as the basis for cutting and shuffling, we establish that all of the map's
Lyapunov exponents are zero. Mixing, as quantified by the interfacial area per
unit volume, is shown to be exponentially fast when there is stretching and
folding, but linear when there is only cutting and shuffling. We also discuss
how a simple computational approach can discern stretching in discrete data.Comment: REVTeX 4.1, 9 pages, 3 figures; v2 corrects some misprints. The
following article appeared in the American Journal of Physics and may be
found at http://ajp.aapt.org/resource/1/ajpias/v79/i4/p359_s1 . Copyright
2011 American Association of Physics Teachers. This article may be downloaded
for personal use only. Any other use requires prior permission of the author
and the AAP
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