610 research outputs found
Mechanisms of the Influence of UV Irradiation on Collagen and Collagen-Ascorbic Acid Solutions
The study of the influence of UV irradiation on collagen solutions has shown the destabilization of the collagen molecule by calorimetric method. It is reflected both in changes of thermodynamic parameters of transition (Tm, ΔH, Cp = f (T)) and in the appearance of a low temperature peak, that is practically irreversible against rescanning. All these indicate that the important defects in the molecule occur. The ESR measurements have shown that the above-mentioned thermal changes are connected with the occurrence of free radicals in solution under UV irradiation. They interact with proline (Pro) residues of the protein with the appearance of secondary free radicals, with following migration to glycine (Gly) residues. The emergence of the free radicals at the Pro and then at the Gly residues may cause the dramatic structural defect resulting from the UV irradiation, which significantly alters the network of hydrogen bonds in the triple helix of the collagen molecule. All this is connected with destabilization of the collagen molecule, because the defects in amino acid residues probably lead to cleavage of covalent bonds near the damaged sites maintaining the triple helical structure. The presence of ascorbic acid in collagen solution protects the collagen molecule from occurring of secondary free radicals
Mechanisms of the influence of UV irradiation on collagen and collagen-ascorbic acid solutions
The study of the influence of UV irradiation on collagen solutions has shown the destabilization of the collagen molecule by calorimetric method. It is reflected both in changes of thermodynamic parameters of transition (Tm, ΔH, Cp=f(t)) and in the appearance of a low temperature peak, that is practically irreversible against rescanning. All these indicate that the important defects in the molecule occur. The ESR measurements have shown that the above-mentioned thermal changes are connected with the occurrence of free radicals in solution under UV irradiation. They interact with proline (Pro) residues of the protein with the appearance of secondary free radicals, with following migration to glycine (Gly) residues. The emergence of the free radicals at the Pro and then at the Gly residues may cause the dramatic structural defect resulting from the UV irradiation, which significantly alters the network of hydrogen bonds in the triple helix of the collagen molecule. All this is connected with destabilization of the collagen molecule, because the defects in amino acid residues probably lead to cleavage of covalent bonds near the damaged sites maintaining the triple helical structure. The presence of ascorbic acid in collagen solution protects the collagen molecule from occurring of secondary free radicals
The model of dynamo with small number of modes and magnetic activity of T Tauri stars
The model that describes operation of dynamo in fully convective stars is
presented. It is based on representation of stellar magnetic field as a
superposition of finite number of poloidal and toroidal free damping modes. In
the frame of adopted low of stellar differential rotation we estimated minimal
value of dynamo number D, starting from which generation of cyclic magnetic
field in stars without radiative core is possible. We also derived expression
for period of the cycle. It was found that dynamo cycles of fully convective
stars and stars with thin convective envelopes differ in a qualitative way: 1)
distribution of spots over latitude during the cycle is different in these
stars; 2) the model predicts that spot formation in fully convective stars
should be strongly suppressed at some phases of the cycle.
We have analyzed historical lightcurve of WTTS star V410 Tau and found that
long term activity of the star is not periodic process. Rather one can speak
about quasi cyclic activity with characteristic time of yr and chaotic
component over imposed. We concluded also that redistribution of cool spots
over longitude is the reason of long term variations of V410 Tau brightness. It
means that one can not compare directly results of photometric observations
with predictions of our axially symmetric (for simplicity) model which allows
to investigate time evolution of spot's distribution over latitude. We then
discuss what kind of observations and in which way could be used to check
predictions of the dynamo theory.Comment: 18 pages, 5 figures, accepted to Astron. Let
Observational Constraints on Interstellar Grain Alignment
We present new multicolor photo-polarimetry of stars behind the Southern
Coalsack. Analyzed together with multiband polarization data from the
literature, probing the Chamaeleon I, Musca, rho Opiuchus, R CrA and Taurus
clouds, we show that the wavelength of maximum polarization (lambda_max) is
linearly correlated with the radiation environment of the grains. Using
Far-Infrared emission data, we show that the large scatter seen in previous
studies of lambda_max as a function of A_V is primarily due to line of sight
effects causing some A_V measurements to not be a good tracer of the extinction
(radiation field strength) seen by the grains being probed. The derived slopes
in lambda_max vs. A_V, for the individual clouds, are consistent with a common
value, while the zero intercepts scale with the average values of the ratios of
total-to-selective extinction (R_V) for the individual clouds. Within each
cloud we do not find direct correlations between lambda_max and R_V. The
positive slope in consistent with recent developments in theory and indicating
alignment driven by the radiation field. The present data cannot conclusively
differentiate between direct radiative torques and alignment driven by H_2
formation. However, the small values of lambda_max(A_V=0), seen in several
clouds, suggest a role for the latter, at least at the cloud surfaces. The
scatter in the lambda_max vs. A_V relation is found to be associated with the
characteristics of the embedded Young Stellar Objects (YSO) in the clouds. We
propose that this is partially due to locally increased plasma damping of the
grain rotation caused by X-rays from the YSOs.Comment: Accepted for publication in the Astrophysical Journa
Численные методы в формировании морских технологических комплексов
For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version). ABSTRACT Active development of the World Ocean dictates the need to intensively develop marine engineering systems, designed to solve a wide variety of scientific research, geological, prospecting, search, and other tasks. Basing on the analysis of scientific works and research in this field, the authors aim to find the optimal mathematical model for increasing the efficiency of such complexes using the example of an underwater unmanned vehicle (UV). As a result, the conclusion is made that the application of mathematical-statistical methods allows correctly and evenly distribute resources (finance, time, labor, etc.), determine the level of innovation, and also more fully and rationally assess the conditions for formation, maintenance and operation of UV. At the same time, the authors especially noted the importance of having qualityrelated solutions within the requirements (standards) of a single system synchronously working at the stages of design, maintenance and operation of marine engineering systems. Keywords: marine engineering systems, unmanned vehicles, mathematical model, physical principles, quality management system, statistical data, scientific research, algebraic solutions.Текст аннотации на англ. языке и полный текст статьи на англ. языке находится в прилагаемом файле ПДФ (англ. версия следует после русской версии). Активное освоение Мирового океана диктует необходимость интенсивно развивать морские технологические комплексы, предназначенные для решения научно-исследовательских, геолого- разведывательных, поисковых и других задач. Авторы на основе анализа научных работ и исследований в этой области ставят целью найти оптимальную математическую модель повышения эффективности подобных комплексов на примере подводного беспилотного необитаемого аппарата (БНА). Сделан вывод о том, что применение математическо-статистических методов позволяет правильно и равномерно распределить ресурсы (финансы, время, трудозатраты и т. п.), определить уровень инноваций. Отмечена важность иметь связанные с менеджментом качества решения в рамках требований (стандартов) единой системы, синхронно работающей на стадиях проектирования, обслуживания и эксплуатации морских технологических комплексов
E835 at FNAL: Charmonium Spectroscopy in Annihilations
I present preliminary results on the search for in its
and decay modes. We observe an excess of \eta_c\gamma{\cal P} \sim 0.001M=3525.8 \pm 0.2 \pm 0.2
\Gamma\leq10.6\pm 3.7\pm3.4(br) <
\Gamma_{\bar{p}p}B_{\eta_c\gamma} < 12.8\pm 4.8\pm4.5(br) J/\psi\pi^0$ mode.Comment: Presented at the 6th International Conference on Hyperons, Charm and
Beauty Hadrons (BEACH 2004), Chicago(Il), June 27-July 3,200
Interference Study of the chi_c0 (1^3P_0) in the Reaction Proton-Antiproton -> pi^0 pi^0
Fermilab experiment E835 has observed proton-antiproton annihilation
production of the charmonium state chi_c0 and its subsequent decay into pi^0
pi^0. Although the resonant amplitude is an order of magnitude smaller than
that of the non-resonant continuum production of pi^0 pi^0, an enhanced
interference signal is evident. A partial wave expansion is used to extract
physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate
the expansion. Both are accessed by L=1 in the entrance proton-antiproton
channel. The product of the input and output branching fractions is determined
to be B(pbar p -> chi_c0) x B(chi_c0 -> pi^0 pi^0)= (5.09 +- 0.81 +- 0.25) x
10^-7.Comment: 4 pages, 4 figures, Accepted by PRL (July 2003
Precision measurements of the total and partial widths of the psi(2S) charmonium meson with a new complementary-scan technique in antiproton-proton annihilations
We present new precision measurements of the psi(2S) total and partial widths
from excitation curves obtained in antiproton-proton annihilations by Fermilab
experiment E835 at the Antiproton Accumulator in the year 2000. A new technique
of complementary scans was developed to study narrow resonances with
stochastically cooled antiproton beams. The technique relies on precise
revolution-frequency and orbit-length measurements, while making the analysis
of the excitation curve almost independent of machine lattice parameters. We
study the psi(2S) meson through the processes pbar p -> e+ e- and pbar p ->
J/psi + X -> e+ e- + X. We measure the width to be Gamma = 290 +- 25(sta) +-
4(sys) keV and the combination of partial widths Gamma_e+e- * Gamma_pbarp /
Gamma = 579 +- 38(sta) +- 36(sys) meV, which represent the most precise
measurements to date.Comment: 17 pages, 3 figures, 3 tables. Final manuscript accepted for
publication in Phys. Lett. B. Parts of the text slightly expanded or
rearranged; results are unchange
Charge Fluctuations in \pi^{+}\rp and \rK^{+}\rp Collisions at 250 GeV/
We report on measurements of event-by-event charge fluctuations in
\pi^{+}\rp and \rK^{+}\rp collisions at 250 GeV/. The dependence of
these fluctuations on the size of the rapidity windows are presented for the
first time in the full phase space domain. The corrections for the influence of
global charge conservation and leading-particle stopping are tested by the
data. The discrepancy due to incomplete correction given by STAR and PHENIX are
estimated. The dependence of the fluctuations on the position of the rapidity
bin and on the multiplicity at different rapidity windows are also presented.Comment: 4pages, 3figure
Rapidity, azimuthal, and multiplicity dependence of mean transverse momentum and transverse momentum correlations in and collisions in =22 GeV
Rapidity, azimuthal and multiplicity dependence of mean transverse momentum and transverse momentum correlations of charged particles is studied in pi/sup positive and K/sup positive collisions at 250 GeV/c incident beam momentum. For the first time, it is found that the rapidity dependence of the two-particle transverse momentum correlation is different from that of the mean transverse momentum, but both have similar multiplicity dependence. In particular, the transverse momentum correlations are boost invariant. This is similar to the recently found boost invariance of the charge balance function. A strong azimuthal dependence of the transverse momentum correlations originates from the constraint of energy-momentum conservation. The results are compared with those from the PYTHIA Monte Carlo generator. The similarities to and differences with the results from current heavy ion experiments are discussed
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