125 research outputs found
Linearization of Cohomology-free Vector Fields
We study the cohomological equation for a smooth vector field on a compact
manifold. We show that if the vector field is cohomology free, then it can be
embedded continuously in a linear flow on an Abelian group
Theoretical prediction of spectral and optical properties of bacteriochlorophylls in thermally disordered LH2 antenna complexes
A general approach for calculating spectral and optical properties of
pigment-protein complexes of known atomic structure is presented. The method,
that combines molecular dynamics simulations, quantum chemistry calculations
and statistical mechanical modeling, is demonstrated by calculating the
absorption and circular dichroism spectra of the B800-B850 BChls of the LH2
antenna complex from Rs. molischianum at room temperature. The calculated
spectra are found to be in good agreement with the available experimental
results. The calculations reveal that the broadening of the B800 band is mainly
caused by the interactions with the polar protein environment, while the
broadening of the B850 band is due to the excitonic interactions. Since it
contains no fitting parameters, in principle, the proposed method can be used
to predict optical spectra of arbitrary pigment-protein complexes of known
structure.Comment: ReVTeX4, 11 pages, 9 figures, submitted to J. Chem. Phy
Excitons in a Photosynthetic Light-Harvesting System: A Combined Molecular Dynamics/Quantum Chemistry and Polaron Model Study
The dynamics of pigment-pigment and pigment-protein interactions in
light-harvesting complexes is studied with a novel approach which combines
molecular dynamics (MD) simulations with quantum chemistry (QC) calculations.
The MD simulations of an LH-II complex, solvated and embedded in a lipid
bilayer at physiological conditions (with total system size of 87,055 atoms)
revealed a pathway of a water molecule into the B800 binding site, as well as
increased dimerization within the B850 BChl ring, as compared to the
dimerization found for the crystal structure. The fluctuations of pigment (B850
BChl) excitation energies, as a function of time, were determined via ab initio
QC calculations based on the geometries that emerged from the MD simulations.
From the results of these calculations we constructed a time-dependent
Hamiltonian of the B850 exciton system from which we determined the linear
absorption spectrum. Finally, a polaron model is introduced to describe quantum
mechanically both the excitonic and vibrational (phonon) degrees of freedom.
The exciton-phonon coupling that enters into the polaron model, and the
corresponding phonon spectral function are derived from the MD/QC simulations.
It is demonstrated that, in the framework of the polaron model, the absorption
spectrum of the B850 excitons can be calculated from the autocorrelation
function of the excitation energies of individual BChls, which is readily
available from the combined MD/QC simulations. The obtained result is in good
agreement with the experimentally measured absorption spectrum.Comment: REVTeX3.1, 23 pages, 13 (EPS) figures included. A high quality PDF
file of the paper is available at
http://www.ks.uiuc.edu/Publications/Papers/PDF/DAMJ2001/DAMJ2001.pd
Supplementary data for article: Pantelić, N. Đ.; Zmejkovski, B. B.; Trifunović-Macedoljan, J.; Savić, A.; Stanković, D.; Damjanović, A.; Juranic, Z.; Kaluđerović, G. N.; Sabo, T. Gold(III) Complexes with Esters of Cyclohexyl-Functionalized Ethylenediamine-N,N ’-Diacetate. Journal of Inorganic Biochemistry 2013, 128, 146–153. https://doi.org/10.1016/j.jinorgbio.2013.08.002
Supplementary material for: [https://doi.org/10.1016/j.jinorgbio.2013.08.002]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1422
Projekat BEWARE - približavanje otvorenim podacima o klizištima
Project on “Harmonization of landslide data and training of municipalities for its monitoring (BEyond landslide aWAREness) BEWARE“, was implemented by the Geological Survey of Serbia, and the University of Belgrade Faculty of Mining and Geology during 2015-2016. The Project partners were UNDP Office in Serbia, Ministry of Mining and Energy and Agency for Public Investments of the Republic of Serbia. The overall aim of BEWARE project was to standardize post-event landslide database and closely involve local community of 27 municipalities affected by May 2014 flooding and landslides episode in Serbia (Figure 1a, 1c), and prepare them to cope with catastrophic events in the future. In this paper, we are presenting main BEWARE project activities and results implemented in local communities of Serbia after the May 2014 event
Lambda production in 40 A GeV/c Pb-Au collisions
During the 1999 lead run, CERES has measured hadron and electron-pair
production at 40 A GeV/c beam momentum with the spectrometer upgraded by the
addition of a radial TPC. Here the analysis of lambda and antilambda will be
presented.Comment: 8 pages, 8 figures. 6th International Conference on Strange Quarks in
Matter, Frankfurt 200
New Results on Pb-Au Collisions at 40 AGeV from the CERES/NA45 Experiment
In 1999 the CERES/NA45 ran at the CERN SPS with a beam energy of 40
GeV/nucleon. The data set comprises about 8.7 millions Pb-Au events with a
trigger selection corresponding to approximately the most central 30% of the
geometrical cross section. Results on low-mass electron pair analysis are
presented.
The upgrade of the experimental setup with the radial drift TPC has allowed
to enhance hadron physics capabilities of the experiment. New results on hadron
spectra (including Lambda) and flow are presented.Comment: Talk at the International Nuclear Physics Conference INPC2001,
Berkeley, CA, July 29th - August 3rd 200
Serum activity of DPPIV and its expression on lymphocytes in patients with melanoma and in people with vitiligo
Background: Dipeptidyl peptidase IV, a multifunctional serine protease, is implicated in regulation of malignant
transformation, promotion and further progression of cancer, exerting tumor-suppressing or even completely
opposite - tumor-promoting activities.
The aim of present research was to determine the serum DPPIV activity, as well as the percentages of CD26+
lymphocytes, CD26+ overall white blood cells and the mean fluorescence intensity of CD26 expression on
lymphocytes in patients with melanoma, people with vitiligo and in healthy controls.
Methods: The activity of DPPIV in serum was determined by colorimetric test. Expression of DPPIV (as CD26) on
immunocompetent peripheral white blood cells was done using flow cytometry analysis.
Results: Data from our study show for the first time statistically significant decrease: in the serum DPPIV activity, in
the percentage of CD26+ overall white blood cells and in the percentage of lymphocytes in patients with
melanoma in comparison to healthy control people. In addition, significantly lower serum DPPIV activity was found
in the group of patients with melanoma in relation to people with vitiligo too.
Conclusion: This study indicates the need for exploring the cause and the importance of the disturbances in the
serum DPPIV activity and in the CD26 expression on immunocompetent cells in complex molecular mechanisms
underlying the development and progression of melanomaThe authors are grateful to the Ministry of Education and Science of the Republic of Serbia for the financial support (Project 175011)S
Universal Pion Freeze-out in Heavy-Ion Collisions
Based on an evaluation of data on pion interferometry and on particle yields
at mid-rapidity, we propose a universal condition for thermal freeze-out of
pions in heavy-ion collisions. We show that freeze-out occurs when the mean
free path of pions lambda_f reaches a value of about 1 fm, which is much
smaller than the spatial extent of the system at freeze-out. This critical mean
free path is independent of the centrality of the collision and beam energy
from AGS to RHIC.Comment: 5 pages, 3 figures, revised version resubmitted to PR
Event-by-event fluctuations of the mean transverse momentum in 40, 80, and 158 A GeV/c Pb-Au collisions
Measurements of event-by-event fluctuations of the mean transverse momentum
in Pb-Au collisions at 40, 80, and 158 A GeV/c are presented. A significant
excess of mean p_T fluctuations at mid-rapidity is observed over the
expectation from statistically independent particle emission. The results are
somewhat smaller than recent measurements at RHIC. A possible non-monotonic
behaviour of the mean p_T fluctuations as function of collision energy, which
may have indicated that the system has passed the critical point of the QCD
phase diagram in the range of mu_B under investigation, has not been observed.
The centrality dependence of mean p_T fluctuations in Pb-Au is consistent with
an extrapolation from pp collisions assuming that the non-statistical
fluctuations scale with multiplicity. The results are compared to calculations
by the RQMD and UrQMD event generators.Comment: 28 pages, 10 figure
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