451 research outputs found
Role of RhoA and rho kinase in lysophosphatidic acid-induced endothelial barrier dysfunction.
The online version of this article, along with updated information and services, is located on th
Influence of Complex Exciton-Phonon Coupling on Optical Absorption and Energy Transfer of Quantum Aggregates
We present a theory that efficiently describes the quantum dynamics of an
electronic excitation that is coupled to a continuous, highly structured phonon
environment. Based on a stochastic approach to non-Markovian open quantum
systems, we develop a dynamical framework that allows us to handle realistic
systems where a fully quantum treatment is desired yet the usual approximation
schemes fail. The capability of the method is demonstrated by calculating
spectra and energy transfer dynamics of mesoscopic molecular aggregates,
elucidating the transition from fully coherent to incoherent transfer
Time-resolved, multi-color photometry and spectroscopy of Virgo 4 (OU Vir): a high orbital inclination, short orbital period dwarf nova
We present multi-color photometry and time resolved spectroscopy of OU Vir.
The analysis of the quiescent light curve shows that OU Vir is characterized by
i) strong cycle-to-cycle brightness variations, and ii) hot spot modulated
light curve with grazing eclipse of the impact region. Colors are derived both
in- and out- of eclipse. The time-resolved spectroscopy allows us to produce
the radial velocity curve from the H accretion disk emission line which
possibly reveals only weak evidence for hot spot line emission. The hot spot is
believed to be a turbulent optically thick region, producing mostly continuum
emission.Comment: 8 pages (including figures), 7 figures. To Be published in A&
Predominant Infection of CD150+ Lymphocytes and Dendritic Cells during Measles Virus Infection of Macaques
Measles virus (MV) is hypothesized to enter the host by infecting epithelial cells of the respiratory tract, followed by viremia mediated by infected monocytes. However, neither of these cell types express signaling lymphocyte activation molecule (CD150), which has been identified as the receptor for wild-type MV. We have infected rhesus and cynomolgus macaques with a recombinant MV strain expressing enhanced green fluorescent protein (EGFP); thus bringing together the optimal animal model for measles and a virus that can be detected with unprecedented sensitivity. Blood samples and broncho-alveolar lavages were collected every 3 d, and necropsies were performed upon euthanasia 9 or 15 d after infection. EGFP production by MV-infected cells was visualized macroscopically, in both living and sacrificed animals, and microscopically by confocal microscopy and FACS analysis. At the peak of viremia, EGFP fluorescence was detected in skin, respiratory and digestive tract, but most intensely in all lymphoid tissues. B- and T-lymphocytes expressing CD150 were the major target cells for MV infection. Highest percentages (up to 30%) of infected lymphocytes were detected in lymphoid tissues, and the virus preferentially targeted cells with a memory phenotype. Unexpectedly, circulating monocytes did not sustain productive MV infection. In peripheral tissues, large numbers of MV-infected CD11c+ MHC class-II+ myeloid dendritic cells were detected in conjunction with infected T-lymphocytes, suggesting transmission of MV between these cell types. Fluorescent imaging of MV infection in non-human primates demonstrated a crucial role for lymphocytes and dendritic cells in the pathogenesis of measles and measles-associated immunosuppression
Secular changes in the quiescence of WZ Sge: the development of a cavity in the inner disk
We find a dimming during optical quiescence of the cataclysmic variable WZ
Sge by about half a magnitude between superoutbursts. We connect the dimming
with the development of a cavity in the inner part of the accretion disk. We
suggest that, when the cavity is big enough, accretion of material is governed
by the magnetic field of the white dwarf and pulsations from the weakly
magnetic white dwarf appear. The time scale of forming the cavity is about a
decade, and it persists throughout the whole quiescent phase. Such a cavity can
be accommodated well by the proposed magnetic propeller model for WZ Sge, where
during quiescence mass is being expelled by the magnetic white dwarf from the
inner regions of the accretion disk to larger radii.Comment: 10 pages, 4 figures, accepted for publication in Astronomy and
Astrophysics; following referee report, many textual changes, figures
improved, more historic data added, conclusions unchange
A Study Of A New Class Of Discrete Nonlinear Schroedinger Equations
A new class of 1D discrete nonlinear Schrdinger Hamiltonians
with tunable nonlinerities is introduced, which includes the integrable
Ablowitz-Ladik system as a limit. A new subset of equations, which are derived
from these Hamiltonians using a generalized definition of Poisson brackets, and
collectively refered to as the N-AL equation, is studied. The symmetry
properties of the equation are discussed. These equations are shown to possess
propagating localized solutions, having the continuous translational symmetry
of the one-soliton solution of the Ablowitz-Ladik nonlinear
Schrdinger equation. The N-AL systems are shown to be suitable
to study the combined effect of the dynamical imbalance of nonlinearity and
dispersion and the Peierls-Nabarro potential, arising from the lattice
discreteness, on the propagating solitary wave like profiles. A perturbative
analysis shows that the N-AL systems can have discrete breather solutions, due
to the presence of saddle center bifurcations in phase portraits. The
unstaggered localized states are shown to have positive effective mass. On the
other hand, large width but small amplitude staggered localized states have
negative effective mass. The collison dynamics of two colliding solitary wave
profiles are studied numerically. Notwithstanding colliding solitary wave
profiles are seen to exhibit nontrivial nonsolitonic interactions, certain
universal features are observed in the collison dynamics. Future scopes of this
work and possible applications of the N-AL systems are discussed.Comment: 17 pages, 15 figures, revtex4, xmgr, gn
Exploring the growth of correlations in a quasi one-dimensional trapped Bose gas
Phase correlations, density fluctuations and three-body loss rates are
relevant for many experiments in quasi one-dimensional geometries. Extended
mean-field theory is used to evaluate correlation functions up to third order
for a quasi one-dimensional trapped Bose gas at zero and finite temperature. At
zero temperature and in the homogeneous limit, we also study the transition
from the weakly correlated Gross-Pitaevskii regime to the strongly correlated
Tonks-Girardeau regime analytically. We compare our results with the exact
Lieb-Liniger solution for the homogeneous case and find good agreement up to
the cross-over regime.Comment: 36 pages, 21 color pdf/jpeg figures, submitted to NJP, corrected
reference
Tissue microarray analysis of human FRAT1 expression and its correlation with the subcellular localisation of ?-catenin in ovarian tumours
The mechanisms involved in the pathogenesis of ovarian cancer are poorly understood, but evidence suggests that aberrant activation of Wnt/?-catenin signalling pathway plays a significant role in this malignancy. However, the molecular defects that contribute to the activation of this pathway have not been elucidated. Frequently rearranged in advanced T-cell lymphomas-1 (FRAT1) is a candidate for the regulation of cytoplasmic ?-catenin. In this study, we developed in situ hybridisation probes to evaluate the presence of FRAT1 and used an anti-?-catenin antibody to evaluate by immunohistochemistry the expression levels and subcellular localisation of ?-catenin in ovarian cancer tissue microarrays. Expression of FRAT1 was found in some human normal tissues and 47% of ovarian adenocarcinomas. A total of 46% of ovarian serous adenocarcinomas were positive for FRAT1 expression. Accumulation of ?-catenin in the nucleus and/or cytoplasm was observed in 55% ovarian adenocarcinomas and in 59% of serous adenocarcinomas. A significant association was observed in ovarian serous adenocarcinomas between FRAT1 and ?-catenin expression (P<0.01). These findings support that Wnt/?-catenin signalling may be aberrantly activated through FRAT1 overexpression in ovarian serous adenocarcinomas. The mechanism behind the overexpression of FRAT1 in ovarian serous adenocarcinomas and its significance is yet to be investigated
Ab-Initio Calculation of Molecular Aggregation Effects: a Coumarin-343 Case Study
We present time-dependent density functional theory (TDDFT) calculations for
single and dimerized Coumarin-343 molecules in order to investigate the quantum
mechanical effects of chromophore aggregation in extended systems designed to
function as a new generation of sensors and light-harvesting devices. Using the
single-chromophore results, we describe the construction of effective
Hamiltonians to predict the excitonic properties of aggregate systems. We
compare the electronic coupling properties predicted by such effective
Hamiltonians to those obtained from TDDFT calculations of dimers, and to the
coupling predicted by the transition density cube (TDC) method. We determine
the accuracy of the dipole-dipole approximation and TDC with respect to the
separation distance and orientation of the dimers. In particular, we
investigate the effects of including Coulomb coupling terms ignored in the
typical tight-binding effective Hamiltonian. We also examine effects of orbital
relaxation which cannot be captured by either of these models
Applying two-photon excitation fluorescence lifetime imaging microscopy to study photosynthesis in plant leaves
This study investigates to which extent two-photon excitation (TPE) fluorescence lifetime imaging microscopy can be applied to study picosecond fluorescence kinetics of individual chloroplasts in leaves. Using femtosecond 860 nm excitation pulses, fluorescence lifetimes can be measured in leaves of Arabidopsis thaliana and Alocasia wentii under excitation-annihilation free conditions, both for the F0- and the Fm-state. The corresponding average lifetimes are ~250 ps and ~1.5 ns, respectively, similar to those of isolated chloroplasts. These values appear to be the same for chloroplasts in the top, middle, and bottom layer of the leaves. With the spatial resolution of ~500 nm in the focal (xy) plane and 2 μm in the z direction, it appears to be impossible to fully resolve the grana stacks and stroma lamellae, but variations in the fluorescence lifetimes, and thus of the composition on a pixel-to-pixel base can be observed
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