3,362 research outputs found
Concentration fluctuations and phase transitions in coupled modulated bilayers
We consider the formation of finite-size domains in lipid bilayers consisting
of saturated and hybrid lipids. First, we describe a monolayer model that
includes a coupling between a compositional scalar field and a two-dimensional
vectorial order-parameter. Such a coupling yields an effective two-dimensional
microemulsion free-energy for the lipid monolayer, and its characteristic
length of compositional modulations can be considered as the origin of
finite-size domains in biological membranes. Next, we consider a coupled
bilayer composed of two modulated monolayers, and discuss the static and
dynamic properties of concentration fluctuations above the transition
temperature. We also investigate the micro-phase separation below the
transition temperature, and compare the micro-phase separated structures with
statics and dynamics of concentration fluctuations above the transition.Comment: 14 pages, 12 figures, 1 tabl
Molecular Discreteness in Reaction-Diffusion Systems Yields Steady States Not Seen in the Continuum Limit
We investigate the effects of spatial discreteness of molecules in
reaction-diffusion systems. It is found that discreteness within the so called
Kuramoto length can lead to a localization of molecules, resulting in novel
steady states that do not exist in the continuous case. These novel states are
analyzed theoretically as the fixed points of accelerated localized reactions,
an approach that was verified to be in good agreement with stochastic particle
simulations. The relevance of this discreteness-induced state to biological
intracellular processes is discussed.Comment: 5 pages, 3 figures, revtex
Photometric Studies of a WZ Sge-Type Dwarf Nova Candidate, ASAS160048-4846.2
We report on our time-resolved CCD photometry during the 2005 June
superoutburst of a WZ Sge-type dwarf nova candidate, ASAS 160048-4846.2. The
ordinary superhumps underwent a complex evolution during the superoutburst. The
superhump amplitude experienced a regrowth, and had two peaks. The superhump
period decreased when the superhump amplitude reached to the first maximum,
successively gradually increased until the second maximum of the amplitude, and
finally decreased again. Investigating other SU UMa-type dwarf novae which show
an increase of the superhump period, we found the same trend of the superhump
evolution in superoutbursts of them. We speculate that the superhump regrowth
in the amplitude has a close relation to the increase of the superhump period,
and all of SU UMa-type dwarf novae with a superhump regrowth follow the same
evolution of the ordinary superhumps as that of ASAS 160048-4846.2.Comment: 7 pages, 4 figure
Experimental Observation of Large Chern numbers in Photonic Crystals
Despite great interest in the quantum anomalous Hall phase and its analogs,
all experimental studies in electronic and bosonic systems have been limited to
a Chern number of one. Here, we perform microwave transmission measurements in
the bulk and at the edge of ferrimagnetic photonic crystals. Bandgaps with
large Chern numbers of 2, 3, and 4 are present in the experimental results
which show excellent agreement with theory. We measure the mode profiles and
Fourier transform them to produce dispersion relations of the edge modes, whose
number and direction match our Chern number calculations.Comment: This experimental work was accepted to PRL on Oct. 13, 2015. Our
theoretical work from PRL http://dx.doi.org/10.1103/PhysRevLett.113.11390
Unobserved Heterogeneity in Auctions
A common concern in the empirical study of auctions is the likely presence of auction-specific factors that are common knowledge among bidders but unobserved to the econometrician. Such unobserved heterogeneity confounds attempts to uncover the underlying structure of demand and information, typically a primary feature of interest in an auction market. Unobserved heterogeneity presents a particular challenge in first-price auctions, where identification arguments rely on the econometrician’s ability to reconstruct from observables the conditional probabilities that entered each bidder’s equilibrium optimization problem; when bidders condition on unobservables, it is not obvious that this is possible. Here we discuss several approaches to identification developed in recent work on first-price auctions with unobserved heterogeneity. Despite the special challenges of this setting, all of the approaches build on insights developed in other areas of econometrics, including those on control functions, measurement error, and mixture models. Because each strategy relies on different combinations of model restrictions, technical assumptions, and data requirements, their relative attractiveness will vary with the application. However, this varied menu of results suggests both a type of robustness of identifiability and the potential for expanding the frontier with additional work
cDNA cloning and inducible expression of human multidrug resistance associated protein 3 (MRP3)1The sequence reported in this paper has been submitted to GenBank with the accession number of AB010887.1
AbstractPreviously, we cloned rat MRP3 as a candidate for an inducible transporter for the biliary excretion of organic anions [Hirohashi et al. (1998) Mol. Pharmacol. 53, 1068–1075]. In the present study, we cloned human MRP3 (1527 amino acids) from Caco-2 cells. Human MRP3 is predominantly expressed in liver, small intestine and colon; hepatic expression of MRP3 was observed in humans but not in normal rats. In HepG2 cells, the expression of MRP3 was induced by phenobarbital. These results suggest that MRP3 may act as an inducible transporter in the biliary and intestinal excretion of organic anions
Switching Dynamics in Reaction Networks Induced by Molecular Discreteness
To study the fluctuations and dynamics in chemical reaction processes,
stochastic differential equations based on the rate equation involving chemical
concentrations are often adopted. When the number of molecules is very small,
however, the discreteness in the number of molecules cannot be neglected since
the number of molecules must be an integer. This discreteness can be important
in biochemical reactions, where the total number of molecules is not
significantly larger than the number of chemical species. To elucidate the
effects of such discreteness, we study autocatalytic reaction systems
comprising several chemical species through stochastic particle simulations.
The generation of novel states is observed; it is caused by the extinction of
some molecular species due to the discreteness in their number. We demonstrate
that the reaction dynamics are switched by a single molecule, which leads to
the reconstruction of the acting network structure. We also show the strong
dependence of the chemical concentrations on the system size, which is caused
by transitions to discreteness-induced novel states.Comment: 11 pages, 5 figure
Chandra Snapshot Observations of Low-Luminosity AGNs with a Compact Radio Source
The results of Chandra snapshot observations of 11 LINERs (Low-Ionization
Nuclear Emission-line Regions), three low-luminosity Seyfert galaxies, and one
HII-LINER transition object are presented. Our sample consists of all the
objects with a flat or inverted spectrum compact radio core in the VLA survey
of 48 low-luminosity AGNs (LLAGNs) by Nagar et al. (2000). An X-ray nucleus is
detected in all galaxies except one and their X-ray luminosities are in the
range 5x10^38 to 8x10^41 erg/s. The X-ray spectra are generally steeper than
expected from thermal bremsstrahlung emission from an advection-dominated
accretion flow (ADAF). The X-ray to Halpha luminosity ratios for 11 out of 14
objects are in good agreement with the value characteristic of LLAGNs and more
luminous AGNs, and indicate that their optical emission lines are predominantly
powered by a LLAGN. For three objects, this ratio is less than expected.
Comparing with properties in other wavelengths, we find that these three
galaxies are most likely to be heavily obscured AGN. We use the ratio RX = \nu
L\nu (5 GHz)/LX, where LX is the luminosity in the 2-10 keV band, as a measure
of radio loudness. In contrast to the usual definition of radio loudness (RO =
L\nu(5 GHz)/L\nu(B)), RX can be used for heavily obscured (NH >~ 10^23 cm^-2,
AV>50 mag) nuclei. Further, with the high spatial resolution of Chandra, the
nuclear X-ray emission of LLAGNs is often easier to measure than the nuclear
optical emission. We investigate the values of RX for LLAGNs, luminous Seyfert
galaxies, quasars and radio galaxies and confirm the suggestion that a large
fraction of LLAGNs are radio loud.Comment: 15 pages, accepted for publication in Ap
A Chandra Observation of M51: Active Nucleus and Nuclear Outflows
We present a Chandra ACIS-S observation of the nuclear region of the nearby
spiral galaxy M51 (NGC 5194), which has a low-luminosity Seyfert 2 nucleus. The
X-ray image shows the nucleus, southern extranuclear cloud, and northern loop,
the morphology of the extended emission being very similar to those seen in
radio continuum and optical emission line images. The X-ray spectrum of the
nucleus is well represented by a model consisting of soft thermal plasma with
kT ~0.5 keV, a very hard continuum, and an Fe Kalpha emission line at 6.45 keV
with an equivalent width of >2 keV. The very strong Fe line and the flat
continuum indicate that the nucleus is obscured by a column density in excess
of 10^24 cm^-2 and the spectrum is dominated by reflected emission from cold
matter near the nucleus. The X-ray spectra of the extranuclear clouds are well
fitted by a thermal plasma model with kT ~0.5 keV. This spectral shape and
morphology strongly suggest that the clouds are shock heated by the bi-polar
outflow from the nucleus. The shock velocities of the extranuclear cloud and
northern loop inferred from the temperatures of the X-ray gas are 690 km/s and
660 km/s, respectively. By assuming a steady-state situation in which the
emission of the extranuclear clouds is powered by the jets, the mechanical
energy in the jets is found to be comparable to the bolometric luminosity of
the nucleus.Comment: 7 pages, 5 figures, Accepted for publication in the Astrophyscal
Jouna
Modulated vortex states in Rashba non-centrosymmetric superconductors
Vortex lattice structures to occur in Rashba non-centrosymmetric
superconductors under a magnetic field parallel to the basal plane are studied
by assuming a singlet Cooper pairing and taking account of both the
paramagnetic and orbital depairings. A vortex lattice of
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type with modulation perpendicular to
the field is expected to occur in the limit of vanishing , where
is the spin-orbit coupling {\it normalized} by Fermi energy. As
increases, however, this state tends to be replaced by another
new vortex lattice with a modulation of the gap amplitude parallel to the
helical phase modulation induced by the absence of inversion symmetry.
Differences of the present results from those in the Pauli limit and a
correlation of a structural transition with the -curve are discussed
in relation to possible experimental realization.Comment: Final version accepted for publication in Phys.Rev.B (Rapid Commmun.
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