1,828 research outputs found
Parallel Excluded Volume Tempering for Polymer Melts
We have developed a technique to accelerate the acquisition of effectively
uncorrelated configurations for off-lattice models of dense polymer melts which
makes use of both parallel tempering and large scale Monte Carlo moves. The
method is based upon simulating a set of systems in parallel, each of which has
a slightly different repulsive core potential, such that a thermodynamic path
from full excluded volume to an ideal gas of random walks is generated. While
each system is run with standard stochastic dynamics, resulting in an NVT
ensemble, we implement the parallel tempering through stochastic swaps between
the configurations of adjacent potentials, and the large scale Monte Carlo
moves through attempted pivot and translation moves which reach a realistic
acceptance probability as the limit of the ideal gas of random walks is
approached. Compared to pure stochastic dynamics, this results in an increased
efficiency even for a system of chains as short as monomers, however
at this chain length the large scale Monte Carlo moves were ineffective. For
even longer chains the speedup becomes substantial, as observed from
preliminary data for
Microscopic Selection of Fluid Fingering Pattern
We study the issue of the selection of viscous fingering patterns in the
limit of small surface tension. Through detailed simulations of anisotropic
fingering, we demonstrate conclusively that no selection independent of the
small-scale cutoff (macroscopic selection) occurs in this system. Rather, the
small-scale cutoff completely controls the pattern, even on short time scales,
in accord with the theory of microscopic solvability. We demonstrate that
ordered patterns are dynamically selected only for not too small surface
tensions. For extremely small surface tensions, the system exhibits chaotic
behavior and no regular pattern is realized.Comment: 6 pages, 5 figure
MatryODShka: Real-time 6DoF Video View Synthesis using Multi-Sphere Images
We introduce a method to convert stereo 360{\deg} (omnidirectional stereo)
imagery into a layered, multi-sphere image representation for six
degree-of-freedom (6DoF) rendering. Stereo 360{\deg} imagery can be captured
from multi-camera systems for virtual reality (VR), but lacks motion parallax
and correct-in-all-directions disparity cues. Together, these can quickly lead
to VR sickness when viewing content. One solution is to try and generate a
format suitable for 6DoF rendering, such as by estimating depth. However, this
raises questions as to how to handle disoccluded regions in dynamic scenes. Our
approach is to simultaneously learn depth and disocclusions via a multi-sphere
image representation, which can be rendered with correct 6DoF disparity and
motion parallax in VR. This significantly improves comfort for the viewer, and
can be inferred and rendered in real time on modern GPU hardware. Together,
these move towards making VR video a more comfortable immersive medium.Comment: 25 pages, 13 figures, Published at European Conference on Computer
Vision (ECCV 2020), Project Page: http://visual.cs.brown.edu/matryodshk
Dirac field on Moyal-Minkowski spacetime and non-commutative potential scattering
The quantized free Dirac field is considered on Minkowski spacetime (of
general dimension). The Dirac field is coupled to an external scalar potential
whose support is finite in time and which acts by a Moyal-deformed
multiplication with respect to the spatial variables. The Moyal-deformed
multiplication corresponds to the product of the algebra of a Moyal plane
described in the setting of spectral geometry. It will be explained how this
leads to an interpretation of the Dirac field as a quantum field theory on
Moyal-deformed Minkowski spacetime (with commutative time) in a setting of
Lorentzian spectral geometries of which some basic aspects will be sketched.
The scattering transformation will be shown to be unitarily implementable in
the canonical vacuum representation of the Dirac field. Furthermore, it will be
indicated how the functional derivatives of the ensuing unitary scattering
operators with respect to the strength of the non-commutative potential induce,
in the spirit of Bogoliubov's formula, quantum field operators (corresponding
to observables) depending on the elements of the non-commutative algebra of
Moyal-Minkowski spacetime.Comment: 60 pages, 1 figur
Modification of the -Meson Lifetime in Nuclear Matter
The photo production of mesons on the nuclei C, Ca, Nb and Pb has
been measured using the Crystal Barrel/TAPS detector at the ELSA tagged photon
facility in Bonn. The dependence of the meson cross section on the
nuclear mass number has been compared with three different types of models, a
Glauber analysis, a BUU analysis of the Giessen theory group and a calculation
by the Valencia theory group. In all three cases, the inelastic width
is found to be at normal nuclear matter density for an
average 3-momentum of 1.1 GeV/c. In the restframe of the meson, this
inelastic width corresponds to a reduction of the lifetime by
a factor . For the first time, the momentum dependent N
cross section has been extracted from the experiment and is in the range of 70
mb.Comment: 5 pages, 4 figure
Citizenship and Inclusion: Rethinking the Analytical Category of Noncitizenship
The paper problematises the category of noncitizenship. It traces its trajectory in accounts of inclusive citizenship and argues that it is difficult to theorise it as a distinct theoretical category outside of citizenship. To support this argument, the paper distinguishes between a pluralist, political and democratic variant of accounts of inclusive citizenship and it shows how they all end up reducing noncitizenship to a journey to citizenship. To overcome this limit, the paper develops the idea of subversive politicisation and suggests that injustices and inequalities can be challenged without falling back on the vocabulary of citizenship
In-medium mass from the reaction
Data on the photoproduction of mesons on nuclei have been
re-analyzed in a search for in-medium modifications. The data were taken with
the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in
Bonn. First results from the analysis of the data set were published by D.
Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming a
lowering of the mass in the nuclear medium by 14 at normal nuclear
matter density. The extracted line shape was found to be sensitive to
the background subtraction. For this reason a re-analysis of the same data set
has been initiated and a new method has been developed to reduce the background
and to determine the shape and absolute magnitude of the background directly
from the data. Details of the re-analysis and of the background determination
are described. The signal on the target, extracted in the
re-analysis, does not show a deviation from the corresponding line shape on a
target, measured as reference. The earlier claim of an in-medium mass
shift is thus not confirmed. The sensitivity of the line shape to
different in-medium modification scenarios is discussed.Comment: 13 pages and 11 figures, submitted for publicatio
Signaling via interleukin-4, receptor alpha chain is required for successful vaccination against schistosomiasis in BALB/c mice
Radiation-attenuated (RA) schistosome larvae are potent stimulators of innate immune responses at the skin site of exposure (pinna) that are likely to be important factors in the development of Th1-mediated protective immunity. In addition to causing an influx of neutrophils, macrophages, and dendritic cells (DCs) into the dermis, RA larvae induced a cascade of chemokine and cytokine secretion following in vitro culture of pinna biopsy samples. While macrophage inflammatory protein 1 and interleukin-1 (IL-1) were produced transiently within the first few days, the Th1-promoting cytokines IL-12 and IL-18 were secreted at high levels until at least day 14. Assay of C3H/HeJ mice confirmed that IL-12 secretion was not due to lipopolysaccharide contaminants binding Toll-like receptor 4. Significantly, IL-12 p40 secretion was sustained in pinnae from vaccinated mice but not in those from nonprotected infected mice. In contrast, IL-10 was produced from both vaccinated and infected mice. This cytokine regulates IL-12-associated dermal inflammation, since in vaccinated IL-10/ mice, pinna thickness was greatly increased concurrent with elevated levels of IL-12 p40. A significant number of IL-12 p40 cells were detected as emigrants from in vitro-cultured pinnae, and most were within a population of rare large granular cells that were Ia, consistent with their being antigen-presenting cells. Labeling of IL-12 cells for CD11c, CD205, CD8, CD11b, and F4/80 indicated that the majority were myeloid DCs, although a proportion were CD11c F4/80, suggesting that macrophages were an additional source of IL-12 in the skin
Photoproduction of pi0 omega off protons for E(gamma) < 3 GeV
Differential and total cross-sections for photoproduction of gamma proton to
proton pi0 omega and gamma proton to Delta+ omega were determined from
measurements of the CB-ELSA experiment, performed at the electron accelerator
ELSA in Bonn. The measurements covered the photon energy range from the
production threshold up to 3GeV.Comment: 8 pages, 13 figure
Observation of in
Using a sample of events recorded with
the BESIII detector at the symmetric electron positron collider BEPCII, we
report the observation of the decay of the charmonium state
into a pair of mesons in the process
. The branching fraction is measured for the first
time to be , where the first uncertainty is
statistical, the second systematic and the third is from the uncertainty of
. The mass and width of the are
determined as MeV/ and
MeV.Comment: 13 pages, 6 figure
- …