2,243 research outputs found
Viscosity in the excluded volume hadron gas model
The shear viscosity in the van der Waals excluded volume
hadron-resonance gas model is considered. For the shear viscosity the result of
the non-relativistic gas of hard-core particles is extended to the mixture of
particles with different masses, but equal values of hard-core radius r. The
relativistic corrections to hadron average momenta in thermal equilibrium are
also taken into account. The ratio of the viscosity to the entropy
density s is studied. It monotonously decreases along the chemical freeze-out
line in nucleus-nucleus collisions with increasing collision energy. As a
function of hard-core radius r, a broad minimum of the ratio near fm is found at high collision energies. For the
charge-neutral system at MeV, a minimum of the ratio is reached for fm. To justify a hydrodynamic approach to
nucleus-nucleus collisions within the hadron phase the restriction from below,
fm, on the hard-core hadron radius should be fulfilled in the
excluded volume hadron-resonance gas.Comment: 12 pages, 3 figure
Vibronic origin of long-lived coherence in an artificial molecular light harvester
Natural and artificial light harvesting processes have recently gained new
interest. Signatures of long lasting coherence in spectroscopic signals of
biological systems have been repeatedly observed, albeit their origin is a
matter of ongoing debate, as it is unclear how the loss of coherence due to
interaction with the noisy environments in such systems is averted. Here we
report experimental and theoretical verification of coherent
exciton-vibrational (vibronic) coupling as the origin of long-lasting coherence
in an artificial light harvester, a molecular J-aggregate. In this
macroscopically aligned tubular system, polarization controlled 2D spectroscopy
delivers an uncongested and specific optical response as an ideal foundation
for an in-depth theoretical description. We derive analytical expressions that
show under which general conditions vibronic coupling leads to prolonged
excited-state coherence
On multiplicity correlations in the STAR data
The STAR data on the multiplicity correlations between narrow psudorapidity
bins in the pp and AuAu collisions are discussed. The PYTHIA 8.145 generator is
used for the pp data, and a naive superposition model is presented for the AuAu
data. It is shown that the PYTHIA generator with default parameter values
describes the pp data reasonably well, whereas the superposition model fails to
reproduce the centrality dependence seen in the data. Some possible reasons for
this failure and a comparison with other models are presented.Comment: 8 pages, 3 figure
Evolutionary conserved networks of human height identify multiple Mendelian causes of short stature
Height is a heritable and highly heterogeneous trait. Short stature affects 3% of the population and in most cases is genetic in origin. After excluding known causes, 67% of affected individuals remain without diagnosis. To identify novel candidate genes for short stature, we performed exome sequencing in 254 unrelated families with short stature of unknown cause and identified variants in 63 candidate genes in 92 (36%) independent families. Based on systematic characterization of variants and functional analysis including expression in chondrocytes, we classified 13 genes as strong candidates. Whereas variants in at least two families were detected for all 13 candidates, two genes had variants in 6 (UBR4) and 8 (LAMA5) families, respectively. To facilitate their characterization, we established a clustered network of 1025 known growth and short stature genes, which yielded 29 significantly enriched clusters, including skeletal system development, appendage development, metabolic processes, and ciliopathy. Eleven of the candidate genes mapped to 21 of these clusters, including CPZ, EDEM3, FBRS, IFT81, KCND1, PLXNA3, RASA3, SLC7A8, UBR4, USP45, and ZFHX3. Fifty additional growth-related candidates we identified await confirmation in other affected families. Our study identifies Mendelian forms of growth retardation as an important component of idiopathic short stature
Superstring Theory on AdS_2 x S^2 as a Coset Supermanifold
We quantize the superstring on the AdS_2 x S^2 background with Ramond-Ramond
flux using a PSU(1,1|2)/U(1) x U(1) sigma model with a WZ term. One-loop
conformal invariance of the model is guaranteed by a general mechanism which
holds for coset spaces G/H where G is Ricci-flat and H is the invariant locus
of a Z_4 automorphism of G. This mechanism gives conformal theories for the
PSU(1,1|2) x PSU(2|2)/SU(2) x SU(2) and PSU(2,2|4)/SO(4,1) x SO(5) coset
spaces, suggesting our results might be useful for quantizing the superstring
on AdS_3 x S^3 and AdS_5 x S^5 backgrounds.Comment: 34 pages, 4 figures, harvmac big mode ; typos corrected, clarified
the choice of the real form
Diversity, Fairness, and Data-Driven Personalization in (News) Recommender System:Report from Dagstuhl Perspectives Workshop 19482
Diversity, Fairness, and Data-Driven Personalization in (News) Recommender System:Report from Dagstuhl Perspectives Workshop 19482
Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters
The initial energy transfer in photosynthesis occurs between the
light-harvesting pigments and on ultrafast timescales. We analyze the
carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium
purpuratum as well as in an artificial light-harvesting dyad system by using
transient grating and two-dimensional electronic spectroscopy with 10 fs time
resolution. We find that F\"orster-type models reproduce the experimentally
observed 60 fs transfer times, but overestimate coupling constants, which leads
to a disagreement with both linear absorption and electronic 2D-spectra. We
show that a vibronic model, which treats carotenoid vibrations on both
electronic ground and excited state as part of the system's Hamiltonian,
reproduces all measured quantities. Importantly, the vibronic model presented
here can explain the fast energy transfer rates with only moderate coupling
constants, which are in agreement with structure based calculations.
Counterintuitively, the vibrational levels on the carotenoid electronic ground
state play a central role in the excited state population transfer to
bacteriochlorophyll as the resonance between the donor-acceptor energy gap and
vibrational ground state energies is the physical basis of the ultrafast energy
transfer rates in these systems
Evolution of T Cell Responses during Measles Virus Infection and RNA Clearance
Measles is an acute viral disease associated both with immune suppression and development of life-long immunity. Clearance of measles virus (MeV) involves rapid elimination of infectious virus during the rash followed by slow elimination of viral RNA. To characterize cellular immune responses during recovery, we analyzed the appearance, specificity and function of MeV-specific T cells for 6 months after respiratory infection of rhesus macaques with wild type MeV. IFN-γ and IL-17-producing cells specific for the hemagglutinin and nucleocapsid proteins appeared in circulation in multiple waves approximately 2-3, 8 and 18-24 weeks after infection. IFN-γ-secreting cells were most abundant early and IL-17-secreting cells late. Both CD4 and CD8 T cells were sources of IFN-γ and IL-17, and IL-17-producing cells expressed RORγt. Therefore, the cellular immune response evolves during MeV clearance to produce functionally distinct subsets of MeV-specific CD4 and CD8 T cells at different times after infection
- …