5,709 research outputs found
Yang-Lee Theory for a Nonequilibrium Phase Transition
To analyze phase transitions in a nonequilibrium system we study its grand
canonical partition function as a function of complex fugacity. Real and
positive roots of the partition function mark phase transitions. This behavior,
first found by Yang and Lee under general conditions for equilibrium systems,
can also be applied to nonequilibrium phase transitions. We consider a
one-dimensional diffusion model with periodic boundary conditions. Depending on
the diffusion rates, we find real and positive roots and can distinguish two
regions of analyticity, which can identified with two different phases. In a
region of the parameter space both of these phases coexist. The condensation
point can be computed with high accuracy.Comment: 4 pages, accepted for publication in Phys.Rev.Let
Thermal limitation of far-field matter-wave interference
We assess the effect of the heat radiation emitted by mesoscopic particles on
their ability to show interference in a double slit arrangement. The analysis
is based on a stationary, phase-space based description of matter wave
interference in the presence of momentum-exchange mediated decoherence.Comment: 8 pages, 2 figures; published versio
Universality of Long-Range Correlations in Expansion-Randomization Systems
We study the stochastic dynamics of sequences evolving by single site
mutations, segmental duplications, deletions, and random insertions. These
processes are relevant for the evolution of genomic DNA. They define a
universality class of non-equilibrium 1D expansion-randomization systems with
generic stationary long-range correlations in a regime of growing sequence
length. We obtain explicitly the two-point correlation function of the sequence
composition and the distribution function of the composition bias in sequences
of finite length. The characteristic exponent of these quantities is
determined by the ratio of two effective rates, which are explicitly calculated
for several specific sequence evolution dynamics of the universality class.
Depending on the value of , we find two different scaling regimes, which
are distinguished by the detectability of the initial composition bias. All
analytic results are accurately verified by numerical simulations. We also
discuss the non-stationary build-up and decay of correlations, as well as more
complex evolutionary scenarios, where the rates of the processes vary in time.
Our findings provide a possible example for the emergence of universality in
molecular biology.Comment: 23 pages, 15 figure
Homologous association of the Bithorax-Complex during embryogenesis: consequences for transvection in Drosophila melanogaster
Transvection is the phenomenon by which the expression of a gene can be controlled by its homologous counterpart in trans, presumably due to pairing of alleles in diploid interphase cells. Transvection or trans-sensing phenomena have been reported for several loci in Drosophila, the most thoroughly studied of which is the Bithorax-Complex (BX-C). It is not known how early trans-sensing occurs nor the extent or duration of the underlying physical interactions. We have investigated the physical proximity of homologous genes of the BX-C during Drosophila melanogaster embryogenesis by applying fluorescent in situ hybridization techniques together with high resolution confocal light microscopy and digital image processing. The association of homologous alleles of the BX-C starts in nuclear division cycle 13, reaches a plateau of 70% in post-gastrulating embryos, and is not perturbed by the transcriptional state of the genes throughout embryogenesis. Pairing frequencies never reach 100% indicative that the homologous associations are in equilibrium with a dissociated state. We determined the effects of translocations and a zeste protein null mutation, both of which strongly diminish transvection phenotypes, on the extent of diploid homologue pairing. Surprisingly, the pairing of homologous alleles was reduced, albeit only to 20 - 30%, by translocating one allele of the BX-C from the right arm of chromosome 3 to the left arm of chromosome 3 or to the X chromosome although trans-regulation of the Ultrabithorax gene was abolished. A zeste protein null mutation neither delayed the onset of pairing nor led to unpairing of the homologous alleles. These data are discussed in light of different models for trans-regulation. We examined the onset of pairing of the chromosome 4 as well as of loci near the centromere of chromosome 3 and near the telomere of 3R in order to test models for the mechanism of homologue pairing
Biotin-ligand complexes with Streptavidin quantum dots for in vivo cell labeling of membrane receptors
The Jabal Akhdar Dome in the Oman Mountains : evolution of a dynamic fracture system
Acknowledgments: This study was carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) research project 718 âMineral Vein Dynamics Modelling,â which is funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, RWE Dea AG and Wintershall Holding GmbH, within the basic research program of the WEG Wirtschaftsverband Erdošl- und Erdgasgewinnung e.V. We thank the companies for their financial support and their permission to publish these results. The German University of Technology in Oman (GU-Tech) is acknowledged for its logistic support. We gratefully acknowledge the reviewers Andrea Billi and Jean-Paul Breton, whose constructive reviews greatly improved the manuscriptPeer reviewedPreprin
Multipole Amplitudes of Pion Photoproduction on Nucleons up to 2GeV within Dispersion Relations and Unitary Isobar Model
Two approaches for analysis of pion photo- and electroproduction on nucleons
in the resonance energy region are checked at using the results of
GWU(VPI) partial-wave analysis of photoproduction data. The approaches are
based on dispersion relations and unitary isobar model. Within dispersion
relations good description of photoproduction multipoles is obtained up to
. Within unitary isobar model, modified with increasing energy by
incorporation of Regge poles, and with unified Breit-Wigner parametrization of
resonance contributions, good description of photoproduction multipoles is
obtained up to .Comment: 23 pages, LaTe
Symmetry breaking through a sequence of transitions in a driven diffusive system
In this work we study a two species driven diffusive system with open
boundaries that exhibits spontaneous symmetry breaking in one dimension. In a
symmetry broken state the currents of the two species are not equal, although
the dynamics is symmetric. A mean field theory predicts a sequence of two
transitions from a strongly symmetry broken state through an intermediate
symmetry broken state to a symmetric state. However, a recent numerical study
has questioned the existence of the intermediate state and instead suggested a
single discontinuous transition. In this work we present an extensive numerical
study that supports the existence of the intermediate phase but shows that this
phase and the transition to the symmetric phase are qualitatively different
from the mean-field predictions.Comment: 19 pages, 12 figure
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