4,059 research outputs found
Counterflow Extension for the F.A.S.T.-Model
The F.A.S.T. (Floor field and Agent based Simulation Tool) model is a
microscopic model of pedestrian dynamics, which is discrete in space and time.
It was developed in a number of more or less consecutive steps from a simple CA
model. This contribution is a summary of a study on an extension of the
F.A.S.T-model for counterflow situations. The extensions will be explained and
it will be shown that the extended F.A.S.T.-model is capable of handling
various counterflow situations and to reproduce the well known lane formation
effect.Comment: Contribution to Crowds and Cellular Automata Workshop 2008. Accepted
for publication in "Cellular Automata -- 8th International Conference on
Cellular Automata for Research and Industry, ACRI 2008, Yokohama, Japan,
September 23-26, Springer 2008, Proceedings
Effective lattice actions for correlated electrons
We present an exact, unconstrained representation of the electron operators
in terms of operators of opposite statistics. We propose a path--integral
representation for the - model and introduce a parameter controlling the
semiclassical behaviour. We extend the functional approach to the Hubbard model
and show that the mean--field theory is equivalent to considering, at
Hamiltonian level, the Falikov--Kimball model. Connections with a bond-charge
model are also discussed.Comment: 12 pages, REVTeX 3.0, no figure
New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn
We report the discovery of new superconducting and novel magnetic phases in
CeIn on the verge of antiferromagnetism (AFM) under pressure () through
the In-nuclear quadrupole resonance (NQR) measurements. We have found a
-induced phase separation of AFM and paramagnetism (PM) without any trace
for a quantum phase transition in CeIn. A new type of superconductivity
(SC) was found in GPa to coexist with AFM that is magnetically
separated from PM where the heavy fermion SC takes place. We propose that the
magnetic excitations such as spin-density fluctuations induced by the
first-order magnetic phase transition might mediate attractive interaction to
form Cooper pairs.Comment: 4 pages, 4 EPS figures, submitted to J. Phys. Soc. Jp
Free expansion of impenetrable bosons on one-dimensional optical lattices
We review recent exact results for the free expansion of impenetrable bosons
on one-dimensional lattices, after switching off a confining potential. When
the system is initially in a superfluid state, far from the regime in which the
Mott-insulator appears in the middle of the trap, the momentum distribution of
the expanding bosons rapidly approaches the momentum distribution of
noninteracting fermions. Remarkably, no loss in coherence is observed in the
system as reflected by a large occupation of the lowest eigenstate of the
one-particle density matrix. In the opposite limit, when the initial system is
a pure Mott insulator with one particle per lattice site, the expansion leads
to the emergence of quasicondensates at finite momentum. In this case,
one-particle correlations like the ones shown to be universal in the
equilibrium case develop in the system. We show that the out-of-equilibrium
behavior of the Shannon information entropy in momentum space, and its contrast
with the one of noninteracting fermions, allows to differentiate the two
different regimes of interest. It also helps in understanding the crossover
between them.Comment: 21 pages, 14 figures, invited brief revie
Fully Off-shell Effective Action and its Supersymmetry in Matrix Theory
As a step toward clarification of the power of supersymmetry (SUSY) in Matrix
theory, a complete calculation, including all the spin effects, is performed of
the effective action of a probe D-particle, moving along an arbitrary
trajectory in interaction with a large number of coincident source D-particles,
at one loop at order 4 in the derivative expansion. Furthermore, exploiting the
SUSY Ward identity developed previously, the quantum-corrected effective
supersymmetry transformation laws are obtained explicitly to the relevant order
and are used to verify the SUSY-invariance of the effective action. Assuming
that the agreement with 11-dimensional supergravity persists, our result can be
regarded as a prediction for supergravity calculation, which, yet unavailable,
is known to be highly non-trivial.Comment: 27 page
Itinerant U 5f band states in the layered compound UFeGa5 observed by soft X-ray angle-resolved photoemission spectroscopy
We have performed angle-resolved photoemission spectroscopy (ARPES)
experiments on paramagnetic UFeGa5 using soft X-ray synchrotron radiation
(hn=500eV) and derived the bulk- and U 5f-sensitive electronic structure of
UFeGa5. Although the agreement between the experimental band structure and the
LDA calculation treating U 5f electrons as being itinerant is qualitative, the
morphology of the Fermi surface is well explained by the calculation,
suggesting that the U 5f states can be essentially understood within the
itinerant-electron model.Comment: 13 pages, 4 figur
Beyond Tryptophan Synthase: Identification of Genes That Contribute to Chlamydia trachomatis Survival during Gamma Interferon-Induced Persistence and Reactivation
Chlamydia trachomatis can enter a viable but nonculturable state in vitro termed persistence. A common feature of C. trachomatis persistence models is that reticulate bodies fail to divide and make few infectious progeny until the persistence-inducing stressor is removed. One model of persistence that has relevance to human disease involves tryptophan limitation mediated by the host enzyme indoleamine 2,3-dioxygenase, which converts l-tryptophan to N-formylkynurenine. Genital C. trachomatis strains can counter tryptophan limitation because they encode a tryptophan-synthesizing enzyme. Tryptophan synthase is the only enzyme that has been confirmed to play a role in interferon gamma (IFN-γ)-induced persistence, although profound changes in chlamydial physiology and gene expression occur in the presence of persistence-inducing stressors. Thus, we screened a population of mutagenized C. trachomatis strains for mutants that failed to reactivate from IFN-γ-induced persistence. Six mutants were identified, and the mutations linked to the persistence phenotype in three of these were successfully mapped. One mutant had a missense mutation in tryptophan synthase; however, this mutant behaved differently from previously described synthase null mutants. Two hypothetical genes of unknown function, ctl0225 and ctl0694, were also identified and may be involved in amino acid transport and DNA damage repair, respectively. Our results indicate that C. trachomatis utilizes functionally diverse genes to mediate survival during and reactivation from persistence in HeLa cells
Robust, Conducting, and Transparent Polymer Composites using Surface-Modified and Individualized Double-Walled Carbon Nanotubes
This is the pre-peer reviewed version of the following article: ADVANCED MATERIALS. 20(23):4509-4512 (2008), which has been published in final form at 10.1002/adma.200801659.ArticleADVANCED MATERIALS. 20(23):4509-4512 (2008)journal articl
Raman study on electrochemical lithium insertion into multiwalled carbon nanotubes
This is the pre-peer reviewed version of the following article: JOURNAL OF RAMAN SPECTROSCOPY 39(9): 1183-1188, 2008, which has been published in final form http://www3.interscience.wiley.com/journal/118639317/abstract.ArticleJOURNAL OF RAMAN SPECTROSCOPY. 39(9): 1183-1188 (2008)journal articl
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