4,097 research outputs found
Quenching of light hadrons at RHIC in a collisional energy loss scenario
We evaluate the nuclear suppression factor, for light hadrons
by taking into account the collisional energy loss. We show that in the
measured domain of RHIC the elastic process is the dominant mechanism for
the partonic energy loss.Comment: 4 pages with 3 figures, Quark Matter 2008 Proceeding
Electric Field Control of Soliton Motion and Stacking in Trilayer Graphene
The crystal structure of a material plays an important role in determining
its electronic properties. Changing from one crystal structure to another
involves a phase transition which is usually controlled by a state variable
such as temperature or pressure. In the case of trilayer graphene, there are
two common stacking configurations (Bernal and rhombohedral) which exhibit very
different electronic properties. In graphene flakes with both stacking
configurations, the region between them consists of a localized strain soliton
where the carbon atoms of one graphene layer shift by the carbon-carbon bond
distance. Here we show the ability to move this strain soliton with a
perpendicular electric field and hence control the stacking configuration of
trilayer graphene with only an external voltage. Moreover, we find that the
free energy difference between the two stacking configurations scales
quadratically with electric field, and thus rhombohedral stacking is favored as
the electric field increases. This ability to control the stacking order in
graphene opens the way to novel devices which combine structural and electrical
properties
Band Structure Mapping of Bilayer Graphene via Quasiparticle Scattering
A perpendicular electric field breaks the layer symmetry of Bernal-stacked
bilayer graphene, resulting in the opening of a band gap and a modification of
the effective mass of the charge carriers. Using scanning tunneling microscopy
and spectroscopy, we examine standing waves in the local density of states of
bilayer graphene formed by scattering from a bilayer/trilayer boundary. The
quasiparticle interference properties are controlled by the bilayer graphene
band structure, allowing a direct local probe of the evolution of the band
structure of bilayer graphene as a function of electric field. We extract the
Slonczewski-Weiss-McClure model tight binding parameters as
eV, eV, and eV.Comment: 12 pages, 4 figure
Percolation in Models of Thin Film Depositions
We have studied the percolation behaviour of deposits for different
(2+1)-dimensional models of surface layer formation. The mixed model of
deposition was used, where particles were deposited selectively according to
the random (RD) and ballistic (BD) deposition rules. In the mixed one-component
models with deposition of only conducting particles, the mean height of the
percolation layer (measured in monolayers) grows continuously from 0.89832 for
the pure RD model to 2.605 for the pure RD model, but the percolation
transition belong to the same universality class, as in the 2- dimensional
random percolation problem. In two- component models with deposition of
conducting and isolating particles, the percolation layer height approaches
infinity as concentration of the isolating particles becomes higher than some
critical value. The crossover from 2d to 3d percolation was observed with
increase of the percolation layer height.Comment: 4 pages, 5 figure
Transcriptional profiling of vaccine-induced immune responses in humans and non-human primates
There is an urgent need for pre-clinical and clinical biomarkers predictive of vaccine immunogenicity, efficacy and safety to reduce the risks and costs associated with vaccine development. Results emerging from immunoprofiling studies in non-human primates and humans demonstrate clearly that (i) type and duration of immune memory are largely determined by the magnitude and complexity of the innate immune signals and (ii) genetic signatures highly predictive of B-cell and T-cell responses can be identified for specific vaccines. For vaccines with similar composition, e.g. live attenuated viral vaccines, these signatures share common patterns. Signatures predictive of vaccine efficacy have been identified in a few experimental challenge studies. This review aims to give an overview of the current literature on immunoprofiling studies in humans and also presents some of our own data on profiling of licensed and experimental vaccines in non-human primates
An Empirical Study of Assumptions in Bayesian Optimisation
Inspired by the increasing desire to efficiently tune machine learning
hyper-parameters, in this work we rigorously analyse conventional and
non-conventional assumptions inherent to Bayesian optimisation. Across an
extensive set of experiments we conclude that: 1) the majority of
hyper-parameter tuning tasks exhibit heteroscedasticity and non-stationarity,
2) multi-objective acquisition ensembles with Pareto-front solutions
significantly improve queried configurations, and 3) robust acquisition
maximisation affords empirical advantages relative to its non-robust
counterparts. We hope these findings may serve as guiding principles, both for
practitioners and for further research in the field
Regulation of Apoptosis in Myeloid Cells by Interferon Consensus Sequence–Binding Protein
Mice with a null mutation of the gene encoding interferon consensus sequence–binding protein (ICSBP) develop a disease with marked expansion of granulocytes and macrophages that frequently progresses to a fatal blast crisis, thus resembling human chronic myelogenous leukemia (CML). One important feature of CML is decreased responsiveness of myeloid cells to apoptotic stimuli. Here we show that myeloid cells from mice deficient in ICSBP exhibit reduced spontaneous apoptosis and a significant decrease in sensitivity to apoptosis induced by DNA damage. In contrast, apoptosis in thymocytes from ICSBP-deficient mice is unaffected. We also show that overexpression of ICSBP in the human U937 monocytic cell line enhances the rate of spontaneous apoptosis and the sensitivity to apoptosis induced by etoposide, lipopolysaccharide plus ATP, or rapamycin. Programmed cell death induced by etoposide was specifically blocked by peptides inhibitory for the caspase-1 or caspase-3 subfamilies of caspases. Studies of proapoptotic genes showed that cells overexpressing ICSBP have enhanced expression of caspase-3 precursor protein. In addition, analyses of antiapoptotic genes showed that overexpression of ICSBP results in decreased expression of Bcl-XL. These data suggest that ICSBP modulates survival of myeloid cells by regulating expression of apoptosis-related genes
Canonical formulation of self-gravitating spinning-object systems
Based on the Arnowitt-Deser-Misner (ADM) canonical formulation of general
relativity, a canonical formulation of gravitationally interacting classical
spinning-object systems is given to linear order in spin. The constructed
position, linear momentum and spin variables fulfill standard Poisson bracket
relations. A spatially symmetric time gauge for the tetrad field is introduced.
The achieved formulation is of fully reduced form without unresolved
constraints, supplementary, gauge, or coordinate conditions. The canonical
field momentum is not related to the extrinsic curvature of spacelike
hypersurfaces in standard ADM form. A new reduction of the tetrad degrees of
freedom to the Einstein form of the metric field is suggested.Comment: 6 pages. v2: extended version; identical to the published one. v3:
corrected misprints in (24) and (39); improved notation; added note regarding
a further reference
Inhomogeneous d-wave superconducting state of a doped Mott insulator
Recent scanning tunneling microscope (STM) measurements discovered remarkable
electronic inhomogeneity, i.e. nano-scale spatial variations of the local
density of states (LDOS) and the superconducting energy gap, in the high-Tc
superconductor BSCCO. Based on the experimental findings we conjectured that
the inhomogeneity arises from variations in local oxygen doping level and may
be generic of doped Mott insulators which behave rather unconventionally in
screening the dopant ionic potentials at atomic scales comparable to the short
coherence length. Here, we provide theoretical support for this picture. We
study a doped Mott insulator within a generalized t-J model, where doping is
accompanied by ionic Coulomb potentials centered in the BiO plane. We calculate
the LDOS spectrum, the integrated LDOS, and the local superconducting gap, make
detailed comparisons to experiments, and find remarkable agreement with the
experimental data. We emphasize the unconventional screening in a doped Mott
insulator and show that nonlinear screening dominates at nano-meter scales
which is the origin of the electronic inhomogeneity. It leads to strong
inhomogeneous redistribution of the local hole density and promotes the notion
of a local doping concentration. We find that the inhomogeneity structure
manifests itself at all energy scales in the STM tunneling differential
conductance, and elucidate the similarity and the differences between the data
obtained in the constant tunneling current mode and the same data normalized to
reflect constant tip-to-sample distance. We also discuss the underdoped case
where nonlinear screening of the ionic potential turns the spatial electronic
structure into a percolative mixture of patches with smaller pairing gaps
embedded in a background with larger gaps to single particle excitations.Comment: 19 pages, final versio
- …