140 research outputs found
Diffused vorticity approach to the oscillations of a rotating Bose-Einstein condensate confined in a harmonic plus quartic trap
The collective modes of a rotating Bose-Einstein condensate confined in an
attractive quadratic plus quartic trap are investigated. Assuming the presence
of a large number of vortices we apply the diffused vorticity approach to the
system. We then use the sum rule technique for the calculation of collective
frequencies, comparing the results with the numerical solution of the
linearized hydrodynamic equations. Numerical solutions also show the existence
of low-frequency multipole modes which are interpreted as vortex oscillations.Comment: 10 pages, 4 figure
A Textured Silicon Calorimetric Light Detector
We apply the standard photovoltaic technique of texturing to reduce the
reflectivity of silicon cryogenic calorimetric light detectors. In the case of
photons with random incidence angles, absorption is compatible with the
increase in surface area. For the geometrically thin detectors studied, energy
resolution from athermal phonons, dominated by position dependence, is
proportional to the surface-to-volume ratio. With the CaWO4 scintillating
crystal used as light source, the time constants of the calorimeter should be
adapted to the relatively slow light-emission times.Comment: Submitted to Journal of Applied Physic
Early marker of ocular neurodegeneration in children and adolescents with type 1 diabetes: the contributing role of polymorphisms in mir146a and mir128a genes
Background: Early ocular neurodegenerative signs of diabetic neuropathy (DN) can be found in children and adolescents with type 1 diabetes (T1D). No data are available on the potential role of polymorphisms in miRNAs genes in predisposing T1D subjects to these signs. Aims: To determine whether MIR146A rs2910164 and MIR128A rs11888095 polymorphisms are associated with early retinal and corneal neurodegenerative changes in pediatric patients with T1D. Methods: A total of 140 T1D children/adolescents underwent spectral domain-optical coherence tomography (SD-OCT) and in vivo confocal microscopy (IVCM) with measurement of retinal and corneal nerve fiber parameters. Risk factors for diabetes complications (diabetes duration, blood pressure, HbA1c) were recorded. Genotyping of rs2910164 and rs1188095 SNPs and genotype-phenotype association analysis were performed. Results: The C allele of rs2910164 in MIR146A was associated with higher values of IVCM parameters and minimum rim width (MRW) of the peripapillary region of optic nerve head measured in the retina, whereas the T allele of rs1188095 in MIR128A was associated with a significant impairment of them. Multiple regression analysis showed that MIR146A and MIR128A polymorphisms were significantly associated with corneal nerve fiber length (beta = 0.225 and - 0.204, respectively) and other IVCM parameters, independently from age, diabetes duration, HbA1c and systolic blood pressure percentile. Similar results were found for MRW (beta = 0.213 and - 0.286, respectively). Conclusions: These results provide new insight into the genetic predisposition to DN showing that two polymorphisms in MIR146A and MIR128A genes could significantly contribute to the development of early ocular preclinical signs of DN
Scissors mode of trapped dipolar gases
We study the scissors modes of dipolar boson and fermion gases trapped in a
spherically symmetric potential. We use the harmonic oscillator states to solve
the time-dependent Gross-Pitaevskii equation for bosons and the time-dependent
Hartree-Fock equation for fermions. It is pointed out that the scissors modes
of bosons and fermions can be of quite different nature
Vortex lattice of a Bose-Einstein Condensate in a rotating anisotropic trap
We study the vortex lattices in a Bose-Einstein Condensate in a rotating
anisotropic harmonic trap. We first investigate the single particle
wavefunctions obtained by the exact solution of the problem and give simple
expressions for these wavefunctions in the small anisotropy limit. Depending on
the strength of the interactions, a few or a large number of vortices can be
formed. In the limit of many vortices, we calculate the density profile of the
cloud and show that the vortex lattice stays triangular. We also find that the
vortex lattice planes align themselves with the weak axis of the external
potential. For a small number of vortices, we numerically solve the
Gross-Pitaevskii equation and find vortex configurations that are very
different from the vortex configurations in an axisymmetric rotating trap.Comment: 15 pages,4 figure
Kelvin Modes of a fast rotating Bose-Einstein Condensate
Using the concept of diffused vorticity and the formalism of rotational
hydrodynamics we calculate the eigenmodes of a harmonically trapped
Bose-Einstein condensate containing an array of quantized vortices. We predict
the occurrence of a new branch of anomalous excitations, analogous to the
Kelvin modes of the single vortex dynamics. Special attention is devoted to the
excitation of the anomalous scissors mode.Comment: 7 pages, 3 figures, submitted to Phys. Rev.
The CRESST Experiment: Recent Results and Prospects
The CRESST experiment seeks hypothetical WIMP particles that could account
for the bulk of dark matter in the Universe. The detectors are cryogenic
calorimeters in which WIMPs would scatter elastically on nuclei, releasing
phonons. The first phase of the experiment has successfully deployed several
262 g sapphire devices in the Gran Sasso underground laboratories. A main
source of background has been identified as microscopic mechanical fracturing
of the crystals, and has been eliminated, improving the background rate by up
to three orders of magnitude at low energies, leaving a rate close to one count
per day per kg and per keV above 10 keV recoil energy. This background now
appears to be dominated by radioactivity, and future CRESST scintillating
calorimeters which simultaneously measure light and phonons will allow
rejection of a great part of it.Comment: To appear in the proceedings of the CAPP2000 Conference, Verbier,
Switzerland, July, 2000 (eds J. Garcia-Bellido, R. Durrer, and M.
Shaposhnikov
Polytetrahedral Clusters
By studying the structures of clusters bound by a model potential that
favours polytetrahedral order, we find a previously unknown series of `magic
numbers' (i.e. sizes of special stability) whose polytetrahedral structures are
characterized by disclination networks that are analogous to hydrocarbons.Comment: 4 pages, 4 figure
Crossovers in Unitary Fermi Systems
Universality and crossover is described for attractive and repulsive
interactions where, respectively, the BCS-BEC crossover takes place and a
ferromagnetic phase transition is claimed. Crossovers are also described for
optical lattices and multicomponent systems. The crossovers, universal
parameters and phase transitions are described within the Leggett and NSR
models and calculated in detail within the Jastrow-Slater approximation. The
physics of ultracold Fermi atoms is applied to neutron, nuclear and quark
matter, nuclei and electrons in solids whenever possible. Specifically, the
differences between optical lattices and cuprates is discussed w.r.t.
antiferromagnetic, d-wave superfluid phases and phase separation.Comment: 50 pages, 15 figures. Contribution to Lecture Notes in Physics
"BCS-BEC crossover and the Unitary Fermi Gas" edited by W. Zwerge
ALADYN: a web server for aligning proteins by matching their large-scale motion
The ALADYN web server aligns pairs of protein structures by comparing their internal dynamics and detecting regions that sustain similar large-scale movements. The latter often accompany functional conformational changes in proteins and enzymes. The ALADYN dynamics-based alignment can therefore highlight functionally-oriented correspondences that could be more elusive to sequence- or structure-based comparisons. The ALADYN server takes the structure files of the two proteins as input. The optimal relative positioning of the molecules is found by maximizing the similarity of the pattern of structural fluctuations which are calculated via an elastic network model. The resulting alignment is presented via an interactive graphical Java applet and is accompanied by a number of quantitative indicators and downloadable data files. The ALADYN web server is freely accessible at the http://aladyn.escience-lab.org address
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