429 research outputs found
Temperature dependence of the energy of a vortex in a two-dimensional Bose gas
We evaluate the thermodynamic critical angular velocity Omega_c(T) for
creation of a vortex of lowest quantized angular momentum in a strictly
two-dimensional Bose gas at temperature T, using a mean-field two-fluid model
for the condensate and the thermal cloud. Our results show that (i) a
Thomas-Fermi description of the condensate badly fails in predicting the
particle density profiles and the energy of the vortex as functions of T; and
(ii) an extrapolation of a simple Thomas-Fermi formula for Omega_c(0) is
nevertheless approximately useful up to T = 0.5 T_c.Comment: 9 pages, 4 figure
Density profile of a strictly two-dimensional Bose gas at finite temperature
We study a Bose-condensed gas at finite temperature, in which the particles
of the condensate and of the thermal cloud are constrained to move in a plane
under radial harmonic confinement and interact via strictly two-dimensional
collisions. The coupling parameters are obtained from a calculation of the
many-body T-matrix and decreases as temperature increases through a dependence
on the chemical potential and on the occupancy of excited states. We discuss
the consequences on the condensate fraction and on the density profiles of the
condensed and thermal components as functions of temperature, within a
simplified form of the two-fluid model.Comment: 12 pages, 4 figure
Feshbach resonance in a strictly two-dimensional atomic Bose gas
We discuss the atom-atom scattering problem across a Feshbach resonance in a
two-dimensional dilute Bose gas at zero temperature, in the limit where the
s-wave scattering length exceeds the width of the vertical confinement. We
determine a tunable coupling-strength parameter and by controlling it we
evaluate how the condensate wave function spreads out with increasing atom-atom
repulsions. We also discuss the stability of the condensate in the
magnetic-field regime where the coupling has become attractive.Comment: 9 pages, 1 figur
Pairing in two-dimensional boson-fermion mixtures
The possibilities of pairing in two-dimensional boson-fermion mixtures are
carefully analyzed. It is shown that the boson-induced attraction between two
identical fermions dominates the p-wave pairing at low density. For a given
fermion density, the pairing gap becomes maximal at a certain optimal boson
concentration. The conditions for observing pairing in current experiments are
discussedComment: 10 pages, 5 figs, revtex
Tomato: a crop species amenable to improvement by cellular and molecular methods
Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures.
In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.
The Effects of Sugars Intake and Frequency of Ingestion on Dental Caries Increment in a Three-year Longitudinal Study
A three-year longitudinal study was carried out with a group of children, initially aged 11-15, residing in non-fluoridated rural communities in south-central Michigan. This report analyzes the relation between caries increment and consumption of sugars from all sources to see if accepted relationships have changed with the caries decline in the United States. There were 499 children who provided three or more 24-hour dietary recall interviews, and who received dental examinations at baseline and after three years. Caries increment averaged 2.91 DMFS over the three years, with 81 % of new lesions on pit-and-fissure surfaces. Consumption of sugars from all sources averaged 156 g per day for males and 127 g per day for females, an average of 52 kg per person per year. Sugars constituted one-quarter of total caloric intake for both boys and girls, and the average number of eating occasions per day was 4.3. Children who consumed a higher proportion of their total energy intake as sugars had a higher increment of approximal caries, though there was little relation to pit-and-fissure caries. The average number of daily eating occasions was not related to caries increment, nor was the average number of sugary snacks (defined as foods with 15% or more of sugars) consumed between meals, but the average consumption of between-meal sugars was related to the approximal caries increment. When children were categorized by high caries increment compared with no caries increment, a tendency toward more frequent snacks was seen in the high-caries children. In an age of generally declining caries, it was concluded that higher average daily consumption of sugars, and higher between-meal consumption of sugars, was still a risk factor for children susceptible to approximal caries. Overall frequency of eating and frequency of ingestion of sugary foods between meals, however, were both poorly related to approximal caries increment. Pit-and-fissure caries could not be related to any aspect of sugars consumption.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67206/2/10.1177_00220345880670111201.pd
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Development, characterization, and in vivo validation of a humanized C6 monoclonal antibody that inhibits the membrane attack complex
Damage and disease of nerves activates the complement system. We demonstrated that activation of the terminal pathway of the complement system leads to the formation of the membrane attack complex (MAC) and delays regeneration in the peripheral nervous system. Animals deficient in the complement component C6 showed improved recovery after neuronal trauma. Thus, inhibitors of the MAC might be of therapeutic use in neurological disease. Here, we describe the development, structure, mode of action, and properties of a novel therapeutic monoclonal antibody, CP010, against C6 that prevents formation of the MAC in vivo. The monoclonal antibody is humanized and specific for C6 and binds to an epitope in the FIM1-2 domain of human and primate C6 with sub-nanomolar affinity. Using biophysical and structural studies, we show that the anti-C6 antibody prevents the interaction between C6 and C5/C5b by blocking the C6 FIM1-2:C5 C345c axis. Systemic administration of the anti-C6 mAb caused complete depletion of free C6 in circulation in transgenic rats expressing human C6 and thereby inhibited MAC formation. The antibody prevented disease in experimental autoimmune myasthenia gravis and ameliorated relapse in chronic relapsing experimental autoimmune encephalomyelitis in human C6 transgenic rats. CP010 is a promising complement C6 inhibitor that prevents MAC formation. Systemic administration of this C6 monoclonal antibody has therapeutic potential in the treatment of neuronal disease.Molecular Epidemiolog
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS
The chi_b(nP) quarkonium states are produced in proton-proton collisions at
the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS
detector. Using a data sample corresponding to an integrated luminosity of 4.4
fb^-1, these states are reconstructed through their radiative decays to
Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks
corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new
structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is
also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes.
This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table,
corrected author list, matches final version in Physical Review Letter
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