841 research outputs found
Supersolid Helium at High Pressure
We have measured the pressure dependence of the supersolid fraction by a
torsional oscillator technique. Superflow is found from 25.6 bar up to 136.9
bar. The supersolid fraction in the low temperature limit increases from 0.6 %
at 25.6 bar near the melting boundary up to a maximum of 1.5% near 55 bar
before showing a monotonic decrease with pressure extrapolating to zero near
170 bar.Comment: 4 pages, 4 figure
The Structure of Cerium at the Temperature of Liquid Air
In a dilatometric investigation of metallic cerium Trombe and Foex observed under certain conditions a transition at 109°K which was accompanied by a 10 percent volume decrease and a decrease in magnetic susceptibility. Professor Linus Pauling suggested to us in 1946 that this transition is caused by the promotion of 4f electron to a bond-forming orbital, and that the dense phase be studied by x-ray diffraction. This investigation described below was completed in 1948. Lawson and Tang have recently produced the transition at 15,000 atmospheres; they found there essentially the same structure which we found at the temperature of liquid air
Valence-bond crystals in the kagome spin-1/2 Heisenberg antiferromagnet: a symmetry classification and projected wave function study
In this paper, we do a complete classification of valence-bond crystals
(VBCs) on the kagome lattice based on general arguments of symmetry only and
thus identify many new VBCs for different unit cell sizes. For the spin-1/2
Heisenberg antiferromagnet, we study the relative energetics of competing
gapless spin liquids (SLs) and VBC phases within the class of
Gutzwiller-projected fermionic wave functions using variational Monte Carlo
techniques, hence implementing exactly the constraint of one fermion per site.
By using a state-of-the-art optimization method, we conclusively show that the
U(1) Dirac SL is remarkably stable towards dimerizing into all 6-, 12- and
36-site unit cell VBCs. This stability is also preserved on addition of a
next-nearest-neighbor super-exchange coupling of both antiferromagnetic and
ferromagnetic (FM) type. However, we find that a 36-site unit cell VBC is
stabilized on addition of a very small next-nearest-neighbor FM super-exchange
coupling, i.e. |J2|~0.045, and this VBC is the same in terms of space-group
symmetry as that obtained in an effective quantum dimer model study. It breaks
reflection symmetry, has a nontrivial flux pattern and is a strong dimerization
of the uniform RVB SL.Comment: 16 pages, 25 figures. Invited paper for Focus issue on "Quantum Spin
Liquids" of the New Journal of Physic
Determinação da concentração inibitĂłria mĂnima do Ăłleo essencial de Cymbopogon citratus em bactĂ©rias causadoras de mastite bovina.
The role of depression in the association between mobilisation timing and live discharge after hip fracture surgery: Secondary analysis of the UK National Hip Fracture Database
Purpose
The aim was to compare the probability of discharge after hip fracture surgery conditional on being alive and in hospital between patients mobilised within and beyond 36-hours of surgery across groups defined by depression.
Methods
Data were taken from the National Hip Fracture Database and included patients 60 years of age or older who underwent hip fracture surgery in England and Wales between 2014 and 2016. The conditional probability of postsurgical live discharge was estimated for patients mobilised early and for patients mobilised late across groups with and without depression. The association between mobilisation timing and the conditional probability of live discharge were also estimated separately through adjusted generalized linear models.
Results
Data were analysed for 116,274 patients. A diagnosis of depression was present in 8.31% patients. In those with depression, 7,412 (76.7%) patients mobilised early. In those without depression, 84,085 (78.9%) patients mobilised early. By day 30 after surgery, the adjusted odds ratio of discharge among those who mobilised early compared to late was 1.79 (95% CI: 1.56â2.05, p<0.001) and 1.92 (95% CI: 1.84â2.00, p<0.001) for those with and without depression, respectively.
Conclusion
A similar proportion of patients with depression mobilised early after hip fracture surgery when compared to those without a diagnosis of depression. The association between mobilisation timing and time to live discharge was observed for patients with and without depression
Exact symmetry breaking ground states for quantum spin chains
We introduce a family of spin-1/2 quantum chains, and show that their exact
ground states break the rotational and translational symmetries of the original
Hamiltonian. We also show how one can use projection to construct a spin-3/2
quantum chain with nearest neighbor interaction, whose exact ground states
break the rotational symmetry of the Hamiltonian. Correlation functions of both
models are determined in closed form. Although we confine ourselves to
examples, the method can easily be adapted to encompass more general models.Comment: 4 pages, RevTex. 4 figures, minor changes, new reference
Avaliação de material crioulo de feijão (Phaseolus vulgaris) para utilização em programas de melhoramento.
HITRAP: A facility at GSI for highly charged ions
An overview and status report of the new trapping facility for highly charged
ions at the Gesellschaft fuer Schwerionenforschung is presented. The
construction of this facility started in 2005 and is expected to be completed
in 2008. Once operational, highly charged ions will be loaded from the
experimental storage ring ESR into the HITRAP facility, where they are
decelerated and cooled. The kinetic energy of the initially fast ions is
reduced by more than fourteen orders of magnitude and their thermal energy is
cooled to cryogenic temperatures. The cold ions are then delivered to a broad
range of atomic physics experiments.Comment: 8 pages, 11 figure
Aclimatização e crescimento de plùntulas de mirtileiro 'Climax' micropropagadas em função do substrato e da cobertura plåstica.
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