153 research outputs found
A natural orbital functional for the many-electron problem
The exchange-correlation energy in Kohn-Sham density functional theory is
expressed as a functional of the electronic density and the Kohn-Sham orbitals.
An alternative to Kohn-Sham theory is to express the energy as a functional of
the reduced first-order density matrix or equivalently the natural orbitals. In
the former approach the unknown part of the functional contains both a kinetic
and a potential contribution whereas in the latter approach it contains only a
potential energy and consequently has simpler scaling properties. We present an
approximate, simple and parameter-free functional of the natural orbitals,
based solely on scaling arguments and the near satisfaction of a sum rule. Our
tests on atoms show that it yields on average more accurate energies and charge
densities than the Hartree Fock method, the local density approximation and the
generalized gradient approximations
Phase transition from straight into twisted vortex-lines in dipolar Bose-Einstein condensates
The non-local non-linearity introduced by the dipole-dipole interaction plays
a crucial role in the physics of dipolar Bose-Einstein condensates. In
particular, it may distort significantly the stability of straight vortex lines
due to the rotonization of the Kelvin-wave spectrum. In this paper we analyze
this instability showing that it leads to a second-order-like phase transition
from a straight vortex-line into novel helical or snake-like configurations,
depending on the dipole orientation.Comment: 11 pages, 6 figures, Accepted for publication in New J. Phy
Observation of vortex formation in an oscillating trapped Bose-Einstein condensate
We report on the observation of vortex formation in a Bose-Einstein
condensate of Rb-87 atoms. Vortices are generated by superimposing an
oscillating excitation to the trapping potential introduced by an external
magnetic field. For small amplitudes of the external excitation field we
observe a bending of the cloud axis. Increasing the amplitude we observe
formation of a growing number of vortices in the sample. Shot-to-shot
variations in both vortex number and position within the condensed cloud are
observed, probably due to the intrinsic vortex nucleation dynamics. We discuss
the possible formation of vortices and anti-vortices in the sample as well as
possible mechanisms for vortex nucleation.Comment: 1 figure added, text modified, accepted for publication Phys. Rev.
pfk13-Independent Treatment Failure in Four Imported Cases of Plasmodium falciparum Malaria Treated with Artemether-Lumefantrine in the United Kingdom.
We present case histories of four patients treated with artemether-lumefantrine for falciparum malaria in UK hospitals in 2015 to 2016. Each subsequently presented with recurrent symptoms and Plasmodium falciparum parasitemia within 6 weeks of treatment with no intervening travel to countries where malaria is endemic. Parasite isolates, all of African origin, harbored variants at some candidate resistance loci. No evidence of pfk13-mediated artemisinin resistance was found. Vigilance for signs of unsatisfactory antimalarial efficacy among imported cases of malaria is recommended
The physics of dipolar bosonic quantum gases
This article reviews the recent theoretical and experimental advances in the
study of ultracold gases made of bosonic particles interacting via the
long-range, anisotropic dipole-dipole interaction, in addition to the
short-range and isotropic contact interaction usually at work in ultracold
gases. The specific properties emerging from the dipolar interaction are
emphasized, from the mean-field regime valid for dilute Bose-Einstein
condensates, to the strongly correlated regimes reached for dipolar bosons in
optical lattices.Comment: Review article, 71 pages, 35 figures, 350 references. Submitted to
Reports on Progress in Physic
A Finitary Characterization of the Ewens Sampling Formula
As the Ewens sampling formula represents an equilibrium distribution satisfying detailed balance, some properties difficult to prove are derived in a simple way
A global invariant for three dimensional CR-manifolds
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46621/1/222_2005_Article_BF01404456.pd
Metabolic responses to the acute ingestion of two commercially available carbonated beverages: A pilot study
<p>Abstract</p> <p>Background</p> <p>The purpose of this placebo-controlled, double-blind cross-over study was to compare the effects of two commercially available soft drinks on metabolic rate.</p> <p>Methods</p> <p>After giving informed consent, twenty healthy men and women were randomly assigned to ingest 12 ounces of Celsiusâą and, on a separate day, 12 ounces of Diet CokeÂź. All subjects completed both trials using a randomized, counterbalanced design. Metabolic rate (via indirect calorimetry) and substrate oxidation (via respiratory exchange ratio) were measured at baseline (pre-ingestion) and at the end of each hour for 3 hours post-ingestion.</p> <p>Results</p> <p>Two-way ANOVA revealed a significant interaction (p < 0.001) between trials in metabolic rate. Scheffe post-hoc testing indicated that metabolic rate increased by 13.8% (+ 0.6 L/min, p < 0.001) 1 hr post, 14.4% (+0.63 L/min, p < 0.001) 2 hr post, and 8.5% (+0.37 L/min, p < 0.004) 3 hr post Celsiusâą ingestion. In contrast, small (~4â6%) but statistically insignificant increases in metabolic rate were noted following Diet Coke<sup>Âź </sup>ingestion. No differences in respiratory exchange ratio were noted between trials.</p> <p>Conclusion</p> <p>These preliminary findings indicate Celsiusâą has thermogenic properties when ingested acutely. The effects of repeated, chronic ingestion of Celsiusâą on body composition are unknown at this time.</p
Patterns of Selection in Anti-Malarial Immune Genes in Malaria Vectors: Evidence for Adaptive Evolution in LRIM1 in Anopheles arabiensis
Co-evolution between Plasmodium species and its vectors may result in adaptive changes in genes that are crucial components of the vector's defense against the pathogen. By analyzing which genes show evidence of positive selection in malaria vectors, but not in closely related non-vectors, we can identify genes that are crucial for the mosquito's resistance against Plasmodium.We investigated genetic variation of three anti-malarial genes; CEC1, GNBP-B1 and LRIM1, in both vector and non-vector species of the Anopheles gambiae complex. Whereas little protein differentiation was observed between species in CEC1 and GNBP-B1, McDonald-Kreitman and maximum likelihood tests of positive selection show that LRIM1 underwent adaptive evolution in a primary malaria vector; An. arabiensis. In particular, two adjacent codons show clear signs of adaptation by having accumulated three out of four replacement substitutions. Furthermore, our data indicate that this LRIM1 allele has introgressed from An. arabiensis into the other main malaria vector An. gambiae.Although no evidence exists to link the adaptation of LRIM1 to P. falciparum infection, an adaptive response of a known anti-malarial gene in a primary malaria vector is intriguing, and may suggest that this gene could play a role in Plasmodium resistance in An. arabiensis. If so, our data also predicts that LRIM1 alleles in An. gambiae vary in their level of resistance against P. falciparum
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