1,470 research outputs found
Geometry of entangled states, Bloch spheres and Hopf fibrations
We discuss a generalization to 2 qubits of the standard Bloch sphere
representation for a single qubit, in the framework of Hopf fibrations of high
dimensional spheres by lower dimensional spheres. The single qubit Hilbert
space is the 3-dimensional sphere S3. The S2 base space of a suitably oriented
S3 Hopf fibration is nothing but the Bloch sphere, while the circular fibres
represent the qubit overall phase degree of freedom. For the two qubits case,
the Hilbert space is a 7-dimensional sphere S7, which also allows for a Hopf
fibration, with S3 fibres and a S4 base. A main striking result is that
suitably oriented S7 Hopf fibrations are entanglement sensitive. The relation
with the standard Schmidt decomposition is also discussedComment: submitted to J. Phys.
Benefits and Risks of Weight-Loss Treatment for Older, Obese Women
Background: A key issue in the treatment of obesity in older adults is whether the health benefits of weight loss outweigh the potential risks with respect to musculoskeletal injury. Objective: To compare change in weight, improvements in metabolic risk factors, and reported musculoskeletal adverse events in middle-aged (50-59 years) and older (65-74 years), obese women. Materials and methods: Participants completed an initial 6-month lifestyle intervention for weight loss, comprised of weekly group sessions, followed by 12 months of extended care with biweekly contacts. Weight and fasting blood samples were assessed at baseline, month 6, and month 18; data regarding adverse events were collected throughout the duration of the study. Results: Both middle-aged (n = 162) and older (n = 56) women achieved significant weight reductions from baseline to month 6 (10.1 +/- 0.68 kg and 9.3 +/- 0.76 kg, respectively) and maintained a large proportion of their losses at month 18 (7.6 +/- 0.87 kg and 7.6 +/- 1.3 kg, respectively); there were no significant differences between the two groups with respect to weight change. Older women further experienced significant reductions in systolic blood pressure, HbA(1c), and C-reactive protein from baseline to month 6 and maintained these improvements at month 18. Despite potential safety concerns, we found that older women were no more likely to experience musculoskeletal adverse events during the intervention as compared with their middle-aged counterparts. Conclusion: These results suggest that older, obese women can experience significant health benefits from lifestyle treatment for obesity, including weight loss and improvements in disease risk factors. Further investigation of the impact of weight loss on additional health-related parameters and risks (eg, body composition, muscular strength, physical functioning, and injuries) in older adults is needed.National Heart, Lung and Blood Institute R18HL73326University of FloridaDivision of Statistics and Scientific Computatio
ZNF804A genotype modulates neural activity during working memory for faces
Copyright © 2013 S. Karger AG, Basel.Peer reviewedPublisher PD
Lowest order in inelastic tunneling approximation: Efficient scheme for simulation of inelastic electron tunneling data
We have developed an efficient and accurate formalism which allows the simulation at the ab initio level of inelastic electron tunneling spectroscopy data under a scanning tunneling microscope setup. It exploits fully the tunneling regime by carrying out the structural optimization and vibrational mode calculations for surface and tip independently. The most relevant interactions in the inelastic current are identified as the inelastic tunneling terms, which are taken into account up to lowest order, while all other inelastic contributions are neglected. As long as the system is under tunneling regime conditions and there is no physisorbed molecule on the surface or tip apex, this lowest order in inelastic tunneling (LOIT) approach reduces drastically the computational cost compared to related approaches while maintaining a good accuracy. Adopting the wide-band limit for both tip and surface further reduces calculation times significantly, and is shown to give similar results to when the full energy dependence of the Green's functions is taken into account. The LOIT is applied to the Cu(111)+CO system probed by a clean and a CO contaminated tip to find good agreement with previous works. Different parameters involved in the calculations such as basis sets, k sampling, tip-sample distance, or temperature, among others, are discussed in detail. © 2013 American Physical Society.J.C. acknowledges financial support from the Spanish Ministry of Innovation and Science under Contract No.MAT2010-18432.Peer Reviewe
Quantum effective potential, electron transport and conformons in biopolymers
In the Kirchhoff model of a biopolymer, conformation dynamics can be
described in terms of solitary waves, for certain special cross-section
asymmetries. Applying this to the problem of electron transport, we show that
the quantum effective potential arising due to the bends and twists of the
polymer enables us to formalize and quantify the concept of a {\it conformon}
that has been hypothesized in biology. Its connection to the soliton solution
of the cubic nonlinear Schr\"{o}dinger equation emerges in a natural fashion.Comment: to appear in J. Phys.
Study of the and reactions close to threshold
Two--kaon production in proton--deuteron collisions has been studied at three
energies close to threshold using a calibrated magnetic spectrograph to measure
the final He and a vertex detector to measure the pair.
Differential and total cross sections are presented for the production of
--mesons, decaying through , as well as for prompt
production. The prompt production seems to follow phase space in both
its differential distributions and in its energy dependence. The amplitude for
the {He} reaction varies little for excess energies below 22
MeV and the value is consistent with that obtained from a threshold
measurement. The angular distribution of the decay pair shows that
near threshold the --mesons are dominantly produced with polarization
along the initial proton direction. No conclusive evidence for
production is found in the data.Comment: 13 figure
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