6,128 research outputs found
Evolution of Fermion Pairing from Three to Two Dimensions
We follow the evolution of fermion pairing in the dimensional crossover from
3D to 2D as a strongly interacting Fermi gas of Li atoms becomes confined
to a stack of two-dimensional layers formed by a one-dimensional optical
lattice. Decreasing the dimensionality leads to the opening of a gap in
radio-frequency spectra, even on the BCS-side of a Feshbach resonance. The
measured binding energy of fermion pairs closely follows the theoretical
two-body binding energy and, in the 2D limit, the zero-temperature mean-field
BEC-BCS theory.Comment: 5 pages, 4 figure
Spin Transport in a Mott Insulator of Ultracold Fermions
Strongly correlated materials are expected to feature unconventional
transport properties, such that charge, spin, and heat conduction are
potentially independent probes of the dynamics. In contrast to charge
transport, the measurement of spin transport in such materials is highly
challenging. We observed spin conduction and diffusion in a system of ultracold
fermionic atoms that realizes the half-filled Fermi-Hubbard model. For strong
interactions, spin diffusion is driven by super-exchange and
doublon-hole-assisted tunneling, and strongly violates the quantum limit of
charge diffusion. The technique developed in this work can be extended to
finite doping, which can shed light on the complex interplay between spin and
charge in the Hubbard model.Comment: 16 pages, 10 figure
A Possible protective effect of nut consumption on risk of coronary heart-disease: the adventist health study
Background -Although dietary factors are suspected to be important determinants of coronary heart disease (CHD) risk, the direct evidence is relatively sparse. Methods. -The Adventist Health Study is a prospective cohort investigation of 31 208 non-Hispanic white California Seventh-Day Adventists. Extensive dietary information was obtained at baseline, along with the values of traditional coronary risk factors. These were related to risk of definite fatal CHD or definite nonfatal myocardial infarction
Physical Function in Young and Older Adult Active Pickleball Players
Limited information exists on pickleball’s impact on physical function in adults, especially older adults (65+ years), despite reported health benefits. PURPOSE: This study evaluated the physical function of active older adult (OA) female and male recreational pickleball players via handgrip strength and fatigue, 6-minute walk distance (6MWD) test, as well as the short physical performance battery (SPPB) compared to sex-matched young adult (YA) controls. METHODS: Thirty YA (18-26 years; n=15 female/male) participants and 27 OA (65-89 years; n=13 female, n=15 male) participants who played pickleball at least three times per week were assessed for physical function outcomes of handgrip strength (HGS) and fatigue (HGF), 6-minute walk distance (6MWD), and the short physical performance battery (SPPB). A two-way ANOVA (age x sex) with repeated measures and Sidak post-hoc test were used (pRESULTS: Compared to sex-matched YA, OA women and men had significantly (p2). Absolute HGF followed the absolute HGS results. In contrast, compared to sex-matched YA, no significant differences (p\u3e0.05) were observed in OA women and men for 6MWD percent predicted (which factored in anthropometrics, age, gender, and activity levels; range: 104.6-115.4%) and the overall SPPB (range: 11.3-12.0) as well as each portion of the SPPB (balance, gait speed, and lower limb strength). CONCLUSION: In OA female and male recreational pickleballers, lower body physical function (e.g., walking speed/distance, balance, lower body strength) is largely maintained compared to sex-matched YA pickleballers, but upper body strength/fatigue were not. Pickleball should be combined with meeting resistance training guidelines to maintain whole body physical function with aging
The medium-term sustainability of organisational innovations in the national health service
Background: There is a growing recognition of the importance of introducing new ways of working into the UK's National Health Service (NHS) and other health systems, in order to ensure that patient care is provided as effectively and efficiently as possible. Researchers have examined the challenges of introducing new ways of working-'organisational innovations'-into complex organisations such as the NHS, and this has given rise to a much better understanding of how this takes place-and why seemingly good ideas do not always result in changes in practice. However, there has been less research on the medium-and longer-term outcomes for organisational innovations and on the question of how new ways of working, introduced by frontline clinicians and managers, are sustained and become established in day-to-day practice. Clearly, this question of sustainability is crucial if the gains in patient care that derive from organisational innovations are to be maintained, rather than lost to what the NHS Institute has called the 'improvement-evaporation effect'.
Methods: The study will involve research in four case-study sites around England, each of which was successful in sustaining its new model of service provision beyond an initial period of pilot funding for new genetics services provided by the Department of Health. Building on findings relating to the introduction and sustainability of these services already gained from an earlier study, the research will use qualitative methods-in-depth interviews, observation of key meetings, and analysis of relevant documents-to understand the longer-term challenges involved in each case and how these were surmounted. The research will provide lessons for those seeking to sustain their own organisational innovations in wide-ranging clinical areas and for those designing the systems and organisations that make up the NHS, to make them more receptive contexts for the sustainment of innovation.
Discussion: Through comparison and contrast across four sites, each involving different organisational innovations, different forms of leadership, and different organisational contexts to contend with, the findings of the study will have wide relevance. The research will produce outputs that are useful for managers and clinicians responsible for organisational innovation, policy makers and senior managers, and academics
What have we already learned from the CMB?
The COBE satellite, and the DMR experiment in particular, was extraordinarily
successful. However, the DMR results were announced about 7 years ago, during
which time a great deal more has been learned about anisotropies in the Cosmic
Microwave Background (CMB). The CMB experiments currently being designed and
built, including long-duration balloons, interferometers, and two space
missions, promise to address several fundamental cosmological issues. We
present our evaluation of what we already know, what we are beginning to learn
now, and what the future may bring.Comment: 20 pages, 3 figures. Changes to match version accepted by PAS
Shift-Symmetric Configurations in Two-Dimensional Cellular Automata: Irreversibility, Insolvability, and Enumeration
The search for symmetry as an unusual yet profoundly appealing phenomenon,
and the origin of regular, repeating configuration patterns have long been a
central focus of complexity science and physics. To better grasp and understand
symmetry of configurations in decentralized toroidal architectures, we employ
group-theoretic methods, which allow us to identify and enumerate these inputs,
and argue about irreversible system behaviors with undesired effects on many
computational problems. The concept of so-called configuration shift-symmetry
is applied to two-dimensional cellular automata as an ideal model of
computation. Regardless of the transition function, the results show the
universal insolvability of crucial distributed tasks, such as leader election,
pattern recognition, hashing, and encryption. By using compact enumeration
formulas and bounding the number of shift-symmetric configurations for a given
lattice size, we efficiently calculate the probability of a configuration being
shift-symmetric for a uniform or density-uniform distribution. Further, we
devise an algorithm detecting the presence of shift-symmetry in a
configuration.
Given the resource constraints, the enumeration and probability formulas can
directly help to lower the minimal expected error and provide recommendations
for system's size and initialization. Besides cellular automata, the
shift-symmetry analysis can be used to study the non-linear behavior in various
synchronous rule-based systems that include inference engines, Boolean
networks, neural networks, and systolic arrays.Comment: 22 pages, 9 figures, 2 appendice
Testing the Unitarity of the CKM Matrix with a Space-Based Neutron Decay Experiment
If the Standard Model is correct, and fundamental fermions exist only in the
three generations, then the CKM matrix should be unitary. However, there
remains a question over a deviation from unitarity from the value of the
neutron lifetime. We discuss a simple space-based experiment that, at an orbit
height of 500 km above Earth, would measure the kinetic-energy, solid-angle,
flux spectrum of gravitationally bound neutrons (kinetic energy K<0.606 eV at
this altitude). The difference between the energy spectrum of neutrons that
come up from the Earth's atmosphere and that of the undecayed neutrons that
return back down to the Earth would yield a measurement of the neutron
lifetime. This measurement would be free of the systematics of laboratory
experiments. A package of mass kg could provide a 10^{-3} precision in
two years.Comment: 10 pages, 4 figures. Revised and updated for publicatio
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