740 research outputs found
Efficient loading of a He* magneto-optic trap using a liquid He cooled source
We report loading large numbers (up to 3Ă10âč) of metastable triplet helium atoms into a magneto-optical trap using an atomic beam derived from a liquid He (LHe) cooled dc discharge source. Moreover, we compare the effect of liquidNâ cooling to LHe cooling the source and demonstrate that LHe cooling offers a significant increase in performance
Surface activation of Concorde by Be-7
Activation analysis of two airframe components from the Concorde aircraft has identified the presence of Be-7, a nuclide found by other investigators that was deposited on the forward edge of the Long Duration Exposure Facility (LDEF) structure. The results of the Concorde analysis indicate that this phenomenon is very much a surface effect, and that the areal densities of the Be-7 are comparable to those found for LDEF. The collection of Be-7 by the aircraft must be greater than in the case of LDEF (since duration for which Concorde is accumulating the nuclide is shorter) and is of the order of 1.2 to 41 nuclei/sq cm(-)s(exp -1) depending upon assumptions made regarding the altitude at which collection becomes appreciable, and the efficiency of the process which removes the radionuclide
The coverage and frequency of mass drug administration required to eliminate persistent transmission of soil-transmitted helminths
A combination of methods, including mathematical model construction, demographic plus epidemiological data analysis and parameter estimation, are used to examine whether mass drug administration (MDA) alone can eliminate the transmission of soil-transmitted helminths (STHs). Numerical analyses suggest that in all but low transmission settings (as defined by the magnitude of the basic reproductive number, R0), the treatment of pre-school-aged children (pre-SAC) and school-aged children (SAC) is unlikely to drive transmission to a level where the parasites cannot persist. High levels of coverage (defined as the fraction of an age group effectively treated) are required in pre-SAC, SAC and adults, if MDA is to drive the parasite below the breakpoint under which transmission is eliminated. Long-term solutions to controlling helminth infections lie in concomitantly improving the quality of the water supply, sanitation and hygiene (WASH). MDA, however, is a very cost-effective tool in long-term control given that most drugs are donated free by the pharmaceutical industry for poor regions of the world. WASH interventions, by lowering the basic reproductive number, can facilitate the ability of MDA to interrupt transmission
Developing Interventions for Children's Exercise (DICE): a pilot evaluation of school-based exercise interventions for primary school children aged 7 to 8 years.
BACKGROUND: Developing Interventions for Children's Exercise (DICE) is an initiative aimed at determining effective school-based exercise programs. To assess feasibility, we conducted a pilot study of exercise sessions which varied in duration and frequency. METHODS: Exercise interventions were delivered to Year 3 pupils (age 7-8 years; n = 73) in primary schools within Yorkshire, UK. Evaluations were conducted using focus group sessions, questionnaires and observations. RESULTS: The study revealed positive aspects of all interventions, including favorable effects on children's concentration during lessons and identified the value of incorporation of the DICE concept into curriculum lessons. Children appeared enthused and reported well-being and enjoyment. Areas requiring attention were the need for appropriate timetabling of sessions and ensuring the availability of space. CONCLUSION: The concept and sessions were well-accepted by teachers who confirmed their full support of any future implementation There appears to be potential for the encouragement and empowerment of teachers to support physical activity and healthy school environments, and to take an interest in the health of their pupils. Ultimately, these findings should assist in the design of successful exercise interventions in the school setting
Paired atom laser beams created via four-wave mixing
A method to create paired atom laser beams from a metastable helium atom
laser via four-wave mixing is demonstrated. Radio frequency outcoupling is used
to extract atoms from a Bose Einstein condensate near the center of the
condensate and initiate scattering between trapped and untrapped atoms. The
unequal strengths of the interactions for different internal states allows an
energy-momentum resonance which leads to the creation of pairs of atoms
scattered from the zero-velocity condensate. The resulting scattered beams are
well separated from the main atom laser in the 2-dimensional transverse atom
laser profile. Numerical simulations of the system are in good agreement with
the observed atom laser spatial profiles, and indicate that the scattered beams
are generated by a four-wave mixing process, suggesting that the beams are
correlated.Comment: 5 pages, 3 figure
Positive reinforcement by general practitioners is associated with greater physical activity in adults with type 2 diabetes
© Author(s) (or their employer(s)) 2019. Objective In a sample of adults with type 2 diabetes mellitus (T2DM), the aim of this study was to examine whether self-reported physical activity level is associated with recall of specific physical activity-related interactions used by general practitioners (GP). Research design and methods Adults with T2DM completed an online survey reporting physical activity behaviors and recall of 14 GP-patient interactions about physical activity, mapped onto discrete behavior change techniques (BCT). Stepped logistical regression examined associations between recommended physical activity (â„600 MET-min/week) and GP-patient interactions, controlling for body mass index, diabetes-related comorbidities, depressive symptoms and self-efficacy. Results In total, 381 respondents (55% men, mean±SD age: 62±10 years and T2DM duration 8±8 years) provided complete data. Most (73%) reported receiving 'general advice', while interactions related to goal setting, monitoring, and relapse prevention were least commonly reported (all <20%). Self-reported achievement of the recommended physical activity level was significantly associated with recall of GP interactions involving praise for 'efforts to be active' (OR 2.1; 95% CI 1.24 to 3.53), 'lost weight' (OR 1.81; 95% CI 1.05 to 3.12) or lowering 'glucose levels as a result of being active' (OR 1.75; 95% CI 1.03 to 2.96). Conclusions Findings suggest GPS can be somewhat effective in promoting physical activity with simple, positive, reinforcing messages/interactions. Future research to develop and evaluate very brief primary care BCT-based physical activity interventions is needed
Instability Heating of Sympathetically-Cooled Ions in a Linear Paul Trap
Sympathetic laser cooling of ions stored within a linear-geometry, radio
frequency, electric-quadrupole trap has been investigated using computational
and theoretical techniques. The simulation, which allows 5 sample ions to
interact with 35 laser-cooled atomic ions, revealed an instability heating
mechanism, which can prevent ions below a certain critical mass from being
sympathetically cooled. This critical mass can however be varied by changing
the trapping field parameters thus allowing ions with a very large range of
masses to be sympathetically cooled using a single ion species. A theoretical
explanation of this instability heating mechanism is presented which predicts
that the cooling-heating boundary in trapping parameter space is a line of
constant (ion trap stability coefficient), a result supported by the
computational results. The threshold value of depends on the masses of
the interacting ions. A functional form of this dependence is given
Whole-field 3D Characterization of a Pulsating Jet using Synthetic Aperture Particle Image Velocimety
In this study synthetic aperture particle image velocimetry is used on an excised human vocal fold model to study the airflow over the vocal folds during voice production. For the first time, a whole-field, time-resolved, 3D description of the flow is presented over one cycle of vocal fold oscillation. Complex, unsteady, 3D flow behavior is observed as the jet evolves
Effective s- and p-Wave Contact Interactions in Trapped Degenerate Fermi Gases
The structure and stability of dilute degenerate Fermi gases trapped in an
external potential is discussed with special emphasis on the influence of s-
and p-wave interactions. In a first step an Effective Contact Interaction for
all partial waves is derived, which reproduces the energy spectrum of the full
potential within a mean-field model space. Using the s- and p-wave part the
energy density of the multi-component Fermi gas is calculated in Thomas-Fermi
approximation. On this basis the stability of the one- and two-component Fermi
gas against mean-field induced collapse is investigated. Explicit stability
conditions in terms of density and total particle number are given. For the
single-component system attractive p-wave interactions limit the density of the
gas. In the two-component case a subtle competition of s- and p-wave
interactions occurs and gives rise to a rich variety of phenomena. A repulsive
p-wave part, for example, can stabilize a two-component system that would
otherwise collapse due to an attractive s-wave interaction. It is concluded
that the p-wave interaction may have important influence on the structure of
degenerate Fermi gases and should not be discarded from the outset.Comment: 18 pages, 11 figures (using RevTEX4
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