36 research outputs found
Large Effects of Electric Fields on Atom-Molecule Collisions at Millikelvin Temperatures
Controlling interactions between cold molecules using external fields can
elucidate the role of quantum mechanics in molecular collisions. We create a
new experimental platform in which ultracold rubidium atoms and cold ammonia
molecules are separately trapped by magnetic and electric fields and then
combined to study collisions. We observe inelastic processes that are faster
than expected from earlier field-free calculations. We use quantum scattering
calculations to show that electric fields can have a major effect on collision
outcomes, even in the absence of dipole-dipole interactions.Comment: 5 pages, 4 figure
Disturbance and Predictability of Flowering Patterns in Bird-Pollinated Cloud Forest Plants
The distribution and flowering patterns of hummingbirdâpollinated plants were compared from July 1981 to June 1983 in three patch types in cloud forest at Monteverde, Costa Rica. Study plots were: (1) four recent, large (1100â2500 m2) disturbances ("cutovers") produced by cutting vegetation, (2) six recent, smaller (200â600 m2) disturbances caused by treefalls, and (3) four plots (1600â1800 m2) of canopied forest. Based on published literature dealing with communities that characterize different regimes of disturbance, we tested one assumption and two hypotheses. Assumption: Plant species composition differs among the three patch types. Hypothesis 1: Phenotypic specialization by plants for coâevolved interactions with hummingbirds will be lowest in large gaps, highest in forest, and intermediate in treefalls. Hypothesis 2: Predictability of flowering phenologies and nectar production will be lowest in large gaps, highest in forest, intermediate in treefalls. Neither the assumption nor the hypotheses were supported by the results. The patch mosaic in this cloud forest was not associated with major differences in species composition of birdâpollinated plants. Most species studied were selfâcompatible. Most abundant in cutovers were species with long corollas, relatively specialized for attracting longâbilled hummingbirds. Species with short corollas, which can be visited by many hummingbird species and some insects, were most abundant in treefalls and forest. Variation in phenological patterns showed no consistent trends among patch types. Predictability of flower and nectar production tended to be greatest in treefalls, which are foci of concentrated flowering activity by all species. Discrepancies between our results and previous studies can be ascribed to two facts. (1) Much of the literature dealing with ecological consequences of disturbance has dealt with largeâscale anthropogenic disturbances such as old fields of the eastern USA, whereas we studied small, natural, or quasiânatural disturbances. (2) Studies of forest disturbance have focused on the tree layer, whereas we studied the understory herbs, shrubs, and epiphytes. Natural disturbance usually involves death and replacement of one or more trees, whereas individuals of other life forms may persist through the disturbance
Condensed Matter Theory of Dipolar Quantum Gases
Recent experimental breakthroughs in trapping, cooling and controlling
ultracold gases of polar molecules, magnetic and Rydberg atoms have paved the
way toward the investigation of highly tunable quantum systems, where
anisotropic, long-range dipolar interactions play a prominent role at the
many-body level. In this article we review recent theoretical studies
concerning the physics of such systems. Starting from a general discussion on
interaction design techniques and microscopic Hamiltonians, we provide a
summary of recent work focused on many-body properties of dipolar systems,
including: weakly interacting Bose gases, weakly interacting Fermi gases,
multilayer systems, strongly interacting dipolar gases and dipolar gases in 1D
and quasi-1D geometries. Within each of these topics, purely dipolar effects
and connections with experimental realizations are emphasized.Comment: Review article; submitted 09/06/2011. 158 pages, 52 figures. This
document is the unedited author's version of a Submitted Work that was
subsequently accepted for publication in Chemical Reviews, copyright American
Chemical Society after peer review. To access the final edited and published
work, a link will be provided soo
Bibliometric Evidence for a Hierarchy of the Sciences
The hypothesis of a Hierarchy of the Sciences, first formulated in the 19(th) century, predicts that, moving from simple and general phenomena (e.g. particle dynamics) to complex and particular (e.g. human behaviour), researchers lose ability to reach theoretical and methodological consensus. This hypothesis places each field of research along a continuum of complexity and "softness", with profound implications for our understanding of scientific knowledge. Today, however, the idea is still unproven and philosophically overlooked, too often confused with simplistic dichotomies that contrast natural and social sciences, or science and the humanities. Empirical tests of the hypothesis have usually compared few fields and this, combined with other limitations, makes their results contradictory and inconclusive. We verified whether discipline characteristics reflect a hierarchy, a dichotomy or neither, by sampling nearly 29,000 papers published contemporaneously in 12 disciplines and measuring a set of parameters hypothesised to reflect theoretical and methodological consensus. The biological sciences had in most cases intermediate values between the physical and the social, with bio-molecular disciplines appearing harder than zoology, botany or ecology. In multivariable analyses, most of these parameters were independent predictors of the hierarchy, even when mathematics and the humanities were included. These results support a "gradualist" view of scientific knowledge, suggesting that the Hierarchy of the Sciences provides the best rational framework to understand disciplines' diversity. A deeper grasp of the relationship between subject matter's complexity and consensus could have profound implications for how we interpret, publish, popularize and administer scientific research
Enhancing Mental and Physical Health of Women through Engagement and Retention (EMPOWER): a protocol for a program of research
Abstract Background The Enhancing Mental and Physical health of Women through Engagement and Retention or EMPOWER program represents a partnership with the US Department of Veterans Health Administration (VA) Health Service Research and Development investigators and the VA Office of Womenâs Health, National Center for Disease Prevention and Health Promotion, Primary Care-Mental Health Integration Program Office, Womenâs Mental Health Services, and the Office of Patient Centered Care and Cultural Transformation. EMPOWER includes three projects designed to improve women Veteransâ engagement and retention in evidence-based care for high-priority health conditions, i.e., prediabetes, cardiovascular, and mental health. Methods/Design The three proposed projects will be conducted in VA primary care clinics that serve women Veterans including general primary care and womenâs health clinics. The first project is a 1-year quality improvement project targeting diabetes prevention. Two multi-site research implementation studies will focus on cardiovascular risk prevention and collaborative care to address women Veteransâ mental health treatment needs respectively. All projects will use the evidence-based Replicating Effective Programs (REP) implementation strategy, enhanced with multi-stakeholder engagement and complexity theory. Mixed methods implementation evaluations will focus on investigating primary implementation outcomes of adoption, acceptability, feasibility, and reach. Program-wide organizational-, provider-, and patient-level measures and tools will be utilized to enhance synergy, productivity, and impact. Both implementation research studies will use a non-randomized stepped wedge design. Discussion EMPOWER represents a coherent program of womenâs health implementation research and quality improvement that utilizes cross-project implementation strategies and evaluation methodology. The EMPOWER Quality Enhancement Research Initiative (QUERI) will constitute a major milestone for realizing women Veteransâ engagement and empowerment in the VA system. EMPOWER QUERI will be conducted in close partnership with key VA operations partners, such as the VA Office of Womenâs Health, to disseminate and spread the programs nationally. Trial registration The two implementation research studies described in this protocol have been registered as required: Facilitating Cardiovascular Risk Screening and Risk Reduction in Women Veterans: Trial registration NCT02991534 , registered 9 December 2016. Implementation of Tailored Collaborative Care for Women Veterans: Trial registration NCT02950961 , registered 21 October 2016
Sensorimotor adaptation as a behavioural biomarker of early spinocerebellar ataxia type 6.
Early detection of the behavioural deficits of neurodegenerative diseases may help to describe the pathogenesis of such diseases and establish important biomarkers of disease progression. The aim of this study was to identify how sensorimotor adaptation of the upper limb, a cerebellar-dependent process restoring movement accuracy after introduction of a perturbation, is affected at the pre-clinical and clinical stages of spinocerebellar ataxia type 6 (SCA6), an inherited neurodegenerative disease. We demonstrate that initial adaptation to the perturbation was significantly impaired in the eighteen individuals with clinical motor symptoms but mostly preserved in the five pre-clinical individuals. Moreover, the amount of error reduction correlated with the clinical symptoms, with the most symptomatic patients adapting the least. Finally both pre-clinical and clinical individuals showed significantly reduced de-adaptation performance after the perturbation was removed in comparison to the control participants. Thus, in this large study of motor features in SCA6, we provide novel evidence for the existence of subclinical motor dysfunction at a pre-clinical stage of SCA6. Our findings show that testing sensorimotor de-adaptation could provide a potential predictor of future motor deficits in SCA6
Cold and Ultracold Molecules: Science, Technology, and Applications
This article presents a review of the current state of the art in the
research field of cold and ultracold molecules. It serves as an introduction to
the Special Issue of the New Journal of Physics on Cold and Ultracold Molecules
and describes new prospects for fundamental research and technological
development. Cold and ultracold molecules may revolutionize physical chemistry
and few body physics, provide techniques for probing new states of quantum
matter, allow for precision measurements of both fundamental and applied
interest, and enable quantum simulations of condensed-matter phenomena.
Ultracold molecules offer promising applications such as new platforms for
quantum computing, precise control of molecular dynamics, nanolithography, and
Bose-enhanced chemistry. The discussion is based on recent experimental and
theoretical work and concludes with a summary of anticipated future directions
and open questions in this rapidly expanding research field.Comment: 82 pages, 9 figures, review article to appear in New Journal of
Physics Special Issue on Cold and Ultracold Molecule
Saturn Atmospheric Structure and Dynamics
2 Saturn inhabits a dynamical regime of rapidly rotating, internally heated atmospheres similar to Jupiter. Zonal winds have remained fairly steady since the time of Voyager except in the equatorial zone and slightly stronger winds occur at deeper levels. Eddies supply energy to the jets at a rate somewhat less than on Jupiter and mix potential vorticity near westward jets. Convective clouds exist preferentially in cyclonic shear regions as on Jupiter but also near jets, including major outbreaks near 35°S associated with Saturn electrostatic discharges, and in sporadic giant equatorial storms perhaps generated from frequent events at depth. The implied meridional circulation at and below the visible cloud tops consists of upwelling (downwelling) at cyclonic (anti-cyclonic) shear latitudes. Thermal winds decay upward above the clouds, implying a reversal of the circulation there. Warm-core vortices with associated cyclonic circulations exist at both poles, including surrounding thick high clouds at the south pole. Disequilibrium gas concentrations in the tropical upper troposphere imply rising motion there. The radiative-convective boundary and tropopause occur at higher pressure in the southern (summer) hemisphere due to greater penetration of solar heating there. A temperature âknee â of warm air below the tropopause, perhaps due to haze heating, is stronger in the summer hemisphere as well. Saturnâs south polar stratosphere is warmer than predicted by radiative models and enhanced in ethane, suggesting subsidence-driven adiabatic warming there. Recent modeling advances suggest that shallow weather laye