Theory of output coupling for trapped fermionic atoms

We develop a dynamic theory of output coupling, for fermionic atoms initially confined in a magnetic trap. We consider an exactly soluble one-dimensional model, with a spatially localized delta-type coupling between the atoms in the trap and a continuum of free-particle external modes. Two important special cases are considered for the confinement potential: the infinite box and the harmonic oscillator. We establish that in both cases a bound state of the coupled system appears for any value of the coupling constant, implying that the trap population does not vanish in the infinite-time limit. For weak coupling, the energy spectrum of the outgoing beam exhibits peaks corresponding to the initially occupied energy levels in the trap; the height of these peaks increases with the energy. As the coupling gets stronger, the energy spectrum is displaced towards dressed energies of the fermions in the trap. The corresponding dressed states result from the coupling between the unperturbed fermionic states in the trap, mediated by the coupling between these states and the continuum. In the strong-coupling limit, there is a reinforcement of the lowest-energy dressed mode, which contributes to the energy spectrum of the outgoing beam more strongly than the other modes. This effect is especially pronounced for the one-dimensional box, which indicates that the efficiency of the mode-reinforcement mechanism depends on the steepness of the confinement potential. In this case, a quasi-monochromatic anti-bunched atomic beam is obtained. Results for a bosonic sample are also shown for comparison.Comment: 16 pages, 7 figures, added discussion on time-dependent spectral distribution and corresponding figur

Cosmological distance indicators

We review three distance measurement techniques beyond the local universe: (1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and (3) HI intensity mapping. We describe the principles and theory behind each method, the ingredients needed for measuring such distances, the current observational results, and future prospects. Time delays from strongly lensed quasars currently provide constraints on $H_0$ with < 4% uncertainty, and with 1% within reach from ongoing surveys and efforts. Recent exciting discoveries of strongly lensed supernovae hold great promise for time-delay cosmography. BAO features have been detected in redshift surveys up to z <~ 0.8 with galaxies and z ~ 2 with Ly-$\alpha$ forest, providing precise distance measurements and $H_0$ with < 2% uncertainty in flat $\Lambda$CDM. Future BAO surveys will probe the distance scale with percent-level precision. HI intensity mapping has great potential to map BAO distances at z ~ 0.8 and beyond with precisions of a few percent. The next years ahead will be exciting as various cosmological probes reach 1% uncertainty in determining $H_0$, to assess the current tension in $H_0$ measurements that could indicate new physics.Comment: Review article accepted for publication in Space Science Reviews (Springer), 45 pages, 10 figures. Chapter of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Ag

Spatial processing of visual information in the movement-detecting pathway of the fly

1. Spatial processing of visual signals in the fly's movement-detecting pathway was studied by recording the responses of directionally-selective movement-detecting (DSMD) neurons in the lobula plate. The summarized results pertain to a type of neuron which preferentially responds to horizontal movement directed toward the animal's midline. Three kinds of visual stimuli were used: moving gratings, reversing-contrast gratings and reversing-contrast bars.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47087/1/359_2004_Article_BF00613743.pd

Deep Underground Neutrino Experiment (DUNE), far detector technical design report, volume III: DUNE far detector technical coordination

The preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay—these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. The Deep Underground Neutrino Experiment (DUNE) is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector technical design report (TDR) describes the DUNE physics program and the technical designs of the single- and dual-phase DUNE liquid argon TPC far detector modules. Volume III of this TDR describes how the activities required to design, construct, fabricate, install, and commission the DUNE far detector modules are organized and managed. This volume details the organizational structures that will carry out and/or oversee the planned far detector activities safely, successfully, on time, and on budget. It presents overviews of the facilities, supporting infrastructure, and detectors for context, and it outlines the project-related functions and methodologies used by the DUNE technical coordination organization, focusing on the areas of integration engineering, technical reviews, quality assurance and control, and safety oversight. Because of its more advanced stage of development, functional examples presented in this volume focus primarily on the single-phase (SP) detector module

Factors influencing the development of evidence-based practice: a research tool

Aim. The paper reports a study to develop and test a tool for assessing a range of factors influencing the development of evidence-based practice among clinical nurses. Background. Achieving evidence-based practice is a goal in nursing frequently cited by the profession and in government health policy directives. Assessing factors influencing the achievement of this goal, however, is complex. Consideration needs to be given to a range of factors, including different types of evidence used to inform practice, barriers to achieving evidence-based practice, and the skills required by nurses to implement evidence-based care. Methods. Measurement scales currently available to investigate the use of evidence in nursing practice focus on nurses’ sources of knowledge and on barriers to the use of research evidence. A new, wider ranging Developing Evidence-Based Practice questionnaire was developed and tested for its measurement properties in two studies. In study 1, a sample of 598 nurses working at two hospitals in one strategic health authority in northern England was surveyed. In study 2, a slightly expanded version of the questionnaire was employed in a survey of 689 community nurses in 12 primary care organizations in two strategic health authorities, one in northern England and the other in southern England. Findings. The measurement characteristics of the new questionnaire were shown to be acceptable. Ten significant, and readily interpretable, factors were seen to underlie nurses’ relation to evidence-based practice. Conclusion. Strategies to promote evidence-based practice need to take account of the differing needs of nurses and focus on a range of sources of evidence. The Developing Evidence-Based Practice questionnaire can assist in assessing the specific‘evidencing’ tendencies of any given group of nurses