Diffraction-contrast imaging of cold atoms

We consider the inverse problem of in-line holography, applied to minimally-destructive imaging of cold atom clouds. Absorption imaging near-resonance provides a simple, but destructive measurement of atom column density. Imaging off resonance greatly reduces heating, and sequential images may be taken. Under the conditions required for off-resonant imaging, the generally-intractable inverse problem may be linearized. A minimally-destructive, quantitative and high-resolution image of the atom cloud column density is then retrieved from a single diffraction pattern.Comment: 4 pages, 3 figures v2: minor changes in response to referee reports, mostly additional experimental detail v3: revisions to figure 3: added trace and changed image. Minor text and referencing changes. Accepted by Phys Rev A (Rapid Commun

Discounting by intervals: a generalized model of intertemporal choice

According to most models of intertemporal choice, an agent's discount rate is a function of how far the outcomes are removed from the present, and nothing else. This view has been challenged by recent studies, which show that discount rates tend to be higher the closer the outcomes are to one another (subadditive discounting) and that this can give rise to intransitive intertemporal choice. We develop and test a generalized model of intertemporal choice, the Discounting By Intervals (DBI) model, according to which the discount rate is a function of both how far outcomes are removed from the present and how far the outcomes are removed from one another. The model addresses past challenges to other models, most of which it includes as special cases, as well as the new challenges presented in this paper: Our studies show that when the interval between outcomes is very short, discount rate tends to increase with interval length (superadditive discounting). In the discussion we place our model and evidence in a broader theoretical context

Relative intensity squeezing by four-wave mixing with loss: an analytic model and experimental diagnostic

Four-wave mixing near resonance in an atomic vapor can produce relative intensity squeezed light suitable for precision measurements beyond the shot-noise limit. We develop an analytic distributed gain/loss model to describe the competition of mixing and absorption through the non-linear medium. Using a novel matrix calculus, we present closed-form expressions for the degree of relative intensity squeezing produced by this system. We use these theoretical results to analyze experimentally measured squeezing from a $^{85}$Rb vapor and demonstrate the analytic model's utility as an experimental diagnostic.Comment: 10 pages, 5 figure

Consequences of wall stiffness for a beta-soft potential

Modifications of the infinite square well E(5) and X(5) descriptions of transitional nuclear structure are considered. The eigenproblem for a potential with linear sloped walls is solved. The consequences of the introduction of sloped walls and of a quadratic transition operator are investigated.Comment: RevTeX 4, 8 pages, as published in Phys. Rev.

A new limit on the Ultra-High-Energy Cosmic-Ray flux with the Westerbork Synthesis Radio Telescope

A particle cascade (shower) in a dielectric, for example as initiated by an ultra-high energy cosmic ray, will have an excess of electrons which will emit coherent \v{C}erenkov radiation, known as the Askaryan effect. In this work we study the case in which such a particle shower occurs in a medium just below its surface. We show, for the first time, that the radiation transmitted through the surface is independent of the depth of the shower below the surface when observed from far away, apart from trivial absorption effects. As a direct application we use the recent results of the NuMoon project, where a limit on the neutrino flux for energies above $10^{22}$\,eV was set using the Westerbork Synthesis Radio Telescope by measuring pulsed radio emission from the Moon, to set a limit on the flux of ultra-high-energy cosmic rays.Comment: Accepted for publication in Phys. Rev.

Laser frequency offset locking using electromagnetically induced transparency

The authors have used an electromagnetically induced transparency resonance in rubidium as a dispersive reference to lock the relative frequency of two lasers to the atomic ground-statehyperfine splitting. The beat frequency between the two lasers directly generates a microwave signal at 3.036GHz (⁸⁵Rb) or 6.835GHz (⁸⁷Rb). High bandwidth (600kHz) feedback was achieved with only low-frequency (10MHz)electronics using the frequency modulation sideband method. The spectral width of the microwave beat frequency was reduced to less than 1kHz. The technique offers a convenient and low-cost method suitable for many topical two-frequency experiments, including coherent population trapping, slow light, lasing without inversion, and Raman sideband cooling.This research was supported under the Discovery funding scheme of the Australian Research Council Project No. DP0557505

Influence of grape rot on the contents of sulfur binding compounds in wine after automated optical grape sorting

In the last years, climate change has played an important role in some wine growing regions because of the increasing hazard of different kinds of bunch rot. Botrytis cinerea is the most important kind of rot on grapes. Beside sensory effects, this rot can influence the content of yeast nutrients, e.g. thiamine, in the must and thus affect the alcoholic fermentation. To get insight into the influence of Botrytis cinerea on the content of sulfur binding compounds formed during the fermentation process in wine, tons of grapes from the Mosel valley were sorted by an automated optical grape sorter, an innovative possibility of grape sorting, in 2011. Wine samples before sulfurisation of the four sorting fractions, namely control (unsorted berries), free-run (juice from opened berries), positive (healthy, intact berries) and negative (rotten berries) were analysed for the sulfur-binding compounds acetaldehyde, pyruvic acid, 2-oxoglutaric acid and for bound sulfur dioxide. The results show that acetaldehyde concentrations were not affected by rot, while pyruvic acid and 2-oxoglutaric acid levels were significantly higher in the negative fractions and lower in the positive fractions. Accordingly, bound sulfur levels were significantly higher in wines from the negative fraction. In conclusion, it could be shown that fractionation of the berries can efficiently help to reduce sulfur binding compounds in wine and thus reduce the addition of sulfur dioxide