Creation of collective many-body states and single photons from two-dimensional Rydberg lattice gases

The creation of collective many-body quantum states from a two-dimensional lattice gas of atoms is studied. Our approach relies on the van-der-Waals interaction that is present between alkali metal atoms when laser excited to high-lying Rydberg s-states. We focus on a regime in which the laser driving is strong compared to the interaction between Rydberg atoms. Here energetically low-lying many-particle states can be calculated approximately from a quadratic Hamiltonian. The potential usefulness of these states as a resource for the creation of deterministic single-photon sources is illustrated. The properties of these photon states are determined from the interplay between the particular geometry of the lattice and the interatomic spacing.Comment: 12 pages, 8 figure

Downward shortwave surface irradiance from 17 sites for the FIRE/SRB Wisconsin experiment

A field experiment was conducted in Wisconsin during Oct. to Nov. 1986 for purposes of both intensive cirrus cloud measurments and SRB algorithm validation activities. The cirrus cloud measurements were part of the FIRE. Tables are presented which show data from 17 sites in the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment/Surface Radiation Budget (FIRE/SRB) Wisconsin experiment region. A discussion of intercomparison results and calibration inconsistencies is also included

Effect of Level of Surface Spoilage on the Nutritive Value of Maize Silage Diets

This study determined the effect of surface spoilage in the diet on feed intake and nutrient digestibilities using growing steers fed whole-plant maize silage-based diets. A bunker silo, 0.9 m in depth, and a 2.7 m diameter AgBag were filled with alternating loads of chopped forage. After 90 days, the bunker was sealed with a sheet of polyethylene, and this silage was designated “spoiled”. The silage in the AgBag was designated “normal”. The four diets contained 90% silage and 10% supplement (dry matter basis), and the proportions of silage in the diets were A) 100% normal, B) 75% normal: 25% spoiled; C) 50% normal: 50% spoiled; and D) 25% normal: 75% spoiled. Feed intake decreased linearly as the proportion of spoiled silage increased from 0 to 75%. Steers consuming the normal silage diet had the highest nutrient digestibilities. Spoiled silage also had negative associative effects on nutrient digestibilities, and the integrity of the forage mat in the rumen was partially destroyed

General state-space population dynamics model for Bayesian stock assessment

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Zone-plate focusing of Bose-Einstein condensates for atom optics and erasable high-speed lithography of quantum electronic components

We show that Fresnel zone plates, fabricated in a solid surface, can sharply focus atomic Bose-Einstein condensates that quantum reflect from the surface or pass through the etched holes. The focusing process compresses the condensate by orders of magnitude despite inter-atomic repulsion. Crucially, the focusing dynamics are insensitive to quantum fluctuations of the atom cloud and largely preserve the condensates' coherence, suggesting applications in passive atom-optical elements, for example zone plate lenses that focus atomic matter waves and light at the same point to strengthen their interaction. We explore transmission zone-plate focusing of alkali atoms as a route to erasable and scalable lithography of quantum electronic components in two-dimensional electron gases embedded in semiconductor nanostructures. To do this, we calculate the density profile of a two-dimensional electron gas immediately below a patch of alkali atoms deposited on the surface of the nanostructure by zone-plate focusing. Our results reveal that surface-induced polarization of only a few thousand adsorbed atoms can locally deplete the electron gas. We show that, as a result, the focused deposition of alkali atoms by existing zone plates can create quantum electronic components on the 50 nm scale, comparable to that attainable by ion beam implantation but with minimal damage to either the nanostructure or electron gas.Comment: 13 pages, 7 figure

Evidence for variation in the effective population size of animal mitochondrial DNA

Background: It has recently been shown that levels of diversity in mitochondrial DNA are remarkably constant across animals of diverse census population sizes and ecologies, which has led to the suggestion that the effective population of mitochondrial DNA may be relatively constant. Results: Here we present several lines of evidence that suggest, to the contrary, that the effective population size of mtDNA does vary, and that the variation can be substantial. First, we show that levels of mitochondrial and nuclear diversity are correlated within all groups of animals we surveyed. Second, we show that the effectiveness of selection on non-synonymous mutations, as measured by the ratio of the numbers of non-synonymous and synonymous polymorphisms, is negatively correlated to levels of mitochondrial diversity. Finally, we estimate the effective population size of mitochondrial DNA in selected mammalian groups and show that it varies by at least an order of magnitude. Conclusions: We conclude that there is variation in the effective population size of mitochondria. Furthermore we suggest that the relative constancy of DNA diversity may be due to a negative correlation between the effective population size and the mutation rate per generation

Recognition of advanced level practice against multiprofessional capabilities: Experiences of the first radiography applicants

INTRODUCTION: Advanced practice is well established in the health professions with multiprofessional capabilities in place in England. To recognise achievement of these capabilities an ePortfolio (supported) route was initiated in 2022. This study aimed to review the demographics and experiences of radiographers applying for recognition in the first year of operation. METHODS: The multi method evaluation consisted of quantitative data analysis of information regarding the first three cohorts of radiographers (n = 40) participating in the NHS England (NHSE) scheme. Interviews with 12 participants was undertaken with thematic analysis of the transcripts. RESULTS: Self-rated scores of expertise were significantly higher by therapeutic radiographers (n = 8) compared to their 32 diagnostic colleagues (t = 5.556; p < 0.01). Radiographers saw the ePortfolio as an opportunity to validate their experience and to evidence parity with other professions. Participants felt the process also enabled critical reflection and gave unseen insight into themselves and their roles. The support of experienced educational supervisors was felt to be vital in this process and for successful completion of portfolio. CONCLUSIONS: Several radiographers have now achieved the necessary standards to achieve NHSE recognition. The evaluation exposed that most radiographers did not have the relevant evidence to hand and the ongoing collection of evidence around capabilities and impact is critical to evidencing advanced practice capabilities. IMPLICATIONS FOR PRACTICE: Radiographers are able to achieve the capabilities expected for multiprofessional practice. Cultural change is required to normalise recording of evidence within practice including case-based discussions, clinical supervision and feedback from colleagues and patients. The support of an experienced educational supervisor aided the critical reflection on practice level

Uterine Torsion Dystocia Complicated by Perosomus Elumbis in an Angus Calf Associated with a Consanguineous Mating

A six-year-old multiparous Angus cow was presented for dystocia. Vaginal and rectal examinations revealed an approximately 360° counterclockwise uterine torsion. The torsion was corrected by rolling the cow counterclockwise (three episodes) with the aid of a plank coupled with manual detorsion via the vagina. The placement of obstetric chains followed by manual traction ultimately delivered a stillborn male calf with evidence of vertebral aplasia, arthrogryposis, and abdominal organ herniation. Patient history and subsequent parentage verification revealed that the calf was the result of a consanguineous (mother to son) mating. Tissue samples from the affected calf and blood samples from the dam, sire, and ten half siblings were collected for genetic testing and parentage verification. Necropsy, radiographic, and computed tomography examinations all supported a diagnosis of perosomus elumbis. Perosomus elumbis is a congenital abnormality of unknown origin(s), and this is the first report of a case associated with a consanguineous mating

Monte Carlo Analysis of a New Interatomic Potential for He

By means of a Quadratic Diffusion Monte Carlo method we have performed a comparative analysis between the Aziz potential and a revised version of it. The results demonstrate that the new potential produces a better description of the equation of state for liquid $^4$He. In spite of the improvement in the description of derivative magnitudes of the energy, as the pressure or the compressibility, the energy per particle which comes from this new potential is lower than the experimental one. The inclusion of three-body interactions, which give a repulsive contribution to the potential energy, makes it feasible that the calculated energy comes close to the experimental result.Comment: 36 pages, LaTex, 11 PostScript figures include

Bilinear Quantum Monte Carlo: Expectations and Energy Differences

We propose a bilinear sampling algorithm in Green's function Monte Carlo for expectation values of operators that do not commute with the Hamiltonian and for differences between eigenvalues of different Hamiltonians. The integral representations of the Schroedinger equations are transformed into two equations whose solution has the form $\psi_a(x) t(x,y) \psi_b(y)$, where $\psi_a$ and $\psi_b$ are the wavefunctions for the two related systems and $t(x,y)$ is a kernel chosen to couple $x$ and $y$. The Monte Carlo process, with random walkers on the enlarged configuration space $x \otimes y$, solves these equations by generating densities whose asymptotic form is the above bilinear distribution. With such a distribution, exact Monte Carlo estimators can be obtained for the expectation values of quantum operators and for energy differences. We present results of these methods applied to several test problems, including a model integral equation, and the hydrogen atom.Comment: 27 page