BEC-BCS Crossover of a Trapped Two-Component Fermi Gas with Unequal Masses

We determine the energetically lowest lying states in the BEC-BCS crossover regime of s-wave interacting two-component Fermi gases under harmonic confinement by solving the many-body Schrodinger equation using two distinct approaches. Essentially exact basis set expansion techniques are applied to determine the energy spectrum of systems with N=4 fermions. Fixed-node diffusion Monte Carlo methods are applied to systems with up to N=20 fermions, and a discussion of different guiding functions used in the Monte Carlo approach to impose the proper symmetry of the fermionic system is presented. The energies are calculated as a function of the s-wave scattering length a_s for N=2-20 fermions and different mass ratios \kappa of the two species. On the BEC and BCS sides, our energies agree with analytically-determined first-order correction terms. We extract the scattering length and the effective range of the dimer-dimer system up to \kappa = 20. Our energies for the strongly-interacting trapped system in the unitarity regime show no shell structure, and are well described by a simple expression, whose functional form can be derived using the local density approximation, with one or two parameters. The universal parameter \xi for the trapped system for various \kappa is determined, and comparisons with results for the homogeneous system are presented.Comment: 11 pages, 6 figures, extended versio

Effects of diet forage source and neutral detergent fiber content on milk production of dairy cattle and methane emissions determined using GreenFeed and respiration chamber techniques

Strategies to mitigate greenhouse gas emissions from dairy cattle are unlikely to be adopted if production or profitability is reduced. The primary objective of this study was to examine the effects of high maize silage (MS) vs. high grass silage (GS) diets, without or with added neutral-detergent fiber (NDF) on milk production and methane emission of dairy cattle, using GreenFeed (GF) or respiration chamber (RC) techniques for methane emission measurements. Experiment 1 was 12-wks in duration with a randomized block continuous design and 40 Holstein cows (74 d in milk; DIM) in free-stall housing, assigned to 1 of 4 dietary treatments (n = 10 per treatment), according to calving date, parity and milk yield. Milk production and dry matter intake (DMI) were measured daily, and milk composition measured weekly, with methane yield (g/kg DMI) estimated using a GF unit (wks 10 to 12). Experiment 2 was a 4 × 4 Latin Square Design with 5-wk periods and 4 dairy cows (114 DIM) fed the same 4 dietary treatments as in experiment 1. Measurements of DMI, milk production and composition occurred in wk 4, and DMI, milk production and methane yield were measured for 2 d in RC during wk 5. Dietary treatments for both experiments were fed as TMRs offered ad libitum and containing 500 g silage/kg DM comprised of either 75:25 MS:GS (MS) or 25:75 MS:GS (GS), without or with added NDF from chopped straw and soy hulls (+47 g NDF/kg DM; MSNDF and GSNDF). In both experiments, compared to high GS, cows fed high MS had a higher (P = 0.01) DMI, greater (P = 0.01) milk production, and lower (P = 0.02) methane yield (24% lower in experiment 1 using GF and 8% lower in experiment 2 using RC). Added NDF increased (or tended to increase) methane yield for high MS, but not high GS diets (P = 0.02 for experiment 1 and P = 0.10 for experiment 2, forage type × NDF interaction). In the separate experiments the GF and RC methods detected similar dietary treatment effects on methane emission (expressed as g/d and g/kg DMI), although the magnitude of the difference varied between experiments for dietary treatments Overall methane emission and yield were 448 g/d and 20.9 g/kg DMI using GF for experiment 1 using GF and 458 g/d and 23.8 g/kg DMI for experiment 2 using RC, respectively

Experimental results for nulling the effective thermal expansion coefficient of fused silica fibres under a static stress

We have experimentally demonstrated that the effective thermal expansion coefficient of a fused silica fibre can be nulled by placing the fibre under a particular level of stress. Our technique involves heating the fibre and measuring how the fibre length changes with temperature as the stress on the fibre was systematically varied. This nulling of the effective thermal expansion coefficient should allow for the complete elimination of thermoelastic noise and is essential for allowing second generation gravitational wave detectors to reach their target sensitivity. To our knowledge this is the first time that the cancelation of the thermal expansion coefficient with stress has been experimentally observed

Formation of atomic tritium clusters and condensates

We present an extensive study of the static and dynamic properties of systems of spin-polarized tritium atoms. In particular, we calculate the two-body |F,m_F>=|0,0> s-wave scattering length and show that it can be manipulated via a Feshbach resonance at a field strength of about 870G. Such a resonance might be exploited to make and control a Bose-Einstein condensate of tritium in the |0,0> state. It is further shown that the quartet tritium trimer is the only bound hydrogen isotope and that its single vibrational bound state is a Borromean state. The ground state properties of larger spin-polarized tritium clusters are also presented and compared with those of helium clusters.Comment: 5 pages, 3 figure

Timing, Duration, and Pathways of Harlequin Duck Migration to Pacific Molting and Wintering Areas

The core breeding range for Harlequin Ducks (Histrionicus histrionicus) in western North America extends from Alaska, and south through the Yukon, Northwest Territories, and British Columbia. Smaller breeding populations exist in southwestern Alberta, Washington, Oregon, Idaho, Wyoming, and Montana. Each state and province in these areas has identified the Harlequin Duck as a species of conservation priority, given its small and isolated populations, its specific nesting requirements, and changes in abundance or distribution. Conservation objectives for all areas have identified the importance of mapping migration routes that connect breeding sites to Pacific coast molting and wintering locations, as well as determining migration timing, duration, habitat use, and stopover sites. In spring 2016, we captured Harlequin Duck pairs on breeding streams and surgically implanted satellite transmitters in the males and attached geolocators to the leg bands of females. We marked 18 harlequin pairs (Alberta = 10 (minus one female), Montana = 5, Wyoming = 2, Washington = 1). Migration initiation dates varied by breeding areas and occurred from June 3 to July 10. Male migration lasted between 1-17 days and stopovers occurred approximately half-way to the coast and included rivers, mountain streams, and lakes. They arrived at their molting areas between June 5-July 24 and these areas ranged from southeast Alaska to northwestern Washington. The majority (71%) of harlequins departed molt locations to differing winter locations. Efforts will be made to retrieve the geolocators from females in spring 2017 to compare locations between males and females from different devices

Stability of Inhomogeneous Multi-Component Fermi Gases

Two-component equal-mass Fermi gases, in which unlike atoms interact through a short-range two-body potential and like atoms do not interact, are stable even when the interspecies s-wave scattering length becomes infinitely large. Solving the many-body Schroedinger equation within a hyperspherical framework and by Monte Carlo techniques, this paper investigates how the properties of trapped two-component gases change if a third or fourth component are added. If all interspecies scattering lengths are equal and negative, our calculations suggest that both three- and four-component Fermi gases become unstable for a certain critical set of parameters. The relevant length scale associated with the collapse is set by the interspecies scattering length and we argue that the collapse is, similar to the collapse of an attractive trapped Bose gas, a many-body phenomenon. Furthermore, we consider a three-component Fermi gas in which two interspecies scattering lengths are negative while the other interspecies scattering length is zero. In this case, the stability of the Fermi system is predicted to depend appreciably on the range of the underlying two-body potential. We find parameter combinations for which the system appears to become unstable for a finite negative scattering length and parameter combinations for which the system appears to be made up of weakly-bound trimers that consist of one fermion of each species.Comment: 15 pages, 8 figure

Energetics and Structural Properties of Trapped Two-Component Fermi Gases

Using two different numerical methods, we study the behavior of two-component Fermi gases interacting through short-range s-wave interactions in a harmonic trap. A correlated Gaussian basis-set expansion technique is used to determine the energies and structural properties, i.e., the radial one-body densities and pair distribution functions, for small systems with either even or odd $N$, as functions of the s-wave scattering length and the mass ratio $\kappa$ of the two species. Particular emphasis is put on a discussion of the angular momentum of the system in the BEC-BCS crossover regime. At unitarity, the excitation spectrum of the four-particle system with total angular momentum L=0 is calculated as a function of the mass ratio $\kappa$. The results are analyzed from a hyperspherical perspective, which offers new insights into the problem. Additionally, fixed-node diffusion Monte Carlo calculations are performed for equal-mass Fermi gases with up to N=30 atoms. We focus on the odd-even oscillations of the ground state energy of the equal-mass unitary system having up to N=30 particles, which are related to the excitation gap of the system. Furthermore, we present a detailed analysis of the structural properties of these systems.Comment: 22 pages, 21 figure

Genetical and comparative genomics of Brassica under altered Ca supply identifies Arabidopsis Ca-transporter orthologs

Although Ca transport in plants is highly complex, the overexpression of vacuolar Ca2+ transporters in crops is a promising new technology to improve dietary Ca supplies through biofortification. Here, we sought to identify novel targets for increasing plant Ca accumulation using genetical and comparative genomics. Expression quantitative trait locus (eQTL) mapping to 1895 cis- and 8015 trans-loci were identified in shoots of an inbred mapping population of Brassica rapa (IMB211 x R500); 23 cis- and 948 trans-eQTLs responded specifically to altered Ca supply. eQTLs were screened for functional significance using a large database of shoot Ca concentration phenotypes of Arabidopsis thaliana. From 31 Arabidopsis gene identifiers tagged to robust shoot Ca concentration phenotypes, 21 mapped to 27 B. rapa eQTLs, including orthologs of the Ca2+ transporters At-CAX1 and At-ACA8. Two of three independent missense mutants of BraA.cax1a, isolated previously by targeting induced local lesions in genomes, have allele-specific shoot Ca concentration phenotypes compared with their segregating wild types. BraA.CAX1a is a promising target for altering the Ca composition of Brassica, consistent with prior knowledge from Arabidopsis. We conclude that multiple-environment eQTL analysis of complex crop genomes combined with comparative genomics is a powerful technique for novel gene identification/prioritization

Job retention vocational rehabilitation for employed people with inflammatory arthritis: adaptations to the WORKWELL trial due to the impact of the COVID-19 pandemic

There are high levels of work disability, absenteeism (sick leave) and presenteeism (reduced productivity) amongst people with inflammatory arthritis. WORKWELL is a multi-centre, randomised controlled trial of job retention vocational rehabilitation for employed people with inflammatory arthritis. The trial tested the effectiveness and cost-effectiveness of the WORKWELL programme compared to the receipt of written self-help information only. Both arms continued to receive usual care. In March 2020, due to the COVID-19 pandemic, the WORKWELL trial paused to recruitment and intervention delivery. To successfully re-start, protocol amendments were rapidly submitted and changes to existing trial procedures were made. The WORKWELL protocol was adapted in response to both the practical issues likely faced by many clinical research studies active across NHS sites during the pandemic and additional trial-specific challenges. A key eligibility criterion for the trial required participants to be in paid work for at least 15 h per week. However, UK national lockdowns led to a substantial proportion of the workforce suddenly being furloughed or unable to work, and many people with arthritis taking immunosuppressive medications were asked to shield themselves. Thus, the number of eligible participants was reduced. Those continuing to work were harder to identify, as hospital clinics moved to remote delivery, and also to then screen, consent and treat, as the hospital research staff and clinical therapists were re-deployed. New recruitment and consent strategies were applied, and where sites had reduced capacity, responsibilities were absorbed by the trial management team. Remote intervention delivery and electronic data capture were also implemented. By rapidly adapting the WORKWELL protocol and procedures, the trial successfully reopened to recruitment in July 2020, only 4 months after the trial pause. We were able to achieve recruitment figures above the pre-COVID target and maintain a high retention rate. In addition, we found many of the protocol changes beneficial, as these streamlined trial procedures, thus improving efficiency. It is likely that many strategies implemented in response to the pandemic may become standard practice in future research within trials of a similar design and methodology. Trial registration: ClinicalTrials.gov NCT03942783. Retrospectively registered on 08 May 2019. ISRCTN Registry ISRCTN61762297. Retrospectively registered on 13 May 2019

Gendered endings: Narratives of male and female suicides in the South African Lowveld

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11013-012-9258-y. Copyright @ Springer Science+Business Media, LLC 2012.Durkheim’s classical theory of suicide rates being a negative index of social solidarity downplays the salience of gendered concerns in suicide. But gendered inequalities have had a negative impact: worldwide significantly more men than women perpetrate fatal suicides. Drawing on narratives of 52 fatal suicides in Bushbuckridge, South Africa, this article suggests that Bourdieu’s concepts of ‘symbolic violence’ and ‘masculine domination’ provide a more appropriate framework for understanding this paradox. I show that the thwarting of investments in dominant masculine positions have been the major precursor to suicides by men. Men tended to take their own lives as a means of escape. By contrast, women perpetrated suicide to protest against the miserable consequences of being dominated by men. However, contra the assumption of Bourdieu’s concept of ‘habitus’, the narrators of suicide stories did reflect critically upon gender constructs