Universal Behaviour of the Superfluid Fraction and Tc of He-3 in 99.5% Open Aerogel

We have investigated the superfluid transition of He-3 in a 99.5% porosity silica aerogel. This very dilute sample shows behaviour intermediary between bulk He-3 and He-3 confined to the denser aerogels previously studied. We present data on both the superfluid transition temperature and the superfluid density and compare our results with previous measurements. Finally, we show that the suppression of the superfluid transition temperature and suppression of the superfluid density of He-3 in aerogel follow a universal relation for a range of aerogel samples.Comment: 4 pages, 5 figures; 1 new figure, minor change

Antecedent flow conditions and nitrate concentrations in the Mississippi River basin

The relationship between antecedent flow conditions and nitrate concentrations was explored at eight sites in the 2.9 million square kilometers (km²) Mississippi River basin, USA. Antecedent flow conditions were quantified as the ratio between the mean daily flow of the previous year and the mean daily flow from the period of record (Qratio), and the Qratio was statistically related to nitrate anomalies (the unexplained variability in nitrate concentration after filtering out season, long-term trend, and contemporaneous flow effects) at each site. Nitrate anomaly and Qratio were negatively related at three of the four major tributary sites and upstream in the Mississippi River, indicating that when mean daily streamflow during the previous year was lower than average, nitrate concentrations were higher than expected. The strength of these relationships increased when data were subdivided by contemporaneous flow conditions. Five of the eight sites had significant negative relationships (<i>p</i> ≤ 0.05) at high or moderately high contemporaneous flows, suggesting nitrate that accumulates in these basins during a drought is flushed during subsequent high flows. At half of the sites, when mean daily flow during the previous year was 50 percent lower than average, nitrate concentration can be from 9 to 27 percent higher than nitrate concentrations that follow a year with average mean daily flow. Conversely, nitrate concentration can be from 8 to 21 percent lower than expected when flow during the previous year was 50 percent higher than average. Previously documented for small, relatively homogenous basins, our results suggest that relationships between antecedent flows and nitrate concentrations are also observable at a regional scale. Relationships were not observed (using all contemporaneous flow data together) for basins larger than 1 million km², suggesting that above this limit the overall size and diversity within these basins may necessitate the use of more complicated statistical approaches or that there may be no discernible basin-wide relationship with antecedent flow. The relationships between nitrate concentration and Qratio identified in this study serve as the basis for future studies that can better define specific hydrologic processes occurring during and after a drought (or high flow period) which influence nitrate concentration, such as the duration or magnitude of low flows, and the timing of low and high flows

Mars Telescopic Observations Workshop II

Mars Telescopic Observations Workshop E convened in Tucson, Arizona, in October 1997 by popular demand slightly over two years following the first successful Mars Telescopic Observations Workshop, held in Ithaca, New York, in August 1995. Experts on Mars from the United Kingdom, Japan, Germany, and the United States were present. Twenty-eight oral presentations were made and generous time allotted for useful discussions among participants. The goals of the workshop were to (1) summarize active groundbased observing programs and evaluate them in the context of current and future space missions to Mars, (2) discuss new technologies and instrumentation in the context of changing emphasis of observations and theory useful for groundbased observing, and (3) more fully understand capabilities of current and planned Mars missions to better judge which groundbased observations are and will continue to be of importance to our overall Mars program. In addition, the exciting new discoveries presented from the Pathfinder experiments and the progress report from the Mars Global Surveyor infused the participants with satisfaction for the successes achieved in the early stages of these missions. Just as exciting was the enthusiasm for new groundbased programs designed to address new challenges resulting from mission science results. We would like to thank the National Aeronautics and Space Administration as well as Dr. David Black, director of the Lunar and Planetary Institute, and the staff of the Institute's Publications and Program Services Department for providing logistical, administrative, and publication support services for this workshop

Effects of Metallicity on the Rotation Rates of Massive Stars

Recent theoretical predictions for low metallicity massive stars predict that these stars should have drastically reduced equatorial winds (mass loss) while on the main sequence, and as such should retain most of their angular momentum. Observations of both the Be/(B+Be) ratio and the blue-to-red supergiant ratio appear to have a metallicity dependence that may be caused by high rotational velocities. We have analyzed 39 archival Hubble Space Telescope Imaging Spectrograph (STIS), high resolution, ultraviolet spectra of O-type stars in the Magellanic Clouds to determine their projected rotational velocities V sin i. Our methodology is based on a previous study of the projected rotational velocities of Galactic O-type stars using International Ultraviolet Explorer (IUE) Short Wavelength Prime (SWP) Camera high dispersion spectra, which resulted in a catalog of V sin i values for 177 O stars. Here we present complementary V sin i values for 21 Large Magellanic Cloud and 22 Small Magellanic Cloud O-type stars based on STIS and IUE UV spectroscopy. The distribution of V sin i values for O type stars in the Magellanic Clouds is compared to that of Galactic O type stars. Despite the theoretical predictions and indirect observational evidence for high rotation, the O type stars in the Magellanic Clouds do not appear to rotate faster than their Galactic counterparts.Comment: accepted by ApJ, to appear 20 December 2004 editio

Spin susceptibility of the superfluid 3^{3}He-B in aerogel

The temperature dependence of paramagnetic susceptibility of the superfluid ^{3}He-B in aerogel is found. Calculations have been performed for an arbitrary phase shift of s-wave scattering in the framework of BCS weak coupling theory and the simplest model of aerogel as an aggregate of homogeneously distributed ordinary impurities. Both limiting cases of the Born and unitary scattering can be easily obtained from the general result. The existence of gapless superfluidity starting at the critical impurity concentration depending on the value of the scattering phase has been demonstrated. While larger than in the bulk liquid the calculated susceptibility of the B-phase in aerogel proves to be conspicuously smaller than that determined experimentally in the high pressure region.Comment: 10 pages, 4 figures, REVTe

Ultrahigh and persistent optical depths of caesium in Kagom\'e-type hollow-core photonic crystal fibres

Alkali-filled hollow-core fibres are a promising medium for investigating light-matter interactions, especially at the single-photon level, due to the tight confinement of light and high optical depths achievable by light-induced atomic desorption. However, until now these large optical depths could only be generated for seconds at most once per day, severely limiting the practicality of the technology. Here we report the generation of highest observed transient ($>10^5$ for up to a minute) and highest observed persistent ($>2000$ for hours) optical depths of alkali vapours in a light-guiding geometry to date, using a caesium-filled Kagom\'e-type hollow-core photonic crystal fibre. Our results pave the way to light-matter interaction experiments in confined geometries requiring long operation times and large atomic number densities, such as generation of single-photon-level nonlinearities and development of single photon quantum memories.Comment: Author Accepted versio

Interfacing GHz-bandwidth heralded single photons with a room-temperature Raman quantum memory

Photonics is a promising platform for quantum technologies. However, photon sources and two-photon gates currently only operate probabilistically. Large-scale photonic processing will therefore be impossible without a multiplexing strategy to actively select successful events. High time-bandwidth-product quantum memories - devices that store and retrieve single photons on-demand - provide an efficient remedy via active synchronisation. Here we interface a GHz-bandwidth heralded single-photon source and a room-temperature Raman memory with a time-bandwidth product exceeding 1000. We store heralded single photons and observe a clear influence of the input photon statistics on the retrieved light, which agrees with our theoretical model. The preservation of the stored field's statistics is limited by four-wave-mixing noise, which we identify as the key remaining challenge in the development of practical memories for scalable photonic information processing

Model of Inhomogeneous Impurity Distribution in Fermi Superfluids

The standard treatment of impurities in metals assumes a homogeneous distribution of impurities. In this paper we study distributions that are inhomogeneous. We discuss in detail the "isotropic inhomogeneous scattering model" which takes into account the spatially varying scattering on the scale of the superfluid coherence length. On a large scale the model reduces to a homogeneous medium with renormalized parameter values. We apply the model to superfluid 3He, where porous aerogel acts as the impurity. We calculate the transition temperature Tc, the order parameter, and the superfluid density. Both A- and B-like phases are considered. Two different types of behavior are identified for the temperature dependence of the order parameter. We compare the calculations with experiments on 3He in aerogel. We find that most of the differences between experiments and the homogeneous theory can be explained by the inhomogeneous model. All our calculations are based on the quasiclassical theory of Fermi liquids. The parameters of this theory for superfluid 3He in aerogel are discussed.Comment: 14 pages, 9 figures, minor change

Elevated Incidence of Fractures in Solid-Organ Transplant Recipients on Glucocorticoid-Sparing Immunosuppressive Regimens

This study was conducted to assess the occurrence of fractures in solid-organ transplant recipients. Methods. Medical record review and surveys were performed. Patients received less than 6 months of glucocorticoids. Results. Of 351 transplant patients, 175 patients provided fracture information, with 48 (27.4%) having fractured since transplant (2–6 years). Transplants included 19 kidney/liver (50% male), 47 kidney/pancreas (53% male), 92 liver (65% male), and 17 pancreas transplants (41% male). Age at transplant was 50.8 ± 10.3 years. Fractures were equally seen across both genders and transplant types. Calcium supplementation (n = 94) and bisphosphonate therapy (n = 52) were observed, and an association with a lower risk of fractures was noted for bisphosphonate users (OR = 0.45 95% C.I. 0.24, 0.85). Fracture location included 8 (16.7%) foot, 12 (25.0%) vertebral, 3 (6.3%) hand, 2 (4.2%) humerus, 5 (10.4%) wrist, 10 (20.8%) fractures at other sites, and 7 (14.6%) multiple fractures. The estimated relative risk of fracture was nearly seventeen-times higher in male liver transplant recipients ages 45–64 years compared with the general male population, and comparable to fracture rates on conventional immunosuppressant regimens. Conclusion. We identify a high frequency of fractures in transplant recipients despite limited glucocorticoid use

On the supranational spell of PISA in policy

BACKGROUND: PISA results appear to have a large impact upon government policy. The phenomenon is growing, with more countries taking part in PISA testing and politicians pointing to PISA results as reasons for their reforms. PURPOSE: The aims of this research were to depict the policy reactions to PISA across a number of jurisdictions, to see whether they exhibited similar patterns and whether the same reforms were evident. SOURCES OF EVIDENCE: We investigated policy and media reactions to the 2009 and 2012 PISA results in six cases: Canada, China (Shanghai), England, France, Norway and Switzerland. Cases were selected to contrast high-performing jurisdictions (Canada, China) with average performers (England, France, Norway and Switzerland). Countries that had already been well reported on in the literature were excluded (Finland, Germany). DESIGN AND METHODS: Policy documents, media reports and academic articles in English, French, Mandarin and Norwegian relating to each of the cases were critically evaluated. RESULTS: A policy reaction of ‘scandalisation’ was evident in four of the six cases; a technique used to motivate change. Five of the six cases showed ‘standards-based reforms’ and two had reforms in line with the ‘ideal-governance’ model. However, these are categorisations: the actual reforms had significant differences across countries. There are chronological problems with the notion that PISA results were causal with regard to policy in some instances. Countries with similar PISA results responded with different policies, reflecting their differing cultural and historical education system trajectories. CONCLUSIONS: The connection between PISA results and policy is not always obvious. The supranational spell of PISA in policy is in the way that PISA results are used as a magic wand in political rhetoric, as though they conjure particular policy choices. This serves as a distraction from the ideological basis for reforms. The same PISA results could motivate a range of different policy solutions