Reconnections of quantized vortex rings in superfluid 4^4He at very low temperatures

Collisions in a beam of unidirectional quantized vortex rings of nearly identical radii $R$ in superfluid $^4$He in the limit of zero temperature (0.05 K) were studied using time-of-flight spectroscopy. Reconnections between two primary rings result in secondary vortex loops of both smaller and larger radii. Discrete steps in the distribution of flight times, due to the limits on the earliest possible arrival times of secondary loops created after either one or two consecutive reconnections, are observed. The density of primary rings was found to be capped at the value $500{\rm \,cm}^{-2} R^{-1}$ independent of the injected density. This is due to collisions between rings causing piling-up of many other vortex rings. Both observations are in quantitative agreement with our theory.Comment: 7 pages, 4 figures, includes supplementary materia

The Role of Crystal Symmetry in the Magnetic Instabilities of β\beta-YbAlB4_4 and α\alpha-YbAlB4_4

Density functional theory methods are applied to investigate the properties of the new superconductor $\beta$-YbAlB$_4$ and its polymorph $\alpha$-YbAlB$_4$. We utilize the generalized gradient approximation + Hubbard U (GGA+U) approach with spin-orbit(SO) coupling to approximate the effects of the strong correlations due to the open $4f$ shell of Yb. We examine closely the differences in crystal bonding and symmetry of $\beta$-YbAlB$_4$ and $\alpha$-YbAlB$_4$. The in-plane bonding structure amongst the dominant itinerant electrons in the boron sheets is shown to differ significantly. Our calculations indicate that, in both polymorphs, the localized 4$f$ electrons hybridize strongly with the conduction sea when compared to the related materials YbRh$_{2}$Si$_{2}$ and YbB$_{2}$. Comparing $\beta$-YbAlB$_4$ to the electronic structure of related crystal structures indicates a key role of the 7-member boron coordination of the Yb ion in $\beta$-YbAlB$_4$ in producing its enhanced Kondo scale and superconductivity. The Kondo scale is shown to depend strongly on the angle between the B neighbors and the Yb ion, relative to the $x-y$ plane, which relates some of the physical behavior to structural characteristics.Comment: 9 pages, 9 figures, 2 table

Access to palivizumab among children at high risk of respiratory syncytial virus complications in English hospitals

Objectives: Palivizumab is a monoclonal antibody which can prevent infection with respiratory syncytial virus (RSV). Due to its high cost, it is recommended for high-risk infants only. We aimed to determine the proportion of infants eligible for palivizumab treatment in England who receive at least one dose. / Methods: We used the Hospital Treatment Insights database containing hospital admission records linked to hospital pharmacy dispensing data for 43/153 hospitals in England. Infants born between 2010 and 2016 were considered eligible for palivizumab if their medical records indicated chronic lung disease (CLD), congenital heart disease (CHD), or severe immunodeficiency (SCID), and they met additional criteria based on gestational age at birth and age at start of the RSV season (beginning of October). We calculated the proportion of infants who received at least one dose of palivizumab in their first RSV season, and modelled the odds of treatment according to multiple child characteristics using logistic regression models. / Results: We identified 3,712 eligible children, of whom 2,479 (67%) had complete information on all risk factors. Palivizumab was prescribed to 832 of eligible children (34%). Being born at <30 weeks’ gestation, aged <6 months at the start of RSV season, and having two or more of CLD, CHD or SCID were associated with higher odds of treatment. / Conclusion: In England, palivizumab is not prescribed to the majority of children who are eligible to receive it. Doctors managing these infants may be unfamiliar with the eligibility criteria or constrained by other considerations, such as cost

Pressure-induced unconventional superconductivity near a quantum critical point in CaFe2As2

75As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe2As2 under pressure. At P = 4.7 and 10.8 kbar, the temperature dependences of nuclear-spin-lattice relaxation rate (1/T1) measured in the tetragonal phase show no coherence peak just below Tc(P) and decrease with decreasing temperature. The superconductivity is gapless at P = 4.7 kbar but evolves to that with multiple gaps at P = 10.8 kbar. We find that the superconductivity appears near a quantum critical point under pressures in the range 4.7 kbar < P < 10.8 kbar. Both electron correlation and superconductivity disappear in the collapsed tetragonal phase. A systematic study under pressure indicates that electron correlations play a vital role in forming Cooper pairs in this compound.Comment: 5pages, 5figure

Synthesis and properties of La-doped CaFe2As2 single crystals with Tc = 42.7 K

Large single crystals of La-doped CaFe2As2 were successfully synthesized by the FeAs self-flux method. The x-ray diffraction patterns suggest high crystalline quality and c-axis orientation. By substitution of trivalent La3+ ions for divalent Ca2+, the resistivity anomaly in the parent compound CaFe2As2 is completely suppressed and a superconducting transition reaches the value of 42.7 K, which is higher than that of about 30 K reported in Saha S. R. et al., arXiv:1105.4798v1. The upper critical field has been determined with the magnetic field along ab-plane and c-axis, yielding an anisotropy of about 3.3.Comment: 13 pages, 5 figure

Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

No abstract available

Impact of unstable housing on all-cause mortality among persons who inject drugs

BACKGROUND: Illicit drug injecting is a well-established risk factor for morbidity and mortality. However, a limited number of prospective studies have examined the independent effect of unstable housing on mortality among persons who inject drugs (PWIDs). In this study we sought to identify if a relationship exists between unstable housing and all-cause mortality among PWIDs living in Vancouver, Canada. METHODS: PWIDs participating in two prospective cohort studies in Vancouver, Canada were followed between May 1996 and December 2012. Cohort data were linked to the provincial vital statistics database to ascertain mortality rates and causes of death. We used multivariate Cox proportional hazards regression to determine factors associated with all-cause mortality and to investigate the independent relationship between unstable housing and time to all-cause mortality. RESULTS: During the study period, 2453 individuals were followed for a median of 69 months (Inter-quartile range [IQR]: 34 – 113). In total, there were 515 (21.0%) deaths for an incidence density of 3.1 (95% Confidence Interval [CI]: 2.8 – 3.4) deaths per 100 person years. In multivariate analyses, after adjusting for potential confounders including HIV infection and drug use patterns, unstable housing remained independently associated with all-cause mortality (adjusted hazard ratio [AHR] = 1.30, 95% CI: 1.08 – 1.56). CONCLUSIONS: These findings demonstrate that unstable housing is an important risk factor for mortality independent of known risk factors including HIV infection and patterns of drug use. This study highlights the urgent need to provide supportive housing interventions to address elevated levels of preventable mortality among this population

Evidence-Based Guideline on Laparoscopy in Pregnancy: Commissioned by the British Society for Gynaecological Endoscopy (BSGE) Endorsed by the Royal College of Obstetricians & Gynaecologists (RCOG).

Laparoscopy is widely utilised to diagnose and treat acute and chronic, gynaecological and general surgical conditions. It has only been in recent years that laparoscopy has become an acceptable surgical alternative to open surgery in pregnancy. To date there is little clinical guidance pertaining to laparoscopic surgery in pregnancy. This is why the BSGE commissioned this guideline. MEDLINE, EMBASE, CINAHL and the Cochrane library were searched up to February 2017 and evidence was collated and graded following the NICE-approved process. The conditions included in this guideline are laparoscopic management of acute appendicitis, acute gall bladder disease and symptomatic benign adnexal tumours in pregnancy. The intended audience for this guideline is obstetricians and gynaecologists in secondary and tertiary care, general surgeons and anaesthetists. However, only laparoscopists who have adequate laparoscopic skills and who perform complex laparoscopic surgery regularly should undertake laparoscopy in pregnant women, since much of the evidence stems from specialised centres

Preparation of TiO2 Anatase Nanocrystals by TiCl4 Hydrolysis with Additive H2SO4

A new methodology was developed to synthesize uniform titania anatase nanocrystals by the hydrolysis of titanium chloride in sulfuric acid aqueous solutions at 0–90°C. The samples were characterized by Raman spectroscopy, UV-visible spectroscopy, transmission electron microscopy (TEM), electron diffraction (ED), and an Energy dispersive X-ray spectroscopy (EDS). The effects of the reaction temperature, mole ratio of SO42− to Ti4+, and the calcinations temperature on the particle size and crystal phase were investigated. Depending on the acidity, the hydrolysis temperature, and the calcination temperature, rhombic anatase nanocrystals sizes in the range of 10 nm to 50 nm were obtained. In the additive of sulfuric acid, Raman spectra and electron diffraction confirmed that the nanoparticles are composed of anatase TiO2. No other titania phases, such as rutile or brookite, were detected