Dark matter results from 225 live days of XENON100 data

We report on a search for particle dark matter with the XENON100 experiment, operated at the Laboratori Nazionali del Gran Sasso for 13 months during 2011 and 2012. XENON100 features an ultralow electromagnetic background of (5.3 ± 0.6) × 10(-3) events/(keV(ee) × kg × day) in the energy region of interest. A blind analysis of 224.6 live days × 34 kg exposure has yielded no evidence for dark matter interactions. The two candidate events observed in the predefined nuclear recoil energy range of 6.6-30.5 keV(nr) are consistent with the background expectation of (1.0 ± 0.2) events. A profile likelihood analysis using a 6.6-43.3 keV(nr) energy range sets the most stringent limit on the spin-independent elastic weakly interacting massive particle-nucleon scattering cross section for weakly interacting massive particle masses above 8 GeV/c(2), with a minimum of 2 × 10(-45) cm(2) at 55 GeV/c(2) and 90% confidence level.

Leishmania mexicana metacaspase is a negative regulator of amastigote proliferation in mammalian cells

Metacaspases (MCAs) are caspase family cysteine peptidases that have been implicated in cell death processes in plants, fungi and protozoa. MCAs have also been suggested to be involved in cell cycle control, differentiation and clearance of aggregates; they are virulence factors. Dissecting the function of MCAs has been complicated by the presence in many organisms of multiple MCA genes or limitations on genetic manipulation. We describe here the creation of a MCA gene-deletion mutant (Δmca) in the protozoan parasite Leishmania mexicana, which has allowed us to dissect the role of the parasite's single MCA gene in cell growth and cell death. Δmca parasites are viable as promastigotes, and differentiate normally to the amastigote form both in in vitro macrophages infection and in mice. Δmca promastigotes respond to cell death inducers such as the drug miltefosine and H₂O₂ similarly to wild-type (WT) promastigotes, suggesting that MCAs do not have a caspase-like role in execution of L. mexicana cell death. Δmca amastigotes replicated significantly faster than WT amastigotes in macrophages and in mice, but not as axenic culture in vitro. We propose that the Leishmania MCA acts as a negative regulator of amastigote proliferation, thereby acting to balance cell growth and cell death.

Anti-ferroelectric polarization transitions in quantum-dot-quantum-well arrays

With the improvement in fabrication techniques it is now possible to produce atom-like semiconductor structures with unique electronic properties. This makes possible periodic arrays of nanostructures in which the Coulomb interaction, polarizability and tunneling may all be varied. This theoretical study investigates the collective properties of 2D arrays and 3D face-centered cubic lattices of singly charged nanospherical shells, sometimes called 'quantum dot-quantum wells' or 'core-shell quantum dots'. We find that, for square arrays, the classical ground state is an Ising anti-ferroelectric (AFE), while the quantum ground state undergoes a transition from a uniform state to an AFE. The triangular lattice, in contrast, displays properties characteristic of frustration. Three-dimensional face-centered cubic lattices polarize in planes, with each layer alternating in direction. We discuss the possible experimental signals of these transitions.

Dark matter results from 100 live days of XENON100 data

We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time-projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows the selection of only the innermost 48 kg as the ultralow background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in the signal region with an expected background of (1.8 ± 0.6) events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic weakly interacting massive particle (WIMP) nucleon scattering cross sections above 7.0 × 10(-45) cm(2) for a WIMP mass of 50 GeV/c(2) at 90% confidence level.

The need for gender specific tobacco control strategies KAP survey findings on environmental tobacco smoke exposure among women in the reproductive age group

OBJECTIVE

The study was done to assess knowledge, attitudes and practices of women within the child bearing age with regard to smoking and exposure to environmental tobacco smoke (ETS) on children's health.

SUBJECTS AND METHODS

A cross-sectional study with quantitative and qualitative components was designed to collect data from women in the child-bearing age. The sample comprised of persons from the two largest combined family planning and antenatal clinics in Kingston, Jamaica.

RESULTS

The women surveyed had a fair level of knowledge about ETS health risks, negative attitudes to smoking in general, and most supported a ban on smoking in public places. Significant knowledge differences existed between young and older women and between smokers and non-smokers.

CONCLUSION

Women with the highest level of knowledge were the non-smokers: of the low knowledge score group (current smokers), 50% were in the 15-24-year age range. There is a need for more public education on smoking and the consequences of environmental tobacco smoke exposure on children's health.

The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus

Males harm females during mating in a range of species. This harm is thought to evolve because it is directly or indirectly beneficial to the male, despite being costly to his mate. The resulting sexually antagonistic selection can cause sexual arms races. For sexually antagonistic co-evolution to occur, there must be genetic variation for traits involved in female harming and susceptibility to harm, but even then intersexual genetic correlations could facilitate or impede sexual co-evolution. Male Callosobruchus maculatus harm their mates during copulation by damaging the female's reproductive tract. However, there have been no investigations of the genetic variation in damage or in female susceptibility to damage, nor has the genetic covariance between these characters been assessed. Here, we use a full-sib/half-sib breeding design to show that male damage is heritable, whereas female susceptibility to damage is much less so. There is also a substantial positive genetic correlation between the two, suggesting that selection favouring damaging males will increase the prevalence of susceptible females. We also provide evidence consistent with intralocus sexual conflict in this species.

First dark matter results from the XENON100 experiment

The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter weakly interacting massive particles (WIMPs) scattering off 62 kg of liquid xenon in an ultralow background dual-phase time projection chamber. In this Letter, we present first dark matter results from the analysis of 11.17 live days of nonblind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the predefined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross sections above 3.4 × 10⁻⁴⁴  cm² for 55  GeV/c² WIMPs at 90% confidence level. Below 20  GeV/c², this result constrains the interpretation of the CoGeNT and DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.

Emergency subtotal colectomy for fulminant Clostridium difficile colitis--is a surgical solution considered for all patients?

INTRODUCTION

Clostridium difficile has been an increasing problem in UK hospitals. At the time of this study, there was a high incidence of C. difficile within our trust and a number of patients developed acute fulminant colitis requiring subtotal colectomy. We review a series of colectomies for C. difficile, examining the associated morbidity and mortality and the factors that predispose to acute fulminant colitis.

PATIENTS AND METHODS

This is a retrospective study of patients undergoing subtotal colectomy for C. difficile colitis in an NHS trust over 18 months. Case notes were reviewed for antibiotic use, duration of diarrhoea, treatment, blood results, preoperative imaging and surgical morbidity and mortality.

RESULTS

A total of 1398 patients tested positive for C. difficile in this period. Of these, 18 (1.29%) underwent colectomy. All were emergency admissions, 35% medical, 35% surgical, 24% neurosurgical and 6% orthopaedic. In the cohort, 29% were aged less than 65 years. Patients had a median of three antibiotics (range, 1-6), for a median of 10 days (range, 0-59 days). Median length of stay prior to C. difficile diagnosis was 13 days. Subtotal colectomy was performed a median of 4 days (range, 0-23 days) after diagnosis. Postoperative mortality was 53% (9 of 17). The median C-reactive protein level for those who died was 302 mg/l, in contrast to 214 mg/l in the survival group. Whilst 62% of all C. difficile cases were medical, the colectomy rate was only 0.7%. In the surgical specialties, the colectomy rates were 3.2% for general surgical, 1.2% for orthopaedic and 8% for neurosurgical patients.

CONCLUSIONS

Colectomy for C. difficile colitis has a high mortality but can be life-saving, even in extremely sick patients. Although heavy antibiotic use is a predisposing factor, this is not an obligatory prerequisite in the development of C. difficile. Neither is it a disease of the elderly, making it difficult to predict vulnerable patients. There are large differences in colectomy rates between specialties and we suggest there may be a place for a surgical opinion in all cases of severe C. difficile colitis.

Hypertension in pregnancy among HIV-infected women in sub-Saharan Africa: prevalence and infant outcomes

This analysis was performed to determine the prevalence of hypertension and association of MAP (mean arterial pressure) with birth outcomes among HIV-infected pregnant women not taking antiretrovirals. HIV-infected pregnant women, enrolled into the HPTN024 trial in Tanzania, Malawi and Zambia were followed up at 26-30, 36 weeks, and delivery. The prevalence of hypertension was <1% at both 20-24 weeks and 26-30 weeks and 1.7% by 36 weeks. A 5 mm Hg elevation in MAP increased the risk of stillbirth at 20-24 weeks by 29% (p = 0.001), 32% (p = 0.001) at 26-30 weeks and of low birth weight (LBW) at 36 weeks by 26% (p = 0.001). MAP was not associated with stillbirth at 36 weeks, LBW prior to 36 weeks, preterm birth, neonatal mortality or the risk of maternal to child transmission (MTCT) of HIV.