Models for Type I X-Ray Bursts with Improved Nuclear Physics

Multi-zone models of Type I X-ray bursts are presented that use an adaptive nuclear reaction network of unprecedented size, up to 1300 isotopes. Sequences of up to 15 bursts are followed for two choices of accretion rate and metallicity. At 0.1 Eddington (and 0.02 Eddington for low metallicity), combined hydrogen-helium flashes occur. The rise times, shapes, and tails of these light curves are sensitive to the efficiency of nuclear burning at various waiting points along the rp-process path and these sensitivities are explored. The bursts show "compositional inertia", in that their properties depend on the fact that accretion occurs onto the ashes of previous bursts which contain left-over hydrogen, helium and CNO nuclei. This acts to reduce the sensitivity of burst properties to metallicity. For the accretion rates studied, only the first anomalous burst in one model produces nuclei as heavy as A=100, other bursts make chiefly nuclei with A~64. The amount of carbon remaining after hydrogen-helium bursts is typically <1% by mass, and decreases further as the ashes are periodically heated by subsequent bursts. At the lower accretion rate of 0.02 Eddington and solar metallicity, the bursts ignite in a hydrogen-free helium layer. At the base of this layer, up to 90% of the helium has already burned to carbon prior to the unstable ignition. These helium-ignited bursts have briefer, brighter light curves with shorter tails, very rapid rise times (<0.1 s), and ashes lighter than the iron group.Comment: Submitted to the Astrophysical Journal (42 pages; 27 figures

The impact of different doses of vitamin A supplementation on male and female mortality. A randomised trial from Guinea-Bissau

<p>Abstract</p> <p>Background</p> <p>Vitamin A supplementation (VAS) given to children between 6 months and 5 years of age is known to reduce mortality in low-income countries. We have previously observed that girls benefit more from a lower dose of VAS than the one recommended by WHO, the effect being strongest if diphtheria-tetanus-pertussis vaccine (DTP) was the most recent vaccination. We aimed to test these observations.</p> <p>Methods</p> <p>During national immunisations days in Guinea-Bissau, West Africa, combining oral polio vaccination and VAS, we randomised 8626 children between 6 months and 5 years of age to receive the dose of VAS recommended by WHO or half this dose. Mortality rate ratios (MRRs) were assessed after 6 and 12 month.</p> <p>Results</p> <p>The overall mortality rate among participants was lower than expected. There was no significant difference in mortality at 6 months and 12 months of follow up between the low dose VAS group and the recommended dose VAS group. The MRRs were 1.23 (0.60-2.54) after 6 months and 1.17 (0.73-1.87) after 12 months. This tendency was similar in boys and girls. The low dose was not associated with lower mortality in girls if the most recent vaccine was DTP (MRR = 0.60 (0.14-2.50) after 6 months).</p> <p>Conclusion</p> <p>Our sample size does not permit firm conclusions since mortality was lower than expected. We could not confirm a beneficial effect of a lower dose of VAS on mortality in girls.</p> <p>Trial registration</p> <p>The study was registered under clinicaltrials.gov, number <a href="http://www.clinicaltrials.gov/ct2/show/NCT00168636">NCT00168636</a></p

Reaction rate sensitivity of 44Ti production in massive stars and implications of a thick target yield measurement of 40Ca(alpha,gamma)44Ti

We evaluate two dominant nuclear reaction rates and their uncertainties that affect 44Ti production in explosive nucleosynthesis. Experimentally we develop thick-target yields for the 40Ca(alpha,gamma)44Ti reaction at E(alpha) = 4.13, 4.54, and 5.36 MeV using gamma-ray spectroscopy. At the highest beam energy, we also performed an activation measurement that agrees with the thick target result. From the measured yields a stellar reaction rate was developed that is smaller than current statistical-model calculations and recent experimental results, which would suggest lower 44Ti production in scenarios for the alpha-rich freeze out. Special attention has been paid to assessing realistic uncertainties of stellar rates produced from a combination of experimental and theoretical cross sections, which we use to develop a re-evaluation of the 44Ti(alpha,p)47V reaction rate. Using these we carry out a sensitivity survey of 44Ti synthesis in eight expansions representing peak temperature and density conditions drawn from a suite of recent supernova explosion models. Our results suggest that the current uncertainty in these two reaction rates could lead to as large an uncertainty in 44Ti synthesis as that produced by different treatments of stellar physics.Comment: Comments: 45 pages, 19 postscript figures Minor corrections from Referee and Proof Editors Figs 9 & 10 now in colo

Electromagnetic Counterparts of Compact Object Mergers Powered by the Radioactive Decay of R-process Nuclei

The most promising astrophysical sources of kHz gravitational waves (GWs) are the inspiral and merger of binary neutron star(NS)/black hole systems. Maximizing the scientific return of a GW detection will require identifying a coincident electro-magnetic (EM) counterpart. One of the most likely sources of isotropic EM emission from compact object mergers is a supernova-like transient powered by the radioactive decay of heavy elements synthesized in ejecta from the merger. We present the first calculations of the optical transients from compact object mergers that self-consistently determine the radioactive heating by means of a nuclear reaction network; using this heating rate, we model the light curve with a one dimensional Monte Carlo radiation transfer calculation. For an ejecta mass ~1e-2 M_sun[1e-3 M_sun] the resulting light curve peaks on a timescale ~ 1 day at a V-band luminosity nu L_nu ~ 3e41[1e41] ergs/s (M_V = -15[-14]); this corresponds to an effective "f" parameter ~3e-6 in the Li-Paczynski toy model. We argue that these results are relatively insensitive to uncertainties in the relevant nuclear physics and to the precise early-time dynamics and ejecta composition. Due to the rapid evolution and low luminosity of NS merger transients, EM counterpart searches triggered by GW detections will require close collaboration between the GW and astronomical communities. NS merger transients may also be detectable following a short-duration Gamma-Ray Burst or "blindly" with present or upcoming optical transient surveys. Because the emission produced by NS merger ejecta is powered by the formation of rare r-process elements, current optical transient surveys can directly constrain the unknown origin of the heaviest elements in the Universe.Comment: 14 pages, 7 figures; accepted to MNRAS; title changed to highlight r-process connection and new figure added

Epidemiology of acute and chronic hepatitis B virus infection in Norway, 1992-2009

<p>Abstract</p> <p>Background</p> <p>Norway is classified as a low prevalence country for hepatitis B virus infection. Vaccination is only recommended for risk groups (intravenous drug users (IDUs), Men who have Sex with Men (MSM), immigrants and contacts of known carriers). We describe the epidemiology of reported cases of hepatitis B in Norway, during the years 1992-2009 in order to assess the validity of current risk groups and recommend preventive measures.</p> <p>Methods</p> <p>We used case based data from the national surveillance system on acute and chronic hepatitis B. The Norwegian Statistics Bureau provided population and migration data and the Norwegian Institute for Alcohol and Drug Research the estimated number of active IDUs between 2002-2007. Incidence rates (IR) and incidence rate ratios (IRR) for acute hepatitis B and notification rates (NR) and notification rate ratios (NRR) for chronic hepatitis B with 95% confidence intervals were calculated.</p> <p>Results</p> <p>The annual IR of acute hepatitis B ranged from 0.7/100,000 (1992) to 10.6/100,000 (1999). Transmission occurred mainly among IDUs (64%) or through sexual contact (24%). The risk of acquiring acute hepatitis B was highest in people aged 20-29 (IRR = 6.6 [3.3-13.3]), and in males (IRR = 2.4 [1.7-3.3]). We observed two peaks of newly reported chronic hepatitis B cases in 2003 and 2009 (NR = 17.6/100,000 and 17.4/100,000, respectively). Chronic hepatitis B was more likely to be diagnosed among immigrants than among Norwegians (NRR = 93 [71.9-120.6]), and among those 20-29 compared to those 50-59 (NRR = 5.2 [3.5-7.9]).</p> <p>Conclusions</p> <p>IDUs remain the largest risk group for acute hepatitis B. The observed peaks of chronic hepatitis B are related to increased immigration from high endemic countries and screening and vaccination of these groups is important to prevent further spread of infection. Universal screening of pregnant women should be introduced. A universal vaccination strategy should be considered, given the high cost of reaching the target populations. We recommend evaluating the surveillance system for hepatitis B as well as the effectiveness of screening and vaccinating immigrant populations.</p

Intratumoural and peripheral blood lymphocyte subsets in patients with metastatic renal cell carcinoma undergoing interleukin-2 based immunotherapy: association to objective response and survival

The aim of the present study was to analyse lymphocyte subsets in consecutive peripheral blood samples and consecutive tumour tissue core needle biopsies performed before and during interleukin-2 based immunotherapy, and to correlate the findings with objective response and survival. Twenty-six patients with metastatic renal cell carcinoma were treated with low dose s.c. interleukin-2, interferon-α and histamine. A total of 250 blood samples and 62 core needle biopsies from 23 and 19 of these patients, respectively, were analysed. After 2 weeks of treatment, a significant positive correlation between absolute number of peripheral blood lymphocytes (P=0.028), CD3 (P=0.017), CD57 (P=0.041) and objective response was demonstrated. There was no correlation between any peripheral blood leukocyte subsets and survival. Cytotoxicity of peripheral blood mononuclear cells was not correlated to objective response or survival. Within the tumour tissue at baseline, a significant positive correlation between CD4 (P=0.027), CD8 (P=0.028), CD57 (P=0.007) and objective response was demonstrated. After one month of immunotherapy, a significant positive correlation between intratumoral CD3 (P=0.026), CD8 (P=0.015), CD57 (P=0.009) and objective response was demonstrated. A significant positive correlation between intratumoral baseline CD4 (P=0.047), baseline CD57 (P=0.035), CD3 at one month (P=0.049) and survival was demonstrated. These data provide novel in vivo evidence of the possible contribution of lymphocyte subsets in the tumour reduction in responding patients during interleukin-2 based immunotherapy. Confirmation of the results requires further studies including a larger number of patients

Stress and its influence on reproduction in pigs: a review

The manifestations of stress, defined as a biological response to an event that the individual perceives as a threat to its homeostasis, are commonly linked to enhanced activity of the hypothalamo-pituitary-adrenal (HPA) axis and the activation of the sympathetic adreno-medullary (SA) system. Activation of the HPA system results in the secretion of peptides from the hypothalamus, principally corticotropin releasing hormone (CRH), which stimulates the release of adrenocorticotropic hormone (ACTH) and beta-endorphin. ACTH induces the secretion of corticosteroids from the adrenal cortex, which can be seen in pigs exposed to acute physical and/or psychological stressors. The present paper is a review of studies on the influence of stressors on reproduction in pigs. The effects of stress on reproduction depend on the critical timing of stress, the genetic predisposition to stress, and the type of stress. The effect of stress on reproduction is also influenced by the duration of the responses induced by various stressors. Prolonged or chronic stress usually results in inhibition of reproduction, while the effects of transient or acute stress in certain cases is stimulatory (e.g. anoestrus), but in most cases is of impairment for reproduction. Most sensitive of the reproductive process are ovulation, expression of sexual behaviour and implantation of the embryo, since they are directly controlled by the neuroendocrine system

Barriers and enablers to reporting pregnancy and adverse pregnancy outcomes in population-based surveys: EN-INDEPTH study.

BACKGROUND: Risks of neonatal death, stillbirth and miscarriage are highest in low- and middle-income countries (LMICs), where data has most gaps and estimates rely on household surveys, dependent on women reporting these events. Underreporting of pregnancy and adverse pregnancy outcomes (APOs) is common, but few studies have investigated barriers to reporting these in LMICs. The EN-INDEPTH multi-country study applied qualitative approaches to explore barriers and enablers to reporting pregnancy and APOs in surveys, including individual, community, cultural and interview level factors. METHODS: The study was conducted in five Health and Demographic Surveillance System sites in Guinea-Bissau, Ethiopia, Uganda, Bangladesh and Ghana. Using an interpretative paradigm and phenomenology methodology, 28 focus group discussions were conducted with 82 EN-INDEPTH survey interviewers and supervisors and 172 women between February and August 2018. Thematic analysis was guided by an a priori codebook. RESULTS: Survey interview processes influenced reporting of pregnancy and APOs. Women found questions about APOs intrusive and of unclear relevance. Across all sites, sociocultural and spiritual beliefs were major barriers to women reporting pregnancy, due to fear that harm would come to their baby. We identified several factors affecting reporting of APOs including reluctance to speak about sad memories and variation in recognition of the baby's value, especially for APOs at earlier gestation. Overlaps in local understanding and terminology for APOs may also contribute to misreporting, for example between miscarriages and stillbirths. Interviewers' skills and training were the keys to enabling respondents to open up, as was privacy during interviews. CONCLUSION: Sociocultural beliefs and psycho-social impacts of APOs play a large part in underreporting these events. Interviewers' skills, careful tool development and translation are the keys to obtaining accurate information. Reporting could be improved with clearer explanations of survey purpose and benefits to respondents and enhanced interviewer training on probing, building rapport and empathy

A Locked Nucleic Acid Antisense Oligonucleotide (LNA) Silences PCSK9 and Enhances LDLR Expression In Vitro and In Vivo

The proprotein convertase subtilisin/kexin type 9 (PCSK9) is an important factor in the etiology of familial hypercholesterolemia (FH) and is also an attractive therapeutic target to reduce low density lipoprotein (LDL) cholesterol. PCSK9 accelerates the degradation of hepatic low density lipoprotein receptor (LDLR) and low levels of hepatic PCSK9 activity are associated with reduced levels of circulating LDL-cholesterol.The present study presents the first evidence for the efficacy of a locked nucleic acid (LNA) antisense oligonucleotide (LNA ASO) that targets both human and mouse PCSK9. We employed human hepatocytes derived cell lines HepG2 and HuH7 and a pancreatic mouse beta-TC3 cell line known to express high endogenous levels of PCSK9. LNA ASO efficiently reduced the mRNA and protein levels of PCSK9 with a concomitant increase in LDLR protein levels after transfection in these cells. In vivo efficacy of LNA ASO was further investigated in mice by tail vein intravenous administration of LNA ASO in saline solution. The level of PCSK9 mRNA was reduced by approximately 60%, an effect lasting more than 16 days. Hepatic LDLR protein levels were significantly up-regulated by 2.5-3 folds for at least 8 days and approximately 2 fold for 16 days. Finally, measurement of liver alanine aminotransferase (ALT) levels revealed that long term LNA ASO treatment (7 weeks) does not cause hepatotoxicity.LNA-mediated PCSK9 mRNA inhibition displayed potent reduction of PCSK9 in cell lines and mouse liver. Our data clearly revealed the efficacy and safety of LNA ASO in reducing PCSK9 levels, an approach that is now ready for testing in primates. The major significance and take home message of this work is the development of a novel and promising approach for human therapeutic intervention of the PCSK9 pathway and hence for reducing some of the cardiovascular risk factors associated with the metabolic syndrome