Gamma-Ray Burst and Relativistic Shells: The Surface Filling Factor

The variability observed in many complex gamma-ray bursts (GRBs) is inconsistent with causally connected variations in a single, symmetric, relativistic shell interacting with the ambient material ("external shocks"). Rather, the symmetry of the shell must be broken on an angular scale much smaller than Gamma^{-1} where Gamma is the bulk Lorentz factor for the shell. The observed variability in the external shock models arises from the number of causally connected regions that (randomly) become active. We define the "surface filling factor" to be the ratio of the area of causally connected regions that become active to the observable area of the shell. From the observed variability in 52 BATSE bursts, we estimate the surface filling factor to be typically 0.005 although some values are near unity. We find that the surface filling factor is about 0.1 Delta T/T in both the constant Gamma phase (which probably produces the GRB) and the deaccelerating phase (which probably produces the x-ray afterglows). Here, \Delta T is a typical time scale of variability and T is the time since the initial signal. We analyze the 2 hr flare seen by ASCA 36 hr after the GRB and conclude that the surface filling factor must be small (0.001) in the x-ray afterglow phase as well. Explanations for low surface filling factor can either require more or less energy (by a factor of about 1000) compared to that expected for a symmetric shell.Comment: 26 pages, 5 embedded figures, Latex, revised version as in press, ApJ, added figure to show the possible expanding shell geometries that can give low filling facto

The temporal pattern and lifestyle associations of respiratory virus infection in a cohort study spanning the first two years of life

Background: Respiratory virus infection is common in early childhood, and children may be symptomatic or symptom-free. Little is known regarding the association between symptomatic/asymptomatic infection and particular clinical factors such as breastfeeding as well as the consequences of such infection. Method: We followed an unselected cohort of term neonates to two years of age (220 infants at recruitment, 159 who remained in the study to 24 months), taking oral swabs at birth and oropharyngeal swabs at intervals subsequently (at 1.5, 6, 9, 12, 18 and 24 months and in a subset at 3 and 4.5 months) while recording extensive metadata including the presence of respiratory symptoms and breastfeeding status. After 2 years medical notes from the general practitioner were inspected to ascertain whether doctor-diagnosed wheeze had occurred by this timepoint. Multiplex PCR was used to detect a range of respiratory viruses: influenza (A&B), parainfluenza (1–4), bocavirus, human metapneumovirus, rhinovirus, coronavirus (OC43, 229E, NL63, HKU1), adenovirus, respiratory syncytial virus (RSV), and polyomavirus (KI, WU). Logistic regression and generalised estimating equations were used to identify associations between clinical factors and virus detection. Results: Overall respiratory viral incidence increased with age. Rhinovirus was the virus most frequently detected. The detection of a respiratory virus was positively associated with respiratory symptoms, male sex, season, childcare and living with another child. We did not observe breastfeeding (whether assessed as the number of completed months of breastfeeding or current feed status) to be associated with the detection of a respiratory virus. There was no association between early viral infection and doctor-diagnosed wheeze by age 2 years. Conclusion: Asymptomatic and symptomatic viral infection is common in the first 2 years of life with rhinovirus infection being the most common. Whilst there was no association between early respiratory viral infection and doctor-diagnosed wheeze, we have not ruled out an association of early viral infections with later asthma, and long-term follow-up of the cohort continues

A walk on the wild side: How interactions with non‐companion animals might help reduce human stress

1. The literature addressing the potential for nature and natural environments to reduce stress and improve health outcomes has a relative paucity of work regarding interactions with animals, particularly those that are not domestic pets. 2. The present observational study sought to understand whether a brief encounter with non-domestic animals might reduce stress and improve wellbeing of participants, and whether participants’ nature relatedness, and their appraisals of the interaction might influence these changes. 3. Participants (N=86, mean age=20.8 years, 81.8% female) took part in a brief wildlife encounter at a UK safari park, walking for approximately 11 minutes around an enclosure with free-roaming lemurs. Heart rate, cortisol, and measures of mood were taken before and after the encounter to understand whether this activity could reduce biological levels of stress and improve psychological wellbeing. 4. There was no decrease in participants’ heart rate after their encounter but there was a statistically significant decrease in salivary cortisol. Measures of mood significantly improved immediately after the encounter. Reductions in cortisol were associated with dimensions of an individual’s nature relatedness, as well as aspects of the animal encounter (number of lemurs and lemur proximity). 5. The findings contribute to parallel literature on nature-health relationships, with the addition of factors seemingly driving the interaction (individuals’ nature relatedness, and the number and proximity of the animals) providing important contributory information. The present study provides new information on how encounters with nature, particularly those involving animals, may be beneficial for health and wellbeing. Critically, this study was carried out in a setting where potential impact of visitors on animals is negligible, thereby demonstrating the potential for creating environments where both human and animal wellbeing is maximised

MINMOD Millennium: A Computer Program to Calculate Glucose Effectiveness and Insulin Sensitivity From the Frequently Sampled Intravenous Glucose Tolerance Test

The Bergman Minimal Model enables estimation of two key indices of glucose/insulin dynamics: glucose effectiveness and insulin sensitivity. In this paper we describe MINMOD Millennium, the latest Windows-based version of minimal model software. Extensive beta testing of MINMOD Millennium has shown that it is user-friendly, fully automatic, fast, accurate, reproducible, repeatable, and highly concordant with past versions of MINMOD. It has a simple interface, a comprehensive help system, an input file editor, a file converter, an intelligent processing kernel, and a file exporter. It provides publication-quality charts of glucose and insulin and a table of all minimal model parameters and their error estimates. In contrast to earlier versions of MINMOD and some other minimal model programs, Millennium provides identified estimates of insulin sensitivity and glucose effectiveness for almost every subject

A stitch in time: Efficient computation of genomic DNA melting bubbles

Background: It is of biological interest to make genome-wide predictions of the locations of DNA melting bubbles using statistical mechanics models. Computationally, this poses the challenge that a generic search through all combinations of bubble starts and ends is quadratic. Results: An efficient algorithm is described, which shows that the time complexity of the task is O(NlogN) rather than quadratic. The algorithm exploits that bubble lengths may be limited, but without a prior assumption of a maximal bubble length. No approximations, such as windowing, have been introduced to reduce the time complexity. More than just finding the bubbles, the algorithm produces a stitch profile, which is a probabilistic graphical model of bubbles and helical regions. The algorithm applies a probability peak finding method based on a hierarchical analysis of the energy barriers in the Poland-Scheraga model. Conclusions: Exact and fast computation of genomic stitch profiles is thus feasible. Sequences of several megabases have been computed, only limited by computer memory. Possible applications are the genome-wide comparisons of bubbles with promotors, TSS, viral integration sites, and other melting-related regions.Comment: 16 pages, 10 figure

Association of the rs2242446 polymorphism in the norepinephrine transporter gene SLC6A2 and anxious arousal symptoms of posttraumatic stress disorder

To the Editor: Recently, we found that greater norepinephrine transporter (NET) availability in the locus ceruleus of trauma survivors with posttraumatic stress disorder (PTSD) was associated with increased severity of anxious arousal (ie, hypervigilance and exaggerated startle) symptoms, but not any of the other empirically derived symptom clusters that characterize this disorder.1 This finding suggests that greater NET availability in the locus ceruleus may serve a compensatory function of clearing elevated synaptic norepinephrine and maintaining anxious arousal symptoms in persons with PTSD

Association of the rs2242446 polymorphism in the norepinephrine transporter gene SLC6A2 and anxious arousal symptoms of posttraumatic stress disorder

To the Editor: Recently, we found that greater norepinephrine transporter (NET) availability in the locus ceruleus of trauma survivors with posttraumatic stress disorder (PTSD) was associated with increased severity of anxious arousal (ie, hypervigilance and exaggerated startle) symptoms, but not any of the other empirically derived symptom clusters that characterize this disorder.1 This finding suggests that greater NET availability in the locus ceruleus may serve a compensatory function of clearing elevated synaptic norepinephrine and maintaining anxious arousal symptoms in persons with PTSD