The unusual γ-ray burst GRB 101225A from a helium star/neutron star merger at redshift 0.33

Long γ-ray bursts (GRBs) are the most dramatic examples of massive stellar deaths, often associated with supernovae. They release ultra-relativistic jets, which produce non-thermal emission through synchrotron radiation as they interact with the surrounding medium. Here we report observations of the unusual GRB 101225A. Its γ-ray emission was exceptionally long-lived and was followed by a bright X-ray transient with a hot thermal component and an unusual optical counterpart. During the first 10 days, the optical emission evolved as an expanding, cooling black body, after which an additional component, consistent with a faint supernova, emerged. We estimate its redshift to be z = 0.33 by fitting the spectral-energy distribution and light curve of the optical emission with a GRB-supernova template. Deep optical observations may have revealed a faint, unresolved host galaxy. Our proposed progenitor is a merger of a helium star with a neutron star that underwent a common envelope phase, expelling its hydrogen envelope. The resulting explosion created a GRB-like jet which became thermalized by interacting with the dense, previously ejected material, thus creating the observed black body, until finally the emission from the supernova dominated. An alternative explanation is a minor body falling onto a neutron star in the Galaxy.     

An asymmetric solar wind termination shock

Voyager 2 crossed the solar wind termination shock at 83.7 au in the southern hemisphere, approximately 10 au closer to the Sun than found by Voyager 1 in the north. This asymmetry could indicate an asymmetric pressure from an interstellar magnetic field, from transient-induced shock motion, or from the solar wind dynamic pressure. Here we report that the intensity of 4-5 MeV protons accelerated by the shock near Voyager 2 was three times that observed concurrently by Voyager 1, indicating differences in the shock at the two locations. (Companion papers report on the plasma, magnetic field, plasma-wave and lower energy particle observations at the shock.) Voyager 2 did not find the source of anomalous cosmic rays at the shock, suggesting that the source is elsewhere on the shock or in the heliosheath. The small intensity gradient of Galactic cosmic ray helium indicates that either the gradient is further out in the heliosheath or the local interstellar Galactic cosmic ray intensity is lower than expected.     

The classical system-organizational insights into what made Periclean Athens great

Periclean Athens represents one of the most remarkable social systems in the world's history in terms of innovative output in almost all fields of thought and endeavour. This paper presents a discussion on some of the findings of a research project analyzing the Athenian sociopolitical organization from a systems perspective. The Viable Systems Model was used by the authors as a framework for examining the reorganization of Athens' sociopolitical structure by Cleisthenes in 508/7 BC; this structure was to provide the basis for Classical Athenian democracy. The analysis provides fresh insight for those with an interest in organization theory or classical history.     

An infrared flash contemporaneous with the gamma-rays of GRB 041219a

The explosion that results in a cosmic gamma-ray burst (GRB) is thought to produce emission from two physical processes: the central engine gives rise to the high-energy emission of the burst through internal shocking, and the subsequent interaction of the flow with the external environment produces long-wavelength afterglows. Although observations of afterglows continue to refine our understanding of GRB progenitors and relativistic shocks, gamma-ray observations alone have not yielded a clear picture of the origin of the prompt emission nor details of the central engine. Only one concurrent visible-light transient has been found and it was associated with emission from an external shock. Here we report the discovery of infrared emission contemporaneous with a GRB, beginning 7.2 minutes after the onset of GRB 041219a (ref. 8). We acquired 21 images during the active phase of the burst, yielding early multi-colour observations. Our analysis of the initial infrared pulse suggests an origin consistent with internal shocks.     

Integration of mitochondrial gene sequences within the nuclear genome during senescence in a fungus

Cellular senescence in the ascomycete fungus Podospora anserina is associated with the appearance of an altered mitochondrial genome. Discrete mitochondrial DNA sequences are excised and amplified and isolated as multimerically arranged, head-to-tail repetitions. We have referred to the most frequently observed excision/amplification product as alpha-event senDNA. It is a 2.6-kilobase pair (kbp) monomeric unit (see refs 1, 3, 7) and is often found in senescent mitochondria in conjunction with other excision products. At the final stage of senescence these plasmids constitute virtually all of the DNA present in senescent mitochondria; they have replicated to high copy number at the expense of the young native genome. Because P. anserina is characterized by race-specific timing of senescence (that is, a programme of senescence), we have begun to contrast rapidly and slowly senescing races in terms of senDNA. Here we present evidence that young mitochondria of the rapidly senescing race, A+, possess an extremely high copy number of alpha-event senDNA plasmid in contrast to the more slowly senescing races s+ or s-. Moreover, we observe that during senescence the alpha-event senDNA and the beta-event senDNA (a 9.8-kbp monomer) are transposed to the nucleus and integrated into nuclear DNA. These plasmids contain the coding information for subunits I and III (respectively) of the mitochondrial cytochrome c oxidase. This constitutes the first clear evidence for the active mobilization of genetic elements from the mitochondrion to the nucleus.     

Travelling waves in the occurrence of dengue haemorrhagic fever in Thailand

Dengue fever is a mosquito-borne virus that infects 50-100 million people each year. Of these infections, 200,000-500,000 occur as the severe, life-threatening form of the disease, dengue haemorrhagic fever (DHF). Large, unanticipated epidemics of DHF often overwhelm health systems. An understanding of the spatial-temporal pattern of DHF incidence would aid the allocation of resources to combat these epidemics. Here we examine the spatial-temporal dynamics of DHF incidence in a data set describing 850,000 infections occurring in 72 provinces of Thailand during the period 1983 to 1997. We use the method of empirical mode decomposition to show the existence of a spatial-temporal travelling wave in the incidence of DHF. We observe this wave in a three-year periodic component of variance, which is thought to reflect host-pathogen population dynamics. The wave emanates from Bangkok, the largest city in Thailand, moving radially at a speed of 148 km per month. This finding provides an important starting point for detecting and characterizing the key processes that contribute to the spatial-temporal dynamics of DHF in Thailand.     

Sequence variants in the autophagy gene IRGM and multiple other replicating loci contribute to Crohn's disease susceptibility

A genome-wide association scan in individuals with Crohn's disease by the Wellcome Trust Case Control Consortium detected strong association at four novel loci. We tested 37 SNPs from these and other loci for association in an independent case-control sample. We obtained replication for the autophagy-inducing IRGM gene on chromosome 5q33.1 (replication P = 6.6 x 10(-4), combined P = 2.1 x 10(-10)) and for nine other loci, including NKX2-3, PTPN2 and gene deserts on chromosomes 1q and 5p13.     

Electron microscopy of mitochondrial DNA in Podospora anserina and the presence of a multimeric range of circular DNA molecules from senescent cultures]

Mitochondrial DNA from young cultures of race s of Podospora anserina was isolated. Its density in Cesium chloride density equilibrium gradients was 1.694 g/cc. Examination by the electron microscope revealed that ca 1% of this DNA consisted of circles, 31 micrometer in contour length; the remaining DNA was composed of linear molecules ranging in length from 2 to 33 micrometer. In DNA of similar density obtained from senescent cultures of the same race s, about 11% of the molecules consisted of a multimeric set of circles ranging in size from 0.9 to 15 micrometer, with most being in the 1.8 and 2.7 micrometer classes. The similarity of these DNA molecules with the mitochondrial DNA from rho(-) yeast mutants is discussed.     

Importance of migrating salmon smolt in Ring-Billed ( Larus delawarensis ) and California Gull ( L. californicus ) diets near Priest Rapids Dam, Washington

Ring-billed ( Larus delawarensis ) and California Gulls ( L. californicus ) have been implicated in depredations on migrating salmon smolt in the Columbia River. As part of a gull management program conducted in 1995 and 1996, we collected L. delawarensis (n = 120) and L. californicus (n = 45) near Priest Rapids Dam, Washington, and analyzed stomach contents to determine food habits and thus the importance of fish in gull diets. Percent volume measurements and index of relative importance rankings suggested a greater reliance on fish by L. californicus than by L. delawarensis . Peak percent consumption of fish by both species occurred in May, coinciding with peak salmon outmigration through Priest Rapids Dam; and for both species number of fish consumed by gulls was higher below Priest Rapids Dam. Gulls collected prior to, and after, peak smolt migration indicated low importance rankings for fish in both L. delawarensis and L. californicus diets. However, the importance ranking of fish in gull diets changed over time and was higher for both species as the smolt migration peaked in May.