A Detection of an Anti-correlated Hard X-ray Lag in AM Herculis

Context {Earlier cross-correlation studies for AM Her were performed in various energy range from optical to X-ray and suggested that it mostly shows a high level of correlation but on occasion it shows a low level of correlation or uncorrelation.} Aims {To investigate the degree of correlation between soft (2-4 keV) and hard (9-20 keV) X-rays, we perform the cross-correlation study of the X-ray data sets of AM Her obtained with {\it RXTE}.} Methods {We cross-correlate the background-subtracted soft and hard X-ray light curves using the XRONOS program crosscor and fit a model to the obtained cross-correlation functions.} Results {We detect a hard X-ray lag of $192\pm33$ s in a specific section of energy-dependent light curve, where the soft X-ray (2-4 keV) intensity decreases but the hard X-ray (9-20 keV) intensity increases. From a spectral analysis, we find that the X-ray emission temperature increases during the anti-correlated intensity variation. In two other observations, the cross-correlation functions show a low level of correlation, which is consistent with the earlier results performed in a different energy range.} Conclusions {We report a detection of an anti-correlated hard X-ray lag of $\sim$190 s from the proto-type polar AM Her. The hard X-ray lag is detected for the first time in the given energy range, and it is the longest lag among those reported in magnetic cataclysmic variables. We discuss the implications of our findings regarding the origin of the hard X-ray lag and the anti-correlated intensity variation.}Comment: Accepted in A&A, 4 page

AX J1910.7+0917 and three newly discovered INTEGRAL sources

We take advantage of the high sensitivity of the IBIS/ISGRI telescope and the improvements in the data analysis software to investigate the nature of the still poorly known X-ray source AX J1910.7+0917, and search for close-by previously undetected objects. We analyze all publicly available INTEGRAL data of AX J1910.7+0917, together with a number of archival observations that were carried out in the direction of the source with Chandra, XMM-Newton, and ASCA. In the IBIS/ISGRI field-of-view around AX J1910.7+0917, we discovered three new sources: IGR J19173+0747, IGR J19294+1327 and IGR J19149+1036; the latter is positionally coincident with the Einstein source 2E 1912.5+1031. For the first two sources, we also report the results of follow-up observations carried out with Swift/XRT. AX J1910.7+0917 features a clear variability in the X-rays. Its spectrum can be well described with an absorbed (N_H~6x10^(22) cm^(-2)) power-law ({\Gamma}~1.5) model plus an iron line at ~6.4 keV. We also obtained a refined position and report on possible infrared counterparts. The present data do not allow for a unique classification of the sources. Based on the property of its X-ray emission and the analysis of a likely infrared counterpart, we investigate different possibilities for the nature of AX J1910.7+0917.Comment: 9 pages, 7 figures. Accepted for publication in A&

Solution structure of the inner DysF domain of myoferlin and implications for limb girdle muscular dystrophy type 2b

Mutations in the protein dysferlin, a member of the ferlin family, lead to limb girdle muscular dystrophy type 2B and Myoshi myopathy. The ferlins are large proteins characterised by multiple C2 domains and a single C-terminal membrane-spanning helix. However, there is sequence conservation in some of the ferlin family in regions outside the C2 domains. In one annotation of the domain structure of these proteins, an unusual internal duplication event has been noted where a putative domain is inserted in between the N- and C-terminal parts of a homologous domain. This domain is known as the DysF domain. Here, we present the solution structure of the inner DysF domain of the dysferlin paralogue myoferlin, which has a unique fold held together by stacking of arginine and tryptophans, mutations that lead to clinical disease in dysferlin

Neural substrates underlying fear-evoked freezing: the periaqueductal grey – cerebellar link

The central neural pathways involved in fear-evoked behaviour are highly conserved across mammalian species, and there is a consensus that understanding them is a fundamental step towards developing effective treatments for emotional disorders in man. The ventrolateral periaqueductal grey (vlPAG) has a well-established role in fear-evoked freezing behaviour. The neural pathways underlying autonomic and sensory consequences of vlPAG activation in fearful situations are well understood, but much less is known about the pathways that link vlPAG activity to distinct fear- evoked motor patterns essential for survival. In adult rats, we have identified a pathway linking the vlPAG to cerebellar cortex, which terminates as climbing fibres in lateral vermal lobule VIII (pyramis). Lesion of pyramis input-output pathways disrupted innate and fear-conditioned freezing behaviour. The disruption in freezing behaviour was strongly correlated to the reduction in the vlPAG-induced facilitation of -motoneurone excitability observed after lesions of the pyramis. The increased excitability of -motoneurones during vlPAG activation may therefore drive theincreaseinmuscletonethatunderliesexpressionoffreezingbehaviour

Multicolor observations of the afterglow of the short/hard GRB 050724

New information on short/hard gamma-ray bursts (GRBs) is being gathered thanks to the discovery of their optical and X-ray afterglows. However, some key aspects are still poorly understood, including the collimation level of the outflow, the duration of the central engine activity, and the properties of the progenitor systems. We want to constrain the physical properties of the short GRB 050724 and of its host galaxy, and make some inferences on the global short GRB population. We present optical observations of the afterglow of GRB 050724 and of its host galaxy, significantly expanding the existing dataset for this event. We compare our results with models, complementing them with available measurements from the literature. We study the afterglow light curve and spectrum including X-ray data. We also present observations of the host galaxy. The observed optical emission was likely related to the large flare observed in the X-ray light curve. The apparent steep decay was therefore not due to the jet effect. Available data are indeed consistent with low collimation, in turn implying a large energy release, comparable to that of long GRBs. The flare properties also constrain the internal shock mechanism, requiring a large Lorentz factor contrast between the colliding shells. This implies that the central engine was active at late times, rather than ejecting all shells simultaneously. The host galaxy has red colors and no ongoing star formation, consistent with previous findings on this GRB. However, it is not a pure elliptical, and has some faint spiral structure. GRB 050724 provides the most compelling case for association between a short burst and a galaxy with old stellar population. It thus plays a pivotal role in constraining progenitors models, which should allow for long delays between birth and explosion.Comment: 8 pages, 5 figures, 4 tables, accepted for publication in A&A, typo fixe

Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics

Very-high energy (VHE) gamma quanta contribute only a minuscule fraction - below one per million - to the flux of cosmic rays. Nevertheless, being neutral particles they are currently the best "messengers" of processes from the relativistic/ultra-relativistic Universe because they can be extrapolated back to their origin. The window of VHE gamma rays was opened only in 1989 by the Whipple collaboration, reporting the observation of TeV gamma rays from the Crab nebula. After a slow start, this new field of research is now rapidly expanding with the discovery of more than 150 VHE gamma-ray emitting sources. Progress is intimately related with the steady improvement of detectors and rapidly increasing computing power. We give an overview of the early attempts before and around 1989 and the progress after the pioneering work of the Whipple collaboration. The main focus of this article is on the development of experimental techniques for Earth-bound gamma-ray detectors; consequently, more emphasis is given to those experiments that made an initial breakthrough rather than to the successors which often had and have a similar (sometimes even higher) scientific output as the pioneering experiments. The considered energy threshold is about 30 GeV. At lower energies, observations can presently only be performed with balloon or satellite-borne detectors. Irrespective of the stormy experimental progress, the success story could not have been called a success story without a broad scientific output. Therefore we conclude this article with a summary of the scientific rationales and main results achieved over the last two decades.Comment: 45 pages, 38 figures, review prepared for EPJ-H special issue "Cosmic rays, gamma rays and neutrinos: A survey of 100 years of research

Challenging GRB models through the broadband dataset of GRB060908

Context: Multiwavelength observations of gamma-ray burst prompt and afterglow emission are a key tool to disentangle the various possible emission processes and scenarios proposed to interpret the complex gamma-ray burst phenomenology. Aims: We collected a large dataset on GRB060908 in order to carry out a comprehensive analysis of the prompt emission as well as the early and late afterglow. Methods: Data from Swift-BAT, -XRT and -UVOT together with data from a number of different ground-based optical/NIR and millimeter telescopes allowed us to follow the afterglow evolution from about a minute from the high-energy event down to the host galaxy limit. We discuss the physical parameters required to model these emissions. Results: The prompt emission of GRB060908 was characterized by two main periods of activity, spaced by a few seconds of low intensity, with a tight correlation between activity and spectral hardness. Observations of the afterglow began less than one minute after the high-energy event, when it was already in a decaying phase, and it was characterized by a rather flat optical/NIR spectrum which can be interpreted as due to a hard energy-distribution of the emitting electrons. On the other hand, the X-ray spectrum of the afterglow could be fit by a rather soft electron distribution. Conclusions: GRB060908 is a good example of a gamma-ray burst with a rich multi-wavelength set of observations. The availability of this dataset, built thanks to the joint efforts of many different teams, allowed us to carry out stringent tests for various interpretative scenarios showing that a satisfactorily modeling of this event is challenging. In the future, similar efforts will enable us to obtain optical/NIR coverage comparable in quality and quantity to the X-ray data for more events, therefore opening new avenues to progress gamma-ray burst research.Comment: A&A, in press. 11 pages, 5 figure

Priority species to support the functional integrity of coral reefs

Ecosystem-based management on coral reefs has historically focussed on biodiversity conservation through the establishment of marine reserves, but it is increasingly recognised that a subset of species can be key to the maintenance of ecosystem processes and functioning. Specific provisions for these key taxa are essential to biodiversity conservation and resilience-based adaptive management. While a wealth of literature addresses ecosystem functioning on coral reefs, available information covers only a subset of specific taxa, ecological processes and environmental stressors. What is lacking is a comparative assessment across the diverse range of coral reef species to synthesise available knowledge to inform science and management. Here we employed expert elicitation coupled with a literature review to generate the first comprehensive assessment of 70 taxonomically diverse and functionally distinct coral reef species from microbes to top predators to summarise reef functioning. Although our synthesis is largely through the lens of the Great Barrier Reef, Australia, a particularly data-rich system, it is relevant to coral reefs in general. We use this assessment to evaluate which taxa drive processes that maintain a healthy reef and whether management of these taxa is considered a priority (i.e. are they vulnerable?) or is feasible (i.e. can they be managed?). Scientific certainty was scored to weight our recommendations, particularly when certainty was low. We use five case studies to highlight critical gaps in knowledge that limit our understanding of ecosystem functioning. To inform the development of novel management strategies and research objectives, we identify taxa that support positive interactions and enhance ecosystem performance, including those where these roles are currently underappreciated. We conclude that current initiatives effectively capture many priority taxa but that there is significant room to increase opportunities for underappreciated taxa in both science and management to maximally safeguard coral reef functioning

The EADGENE Microarray Data Analysis Workshop (Open Access publication)

Microarray analyses have become an important tool in animal genomics. While their use is becoming widespread, there is still a lot of ongoing research regarding the analysis of microarray data. In the context of a European Network of Excellence, 31 researchers representing 14 research groups from 10 countries performed and discussed the statistical analyses of real and simulated 2-colour microarray data that were distributed among participants. The real data consisted of 48 microarrays from a disease challenge experiment in dairy cattle, while the simulated data consisted of 10 microarrays from a direct comparison of two treatments (dye-balanced). While there was broader agreement with regards to methods of microarray normalisation and significance testing, there were major differences with regards to quality control. The quality control approaches varied from none, through using statistical weights, to omitting a large number of spots or omitting entire slides. Surprisingly, these very different approaches gave quite similar results when applied to the simulated data, although not all participating groups analysed both real and simulated data. The workshop was very successful in facilitating interaction between scientists with a diverse background but a common interest in microarray analyses

Analysis of the real EADGENE data set: Comparison of methods and guidelines for data normalisation and selection of differentially expressed genes (Open Access publication)

A large variety of methods has been proposed in the literature for microarray data analysis. The aim of this paper was to present techniques used by the EADGENE (European Animal Disease Genomics Network of Excellence) WP1.4 participants for data quality control, normalisation and statistical methods for the detection of differentially expressed genes in order to provide some more general data analysis guidelines. All the workshop participants were given a real data set obtained in an EADGENE funded microarray study looking at the gene expression changes following artificial infection with two different mastitis causing bacteria: Escherichia coli and Staphylococcus aureus. It was reassuring to see that most of the teams found the same main biological results. In fact, most of the differentially expressed genes were found for infection by E. coli between uninfected and 24 h challenged udder quarters. Very little transcriptional variation was observed for the bacteria S. aureus. Lists of differentially expressed genes found by the different research teams were, however, quite dependent on the method used, especially concerning the data quality control step. These analyses also emphasised a biological problem of cross-talk between infected and uninfected quarters which will have to be dealt with for further microarray studies