The Fate of a WD Accreting H-Rich Material at High Rates

We study C/O white dwarfs with masses of 1.0 to 1.4 Msun accreting solar-composition material at very high accretion rates. We address the secular changes in the WDs, and in particular, the question whether accretion and the thermonuclear runaways result is net accretion or erosion. The present calculation is unique in that it follows a large number of cycles, thus revealing the secular evolution of the WD system. We find that counter to previous studies, accretion does not give rise to steady state burning. Instead, it produces cyclic thermonuclear runaways of two types. During most of the evolution, many small cycles of hydrogen ignition and burning build a helium layer over the surface of the white dwarf. This He layer gradually thickens and progressively becomes more degenerate. Once a sufficient amount of He has accumulated, several very large helium burning flashes take place and expel the accreted envelope, leaving no net mass accumulation. The results imply that such a system will not undergo an accretion induced collapse, nor will it lead to a SN Type Ia, unless a major new physical process is found.Comment: 8 pages, 7 figures, submitted to MNRA

Long term evolution of an interacting binary system

We describe a new code to simulate the stellar evolution of a close interacting binary system. It is then used to calculate the evolution of a classical nova system composed of a 1.25 Msun Main-Sequence (MS) star and a 1.0 Msun white dwarf (WD) companion. The system begins as a well separated non-interacting binary system. Initially, the two stars evolve independently of each other. However, Roche lobe overflow begins as the MS star expands on its way to become a Red Giant. We follow the mass accreted onto the WD and the ensuing nuclear runaways for several thousand flashes. The main finding is that the Roche-Lobe mass transfer rate is modulated by oscillations in the MS star, with a period that is somewhat shorter than the thermal time scale of the star. This periodically modulates the rate of thermonuclear flashes on the WD, between once every 12000 yrs, such that the WD can cool, to once every 300 yrs, such that it cannot. The system is further complicated by the secular drift in the secondary modulation. Such secondary modulation could explain systems like T Pyxidis. Last, we find that the overall process of mass gain by the WD has an efficiency of roughly 9%, thus requiring a donor with an initial mass of larger than about 5 Msun MS for an initial 1 Msun WD, if the WD is to reach the Chandrasekhar mass.Comment: submitted to MNRA

Deciphering molecular circuits from genetic variation underlying transcriptional responsiveness to stimuli

Individual genetic variation affects gene expression in response to stimuli, often by influencing complex molecular circuits. Here we combine genomic and intermediate-scale transcriptional profiling with computational methods to identify variants that affect the responsiveness of genes to stimuli (responsiveness QTLs; reQTLs) and to position these variants in molecular circuit diagrams. We apply this approach to study variation in transcriptional responsiveness to pathogen components in dendritic cells from recombinant inbred mouse strains. We identify reQTLs that correlate with particular stimuli and position them in known pathways. For example, in response to a virus-like stimulus, a trans-acting variant acts as an activator of the antiviral response; using RNAi, we identify Rgs16 as the likely causal gene. Our approach charts an experimental and analytic path to decipher the mechanisms underlying genetic variation in circuits that control responses to stimuli

Microbial dark matter sequences verification in amplicon sequencing and environmental metagenomics data

Although microorganisms constitute the most diverse and abundant life form on Earth, in many environments, the vast majority of them remain uncultured. As it is based on information gleaned mainly from cultivated microorganisms, our current body of knowledge regarding microbial life is partial and does not reflect actual microbial diversity. That diversity is hidden in the uncultured microbial majority, termed by microbiologists as “microbial dark matter” (MDM), a term borrowed from astrophysics. Metagenomic sequencing analysis techniques (both 16S rRNA gene and shotgun sequencing) compare gene sequences to reference databases, each of which represents only a small fraction of the existing microorganisms. Unaligned sequences lead to groups of “unknown microorganisms” that are usually ignored and rarefied from diversity analysis. To address this knowledge gap, we analyzed the 16S rRNA gene sequences of microbial communities from four different environments—a living organism, a desert environment, a natural aquatic environment, and a membrane bioreactor for wastewater treatment. From those datasets, we chose representative sequences of potentially unknown bacteria for additional examination as “microbial dark matter sequences” (MDMS). Sequence existence was validated by specific amplification and re-sequencing. These sequences were screened against databases and aligned to the Genome Taxonomy Database to build a comprehensive phylogenetic tree for additional sequence classification, revealing potentially new candidate phyla and other lineages. These putative MDMS were also screened against metagenome-assembled genomes from the explored environments for additional validation and for taxonomic and metabolic characterizations. This study shows the immense importance of MDMS in environmental metataxonomic analyses of 16S rRNA gene sequences and provides a simple and readily available methodology for the examination of MDM hidden behind amplicon sequencing results

A physical and regulatory map of host-influenza interactions reveals pathways in H1N1 infection

available in PMC 2010 June 28.During the course of a viral infection, viral proteins interact with an array of host proteins and pathways. Here, we present a systematic strategy to elucidate the dynamic interactions between H1N1 influenza and its human host. A combination of yeast two-hybrid analysis and genome-wide expression profiling implicated hundreds of human factors in mediating viral-host interactions. These factors were then examined functionally through depletion analyses in primary lung cells. The resulting data point to potential roles for some unanticipated host and viral proteins in viral infection and the host response, including a network of RNA-binding proteins, components of WNT signaling, and viral polymerase subunits. This multilayered approach provides a comprehensive and unbiased physical and regulatory model of influenza-host interactions and demonstrates a general strategy for uncovering complex host-pathogen relationships.National Institutes of Health (U.S.) (grant U01 AI074575)National Institutes of Health (U.S.) (grant U54 AI057159)National Institutes of Health (U.S.) (NIH New Innovator Award)Ford Foundation (Predoctoral Fellowship)Ellison Medical FoundationNational Institutes of Health (U.S.) (NIH grant R01 HG001715)National Institutes of Health (U.S.) (grant P50 HG004233)National Institutes of Health (U.S.) (PIONEER award)Howard Hughes Medical InstituteBurroughs Wellcome Fund (Career Award at the Scientific Interface)Alfred P. Sloan Foundatio

How Attention Modulates Encoding of Dynamic Stimuli

When encoding a real-life, continuous stimulus, the same neural circuits support processing and integration of prior as well as new incoming information. This ongoing interplay is modulated by attention, which is evident in the prefrontal cortex sections of the task positive network (TPN), and in the posterior cingulate cortex (PCC), a hub of the default mode network (DMN). Yet the exact nature of such modulation is still unclear. To investigate this issue, we utilized an fMRI task that employed movies as the encoded stimuli and manipulated attentional load via an easy or hard secondary task that was performed simultaneously with encoding. Results showed increased intersubject correlation (inter-SC) levels when encoding movies in a condition of high, as compared to low attentional load. This was evident in bilateral ventrolateral and dorsomedial prefrontal cortices and the dorsal PCC (dPCC). These regions became more attuned to the combination of the movie and the secondary task as the attentional demand of the task increased. Activation analyses revealed that at higher load the frontal TPN regions were more activated, whereas the dPCC was more deactivated. Attentional load also influenced connectivity within and between the networks. At high load the dPCC was anti-correlated to the frontal regions, which were more functionally coherent amongst themselves. Finally and critically, greater inter-SC in the dPCC at high load during encoding predicted lower memory strength when that information was retrieved. This association between inter-SC levels and memory strength suggest that as attentional demands increased, the dPCC was more attuned to the secondary task at the expense of the encoded stimulus, thus weakening memory for the encoded stimulus. Together, our findings show that attentional load modulated the function of core TPN and DMN regions. Furthermore, the observed correlation between memory strength and the modulation of the dPCC points to this region as a key area involved in the manipulation of attentional load on memory function

Israeli <i>Rousettus aegyptiacus</i> Pox Virus (IsrRAPXV) Infection in Juvenile Egyptian Fruit Bat (<i>Rousettus aegyptiacus</i>): Clinical Findings and Molecular Detection

During 2019, five carcasses of juvenile Egyptian fruit bats (Rousettus aegyptiacus) were submitted to the Kimron Veterinary Institute. These bats exhibited typical poxvirus like lesion plaques of different sizes on the skin, abdomen and the ventral side of the wings. Clinical and histopathological findings suggested a poxvirus infection. Infectious virus was isolated from skin swabs, skin tissue and tongue of the dead bats and was further confirmed to be a Poxvirus by molecular diagnosis using PCR with pan-chordopoxviruses primers. All the dead bats were found positive for two Poxvirus genes encoding a metalloproteinase and DNA dependent DNA polymerase. In this study, a novel real time quantitative PCR (qPCR) assay was established to further confirmed the presence of specific poxvirus viral DNA in all pathologically tested tissues. Moreover, according to sequence analysis, the virus was found to be highly similar to the recently discovered Israeli Rousettus aegyptiacus Pox Virus (IsrRAPXV)