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  • Elsevier  (68)
  • Oxford University Press  (56)
  • 2015-2019  (82)
  • 1980-1984  (41)
  • 1950-1954  (1)
  • 1
    Publication Date: 1982-08-01
    Print ISSN: 0021-9797
    Electronic ISSN: 1095-7103
    Topics: Chemistry and Pharmacology , Physics
    Published by Elsevier
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  • 2
    Publication Date: 2016-06-24
    Description: We explore the predictions for detectable gravitational-wave signals from merging binary black holes formed through chemically homogeneous evolution in massive short-period stellar binaries. We find that ~500 events per year could be detected with advanced ground-based detectors operating at full sensitivity. We analyse the distribution of detectable events, and conclude that there is a very strong preference for detecting events with nearly equal components (mass ratio 〉0.66 at 90 per cent confidence in our default model) and high masses (total source-frame mass between 57 and 103 M at 90 per cent confidence). We consider multiple alternative variations to analyse the sensitivity to uncertainties in the evolutionary physics and cosmological parameters, and conclude that while the rates are sensitive to assumed variations, the mass distributions are robust predictions. Finally, we consider the recently reported results of the analysis of the first 16 double-coincident days of the O1 LIGO (Laser Interferometer Gravitational-wave Observatory) observing run, and find that this formation channel is fully consistent with the inferred parameters of the GW150914 binary black hole detection and the inferred merger rate.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 3
    Publication Date: 2015-05-03
    Description: We analyse the distinguishability of populations of coalescing binary neutron stars, neutron-star black hole binaries, and binary black holes, whose gravitational-wave signatures are expected to be observed by the advanced network of ground-based interferometers LIGO and Virgo. We consider population-synthesis predictions for plausible merging binary distributions in mass space, along with measurement accuracy estimates from the main gravitational-wave parameter-estimation pipeline. We find that for our model compact-object binary mass distribution, we can always distinguish binary neutron stars and black hole–neutron-star binaries, but not necessarily black hole–neutron-star binaries and binary black holes; however, with a few tens of detections, we can accurately identify the three subpopulations and measure their respective rates.
    Print ISSN: 1745-3925
    Electronic ISSN: 1745-3933
    Topics: Physics
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  • 4
    Publication Date: 2015-04-21
    Description: DNA methylation is an important epigenetic marker associated with gene expression regulation in eukaryotes. While promoter methylation is relatively well characterized, the role of intragenic DNA methylation remains unclear. Here, we investigated the relationship of DNA methylation at exons and flanking introns with gene expression and histone modifications generated from a human fibroblast cell-line and primary B cells. Consistent with previous work we found that intragenic methylation is positively correlated with gene expression and that exons are more highly methylated than their neighboring intronic environment. Intriguingly, in this study we identified a unique subset of hypomethylated exons that demonstrate significantly lower methylation levels than their surrounding introns. Furthermore, we observed a negative correlation between exon methylation and the density of the majority of histone modifications. Specifically, we demonstrate that hypo-methylated exons at highly expressed genes are associated with open chromatin and have a characteristic histone code comprised of significantly high levels of histone markings. Overall, our comprehensive analysis of the human exome supports the presence of regulatory hypomethylated exons in protein coding genes. In particular our results reveal a previously unrecognized diverse and complex role of the epigenetic landscape within the gene body.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 5
    Publication Date: 2016-03-30
    Description: We explore a newly proposed channel to create binary black holes of stellar origin. This scenario applies to massive, tight binaries where mixing induced by rotation and tides transports the products of hydrogen burning throughout the stellar envelopes. This slowly enriches the entire star with helium, preventing the build-up of an internal chemical gradient. The stars remain compact as they evolve nearly chemically homogeneously, eventually forming two black holes, which we estimate typically merge 4–11 Gyr after formation. Like other proposed channels, this evolutionary pathway suffers from significant theoretical uncertainties, but could be constrained in the near future by data from advanced ground-based gravitational-wave detectors. We perform Monte Carlo simulations of the expected merger rate over cosmic time to explore the implications and uncertainties. Our default model for this channel yields a local binary black hole merger rate of about 10 Gpc –3  yr –1 at redshift z = 0, peaking at twice this rate at z = 0.5. This means that this channel is competitive, in terms of expected rates, with the conventional formation scenarios that involve a common-envelope phase during isolated binary evolution or dynamical interaction in a dense cluster. The events from this channel may be distinguished by the preference for nearly equal-mass components and high masses, with typical total masses between 50 and 110  M . Unlike the conventional isolated binary evolution scenario that involves shrinkage of the orbit during a common-envelope phase, short time delays are unlikely for this channel, implying that we do not expect mergers at high redshift.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 6
    Publication Date: 2016-03-08
    Description: Gravitational waves from coalescences of neutron stars or stellar-mass black holes into intermediate-mass black holes (IMBHs) of 100 solar masses represent one of the exciting possible sources for advanced gravitational-wave detectors. These sources can provide definitive evidence for the existence of IMBHs, probe globular-cluster dynamics, and potentially serve as tests of general relativity. We analyse the accuracy with which we can measure the masses and spins of the IMBH and its companion in intermediate-mass-ratio coalescences. We find that we can identify an IMBH with a mass above 100 M with 95 per cent confidence provided the massive body exceeds 130 M . For source masses above ~200 M , the best measured parameter is the frequency of the quasi-normal ringdown. Consequently, the total mass is measured better than the chirp mass for massive binaries, but the total mass is still partly degenerate with spin, which cannot be accurately measured. Low-frequency detector sensitivity is particularly important for massive sources, since sensitivity to the inspiral phase is critical for measuring the mass of the stellar-mass companion. We show that we can accurately infer source parameters for cosmologically redshifted signals by applying appropriate corrections. We investigate the impact of uncertainty in the model gravitational waveforms and conclude that our main results are likely robust to systematics.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 7
    Publication Date: 2016-03-08
    Description: Gravitational waves from coalescences of neutron stars or stellar-mass black holes into intermediate-mass black holes (IMBHs) of 100 solar masses represent one of the exciting possible sources for advanced gravitational-wave detectors. These sources can provide definitive evidence for the existence of IMBHs, probe globular-cluster dynamics, and potentially serve as tests of general relativity. We analyse the accuracy with which we can measure the masses and spins of the IMBH and its companion in intermediate-mass-ratio coalescences. We find that we can identify an IMBH with a mass above 100 M with 95 per cent confidence provided the massive body exceeds 130 M . For source masses above ~200 M , the best measured parameter is the frequency of the quasi-normal ringdown. Consequently, the total mass is measured better than the chirp mass for massive binaries, but the total mass is still partly degenerate with spin, which cannot be accurately measured. Low-frequency detector sensitivity is particularly important for massive sources, since sensitivity to the inspiral phase is critical for measuring the mass of the stellar-mass companion. We show that we can accurately infer source parameters for cosmologically redshifted signals by applying appropriate corrections. We investigate the impact of uncertainty in the model gravitational waveforms and conclude that our main results are likely robust to systematics.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 8
    Publication Date: 2016-07-06
    Description: Germline mutations in the X-linked gene, methyl-CpG-binding protein 2 (MECP2), underlie most cases of Rett syndrome (RTT), an autism spectrum disorder affecting approximately one in 10 000 female live births. The disease is characterized in affected girls by a latent appearance of symptoms between 12 and 18 months of age while boys usually die before the age of two. The nature of the latency is not known, but RTT-like phenotypes are recapitulated in mouse models, even when MeCP2 is removed at different postnatal stages, including juvenile and adolescent stages. Unexpectedly, here, we show that within a very brief developmental window, between 10 (adolescent) and 15 (adult) weeks after birth, symptom initiation and progression upon removal of MeCP2 in male mice transitions from 3 to 4 months to only several days, followed by lethality. We further show that this accelerated development of RTT phenotype and lethality occur at the transition to adult stage (15 weeks of age) and persists thereafter. Importantly, within this abbreviated time frame of days, the brain acquires dramatic anatomical, cellular and molecular abnormalities, typical of classical RTT. This study reveals a new postnatal developmental stage, which coincides with full-brain maturation, where the structure/function of the brain is extremely sensitive to levels of MeCP2 and loss of MeCP2 leads to precipitous collapse of the neuronal networks and incompatibility with life within days.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 9
    Publication Date: 2016-07-06
    Description: Gene expression is a multi-step process involving many layers of regulation. The main regulators of the pathway are DNA and RNA binding proteins. While over the years, a large number of DNA and RNA binding proteins have been identified and extensively studied, it is still expected that many other proteins, some with yet another known function, are awaiting to be discovered. Here we present a new web server, BindUP, freely accessible through the website http://bindup.technion.ac.il/ , for predicting DNA and RNA binding proteins using a non-homology-based approach. Our method is based on the electrostatic features of the protein surface and other general properties of the protein. BindUP predicts nucleic acid binding function given the proteins three-dimensional structure or a structural model. Additionally, BindUP provides information on the largest electrostatic surface patches, visualized on the server. The server was tested on several datasets of DNA and RNA binding proteins, including proteins which do not possess DNA or RNA binding domains and have no similarity to known nucleic acid binding proteins, achieving very high accuracy. BindUP is applicable in either single or batch modes and can be applied for testing hundreds of proteins simultaneously in a highly efficient manner.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 10
    Publication Date: 2015-12-18
    Description: The birth kicks of black holes, arising from asymmetric mass ejection or neutrino emission during core-collapse supernovae, are of great interest for both observationally constraining supernova models and population-synthesis studies of binary evolution. Recently, several efforts were undertaken to estimate black hole birth kicks from observations of black hole low-mass X-ray binaries. We follow up on this work, specifically focusing on the highest estimated black hole kick velocities. We find that existing observations do not require black hole birth kicks in excess of approximately 80 km s –1 , although higher kicks are not ruled out.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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