1,500 research outputs found
Quantum Black Holes as the Link Between Microphysics and Macrophysics
There appears to be a duality between elementary particles, which span the
mass range below the Planck scale, and black holes, which span the mass range
range above it. In particular, the Black Hole Uncertainty Principle
Correspondence posits a smooth transition between the Compton and Schwarzschild
scales as a function of mass. This suggests that all black holes are in some
sense quantum, that elementary particles can be interpreted as sub-Planckian
black holes, and that there is a subtle connection between quantum and
classical physics.Comment: 9 pages, 7 figures, 2015 Karl Schwarzschild Meeting on Gravitational
Physics, eds. P. Nicolini, J. Mureika, M. Kaminski and M. Bleiche
A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33
Stellar-mass black holes are discovered in X-ray emitting binary systems,
where their mass can be determined from the dynamics of their companion stars.
Models of stellar evolution have difficulty producing black holes in close
binaries with masses >10 solar masses, which is consistent with the fact that
the most massive stellar black holes known so all have masses within 1 sigma of
10 solar masses. Here we report a mass of 15.65 +/- 1.45 solar masses for the
black hole in the recently discovered system M33 X-7, which is located in the
nearby galaxy Messier 33 (M33) and is the only known black hole that is in an
eclipsing binary. In order to produce such a massive black hole, the progenitor
star must have retained much of its outer envelope until after helium fusion in
the core was completed. On the other hand, in order for the black hole to be in
its present 3.45 day orbit about its 70.0 +/- 6.9 solar mass companion, there
must have been a ``common envelope'' phase of evolution in which a significant
amount of mass was lost from the system. We find the common envelope phase
could not have occured in M33 X-7 unless the amount of mass lost from the
progenitor during its evolution was an order of magnitude less than what is
usually assumed in evolutionary models of massive stars.Comment: To appear in Nature October 18, 2007. Four figures (one color figure
degraded). Differs slightly from published version. Supplementary Information
follows in a separate postin
Maternal race-ethnicity, immigrant status, country of birth, and the odds of a child with autism spectrum disorder
The risk of autism spectrum disorder varies by maternal race–ethnicity, immigration status, and birth region. In this retrospective cohort study, Western Australian state registries and a study population of 134 204 mothers enabled us to examine the odds of autism spectrum disorder with intellectual disability in children born from 1994 to 2005 by the aforementioned characteristics. We adjusted for maternal age, parity, socioeconomic status, and birth year. Indigenous women were 50% less likely to have a child with autism spectrum disorder with intellectual disability than Caucasian, nonimmigrant women. Overall, immigrant women were 40% less likely to have a child with autism spectrum disorder with intellectual disability than nonimmigrant women. However, Black women from East Africa had more than 3.5 times the odds of autism spectrum disorder with intellectual disability in their children than Caucasian nonimmigrant women. Research is implicated on risk and protective factors for autism spectrum disorder with intellectual disability in the children of immigrant women
Dnmt3a regulates emotional behavior and spine plasticity in the nucleus accumbens.
Despite abundant expression of DNA methyltransferases (Dnmts) in brain, the regulation and behavioral role of DNA methylation remain poorly understood. We found that Dnmt3a expression was regulated in mouse nucleus accumbens (NAc) by chronic cocaine use and chronic social defeat stress. Moreover, NAc-specific manipulations that block DNA methylation potentiated cocaine reward and exerted antidepressant-like effects, whereas NAc-specific Dnmt3a overexpression attenuated cocaine reward and was pro-depressant. On a cellular level, we found that chronic cocaine use selectively increased thin dendritic spines on NAc neurons and that DNA methylation was both necessary and sufficient to mediate these effects. These data establish the importance of Dnmt3a in the NAc in regulating cellular and behavioral plasticity to emotional stimuli
Mitigation-driven translocations: are we moving wildlife in the right direction?
Despite rapid growth in the field of reintroduction biology, many lessons learned from scientific research are not being applied to translocations initiated when human land-use conflicts with persistence of a species. Mitigation-driven translocations outnumber and receive better funding than science-based conservation translocations worldwide, yet their conservation benefit is unclear. As mitigation releases are economically motivated, outcomes may diverge greatly from releases designed to serve the biological needs of species. Translocation as a regulatory tool may be ill-fitted to biologically mitigate environmental damage wrought by development. Evidence suggests that many mitigation-driven translocations fail, though application of scientific principles and best-practices could likely increase success. Furthermore, lack of transparency and documentation of outcomes hinder efforts to understand the scope of the problem. If mitigation-driven translocations continue unabated as a part of the growing billion-dollar ecological consulting industry, it is imperative that the scale and effects of these releases are reported and evaluated
Fluid dynamics - Turbulence without inertia
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62901/1/405027a0.pd
Polyglutamine Disruption of the Huntingtin Exon 1 N Terminus Triggers a Complex Aggregation Mechanism
Simple polyglutamine (polyQ) peptides aggregate in vitro via a nucleated growth pathway directly yielding amyloid-like aggregates. We show here that the 17-amino-acid flanking sequence (HTTNT) N-terminal to the polyQ in the toxic huntingtin exon 1 fragment imparts onto this peptide a complex alternative aggregation mechanism. In isolation, the HTTNT peptide is a compact coil that resists aggregation. When polyQ is fused to this sequence, it induces in HTTNT, in a repeat-length dependent fashion, a more extended conformation that greatly enhances its aggregation into globular oligomers with HTTNT cores and exposed polyQ. In a second step, a new, amyloid-like aggregate is formed with a core composed of both HTTNT and polyQ. The results indicate unprecedented complexity in how primary sequence controls aggregation within a substantially disordered peptide and have implications for the molecular mechanism of Huntington\u27s disease
Exploring the potential of phone call data to characterize the relationship between social network and travel behavior
[EN] Social network contacts have significant influence on individual travel behavior. However, transport models rarely consider social interaction. One of the reasons is the difficulty to properly model social influence based on the limited data available. Non-conventional, passively collected data sources, such as Twitter, Facebook or mobile phones, provide large amounts of data containing both social interaction and spatiotemporal information. The analysis of such data opens an opportunity to better understand the influence of social networks on travel behavior. The main objective of this paper is to examine the relationship between travel behavior and social networks using mobile phone data. A huge dataset containing billions of registers has been used for this study. The paper analyzes the nature of co-location events and frequent locations shared by social network contacts, aiming not only to provide understanding on why users share certain locations, but also to quantify the degree in which the different types of locations are shared. Locations have been classified as frequent (home, work and other) and non-frequent. A novel approach to identify co-location events based on the intersection of users' mobility models has been proposed. Results show that other locations different from home and work are frequently associated to social interaction. Additionally, the importance of non-frequent locations in co-location events is shown. Finally, the potential application of the data analysis results to improve activity-based transport models and assess transport policies is discussed.The authors would like to thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper. The research leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement no 318367 (EUNOIA project) and no 611307 (INSIGHT project). The work of ML has been funded under the PD/004/2013 project, from the Conselleria de Educacion, Cultura y Universidades of the Government of the Balearic Islands and from the European Social Fund through the Balearic Islands ESF operational program for 2013-2017.Picornell Tronch, M.; Ruiz Sánchez, T.; Lenormand, M.; Ramasco, JJ.; Dubernet, T.; Frías-Martínez, E. (2015). Exploring the potential of phone call data to characterize the relationship between social network and travel behavior. Transportation. 42(4):647-668. https://doi.org/10.1007/s11116-015-9594-1S647668424Ahas, R., Aasa, A., Silm, S., Tiru, M.: Daily rhythms of suburban commuters’ movements in the tallinn metropolitan area: case study with mobile positioning data. Transp. Res. 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An Automated Method for Rapid Identification of Putative Gene Family Members in Plants
BACKGROUND: Gene duplication events have played a significant role in genome evolution, particularly in plants. Exhaustive searches for all members of a known gene family as well as the identification of new gene families has become increasingly important. Subfunctionalization via changes in regulatory sequences following duplication (adaptive selection) appears to be a common mechanism of evolution in plants and can be accompanied by purifying selection on the coding region. Such negative selection can be detected by a bias toward synonymous over nonsynonymous substitutions. However, the process of identifying this bias requires many steps usually employing several different software programs. We have simplified the process and significantly shortened the time required by condensing many steps into a few scripts or programs to rapidly identify putative gene family members beginning with a single query sequence. RESULTS: In this report we 1) describe the software tools (SimESTs, PCAT, and SCAT) developed to automate the gene family identification, 2) demonstrate the validity of the method by correctly identifying 3 of 4 PAL gene family members from Arabidopsis using EST data alone, 3) identify 2 to 6 CAD gene family members from Glycine max (previously unidentified), and 4) identify 2 members of a putative Glycine max gene family previously unidentified in any plant species. CONCLUSION: Gene families in plants, particularly that subset where purifying selection has occurred in the coding region, can be identified quickly and easily by integrating our software tools and commonly available contig assembly and ORF identification programs
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