76 research outputs found
Formation of the black-hole binary M33 X-7 via mass-exchange in a tight massive system
M33 X-7 is among the most massive X-Ray binary stellar systems known, hosting
a rapidly spinning 15.65 Msun black hole orbiting an underluminous 70 Msun Main
Sequence companion in a slightly eccentric 3.45 day orbit. Although
post-main-sequence mass transfer explains the masses and tight orbit, it leaves
unexplained the observed X-Ray luminosity, star's underluminosity, black hole's
spin, and eccentricity. A common envelope phase, or rotational mixing, could
explain the orbit, but the former would lead to a merger and the latter to an
overluminous companion. A merger would also ensue if mass transfer to the black
hole were invoked for its spin-up. Here we report that, if M33 X-7 started as a
primary of 85-99 Msun and a secondary of 28-32 Msun, in a 2.8-3.1 day orbit,
its observed properties can be consistently explained. In this model, the Main
Sequence primary transferred part of its envelope to the secondary and lost the
rest in a wind; it ended its life as a ~16 Msun He star with a Fe-Ni core which
collapsed to a black hole (with or without an accompanying supernova). The
release of binding energy and, possibly, collapse asymmetries "kicked" the
nascent black hole into an eccentric orbit. Wind accretion explains the X-Ray
luminosity, while the black hole spin can be natal.Comment: Manuscript: 18 pages, 2 tables, 2 figure. Supplementary Information:
34 pages, 6 figures. Advance Online Publication (AOP) on
http://www.nature.com/nature on October 20, 2010. To Appear in Nature on
November 4, 201
Selective inhibition of T suppressor-cell function by a monosaccharide
Interactions between regulatory T lymphocytes and other cells are assumed to occur at the level of the cell surface. T cells which suppress the generation of specifically effector cells have been described as having antigenic, idiotypic, allotypic and I-region specificity1−4. Other T suppressor cells generated by in vitro cultivation with or without mitogenic stimulation5,6 have suppressive activity for T and B cells but no specificity can be assigned to them. These T suppressor cells (Ts) inhibit various lymphoid functions—this either reflects their polyclonal origin or indicates that the structures recognized by the Ts receptors must be common for many cell types. Carbohydrates on cell membrane-inserted glycoproteins or glycolipids might function as specific ligands for recognition by cellular receptors or soluble factors. Almost all cell-surface proteins of mammalian cells are glycosylated. There is evidence for lectin-like carbohydrate binding proteins not only in plants7 but also in toxins8, viruses9, prokaryotic cells10 and even mammalian cells, including T cells11. A functional role for these lectin-like proteins has been described for slime moulds and suggested for the selective association of embryonic cells12,13. We report here that addition of a monosaccharide can counteract the effect of T suppressor cells during the generation of alloreactive cytotoxic T cells (CTLs) in vitro
The magnetic nature of disk accretion onto black holes
Although disk accretion onto compact objects - white dwarfs, neutron stars,
and black holes - is central to much of high energy astrophysics, the
mechanisms which enable this process have remained observationally elusive.
Accretion disks must transfer angular momentum for matter to travel radially
inward onto the compact object. Internal viscosity from magnetic processes and
disk winds can in principle both transfer angular momentum, but hitherto we
lacked evidence that either occurs. Here we report that an X-ray-absorbing wind
discovered in an observation of the stellar-mass black hole binary GRO J1655-40
must be powered by a magnetic process that can also drive accretion through the
disk. Detailed spectral analysis and modeling of the wind shows that it can
only be powered by pressure generated by magnetic viscosity internal to the
disk or magnetocentrifugal forces. This result demonstrates that disk accretion
onto black holes is a fundamentally magnetic process.Comment: 15 pages, 2 color figures, accepted for publication in Nature.
Supplemental materials may be obtained by clicking
http://www.astro.lsa.umich.edu/~jonmm/nature1655.p
New Insights into X-ray Binaries
X-ray binaries are excellent laboratories to study collapsed objects. On the
one hand, transient X-ray binaries contain the best examples of stellar-mass
black holes while persistent X-ray binaries mostly harbour accreting neutron
stars. The determination of stellar masses in persistent X-ray binaries is
usually hampered by the overwhelming luminosity of the X-ray heated accretion
disc. However, the discovery of high-excitation emission lines from the
irradiated companion star has opened new routes in the study of compact
objects. This paper presents novel techniques which exploits these irradiated
lines and summarises the dynamical masses obtained for the two populations of
collapsed stars: neutron stars and black holes.Comment: 12 pages, 5 figures, 2 tables, Invited review to plenary session in
"Highlights of Spanish Astrophysics V", Proceedings of the VIII Scientific
Meeting of the Spanish Astronomical Society (SEA) held in Santander, 7-11
July, 2008. Edited by J. Gorgas, L. J. Goicoechea, J. I. Gonzalez-Serrano, J.
M. Dieg
An interdisciplinary intervention for older Taiwanese patients after surgery for hip fracture improves health-related quality of life
Abstract Background The effects of intervention programs on health-related quality of life (HRQOL) of patients with hip fracture have not been well studied. We hypothesized that older patients with hip fracture who received our interdisciplinary intervention program would have better HRQOL than those who did not. Methods A randomized experimental design was used. Older patients with hip fracture (N = 162), 60 to 98 years old, from a medical center in northern Taiwan were randomly assigned to an experimental (n = 80) or control (n = 82) group. HRQOL was measured by the SF-36 Taiwan version at 1, 3, 6, and 12 months after discharge. Results The experimental group had significantly better overall outcomes in bodily pain (β = 9.38, p = 0.002), vitality (β = 9.40, p < 0.001), mental health (β = 8.16, p = 0.004), physical function (β = 16.01, p < 0.001), and role physical (β = 22.66, p < 0.001) than the control group at any time point during the first year after discharge. Physical-related health outcomes (physical functioning, role physical, and vitality) had larger treatment effects than emotional/mental- and social functioning-related health outcomes. Conclusions This interdisciplinary intervention program may improve health outcomes of elders with hip fracture. Our results may provide a reference for health care providers in countries using similar programs with Chinese/Taiwanese immigrant populations. Trial registration NCT01052636http://deepblue.lib.umich.edu/bitstream/2027.42/78259/1/1471-2474-11-225.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78259/2/1471-2474-11-225.pdfPeer Reviewe
Patient preferences for emergency or planned hip fracture surgery: a cross-sectional study
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Latency Associated Peptide Has In Vitro and In Vivo Immune Effects Independent of TGF-β1
Latency Associated Peptide (LAP) binds TGF-β1, forming a latent complex.
Currently, LAP is presumed to function only as a sequestering agent for active
TGF-β1. Previous work shows that LAP can induce epithelial cell
migration, but effects on leukocytes have not been reported. Because of the
multiplicity of immunologic processes in which TGF-β1 plays a role, we
hypothesized that LAP could function independently to modulate immune responses.
In separate experiments we found that LAP promoted chemotaxis of human monocytes
and blocked inflammation in vivo in a murine model of the
delayed-type hypersensitivity response (DTHR). These effects did not involve
TGF-β1 activity. Further studies revealed that disruption of specific
LAP-thrombospondin-1 (TSP-1) interactions prevented LAP-induced responses. The
effect of LAP on DTH inhibition depended on IL-10. These data support a novel
role for LAP in regulating monocyte trafficking and immune modulation
Understanding the programmatic and contextual forces that influence participation in a government-sponsored international student-mobility program
Although prior research establishes the forces that “push” and “pull” students to participate in foreign study, the transferability of findings from earlier studies is limited by the absence of theoretical grounding. In addition, relatively little is known about how a government-sponsored student mobility program promotes foreign study in a nation with a transitioning economy. Using case study methods, this study explores the characteristics of students who participate in such a program and identifies the programmatic characteristics and contextual forces that promote and limit participation. The findings shed light on the appropriate theoretical perspectives for understanding student participation in a government-sponsored mobility program and illustrate the need to consider how aspects of the national cultural, economic, and political context influence participation. The findings also raise several questions about how an international student mobility program should be structured to encourage participation and maximize benefits to individuals and society within a particular national context
The relationships between workaholism and symptoms of psychiatric disorders: a large-scale cross-sectional study
Despite the many number of studies examining workaholism, large-scale studies have been lacking. The present study utilized an open web-based cross-sectional survey assessing symptoms of psychiatric disorders and workaholism among 16,426 workers (Mage = 37.3 years, SD = 11.4, range = 16–75 years). Participants were administered the Adult ADHD Self-Report Scale, the Obsession-Compulsive Inventory-Revised, the Hospital Anxiety and Depression Scale, and the Bergen Work Addiction Scale, along with additional questions examining demographic and work-related variables. Correlations between workaholism and all psychiatric disorder symptoms were positive and significant. Workaholism comprised the dependent variable in a three-step linear multiple hierarchical regression analysis. Basic demographics (age, gender, relationship status, and education) explained 1.2% of the variance in workaholism, whereas work demographics (work status, position, sector, and annual income) explained an additional 5.4% of the variance. Age (inversely) and managerial positions (positively) were of most importance. The psychiatric symptoms (ADHD, OCD, anxiety, and depression) explained 17.0% of the variance. ADHD and anxiety contributed considerably. The prevalence rate of workaholism status was 7.8% of the present sample. In an adjusted logistic regression analysis, all psychiatric symptoms were positively associated with being a workaholic. The independent variables explained between 6.1% and 14.4% in total of the variance in workaholism cases. Although most effect sizes were relatively small, the study’s findings expand our understanding of possible psychiatric predictors of workaholism, and particularly shed new insight into the reality of adult ADHD in work life. The study’s implications, strengths, and shortcomings are also discussed
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