257 research outputs found
Mass Accretion onto T Tauri Stars
It is now accepted that accretion onto classical T Tauri stars is controlled
by the stellar magnetosphere, yet to date most accretion models have assumed
that their magnetic fields are dipolar. By considering a simple steady state
accretion model with both dipolar and complex magnetic fields we find a
correlation between mass accretion rate and stellar mass of the form , with our results consistent within observed
scatter. For any particular stellar mass there can be several orders of
magnitude difference in the mass accretion rate, with accretion filling factors
of a few percent. We demonstrate that the field geometry has a significant
effect in controlling the location and distribution of hot spots, formed on the
stellar surface from the high velocity impact of accreting material. We find
that hot spots are often at mid to low latitudes, in contrast to what is
expected for accretion to dipolar fields, and that particularly for higher mass
stars, the accretion flow is predominantly carried by open field lines.Comment: 17 pages, 10 figures, accepted for publication by MNRA
A Strategy to Address the Stigmatisation of People and Communities Affected by Drug Use
The aim of this strategy is to lead a more informed and compassionate approach across society toward people with a drug problem, lived experience of drug use and their families. We acknowledge that people across society use drugs. This strategy is focussed on those for whom drug use is, or drug use has been, problematic
A Strategy to Address the Stigmatisation of People and Communities Affected by Drug Use
The aim of this strategy is to lead a more informed and compassionate approach across society toward people with a drug problem, lived experience of drug use and their families. We acknowledge that people across society use drugs. This strategy is focussed on those for whom drug use is, or drug use has been, problematic
Pretreatment with beta-blockers and the frequency of hypokalemia in patients with acute chest pain
Plasma potassium concentration was measured at admission in 1234 patients who presented with acute chest pain. One hundred and ninety five patients were on P blockers before admission. The potassium concentrations of patients admitted early (within four hours of onsetof symptoms) were compared with those admitted later (4-18 hours after onset of symptoms). There was a transient fall in plasma potassium concentrations in patients not pre-treated with , B blockers. This was not seen in patients who had been on P blockers before admission. Nonselective, B blockers were more effective than cardioselective agents in maintaining concentrationsof plasma potassium. These findings suggest a mechanism for the beneficial effects of ,B blockers on morbidity and mortality in acute myocardial infarction
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Resprouting grasses are associated with less frequent fire than seeders
Plant populations persist under recurrent fire via resprouting from surviving tissues (resprouters) or seedling recruitment (seeders). Woody species are inherently slow maturing, meaning that seeders are confined to infrequent fire regimes. However, for grasses, which mature faster, the relationships between persistence strategy and fire regime remain unknown.
Globally, we analysed associations between fire regimes experienced by hundreds of grass species and their persistence strategy, within a phylogenetic context. We also tested whether persistence strategies are associated with morphological and physiological traits.
Resprouters were associated with less frequent fire than seeders. Whilst modal fire frequencies were similar (fire return interval of 4â6 yr), seeders were restricted to regions with more frequent fire than resprouters, suggesting that greater competition with longâlived resprouters restricts seeder recruitment and survival when fire is rare. Resprouting was associated with lower leaf N, higher C:N ratios and the presence of belowground buds, but was unrelated to photosynthetic pathway.
Differences between the life histories of grasses and woody species led to a contrasting prevalence of seeders and resprouters in relation to fire frequency. Rapid sexual maturation in grasses means that seeder distributions, relative to fire regime, are determined by competitive ability and recruitment, rather than time to reproductive maturity
The de Rham homotopy theory and differential graded category
This paper is a generalization of arXiv:0810.0808. We develop the de Rham
homotopy theory of not necessarily nilpotent spaces, using closed dg-categories
and equivariant dg-algebras. We see these two algebraic objects correspond in a
certain way. We prove an equivalence between the homotopy category of schematic
homotopy types and a homotopy category of closed dg-categories. We give a
description of homotopy invariants of spaces in terms of minimal models. The
minimal model in this context behaves much like the Sullivan's minimal model.
We also provide some examples. We prove an equivalence between fiberwise
rationalizations and closed dg-categories with subsidiary data.Comment: 47 pages. final version. The final publication is available at
http://www.springerlink.co
The Analysis of Association Between Traits When Differences Between Trait States Matter
Because of their elementary significance in almost all fields of science, measures of association between two variables or traits are abundant and multiform. One aspect of association that is of considerable interest, especially in population genetics and ecology, seems to be widely ignored. This aspect concerns association between complex traits that show variable and arbitrarily defined state differences. Among such traits are genetic characters controlled by many and potentially polyploid loci, species characteristics, and environmental variables, all of which may be mutually and asymmetrically associated. A concept of directed association of one trait with another is developed here that relies solely on difference measures between the states of a trait. Associations are considered at three levels: between individual states of two variables, between an individual state of one variable and the totality of the other variable, and between two variables. Relations to known concepts of association are identified. In particular, measures at the latter two levels turn out to be interpretable as measures of differentiation. Examples are given for areas of application (search for functional relationships, distribution of variation over populations, genomic associations, spatiogenetic structure)
Biallelic interferon regulatory factor 8 mutation: A complex immunodeficiency syndrome with dendritic cell deficiency, monocytopenia, and immune dysregulation
Background: The homozygous K108E mutation of interferon regulatory factor 8 (IRF8) is reported to cause dendritic cell (DC) and monocyte deficiency. However, more widespread immune dysfunction is predicted from the multiple roles ascribed to IRF8 in immune cell development and function.
Objective: We sought to describe the effect on hematopoiesis and immunity of the compound heterozygous R83C/R291Q mutation of IRF8, which is present in a patient with recurrent viral infection, granuloproliferation, and intracerebral calcification.
Methods: Variant IRF8 alleles were identified by means of exome sequencing, and their function was tested by using reporter assays. The cellular phenotype was studied in detail by using flow cytometry, functional immunologic assay transcriptional profiling, and antigen receptor profiling.
Results: Both mutations affected conserved residues, and R291Q is orthologous to R294, which is mutated in the BXH2 IRF8-deficient mouse. R83C showed reduced nuclear translocation, and neither mutant was able to regulate the Ets/IRF composite element or interferon-stimulated response element, whereas R291Q retained BATF/JUN interactions. DC deficiency and monocytopenia were observed in blood, dermis, and lung lavage fluid. Granulocytes were consistently increased, dysplastic, and hypofunctional. Natural killer cell development and maturation were arrested. TH1, TH17, and CD8+ memory T-cell differentiation was significantly reduced, and T cells did not express CXCR3. B-cell development was impaired, with fewer memory cells, reduced class-switching, and lower frequency and complexity of somatic hypermutation. Cell-specific gene expression was widely disturbed in interferon- and IRF8-regulated transcripts.
Conclusions: This analysis defines the clinical features of human biallelic IRF8 deficiency, revealing a complex immunodeficiency syndrome caused by DC and monocyte deficiency combined with widespread immune dysregulation
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