Oscillatory instability of radiative shocks with multiple cooling processes

The stand-off shock formed in the accretion flow on to a stationary wall, such as the surface of a white dwarf, may be thermally unstable, depending on the cooling processes which dominate the post-shock flow. Some processes lead to instability, while others tend to stabilize the shock. We consider competition between the destabilizing influence of thermal bremsstrahlung cooling, and a stabilizing process which is a power law in density and temperature. Cyclotron cooling and processes which are of order 1, 3/2 and 2 in density are considered. The relative efficiency and power-law indices of the second mechanism are varied, and particular effects on the stability properties and frequencies of oscillation modes are examined

On the interaction of a thin, supersonic shell with a molecular cloud

Molecular clouds (MCs) are stellar nurseries, however, formation of stars within MCs depends on the ambient physical conditions. MCs, over a free-fall time are exposed to numerous dynamical phenomena, of which, the interaction with a thin, dense shell of gas is but one. Below we present results from self-gravitating, 3-D smoothed particle hydrodynamics ({\small SPH}) simulations of the problem; seven realisations of the problem have been performed by varying the precollision density within the cloud, the nature of the post-collision shock, and the spatial resolution in the computational domain. Irrespective of the type of shock, a complex network of dense filaments, seeded by numerical noise, readily appears in the shocked cloud. Segregation of the dense and rarefied gas phases also manifests itself in a bimodal distribution of gas density. We demonstrate that the power-spectrum for rarefied gas is Kolomogorov like, while that for the denser gas is considerably steeper. As a corollary to the main problem, we also look into the possibly degenerative effect of the {\small SPH} artificial viscosity on the impact of the incident shell. It is observed that stronger viscosity leads to greater post-shock dissipation, that strongly decelerates the incident shock-front and promotes formation of contiguous structure, albeit on a much longer timescale. We conclude that too much viscosity is likely to enhance the proclivity towards gravitational boundedness of structure, leading to unphysical fragmentation.On the other hand, insufficient resolution appears to suppress fragmentation. Convergence of results is tested at both extremes, first by repeating the test case with more than a million particles and then with only half the number of particles in the original test case.Comment: 15 pages, 15 figures, and 1 Table; To appear in Monthly Notices to the RA

Heterogeneity of magnitude, allergen immunodominance, and cytokine polarization of cockroach allergen-specific T cell responses in allergic sensitized children.

Background: Characterization of allergic responses to cockroach (CR), a common aeroallergen associated with asthma, has focused mainly on IgE reactivity, but little is known about T cell responses, particularly in children. We conducted a functional evaluation of CR allergen-specific T cell reactivity in a cohort of CR allergic children with asthma. Methods: Peripheral blood mononuclear cells (PBMCs) were obtained from 71 children, with mild-to-moderate asthma who were enrolled in a CR immunotherapy (IT) clinical trial, prior to treatment initiation. PBMC were stimulated with peptide pools derived from 11 CR allergens, and CD4+ T cell responses assessed by intracellular cytokine staining. Results: Highly heterogeneous responses in T cell reactivity were observed among participants, both in terms of the magnitude of cytokine response and allergen immunodominance. Reactivity against Bla g 9 and Bla g 5 was most frequent. The phenotype of the T cell response was dominated by IL-4 production and a Th2 polarized profile in 54.9% of participants, but IFNγ production and Th1 polarization was observed in 25.3% of the participants. The numbers of regulatory CD4+ T cells were also highly variable and the magnitude of effector responses and Th2 polarization were positively correlated with serum IgE levels specific to a clinical CR extract. Conclusions: Our results demonstrate that in children with mild-to-moderate asthma, CR-specific T cell responses display a wide range of magnitude, allergen dominance, and polarization. These results will enable examination of whether any of the variables measured are affected by IT and/or are predictive of clinical outcomes

Inducible expression quantitative trait locus analysis of the MUC5AC gene in asthma in urban populations of children

BACKGROUND: Mucus plugging can worsen asthma control, lead to reduced lung function and fatal exacerbations. MUC5AC is the secretory mucin implicated in mucus plugging, and MUC5AC gene expression has been associated with development of airway obstruction and asthma exacerbations in urban children with asthma. However, the genetic determinants of MUC5AC expression are not established. OBJECTIVE: To assess single-nucleotide polymorphisms (SNPs) that influence MUC5AC expression and relate to pulmonary functions in childhood asthma. METHODS: We used RNA-sequencing data from upper airway samples and performed cis-expression quantitative trait loci (eQTL) and allele specific expression (ASE) analyses in two cohorts of predominantly Black and Hispanic urban children, a high asthma-risk birth cohort and an exacerbation-prone asthma cohort. We further investigated inducible MUC5AC eQTLs during incipient asthma exacerbations. We tested significant eQTLs SNPs for associations with lung function measurements and investigated their functional consequences in DNA regulatory databases. RESULTS: We identified two independent groups of SNPs in the MUC5AC gene that were significantly associated with MUC5AC expression. Moreover, these SNPs showed stronger eQTL associations with MUC5AC expression during asthma exacerbations, consistent with inducible expression. SNPs in one group also showed significant association with decreased pulmonary functions. These SNPs included multiple EGR1 transcription factor binding sites suggesting a mechanism of effect. CONCLUSIONS: These findings demonstrate the applicability of organ specific RNA-sequencing data to determine genetic factors contributing to a key disease pathway. Specifically, they suggest important genetic variations that may underlie propensity to mucus plugging in asthma and could be important in targeted asthma phenotyping and disease management strategies

Genome-wide association study identifies peanut allergy-specific loci and evidence of epigenetic mediation in US children

Food allergy (FA) affects 2%-10% of US children and is a growing clinical and public health problem. Here we conduct the first genome-wide association study of well-defined FA, including specific subtypes (peanut, milk and egg) in 2,759 US participants (1,315 children and 1,444 parents) from the Chicago Food Allergy Study, and identify peanut allergy (PA)-specific loci in the HLA-DR and -DQ gene region at 6p21.32, tagged by rs7192 (P=5.5 × 10 -8) and rs9275596 (P=6.8 × 10 -10), in 2,197 participants of European ancestry. We replicate these associations in an independent sample of European ancestry. These associations are further supported by meta-analyses across the discovery and replication samples. Both single-nucleotide polymorphisms (SNPs) are associated with differential DNA methylation levels at multiple CpG sites (

Izloženost alergenima plijesni u unutarnjem okolišu

Humid indoor environments may be colonised by allergenic fi lamentous microfungi (moulds), Aspergillus spp., Penicillium spp., Cladosporium spp., and Alternaria spp. in particular. Mould-induced respiratory diseases are a worldwide problem. In the last two decades, mould allergens and glucans have been used as markers of indoor exposure to moulds. Recently, mould allergens Alt a 1 (Alternaria alternata) and Asp f 1 (Aspergillus fumigatus) have been analysed in various environments (residential and occupational) with enzyme-linked immunosorbent assays, which use monoclonal or polyclonal antibodies. Household Alt a 1 and Asp f 1 levels were usually under the limit of the method detection. By contrast, higher levels of mould allergens were found in environments with high levels of bioaerosols such as poultry farms and sawmills. Data on allergen Alt a 1 and Asp f 1 levels in agricultural settings may provide information on possible colonisation of respective moulds and point out to mould-related diseases in occupants.Vlažni, unutarnji prostori mogu biti kolonizirani alergogenim, filamentoznim mikrogljivicama (plijesni) uglavnom rodova Aspergillus, Penicillium, Cladosporium i Alternaria. Respiratorne bolesti uzrokovane plijesnima zdravstveni su problem diljem svijeta. U posljednja dva desetljeća, neki sastavni dijelovi plijesni kao alergeni i glukan rabe se kao pokazatelji izloženosti plijesni u unutarnjem okolišu. Nedavno su alergeni plijesni Alt a 1 (Alternaria alternata) i Asp f 1 (Aspergillus fumigatus) određivani u različitom okolišu (kućnom i profesionalnom) enzim-imunokemijskom metodom koja rabi monoklonska ili poliklonska antitijela. Razina Alt a 1 i Asp f 1 u kućnoj prašini ispod je granice detekcije. Nasuprot tomu, alergeni plijesni su određeni u okolišu s visokom razinom bioaerosola kao peradarnici i pilane. Razine alergena Alt a 1 i Asp f 1 u nekim poljoprivrednim objektima pružaju informaciju o mogućoj kolonizaciji plijesnima, što upućuje na moguće zdravstvene učinke kod zaposlenika

Star formation via interaction of shocks with molecular clouds

One mechanism whereby regions of molecular clouds can become locally unstable to collapse and form stars is shock compression. Here the authors investigate the compression arising from a shock (from a supernova remnant for example) overrunning a molecular cloud and determine under what conditions it becomes locally unstable to gravitational collapse. Preliminary results from 3-D hydrodynamic simulations (using Smoothed Particle Hydrodynamics and Tree Code Gravity) are presented