990 resultados para Schurer-Stancu type operators
Resumo:
In many instances we find it advantageous to display a quantum optical density matrix as a generalized statistical ensemble of coherent wave fields. The weight functions involved in these constructions turn out to belong to a family of distributions, not always smooth functions. In this paper we investigate this question anew and show how it is related to the problem of expanding an arbitrary state in terms of an overcomplete subfamily of the overcomplete set of coherent states. This provides a relatively transparent derivation of the optical equivalence theorem. An interesting by-product is the discovery of a new class of discrete diagonal representations.
Resumo:
Abstract is not available.
Resumo:
Abstract is not available.
Resumo:
Escherichia coli sequence type 131 (ST131) have emerged as a pandemic lineage of important multidrug resistant pathogens worldwide. Despite many studies examining the epidemiology of ST131, only a few studies to date have investigated the capacity of ST131 strains to form biofilms. Some of these studies have reported contrasting findings, with no specific ST131 biofilm-promoting factors identified. Here we examined a diverse collection of ST131 isolates for in vitro biofilm formation in different media and assay conditions, including urine from healthy adult women. We found significant differences among strains and assay conditions, which offers an explanation for the contrasting findings reported by previous studies using a single condition. Importantly, we showed that expression of type 1 fimbriae is a critical determinant for biofilm formation by ST131 strains and that inhibition of the FimH adhesin significantly reduces biofilm formation. We also offer direct genetic evidence for the contribution of type 1 fimbriae in biofilm formation by the reference ST131 strain EC958, a representative of the clinically dominant H30-Rx ST131 subgroup. This is the first study of ST131 biofilm formation in biologically relevant conditions and paves the way for the application of FimH inhibitors in treating drug resistant ST131 biofilm infections.
Resumo:
Abstract is not available.
Resumo:
Magnetoplasmon-type surface polaritons are studied at the interfaces of sandwich structures in the configuration with a magnetic field oriented parallel to the interface but perpendicular to the direction of wave propagation. It is shown that the propagation window for the surface polaritons is shifted to higher frequencies in the presence of the magnetic field directed positively. On reversal of the magnetic field an additional low frequency propagation band appears. Irrespective of the direction and strength of the magnetic field there exists a certain frequency range in which interface polaritons cannot propagate. For sandwich structures for which the dielectric constant and the plasma frequency of one medium are simultaneously greater or less than those of the second medium gaps and multiple branches can appear in the propagation window either for n > 0 or n <; 0 waves. A graphical method for the estimation of critical ranges of B0 and dielectric constant ratios for different sandwich structures, within which gaps and multiple branches appear, is given
Resumo:
Abstract is not available.
Identification of a secretion signal for the type II protein secretion pathway in Erwinia carotovora
Resumo:
Type 1 diabetes (T1D) is considered to be an autoimmune disease. The cause of T1D is the destruction of insulin-producing β-cells in the pancreatic islets. The autoimmune nature of T1D is characterized by the presence of autoreactive T-cells and autoantibodies against β-cell molecules. Insulin is the only β-cell-specific autoantigen associated with T1D but the insulin autoantibodies (IAAs) are difficult to measure with proper sensitivity. T-cell assays for detection of autoreactive T-cells, such as insulin-specific T-cells, have also proven to be difficult to perform. The genetic risk of T1D is associated with the HLA gene region but the environmental factors also play an important role. The most studied environmental risk factors of T1D are enteroviruses and cow's milk which both affect the immune system through the gut. One hypothesis is that the insulin-specific immune response develops against bovine insulin in cow's milk during early infancy and later spreads to include human insulin. The aims of this study were to determine whether the separation of immunoglobulin (Ig)G from plasma would improve the sensitivity of the IAA assay and how insulin treatment affects the cellular immune response to insulin in newly diagnosed patients. Furthermore, the effect of insulin concentration in mother's breast milk on the development of antibodies to dietary insulin in the child was examined. Small intestinal biopsies were also obtained from children with T1D to characterize any immunological changes associated with T1D in the gut. The isolation of the IgG fraction from the plasma of T1D patients negative for plasma IAA led to detectable IAA levels that exceeded those in the control children. Thus the isolation of IgG may improve the sensitivity of the IAA assay. The effect of insulin treatment on insulin-specific T-cells was studied by culturing peripheral blood mononuclear cells with insulin. The insulin stimulation induced increased expression of regulatory T-cell markers, such as Foxp3, in those patients treated with insulin than in patients examined before initiating insulin treatment. This finding suggests that insulin treatment in patients with T1D stimulates regulatory T-cells in vivo and this may partly explain the difficulties in measuring autoantigen-specific T-cell responses in recently diagnosed patients. The stimulation of regulatory T-cells by insulin treatment may also explain the remission period often seen after initiating insulin treatment. In the third study we showed that insulin concentration in mother's breast milk correlates inversely with the levels of bovine insulin-specific antibodies in those infants who were exposed to cow's milk proteins in their diet, suggesting that human insulin in breast milk induces tolerance to dietary bovine insulin. However, in infants who later developed T1D-associated autoantibodies, the insulin concentration in their mother's breast milk was increased. This finding may indicate that in those children prone to β-cell autoimmunity, breast milk insulin does not promote tolerance to insulin. In the small intestinal biopsies the presence of several immunological markers were quantified with the RT-PCR. From these markers the expression of the interleukin (IL)-18 cytokine was significantly increased in the gut in patients with T1D compared with children with celiac disease or control children. The increased IL-18 expression lends further support for the hypothesis that the gut immune system is involved in the pathogenesis of T1D.
Resumo:
Accompanying the decrease in serum cholesterol and increase in concentration of ubiquinone in liver and its microsomes, the activity, but not the protein, of HMG-CoA reductase decreased in ubiquinone-supplemented rats. A soluble 58-kDa preparation of HMG-CoA reductase was partially inhibited on addition of ubiquinone indicating a possible feedback type of action.
Resumo:
The removal of non-coding sequences, introns, is an essential part of messenger RNA processing. In most metazoan organisms, the U12-type spliceosome processes a subset of introns containing highly conserved recognition sequences. U12-type introns constitute less than 0,5% of all introns and reside preferentially in genes related to information processing functions, as opposed to genes encoding for metabolic enzymes. It has previously been shown that the excision of U12-type introns is inefficient compared to that of U2-type introns, supporting the model that these introns could provide a rate-limiting control for gene expression. The low efficiency of U12-type splicing is believed to have important consequences to gene expression by limiting the production of mature mRNAs from genes containing U12-type introns. The inefficiency of U12-type splicing has been attributed to the low abundance of the components of the U12-type spliceosome in cells, but this hypothesis has not been proven. The aim of the first part of this work was to study the effect of the abundance of the spliceosomal snRNA components on splicing. Cells with a low abundance of the U12-type spliceosome were found to inefficiently process U12-type introns encoded by a transfected construct, but the expression levels of endogenous genes were not found to be affected by the abundance of the U12-type spliceosome. However, significant levels of endogenous unspliced U12-type intron-containing pre-mRNAs were detected in cells. Together these results support the idea that U12-type splicing may limit gene expression in some situations. The inefficiency of U12-type splicing has also promoted the idea that the U12-type spliceosome may control gene expression, limiting the mRNA levels of some U12-type intron-containing genes. While the identities of the primary target genes that contain U12-type introns are relatively well known, little has previously been known about the downstream genes and pathways potentially affected by the efficiency of U12-type intron processing. Here, the effects of U12-type splicing efficiency on a whole organism were studied in a Drosophila line with a mutation in an essential U12-type spliceosome component. Genes containing U12-type introns showed variable gene-specific responses to the splicing defect, which points to variation in the susceptibility of different genes to changes in splicing efficiency. Surprisingly, microarray screening revealed that metabolic genes were enriched among downstream effects, and that the phenotype could largely be attributed to one U12-type intron-containing mitochondrial gene. Gene expression control by the U12-type spliceosome could thus have widespread effects on metabolic functions in the organism. The subcellular localization of the U12-type spliceosome components was studied as a response to a recent dispute on the localization of the U12-type spliceosome. All components studied were found to be nuclear indicating that the processing of U12-type introns occurs within the nucleus, thus clarifying a question central to the field. The results suggest that the U12-type spliceosome can limit the expression of genes that contain U12-type introns in a gene-specific manner. Through its limiting role in pre-mRNA processing, the U12-type splicing activity can affect specific genetic pathways, which in the case of Drosophila are involved in metabolic functions.