Finite Element Model of Stress Wave Topology in Unidirectional Graphite/Epoxy: Wave Velocities and Flux Deviations

Until recently, the use of a finite element model (FEM) to simulate stress wave propagation has been limited to solutions where the number of degrees of freedom are kept to a minimum, because of hardware limitations on computer memory and computational speed. With the advent of a numte

Afferent arteriolopathy and glomerular collapse but not segmental sclerosis induce tubular atrophy in old spontaneously hypertensive rats

In chronic renal disease, the temporal and spatial relationship between vascular, glomerular and tubular changes is still unclear. Hypertension, an important cause of chronic renal failure, leads to afferent arteriolopathy, segmental glomerulosclerosis and tubular atrophy in the juxtamedullary cortex. We investigated the pathological changes of hypertensive renal disease in aged spontaneously hypertensive rats using a large number of serial sections, where we traced and analyzed afferent arteriole, glomerulus and proximal tubule of single nephrons. Our major finding was that both afferent arteriolopathy and glomerular capillary collapse were linked to tubular atrophy. Only nephrons with glomerular collapse (n = 13) showed tubules with reduced diameter indicating atrophy [21.66 ± 2.56 μm vs. tubules in normotensive Wistar Kyoto rats (WKY) 38.56 ± 0.56 μm, p < 0.05], as well as afferent arteriolar wall hypertrophy (diameter 32.74 ± 4.72 μm vs. afferent arterioles in WKY 19.24 ± 0.98 μm, p < 0.05). Nephrons with segmental sclerosis (n = 10) did not show tubular atrophy and tubular diameters were unchanged (35.60 ± 1.43 μm). Afferent arteriolar diameter negatively correlated with glomerular capillary volume fraction (r = −0.36) and proximal tubular diameter (r = −0.46) implying reduced glomerular and tubular flow. In line with this, chronically damaged tubules showed reduced staining for the ciliary protein inversin indicating changed ciliary signalling due to reduced urinary flow. This is the first morphological study on hypertensive renal disease making correlations between vascular, glomerular and tubular components of individual nephron units. Our data suggest that afferent arteriolopathy leads to glomerular collapse and reduced urinary flow with subsequent tubular atrophy

AcDc - A new code for the NLTE spectral analysis of accretion discs: application to the helium CV AM CVn

We present a recently developed code for detailed NLTE calculations of accretion disc spectra of cataclysmic variables and compact X-ray binaries. Assuming a radial structure of a standard alpha-disc, the disc is divided into concentric rings. For each disc ring the solution of the radiation transfer equation and the structure equations, comprising the hydrostatic and radiative equilibrium, the population of the atomic levels as well as charge and particle conservation, is done self-consistently. Metal-line blanketing and irradiation by the central object are taken into account. As a first application, we show the influence of different disc parameters on the disc spectrum for the helium cataclysmic variable AM CVn.Comment: 7 pages, 11 figures to be published in A&

Putting theory oriented evaluation into practice

Evaluations of gaming simulations and business games as teaching devices are typically end-state driven. This emphasis fails to detect how the simulation being evaluated does or does not bring about its desired consequences. This paper advances the use of a logic model approach which possesses a holistic perspective that aims at including all elements associated with the situation created by a game. The use of the logic model approach is illustrated as applied to Simgame, a board game created for secondary school level business education in six European Union countries

L∞L_\infty-Algebras, the BV Formalism, and Classical Fields

We summarise some of our recent works on $L_\infty$-algebras and quasi-groups with regard to higher principal bundles and their applications in twistor theory and gauge theory. In particular, after a lightning review of $L_\infty$-algebras, we discuss their Maurer-Cartan theory and explain that any classical field theory admitting an action can be reformulated in this context with the help of the Batalin-Vilkovisky formalism. As examples, we explore higher Chern-Simons theory and Yang-Mills theory. We also explain how these ideas can be combined with those of twistor theory to formulate maximally superconformal gauge theories in four and six dimensions by means of $L_\infty$-quasi-isomorphisms, and we propose a twistor space action.Comment: 19 pages, Contribution to Proceedings of LMS/EPSRC Durham Symposium Higher Structures in M-Theory, August 201

Renal pericytes: regulators of medullary blood flow

Regulation of medullary blood flow (MBF) is essential in maintaining normal kidney function. Blood flow to the medulla is supplied by the descending vasa recta (DVR), which arise from the efferent arterioles of juxtamedullary glomeruli. DVR are composed of a continuous endothelium, intercalated with smooth muscle-like cells called pericytes. Pericytes have been shown to alter the diameter of isolated and in situ DVR in response to vasoactive stimuli that are transmitted via a network of autocrine and paracrine signalling pathways. Vasoactive stimuli can be released by neighbouring tubular epithelial, endothelial, red blood cells and neuronal cells in response to changes in NaCl transport and oxygen tension. The experimentally described sensitivity of pericytes to these stimuli strongly suggests their leading role in the phenomenon of MBF autoregulation. Because the debate on autoregulation of MBF fervently continues, we discuss the evidence favouring a physiological role for pericytes in the regulation of MBF and describe their potential role in tubulo-vascular cross-talk in this region of the kidney. Our review also considers current methods used to explore pericyte activity and function in the renal medulla

Sequence organization and molecular cloning of mouse mammary tumor virus DNA endogenous to C57BL/6 mice.

The sequence organization of mouse mammary tumor virus DNA endogenous to the C57BL/6 inbred mouse strain was characterized by Southern blot analysis, utilizing probes specific for particular regions of the mouse mammary tumor virus provirus and by molecular cloning of endogenous mouse mammary tumor virus DNA. The genome of C57BL/6 mice contains three apparently intact, endogenous proviral units; two of these units comprise the Mtv-8 (unit II) and Mtv-9 (unit III) genetic loci that are also present in the DNA of BALB/c mice. The third unit is defined by EcoRI restriction fragments of 10.0 and 8.4 kilobases that contain the 5' and 3' portions of the provirus, respectively. This unit, termed unit XI and encoded by the genetic locus Mtv-17, has not been previously recognized in C57BL/6 DNA, but it can be clearly distinguished from the proviral units at Mtv-8 and Mtv-9 by Southern blot analysis under appropriate conditions. The proviral unit at Mtv-17 is not present in BALB/c DNA. DNAs comprising the entire Mtv-8 locus and the 3' portions of Mtv-9 and Mtv-17 were cloned. Analysis of the cloned DNA revealed no obvious deletions or rearrangements that would render proviral DNA defective; however, these endogenous genes are normally not transcriptionally active

Long-term evolution of antigen repertoires among carried meningococci

Most studies of bacterial pathogen populations have been based on isolates collected from individuals with disease, or their contacts, over short time periods. For commensal organisms that occasionally cause disease, such as Neisseria meningitidis, however, the analysis of isolates from long-term asymptomatic carriage is necessary to elucidate their evolution and population structure. Here, we use mathematical models to analyse the structuring and dynamics of three vaccine-candidate antigens among carried meningococcal isolates collected over nearly 30 years in the Czech Republic. The data indicate that stable combinations of antigenic alleles were maintained over this time period despite evidence for high rates of recombination, consistent with theoretical models in which strong immune selection can maintain non-overlapping combinations of antigenic determinants in the presence of recombination. We contrast this antigenic structure with the overlapping but relatively stable combinations of the housekeeping genes observed among the same isolates, and use a novel network approach to visualize these relationships

Regulation of expression of the rat orthologue of mouse double minute 2 (MDM2) by H2O2-induced oxidative stress in neonatal rat cardiac myocytes.

The Mdm2 ubiquitin ligase is an important regulator of p53 abundance and p53-dependent apoptosis. Mdm2 expression is frequently regulated by a p53 Mdm2 autoregulatory loop whereby p53 stimulates Mdm2 expression and hence its own degradation. Although extensively studied in cell lines, relatively little is known about Mdm2 expression in heart where oxidative stress (exacerbated during ischemia-reperfusion) is an important pro-apoptotic stimulus. We demonstrate that Mdm2 transcript and protein expression are induced by oxidative stress (0.2 mm H(2)O(2)) in neonatal rat cardiac myocytes. In other cells, constitutive Mdm2 expression is regulated by the P1 promoter (5' to exon 1), with inducible expression regulated by the P2 promoter (in intron 1). In myocytes, H(2)O(2) increased Mdm2 expression from the P2 promoter, which contains two p53-response elements (REs), one AP-1 RE, and two Ets REs. H(2)O(2) did not detectably increase expression of p53 mRNA or protein but did increase expression of several AP-1 transcription factors. H(2)O(2) increased binding of AP-1 proteins (c-Jun, JunB, JunD, c-Fos, FosB, and Fra-1) to an Mdm2 AP-1 oligodeoxynucleotide probe, and chromatin immunoprecipitation assays showed it increased binding of c-Jun or JunB to the P2 AP-1 RE. Finally, antisense oligonucleotide-mediated reduction of H(2)O(2)-induced Mdm2 expression increased caspase 3 activation. Thus, increased Mdm2 expression is associated with transactivation at the P2 AP-1 RE (rather than the p53 or Ets REs), and Mdm2 induction potentially represents a cardioprotective response to oxidative stress