228 research outputs found
A proposed approach to the application of nonlinear irreversible thermodynamics to fracture in composite materials
The fracture criteria upon which most fracture mechanics is based involves an energy balance that is not appropriate for the fracture mechanics of viscoelastic materials such as polymer matrix composites. A more appropriate criterion based upon nonequilibrium thermodynamics and involving a power balance rather than an energy balance is proposed. This crierion is based upon a reformulation of the second law of thermodynamics which focuses attention on the total Legendre transform of energy expressed as a functional over time and space. This excess energy functional can be shown to be equivalent to the Rice J integral if the only irreversible process is the propogation of a single crack completely through the thickness of the specimen and if the crack propogation is assured to be independent of time. For the more general case of more than one crack in a viscoelastic medium integration over both time and space is required. Two experimentally measurable parameters are proposed which should permit the evaluation of this more general fracture criterion
Laser measuring system accurately locates point coordinates on photograph
Laser activated ultraprecision ranging apparatus interfaced with a computer determines point coordinates on a photograph. A helium-neon gas CW laser provides collimated light for a null balancing optical system. This system has no mechanical connection between the ranging apparatus and the photograph
Effects of depressive symptoms and peripheral DAT methylation on neural reactivity to alcohol cues in alcoholism
In alcohol-dependent (AD) patients, alcohol cues induce strong activations in
brain areas associated with alcohol craving and relapse, such as the nucleus
accumbens (NAc) and amygdala. However, little is known about the influence of
depressive symptoms, which are common in AD patients, on the brain’s
reactivity to alcohol cues. The methylation state of the dopamine transporter
gene (DAT) has been associated with alcohol dependence, craving and
depression, but its influence on neural alcohol cue reactivity has not been
tested. Here, we compared brain reactivity to alcohol cues in 38 AD patients
and 17 healthy controls (HCs) using functional magnetic resonance imaging and
assessed the influence of depressive symptoms and peripheral DAT methylation
in these responses. We show that alcoholics with low Beck’s Depression
Inventory scores (n=29) had higher cue-induced reactivity in NAc and amygdala
than those with mild/moderate depression scores (n=9), though subjective
perception of craving was higher in those with mild/moderate depression
scores. We corroborated a higher DAT methylation in AD patients than HCs, and
showed higher DAT methylation in AD patients with mild/moderate than low
depression scores. Within the AD cohort, higher methylation predicted craving
and, at trend level (P=0.095), relapse 1 year after abstinence. Finally, we
show that amygdala cue reactivity correlated with craving and DAT methylation
only in AD patients with low depression scores. These findings suggest that
depressive symptoms and DAT methylation are associated with alcohol craving
and associated brain processes in alcohol dependence, which may have important
consequences for treatment. Moreover, peripheral DAT methylation may be a
clinically relevant biomarker in AD patients
Measurement of the CMS Magnetic Field
The measurement of the magnetic field in the tracking volume inside the
superconducting coil of the Compact Muon Solenoid (CMS) detector under
construction at CERN is done with a fieldmapper designed and produced at
Fermilab. The fieldmapper uses 10 3-D B-sensors (Hall probes) developed at
NIKHEF and calibrated at CERN to precision 0.05% for a nominal 4 T field. The
precise fieldmapper measurements are done in 33840 points inside a cylinder of
1.724 m radius and 7 m long at central fields of 2, 3, 3.5, 3.8, and 4 T. Three
components of the magnetic flux density at the CMS coil maximum excitation and
the remanent fields on the steel-air interface after discharge of the coil are
measured in check-points with 95 3-D B-sensors located near the magnetic flux
return yoke elements. Voltages induced in 22 flux-loops made of 405-turn
installed on selected segments of the yoke are sampled online during the entire
fast discharge (190 s time-constant) of the CMS coil and integrated offline to
provide a measurement of the initial magnetic flux density in steel at the
maximum field to an accuracy of a few percent. The results of the measurements
made at 4 T are reported and compared with a three-dimensional model of the CMS
magnet system calculated with TOSCA.Comment: 4 pages, 5 figures, 15 reference
Pioglitazone Prevents Capillary Rarefaction in Streptozotocin-Diabetic Rats Independently of Glucose Control and Vascular Endothelial Growth Factor Expression
Background/Aims: Reduction of capillary network density occurs early in the development of metabolic syndrome and may be relevant for the precipitation of diabetes. Agonists of the peroxisome proliferator-activated receptor (PPAR)-gamma transcription factor are vasculoprotective, but their capacity for structural preservation of the microcirculation is unclear. Methods: Male Wistar rats were rendered diabetic by streptozotocin and treated with pioglitazone in chow for up to 12 weeks. Capillary density was determined in heart and skeletal muscle after platelet endothelial cell adhesion molecule-1 (PECAM-1) immunostaining. Hallmarks of apoptosis and angiogenesis were determined. Results: Capillary density deteriorated progressively in the presence of hyperglycemia (from 971/mm(2) to 475/mm(2) in quadriceps muscle during 13 weeks). Pioglitazone did not influence plasma glucose, left ventricular weight, or body weight but nearly doubled absolute and relative capillary densities compared to untreated controls (1.2 vs. 0.6 capillaries/myocyte in heart and 1.5 vs. 0.9 capillaries/myocyte in quadriceps muscle) after 13 weeks of diabetes. No antiapoptotic or angiogenic influence of pioglitazone was detected while a reduced expression of hypoxia-inducible factor-3 alpha and PPAR coactivator-1 alpha (PGC-1 alpha) mRNA as well as vascular endothelial growth factor (VEGF) protein possibly occurred as a consequence of improved vascularization. Conclusion: Pioglitazone preserves microvascular structure in diabetes independently of improvements in glycemic control and by a mechanism unrelated to VEGF-mediated angiogenesis. Copyright (C) 2012 S. Karger AG, Base
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A qualitative study of the experiences of people who identify themselves as having adjusted positively to a visible difference
Individual and group interviews explored experiences of positive adjustment among 12 people with a range of visible differences. Thematic analysis identified four main themes: importance of appearance; personal growth; relationships with others; and coping (factors in the coping theme considered to be paramount to positive adjustment were inner strength and positivity, active coping techniques, downward social comparisons, taking things day-by-day, spirituality and humour). The findings provide insight into behaviours and personal outlooks that may contribute to adaptive coping and have implications for future research and interventions aimed at those who exhibit poor adjustment to visible difference. The article reflects on the use of both individual and group interviews for research in this field
Transcript-Specific Expression Profiles Derived from Sequence-Based Analysis of Standard Microarrays
Background: Alternative mRNA processing mechanisms lead to multiple transcripts (i.e. splice isoforms) of a given gene
which may have distinct biological functions. Microarrays like Affymetrix GeneChips measure mRNA expression of genes
using sets of nucleotide probes. Until recently probe sets were not designed for transcript specificity. Nevertheless, the reanalysis of established microarray data using newly defined transcript-specific probe sets may provide information about expression levels of specific transcripts.
Methodology/Principal Findings: In the present study alignment of probe sequences of the Affymetrix microarray HGU133A with Ensembl transcript sequences was performed to define transcript-specific probe sets. Out of a total of 247,965 perfect match probes, 95,008 were designated ‘‘transcript-specific’’, i.e. showing complete sequence alignment, no crosshybridization, and transcript-, not only gene-specificity. These probes were grouped into 7,941 transcript-specific probe sets and 15,619 gene-specific probe sets, respectively. The former were used to differentiate 445 alternative transcripts of 215
genes. For selected transcripts, predicted by this analysis to be differentially expressed in the human kidney, confirmatory real-time RT-PCR experiments were performed. First, the expression of two specific transcripts of the genes PPM1A (PP2CA_HUMAN and P35813) and PLG (PLMN_HUMAN and Q5TEH5) in human kidneys was determined by the transcriptspecific array analysis and confirmed by real-time RT-PCR. Secondly, disease-specific differential expression of single transcripts of PLG and ABCA1 (ABCA1_HUMAN and Q5VYS0_HUMAN) was computed from the available array data sets and confirmed by transcript-specific real-time RT-PCR.
Conclusions: Transcript-specific analysis of microarray experiments can be employed to study gene-regulation on the
transcript level using conventional microarray data. In this study, predictions based on sufficient probe set size and foldchange are confirmed by independent mean
Connective tissue growth factor(CCN2), a pathogenic factor in diabetic nephropathy. What does it do? How does it do it?
Connective tissue growth factor (CTGF/CCN2) is a member of the CCN family of matricellular proteins. Its expression is induced by a number of factors including TGF-β. It has been associated with fibrosis in various tissues including the kidney. Diabetic nephropathy (DN) develops in about 30% of patients with diabetes and is characterized by thickening of renal basement membranes, fibrosis in the glomerulus (glomerulosclerosis), tubular atrophy and interstitial fibrosis, all of which compromise kidney function. This review examines changes in CTGF expression in the kidney in DN, the effects they have on glomerular mesangial and podocyte cells and the tubulointerstitium, and how these contribute to driving fibrotic changes in the disease. CTGF can bind to several other growth factors modifying their function. CTGF is also able to interact with receptors on cells, including integrins, tyrosine receptor kinase A (TrkA), low density lipoprotein receptor-related protein (LRP) and heparan sulphate proteoglycans. These interactions, the intracellular signalling pathways they activate, and the cellular responses evoked are reviewed. CTGF also induces the expression of chemokines which themselves have pharmacological actions on cells. CTGF may prompt some responses by acting through several different mechanisms, possibly simultaneously. For example, CTGF is often described as an effector of TGF-β. It can promote TGF-β signalling by binding directly to the growth factor, promoting its interaction with the TGF-β receptor; by triggering intracellular signalling on binding the TrkA receptor, which leads to the transcriptional repression of Smad7, an inhibitor of the TGF-β signalling pathway; and by binding to BMP-7 whose own signalling pathway opposing TGF-β is inhibited, leading to enhanced TGF-β signalling
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