571 research outputs found
Photoluminescence quantum efficiency of dense silicon nanocrystal ensembles in SiO2
The photoluminescence decay characteristics of silicon nanocrystals in dense ensembles fabricated by ion implantation into silicon dioxide are observed to vary in proportion to the calculated local density of optical states. A comparison of the experimental 1/e photoluminescence decay rates to the expected spontaneous emission rate modification yields values for the internal quantum efficiency and the intrinsic radiative decay rate of silicon nanocrystals. A photoluminescence quantum efficiency as high as 59%±9% is found for nanocrystals emitting at 750 nm at low excitation power. A power dependent nonradiative decay mechanism reduces the quantum efficiency at high pump intensity
Development of a National Core Dataset for Preoperative Assessment
Objective:To define a core dataset for preoperative assessment to leverage uniform data
collection in this domain. This uniformity is a
prerequisite for data exchange between care
providers and semantic interoperability between health record systems.
Methods: To design this core dataset a combination of literature review and expert consensus meetings were used. In the first meeting a working definition for “core dataset” was
specified. Subgroups were formed to address
major headings of the core dataset. In the following eight meetings data items for each
subheading were discussed. The items in the
resulting draft of the dataset were compared
to those retrieved from an earlier literature review study. In the last two expert meetings modifications of the dataset were performed
based on the result of this literature study.
Results: Based on expert consensus a draft
dataset including 82 data items was designed. Seventy-six percent of data items in
the draft dataset were covered by the literature study. Nine data items were modified in
the draft and 14 data items were added to the
dataset based on input from the literature review. The final dataset of 93 data items covers
patient history, physical examination, supplementary examination and consultation, and
final judgment.
Conclusions: This preoperative-assessment
dataset was defined based on expert con -
sensus and literature review. Both methods
proved to be valuable and complementary.
This dataset opens the door for creating standardized approaches in data collection in the
preoperative assessment field which will
facilitate interoperability between different
electronic health records and different users
Endocytosis in filamentous fungi
Endocytosis is little understood in filamentous fungi. For some time it has been
controversial as to whether endocytosis occurs in filamentous fungi. A comparative
genomics analysis between Saccharomyces cerevisiae and 10 genomes of filamentous
fungal species showed that filamentous fungi possess complex endocytic machineries.
The use of the endocytic marker dye FM4-64, and various vesicle trafficking
inhibitors revealed many similarities between endocytosis in the filamentous fungus
Neurospora crassa, and endocytosis in budding yeast and mammalian cells. Actin
polymerization was found to be crucial for endocytosis in N. crassa, and the microtubule
cytoskeleton seemed to be necessary for long distance movement of putative early
endosomes. Brefeldin A (BFA) blocked vesicular transport to the Spitzenkörper.
Three putative endocytic proteins (WASP, clathrin light chain and Rab5) were
labelled with fluorescent proteins in N. crassa. WASP-GFP was found to localise to
motile, punctate structures in the plasma membrane just behind the hyphal apex in
growing hyphae. This localisation changed to the hyphal apex when growth was
temporarily arrested, indicating a possible role in endocytosis and polarized growth.
Clathrin light chain-GFP was found to be concentrated in a region just behind the
Spitzenkörper, which is consistent with there being a high concentration of clathrinmediated
endocytosis in this region. Clathrin light chain-GFP also labelled putative
Golgi and this labelling was found to be BFA sensitive, whereas BFA did not have a
detectable effect on FM4-64 internalisation and organelle staining. GFP-Rab5 labelled
putative early endosomes and decorated microtubules.
Knock-outs of putative endocytic proteins in N. crassa, generated as part of the
Neurospora genome consortium gene knock-out project, were analysed for defects in
endocytosis. 14 out of 17 gene knock-outs were found to be ascospore lethal. The Rab5
knock-out was viable, but did not show a detectable effect on the endocytic
internalisation of FM4-64 or its pattern of staining. However, it did exhibit a defect in
sexual crossing
Evaluation of multi-exponential curve fitting analysis of oxygen-quenched phosphorescence decay traces for recovering microvascular oxygen tension histograms
Insulating fcc YH3-ô stabilized by MgH2
We study the structural, optical, and electrical properties of MgzY1-z switchable mirrors upon hydrogenation. It is found that the alloys disproportionate into essentially pure YH3-δ and MgH2 with the crystal structure of YH3-δ dependent on the Mg concentration z. For 0~0.1 only cubic YH3-δ is present. Interestingly, cubic YH3-δ is expanded compared to YH2, in disagreement with theoretical predictions. From optical and electrical measurements we conclude that cubic YH3-δ is a transparent insulator with properties similar to hexagonal YH3-δ. Our results are inconsistent with calculations predicting fcc YH3-δ to be metallic, but they are in good agreement with recent GW calculations on both hcp and fcc YH3. Finally, we find an increase in the effective band gap of the hydrided MgzY1-z alloys with increasing z. Possibly this is due to quantum confinement effects in the small YH3 clusters
Identification of novel small molecule inhibitors of adenovirus gene transfer using a high throughput screening approach
Due to many favourable attributes adenoviruses (Ads) are the most extensively used vectors for clinical gene therapy applications. However, following intravascular administration, the safety and efficacy of Ad vectors are hampered by the strong hepatic tropism and induction of a potent immune response. Such effects are determined by a range of complex interactions including those with neutralising antibodies, blood cells and factors, as well as binding to native cellular receptors (coxsackie adenovirus receptor (CAR), integrins). Once in the bloodstream, coagulation factor X (FX) has a pivotal role in determining Ad liver transduction and viral immune recognition. Due to difficulties in generating a vector devoid of multiple receptor binding motifs, we hypothesised that a small molecule inhibitor would be of value. Here, a pharmacological approach was implemented to block adenovirus transduction pathways. We developed a high throughput screening (HTS) platform to identify the small molecule inhibitors of FX-mediated Ad5 gene transfer. Using an in vitro fluorescence and cell-based HTS, we evaluated 10,240 small molecules. Following sequential rounds of screening, three compounds, T5424837, T5550585 and T5660138 were identified that ablated FX-mediated Ad5 transduction with low micromolar potency. The candidate molecules possessed common structural features and formed part of the one pharmacophore model. Focused, mini-libraries were generated with structurally related molecules and in vitro screening revealed novel hits with similar or improved efficacy. The compounds did not interfere with Ad5:FX engagement but acted at a subsequent step by blocking efficient intracellular transport of the virus. In vivo, T5660138 and its closely related analogue T5660136 significantly reduced Ad5 liver transgene expression at 48 h post-intravenous administration of a high viral dose (1 × 10<sup>11</sup> vp/mouse). Therefore, this study identifies novel and potent small molecule inhibitors of the Ad5 transduction which may have applications in the Ad gene therapy setting
BRST Cohomology of N=2 Super-Yang-Mills Theory in 4D
The BRST cohomology of the N=2 supersymmetric Yang-Mills theory in four
dimensions is discussed by making use of the twisted version of the N=2
algebra. By the introduction of a set of suitable constant ghosts associated to
the generators of N=2, the quantization of the model can be done by taking into
account both gauge invariance and supersymmetry. In particular, we show how the
twisted N=2 algebra can be used to obtain in a straightforward way the relevant
cohomology classes. Moreover, we shall be able to establish a very useful
relationship between the local gauge invariant polynomial and the
complete N=2 Yang-Mills action. This important relation can be considered as
the first step towards a fully algebraic proof of the one-loop exactness of the
N=2 beta function.Comment: 22 pages, LaTeX, final version to appear in Journ. Phys.
Chronic aspirin treatment affects collagen deposition in non-infarcted myocardium during remodeling after coronary artery ligation in the rat
Low-dose aspirin (acetylsalicylic acid; ASA), inhibiting platelet thromboxane production in favor of endothelium formation of prostaglandins, is successfully used as primary or secondary prophylaxis against myocardial infarction. Although prognosis may be improved, effects of long-term ASA treatment on wound healing and cardiac remodeling are not well understood. The aim of the present study was to mimic the clinical situation by inducing myocardial infarction in low-dose ASA (25 mg/kg/day, i.p.) pretreated rats, and to determine effects on plasma eicosanoid levels, cardiac hypertrophy and collagen deposition, and left ventricular function during continued ASA treatment. The effects of this dose were verified to selectively inhibit platelet thromboxane production, and lower plasma levels of thromboxane, but did not affect plasma levels of prostacyclin and prostaglandin E2during the acute inflammatory stage following myocardial infarction. As measured by heart dry weight/body weight, cardiac hypertrophy was not affected by ASA treatment. However, interstitial fibrosis in the spared myocardium as well as perivascular fibrosis, associated with infarction-induced cardiac remodeling, were affected by ASA treatment. Replacement fibrosis in the infarct itself, considered as representing wound healing, was not significantly influenced by ASA treatment. Wall thinning following infarction was not aggravated, nor did treatment influence left ventricular cavity diameter in a relaxed state. Results fromin vitroleft ventricular function measurements showed no effects on left ventricular peak velocity of contraction or relaxation after ASA treatment. In conclusion, although low-dose ASA may not be expected to have anti-inflammatory action, it did influence post-infarct cardiac remodeling by affecting interstitial and perivascular fibrosis. ASA treatment did not have effects onin vitroleft ventricular dysfunction
Determinants of coronary reserve in rats subjected to coronary artery ligation or aortic banding
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