22,727 research outputs found
Monotonicity and stability of periodic polling models
Polling Systems;Stability;operations research
Bubble statistics and positioning in superhelically stressed DNA
We present a general framework to study the thermodynamic denaturation of
double-stranded DNA under superhelical stress. We report calculations of
position- and size-dependent opening probabilities for bubbles along the
sequence. Our results are obtained from transfer-matrix solutions of the
Zimm-Bragg model for unconstrained DNA and of a self-consistent linearization
of the Benham model for superhelical DNA. The numerical efficiency of our
method allows for the analysis of entire genomes and of random sequences of
corresponding length ( base pairs). We show that, at physiological
conditions, opening in superhelical DNA is strongly cooperative with average
bubble sizes of base pairs (bp), and orders of magnitude higher
than in unconstrained DNA. In heterogeneous sequences, the average degree of
base-pair opening is self-averaging, while bubble localization and statistics
are dominated by sequence disorder. Compared to random sequences with identical
GC-content, genomic DNA has a significantly increased probability to open large
bubbles under superhelical stress. These bubbles are frequently located
directly upstream of transcription start sites.Comment: to be appeared in Physical Review
Trust, Reciprocity, and Guanxi in China: An Experimental Investigation
We examine the influence of social distance on levels of trust and reciprocity in China. Social distance, reflected in the indigenous concept of guanxi, is of central importance to Chinese culture. In Study 1, some participants participated in two financially salient trust games to measure behavior, one with an anonymous classmate and the other with an anonymous, demographically identical nonclassmate. Other participants, drawn from the same population, completed hypothetical surveys to gauge both hypothetical behavior and expectations of others. Social distance effects on actual and hypothetical behavior were statistically consistent. The results together corroborated the hypothesized negative relationship between trust and social distance. However, reciprocity was not responsive to social distance. Study 2 found that affect-based trust, but not cognition-based trust, played a mediating role in the relationship between social distance and interpersonal trust in a hypothetical scenario. We conclude that close guanxi ties in China engender affect-based trust, which is extended to shouren classmates. This is true despite the fact that no more cognition-based trust is placed nor reciprocity received or expected from classmates compared to demographically identical shengren nonclassmates.Experiment; Affect-based Trust; China; Guanxi; Reciprocity; Trust; Social Distance
Resistance status of the carmine spider mite, Tetranychus cinnabarinus and the twospotted spider mite, Tetranychus urticae to selected acaricides on strawberries.
The carmine spider mite, Tetranychus cinnabarinus (Boisduval) and the twospotted spider mite, Tetranychus urticae Koch, are serious pests of strawberries and many other horticultural crops. Control of these pests has been heavily dependent upon chemical acaricides. Objectives of this study were to determine the resistance status of these two pest species to commonly used acaricides on strawberries in a year-round intensive horticultural production region. LC90 of abamectin for adult carmine spider mites was 4% whereas that for adult twospotted spider mites was 24% of the top label rate. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 0.5%, 0.5%, 1.4% and 83% of their respective highest label rates for carmine spider mite eggs, 0.7%, 2.7%, 12.1% and 347% of their respective highest label rates for the nymphs. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respective highest label rates for twospotted spider mite eggs, 3%, 13%, 432,214% and 15% of their respective highest label rates for the nymphs. Our results suggest that T. cinnabarinus have developed resistance to bifenazate and that the T. urticae have developed resistance to hexythiazox. These results strongly emphasize the need to develop resistance management strategies in the region
Synergistic actions between angiotensin-converting enzyme inhibitors and statins in atherosclerosis
Aims: Hypertension and hypercholesterolemia are independent risk factors for atherosclerotic cardiovascular disease (ASCVD) by acting directly on the endothelium and activating the renin-angiotensin aldosterone system (RAAS) and mevalonate pathways. This review examines how the severity and duration of these risk factors may influence the cardiovascular risk through a reciprocal interplay leading to oxidative stress and pro-inflammatory response.
Data synthesis: The review highlights the clinical evidence supporting the benefits of statins and angiotensin-converting enzyme (ACE) inhibitors for hypertension, lipid disorders and ASCVD management, both individually and combined, at all stages of the cardiovascular continuum.
Conclusion: Drug strategies incorporating an ACE-inhibitor and a statin, and in particular perindopril and atorvastatin, have consistently demonstrated reductions in the rate of ASCVD events in patients with hypertension and lipid disorders, cementing their position as first-line therapies for the management of atherosclerosis complications
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Study on thermal conductivity of gas phase in nano-porous aerogel
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Nano-porous aerogel has an ultra low thermal conductivity and is usually used as the super
insulator. To evaluate the insulation performance of the aerogel, we focus on studying the thermal
conductivity of gas phase in the aerogel. We present a modified model to take into account the effect of nonuniform
pore-size distribution on the gaseous thermal conductivity, and the present model predicts more
agreement results with available data than the existing models. The gaseous thermal conductivity of the
aerogel at high temperature gradient condition is also numerically studied. We also study the effect of the
thermal transpiration flow on the gaseous thermal conductivity, and the results shows that the thermal
transpiration flow effect leads to a reduction of the gaseous thermal conductivity
Isoform-level gene signature improves prognostic stratification and accurately classifies glioblastoma subtypes.
Molecular stratification of tumors is essential for developing personalized therapies. Although patient stratification strategies have been successful; computational methods to accurately translate the gene-signature from high-throughput platform to a clinically adaptable low-dimensional platform are currently lacking. Here, we describe PIGExClass (platform-independent isoform-level gene-expression based classification-system), a novel computational approach to derive and then transfer gene-signatures from one analytical platform to another. We applied PIGExClass to design a reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) based molecular-subtyping assay for glioblastoma multiforme (GBM), the most aggressive primary brain tumors. Unsupervised clustering of TCGA (the Cancer Genome Altas Consortium) GBM samples, based on isoform-level gene-expression profiles, recaptured the four known molecular subgroups but switched the subtype for 19% of the samples, resulting in significant (P = 0.0103) survival differences among the refined subgroups. PIGExClass derived four-class classifier, which requires only 121 transcript-variants, assigns GBM patients' molecular subtype with 92% accuracy. This classifier was translated to an RT-qPCR assay and validated in an independent cohort of 206 GBM samples. Our results demonstrate the efficacy of PIGExClass in the design of clinically adaptable molecular subtyping assay and have implications for developing robust diagnostic assays for cancer patient stratification
Large-Scale Structure Shocks at Low and High Redshifts
Cosmological simulations show that, at the present time, a substantial
fraction of the gas in the intergalactic medium (IGM) has been shock-heated to
T>10^5 K. Here we develop an analytic model to describe the fraction of
shocked, moderately overdense gas in the IGM. The model is an extension of the
Press & Schechter (1974) description for the mass function of halos: we assume
that large-scale structure shocks occur at a fixed overdensity during nonlinear
collapse. This in turn allows us to compute the fraction of gas at a given
redshift that has been shock-heated to a specified temperature. We show that,
if strong shocks occur at turnaround, our model provides a reasonable
description of the temperature distribution seen in cosmological simulations at
z~0, although it does overestimate the importance of weak shocks. We then apply
our model to shocks at high redshifts. We show that, before reionization, the
thermal energy of the IGM is dominated by large-scale structure shocks (rather
than virialized objects). These shocks can have a variety of effects, including
stripping ~10% of the gas from dark matter minihalos, accelerating cosmic rays,
and creating a diffuse radiation background from inverse Compton and cooling
radiation. This radiation background develops before the first stars form and
could have measurable effects on molecular hydrogen formation and the spin
temperature of the 21 cm transition of neutral hydrogen. Finally, we show that
shock-heating will also be directly detectable by redshifted 21 cm measurements
of the neutral IGM in the young universe.Comment: 12 pages, 8 figures, submitted to Ap
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