Energy dissipation via radiative recombination and vibronic relaxation in σ-delocalized silicon backbone network polymers

The nature of ultrafast energy dissipation in poly(n-hexylsilyne), a prototypical σ-delocalized alkysilicon network polymer, is explored. This disordered silicon backbone material exhibits strong near-UV to visible band-edge absorption and a high quantum yield of visible emission. The time evolution of the emission band is studied over four decades of time using time-resolved luminescence as a probe. The data indicate that while there is an ‘intrinsic’ Stokes shift after photoexcitation due to kinetic energy relaxation (<10ps), thermalization within a dense band of vibronic states via intramolecular phonon-assisted hopping on a nanosecond timescale is the dominant mechanism for excited-state decay. The data can be understood in terms of theoretical predictions for energy relaxation in disordered materials.     

Survey of animal livers for vitamin A content.

Retail samples of livers from calf (23), ox (18), lamb (17), pig (15), chicken (16) and turkey (1) were analysed to determine levels of vitamin A (all trans-retinol) and to aid assessment of the effects of using vitamin supplemented compound feedingstuffs for livestock. For comparison, 22 liver samples from lambs reared on diets not containing vitamin-supplemented compound feedingstuffs and four samples of liver from ox which had received supplemented feed but not during the last four months prior to slaughter were also analysed. The chosen method of analysis utilized saponification, solvent extraction and normal-phase high performance liquid chromatography with fluorescence detection. For all species analysed, the levels of vitamin A ranged from 10 to 1100 mg/kg, with all but seven at or below 400 mg/kg. For lamb and ox livers, the mean levels were 310 mg/kg and 200 mg/kg respectively for retail samples. The mean levels were 220 mg/kg (lamb) and 120 mg/kg (ox) in liver samples from animals fed controlled diets. The results are of the same order as those reported over recent years.     

Spectral predictions for pulse interval and width modulation

An expression for the frequency spectrum of pulse interval and width modulation (PIWM) is presented. Experimental results obtained have shown close agreement with spectral predictions from the formula. Performance figures are also included from a practical PIWM optical-fibre transmission system intended for use with TV and video signals.<>     

伍尔弗汉普敦市中心的公共空间概念设计，英国

2004年伍尔弗汉普敦(Wolverhampton)市政府授权伟信公司对该市中心公共空间进行全面改造概念设计和进一步的详细设计。市政府希望制定发展策略框架及实施步骤,以建造能够顺应大众和社团活动的核心主题公共空间。这些主题包括:安全城市、绿色城市、促进经济发展的城市等。现状是一些靠近大学区的地方出现的新的广场,如知识广场(LearningQuarter)、圣约翰城市村(StJohns’UrbanVillage),以改变城市中心看起来非常陈旧的状态。伟信公司接受了这项挑战,从深入城市的“表皮”入手,剖析城市的特征,以及所面临的问题,逐街分析。正如很多城市中心…     

Cardiovascular responses to occupational stress in male medical students: A paradigm for ambulatory monitoring studies.

Examined hemodynamic responses to systematic variations in occupational stress using ambulatory blood pressure monitors. Heart rate, systolic blood pressure, diastolic blood pressure, rate–pressure product, and mood states were measured before, during, and after low-stress (lecture) and high-stress (examination) work in 44 healthy White male medical students. The lecture day was characterized by stable patterns of cardiovascular activity across all 3 periods. Hemodynamic activity and reports of activation and distress were greater on the examination day than on the lecture day. Cardiovascular activity during the pre-examination period was as high as that seen during the examination period itself, indicating an anticipatory stress effect. Pressor activity decreased after the examination, although some residual chronotropic activity was seen. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nonparametric Analysis of the Order-Statistic Model in Software Reliability

In the literature on statistical inference in software reliability, the assumptions of parametric models and random sampling of bugs have been pervasive. We argue that both assumptions are problematic, the first because of robustness concerns and the second due to logical and practical difficulties. These considerations motivate the approach taken in this paper. We propose a nonparametric software reliability model based on the order-statistic paradigm. The objective of the work is to estimate, from data on discovery times observed within a type I censoring framework, both the underlying distribution F from which discovery times are generated and N, the unknown number of bugs in the software. The estimates are used to predict the next time to failure. The approach makes use of Bayesian nonparametric inference methods, in particular, the beta-Stacy process. The proposed methodology is illustrated on both real and simulated data     

Rogue Servers

Rogue servers are a constant threat and pose a variety of problems for the IT security team. This article summarises the threats that come from not managing rogue servers and gives prevention and detection tips.