Multiphoton imaging with a direct‐diode pumped femtosecond Ti:sapphire laser

A direct‐diode pumped Ti:sapphire femtosecond oscillator is used to perform multiphoton imaging for the first time.     

Femtosecond pulse width control in microscopy by two-photon absorption autocorrelation

A technique for both the measurement and the control of the pulse width at the focal point of a high-NA lens, based on two-photon absorption interferometric autocorrelation, is presented. The technique is applied to measuring the pulse broadening induced on a pulse propagating through a high-NA lens system for several objectives. It is known that the pulse width may increase by up to ?50% of its original value by propagation through an objective which has wide field compensation for spherical and chromatic aberrations. The two-photon absorption autocorrelation technique allows adjustment of the actual pulse width in the focus of a high-NA lens through pre-chirp compensation. The pulse width is shown to be almost independent of penetration depth into the sample, while the amplitude of the autocorrelation signal shows a strong decrease with depth. The ability to both measure and control the actual pulse width under strong focusing conditions is of direct importance to, among others, two-photon absorption imaging approaches.     

Discovering Patterns: An Industry Report

Design patterns are a relatively new topic of study in software engineering. As such, the ideas have yet to make a widespread transfer to industry. What may help are some early success stories that will complement the intuitively appealing idea of patterns, and provide more incentive for the skeptical, time-pressed, practising software engineer to explore them. This paper describes one such successful introduction of patterns into a real development project, and the ways in which they are affecting the ongoing course of the work. Some background material on the company and the project is given to provide context, followed by a discussion of how patterns were introduced to the project and which patterns were found to be especially useful. Along the way, observations about the nature and use of patterns are offered for further consideration.     

TOUGHENING IN BLANCHED ASPARAGUS: IDENTIFICATION OF PHENOLIC COMPOUNDS AND EVIDENCE FOR A FREE RADICAL MECHANISM

Prior research in this laboratory established apparent nonenzymatic toughening occurs in heat treated asparagus tissue. The present work attempted to identify the phenol compounds involved and to discern the mechanism(s) of this reaction. Toughness (Warner-Bratzler shear) of blanched (no detectable per-oxidase or polyphenol oxidase activity) spears stored at 22°C increased significantly over a 4 day period. Reverse phase-high pressure liquid chromatography (RP-HPLC) of methanolic tissue extracts indicated 7 major phenolic peaks. HPLC retention times and Fourier transform-infrared spectroscopy tentatively identified the extracted phenols as: (1) 4-hydroxybenzoic acid; (2) caffeic acid; (3) vanillic acid; (4) syringic acid; (5) p-coumaric acid; (6) syringaldehyde; and (7) ferulic acid. A significant decrease in the concentration (HPLC peak area) of 1, 2, 5, 6 and 7 occurred after 4 days storage. In vitro studies with homogenized (blanched and unblanched) asparagus tissue indicated a significant decrease in the concentration of added phenols. Unblanched tissue produced greater changes. The site of added phenol incorporation (a significant increase in fluorescence intensity) was determined to be the vascular bundle region. Metal ion chelation (EDTA), addition of iron (Fe²⁺) and reduction of metal ions using L-ascorbic acid affected added phenol utilization variably. Only the addition of a mixed antioxidant (BHA, PG, citric acid) served to significantly decrease utilization of the added phenols by blanched tissue blends, therefore implicating a free radical mediated phenol coupling mechanism. ESR spectroscopy detected the ascorbate radical anion in the blanched homogenate.     

Analytical Derivatives for Markov Switching Models

This paper presents analytical gradients for a broad class of regime-switching models with Markovian state-transition probabilities. Such models are usually estimated by maximum likelihood methods, which require the derivatives of the likelihood function with respect to the parameter vector. These gradients are usually calculated by means of numerical techniques. The paper shows that analytical gradients considerably speed up maximum-likelihood estimation.     

表面贴技术选择的问题探讨

表面贴连接器的设计优点更胜以往，但更为重要的是了解其关键功能的细节以配合与满足不同性能的要求。     

建立自己的FTP服务器

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ENZYMIC LIPID PEROXIDATION IN BEEF MUSCLE MICROSOMES AS AFFECTED BY ELECTRICAL STIMULATION AND POSTMORTEM MUSCLE EXCISION TIME

Left sides of 10 beef carcasses were electrically stimulated at I h postmortem; right sides were not stimulated. Longissimus dorsi (LD) and trapezius (TP) muscles were removed from stimulated and nonstimulated sides after 1.5 and 24 h of chilling (0–2°C). Microsomal lipid peroxidizing activity (the amount of malonalde-hyde produced per mg of microsomal protein) was not affected by electrical stimulation, was higher for muscles removed after 24 h chilling than for those removed after 1.5 h chilling, and was higher for TP than for LD muscles. Differences observed in lipid peroxidizing activity could not be explained readily by microsomal fatty acid compositions.     

简约 专注 丰富 均衡——Arcam DivA AVP700环绕声前级放大器与DivA P1000七声道后级放大器

来自英国的Arcam（雅骏）一个以生产高性价比影音产品而闻名欧美的品牌，它一直专注于为广大Hi-Fi及AV爱好者生产出而高品质的影音器材，同时，它也是《What Hi Fi？》BEST BUY榜和欧洲影音器材销量排行榜的常客，久闻其名．今天笔者有幸接触到这一款来源于极品FMJ系列，装备了先进影音数码及模拟技术的Arcam AV分体式功效——DiVA AVP700环绕声前级放大器及DiVA P1000七声道后级放大器，怀着激动的心情，我们开始了这段不同凡响的影音之旅。