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排序方式: 共有5317条查询结果,搜索用时 218 毫秒
971.
Alexis Pacquit June Frisby Danny Diamond King Tong Lau Alan Farrell Brid Quilty Dermot Diamond 《Food chemistry》2007,102(2):466-470
There is much interest from the fisheries industry in developing rapid methods to evaluate real-time freshness of fish and seafood products. Emphasis is on the ones that would reflect and account for the products history and their storage conditions from “harvest-to-home”. The development of a “smart packaging” that monitors the microbial breakdown products in the headspace of packaged fish is described. When fish spoils it releases a variety of basic volatile amines which are detectable with appropriate pH indicating sensors. These are prepared by entrapping within a polymer matrix a pH sensitive dye that responds, through visible color changes to the spoilage volatile compounds that contribute to a quantity known as total volatile basic nitrogen (TVB-N). Laboratory trials on fresh fish filets showed that the sensor accurately tracks the increase in amines concentration in the package headspace. The response was also found to correlate to changing microbial populations (total viable count or TVC and Pseudomonas spp.). In addition, leaching of the dye was assessed over time to assess the suitability of the sensor formulation for food packaging application. 相似文献
972.
Maguen Shira; Vogt Dawne S.; King Lynda A.; King Daniel W.; Litz Brett T.; Knight Sara J.; Marmar Charles R. 《Canadian Metallurgical Quarterly》2011,3(1):21
This study examined the impact of killing on posttraumatic stress symptomatology (PTSS), depression, and alcohol use among 317 U.S. Gulf War veterans. Participants were obtained via a national registry of Gulf War veterans and were mailed a survey assessing deployment experiences and postdeployment mental health. Overall, 11% of veterans reported killing during their deployment. Those who reported killing were more likely to be younger and male than those who did not kill. After controlling for perceived danger, exposure to death and dying, and witnessing killing of fellow soldiers, killing was a significant predictor of PTSS, frequency and quantity of alcohol use, and problem alcohol use. Military personnel returning from modern deployments are at risk of adverse mental health symptoms related to killing in war. Postdeployment mental health assessment and treatment should address reactions to killing in order to optimize readjustment. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
973.
Drew Linda M.; Berg Cynthia; King Pamela; Verdant Claudia; Griffith Katrina; Butler Jorie; Wiebe Deborah J. 《Canadian Metallurgical Quarterly》2011,25(5):751
For adolescents with Type 1 diabetes, lower family income may be associated with poorer diabetes management through depleted parental psychological resources (i.e., higher parental depressive symptoms, lower parental acceptance). Adolescents (N = 252; 46% male) aged 10–14 years with Type 1 diabetes assessed the acceptance of their mother and father (e.g., “gives me the feeling that she likes me as I am”; “she doesn't feel she has to make me over into someone else”). Mothers provided information on family income and demographics. Both mothers and fathers reported their depressive symptoms. HbA1c scores were indexed via medical records. Lower family income was associated with higher (i.e., worse) HbA1c, more mother and father depressive symptoms, and less acceptance from both parents. Mediation analyses revealed that the relationship of lower family income with metabolic control occurred indirectly through lower maternal and paternal acceptance and lower adherence. Lower family income may impair the quality of parent—adolescent relationships that are beneficial for good diabetes management. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
974.
The performance and scaling of graphene-based electronics is limited by the quality of contacts between the graphene and metal electrodes. However, the nature of graphene-metal contacts remains incompletely understood. Here, we use atomic force microscopy to measure the temperature distributions at the contacts of working graphene transistors with a spatial resolution of ~ 10 nm (refs 5-8), allowing us to identify the presence of Joule heating, current crowding and thermoelectric heating and cooling. Comparison with simulation enables extraction of the contact resistivity (150-200 Ω μm2) and transfer length (0.2-0.5 μm) in our devices; these generally limit performance and must be minimized. Our data indicate that thermoelectric effects account for up to one-third of the contact temperature changes, and that current crowding accounts for most of the remainder. Modelling predicts that the role of current crowding will diminish and the role of thermoelectric effects will increase as contacts improve. 相似文献
975.
Aikman D Barrett P Kapadia S King M Proudman J Taylor T de Weymarn I Yates T 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1956):4798-4817
Uncertainty is pervasive in economic policy-making. Modern economies share similarities with other complex systems in their unpredictability. But economic systems also differ from those in the natural sciences because outcomes are affected by the state of beliefs of the systems' participants. The dynamics of beliefs and how they interact with economic outcomes can be rich and unpredictable. This paper relates these ideas to the recent crisis, which has reminded us that we need a financial system that is resilient in the face of the unpredictable and extreme. It also highlights how such uncertainty puts a premium on sound communication strategies by policy-makers. This creates challenges in informing others about the uncertainties in the economy, and how policy is set in the face of those uncertainties. We show how the Bank of England tries to deal with some of these challenges in its communications about monetary policy. 相似文献
976.
Silk is an exceptionally strong, extensible, and tough material made from simple protein building blocks. The molecular structure of dragline spider silk repeat units consists of semiamorphous and nanocrystalline β-sheet protein domains. Here we show by a series of computational experiments how the nanoscale properties of silk repeat units are scaled up to create macroscopic silk fibers with outstanding mechanical properties despite the presence of cavities, tears, and cracks. We demonstrate that the geometric confinement of silk fibrils to diameters of 50 ± 30 nm is critical to facilitate a powerful mechanism by which hundreds of thousands of protein domains synergistically resist deformation and failure to provide enhanced strength, extensibility, and toughness at the macroscale, closely matching experimentally measured mechanical properties. Through this mechanism silk fibers exploit the full potential of the nanoscale building blocks, regardless of the details of microscopic loading conditions and despite the presence of large defects. Experimental results confirm that silk fibers are composed of silk fibril bundles with diameters in the range of 20-150 nm, in agreement with our predicted length scale. Our study reveals a general mechanism to map nanoscale properties to the macroscale and provides a potent design strategy toward novel fiber and bulk nanomaterials through hierarchical structures. 相似文献
977.
Charles?Hoi?King?LamEmail author John?Patrick?Barford Gordon?McKay 《Clean Technologies and Environmental Policy》2011,13(4):607-615
Municipal solid waste incineration (MSWI) ash is used in part as raw materials for cement clinker production by taking advantage
of the high contents of SiO2, Al2O3, and CaO. It is necessary for environmental reasons to establish a material utilization system for the incineration waste
ash residue instead of disposing these ashes into landfill. The aim of this paper is to study the feasibility of replacing
clinker raw materials by waste ash residue for cement clinker production. MSWI bottom ash and MSWI fly ash are the main types
of ashes being evaluated. The ashes were mixed into raw mixture with different portions of ash residue to produce cement clinker
in a laboratory furnace at approximately 1400°C. X-ray diffraction and X-ray florescence techniques were used to analyze the
phase chemistry and chemical composition of clinkers in order to compare these ash-based clinkers with commercial Portland
cement clinker. 相似文献
978.
Ronsse R Vitiello N Lenzi T van den Kieboom J Carrozza MC Ijspeert AJ 《IEEE transactions on bio-medical engineering》2011,58(4):1001-1012
We propose a novel method for movement assistance that is based on adaptive oscillators, i.e., mathematical tools that are capable of extracting the high-level features (amplitude, frequency, and offset) of a periodic signal. Such an oscillator acts like a filter on these features, but keeps its output in phase with respect to the input signal. Using a simple inverse model, we predicted the torque produced by human participants during rhythmic flexion-extension of the elbow. Feeding back a fraction of this estimated torque to the participant through an elbow exoskeleton, we were able to prove the assistance efficiency through a marked decrease of the biceps and triceps electromyography. Importantly, since the oscillator adapted to the movement imposed by the user, the method flexibly allowed us to change the movement pattern and was still efficient during the nonstationary epochs. This method holds promise for the development of new robot-assisted rehabilitation protocols because it does not require prespecifying a reference trajectory and does not require complex signal sensing or single-user calibration: the only signal that is measured is the position of the augmented joint. In this paper, we further demonstrate that this assistance was very intuitive for the participants who adapted almost instantaneously. 相似文献
979.
Calogero Maria Oddo Lucia Beccai Nicola Vitiello Helena Backlund Wasling Johan Wessberg Maria Chiara Carrozza 《Mechatronics》2011,21(3):604-613
The development of a mechatronic tactile stimulation platform for touch studies is presented. The platform was developed for stimulation of the fingertip using textured surfaces, providing repeatable tangential sliding motion of stimuli with controlled indentation force. Particular requirements were addressed to make the platform suitable for neurophysiological studies in humans with particular reference to electrophysiological measurements, but allowing a variety of other studies too, such as psychophysical, tribological and artificial touch ones. The design of the mechatronic tactile stimulator is detailed, as well as the performance in tracking reference trajectories. Using microneurography, we recorded from human tactile afferents and validated the platform compatibility with the exacting demands of electrophysiological methods, comprising the absence of spurious vibrations and the lack of relevant electromagnetic interference. 相似文献
980.
Dapore AJ King MR Harter J Sarwate S Oelze ML Zagzebski JA Do MN Hall TJ O'Brien WD 《IEEE transactions on medical imaging》2011,30(6):1206-1213
Three-dimensional impedance maps (3DZMs) are virtual volumes of acoustic impedance values constructed from histology to represent tissue microstructure acoustically. From the 3DZM, the ultrasonic backscattered power spectrum can be predicted and model based scatterer properties, such as effective scatterer diameter (ESD), can be estimated. Additionally, the 3DZM can be exploited to visualize and identify possible scattering sites, which may aid in the development of more effective scattering models to better represent the ultrasonic interaction with underlying tissue microstructure. In this study, 3DZMs were created from a set of human fibroadenoma samples. ESD estimates were made assuming a fluid-filled sphere form factor model from 3DZMs of volume 300×300×300 μm. For a collection of 33 independent human fibroadenoma tissue samples, the ESD was estimated to be 111±40.7 μm. The 3DZMs were then investigated visually to identify possible scattering sources which conformed to the estimated model scatterer dimensions. This estimation technique allowed a better understanding of the spatial distribution and variability of the estimates throughout the volume. 相似文献