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The occurrence of neck, shoulder and low back complaints in relation to schoolbag carriage and other potential risk factors were investigated in a cross-sectional study of 586 Iranian schoolchildren aged 12–14 years. The average load carried by schoolchildren was 2.8 kg. Neck, shoulder and low back complaints during the preceding month were reported by 35.3%, 26.1% and 33% of the students, respectively. Gender was an independent factor predicting musculoskeletal symptoms in schoolchildren. Girls were more likely than boys to suffer from neck, shoulder and low back complaints, although there was no significant difference between genders in terms of schoolbag carriage variables. The findings suggest that the recommended weight limit for schoolbag carriage may need to differ between boys and girls. The associations between schoolbag variables and reported symptoms are also discussed. The results provide evidence that the current weight limit should consider a broader combination of factors that influence the use of schoolbags.  相似文献   
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Overall performance of a peer‐to‐peer system can be highly variable and unpredictable as there is no central authority to set and coordinate the amount of resource contributions made by constituent peers. In this paper, we address the problem of optimal cooperation policy setting for individual peers by taking into account their rationality, and with respect to a set of overall constraints imposed by resource‐driven requirements of the system. We formalize distributed cooperation policy setting as an asynchronous distributed decision making (ADDM) process and represent an integrated design for this process in two top‐down and bottom‐up phases. In top‐down design, we specify the overall objective and constraints and in line with them, we synthesize the local objectives of individual peers. We show that the rational peers should continuously adapt their cooperation policies asynchronously and autonomously according to the policies of the other participants in order to maximize their local objectives. To this end, we devise a self‐organizing interaction mechanism in the bottom‐up phase and demonstrate that it coordinates asynchronous distributed decisions of individual peers with respect to the overall objective and constraints through local interactions. ©2012 Wiley Periodicals, Inc. Syst Eng 16  相似文献   
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The fabrication of asymmetric polymer membranes via vapor phase deposition is demonstrated. In this solventless process, the dense layer is deposited first and then the porous layer is subsequently deposited onto the dense layer. A variety of functional polymer membranes can be produced by varying the precursor molecules. The functionality of the dense and porous layers can be independently tailored to be either hydrophobic or hydrophilic, resulting in membranes that are fully hydrophilic, fully hydrophobic, or asymmetric in both structure and chemical functionality. The thickness of both the porous and dense layers can be separately tuned by controlling the deposition time.

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To date, the scaled-up manufacturing and efficient drug loading of exosomes are two existing challenges limiting the clinical translation of exosome-based drug delivery. Herein, a facile magnetic extrusion method is developed for preparing endosome-derived vesicles, also known as exosome mimetics (EMs), which share the same biological origin and similar morphology, composition, and biofunctions with native exosomes. The high yield and consistency of this magnetic extrusion method help to overcome the manufacturing bottleneck in exosome research. Moreover, the proposed standardized multi-step method readily facilitates the ammonium sulfate gradient approach to actively load chemodrugs such as doxorubicin into EMs. The engineered EMs developed and tested here exhibit comparable drug delivery properties as do native exosomes, and potently inhibit tumor growth by delivering doxorubicin in an orthotopic breast tumor model. These findings demonstrate that EMs can be prepared in a facile and scaled-up manner as a promising biological nanomedicine for cancer drug delivery.  相似文献   
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In this article, a mutual multilevel trust framework is proposed, which involves managing trust from the perspective of cloud users (CUs) and cloud service providers (CSPs) in a multicloud environment based on a set of trusted third parties (TTPs). These independent agents are trusted by CUs and CSPs and distributed on different clouds. The TTPs evaluate the CUs' trustworthiness based on the accuracy of feedback ratings and assess the CSPs' trustworthiness based on the quality of service monitoring information. They are connected themselves through the trusted release network, which enables a TTP to obtain trust information about CSPs and CUs from other clouds. With the objective of developing an effective trust management framework, a new approach has been provided to improve trust-based interactions, that is, able to rank the trusted cloud services (CSs) based on CU's priorities via fuzzy logic. Fuzzy logic is applied to manage the different priorities of CUs, all the CUs do not have the same priorities to use trusted CSs. Customizing service ranking allows CUs to apply trusted CSs based on their priorities. Experiments on real datasets well matched the analytical results, indicating that our proposed approach is effective and outperforms the existing approaches.  相似文献   
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A pulsed wall gauge has been used to obtain measurements of the mean and fluctuating skin friction on the top surface of bluff bodies mounted in thick turbulent boundary layers. The mean flow results presented in our earlier paper [2] are complemented here by further mean surface shear stress data and by fluctuating data, which include some measurements of the probability density function of the instantaneous surface shear stress. By suitable combinations of body geometry and upstream flow properties three different “types” of flow, characterised by very different mean flow behaviour in the vicinity of the body, have been investigated. It is argued that the practically important effects of the flow around such bodies often depend much less on the mean flow structure than on the nature of the fluctuating flow.  相似文献   
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[Correction Notice: An erratum for this article was reported in Vol 8(4) of Emotion (see record 2008-12765-001). The URL provided for the supplemental materials was incorrect. The correct URL is provided in the erratum.] Previous studies have shown that mere words, particularly affective words, can dampen emotional responses. However, the effect of affective labels on emotional responding in the long term is unknown. The authors examined whether repeated exposure to aversive images would lead to more reduction in autonomic reactivity a week later if the images were exposed with single-word labels than without labels. In Experiment 1, healthy individuals were exposed to pictures of disturbing scenes with or without labels on Day 1. On Day 8, the same pictures from the previous week were exposed, this time without labels. In Experiment 2, participants were spider fearful and were exposed to pictures of spiders. In both experiments, although repeated exposure to aversive images (without labels) led to long-term attenuation of autonomic reactivity, exposure plus affective labels, but not nonaffective labels, led to more attenuation than exposure alone. Thus, affective labels may help dampen emotional reactivity in both the short and long terms. Implications for exposure therapy and translational studies are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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Many security breaches occur because of exploitation of vulnerabilities within the system. Vulnerabilities are weaknesses in the requirements, design, and implementation, which attackers exploit to compromise the system. This paper proposes a methodological framework for security requirements elicitation and analysis centered on vulnerabilities. The framework offers modeling and analysis facilities to assist system designers in analyzing vulnerabilities and their effects on the system; identifying potential attackers and analyzing their behavior for compromising the system; and identifying and analyzing the countermeasures to protect the system. The framework proposes a qualitative goal model evaluation analysis for assessing the risks of vulnerabilities exploitation and analyzing the impact of countermeasures on such risks.  相似文献   
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