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Tracing watermarking has been recently proposed as a technique to provide a blind measure of the quality of service of the communication link, focusing on multimedia communication scenarios. 3G communication scenarios, where each customer transmits both voice and MPEG-4 video sequences in real time, have been considered. Typical video-phone call consists of close shots of speakers, framing their face in the foreground. For such particular application, a novel colour space (YST) is adopted to minimise the perceptual distortions on face coding introduced by watermarking. In the YST space, the luminance component (Y) is the same as in conventional YUV space, whereas the vectors S and T lie within the chrominance (UV) plane. The S (skin) component is a linear combination of U and V obtained as the 'average' chrominance estimated from an assorted set human faces to achieve a reasonable generalisation. The third component, T, is defined as orthogonal to the YS plane. The results show the benefits obtained in digital watermarking by the new representation against the conventional approach. In fact, the sensitivity of the YST representation outperforms the conventional one in terms of objective (mean square error, peak signal-to-noise ratio) and subjective (video-quality metrics) indicators.  相似文献   
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Text search is a type of strategic reading that involves locating specific goal-relevant information. Previous research has indicated that college and high school students often exhibit inefficient or unsuccessful text-search performance. Consequently, the effects of 2 manipulations on text-search performance were investigated: (1) the presence of indexed terms in a text-search task and (2) the use of a planning prompt before beginning a task. 34 college students engaged in 6 text-search tasks. Half of these tasks contained terms that could be used in an index; half required that a search term be generated. Half of the subjects were randomly assigned to a prompt condition in which they were prompted to plan their search before beginning each task. The results indicated that a planning prompt raised the success level of search performance, as did the presence of terms that were searchable in the textbook's index. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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Community studies in Guinea-Bissau have found that exposure to measles prior to 6 months of age is associated with delayed mortality later in childhood. In an attempt to understand the underlying mechanism, we examined the role of pre-exposure nutritional status and the impact of exposure to measles on growth and subsequent mortality in these outbreaks. Though exposed children were lighter than controls, there was no association between pre-exposure weight-for-age and subsequent mortality adjusting for age. Although exposure was strongly associated with excess mortality, it did not have a negative impact on growth. Adjustment for state of nutrition did not alter the mortality ratio (MR) between 6 and 59 months of age for exposed children and controls; exposed children examined anthropometrically between 6-17 months had a MR of 3.70 compared with controls. This trend was the same for anthropometric measurements obtained at 18-59 months of age. Among the controls, there was a significant association between weight-for-age and subsequent mortality to the age of 5 years. However, for exposed children there was no association; the relation between weight-for-age and subsequent mortality was significantly different for exposed children compared with controls (tests for interaction between exposure and anthropometric measurements at 6-17 months: P = 0.05). Growth faltering as a consequence of early exposure to measles does not explain the marked excess mortality among these children. Further studies of the process underlying delayed mortality after early exposure to measles are warranted.  相似文献   
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Abstract: Environmental justice advocates have recently focused attention on cumulative exposure in minority neighborhoods due to multiple sources of pollution. This article uses U.S. EPA's National Air Toxics Assessment (NATA) for 1996 to examine environmental inequality in California, a state that has been a recent innovator in environmental justice policy. We first estimate potential lifetime cancer risks from mobile and stationary sources. We then consider the distribution of these risks using both simple comparisons and a multivariate model in which we control for income, land use, and other explanatory factors, as well as spatial correlation. We find large racial disparities in California's “riskscape” as well as inequalities by other factors and suggest several implications for environmental and land use policy.  相似文献   
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The high expectations and demand for users to access the Internet from anywhere at anytime has made user mobility an important part of the design and development of the next generation mobile communications and computing. Traditionally user mobility has been divided into two areas: Terminal Mobility and Personal Mobility. In recent years terminal mobility has focused on the movement of the terminal and developed extensions to IP protocols such as Mobile IP. In contrast, personal mobility has only received limited attention, and is somewhat lagging behind. This research has either focussed on personal mobility in communications or personalisation of operating environments. As a result, to date no framework for providing true personal mobility has emerged. In this paper, we introduce a new personal mobility framework called IPMoA (Integrated Personal Mobility Architecture), which integrates both aspects of personal mobility to provide a complete personal mobility solution, and illustrate the viability of this approach through a proof-of-concept implementation.  相似文献   
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OBJECTIVES: Amitriptyline poisoning is associated with ventricular arrhythmias. Standard treatment is sodium bicarbonate but further intervention may be necessary. The present study compared the actions of lidocaine and magnesium sulfate on ventricular tachycardia induced by amitriptyline. DESIGN: Nonrandomized, controlled, intervention trial. SETTING: University laboratory. SUBJECTS: Thirty male Wistar rats anesthetized with pentobarbital and mechanically ventilated. INTERVENTIONS: After pretreatment with norepinephrine, the animals were subjected to a continuous infusion of amitriptyline. After the appearance of ventricular tachycardia, they were treated with magnesium sulfate (45 mg/kg + 15 mg/kg/min) or lidocaine (1 mg/kg + 0.5 mg/kg/min) or glucose infusion as a control. MEASUREMENTS AND MAIN RESULTS: In the group treated with magnesium sulfate, electrocardiogram tracings demonstrated that nine of ten animals converted from ventricular tachycardia to sinus rhythm compared with one of ten in both the lidocaine- and glucose-treated groups (p < .001). The animals treated with magnesium sulfate also had a significantly longer total time in sinus rhythm (10.0 +/- 1.6 mins) than those rats treated with lidocaine (1.7 +/- 1.5 mins) or glucose (1.5 +/- 1.5 mins). Magnesium sulfate significantly decreased blood pressure and heart rate, but no severe hemodynamic side effects were observed. CONCLUSIONS: Magnesium sulfate is effective in converting ventricular tachycardia in hyperadrenergic amitriptyline poisoning. In contrast, lidocaine had no effect on arrhythmias.  相似文献   
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Infants were presented with a moving object under 2 lighting conditions to investigate the role of vision in early reaching. The motion of the target object also allowed for an analysis of the infants' ability to use a predictive style of reaching. Infants were tested twice, at 5 and 7.5 months of age, with a moving object in the light and the same object painted with luminescent paint in the dark. Infants successfully contacted the glowing object on about half of their attempts at both ages, although 7.5 month-olds reached more often. Infants also took into account the motion of the target object by aiming their reaches ahead of the object and by reaching with their contralateral hand. These results suggest that proprioceptive feedback and sight of the target allow for successful reaching with limited visual information, even in relatively complex reaching tasks. The infants' success also demonstrates their ability to adapt their movements and reaching strategy to the speed and trajectory of the target object in order to reach predictively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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