Abstract
Inspired by recent results on information-theoretic security, we consider the transmission of confidential messages over wireless networks, in which the legitimate communication partners are aided by friendly jammers. We characterize the security level of a confined region in a quasi-static fading environment by computing the probability of secrecy outage in connection with two new measures of physical-layer security: the jamming coverage and the jamming efficiency. Our analysis for various jamming strategies based on different levels of channel state information provides insight into the design of optimal jamming configurations and shows that a single jammer is not sufficient to maximize both figures of merit simultaneously. Moreover, a single jammer requires full channel state information to provide security gains in the vicinity of the legitimate receiver.

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This paper presents the evaluation of a serious game project, where the primary goal was to develop a set of collaborative game levels on a virtual campus, in order to help the integration process of newcomer students to the university. The global activities that can be performed by the students were designed for a group approach in a controlled virtual environment. For the present work we have selected Second Life for the implementation of these collaborative "game levels". A prototype evaluation was conducted to collect results with a sample of university students. With this data, some conclusions were extracted in order to delineate future developments.

Abstract
A fiber-optic curvature sensor based on a core offset single-mode fiber (SMF) combined with a fiber Bragg grating (FBG) is presented. The FBG cladding modes are efficiently excited by the large core misalignment. The curvature of the fiber can be obtained by the ratio between the recoupled cladding mode power and the reflected core mode power. These measurements are independent from temperature variation.

Abstract
The Web is being increasingly used by health consumers to search for health information. In this domain, the quality of the retrieved contents is crucial to avoid healthcare hazards. To address this problem and help the user identify reliable and credible contents, initiatives have appeared that certify the compliance of health websites to quality standards. In this work we explore the impact of medical certification on several aspects of health information retrieval performance. Moreover, we analyze the usefulness of certification categories to the personalization of the search experience. Our findings suggest that medical certification might be incorporated as a ranking criterion. We conclude that the medical accuracy of the resulting knowledge is enhanced by the use of certified information and depends on the users' comprehension of the document. In general, we also conclude that there is space for personalization in search by health consumers. © 2011 Springer-Verlag Berlin.