Sharing in the Rain: Secure and Efficient Data Sharing for the Cloud

Cloud storage has rapidly become a cornerstone of many businesses and has moved from an early adopters stage to an early majority, where we typically see explosive deployments. As companies rush to join the cloud revolution, it has become vital to create the necessary tools that will effectively protect users' data from unauthorized access. Nevertheless, sharing data between multiple users' under the same domain in a secure and efficient way is not trivial. In this paper, we propose Sharing in the Rain – a protocol that allows cloud users' to securely share their data based on predefined policies. The proposed protocol is based on Attribute-Based Encryption (ABE) and allows users' to encrypt data based on certain policies and attributes. Moreover, we use a Key-Policy Attribute-Based technique through which access revocation is optimized. More precisely, we show how to securely and efficiently remove access to a file, for a certain user that is misbehaving or is no longer part of a user group, without having to decrypt and re-encrypt the original data with a new key or a new policy.

James Sacré, a writing of life gesture

In French contemporary poetry, some poets have wished to return to —and so to increase the value of— the enunciation of the poetic subject. In such poetic scenario, the poet James Sacré exemplifies a new approach that tries to re-establish contact with the expression of the poetic subject, albeit always avoiding the pitfalls of excessive ornamentation and poetic effusiveness. Based on the use of simple language, this approach attaches value to legibility and does not hesitate to tap into the most banal or dullest aspects of reality. This article studies one of the procedures used by the poet to reestablish the expression of the poetic subject. This procedure seeks to rewrite life gestures—a technique that evinces an unavoidable relationship between life and poetic words in the work of James Sacré.

Cross-section and panel estimates of peer effects in early adolescent cannabis use: With a little help from my ‘friends once removed’

Peer effects in adolescent cannabis are difficult to estimate, due in part to the lack of appropriate data on behaviour and social ties. This paper exploits survey data that have many desirable properties and have not previously been used for this purpose. The data set, collected from teenagers in three annual waves from 2002-2004 contains longitudinal information about friendship networks within schools (N = 5,020). We exploit these data on network structure to estimate peer effects on adolescents from their nominated friends within school using two alternative approaches to identification. First, we present a cross-sectional instrumental variable (IV) estimate of peer effects that exploits network structure at the second degree, i.e. using information on friends of friends who are not themselves ego’s friends to instrument for the cannabis use of friends. Second, we present an individual fixed effects estimate of peer effects using the full longitudinal structure of the data. Both innovations allow a greater degree of control for correlated effects than is commonly the case in the substance-use peer effects literature, improving our chances of obtaining estimates of peer effects than can be plausibly interpreted as causal. Both estimates suggest positive peer effects of non-trivial magnitude, although the IV estimate is imprecise. Furthermore, when we specify identical models with behaviour and characteristics of randomly selected school peers in place of friends’, we find effectively zero effect from these ‘placebo’ peers, lending credence to our main estimates. We conclude that cross-sectional data can be used to estimate plausible positive peer effects on cannabis use where network structure information is available and appropriately exploited.

Factors affecting transition to second year of an engineering degree

Much research has focused on students’ transition from secondary school to university. Less is known about the transition from first to second year of a university degree programme. Given the difficulties that many students face at this stage of their education, research into the relevant factors is required. Through questionnaires and focus groups, views of second- and third-year aerospace and mechanical engineering students in our university have been gathered. A large majority believed that both the volume and difficulty of work increased in second year. Many stated that first year was slightly too trivial and could have been made more challenging to prepare them better for second year. Different teaching and assessment styles in second year were considered to affect attendance and performance. The survey revealed that students were generally very well settled into university life by the end of first year and were happy with their choice of course and only 23% reported that financial responsibilities have had a negative effect on their academic performance. Differences were observed between male and female students. Male students believed that transition was helped by having regular assessments and by worked examples in lectures. Females found the teaching staff were the most helpful factor for a successful transition. The results indicate that males require more structure and guidance whereas females are more independent and settle in better.

Experimental evaluation of the response of micro-channel plate detector to ions with 10s of MeV energies

The absolute calibration of a microchannel plate (MCP) assembly using a Thomson spectrometer for laser-driven ion beams is described. In order to obtain the response of the whole detection system to the particles’ impact, a slotted solid state nuclear track detector (CR-39) was installed in front of the MCP to record the ions simultaneously on both detectors. The response of the MCP (counts/particles) was measured for 5–58 MeV carbon ions and for protons in the energy range2–17.3 MeV. The response of the MCP detector is non-trivial when the stopping range of particles becomes larger than the thickness of the detector. Protons with energiesE>~ 10 MeV are energetic enough that they can pass through the MCP detector. Quantitative analysis of the pits formed in CR-39 and the signal generated in the MCP allowed to determine the MCP response to particles in this energy range. Moreover, a theoretical model allows to predict the response of MCP at even higher proton energies. This suggests that in this regime the MCP response is a slowly decreasing function of energy, consistently with the decrease of the deposited energy. These calibration data will enable particle spectra to be obtained in absolute terms over a broad energy range.

Alinhamento dos projetos de TI aos modelos de negócio das organizações

A necessidade de alinhar objetivos e estratégias da organização à execução dos portfólios, programas e projetos não é uma tarefa trivial. Muitas vezes, os projetos de TI são entregues com tecnologia revolucionária, no entanto, não em aderência plena às necessidades do negócio. O modelo de negócio (MN) pode ser visto como ferramenta conceitual essencial para capturar, compartilhar e criar uma visão comum do modelo da organização. O presente estudo buscou identificar o nível de maturidade do alinhamento dos projetos de tecnologia da informação (TI) aos modelos de negócio nas organizações no Brasil. Para tanto, foi realizada uma pesquisa exploratório-descritiva de natureza quantitativa com utilização do método levantamento de campo (survey). Responderam ao questionário 327 profissionais atuantes em projetos de TI de fevereiro a abril de 2012. Foram aplicadas técnicas estatísticas descritivas e univariadas, como a distribuição das frequências percentuais, além da análise multivariada, especificamente a técnica exploratória de Análise de Componentes Principais para Dados Categóricos (CATPCA). Em resposta ao objetivo principal desta pesquisa, obteve-se um escore de 3,42, classificado como nível de maturidade ‘3-estabilizado/ focado’, isto indica o início da utilização da TI de forma estratégica nos negócios. A análise dos resultados também demonstrou que a formalização de uma sistemática de gestão de projetos de TI é um processo em solidificação crescente dentro das organizações, a estrutura organizacional funcional ainda é a mais praticada, embora a estrutura ‘projetizada’ tenha conquistado seu espaço, apresentando-se na segunda posição. O escritório de projetos lidera como sendo a área que seleciona, prioriza e monitora projetos. Por meio de testes de hipóteses, verificou-se que o escritório de projetos e a estrutura organizacional ‘projetizada’ são aspectos positivos e significativos no alinhamento dos projetos de TI aos modelos de negócios.

A representação social do cuidado no programa saúde da família na cidade de Natal

RODRIGUES, M. P.; LIMA, K. C.; RONCALLI, A. G. A representação social do cuidado no programa saúde da família na cidade de Natal. Ciênc. Saúde Coletiva, v. 13, n. 1, p. 71-82. 2008. ISSN 1413-8123.

Laser IInduced Liinear and Nonlliinear Optiicall Studiies on Certaiin Metall Halliides and Tartrate Crystalls ffor Photoniic Applliicatiions

Nonlinear optics is a broad field of research and technology that encompasses subject matter in the field of Physics, Chemistry, and Engineering. It is the branch of Optics that describes the behavior of light in nonlinear media, that is, media in which the dielectric polarization P responds nonlinearly to the electric field E of the light. This nonlinearity is typically only observed at very high light intensities. This area has applications in all optical and electro optical devices used for communication, optical storage and optical computing. Many nonlinear optical effects have proved to be versatile probes for understanding basic and applied problems. Nonlinear optical devices use nonlinear dependence of refractive index or absorption coefficient on the applied field. These nonlinear optical devices are passive devices and are referred to as intelligent or smart materials owing to the fact that the sensing, processing and activating functions required for optical processes are inherent to them which are otherwise separate in dynamic devices.The large interest in nonlinear optical crystalline materials has been motivated by their potential use in the fabrication of all-optical photonic devices. Transparent crystalline materials can exhibit different kinds of optical nonlinearities which are associated with a nonlinear polarization. The choice of the most suitable crystal material for a given application is often far from trivial; it should involve the consideration of many aspects. A high nonlinearity for frequency conversion of ultra-short pulses does not help if the interaction length is strongly limited by a large group velocity mismatch and the low damage threshold limits the applicable optical intensities. Also, it can be highly desirable to use a crystal material which can be critically phasematched at room temperature. Among the different types of nonlinear crystals, metal halides and tartrates have attracted due to their importance in photonics. Metal halides like lead halides have drawn attention because they exhibit interesting features from the stand point of the electron-lattice interaction .These materials are important for their luminescent properties. Tartrate single crystals show many interesting physical properties such as ferroelectric, piezoelectric, dielectric and optical characteristics. They are used for nonlinear optical devices based on their optical transmission characteristics. Among the several tartrate compounds, Strontium tartrate, Calcium tartrate and Cadmium tartrate have received greater attention on account of their ferroelectric, nonlinear optical and spectral characteristics. The present thesis reports the linear and nonlinear aspects of these crystals and their potential applications in the field of photonics.

A representação social do cuidado no programa saúde da família na cidade de Natal

RODRIGUES, Maisa Paulino; LIMA, Kenio Costa de; RONCALLI, Angelo Giuseppe. A representaçao social do cuidado no programa saúde da familia na cidade de Natal. Ciência & Saúde Coletiva, v. 13, n. 1, p. 71-82, 2008.Disponivel em: . Acesso em: 04 out. 2010.

Dispositifs optoélectroniques à base de semi-conducteurs organiques en couches minces

Les petites molécules de type p à bandes interdites étroites sont de plus en plus perçues comme des remplaçantes possibles aux polymères semi-conducteurs actuellement utilisés conjointement avec des dérivés de fullerènes de type n, dans les cellules photovoltaïques organiques (OPV). Par contre, ces petites molécules tendent à cristalliser facilement lors de leur application en couches minces et forment difficilement des films homogènes appropriés. Des dispositifs OPV de type hétérojonction de masse ont été réalisés en ajoutant différentes espèces de polymères semi-conducteurs ou isolants, agissant comme matrices permettant de rectifier les inhomogénéités des films actifs et d’augmenter les performances des cellules photovoltaïques. Des polymères aux masses molaires spécifiques ont été synthétisés par réaction de Wittig en contrôlant précisément les ratios molaires des monomères et de la base utilisée. L’effet de la variation des masses molaires en fonction des morphologies de films minces obtenus et des performances des diodes organiques électroluminescentes reliées, a également été étudié. La microscopie électronique en transmission (MET) ou à balayage (MEB) a été employée en complément de la microscopie à force atomique (AFM) pour suivre l’évolution de la morphologie des films organiques minces. Une nouvelle méthode rapide de préparation des films pour l’imagerie MET sur substrats de silicium est également présentée et comparée à d’autres méthodes d’extraction. Motivé par le prix élevé et la rareté des métaux utilisés dans les substrats d’oxyde d’indium dopé à l’étain (ITO), le développement d’une nouvelle méthode de recyclage eco-responsable des substrats utilisés dans ces études est également présenté.

Koffeinets ergogena effekter på power i överkropp

Koffein har sedan 1962 fram och tillbaka varit dopingklassat men är sedan 2004 ett tillåtet ergogent preparat inom idrotten. Flera studier har visat positiva resultat i uthållighetsidrotter och på maximal styrkeförmåga. Syftet med denna studie var att se om koffein har någon ergogen effekt på power i överkroppsmuskulaturen. I denna studie användes en dubbel-blindad, randomiserad cross-over design. En slumpmässig indelning inför det första testtillfället avgjorde ifall deltagarna började studien med koffein- eller placebosupplementering och bytte sedan supplementering inför testtillfälle två. Som supplementeringsmetod användes koffein i tuggummiform på grund av att det ger ett snabbare upptag. Power mättes genom testet sittande stöt med en kula på 5 kg. Resultatet visar på en mycket svag (ES=0,13) positiv förbättring av stötlängderna mellan interventionerna. En av anledningarna till det triviala resultatet tros kunna bero på att det urval som användes ej bestod av en homogengrupp vad gäller träningsbakgrund och prestationsnivå. På grund av detta är det svårt att dra några slutsatser om koffeinet har eller inte har några ergogena effekter på power i överkroppen.

House of Flora (illustrations)

McLean builds strong connections between the cultural capital of the Jerwood prizewinning craft maker and the world of business and trade. It is crucial that higher education research can consider its relationship to the creative industries. London is a fashion capital, known for its style experimentation and playful creativity. The wit and anarchic play of the art school is a leading force in fashion innovation and Mclean's work articulates this clearly. Designing hats that reference the stylised coiffures of Hollywood icons, in the soft medium of felted wool, is a sophisticated play on the relations between nature and culture that, according to Levi Straus, are at the heart of all culture. The Fifty Hats that Changed the World makes direct allusion to the way that fashion is often regarded with mild disdain as insignificant or trivial, and the Design Museum London, an international leader in disseminating design discourse has, recently, included fashion design within its agenda for exhibition. McLean's work is a leading component of this transformation of design culture.

Climbing Up the Leaderboard: An Empirical Study of Applying Gamification Techniques to a Computer Programming Class

Conventional taught learning practices often experience difficulties in keeping students motivated and engaged. Video games, however, are very successful at sustaining high levels of motivation and engagement through a set of tasks for hours without apparent loss of focus. In addition, gamers solve complex problems within a gaming environment without feeling fatigue or frustration, as they would typically do with a comparable learning task. Based on this notion, the academic community is keen on exploring methods that can deliver deep learner engagement and has shown increased interest in adopting gamification – the integration of gaming elements, mechanics, and frameworks into non-game situations and scenarios – as a means to increase student engagement and improve information retention. Its effectiveness when applied to education has been debatable though, as attempts have generally been restricted to one-dimensional approaches such as transposing a trivial reward system onto existing teaching materials and/or assessments. Nevertheless, a gamified, multi-dimensional, problem-based learning approach can yield improved results even when applied to a very complex and traditionally dry task like the teaching of computer programming, as shown in this paper. The presented quasi-experimental study used a combination of instructor feedback, real time sequence of scored quizzes, and live coding to deliver a fully interactive learning experience. More specifically, the “Kahoot!” Classroom Response System (CRS), the classroom version of the TV game show “Who Wants To Be A Millionaire?”, and Codecademy’s interactive platform formed the basis for a learning model which was applied to an entry-level Python programming course. Students were thus allowed to experience multiple interlocking methods similar to those commonly found in a top quality game experience. To assess gamification’s impact on learning, empirical data from the gamified group were compared to those from a control group who was taught through a traditional learning approach, similar to the one which had been used during previous cohorts. Despite this being a relatively small-scale study, the results and findings for a number of key metrics, including attendance, downloading of course material, and final grades, were encouraging and proved that the gamified approach was motivating and enriching for both students and instructors.

Random extremal solutions of differential inclusions

Given a Lipschitz continuous multifunction $F$ on ${\mathbb{R}}^{n}$, we construct a probability measure on the set of all solutions to the Cauchy problem $\dot x\in F(x)$ with $x(0)=0$. With probability one, the derivatives of these random solutions take values within the set $ext F(x)$ of extreme points for a.e.~time $t$. This provides an alternative approach in the analysis of solutions to differential inclusions with non-convex right hand side.

Some results on orbifold quotients and related objects

The quotient of a finite-dimensional Euclidean space by a finite linear group inherits different structures from the initial space, e.g. a topology, a metric and a piecewise linear structure. The question when such a quotient is a manifold leads to the study of finite groups generated by reflections and rotations, i.e. by orthogonal transformations whose fixed point subspace has codimension one or two. We classify such groups and thereby complete earlier results by M. A. Mikhaîlova from the 70s and 80s. Moreover, we show that a finite group is generated by reflections and) rotations if and only if the corresponding quotient is a Lipschitz-, or equivalently, a piecewise linear manifold (with boundary). For the proof of this statement we show in addition that each piecewise linear manifold of dimension up to four on which a finite group acts by piecewise linear homeomorphisms admits a compatible smooth structure with respect to which the group acts smoothly. This solves a challenge by Thurston and confirms a conjecture by Kwasik and Lee. In the topological category a counterexample to the above mentioned characterization is given by the binary icosahedral group. We show that this is the only counterexample up to products. In particular, we answer the question by Davis of when the underlying space of an orbifold is a topological manifold. As a corollary of our results we generalize a fixed point theorem by Steinberg on unitary reflection groups to finite groups generated by reflections and rotations. As an application thereof we answer a question by Petrunin on quotients of spheres.