8,655 research outputs found

    A Machine-Checked Formalization of the Generic Model and the Random Oracle Model

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    Most approaches to the formal analyses of cryptographic protocols make the perfect cryptography assumption, i.e. the hypothese that there is no way to obtain knowledge about the plaintext pertaining to a ciphertext without knowing the key. Ideally, one would prefer to rely on a weaker hypothesis on the computational cost of gaining information about the plaintext pertaining to a ciphertext without knowing the key. Such a view is permitted by the Generic Model and the Random Oracle Model which provide non-standard computational models in which one may reason about the computational cost of breaking a cryptographic scheme. Using the proof assistant Coq, we provide a machine-checked account of the Generic Model and the Random Oracle Mode

    Enceladus: Cassini observations and implications for the search for life

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    Aims. The recent Cassini discovery of water vapor plumes ejected from the south pole of the Saturnian satellite, Enceladus, presents a unique window of opportunity for the detection of extant life in our solar system. Methods. With its significant geothermal energy source propelling these plumes >80 km from the surface of the moon and the ensuing large temperature gradient with the surrounding environment, it is possible to have the weathering of rocks by liquid water at the rock/liquid interface. For the cases of the putatively detected salt-water oceans beneath the ice crusts of Europa and Callisto, an isolated subsurface ocean without photosynthesis or contact with an oxidizing atmosphere will approach chemical equilibrium and annihilate any ecosystems dependent on redox gradients unless there is a substantial alternative energy source. This thermodynamic tendency imposes severe constraints on any biota that is based on chemical energy. On Enceladus, the weathering of rocks by liquid water and any concomitant radioactive emissions are possible incipient conditions for life. If there is CO, CO2 and NH3 present in the spectra obtained from the plume, then this is possible evidence that amino acids could be formed at the rock/liquid interface of Enceladus. The combination of a hydrological cycle, chemical redox gradient and geochemical cycle give favorable conditions for life. Results. We discuss the search for signatures of these species and organics in the Cassini UVIS spectra of the plume and implications for the possible detection of life

    Roles of binding elements, FOXL2 domains, and interactions with cJUN and SMADs in regulation of FSHβ.

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    We previously identified FOXL2 as a critical component in FSHβ gene transcription. Here, we show that mice deficient in FOXL2 have lower levels of gonadotropin gene expression and fewer LH- and FSH-containing cells, but the same level of other pituitary hormones compared to wild-type littermates, highlighting a role of FOXL2 in the pituitary gonadotrope. Further, we investigate the function of FOXL2 in the gonadotrope cell and determine which domains of the FOXL2 protein are necessary for induction of FSHβ transcription. There is a stronger induction of FSHβ reporter transcription by truncated FOXL2 proteins, but no induction with the mutant lacking the forkhead domain. Specifically, FOXL2 plays a role in activin induction of FSHβ, functioning in concert with activin-induced SMAD proteins. Activin acts through multiple promoter elements to induce FSHβ expression, some of which bind FOXL2. Each of these FOXL2-binding sites is either juxtaposed or overlapping with a SMAD-binding element. We determined that FOXL2 and SMAD4 proteins form a higher order complex on the most proximal FOXL2 site. Surprisingly, two other sites important for activin induction bind neither SMADs nor FOXL2, suggesting additional factors at work. Furthermore, we show that FOXL2 plays a role in synergistic induction of FSHβ by GnRH and activin through interactions with the cJUN component of the AP1 complex that is necessary for GnRH responsiveness. Collectively, our results demonstrate the necessity of FOXL2 for proper FSH production in mice and implicate FOXL2 in integration of transcription factors at the level of the FSHβ promoter

    A physical control interface with proprioceptive feedback and multiple degrees of freedom

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    The use of the drug thalidomide by pregnant mothers in Britain resulted in a variety of deformities including the birth of children having no arms. Such children were provided with powered artificial arms with up to five degrees of freedom simultaneously controlled in real time by shoulder movement. The physiological sense of proprioception was extended from the user into the device, reducing the need for visual feedback and conscious control. With the banning of thalidomide, this technique fell into disuse but it is now being re-examined as a control mechanism for other artificial limbs and it may have other medical applications to allow patients to control formerly paralyzed limbs moved by electrical stimulation. It may also have commercial applications in robotic manipulation or physical interaction with virtual environments. To allow it to be investigated further, the original pneumatic control system has recently been converted to an electrical analogue to allow interfacing to electronic and computer-assisted systems. A harness incorporates force-sensitive resistors and linear potentiomenters for sensing position and force at the interface with the skin, and miniature electric motors and lead screws for feeding back to the user the position of the robotic arm and the forces applied to it. In the present system, control is applied to four degrees of freedom using elevation/depression and protraction/reaction of each shoulder so that each collar bone emulates a joystick. However, both electrical and mechanical components have been built in modular form to allow rapid replication and testing of a variety of force and position control strategies

    Experience of Using Simulation Technology and Analytics During the Ebola Crisis to Empower Frontline Health Workers and Improve the Integrity of Public Health Systems

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    Humanitarian Technology: Science, Systems and Global Impact 2016, HumTech2016 keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytics keywords: Analytic

    Attacking Group Protocols by Refuting Incorrect Inductive Conjectures

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    Automated tools for finding attacks on flawed security protocols often fail to deal adequately with group protocols. This is because the abstractions made to improve performance on fixed 2 or 3 party protocols either preclude the modelling of group protocols all together, or permit modelling only in a fixed scenario, which can prevent attacks from being discovered. This paper describes Coral, a tool for finding counterexamples to incorrect inductive conjectures, which we have used to model protocols for both group key agreement and group key management, without any restrictions on the scenario. We will show how we used Coral to discover 6 previously unknown attacks on 3 group protocols

    Discrete Model of Ideological Struggle Accounting for Migration

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    A discrete in time model of ideological competition is formulated taking into account population migration. The model is based on interactions between global populations of non-believers and followers of different ideologies. The complex dynamics of the attracting manifolds is investigated. Conversion from one ideology to another by means of (i) mass media influence and (ii) interpersonal relations is considered. Moreover a different birth rate is assumed for different ideologies, the rate being assumed to be positive for the reference population, made of initially non-believers. Ideological competition can happen in one or several regions in space. In the latter case, migration of non-believers and adepts is allowed; this leads to an enrichment of the ideological dynamics. Finally, the current ideological situation in the Arab countries and China is commented upon from the point of view of the presently developed mathematical model. The massive forced conversion by Ottoman Turks in the Balkans is briefly discussed.Comment: 24 pages, with 5 figures and 52 refs.; prepared for a Special issue of Advances in Complex System

    VPLanet: The Virtual Planet Simulator

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    We describe a software package called VPLanet that simulates fundamental aspects of planetary system evolution over Gyr timescales, with a focus on investigating habitable worlds. In this initial release, eleven physics modules are included that model internal, atmospheric, rotational, orbital, stellar, and galactic processes. Many of these modules can be coupled simultaneously to simulate the evolution of terrestrial planets, gaseous planets, and stars. The code is validated by reproducing a selection of observations and past results. VPLanet is written in C and designed so that the user can choose the physics modules to apply to an individual object at runtime without recompiling, i.e., a single executable can simulate the diverse phenomena that are relevant to a wide range of planetary and stellar systems. This feature is enabled by matrices and vectors of function pointers that are dynamically allocated and populated based on user input. The speed and modularity of VPLanet enables large parameter sweeps and the versatility to add/remove physical phenomena to assess their importance. VPLanet is publicly available from a repository that contains extensive documentation, numerous examples, Python scripts for plotting and data management, and infrastructure for community input and future development.Comment: 75 pages, 34 figures, 10 tables, accepted to the Proceedings of the Astronomical Society of the Pacific. Source code, documentation, and examples available at https://github.com/VirtualPlanetaryLaboratory/vplane

    Gender Discrimination and Ageist Perceptions:

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    This report presents the findings from an ESF Objective 3 Project “Gender Discrimination and Ageist Perceptions”. The project is based at Liverpool John Moores University, in the Faculty of Education, Community and Leisure. Context Older age groups have consistently been undervalued and often discarded by employers, for being too old. They are now being encouraged to re-enter the workplace through schemes such as New Deal 50 plus and Pathways to Work, or to take up volunteering through the promotion of “Active Citizenship”. In addition, the concept of lifelong learning has been advocated by New Labour as an attempt to move away from the traditional notions of education, towards a vision in which education forms a lifelong process, which can be accessed at any time during the life course. Yet, despite the lower labour market attachment of the over fifties, people of this age group in higher education account for only around 1% of the student population. There is a variety of ways in which people approaching their mid life would, on the face of it, be able to access work, education or volunteering experiences. However, past research and current data suggest that there appear to be barriers to the take up of such opportunities. The Aim This study set out to investigate the experiences and perceptions of women and men aged over fifty and the organisations which impact upon their lives, in an effort to understand more fully the potential barriers this age group may face when accessing opportunities, employment, training or education. Background Gender disadvantages in the world of work have been well documented. Increasingly, age perceptions are thought to be a factor in older peoples’ access to employment and training opportunities. Data shows that the and only a tenth of those are on employer and government training programmes (TAEN, 2006). The demographic change, with more people living longer, coupled with low birth rates, is creating an expanding older population and fuelling oncerns over labour shortages. There is, therefore, an economic imperative to draw workers back into work via a variety of avenues. Despite over 70% of women now participating in the workforce, the employment patterns of men and women show that only 21% of women over 40 are in full-time employment, compared with 46% of men. Women have not had the same opportunities as men to build a career or to earn the equivalent of males due to their child-rearing and caring responsibilities, with many continuing to be concentrated in traditionally low paid sectors. The pay gap between some men and women is widening,despite the long history of legislation on equal pay. To compound the situation, older women are now said to be facing a double jeopardy of age and gender discrimination. Tackling discrimination has been at the heart of equal opportunities legislation designed to prevent unequal treatment regardless of gender,race and disability. The Sex Discrimination Act (SDA) and Equal Pay Act (EPA) both came into force in 1975. Each Act attempted to redress the inequalities suffered by (mainly) women in terms of employment and education. The Bill to establish the Commission for Equality and Human Rights (CEHR) received Royal Assent on 16th February 2006 and will provide an integrated approach to all forms of discrimination including that on the grounds of age
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