9,142 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

    Automating Security Analysis: Symbolic Equivalence of Constraint Systems

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    We consider security properties of cryptographic protocols, that are either trace properties (such as confidentiality or authenticity) or equivalence properties (such as anonymity or strong secrecy). Infinite sets of possible traces are symbolically represented using deducibility constraints. We give a new algorithm that decides the trace equivalence for the traces that are represented using such constraints, in the case of signatures, symmetric and asymmetric encryptions. Our algorithm is implemented and performs well on typical benchmarks. This is the first implemented algorithm, deciding symbolic trace equivalence

    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

    The nuclear spectrum of the radio galaxy NGC 5128 (Centaurus A)

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    We present near-infrared spectra of the nuclear disk in the nearby radio galaxy NGC 5128 (Centaurus A). On the basis of the observed strengths of the [S III] 0.9532um and [Fe II] 1.2567um lines, we classify NGC 5128 as a LINER. Modeling of the strengths of these and additional lines suggests that the nuclear region is powered by shocks rather than photoionization.Comment: 12 pages including 2 figures, accepted by ApJ Letter

    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

    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

    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

    Surface Transitions for Confined Associating Mixtures

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    Thin films of binary mixtures that interact through isotropic forces and directionally specific "hydrogen bonding" are considered through Monte Carlo simulations. We show, in good agreement with experiment, that the single phase of these mixtures can be stabilized or destabilized on confinement. These results resolve a long standing controversy, since previous theories suggest that confinement only stabilizes the single phase of fluid mixtures.Comment: LaTeX document, documentstyle[aps,preprint]{revtex}, psfig.sty, bibtex, 13 pages, 4 figure

    A phase I/II study of irinotecan when added to 5-fluorouracil and leucovorin and pelvic radiation in locally advanced rectal cancer: a Colorectal Clinical Oncology Group Study

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    The objective of this study was to evaluate the maximum tolerated dose (MTD) and recommended dose of irinotecan administered as a 5-day schedule synchronously with 5-fluorouracil (5FU), leucovorin (LV) and preoperative pelvic radiation (45 Gy) for primary borderline/unresectable, locally advanced rectal cancer. The study used escalating doses of intravenous irinotecan (6, 8, 10, 12, 14, 16, 18, and 20 mg m−2) administered on days 1–5 and 29–33 followed by low dose LV (20 mg m−2) and 5FU (350 mg m−2 over 1 h) in sequential cohorts. Preoperative pelvic radiotherapy using a three- or four-field technique and megavoltage photons comprised 45 Gy given in 25 fractions, 1.8 Gy per fraction. Surgery in the form of mesorectal excision was performed 6–10 weeks later. Histopathological examination of the resected specimen was performed according to techniques of Quirke, and compared with clinical staging. A distance of 1 mm or less between the peripheral extent of the tumour and the radial resection margin defined an involved circumferential resection margin (CRM). The MTD was determined as the dose causing more than a third of patients to have a dose-limiting toxicity (DLT) defined as specific grade 3 or 4 toxicities. Once the MTD was reached, a further 14 patients were treated at the dose level below the MTD. In total, 57 patients received irinotecan at the eight dose levels. The final cohort reached DLT after only four patients had been enrolled. The median age was 62 years (range 26–75), 37 male and 20 female subjects. The MTD of irinotecan in this schedule was 20 mg m−2 when three out of four patients experienced DLT. Dose limiting grade 3 or 4 diarrhoea was reported in seven out of 57 patients, three at the 20 mg m−2 dose level. Serious haematological toxicity (grade 3) was minimal and reported in only three patients; one grade 3 neutropaenia, one grade 4 neutropaenia and one grade 3 febrile neutropaenia and anaemia. Compliance was good with 93 and 89% of patients completing radiotherapy and chemotherapy, respectively. The remaining patients had only minor deviations from protocol therapy. Eight patients did not proceed to surgery, in six cases because they remained unresectable or had developed metastatic disease, one patient was unfit for surgery and one died as a result of complications from radiotherapy. Forty-nine patients underwent a potentially curative surgical resection. Histopathological examination of the resected specimen demonstrated pCR 12 out of 49 (24%) and 12 out of 57 (21%) overall. A histologically confirmed clear circumferential resection margin (CRM) was achieved in 39 out of 49 (80%) of those resected, and 39 out of 57 (68%) overall. In conclusion, MTD with this scheduled regimen of irinotecan is 20 mg m−2 (days 1–5 and 29–33). The acceptable toxicity and compliance at 18 mg m−2 recommend testing this dose in future phase III studies. The tumour downstaging and complete resection rates (negative CRM) are encouragingly high for this very locally advanced group
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