Recherches sur la toxicité et la valeur trypanopréventive du moranylate d'éthidium. I

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Resolution of Linear Algebra for the Discrete Logarithm Problem Using GPU and Multi-core Architectures

In cryptanalysis, solving the discrete logarithm problem (DLP) is key to assessing the security of many public-key cryptosystems. The index-calculus methods, that attack the DLP in multiplicative subgroups of finite fields, require solving large sparse systems of linear equations modulo large primes. This article deals with how we can run this computation on GPU- and multi-core-based clusters, featuring InfiniBand networking. More specifically, we present the sparse linear algebra algorithms that are proposed in the literature, in particular the block Wiedemann algorithm. We discuss the parallelization of the central matrix--vector product operation from both algorithmic and practical points of view, and illustrate how our approach has contributed to the recent record-sized DLP computation in GF($2^{809}$).Comment: Euro-Par 2014 Parallel Processing, Aug 2014, Porto, Portugal. \<http://europar2014.dcc.fc.up.pt/\&gt

The meaning of having to live with cancer in old age.

Little is known about how older people with cancer experience their life situation. To increase the understanding of how illness is experienced in older people with cancer, the aim of this study was to investigate the meaning of living with cancer in old age. The hermeneutic phenomenological method as described by van Manen and referred to as 'phenomenology of praxis' was used. Ten persons (seven women and three men) aged 75 and over, who had a diagnosis of cancer and who had just completed cancer treatment, were interviewed in their own homes. The analysis revealed a life world affected to varying degrees by the cancer disease. The lived experiences across the interviews were revealed in four overarching essential themes: transition into a more or less disintegrated existence, sudden awareness of the finiteness of life, redefinition of one's role in life for good and for bad, meeting disease and illness. To provide individual support and appropriate care to older people with cancer it is important for health care professionals to identify and take care of disabilities and to support the reorientation in the disintegrated life situation. It is also important to have preparedness to meet the old person's thoughts about death. Thus, it is important to encourage the old person to describe her/his illness experience to increase understanding about what is meaningful for her/him

The Bianchi Ix (MIXMASTER) Cosmological Model is Not Integrable

The perturbation of an exact solution exhibits a movable transcendental essential singularity, thus proving the nonintegrability. Then, all possible exact particular solutions which may be written in closed form are isolated with the perturbative Painlev\'e test; this proves the inexistence of any vacuum solution other than the three known ones.Comment: 14 pages, no figure

Competitividade de um grupo de produtores da cadeia produtiva da maçã na região de Vacaria/RS.

O objetivo deste trabalho foi identificar se um grupo de produtores da cadeia produtiva da maçã na microrregião dos Campos de Cima da Serra está enfrentando dificuldades, e quais seriam elas, bem como identificar possíveis oportunidades que possam impactar na continuidade desta cadeia, através da metodologia de pesquisa exploratória, com caráter qualitativo e quantitativo quanto à abordagem metodológica, e, descritivo-explicativa quanto aos objetivos e levantamento de bibliografia. A coleta de informações foi realizada pelo método de entrevistas semiestruturadas, por meio de questionário. Os resultados indicaram que os produtores vêm enfrentando problemas de ordem produtiva e comercial, como fatores vinculados à mão de obra e clima, estabilização de preços, baixo consumo nacional da fruta, dentre outros, podendo ser amenizados pela introdução de técnicas, variedades e controle de custos. Além disso, a introdução paralela de novas culturas similares, como uva e pêra, pode aperfeiçoar o processo produtivo pela redução do custo. Palavras-chave: Maleicultura, produtividade, competitividade

Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

International audienceA comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320 keV Ar+ ions at fluencies ranging from 1 × 1012 to 2 × 1016 cm−2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013 cm−2 and second at about 1015 cm−2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials

A kilobit hidden SNFS discrete logarithm computation

We perform a special number field sieve discrete logarithm computation in a 1024-bit prime field. To our knowledge, this is the first kilobit-sized discrete logarithm computation ever reported for prime fields. This computation took a little over two months of calendar time on an academic cluster using the open-source CADO-NFS software. Our chosen prime $p$ looks random, and $p--1$ has a 160-bit prime factor, in line with recommended parameters for the Digital Signature Algorithm. However, our p has been trapdoored in such a way that the special number field sieve can be used to compute discrete logarithms in $\mathbb{F}\_p^*$ , yet detecting that p has this trapdoor seems out of reach. Twenty-five years ago, there was considerable controversy around the possibility of back-doored parameters for DSA. Our computations show that trapdoored primes are entirely feasible with current computing technology. We also describe special number field sieve discrete log computations carried out for multiple weak primes found in use in the wild. As can be expected from a trapdoor mechanism which we say is hard to detect, our research did not reveal any trapdoored prime in wide use. The only way for a user to defend against a hypothetical trapdoor of this kind is to require verifiably random primes

Protocolized Brain Oxygen Optimization in Subarachnoid Hemorrhage.

Brain tissue hypoxia (P <sub>bt</sub> O <sub>2</sub> < 20 mmHg) is common after subarachnoid hemorrhage (SAH) and associated with poor outcome. Recent data suggest that brain oxygen optimization is feasible and reduces the time spent with P <sub>bt</sub> O <sub>2</sub> < 20 mmHg from 45 to 16% in patients with severe traumatic brain injury. Here, we intended to quantify the brain tissue hypoxia burden despite implementation of a protocolized treatment approach in poor-grade SAH patients and to identify the simultaneous occurrence of pathologic values potentially amenable to treatment. We present a bi-centric observational cohort study including 100 poor-grade SAH patients admitted to two tertiary care centers who underwent multimodal brain monitoring and were managed with a P <sub>bt</sub> O <sub>2</sub> -targeted protocolized approach. P <sub>bt</sub> O <sub>2</sub> optimization (≥ 20 mmHg) included a stepwise neuro-intensive care approach, aiming to prevent low cerebral perfusion pressure (CPP), and blood hemoglobin, and to keep normocapnia, normoxemia, and normothermia. Based on routine blood gas analysis, hemoglobin, PaCO <sub>2,</sub> and PaO <sub>2</sub> data were matched to 2-h averaged data of continuous CPP, P <sub>bt</sub> O <sub>2</sub> , core temperature, and to hourly cerebral microdialysis (CMD) samples over the first 11 days. Patients had a Glasgow Coma Scale of 3 (IQR 3-4) and were 58 years old (IQR 48-66). Overall incidence of brain tissue hypoxia was 25%, which was not different between both sites despite differences in the treatment approach. During brain tissue hypoxia, episodes of CPP < 70 mmHg (27%), PaCO <sub>2</sub> < 35 mmHg (19%), PaO <sub>2</sub> < 80 mmHg (14%), Hb < 9 g/dL (11%), metabolic crisis (CMD-lactate/pyruvate ratio > 40, and CMD-glucose < 0.7 mmol/L; 7%), and temperature > 38.3 °C (4%) were common. Our results demonstrate that brain tissue hypoxia remains common despite implementation of a P <sub>bt</sub> O <sub>2</sub> -targeted therapy in poor-grade SAH patients, suggesting room for further optimization

Fluctuations in Hadronic and Nuclear Collisions

We investigate several fluctuation effects in high-energy hadronic and nuclear collisions through the analysis of different observables. To introduce fluctuations in the initial stage of collisions, we use the Interacting Gluon Model (IGM) modified by the inclusion of the impact parameter. The inelasticity and leading-particle distributions follow directly from this model. The fluctuation effects on rapidity distributions are then studied by using Landau's Hydrodynamic Model in one dimension. To investigate further the effects of the multiplicity fluctuation, we use the Longitudinal Phase-Space Model, with the multiplicity distribution calculated within the hydrodynamic model, and the initial conditions given by the IGM. Forward-backward correlation is obtained in this way.Comment: 22 pages, RevTex, 8 figures (included); Invited paper to the special issue of Foundation of Physics dedicated to Mikio Namiki's 70th. birthda