Toward a validation process for model based safety analysis

International audienceToday, Model Based Safety Analysis processes become more and more widespread to achieve the safety analysis of a system. However and at our knowledge, there is no formal testing approach to ensure that the formal model is compliant with the real system. In the paper, we choose to study AltaRica model. We present a general process to well construct and validate an AltaRica formal model. The focus is made on this validation phase, i.e. verifying the compliance between the model and the real system. For it, the proposed process recommends to build a specification for the AltaRica model. Then, the validation process is transformed to a classical verification problem between an implementation and a specification. We present the first phase of a method to verify the compliance between the model and the specification

Exact and explicit probability densities for one-sided Levy stable distributions

We study functions g_{\alpha}(x) which are one-sided, heavy-tailed Levy stable probability distributions of index \alpha, 0< \alpha <1, of fundamental importance in random systems, for anomalous diffusion and fractional kinetics. We furnish exact and explicit expression for g_{\alpha}(x), 0 \leq x < \infty, satisfying \int_{0}^{\infty} exp(-p x) g_{\alpha}(x) dx = exp(-p^{\alpha}), p>0, for all \alpha = l/k < 1, with k and l positive integers. We reproduce all the known results given by k\leq 4 and present many new exact solutions for k > 4, all expressed in terms of known functions. This will allow a 'fine-tuning' of \alpha in order to adapt g_{\alpha}(x) to a given experimental situation.Comment: 4 pages, 3 figures and 1 tabl

Exceptional Laguerre and Jacobi polynomials and the corresponding potentials through Darboux-Crum Transformations

Simple derivation is presented of the four families of infinitely many shape invariant Hamiltonians corresponding to the exceptional Laguerre and Jacobi polynomials. Darboux-Crum transformations are applied to connect the well-known shape invariant Hamiltonians of the radial oscillator and the Darboux-P\"oschl-Teller potential to the shape invariant potentials of Odake-Sasaki. Dutta and Roy derived the two lowest members of the exceptional Laguerre polynomials by this method. The method is expanded to its full generality and many other ramifications, including the aspects of generalised Bochner problem and the bispectral property of the exceptional orthogonal polynomials, are discussed.Comment: LaTeX2e with amsmath, amssymb, amscd 26 pages, no figure

Madagascar's grasses and grasslands:anthropogenic or natural?

Grasses, by their high productivity even under very low pCO2, their ability to survive repeated burning and to tolerate long dry seasons, have transformed the terrestrial biomes in the Neogene and Quaternary. The expansion of grasslands at the cost of biodiverse forest biomes in Madagascar is often postulated as a consequence of the Holocene settlement of the island by humans. However, we show that the Malagasy grass flora has many indications of being ancient with a long local evolutionary history, much predating the Holocene arrival of humans. First, the level of endemism in the Madagascar grass flora is well above the global average for large islands. Second, a survey of many of the more diverse areas indicates that there is a very high spatial and ecological turnover in the grass flora, indicating a high degree of niche specialization. We also find some evidence that there are both recently disturbed and natural stable grasslands: phylogenetic community assembly indicates that recently severely disturbed grasslands are phylogenetically clustered, whereas more undisturbed grasslands tend to be phylogenetically more evenly distributed. From this evidence, it is likely that grass communities existed in Madagascar long before human arrival and so were determined by climate, natural grazing and other natural factors. Humans introduced zebu cattle farming and increased fire frequency, and may have triggered an expansion of the grasslands. Grasses probably played the same role in the modification of the Malagasy environments as elsewhere in the tropics

Dry-season length and runoff control annual variability in stream DOC dynamics in a small, shallowgroundwater-dominated agricultural watershed

International audienceAs a phenomenon integrating climate conditions and hydrological control of the connection betweenstreams and terrestrial dissolved organic carbon (DOC) sources, groundwater dynamics controlpatterns of stream DOC characteristics (concentrations and fluxes). Influence of intra-annualvariations in groundwater level, discharge and climatic factors on DOC concentrations and fluxeswere assessed over 13 years at the headwater watershed of Kervidy-Naizin (5 km²) in westernFrance. Four seasonal periods were delineated within each year according to groundwaterfluctuations (A: rewetting, B: high flow, C: recession, and D: drought). Annual and seasonal baseflow vs stormflow DOC concentrations were defined based on daily hydrograph readings. Highinter-annual variability of annual DOC fluxes (5.4-39.5 kg.ha-1.yr-1) indicates that several years ofdata are required to encompass variations in water flux to evaluate the actual DOC export capacity ofa watershed. Inter-annual variability of mean annual DOC concentrations was much lower (4.9-7.5mg C.l-1), with concentrations decreasing within each year from ca. 9.2 mg C.l-1 in A to ca. 3.0 mgC.l-1 in C. This indicates an intra-annual pattern of stream DOC concentrations controlled by DOCsource characteristics and groundwater dynamics very similar across years. Partial least squareregressions combined with multiple linear regressions showed that the dry season characteristics(length and drawdown) determine the mean annual DOC concentration while annual runoffdetermines the annual flux. Antagonistic mechanisms of production-accumulation and dilution depletioncombined with an unlimited DOC supply from riparian wetland soils can mitigate theresponse of stream concentrations to global changes and climatic variations

Ripple edge engineering of graphene nanoribbons

It is now possible to produce graphene nanoribbons (GNRs) with atomically defined widths. GNRs offer many opportunities for electronic devices and composites, if it is possible to establish the link between edge structure and functionalisation, and resultant GNR properties. Switching hydrogen edge termination to larger more complex functional groups such as hydroxyls or thiols induces strain at the ribbon edge. However we show that this strain is then relieved via the formation of static out-of-plane ripples. The resultant ribbons have a significantly reduced Young's Modulus which varies as a function of ribbon width, modified band gaps, as well as heterogeneous chemical reactivity along the edge. Rather than being the exception, such static edge ripples are likely on the majority of functionalized graphene ribbon edges.Comment: Supplementary Materials availabl

SCRIB expression is deregulated in human prostate cancer, and its deficiency in mice promotes prostate neoplasia

Loss of cellular polarity is a hallmark of epithelial cancers, raising the possibility that regulators of polarity have a role in suppressing tumorigenesis. The Scribble complex is one of at least three interacting protein complexes that have a critical role in establishing and maintaining epithelial polarity. In human colorectal, breast, and endometrial cancers, expression of the Scribble complex member SCRIB is often mislocalized and deregulated. Here, we report that Scrib is indispensable for prostate homeostasis in mice. Scrib heterozygosity initiated prostate hyperplasia, while targeted biallelic Scrib loss predisposed mice to prostate intraepithelial neoplasia. Mechanistically, Scrib was shown to negatively regulate the MAPK cascade to suppress tumorigenesis. Further analysis revealed that prostate-specific loss of Scrib in mice combined with expression of an oncogenic Kras mutation promoted the progression of prostate cancer that recapitulated the human disease. The clinical significance of the work in mice was highlighted by our observation that SCRIB deregulation strongly correlated with poor survival in human prostate cancer. These data suggest that the polarity network could provide a new avenue for therapeutic intervention

Associations of health-related quality of life, fear of falling and objective measures of physical function with bone health in postmenopausal women with low bone mass

Health-related quality of life (HRQoL) and physical function deteriorate with age and may adversely impact bone health in older adults. We determined associations of objective measures of physical function and HRQoL with bone health in postmenopausal women with low areal bone mineral density (aBMD). Fifty postmenopausal women (64.4 ± 7.7 years old, mean ± standard deviation) with low spine, hip or femoral neck aBMD (T- or Z-score < −1.0) on dual-energy X-ray absorptiometry (DXA) participated. Femoral surface BMD, trabecular, integral and cortical volumetric BMD (vBMD) measurements were obtained using 3D-SHAPER software on DXA. Distal tibial vBMD and microarchitecture were assessed using high-resolution peripheral quantitative computed tomography (HRpQCT). Participants completed self-administered EuroQol-5D (EQ-5D) and modified falls efficacy scale (MFES) questionnaires, and physical function assessments. Stair climb power was positively associated with bone parameters at the hip, femoral neck, and distal tibia (all p < 0.05) in multivariable linear regression. EQ-5D demonstrated no significant associations with bone parameters and MFES was positively associated only with distal tibial cortical vBMD and cortical von Mises stress (both p < 0.05). Objective measures of physical function, particularly muscle power, are more consistently associated with bone parameters compared with self-administered HRQoL questionnaires

Stable hydrogenated graphene edge types: Normal and reconstructed Klein edges

Hydrogenated graphene edges are assumed to be either armchair, zigzag or a combination of the two. We show that the zigzag is not the most stable fully hydrogenated structure along the direction. Instead hydrogenated Klein and reconstructed Klein based edges are found to be energetically more favourable, with stabilities approaching that of armchair edges. These new structures "unify" graphene edge topology, the most stable flat hydrogenated graphene edges always consisting of pairwise bonded C2H4 edge groups, irrespective the edge orientation. When edge rippling is included, CH3 edge groups are most stable. These new fundamental hydrogen terminated edges have important implications for graphene edge imaging and spectroscopy, as well as mechanisms for graphene growth, nanotube cutting, and nanoribbon formation and behaviour.Fundação para a Ciência e a Tecnologia (FCT