208 research outputs found
Boundary value for a nonlinear transport equation emerging from a stochastic coagulation-fragmentation type model
We investigate the connection between two classical models of phase
transition phenomena, the (discrete size) stochastic Becker-D\"oring, a
continous time Markov chain model, and the (continuous size) deterministic
Lifshitz-Slyozov model, a nonlinear transport partial differential equation.
For general coefficients and initial data, we introduce a scaling parameter and
prove that the empirical measure associated to the stochastic Becker-D\"oring
system converges in law to the weak solution of the Lifshitz-Slyozov equation
when the parameter goes to 0. Contrary to previous studies, we use a weak
topology that includes the boundary of the state space (\ie\ the size )
allowing us to rigorously derive a boundary value for the Lifshitz-Slyozov
model in the case of incoming characteristics. The condition reads where is the volume distribution
function, solution of the Lifshitz-Slyozov equation, and the
aggregation and fragmentation rates, the concentration of free particles
and a nucleation constant emerging from the microscopic model. It is
the main novelty of this work and it answers to a question that has been
conjectured or suggested by both mathematicians and physicists. We emphasize
that this boundary value depends on a particular scaling (as opposed to a
modeling choice) and is the result of a separation of time scale and an
averaging of fast (fluctuating) variables.Comment: 42 pages, 3 figures, video on supplementary materials at
http://yvinec.perso.math.cnrs.fr/video.htm
Non-conservative evolution in Algols: where is the matter?
There is gathering indirect evidence suggesting non-conservative evolutions
in Algols. However, the systemic mass-loss rate is poorly constrained by
observations and generally set as a free parameter in binary-star evolution
simulations. Moreover, systemic mass loss may lead to observational signatures
that are still to be found. We investigate the impact of the outflowing gas and
the possible presence of dust grains on the spectral energy distribution (SED).
We used the 1D plasma code Cloudy and compared the results with the 3D
Monte-Carlo radiative transfer code Skirt for dusty simulations. The
circumbinary mass-distribution and binary parameters are computed with
state-of-the-art binary calculations done with the Binstar evolution code. The
outflowing material reduces the continuum flux-level of the stellar SED in the
optical and UV. Due to the time-dependence of this effect, it may help to
distinguish between different ejection mechanisms. Dust, if present, leads to
observable infrared excesses even with low dust-to-gas ratios and traces the
cold material at large distances from the star. By searching for such dust
emission in the WISE catalogue, we found a small number of Algols showing
infrared excesses, among which the two rather surprising objects SX Aur and CZ
Vel. We find that some binary B[e] stars show the same strong Balmer continuum
as we predict with our models. However, direct evidence of systemic mass loss
is probably not observable in genuine Algols, since these systems no longer
eject mass through the hotspot mechanism. Furthermore, owing to its high
velocity, the outflowing material dissipates in a few hundred years. If hot
enough, the hotspot may produce highly ionised species such as SiIV and
observable characteristics that are typical of W Ser systems.Comment: Accepted for piblications in A&A; 21 pages, 19 figure
DRELIO : Un drone hélicoptÚre pour le suivi des zones littorales
International audienceLa connaissance du littoral, sa protection, son amĂ©nagement nĂ©cessitent un suivi des changements qui s'y produisent. Toutefois, en France, devant l'Ă©tendue des façades maritimes Ă couvrir, les techniques de mesures in situ ne peuvent ĂȘtre appliquĂ©es de façon systĂ©matique. Dans ce cas, les techniques de tĂ©lĂ©dĂ©tection spatiale ou aĂ©rienne sont des approches complĂ©mentaires. A partir de ces plates-formes, des images stĂ©rĂ©oscopiques multi-temporelles sont, aprĂšs une sĂ©rie de traitements photogrammĂ©triques appropriĂ©s, directement exploitables sous formes d'orthophotographies et de ModĂšles NumĂ©riques de Terrain (MNT). Ce type de produits permet notamment la quantification des changements morphosĂ©dimentaires Ă l'interface Terre-Mer (transport transversal et longitudinal de sĂ©diments, Ă©rosion,...). Actuellement, la rĂ©solution spatiale des MNT gĂ©nĂ©rĂ©s Ă partir d'images aĂ©riennes ou satellitaires (<50 cm) est insuffisante pour la plupart des applications sur la frange littorale. En outre, dans le cas d'interventions consĂ©cutives Ă un Ă©vĂ©nement extrĂȘme (tempĂȘte, raz de marĂ©e, pollution...), ces systĂšmes manquent de souplesse (trajectoires prĂ©dĂ©finies, contraintes d'altitude, de vitesse, coĂ»t de mise en oeuvre...) L'utilisation de drones constitue donc une alternative intĂ©ressante pour des suivis de prĂ©cision ou des interventions rapides
Blue light absorption enhancement based on vertically channelling modes in nano-holes arrays
We investigate the specific optical regime occurring at short wavelengths, in
the high absorption regime, in silicon thin-films patterned by periodically
arranged nano-holes. Near-field scanning optical microscopy indicates that the
incoming light is coupled to vertically channelling modes. Optical modelling
and simulations show that the light, travelling inside the low-index regions,
is absorbed at the direct vicinity of the nano-holes sidewalls. This
channelling regime should be taken into account for light management in
optoelectronic devices
Direct sediment transfer from land to deep-sea: Insights into shallow multibeam bathymetry at La RĂ©union Island
International audienceSubmarine canyon heads are key areas for understanding the triggering factors of gravity currents responsible for the transfer of detrital sediment to the deep basins. This contribution offers a detailed picture of canyon heads off La RĂ©union Island, with high-resolution multibeam bathymetry in the water depth range of 4-220 m. The present feeding of the Cilaos turbidite system, one of the largest modern volcaniclastic systems in the world, is deduced from morphological and sedimentological interpretations of newly acquired data. The study highlights small-scale sedimentary features indicating hydrodynamic and sedimentary processes. A direct connexion between the Saint-Etienne river mouth and submarine canyons is evidenced by the complete incision of the shelf and the presence of canyon heads connected to the modern deltaic bar. This direct connection, supplied by river torrential floods (cyclonic floods every two or three years), suggests the continuity of high-density fluvial flows to submarine gravity flows, forming hyperpycnal flows in the canyon. The initiation of secondary submarine gravity flows by storm waves (large austral waves and cyclonic waves) is also proposed for submarine canyons with large canyon heads developed in the surf zone from a sandy coastal bar. Bedforms in active canyon axis are considered as an indicator of the frequent activity of high-density turbidity currents. Moreover, a morphological record of last glacial and deglacial sea level variations is preserved, and particularly the Last Glacial Maximum sea level with the presence of small vertical cliffs, observed in this bathymetric data, which likely corresponds to a paleo-shoreline or paleo-reefs
Rethinking business models for innovation
One of the major challenges confronted by those in charge of technological innovation involves anticipating the value creation model sufficiently early on,in a highly uncertain context both as far as the technology itself is concerned and the potential market. Today, in many industrial sectors, the innovation boundaries have moved towards projects that are more and more exploratory and fuzzy. The simple optimisation of linear processes of the "stage-gate" type is no longer sufficient to build sustainable competitive advantages. The notion of Business Models, when applied to innovation, enables us to describe how a company creates value through innovation, generally within a business ecosystem, and how the value will be distributed between the actors involved. The authors of this book believe that the notions of Business Modelling and value creation are key to all the dimensions of successful innovation, whether technology, marketing, organisational or economically based. Rethinking Business Models for Innovation: this title describes the relationship between thinking, modelling, and also field-testing. The book is based on a series of nine recent cases of innovation involving company managers, often assisted by researchers (the co-authors of each chapter), and how they built and formalised their Business Models and then tested their strategies. After having discovered the variety of the cases, the reader will understand that every innovation situation generates specific questions about Business Models. However, we feel that we can identify three key issues that arise, more or less, in each of these projects. The chapters in this book build on these issues: the identification of sources of value and revenue models (the notion of value creation), the position of the company in the value-network or ecosystem (the sharing of value) and finally the evolution of Business MoDdels over time (the sustainability and the competitiveness of the company). The last chapter goes over all the contributions, exploring the notion of value in the Business Model approach.business model ; innovation ; value ; entrepreneurial project
Evaluation of treatment response in adults with relapsing MOG-Ab-associated disease
Background: Myelin oligodendrocyte glycoprotein antibodies (MOG-Ab) are related to several acquired demyelinating syndromes in adults, but the therapeutic approach is currently unclear. We aimed to describe the response to different therapeutic strategies in adult patients with relapsing MOG-Ab-associated disease. Methods: This is a retrospective study conducted in France and Spain including 125 relapsing MOG-Ab patients aged â„ 18 years. First, we performed a survival analysis to investigate the relapse risk between treated and non-treated patients, performing a propensity score method based on the inverse probability of treatment weighting. Second, we assessed the annualised relapse rates (ARR), Expanded Disability Status Scale (EDSS) and visual acuity pre-treatment and on/end-treatment. Results: Median age at onset was 34.1 years (range 18.0-67.1), the female to male ratio was 1.2:1, and 96% were Caucasian. At 5 years, 84% (95% confidence interval [CI], 77.1-89.8) patients relapsed. At the last follow-up, 66 (52.8%) received maintenance therapy. Patients initiating immunosuppressants (azathioprine, mycophenolate mophetil [MMF], rituximab) were at lower risk of new relapse in comparison to non-treated patients (HR, 0.41; 95CI%, 0.20-0.82; p = 0.011). Mean ARR (standard deviation) was reduced from 1.05(1.20) to 0.43(0.79) with azathioprine (n = 11; p = 0.041), from 1.20(1.11) to 0.23(0.60) with MMF (n = 11; p = 0.033), and from 1.08(0.98) to 0.43(0.89) with rituximab (n = 26; p = 0.012). Other immunosuppressants (methotrexate/mitoxantrone/cyclophosphamide; n = 5), or multiple sclerosis disease-modifying drugs (MS-DMD; n = 9), were not associated with significantly reduced ARR. Higher rates of freedom of EDSS progression were observed with azathioprine, MMF or rituximab. Conclusion: In adults with relapsing MOG-Ab-associated disease, immunosuppressant therapy (azathioprine, MMF and rituximab) is associated with reduced risk of relapse and better disability outcomes. Such an effect was not found in the few patients treated with MS-DMD
: Lessons from entrepreneurial projects
International audienceOne of the major challenges confronted by those in charge of technological innovation involves anticipating the value creation model sufficiently early on,in a highly uncertain context both as far as the technology itself is concerned and the potential market. Today, in many industrial sectors, the innovation boundaries have moved towards projects that are more and more exploratory and fuzzy. The simple optimisation of linear processes of the "stage-gate" type is no longer sufficient to build sustainable competitive advantages. The notion of Business Models, when applied to innovation, enables us to describe how a company creates value through innovation, generally within a business ecosystem, and how the value will be distributed between the actors involved. The authors of this book believe that the notions of Business Modelling and value creation are key to all the dimensions of successful innovation, whether technology, marketing, organisational or economically based. Rethinking Business Models for Innovation: this title describes the relationship between thinking, modelling, and also field-testing. The book is based on a series of nine recent cases of innovation involving company managers, often assisted by researchers (the co-authors of each chapter), and how they built and formalised their Business Models and then tested their strategies. After having discovered the variety of the cases, the reader will understand that every innovation situation generates specific questions about Business Models. However, we feel that we can identify three key issues that arise, more or less, in each of these projects. The chapters in this book build on these issues: the identification of sources of value and revenue models (the notion of value creation), the position of the company in the value-network or ecosystem (the sharing of value) and finally the evolution of Business MoDdels over time (the sustainability and the competitiveness of the company). The last chapter goes over all the contributions, exploring the notion of value in the Business Model approach.L'innovation technologique, qu'elle soit conduite par des start-ups ou par de grandes entreprises, n'est plus une condition suffisante de la crĂ©ation de valeur. CrĂ©er de la valeur sur des marchĂ©s nouveaux nĂ©cessite le plus souvent de repenser l'organisation de l'entreprise, sa façon de faire des affaires, ses partenariats stratĂ©giques, autrement dit, son business model. Cet ouvrage se veut un guide pour les porteurs de projets d'innovation en leur fournissant des outils de comprĂ©hension et d'analyse de la dimension stratĂ©gique de leur projet. Les Ă©tudes de cas prĂ©sentĂ©es sont le fruit d'une collaboration Ă©troite entre les porteurs de chacun des projets et des chercheurs en management de l'innovation reconnus. Au travers de ces cas, trois grandes problĂ©matiques sont abordĂ©es : l'identification des sources de valeur chez les clients potentiels, la position que l'entreprise pourra prendre dans son Ă©cosystĂšme et enfin l'Ă©volution des business models dans le temps. Sur chacun des cas, le lecteur aura accĂšs Ă une comprĂ©hension fine des problĂšmes stratĂ©giques posĂ©s par l'innovation ainsi que des outils de management mis en Ćuvre pour aider Ă rĂ©flĂ©chir et Ă agir. (http://www.rethinkingbusinessmodel.net/
Interleukin-6 receptor blockade in treatment-refractory MOG-IgGâassociated disease and neuromyelitis optica spectrum disorders
BACKGROUND AND OBJECTIVES: To evaluate the long-term safety and efficacy of tocilizumab (TCZ), a humanized antiâinterleukin-6 receptor antibody in myelin oligodendrocyte glycoproteinâIgGâassociated disease (MOGAD) and neuromyelitis optica spectrum disorders (NMOSD). METHODS: Annualized relapse rate (ARR), Expanded Disability Status Scale score, MRI, autoantibody titers, pain, and adverse events were retrospectively evaluated in 57 patients with MOGAD (n = 14), aquaporin-4 (AQP4)-IgG seropositive (n = 36), and seronegative NMOSD (n = 7; 12%), switched to TCZ from previous immunotherapies, particularly rituximab. RESULTS: Patients received TCZ for 23.8 months (median; interquartile range 13.0â51.1 months), with an IV dose of 8.0 mg/kg (median; range 6â12 mg/kg) every 31.6 days (mean; range 26â44 days). For MOGAD, the median ARR decreased from 1.75 (range 0.5â5) to 0 (range 0â0.9; p = 0.0011) under TCZ. A similar effect was seen for AQP4-IgG+ (ARR reduction from 1.5 [range 0â5] to 0 [range 0â4.2]; p < 0.001) and for seronegative NMOSD (from 3.0 [range 1.0â3.0] to 0.2 [range 0â2.0]; p = 0.031). During TCZ, 60% of all patients were relapse free (79% for MOGAD, 56% for AQP4-IgG+, and 43% for seronegative NMOSD). Disability follow-up indicated stabilization. MRI inflammatory activity decreased in MOGAD (p = 0.04; for the brain) and in AQP4-IgG+ NMOSD (p < 0.001; for the spinal cord). Chronic pain was unchanged. Regarding only patients treated with TCZ for at least 12 months (n = 44), ARR reductions were confirmed, including the subgroups of MOGAD (n = 11) and AQP4-IgG+ patients (n = 28). Similarly, in the group of patients treated with TCZ for at least 12 months, 59% of them were relapse free, with 73% for MOGAD, 57% for AQP4-IgG+, and 40% for patients with seronegative NMOSD. No severe or unexpected safety signals were observed. Add-on therapy showed no advantage compared with TCZ monotherapy. DISCUSSION: This study provides Class III evidence that long-term TCZ therapy is safe and reduces relapse probability in MOGAD and AQP4-IgG+ NMOSD
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