Quantification and localization of the liquid zone of partially remelted M2 tool steel using X-ray microtomography and scanning electron microscopy

The authors warmly thank Luc Morhain and Marc Wary (Arts et Métiers ParisTech CER Metz) for their technical support.Thixoforming of steels poses challenges due to the high temperatures involved and the lack of understanding of thermomechanical behavior. The volume fractions of the liquid and solid phases in the semi-solid state are the most important parameters for such a form-ing process, as they affect the viscosity and hence the flow behavior of the material. Two-dimensional observations might not always be sufficient, as the size distribution and the connectivity of phases cannot be obtained from associated measurements, which can only be determined by three-dimensional (3-D) investigation. This paper presents the first application of high-energy X-ray microtomography to the microstructure of steel in the semi-solid state. The microstructure of M2 high-speed tool steel was studied in both as-received and heated-and-quenched states. From the reconstructed images, 3-D information could be obtained and was compared with scanning elec-tron microscopy and energy dispersive spectrometry observations. The volume fraction and the location of liquid phase in the semi-solid state were determined in particular, and the continuous solid skeleton was investigated

Stochastic and deterministic models for age-structured populations with genetically variable traits

Understanding how stochastic and non-linear deterministic processes interact is a major challenge in population dynamics theory. After a short review, we introduce a stochastic individual-centered particle model to describe the evolution in continuous time of a population with (continuous) age and trait structures. The individuals reproduce asexually, age, interact and die. The 'trait' is an individual heritable property (d-dimensional vector) that may influence birth and death rates and interactions between individuals, and vary by mutation. In a large population limit, the random process converges to the solution of a Gurtin-McCamy type PDE. We show that the random model has a long time behavior that differs from its deterministic limit. However, the results on the limiting PDE and large deviation techniques \textit{\`a la} Freidlin-Wentzell provide estimates of the extinction time and a better understanding of the long time behavior of the stochastic process. This has applications to the theory of adaptive dynamics used in evolutionary biology. We present simulations for two biological problems involving life-history trait evolution when body size is plastic and individual growth is taken into account.Comment: This work is a proceeding of the CANUM 2008 conferenc

Evaluation of an offshore disposal site in then Loire estuary through field monitoring and 3D numerical modelling

Water Qualit

Recent Advances in the Management of Diabetes Mellitus

peer reviewedThe recent epidemic of type 2 diabetes and the recognition that achieving specific glycemic goals can reduce morbidity have made the effective treatment of hyperglycemia a priority. The new therapeutic agents and the development of algorithms for the adjustment of therapy might contribute to an improved management of the disease. Moreover, type 2 diabetes is frequently associated with other co-morbidities (obesity, hypertension, dyslipidaemia, prothrombotic state). The appropriate management of patients with type 2 diabetes requires a global approach targeting each risk factor in order to reduce cardiovascular morbidity and mortality. This challenge represents a major public health issue. In type 1 diabetes patients, intensive therapy such as in the Diabetes Control and Complications Trial (DCCT) has been shown to obtain long-term beneficial effects on the reduction of the risk of progressive retinopathy, neuropathy and nephropathy and of the risk of cardiovascular disease. This benefit reinforces the original DCCT message that intensive therapy should be implemented as early as possible in people with type 1 diabetes. The recent development of new insulin analogues and the technical improvements of portable insulin pumps might contribute to obtain such a better metabolic control.RÉSUMÉ : L’augmentation d’incidence, quasi épidémique, du diabète de type 2 et la démonstration que l’obtention de bons taux glycémiques permettait de réduire la morbidité ont fait du traitement de l’hyperglycémie une priorité. Le développement de nouvelles classes thérapeutiques et la mise au point d’algorithmes de traitement contribuent à améliorer cette prise en charge. De plus, le diabète de type 2 est souvent associé à d’autres comorbidités (obésité, hypertension artérielle, dyslipidémies, état pro-thrombotique). La prise en charge du patient diabétique de type 2 requiert une approche globale visant à corriger chaque facteur de risque, ce qui permet de réduire substantiellement la mortalité cardio-vasculaire. Cette stratégie doit être considérée comme un objectif majeur de santé publique. Chez le sujet diabétique de type 1, un traitement intensif, comme celui imposé dans l’étude DCCT, permet d’obtenir une réduction prolongée du risque de survenue et de progression de la rétinopathie, de la neuropathie, de la néphropathie ainsi que du risque de maladie cardio-vasculaire. Ce bénéfice persistant renforce le message initial de l’étude DCCT qui avait démontré que le traitement intensif du diabète de type 1 devait être instauré dès le début de la maladie. Le développement récent des analogues de l’insuline et les améliorations techniques des pompes à insuline portables pourraient contribuer à atteindre un meilleur contrôle métabolique

Cognitive ability experiment with photosensitive organic molecular thin films

We present an optical experiment which permits to evaluate the information exchange necessary to self-induce cooperatively a well-organized pattern in a randomly activated molecular assembly. A low-power coherent beam carrying polarization and wavelength information is used to organize a surface relief grating on a photochromic polymer thin film which is photo-activated by a powerful incoherent beam. We demonstrate experimentally that less than 1% of the molecules possessing information cooperatively transmit it to the entire photo-activated polymer film.Comment: 16 pages, 4 figure

Role for T-type Ca2+Ca 2+ channels in sleep waves

International audienceSince their discovery more than 30 years ago, low-threshold T-type $Ca 2+$ channels (T channels) have been suggested to play a key role in many EEG waves of non-REM sleep, which has remained exclusively linked to the ability of these channels to generate low-threshold $Ca 2+$ potentials and associated high-frequency bursts of action potentials. Our present understanding of the biophysics and physiology of T channels, however, highlights a much more diverse and complex picture of the pivotal contributions that they make to different sleep rhythms. In particular, recent experimental evidence has conclusively demonstrated the essential contribution of thalamic T channels to the expression of slow waves of natural sleep and the key role played by $Ca 2+$ entry through these channels in the activation or modulation of other voltage-dependent channels that are important for the generation of both slow waves and sleep spindles. However, the precise contribution to sleep rhythms of T channels in cortical neurons and other sleep-controlling neuronal networks remains unknown, and a full understanding of the cellular and network mechanisms of sleep delta waves is still lacking