Kinetics of crystallization of FeB-based amorphous alloys studied by neutron thermo-diffractometry

Kinetics of crystallization of two amorphous alloys, Fe70Cr10B20 and Fe80Zr10B10, have been followed up by neutron thermodiffractometry experiments performed in the two axis diffractometer D20 (ILL, Grenoble). The structural changes are directly correlated with the temperature dependence of the magnetization. Fe70Cr10B20 crystallizes following a two-step process: an eutectic crystallization of alfa-Fe (bcc) and the metastable tetragonal phase (Fe0.8Cr0.2)3B followed by another eutectic transformation to the stable phase (Fe0.75Cr0.25)2B and more segregation of alfa-Fe. These tetragonal phases are magnetically anisotropic, giving rise to a large increase of the coercivity. This behaviour is similar to that of Fe80B20 alloys, with Cr atoms replacing the Fe positions in both crystalline phases. Fe80Zr10B10 shows also a two-step process in which two polymorphic transformations take place.Comment: 3 pages. Proceedings International Workshop Non-Crystalline Solids 2006, Gijon (Spain

Predicting the coefficient of permeability of soils using the Kozeny-Carman equation

Résumé: La conductivité hydraulique saturée d'un sol peut être prédite par des relations empiriques, des modèles capillaires, des modèles statistiques et des théories de rayon hydraulique. Une relation bien connue entre perméabilité et propriétés des pores fut proposée par Kozeny et modifiée par Carman. L'équation résultante est largement connue sous le nom Kozeny-Carman (KC), bien que ces auteurs n'aient jamais publié ensemble. Dans la littérature géotechnique, il existe un large consensus à l'effet que l'équation de Kozeny-Carman s'applique aux sables mais pas aux argiles. Cependant, cette opinion n'est appuyée que par une démonstration partielle. Cet article examine les fondements et la validité de l'équation KC à l'aide d'essais de perméabilité en laboratoire. Les résultats d'essais proviennent de diverses publications qui ont fourni toute l'information requise pour faire une prédiction : indice des vides et soit la surface spécifique mesurée pour les sols cohérents, soit la courbe granulométrique pour les sols pulvérulents. L'article montre comment calculer la surface spécifique d'un sol pulvérulent à partir de sa courbe granulométrique. Les résultats présentés ici indiquent qu'en général, l'équation de Kozeny-Carman prédit assez bien la conductivité hydraulique saturée de la plupart des sols. Plusieurs des divergences constatées peuvent être reliées soit à des raisons pratiques (e.g. valeur imprécise de la surface spécifique, régime permanent pas établi, échantillons non saturés, etc.) soit à des raisons théoriques (une partie de l'eau est immobile, et l'équation de prédiction est isotrope alors que la conductivité hydraulique est une propriété anisotrope). Ces aspects sont discutés dans l'article en relation avec la capacité de prédiction de l'équation de Kozeny-Carman. --------- Abstract: The saturated hydraulic conductivity of a soil can be predicted using empirical relationships, capillary models, statistical models and hydraulic radius theories. A well-known relationship between permeability and properties of pores was proposed by Kozeny and later modified by Carman. The resulting equation is largely known under the name of Kozeny-Carman, although these authors never published together. In the geotechnical literature, there is a large consensus that the Kozeny-Carman (KC) equation applies to sands but not to clays. Such opinion, however, is supported only by partial demonstration. This report evaluates the background and the validity of the KC equation with laboratory permeability tests. Considered test results were taken from publications that provided all information needed to make a prediction: void ratio, and either the measured specific surface for cohesive soils, or the gradation curve for non-cohesive soils. This report shows how to estimate the specific surface of a non-cohesive soil from its gradation curve. The results presented here show that, as a general rule, the KC equation predicts fairly well the saturated hydraulic conductivity of most soils. Many of the observed discrepancies can be related to either practical reasons (e.g. inaccurate specific surface value, steady flow not reached, unsaturated specimens, etc.) or theoretical reasons (some water is motionless, and the predictive equation is isotropic whereas hydraulic conductivity is an anisotropic property). Theses issues are discussed in relation to the predictive capabilities of the KC equation

Development of a model to predict the water retention curve using basic geotechnical properties

Résumé: La courbe de rétention d’eau (CRE) est devenue une fonction clé pour définir le comportement non saturé des sols et d'autres matériaux meubles. Dans beaucoup de cas, il peut être très utile d'avoir une évaluation de la CRE dans les pr emières phases d’un projet, lorsque peu ou pas de résultats d'essais sont disponibles. Des modèles prédictifs, basés sur les propriétés géotechniques de base, peuvent aussi être utilisés pour évaluer comment le changement des paramètres (en termes de porosité ou de granulométrie) affecte la CRE. Dans cet article, les auteurs présentent un ensemble d'équations développées pour prédire la relation entre la teneur en eau volumique θ (et le degré de saturation S r correspondant) et la succion ψ . Le modèle proposé pour la prédiction de la CRE est une version modifiée du modèle de Kovács (1981), qui fait une distinction entre la rétention d’eau due aux forces capillaires et celle par adhésion. Ce jeu d'équations est donné avec des relations complémentaires développées pour des applications spécifiques sur des matériaux granulaires et sur des sols (argileux) plastiques/c ohérents. Il est montré que le modèle constitue un moyen simple et pratique pour estimer la courbe de rétention d’eau à partir des propriétés géotechniques de base. Une discussion suit sur les capacités et les limitations du modèle. ---------- Abstract: The water retention curve (WRC) has become a key material function to define the unsaturated behavior of soils and of other particulate media. In many instances, it can be very useful to have an estimate of the WRC early in a project, when little or no test results are available. Predictive models, based on easy to obtain geotechnical prope rties, can also be employed to evaluate how changing parameters (e.g. porosity or grain size) affect the WRC. In this paper, the authors present a general set of equations developed for predicting the relationship between volumetric water content θ (and the corresponding degree of saturation S r ) and suction ψ . The proposed WRC model is a modified version of the Kovács (1981) model, which makes a distinction between water retention due to capillary forces and retention by adhesion. The complete set of equations is given together with complementary relationships developed for specific applications on granular materials and on plastic/cohesive (clayey) soils. It is shown that the model provides a simple and practical means to estimate the water retention curve from basic properties. A discussion follows on the capabilities and limitations of the model

An elastic, plastic, viscous model for slow shear of a liquid foam

We suggest a scalar model for deformation and flow of an amorphous material such as a foam or an emulsion. To describe elastic, plastic and viscous behaviours, we use three scalar variables: elastic deformation, plastic deformation rate and total deformation rate; and three material specific parameters: shear modulus, yield deformation and viscosity. We obtain equations valid for different types of deformations and flows slower than the relaxation rate towards mechanical equilibrium. In particular, they are valid both in transient or steady flow regimes, even at large elastic deformation. We discuss why viscosity can be relevant even in this slow shear (often called "quasi-static") limit. Predictions of the storage and loss moduli agree with the experimental literature, and explain with simple arguments the non-linear large amplitude trends

Simulating water flow and reactive transport in waste rock piles using stochastic properties

Résumé: Ce rapport présente une approche de modélisation numérique visant à évaluer l’écoulement d'eau et le transport géochimique dans une halde à stériles réactifs, en utilisant des propriétés stochastiques pour les matériaux sulfureux. De telles simulations peuvent servir à mieux comprendre la réponse à long terme d'une halde à stériles typique. La courbe de rétention d'eau et la fonction de conductivité hydraulique non saturée sont utilisées pour représenter la variabilité spatiale de l'écoulement de l'eau ; une distribution des paramètres géochimiques sert pour l’analyse du transport réactif. Les résultats illustrent comment la corrélation spatiale des propriétés hydrauliques affecte la distribution et la circulation de l'eau au sein de l’empilement, produisant, dans certains cas des chemins d’écoulement préférentiels dans la direction de la plus forte corrélation des propriétés hydrauliques. Les simulations numériques montrent également que les taux d'oxydation des minéraux sulfureux sont influencés par la taille des grains, la proportion de sulfure et la distribution de l’eau, qui peuvent être la cause de grandes variations spatiales dans la composition des eaux de drainage. ---------- Abstract: This report presents a numerical modeling approach to assess unsaturated water flow and geochemical transport in a sulphidic waste rock pile using selected realizations of stochastically distributed material properties. Such simulations can serve to better understand the long-term response of a typical waste rock pile. The water retention curve and hydraulic conductivity function are used to represent spatial variability for water flow, while distributed geochemical parameters are used for reactive transport. The results illustrate how the spatial correlation of hydraulic properties directly affects the moisture distribution and flow within the pile, which in some cases creates local preferential flow paths along the direction of the strongest correlation of hydraulic properties. The numerical simulations also show how sulphide mineral oxidation rates can be influenced by the grain size, sulphide fraction and moisture content distribution, which may explain large observed spatial variations in the composition of drainage water

Interferon β-1a in relapsing multiple sclerosis: four-year extension of the European IFNβ-1a Dose-C omparison Study

Background: Multiple sclerosis (MS) is a chronic disease requiring long-term monitoring of treatment. Objective: To assess the four-year clinical efficacy of intramuscular (IM) IFNb-1a in patients with relapsing MS from the European IFNb-1a Dose-C omparison Study. Methods: Patients who completed 36 months of treatment (Part 1) of the European IFNb-1a Dose-C omparison Study were given the option to continue double-blind treatment with IFNb-1a 30 mcg or 60 mcg IM once weekly (Part 2). Analyses of 48-month data were performed on sustained disability progression, relapses, and neutralizing antibody (NA b) formation. Results: O f 608/802 subjects who completed 36 months of treatment, 493 subjects continued treatment and 446 completed 48 months of treatment and follow-up. IFNb-1a 30 mcg and 60 mcg IM once weekly were equally effective for up to 48 months. There were no significant differences between doses over 48 months on any of the clinical endpoints, including rate of disability progression, cumulative percentage of patients who progressed (48 and 43, respectively), and annual relapse rates; relapses tended to decrease over 48 months. The incidence of patients who were positive for NAbs at any time during the study was low in both treatment groups. Conclusion: C ompared with 60-mcg IM IFNb-1a once weekly, a dose of 30 mcg IM IFNb-1a once weekly maintains the same clinical efficacy over four years

Sarcopenia Exacerbates Obesity-Associated Insulin Resistance and Dysglycemia: Findings from the National Health and Nutrition Examination Survey III

Sarcopenia often co-exists with obesity, and may have additive effects on insulin resistance. Sarcopenic obese individuals could be at increased risk for type 2 diabetes. We performed a study to determine whether sarcopenia is associated with impairment in insulin sensitivity and glucose homeostasis in obese and non-obese individuals.We performed a cross-sectional analysis of National Health and Nutrition Examination Survey III data utilizing subjects of 20 years or older, non-pregnant (N = 14,528). Sarcopenia was identified from bioelectrical impedance measurement of muscle mass. Obesity was identified from body mass index. Outcomes were homeostasis model assessment of insulin resistance (HOMA IR), glycosylated hemoglobin level (HbA1C), and prevalence of pre-diabetes (6.0≤ HbA1C<6.5 and not on medication) and type 2 diabetes. Covariates in multiple regression were age, educational level, ethnicity and sex.Sarcopenia was associated with insulin resistance in non-obese (HOMA IR ratio 1.39, 95% confidence interval (CI) 1.26 to 1.52) and obese individuals (HOMA-IR ratio 1.16, 95% CI 1.12 to 1.18). Sarcopenia was associated with dysglycemia in obese individuals (HbA1C ratio 1.021, 95% CI 1.011 to 1.043) but not in non-obese individuals. Associations were stronger in those under 60 years of age. We acknowledge that the cross-sectional study design limits our ability to draw causal inferences.Sarcopenia, independent of obesity, is associated with adverse glucose metabolism, and the association is strongest in individuals under 60 years of age, which suggests that low muscle mass may be an early predictor of diabetes susceptibility. Given the increasing prevalence of obesity, further research is urgently needed to develop interventions to prevent sarcopenic obesity and its metabolic consequences

Is there a role for menopausal hormone therapy in the management of postmenopausal osteoporosis?

We provide an evidence base and guidance for the use of menopausal hormone therapy (MHT) for the maintenance of skeletal health and prevention of future fractures in recently menopausal women. Despite controversy over associated side effects, which has limited its use in recent decades, the potential role for MHT soon after menopause in the management of postmenopausal osteoporosis is increasingly recognized. We present a narrative review of the benefits versus risks of using MHT in the management of postmenopausal osteoporosis. Current literature suggests robust anti-fracture efficacy of MHT in patients unselected for low BMD, regardless of concomitant use with progestogens, but with limited evidence of persisting skeletal benefits following cessation of therapy. Side effects include cardiovascular events, thromboembolic disease, stroke and breast cancer, but the benefit-risk profile differs according to the use of opposed versus unopposed oestrogens, type of oestrogen/progestogen, dose and route of delivery and, for cardiovascular events, timing of MHT use. Overall, the benefit-risk profile supports MHT treatment in women who have recently (< 10 years) become menopausal, who have menopausal symptoms and who are less than 60 years old, with a low baseline risk for adverse events. MHT should be considered as an option for the maintenance of skeletal health in women, specifically as an additional benefit in the context of treatment of menopausal symptoms, when commenced at the menopause, or shortly thereafter, in the context of a personalized benefit-risk evaluation

Online physical exercise intervention in older adults during lockdown: Can we improve the recipe?

peer reviewed[en] BACKGROUND: Recorded and live online physical exercise (PE) interventions are known to provide health benefits. However, the effects of prioritizing the number of live or recorded sessions remain unclear. AIMS: To explore which recorded-live sessions ratio leads to the best implementation and benefits in older adults. METHODS: Forty-six community-dwelling adults (> 60y.o.) were randomized into two groups completing a 12-week online PE intervention. Each group had a different ratio of live-recorded online sessions as follows: Live-Recorded-Live sessions (LRL; n = 22) vs. Recorded-Live-Recorded sessions (RLR; n = 24). RESULTS: Drop-out rates did not reach significance (LRL:14% vs. RLR: 29%, p = 0.20), and adherence was similar (> 85%) between groups. Both groups reported similar levels of satisfaction (> 70%), enjoyment (> 75%), and perceived exertion (> 60%). Both groups increased physical health and functional capacities, with greater improvements in muscle power (LRL: LRL: + 35 ± 16.1% vs. RLR: + 7 ± 13.9%; p = 0.010) and endurance (LRL: + 34.7 ± 15.4 vs. RLR: + 27.0 ± 26.5, p < 0.001) in the LRL group. DISCUSSION: Both online PE intervention modalities were adapted to the participants' capacities and led to a high level of enjoyment and retention. The greater physical improvements observed in the LRL group are likely due to the higher presence of the instructor compared to the RLR group. Indeed, participants received likely more feedback to appropriately adjust postures and movements, increasing the quality of the exercises. CONCLUSION: When creating online PE interventions containing both recorded and live sessions, priority should be given to maximizing the number of live sessions and not the number of recorded sessions