Testing the effects of basic numerical implementations of water migration on models of subduction dynamics

Subduction of oceanic lithosphere brings water into the Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in the lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, computational models use different numerical schemes to simulate the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three simple migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the flow of the solid phase; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is a function of the pressure gradient caused by the difference in density between water and the surrounding rocks. In addition, the flow of the solid material field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple model that simulates the sinking of a cold, hydrated cylinder into a dry, warm mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models demonstrate that the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a bound water-dependent creep flow law results in a broader area of hydration in the mantle wedge, which feeds back to the dynamics of the system by the associated weakening. This finding underlines the importance of using dynamic time evolution models to investigate the effects of (de)hydration. We also show that hydrated material can be transported down to the base of the upper mantle at 670 km. Although (de)hydration processes influence subduction dynamics, we find that the exact numerical implementation of free water migration is not important in the basic schemes we investigated. A simple implementation of water migration could be sufficient for a first-order impression of the effects of water for studies that focus on large-scale features of subduction dynamics

A time-frequency approach to blind deconvolution in multipath underwater channels

Blind deconvolution is presented in the underwater acoustic channel context, by time-frequency processing. The acoustic propagation environment was modelled as a multipath propagation channel. For noiseless simulated data, source signature estimation was performed by a model-based method. The channel estimate was obtained via a time-frequency formulation of the conventional matched-filter. Simulations used a ray-tracing physical model, initiated with at-sea recorded environmental data, in order to produce realistic underwater channel conditions. The quality of the estimates was 0.793 for the source signal, and close to I for the resolved amplitudes and time-delays of the impulse response. Time-frequency processing has proved to overcome the typical ill-conditioning of single sensor deterministic deconvolution techniques

Foresterie urbaine et périurbaine. Quelles perspectives pour le bois-énergie en Afrique ?

L'urbanisation croissante des pays africains représente, pour des populations traditionnellement rurales, un changement fondamental de société et de mode de vie. Dans ce contexte. la fourniture durable d'énergie à usage domestique aux populations urbaines est un enfeu majeur de développement. Contrairement à d'autres continents, le bois énergie continue à occuper en Afrique une partie essentielle de la consommation domestique et cette tendance devrait se poursuivre pendant les prochaines décennies. Cette augmentation de la consommation entraine une pression de plus en plus forte sur des écosystemes forestiers périurbains déjà largement mis á contribution pour d'autres services tels que les infrastructures, l'urbanisation, l'agriculture. etc. Cette compétition pour l'usage des terres et les besoins toujours croissants des populations urbaines conditionnent l'évolution. et souvent la dégradation. de ces territoires á l'interface entre villes et monde rural. La gestion de ces espaces forestiers périrbains, souvent dégradés et délaissés, car compexes et difficiles à appréhender, devient donc une nécessité absolue pour assurer un approvisionnement durable en bois et maintenir les principales fonctions écologiques et sociales qui leur sont traditionnellement déwlues. La FAO, consciente de l'importance de cette thématique et de la spécifcité de l'Afrique dans las relations villes/forêts périurbaines, a demandé au Centre de Coopération International en Recherche Agronomique pour le Développement (CIRADI de faire le point sur cette question à l'occasion du colloque international) "Les arbres tissent des liens : agissons ensemble" (Trees connecting people: in action together) tenu á Bogota (Colombie), du 29 juillet au 1er août 2008. Ce rapport a été rédigé pour servir de base de réflexion. (Résumé d'auteur

Гамма-спектрометрический метод контроля активности и нуклидного состава низкоактивных твердых радиоактивных отходов

Разработан гамма-спектрометрический метод контроля низкоактивных твердых радиоактивных отходов, основанный на непосредственном измерении активности и нуклидного состава. Измерения проводятся в геометрии стандартного стального контейнера объемом 200 л, в который помещаются низкоактивные отходы. Для учета неравномерности распределения твердых радиоактивных отходов по измеряемой геометрии используется специальная вращающаяся площадка, на которую помещается контейнер. Проведена метрологическая аттестация и определены основные погрешности предлагаемого метода для доверительной вероятности 95 %

Tool selection during foraging in two species of funnel ants

This work was supported by European Commission (FP7-MC-ERG-2009-256524 to PdE).Tool use by non-human animals has received much research attention in the last couple of decades. Nonetheless, research has focused mostly on vertebrates, particularly primates and corvids, even though tool use has also been documented in insects. One of the best documented examples involves ants using debris (e.g., sand grains, mud, leaf fragments) to collect and transport liquid food to their nest. However, little is known about the factors that determine the selection of materials to be used as tool. We investigated tool selection in two species of Aphaenogaster ants by giving them the choice between different kinds of potential tools (natural and artificial objects). Ant workers showed a clear preference for certain materials to be used as tool objects. Tool selection was also shaped by familiarity with the material as ants developed a preference for artificial tools with a good soaking capacity that cannot be found in their natural environment. Our results indicate that ants of this genus evolved unique foraging strategies and show plasticity in their behaviour.PostprintPeer reviewe

Исследование морфологии и фазового состава нанодисперсных оксидов TiO2 и x•TiO2+y•SiO2, полученных методом неравновесного плазмохимического синтеза

Приведены результаты исследования нанодисперсного диоксида титана и композиционного наноразмерного порошка x•TiO2+y•SiO2. Порошки синтезированы в неравновесном плазмохимическом процессе, который инициируется импульсным электронным пучком. Исходная смесь содержит кислород, водород и газофазный тетрахлорид титана (или смесь тетрахлорида титана и тетрахлорида кремния). Исследовано влияние режима синтеза на распределение частиц по размеру и величину среднечислового размера порошка. Выполнен рентгенофазовый и рентгенофлуоренсцентный анализ порошков. Показано, что процесс синтеза носит объемный характер. Произведен расчет затрат энергии электрофизической установки на синтез нанопорошка

What can a studio approach to teaching tell us about the academic and social learning of middle school students? An exploration of student understanding of how making art supports their academic and social learning.

This study explores the types of social and academic learning typically overlooked in public school education. Art-based approaches to academic learning have been labeled as“fluff.” Education policymakers hold a biased view of the arts. When asked to consider art as a viable epistemology, cognition theorists have dismissed art as irrational. These biased views have contributed to the marginalization of the field of art education. The purpose of this study was to question this bias through an art-based studio approach to research. The goal was to explore how middle school students understand the role of visual arts in their own academic and social learning in this context. This qualitative study took place in a middle school in Northeast Massachusetts. Modifications of the research methods of Studio Thinking II (Hetland, Winner, Veneema, & Sheridan, 2013) and additional methods were used in the study. The student participants experienced “Eight Studio Habits of Mind” throughout eight sessions. These included: “Understanding Art worlds; Stretch and Explore; Reflect; Observe; Express; Envision; Engage and Persist, Develop Craft” (p.6). Throughout eight weeks seven classroom observations and two student interviews were conducted. During the eight sessions, students created art individually and in groups. To collect data, the researcher used the methods of pre-drawings and post-drawings (Chang, 2012, Einasdottir, Dockett, & Perry 2008), pre-questionnaires and post-questionnaires, (Song & Creegan- Quinquis, 2017), interviews, (Strauss & Corbin, 1990), art-making (Hetland, Veneema, Winner & Sheridan, 2013) and classroom observations (Behar,1996). To evaluate the data the researcher used grounded theory methods (Strauss & Corbin, 1990), which included the open and axial coding of interviews, drawings, and written responses. There were several findings. Findings showed significant changes in participants’ perceptions of themselves as artists. Findings included evidence of the negative effects of an outdated curriculum on students’ perceptions of the value of visual art in their lives. In addition, questionnaire and interview findings showed negative student perceptions regarding the ability of their existing curriculum to prepare them for a successful life after middle school. Student individual and collaborative drawings showed changes in artistic thinking and social engagement with their peers, art content, and larger societal issues

Некоторые вопросы развития физической культуры и спорта в высшей школе Сибири (конец 50-х - начало 90-х гг. XX в.)

Отражено состояние и развитие физической культуры и спорта в высших учебных заведениях Сибири в конце 1950-х - начале 1990-х гг. Проанализированы и оценены формы, содержание и результаты работы коллективов сибирских вузов в этой сфере деятельности

Lactobacillus delbrueckii ssp. lactis and ssp. bulgaricus: a chronicle of evolution in action

Lactobacillus delbrueckii ssp. lactis and ssp. bulgaricus are lactic acid producing bacteria that are largely used in dairy industries, notably in cheese-making and yogurt production. An earlier in-depth study of the first completely sequenced ssp. bulgaricus genome revealed the characteristics of a genome in an active phase of rapid evolution, in what appears to be an adaptation to the milk environment. Here we examine for the first time if the same conclusions apply to the ssp. lactis, and discuss intra- and inter-subspecies genomic diversity in the context of evolutionary adaptation. RESULTS: Both L. delbrueckii ssp. show the signs of reductive evolution through the elimination of superfluous genes, thereby limiting their carbohydrate metabolic capacities and amino acid biosynthesis potential. In the ssp. lactis this reductive evolution has gone less far than in the ssp. bulgaricus. Consequently, the ssp. lactis retained more extended carbohydrate metabolizing capabilities than the ssp. bulgaricus but, due to high intra-subspecies diversity, very few carbohydrate substrates, if any, allow a reliable distinction of the two ssp.. We further show that one of the most important traits, lactose fermentation, of one of the economically most important dairy bacteria, L. delbruecki ssp. bulgaricus, relies on horizontally acquired rather than deep ancestral genes. In this sense this bacterium may thus be regarded as a natural GMO avant la lettre. CONCLUSIONS: The dairy lactic acid producing bacteria L. delbrueckii ssp. lactis and ssp. bulgaricus appear to represent different points on the same evolutionary track of adaptation to the milk environment through the loss of superfluous functions and the acquisition of functions that allow an optimized utilization of milk resources, where the ssp. bulgaricus has progressed further away from the common ancestor

Étude de la mortalité aux grands âges à l’aide du Registre des décès d’Antananarivo (Madagascar)

Depuis 60 ans, la mortalité a fortement décliné à Madagascar, essentiellement aux jeunes âges. La baisse de la fécondité est également marquée depuis environ une vingtaine d’années. La population des 65 ans et plus, qui représente actuellement 3 % de la population totale, est ainsi amenée à occuper une proportion de plus en plus considérable dans les années futures. Sachant que près de 60 % de la population active travaille dans le secteur informel et n’aura pas accès au système de retraite, il devient impératif de mieux comprendre l’évolution récente de la mortalité aux âges avancés afin de pouvoir déterminer l’ampleur du phénomène à venir. Dans cette optique, la présente recherche analyse l’évolution de l’âge le plus fréquent au décès (M), indicateur particulièrement adapté pour rendre compte des changements en matière de longévité. Notre étude se focalise sur Antananarivo, capitale de Madagascar et ville pour laquelle nous disposons de données quasi exhaustives et détaillées sur les décès depuis 1976. En utilisant une méthode de lissage par P-splines, ces données, jumelées à des estimations de la population soumise au risque, nous permettent d’obtenir des estimations relativement précises de l’évolution de M et de la dispersion des décès au-delà de M, par sexe. Nos résultats montrent que d’importants progrès de longévité, en particulier chez les hommes, ont été réalisés dans la capitale malgache depuis le milieu des années 1980. L’augmentation de l’âge modal au décès a également été accompagnée d’une compression de la mortalité au-delà du mode. En d’autres termes, les inégalités devant la mort ont clairement diminué aux âges avancés. Ces avancées s’expliquent principalement par une réduction forte et continue de la mortalité liée aux maladies infectieuses. Cependant, de nouveaux progrès passeront désormais par des mesures visant à réduire la mortalité associée aux affections de l’appareil circulatoire (cardiovasculaire, cérébrovasculaire).For 60 years now, mortality has been declining sharply in Madagascar, mainly at young ages. Fertility has also decreased significantly in the last two decades. Individuals aged 65 and over, which currently accounts for 3% of the total population, are to represent an increasing share of the population in future years. Given that around 60% of the workforce labors in the informal economy and as a consequence will not have access to a pension system, it becomes crucial to better understand old age mortality in order to determine the extent of the coming phenomenon. In this context, this research examines the evolution of the modal (i.e. most frequent) age at death (M), a suitable indicator for monitoring improvements in old-age survival. Our paper focuses on Antananarivo, the capital and a city for which detailed and virtually complete data on deaths since 1976 are available. From a nonparametric P-spline smoothing approach, and estimates of the population exposed to the risk of death for each year, we obtain relatively accurate estimates of M and the standard deviation of ages at death above the mode for both sexes. Our results show that great progress in longevity has been made in Antananarivo since the mid-1980’s, especially for men. This increase in modal age at death came with a mortality compression above the mode. In other words, inequalities in old age mortality noticeably narrowed. These positive developments are due primarily to a continued strong reduction in infectious-related mortality. However, further progress will now require efficient measures aimed at fighting circulatory system diseases (cardiovascular and cerebrovascular diseases)