Estimation of a maximum Lu diffusion rate in a natural eclogite garnet

Lutetium zoning in garnet within eclogites from the Zermatt-Saas Fee zone, Western Alps, reveal sharp, exponentially decreasing central peaks. They can be used to constrain maximum Lu volume diffusion in garnets. A prograde garnet growth temperature interval of 450-600 A degrees C has been estimated based on pseudosection calculations and garnet-clinopyroxene thermometry. The maximum pre-exponential diffusion coefficient which fits the measured central peak is in the order of D-0= 5.7*10(-6) m(2)/s, taking an estimated activation energy of 270 kJ/mol based on diffusion experiments for other rare earth elements in garnet. This corresponds to a maximum diffusion rate of D (600 A degrees C) = 4.0*10(-22) m(2)/s. The diffusion estimate of Lu can be used to estimate the minimum closure temperature, T-c, for Sm-Nd and Lu-Hf age data that have been obtained in eclogites of the Western Alps, postulating, based on a literature review, that D (Hf) < D (Nd) < D (Sm) a parts per thousand currency sign D (Lu). T-c calculations, using the Dodson equation, yielded minimum closure temperatures of about 630 A degrees C, assuming a rapid initial exhumation rate of 50A degrees/m.y., and an average crystal size of garnets (r = 1 mm). This suggests that Sm/Nd and Lu/Hf isochron age differences in eclogites from the Western Alps, where peak temperatures did rarely exceed 600 A degrees C must be interpreted in terms of prograde metamorphism.

Preferential infection of immature dendritic cells and B cells by mouse mammary tumor virus.

Until now it was thought that the retrovirus mouse mammary tumor virus preferentially infects B cells, which thereafter proliferate and differentiate due to superantigen-mediated T cell help. We describe in this study that dendritic cells are infectable at levels comparable to B cells in the first days after virus injection. Moreover, IgM knockout mice have chronically deleted superantigen-reactive T cells after MMTV injection, indicating that superantigen presentation by dendritic cells is sufficient for T cell deletion. In both subsets initially only few cells were infected, but there was an exponential increase in numbers of infected B cells due to superantigen-mediated T cell help, explaining that at the peak of the response infection is almost exclusively found in B cells. The level of infection in vivo was below 1 in 1000 dendritic cells or B cells. Infection levels in freshly isolated dendritic cells from spleen, Langerhans cells from skin, or bone marrow-derived dendritic cells were compared in an in vitro infection assay. Immature dendritic cells such as Langerhans cells or bone marrow-derived dendritic cells were infected 10- to 30-fold more efficiently than mature splenic dendritic cells. Bone marrow-derived dendritic cells carrying an endogenous mouse mammary tumor virus superantigen were highly efficient at inducing a superantigen response in vivo. These results highlight the importance of professional APC and efficient T cell priming for the establishment of a persistent infection by mouse mammary tumor virus.

Cluster glasses of ultrasoft particles

We present molecular dynamics (MD) simulations results for dense fluids of ultrasoft, fully penetrable particles. These are a binary mixture and a polydisperse system of particles interacting via the generalized exponential model, which is known to yield cluster crystal phases for the corresponding monodisperse systems. Because of the dispersity in the particle size, the systems investigated in this work do not crystallize and form disordered cluster phases. The clusteringtransition appears as a smooth crossover to a regime in which particles are mostly located in clusters, isolated particles being infrequent. The analysis of the internal cluster structure reveals microsegregation of the big and small particles, with a strong homo-coordination in the binary mixture. Upon further lowering the temperature below the clusteringtransition, the motion of the clusters" centers-of-mass slows down dramatically, giving way to a cluster glass transition. In the cluster glass, the diffusivities remain finite and display an activated temperature dependence, indicating that relaxation in the cluster glass occurs via particle hopping in a nearly arrested matrix of clusters. Finally we discuss the influence of the microscopic dynamics on the transport properties by comparing the MD results with Monte Carlo simulations.

Brittle to ductile transition in a fiber bundle with strong heterogeneity

We analyze the failure process of a two-component system with widely different fracture strength in the framework of a fiber bundle model with localized load sharing. A fraction 0≤α≤1 of the bundle is strong and it is represented by unbreakable fibers, while fibers of the weak component have randomly distributed failure strength. Computer simulations revealed that there exists a critical composition αc which separates two qualitatively different behaviors: Below the critical point, the failure of the bundle is brittle, characterized by an abrupt damage growth within the breakable part of the system. Above αc, however, the macroscopic response becomes ductile, providing stability during the entire breaking process. The transition occurs at an astonishingly low fraction of strong fibers which can have importance for applications. We show that in the ductile phase, the size distribution of breaking bursts has a power law functional form with an exponent μ=2 followed by an exponential cutoff. In the brittle phase, the power law also prevails but with a higher exponent μ=92. The transition between the two phases shows analogies to continuous phase transitions. Analyzing the microstructure of the damage, it was found that at the beginning of the fracture process cracks nucleate randomly, while later on growth and coalescence of cracks dominate, which give rise to power law distributed crack sizes.

GacS sensor domains pertinent to the regulation of exoproduct formation and to the biocontrol potential of Pseudomonas fluorescens CHA0.

In the root-colonizing biocontrol strain CHA0 of Pseudomonas fluorescens, cell density-dependent synthesis of extracellular, plant-beneficial secondary metabolites and enzymes is positively regulated by the GacS/GacA two-component system. Mutational analysis of the GacS sensor kinase using improved single-copy vectors showed that inactivation of each of the three conserved phosphate acceptor sites caused an exoproduct null phenotype (GacS-), whereas deletion of the periplasmic loop domain had no significant effect on the expression of exoproduct genes. Strain CHA0 is known to synthesize a solvent-extractable extracellular signal that advances and enhances the expression of exoproduct genes during the transition from exponential to stationary growth phase when maximal exoproduct formation occurs. Mutational inactivation of either GacS or its cognate response regulator GacA abolished the strain's response to added signal. Deletion of the linker domain of the GacS sensor kinase caused signal-independent, strongly elevated expression of exoproduct genes at low cell densities. In contrast to the wild-type strain CHA0, the gacS linker mutant and a gacS null mutant were unable to protect tomato plants from crown and root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici in a soil-less microcosm, indicating that, at least in this plant-pathogen system, there is no advantage in using a signal-independent biocontrol strain.

Statistical significance of quantitative PCR.

BACKGROUND: PCR has the potential to detect and precisely quantify specific DNA sequences, but it is not yet often used as a fully quantitative method. A number of data collection and processing strategies have been described for the implementation of quantitative PCR. However, they can be experimentally cumbersome, their relative performances have not been evaluated systematically, and they often remain poorly validated statistically and/or experimentally. In this study, we evaluated the performance of known methods, and compared them with newly developed data processing strategies in terms of resolution, precision and robustness. RESULTS: Our results indicate that simple methods that do not rely on the estimation of the efficiency of the PCR amplification may provide reproducible and sensitive data, but that they do not quantify DNA with precision. Other evaluated methods based on sigmoidal or exponential curve fitting were generally of both poor resolution and precision. A statistical analysis of the parameters that influence efficiency indicated that it depends mostly on the selected amplicon and to a lesser extent on the particular biological sample analyzed. Thus, we devised various strategies based on individual or averaged efficiency values, which were used to assess the regulated expression of several genes in response to a growth factor. CONCLUSION: Overall, qPCR data analysis methods differ significantly in their performance, and this analysis identifies methods that provide DNA quantification estimates of high precision, robustness and reliability. These methods allow reliable estimations of relative expression ratio of two-fold or higher, and our analysis provides an estimation of the number of biological samples that have to be analyzed to achieve a given precision.

Bayes linear spaces

Linear spaces consisting of σ-finite probability measures and infinite measures (improper priors and likelihood functions) are defined. The commutative group operation, called perturbation, is the updating given by Bayes theorem; the inverse operation is the Radon-Nikodym derivative. Bayes spaces of measures are sets of classes of proportional measures. In this framework, basic notions of mathematical statistics get a simple algebraic interpretation. For example, exponential families appear as affine subspaces with their sufficient statistics as a basis. Bayesian statistics, in particular some well-known properties of conjugated priors and likelihood functions, are revisited and slightly extended

Partial correlation : Network analysis

The final year project came to us as an opportunity to get involved in a topic which has appeared to be attractive during the learning process of majoring in economics: statistics and its application to the analysis of economic data, i.e. econometrics.Moreover, the combination of econometrics and computer science is a very hot topic nowadays, given the Information Technologies boom in the last decades and the consequent exponential increase in the amount of data collected and stored day by day. Data analysts able to deal with Big Data and to find useful results from it are verydemanded in these days and, according to our understanding, the work they do, although sometimes controversial in terms of ethics, is a clear source of value added both for private corporations and the public sector. For these reasons, the essence of this project is the study of a statistical instrument valid for the analysis of large datasets which is directly related to computer science: Partial Correlation Networks.The structure of the project has been determined by our objectives through the development of it. At first, the characteristics of the studied instrument are explained, from the basic ideas up to the features of the model behind it, with the final goal of presenting SPACE model as a tool for estimating interconnections in between elements in large data sets. Afterwards, an illustrated simulation is performed in order to show the power and efficiency of the model presented. And at last, the model is put into practice by analyzing a relatively large data set of real world data, with the objective of assessing whether the proposed statistical instrument is valid and useful when applied to a real multivariate time series. In short, our main goals are to present the model and evaluate if Partial Correlation Network Analysis is an effective, useful instrument and allows finding valuable results from Big Data.As a result, the findings all along this project suggest the Partial Correlation Estimation by Joint Sparse Regression Models approach presented by Peng et al. (2009) to work well under the assumption of sparsity of data. Moreover, partial correlation networks are shown to be a very valid tool to represent cross-sectional interconnections in between elements in large data sets.The scope of this project is however limited, as there are some sections in which deeper analysis would have been appropriate. Considering intertemporal connections in between elements, the choice of the tuning parameter lambda, or a deeper analysis of the results in the real data application are examples of aspects in which this project could be completed.To sum up, the analyzed statistical tool has been proved to be a very useful instrument to find relationships that connect the elements present in a large data set. And after all, partial correlation networks allow the owner of this set to observe and analyze the existing linkages that could have been omitted otherwise.

Atomic Ordering and Martensitic Transitions in Cu-Zn-Al Shape Memory Alloys

We present results from both, calorimetric and dilatometric studies of the isothermal ordering process taking place in a Cu-Zn-Al shape memory alloy after quenches from Tq temperatures ranging from 350 K to 1200 K. The dissipated energy and the length variations of the system are obtained during the process. The change of these quantities in the whole process have been compared with the difference [MATH] between Ms, measured after the relaxation and Ms measured just after the quench. We obtain that these three quantities present, as a function of Tq, the same qualitative behaviour. These changes are then associated with changes of the L21 ordering after the quench in the system. The relaxational process does not follow a single exponential decay. Instead, a continuous slowing down is observed. A relaxation time [MATH] has been defined to characterize the relaxation rate. We show that [MATH] depends on both the annealing and the quenching (Tq [MATH] 800 K) temperatures through an Arrhenius law.

Modeling morphogen gradient formation from arbitrary realistically shaped sources.

Much of the analytical modeling of morphogen profiles is based on simplistic scenarios, where the source is abstracted to be point-like and fixed in time, and where only the steady state solution of the morphogen gradient in one dimension is considered. Here we develop a general formalism allowing to model diffusive gradient formation from an arbitrary source. This mathematical framework, based on the Green's function method, applies to various diffusion problems. In this paper, we illustrate our theory with the explicit example of the Bicoid gradient establishment in Drosophila embryos. The gradient formation arises by protein translation from a mRNA distribution followed by morphogen diffusion with linear degradation. We investigate quantitatively the influence of spatial extension and time evolution of the source on the morphogen profile. For different biologically meaningful cases, we obtain explicit analytical expressions for both the steady state and time-dependent 1D problems. We show that extended sources, whether of finite size or normally distributed, give rise to more realistic gradients compared to a single point-source at the origin. Furthermore, the steady state solutions are fully compatible with a decreasing exponential behavior of the profile. We also consider the case of a dynamic source (e.g. bicoid mRNA diffusion) for which a protein profile similar to the ones obtained from static sources can be achieved.

Synchronization of symmetric chaotic systems

This paper contains a study of the synchronization by homogeneous nonlinear driving of systems that are symmetric in phase space. The main consequence of this symmetry is the ability of the response to synchronize in more than just one way to the driving systems. These different forms of synchronization are to be understood as generalized synchronization states in which the motions of drive and response are in complete correlation, but the phase space distance between them does not converge to zero. In this case the synchronization phenomenon becomes enriched because there is multistability. As a consequence, there appear multiple basins of attraction and special responses to external noise. It is shown, by means of a computer simulation of various nonlinear systems, that: (i) the decay to the generalized synchronization states is exponential, (ii) the basins of attraction are symmetric, usually complicated, frequently fractal, and robust under the changes in the parameters, and (iii) the effect of external noise is to weaken the synchronization, and in some cases to produce jumps between the various synchronization states available

Growth of champa fruit under agroecological conditions of Miraflores, Boyacá, Colombia

The objective of this work was to analyze the growth of champa fruit (Campomanesia lineatifolia) as a function of growing-degree days (GDD) in the municipality of Miraflores, in Boyacá, Colombia. Thirty trees were selected at random, and 100 flowers in full bloom were marked in each tree. From the 26th day after flowering until harvest, 10 samples were taken every 15 days to determine the fruit parameters and growth rate. Temperature was recorded to calculate the GDD. From flowering until harvest, 1,489.1 GDD were accumulated over 145 days. Dry and fresh matter mass of pulp, seed, and total fruit were fitted to a logistic growth model, and three growth stages (S1, S2 and S3) were defined. In the S1, growth was slow, and the relative growth remained nearly stable, whereas the absolute growth rate (AGR) increased slowly. In the S2, maximum growth was observed. In the S3, which corresponds to maturation, dry mass increased gradually, and the AGR decreased, while the fresh pulp and total mass did not cease to increase. The polar and equatorial diameters increased linearly, while the volume followed an exponential model. Champa fruit show a simple sigmoid growth curve.

Growth of Crassostrea gasar cultured in marine and estuary environments in Brazilian waters

The objective of this work was to evaluate the growth of the mangrove oyster Crassostrea gasar cultured in marine and estuarine environments. Oysters were cultured for 11 months in a longline system in two study sites - São Francisco do Sul and Florianópolis -, in the state of Santa Catarina, Southern Brazil. Water chlorophyll-α concentration, temperature, and salinity were measured weekly. The oysters were measured monthly (shell size and weight gain) to assess growth. At the end of the culture period, the average wet flesh weight, dry flesh weight, and shell weight were determined, as well as the distribution of oysters per size class. Six nonlinear models (logistic, exponential, Gompertz, Brody, Richards, and Von Bertalanffy) were adjusted to the oyster growth data set. Final mean shell sizes were higher in São Francisco do Sul than in Florianópolis. In addition, oysters cultured in São Francisco do Sul were more uniformly distributed in the four size classes than those cultured in Florianópolis. The highest average values of wet flesh weight and shell weight were observed in São Francisco do Sul, whereas dry flesh weight did not differ between the sites. The estuary environment is more promising for the cultivation of oysters.

Mechanisms of garnet growth in eclogites of the Zermatt-Saas Fee unit, Western Alps

THESIS ABSTRACT Garnets are one of the key metamorphic minerals used to study peak metamorphic conditions or crystallization ages. Equilibrium is typically assumed between the garnet and the matrix. This thesis attempts to understand garnet growth in the Zermatt-Saas Fee (ZSF) eclogites, and discusses consequences for Sm/Nd and Lu/Hf dating and the equilibrium assumption. All studied garnets from the ZSF eclogites are strongly zoned in Mn, Fe, Mg, and Ca. Methods based on chemical zoning patterns and on 3D spatial statistics indicate different growth mechanisms depending on the sample studied. Garnets from the Pfulwe area are grown in a system where surface kinetics likely dominated over intergranular diffusion kinetics. Garnets fram two other localities, Nuarsax and Lago di Cignana, seem to have grown in a system where intergranular diffusion kinetics were dominating over surface kinetics, at least during initial growth. Garnets reveal strong prograde REE+Y zoning. They contain narrow central peaks for Lu + Yb + Tm ± Er and at least one additional small peak towards the rim. The REE Sm + Eu + Gd + Tb ± Dy are depleted in the cores but show one prominent peak close to the rim. It is shown that these patterns cam be explained using a transient matrix diffusion model where REE uptake is limited by diffusion in the matrix surrounding the porphyroblast. The secondary peaks in the garnet profiles are interpreted to reflect thermally activated diffusion due to a temperature increase during prograde metamorphism. The model predicts anomalously low 176Lu/177Hf and 147Sm/144Nd ratios in garnets where growth rates are fast compared to diffusion of the REE, which decreases garnet isochron precisions. The sharp Lu zoning was further used to constrain maximum Lu volume diffusion rates in garnet. The modeled minimum pre-exponential diffusion coefficient which fits the measured central peak is in the order of Do = 5.7* 106 m2/s, taking an activation energy of 270 kJ/mol. The latter was chosen in agreement with experimentally determined values. This can be used to estimate a minimum closure temperature of around 630°C for the ZSF zone. Zoning of REE was combined with published Lu/Hf and Sm/Nd age information to redefine the prograde crystallization interval for Lago di Cignana UHP eclogites. Modeling revealed that a prograde growth interval in the order of 25 m.y. is needed to produce the measured spread in ages. RÉSUMÉ Le grenat est un minéral métamorphique clé pour déterminer les conditions du pic de métamorphisme ainsi que l'âge de cristallisation. L'équilibre entre le grenat et la matrice est requis. Cette étude a pour but de comprendre la croissance du grenat dans les éclogites de la zone de Zermatt-Saas Fee (ZSF) et d'examiner quelques conséquences sur les datations Sm/Nd et Lu/Hf. Tous les grenats des éclogites de ZSF étudiés sont fortement zonés en Mn, Fe, Mg et partiellement en Ca. Les différentes méthodes basées sur le modèle de zonation chimique ainsi que sur les statistiques de répartition spatiale en 3D indiquent un mécanisme de croissance différent en fonction de la localité d'échantillonnage. Les grenats provenant de la zone de Pfulwe ont probablement crû dans un système principalement dominé par la cinétique de surface au détriment de 1a cinétique de diffusion intergranulaire. Les grenats provenant de deux autres localités, Nuarsax et Lago di Cignana, semblent avoir cristallisé dans un système dominé par la diffusion intergranulaire, au moins durant les premiers stades de croissance. Les grenats montrent une forte zonation prograde en Terres Rares (REE) ainsi qu'en Y. Les profils présentent au coeur un pic étroit en Lu + Yb+ Tm ± Er et au moins un petit pic supplémentaire vers le bord. Les coeurs des grenats sont appauvris en Sm + Eu + Gd + Tb ± Dy, mais les bords sont marqués par un pic important de ces REE. Ces profils s'expliquent par un modèle de diffusion matricielle dans lequel l'apport en REE est limité par la diffusion dans la matrice environnant les porphyroblastes. Les pics secondaires en bordure de grain reflètent la diffusion activée par l'augmentation de la température lors du métamorphisme prograde. Ce modèle prédit des rapports 176Lu/177Hf et 147Sm/144Nd anormalement bas lorsque les taux de croissance sont plus rapides que la diffusion des REE, ce qui diminue la précision des isochrones impliquant le grenat. La zonation nette en Lu a permis de contraindre le maximum de diffusion volumique par une approche numérique. Le coefficient de diffusion minimum modélisé en adéquation avec les pics mesurés est de l'ordre de Do = 5.7*10-6 m2/s, en prenant une énergie d'activation ~270 kJ/mol déterminée expérimentalement. Ainsi, la température de clôture minimale est estimée aux alentours de 630°C pour la zone ZSF. Des nouvelles données de zonation de REE sont combinées aux âges obtenus avec les rapports Lu/Hf et Sm/Nd qui redéfissent l'intervalle de cristallisation prograde pour les éclogites UHP de Lago di Cignana. La modélisation permet d'attribuer au minimum un intervalle de croissance prograde de 25 Ma afin d'obtenir les âges préalablement mesurés. RESUME GRAND PUBLIC L'un des principaux buts du pétrologue .métamorphique est d'extraire des roches les informations sur l'évolution temporelle, thermique et barométrique qu'elles ont subi au cours de la formation d'une chaîne de montagne. Le grenat est l'un des minéraux clés dans une grande variété de roches métamorphiques. Il a fait l'objet de nombreuses études dans des terrains d'origines variées ou lors d'études expérimentales afin de comprendre ses domaines de stabilité, ses réactions et sa coexistence avec d'autres minéraux. Cela fait du grenat l'un des minéraux les plus attractifs pour la datation des roches. Cependant, lorsqu'on l'utilise pour la datation et/ou pour la géothermobarométrie, on suppose toujours que le grenat croît en équilibre avec les phases coexistantes de la matrice. Pourtant, la croissance d'un minéral est en général liée au processus de déséquilibre. Cette étude a pour but de comprendre comment croît le grenat dans les éclogites de Zermatt - Saas Fee et donc d'évaluer le degré de déséquilibre. Il s'agit aussi d'expliquer les différences d'âges obtenues grâce aux grenats dans les différentes localités de l'unité de Zermatt-Saas Fee. La principale question posée lors de l'étude des mécanismes de croissance du grenat est: Parmi les processus en jeu lors de la croissance du grenat (dissolution des anciens minéraux, transport des éléments vers le nouveau grenat, précipitation d'une nouvelle couche en surface du minéral), lequel est le plus lent et ainsi détermine le degré de déséquilibre? En effet, les grenats d'une des localités (Pfulwe) indiquent que le phénomène d'adhérence en surface est le plus lent, contrairement aux grenats des autres localités (Lago di Cignana, Nuarsax) dans lesquels ce sont les processus de transport qui sont les plus lents. Cela montre que les processus dominants sont variables, même dans des roches similaires de la même unité tectonique. Ceci implique que les processus doivent être déterminés individuellement pour chaque roche afin d'évaluer le degré de déséquilibre du grenat dans la roche. Tous les grenats analysés présentent au coeur une forte concentration de Terres Rares: Lu + Yb + Tm ± Er qui décroît vers le bord du grain. Inversement, les Terres Rares Sm + Eu + Gd + Tb ± Dy sont appauvries au coeur et se concentrent en bordure du grain. La modélisation révèle que ces profils sont-dus à des cinétiques lentes de transport des Terres Rares. De plus, les modèles prédisent des concentrations basses en éléments radiogéniques pères dans certaines roches, ce qui influence fortement sur la précision des âges obtenus par la méthode d'isochrone. Ceci signifie que les roches les plus adaptées pour les datations ne doivent contenir ni beaucoup de grenat ni de très gros cristaux, car dans ce cas, la compétition des éléments entre les cristaux limite à de faibles concentrations la quantité d'éléments pères dans chaque cristal.

Traitement des plagiocéphalies postérieures d'origine positionnelle [Treatment of posterior positional plagiocephaly]

In 1992, the American academy of paediatrics has recommended that infants be placed on their backs to sleep, because prone sleeping has been correlated with sudden infant death syndrome. Following this article, medical paediatric community has documented an exponential increase in the diagnosis of posterior cranial deformities, which were considered as the consequence of unrelieved pressure onto the occiput during infant sleep. These last 15 years, management of posterior positional plagiocephaly has evolved but is still not standardized; it varies according to local specificities, and medical or parental preferences. Treatment of deformational plagiocephaly includes preventive counseling, repositioning adjustments and exercises, physiotherapy, osteopathy, treatment by dynamic cranial orthosis. On extremely rare occasions, corrective surgery is proposed. This article aims at reviewing the epidemiologic, diagnostic, and various therapeutic options of posterior positional plagiocephaly.