The risk of divorce and household saving behavior

We analyze the impact of an increase in the risk of divorce on the savingbehaviour of married couples. From a theoretical perspective, the expected sign of theeffect is ambiguous. We take advantage of the legalization of divorce in Ireland in 1996as an exogenous increase in the likelihood of marital dissolution. We analyze the savingbehaviour over time of couples who were married before the law was passed. We proposea difference-in-differences approach where we use as comparison groups either marriedcouples in other European countries (not affected by the law change), or Irish familieswho did not experience a significant increase in the expected risk of divorce (such as veryreligious families, or single individuals). Our results suggest that the increase in the riskof divorce brought about by the law was followed by an increase in the propensity to saveof married couples, consistent with a rise in precautionary savings interpretation. Anincrease in the risk of marital dissolution of about 40 percent led to a 7 to 13 percent risein the proportion of married couples reporting positive savings.

Dispersion of natural arsenic in the Malcantone watershed, Southern Switzerland: field evidence for repeated sorption-desorption and oxidation-reduction processes

In recent years, elevated arsenic concentrations have been found in waters and soils of many, countries, often resulting in a health threat for the local population. Switzerland is not an exception and this paper deals with the release and subsequent fate of arsenic in a 200-km(2) mountainous watershed, characterized by crystalline silicate rocks (gneisses, schists, amphibolites) that contain abundant As-bearing sulfide ore deposits, some of which have been mined for iron and gold in the past. Using analytical methods common for mineralogical, ground water and soil studies (XRD, XRF, XAS-XANES and -EXAFS, electron microprobe, extraction, ICP, AAS with hydride generator, ion chromatography), seven different field situations and related dispersion processes of natural arsenic have been studied: (1) release by rock weathering, (2) transport and deposition by water and ice; (3) release of As to the ground and surface water due to increasing pH; (4) accumulation in humic soil horizons; (5) remobilization by reduction in water-saturated soils and stagnant ground waters; (6) remobilization by using P-rich fertilizers or dung and (7) oxidation, precipitation and dilution in surface waters. Comparison of the results with experimental adsorption studies and speciation diagrams from the literature allows us to reconstruct and identify the typical behavior of arsenic in a natural environment under temperate climatic conditions. The main parameters identified are: (a) once liberated from the primary minerals, sorption processes on Fe-oxy-hydroxides dominate over Al-phases, such as Al-hydroxides or clay minerals and limit the As concentrations in the spring and well waters between 20 and 300 mug/l. (b) Precipitation as secondary minerals is limited to the weathering domain, where the As concentrations are still high and not yet too diluted by rain and soils waters. (c) Although neutral and alkaline pH conditions clearly increase the mobility of As, the main factor to mobilize As is a low redox potential (Eh close or below 0 mV), which favors the dissolution of the Fe-oxy-hydroxides on which the As is sorbed. (d) X-ray absorption spectroscopy (XAS) of As in water-logged humic forest soils indicates that the reduction to As III only occurs at the solid-water interface and that the solid contains As as As V (e) A and Bh horizons of humic cambisols can effectively capture As when As-rich waters flow through them. Complex spatial and temporal variation of the various parameters in a watershed results in repeated mobilization and immobilization of As, which continuously transports As from the upper to the lower part of a watershed and ultimately to the ocean. (C) 2004 Elsevier B.V. All rights reserved.

Les contributions d'entretien entre époux divorcés de 1907 à nos jours : influence réciproque du droit du mariage, du droit du divorce et du principe d'égalité

INTRODUCTION De nos jours, le divorce est devenu un événement courant de la vie conjugale. Un des sujets qui restent au coeur de la polémique dans le domaine du droit du divorce depuis toujours, est celui de la contribution d'entretien après divorce. En effet, il s'agit de savoir dans quelles circonstances l'ancien conjoint (épouse ou époux) peut prétendre au maintien de l'entretien auquel il avait droit durant le beau et bon temps du mariage de la part de son ex-partenaire. Pour se convaincre de la complexité des problèmes que la dissolution de l'union conjugale peut créer, il suffit de parcourir la masse des décisions des différents tribunaux en la matière. Quant à l'actualité de la question, on peut simplement observer le nombre de divorces qui va croissant chaque année. Le demandeur peut être aussi bien l'ex-épouse que l'ex-époux ; c'est cette constatation qui a fondé notre démarche et qui est le fil conducteur de ce travail. Mais, alors qu'initialement nous nous demandions si un homme pouvait réellement être dans la situation de l'époux demandeur, notre réflexion s'est peu à peu orientée dans une direction différente et une autre question s'est profilée : qu'en est-il dans les faits de l'égalité acceptée juridiquement et intégrée dans les textes de loi ? La présente thèse examine l'évolution opérée parallèlement dans trois domaines qui s'influencent réciproquement : le droit du mariage, le droit du divorce et le principe constitutionnel de l'égalité. En effet, la révision constitutionnelle qui a abouti à l'adoption en 1981 du principe explicite de l'égalité entre homme et femme, a conduit à certaines modifications législatives. C'est ainsi que ce principe constitutionnel a été, par exemple, concrétisé dans le domaine du droit du mariage en 1984. Il a, par la même occasion, contribué au bouleversement du petit monde traditionnel familial et du système légal qui le soutenait. Nous avons donc analysé les conséquences que cette réforme législative a entraînées au sein du couple, et plus précisément, lors de sa désunion. Le présent travail consacre une partie à chacune des étapes qui a permis de faire évoluer ce domaine du droit si controversé qu'est la contribution d'entretien après divorce. Ainsi, la première partie montre l'influence de la situation de la femme sur les règles régissant le mariage en 1984 : alors que son statut était imprégné des principes patriarcaux justifiant, en 1907, une distribution législative traditionnelle des rôles au sein de l'union conjugale, la femme a, en 1984, été placée devant le même rôle que son mari. Ce titre premier s'intéresse donc à la réforme du droit du mariage entrée en vigueur en 1988 et qui va servir de cadre au bouleversement ultérieur qu'est la révision du droit du divorce. Dans la deuxième partie, nous avons étudié le droit du divorce tel qu'il ressortait du Code civil adopté en 1907 jusqu'à sa révision en 1998. Notre étude a donc porté sur les conditions essentielles que le Code d'Eugen Huber imposait pour obtenir une prestation lors de la dissolution des liens du mariage, ainsi que sur l'articulation entre les deux dispositions clés dans ce domaine : les articles 151 et 152 CC 1907. Cette analyse est divisée en deux sous-chapitres qui illustrent l'influence de la révision du droit du mariage de 1984 sur le droit du divorce de 1907. Le premier sous-chapitre examine ainsi les règles régissant la dissolution de l'union conjugale au regard du droit du mariage de 1907 jusqu'à sa révision entrée en vigueur en 1988; le second sous-chapitre porte sur ces mêmes règles de 1988 à 2000 (date de l'entrée en vigueur du nouveau droit du divorce) mais sous un nouvel éclairage, puisque le nouveau droit du mariage et ses nouveaux principes s'appliquent en marge du droit du divorce de 1907. La question se pose de savoir quelle a été l'influence réelle de la réforme de 1984, elle-même marquée par la modification constitutionnelle de 1981, sur le droit du divorce qui date, lui, de 1907 et qui a alors été adopté dans un contexte différent et baigné d'anciens principes traditionnels. En effet, qu'en est-il du droit aux prestations des articles 151 et 152 CC 1907 justifiées par le modèle traditionnel de répartition des tâches, dans un système basé sur la libre attribution des rôles au sein du couple ? Quelles sont les conséquences juridiques de l'indifférenciation des rôles masculin et féminin au sein de l'entité familiale ? Enfin, la troisième partie est consacrée à l'étude du nouveau droit du divorce de 1998, entré en vigueur en l'an 2000. Cette réforme suit l'évolution qui a eu lieu dans le domaine du droit de la famille ; elle a été en quelque sorte imposée par les différents développements législatifs de notre société. Nous nous trouvons ainsi face à de nouvelles interrogations : qu'en est-il des traditions familiales actuelles dans la pratique ? Qu'en est-il de l'évolution du principe constitutionnel de l'égalité et de son application dans les nouveaux droits du mariage et du divorce sous l'angle des contributions d'entretien ?

Biosphere/lithosphere interface : microbially-mediated CaCO3 precipitation in hypersaline and freshwater environments

Abstract: Microbial mats very efficiently cycle elements, such as C, 0, N, S and H, which makes them key players of redox processes at the biosphere-lithosphere interface. They are characterized by high metabolic activities and high turnover rates (production and consumption) of biomass, which mainly consists of cell material and of extracellular organic matter (EOM). The EOM forms a matrix, embedding the microbial cells and fulfilling various functions within the microbial mat, including: mat attachment to surfaces; creation of micro-domains within the mat; physical stabilization under hy- drodynamic stress and the protection of the cells in multiple other stress conditions. EOM mainly consists of polysaccharides, amino acids, and a variety of chemical func-tional groups {e.g., -C00H, - SH -OH). These groups strongly bind cations such as Ca2+ and Mg2+ and thus exert a strong control on carbonate mineral formation within the microbial mat. A feedback mechanism between community metabolisms, their prod¬ucts, and the surrounding physicochemical microenvironment thus influences the de¬gree of carbonate saturation favoring either carbonate precipitation or dissolution. We investigated the driving forces and mechanisms of microbialite formation in the Sari ne River, FR, Switzerland, the hypersaline lake, Big Pond, Bahamas and in labo¬ratory experiments. The two fundamentally different natural systems allowed us to compare the geochemical conditions and microbial metabolisms, necessary for car¬bonate formation in microbial mats. Although carbonates are oversaturated in both environments, precipitation does not occur on physicochemical substrates (i.e. out¬side the microbial mats). In the Sarine a high crystal nucleation threshold exceeds the carbonate saturation, despite the high carbonate alkalinity in the water column. Cyanobacterial photosynthesis strongly locally enhances the carbonate alkalinity, whereas the EOM attract and immobilize calcium, which increases the saturation state and finally leads to carbonate precipitation within the EOM (in this case the cyanobacterial sheath) as nucleation template. In Big Pond, the presence of calcium- chelating anions (i.e. sulfate) and EOM, as well as the presence of magnesium, lowers the calcium activity in the water column and mat, and thus inhibits carbonate pre¬cipitation. Coupled with other heterotrophic metabolisms, sulfate reduction uses the EOM as carbon source, degrading it. The resulting EOM consumption creates alkalin¬ity, releases calcium and consumes sulfate in mat-micro domains, which leads to the formation of carbonate layers at the top of the microbial mat. Résumé: Interface biosphère/lithosphère: médiation microbienne de la précipitation de CaC03 dans des environnements en eaux douces et hypersalines Les tapis microbiens engendrent une circulation très efficace des éléments, tels que C, 0, N, S et H, ce qui en fait des acteurs clé pour les processus d'oxydoréduction à l'inter¬face biosphère-lithosphère. Ils sont caractérisés par des taux élevés d'activité méta¬bolique, ainsi que par la production et la consommation de biomasse, principalement constituée de cellules microbiennes et de matière organique extracellulaire (MOE). Dans un tapis microbien, les cellules microbiennes sont enveloppées par une matrice de MOE qui a différentes fonctions dont l'attachement du tapis aux surfaces, la créa¬tion de micro-domaines dans le tapis, la stabilisation physique en situation de stress hydrodynamique, et la protection des cellules dans de multiples autres conditions de stress. La MOE se compose principalement de polysaccharides, d'acides aminés, et d'une variété de groupes fonctionnels chimiques (par exemple, COOH, -SH et -OH). Ces groupes se lient fortement aux cations, tels que Ca2+ et Mg2+, et exercent ainsi un contrôle fort sur la formation de CaC03 dans le tapis microbien. Un mécanisme de rétroaction, entre les métabolismes de la communauté microbienne, leurs produits, et le microenvironnement physico-chimique, influence le degré de saturation de car¬bonate, favorisant soit leur précipitation, soit leur dissolution. Nous avons étudié le moteur et les mécanismes de minéralisation dans des tapis de la Sarine, FR, Suisse et du lac hypersalin, Big Pond, aux Bahamas, ainsi que durant des expériences en laboratoire. Les deux systèmes naturels, fondamentalement dif¬férents, nous ont permis de comparer les conditions géochimiques et les métabolis¬mes nécessaires à la formation des carbonates dans des tapis microbiens. Bien que les carbonates soient sursaturés dans les deux environnements, la précipitation ne se produit pas sur des substrats physico-chimiques (en dehors du tapis microbien). Dans la Sarine, malgré un taux d'alcalinité élevé, les valeurs de seuil pour la nucléa- tion de carbonates sont plus hautes que la saturation du carbonate. La photosynthèse cyanobactérienne augmente localement l'alcalinité, alors que la MOE attire et immo¬bilise le calcium, ce qui augmente l'état de saturation et conduit finalement à la pré¬cipitation des carbonates, en utilisant la MOE comme substrat de nucléation. À Big Pond, la présence de chélateurs de calcium, notamment les anions (p.ex. le sulfate) et la MOE, ainsi que la présence de magnésium, réduit l'activité du calcium et inhibe en conséquence la précipitation des carbonates. Couplée avec d'autres métabolismes hétérotrophes, la réduction des sulfates utilise la MOE comme source de carbone, en la dégradant. Cette consommation de MOE crée l'alcalinité, consomme des sulfates et libère du calcium dans des micro-domaines, conduisant à la formation de couches de carbonates dans le haut du tapis microbien.

Morfogénesis del valle de Sant Miquel de Campmajor

A series of circumstances which converge in a little valley in the province of Girona, result in a peculiar type of morphogenetic evolution and a quite singular mechanical instability of its buttons. Very recent tectonic movements as well as dissolution phenomena of its subsoil due to pressurized underground water have played an important role in the morphogenesis. Such conditions have resulted in a fast morphological evolution which a progressive lowering of the valley floor as well as peculiar morphological features which favour the existence of numerous pits caused by sudden collapses distributed in altitude and time

Estudio comparado de la génesis de espeleotemas silíceos en granitoides de climas semiáridos y templados húmedos

Silica speleothems take differenr forms such as cylindrical stems growing from either the floor or the ceiling in granitic caves. Mineralogically they are opal-A and accumulate in successive layers with a whiskery druse tip formed by gypsum crystals. Initially they are porous but progressively become infilled by opal precipitation. This results in formation of solid speleothems. their size is only a few millimetres long. Bacterial activity accelerate quartz dissolution

Estudio sobre la resistencia quimica de baldosas ceramicas no-esmaltadas para pavimentos industriales

The chemical resistance of ceramic tiles is the subject of the European Standard UNE-EN ISO 10545-13. In order to evaluate the effect of aqueous solutions of several chemicals agents on the aspect of the tile surface, this standard establishes a series of tests at room temperature followed by visual inspection. According to this standard the tiles of this study are classified as being of maximum resistance (UHA). However operating conditions can be more aggressive than those detailed in the standard. So, a systematic study has been undertaken. In the present work, the effect of aqueous solutions of several organic and inorganic acids on the tile surface is evaluated. Samples immersed in different solutions are subjected to the following conditions: T= 60º C; pH=2 and to agitation processes. Visual analysis, as well as optical microscopy and scanning electron microscopy (SEM) were performed in order to determine the possible variation of the superficial aspect of tiles. Moreover, atomic absorption spectrophotometry has been used in order to obtain quantitative information concerning the solubility of system M (III)-L (M= Fe; L= H2O or L= ligand). The results obtained show, in all cases, a progressive dissolution of iron oxide precipitates presents in the ceramic body

Postgraduate Symposium: Positive influence of nutritional alkalinity on bone health.

There is growing evidence that consumption of a Western diet is a risk factor for osteoporosis through excess acid supply, while fruits and vegetables balance the excess acidity, mostly by providing K-rich bicarbonate-rich foods. Western diets consumed by adults generate approximately 50-100 mEq acid/d; therefore, healthy adults consuming such a diet are at risk of chronic low-grade metabolic acidosis, which worsens with age as a result of declining kidney function. Bone buffers the excess acid by delivering cations and it is considered that with time an overstimulation of this process will lead to the dissolution of the bone mineral content and hence to reduced bone mass. Intakes of K, Mg and fruit and vegetables have been associated with a higher alkaline status and a subsequent beneficial effect on bone health. In healthy male volunteers an acid-forming diet increases urinary Ca excretion by 74% and urinary C-terminal telopeptide of type I collagen (C-telopeptide) excretion by 19% when compared with an alkali (base-forming) diet. Cross-sectional studies have shown that there is a correlation between the nutritional acid load and bone health measured by bone ultrasound or dual-energy X-ray absorptiometry. Few studies have been undertaken in very elderly women (>75 years), whose osteoporosis risk is very pertinent. The EVAluation of Nutrients Intakes and Bone Ultra Sound Study has developed and validated (n 51) an FFQ for use in a very elderly Swiss population (mean age 80.4 (sd 2.99) years), which has shown intakes of key nutrients (energy, fat, carbohydrate, Ca, Mg, vitamin C, D and E) to be low in 401 subjects. A subsequent study to assess net endogenous acid production (NEAP) and bone ultrasound results in 256 women aged > or = 75 years has shown that lower NEAP (P=0.023) and higher K intake (P=0.033) are correlated with higher bone ultrasound results. High acid load may be an important additional risk factor that may be particularly relevant in very elderly patients with an already-high fracture risk. The latter study adds to knowledge by confirming a positive link between dietary alkalinity and bone health indices in the very elderly. In a further study to complement these findings it has also been shown in a group of thirty young women that in Ca sufficiency an acid Ca-rich water has no effect on bone resorption, while an alkaline bicarbonate-rich water leads to a decrease in both serum parathyroid hormone and serum C-telopeptide. Further investigations need to be undertaken to study whether these positive effects on bone loss are maintained over long-term treatment. Mineral-water consumption could be an easy and inexpensive way of helping to prevent osteoporosis and could be of major interest for long-term prevention of bone loss.

Open to closed system transition traced through the TDIC isotopic signature at the aquifer recharge stage, implications for groundwater 14C dating

14C dating models are limited when considering recent groundwater for which the carbon isotopic signature of the total dissolved inorganic carbon (TDIC) is mainly acquired in the unsaturated zone. Reducing the uncertainties of dating thus implies a better identification of the processes controlling the carbon isotopic composition of the TDIC during groundwater recharge. Geochemical interactions between gas, water and carbonates in the unsaturated zone were investigated for two aquifers (the carbonate-free Fontainebleau sands and carbonate-bearing Astian sands, France) in order to identify the respective roles of CO2 and carbonates on the carbon isotopic signatures of the TDIC; this analysis is usually approached using open or closed system terms. Under fully open system conditions, the seasonality of the 13C values in the soil CO2 can lead to important uncertainties regarding the so-called "initial 14C activity" used in 14C correction models. In a carbonate-bearing unsaturated zone such as in the Astian aquifer, we show that an approach based on fully open or closed system conditions is not appropriate. Although the chemical saturation between water and calcite occurs rapidly within the first metre of the unsaturated zone, the carbon isotopic contents (δ13C) of the CO2 and the TDIC evolve downward, impacted by the dissolution-precipitation of the carbonates. In this study, we propose a numerical approach to describe this evolution. The δ13C and the A 14C (radiocarbon activity) of the TDIC at the base of the carbonate-hearing unsaturated zone depends on (i) the δ13C and the A 14C of the TDIC in the soil determined by the soil CO2, (ii) the water's residence time in the unsaturated zone and (iii) the carbonate precipitation-dissolution fluxes. In this type of situation, the carbonate δ13C-A 14C evolutions indicate the presence of secondary calcite and permit the calculation of its accretion flux, equal to ~ 4.5 ± 0.5 x 10-9 mol grock-1 yr-1. More generally, for other sites under temperate climate and with similar properties to the Astian sands site, this approach allows for a reliable determination of the carbon isotopic composition at the base of the unsaturated zone as the indispensable "input function" data of the carbon cycle into the aquifer.

Peut-on accepter les progrès en sciences biomèdicales sans progrès en éthique ? [Can we take for granted medical progress without progress in ethics ?].

Since the mid 20th century progress in biomedical science has been punctuated by the emergence of bioethics which has fashioned the moral framework of its application to both research and clinical practice. Can we, however, consider the advent of bioethics as a form of progress marking the advances made in biomedical science with an adequate ethical stamp? The argument put forward in this chapter is based on the observation that, far from being a mark of progess, the development of bioethics runs the risk of favouring, like modern science, a dissolution of the links that unite ethics and medicine, and so of depriving the latter of the humanist dimensions that underlie the responsibilities that fall to it. Faced with this possible pitfall, this contribution proposes to envisage as a figure of moral progress, consubstantial with the development of biomedical science, an ethical approach conceived as a means of social intervention which takes the first steps towards an ethics of responsibility integrating the bioethical perspective within a hermeneutic and deliberative approach. By the yardstick of a prudential approach, it would pay particular attention to the diverse sources of normativity in medical acts. It is suggested that this ethical approach is a source of progress insofar as it constitutes an indispensable attitude of watchfulness, which biomedical science can lean on as it advances, with a view to ensuring that the fundamental link uniting ethics and medicine is maintained.

La coordination des dirigeants économiques face à la financiarisation : gouvernance d'entreprise, relations industrielles et élites dirigeantes dans l'industrie suisse des machines, de l'électrotechnique et de la métallurgie (1970-2008)

Résumé Cette recherche analyse les transformations de la gouvernance d'entreprise et des relations industrielles entre 1970 et 2008 dans le contexte suisse, en mettant l'accent sur les changements survenus depuis les années 1990. Elle se centre sur le secteur de l'industrie des machines, de l'électrotechnique et de la métallurgie -noyau historique du capitalisme helvétique et principal employeur et exportateur industriel du pays - et discute l'hypothèse de la convergence des économies coordonnées vers le modèle libéral. Elle examine d'abord les formes de coordination hors-marché qui se sont consolidées entre les élites économiques suisses au cours de la période d'après-guerre. Les stratégies d'innovation incrémentale des grandes sociétés étaient soutenues par une gouvernance marquée par la faible pression des marchés des capitaux, en raison notamment de la forte concentration de l'actionnariat, de mécanismes protectionnistes en matière d'accès au contrôle des sociétés, ainsi que d'une grande interdépendance entre banques et entreprises. Cette interdépendance apparaît dans la forte densité du réseau d'interconnexions des Conseils d'administration, où les principales banques tiennent une place centrale. Le réseau met également en relation les sociétés du secteur entre elles, ainsi qu'avec des firmes actives sur d'autres marchés, ce qui témoigne de l'irréductibilité des stratégies industrielles à une pure logique de compétition centrée sur les marchés. Les stratégies à long terme du management peuvent également s'appuyer sur un système pacifié de relations industrielles, caractérisé par l'autorégulation des acteurs privés dans le cadre d'un partenariat social de branche entre des associations aux stratégies modérées, « néocorporatistes ». Nous analysons alors l'impact de la libéralisation et de la financiarisation de l'économie suisse sur la coordination des élites économiques durant les années 1990. Nous montrons que l'affirmation des fonds d'investissement a déstabilisé le système traditionnel de gouvernance d'entreprise. Ce dernier a ainsi été marqué par l'émergence d'un marché pour le contrôle de l'entreprise -fin du «capital patient » -, la dissolution de l'interdépendance entre banques et industries et plus globalement des formes de coordination hors-marché reposant sur le réseau d'interconnexions des Conseils d'administration, ainsi que par de profondes restructurations des grandes sociétés orientées vers la création de richesse pour les actionnaires. La recherche explore alors les logiques d'interactions entre la sphère de la gouvernance d'entreprise et celle des relations industrielles, l'affirmation du capital financier faisant pression sur le partenariat social dans le sens d'une flexibilisation et déréglementation du marché du travail. Par ailleurs, nous mettons en perspective le rôle central des élites dans le changement institutionnel. Loin de subir la pression des actionnaires, les préférences d'une nouvelle élite managériale au profil financier ont convergé avec les intérêts des investisseurs dans le processus de financiarisation. Ces préférences ont également participé à l'érosion du partenariat social de branche. Du côté syndical, l'émergence -ici aussi - d'une nouvelle élite, académique et issue de la gauche politique, au cours des années 1990, a remis en cause les recettes de l'ancienne génération de syndicalistes ouvriers. La principale association du secteur a ainsi diversifié ses registres d'action en investissant la sphère politique et en relativisant la paix absolue du travail, deux stratégies activement rejetées par le syndicat au cours du régime de croissance d'après-guerre. Tout en mettant la sociologie des élites au service d'une meilleure compréhension des processus de changement institutionnel dans les capitalismes contemporains, cette recherche souligne des logiques de changement différentes dans les sphères sous revue :changement disruptif dans la gouvernance d'entreprise, incrémentai dans les relations industrielles. L'analyse s'est appuyée sur le croisement de différentes méthodes : analyse documentaire, entretiens semi-directifs, analyse du parcours et profil des élites, analyse de réseau, études de cas.

Resting-state temporal synchronization networks emerge from connectivity topology and heterogeneity.

Spatial patterns of coherent activity across different brain areas have been identified during the resting-state fluctuations of the brain. However, recent studies indicate that resting-state activity is not stationary, but shows complex temporal dynamics. We were interested in the spatiotemporal dynamics of the phase interactions among resting-state fMRI BOLD signals from human subjects. We found that the global phase synchrony of the BOLD signals evolves on a characteristic ultra-slow (<0.01Hz) time scale, and that its temporal variations reflect the transient formation and dissolution of multiple communities of synchronized brain regions. Synchronized communities reoccurred intermittently in time and across scanning sessions. We found that the synchronization communities relate to previously defined functional networks known to be engaged in sensory-motor or cognitive function, called resting-state networks (RSNs), including the default mode network, the somato-motor network, the visual network, the auditory network, the cognitive control networks, the self-referential network, and combinations of these and other RSNs. We studied the mechanism originating the observed spatiotemporal synchronization dynamics by using a network model of phase oscillators connected through the brain's anatomical connectivity estimated using diffusion imaging human data. The model consistently approximates the temporal and spatial synchronization patterns of the empirical data, and reveals that multiple clusters that transiently synchronize and desynchronize emerge from the complex topology of anatomical connections, provided that oscillators are heterogeneous.

Plant availability of trace elements in sewage sludge-treated soils: methodology¹

Synthetic root exudates were formulated based on the organic acid composition of root exudates derived from the rhizosphere of aseptically grown corn plants, pH of the rhizosphere, and the background chemical matrices of the soil solutions. The synthetic root exudates, which mimic the chemical conditions of the rhizosphere environment where soil-borne metals are dissolved and absorbed by plants, were used to extract metals from sewage-sludge treated soils 16 successive times. The concentrations of Zn, Cd, Ni, Cr, and Cu of the sludge-treated soil were 71.74, 0.21, 15.90, 58.12, and 37.44 mg kg-1, respectively. The composition of synthetic root exudates consisted of acetic, butyric, glutaric, lactic, maleic, propionic, pyruvic, succinic, tartaric, and valeric acids. The organic acid mixtures had concentrations of 0.05 and 0.1 mol L-1 -COOH. The trace elements removed by successive extractions may be considered representative for the availability of these metals to plants in these soils. The chemical speciation of the metals in the liquid phase was calculated; results showed that metals in sludge-treated soils were dissolved and formed soluble complexes with the different organic acid-based root exudates. The most reactive organic acid ligands were lactate, maleate, tartarate, and acetate. The inorganic ligands of chloride and sulfate played insignificant roles in metal dissolution. Except for Cd, free ions did not represent an important chemical species of the metals in the soil rhizosphere. As different metals formed soluble complexes with different ligands in the rhizosphere, no extractor, based on a single reagent would be able to recover all of the potentially plant-available metals from soils; the root exudate-derived organic acid mixtures tested in this study may be better suited to recover potentially plant-available metals from soils than the conventional extractors.

Chemical properties and mineralogy of soils with plinthite and petroplinthite in Iranduba (AM), Brazil

Large areas of Plinthosols with ferruginous materials such as plinthite and/or petroplinthite are fairly common in the Brazilian Amazon basin. This work was carried out to investigate the chemical behavior, mineralogical composition and weathering stage of four representative soil profiles with plinthite and petroplinthite, in Iranduba, AM (Central Amazon). Three well-drained soil profiles at high elevations were studied (P1, Plinthic Vetic Ferralsol; P2 and P3, Vetic Endopetric Plinthosol) and a contrasting poorly drained soil (P4 Haplic Plinthosol), located at low elevation. After profile descriptions, soil samples were collected from each horizon, air-dried, sieved (2 mm), and analyzed for particle-size distribution, pH, exchangeable cations (Al3+, Ca2+, Mg2+, K+, and Na+), as well as available P and total organic carbon (TOC) content. The minerals present in the clay and sand fractions, as well as in the ferruginous materials were identified by X-ray Diffraction (XRD). The weathering stage of these soils was assessed by means of Ki and Kr indexes, and the amounts of free and amorphous Fe and Al oxides by using dithionite citrate bicarbonate (DBC) and ammonium oxalate dissolution procedures, respectively. The results showed that all soils were extremely unfertile, with pH levels ranging between strong and moderate acidity, very low sum of bases and organic matter content, and of available P. The mineralogy of the soil profiles was very similar, mainly of the well-drained soils, with predominance of kaolinite and quartz in the clay and sand fractions, respectively. In the poorly-drained P4, 2:1 clay particles were also observed. These profiles can be considered highly developed according to the Ki index, however, the Ki value of P4 was higher, indicating that this soil was less developed than the others. In summary, these profiles with plinthite and petroplinthite can be characterized as highly developed and infertile soils and are, with exception of P4, well-drained.

Plasma-enhanced chemical vapor deposition of boron nitride thin films from B2H6-H2-NH3 and B2H6-N2 gas mixtures

Highly transparent and stoichiometric boron nitride (BN) films were deposited on both electrodes (anode and cathode) of a radio-frequency parallel-plate plasma reactor by the glow discharge decomposition of two gas mixtures: B2H6-H2-NH3 and B2H6-N2. The chemical, optical, and structural properties of the films, as well as their stability under long exposition to humid atmosphere, were analyzed by x-ray photoelectron, infrared, and Raman spectroscopies; scanning and transmission electron microscopies; and optical transmittance spectrophotometry. It was found that the BN films grown on the anode using the B2H6-H2-NH3 mixture were smooth, dense, adhered well to substrates, and had a textured hexagonal structure with the basal planes perpendicular to the film surface. These films were chemically stable to moisture, even after an exposition period of two years. In contrast, the films grown on the anode from the B2H6-N2 mixture showed tensile stress failure and were very unstable in the presence of moisture. However, the films grown on the cathode from B2H6-H2-NH3 gases suffered from compressive stress failure on exposure to air; whereas with B2H6-N2 gases, adherent and stable cathodic BN films were obtained with the same crystallographic texture as anodic films prepared from the B2H6-H2-NH3 mixture. These results are discussed in terms of the origin of film stress, the effects of ion bombardment on the growing films, and the surface chemical effects of hydrogen atoms present in the gas discharge.