The smectitic minerals in a bentonite deposit from melo (Uruguay)

International audienceA nearly monomineralic 1.5 m thick bentonite bed sampled in Melo (Uruguay) appears to be a pure high-charge montmorillonite: [Si3.94 Al0.06] (Al1.40 Fe 3+ 0.11 Ti0.02 Mg0.49 Mn0.01) O10 (OH)2 Na0.01 K0.08 Ca0.18. However, contrasting swelling behaviors have been evidenced by fitting the experimental X-ray diffraction patterns recorded on oriented preparations of the same sample in different saturation states. According to the expandability of the layers in the Ca-, K- and K-Ca-saturated (that is saturated first with K + and subsequently with Ca2+) states, three "layer types" were defined. Low-, intermediate-, and high-charge layers are fully, partly, and not expandable, respectively, after K-saturation. Collapse of high-charge layers is not reversible after subsequent Ca-saturation, most likely because of tetrahedral substitutions. These three different layer types are segregated in two distinct randomly interstratified mixedlayer phases. TSA and CEC are shown to depend on the interlayer cation composition

Rápidas bajadas de peso corporal en deportes de combate. Efecto sobre las capacidades físicas

Introduction: Judo is a combat sport whose competitive classification depends on body weight. Nearly 48 hours before an important competition, 90 % of judokas perform aggressive weight loss strategies looking for relative advantages concerning muscle size and strength. These procedures are generically called rapid weight loss (RWL). There are currently controversies regarding health consequences related to these procedures. Methods: Consisted in a descriptive simulation study of pre-competitive weight adjustment to 14 athletes of the Argentine national judo team. Specific physical tests validated for sport were performed under normal conditions vs conditions of caloric/water volunteer restriction in which a reduction of body weight > = 1,5 kg in 48 hours has been evidenced. Results: The RWL methods most used by those athletes are aggressive calorie/water restriction and active dehydration. The main consequences of these procedures were the increase in heart rate and the greater difficulty in restoring baseline values. Marginal values were found for the measurement of resistance strength of upper limbs. Conclusions: RWL procedures involve more cardiovascular stress, alter the resistance strength of upper limbs, and are generators of a greater possibility of developing eating disorders. Health professionals should be actively involved in the development of safer and more effective strategies. We suggest changes to the guidelines for qualifying weight in.Introducción: el judo es un deporte de combate cuya clasificación competitiva depende del peso corporal. El 90% de los judocas, en el afán de obtener ventajas relativas con relación al tamaño y fuerza muscular, realizan abordajes agresivos de descenso de peso 48 hs previas a una competencia. Estos procedimientos se denominan genéricamente descenso rápido de peso o rapid weight loss (RWL). Existen controversias respecto de las consecuencias para la salud de estos procedimientos. Evaluar el efecto de las RWL sobre las capacidades físicas de los judocas de selección nacional. Métodos: Estudio descriptivo de simulación de reducción de peso precompetitivo a 14 atletas de selección argentina de judo. Se realizaron pruebas físicas específicas validadas para el deporte, en condiciones normales vs en condiciones de restricción calórica / hídricas voluntarias, a judocas que evidenciaron una bajada de peso corporal >= 1,5 kg en 48 hs. Resultados: Los métodos de RWL más usados son la restricción calórica/ hídrica agresiva y la deshidratación activa. Su principal consecuencia fue el aumento de la frecuencia cardíaca y la mayor dificultad para restituir los valores basales. Se hallaron valores marginales para la medición de fuerza resistencia de miembros superiores. Conclusión: Los procedimientos de RWL implican más stress cardiovascular, alteran la fuerza resistencia de miembros superiores y son generadoras de mayor posibilidad de desarrollo de trastornos de la conducta alimentaria. Los profesionales de salud deben participar activamente en el desarrollo de estrategias más seguras y efectivas. Se sugieren cambios en las directrices para el pesaje clasificatorio

REVISÃO DA EXTENSÃO AREAL E DO VOLUME DA FORMAÇÃO SERRA GERAL, BACIA DO PARANÁ, AMÉRICA DO SUL

In the discussion of the origin of continental flood basalt provinces, one of the most important constraints is the volume of the mobilized magma. Concerning the Serra Geral Formation in the Paraná Basin (South America), most authors cite an actual areal extent of 1,200,000 km2 and a volume of approximately 800,000 km3 . The same volume is often used for the Paraná-Etendeka Continental Flood Basalt Province, from which the Serra Geral Formation is the major part. We investigated the precision of these numbers through a complete historical review of their origin. We found that the areal extent cut off of 1,200,000 km2 is only an estimate made in 1934, and that the volume cut off of 800,000 km3 aroused using this areal extent estimate and an estimate of a mean thickness of 650 m of the flows made in 1966. Using a new map, we found that the area covered by the volcanic rocks in the Paraná Basin is of only 917,000 km2 (+- 15,000 km2 ). With isopach maps of 1987 and 1990, we calculated the volume of the extrusive rocks to be of at least 450,000 km3 and of the intrusive sill-type bodies to be of at least 112,000 km3 . With these estimates, the volume of the Serra Geral Formation should be considered to be of more than 600,000 km3 . For the Paraná-Etendeka Continental Flood Basalt Province as a whole, a volume of at least 1,700,000 km3 should be considered. A discussão sobre a origem das Províncias de Basaltos de Platô Continentais tem como um de seus elementos mais importantes o volume do magma mobilizado. Em relação às rochas da Formação Serra Geral na Bacia do Paraná (América do Sul), a maioria dos autores cita uma extensão de 1.200.000 km2 e um volume de aproximadamente 800.000 km3 . O mesmo volume é usado frequentemente para a Província de Basaltos de Platô Continental Paraná-Etendeka, da qual a Formação Serra Geral constitui a maior parte. Nós investigamos a precisão desses números através de uma revisão histórica completa acerca de sua origem. Verificamos que o valor relativo à extensão, de 1.200.000 km2 , é apenas uma estimativa apresentada em 1934 e que o volume de 800.000 km3 foi obtido multiplicando este valor de extensão por uma estimativa da espessura média dos derrames de lava de 650 metros apresentada em 1966. Usando um mapa recente, verificamos que a área coberta por rochas vulcânicas na Bacia do Paraná é de apenas 917.000 km2 (+- 15.000 km2 ). Através de mapas de isópacas de 1987 e 1990, calculamos o volume das rochas extrusivas como sendo de pelo menos 450.000 km3 e que o volume referente aos corpos intrusivos do tipo sill é de pelo menos 112.000 km3 . Através destas estimativas, o volume de rochas da Formação Serra Geral deve ser considerado como sendo superior a 600.000 km3 . A Província de Basaltos de Platô Continental Paraná-Etendeka como um todo possui um volume de no mínimo 1.700.000 km3

Optimization of pixel size and propagation distance in X-ray phase-contrast virtual histology

X-ray phase-contrast coupled to high-spatial resolution imaging systems provides a high sensitivity for distinguishing soft tissue structures in small samples, thus being suited for X-ray virtual histology. Propagation-based phase-contrast tomography can deliver a considerable gain in signal-to-noise ratio (SNR) at small pixel sizes when it is combined to a suitable phase retrieval filter. We optimized acquisition parameters, namely the propagation distance and the pixel size, with the aim of providing adequate spatial resolution and sensitivity for virtual histology of breast surgery specimens, scanned with a phase-contrast microtomography (mu CT) system employing a commercial sCMOS detector at the SYRMEP beamline of the Italian synchrotron facility Elettra (Trieste, Italy). A pathological breast tissue sample was embedded in paraffin and imaged using a polychromatic synchrotron beam at an average energy of 24 keV. The high numerical optical aperture of the imaging system enabled to adjust the pixel size to 1, 2.5 and 4 mu m. The scans were acquired at five sample-to-detector distances: 4.5, 150, 250, 500 and 1000 mm. SNR was measured in an homogeneous region portion of the mu CT image for each combination of pixel size and propagation distance. Experimental results were compared to a theoretical model taking into account the actual point spread function of the employed imaging system. The measured gain of SNR associated with the application of the phase-retrieval matched the predictions for large Fresnel numbers (N-F > 2). For each pixel size, an optimal range of propagation distances was found. Optimal mu CT reconstructions were then compared with their respective histopatological images, showing an excellent visibility of relevant structures. The optimization performed in this study will allow to select the most appropriate geometrical configurations for future acquisitions of virtual histology images of different specimens via phase-contrast microtomography

Clinical Evidence: a useful tool for promoting evidence-based practice?

Background: Research has shown that many healthcare professionals have problems with guidelines as they would prefer to be given all relevent information relevent to decision-making rather than being told what they should do. This study assesses doctors' judgement of the validity, relevance, clarity and usability of the Italian translation of Clinical Evidence (CE) after its free distribution launched by the Italian Ministry of Health. Methods: Opinions elicited using a standardised questionnaire delivered either by mail or during educational or professional meetings. Results: Twenty percent (n = 1350) doctors participated the study. Most of them found CE's content valid, useful and relevant for their clinical practice, and said CE can foster communications among clinicians, particularly among GPs and specialists. Hospital doctors (63%) more often than GPs (48%) read the detailed presentation of individual chapters. Twenty-nine percent said CE brought changes in their clinical practice. Doctors appreciated CE's nature of an evidence-based information compendium and would have not preferred a collection of practice guidelines. Conclusions: Overall, the pilot initiative launched by the Italian Ministry of Health seems to have been well received and to support the subsequent decision to make the Italian edition of Clinical Evidence concise available to all doctors practising in the country. Local implementation initiatives should be warranted to favour doctor's use of CE

Coexistence of halloysite and kaolinite: a study on the genesis of kaolin clays of Campo Alegre Basin, Santa Catarina State, Brazil

Kaolin at Campo Alegre Basin, Santa Catarina State, Brazilwas formed from alteration of volcanic acid rocks. Halloysite clays dominate the clay fraction of the matrix of the kaolin body, whereas a poorly crystalline kaolinite is abundant in veins. Some primary blocky structures have high amounts of illite, in one mine, but in general, only low contents of illite-smectite, illite, chlorite-vermiculite, vermiculite and quartz were identified in the clay fraction of the samples. Toward the top of the mines, hematite and lepidocrocite appear in horizontal red and ochre colored levels and the amount of kaolinite increases compared to halloysite. The vertical zoning of alteration levels, the changes in mineralogy, the positive correlation between depth and Cation Exchange Capacity of the clays, the preservation of different types of rock textures in the kaolin bodies, the dominant tube morphology of the halloysite clays indicate a supergene genesis for the deposits. Criteria to distinguish between supergene and hypogene kaolin are discussed. Transmission Electron Microscopy of the cross sections of halloysite tubes showed polygonal forms that are ascribed to be transitional between kaolinite and halloysite. It is proposed that some of the kaolinite of these deposits be inherited from the dehydration of halloysite tubes

Use of Green Sulla Forage for Feeding. 1. Effects on Lamb Growth and Gastrointestinal Nematode Parasite Infestation

Recent studies have shown that some forage legumes containing condensed tannins (CT), such as sulla (Hedysarum coronarium L.), can reduce the gastrointestinal nematode burden in sheep (Niezen et al., 1998) and increase post-ruminal protein availability (Waghorn et al., 1994). This study aimed to evaluate the anthelmintic and nutritional properties of sulla forage in relation to its CT content. Thus, the growth performance and the level of nematode infestation of lambs fed sulla were compared with those of lambs fed ryegrass (Lolium multiflorum Lam. subsp. wersterwoldicum), lacking in CT