Novel structural features of the ripple phase of phospholipids

We have calculated the electron density maps of the ripple phase of dimyristoylphosphatidylcholine (DMPC) and palmitoyl-oleoyl phosphatidylcholine (POPC) multibilayers at different temperatures and fixed relative humidity. Our analysis establishes, for the first time, the existence of an average tilt of the hydrocarbon chains of the lipid molecules along the direction of the ripple wave vector, which we believe is responsible for the occurrence of asymmetric ripples in these systems

Protracted late Neoproterozic – early Palaeozoic deformation and cooling history of Sør Rondane, East Antarctica, from 40Ar/39Ar and U–Pb geochronology

40Ar/39Ar and U–Pb data from five structural domains constrain the late Neoproterozoic – early Palaeozoic tectonothermal history of the eastern part of the East African–Antarctic Orogen in Sør Rondane. A total of 27 new Ar/Ar ages span 570–474 Ma, roughly corresponding to the age range of three generations of syn- to post-tectonic granitoids. The ages are distinct for the five structural domains. The oldest cooling ages come from the weakly deformed southern part of the SW Terrane of Sør Rondane (SW Terrane S), a sliver of a Tonian island arc, which escaped much of the late Neoproterozoic accretionary deformation. This terrane was intruded by the oldest and largest granitoid complex at c. 640–620 Ma. The oldest Ar/Ar amphibole and biotite ages of 570–524 Ma are from the Main Shear Zone, along the northern margin of the SW Terrane S sliver. It hosts granites of age c. 584–570 Ma strung out along the shear zone. Two younger granitoid phases are recorded in the adjacent four terranes to the west, north and east of the SW Terrane S, and correlate with the younger group of Ar/Ar biotite ages spanning 513–474 Ma. We interpret the magmatic and cooling history of duration > 150 Ma to reflect repeated phases of accretion, magmatism and reactivation, that is, collage-style tectonism, partly pre-dating the incorporation of Sør Rondane into Gondwana. The study area first accreted to the cryptic Valkyrie Craton in Tonian times, was then ‘sandwiched’ between the Kalahari and Indo-Antarctica cratons, and experienced extensional tectonics and elevated heat flux due to lithospheric delamination, which resulted in slow cooling during the Pan-African Orogeny.publishedVersio

Wheat x Azotobacter x VA Mycorrhiza interactions towards plant nutrition and growth – a review

Nitrogen-fixing and phosphate-mobilizing bateria, as well as mycorrhizal fungi, can influence plant nutrition beneficially and thus be used as biofertilizers in agriculture. This paper briefly reviews the role of wheat genotypes in the interaction of wheat with soil microorganisms like phosphate solubilizing and nitrogen fixing bacteria, specifically Azotobacter sp., and with mycorrhizal fungi for the development of sustainable wheat crop production. The role of rhizosphere microorganisms and the mechanisms, factors affecting response of bioinoculants and the possibilities of breeding wheat genotypes responsive to these bioinoculants for sustainable wheat production in semi-arid tropics are discussed.

Quantum criticality of dipolar spin chains

We show that a chain of Heisenberg spins interacting with long-range dipolar forces in a magnetic field h perpendicular to the chain exhibits a quantum critical point belonging to the two-dimensional Ising universality class. Within linear spin-wave theory the magnon dispersion for small momenta k is [Delta^2 + v_k^2 k^2]^{1/2}, where Delta^2 \propto |h - h_c| and v_k^2 \propto |ln k|. For fields close to h_c linear spin-wave theory breaks down and we investigate the system using density-matrix and functional renormalization group methods. The Ginzburg regime where non-Gaussian fluctuations are important is found to be rather narrow on the ordered side of the transition, and very broad on the disordered side.Comment: 6 pages, 5 figure

Propiedades bioactivas y nutricionales del polen apícola de la provincia del Chubut, Argentina

El polen recolectado por las abejas es un producto apícola usado en la dieta humana por su alto valor nutricional y por ser un alimento balanceado. El polen comercializado consiste en una mezcla de pólenes de distinto origen botánico, néctar y secreciones de las abejas. Este producto de la colmena, rico en azúcares, lípidos y compuestos polifenólicos, principalmente flavonoides, presenta, además, propiedades bioactivas tanto farmacológicas como antioxidantes. El objetivo de este trabajo fue determinar la composición nutricional y la actividad antioxidante del polen apícola proveniente de las zonas melíferas más importantes de la provincia del Chubut: la región cordillerana y la región del valle inferior del río Chubut (VIRCH). Para determinar el contenido proteico se empleó el método de Bradford y los valores fueron expresados en % (g proteínas/100 g polen seco). Las cantidades de polifenoles totales y flavonoides fueron determinadas mediante los métodos de Folin-Ciocalteu y la técnica espectrofotométrica de nitrato de aluminio [Al(NO3)3] respectivamente. La capacidad antioxidante fue evaluada empleando la técnica del radical libre 1,1-difenil-2 picrilhidracilo (DPPH*). El contenido de proteínas presentó un valor medio de 20,2%. Los contenidos de polifenoles totales y flavonoides para las dos regiones melíferas oscilaron entre 50,5 mg y 163,9 mg de ácido gálico (GAE)/ g de polen seco y 10,3 mg y 65,6 mg de rutina (RE)/ g de polen seco. La actividad antirradicalaria en los extractos polínicos de ambas zonas fue alto y el EC50 varió entre 0,34 mg/ml y 5,82 mg/ml. La mayor capacidad antioxidante correspondió al polen apícola de la región del VIRCH, la cual también presentó un alto contenido de compuestos fenólicos.Pollen collected by bees is a beekeeping product used in human diet for its high nutritional value and for being a balanced food. It consists in a mixture of pollen with different botanical origin, nectar and bee secretions. This beehive product rich in sugars, lipids and polyphenolic compounds, mainly flavonoids, has also bioactive properties such as pharmacological and antioxidant. The aim of this study was to determine the nutritional composition and antioxidant activity of bee pollen from the most important apicultural areas from Chubut: the Andean region and the region of the lower valley of the Chubut River (VIRCH). Bradford method was used for the determination of protein content and the values were expressed in % (g protein/100 g dry pollen). The amounts of total polyphenols and flavonoids were determined by the Folin-Ciocalteu method and the spectrophotometric technique of aluminum nitrate (Al (NO3 )3 ) respectively. The antioxidant activity was evaluated using the technique of free radical 1, 1 -diphenyl -2 - picrylhydrazyl (DPPH *). The protein content presented a mean value of 20.2%. The content of total polyphenols and flavonoids from both apicultural regions varied between 50.5 and 163.9 mg of gallic acid (GAE) / g of dry pollen and 10.3 and 65.6 mg of rutin (RE)/ g of dry pollen. The antiradical activity in pollen extracts from both regions was high and the EC50 ranged from 0.34 mg / ml and 5.82 mg / ml. The highest antioxidant capacity corresponded to bee pollen from VIRCH, which also exhibited a higher content of phenolic compounds.Gerencia de Comunicación e Imagen InstitucionalFil: Aloisi, P.V. Universidad Nacional de la Patagonia San Juan Bosco. Facultad de Ciencias Naturales y Ciencias de la Salud. Laboratorio de Palinología y Control de Calidad de Mieles y Productos Apícolas; ArgentinaFil: Ruppel, S. Universidad Nacional de la Patagonia San Juan Bosco. Facultad de Ciencias Naturales y Ciencias de la Salud. Laboratorio de Palinología y Control de Calidad de Mieles y Productos Apícolas; Argentin

Longitude : a privacy-preserving location sharing protocol for mobile applications

Location sharing services are becoming increasingly popular. Although many location sharing services allow users to set up privacy policies to control who can access their location, the use made by service providers remains a source of concern. Ideally, location sharing providers and middleware should not be able to access users’ location data without their consent. In this paper, we propose a new location sharing protocol called Longitude that eases privacy concerns by making it possible to share a user’s location data blindly and allowing the user to control who can access her location, when and to what degree of precision. The underlying cryptographic algorithms are designed for GPS-enabled mobile phones. We describe and evaluate our implementation for the Nexus One Android mobile phone

Study of Reduced-Enrichment Uranium Fuel Possibility for Research Reactors

Having analyzed the results obtained in the work, it is possible to conclude that the flux density of fast and thermal neutrons in the shell of fuel elements in EFA in REU-zone decreased on average by 5% for UO2 fuel and by 7% for U9%Mo fuel. Change of neutrons flux density during the cycle does not exceed 4% for both fuel types. On average the fuel burnup in reactor core during the cycle for UO2 and U9%Mo increased by 2.8%. It is 1% less that in HEU-zone, which is conditioned by higher initial loading of 235U in fuel assembly with REU fuel

Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps

The recent discovery of active methane venting along the US northern and mid-Atlantic margin represents a new source of global methane not previously accounted for in carbon budgets from this region. However, uncertainty remains as to the origin and history of methane seepage along this tectonically inactive passive margin. Here we present the first isotopic analyses of authigenic carbonates and methanotrophic deep-sea mussels, Bathymodiolus sp., and the first direct constraints on the timing of past methane emission, based on samples collected at the upper slope Baltimore Canyon (∼385 m water depth) and deepwater Norfolk (∼1600 m) seep fields within the area of newly-discovered venting. The authigenic carbonates at both sites were dominated by aragonite, with an average image signature of image, a value consistent with microbially driven anaerobic oxidation of methane-rich fluids occurring at or near the sediment–water interface. Authigenic carbonate U and Sr isotope data further support the inference of carbonate precipitation from seawater-derived fluids rather than from formation fluids from deep aquifers. Carbonate stable and radiocarbon (image and image) isotope values from living Bathymodiolus sp. specimens are lighter than those of seawater dissolved inorganic carbon, highlighting the influence of fossil carbon from methane on carbonate precipitation. U–Th dates on authigenic carbonates suggest seepage at Baltimore Canyon between image to image, and at the Norfolk seep field between image to image, providing constraint on the longevity of methane efflux at these sites. The age of the brecciated authigenic carbonates and the occurrence of pockmarks at the Baltimore Canyon upper slope could suggest a link between sediment delivery during Pleistocene sea-level lowstand, accumulation of pore fluid overpressure from sediment compaction, and release of overpressure through subsequent venting. Calculations show that the Baltimore Canyon site probably has not been within the gas hydrate stability zone (GHSZ) in the past 20 ka, meaning that in-situ release of methane from dissociating gas hydrate cannot be sustaining the seep. We cannot rule out updip migration of methane from dissociation of gas hydrate that occurs farther down the slope as a source of the venting at Baltimore Canyon, but consider that the history of rapid sediment accumulation and overpressure may play a more important role in methane emissions at this site