547 research outputs found

    Extreme mechanical resilience of self-assembled nanolabyrinthine materials

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    Low-density materials with tailorable properties have attracted attention for decades, yet stiff materials that can resiliently tolerate extreme forces and deformation while being manufactured at large scales have remained a rare find. Designs inspired by nature, such as hierarchical composites and atomic lattice-mimicking architectures, have achieved optimal combinations of mechanical properties but suffer from limited mechanical tunability, limited long-term stability, and low-throughput volumes that stem from limitations in additive manufacturing techniques. Based on natural self-assembly of polymeric emulsions via spinodal decomposition, here we demonstrate a concept for the scalable fabrication of nonperiodic, shell-based ceramic materials with ultralow densities, possessing features on the order of tens of nanometers and sample volumes on the order of cubic centimeters. Guided by simulations of separation processes, we numerically show that the curvature of self-assembled shells can produce close to optimal stiffness scaling with density, and we experimentally demonstrate that a carefully chosen combination of topology, geometry, and base material results in superior mechanical resilience in the architected product. Our approach provides a pathway to harnessing self-assembly methods in the design and scalable fabrication of beyond-periodic and nonbeam-based nano-architected materials with simultaneous directional tunability, high stiffness, and unsurpassed recoverability with marginal deterioration

    Analysis of the relationships between Patagonian squid (Doryteuthis gahi)

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    Doryteuthis (Loligo) gahi is the second most important cephalopod species in the SW Atlantic from a fisheries point of view. This species and hence, the fisheries profitability and sustainability, are subject to large inter-annual variability in recruitment strength, mainly due to interannual and seasonal variations of the Falkland/Malvinas Current. In this working document we analyse the environmental, geographical, temporal and physical factors affecting the distribution (abundance) of D. gahi in two areas where its abundance is highest, using geographic information systems tools. We found a slight positive correlation between CPUE and longitude, as well as between CPUE and depth in the northern area, but no correlations could be found between SST and the other explanatory variables. Regarding the southern area in summer-autumn, we found that CPUE increases with longitude as we go to the east, and with latitude. We also found positive correlations between SST and CPUE, as well as with depth. In winter spring our study revealed a slight relationship between CPUE and location, and with depth

    Analysis of the relationship between Argentine short-finned squid (Illex argentinus) abundance and environmental parameters in the SW Atlantic Ocean using GIS tools

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    The Argentine short-finned squid Illex argentinus is the main cephalopod species which occurs in the Southwest Atlantic Ocean. It is the most highly fished species in terms of catches and is the major target of large-scale directed fishing carried out by “jiggers”, and to a lesser extent, by trawlers. The variability of main current systems in the region (Brazil and Falkland/Malvinas Currents) has been suggested to influence the abundance and distribution of I. argentinus, thus largely affecting profitability and sustainability of the fisheries. In this working document we analyse the environmental, geographical, temporal and physical factors affecting the distribution (abundance) of I. argentinus in two areas of highest distribution, using geographic information systems tools. Strong correlation was found between Illex abundance and the season of the year, as well as with latitude, confirming our knowledge of the fishery and the literature on this specie

    Measurement of the branching ratio for beta-delayed alpha decay of 16N

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    While the 12C(a,g)16O reaction plays a central role in nuclear astrophysics, the cross section at energies relevant to hydrostatic helium burning is too small to be directly measured in the laboratory. The beta-delayed alpha spectrum of 16N can be used to constrain the extrapolation of the E1 component of the S-factor; however, with this approach the resulting S-factor becomes strongly correlated with the assumed beta-alpha branching ratio. We have remeasured the beta-alpha branching ratio by implanting 16N ions in a segmented Si detector and counting the number of beta-alpha decays relative to the number of implantations. Our result, 1.49(5)e-5, represents a 24% increase compared to the accepted value and implies an increase of 14% in the extrapolated S-factor

    Isotope Shifts of the 6d\,^2D3/2_{3/2}\, - 7p\,^2P1/2_{1/2}\, Transition in Trapped Short-Lived 209214^{209-214}Ra+^+

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    Laser spectroscopy of short-lived radium isotopes in a linear Paul trap has been performed. The isotope shifts of the 6d\,^2D3/2_{3/2}\, - 7p\,^2P1/2_{1/2}\, transition in 209214^{209-214}Ra+^+ were measured, which are sensitive to the short range part of the atomic wavefunctions. The results are essential experimental input for improving the precision of atomic structure calculation. This is indispensable for parity violation in Ra+^+ aiming at the determination of the weak mixing angle.Comment: Accepted for publication in Physical Review A as a Rapid Communicatio

    Real-Time decision support using data mining to predict blood pressure critical events in intensive medicine patients

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    Patient blood pressure is an important vital signal to the physicians take a decision and to better understand the patient condition. In Intensive Care Units is possible monitoring the blood pressure due the fact of the patient being in continuous monitoring through bedside monitors and the use of sensors. The intensivist only have access to vital signs values when they look to the monitor or consult the values hourly collected. Most important is the sequence of the values collected, i.e., a set of highest or lowest values can signify a critical event and bring future complications to a patient as is Hypotension or Hypertension. This complications can leverage a set of dangerous diseases and side-effects. The main goal of this work is to predict the probability of a patient has a blood pressure critical event in the next hours by combining a set of patient data collected in real-time and using Data Mining classification techniques. As output the models indicate the probability (%) of a patient has a Blood Pressure Critical Event in the next hour. The achieved results showed to be very promising, presenting sensitivity around of 95%

    Toposseqüência de solos cultivada com milho no estado de Sergipe.

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    O oeste de Sergipe vem se destacando na produção de milho numa extensa área de solos férteis com boas características edáficas. A potencialidade e extensão dos solos, bem como a necessidade de introdução de técnicas agrícolas e avaliação dos resultados das pesquisas ali desenvolvidas tanto para seu melhor aproveitamento agrícola, quanto para a preservação ambiental, justificam o estudo pormenorizado da área. O objetivo deste trabalho foi estudar uma toposseqüência de solos característica da região, cultivados com milho em regime dependente de chuvas, buscando interpretar sua dinâmica a fim de aportar subsídios para seu melhor manejo, visando a sustentabilidade dos cultivos desenvolvidos. Foram descritos e amostrados cinco perfis de solos em toposseqüência numa encosta de relevo suave ondulado. Características morfológicas, físicas e químicas foram estudadas tanto entre os horizontes do perfil, quanto entre os perfis ao longo do relevo. A variabilidade observada reflete as condições impostas pelo posicionamento dos solos na paisagem, sobretudo no que se refere às condições de infiltração de água e drenagem diferenciada

    First Test of Lorentz Invariance in the Weak Decay of Polarized Nuclei

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    A new test of Lorentz invariance in the weak interactions has been made by searching for variations in the decay rate of spin-polarized 20Na nuclei. This test is unique to Gamow-Teller transitions, as was shown in the framework of a recently developed theory that assumes a Lorentz symmetry breaking background field of tensor nature. The nuclear spins were polarized in the up and down direction, putting a limit on the amplitude of sidereal variations of the form |(\Gamma_{up} - \Gamma_{down})| / (\Gamma_{up} + \Gamma_{down}) < 3 * 10^{-3}. This measurement shows a possible route toward a more detailed testing of Lorentz symmetry in weak interactions.Comment: 11 pages, 6 figure

    Solos do Campo Experimental Pedro Arle em Frei Paulo - Sergipe.

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    A Embrapa Tabuleiros Costeiros vem desenvolvendo estudos comparativos de variedades e híbridos adaptados às condições semiáridas do Nordeste, selecionando os melhores para indicar seu cultivo e, assim, participar efetivamente do progresso da agricultura da Região. Estudar as características dos solos onde estes trabalhos estão sendo conduzidos é de fundamental importância para o planejamento de novas pesquisas, para a avaliação dos resultados obtidos e para que as informações possam ser extrapoladas para locais com condições edafoclimáticas semelhantes. O objetivo deste trabalho foi estudar os solos do Campo Experimental Pedro Arle, da Embrapa Tabuleiros Costeiros, localizado no município de Frei Paulo, em Sergipe. Para tanto, foi estudada uma topossequência em área onde vem sendo conduzidos experimentos com milho, obtendo-se altas produtividades. Vertissolo Háplico Órtico típico e Cambissolo Háplico Ta Eutrófico vertissólico foram encontrados na parte mais elevada da topossequência. Cambissolos Háplicos Ta Eutróficos, variando entre léptico e lítico, ocupam as posições de terço médio, inferior e a baixada. As análises refletem as limitações agrícolas destes solos relacionadas à sua profundidade efetiva e sua potencialidade que está diretamente relacionada à fertilidade natural
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