923 research outputs found

    Increasing Temperature and Microplastic Fibers Jointly Influence Soil Aggregation by Saprobic Fungi

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    Microplastic pollution and increasing temperature have potential to influence soil quality; yet little is known about their effects on soil aggregation, a key determinant of soil quality. Given the importance of fungi for soil aggregation, we investigated the impacts of increasing temperature and microplastic fibers on aggregation by carrying out a soil incubation experiment in which we inoculated soil individually with 5 specific strains of soil saprobic fungi. Our treatments were temperature (ambient temperature of 25°C or temperature increased by 3°C, abruptly versus gradually) and microplastic fibers (control and 0.4% w/w). We evaluated the percentage of water stable aggregates (WSA) and hydrolysis of fluorescein diacetate (FDA) as an indicator of fungal biomass. Microplastic fiber addition was the main factor influencing the WSA, decreasing the percentage of WSA except in soil incubated with strain RLCS 01, and mitigated the effects of temperature or even caused more pronounced decrease in WSA under increasing temperature. We also observed clear differences between temperature change patterns. Our study shows that the interactive effects of warming and microplastic fibers are important to consider when evaluating effects of global change on soil aggregation and potentially other soil processes

    Characterization and Compensation of Network-Level Anomalies in Mixed-Signal Neuromorphic Modeling Platforms

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    Advancing the size and complexity of neural network models leads to an ever increasing demand for computational resources for their simulation. Neuromorphic devices offer a number of advantages over conventional computing architectures, such as high emulation speed or low power consumption, but this usually comes at the price of reduced configurability and precision. In this article, we investigate the consequences of several such factors that are common to neuromorphic devices, more specifically limited hardware resources, limited parameter configurability and parameter variations. Our final aim is to provide an array of methods for coping with such inevitable distortion mechanisms. As a platform for testing our proposed strategies, we use an executable system specification (ESS) of the BrainScaleS neuromorphic system, which has been designed as a universal emulation back-end for neuroscientific modeling. We address the most essential limitations of this device in detail and study their effects on three prototypical benchmark network models within a well-defined, systematic workflow. For each network model, we start by defining quantifiable functionality measures by which we then assess the effects of typical hardware-specific distortion mechanisms, both in idealized software simulations and on the ESS. For those effects that cause unacceptable deviations from the original network dynamics, we suggest generic compensation mechanisms and demonstrate their effectiveness. Both the suggested workflow and the investigated compensation mechanisms are largely back-end independent and do not require additional hardware configurability beyond the one required to emulate the benchmark networks in the first place. We hereby provide a generic methodological environment for configurable neuromorphic devices that are targeted at emulating large-scale, functional neural networks

    Simulations of the progenitors of black hole-neutron star gravitational wave sources

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    Recent discoveries of gravitational wave (GW) events most likely originating from black hole (BH) + neutron star (NS) mergers reveal the existence of BH+NS binaries. The formation of BH+NS binaries and their merger rates through isolated binary evolution have been investigated extensively with population synthesis simulations. A detailed stellar evolution modelings of the formation of this population, however, is missing in the literature. In this work, we perform the first complete 1D model of more than 30 BH+NS progenitor systems which are calculated self-consistently until the iron core collapse with infall velocity exceeds 1000 km s^-1. Focusing on the progenitors of BH- NS GW sources, we apply the MESA code starting from a post-common envelope binary with short orbital period (< 1 day) consisting of a BH and a zero-age main-sequence helium star that experiences stable mass transfer. These NS masses could be significantly larger depending on the exact mass cut during the supernova explosion. These BH+NS systems are likely to merge and produce GW events within a Hubble time. System C is a potential progenitor of a GW200115-like event, while Systems A and B are possible candidates for a GW200105-like event and may represent the final destiny of the X-ray binary SS433.Comment: 14pages, 9 figures, Accepted to be published on Ap

    Neuromorphic Hardware In The Loop: Training a Deep Spiking Network on the BrainScaleS Wafer-Scale System

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    Emulating spiking neural networks on analog neuromorphic hardware offers several advantages over simulating them on conventional computers, particularly in terms of speed and energy consumption. However, this usually comes at the cost of reduced control over the dynamics of the emulated networks. In this paper, we demonstrate how iterative training of a hardware-emulated network can compensate for anomalies induced by the analog substrate. We first convert a deep neural network trained in software to a spiking network on the BrainScaleS wafer-scale neuromorphic system, thereby enabling an acceleration factor of 10 000 compared to the biological time domain. This mapping is followed by the in-the-loop training, where in each training step, the network activity is first recorded in hardware and then used to compute the parameter updates in software via backpropagation. An essential finding is that the parameter updates do not have to be precise, but only need to approximately follow the correct gradient, which simplifies the computation of updates. Using this approach, after only several tens of iterations, the spiking network shows an accuracy close to the ideal software-emulated prototype. The presented techniques show that deep spiking networks emulated on analog neuromorphic devices can attain good computational performance despite the inherent variations of the analog substrate.Comment: 8 pages, 10 figures, submitted to IJCNN 201

    Soil Saprobic Fungi Differ in Their Response to Gradually and Abruptly Delivered Copper

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    The overwhelming majority of studies examining environmental change deliver treatments abruptly, although, in fact, many important changes are gradual. One example of a gradually increasing environmental stressor is heavy metal contamination. Essential heavy metals, such as copper, play an important role within cells of living organisms but are toxic at higher concentrations. In our study, we focus on the effects of copper pollution on filamentous soil fungi, key players in terrestrial ecosystem functioning. We hypothesize that fungi exposed to gradually increasing copper concentrations have higher chances for physiological acclimation and will maintain biomass production and accumulate less copper, compared to fungi abruptly exposed to the highest copper concentration. To test this hypothesis, we conducted an experiment with 17 fungal isolates exposed to gradual and abrupt copper addition. Contrary to our hypothesis, we find diverse idiosyncratic responses, such that for many fungi gradually increasing copper concentrations have more severe effects (stronger growth inhibition and higher copper accumulation) than an abrupt increase. While a number of environmental change studies have accumulated evidence based on the magnitude of changes, the results of our study imply that the rate of change can be an important factor to consider in future studies in ecology, environmental science, and environmental management

    Tolerance of allogromiid Foraminifera to severely elevated carbon dioxide concentrations : implications to future ecosystem functioning and paleoceanographic interpretations

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    Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Global and Planetary Change 65 (2009): 107-114, doi:10.1016/j.gloplacha.2008.10.013.Increases in the partial pressure of carbon dioxide (pCO2) in the atmosphere will significantly affect a wide variety of terrestrial fauna and flora. Because of tight atmospheric-oceanic coupling, shallow-water marine species are also expected to be affected by increases in atmospheric carbon dioxide concentrations. One proposed way to slow increases in atmospheric pCO2 is to sequester CO2 in the deep sea. Thus, over the next few centuries marine species will be exposed to changing seawater chemistry caused by ocean-atmospheric exchange and/or deep-ocean sequestration. This initial case study on one allogromiid foraminiferal species (Allogromia laticollaris) was conducted to begin to ascertain the effect of elevated pCO2 on benthic Foraminifera, which are a major meiofaunal constituent of shallow- and deep-water marine communities. Cultures of this thecate foraminiferan protist were used for 10-14-day experiments. Experimental treatments were executed in an incubator that controlled CO2 (15 000; 30 000; 60 000; 90 000; 200 000 ppm), temperature and humidity; atmospheric controls (i.e., ~375 ppm CO2) were executed simultaneously. Although the experimental elevated pCO2 values are far above foreseeable surface water pCO2, they were selected to represent the spectrum of conditions expected for the benthos if deep-sea CO2 sequestration becomes a reality. Survival was assessed in two independent ways: pseudopodial presence/absence and measurement of adenosine triphosphate (ATP), which is an indicator of cellular energy. Substantial proportions of A. laticollaris populations survived 200 000 ppm CO2 although the mean of the median [ATP] of survivors was statistically lower for this treatment than for that of atmospheric control specimens. After individuals that had been incubated in 200 000 ppm CO2 for 12 days were transferred to atmospheric conditions for ~24 hours, the [ATP] of live specimens (survivors) approximated those of the comparable atmospheric control treatment. Incubation in 200 000 ppm CO2 also resulted in reproduction by some individuals. Results suggest that certain Foraminifera are able to tolerate deep-sea CO2 sequestration and perhaps thrive as a result of elevated pCO2 that is predicted for the next few centuries, in a high-pCO2 world. Thus, allogromiid foraminiferal “blooms” may result from climate change. Furthermore, because allogromiids consume a variety of prey, it is likely that they will be major players in ecosystem dynamics of future coastal sedimentary environments.This work was funded by US Department of Energy grant # DE-FG02-03ER63696 (to J. Kennett and J. Bernhard), NSF OCE-0725966, and the WHOI Summer Student Fellow Program, which is funded by NSF Research Experience for Undergraduates Program grant #OCE-0139423

    IMPACTO DAS ATIVIDADES DO PET-REDE CEGONHA NO ÍNDICE DE GESTAÇÕES DE UMA UNIDADE DE SAÚDE

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    Introducción: El planeamiento familiar representa un conjunto de acciones que auxilian la pareja que pretende tener hijos y también a quien prefiera adiar el crecimiento de la familia con anticoncepción. Objetivo: Evaluar el impacto de las actividades de planeamiento familiar del PET-Red Cigüeña en visitas domiciliarias y salas de espera. Metodología: Estudio transversal de naturaleza cuantitativa a través del análisis retrospectivo de las actividades del PET-Red Cigüeña en el periodo de enero de 2013 a enero de 2014, y contabilización del número de gestaciones de la unidad antes y después de las actividades del proyecto. Resultados/Conclusión: Había 47 gestantes en el comienzo de las actividades del PET-Red Cigüeña. Tras las actividades de visitas domiciliares a las mujeres y salas de espera con orientaciones sobre asuntos referentes a la gestación y planeamiento familiar, ese número cayó para 30 gestantes. Eso significa una reducción de 38% en el índice de gestaciones de la ESF Menino Deus.Introdução: O planejamento familiar representa um conjunto de ações que auxiliam o casal que pretende ter filhos e também quem prefere adiar o crescimento da família com anticoncepção. Objetivo: Avaliar o impacto das atividades de planejamento familiar do PET-Rede Cegonha em visitas domiciliares e salas de espera. Metodologia: Estudo transversal de natureza quantitativa através da análise retrospectiva das atividades do PET-Rede Cegonha, no período de janeiro de 2013 a janeiro de 2014, e contabilização do número de gestações da unidade antes e depois das atividades do projeto. Resultados/Conclusão: Havia 47 gestantes no início das atividades do PET-Rede Cegonha. Após as atividades de visitas domiciliares às mulheres e salas de espera com orientações sobre assuntos referentes à gestação e planejamento familiar esse número caiu para 30 gestantes. Isso significa uma redução de 38% no índice de gestações da ESF Menino Deus

    Multiple immune abnormalities in tumor necrosis factor and lymphotoxin-α double-deficient mice

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    To investigate the roles of tumor necrosis factor (TNF) and lymphotoxin (LT)-α in the development and function of the immune system, the Tnf and Ltα genes were simultaneously inactivated in mice by homologous recombination. These mutant mice are highly susceptible to Listeria monocytogenes infection and resistant to endotoxic shock induced by the combined administration of D-galactosamine (D-GaIN) and lipopolysaccharide (LPS). Their splenic microarchitecture is disorganized, characterized by the loss of the clearly defined marginal zone, ill defined T and B cell areas, and absence of MAdCAM-1 and reduced ICAM-1, VCAM-1 and Mac-1 expression. They are devoid of peripheral lymph nodes and Peyer's patches, and show a strong reduction of lgA+ plasma cells in the intestinal lamina propria. The alymphoplasia is accompanied by a marked B lymphocytosis and reduced basal Ig levels. Ig depositions in the renal glomerulus and a strong up-regulation of MHC class I antigen expression on endothelial cells of different tissues are observed. The primary humoral immune response towards sheep red blood cells reveals a defective IgG isotype switch, while that against vescicular stomatitis virus is normal. The cytotoxic T cell responses are attenuated, although still effective, against vaccinia, lymphocytic choriomeningitis virus (LCMV-ARM) and LCMV-WE. In conclusion, the combined inactivation of Tnf and Ltα confirms their essential role in the normal development and function of the immune syste

    Intergranular flux pinning in underdoped and overdoped R(1-x)CaxBa2Cu3Oz (R=Y,Gd; x=0,0.2) samples

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    The temperature dependences of AC magnetic susceptibility at different magnetic field amplitudes and frequencies are investigated for underdoped and overdoped R(1-x)Ca(x)Ba(2)Cu(3)O(7-delta)(R=Y; Gd and x=0; 0.2) polycrystalline samples. The activation energy, Ea, for thermally assisted flux flow (TAFF) in intergranular region is determined. It was established that a correlation exists between the intergranular critical current and flux pinning activation energy. In underdoped samples the intergranular current shows S-I-S behaviour and the activation energy is small, while in overdoped samples the intergranular current is changed to S-N-S type and the activation energy increases. 2D pancake vortices are characteristic of underdoped samples, while 3D vortex system exists in overdoped samples. In fact we demonstrate that Ca substitution not only increases carrier concentration, but improves intergranular activation energy for TAFF.Comment: 20 pages including 7 figures and one Table. accepted in Physica
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