24,652 research outputs found

    Rapid and mask-less laser-processing technique for the fabrication of microstructures in polydimethylsiloxane

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    We report a rapid laser-based method for structuring polydimethylsiloxane (PDMS) on the micron-scale. This mask-less method uses a digital multi-mirror device as a spatial light modulator to produce a given spatial intensity pattern to create arbitrarily shaped structures via either ablation or multi-photon photo-polymerisation in a master substrate, which is subsequently used to cast the complementary patterns in PDMS. This patterned PDMS mould was then used for micro-contact printing of ink and biological molecules

    A 2D Microphysical Analysis of Aerosol Nucleation in the Polar Winter Stratosphere: Implications for H2SO4 Photolysis and Nucleation Mechanisms

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    Each spring a layer of small particles forms between 20 and 30 km in the polar regions. Results are presented from a 2D microphysical model of sulfate aerosol, which provide the first self-consistent explanation of the observed "CN layer." Photochemical conversion of sulfuric acid to SO2 in the upper stratosphere and mesosphere is necessary for this layer to form. Recent laboratory measurements of H2SO4 and SO3 photolysis rates are consistent with such conversion, though an additional source of SO2 may be required. Nucleation throughout the polar winter extends the top of the aerosol layer to higher altitudes, despite strong downward transport of ambient air. This finding may be important to heterogeneous chemistry at the top of the aerosol layer in polar winter and spring

    Microphysical simulations of sulfur burdens from stratospheric sulfur geoengineering

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    Recent microphysical studies suggest that geoengineering by continuous stratospheric injection of SO<sub>2</sub> gas may be limited by the growth of the aerosols. We study the efficacy of SO<sub>2</sub>, H<sub>2</sub>SO<sub>4</sub> and aerosol injections on aerosol mass and optical depth using a three-dimensional general circulation model with sulfur chemistry and sectional aerosol microphysics (WACCM/CARMA). We find increasing injection rates of SO<sub>2</sub> in a narrow band around the equator to have limited efficacy while broadening the injecting zone as well as injecting particles instead of SO<sub>2</sub> gas increases the sulfate burden for a given injection rate, in agreement with previous work. We find that injecting H<sub>2</sub>SO<sub>4</sub> gas instead of SO<sub>2</sub> does not discernibly alter sulfate size or mass, in contrast with a previous study using a plume model with a microphysical model. However, the physics and chemistry in aircraft plumes, which are smaller than climate model grid cells, need to be more carefully considered. We also find significant perturbations to tropospheric aerosol for all injections studied, particularly in the upper troposphere and near the poles, where sulfate burden increases by up to 100 times. This enhanced burden could have implications for tropospheric radiative forcing and chemistry. These results highlight the need to mitigate greenhouse gas emissions rather than attempt to cool the planet through geoengineering, and to further study geoengineering before it can be seriously considered as a climate intervention option

    Proteomic analysis of Bifidobacterium longum subsp. infantis reveals the metabolic insight on consumption of prebiotics and host glycans.

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    Bifidobacterium longum subsp. infantis is a common member of the intestinal microbiota in breast-fed infants and capable of metabolizing human milk oligosaccharides (HMO). To investigate the bacterial response to different prebiotics, we analyzed both cell wall associated and whole cell proteins in B. infantis. Proteins were identified by LC-MS/MS followed by comparative proteomics to deduce the protein localization within the cell. Enzymes involved in the metabolism of lactose, glucose, galactooligosaccharides, fructooligosaccharides and HMO were constitutively expressed exhibiting less than two-fold change regardless of the sugar used. In contrast, enzymes in N-Acetylglucosamine and sucrose catabolism were induced by HMO and fructans, respectively. Galactose-metabolizing enzymes phosphoglucomutase, UDP-glucose 4-epimerase and UTP glucose-1-P uridylytransferase were expressed constitutively, while galactokinase and galactose-1-phosphate uridylyltransferase, increased their expression three fold when HMO and lactose were used as substrates for cell growth. Cell wall-associated proteomics also revealed ATP-dependent sugar transport systems associated with consumption of different prebiotics. In addition, the expression of 16 glycosyl hydrolases revealed the complete metabolic route for each substrate. Mucin, which possesses O-glycans that are structurally similar to HMO did not induced the expression of transport proteins, hydrolysis or sugar metabolic pathway indicating B. infantis do not utilize these glycoconjugates

    The impact of freeze-drying infant fecal samples on measures of their bacterial community profiles and milk-derived oligosaccharide content.

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    Infant fecal samples are commonly studied to investigate the impacts of breastfeeding on the development of the microbiota and subsequent health effects. Comparisons of infants living in different geographic regions and environmental contexts are needed to aid our understanding of evolutionarily-selected milk adaptations. However, the preservation of fecal samples from individuals in remote locales until they can be processed can be a challenge. Freeze-drying (lyophilization) offers a cost-effective way to preserve some biological samples for transport and analysis at a later date. Currently, it is unknown what, if any, biases are introduced into various analyses by the freeze-drying process. Here, we investigated how freeze-drying affected analysis of two relevant and intertwined aspects of infant fecal samples, marker gene amplicon sequencing of the bacterial community and the fecal oligosaccharide profile (undigested human milk oligosaccharides). No differences were discovered between the fecal oligosaccharide profiles of wet and freeze-dried samples. The marker gene sequencing data showed an increase in proportional representation of Bacteriodes and a decrease in detection of bifidobacteria and members of class Bacilli after freeze-drying. This sample treatment bias may possibly be related to the cell morphology of these different taxa (Gram status). However, these effects did not overwhelm the natural variation among individuals, as the community data still strongly grouped by subject and not by freeze-drying status. We also found that compensating for sample concentration during freeze-drying, while not necessary, was also not detrimental. Freeze-drying may therefore be an acceptable method of sample preservation and mass reduction for some studies of microbial ecology and milk glycan analysis

    Magnon Mediated Electric Current Drag Across a Ferromagnetic Insulator Layer

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    In a semiconductor hererostructure, the Coulomb interaction is responsible for the electric current drag between two 2D electron gases across an electron impenetrable insulator. For two metallic layers separated by a ferromagnetic insulator (FI) layer, the electric current drag can be mediated by a nonequilibrium magnon current of the FI. We determine the drag current by using the semiclassical Boltzmann approach with proper boundary conditions of electrons and magnons at the metal-FI interface.Comment: 13 pages, 2 figures: to appear in PR

    Assessing the link between implementation fidelity and health outcomes for a trial of intensive case management by community health workers: a mixed methods study protocol

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    Background: Better systems of care are required to address chronic disease in Indigenous people to ensure they can access all their care needs. Health research has produced evidence about effective models of care and chronic disease strategies to address Indigenous health, however the transfer of research findings into routine clinical practice has proven challenging. Complex interventions, such as those related to chronic disease, have many components that are often poorly implemented and hence rarely achieve implementation fidelity. Implementation fidelity is "the degree to which programs are implemented as intended by the program developer". Knowing if an intervention was implemented as planned is fundamental to knowing what has contributed to the success of an intervention. Methods: The aim of this study is to adapt the implementation fidelity framework developed by Keith et al. and apply it to the intervention implemented in phase 1 of the Getting Better at Chronic Care in North Queensland study. The objectives are to quantify the level of implementation fidelity achieved during phase 1 of the study, measure the association between implementation fidelity and health outcomes and to explore the features of the primary health care system that contributed to improved health outcomes. A convergent parallel mixed methods study design will be used to develop a process for assessing implementation fidelity. Information collected via a questionnaire and routine data generated during phase 1 of the study will be used to explain the context for the intervention in each site and develop an implementation fidelity score for each component of the intervention. A weighting will be applied to each component of the intervention to calculate the overall implementation score for each participating community. Statistical analysis will assess the level of association between implementation fidelity scores and health outcomes. Discussion: Health services research seeks to find solutions to social and technical problems to improve health outcomes. The development of a tool and methodology for assessing implementation fidelity in the Indigenous primary health care context will help address some of the barriers to the translation of research into practice.Barbara Schmidt, Kerrianne Watt, Robyn McDermott and Jane Mill
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