4,235 research outputs found

    Surface coatings and catalyst production by electrodeposition

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    Electrodeposition and electrocodeposition in low gravity are discussed. The goal is to provide a better understanding of the role of convection and buoyancy in the mechanisms of formation of some electrodeposited surfaces, fluid flow in the vicinity of electrodepositing surfaces, the influence of a moving medium upon codeposition, the effect of gravity upon the dispersion (coagulation) of neutral particles that are desired for codeposition and preparation of improved surface coatings and metal catalysts

    Spatially explicit threat assessment to target food tree species in Burkina Faso

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    There is a general agreement on the need to ensure the in situ conservation and availability of valuable genetic resources of wild species that are important for food security and nutrition. In order to be able to adopt adequate conservation measures a spatial assessment of their distribution and a sound analysis of the causes of and their sensitivity to threats is required. The ADA funded project “Threats to priority food tree species in Burkina Faso: Drivers of resource losses and mitigation measures” gave us the opportunity to develop a spati- ally explicit threat assessment methodology with focus on expert feedback, as there is no comprehensive and standardised approach available at the moment. Relevant threats were identified jointly with regional project partners from INERA and CNSF during meetings in Ouagadougou in 2012 and 2013 and by means of a case study on farmers’ perception. Once determined were the most important ones (overexploitation, overgrazing, fire, climate change, cotton production and mining) we identified openly accessible datasets suitable to represent the spatial patterns of threat intensities throughout the country. Now we needed to transform the threat intensities into potential impact over the target species distribution ranges. To do so the distribution and threat sensitivity of 16 food tree species were assessed by 17 local and international experts by means of an online feedback survey that was specifically developed for this project. These experts were asked to rate on a five point scale different distribution models and the sensitivity to threats. The survey was analysed applying a consensus method to identify the most consistent distribution model and threat specific sensitivity rating on a species by species basis. The potential impact of climate change was modeled using Global Circulation Models (GCM’s) deriving from the fifth assessment of the Intergovernmental Panel on Climate Change (IPCC5) in 2014. The results were then used to calculate and create individual and combined threat potential maps that enable the identification of areas in Burkina Faso where species are highly threatened. The spatial patterns of the threat levels provides evidence to prioritise food tree populations with relative urgency for undertaking conservation actions

    Some aspects of electron–phonon interaction in the thermal modulation spectra of molecular crystals

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    The details of the temperature dependent intensity and linewidth of zero‐phonon bands in molecular crystal absorption and emission spectra are considered in relation to the line shape functions observed in thermal modulation spectra. Theory suggests and experiment confirms that in the limit of the Condon and adiabatic approximations for linear electron–phonon coupling, the extraordinary temperature dependence of zero‐phonon bands may be utilized to separate them from diffuse background absorption or emission. Qualitative consideration of line broadening from quadratic electron–phonon coupling utilizing a configuration coordinate model suggests that even when these terms dominate the linear interaction, increased resolution may be obtained in a thermal modulation spectrum. The theoretical considerations are illustrated with several experimental examples and some applications of the technique are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70661/2/JCPSA6-65-12-5068-1.pd

    Concave Plasmonic Particles: Broad-Band Geometrical Tunability in the Near Infra-Red

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    Optical resonances spanning the Near and Short Infra-Red spectral regime were exhibited experimentally by arrays of plasmonic nano-particles with concave cross-section. The concavity of the particle was shown to be the key ingredient for enabling the broad band tunability of the resonance frequency, even for particles with dimensional aspect ratios of order unity. The atypical flexibility of setting the resonance wavelength is shown to stem from a unique interplay of local geometry with surface charge distributions

    Fourier transform infrared and Raman spectroscopic characterization of homogeneous solution concentration gradients near a container wall at different temperatures

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    Fourier transform infrared (FTIR) and Raman spectroscopic techniques were used to study the solution concentration gradient in succino nitrile-rich and water-rich homogeneous solutions. The spectroscopic data shows significant concentration dependency. Although FTIR-attenuated total reflectance could not yield surface spectra since the evanescent infrared wave penetrated deep into the bulk solution, it showed that water-rich clusters were decreased at higher temperatures. This result is consistent with the calorimetric results reported earlier

    Processing of strong flux trapping high T(subc) oxide superconductors: Center director's discretionary fund

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    Magnetic suspension effect was first observed in samples of YBa2Cu3O7/AgO(Y-123/AgO) composites. Magnetization measurements of these samples show a much larger hysteresis which corresponds to a large critical current density. In addition to the Y-123AgO composites, recently similar suspension effects in other RE-123/AgO, where RE stands for rare-Earth elements, were also observed. Some samples exhibit even stronger flux pinning than that of the Y-123/AgO sample. An interesting observation was that in order to form the composite which exhibits strong flux trapping effect the sintering temperature depends on the particular RE-123 compound used. The paper presents the detailed processing conditions for the formation of these RE-123/AgO composites, as well as the magnetization and critical field data

    Identifying tree populations for conservation action through geospatial analyses

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    Rapid development of information and communication technologies has made it possible to easily collect georeferenced information on species and their environment, and to use it for analyzing biological diversity, its distribution and threats to it. Such analyses can importantly inform development of conservation strategies and priorities, especially across countries or species distribution ranges (Guarino et al. 2002). Data for spatial analyses on species or genetic diversity and its distribution are collected in specifically designed studies, obtained from existing records of species occurrence, or both. Observations may be complemented by species distribution modelling, where the potential occurrence of a species is predicted based on its documented geographic distribution and climate in those areas. Results on the distribution of diversity, documented or modelled, can then be compared, for example, with existing protected areas, rates of forest degradation, threats of environmental changes, or socio-economic indicators, to identify priority tree populations and tailor strategies for their conservation and sustainable use (Pautasso 2009). In this paper recent case studies on spatial biodiversity analyses across the tropics are presented, demonstrating how such analyses can help to identify most unique or most threatened populations of a tree species for conservation actions. Insights on initiating collaborative research on diversity and distributions of important Asian tree species are also discussed

    Rigorous Real-Time Feynman Path Integral for Vector Potentials

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    we will show the existence and uniqueness of a real-time, time-sliced Feynman path integral for quantum systems with vector potential. Our formulation of the path integral will be derived on the L2L^2 transition probability amplitude via improper Riemann integrals. Our formulation will hold for vector potential Hamiltonian for which its potential and vector potential each carries at most a finite number of singularities and discontinuities

    Pyrophosphate-Dependent ATP Formation from Acetyl Coenzyme A in Syntrophus aciditrophicus, a New Twist on ATP Formation.

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    UnlabelledSyntrophus aciditrophicus is a model syntrophic bacterium that degrades key intermediates in anaerobic decomposition, such as benzoate, cyclohexane-1-carboxylate, and certain fatty acids, to acetate when grown with hydrogen-/formate-consuming microorganisms. ATP formation coupled to acetate production is the main source for energy conservation by S. aciditrophicus However, the absence of homologs for phosphate acetyltransferase and acetate kinase in the genome of S. aciditrophicus leaves it unclear as to how ATP is formed, as most fermentative bacteria rely on these two enzymes to synthesize ATP from acetyl coenzyme A (CoA) and phosphate. Here, we combine transcriptomic, proteomic, metabolite, and enzymatic approaches to show that S. aciditrophicus uses AMP-forming, acetyl-CoA synthetase (Acs1) for ATP synthesis from acetyl-CoA. acs1 mRNA and Acs1 were abundant in transcriptomes and proteomes, respectively, of S. aciditrophicus grown in pure culture and coculture. Cell extracts of S. aciditrophicus had low or undetectable acetate kinase and phosphate acetyltransferase activities but had high acetyl-CoA synthetase activity under all growth conditions tested. Both Acs1 purified from S. aciditrophicus and recombinantly produced Acs1 catalyzed ATP and acetate formation from acetyl-CoA, AMP, and pyrophosphate. High pyrophosphate levels and a high AMP-to-ATP ratio (5.9 ± 1.4) in S. aciditrophicus cells support the operation of Acs1 in the acetate-forming direction. Thus, S. aciditrophicus has a unique approach to conserve energy involving pyrophosphate, AMP, acetyl-CoA, and an AMP-forming, acetyl-CoA synthetase.ImportanceBacteria use two enzymes, phosphate acetyltransferase and acetate kinase, to make ATP from acetyl-CoA, while acetate-forming archaea use a single enzyme, an ADP-forming, acetyl-CoA synthetase, to synthesize ATP and acetate from acetyl-CoA. Syntrophus aciditrophicus apparently relies on a different approach to conserve energy during acetyl-CoA metabolism, as its genome does not have homologs to the genes for phosphate acetyltransferase and acetate kinase. Here, we show that S. aciditrophicus uses an alternative approach, an AMP-forming, acetyl-CoA synthetase, to make ATP from acetyl-CoA. AMP-forming, acetyl-CoA synthetases were previously thought to function only in the activation of acetate to acetyl-CoA
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