7,624 research outputs found

    From Drug War to Culture War: Russia’s Growing Role in the Global Drug Debate

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    Global Commodity Chains and LINKSCH

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    Will a God of love punish any of His creatures forever?

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    https://place.asburyseminary.edu/ecommonsatsdigitalresources/1156/thumbnail.jp

    Removal of Carboxylic Acids and Water from Pyrolysis Oil

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    Over 70% of the world’s energy consumption is provided by fossil fuels and with those reserves depleting at a fast rate, alternative energy sources or methods are needed to support the world’s energy needs. This research was done in an attempt to make it more economically feasible to produce fuel products, such as bio-diesel, from the upgrading of bio-oil obtained from the pyrolysis of biomass waste material such as sawdust. The high water and oxygenated compound content of bio-oil make it undesirable for fuel use; however, two methods involving surface modified commercial membranes were utilized in hopes of overcoming these problems: electrodialysis and a pressure-driven system. Nafion 117 membrane pores were expanded and then the membrane was subjected to bio-oil at pressures up to 700 psi with the goal of removing the water. Although the pores were enlarged, removing water through this method was unsuccessful. Electrodialysis was used in an effort to remove carboxylic acids from bio-oil, which are known to cause storage instability. The membranes used for this separation were Neosepta CMX and AMX commercial membranes. Modifications to the AMX membrane surface were made by adding crosslinked polyethylenimine groups to the surface of the membrane and its performance was compared to that of the unmodified one. A XPS and FTIR analysis proved the modified membrane to be more resistant to bio-fouling

    Nickel Silicide as a Contact and Diffusion Barrier for Copper Metallization in Silicon Photovoltaics

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    In this study, NiSi has been formed as the contact for copper front metallization on laboratory silicon solar cells. Transfer length method (TLM) measurements were used to examine the resistive nature of the contact. The scalability of the measurement itself was also examined. Characterization of the NiSi films for thickness, resistivity and composition were performed. Single crystal silicon solar cells were fabricated and used in temperature stress tests of the degradation of the pseudo-fill factor (pFF) and quantum efficiency (QE) to assess the capabilities of the NiSi diffusion barrier. Best contact resistivities of 7.3e-6 Ohm-cm2 with NiSi only and 4.0e-5 Ohm-cm2 with NiSi/Cu/TiN were measured. Even following a week of temperature stress, NiSi maintained solar cell performance parameters such as pseudo fill factor (pFF) and quantum efficiency (QE) better than Cu/TiN contacts without NiSi and at least as good as Ti/Pd/Ag contacts on average. These methods and materials were applied to high efficiency, textured, solar cells with passivated tunneling contacts. The viability of NiSi in this regime was evaluated by photoluminescence (PL), optical, and TLM measurements. Although the NiSi contact was shown to damage the passivation quality of the contact, a cell capable of an open circuit voltage near 700 mV could be produced using such a contact scheme. Contact resistances as low as 1.8 mOhm-cm2 were formed, as compared with industry standard screen printed Ag contacts which form best contact resistivities in the range of 1.5 mOhm-cm2

    A classified list of activities for plane geometry suggested by current books

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    Thesis (M.A.)--Boston Universit

    Three-dimensional imaging of direct-written photonic structures

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    Third harmonic generation microscopy has been used to analyze the morphology of photonic structures created using the femtosecond laser direct-write technique. Three dimensional waveguide arrays and waveguide-Bragg gratings written in fused-silica and doped phosphate glass were investigated. A sensorless adaptive optical system was used to correct the optical aberrations occurring in the sample and microscope system, which had a lateral resolution of less than 500 nm. This non-destructive testing method creates volume reconstructions of photonic devices and reveals details invisible to other linear microscopy and index profilometry techniques.Comment: 8 pages, 3 color figures, 2 hyper-linked animation

    Molecular Dynamics Studies of Water Flow in Carbon Nanotubes

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    We present classical molecular dynamics (MD) simulations providing insight into the behaviour of water. We focus on confined water, the properties of which are often significantly different from the properties of bulk water. First, we performed several simulations investigating the handling of long-range interactions in GROMACS [1], a MD simulation package. Selection of simulation protocols such as handling of long-range interactions is often overlooked, sometimes to the significant detriment of the final result [2, 3, 4]. Ensuring that the chosen simulation protocols are appropriate is a critical step in computer simulation. Second, we performed MD simulations where water flowed between two reservoirs con- nected by a carbon nanotube. We analyzed 10 simulations where two types of changes were made to induce flow: The removal of water molecules from one reservoir and the addition of NaCl to one reservoir at one of two concentrations. We study the effects of these changes in isolation, cooperation and competition. [1] B Hess, C Kutzner, D van der Spoel, and E Lindahl. Gromacs 4: Algorithms for highly efficient, load-balanced, and scalable molecular simulation. J. Chem. Theory Comput., 4:435–447, 2008. [2] D. J. Bonthuis, K. F. Rinne, K. Falk, C. N. Kaplan, D. Horinek, A. N. Berker, L. Bocquet, and R. R. Netz. Theory and simulations of water flow through carbon nanotubes: prospects and pitfalls. J. Phys.: Condens. Matter, 23:184110, 2011. [3] J. Wong-ekkabut and M. Karttunen. Assessment of common simulation protocols for simulations of nanopores, membrane proteins, and channels. J. Chem. Theory Comput. DOI: 10.1021/ct3001359. [4] J. Wong-ekkabut,M. S. Miettinen, C. Dias, and M. Karttunen. Static charges cannot drive a continuous flow of water molecules through a carbon nanotube. Nat. Nanotechnol., 5:555–557, 2010
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