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Metallic hydrogen

C Zapata, B Paillavil, R Chávez, P Álamos, G Levicán
Bioleaching processes are used to recover metals from sulfidic ores. Biofilm formation on ores is important for bioleaching because the attached microorganisms start the leaching process by concentrating ferric ions in the extracellular matrix. It has been shown that hydrogen peroxide is spontaneously generated on the surface of ores and that it negatively influences the growth and activity of microorganisms. However, the mechanism by which bioleaching microorganisms tolerate exogenous H2O2 as an adaptive trait remains elusive...
January 12, 2017: FEMS Microbiology Ecology
Leif Holmlid
Large signals of charged light mesons are observed in the laser-induced particle flux from ultra-dense hydrogen H(0) layers. The mesons are formed in such layers on metal surfaces using < 200 mJ laser pulse-energy. The time variation of the signal to metal foil collectors and the magnetic deflection to a movable pin collector are now studied. Relativistic charged particles with velocity up to 500 MeV u-1 thus 0.75 c are observed. Characteristic decay time constants for meson decay are observed, for charged and neutral kaons and also for charged pions...
2017: PloS One
Shiyou Xing, Pengmei Lv, Jiayan Wang, Junying Fu, Pei Fan, Lingmei Yang, Gaixiu Yang, Zhenhong Yuan, Yong Chen
For high caloricity and stability in bio-aviation fuels, a certain content of aromatic hydrocarbons (AHCs, 8-25 wt%) is crucial. Fatty acids, obtained from waste or inedible oils, are a renewable and economic feedstock for AHC production. Considerable amounts of AHCs, up to 64.61 wt%, were produced through the one-step hydroprocessing of fatty acids over Ni/HZSM-5 catalysts. Hydrogenation, hydrocracking, and aromatization constituted the principal AHC formation processes. At a lower temperature, fatty acids were first hydrosaturated and then hydrodeoxygenated at metal sites to form long-chain hydrocarbons...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
Ranajit Nivrutti Shinde, Subramanian Karthikeyan, Balvinder Singh
3,4-dihydroxy-2-butanone-4-phosphate synthase (DHBPS) catalyzes the conversion of D-ribulose 5-phosphate (Ru5P) to L-3,4-dihydroxy-2-butanone-4-phosphate in the presence of Mg(2+). Although crystal structures of DHBPS in complex with Ru5P and non-catalytic metal ions have been reported, structure with Ru5P along with Mg(2+) is still elusive. Therefore, mechanistic role played by Mg(2+) in the structure of DHBPS is poorly understood. In this study, molecular dynamics simulations of DHBPS-Ru5P complex along with Mg(2+) have shown entry of Mg(2+) from bulk solvent into active site...
January 12, 2017: Scientific Reports
Jitang Chen, Yang Yang, Jianwei Su, Peng Jiang, Guoliang Xia, Qianwang Chen
The hydrogen evolution reaction (HER) is highly relied on Pt-based electrocatalysts with high activity and stability. For a long time, a host of efforts have been made in the development of novel platinum nano-structures with a low amount of Pt because the scarcity and high price of Pt hinders its practical applications. Here, we report the preparation of PtCoFe@C electrocatalysts with remarkably reduced Pt loading amount of 4.60%by annealing Pt-doped metal-organic frameworks (MOFs). The electrocatalyst demonstrated an outstanding performance with only 45 mV overpotential to achieve the 10 mA cm-2 current density, which is quite close to that of the commercial 20% Pt/C catalyst...
January 12, 2017: ACS Applied Materials & Interfaces
Subrata Chakraborty, Gregory Leitus, David Milstein
The first example of a base-metal-catalyzed homogeneous hydrogenative coupling of nitriles and amines to selectively form secondary cross-imines is reported. The reaction is catalyzed under mild conditions by a well-defined (iPr-PNP)Fe(H)Br(CO) pincer pre-catalyst and catalytic tBuOK.
January 12, 2017: Angewandte Chemie
Jacob Schneidewind, Rosa Adam, Wolfgang Baumann, Ralf Jackstell, Matthias Beller
Herein we describe the first homogeneous non-noble metal catalyst for the hydrogenation of CO2 to methanol. The catalyst is formed in situ from [Co(acac)3 ], Triphos, and HNTf2 and enables the reaction to be performed at 100 °C without a decrease in activity. Kinetic studies suggest an inner-sphere mechanism, and in situ NMR and MS experiments reveal the formation of the active catalyst through slow removal of the acetylacetonate ligands.
January 12, 2017: Angewandte Chemie
Nicklas Deibl, Rhett Kempe
The development of catalytic reactions for synthesizing different compounds from alcohols to save fossil carbon feedstock and reduce CO2 emissions is of high importance. Replacing rare noble metals with abundantly available 3d metals is equally important. We report a manganese-complex-catalyzed multicomponent synthesis of pyrimidines from amidines and up to three alcohols. Our reaction proceeds through condensation and dehydrogenation steps, permitting selective C-C and C-N bond formations. β-Alkylation reactions are used to multiply alkylate secondary alcohols with two different primary alcohols to synthesize fully substituted pyrimidines in a one-pot process...
January 12, 2017: Angewandte Chemie
Solène Gentil, Noémie Lalaoui, Arnab Dutta, Yannig Nedellec, Serge Cosnier, Wendy J Shaw, Vincent Artero, Alan Le Goff
A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2 /2 H(+) interconversion from pH 0 to 9, with catalytic preference for H2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode...
January 12, 2017: Angewandte Chemie
Uk Sim, Joonhee Moon, Joohee Lee, JungHyun An, Hyo-Yong Ahn, Dong Jin Kim, Insu Jo, Cheolho Jeon, Seungwu Han, Byung Hee Hong, Ki Tae Nam
Photoelectrochemical cells are used to split hydrogen and oxygen from water molecules to generate chemical fuels to satisfy our ever-increasing energy demands. However, it is a major challenge to design efficient catalysts to use in the photoelectochemical process. Recently, research has focused on carbon-based catalysts, as they are non-precious and environmentally benign. Interesting advances have also been made in controlling nanostructure interfaces and in introducing new materials as catalysts in the photoelectrochemical cell...
January 11, 2017: ACS Applied Materials & Interfaces
U Khalilov, A Bogaerts, B Xu, T Kato, T Kaneko, E C Neyts
Unlocking the enormous technological potential of carbon nanotubes strongly depends on our ability to specifically produce metallic or semiconducting tubes. While selective etching of both has already been demonstrated, the underlying reasons, however, remain elusive as yet. We here present computational and experimental evidence on the operative mechanisms at the atomic scale. We demonstrate that during the adsorption of H atoms and their coalescence, the adsorbed ortho hydrogen pairs on single-walled carbon nanotubes induce higher shear stresses than axial stresses, leading to the elongation of HC-CH bonds as a function of their alignment with the tube chirality vector, which we denote as the γ-angle...
January 11, 2017: Nanoscale
Takuya Iwasaki, Manoharan Muruganathan, Marek E Schmidt, Hiroshi Mizuta
The transformation of systematic vacuum and hydrogen annealing effects in graphene devices on the SiO2 surface is reported based on experimental and van der Waals interaction corrected density functional theory (DFT) simulation results. Vacuum annealing removes p-type dopants and reduces charged impurity scattering in graphene. Moreover, it induces n-type doping into graphene, leading to the improvement of the electron mobility and conductivity in the electron transport regime, which are reversed by exposing to atmospheric environment...
January 11, 2017: Nanoscale
Bingya Hou, Lang Shen, Haotian Shi, Rehan Kapadia, Stephen B Cronin
We report measurements of photocatalytic water splitting using Au films with and without TiO2 coatings. In these structures, a thin (3-10 nm) film of TiO2 is deposited using atomic layer deposition (ALD) on top of a 100 nm thick Au film. We utilize an AC lock-in technique, which enables us to detect the relatively small photocurrents (∼μA) produced by the short-lived hot electrons that are photoexcited in the metal. Under illumination, the bare Au film produces a small AC photocurrent (<1 μA) for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) due to hot electrons and hot holes, respectively, that are photoexcited in the Au film...
January 11, 2017: Physical Chemistry Chemical Physics: PCCP
Gopi Kolluru, Shuai Yuan, XInggui Shen, Christopher G Kevil
SIGNIFICANCE: The family of gasotransmitter molecules nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), has emerged as important mediators of numerous cellular signal transduction and pathophysiological responses. As such, these molecules have been reported to influence a diverse array of biochemical, molecular, and cell biology events often impacting one another. Recent Advances: Discrete regulation of gasotransmitter molecule formation, movement, and reaction are critical to their biological function...
January 9, 2017: Antioxidants & Redox Signaling
Patrick Frank, Robert K Szilagyi, Volker Gramlich, Hua-Fen Hsu, Britt Hedman, Keith O Hodgson
Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M(II)(itao)(SO4)(H2O)0,1] (M = Co, Ni, Cu) and [Cu(Me6tren)(SO4)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO4)] but not of [Cu(Me6tren)(SO4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge...
January 9, 2017: Inorganic Chemistry
Arindam Indra, Amitava Acharjya, Prashanth W Menezes, Christoph Merschjann, Dirk Hollmann, Michael Schwarze, Mesut Aktas, Aleksej Friedrich, Stefan Lochbrunner, Arne Thomas, Matthias Driess
Solar light harvesting by photocatalytic H2 evolution from water could solve the problem of greenhouse gas emission from fossil fuels with alternative clean energy. However, the development of more efficient and robust catalytic systems remains a great challenge for the technological use on a large scale. Here we report the synthesis of a sol-gel prepared mesoporous graphitic carbon nitride (sg-CN) combined with nickel phosphide (Ni2 P) which acts as a superior co-catalyst for efficient photocatalytic H2 evolution by visible light...
January 9, 2017: Angewandte Chemie
Rosa Adam, Charles Bheeter, Jose Cabrero-Antonino, Kathrin Junge, Ralf Jackstell, Matthias Beller
A general protocol for the catalytic hydrogenation of nitriles to primary amines using a non-noble metal based system is presented. Co(acac)3 in combination with tris(2-(dicyclohexylphosphanyl)ethyl) phosphane L3 catalyses efficiently the selective hydrogenation of a wide range of (hetero)aromatic and aliphatic nitriles to the corresponding amines.
January 9, 2017: ChemSusChem
Cristiana Margarita, Pher G Andersson
The catalytic enantioselective hydrogenation of prochiral olefins is a key reaction in asymmetric synthesis. Its relevance applies to both industry and academia as an inherently direct and sustainable strategy to induce chirality. Here we briefly recount the early breakthroughs concerning the asymmetric hydrogenation of largely unfunctionalized olefins, from the first reports to the advent of chiral Crabtree-like catalysts. The mechanism and its implications on the enantioselectivity are shortly discussed. The main focus of this Perspective lies on the more recent advances in the field, such as the latest developed classes of ligands and the opportunity to employ more earth-abundant metals...
January 7, 2017: Journal of the American Chemical Society
Soo-Hwan Byun, Ho-Kyung Lim, Soung-Min Kim, Sung-Mi Lee, Hyoun-Ee Kim, Jong-Ho Lee
INTRODUCTION: Nonabsorbable metallic membrane for guided bone regeneration is remained permanently even though after complete healing. There would be metallic exposure followed by the risk of infection; the membrane should be removed for the additional procedure such as implant installation. Since absorbable nonmetallic mesh is absorbed within 3 to 6 months, it is unnecessary to be removed. However, the absorbable membrane shows lower retention, lower mechanical strength, and difficulty of manipulation than the nonabsorbable ones...
January 5, 2017: Journal of Craniofacial Surgery
Marcelo F Ciappina, J Perez-Hernandez, Alexandra Landsman, William Okell, Sergey Zherebtsov, Benjamin Förg, Johannes Schötz, Lennart Seiffert, Thomas Fennel, Tahir Shaaran, Tomas Zimmermann, Alexis Chacón, Roland Guichard, Amelle Zair, John Tisch, J Marangos, Tobias Witting, Avi Braun, Stefan Maier, Luis Roso, Michael Krüger, Peter Hommelhoff, Matthias Kling, Ferenc Krausz, Maciej Lewenstein
Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is 152 as...
January 6, 2017: Reports on Progress in Physics
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