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https://www.readbyqxmd.com/read/28922801/effect-of-severe-weather-events-on-the-shedding-of-shiga-toxigenic-escherichia-coli-in-slaughter-cattle-and-phenotype-of-serogroup-o157-isolates
#1
Kim Stanford, Tim Reuter, Susan J Bach, Linda Chui, Angela Ma, Cheyenne C Conrad, Renata Tostes, Tim A McAllister
High-event periods (HEPs) occur sporadically when beef carcasses and meat have episodes of acute contamination with Shiga toxin-producing Escherichia coli (STEC). In this study, severe weather events were investigated as catalysts for HEPs based on PCR and isolate prevalence of seven E. coli serogroups in slaughter cattle feces. Winter ambient temperatures with daily means 10.5oC warmer or 12.3°C colder than seasonal norms (-10.4°C) most altered STEC shedding. Fecal samples yielded increased proportions (P < 0...
September 1, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/28922570/catalyst-stability-benchmarking-for-the-oxygen-evolution-reaction-the-importance-of-backing-electrode-material-and-dissolution-in-accelerated-aging-studies
#2
Simon Geiger, Olga Kasian, Andrea M Mingers, Shannon S Nicley, Ken Haenen, Karl J J Mayrhofer, Serhiy Cherevko
In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of materials intrinsic activity and stability in half-cell tests is of vital importance. It significantly accelerates the discovery of new promising materials without the need of time-consuming real cell analysis. In commonly employed tests, a conclusion on the catalyst stability is drawn solely on the basis of pure electrochemical information, e.g. by evaluating potential vs. time profiles. In this work we demonstrate important limitations of such approaches, which are related to the degradation of the backing electrode material...
September 18, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28922550/mesoporous-nanosheet-networked-hybrids-of-cobalt-oxide-and-cobalt-phosphate-for-efficient-electrochemical-and-photoelectrochemical-oxygen-evolution
#3
Bin Liu, Hui-Qing Peng, Cheuk-Nam Ho, Hongtao Xue, Shuilin Wu, Tsz-Wai Ng, Chun-Sing Lee, Wenjun Zhang
A novel mesoporous nanosheet networked hybrid comprising Co3 O4 and Co3 (PO4 )2 is successfully synthesized using a facile and scalable method through calcinating the carbon, cobalt hydroxy carbonate, and cobalt phosphate composite precursor. Electron transfer from Co3 O4 to Co3 (PO4 )2 , together with the special networked structure and the porous nature of the nanosheets enable the Co3 (PO4 )2 -Co3 O4 hybrid to have a high oxygen evolution reaction (OER) activity and outstanding stability in alkaline electrolyte, e...
September 18, 2017: Small
https://www.readbyqxmd.com/read/28922531/stoichiometric-reactions-of-co2-and-indium-silylamides-and-catalytic-synthesis-of-ureas
#4
Maotong Xu, Andrew Jupp, Douglas Wade Stephan
The indium compounds In(N(SiMe3)2)2Cl*THF (2) and In(N(SiMe3)2)Cl2*(THF)n¬ (3) were shown to react with CO2 to give [(Me3Si)2N)InX(-OSiMe3)]2 (X = N(SiMe3)2 4, Cl 5). 0.05-2.0 mol% of the species 3 acts as a pre-catalyst for the conversion of aryl and alkyl silylamines under CO2 (2-3 atm.) to give the corresponding ureas in 70-99% yields. A proposed mechanism is supported by experimental and computational data.
September 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28922530/a-space-charge-treatment-of-the-increased-concentration-of-reactive-species-at-the-surface-of-a-ceria-solid-solution
#5
Alexander F Zurhelle, Xiaorui Tong, Andreas Klein, David S Mebane, Roger A De Souza
We apply a space-charge theory applicable to concentrated solid solutions-Poisson-Cahn theory-to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy (XPS) for the concentration of Ce3+ (the reactive species) at the surface of the oxide catalyst Ce0.8Sm0.2O1.9. In contrast to previous theoretical treatments, our calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space-charge zone...
September 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28921983/the-first-state-in-the-catalytic-cycle-of-the-water-oxidizing-enzyme-identification-of-a-water-derived-%C3%AE-hydroxo-bridge
#6
Thomas Lohmiller, Vera Krewald, Arezki Sedoud, A William Rutherford, Frank Neese, Wolfgang Lubitz, Dimitrios A Pantazis, Nicholas Cox
Nature's water splitting catalyst, an oxygen-bridged tetra-manganese calcium (Mn4O5Ca) complex, sequentially activates two substrate water molecules generating molecular O2. Its reaction cycle is composed of five intermediate (Si) states, where the index i indicates the number of oxidizing equivalents stored by the cofactor. After formation of the S4 state, the product dioxygen is released and the cofactor returns to its lowest oxidation state, S0. Membrane-inlet mass spectrometry measurements suggest that at least one substrate is bound throughout the catalytic cycle, as the rate of (18)O-labeled water incorporation into the product O2 is slow, on a millisecond to second timescale depending on the S state...
September 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28921981/the-use-of-cyclopentadienone-iron-tricarbonyl-complexes-for-c-n-bond-formation-reactions-between-amines-and-alcohols
#7
Thomas J Brown, Madeleine Cumbes, Louis J Diorazio, Guy J Clarkson, Martin Wills
The application of a series of (cyclopentadienone)iron tricarbonyl complexes to 'borrowing hydrogen' reactions between amines and alcohols was completed in order to assess their catalytic activity. The electronic variation of the aromatic groups flanking the C=O of the cyclopentadienone influenced the efficiency of the reactions, however in other cases the Knölker catalyst 1, containing trimethylsilyl groups flanking the cyclopentadienone ketone, gave the best results. In some cases, the change of the ratio of amine to alcohol improves the conversion significantly...
September 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28921978/electrocatalytic-co2-reduction-by-imidazolium-functionalized-molecular-catalysts
#8
Siyoung Sung, Davinder Kumar, Marcos Gil-Sepulcre, Michael Nippe
We present the first examples of CO2 electro-reduction catalysts that feature charged imidazolium groups in the secondary coordination sphere. The functionalized Lehn-type catalysts display significant differences in their redox properties and improved catalytic activities as compared to the conventional reference catalyst. Our results suggest that the incorporated imidazolium moieties do not solely function as a charged tag but also alter mechanistic aspects of catalysis.
September 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28921973/evans-showell-type-polyoxometalates-constructing-high-dimensional-inorganic-organic-hybrid-compounds-with-copper-organic-coordination-complexes-synthesis-and-oxidation-catalysis
#9
Haiyan An, Yujiao Hou, Lin Wang, Yumeng Zhang, Wei Yang, ShenZhen Chang
Four new hybrid architectures containing a [Co2Mo10H4O38](6-) polyoxoanion, (en)[Cu3(ptz)4(H2O)4][Co2Mo10H4O38]·24H2O (1), (Hbim)2[{Cu(bim)2(H2O)2}2{Co2Mo10H4O38}]·5H2O (2), H2[Cu(dpdo)3(H2O)4][{Cu2(dpdo)3(H2O)4(CH3CN)}2{Co2Mo10H4O38}2]·9H2O (3), and (H2bpp)4[{Cu(H2O)2}{NaCo2Mo10H4O38}2]·10H2O (4), where ptz = 5-(4-pyridyl)-1H-tetrazole, en = ethylenediamine, bim = benzimidazole, dpdo = 4,4'-bipyridine-N,N'-dioxide, and bpp = 1,3-bis(4-pyridyl)propane, have been prepared and characterized through elemental analysis, thermogravimetric analysis, IR spectroscopy, and powder and single-crystal X-ray diffraction...
September 18, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28921968/automated-solid-phase-click-synthesis-of-oligonucleotide-conjugates-from-small-molecules-to-diverse-n-acetylgalactosamine-clusters
#10
Valentina M Farzan, Egor A Ulashchik, Yury V Martynenko-Makaev, Maksim V Kvach, Ilya Olegovich Aparin, Vladimir A Brylev, Tatiana A Prikazchikova, Svetlana Yu Maklakova, Alexander G Majouga, Alexey V Ustinov, German A Shipulin, Vadim V Shmanai, Vladimir A Korshun, Timofei S Zatsepin
We developed a novel technique for efficient conjugation of oligonucleotides with various alkyl azides (fluorescent dyes, biotin, cholesterol, GalNAc, etc.) using CuAAC on solid phase and CuI·P(OEt)3 as a catalyst. Conjugation is carried out in an oligonucleotide synthesizer in fully automated mode and is coupled to oligonucleotide synthesis and on-column deprotection. We also suggest a set of reagents for the construction of diverse conjugates. The sequential double click procedure using a pentaerythritol-derived tetraazide followed by the addition of a GalNAc or tris-GalNAc alkyne gives oligonucleotide-GalNAc dendrimer conjugates in good yields with minimal excess of sophisticated alkyne reagents...
September 18, 2017: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/28921962/pentafluorosulfanyl-substituents-in-polymerization-catalysis
#11
Philip Kenyon, Stefan Mecking
Highly electron-withdrawing pentafluorosulfanyl groups were probed as substituents in an organometallic catalyst. In Ni(II) salicylaldiminato complexes as an example case, these highly electron-withdrawing substituents allow for polymerization of ethylene to higher molecular weights with reduced branching due to significant reductions in β-hydrogen elimination. Combined with the excellent functional group tolerance of neutral Ni(II) complexes, this suppression of β-hydrogen elimination allows for the direct polymerization of ethylene in water to nanocrystal dispersions of disentangled, ultrahigh-molecular-weight linear polyethylene...
September 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28921958/electronic-structural-analysis-of-copper-ii-tempo-abno-complexes-provides-evidence-for-copper-i-oxoammonium-character
#12
Richard C Walroth, Kelsey C Miles, James T Lukens, Samantha N MacMillan, Shannon S Stahl, Kyle M Lancaster
Copper/aminoxyl species are proposed as key intermediates in aerobic alcohol oxidation. Several possible electronic structural descriptions of these species are possible, and the present study probes this issue by examining four crystallographically characterized Cu/aminoxyl halide complexes by Cu K-edge, Cu L2,3-edge, and Cl K-edge X-ray absorption spectroscopy. The mixing coefficients between Cu, aminoxyl, and halide orbitals are determined via these techniques with support from density functional theory...
September 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28921879/natural-and-artificial-mn4ca-cluster-for-water-splitting-reaction
#13
Chunxi Zhang, Changhui Chen, Yanxi Li, Guoqing Zhao, Ruoqing Yao
The oxygen-evolving center (OEC) in photosystem II (PSII) is a unique biological catalyst that splits water into electrons, protons and O2 by using solar energy. Recent crystallographic studies have revealed that the structure of the OEC is an asymmetric Mn4Ca-cluster, which provides a blueprint to develop man-made water-splitting catalysts in artificial photosynthesis. Although it is a great challenge to mimic the whole structure and function of the OEC in the laboratory, significant advances have recently been achieved...
September 17, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28921759/a-pedagogical-framework-for-facilitating-parents-learning-in-nurse-parent-partnership
#14
Nick Hopwood, Teena Clerke, Anne Nguyen
Nursing work increasingly demands forms of expertise that complement specialist knowledge. In child and family nursing, this need arises when nurses work in partnership with parents of young children at risk. Partnership means working with parents in respectful, negotiated and empowering ways. Existing partnership literature emphasises communicative and relational skills, but this paper focuses on nurses' capacities to facilitate parents' learning. Referring to data from home visiting, day-stay and specialist toddler clinic services in Sydney, a pedagogical framework is presented...
September 17, 2017: Nursing Inquiry
https://www.readbyqxmd.com/read/28921703/poly-vinylidene-fluoride-co-chlorotrifluoroethylene-modification-via-organocatalyzed-atom-transfer-radical-polymerization
#15
Xin Hu, Yajun Zhang, Guopeng Cui, Ning Zhu, Kai Guo
To address the challenge of metal contamination, a "graft from" approach via organocatalyzed atom transfer radical polymerization (O-ATRP) is developed to synthesize poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) graft copolymers. N-phenylphenothiazine is utilized as a model organic photoredox catalyst for catalyzing the (co)polymerization of methyl methacrylate (MMA), methacrylate (MA), and n-butyl acrylate (BA). By employing this technique, high temporal control of polymerization and graft content are achieved...
September 15, 2017: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/28921692/mechanistic-studies-on-the-role-of-cuii-co3-n-2-2n-as-a-water-oxidation-catalyst-carbonate-as-a-non-innocent-ligand
#16
Amir Mizrahi, Dan Meyerstein, Israel Zilbermann, Haya Kornweitz, Eric Maimon, Haim Cohen
Recently it was reported that copper bicarbonate/ carbonate complexes are good electro-catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n3-2n complexes are the active intermediates in the electrolysis of CuII(CO3)n2-2n solution. The results enable the evaluation of E°((CuIII/II(CO3)n)aq) ~ 1.42 V vs. NHE at pH 8.4. This redox potential is in accord with the electrochemical report...
September 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28920990/a-ruthenium-water-oxidation-catalyst-containing-a-bipyridine-glycoluril-ligand
#17
Vishwanath S Mane, Avinash S Kumbhar, Randolph P Thummel
A mononuclear ruthenium complex [Ru(tpy)(bpg)H2O](2+) bearing a bipyridine glycoluril where bpg = 4b,5,7,7a-tetrahydro-4b,7a-nepiminomethanoimino-6H-imidazo[4,5-f][1,10]phenanthro-line-6,13-dione acts as a robust water oxidation catalyst (WOC) at pH = 1 using Ce(iv) as a sacrificial oxidant. The turn over number (TON) for water oxidation is found to be ∼5 times higher than the parent complex [Ru(tpy)(bpy)H2O](2+) where tpy = 2,2':6',2''-terpyridine; bpy = 2,2'-bipyridine. The presence of intermolecular H-bonding groups and the electronic effect of the functionalized bipyridine ligand may play a significant role in water oxidation...
September 18, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28920700/highly-selective-construction-of-medium-sized-lactams-by-palladium-catalyzed-intramolecular-hydroaminocarbonylation-of-aminoalkynes
#18
Yue Hu, Hanmin Huang
A novel palladium-catalyzed intramolecular hydroaminocarbonylation of aminoalkynes has been developed. This direct and operationally simple protocol provides a rapid and reliable approach to a diverse array of valuable seven- and eight-membered lactams with high chemoselectivity and regioselectivity. The high selectivity might be attributed to rational tuning the electronic nature of the amine moiety and the palladium catalyst, which enabled this transformation to proceed in the absence of acidic or any other additives under fairly mild reaction conditions...
September 18, 2017: Organic Letters
https://www.readbyqxmd.com/read/28920688/enantioselective-construction-of-cyclopenta-b-indole-scaffolds-via-the-catalytic-asymmetric-3-2-cycloaddition-of-2-indolylmethanols-with-p-hydroxystyrenes
#19
Meng-Meng Xu, Hai-Qing Wang, Ying Wan, Shu-Liang Wang, Feng Shi
The catalytic asymmetric [3+2] cycloaddition of 2-indolylmethanols to p-hydroxystyrenes was established in the presence of a chiral phosphoramide, and this reaction provided chiral cyclopenta[b]indole scaffolds in generally high yields and with good enantioselectivities (up to 98% yield, 99:1 er). The control experiments demonstrated that the dual hydrogen-bonding activation mode of the chiral catalyst toward the two substrates played an important role in the reaction. In addition, the large-scale reaction indicated that this catalytic asymmetric [3+2] cycloaddition could be scaled up for the synthesis of chiral cyclopenta[b]indole derivatives...
September 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28920681/access-to-cyano-containing-isoxazolines-via-copper-catalyzed-domino-cyclization-cyanation-of-alkenyl-oximes
#20
Fei Meng, Honglin Zhang, Kang Guo, Jiayue Dong, Ai-Min Lu, Yingguang Zhu
A highly efficient copper-catalyzed cyclization/cyanation cascade of unactivated olefins bearing oximes is described. A variety of cyano-containing isoxazolines have been obtained in high yields with cheap Cu(NO3)2·3H2O as the catalyst and TMSCN as the non-metallic cyanide source. The present method provides a mild, simple, and practical access to cyano-substituted isoxazolines and is amenable to gram scale. The simultaneous construction of C(sp3)-CN and C-O bonds can be achieved in one step.
September 18, 2017: Journal of Organic Chemistry
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