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https://www.readbyqxmd.com/read/27926882/effect-of-reduced-humic-acid-on-the-transport-of-ferrihydrite-nanoparticles-under-anoxic-conditions
#1
Peng Liao, Wenlu Li, Dengjun Wang, Yi Jiang, Chao Pan, John D Fortner, Songhu Yuan
Humic acid (HA) occurs ubiquitously in the subsurface environments and is well-known to play a critical role in the fate and transport of ferrihydrite nanoparticles (NPs) and NPs-associated contaminants. Under anoxic conditions, HA can readily be reduced by microorganisms or geochemical reducing species, and the mechanisms and kinetics of ferrihydrite reduction by reduced HA (HAred) are well-documented; however, the role of these redox reactions on the transport of ferrihydrite NPs is largely underestimated...
December 1, 2016: Water Research
https://www.readbyqxmd.com/read/27926850/background-suppression-in-imaging-gold-nanorods-through-detection-of-anti-stokes-emission
#2
Aquiles Carattino, Veer I P Keizer, Marcel J M Schaaf, Michel Orrit
Metallic nanoparticles have opened the possibility of imaging, tracking, and manipulating biological samples without time limitations. Their low photoluminescence quantum yield, however, makes them hard to detect under high background conditions. In this study we show that it is possible to image gold nanorods by detecting their anti-Stokes emission under resonant excitation. We show that even in the membrane of a cell containing the fluorescent dye Atto 647N, the signal/background of the anti-Stokes emission can be >10, while it is impossible to image the particles with the Stokes emission...
December 6, 2016: Biophysical Journal
https://www.readbyqxmd.com/read/27926429/biologically-produced-methane-as-a-renewable-energy-source
#3
D E Holmes, J A Smith
Methanogens are a unique group of strictly anaerobic archaea that are more metabolically diverse than previously thought. Traditionally, it was thought that methanogens could only generate methane by coupling the oxidation of products formed by fermentative bacteria with the reduction of CO2. However, it has recently been observed that many methanogens can also use electrons extruded from metal-respiring bacteria, biocathodes, or insoluble electron shuttles as energy sources. Methanogens are found in both human-made and natural environments and are responsible for the production of ∼71% of the global atmospheric methane...
2016: Advances in Applied Microbiology
https://www.readbyqxmd.com/read/27925850/metallic-taste-in-cancer-patients-treated-with-systemic-therapy-a-questionnaire-based-study
#4
Irene IJpma, Erik R Timmermans, Remco J Renken, Gert J Ter Horst, Anna K L Reyners
A metallic taste is reported by cancer patients as a side effect of systemic therapy. Despite the high prevalence, this taste alteration has received limited attention. The present study investigated: 1) the prevalence of metallic taste in cancer patients treated with systemic therapy; 2) possible predictors of metallic taste; and 3) characteristics of metallic taste. A heterogeneous population of 127 cancer patients, who had received systemic treatment in the past year or were still on treatment, completed a questionnaire developed for this study...
December 7, 2016: Nutrition and Cancer
https://www.readbyqxmd.com/read/27925795/oxidants-at-the-surface-of-mars-a-review-in-light-of-recent-exploration-results
#5
J Lasne, A Noblet, C Szopa, R Navarro-González, M Cabane, O Poch, F Stalport, P François, S K Atreya, P Coll
In 1976, the Viking landers carried out the most comprehensive search for organics and microbial life in the martian regolith. Their results indicate that Mars' surface is lifeless and, surprisingly, depleted in organics at part-per-billion levels. Several biology experiments on the Viking landers gave controversial results that have since been explained by the presence of oxidizing agents on the surface of Mars. These oxidants may degrade abiotic or biological organics, resulting in their nondetection in the regolith...
December 7, 2016: Astrobiology
https://www.readbyqxmd.com/read/27925752/emergent-structural-mechanisms-for-high-density-collective-motion-inspired-by-human-crowds
#6
Arianna Bottinelli, David T J Sumpter, Jesse L Silverberg
Collective motion of large human crowds often depends on their density. In extreme cases like heavy metal concerts and black Friday sales events, motion is dominated by physical interactions instead of conventional social norms. Here, we study an active matter model inspired by situations when large groups of people gather at a point of common interest. Our analysis takes an approach developed for jammed granular media and identifies Goldstone modes, soft spots, and stochastic resonance as structurally driven mechanisms for potentially dangerous emergent collective motion...
November 25, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/27925698/frustrated-lewis-pairs-like-reactivity-of-rare-earth-metal-complexes-1-4-addition-reactions-and-polymerizations-of-conjugated-polar-alkenes
#7
Pengfei Xu, Yingming Yao, Xin Xu
Three rare-earth aryloxide ion pairs ([L1REOAr]+[B(C6F5)4]-; L1 = CH3C(2,6-iPr2C6H3N)CHC(CH3)(NCH2CH2PPh2); RE = Sc, Y, Lu; Ar = 2,6-tBu2C6H3) are reported, which feature RE/P combinations exhibiting frustrated Lewis pair (FLP)-like 1,4-addition reactions towards conjugated carbonyl substrates e.g. enone, ynone and acrylic substrates. Furthermore, these RE/P complexes are found to be effective catalysts for polymerizations of conjugated polar alkene monomers. Mechanistic studies reveal that the polymerizations are initiated by novel FLP-type 1,4-additions, rather than traditional and ubiquitous covalent RE-E (E = H, C, N, etc...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925690/purification-and-characterization-of-a-platelet-aggregation-inhibitor-and-anticoagulant-cc-5_ntase-cd-73-like-from-cerastes-cerastes-venom
#8
Samah Saoud, Fatah Chérifi, Traki Benhassine, Fatima Laraba-Djebari
The present study is the first attempt to report the characterization of a nucleotidase from Cerastes cerastes venom. A 70 kDa 5'-nucleotidase (Cc-5'NTase) was purified to homogeneity. The amino acid sequence of Cc-5'NTase displayed high homology with many nucleotidases. Its activity was optimal at pH 7 with a specific hydrolytic activity toward mono-, di-, and triphosphate adenylated nucleotides. Cc-5'NTase preferentially hydrolyzed ADP and obeyed Michaelis-Menten kinetics. Among the metals and inhibitors tested, Ni(2+) and Mg(2+) completely potentiated enzyme activity, whereas EGTA, PMSF, iodoacetamide, vanillic acid, vanillyl mandelic acid, and 1,10-phenanthroline partially abolished its activity...
December 7, 2016: Journal of Biochemical and Molecular Toxicology
https://www.readbyqxmd.com/read/27925442/organocatalytic-coupling-of-co2-with-a-propargylic-alcohol-a-comprehensive-study-of-the-reaction-mechanism-combining-in-situ-atr-ir-spectroscopy-and-dft-calculations
#9
Amélie Boyaval, Raphaël Mereau, Bruno Grignard, Christophe Detrembleur, Christine Jerome, Thierry Tassaing
The metal-free coupling of propargylic alcohols with carbon dioxide catalysed by guanidine derivatives was investigated in detail through the combination of online kinetic studies by in-situ ATR-IR spectroscopy and DFT calculations. Bicyclic guanidines, namely TBD and MTBD, are effective catalysts for the conversion of 2-methyl-3-butyn-2-ol to α-methylene cyclic carbonate and oxoalkyl acyclic carbonate under mild reaction conditions. The lower selectivity of TBD in comparison with MTBD towards the formation of α-methylene cyclic carbonate was elucidated from DFT calculations and is related to the bifunctional activity (base/H-bond donor) of TBD decreasing the Gibbs free energy of the reaction path for the formation of the acyclic carbonate...
December 7, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27925439/surface-faceting-and-reconstruction-of-ceria-nanoparticles
#10
Chengwu Yang, Xiaojuan Yu, Stefan Heißler, Alexei Nefedov, Sara Colussi, Jordi Llorca, Alessandro Trovarelli, Yuemin Wang, Christof Wöll
The surface atomic arrangement of metal oxides determines their physical and chemical properties, and the ability to control and optimize structural parameters is of crucial importance for many applications, in particular in heterogeneous catalysis and photocatalysis. Whereas the structures of macroscopic single crystals can be determined with established methods, for nanoparticles (NPs), this is a challenging task. Herein, we describe the use of CO as a probe molecule to determine the structure of the surfaces exposed by rod-shaped ceria NPs...
December 7, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27925406/iodide-photocatalyzed-reduction-of-carbon-dioxide-to-formic-acid-with-thiols-and-hydrogen-sulfide
#11
Mateo Berton, Rossella Mello, María Elena González-Núñez
The photolysis of iodide anions promotes the reaction of carbon dioxide with hydrogen sulfide or thiols to quantitatively yield formic acid and sulfur or disulfides. The reaction proceeds in acetonitrile and aqueous solutions, at atmospheric pressure and room temperature by irradiation using a low-pressure mercury lamp. This transition-metal-free photocatalytic process for CO2 capture coupled with H2 S removal may have been relevant as a prebiotic carbon dioxide fixation.
December 7, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27925403/heterogeneously-catalyzed-aerobic-oxidation-of-5-hydroxymethylfurfural-to-2-5-furandicarboxylic-acid-with-manganese-dioxide
#12
Eri Hayashi, Tasuku Komanoya, Keigo Kamata, Michikazu Hara
A simple non-precious metal catalyst system based on cost-effective and ubiquitously available MnO2, NaHCO3, and molecular oxygen was used to convert 5-hydroxymethylfurfural to 2,5-difurandicarboxylic acid as a bioplastics precursor in 91% yield. The MnO2 catalyst could be recovered by simple filtration and reused several times. The present system was also applicable to the aerobic oxidation of other biomass-derived substrates and the gram-scale oxidation of HMF to FDCA, in which 2.36 g (86% yield) of the analytically pure FDCA could be isolated...
December 7, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27925400/hydrothermal-carbon-enriched-with-oxygenated-groups-from-biomass-glucose-as-an-efficient-carbocatalyst
#13
Guodong Wen, Bolun Wang, Congxin Wang, Jia Wang, Zhijian Tian, Robert Schlögl, Dang Sheng Su
Metal-free carbocatalysts enriched with specific oxygenated groups with different morphology and size were synthesized from glucose by hydrothermal carbonization, in which cheap and widely available biomass could be converted into functionalized carbon using an environmentally benign process. The hydroxy- and carbonyl-enriched hydrothermal carbon (HTC) could be used in nitrobenzene reduction, and higher conversion was obtained on the sphere morphology with smaller size. In the Beckmann rearrangement of cyclohexanone oxime, carboxyl-enriched HTC exhibited superior performance compared with conventional solid acid (such as HY and HZSM-5), on which the strong acid sites and weak Lewis acid sites lead to high selectivity for the side product...
December 7, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27925394/markovnikov-selective-radical-addition-of-s-nucleophiles-to-terminal-alkynes-through-a-photoredox-process
#14
Huamin Wang, Qingquan Lu, Chien-Wei Chiang, Yi Luo, Jiufu Zhou, Guangyu Wang, Aiwen Lei
Direct radical additions to terminal alkynes have been widely employed in organic synthesis, providing credible access to the anti-Markovnikov products. Because of the Kharasch effect, regioselective control for the formation of Markovnikov products still remains a great challenge. Herein, we develop a transition-metal-free, visible light-mediated radical addition of S-nucleophiles to terminal alkynes, furnishing a wide array of α-substituted vinyl sulfones with exclusive Markovnikov regioselectivity. Mechanistic investigations demonstrated that radical/radical cross-coupling might be the key step in this transformation...
December 7, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27925327/crystal-structure-of-a-metalled-double-helix-generated-by-infinite-and-consecutive-c-agi-c-c-n1-hexylcytosine-base-pairs-through-argentophilic-and-hydrogen-bond-interactions
#15
Angel Terron, Blas Moreno-Vachiano, Antonio Bauza, Angel Garcia-Raso, Juan J Fiol, Miquel Barcelo-Oliver, Elies Molins, Antonio Frontera
The synthesis of a metalled double-helix containing exclusively silver-mediated C*-C* base pairs is reported herein (C* = N1hexylcytosine). Remarkably, it is the first crystal structure containing infinite and consecutive C*-AgI-C* base pairs that form a double helix. The AgI ion occupies the center between two C* residues with N(3)-Ag bond distances of 2.1 Å and short AgI-AgI distances (3.1 Å) suggesting an interesting argentophilic attraction as a stabilization source of the helical disposition. The solid state structure is further stabilized by metal-mediated base-pairs, hydrogen bonding and π-stacking interactions...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925316/functional-species-encapsulated-in-nitrogen-doped-porous-carbon-as-a-highly-efficient-catalyst-to-oxygen-reduction-reaction
#16
Li Song, Tao Wang, Yiou Ma, Hairong Xue, Hu Guo, Xiaoli Fan, Wei Xia, Hao Gong, Jianping He
The scarcity, high cost and poor stability of precious metal-based electrocatalysts have stimulated the development of novel non-precious metal catalysts to oxygen reduction reaction (ORR) for the use in fuel cells and metal-air batteries. Here, we in-situ fabricated a hybrid material (Co-W-C/N) with functional species (tungsten carbide and cobalt nanoparticles) encapsulated in N-doped porous carbon framework, through a facile multi-constituents co-assembly method combined with subsequent annealing treatment...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925302/a-three-dimensionally-structured-electrocatalyst-cobalt-embedded-nitrogen-doped-carbon-nanotubes-nitrogen-doped-reduced-graphene-oxide-hybrid-for-efficient-oxygen-reduction
#17
Changting Wei, Hongjing Wang, Kamel Eid, Jeonghun Kim, Jung Ho Kim, Zeid Abdullah Alothman, Yusuke Yamauchi, Liang Wang
To develop low-cost and efficient oxygen reduction reaction (ORR) catalysts, a novel hybrid comprising cobalt-embedded nitrogen-doped carbon nanotubes and nitrogen-doped reduced graphene oxide (Co-NCNT/NrGO-800) was simply prepared by pyrolysis. The combination of nanotubes and graphene, and the efficient doping with cobalt and nitrogen, greatly contribute to the excellent ORR performance. This optimized Co-NCNT/NrGO catalyst exhibits a positive onset potential of 0.91 V and a half-wave potential of 0.82 V, combined with a relatively low peroxide yield, better durability, and better methanol tolerance than commercially available Pt/C, which makes it a promising candidate as a low-cost and effective non-precious-metal ORR catalyst...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925296/metal-organic-framework-as-a-protective-coating-for-biodiagnostic-chips
#18
Congzhou Wang, Sirimuvva Tadepalli, Jingyi Luan, Keng-Ku Liu, Jeremiah J Morrissey, Evan D Kharasch, Rajesh R Naik, Srikanth Singamaneni
A zeolitic imidazolate framework-8 (ZIF-8) grown around antibodies anchored to plasmonic nanostructures serve as a protective layer to preserve the biorecognition ability of antibodies stored at room and elevated temperatures for several days. The biofunctionality of the ZIF-8 protected biochip can be restored by a simple water rinsing step, making it highly convenient for use in point-of-care and resource-limited settings.
December 7, 2016: Advanced Materials
https://www.readbyqxmd.com/read/27925282/hypobaric-hypoxia-regulates-brain-iron-homeostasis-in-rats
#19
Yaru Li, Peng Yu, Shi-Yang Chang, Qiong Wu, Panpan Yu, Congcong Xie, Wenyue Wu, Baolu Zhao, Guofen Gao, Yan-Zhong Chang
Disruption of iron homeostasis in brain has been found to be closely involved in several neurodegenerative diseases. Recent studies have reported that appropriate intermittent hypobaric hypoxia played a protective role in brain injury caused by acute hypoxia. However, the mechanisms of this protective effect have not been fully understood. In this study, Sprague-Dawley rat models were developed by hypobaric hypoxia treatment in an altitude chamber, and the iron level and iron related protein levels were determined in rat brain after four weeks of treatment...
December 6, 2016: Journal of Cellular Biochemistry
https://www.readbyqxmd.com/read/27925277/identification-of-sources-of-metal-in-the-agricultural-soils-of-guanzhong-plain-northwest-china
#20
Wenbo Deng, Xuxiang Li, Zhisheng An, Liu Yang, Kang Hou, Yue Zhang
In this study, we conducted a comprehensive survey to assess the possible sources and distribution of metals in the agricultural soils of Guanzhong Plain, northwest China. A total of 227 samples of agricultural soil were collected to determine the content of Pb, Cr, Co, V, Ni, Zn, Cu, As and Mn by X-ray fluorescence spectrometry. The mean concentrations of metals were 26.2 ± 10.8 mg · kg(-1) , 71.5 ± 16.8 mg · kg(-1) , 12.7 ± 1.81 mg · kg(-1) , 85.1 ± 7.86 mg · kg(-1) , 30...
December 7, 2016: Environmental Toxicology and Chemistry
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