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Toru Amaya, Yuma Osafune, Yusuke Maegawa, Toshikazu Hirao
Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates was achieved to give the corresponding unsymmetrical 1,4-dicarbonyl compounds, where combination of various boron and silyl enolates such as ketone-ester, ester-ketone, ester-ester, amide-ketone, and amide-ester enolates was adapted. These results clearly exhibit the versatility of the present oxidative cross-coupling protocol...
April 20, 2017: Chemistry, An Asian Journal
Julie A Korak, Richard Huggins, Miguel Arias-Paic
Due to stricter regulations, some drinking water utilities must implement additional treatment processes to meet potable water standards for hexavalent chromium (Cr(VI)), such as the California limit of 10 μg/L. Strong base anion exchange is effective for Cr(VI) removal, but efficient resin regeneration and waste minimization are important for operational, economic and environmental considerations. This study compared multiple regeneration methods on pilot-scale columns on the basis of regeneration efficiency, waste production and salt usage...
March 9, 2017: Water Research
Xu-Liang Xue, Wan-Zhong Lang, Xi Yan, Ya Jun Guo
The uniform monodispersed vanadium-doped three-dimensional dendritic mesoporous silica nanospheres (nV-MSNSs) were successfully synthesized in a heterogeneous oil-water biphase stratification reaction system, and characterized by several state-of-art methods. The synthesized nV-MSNSs were applied to the oxidative dehydrogenation of propane (ODHP) reaction with the presence of CO2 and exhibited excellent catalytic performances. The results show that the vanadium loading (1.3-8.0 wt %) evidently influences the textural properties, oxidation state and polymerization degree of vanadium species of nV-MSNSs...
April 20, 2017: ACS Applied Materials & Interfaces
Abhinav Parihar, Nikhil Shukla, Matthew Jerry, Suman Datta, Arijit Raychowdhury
While Boolean logic has been the backbone of digital information processing, there exist classes of computationally hard problems wherein this paradigm is fundamentally inefficient. Vertex coloring of graphs, belonging to the class of combinatorial optimization, represents one such problem. It is well studied for its applications in data sciences, life sciences, social sciences and technology, and hence, motivates alternate, more efficient non-Boolean pathways towards its solution. Here we demonstrate a coupled relaxation oscillator based dynamical system that exploits insulator-metal transition in Vanadium Dioxide (VO2) to efficiently solve vertex coloring of graphs...
April 19, 2017: Scientific Reports
Kyung Hwa Jung, David Torrone, Stephanie Lovinsky-Desir, Matthew Perzanowski, Joshua Bautista, Jacqueline R Jezioro, Lori Hoepner, Jamie Ross, Frederica P Perera, Steven N Chillrud, Rachel L Miller
BACKGROUND: Both short and long-term exposure to traffic-related air pollutants have been associated with asthma and reduced lung function. We hypothesized that short-term indoor exposure to fine particulate matter <2.5 μm (PM2.5) and vanadium (V) would be associated with altered buccal cell DNA methylation of targeted asthma genes and decreased lung function among urban children in a nested subcohort of African American and Dominican children. METHODS: Six day integrated levels of air pollutants were measured from children's homes (age 9-14; n = 163), repeated 6 months later (n = 98)...
April 19, 2017: Respiratory Research
Allan R Petersen, Peter Fristrup
The deoxydehydration (DODH) reaction remains one of the most efficient methods of reducing the oxygen content of biomass while keeping important functionality in place. This reaction is traditionally catalysed by high-valent oxorhenium species. Recent research into heterogeneous rhenium-based catalysts for DODH demonstrates their ability to rival and in some cases surpass their homogeneous counterparts. Furthermore, catalysts based on the metals molybdenum and vanadium show great potential as inexpensive alternatives to rhenium catalysts...
April 17, 2017: Chemistry: a European Journal
Makoto Sako, Kazuya Ichinose, Shinobu Takizawa, Hiroaki Sasai
Short-step syntheses of 4-deoxycarbazomycin B and sorazolon E were established through the condensation of cyclohexanone and commercially available 4-methoxy-2,3-dimethylaniline, followed by Pd(II)-catalyzed dehydrogenative aromatization/intramolecular C-C bond coupling and deprotection. A chiral dinuclear vanadium complex (Ra,S,S)-6 mediated the first enantioselective oxidative coupling of sorazolon E, affording (+)-sorazolon E2 in good enantioselectivity.
April 18, 2017: Chemistry, An Asian Journal
Chaouki Siouani, Sofiane Mahtout, Sofiane Safer, Franck Rabilloud
We systematically study the equilibrium geometries, electronic and magnetic properties of Gen+1 and VGen (n = 1-19) clusters using the density functional theory approach (DFT) within the generalized gradient approximation (GGA). Endohedral structures in which the vanadium atom is encapsulated inside a Gen cage are predicted to be favored for n ≥ 10. The dopant V atom in the Gen clusters has not an immediate effect on the stability of small germanium clusters (n<6) but it largely contributes to strengthen the stability for n ≥ 7...
April 18, 2017: Journal of Physical Chemistry. A
Tobias Janoschka, Christian Friebe, Martin D Hager, Norbert Martin, Ulrich S Schubert
By combining a viologen unit and a 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) radical in one single combi-molecule, an artificial bipolar redox-active material, 1-(4-(((1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy)carbonyl)benzyl)-1'-methyl-[4,4'-bipyridine]-1,1'-diium-chloride (VIOTEMP), was created that can serve as both the anode (-0.49 V) and cathode (0.67 V vs. Ag/AgCl) in a water-based redox-flow battery. While it mimics the redox states of flow battery metals like vanadium, the novel aqueous electrolyte does not require strongly acidic media and is best operated at pH 4...
April 2017: ChemistryOpen
Jianguo Jiang, Meng Yang, Yuchen Gao, Jiaming Wang, Dean Li, Tianran Li
Vanadium (V) contamination in soils is an increasing worldwide concern facing human health and environmental conservation. The fractionation of a metal influences its mobility and biological toxicity. We analyzed the fractionations of V and several other metals using the BCR three-step sequential extraction procedure. Among methods for removing metal contamination, soil washing is an effective permanent treatment. We conducted experiments to select the proper reagents and to optimize extraction conditions. Citric acid, tartaric acid, oxalic acid, and Na2EDTA all exhibited high removal rates of the extractable state of V...
March 31, 2017: Chemosphere
Xi-Yuan Xiao, Ming-Wei Wang, Hui-Wen Zhu, Zhao-Hui Guo, Xiao-Qing Han, Peng Zeng
High levels of vanadium (V) have long-term, hazardous impacts on soil ecosystems and biological processes. In the present study, the effects of V on soil enzymatic activities, basal respiration (BR), microbial biomass carbon (MBC), and the microbial community structure were investigated through 12-week greenhouse incubation experiments. The results showed that V content affected soil dehydrogenase activity (DHA), BR, and MBC, while urease activity (UA) was less sensitive to V stress. The average median effective concentration (EC50) thresholds of V were predicted using a log-logistic dose-response model, and they were 362mgV/kg soil for BR and 417mgV/kg soil for DHA...
April 12, 2017: Ecotoxicology and Environmental Safety
Aviva Levina, Peter Andrew Lay
Diverse biological activities of vanadium(V) drugs mainly arise from their abilities to inhibit phosphate-dependent enzymes and to alter cell signaling. Initial interest focused on anti-diabetic activities but has shifted to anti-cancer and anti-parasitic drugs. V-based anti-diabetics are pro-drugs that release active components (e.g., H₂VO₄¯) in biological media. By contrast, V anti-cancer drugs are generally assumed to enter cells intact; however, speciation studies indicate that nearly all drugs are likely to react in cell culture media during in-vitro assays and the same would apply in vivo...
April 11, 2017: Chemistry, An Asian Journal
Weijie Nie, Rang Li, Chen Cheng, Yanxue Chen, Qingming Lu, Carolina Romero, Javier R Vázquez de Aldana, Xiaotao Hao, Feng Chen
We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO2). The unique feature of VO2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66...
April 6, 2017: Scientific Reports
María C Nevárez-Martínez, Paweł Mazierski, Marek P Kobylański, Grażyna Szczepańska, Grzegorz Trykowski, Anna Malankowska, Magda Kozak, Patricio J Espinoza-Montero, Adriana Zaleska-Medynska
V₂O₅-TiO₂ mixed oxide nanotube (NT) layers were successfully prepared via the one-step anodization of Ti-V alloys. The obtained samples were characterized by scanning electron microscopy (SEM), UV-Vis absorption, photoluminescence spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), and micro-Raman spectroscopy. The effect of the applied voltage (30-50 V), vanadium content (5-15 wt %) in the alloy, and water content (2-10 vol %) in an ethylene glycol-based electrolyte was studied systematically to determine their influence on the morphology, and for the first-time, on the photocatalytic properties of these nanomaterials...
April 5, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Zi Wei, Yi Shen, Dong Liu, Fuqiang Liu
Greater levels of solar energy storage provide an effective solution to the inherent nature of intermittency, and can substantially improve reliability, availability, and quality of the renewable energy source. Here we demonstrated an all-vanadium (all-V) continuous-flow photoelectrochemical storage cell (PESC) to achieve efficient and high-capacity storage of solar energy, through improving both photocurrent and photocharging depth. It was discovered that forced convective flow of electrolytes greatly enhanced the photocurrent by 5 times comparing to that with stagnant electrolytes...
April 4, 2017: Scientific Reports
Maria Le, Oliver Rathje, Aviva Levina, Peter A Lay
Cytotoxic effects of Metvan (cis-[V(IV)O(OSO3)(Me2phen)2], where Me2phen = 4,7-dimethyl-1,10-phenanthroline) and its analogues with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) ligands in cultured human lung cancer (A549) cells have been re-investigated in conjunction with reactivity of the V(IV) complexes in neutral aerated aqueous solutions and in cell culture medium. All the V(IV) complexes underwent rapid oxidation to the corresponding V(V) species (cis-[V(V)(O)2L2](+)), followed by release of free ligands (shown by electrospray mass spectrometry)...
April 3, 2017: Journal of Biological Inorganic Chemistry: JBIC
Yu-Hui Xu, Jen-How Huang, Helmut Brandl
Reviewing the current state of knowledge about sequential extraction applied for soil vanadium (V) fractionation, we identified an urgent requirement of an sequential extraction (SE) specified for V. Namely, almost all previous SE extracted only 8.4%-48% of total V in soils (excluding residue). Thus, we proposed an eight-step SE for V fractionation in soils according to the knowledge gained from literature and our own dissolution experiments with model minerals. After extracting the mobilisable and adsorbed V with de-ionised water and 5mmol/L phosphate, 1mol/L pyrophosphate was applied to gather organic matter bound V which minimised the artefact dissolving Al and Fe (hydr)oxides occurred when using HNO3-H2O2 for extraction...
March 2017: Journal of Environmental Sciences (China)
Donata Passarello, Simone G Altendorf, Jaewoo Jeong, Charles Rettner, Noel Arellano, Teya Topuria, Mahesh G Samant, Stuart S P Parkin
It has recently been shown that the metal-insulator transition in vanadium dioxide epitaxial films can be suppressed and the material made metallic to low temperatures by ionic liquid gating due to migration of oxygen. The gating is only possible on certain crystal facets where volume channels along the VO2's rutile c axis intersect the surface. Here, we fabricate bars with the c axis in plane and oriented parallel to or perpendicular to the length of the bars. We show that only bars with the c axis perpendicular to the bars, for which the volume channels are accessible from the sides of the bar, can be metallized by ionic liquid gating...
April 3, 2017: Nano Letters
Will J Hardy, Heng Ji, Hanjong Paik, Darrell G Schlom, Douglas Natelson
The standard treatment of quantum corrections to semiclassical electronic conduction assumes that charge carriers propagate many wavelengths between scattering events, and succeeds in explaining multiple phenomena (weak localization magnetoresistance (WLMR), universal conductance fluctuations, Aharonov-Bohm oscillations) observed in polycrystalline metals and doped semiconductors in various dimensionalities. We report apparent WLMR and conductance fluctuations in H x VO2, a poor metal (in violation of the Mott-Ioffe-Regel limit) stabilized by the suppression of the VO2 metal-insulator transition through atomic hydrogen doping...
March 31, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Felix Mattelaer, Kobe Geryl, Geert Rampelberg, Jolien Dendooven, Christophe Detavernier
Flexible wearable electronics and on-chip energy storage for wireless sensors drive rechargeable batteries toward thin-film lithium ion batteries. To enable more charge storage on a given surface, higher energy density materials are required, while faster energy storage and release can be obtained by going to thinner films. Vanadium oxides have been examined as cathodes in classical and thin-film lithium ion batteries for decades, but amorphous vanadium oxide thin films have been mostly discarded. Here, we investigate the use of atomic layer deposition, which enables electrode deposition on complex three-dimensional (3D) battery architectures, to obtain both amorphous and crystalline VO2 and V2O5, and we evaluate their thin-film cathode performance...
April 7, 2017: ACS Applied Materials & Interfaces
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