Abstract  BACKGROUND: The need for systematic methods for reviewing evidence is continuously increasing. Evidence mapping is one emerging method. There are no authoritative recommendations for what constitutes an evidence map or what methods should be used, and anecdotal evidence suggests heterogeneity in both. Our objectives are to identify published evidence maps and to compare and contrast the presented definitions of evidence mapping, the domains used to classify data in evidence maps, and the form the evidence map takes.

METHODS: We conducted a systematic review of publications that presented results with a process termed "evidence mapping" or included a figure called an "evidence map." We identified publications from searches of ten databases through 8/21/2015, reference mining, and consulting topic experts. We abstracted the research question, the unit of analysis, the search methods and search period covered, and the country of origin. Data were narratively synthesized.

RESULTS: Thirty-nine publications met inclusion criteria. Published evidence maps varied in their definition and the form of the evidence map. Of the 31 definitions provided, 67 % described the purpose as identification of gaps and 58 % referenced a stakeholder engagement process or user-friendly product. All evidence maps explicitly used a systematic approach to evidence synthesis. Twenty-six publications referred to a figure or table explicitly called an "evidence map," eight referred to an online database as the evidence map, and five stated they used a mapping methodology but did not present a visual depiction of the evidence.

CONCLUSIONS: The principal conclusion of our evaluation of studies that call themselves "evidence maps" is that the implied definition of what constitutes an evidence map is a systematic search of a broad field to identify gaps in knowledge and/or future research needs that presents results in a user-friendly format, often a visual figure or graph, or a searchable database. Foundational work is needed to better standardize the methods and products of an evidence map so that researchers and policymakers will know what to expect of this new type of evidence review.

SYSTEMATIC REVIEW REGISTRATION: Although an a priori protocol was developed, no registration was completed; this review did not fit the PROSPERO format.

Abstract  Novel flower-like vanadium carbide (V8C7) hierarchical nanocrystals have been successfully synthesized in a large-scale hydrothermal process using a mixture of diethanolamine (HN(C2H4OH)(2), DEA) and V2O5 powder. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), selected-area electron diffraction (SAED) and energy-dispersive spectra (EDS). The results showed that flower-like products consist of very thin sheets with an average thickness of 10 nm and the nanosheets were a uniform single-crystalline V8C7 phase. It was found that reaction temperature and type of capping molecules have a crucial influence on the morphology of the products. A possible growth mechanism of the flower-like V8C7 hierarchical nanocrystals is proposed and discussed.

Abstract  Background and aim: Among various soils pollutants, heavy metals have great importance due to their toxicity and adverse effect on human health and environment. Therefore the aim of this study is comparing the concentration of heavy metals in surface soil of squares with high traffic at Kermanshah metropolises in 2015.

Materials and methods: For conducting this study, five high traffic area and five area as a reference soil were selected and from each location, five samples were collected. Finally a total of 50 point sample and 10 composite samples were obtained from these areas. The concentration of metals were evaluated based on the standard methods with ICP (Inductively Coupled Plasma) device.

Results: The results showed that the level of heavy metals in high traffic area and reference's soil samples were as bellow: Lead (Pb) > Nickel (Ni) > Chromium (Cr) > Vanadium (V) > Cadmium (Cd) > Selenium (Se). Also, the level of Cr, Cd and Ni in high traffic area were higher than references soil area.

Conclusion: According to the results, it is necessary to take some action for controlling the pollutants emission from mobile sources in high traffic area in order to reduce the heavy metals emission in the environment.

Abstract  Chemically demanding reductive conversions in biology, such as the reduction of dinitrogen to ammonia or the Birch-type reduction of aromatic compounds, depend on Fe/S-cluster-containing ATPases. These reductions are typically catalyzed by two-component systems, in which an Fe/S-cluster-containing ATPase energizes an electron to reduce a metal site on the acceptor protein that drives the reductive reaction. Here, we show a two-component system featuring a double-cubane [Fe8S9]-cluster [{Fe4S4(SCys)3}2(μ2-S)]. The double-cubane-cluster-containing enzyme is capable of reducing small molecules, such as acetylene (C2H2), azide (N3-), and hydrazine (N2H4). We thus present a class of metalloenzymes akin in fold, metal clusters, and reactivity to nitrogenases.

Abstract  Selected examples in V K-edge X-ray Absorption Near Edge Structure (XANES) analysis of a series of vanadium complexes containing imido ligands (possessing metal-nitiogen double bond) in toluene solution have been introduced, and their pre-edge and the edge were affected by then structures and nature of ligands. Selected results m exploring the oxidation states of the active species in ethylene dimerization/polymerization using homogeneous vanadium catalysts [consisting of (imido)vanadium(V) complexes and Al cocatalysts] by X-ray absorption spectroscopy (XAS) analyses have been introduced. It has been demonstrated that the method should provide more clear information concerning the active species in situ, especially by combination with the other methods (NMR and ESR spectra, X-ray ciystallographic analysis, and leaction chemistry), and should he powerful tool for study of catalysis mechanism as well as for the structural analysis in solution.

Abstract  Nitrogenase is the only known biological system capable of reducing N2 to NH3 , which is a critical component of bioavailable nitrogen fixation. Since the discovery of discrete iron-sulfur metalloclusters within the nitrogenase MoFe protein, synthetic inorganic chemists have sought to reproduce the structural features of these clusters in order to understand how they facilitate the binding, activation and hydrogenation of N2 . Through the decades following the initial identification of these clusters, significant progress has been made to synthetically replicate certain compositional and functional aspects of the biogenic clusters. Although much work remains to generate synthetic iron-sulfur clusters that can reduce N2 to NH3 , the insights borne from past and recent developments are discussed in this concept article.

Abstract  In order to develop a process for the separation of small amount of tungsten from macro amount of molybdenum, the selective loading of tungsten over molybdenum from sulfuric acid solution was investigated by ion exchange with TEVA resin. The separation factor between tungsten and molybdenum depended strongly on the equilibrium pH and tungsten concentration. A separation factor of 28 was obtained at an optimum condition. The loading behavior of tungsten into the resin fitted well with the Langmuir adsorption isotherm and the loading capacity for tungsten was determined. H2SO4 solution was more effective than NaOH solution as an eluent.

Abstract  This study investigated the methylene blue (MB) decolorization through heterogeneous UV-Fenton reaction catalyzed by V-Ti co-doped magnetites, with emphasis on comparing the contribution of V and Ti cations on improving the adsorption and catalytic activity of magnetite. In the well crystallized spinel structure, both Ti(4+) and V(3+) occupied the octahedral sites. Ti(4+) showed a more obvious effect on increasing specific surface area and superficial hydroxyl amount than V(3+) did, resulting in a significant improvement of the adsorption ability of magnetite to MB. The UV introduction greatly accelerated MB degradation. And magnetite with more Ti and less V displayed better catalytic activity in MB degradation through heterogeneous UV-Fenton reaction. The transformation of degradation products and individual contribution from vanadium and titanium on improving adsorption and catalytic activity of magnetite were also investigated. These new insights are of high importance for well understanding the interface interaction between contaminants and metal doped magnetites, and the environmental application of natural and synthetic magnetites.

Abstract  The oxygen transfer from the vanadium(v) complexes containing peroxo, oxo, and ozorficle ligands to electron-donating substrates (ethylene and vinyl methyl ether) was studied in the framework of the DFT with the M06 hybrid functional. The O atom of the ozonide fragment in the O3VO(eta-O2)(-) complex is transferred to the electron-donating substrates with lower energy expenses than the O atom of the peroxo group of the isomeric triperoxo complex, in spite of the fact that the presence of the peroxo group in the ozonide complexes stabilizes it favoring the formation of the V-Or bond according to the data of topological analysis of the electron density in terms of the theory of atoms in molecules (AIM). The calculation results are in agreement with the experimental kinetic data indicating somewhat lower reactivity of triper-oxovanadate compared to the isomeric oxygenyl complexes.

Abstract  Anion exchange membranes for a vanadium redox flow battery (VRB) were prepared by pore-filling on a PE substrate with the copolymerization of vinylbenzyl chloride (VBC) and glycidyl methacrylate (GMA). The ion exchange capacity, water uptake and weight gain ratio were increased with a similar tendency up to 65% of GMA content, indicating that the monomer improved the pore-filling degree and membrane properties. The vanadium ion permeability and open-circuit voltage were also investigated. The permeability of the VG65 membrane was only 1.23 x 10(-7) cm(2) min(-1) compared to 17.9 x 10(-7) cm(2) min(-1) for Nafion 117 and 1.8 x 10(-7) cm(2) min(-1) for AMV. Consequently, a VRB single cell using the prepared membrane showed higher energy efficiency (over 80%) of up to 100 cycles compared to the commercial membranes, Nafion 117 (ca. 58%) and AMV (ca. 70%).

Abstract  Effect of zirconium presence in the silica framework and content and speciation of vanadium surface oxo-complexes on the catalytic behavior of VOx/Zr-SBA-15 catalysts in oxidative dehydrogenation of ethanol was investigated. Experimental results bring evidence of successful incorporation of zirconium into ordered mesoporous silica framework with the preservation of ordered mesoporosity by hydrothermal template base synthesis method. The presence of zirconium in the SBA-15 framework increases reducibility of vanadium species and acidity of the catalysts. It is reflected in higher activity of vanadium species expressed as turn-over frequency (e.g., TOF of 20 h(-1) for 5%VOx/Zr-SBA-15 sample in comparison with TOF of 12 h(-1) for 5%VOx/SBA-15 sample) and also in significant decrease of selectivity to acetaldehyde (65% in comparison with 90% for mentioned samples) followed by increase in selectivity to ethylene (25% in comparison with 5%). This change in distribution of reaction products is related to stronger acidity character of surface OH groups and inhibition effect of formed water vapours on the oxidative dehydrogenation products (acetaldehyde). Catalytic data also reveal that oligomeric/polymeric tetrahedrally coordinated vanadium species exhibit higher activity in ethanol oxidative dehydrogenation than monomeric complexes. In addition, comparison of the catalytic performance of VOx/Zr-SBA-15 catalysts with VOx/SBA-15 catalysts showed that catalytic properties of VOx/Zr-SBA-15 catalysts can be tuned by incorporation of controlled amount of zirconium into silica framework.

Abstract  We demonstrated in 1985 that vanadium administered in the drinking water to streptozotocin (STZ) diabetic rats restored elevated blood glucose to normal. Subsequent studies have shown that vanadyl sulfate can lower elevated blood glucose, cholesterol and triglycerides in a variety of diabetic models including the STZ diabetic rat, the Zucker fatty rat and the Zucker diabetic fatty rat. Long-term studies of up to one year did not show toxicity in control or STZ rats administered vanadyl sulfate in doses that lowered elevated blood glucose. In the BB diabetic rat, a model of insulin-dependent diabetes, vanadyl sulfate lowered the insulin requirement by up to 75%. Vanadyl sulfate is effective orally when administered by either single dose or chronic doses. It is also effective by the intraperitoneal route. We have also been able to demonstrate marked long-term effects of vanadyl sulfate in diabetic animals following treatment and withdrawal of vanadyl sulfate. Because vanadyl sulfate is not well absorbed we have synthesized and tested a number of organic vanadium compounds. One of these, bismaltolato-oxovanadium IV (BMOV), has shown promise as a therapeutic agent. BMOV is 2-3x more potent than vanadyl sulfate and has shown less toxicity. Recent studies from our laboratory have shown that the effects of vanadium are not due to a decrease in food intake and that while vanadium is deposited in bone it does not appear to affect bone strength or architecture. The mechanism of action of vanadium is currently under investigation. Several studies indicate that vanadium is a phosphatase inhibitor and that vanadium can activate serine/threonine kinases distal to the insulin receptor presumably by preventing dephosphorylation due to inhibition of phosphatases Short-term clinical trials using inorganic vanadium compounds in diabetic patients have been promising.

Abstract  The aquatic chemistry of vanadium is dominated by V(IV) and V(V). Their species VO2+, VO(OH)+ and H2VO−4, HVO2−4, respectively, occur primarily in natural waters. VO2+, as a very hard Lewis acid, has a strong tendency to coordinate with oxygen donor atoms and is thus capable of both forming strong complexes with soluble organic chelates and becoming specifically adsorbed to particles, especially hydrous oxides. Vanadates (V), like phosphates, also have a tendency to form, by ligand exchange, surface complexes with hydrous oxides. The V(IV)–V(V) couple is an interesting redox sensor because the redox transition occurs at EH-values typically often encountered at the sediment water interface; organic chelate formation may extend the redox boundary to EH-values of about +0.4V (pH 7–8), but in the presence of dissolved oxygen vanadate(V) prevails. Experimental data on the adsorption of VO2+ and of V(V) (HVO2−4, VO+2) on δ-Al2O3 and TiO2 (anatase) surfaces provide evidence for strong specific adsorption. The interaction of VO2+ with oxide surfaces is interpreted in terms of inner-sphere bidentate surface complexes with the surface central metal ions of the oxide VO(OM<)2; vanadate and VO2+ form monodentate surface species. The rate of oxidation of VO2+ by oxygen is significantly enhanced by hydrolysis or adsorption to hydrous oxide surfaces. The rate law, derived earlier (Wehrli and Stumm, 1988) shows a first order dependence on the concentration of VO(OH)+ in homogeneous solution or on the concentration of the surface complex of VO(OM<)2 in heterogeneous systems. A comparison with published data on Mn(II) and Fe(II) oxidation shows that coordinated OH-groups of solid surfaces are able, like soluble hydroxo complexes, to mediate the electron transfer from the metal ions to the O2-molecule.

Abstract  Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. Understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions is therefore critical to developing conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring within organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250km transect of the central UCRB. The results of this study support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. We found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.

Abstract  A green route is designed to gain a clear idea of growth mechanism of complex VO2 (B) hierarchical microstructures, since this kind of metal oxide has various metastable phases due to their diverse valence states. Three-dimensional (3D) uniform flower-like VO2 (B) hierarchical microstructure has thus been assembled with the interleaving nanoplates, which are about 25 nm in thickness and well-crystallized in structure with {114} planes as the dominant surfaces. Results of the systemic control experiments revealed that formation of the flower-like VO2 (B) results from a fast nucleation-growth process, where ethylene glycol (EG) not only acts as a green solvent and reductive agent, but also plays a key role in self-assembly of the resulted VO2 (B) hierarchical microstructures. Hydroxyl amount on the solvent molecule is crucial in formation and shape control of VO2 (B) hierarchical microstructures. Result of this work would be helpful to understand the growth mechanism of complex three-dimensional hierarchical superstructures of different metal oxides, which is very important to material science and inorganic synthetic chemistry.

Abstract  Utilization of CO 2 as a feedstock for synthesis of chemicals is an alternate and most promising option for CO 2 abatement. In the present study, CO 2 has been utilized as a soft oxidant for oxidative dehydrogenation of ethylbenzene and n-butane to the corresponding olefins. For this, TiO 2?ZrO 2 (TZ) mixed oxide-supported V 2O 5, C eO 2 and V 2O 5-C eO 2 catalysts has been synthesized, characterized and evaluated for the oxidative dehydrogenation reactions. The physicochemical characterization has been achieved by various techniques such as, powder X-ray diffraction, CO 2 and NH3 temperature-preprogrammed desorption, temperature-preprogrammed reduction, X-ray photoelectron spectroscopy and BET surface area methods. XRD analysis of the samples calcined at 550 °C indicates that the impregnated active components are in a highly dispersed state on the support. XP spectra shows the existence of vanadium and cerium in V 4+ and C e4+/C e3+ oxidation states, respectively. Among the various catalysts investigated, V 2O 5?C eO 2/TiO 2?ZrO 2 exhibits a high conversion and product selectivity for the oxidative dehydrogenation of ethyl benzene. On the other hand, a high conversion and selectivity in the oxidative dehydrogenation of n-butane is noted over V 2O 5/SnO 2?Z rO 2 mixed oxide catalyst. The combined acid-base and redox properties of the catalysts play a major role in these reactions. In particular, the characterization studies reveal that mixed oxides show a high specific surface area, superior acid-base properties and better redox characteristics. All these properties enhance the catalytic performance of mixed oxide catalysts.