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  This paper presents the characterization studies conducted by Milwaukee School of Engineering senior undergraduate students in South Africa under the Research Experiences for Undergraduates grant EEC-1460183 sponsored by the National Science Foundation (Principal Investigator Dr. Kumpaty). Robert Mueller and Christopher Reynolds conducted research in summer of 2015 under advisement of Dr. Kumpaty and his South African collaborators, Dr. Esther Akinlabi and Dr. Sisa Pityana. The foreign collaborators' excellent support was pivotal to the success of our U.S. students.

Ti-6Al-4V is a titanium alloy that accounts for about 80% of the titanium market. The Ti-64 alloy contains 6 wt% Aluminum and 4 wt% Vanadium, an almost equal ratio of alpha + beta phases. Through the laser surface modification process known as Laser Meal Deposition, this alloy offers the optimum combination of enhanced properties. This research focuses on the application of adding a combination of molybdenum (Mo) and Ti-64 powders to a Ti-64 substrate surface in order to improve the durability for various biomedical/aerospace applications. Deposition of the powders was completed at the CSIR - National Laser Center, in Pretoria, South Africa. The characterization studies were carried out at the University of Johannesburg. The results of the hardness tests showed that the addition of molybdenum to Ti-64 increased the hardness of the deposited material compared to that of the substrate. This verifies that the addition of Mo to metals can affect the mechanical properties to better suit various applications.

While Robert Mueller studied the effect of laser power on the properties of laser metal deposited Ti-6Al-4V + Mo for wear resistance enhancement, Christopher Reynolds investigated scanning velocity influence on the evolving properties of laser metal deposited Ti-6Al-4V + Mo. The results of this promising research and various options for further investigation are presented. The beneficial value of such a global research enterprise on the budding engineers will be apparent and the paper details the process of the international component of the Research Experiences for Undergraduates.

Abstract  V(0.5)Mo(0.5)Nx/MgO(001) alloys with the B1-NaCI structure are grown by ultra-high-vacuum reactive magnetron sputter deposition in 5 mTorr mixed Ar/N-2 atmospheres at temperatures T-s between 100 and 900 degrees C. Alloy films grown at T-s <= 500 degrees C are polycrystalline with a strong 002 preferred orientation; layers grown at T-s >= 700 degrees C are epitaxial single-crystals. The N/Metal composition ratio x ranges from 1.02 +/- 0.05 with T-s = 100-500 degrees C to 0.94 +/- 0.05 at 700 degrees C to 0.64 +/- 0.05 at T-s = 900 degrees C. N loss at higher growth temperatures leads to a corresponding decrease in the relaxed lattice parameter a(0) from 4.212 A with x = 1.02 to 4.175 angstrom at x = 0.94 to 4.120 angstrom with x = 0.64. V(0.5)Mo(0.5)Nx nanoindentation hardnesses H and elastic moduli E increase with increasing T-s, from 17 +/- 3 and 323 +/- 30 GPa at 100 degrees C to 26 +/- 1 and 370 +/- 10 GPa at 900 degrees C. Both polycrystalline and single-crystal V(0.5)Mo(0.5)Nx films exhibit higher toughnesses than that of the parent binary compound VN. V(0.5)Mo(0.5)Nx films deposited at higher Ts also exhibit enhanced wear resistance. Valence-band x-ray photoelectron spectroscopy analyses reveal an increased volume density of shear-sensitive d-t(2g) d-t(2g) metallic states for V(0.5)Mo(0.5)Nx compared to VN and the density of these orbitals increases with increasing deposition temperature, i.e., with increasing N-vacancy concentration.(C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Abstract  Focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller gas adsorption methods have been used for the characterisation of physical properties of microporous carbide-derived carbon electrodes, prepared from Mo2C at 600 A degrees C (noted as Mo2C-CDC) before and after electrochemical tests conducted within a very wide two-electrode cell potential region. Cyclic voltammetry, constant current charge/discharge and impedance data have been analysed to establish the electrochemical characteristics of the hybrid devices consisting of the 1 M Na2SO4 and 1 M Rb2SO4 aqueous electrolytes and Mo2C-CDC electrodes within the very wide cell potential region (Delta E a parts per thousand currency signaEuro parts per thousand 2.4 V). The influence of cation chemical composition on the electrochemical characteristics of supercapacitors/electrochemical hybrid devices has been analysed. The complex kinetics behaviour of completed devices (adsorption, blocking adsorption and intercalation of Na+ and Rb+ ions; faradic and mass transfer; gas adsorption; etc.) has been established at Delta E a parts per thousand yenaEuro parts per thousand 1.5 V. At least three different characteristic time constants dependent on the electrolyte cation composition and cell potential applied have been established.

Abstract  A method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwaveassisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO3, HF, HBF4, and H3BO3) combined or not with H2O2 were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO3 + 1 mL HBF4 + 2 mL H2O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.

Abstract  High quality 2D and 3D inverse opals and hollow sphere arrays of vanadium oxide are grown on conductive substrates from colloidal polymer sphere templates formed by electrophoretic deposition or surfactant-assisted dip-coating. Inverse opals (IOs) are formed using variants of solution drop-casting, N-2-gun assisted infiltration and high-rate (200 mm min(-1)) iterative dip-coating methods. Through Raman scattering, transmission electron microscopy and optical diffraction, we show how the oxide phase, crystallinity and structure are inter-related and controlled. Opal template removal steps are demonstrated to determine the morphology, crystallinity and phase of the resulting 2D and 3D IO structures. The ability to form high quality 2D IOs is also demonstrated using UV Ozone removal of PMMA spheres. Rapid hydrolysis of the alkoxide precursor allows the formation of 2D arrays of crystalline hollow spheres of V2O5 by utilizing over-filling during iterative dip-coating. The methods and crystallinity control allow 2D and 3D hierarchically structured templates and inverse opal vanadium oxides directly on conductive surfaces. This can be extended to a wide range of other functional porous materials for energy storage and batteries, electrocatalysis, sensing, solar cell materials and diffractive optical coatings.

Abstract  Bulk VO2 (B) nanobelts with high quality have been fabricated via a simple one-step hydrothermal route and found to possess intrinsic peroxidase-like activity. The catalysts with excellent affinity to hydrogen peroxide (H2O2) and 3,3',5,5'-tetramethylbenzidine (TMB) could be used for the colorimetric assay of H2O2 and glucose.

Abstract  A new atomic layer deposition (ALD) process for V2O5 using ozone (O-3) as oxidant has been developed that resulted in crystalline V2O5 thin films which are single-phase and orthorhombic on various substrates (silicon, Au-coated stainless steel, and anodic aluminum oxide (AAO)) without any thermal post-treatment. Within a fairly narrow temperature window (170-185 degrees C), this low temperature process yields a growth rate of similar to 0.27 angstrom/cycle on Si. It presents good uniformity on planar substrates. Excellent conformality enables deposition into high aspect ratio (AR) nanopores (AR > 100), as needed for fabrication of three-dimensional (3D) nanostructures for next generation electrochemical energy storage devices. V2O5 films obtained using O-3-based ALD showed superior electrochemical performance in lithium cells, with initial specific discharge capacity of 142 mAh/g in the potential range of 2.6-4.0 V, as well as excellent rate capability and cycling stability. These benefits are attributed primarily to the crystallinity of the material and to fast transport through the thin active storage layers used.

Abstract  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. With a liquid-to-solid ratio of 10, washing with 0.4 mol/L citric acid, 0.4 mol/L tartaric acid, 0.4 mol/L oxalic acid, and 0.12 mol/L Na2EDTA led to removal rates of 91%, 88%, 88%, and 61%, respectively. The effect of multiple washing on removal rate was also explored. According to the changes observed in metal fractionations, differences in removal rates among reagents is likely associated with their pKa value, pH in solution, and chemical structure. We concluded that treating with appropriate washing reagents under optimal conditions can greatly enhance the remediation of vanadium-contaminated soils.

Abstract  The co-effect of Cordyceps sinensi (CS; caterpillar fungus) and strontium on ovariectomized osteopenic rats was studied in this paper. After the rats were treated orally with CS, strontium (SR), and CS rich in strontium (CSS), respectively, the urine calcium, plasma calcium, plasma phosphorus, bone mineral content, mechanical testing, and the mass of uterus, thymus, and body were examined. Both CSS and SR have a positive effect on mechanical strength and mineral content of ovariectomized osteopenic rats. However, femoral neck strength in the CSS-treated group was higher than those in the SR-treated groups. CSS and SR significantly decreased urinary calcium excretion and plasma total calcium and inorganic phosphate concentrations. On the contrary, CS and CSS significantly increased weights of atrophic uteri and weights of body and also decreased the thymus mass in animals, whereas SR did not exhibit any such effects. Our experiments have demonstrated that CSS possess a preferable effect against the decrease of bone strength and bone mineral mass caused by osteoporosis. It was caused by the co-effect of CS and strontium. The mechanism of it includes decreases bone resorption, increases bone formation, increases in body weight, and enhances 17β-estradiol-producing as well as enhancing the immune functions in animals. The data provide an important proof of concept that CSS might be a new potential therapy for the management of postmenopausal osteoporosis in humans.

Abstract  Cost efficient and long-term stable catalysts are in great demand for the oxygen evolution reaction (OER), a key process involved in water splitting cells and metal-air batteries. Here, we demonstrate that the ultrathin amorphous cobalt-vanadium hydr(oxy)oxide we synthesized is a highly promising electrocatalytic material for the OER with a low overpotential of 0.250 V (even lower down to 0.215 V when supported on Au foam) at 10 mA cm(-2) and a long stable operation time (170 h) in alkaline media. In combination with in situ X-ray absorption spectral characterization and first-principles simulations, we reveal that the ultrathin, amorphous and alloyed structural characteristics have enabled its facile transformation to the desirable active phase, leading to a dramatically enhanced catalytic activity. Our finding highlights the remarkable advantages of the two-dimensional amorphous material and sheds new light on the design of high-performance electrocatalysts.

Abstract  The alternative, vanadium-dependent nitrogenase is employed by Azotobacter vinelandii for the fixation of atmospheric N2 under conditions of molybdenum starvation. While overall similar in architecture and functionality to the common Mo-nitrogenase, the V-dependent enzyme exhibits a series of unique features that on one hand are of high interest for biotechnological applications. As its catalytic properties differ from Mo-nitrogenase, it may on the other hand also provide invaluable clues regarding the molecular mechanism of biological nitrogen fixation that remains scarcely understood to date. Earlier studies on vanadium nitrogenase were almost exclusively based on a ΔnifHDK strain of A. vinelandii, later also in a version with a hexahistidine affinity tag on the enzyme. As structural analyses remained unsuccessful with such preparations we have developed protocols to isolate unmodified vanadium nitrogenase from molybdenum-depleted, actively nitrogen-fixing A. vinelandii wild-type cells. The procedure provides pure protein at high yields whose spectroscopic properties strongly resemble data presented earlier. Analytical size-exclusion chromatography shows this preparation to be a VnfD2K2G2 heterohexamer.

Abstract  V0.3Mo0.7O3 and V0.6Mo0.4O3 nanoparticles were synthesized through reducing acidified vanadate and molybdate solution at around 60-70 degrees C. The catalysts are aimed to be used as anode in alkaline fuel cells. BET and SEM analysis are done to characterize the obtained particles. According to the SEM results, both compounds were formed in nanosized particles and BET results showed that BET surface area of V0.3Mo0.7O3 catalyst has 5 times higher than that of V0.6Mo0.4O3.

Abstract  Recently, two-dimensional (2D) layered transition metal dichalcogenides (LTMDs) have attracted great scientific interest for ion battery applications. Because of its remarkable metallic property, vanadium disulfide (VS2) as a typical family member of LTMDs, can be an alternative anode material for ion battery applications. In this paper, we systematically investigate the adsorption energy and diffusion coefficient of the lithium and sodium ions in monolayer and bulk VS2 for lithium and sodium ion batteries by a density functional theory method. Our calculations show that the VS2 capacity can reach up to 466 mA h g(-1). It exhibits a low output voltage of 0.72 and 0.48 V for lithium and sodium ion batteries in the monolayer VS2 as well as an output voltage of 0.88 and 0.6 V in the bulk VS2, respectively. The calculated lithium and sodium ion diffusion coefficients in the bulk VS2 are enhanced by five and seven orders of magnitude compared to the reported bulk MoS2, respectively. Our investigations also reveal that VS2 exhibits better electrochemical performance as an anode in the sodium ion battery than in the lithium ion battery.

Abstract  Efficient and selective total syntheses of spliceosome modulating natural products thailanstatins A-C and spliceostatin D are reported. A number of stereoselective methods for the construction of various tetrasubstituted dihydro- and tetrahydropyrans were developed as a prerequisite for the syntheses of these naturally occurring molecules and variations thereof. The pyran-forming reactions utilize a Heck/Saegusa-Ito cascade sequence to generate hydroxy α,β,γ,δ-unsaturated aldehyde precursors followed by a catalyst-controlled oxa-Michael cyclization to furnish tetrasubstituted dihydropyrans with high stereocontrol. Subsequent optimized homogeneous or heterogeneous hydrogenations of these dihydropyran systems afford their tetrahydropyran counterparts, also in a highly stereoselective manner. The synthesized thailanstatins and related analogues were biologically evaluated for their cytotoxic properties, leading to the identification of a number of compounds with exceptionally potent antitumor activities suitable for further development as potential antibody-drug conjugate payloads, single drugs, or drug combinations for cancer therapies. Important structure-activity relationships within the thailanstatin family and structurally related compounds are discussed and are expected to be path-pointing for future studies.

Abstract  In this work the speciation in aqueous solution of the compound [VIVO(oda)(H2O)2], where oda is oxydiacetate dianion (OOCCH2)2O, which shows in vitro anticancer activity, was studied. Its interaction with the two serum bioligands with highest affinity for VIV, lactic (Hlact) and citric (H3citr) acid, and with the two proteins candidate to participate to the transport of VIVO compounds in the organism, transferrin (hTf) and albumin (HSA), was also examined. The study was carried out with the combined application of spectroscopic (Electron Paramagnetic Resonance, EPR), analytical (pH-potentiometry) and computational (Density Functional Theory, DFT) methods. The results showed that in aqueous solution [VO(oda)(H2O)2] undergoes hydrolysis above pH 4–5 with formation of the EPR-active species [(VO)2(oda)2(OH)2]2− around pH 6 and of [(VO)2(OH)5]− at physiological pH. DFT calculations suggested that the most stable isomers of 1:1 species are the hexa-coordinated OC-6-23 with a mer arrangement of oda – similar to that observed in the solid state – and the penta-coordinated SPY-5-14, whereas for 1:2 species the fac arrangement of oda is favored. Citrate is able to displace completely the oda ligand in [VO(oda)(H2O)2] and only the dinuclear species [(VO)2(citrH-1)2]4− was detected at pH 7.4, while with lactate the formation of a mixed complex VIVO–oda–lact was observed. [VO(oda)(H2O)2] interacts with apo-transferrin forming a mixed complex (VO)(hTf)(oda) where vanadium is bound in the iron sites and oda behaves as a synergistic anion, while with albumin no interaction was revealed. Model calculations suggest that when [VO(oda)(H2O)2] is administered orally (concentration ca. 1–10 μM) or by injection (concentration approximately in the range 10–100 μM), (VO)(hTf) and (VO)2(hTf) should be formed; these species could reach the target organs and be recognized by the hTf receptors of the cells, favoring the vanadium uptake.