Tungsten Compounds

Thermogravimetric Analysis (TGA): Thermogravimetric analyses were performed on a TGA Q500 (TA Instruments) and recorded under N 2 or under air, upon equilibration at 100 °C, followed by a ramp of 10 °C/min up to 1000 °C. Resonance Raman (rRaman): Micro-Raman spectra were recorded with a inVia Reflex Renishaw spectrometer equipped with three lasers (532, 632.8 and 785 nm). The laser beam was focused on an area of about 2x2 μm and with power lower than 1 mW. An Ocean Optics oxygen sensor system (FOXY R-AF) was used for the quantitative detection of O 2 . The experiments were performed in a custom built reactor, closed with a special cap in which the sensor is inserted. The calibration was performed using a temperature sensor. UV-Vis: UV-Vis spectra were recorded using a Perkin-Elmer Lambda 45 spectrophotometer. Syntheses of transition metal substituted polyoxometalates.

To determine the biodistribution properties of cleistanthin A and cleistanthin B in rodents using magnetic resonance imaging (MRI). Materials and Methods: Cleistanthins A and B, constituents of Cleistanthus collinus Roxb., were labelled with gadolinium (Gd 3+ ) directly and injected into normal and tumoric nude mice. The tissue signal intensity was measured using MRI to perform a noninvasive kinetic assay. Wistar rats were used for determination of the grayscale intensity to observe the distribution patterns of of cleistanthins A and B. Results: Cleistanthin A is kinetically more attractive to the gastrointestinal tract than is cleistanthin B, which gets accumulated in muscular tissues of mice in greater concentrations compared with cleistanthin A. Cleistanthin B but not cleistanthin A showed tumoric affinity and exhibited a tumor kinetic attraction in tumoric mice. In rats, cleistanthin A showed greater grayscale intensities in the brain, liver, and skeletal muscles in immediate post contrast MRI images, whereas the gadolinium tagged cleistanthin B showed higher grayscale intensities in the cardiac muscle and skeletal muscles in delayed post contrast MRI images. Conclusions: Cleistanthin A is more pharmacokinetically attractive to the gastrointestinal tract than cleistanthin B.

Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten (W), remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. Here, for the first time, we demonstrate tungsten's ability to induce carcinogenic related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer related pathways in transformed clones as determined by RNA seq. Human bronchial epithelial cell line (Beas-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA-sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten. Taken together, our data shows the carcinogenic potential of tungsten. Further tests are needed, including in vivo and human studies, in order to validate tungsten as a carcinogen to humans.

The present study reports a process for simultaneous mineralization and detoxification of Mordant Black 17 with high electrical energy efficiency. Hydrogen peroxide and ammonium persulphate (APS) were used for the generation of hydroxyl and sulphate radicals using UV light (λ = 254 nm) and Fe and Ag ions as catalysts. The detoxification and energy efficiency of various processes were measured by monitoring growth inhibition of Escherichia coli and Electrical Energy per Order (EE/O) applicable for low concentration contaminants respectively. Systems catalyzed by Fe are more energy efficient and possess higher mineralization and detoxification efficiency than that of Ag. The concentration of the catalysts and oxidants were found to strongly influence the EE/O of the systems. The most cost efficient processes for simultaneous mineralization and detoxification are Fe/APS/UV at pH 3.00 and Fe/HO/UV at pH 3.00 and 5.78. The upper limit concentration of Fe is fixed at 0.01 mM for complete ...

Vanadium compounds have been primarily investigated as potential therapeutic agents for the treatment of various major health issues, including cancer, atherosclerosis, and diabetes. The translation of vanadium-based compounds into clinical trials and ultimately into disease treatments remains hampered by the absence of a basic pharmacological and metabolic comprehension of such compounds. In this review, we examine the development of vanadium-containing compounds in biological systems regarding the role of the physiological environment, dosage, intracellular interactions, metabolic transformations, modulation of signaling pathways, toxicology, and transport and tissue distribution as well as therapeutic implications. From our point of view, the toxicological and pharmacological aspects in animal models and humans are not understood completely, and thus, we introduced them in a physiological environment and dosage context. Different transport proteins in blood plasma and mechanistic...

Two high nuclearity uranyl cages were crystallized in high yield under mild solvothermal conditions using rigid aryl phosphonate ligands. These compounds are prepared either through an in situ phosphonate ligand condensation reaction or via serendipitous assembly with a bulky phosphonate ligand. Firstly, the flexibility of the phosphonate ligands enhances the curvature of the uranyl polyhedra in the assembly of both compounds. Secondly, the formation of bent pyrophosphonate li- [a]

Two high nuclearity uranyl cages were crystallized in high yield under mild solvothermal conditions using rigid aryl phosphonate ligands. These compounds are prepared either through an in situ phosphonate ligand condensation reaction or via serendipitous assembly with a bulky phosphonate ligand. Firstly, the flexibility of the phosphonate ligands enhances the curvature of the uranyl polyhedra in the assembly of both compounds. Secondly, the formation of bent pyrophosphonate ligands through temperature and solvent‐driven in situ ligand synthesis is crucial for the assembly of UPhPO3. Thirdly, the serendipitous assembly of UPh2CPO3 is favored by the use of sterically hindered bulky phosphonate ligands. The overall structure of UPhPO3 consists of 16 uranyl cations that are coordinated by phenyl phosphonate and pyrophosphonate ligands while UPh2CPO3 structure is built from uranyl dimers and bulky fluorenyl phosphonate ligand to yield a 12 membered cage.

X-ray diffraction data for [(n-C 4 H 9 ) 4 N] 2 W 6 O 19 were collected at 100 K using a Bruker SMART APEX diffractometer at the University of Notre Dame (λ = 0.71073 Å). A sphere of data was collected using frame-widths of 0.3º in ω. Data were corrected for Lorentz and polarization using the Bruker program SAINT, absorption corrections were performed using the Bruker program XPREP (version 5.1, 1997), and the structure was solved by direct methods and refined on the basis of F 2 for all unique reflections using the Bruker SHELXTL system of programs (v. 6.10). Refinement of the structure was straightforward: 86,257 total reflections of which all 21,989 unique reflections were used in the refinement, 71.81º maximum 2-theta, R1 = 0.0272, wR2 = 0.0669, GOF = 1.132, μ = 14.57, cell weight = 3783.92, space group P-1, triclinic, a = 11.5863(3) Å, b = 12.5910(4) Å, c = 19.0145(6) Å, α = 78.832(2)º, β = 74.601(2)º, γ = 62.805(1)º, V = 2370.21(12) Å 3 , Z = 2. The unit cell and parameters as well as the individual W-O 6 octahedra as well as the framework -W-O-W-connectivity are in agreement with previously reported structures. 1-4 The crystallographic data in CIF format are available on line. Details about the crystal data and structure refinement are presented in Table .

Physically adsorbed gas molecules have dramatic effects on the inherent properties of 2D nanomaterials due to their atomic/molecular-level thinness. In this work, we applied laser THz emission spectroscopy to study the gas adsorption-desorption dynamics of tungsten disulfide (WS2) nanosheets prepared by liquid phase exfoliation technique. We find that in low vacuum conditions, NIR irradiation promotes desorption of O2 molecules from WS2 nanosheets. Upon exposure to atmospheric air, results suggest slight photo-oxidation caused by NIR irradiation. Strong photo-oxidation by UV illumination is also confirmed, and we also observed subsequent O2 desorption from WS2 nanosheets by NIR irradiation when the UV illumination is turned off. These results are discussed using the Langmuir adsorption isotherm, which explains the variation of gas adsorption with the gas pressure.

The tetraruthenium polyoxometalate [Ru 4 (μ-O) 4 (μ-OH) 2 (H 2 O) 4 (γ-SiW 10 O 36 ) 2 ] 10-(1) behaves as a very efficient water oxidation catalyst in photocatalytic cycles using Ru(bpy) 3 2+ as sensitizer and persulfate as sacrificial oxidant. Two interrelated issues relevant to this behavior have been examined in detail: (i) the effects of ion pairing between the polyanionic catalyst and the cationic Ru(bpy) 3 2+ sensitizer, and (ii) the kinetics of hole transfer from the oxidized sensitizer to the catalyst. Complementary charge interactions in aqueous solution leads to an efficient static quenching of the Ru(bpy) 3 2+ excited state. The quenching takes place in ionpaired species with an average 1:Ru(bpy) 3 2+ stoichiometry of 1:4. It occurs by very fast (ca. 2 ps) electron transfer from the excited photosensitizer to the catalyst followed by fast (15-150 ps) charge recombination (reversible oxidative quenching mechanism). This process competes appreciably with the primary photoreaction of the excited sensitizer with the sacrificial oxidant, even in high ionic strength media. The Ru(bpy) 3 3+ generated by photoreaction of the excited sensitizer with the sacrificial oxidant undergoes primary bimolecular hole scavenging by 1 at a remarkably high rate (3.6 ± 0.1 × 10 9 M -1 s -1 ), emphasizing the kinetic advantages of this molecular species over, e.g., colloidal oxide particles as water oxidation catalysts. The kinetics of the subsequent steps and final oxygen evolution process involved in the full photocatalytic cycle are not known in detail. An indirect indication that all these processes are relatively fast, however, is provided by the flash photolysis experiments, where a single molecule of 1 is shown to undergo, in 40 ms, ca. 45 turnovers in Ru(bpy) 3 3+ reduction. With the assumption that one molecule of oxygen released after four hole-scavenging events, this translates into a very high average turnover frequency (280 s -1 ) for oxygen production.

Tracing of neuroanatomical pathways commonly involves the histochemical demonstration of horseradish peroxidase, using the chromogen tetramethylbenzidine. A new modification of this reaction using ammonium paratungstate stabilizer retains high sensitivity while permitting the reaction to be performed at pH 6.0 in isotonic solutions. The reaction product resists solvents, allowing Nissl-stained sections to retain their peroxidase labeling. With subsequent stabilization by diaminobenzidine, the tissue is suitable for electron microscopic study and is compatible with post-embedding immunocytochemistry.

Tungsten carbide exhibits platinum‐like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N4 (mpg‐C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H2O decomposit...

The Folin-Ciocalteu (FC) method of performing a total phenolics assay, originally developed for protein determination, has recently evolved as a total antioxidant capacity assay but was found to be incapable of measuring lipophilic antioxidants due to the high affinity of the FC chromophore, that is, multivalent-charged phospho-tungsto-molybdate(V), toward water. Thus, the FC method was modified and standardized so as to enable simultaneous measurement of lipophilic and hydrophilic antioxidants in NaOH-added isobutanol-water medium. Optimal conditions were as follows: dilution ratio of aqueous FC reagent with iso-BuOH (1:2, v/v), final NaOH concentration of 3.5 × 10 -2 M, reaction time of 20 min, and maximum absorption wavelength of 665 nm. The modified procedure was successfully applied to the total antioxidant capacity assay of trolox, quercetin, ascorbic acid, gallic acid, catechin, caffeic acid, ferulic acid, rosmarinic acid, glutathione, and cysteine, as well as of lipophilic antioxidants such as α-tocopherol (vitamin E), butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, lauryl gallate, and β-carotene. The modified FC method reliably quantified ascorbic acid, whereas the conventional method could not. The modified method was reproducible and additive in terms of total antioxidant capacity values of constituents of complex mixtures such as olive oil extract and herbal tea infusion. The trolox equivalent antioxidant capacities of the tested antioxidant compounds correlated well with those found by the Cupric Reducing Antioxidant Capacity reference method.

The Folin-Ciocalteu (FC) method of performing a total phenolics assay, originally developed for protein determination, has recently evolved as a total antioxidant capacity assay but was found to be incapable of measuring lipophilic antioxidants due to the high affinity of the FC chromophore, that is, multivalent-charged phospho-tungsto-molybdate(V), toward water. Thus, the FC method was modified and standardized so as to enable simultaneous measurement of lipophilic and hydrophilic antioxidants in NaOH-added isobutanol-water medium. Optimal conditions were as follows: dilution ratio of aqueous FC reagent with iso-BuOH (1:2, v/v), final NaOH concentration of 3.5 × 10 -2 M, reaction time of 20 min, and maximum absorption wavelength of 665 nm. The modified procedure was successfully applied to the total antioxidant capacity assay of trolox, quercetin, ascorbic acid, gallic acid, catechin, caffeic acid, ferulic acid, rosmarinic acid, glutathione, and cysteine, as well as of lipophilic antioxidants such as α-tocopherol (vitamin E), butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, lauryl gallate, and β-carotene. The modified FC method reliably quantified ascorbic acid, whereas the conventional method could not. The modified method was reproducible and additive in terms of total antioxidant capacity values of constituents of complex mixtures such as olive oil extract and herbal tea infusion. The trolox equivalent antioxidant capacities of the tested antioxidant compounds correlated well with those found by the Cupric Reducing Antioxidant Capacity reference method.

Sensitive and selective spectrophotometric assay of doxycycline hyclate in pharmaceuticals using Folin-Ciocalteu reagentA spectrophotometric method for the determination of doxycycline (DOX) is described. The method is based on the formation of blue colored chromogen due to reduction of tungstate and/or molybdate in Folin-Ciocalteu (F-C) reagent by DOX in alkaline medium. The colored species has an absorption maximum at 770 nm and the system obeys Beer's law over the concentration range 0.75-12.0 μg mL-1DOX. The apparent molar absorptivity is 2.78 × 104L mol-1cm-1. The limit of quantification and detection values are reported to be 0.20 and 0.08 μg mL-1, respectively. Over the linear range applicable, the accuracy and precision of the method were evaluated on intra-day and inter-day basis. The reported mean accuracy value was 101.0 ± 1.7 %, the relative error was ≤ 2.7 % and the relative standard deviation was ≤ 2.5 %. Application of the proposed method to bulk powder and commer...

The ability to efficiently evolve hydrogen via electrocatalysis at low overpotentials holds tremendous promise for clean energy [1-10]. Hydrogen evolution reaction (HER, 2H + + 2e -→ H 2 ) can be easily achieved from water if a voltage above the thermodynamic potential of the HER is applied. Large overpotentials are energetically inefficient but can be lowered with expensive platinum based catalysts. Replacement of Pt with inexpensive, earth abundant electrocatalysts would be significantly beneficial for clean and efficient hydrogen evolution. Towards this end, promising HER characteristics have been reported using 2H (trigonal prismatic) XS 2 (where X = Mo or W) nanoparticles with a high concentration of metallic edges [11] as electrocatalysts [3,4,6]. The key challenges for HER with XS 2 are increasing the number and catalytic activity of active sites [2]. Here we report atomically thin

A novel approach to quadrupolar-echo (QE) NMR of half-integer quadrupolar nuclei in static powders is analyzed. By acquisition of the QE spectrum during a Carr-Purcell-Meiboom-Gill (CPMG) train of selective π pulses, the second-order quadrupolar line shape for the central transition is split into a comb of sidebands leading to a considerable increase in the sensitivity compared to a conventional QE spectrum. The applicability of the method for determination of magnitudes and relative orientation of chemical shielding and quadrupolar coupling tensors is examined. Through numerical simulation and iterative fitting of experimental 87 Rb (RbClO 4 and RbVO 3 ) and 59 Co spectra (Co(NH 3 ) 5 Cl 3 ), it is demonstrated that the quadrupolar CPMG experiment represents a useful method for studying half-integer quadrupolar nuclei exhibiting large quadrupolar coupling combined with anisotropic chemical shielding interactions. Sensitivity enhancements by a factor of up to about 30 are observed for the samples studied.

We have identified excited exciton states in monolayers of MoS2 and WS2 supported on fused silica by means of photoluminescence excitation spectroscopy. In monolayer WS2, the positions of the excited A exciton states imply an exciton binding energy of 0.32 eV. In monolayer MoS2, excited exciton transitions are observed at energies of 2.24 and 2.34 eV. Assigning these states to the B exciton Rydberg series yields an exciton binding energy of 0.44 eV.

We introduce the use of pure molten ortho-phosphoric acid (o-H 3 PO 4 ) as an electrolyte for selforganizing electrochemistry. This electrolyte allows for the formation of self-organized oxide architectures (one-dimensional nanotubes, nanochannels, nanopores) on metals such as tungsten that up to now were regarded as very difficult to grow self-ordered anodic oxide structures. In this work, we show particularly the fabrication of thick, vertically aligned tungsten oxide nanochannel layers, with pore diameter of ca. 10 nm, and illustrate their potential use in some typical applications.

We report a computational study on the spontaneous self-assembly of spherical particles into two-dimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far. We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin - a quasi-spherical protein.

Metal organic chemical vapor deposition (MOCVD) is one of the main methodologies used for thin film fabrication in the semiconductor industry today and is considered one of the most promising routes to achieve large-scale and high-quality 2D transition metal dichalcogenides (TMDCs). However, MOCVD suffers from some serious drawbacks, such as small domain size (low crystallinity) and carbon contamination, resulting in poor optical quality, which may inhibit its implementation for the large-scale fabrication of atomic-thin semiconductors. Here we present a Growth-Etch MOCVD (GE-MOCVD) methodology, in which a small amount of water vapor is introduced during the growth, while the precursors are delivered in pulses. The evolution of the growth as a function of the amount of water vapor, the number and type of cycles and the gas composition is described. We show a domain size increase of more than four orders of magnitude relative to the conventional process. The improved crystal quality ...

In this article we reconsider the discussion of the magnetic measurements for the two novel polyoxotungstates, (n-BuNH 3 ) 12 [(CuCl) 6 (AsW 9 O 33 )2]‚6H 2 O and (n-BuNH 3 ) 12 [(MnCl) 6 (SbW 9 O 33 ) 2 ]‚6H 2 O, which have been synthesized and characterized by Yamase et al. (Inorg.Chem. 2006, 45, 7698). Analysis of the magnetic susceptibility and magnetization for Cu 6 12+ and Mn 6 12+ hexagons based on the exact diagonalization of isotropic exchange Hamiltonian shows that the best-fit first-neighbor coupling parameters are J ) 35 and 0.55 cm -1 , respectively, while the secondneighbor interactions are very small. These values exceed considerably those obtained by Yamase et al. (J ) 8.82 and 0.14 cm -1 ) on the basis of the Kambe-Van Vleck formula that is inappropriate for six-membered rings. We also got perfect fits to the experimental data for the field dependence of magnetization at 1.8 K. The results imply the importance of axial anisotropy, which is shown to be especially pronounced for the Mn 6 12+ cluster. We discuss also the symmetry assignments of exchange multiplets to the exact SΓ terms (full spin, S, and irreducible representation, Γ, of the point group) and correlate the results with the selection rules for the anisotropic magnetic contributions. The antisymmetric exchange is shown to appear in orbitally degenerate multiplets as a first-order perturbation and gives rise to an easy axis of magnetization along the C 6 axis. Evaluation of the Zeeman levels shows that the field applied in the plane of the hexagon fully reduces the effect of the antisymmetric exchange.

During the last 20 years multiple roles of the nitric oxide gas (•NO) have been uncovered in plant growth, development and many physiological processes. In seed plants the enzymatic synthesis of •NO is mediated by a nitric oxide synthase (NOS)-like activity performed by a still unknown enzyme(s) and nitrate reductase (NR). In green algae the •NO production has been linked only to NR activity, although a NOS gene was reported for Ostreococcus tauri and O. lucimarinus, no other Viridiplantae species has such gene. As there is no information about •NO synthesis neither for non-vascular plants nor for non-seed vascular plants, the interesting question regarding the evolution of the enzymatic •NO production systems during land plant natural history remains open. To address this issue the endogenous •NO production by protonema was demonstrated using Electron Paramagnetic Resonance (EPR). The •NO signal was almost eliminated in plants treated with sodium tungstate, which also reduced the NR activity, demonstrating that in P. patens NR activity is the main source for •NO production. The analysis with confocal laser scanning microscopy (CLSM) confirmed endogenous NO production and showed that •NO signal is accumulated in the cytoplasm of protonema cells. The results presented here show for the first time the •NO production in a non-vascular plant and demonstrate that the NR-dependent enzymatic synthesis of •NO is common for embryophytes and green algae.

Reaction of monosubstituted Keggin polyoxometalates (POMs) and [Cu(ac)(pmdien)]+ generated in situ led to the formation of the hybrid metal organic–inorganic compound K5[Cu(ac)(pmdien)][SiW11CuO39]⋅12 H2O; its crystal structure and magnetic properties have also been determined. The packing of this compound can be viewed as a stacking of hydrogen‐bonded chiral double chains, with the cationic complexes located between the two‐dimensional arrangement of POM double chains. DFT calculations performed on [Cu(ac)(pmdien)]+ suggest that the distortion presented in this cationic copper complex is due to electronic effects. An AIM stability study of the cationic copper complex, in order to determine the relationship between the bond angle Cu‐O‐C and the denticity of the acetate ligand, has been carried out. Topological analyses over the polyhedral distortion, both of the monosubstituted polyanion and copper complexes, have been performed by means of continuous shape measures (CSM).

Reactivity control of graphene is an important issue because chemical functionalization can modulate graphene's unique mechanical, optical, and electronic properties. Using systematic optical studies, we demonstrate that van der Waals interaction is the dominant factor for the chemical reactivity of graphene on two-dimensional (2D) heterostructures. A significant enhancement in the chemical stability of graphene is achieved by replacing the common SiO 2 substrate with 2D crystals such as an additional graphene layer, WS 2 , MoS 2 , or h-BN. Our theoretical and experimental results show that its origin is a strong van der Waals interaction between the graphene layer and the 2D substrate. This results in a high resistive force on graphene toward geometric lattice deformation. We also demonstrate that the chemical reactivity of graphene can be controlled by the relative lattice orientation with respect to the substrates and thus can be used for a wide range of applications including hydrogen storage.

La 3+ ions were incorporated into an organic/inorganic hybrid mesoporous SBA-15 functionalized with polyoxometalates (POMs). EXAFS spectroscopy at the La L III edge gave definitive clues for a selective uptake of the incorporated La 3+ ions by the POMs grafted onto the mesoporous supports, due to their chelate effect even in the presence of competitive adsorption sites. ABSTRACT. In this work, mesoporous materials based on inorganic/organic polyoxometalate (POM) hybrids with the ability of further incorporating heterometallic lanthanum cations were designed. On the basis of the La 3+ coordination to vacant organophosphonyle derivatives of POMs previously studied, herein POMs-grafted onto an amino-functionalized mesoporous SBA-15 ({NH 2 }-SBA-15) with incorporated La 3+ ions were synthesized with various amounts of La 3+ . L III -edge La EXAFS spectroscopy of the resulting materials provided local structural information around La III ions (i.e. number, nature and distances of neighboring atoms), which are comparable to that of the La III complexes of POMs hybrids. This technique, in addition with 31 P CP-MAS NMR spectroscopy, gave definitive clues for a selective uptake of the incorporated La 3+ ions by the POMs grafted onto the {NH 2 }-SBA-15 supports. This study is a clear demonstration that, due to their chelate effect, POMs hybrids act as efficient ligands for La 3+ even in the presence of competitive adsorption sites. Consequently, a regular distribution of the La 3+ ions along the channels of the SBA-15 is thus observed in these materials due to the nanostructuration of the POMs onto the support.

The potential roles of protein tyrosine kinases (TKs) and of phosphotyrosine phosphatases (PTPs) in pancreatic islet function are not known. In this study, we investigated whether vanadate, a potent PTP inhibitor, affects phosphoinositide (PI) metabolism by a TK-dependent pathway in isolated mouse islets. To avoid the confounding effects of changes in Ca# + influx, all experiments were performed in the absence of Ca# + . In the presence of 15 mM glucose, vanadate, acetylcholine (ACh) or [Arg]vasopressin (AVP) strongly stimulated InsP production. Vanadate also increased PtdInsP levels in membranes. The TK inhibitor genistein (not its inactive analogues genistin and daidzein) significantly reduced vanadate effects, but was without effect in the absence of stimulation or in the presence of ACh or AVP. Islet proteins resolved by SDS\PAGE were analysed by immunoblotting with anti-phosphotyrosine antibody. Under control conditions, several phosphotyrosyl-proteins (PYPs) were

WTe2 and MoTe2 single crystals were grown, and their electrical resistivity in the temperature range from 80 K to 300 K, optical properties at room temperature in the spectral range of 0.17-5.0 eV were studied as well as theoretical calculations of the electronic structure were performed. It is shown that the temperature dependence of the electrical resistivity of orthorhombic WTe2 has a metallic type with resistivity value of (0.5-1) mOhmcm, while hexagonal MoTe2 has a semiconductor one and resistivity value (0.5-1) Ohmcm, which is three orders of magnitude larger than the resistivity of WTe2. Optical properties indicated that there is no contribution from free carriers in the entire spectral range studied. The calculated densities of the electronic states of MoTe2 and WTe2 showed the presence of a bunch of the molybdenum and tungsten electronic states in a wide energy interval with strong admixing of tellurium states. In the WTe2 compound, the larger number of the electronic state...

Nitric oxide (NO) is a highly reactive gaseous free radical, which in plants was found to stimulate seed germination and ending of dormancy. Experiments were conducted to study the effect of NO inhibitors sodium tungstate (ST) and Nv-nitro-L-arginine methyl ester hydrochloride (L-NAME), NADPH oxidase inhibitor diphenyleneiodonium (DPI) and NO donor sodium nitroprusside (SNP) on untreated and magnetoprimed maize (Zea mays var: GSF-2) seeds. Treatment of maize seeds with these inhibitors inhibited germination related parameters like seedling length, fresh weight, dry weight and vigour indices and a-amylase activity of maize seeds under laboratory conditions, whereas NO donor (SNP) promoted all these parameters. Among 3 different inhibitors used ST was most effective and showed an inhibition in seedling length of 67% and 71% at 1 mM concentration for untreated (UT) and magnetically treated (MT) seeds respectively. Data presented here indicate the involvement of nitric oxide in enhanced germination and seedling growth of magnetoprimed maize seeds. ROS are continuosly produced by the cells of germinating seeds and play a positive role in germination of magnetoprimed maize seeds. ROS inhibitor (DPI) inhibited seedling length by 34% and 40% for control and MT seeds respectively. a-amylase activity was also inhibited by all the 3 inhibitors used. It is concluded that NO inhibitors and ROS inhibitor inhibited magnetic field induced promotion of seedling parameters and aamylase activity of maize seeds.

It has been found that polyoxometalates (POMs) can act as mediators in the electrochemical oxidation of lignin in pulps. An electrochemical cell, with a Nafion ® membrane separating the anode and cathode compartments, was used in the delignification experiments. A softwood kraft pulp was placed in the anode compartment with a buffered 0.01M solution of the polyoxometalate Na 5 [SiVW 11 O 40 ]. During electrolysis the lignin content of the pulp was reduced from kappa number 26 to 6. The energy required for this delignification was equivalent to 120 kW•hr per ton of pulp. At $0.05/ kW•hr, the cost for this 20-point drop in kappa number would be $6 per ton of pulp. Based on this and other data, it may be both technically and economically feasible to delignify pulps electrochemically using POMs as mediators. The POMs are neither consumed nor modified during the reaction and can, therefore, be recovered and reused in this novel, closed-mill, delignification process.

Electrochromic (EC) and thermochromic (TC) materials are of much interest for "smart" windows which combine energy efficiency with the provision of indoor comfort. This paper summarizes results from several recent studies related to nanoparticles of transparent and electrically conducting ITO (i.e., In 2 O 3 :Sn) and of thermochromic VO 2 . Specifically, we consider (i) the use of ITO nanoparticles in polaronic EC devices in order to suppress near-infrared solar transmittance, (ii) performance limits for plasmonic EC devices embodying ITO nanoparticles, and (iii) ITO-VO 2 -based nanocomposites with joint low thermal emittance and TC properties, and with Mg-doping of the VO 2 as a means for boosting the luminous transmittance. Both experimental and theoretical results are presented.

Electrochromic (EC) and thermochromic (TC) materials are of much interest for "smart" windows which combine energy efficiency with the provision of indoor comfort. This paper summarizes results from several recent studies related to nanoparticles of transparent and electrically conducting ITO (i.e., In 2 O 3 :Sn) and of thermochromic VO 2 . Specifically, we consider (i) the use of ITO nanoparticles in polaronic EC devices in order to suppress near-infrared solar transmittance, (ii) performance limits for plasmonic EC devices embodying ITO nanoparticles, and (iii) ITO-VO 2 -based nanocomposites with joint low thermal emittance and TC properties, and with Mg-doping of the VO 2 as a means for boosting the luminous transmittance. Both experimental and theoretical results are presented.

The ever-increasing appearance of inorganic-organic hybrid materials incorporating organic metalloporphyrins (MPs) and inorganic polyoxometalates (POMs)-separately, two groups of effective molecular catalystswhich combine to form the groundbreaking class of metal-organic frameworks (MOFs), has allowed this class to participate in numerous kinds of chemical reactions and mimic the activity of heterogeneous bio-, photo-and electrocatalysts. Recent results have shown that the integration of POMs and MPs in a porous structure not only maintains the characteristic functionalities of both components, but can also generate novel and unparalleled features including augmented stabilities, remarkable selectivity, improvable porosity, and novel and more favorable topologies. Furthermore, the immobilization of these component species (POMs and MPs) within a unified framework can prevent their catalytic deactivation, which mostly arises from suicidal self-oxidation of porphyrin moieties. It has also been established that the introduction of POMsowing to their broad range of size, structure, and highly negative charge distribution throughout the clustercan further expand their structural diversity and greatly influence the stability and catalytic performance of porous porphyrinic MOFs. What is more, the incorporation of POMs inside the pores or their use as secondary building units (SBUs) within the framework can give rise to an increase in their original reusability, perpetuity, and adsorption ability. Moreover, their incorporation can also boost the transfer of electrons (e.g., photoexcited charge carriers) through the network. Therefore, POM-based porphyrinic MOFs (porphyrinic POMMOFs) are materials that can

Studded tyres made of tungsten carbide cobalt (WC-Co) are in the Northern countries commonly used during the winter time. Tungsten (W)-containing nano-and micron-sized particles have been detected close to busy roads in several European countries. Other typical traffic wear particles consist of copper (Cu). The aims of this study were to investigate particle stability and transformation/dissolution properties of nanoparticles (NPs) of WC-Co compared with NPs of tungsten carbide (WC), cobalt (Co), and Cu. Their physicochemical characteristics (primarily surface oxide and charge) are compared with their extent of sedimentation and metal release in synthetic surface water (SW) with and without two different model organic molecules, 2,3-and 3,4-dihydroxybenzoic acid (DHBA) mimicking certain sorption sites of humic substances, for time periods up to 22 days. The WC-Co NPs possessed a higher electrochemical and chemical reactivity in SW with and without DHBA molecules as compared with NPs of WC, Co, and Cu. Co was completely released from the WC-Co NPs within a few hours of exposure, although it remained adsorbed/bonded to the particle surface and enabled the adsorption of negatively charged DHBA molecules, in contrast with the WC NPs (no adsorption of DHBA). The DHBA molecules were found to rapidly adsorb on the Co and Cu NPs. The sedimentation of the WC and WC-Co NPs was not influenced by the presence of the 2,3-or 3,4-DHBA molecules. A slight influence (slower sedimentation) was observed for the Co NPs, and a strong influence (slower sedimentation) was observed for the Cu NPs in SW with 2,3-DHBA compared with SW alone. The extent of metal release increased in the order: WC < Cu < Co < WC-Co NPs. All NPs released more than 1 wt-% of their metal total mass. The release from the Cu NPs was most influenced by the presence of DHBA molecules.

The cloud point extraction behavior of Sn(II) and Sn(IV) using ␣-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with ␣-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5 × 10 −5 mol L −1 CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 g L −1 of Sn(II) and 46-750 g L −1 of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 g L −1 for Sn(IV) and 8.4 g L −1 for Sn(II). The relative standard deviation of seven replicate determination of 100 g L −1 both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.

Every day, human lungs filter an infinite number of particles from inhaled air. Lungs behave as serial filters with increasing order of filtration from nose and trachea up to the terminal alveoli. The filtration of inhaled air is related to the health of the mucociliary system. The particulate matter from air gets deposited in lungs and is influenced by size, composition, diffusivity and environmental setting. Such factors play a key role in differentiating the noxious potential in aerosol and splatter. In the dental microenvironment, the dental team is constantly exposed to bioaerosols generated during treatment procedures. An adequate knowledge of risk factors encountered is required in understanding the health risk potential of airborne spread of allergens and infectious materials. Further, an awareness of modes of generation, spread, infection control measures and preventive strategies are required for maintaining a safe dental setup .

The tungsten alloy 91% tungsten, 6% nickel and 3% cobalt (WNC 91-6-3) induces rhabdomyosarcoma when implanted into rat thigh muscle. To investigate whether this effect is species-specific human HSkMc primary muscle cells were exposed to WNC 91-6-3 particles and responses were compared with those from a rat skeletal muscle cell line (L6-C11). Toxicity was assessed by the adenylate kinase assay and microscopy, DNA damage by the Comet assay. Caspase 3 enzyme activity was measured and oligonucleotide microarrays were used for transcriptional profiling. WNC 91-6-3 particles caused toxicity in cells adjacent to the particles and also increased DNA strand breaks. Inhibition of caspase 3 by WNC 91-6-3 occurred in rat but not human cells. In both rat and human cells, the transcriptional response to WNC 91-6-3 showed repression of transcripts encoding muscle-specific proteins with induction of glycolysis, hypoxia, stress responses and transcripts associated with DNA damage and cell death. In human cells, genes encoding metallothioneins were also induced, together with genes related to angiogenesis, dysregulation of apoptosis and proliferation consistent with pre-neoplastic changes. An alloy containing iron, WNF 97-2-1, which is non-carcinogenic in vivo in rats, did not show these transcriptional changes in vitro in either species while the corresponding cobalt-containing alloy, WNC 97-2-1 elicited similar responses to WNC 91-6-3. Tungsten alloys containing both nickel and cobalt therefore have the potential to be carcinogenic in man and in vitro assays coupled with transcriptomics can be used to identify alloys, which may lead to tumour formation, by dysregulation of biochemical processes.

Many efforts have been made towards improving perovskite (PVK) solar cell stability, but their thermal stability, particularly at 85 °C (IEC 61646 climate chamber tests), remains a challenge. Outdoors, the installed solar cell temperature can reach up to 85 °C, especially in desert regions, providing sufficient motivation to study the effect of temperature stress at or above this temperature (e.g., 100 °C) to confirm the commercial viability of PVK solar cells for industrial companies. In this work, a three-layer printable HTM-free CH3NH3PbI3 PVK solar cell with a mesoporous carbon back contact and UV-curable sealant was fabricated and tested for thermal stability over 1500 h at 100 °C. Interestingly, the position of the UV-curing glue was found to drastically affect the device stability. The side-sealed cells show high PCE stability and represent a large step toward commercialization of next generation organic–inorganic lead halide PVK solar cells.

Antioxidants activities from plants sources have attracted a wide range of interest across the world in recent times. This is due to growing concern for safe and alternative sources of antioxidants. The free radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), reducing power assay, total antioxidant capacity of the phosphomolybdenum method and the total phenolics content using the Folin-Ciocalteu reagent were carried out on the acetone, n-butanol and methanol root extracts of Anchomanes difformis. The results of the total phenolics content expressed in mg/100 g of gallic acid equivalent (GAE) showed that the n-butanol extract has significantly (p &lt; 0.05) higher phenolics content (381 +/- 1.13) than the methanol and acetone extracts. All the extracts displayed strong concentration dependent radical scavenging activity. It was also observed that the n-butanol extract showed higher activity of 70.87% and 78.59% at low concentrations of 31.25 microg/mL and ...

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires Open Archive Toulouse Archive Ouverte (OATAO) OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.

This in vitro study compared the effect of a concave with a straight-bevelled cavity margin on the microleakage of Class V composite resin restorations in primary teeth. Standardised Class V cavity preparations were made in vitro on the buccal (all margins placed in enamel) and on the lingual (margins placed in enamel and cementum) surfaces of 20 sound primary molars. The teeth were randomly assigned to two groups of 10 each: in Group 1, a concave bevel was made with a high-speed No. 04 tungsten carbide bur and in Group 2, a straight bevel was made with a high-speed No. 556 tungsten carbide bur. The teeth were restored incrementally with Adper Single Bond 2 (3M) adhesive and Filtek Z 350 (3M) composite resin. All specimens were subsequently thermocycled and immersed in 50% silver nitrate solution. Microleakage of the restorations was then assessed by silver penetration. A grading scale of 0 to 4 was used as the scoring criterion. At the enamel margins no statistically significant di...

Non-aqueous methodologies provide an opportunity to access a range of polyoxometalates that may not be stable in H2O and enable mechanistic studies into hydrolytic and protonation behaviours, which are fundamental to polyoxometalate chemistry. 17 O-enriched (TBA)6[NaPW11O39] was prepared via an efficient non-aqueous route and shown to be a suitable precursor to [(L)MPW11O39] n-(M = Sn 2+ , Pb 2+ , Bi 3+ , Sb 3+ , Sn 4+ , Ti 4+) for detailed systematic studies. Reactions were monitored by 31 P NMR while products were characterised by FT-IR, multinuclear NMR (1 H, 13 C, 17 O, 31 P, 119 Sn, 183 W and 207 Pb), solid state NMR, ESI-MS, CHN microanalysis, UV-Vis and/or single crystal XRD. Using this approach, the readily-hydrolysable tin derivatives, (TBA)4[(CH3O)SnPW11O39] and (TBA)8[(µ-O)(SnPW11O39)2] were prepared for the first time and the previously reported (TBA)4[(HO)TiPW11O39] was shown to be stable in DMSO for up to 3 months possibly due to interaction between HO-and DMSO. As a result of the more ionic character of Sn-OCH3 bond compared with Ti-OCH3, (TBA)4[(CH3O)SnPW11O39] was observed to hydrolyse faster than (TBA)4[(CH3O)TiPW11O39] whereas (TBA)4[ClTiPW11O39] with a large excess of H2O hydrolysed more readily than (TBA)4[ClSnPW11O39]. Although (TBA)4[(HO)TiPW11O39] underwent condensation to (TBA)8[(µ-O)(TiPW11O39)2] easily in acetonitrile at room temperature, this reaction only occured for (TBA)4[(HO)SnPW11O39] at elevated temperature (~120 o C) in the presence of a waterscavenging agent such as N, N'-dicyclohexylcarbodiimide (DCC). These experimental observations were consistent with DFT calculations on the energetics of the hydrolysis and condensation of (TBA)4[(CH3O)SnPW11O39] and (TBA)4[(CH3O)TiPW11O39]. Protonation studies on the 17 O-enriched POMs provided insights into protonation of the MOW sites in (TBA)4[(CH3O)TiPW11O39], (TBA)4[ClM IV PW11O39] (M = Sn, Ti), (TBA)5[M II PW11O39] (M = Sn, Pb) and (TBA)4[M III PW11O39] (M = Sb, Bi) and protonation at both TiOW and TiOTi sites in (TBA)8[(µ-O)(TiPW11O39)2] whilst reactions between (TBA)8[(µ-O)(TiPW11O39)2] and electrophiles indicated possible formation of adducts. Treatment of (TBA)4[(L)SnPW11O39] (L = Cl, HO) with NaBH4 resulted in reduction of the tin heteroatom only whereas reaction between (TBA)5[Sn II PW11O39] and halogens (Br2 and I2) or the molybdate (TBA)3[PMo12O40] showed oxidation of tin (II). Electrochemical studies in acetonitrile revealed no redox processes associated with the heterometals in (TBA)4[(L)Sn IV PW11O39] and (TBA)5[Pb II PW11O39] while redox waves assigned to Sn 2+ /Sn 4+ were observed for Abstract ii (TBA)5[Sn II PW11O39] within the potential range studied. Finally, attempts to prepare Lindqvist-type derivatives, [(L)MW5O18] n-(

Non-aqueous methodologies provide an opportunity to access a range of polyoxometalates that may not be stable in H2O and enable mechanistic studies into hydrolytic and protonation behaviours, which are fundamental to polyoxometalate chemistry. 17 O-enriched (TBA)6[NaPW11O39] was prepared via an efficient non-aqueous route and shown to be a suitable precursor to [(L)MPW11O39] n-(M = Sn 2+ , Pb 2+ , Bi 3+ , Sb 3+ , Sn 4+ , Ti 4+ ) for detailed systematic studies. Reactions were monitored by 31 P NMR while products were characterised by FT-IR, multinuclear NMR ( 1 H, 13 C, 17 O, 31 P, 119 Sn, 183 W and 207 Pb), solid state NMR, ESI-MS, CHN microanalysis, UV-Vis and/or single crystal XRD. Using this approach, the readily-hydrolysable tin derivatives, (TBA)4[(CH3O)SnPW11O39] and (TBA)8[(µ-O)(SnPW11O39)2] were prepared for the first time and the previously reported (TBA)4[(HO)TiPW11O39] was shown to be stable in DMSO for up to 3 months possibly due to interaction between HO-and DMSO. As a result of the more ionic character of Sn-OCH3 bond compared with Ti-OCH3, (TBA)4[(CH3O)SnPW11O39] was observed to hydrolyse faster than (TBA)4[(CH3O)TiPW11O39] whereas (TBA)4[ClTiPW11O39] with a large excess of H2O hydrolysed more readily than (TBA)4[ClSnPW11O39]. Although (TBA)4[(HO)TiPW11O39] underwent condensation to (TBA)8[(µ-O)(TiPW11O39)2] easily in acetonitrile at room temperature, this reaction only occured for (TBA)4[(HO)SnPW11O39] at elevated temperature (~120 o C) in the presence of a waterscavenging agent such as N, N'-dicyclohexylcarbodiimide (DCC). These experimental observations were consistent with DFT calculations on the energetics of the hydrolysis and condensation of (TBA)4[(CH3O)SnPW11O39] and (TBA)4[(CH3O)TiPW11O39]. Protonation studies on the 17 O-enriched POMs provided insights into protonation of the MOW sites in (TBA)4[(CH3O)TiPW11O39], (TBA)4[ClM IV PW11O39] (M = Sn, Ti), (TBA)5[M II PW11O39] (M = Sn, Pb) and (TBA)4[M III PW11O39] (M = Sb, Bi) and protonation at both TiOW and TiOTi sites in (TBA)8[(µ-O)(TiPW11O39)2] whilst reactions between (TBA)8[(µ-O)(TiPW11O39)2] and electrophiles indicated possible formation of adducts. Treatment of (TBA)4[(L)SnPW11O39] (L = Cl, HO) with NaBH4 resulted in reduction of the tin heteroatom only whereas reaction between (TBA)5[Sn II PW11O39] and halogens (Br2 and I2) or the molybdate (TBA)3[PMo12O40] showed oxidation of tin (II). Electrochemical studies in acetonitrile revealed no redox processes associated with the heterometals in (TBA)4[(L)Sn IV PW11O39] and (TBA)5[Pb II PW11O39] while redox waves assigned to Sn 2+ /Sn 4+ were observed for