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The electronic conductivity of the metal oxides is generally increased by hybridization of highly conductive carbon supportive materials. In this present work, we have demonstrated a novel one-pot preparation of cerium niobate (CeNbO 4 ) nanoparticles embedded with graphene oxide (GO/CeNbO 4 ) composite, for ultrasensitive detection of the photographic developing agent, metol (MTL). The as-prepared GO/CeNbO 4 was analyzed by various characterization techniques. The intensive characterization techniques were used to affirm the detailed structural moiety, size, morphology, and surface area of GO/CeNbO 4. The GO/CeNbO 4 modified glassy carbon electrode (GCE) affords a superior electrocatalytic activity toward MTL. The obtained amperometric response on the GO/CeNbO 4 /GCE holding an extremely low level detection of 10 nM and superior sensitivity of 10.97 µA µM -1 cm -2 toward MTL detection. Besides, the GO/CeNbO 4 /GCE also gives excellent selectivity, stability, repeatability, and reproducibility. We achieved excellent recovery results in real photographic solution and river water samples analysis with great accuracy. This work offers a novel insight into the growth of the carbon-based niobate family with electrochemical sensor applications., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

In coated conductor (CC) tapes used in magnet and coil applications, delamination due to excessive transverse tensile stresses is still one of the major issues that need considerations. Recently, several methods in evaluating the delamination strength of CC tapes are being used. In the case of anvil test, size of the anvils will be an important factor considering its applications (i.e., superconducting coil impregnation). In this study, delamination strength of CC tape was examined using different upper anvil sizes and their effects were discussed. Finally, reasonable sizes of upper anvil to be used were proposed considering the application conditions.

In this study, we theoretically investigated the mechanism underlying the high-valent mono-oxo-rhenium(V) hydride Re(O)HCl2(PPh3)2 (1) catalyzed hydrosilylation of C=N functionalities. Our results suggest that an ionic S(N)2-Si outer-sphere pathway involving the heterolytic cleavage of the Si-H bond competes with the hydride pathway involving the C=N bond inserted into the Re-H bond for the rhenium hydride (1) catalyzed hydrosilylation of the less steric C=N functionalities (phenylmethanimine, PhCH=NH, and N-phenylbenzylideneimine, PhCH=NPh). The rate-determining free-energy barriers for the ionic outer-sphere pathway are calculated to be ∼28.1 and 27.6 kcal mol(-1), respectively. These values are slightly more favorable than those obtained for the hydride pathway (by ∼1-3 kcal mol(-1)), whereas for the large steric C=N functionality of N,1,1-tri(phenyl)methanimine (PhCPh=NPh), the ionic outer-sphere pathway (33.1 kcal mol(-1)) is more favorable than the hydride pathway by as much as 11.5 kcal mol(-1). Along the ionic outer-sphere pathway, neither the multiply bonded oxo ligand nor the inherent hydride moiety participate in the activation of the Si-H bond., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new paper-based colorimetric immunosensor for the detection of carcinoembryonic antigen (CEA) was developed based on the intrinsic peroxidase activity of ZnFe2O4-multiwalled carbon nanotubes (ZnFe2O4@MWNTs). The immunosensor platform was prepared by depositing chitosan and porous gold onto filter paper and entrapping the primary antibodies (Ab1) onto the layers. Secondary antibodies (Ab2) were assembled on the surface of the functionalized ZnFe2O4@MWNTs. The immunosensor response was quantified as a color change resulting from ZnFe2O4@MWNTs catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. The catalytic performance of ZnFe2O4@MWNTs was higher than ZnFe2O4 due to the high electrical conductance of MWNTs, moreover, the electron communications between ZnFe2O4@MWNTs and substrates are electrically "wired". Detection was achieved by measuring the color change when the concentrations of CEA were different. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. This method was simple for CEA detection with a linear range from 0.005 to 30 ng mL(-1) and a detection limit of 2.6 pg mL(-1). Such an equipment-free immunoassay has great potential in resource-limited environments.

An ionic liquid (IL) system for the enzymatic epoxidation of soybean oil was studied. The effects of active oxygen carriers (different fatty acids) and ILs ([Bmim]PF6 and [Bmim]BF4) on the enzymatic epoxidation were investigated. Response surface methodology (RSM) was used to study and optimize the effects of variables (reaction time, reaction temperature, molar ratio of H2O2/C=C-bonds, and molar ratio of fatty acid/C=C-bonds) on the epoxy oxygen group content (EOC) of epoxidized soybean oil (ESO). Results showed that the enzymatic epoxidation of soybean oil can be enhanced using tetradecanoic acid (C13H27COOH) as active oxygen carrier and [Bmim]PF6 as reaction medium. The optimum EOC of ESO was 5.9 ± 0.3% under the following conditions: reaction temperature 46°C, reaction time 11 h, enzyme load 3% (w/w, relative to the weight of soybean oil), molar ratio of H2O2/C=C-bonds 1.8:1, and molar ratio of C13H27COOH/C=C-bonds 0.5:1.

The two oxoborates β-ZnB4O7 and β-CaB4O7 were synthesized and investigated by FTIR- and Raman spectroscopy and ab initio quantum chemical calculations. Maximum and mean deviations between experimentally determined bands and calculated modes ranged between 15-36 cm(-1) and 5-7 cm(-1), respectively, allowing band assignments to vibrational modes in most cases. The complex network structures with tetrahedral BO4 and planar OB3 groups are mirrored by the spectra and numerous vibrational modes, not assignable by standard borates classification schemes. It was confirmed that OB3 units, despite similar force constants and geometry, do not absorb in the same range as BO3 units. Bands in the high wavenumber range are rather caused by B-O-(Zn/Ca), O-B-O, B-O-B, and B-O stretching and bending vibrations. The experimental observation of inactive or Raman-active modes in the absorption spectra indicates defects or structural distortions in both compounds., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Cerium doped oxyfluoroborate glasses have been prepared and its spectroscopic properties have been discussed. It is found that the absorption edge shifts towards the lower energy side for the higher concentration of cerium dopant. Optical band gap for these glasses have been calculated and it is found that the number of non-bridging oxygen increases with cerium content. The emission spectra of these glasses have been recorded using UV laser radiations (266 and 355 nm) and it is observed that these glasses show bright blue emission. On the basis of excitation and emission spectra we have reported the existence of at least two different emission centers of Ce(3+)ions., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The first structural characterization of a mononuclear, EPR-active, oxosulfido-Mo(V) compound related to the very rapid form of xanthine oxidase (VR-XnO) is reported. The compound, [CoCp2][Tp(iPr)Mo(V)OS(2-OC6H4CO2Et)] [Cp = cyclopentadienyl; Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate], exhibits a distorted octahedral geometry with Mo═O and Mo=/--S distances of 1.761(5) and 2.215(2) Å, respectively, and an O═Mo=/--S angle of 107.33(14)°. Significantly, the Mo(V)=/--S distance is much shorter than the value of 2.36 Å reported for oxosulfido-Mo(V) compounds (Singh, R.; et al. Inorg. Chem. 1989, 28, 8) but close to the range established for VR-XnO by protein crystallography. The methyl and phenyl esters were also prepared but the latter is highly reactive and undergoes an intramolecular, radical-based cyclization/elimination reaction to form [CoCp2][Tp(iPr)Mo(IV)O{2-OC6H4C(O)S-κO,κS}]. This study provides the first definitive measurement of the Mo(V)=/--S bond distance in an unambiguously characterized oxosulfido-Mo(V) compound and supports the presence of a short (ca. 2.22 Å) Mo=/--S bond in VR-XnO. It also demonstrates that the Mo(V)=/--S moiety participates in radical-based reactions that are facilitated by the facile redox interplay of Mo and S and by substrates susceptible to radical eliminations.

Mustard gas, bis(β-chloroethyl) sulfide (HD), is highly toxic and harmful to humans and the environment. It comprises one class of chemical warfare agents (CWAs) that was used in both World Wars I and II. The three basic analogues or surrogates are: the monochloro derivative, known as the half mustard, 2-chloroethyl ethyl sulfide (CEES); an oxygen analogue, bis(β-chloroethyl) ether (BCEE); and several nitrogen analogues based on the 2,2'-dichlorodiethylamine framework (e.g., HN1, HN2, and HN3). The origin of their toxicity is considered to be from the formation of three-membered heterocyclic ions, a reaction that is especially accelerated in aqueous solution. The reaction of these cyclic ion intermediates with a number of important biological species such as DNA, RNA and proteins causes cell toxicity and is responsible for the deleterious effects of the mustards. While a number of studies have been performed over the last century to determine the chemistry of these compounds, early studies suffered from a lack of more sophisticated NMR and X-ray techniques. It is now well-established that the sulfur and nitrogen mustards are highly reactive in water, while the oxygen analog is much more stable. In this study, we review and summarize results from previous studies, and add results of our own studies of the reactivity of these mustards toward various nonaqueous solvents and nucleophiles. In this manner a more comprehensive evaluation of the stability and reactivity of these related mustard compounds is achieved.

The crystal structure of a binuclear Mn(III) complex of a scorpiand-like ligand (L) displays an unsupported single oxo bridging ligand with a Mn(III)-O-Mn(III) angle of 174.7°. Magnetic susceptibility measurements indicate strong antiferromagnetic coupling between the two metal centers. DFT calculations have been carried out to understand the magnetic behavior and to analyze the nature of the observed Jahn-Teller distortion. Paramagnetic (1)H NMR has been applied to rationalize the formation and magnetic features of the complexes formed in solution.

Oxygenation of a diiron(II) complex, [Fe(II)(2)(μ-OH)(2)(BnBQA)(2)(NCMe)(2)](2+) [2, where BnBQA is N-benzyl-N,N-bis(2-quinolinylmethyl)amine], results in the formation of a metastable peroxodiferric intermediate, 3. The treatment of 3 with strong acid affords its conjugate acid, 4, in which the (μ-oxo)(μ-1,2-peroxo)diiron(III) core of 3 is protonated at the oxo bridge. The core structures of 3 and 4 are characterized in detail by UV-vis, Mössbauer, resonance Raman, and X-ray absorption spectroscopies. Complex 4 is shorter-lived than 3 and decays to generate in ~20% yield of a diiron(III/IV) species 5, which can be identified by electron paramagnetic resonance and Mössbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (μ-oxo)(μ-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O-O bond and formation of a high-valent diiron complex, thereby mimicking the steps involved in the formation of intermediate X in the activation cycle of ribonucleotide reductase.

High-spin Fe(IV)-oxo species are known to be kinetically competent oxidants in non-heme iron enzymes. The properties of these oxidants are not as well understood as the corresponding intermediate-spin oxidants of heme complexes. The present work gives a detailed characterization of the structurally similar complexes [Fe(IV)H(3)buea(O)](-), [Fe(III)H(3)buea(O)](2-), and [Fe(III)H(3)buea(OH)](-) (H(3)buea = tris[(N'-tert-butylureaylato)-N-ethylene]aminato) using Mössbauer and dual-frequency/dual-mode electron paramagnetic resonance (EPR) spectroscopies. The [Fe(IV)H(3)buea(O)](-) complex has a high-spin (S = 2) configuration imposed by the C(3)-symmetric ligand. The EPR spectra of the [Fe(IV)H(3)buea(O)](-) complex presented here represent the first documented examples of an EPR signal from an Fe(IV)-oxo complex, demonstrating the ability to detect and quantify Fe(IV) species with EPR spectroscopy. Quantitative simulations allowed the determination of the zero-field parameter, D = +4.7 cm(-1), and the species concentration. Density functional theory (DFT) calculations of the zero-field parameter were found to be in agreement with the experimental value and indicated that the major contribution to the D value is from spin-orbit coupling of the ground state with an excited S = 1 electronic configuration at 1.2 eV. (17)O isotope enrichment experiments allowed the determination of the hyperfine constants ((17)O)A(z) = 10 MHz for [Fe(IV)H(3)buea(O)](-) and ((17)O)A(y) = 8 MHz, ((17)O)A(z) = 12 MHz for [Fe(III)H(3)buea(OH)](-). The isotropic hyperfine constant (((17)O)A(iso) = -16.8 MHz) was derived from the experimental value to allow a quantitative determination of the spin polarization (ρ(p) = 0.56) of the oxo p orbitals of the Fe-oxo bond in [Fe(IV)H(3)buea(O)](-). This is the first experimental determination for non-heme complexes and indicates significant covalency in the Fe-oxo bond. High-field Mössbauer spectroscopy gave an (57)Fe A(dip) tensor of (+5.6, +5.3, -10.9) MHz and A(iso) = -25.9 MHz for the [Fe(IV)H(3)buea(O)](-) complex, and the results of DFT calculations were in agreement with the nuclear parameters of the complex.

The oxygen-evolving complex (OEC) of Photosystem II (PSII) is an oxomanganese complex that catalyzes water-splitting into O2, protons and electrons. Recent breakthroughs in X-ray crystallography have resolved the cuboidal OEC structure at 1.9 Å resolution, stimulating significant interest in studies of structure/function relations. This article summarizes recent advances on studies of the OEC along with studies of synthetic oxomanganese complexes for artificial photosynthesis. Quantum mechanics/molecular mechanics hybrid methods have enabled modeling the S1 state of the OEC, including the ligation proposed by the most recent X-ray data where D170 is bridging Ca and the Mn center outside the CaMn3 core. Molecular dynamics and Monte Carlo simulations have explored the structural/functional roles of chloride, suggesting that it regulates the electrostatic interactions between D61 and K317 that might be critical for proton abstraction. Furthermore, structural studies of synthetic oxomanganese complexes, including the [H2O(terpy)MnIII(μ-O)2MnIV(terpy)OH2]3+ (1, terpy=2,2':6',2″-terpyridine) complex, provided valuable insights on the mechanistic influence of carboxylate moieties in close contact with the Mn catalyst during oxygen evolution. Covalent attachment of 1 to TiO2 has been achieved via direct deposition and by using organic chromophoric linkers. The (III,IV) oxidation state of 1 attached to TiO2 can be advanced to (IV,IV) by visible-light photoexcitation, leading to photoinduced interfacial electron transfer. These studies are particularly relevant to the development of artificial photosynthetic devices based on inexpensive materials., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Different reaction pathways of the carboxylic group in a brown coal model were investigated by applying density function quantum chemical theory, examining the possible cross-linking and decomposition reactions between the hydrogen bonded carboxylic group-carboxylic group and the carboxylic group-hydroxyl group during the thermal pyrolysis process. The results show that bimolecular dehydration and decarboxylation of hydrogen bonded carboxylic groups have distinctly lower activation barriers and therefore, proceed preferentially at low temperature. The esterification reaction between the hydrogen bonded carboxylic group and hydroxyl group, together with unimolecular decarboxylation of isolated single carboxylic groups were also possible at moderate temperature. Aryl-aryl coupling is thought to occur via radical pyrolysis and recombination at relatively high temperature.

Atmospheric particulate matter with diameter <2.5 um (PM(2.5)) was collected at Peking University (PKU) in Beijing, China before, during, and after the 2008 Olympics and analyzed for black carbon (BC), organic carbon (OC), lower molecular weight (MW < 300) and MW302 Polycyclic Aromatic Hydrocarbons (PAHs), nitrated PAHs (NPAHs) and oxygenated PAHs (OPAHs). In addition, the direct and indirect acting mutagenicity of the PM(2.5) and the potential for DNA damage to human lung cells were also measured. Significant reductions in BC (45%), OC (31%), MW< 300 PAH (26-73%), MW 302 PAH (22-77%), NPAH (15-68%), and OPAH (25-53%) concentrations were measured during the source control and Olympic periods. However, the mutagenicity of the PM(2.5) was significantly reduced only during the Olympic period. The PAH, NPAH, and OPAH composition of the PM(2.5) was similar throughout the study, suggesting similar sources during the different periods. During the source control period, the parent PAH concentrations were correlated with NO, CO, and SO(2) concentrations, indicating that these PAHs were associated with both local and regional emissions. However, the NPAH and OPAH concentrations were only correlated with the NO concentrations, indicating that the NPAH and OPAH were primarily associated with local emissions. The relatively high 2-nitrofluoranthene/1-nitropyrene ratio (25-46) and 2-nitrofluoranthene/2-nitropyrene ratio (3.4-4.8), suggested a predominance of photochemical formation of NPAHs through OH-radical-initiated reactions in the atmosphere. On average, the ∑NPAH and ∑OPAH concentrations were 8% of the parent PAH concentrations, while the direct-acting mutagenicity (due to the NPAH and OPAH) was 200% higher than the indirect-acting mutagenicity (due to the PAH). This suggests that NPAH and OPAH make up a significant portion of the overall mutagenicity of PM(2.5) in Beijing.

A stereocontrolled approach to a key platensimycin intermediate was achieved from a commercially available furylcarboxylate. Key to our approach is the highly efficient formal [4 + 3] cyclocondensation of a substituted furan with tetrabromocyclopropene along with an intramolecular γ-alkylation to construct the final ring of the caged intermediate.

A novel 1,3-dioxopyrrolo[3,4-b]porphyrin (2) has been synthesized in 70% yield following a [4 + 2] cycloaddition reaction of pyrrolo[3,4-b]porphyrin 1 with (1)O(2). The new imide was used as a template to other 1,3-dioxopyrrolo[3,4-b]porphyrins and to the corresponding open counterparts. The UV/vis absorption spectra of the new compounds show significant red-shifts when compared with those of the nonsubstituted analogues. The structure of an imide derivative was confirmed by single-crystal X-ray diffraction.

A method was developed for the speciation analysis of the oxyanions of As(III), As(V), Cr(VI), Mo(VI), Sb(III), Sb(V), Se(IV), Se(VI) and V(V) in leachates from cement-based materials, based on anion-exchange HPLC coupled with ICP-MS. The method was optimized in a two-step multivariate approach: the effect of sample pH and mobile phase composition on resolution, peak symmetry and analysis time was studied. Optimum conditions were then identified for the significant experimental factors by studying their interdependence. A mobile phase composition of 20 mM ammonium nitrate, 50 mM ammonium tartrate and pH 9.5 was found to be a compromise optimum for the separation of the target analytes using isocratic elution. The optimum condition provided separation of the analytes in less than 6 min, at a mobile phase flow rate of 1.0 mL/min. The signal intensities of the analytes were improved by adding 1% methanol to the mobile phase. The limit of detection of the method was in the range 0.2-2.2 μg/L for the various species. The effect of sample constituents was studied using spiked concrete leachates. The method was used to determine the target oxyanionic species in leachates generated from a concrete material in the pH range 3.5-12.4; CrO(4)(2-), MoO(4)(2-) and VO(4)(3-) were detected in most of the leachates., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Electron attachment to SOF(2), SOCl(2), SO(2)F(2), SO(2)FCl, and SO(2)Cl(2) was studied with two flowing-afterglow Langmuir-probe apparatuses over the temperature range 300-900 K. Attachment rate coefficients at 300 K are k(a) = 2.6+/-0.8x10(-10)(SOF(2)), 1.8+/-0.5x10(-8)(SOCl(2)), 4.8+/-0.7x10(-10)(SO(2)F(2)), 2.4+/-0.7x10(-9)(SO(2)Cl(2)), and 2.0+/-0.6x10(-7) cm(3) s(-1)(SO(2)FCl). Arrhenius plots of the data imply activation energies of 56+/-22 meV(SOF(2)), 92+/-40(SO(2)F(2)), 44+/-22 meV(SOCl(2)), and 29+/-15 meV(SO(2)Cl(2)). The rate coefficients for SO(2)FCl decrease slightly with temperature, commensurate with the decrease in the capture rate coefficient. Electron attachment to SOF(2) and SO(2)F(2) is nondissociative, while reaction with SOCl(2), SO(2)FCl, and SO(2)Cl(2) is dissociative. Dissociative attachment is dominated by channels arising from S-Cl bond cleavage but also includes a minor channel forming a dihalide product ion. Branching fraction data are reported for the dissociative attachment channels.

A mass spectrometric method has been developed for the identification of carbonyl and hydroxyl functional groups, as well as for counting the functional groups, in previously unknown protonated bifunctional oxygen-containing analytes. This method utilizes solution reduction before mass spectrometric analysis to convert the carbonyl groups to hydroxyl groups. Gas-phase ion-molecule reactions of the protonated reduced analytes with neutral trimethylborate (TMB) in a FT-ICR mass spectrometer give diagnostic product ions. The reaction sequence likely involves three consecutive steps, proton abstraction from the protonated analyte by TMB, addition of the neutral analyte to the boron reagent, and elimination of a neutral methanol molecule. The number of methanol molecules eliminated upon reactions with TMB reveals the number of hydroxyl groups in the analyte. Comparison of the reactions of the original and reduced analytes reveals the presence and number of carbonyl and hydroxyl groups in the analyte., (Copyright 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.)

Willemite (Zn(2)SiO(4)) ceramics were prepared by sintering the willemite green compacts. The effects of sintering temperature on the linear shrinkage, porosity and mechanical strength of the ceramics were examined. With the sintering temperature increased, the linear shrinkage of the ceramics increased and the porosity decreased. When sintered at 1,300 degrees C, willemite ceramics showed mechanical properties of the same order of magnitude as values for human cortical bone, as measured by bending strength (91.2 +/- 4.2 MPa) and Young's modulus (37.5 +/- 1.5 GPa). In addition, the adhesion and proliferation of rabbit bone marrow stromal cells (BMSCs) on willemite ceramics was investigated. The results showed that the ceramics supported cell adhesion and stimulated the proliferation. All these findings suggest that willemite ceramics possess suitable mechanical properties and favorable biocompatibility and might be a promising biomaterial for bone implant applications.

The structures of (1 - x)Na(0.5)Bi(0.5)TiO(3)-(x)CaTiO(3) at room temperature have been investigated using neutron powder diffraction and dielectric studies. The system exhibits an orthorhombic (Pbnm) structure for x ≥ 0.15 and rhombohedral (R3c) for x ≤ 0.05. For x = 0.10, though the neutron diffraction pattern shows features of the orthorhombic (Pbnm) structure, Rietveld refinement using this structure shows a drastic reduction in the in-phase tilt angle (∼4°) as compared to the corresponding value (∼8°) for a neighbouring composition x = 0.15. The neutron diffraction pattern of x = 0.10 could be fitted equally well using a two-phase model (R3c + Pbnm) with orthorhombic as the minor phase (22%), without the need for a drastic decrease in the in-phase tilt angle. The dielectric studies of x = 0.10 revealed the presence of the polar R3c phase, thereby favouring the phase coexistence model, instead of a single-phase Pbnm structure, for this composition.

The composition of aroma compounds of dry champignons (Agaricus bisporus L.) were identified using capillary gas chromatography and chromatography-mass spectrometry. In total, 56 compounds were identified. It was found that the flavor of dry mushrooms was formed by the volatile compounds produced as a result of enzymatic and oxidative conversion of unsaturated fatty acids as well as in the Maillard reaction. Unsaturated alcohols and ketones containing eight carbon atoms determined the mushroom note of the product. The specific aroma of dry mushrooms was determined by a complex composition of substituted sulfur-, oxygen-, and nitrogen-containing heterocyclic compounds as well as by aliphatic carbonyl compounds and methional. It was found that the concentrations of volatile carbonylic and heterocyclic compounds increased after the addition of a mixture of amino acids to mushrooms before drying. As a result, the intensity of the aroma of dry mushrooms increased.

1, 8-(3, 6, 9-Trioxaundecane-1, 11-diyldioxy)xanthone (L), and its new Cu (II) complex [Cu.L.(CH3CN)2](ClO4)2 have been synthesized and characterized by 1H NMR, electrospray mass spectra (ESI-MS), elemental analyses, infrared spectra (IR) and X-ray single crystal diffraction. The crystal structure of complex shows that Cu (II) ion is encapsulated within the macrocycle of L. The geometry around copper is a distorted square bipyramid with two acetonitrile molecules at axial position, and four macrocyclic oxygens including the carbonyl oxygen on the equatorial positions. The interaction of Cu (II) complex with calf thymus DNA (ct DNA) has been investigated by spectrophotometric titrations, ethidium bromide (EB) displacement experiments, circular dichroism (CD) spectra and viscosity measurements. Results indicate that Cu (II) complex can intercalate into the DNA base pairs by the plane of xanthone ring. Furthermore, the Cu (II) complex was tested against tumor cell lines including ECA109, SGC7901 and GLC-82 by MTT (microculture tetrazolium) method. The studies of DNA-binding agree with the effects on the inhibition of tumor cells in vitro.

We investigated three amino derivatives of ortho-aminobenzoic or anthranilic acid (o-Abz): a) 2-Amino-benzamide (AbzNH2); b) 2-Amino-N-methyl-benzamide (AbzNHCH3) and c) 2-Amino-N-N'-dimethyl-bezamide (AbzNH(CH3)2), see Scheme 1. We describe the results of ab-initio calculations on the structural characteristics of the compounds and experimental studies about solvent effects in their absorption and steady-state and time-resolved emission properties. Ab-initio calculations showed higher stability for the rotameric conformation in which the oxygen of carbonyl is near to the nitrogen of ortho-amino group. The derivatives present decrease in the delocalization of pi electron, and absorption bands are blue shifted compared to the parent compound absorption, the extent of the effect increasing from to Abz-NH2 to Abz-NHCH3 Abz-NH(CH3)2. Measurements performed in several solvents have shown that the the dependence of Stokes shift of the derivatives with the orientational polarizability follows the Onsager-Lippert model for general effects of solvent. However deviation occurred in solvents with properties of Bronsted acids, or electron acceptor characteristics, so that hydrogen bonds formed with protic solvents predominates over intramolecular hydrogen bond. In most solvents the fluorescence decay of AbzNH2 and AbzNHCH3 was fitted to a single exponential with lifetimes around 7.0 ns and no correlation with polarity of the solvent was observed. The fluorescence decay of AbzN(CH3)2 showed lifetimes around 2.0 ns, consistent with low quantum yield of the compound. The spectroscopic properties of the monoamino derivative AbzNHCH3 are representative of the properties presented by Abz labelled peptides and fatty acids previously studied.

X-band electron paramagnetic resonance (EPR) studies of VO(2+) ions in sodium citrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO(2+) sites. Both the vanadyl complexes are found to take up substitutional position. The angular variation of the EPR spectra in three planes ba*, bc and ca* are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, Site I: g(x)=1.9680, g(y)=2.0053, g(z)=1.9124, A(x)=79, A(y)=76, A(z)=185; Site II: g(x)=1.9650, g(y)=2.0067, g(z)=1.9418, A(x)=78, A(y)=70, A(z)=186 x 10(-4)cm(-1). The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

X-Band electron paramagnetic resonance (EPR) studies of VO(2+) ions in l-asparagine monohydrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO(2+) sites. Both the vanadyl complexes are found to take up interstitial position. The angular variation of the EPR spectra in three planes ab, bc and ca are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, site I: g(x)=1.9633, g(y)=2.0274, g(z)=1.9797, A(x)=88, A(y)=61, A(z)=161x10(-4)cm(-1); site II: g(x)=1.9627, g(y)=1.9880, g(z)=1.9425, A(x)=90, A(y)=66, A(z)=167x10(-4)cm(-1). The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

Large-size and high-quality ReCa(4)O(BO(3))(3) (ReCOB, Re = rare earth) single crystals were grown by the Czochralski pulling method. In this work, the electrical properties were investigated at room temperature and elevated temperature for YCa(4)O(BO(3))(3) (YCOB). The dielectric permittivity, piezoelectric strain coefficient, and electromechanical coupling were found to be on the order of 11, 6.5 pC/N, and 12.5%, respectively, with a high piezoelectric voltage coefficient around 0.067 Vm/N. The electrical resistivity of YCOB was found to be 2 x 10(8) Ohm.m at 800 degrees C, with Q values of 4,500 at 950 degrees C. The frequency/temperature coefficient of YCOB was found to be -75 to -85ppm/K in the temperature range of 30 to 950 degrees C, depending on the crystal orientations. Together with their temperature-independent properties, ReCOB crystals are promising candidates for sensing applications at elevated temperatures.

A new series of asymmetric salicyl-, furanyl-, thienyl- and pyrrolyl-derived ONNO, NNNO, ONNS & NNNS donor antibacterial and antifungal Schiff-bases and their copper(II) and zinc(II) metal complexes have been synthesized and characterized. IR spectra indicated the ligands to act as quartdentate towards divalent metal ions via two azomethine-N, deprotonated-O of salicyl, furanyl-O, thienyl-S and/or pyrrolyl-N. The magnetic moments and electronic spectral data suggest octahedral geometry for Cu(II) and Zn(II) complexes. NMR spectral data of the ligands and their diamagnetic zinc(II) complexes well-define their proposed structures/geometries. Elemental analyses data of the ligands and metal complexes agree with their proposed structures/geometries. The synthesized ligands, along with their metal complexes were screened for their antibacterial activity against B. cereus, C. diphtheriae, E. coli, K. pneumoniae, P. mirabilis, P. aeruginosa, S. typhi, S. dysenteriae and S. aureus strains and for in-vitro antifungal activity against T. schoenleinii, C. glabrata, P. boydii, C. albicans, A. niger, M. canis and T. mentagrophytes. The results of these studies show the metal complexes to be more antibacterial/antifungal against one or more species as compared to the uncomplexed ligands. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. Eight compounds, L(4), (1), (7), (8), (11), (17), (19) and (23) displayed potent cytotoxic activity with LD(50) = 1.445 x 10(- 3), 1.021 x 10(- 3), 7.478 x 10(- 4), 8.566 x 10(- 4), 1.028 x 10(- 3), 9.943 x 10(- 4), 8.730 x 10(- 4) and 1.124 x 10(- 3) M respectively, against Artemia salina.

Na(x)Nd((2-x)/3)TiO(3) solid solutions possess tetragonal or orthorhombic perovskite structure, where the A-sites are characterized by 2 kinds of cations (Na(+), Nd(3+)) and vacancies. We have measured microwave dielectric properties of Na(x)Nd((2-x)/3)TiO(3) solid solutions (x = 0.05 to 0.5) to investigate an effect of the compositional ordering in the A-sites of the perovskite structure. According to powder x-ray diffraction, the A-site is disordered in the composition range of x = 0.29 to 0.5. A compositional ordering (Na(+), vacancy / Nd(3+)) in A-sites appeared when x = 0.05 to 0.2. The quality factor (Q x f), where Q is the inverse of dielectric loss and f is frequency, was found to be slightly improved with decreasing Na content in the range of x = 0.05 to 0.2, suggesting that the Q x f of the Na(x)Nd((2-x)/3)TiO(3) solid solutions depends on the compositional ordering in A-sites.

Hepatocellular carcinoma arises from hepatocytes, it is the most common primary malignant tumor of the liver and accounts for the majority of liver cancers. Pirarubicin is a compound analog to the antineoplastic anthracycline antibiotic doxorubicin. Thereby as an intercalator of DNA, pirarubicin has shown efficacy in reducing tumor activity of hepatocellular carcinoma. Utilizing in silico optimized similarity of structure search of data base and replacement by isosteres, a total of nine analogs to pirarubicin were generated. The molecular size of ring substituents (approximately a base pair) were preserved and isosteres chosen to preserve the weak electrostatic properties permitting DNA intercalation. Only a small range in molecular weight and volume was permitted in order to preserve intercalation activity. Standard deviations for polar surface area, number of heavy atoms, molecular weight, molecular volume, and number of oxygens and nitrogens, were only 3.98%, 1.76%, 16.5%, 2.51%, and 0%, respectively, of the overall average for these properties. Variation of the target substituent resulted in insignificant changes in many properties; there was a striking variation in the lipophilic property Log P. Values of Log P ranged from 0.142 to 2.078 inclusive of pirarubicin and plays an important role in bioavailability. Hierarchical cluster analysis indicated that all analogs, except analog 6, were substantially similar to pirarubicin. A similar outcome was obtained from non-metric multidimensional scaling of descriptors. However detrended correspondence analysis distinguished both analogs 6 and 5 from the remaining analogs and pirarubicin. Nonhierarchical K-means clustering analysis determined greater differentiation among the analogs and pirarubicin. Analysis of similarity (ANOSIM) affirmed all compounds to be highly similar which shows structural optimization was achieved.

Over one-third of the world's population has been exposed to Mycobacterium tuberculosis (TB). New drug designs are necessitated by the appearance of multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB). This work presents four hydrazide compounds that inhibit Mycobacterium tuberculosis growth at potency comparable to isoniazid. The hydrazide drugs A, B, C, and D were synthesized utilizing microwave excitation methodologies. Hydrazide agents are produced from parent carboxyl compounds. All reactions were accomplished in dry conditions. Using suitable molecular scaffolds the final hydrazides possessed the desired properties in Log P, polar surface area, molecular weight, etc. All four hydrazide compounds induced at least 60% inhibition of TB at concentrations at less than 31.5 microgram/mL. Measured as relative survival, all four hydrazide compounds induced greater than 95% death of TB bacteria at concentrations less than 31.5 microgram/mL. Drugs A, B, C, D exhibited zero violations of the Rule of 5, indicating favorable bioavailability. Although isoniazid, A, B, C, and D were determined to have a polar surface area less than 70 Angstroms2, the values of Log P (a measurement of lipophilicity) showed a broad range of -1.463 (drug C) to 4.46 (drug A). The numerical values of polar surface area suggests that all drugs would have greater than 50% intestinal absorption. For all drugs the number of amine (-NH) and hydroxyl (-OH) groups remains constant at three, with number of oxygens and nitrogens varying only three to four. ANOSIM (analysis of similarity) indicated that isoniazid, A, B, C, and D are highly similar. Correlation of molecular properties for all five drugs is greater than r = 0.9500. Drugs A, B, C, and D are members of two homologous series of anti-tuberculosis agents. All hydrazides effectively inhibited TB at 31.5 micrograms/mL and lower concentrations.

Two dinuclear oxovanadium(IV) thiolate complexes, [N(C5H11)4]2[VOL1]2 (1) and [N(C4H9)4][(VOL2)2(mu-OCH3)] (2) (where L1 = [(CH3)SiO(C6H4-2-S)2]3- and L2 = [(C6H5)PO(C6H4-2-S)2]2-), have been synthesized and characterized. The geometry of the anion in 1 can be classified to an edge-sharing bi-square-pyramid with a syn-orthogonal configuration. The one in 2 can be view as a face-sharing bioctahedron with two oxo groups in syn positions. Of note, these two complexes display intramolecular ferromagnetic interaction between two metal centers.

A pilot-scale subsurface-flow constructed wetland was installed at the Jones County Municipal Landfill, near Anamosa, Iowa, in August 1999 to demonstrate the use of constructed wetlands as a viable low-cost treatment option for leachate generated at small landfills. The system was equipped with a patented wetland aeration process to aid in removal of organic matter and ammonia nitrogen. The high iron content of the leachate caused the aeration system to cease 2 years into operation. Upon the installation of a pretreatment chamber for iron removal and a new aeration system, treatment efficiencies dramatically improved. Seasonal performance with and without aeration is reported for 5-day biochemical oxygen demand (BOD(5)), chemical oxygen demand (COD), ammonia nitrogen (NH(4)-N), and nitrate nitrogen (NO(3)-N). Since winter air temperatures in Iowa can be very cold, a layer of mulch insulation was installed on top of the wetland bed to keep the system from freezing. When the insulation layer was properly maintained (either through sufficient litterfall or replenishing the mulch layer), the wetland sustained air temperatures of as low as -26 degrees C without freezing problems.

The hot acid hydrolysis followed by chlorine dioxide (A/D*) and hot chlorine dioxide (D*) technologies have proven very useful for bleaching of eucalyptus kraft pulp. Although the characteristics and biodegradability of effluents from conventional chlorine dioxide bleaching are well known, such information is not yet available for effluents derived from hot acid hydrolysis and hot chorine dioxide bleaching. This study discusses the characteristics and biodegradability of such effluents. Combined whole effluents from the complete sequences DEpD, D*EpD, A/D*EpD and ADEpD, and from the pre-bleaching sequences DEp, D*Ep, A/D*Ep and ADEp were characterized by quantifying their colour, AOX and organic load (BOD, COD, TOC). These effluents were also evaluated for their treatability by simulation of an activated sludge system. It was concluded that treatment in the laboratory sequencing batch reactor was efficient for removal of COD, BOD and TOC of all effluents. However, colour increased after biological treatment, with the greatest increase found for the effluent produced using the AD technology. Biological treatment was less efficient at removing AOX of effluents from the sequences with D*, A/D* and AD as the first stages, when compared to the reference D stage; there was evidence of the lower treatability of these organochlorine compounds from these sequences.

The geometry, IR and Raman spectra and electronic properties of Anderson-type heteropolyanions with main-group high oxidation state heteroatom, [Te(VI)Mo(6)O(24)](6-), [I(VII)Mo(6)O(24)](5-), [Sb(V)W(6)O(24)](7-), [Te(VI)W(6)O(24)](6-) and [I(VII)W(6)O(24)](5-) have been investigated using Hartree-Fock (HF) and density functional theory (DFT) methods. HF method has good results in geometry parameters but poorer than DFT method in the results of vibrational frequencies. Also we have investigated the effect of LanL2DZ augmented in the vibrational frequencies. With attention to relative charge and size of the cavity occupied by XO(6) subunit in these anions, we suggest that the general formula [XO(6)(n-)@M(6)O(18)] to describe electronic properties of these anions.

The ternary oxide MnReO(4), manganese rhenium oxide, has been synthesized under a high pressure of 5.5 GPa at 1473 K and its crystal structure has been determined by single-crystal X-ray diffraction. MnReO(4) crystallizes in a wolframite-type structure with average bond lengths of Re-O = 1.935 and Mn-O = 2.160 A that are in good agreement with the ionic radii of Re(6+) and Mn(2+). The magnetic properties of MnReO(4) have been studied by SQUID measurements, revealing magnetic ordering below 275 (10) K and a weak ferromagnetic component of the ordered magnetic structure.

The MnNb(2)O(6)-FeNb(2)O(6) solid solution has been investigated by Fe-K- and Mn-K-edge X-ray absorption (XANES and EXAFS), and Mossbauer spectroscopy. The first-shell M-O bond lengths deduced from EXAFS show a fairly small compositional dependence. A degree of static disorder, which increases with increasing manganese content, is clearly seen by the loss of correlation for the next-neighbour (NN) interaction. Hyperfine parameters from Mossbauer spectra are consistent with variations in the average environment, as recorded by X-ray data. Line broadening of the Mossbauer spectra provides evidence for next-neighbour effects and is consistent with there being no significant clustering of Fe or Mn within the samples. There appear to be differences in the way the columbite structure accommodates Fe(2+) and Mn(2+) ions. In ferrocolumbite all the Fe octahedra are close to being identical, while there are local structural heterogeneities at a longer length scale, presumably in ordering the precise topology of polyhedra immediately adjacent to the octahedron. By contrast, the manganocolumbite seems to have some diversity in the precise coordination at the MnO(6) octahedra, but a greater uniformity in how the adjacent polyhedra are configured around them.

The ordered perovskite Sr(2)YTaO(6), distrontium yttrium tantalum hexaoxide, has been reported as showing an unusual triclinic structure, at odds with the results from a recent group-theoretical analysis. A new investigation establishes that Sr(2)YTaO(6) and the isostructural Sr(2)YNbO(6), distrontium yttrium niobium hexaoxide, in fact both adopt the commonly occurring monoclinic structure, with the space-group symmetry P2(1)/n.

The infrared spectra of polyoxometalates are addressed. The vibration frequencies of some synthesized polyoxometalates in recent years are emphasized. It was found that the infrared spectra of polyoxometalates result from stretch vibration frequency of the metal-oxygen, and 1 100-400 cm(-1) is the region of the characteristic absorption peak. The infrared spectrum contains information about the symmetry of polyoxoanion as well. As an analytical means, the infrared spectrum can be used to distinguish heteropolyanion and provide information on structure.

The three-isotope tracer Delta(17)O is increasingly used in atmospheric chemistry and other research areas. Thanks to the development of isotope-ratio mass spectrometry (IRMS), delta(17)O and delta(18)O can be determined with a precision of a few 0.01 per thousand, and values for Delta(17)O may be calculated with similar precision. However, interpreting small and precisely determined Delta(17)O values as a deviation from an expected mass-dependent fractionation process is not straightforward. Several aspects are of high importance. In the present paper we review existing definitions, formulas and some other aspects of Delta(17)O reporting. One of the most confusing aspects is a variance of definitions and corresponding formulas. While Delta(17)O is traditionally defined to characterise a data point, i.e. Delta(17)O is considered as a deviation from an expected mass-fractionation line, the recently introduced definition (Miller MF. Geochim. Cosmochim. Acta 2002; 66: 188) characterises a fractionation line itself, in terms of its ordinate intercept. The formulas corresponding to this definition gives a characteristic for a specific process. When the 'traditionally defined' Delta(17)O is in use, an expected fractionation processes--the key point for Delta(17)O reporting--should be defined and parameterised with the same accuracy as intended for reporting Delta(17)O. When Delta(17)O is reported for a data point, not only a value for lambda but an ordinate intercept of a reference fractionation line should be given with high accuracy. We note that defining a single fractionation process is hardly possible for many natural compounds. For such compounds we propose to use a phenomenological reference line, namely an isotope composition range of natural sources. Next, aspects of Delta(17)O comparison and mass-balance calculations are considered. All the aspects considered for Delta(17)O may be relevant for others three-isotope tracers, e.g. Delta(33)S.

Polyoxometalates have been traditionally the subject of study of molecular inorganic chemistry. Yet, these polynuclear molecules, reminiscent of oxide clusters, present a wide range of structures and with them ideal frameworks for the deployment of a plethora of useful magnetic, electroionic, catalytic, bioactive and photochemical properties. With this in mind, a new trend towards the application of these remarkable species in materials science is beginning to develop. In this review we analyze this trend and discuss two main lines of thought for the application of polyoxometalates as materials. On the one hand, there is their use as clusters with inherently useful properties on themselves, a line which has produced fundamental studies of their magnetic, electronic or photoelectrochemical properties and has shown these clusters as models for quantum-sized oxides. On the other hand, the encapsulation or integration of polyoxometalates into organic, polymeric or inorganic matrices or substrates opens a whole new field within the area of hybrid materials for harnessing the multifunctional properties of these versatile species in a wide variety of applications, ranging from catalysis to energy storage to biomedicine.

NMR spectroscopy is a relatively insensitive technique and many biomolecular applications operate near the limits of sensitivity and resolution. A particularly challenging example is detection of the quadrupolar nucleus 17O, due to its low natural abundance, large quadrupole couplings, and low gyromagnetic ratio. Yet the chemical shift of 17O spans almost 1000 ppm in organic molecules and it serves as a potentially unique reporter of hydrogen bonding in peptides, nucleic acids, and water, and as a valuable complement to 13C and 15N NMR. Recent developments including the multiple-quantum magic-angle spinning (MQMAS) experiment have enabled the detection of 17O in biological solids, but very long data acquisitions are required to achieve sufficient sensitivity and resolution. Here, we perform nonlinear sampling in the indirect dimension of MQMAS experiments to substantially reduce the total acquisition time and improve sensitivity and resolution. Nonlinear sampling prevents the use of the discrete Fourier transform; instead, we employ maximum entropy (MaxEnt) reconstruction. Nonlinearly sampled MQMAS spectra are shown to provide high resolution and sensitivity in several systems, including lithium sulfate monohydrate (LiSO(4)-H(2)17O) and L-asparagine monohydrate (H(2)17O). The combination of nonlinear sampling and MaxEnt reconstruction promises to make the application of 17O MQMAS practical in a wider range of biological systems.

Investigations of various CeO2 catalysts using XRD, 02-TPD, H2-TPR and catalytic wet air oxidation of phenol showed that CeO2 calcined under higher thermal impact (designated as type A) displayed excellent catalytic ability for the redox reaction of organics. Results of the investigations mentioned above showed that type A CeO2 has a less stable structure, more structure oxygen exchangeable and more oxidizing ability for the consumption of H2 and conversion of phenol. At phenol concentrations between 400 and 2,500 mg/L, oxygen pressure in the range of 0.5-1.0 MPa, and temperatures above 160 degrees C phenol conversion stood at > or = 90% after 4 h. Total organic carbon removal increased with the reaction temperature. Under the reaction conditions, CO2 selectivity was about 80% or more after 4 h reaction. The reduced catalytic ability of regenerated CeO2 was caused either by stabilization of CeO2 during the process of regeneration or by the deposition of some reaction residues.

This paper will report on the measurements of the thermal coefficients of expansion and density of langasite (LGS), langanite (LGN), and langatate (LGT). The data were obtained by fabricating cubes with X, Y, and Z faces with nominal dimensions of 1 cm on a side for each material under test. The techniques used for measurement of density and thermal coefficients of expansion (TCE) of the materials are discussed. The data sets obtained and the extracted coefficients are presented.

Cross-polarization from (1)H to the multiple-quantum coherences of a quadrupolar nucleus is used in combination with the two-dimensional multiple-quantum magic angle spinning (MQMAS) NMR experiment in order to extract high-resolution CPMAS NMR spectra. The technique is demonstrated on (23)Na (S = 3/2), (17)O, (27)Al (both S = 5/2), and (45)Sc (S = 7/2) nuclei, showing the applicability of multiple-quantum cross-polarization to systems with differing spin quantum number, gyromagnetic ratio, and relative nuclide abundance. The utility of this two-dimensional MAS NMR experiment for spectral editing and site-specific measurement of cross-polarization intensities is demonstrated. The possibility of direct cross-polarization to higher order multiple-quantum coherences is also considered and three-, five-, and seven-quantum cross-polarized (45)Sc MAS NMR spectra are presented., (Copyright 2000 Academic Press.)

The chemistry in a supersonic plasma source flow was studied as a laboratory model for interstellar chemical evolution. It is important to match the similarity parameters for cosmic and laboratory conditions, which connect the temporal and spatial scales of the two cases. The apparatus simulated the conditions in a molecular cloud with respect to molecular-ionic reaction fraction, temperature, and non-equilibrium kinetics. The plasma flow was found to be cold enough, by the radical expansion, to produce polyatomic molecules. From the simple atomic plasma as reactant, cyanopolyyne and unsaturated hydrocarbons were synthesized in the present experiment. These molecules are also inherent in molecular clouds. The reaction mechanism is discussed.