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An attempt has been made to graft copolymerize the vinyl monomer methacrylonitrile onto poly tetrafluoroethylene-co-ethylene, known as Tefzel film, by the double-irradiation method in aqueous medium. Optimum conditions for attaining the maximum percentage of grafting were evaluated. The maximum percentage of grafting for methacrylonitrile was obtained 128.7 % at an optimum dose of 24.9 kGy using 2.98 mol L-1 of methacrylonitrile. Investigations on the effects of different chain-length aliphatic alcohols, methanol, ethanol, n-butanol, cyclohexanol and amyl alcohol on the grafting percentages of methacrylonitrile have been performed. Characterization of Tefzel and grafted Tefzel films have been performed by infrared spectroscopy and Thermogravimetric Analysis. Methacrylonitrile grafted Tefzel films showed better thermal stability. [ABSTRACT FROM AUTHOR]

Natural fibers have received increasing attention as starting materials for innovative applications in many research fields, from biomedicine to engineering. Bombyx mori silk fibroin has become a material of choice in the development of many biomedical devices. Grafting represents a good strategy to improve the material properties according to the desired function. In the present study, Bombyx mori silk fibroin fibers were grafted with methacrylonitrile (MAN) with different weight gains. The potential interest in biomedical applications of MAN functionalization relies on the presence of the nitrile group, which is an acceptor of H bonds and can bind metals. IR and Raman spectroscopy were used to characterize the grafted samples and the possible structural changes induced by grafting. Afterward, the same techniques were used to study the bioactivity (i.e., the calcium phosphate nucleation ability) of MAN-grafted silk fibroins after ageing in simulated body fluid (SBF) for possible application in bone tissue engineering, and their interaction with Ag+ ions, for the development of biomaterials with enhanced anti-microbial properties. MAN was found to efficiently polymerize on silk fibroin through polar amino acids (i.e., serine and tryptophan), inducing an enrichment in silk fibroin-ordered domains. IR spectroscopy allowed us to detect the nucleation of a thin calcium phosphate layer and the uptake of Ag+ ions through the nitrile group, which may foster the application of these grafted materials in biomedical applications. [ABSTRACT FROM AUTHOR]

Natural fibers have received increasing attention as starting materials for innovative applications in many research fields, from biomedicine to engineering. Bombyx mori silk fibroin has become a material of choice in the development of many biomedical devices. Grafting represents a good strategy to improve the material properties according to the desired function. In the present study, Bombyx mori silk fibroin fibers were grafted with methacrylonitrile (MAN) with different weight gains. The potential interest in biomedical applications of MAN functionalization relies on the presence of the nitrile group, which is an acceptor of H bonds and can bind metals. IR and Raman spectroscopy were used to characterize the grafted samples and the possible structural changes induced by grafting. Afterward, the same techniques were used to study the bioactivity (i.e., the calcium phosphate nucleation ability) of MAN-grafted silk fibroins after ageing in simulated body fluid (SBF) for possible application in bone tissue engineering, and their interaction with Ag+ ions, for the development of biomaterials with enhanced anti-microbial properties. MAN was found to efficiently polymerize on silk fibroin through polar amino acids (i.e., serine and tryptophan), inducing an enrichment in silk fibroin-ordered domains. IR spectroscopy allowed us to detect the nucleation of a thin calcium phosphate layer and the uptake of Ag+ ions through the nitrile group, which may foster the application of these grafted materials in biomedical applications.

The binary mutual neutralization (MN) of a series of 17 cations ( O2+, NO+, NO2+, CO+, CO2+, Cl+, Cl2+, SO2+, CF3+, C2F5+, NH3+, H3+, D3+, H2O+, H3O+, ArH+, ArD+) with 3 halide anions (Cl-, Br-, I-) has been investigated in a flowing afterglow-Langmuir probe apparatus using the variable electron and neutral density attachment mass spectrometry technique. The MN rate constants of atom-atom reactions are dominated by the chemical nature of the system (i.e., the specific locations of curve crossings). As the number of atoms in the system increases, the MN rate constants become dominated instead by the physical nature of the system (e.g., the relative velocity of the reactants). For systems involving 4 or more atoms, the 300 K MN rate constants are well described by 2.7 × 10-7 μ-0.5, where the reduced mass is in Da and the resulting rate constants in cm³ s-1. An upper limit to the MN rate constants appears well described by the complex potential model described by Hickman assuming a cross-section to neutralization of 11 000 Ų at 300 K, equivalent to 3.5 × 10-7 μ-0.5. [ABSTRACT FROM AUTHOR]

We have studied a range of pseudo-ternaries derived from the parent compound PrMn2Ge2, substituting for each constituent element with a smaller one to contract the lattice. This enables us to observe the magneto-elastic transitions that occur as the Mn-Mn nearest neighbour distance is reduced and to assess the role of Pr on the magnetism. Here, we report on the PrMn2Ge2-xSix, Pr1-xYxMn2Ge2, and PrMn2-xFexGe2 systems. The pressure produced by chemical substitution in these pseudo-ternaries is inherently non-uniform, with local pressure variations dependent on the local atomic distribution. We find that concentrated chemical substitution on the R or X site (e.g., in Pr0.5Y0.5Mn2Ge2 and PrMn2Ge0.8Si1.2) can produce a separation into two distinct magnetic phases, canted ferromagnetic and canted antiferromagnetic, with a commensurate phase gap in the crystalline lattice. This phase gap is a consequence of the combination of phase separation and spontaneous magnetostriction, which is positive on transition to the canted ferromagnetic phase and negative on transition to the canted antiferromagnetic phase. Our results show that co-existence of canted ferromagnetic and antiferromagnetic phases depends on chemical pressure from the rare earth and metalloid sites, on local lattice strain distributions and on applied magnetic field. We demonstrate that the effects of chemical pressure bear close resemblance to those of mechanical pressure on the parent compound. [ABSTRACT FROM AUTHOR]

We present the studies of structural, electrical, and magnetic properties of bulk Cd1-xMnxGeAs2 crystals with low Mn content, x, varying from 0 to 0.037. The studied samples have excellent crystallographic quality indicated by the presence of diffraction patterns never before observed experimentally for this compound. The electrical transport in our samples is dominated by thermal activation of conducting holes from the impurity states to the valence band with activation energy of about 200 meV. The defect states acting as ionic scattering centers with concentration in the range from 6 to 15 × 1017 cm-3 are observed. The effective Mn content in our samples, xθ, determined from fit of the susceptibility data to the Curie-Weiss law, is very close to the average chemical content, x. It indicates that the Mn ions are distributed randomly, substituting the Cd sites in the host CdGeAs2 lattice. We observe a negative Curie-Weiss temperature, ∣θ∣ ⩽ 3:1K, increasing as a function of x. This indicates the significance of the short-range interactions between the Mn ions. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]

We present systematic studies of magnetic and transport properties of Zn1-xMnxGeAs2 semimagnetic semiconductor with the chemical composition varying between 0.053≤x≤0.182. The transport characterization showed that all investigated samples had p-type conductivity strongly depending on the chemical composition of the alloy. The Hall effect measurements revealed carrier concentrations p≥1019 cm-3 and relatively low mobilities, μ≤15 cm2/(V s), also chemical composition dependent. The magnetic investigations showed the presence of paramagnet-ferromagnet phase transitions with transition temperatures greater than 300 K for the samples with x≥0.078. We prove by means of x-ray diffraction, nuclear magnetic resonance, and scanning electron microscopy techniques that the observed room temperature ferromagnetism is due to the presence of MnAs inclusions. The high field magnetoresistance showed the presence of giant magnetoresistance effect with maximum amplitudes around 50% due to the presence of nanosize ferromagnetic grains. [ABSTRACT FROM AUTHOR]

The influences of Mn doping on the electrical and optical properties of the Zn1-xMnxO:N films have been investigated. Mn incorporation occupying on the Zn site has led the lattice constants and the bandgap of the films increased with the structural quality deteriorated. The electrical properties have been found to change significantly with the content of Mn in the films, due to the changes in the amount of the NO acceptors and CN compensation centers formed in the films by Mn incorporation as revealed by x-ray photoelectron spectrometry measurements. The chemical states of Mn have been identified as Mn2+ and Mn4+, corresponding to Mn occupying on the Zn site and MnO2 second phase, respectively. The conductive type and the Mn2+ content of the films show a strong effect on the magnetic properties, which can be explained from the theoretical predication on the Mn 3d and N 2p ferromagnetic (hole) coupling on the ferromagnetism. However, uncompensated spins from nonuniform distribution of Mn atoms in ZnO may also be responsible for the observation of ferromagnetism signature at least on the high resistant samples. [ABSTRACT FROM AUTHOR]

Local crystal structures associated with nanoscale variations of the concentration ratio of Fe ions to Mn ions in each single Li1.2Mn0.4Fe0.4O2 particle have been studied by nanobeam electron diffraction, high-resolution transmission electron microscopy, and electron energy-loss spectroscopy combined with scanning transmission electron microscopy. We have found the direct evidence that the Li1.2Mn0.4Fe0.4O2 particle is comprised of Mn-rich nanodomains with the layered rocksalt structure and Fe-rich nanodomains with the cubic rocksalt structure featured by the cation short-range order, within a common oxygen lattice framework of the cubic close-packed structure. Possible oxygen-centered octahedra in the present material are suggested. We discuss both origin and stability of the chemical-nanodomain structure. [ABSTRACT FROM AUTHOR]

We have investigated structural, magnetic, optical, and electrical transport properties of Zn0.9-xFe0.1(Co/Mn)xO (x=0.05,0.1 for Co and x=0.1 for Mn) diluted magnetic semiconducting nanoparticles synthesized through low temperature chemical “pyrophoric reaction process.” From transmission electron micrograph, particle sizes are found to be in the nanometric regime (∼7 nm) and single crystalline in nature. The magnetization measurements reveal that doping of Co or Mn ions in ZnFeO nanometric matrix decreases the values of coercive field and average magnetization, not due to just increasing the total dopant concentration. It has been attributed to the formation of antiferromagnetic or paramagnetic states in ferromagnetic infinite cluster (spanning of magnetic polarons) by doping of Co or Mn ions. The strong irreversibility has been observed to persist at and above room temperature in magnetization versus temperature curve. The semiconducting band gap of those nanoparticles has been estimated using recorded absorbance spectra. The electrical behaviors of those samples have been investigated over the wide temperature and frequency range using ac complex impedance spectroscopy. [ABSTRACT FROM AUTHOR]

The magnetic and chemical interface properties of Mn–Ir/Co–Fe/Al+oxidation/Ni–Fe magnetic tunnel junctions are investigated for different barrier thickness, oxidation times, and annealing conditions by x-ray absorption spectroscopy and x-ray magnetic circular dichroism. For underoxidized samples the formation of Co–Fe–Al alloy at the lower barrier interface during optimal annealing is observed. For optimally oxidized and overoxidized samples FeOx is formed during oxidation, which is reduced by Mn diffusing to the barrier during annealing. The reduction of FeOx is accompanied by an increase of the interfacial magnetic Fe moment, whereas the Co moments hardly change with the postannealing. Comparison of these results with transport properties of the junctions shows that their polycrystalline structure has to be taken into account to understand the annealing temperature and oxidation state dependence of the tunneling magnetoresistance effect. [ABSTRACT FROM AUTHOR]

A detailed computational study of the Diels‐Alder reaction of cyclopentadiene with acrylonitrile, methylacrylate and their α‐methylated counterparts methacrylonitrile and methyl methacrylate at the M06‐2X(PCM)/TZVP level of theory has been performed. We want to understand the excellent exo‐selectivities observed experimentally due the presence of this substituent. To this end, analysis of the reaction coordinate by means of activation strain model of chemical reactivity (ASM‐distortion interaction model) including solvation effects and NBO second order perturbation energy have been carried out. What does methyl do? Experimental evidence has shown that the presence of a methyl group in the dienophile drastically affects the endo:exo selectivity in Diels‐Alder cycloadditions. In this work, a detailed computational study including activation strain – distortion/interaction modelling and NBO second order perturbation energy calculations have been performed in order to shed light on the phenomenon. [ABSTRACT FROM AUTHOR]

We report a combined study of hydrostatic pressure (P ⩽ 25 kbar) and chemical substitution on the magnetic pair-breaking effect in Eu- and Mn-substituted BaFe2As2 single crystals. At ambient pressure, both substitutions suppress the superconducting (SC) transition temperature (Tc) of BaFe2-xCoxAs2 samples slightly under the optimally doped region, indicating the presence of a pair-breaking effect. At low pressures, an increase of Tc is observed for all studied compounds followed by an expected decrease at higher pressures. However, in the Eu dilute system, Tc further increases at higher pressure along with a narrowing of the SC transition, suggesting that a pair-breaking mechanism reminiscent of the Eu Kondo single impurity regime is being suppressed by pressure. Furthermore, Electron Spin Resonance (ESR) measurements indicate the presence of Mn2+ and Eu2+ local moments and the microscopic parameters extracted from the ESR analysis reveal that the Abrikosov-Gor'kov expression for magnetic pair-breaking in a conventional sign-preserving superconducting state cannot describe the observed reduction of Tc. [ABSTRACT FROM AUTHOR]

We report a combined study of hydrostatic pressure (P ⩽ 25 kbar) and chemical substitution on the magnetic pair-breaking effect in Eu- and Mn-substituted BaFe2As2 single crystals. At ambient pressure, both substitutions suppress the superconducting (SC) transition temperature (Tc) of BaFe2-xCoxAs2 samples slightly under the optimally doped region, indicating the presence of a pair-breaking effect. At low pressures, an increase of Tc is observed for all studied compounds followed by an expected decrease at higher pressures. However, in the Eu dilute system, Tc further increases at higher pressure along with a narrowing of the SC transition, suggesting that a pair-breaking mechanism reminiscent of the Eu Kondo single impurity regime is being suppressed by pressure. Furthermore, Electron Spin Resonance (ESR) measurements indicate the presence of Mn2+ and Eu2+ local moments and the microscopic parameters extracted from the ESR analysis reveal that the Abrikosov-Gor'kov expression for magnetic pair-breaking in a conventional sign-preserving superconducting state cannot describe the observed reduction of Tc. [ABSTRACT FROM AUTHOR]

Polymer brushes are surface coatings that can be tailored in many ways to suit specific demands including reduction of protein and bacterial fouling of biomaterials. Previously, we reported that antifouling poly (2‐(methacryloxy)ethyl)dimethyl‐3‐sulphopropyl ammonium hydroxide) brushes dramatically reduced formation of bacterial biofilm. We hypothesized that: (1) this brush could be efficiently functionalized with a small molecule (2‐oxo‐2‐[N‐(2,4,6‐trihydroxybenzylidene)‐hydrazino]‐acetamide, ME0163, hydrazone) and that (2) the antifouling property would remain also after functionalization. Diblock co‐polymer brushes of 2‐(methacryloxy)ethyl)dimethyl‐3‐sulphopropyl ammonium hydroxide and poly (glycidyl methacrylate) were formed by surface‐initiated atom transfer radical polymerization (SI‐ATRP), and the ME0163 hydrazone was covalently bound to the surface via a ring‐opening reaction. Functionalization of the surfaces was followed by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV‐Vis spectroscopy. The influence of temperature, reaction time, and reagent concentrations on the immobilization process was investigated. Surfaces with high degree of functionalization could be made in this way. However, the functionalization rendered the surface more hydrophobic, and the antifouling property of the brush was lost, thus, disproving the second of our starting hypotheses but corroborating the first. [ABSTRACT FROM AUTHOR]

We report the development of an efficient, customized spherical indentation-based testing method to systematically estimate the hydraulic permeability of gelatin methacryloyl (GelMA) hydrogels fabricated in a wide range of mass concentrations and photocrosslinking conditions. Numerical simulations and Biot’s theory of poroelasticity were implemented to calibrate our experimental data. We correlated elastic moduli and permeability coefficients with different GelMA concentrations and crosslinking densities. Our model could also predict drug release rates from the GelMA hydrogels and diffusion of biomolecules into the three-dimensional GelMA hydrogels. The results potentially provide a design map for choosing desired GelMA-based hydrogels for use in drug delivery, tissue engineering, and regenerative medicine, which may be further expanded to predicting the permeability behaviors of various other hydrogel types. Statement of Significance GelMA hydrogels have attracted increasing attention in recent years as matrices for cell cultures and biomolecule delivery. This inexpensive polymer is derived from gelatin functionalized with methacryloyl groups that can be crosslinked by photochemical reactions. Here we report the development of an efficient, customized testing method to systematically estimate the hydraulic permeability of GelMA hydrogels. Hydraulic permeability indicates the resistance of GelMA hydrogels to the movement of saturated fluid. We used the model to measure the elastic moduli and permeability coefficients, providing a permeability map for various GelMA hydrogel formulations. [ABSTRACT FROM AUTHOR]

Examines the tilted antiferromagnetic ordering of the methacrylonitrile (Mn )spins in polycrystalline Nd0.62Ca0.38MnO3. Information on the discovery of colossal magnetoresistance (CMR) in many systems; Preparation of polycrystalline samples; Observation of charge ordering, tilted antiferromagnetic ordering of the Mn spins.

Gelatin methacryloyl (GelMA) is a versatile biomaterial that has been used in various biomedical fields. Thus far, however, GelMA is mostly obtained from mammalian sources, which are associated with a risk of transmission of diseases, such as mad cow disease, as well as certain religious restrictions. In this study, we synthesized GelMA using fish-derived gelatin by a conventional GelMA synthesis method, and evaluated its physical properties and cell responses. The lower melting point of fish gelatin compared to porcine gelatin allowed larger-scale synthesis of GelMA and enabled hydrogel fabrication at room temperature. The properties (mechanical strength, water swelling degree and degradation rate) of fish GelMA differed from those of porcine GelMA, and could be tuned to suit diverse applications. Cells adhered, proliferated, and formed networks with surrounding cells on fish GelMA, and maintained high initial cell viability. These data suggest that fish GelMA could be utilized in a variety of biomedical fields as a substitute for mammalian-derived materials. [ABSTRACT FROM AUTHOR]

The cationic half-sandwich aqua-complexes [( η 5 -C 5 Me 5 )M(PP ∗ )(H 2 O)][SbF 6 ] 2 [M = Rh, Ir; PP ∗ = ( R )-Benphos, ( R )-Cyphos, (2 R ,4 R )-Norphos] catalyse the 1,3-dipolar cycloaddition reaction of nitrones with methacrylonitrile with perfect regioselectivity, low-to-perfect endo -selectivity and low-to-moderate enantioselectivity. The active species involved in the catalytic process, [( η 5 -C 5 Me 5 )M(PP ∗ )(methacrylonitrile)][SbF 6 ] 2 , have been isolated and characterised as mixtures of the ( S )- and ( R )-at-metal epimers. NMR measurements of these mixtures indicated that the ( R M )-isomers epimerise to the corresponding ( S M ) counterparts. The molecular structure of the rhodium complex ( S Rh , R C )-[( η 5 -C 5 Me 5 )Rh{( R )-Benphos}(methacrylonitrile)][SbF 6 ] 2 has been determined by X-ray diffraction methods. Diastereomerically pure ( S Rh , R C )-[( η 5 -C 5 Me 5 )Rh(PP ∗ )(methacrylonitrile)][SbF 6 ] 2 compounds catalyse stoichiometrically the above mentioned dipolar cycloaddition reaction with up to 90% enantiomeric excess, thus indicating the influence of the metal handedness on the catalytic stereochemical outcome. Catalysts can be recycled up to three times without a significant loss of either activity or selectivity. [ABSTRACT FROM AUTHOR]

Purpose - This paper aims to examine the loss of tenacity and colorfastness properties of bleached and modified (acrylonitrile, AN and methacrylonitrile, MAN) jute fibres dyed with Reactive Orange 14 and Basic Violet 14. Design/methodology/approach - Jute fibres dyed with Reactive Orange 14 and Basic Violet 14 were studied as a function of exposure to sunlight in air,washingwith soap solutionandspotting with acidsandalkalis. Findings - Dye absorption of Basic Violet 14 was higher compared to Reactive Orange 14 at optimum dyeing conditions. Optimum dye uptake of Reactive Orange 14 required relatively severe conditions compared to that of Basic Violet 14. Whereas, Reactive Orange 14 showed overall good colorfastness to sunlight and moderate in washing compared to Basic Violet 14. All the bleached and modified fibres showed good colorfastness to weak acids and alkalis regardless of Reactive Orange 14 and Basic Violet 14 dyes. The loss in tenacity was higher in the case of non-modified fibres, and among the modified fibres, Basic Violet 14 showed the lowest loss in tenacity in the exposure to sunlight. Originality/value - Many studies have been devoted to improve the substantivity of cellulosic fibre for reactive dyes. A few efforts were made to improve the light fastness. In this work, investigation will be made on a comparative study of loss of tenacity and colorfastness properties of bleached and modified (AN and MAN) jute fibres dyed with both Reactive Orange 14 and Basic Violet 14 on exposure to sunlight, washing and acid and alkali spotting. Optimum dyeing conditions will also be investigated for economic dyeing. [ABSTRACT FROM AUTHOR]

Photoactivatable CO releasing protein crystals were developed by immobilization of Mn carbonyl complexes in polyhedral crystals, which are spontaneously formed in insect cells. The photoactivatable CO release from the engineered protein crystals activates nuclear factor kappa B (NF-κB) upon stimulation by visible light irradiation with suppression of cytotoxicity of the Mn complex. [ABSTRACT FROM AUTHOR]

Silicon (Si) is known to alleviate manganese (Mn) toxicity in a number of plant species; however, the mechanisms responsible for this effect are poorly understood. Here, we investigated the interaction between Si and Mn in rice (Oryza sativa) by using a mutant defective in Si uptake. Silicon alleviated Mn toxicity in the wild-type (WT) rice, but not in the mutant exposed to high Mn. The Mn concentration in the shoots was decreased, but that in the roots was increased by Si in the WT. In contrast, the Mn concentration in the roots and shoots was unaffected by Si in the mutant. Furthermore, Si supply resulted in an increased Mn in the root cell sap, decreased Mn in the xylem sap in the WT, but these effects of Si were not observed in the mutant. A short-term labelling experiment with 54Mn showed that the uptake of Mn was similar between plants with and without Si and between WT and the mutant. However, Si decreased root-to-shoot translocation of Mn in the WT, but not in the mutant. The expression of a Mn transporter gene for uptake, OsNramp5, was unaffected by a short exposure (<1 d) to Si, but down-regulated by relatively long-term exposure to Si in WT. In contrast, the expression of OsNramp5 was unaffected by Si in the mutant. These results indicated that Si-decreased Mn accumulation results from both Si-decreased root-to-shoot translocation of Mn, probably by the formation of Mn-Si complex in root cells, and uptake by down-regulating Mn transporter gene. [ABSTRACT FROM AUTHOR]

Copper-catalyzed reactions of glycine ester arylimines and methacrylonitrile provide selective access to either the endo or exo pyrrolidine cycloadducts. DFT calculations have elucidated the origins of ligand-controlled diastereoselectivity. [ABSTRACT FROM AUTHOR]

We examined the feasibility of Cr(OH)3(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)3(s) (1.0 g/L) at pH 7.0-9.0 under oxic or anoxic conditions. Homogeneous Mn(II) oxidation by dissolved O2 was not observed at pH ⩽ 8.0 for 50 days. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 days and precipitated as hausmannite. When Cr(OH)3(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ⩾ 8.0 under oxic conditions. Production of Cr(VI) was attributed to Cr(OH)3(s) oxidation by a newly formed Mn oxide via Mn(II) oxidation catalyzed on Cr(OH)3(s) surface. XANES results indicated that this surface-catalyzed Mn(II) oxidation produced a mixed valence Mn(III/IV) solid phase. Our results suggest that toxic Cr(VI) can be naturally produced via Cr(OH)3(s) oxidation coupled with the oxidation of dissolved Mn(II). In addition, this study evokes the potential environmental hazard of sparingly soluble Cr(OH)3(s), which has been considered the most common and a stable remediation product of Cr(VI) contamination. [ABSTRACT FROM AUTHOR]

Manganese (Mn) and iron (Fe) concentrations were measured in coral skeletons ( Porites spp.) collected from the Todoroki River on Ishigaki Island, Japan, to reconstruct the history of land use in the river catchment area. We prepared (1) five bulk samples to investigate the present spatial distribution and (2) micro-samples from two long cores to study the temporal variability of sediment loading from the Todoroki River. The existing state of the elements Mn and Fe in bulk coral skeleton samples was examined by a chemical cleaning experiment. The results of the experiment suggested that Fe was not incorporated into the crystal lattice of the coral skeleton but that Mn was incorporated, as previously reported. The bulk sample data, with and without chemical cleaning, indicated that the spatial distribution of both elements in corals collected along a sampling line from the river mouth toward the reef crest was complex and most likely reflected salinity changes and the amount of suspended particulate matter. The temporal variation of Mn and Fe, in particular the variation of baseline/background levels, mainly reflected the history of land development on Ishigaki Island. In addition, Mn showed clear seasonal variability that appeared to be controlled by a combination of temperature, primary productivity, and precipitation. The results of the present study suggest that Mn may be a useful proxy for river discharge or biological activity depending on local marine conditions, if the specific behavior of Mn at the coral growth site is known. [ABSTRACT FROM AUTHOR]

The first tail-to-tail dimerization of methacrylonitrile (MAN) has been realized by the cooperative use of N-heterocyclic carbene (NHC) and Bronsted acid catalysts, producing 2,5-dimethylhex-2-enedinitrile with the E/Z ratio of 24:76. Although the NHC alone was not effective for the catalysis, the addition of alcohols resulted in the significant increase of the dimer yield up to 82% in the presence of 5 mol % NHC. Detailed experimental studies including the ESI-MS analysis of the intermediates, stoichiometric (co)dimerizations; and deuterium-labeling experiments revealed the mechanistic aspects of the proton transfer, isomerization, umpolung, and rate-limiting steps, allowing us to observe several mechanistic differences between the dimerization of MAN and that of methyl methacrylate. The stoichiometric reactions in the presence and absence of an alcohol suggest that the alcohol additives play a role in promoting the intermolecular proton transfers from the deoxy-Breslow intermediate to the regenerated NHC in the second half of the catalytic cycle. In addition, the codimerizations of MAN with n-butyl methacrylate (n-BuMA) have been studied. While the dimerization of n-BuMA was sluggish in the presence of an alcohol, the catalytic activity for the codimerization was enhanced by the cooperative systems. [ABSTRACT FROM AUTHOR]

Abstract: Radiation grafted membranes with controlled monomer content were prepared to investigate the role of nitrile containing comonomers on the properties of proton conducting membranes. The membranes consist of a partially fluorinated backbone of ETFE with grafted chains containing styrene sulfonic acid and its comonomer, methacrylonitrile (MAN) or acrylonitrile (AN). Upon grafting, the comonomers show a tendency to form an alternating copolymer with styrene. The ex situ properties of both types of co-grafted membrane, i.e., proton conductivity, water uptake, and dimensional stability, are largely insensitive to the type of comonomer but mainly governed by the ion exchange capacity (IEC). Styrene/AN co-grafted membranes undergo substantial nitrile hydrolysis during the sulfonation procedure compared to styrene/MAN co-grafted membranes. The substituent at the alpha position of the comonomer determines the susceptibility of the nitrile to hydrolysis during membrane preparation as well as during fuel cell operation. Despite the change in the chemical properties as a result of hydrolysis, the mechanical integrity of the co-grafted membranes is retained. However, the styrene/AN co-grafted membrane showed considerably inferior performance in the fuel cell compared to the styrene/MAN co-grafted membrane. These findings bring about a design rationale for membrane materials with enhanced stability against hydrolysis. [Copyright &y& Elsevier]

Abstract: The fuel cell performance and durability of three kinds of styrene based radiation grafted membranes are investigated and compared in the single cell. The styrene/methacrylonitrile (MAN) co-grafted membrane exhibits the best performance among the tested radiation grafted membranes. The accelerated tests under open circuit voltage (OCV) conditions and post-mortem analysis demonstrate that the nitrile-containing membranes exhibit significantly enhanced durability compared to the pure styrene grafted membrane, which is associated with the reduced gas crossover rates and attributed to the improved gases barrier properties due to the polarity of the nitrile group. To understand the influence of each functional group in the co-monomer units, both styrene/MAN and styrene/acrylonitrile (AN) co-grafted membranes are evaluated in a set of tests at OCV. The degrees of loss of the graft components are subsequently quantitatively analyzed based on FTIR spectra, showing a comparable decomposition rate of grafted styrene units, but more loss of nitrile in case of the styrene/AN co-grafted membrane. The styrene/AN co-grafted membrane, with AN lacking protection at the α-position in contrast to MAN, is found to be susceptible to significant hydrolysis, directly leading to an accelerated degradation in the late stages of the 130 h OCV test and inhomogeneous in-plane degradation. [Copyright &y& Elsevier]

Abstract: A new membrane material for polymer electrolyte fuel cells (PEFC), ETFE-graft-poly(α-methylstyrenesulfonic acid-co-methacrylonitrile), is presented. Its preparation by radiation-induced grafting and the dependence of the reaction kinetics on the irradiation dose (3 and 15kGy) and crosslinker concentration are reported. A series of divinylbenzene crosslinked and uncrosslinked membranes is characterised with respect to ion exchange capacity (IEC) (up to 2.1mmol/g), proton conductivity (up to 92mS/cm at room temperature), and water uptake (10–67%). Furthermore, the correlation between the dimensional stability of the membrane and the graft level is presented. The ex situ hydrolytic stability of the membranes was tested and analysed by infrared (IR) spectroscopy. In a hydrogen/oxygen PEFC at 80°C, Nafion 212 and a 35μm thick grafted membrane showed the same performance, whereas the hydrogen permeability of the grafted membrane is only one third compared to that of Nafion 212. [Copyright &y& Elsevier]

The study on spatial variability of soil properties performed through geostatistical techniques allow us to identify the spatial distribution of phenomena by means of a spatial model that considers degree of dependence among observed data, depending on distance and also the direction that separate them, if there is geometric anisotropy, in other words, a directional trend in spatial continuity. However, the main difficulty in decision making regarding the use of anisotropic spatial model focuses on its relevance to the parameters that express the geometric anisotropy in a spatial model exercise in relation to the estimation space. This study aims at identifying the degree of influence of geometric anisotropy on the accuracy of spatial estimation using simulated data sets with different sample sizes and soil chemical properties such as: Fe, potential acidity (H + Al), organic matter and Mn. Comparing the isotropic and anisotropic models, especially for smaller sample sizes (100 and 169) showed an increased sum of squares of differences between predictions anisotropy factor (Fa) equals 2. Furthermore, from Fa equals 2.5, over 50% of the simulations showed values of overall accuracy (OA) of less than 0.80 and values for the concordance index Kappa (K) and Tau (T) from 0.67 to 0.80, indicating differences between thematic maps. Similar conclusions were obtained for chemical properties of the soil, from Fa equals 2, showing that there are relevant differences regarding the inclusion or not of geometric anisotropy. [ABSTRACT FROM AUTHOR]

Ce3+-, Tb3+-, and Mn2+-activated Ca9MgNa(PO4)7 (CMNP) phosphors have been prepared by a Pechini-type sol-gel method. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) and cathodoluminescence (CL) spectroscopy were used to characterize the samples. The energy transfer from Ce3+ to Tb3+ in CMNP phosphors has been demonstrated to be a resonant type by a dipole-quadrupole mechanism, and the Ce3+ to Tb3+ critical distances ( RC) calculated by the concentration-quenching method and the spectral-overlap method are 12.21 and 12.11 Å, respectively. A color-tunable emission in CMNP phosphors can be realized by Ce3+→Tb3+ or Ce3+→Mn2+ energy transfer. White cathodoluminescence has been realized in a single-phase Ca9MgNa(PO4)7 host by codoping with Ce3+, Tb3+, and Mn2+ for the first time with International Commission on Illumination (CIE) chromaticity coordinates (0.319, 0.327). Furthermore, the cathodoluminescence (CL) properties of CMNP:Ce3+/Tb3+/Mn2+ phosphors, including the dependence of the CL intensity on accelerating voltage and filament current, the decay behavior of CL intensity under electron bombardment, and the stability of the CIE chromaticity coordinates, have been investigated in detail. Owing to their good CL properties and good CIE chromaticity coordinates, the as-prepared phosphors have potential application in field emission display (FED) devices. [ABSTRACT FROM AUTHOR]

First, the second-generation hyperbranched poly(amine-ester) (G2-OH) was successfully prepared by thiol-ene 'click' chemistry. Subsequently, a series of photosensitive hyperbranched oligomers (G2-ORs) were synthesized by facile modifications of the G2-OH with acryloyl chloride, methacryloyl chloride, IPDI-HEA, and IPDI-HEMA, respectively. The structures of hyperbranched oligomers were characterized by element analysis, FT-IR, 1H NMR, GPC and viscosity measurement. It was shown that these synthesized oligomers have narrow molecular weight distribution and low intrinsic viscosity at 30°C. UV-vis spectra results showed that the G2-ORs had sharp absorption bands at around 202 nm. The results of photosensitivities measurement indicated that the G2-Macr shows the highest photosensitive than other hyperbranched oligomers in the absence of photoinitiator. In addition, these UV-cured photosensitive G2-ORs had good thermal properties. The solubilities of the synthesized hyperbranched oligomers were also examined. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Abstract: Fourteen trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were analyzed in livers and muscles from 22 fish species from the New Caledonia lagoon, which is subjected to important chemical inputs due to intense land-based mining activities (New Caledonia is the third largest world producer of Ni). The results of this baseline research indicated that livers generally concentrated trace elements to a greater extent than muscles. Nevertheless, the overall trace element concentrations in both tissues were barely above the levels reported in fish and thus contamination at the local scale was poorly discriminated. Although these levels were low, preliminary risk assessment from a global health standpoint suggests that As would be an element potentially leading to exposure of concern for fish consumers. Based on the trace element concentrations in livers and the fish trophic preferences, some trends have been observed among trophic groups: Ag, Cu, Fe, Hg, and Zn concentrations were generally higher in liver of fish with the highest trophic position whereas Cd concentrations were lower in these groups. The use of the leopard coral grouper Plectropomus leopardus as a resident top predator allowed determining the geographical variations in contamination levels with significant differences for six out of the fourteen elements investigated. The sampling sites influenced by anthropogenic inputs were revealed by high Ag, Cd, Cu, Hg, and Pb concentrations. Such geographic differences also applied to Zn but surprisingly not for the typical elements associated with Ni mining, i.e., Co, Cr, Mn and Ni. [Copyright &y& Elsevier]

With the aim of developing dielectric polymers containing CN groups with strong dipole moment, alternating and statistical copolymers of the cyano monomers vinylidene cyanide (VCN), acrylonitrile and methacrylonitrile with methyl α-acetoxyacrylate (MAA) were synthesized and characterized. The copolymer's composition and microstructure were analysed by NMR spectroscopy, SEC and elemental analysis. The reactivity ratios calculated from the Q- e Alfrey-Price parameters for these copolymers indicated the alternating and statistical structures confirmed by NMR analysis. The copolymers have glass transition temperatures Tg in the range 83-146 °C and are stable up to 230 °C. The thermal stability of the copolymers depends on the nature of the cyano monomers. Their molecular dynamics were investigated by dielectric relaxation spectroscopy. We revealed a weak relaxation β at sub- Tg temperature for poly(VCN- co-MAA) usually originating from molecular motions that are restricted to the scale of a few bond lengths. Strong α-relaxation processes occurred above Tg for these copolymers. This primary relaxation was associated with cooperative movements of the polar groups (CN) at the time of mobility of the principal chains. The activation energy of the α-relaxation process was also calculated. The values of the dielectric increment Δε for these copolymers were determined by Cole-Cole plots and indicated that the copolymers exhibit interesting dielectric properties compared with similar cyano materials. The polarity-permittivity relationship was also established. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Up to date, very few studies have examined the phytoextraction ability of hyperaccumulators in the real soils contaminated with heavy metals following the identification of the hyperaccumulators using hydroponics tests. In the present study, amended with a chemical-mobilizing agent of ethylene diamine triacetic acid (EDTA), the manganese accumulation, tolerance and the hyperaccumulating ability of two hyperaccumulators Phytolacca americana L. (Phytolaccaceae) and Polygonum hydropiper L. (Polygonaceae) proved by previous hydroponics tests were examined using pot experiments with paddy soils contaminated with Mn (1,047 ± 53 mg kg) collected from one site in the vicinity of one manganese mine in Xiushan county of Chongqing, China. Results showed that the root and shoot biomass of P. americana and the chlorophyll production of P. hydropiper were significantly inhibited by EDTA treatments while the chlorophyll production of P. americana was oppositely obviously promoted by EDTA. It is noteworthy that, with or without EDTA treatment, the shoot Mn concentrations of both plant species were significantly below the hyperaccumulator threshold, indicating these two plants concealed their hyperaccumulating ability in the studied soils. Thus, further detailed studies need to be conducted to promote the metal hyperaccumulating capacity of these two plant species under comparably low Mn-contaminated soil conditions as shown in this study before the successful application of these Mn hyperaccumulators identified in laboratories to the phytoextraction of lightly or moderately Mn-contaminated agricultural soils. [ABSTRACT FROM AUTHOR]