XANES and EXAFS of copper compounds: Studies of copper carboxylates with metal-metal bonds and of the complex formed byPseudomonas aeruginosa

X-ray absorpion near edge structure (xanes) of copper compounds with copper in 1+, 2+ and 3+ states has been studied. Extended x-ray absorption fine structure (exafs) has been employed to determine bond distances and coordination numbers in several model copper compounds. Employing bothxanes andexafs, the structure of the copper complex formed by the micro-organismPseudomonas aeruginosa has been shown to be square-planar with the Cu-O distance close to that in cupric glucuronates and cupric acetylacetonate.exafs has been shown to be useful for studying metal-metal bonds in copper carboxylates.

Crystal structures of 1,4-diaza bicyclo[2.2.2.]octane and N,N-dimethyl formamide adducts of copper acetate

The crystal structures of copper acetate adducts with 1,4-diaza bicyclo [2.2.2.]octane and N,N-dimethyl formamide are shown to be dimeric with Cu---Cu distances of 2.633 Å and 2.616 Å respectively.

Influence of concentration, temperature and humidity on the toxicity of phosphine to the strongly phosphine-resistant psocid Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae)

BACKGROUND: The psocid Liposcelis bostrychophila Badonnel, is a widespread, significant pest of stored commodities, has developed strong resistance to phosphine, the major grain disinfestant. The aim was to develop effective fumigation protocols to control this resistant pest. RESULTS: Time to population extinction of all life stages (TPE) in days was evaluated at a series of phosphine concentrations and temperatures at two relative humidities. Regression analysis showed that temperature, concentration and relative humidity all contributed significantly to describing TPE (P < 0.001, R2 = 0.95), with temperature being the dominant variable, accounting for 74.4% of the variation. Irrespective of phosphine concentration, TPE was longer at lower temperatures and high humidity (70% RH) and shorter at higher temperatures and low humidity (55% RH). At any concentration of phosphine, a combination of higher temperature and lower humidity provides the shortest fumigation period to control resistant L. bostrychophila. For example, 19 and 11 days of fumigation are required at 15 °C and 70% RH at 0.1 and 1.0 mg L-1 of phosphine respectively, whereas only 4 and 2 days are required at 35 °C and 55% RH for the same respective concentrations. CONCLUSIONS: The developed fumigation protocols will provide industry with flexibility in application of phosphine.

Size dependence and dispersion behavior of the first hyperpolarizability of copper nanoparticles

We have probed the size dependency of the first hyperpolarizability (b) of copper nanoparticles by hyper-Rayleigh scattering (HRS). Our results indicate that second harmonic generation (SHG) originates predominantly at the surface of the nanoparticles as long as the size (d) remains small compared to the wavelength (k). However, volume contribution to the SH response due to the retardation effect becomes important when particle size grows beyond the `small particle limit'. There is a significant dispersion in the b values of copper nanoparticles owing tothe presence of the strong surface plasmon resonance (SPR) band.

Adsorption Of Methanol On The Surfaces Of Copper-Alloys - Ups And Eels Studies

Methanol adsorbs molecularly on the surfaces of Cu–Pd alloys at low temperatures and transforms to CH3O or CO on warming, depending upon the alloy composition. On oxygen presorbed Cu–Pd alloy surfaces, adsorption of methanol gives rise to H2O and H2CO. CH3OH adsorbed molecularly on the surfaces of Cu–Au alloys and CH3O is formed only at relatively high temperatures.

Enhancement of organic phase controlled extraction of copper by activated carbon

The addition of activated carbon particles (Darco-G, average size 4.3,μm) is shown to enhance the initial rate of extraction of copper in a Lewis cell by a mixture of α- and β-hydroxyoximes, when the rate of extraction is controlled by resistances in the organic phase. It is likely that the copper complex is adsorbed by carbon near the interace and partially released in the bulk. The enhancing effect of carbon vanishes when toluene is used as a diluent instead of heptane, presumably because toluene preferentially adsorbs on its surface.

Toxicity of dioxin to developing teeth and salivary glands : An experimental study

Dioxins are ubiquitous environmental poisons having unequivocal adverse health effects on various species. The majority of their effects are thought to be mediated by the aryl hydrocarbon receptor (AhR). Developing human teeth may be sensitive to dioxins and the most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is developmentally toxic to rodent teeth. Mechanisms of TCDD toxicity can be studied only experimentally. The aim of the present thesis work was to delineate morphological end points of developmental toxicity of TCDD in rat and mouse teeth and salivary glands in vivo and in vitro and to characterize their cellular and molecular background. Mouse embryonic teeth and submandibular gland explants were grown in organ culture without/with TCDD at various concentrations, examined stereomicroscopically and processed for histological examination. The effects of TCDD on cellular mechanisms essential for organogenesis were investigated. The expression of various genes eliciting the response to TCDD exposure or involved in tooth and salivary gland development was studied at the mRNA and/or protein levels by in situ hybridization and immunohistochemistry. Association of the dental effects of TCDD with the resistance of a rat strain to TCDD acute lethality was analyzed in two lactationally exposed rat strains. The effect of TCDD on rat molar tooth mineralization was studied in tissue sections. TCDD dose- and developmental stage-dependently interfered with tooth formation. TCDD prevented early mouse molar tooth morphogenesis and altered cuspal morphology by enhancing programmend cell death, or apoptosis, in dental epithelial cells programmed to undergo apotosis. Cell proliferation was not affected. TCDD impaired mineralization of rat molar dental matrices, possibly by specifically reducing the expression of the mineralization-related dentin sialophosphoprotein gene shown in cultured mouse teeth. The impaired mineralization of rat teeth was accompanied by decreased expression of AhR and the TCDD-inducible xenobiotic-metabolozing enzyme P4501 A1 (CYP1A1), suggesting mediation of the TCDD effect by the AhR pathway. The severe interference by TCDD with rat incisor formation was independent of the genotypic variation of AhR determining the resistance of a rat strain to TCDD acute lethality. The impairment by TCDD of mouse submandibular gland branching morphogenesis was associated with CYP1A1 induction and involved blockage of EGF receptor signalling. In conclusion, TCDD exposure is likely to have activated the AhR pathway in target organs with the consequent activation of other signalling pathways involving developmentally regulated genes. The resultant phenotype is organ specific and modified by epithelial-mesenchymal interactions and dependent on dose as well as the stage of organogenesis at the time of TCDD exposure. Teeth appear to be responsive to TCDD exposure throughout their development.

Effects of Isothermal and Adiabatic Thermal Loadings on Size and Strain Rate Dependence of Copper Nanowire

In the present paper, the size and strain rate effects on ultra-thin < 100 >/{100} Cu nanowires at an initial temperature of 10 K have been discussed. Extensive molecular dynamics (MD) simulations have been performed using Embedded atom method (EAM) to investigate the structural behaviours and properties under high strain rate. Velocity-Verlet algorithm has been used to solve the equation of motions. Two different thermal loading cases have been considered: (i) Isothermal loading, in which Nose-Hoover thermostat is used to maintain the constant system temperature, and (ii) Adiabatic loading, i.e., without any thermostat. Five different wire cross-sections were considered ranging from 0.723 x 0.723 nm(2) to 2.169 x 2.169 nm(2) The strain rates used in the present study were 1 x 10(9) s(-1), 1 x 10(8) s(-1), and 1 x 10(7) s(-1). The effect of strain rate on the mechanical properties of copper nanowires was analysed, which shows that elastic properties are independent of thermal loading for a given strain rate and cross-sectional dimension of nanowire. It showed a decreasing yield stress and yield strain with decreasing strain rate for a given cross- section. Also, a decreasing yield stress and increasing yield strain were observed for a given strain rate with increasing cross-sectional area. Elastic modulus was found to be similar to 100 GPa, which was independent of processing temperature, strain rate, and size for a given initial temperature. Reorientation of < 100 >/{100} square cross-sectional copper nanowire into a series of stable ultra-thin Pentagon copper nanobridge structures with dia of similar to 1 nm at 10 K was observed under high strain rate tensile loading. The effect of isothermal and adiabatic loading on the formation of such pentagonal nanobridge structure has been discussed.

The Occurrence and Toxicity of Indospicine to Grazing Animals

Indospicine is a non-proteinogenic amino acid which occurs in Indigofera species with widespread prevalence in grazing pastures across tropical Africa, Asia, Australia, and the Americas. It accumulates in the tissues of grazing livestock after ingestion of Indigofera. It is a competitive inhibitor of arginase and causes both liver degeneration and abortion. Indospicine hepatoxicity occurs universally across animal species but the degree varies considerably between species, with dogs being particularly sensitive. The magnitude of canine sensitivity is such that ingestion of naturally indospicine-contaminated horse and camel meat has caused secondary poisoning of dogs, raising significant industry concern. Indospicine impacts on the health and production of grazing animals per se has been less widely documented. Livestock grazing Indigofera have a chronic and cumulative exposure to this toxin, with such exposure experimentally shown to induce both hepatotoxicity and embryo-lethal effects in cattle and sheep. In extensive pasture systems, where animals are not closely monitored, the resultant toxicosis may well occur after prolonged exposure but either be undetected, or even if detected not be attributable to a particular cause. Indospicine should be considered as a possible cause of animal poor performance, particularly reduced weight gain or reproductive losses, in pastures where Indigofera are prevalent.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g = 2.085, g =2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu S bonds. The experimentally determined hyperfine constants are A =34.9×10−4 cm−1, B =26.1×10−4 cm−1, A =60.4×10−4 cm−1, B =55.5×10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the bond, the bonds are also strongly covalent. ©1973 The American Institute of Physics

Electron spin resonance study of copper(II) doped ferroelectric ammonium sulphate

Single crystal electron spin resonance studies of Cu2+ doped ferroelectric ammonium sulphate ((NH4)2SO4, Tc = 223 K) are reported at 300 and 77 K. The Cu2+ ion is found to enter the lattice interstitially with a trigonal bipyramidal coordination. Proton superhyperfine interaction is found for magnetic field directions close to the a-axis. Changes are observed in the 77 K recordings indicating a distortion of the trigonal bipyramid consistent with crystal structure data. An increase of the proton superhyperfine constant in the ferroelectric phase is indicative of stronger hydrogen bonding. The Cu2+ ion doped as an impurity in a trigonal bipyramid environment in a diamagnetic host lattice is reported for the first time.

Bioavailability and toxicity of chemicals in inland waters : the importance of prevailing water chemistry and implications for risk assessment

Physicochemical characterization of freshwater samples from Finland, Sweden, the Netherlands, and Spain revealed that water hardness and pH decreased and the quantity and quality of humic substances changed considerably in this geographical series from south to north. Since the ambient water chemistry may affect the availability of chemicals, the total aqueous concentration of a chemical may be insufficient to predict the bioconcentration, subsequent biological response, and thus risk. In addition, organisms could be affected directly by water quality characteristics. In this context the main objective of this thesis was to investigate the bioavailability of selected ecotoxicologically relevant chemicals (cadmium, benzo(a)pyrene, and pyrene) in various European surface waters and to show the importance of certain water chemistry characteristics in interpreting the bioavailability and toxicity results. The bioavailability of cadmium to Daphnia magna was examined in very soft humic lake water. Humic substances as natural ligands decreased the free and bioavailable proportion of cadmium in soft lake water. As a consequence the uptake rate and the acute toxicity decreased compared with the humic-free reference. When the hardness of humic lake water was artificially elevated, the acute toxicity of cadmium decreased, although the proportion of free cadmium increased. The decreased bioavailability of cadmium in hard water was a result of effective competition for uptake by the hardness cations, especially calcium ions. The protective role of humic substances and water hardness against cadmium toxicity was also observed in Lumbriculus variegatus, although D. magna was more sensitive to cadmium. The bioavailability of two polycyclic aromatic hydrocarbons (PAHs), pyrene and benzo(a)pyrene, was studied in European surface waters of varying water chemistry. Humic substances acted as complexing ligands with both PAHs, but the bioavailability of the more lipophilic benzo(a)pyrene to D. magna was affected more by humic substances than that of pyrene. In addition, not only the quantity of humic substances, but also their quality affected the bioavailability of benzo(a)pyrene. Nevertheless, the humic substances played a protective role in the photo-enhanced toxicity of pyrene under UV-B radiation. Water hardness had no effect on pyrene toxicity. Results indicate that the typical physicochemical characteristics of boreal freshwaters should be considered carefully in local and regional risk assessment of chemicals concerning the Fennoscandian region.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g|| = 2.085, g[perpendicular]=2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu [infinity] 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu[Single Bond]S bonds. The experimentally determined hyperfine constants are A ₁^s=34.9×10−4 cm−1, B ₁^s=26.1×10−4 cm−1, A ₂^s=60.4×10−4 cm−1, B₂^s=55.5×10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the sigma bond, the pi bonds are also strongly covalent. ©1973 The American Institute of Physics.

X-ray crystal structure of a ternary copper(II) vitamin B6 complex, hydroxo(2,2'-bipyridyl)(pyridoxinato) copper(II) monohydrate. A rare example of monodentate coordination of copper(II) by the hydroxyl ion

A ternary metal complex involving Vitamin B6 with the formula [Cu(bipy)(pn) (OH)]H2O (bipy = 2,2'²-bipyridine, PN = anionic pyridoxine) has been synthesized and studied in the solid state by means of spectroscopy and X-ray crystallography. The geometry around copper(II) is distorted square pyramidal, two oxygens from phenolic and 4-(hydroxymethyl) groups of pn, two nitrogens from bipy and an axial OH- ion forming the coordination sphere. In this structure pn exists in a new anionic form with deprotonation of the phenolic group. The structure also provides a rare example of monodentate hydroxyl coordination to copper.