Showing papers on "Copper published in 1982"

A comparison of the toxicity of heavy metals, using root elongation of rye grass, lolium perenne

Abstract: SUMMARY The order of toxicity of different metals affecting root growth of seedlings of rye grass (Lolium perenne S24) was: copper > nickel > manganese > lead > cadmium > zinc > aluminium > mercury > chromium > iron. With the sole exception of manganese, these results confirm those of other studies and the order follows that of the stability of the metallic-organic complexes. The results are of value in predicting the toxicity of heavy metals in plant growth on contaminated soils.

Ceruloplasmin, copper ions, and angiogenesis.

Abstract: The ability to induce new formation of capillaries in the cornea was tested for ceruloplasmin, the copper carrier of serum, for fragments of the ceruloplasmin molecule with and without copper, for heparin, and for glycyl-L-histidyl-L-lysine, bound or not bound to copper ions. Male or female 2- to 3-kg New Zealand White rabbits were used. These experiments were prompted by the previous observation of copper accumulation in the cornea during angiogenesis and by the inability of copper-deficient rabbits to mount an angiogenic response. The results showed that the three different molecules were all able to induce angiogenesis provided that they were bound to copper. Fragments of the ceruloplasmin molecule also induced angiogenesis but only when copper was bound to the peptides. The data are interpreted to indicate that copper ions are involved in the sequence of events leading to angiogenesis and that the carrier molecules may be of quite a different nature.

The effects of proteins on metallic corrosion.

Abstract: The corrosion of the pure metals aluminium, cobalt, copper, chromium, molybdenum, nickel, and titanium and of a cobalt-chromium molybdenum casting alloy has been studied in buffered saline with and without the presence of the proteins serum albumin and fibrinogen. The corrosion of aluminium and titanium was unaffected by the protein. The corrosion rates of chromium and nickel showed a slight increase, while cobalt and copper dissolved to a very much greater extent in the presence of protein. However, with molybdenum the corrosion was inhibited by protein.

Fulvic acid: modifier of metal-ion chemistry.

Abstract: Fulvic acid, which is derived from the decay of plants and animals, is being studied for its role in the transport and toxicity of metal ions in soil and water. It is discussed in relation to the origin of humic substances and its interactions with metal ions. Techniques for investigating complexes of fulvic acid and metal ions are presented. They are separation and nonseparation analyses which are applied to speciation problems. The applicability, advantages, and disadvantages of both methods are presented. Separation of free and complexed metal ions can be done by chromatography, or with membranes that exclude the metal-ion complexes. Chromatographic techniques include liquid chromatography by size exclusion. Nonseparation techniques include voltametry and potentiometry, as well as fluorescence. A comparison of methods for calculation of the conditional stability constant K for complexes containing fulvic acid and copper (II) or cadmium (II) is presented.

Bronze Age Copper Sources in the Mediterranean: A New Approach

Abstract: Efforts by scientists to locate the sources of copper used in ancient Mediterranean and Near Eastern cultures through comparative chemical analyses of copper ores and archeological artifacts have largely failed for various mineralogical and metallurgical reasons. The isotopic composition of lead, an element present in a minor amount in many copper ores and bronze objects, is unchanged through metallurgical processes and may in principle be used to determine the sources of the copper used in Bronze Age artifacts. Results suggest that for Late Bronze Age Crete the Laurion region in Attica, Greece, may have been a more important copper source than Cyprus.

Bioavailability of dissolved copper to the American oyster Crassostrea virginica. I. Importance of chemical speciation

Abstract: The effect of complexation on the accumulation of dissolved copper by the American oyster Crassostrea virginica was determined in chemically defined exposure media. The speciation of copper was varied by varying the concentrations of total copper and model chelator, nitrilotriacetic acid (NTA). Accumulation of copper in 14-d experiments was related to the cupric ion activity and not the concentration of chelated copper. Rapid accumulation of copper occurred at cupric ion activities above 10-10 M and there was no measurable accumulation at 10-11 M.

Optical properties of copper in silicon: Excitons bound to isoelectronic copper pairs

Abstract: Copper doping of silicon crystals results in an intense emission at 1.014 eV. The photoluminescence spectrum exhibits a characteristic structure consisting of a narrow nophonon line and equispaced lower-energy resonant-mode phonon replicas. The typical phonon energy is 7.0 meV. We observe isotope shifts of the lines which conclusively show that copper is incorporated in the luminescent defect. Combination with the observed quadratic dependence of the emission intensity on copper concentration leads us to suggest copper pairs as recombination centers. The symmetry of the pair as determined from uniaxial stress and Zeeman data is that of a $〈111〉$ configuration. The no-phonon line structure and the splitting in external fields indicate an exciton localized at an isoelectronic trap. The exciton is discussed in terms of an isoelectronic donor combining the present data with recent deep-level transient-spectroscopy results.

Thermochemistry of alloys of transition metals: Part III. Copper-Silver, -Titanium, Zirconium, and -Hafnium at 1373 K

Abstract: The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: ΔHmix = ϰAgϰCu(17.66 − 5.46 ϰAg) kJ mol−1. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol−1 for Ti, -52.5 kJ mol−1 for Zr, and -46.3 kJ mol−1 for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.

Food chain relationships of copper and cadmium in contaminated grassland ecosystems

Abstract: An analysis of the distribution of copper and cadmium between components of a contaminated grassland ecosystem has established a much greater food chain transfer potential for cadmium than for copper. Almost regardless of the degree of environmental contamination, the retention of copper in mammalian systems is regulated by absorption-excretion equilibria that adapt to maintain a homeostatic situation. However, accumulation of copper does occur in some groups of terrestrial invertebrates in relation to dietary concentrations of the metal. No body retention control mechanisms were evident in mammals or invertebrates in respect of cadmium, a non-essential trace element whose distribution is characterised by preferential accumulation in the liver and kidney target organs of mammals, and by food chain concentration through predator-prey relationships.

Platinum-group metals in the Zechstein copper deposits, Poland

Abstract: In the Zechstein copper deposits, Poland, Au and platinum-group elements are concentrated by a process of autooxidation and desulfurization of organic matter. Platinum-group elements, acting as catalysts of the autooxidation process, are concentrated at the border between oxicanoxic conditions, i.e., between kerogen and calcite, thucholite and calcite, black shale and white sandstone, etc. The gamma radiation accelerated and enhanced the process of autooxidation, and phosphates and borates coagulated noble metals from solutions. For these two reasons the highest Au and platinum-group-element-bearing contents (Au, up 3,000 ppm; Pt, 10-370 ppm; and Pd, 10-120 but sometimes up to 1,000 ppm) are present in a layer a few centimeters thick at the bottom of the black shale (platinum-group-element-bearing shale) when this shale is overlain by phosphates, borates, and thucholite-bearing shale.

Acid copper electroplating baths containing brightening and leveling additives

Abstract: The invention is concerned with the electrodeposition of copper from an aqueous acidic bath containing the following additives: a. An alkylated polyalkyleneimine obtained as the reaction product of a polyalkyleneimine represented by the formula : H.sub.2 N--(CH.sub.2).sub.n NH--R wherein R is H or (CH 2 ) n NH 2 and n=1 to 6 with an epihalohydrin and an alkylating agent; an organic sulfo sulfonate; a polyether; and optionally a thioorganic compound.