Showing papers on "Copper published in 1968"
TL;DR: In this paper, the electronic properties and i.r.s. spectra of a series of bis(ethylenediamine)copper(II) complexes are reported, and an infrared criterion is established for detecting the presence of weakly co-ordinated polyanions in the long tetragonal positions above and below the [Cu en2]2+ cation.
Abstract: The electronic properties and i.r. spectra of a series of bis(ethylenediamine)copper(II) complexes are reported. From a gaussian analysis of the electronic spectra, measured at room temperature and at the temperature of liquid nitrogen, of the seven complexes of known crystal structure, and three transitions 2A1gâ†�2B1g, 2B2gâ†�2B1g, and 2Egâ†�2B1g in D4h symmetry are tentatively assigned. From the e.s.r. spectra of polycrystalline samples of the complexes, which yield tetragonal spectra, the values of (g‖– 2)/(g⊥– 2) have been determined. Where the ratio is 4·0 the observed g-values are considered to reflect approximately the local copper(II) ion g-values. In the latter case the g-values have been combined with the appropriate electronic transitions and the orbital reduction factors k⊥ and k‖ evaluated. From the i.r. spectra of the polyanions, an infrared criterion is established for recognising the presence of weakly co-ordinated polyanions in the long tetragonal positions above and below the [Cu en2]2+ cation. The term semi-co-ordination is introduced to describe this structural situation.
351 citations
TL;DR: In this paper, a series of bi-and tri-nuclear complexes formed by using the donor properties of the two cis-oxygen atoms in metal (M) complexes of tetradentate Shiff bases (TSB) derived from salicylaldehyde or o-hydroxyacetophenone are reported.
272 citations
219 citations
TL;DR: In this article, a very fine stylus is pressed against the surface of a metal crystal with a load which can be as small as 10−4 g, and the deformation observed simultaneously by performing the experiment in a scanning electron microscope.
Abstract: A technique is described for observing and measuring the deformation of solids on a very small scale. A very fine stylus (approx 1000 A in diameter) is pressed against the surface of a metal crystal with a load which can be as small as 10−4 g, and the deformation observed simultaneously by performing the experiment in a scanning electron microscope. Measurements were made on crystals of gold, copper, and aluminium. The behavior under these conditions of microdeformation was unusual in that no penetration occured until a critical load was reached. This critical load was frequently very high and corresponded to a shear strength which approached the theoretical shear strength of metals. Microfriction experiments could also be performed by allowing the stylus to slide over the crystal and the nature of the surface deformation could be examined during the sliding process.
205 citations
TL;DR: In this article, transmission electron microscopy of surface thin foils, both parallel and non-parallel to the surface, was used to study persistent slip bands in fatigued copper single crystals.
Abstract: Persistent slip bands in fatigued copper single crystals are studied by means of transmission electron microscopy of surface thin foils, both parallel and nonparallel to the surface. Comparing the observations from the different nonparallel sections a three-dimensional model of the internal structure may be constructed. Dislocations with all six possible Burgers vectors of the type 1/2 〈0011〉 are found in the structure. This demonstrates the microscopic action of the secondary slip systems during the low stress fatigue. The macroscopic action of the secondary systems, which is connected with the cell structure formation, is typical for the high stress fatigue. Surface extrusions are found to be related to the dislocation structure below the surface.
190 citations
TL;DR: Catalytic amounts of o -phenanthroline were found to enhance the rate of air-oxidation of all sulfhydryl groups tested in the presence of copper ions at neutral pH, and the interpretation is discussed that o-phenan Throline necessarily acts as a metal chelator in the inhibitory action of this reagent on any enzyme.
184 citations
TL;DR: In this paper, the authors used low-energy electron diffraction to define the structure and the growth mechanism of the adsorbed layers of two-dimensional compounds, based on the mean distance between atoms.
177 citations
TL;DR: Human lactoferrin, the red iron-binding protein from milk, was prepared by chromatography on DEAE-cellulose of the milk proteins soluble in 2 M ammonium sulfate of the metal-protein complexes by acidification.
Abstract: Human lactoferrin, the red iron-binding protein from milk, was prepared by chromatography on DEAE-cellulose of the milk proteins soluble in 2 M ammonium sulfate Several preparations differing in iron content were obtained Apolactoferrin was prepared by dialyzing the protein against 01 M citric acid
Saturation experiments with iron ascorbate indicated the iron: protein ratio at saturation to be 0025 micromoles of metal per mg of protein Assuming 80,000 to be the molecular weight of lactoferrin, this would correspond to a ratio of two iron atoms per molecule With copper, a similar molar proportion at saturation was obtained Gasometrie measurements were used to calculate the amount of carbon dioxide liberated upon dissociation of the metal-protein complexes by acidification One mole of CO2 was freed per atom of iron or copper
166 citations
TL;DR: In this article, the authors show that grain boundaries, introduced into a copper single crystal by indenting and annealing the crystal, are shown to drag certain small (4000 A diameter) oxide particles with them when they migrate.
165 citations
TL;DR: In this paper, the authors analyzed tracer measurements of self-diffusion coefficient by Rothman and Peterson in conjunction with the determination of equilibrium concentrations of vacant lattice sites by Simmons and Balluffi and the isotope effect on selfdiffusion.
Abstract: Recent tracer measurements of the self-diffusion coefficient by Rothman and Peterson are analysed in conjunction with the determination of equilibrium concentrations of vacant lattice sites by Simmons and Balluffi and the isotope effect on self-diffusion. The following values for monovacancy and divacancy properties are obtained (in the usual notation): E = 1.03 eV, E = 1.06 eV, S ≈ 0.3 k, E − E 0.54 eV, divacancy association entropy ΔS2 V ≈ 2 k, temperature coefficient of monovacancy self-diffusion energy 2 α = d (E + E)/d(kT) ≈ 0.5, frequency factors for mono- and divacancy migration v exp (S) = 1.4 × 1014 s−1, v exp (S/k) = 1.6 × 1014s−1. The monovacancy jump frequencies near room temperature are in excellent agreement with the values obtained from dislocation pinning experiments of Thompson and Pare.
Neue Messungen des Selbstdiffusionskoeffizienten mit radioaktiven Tracern von Rothman und Peterson werden in Verbindung mit der Bestimmung der Gleichgewichtskonzentration leerer Gitterplatze von Simmons und Balluffi und mit Messungen des Isotopen-effektes bei der Selbstdiffusion ausgewertet. Man erhalt folgende Werte fur die Eigenschaften von Einfach- und Doppelleerstellen (in der ublichen Bezeichnungsweise): E = 1,03 eV, E = 1,06 eV, S ≈ 0,3 k, E − E 0,54 eV, Assoziationsentropie der Doppelleerstelle ΔS2 V ≈ 2 k, Temperaturkoeffizient der Selbstdiffusionsenergie fur Einfachleerstellen 2 α = d (E + E)/d(kT) ≈ 0,5, Frequenzfaktoren fur Einfach- und Doppelleerstellenwanderung v exp (S) = 1,4 × 1014 s−1, v exp (S/k) = 1,6 × 1014s−1. Die Sprung-frequenzen der Einfachleerstellen in der Nahe der Raumtemperatur sind in ausgezeichneter Ubereinstimmung mit Werten, die man aus Experimenten von Thompson und Pare uber Versetzungsverankerung erhalt.
148 citations
TL;DR: Cobalt was deposited in ultra-high vacuum onto (001) copper surfaces prepared inside the vacuum chamber and the structure and lattice parameter of the cobalt remained the same as the copper until its thickness reached about 20 A. Many of these dislocations were unusual in that they were imperfect.
Abstract: Cobalt was deposited in ultra-high vacuum onto (001) copper surfaces prepared inside the vacuum chamber. If the copper substrate was at room temperature during film growth then the cobalt grew approximately as a monolayer. The structure and lattice parameter of the cobalt remained the same as the copper until its thickness reached about 20 A. At this thickness long dislocations to accommodate part of the difference between the lattice parameters of cobalt and copper were generated. Many of these dislocations were unusual in that they were imperfect. The stacking faults associated with them converted a little of the f.c.c. cobalt into the stable h.c.p. structure. If the copper was hot (350°C) during the deposition of cobalt, then film growth began with the formation of three-dimensional nuclei. Nuclei less than about 375 A in radius were f.c.c. and were strained to match the copper lattice.
TL;DR: In this paper, the angular behavior of the sputtering ratio for Ar+ on (100) Cu turned around a [011] axis was studied for energies of 5, 10, 15, 20, and 35 V.
Abstract: Measurements of the angular behavior of the sputtering ratio for Ar+ on (100) Cu turned around a [011] axis are presented for Ar+ energies of 5, 10, 15, 20, and 35 keV. It is shown that the widths ...
TL;DR: In this article, a high voltage electron microscope was used to examine copper and aluminium at ∼20°C with high voltage and high beam current, and it was shown that the damage is the result of the direct displacement of lattice atoms by the electron beam.
Abstract: Defect clusters are observed to form in copper and aluminium during examination at ∼20°C in a high voltage electron microscope when the voltage is greater than ∼500 kv and the beam current is high (0·1–0·4 μamps in a 5 μ spot). Experimental and theoretical considerations show that the damage is the result of the direct displacement of lattice atoms by the electron beam, resulting in the homogeneous nucleation of point defect clusters. In annealed copper the threshold electron energy required to produce the effect is orientation dependent, and the effective displacement energy Ed' is ≥ ∼30 ev in the 〈100〉 and 〈110〉 directions, and ≤26 ev in directions away from the corners of the unit triangle. Complex effects are observed in copper previously neutron irradiated and partially annealed, quenched, or cold worked. The results are interpreted in terms of the nucleation of interstitial loops and the formation of sub-microscopic vacancy clusters.
TL;DR: A simplified method for trace-element analysis employing atomic-absorption spectrophotometry to determine plasma concentrations of zinc and copper found a lowered zinc concentration in the presence of considerable raised copper concentration as compared with normal controls.
TL;DR: In this article, the interstitial waters of four piston cores from the continental borderland area off the coast of Southern California were determined directly by atomic absorption spectrophotometry, and the trace elements: cadmium, cobalt, copper, iron, nickel and zinc, were determined by extraction of the chelate complexes with ammonium pyrollidine dithiocarbamate into methylisobutyl ketone and subsequent analysis.
TL;DR: In this paper, an iron deposit in which there was a thickness gradient was grown in ultra-high vacuum (< 10−7 torr) on a hot (400°C) copper surface prepared inside the vacuum chamber.
Abstract: An iron deposit in which there was a thickness gradient was grown in ultra-high vacuum (< 10−7 torr) on a hot (400°C) copper surface prepared inside the vacuum chamber. Electron micrographs of the iron-copper bicrystal revealed that the growth of iron began with the generation of three-dimensional iron nuclei. These nuclei were f.c.c. and their lattices were strained to give a coherent copper-iron interface. The nuclei grew in size as the thickness of the iron increased and dislocations to accommodate part of the misfit between γ-iron and copper were generated. The dislocations were in mixed orientation and had Burgers vectors which were inclined to the iron-copper interface. A further increase in deposit thickness was accompanied by the nucleation of b.c.c. (α) iron.
TL;DR: The concentrations of copper, zinc, iron, and magnesium have been determined by atomic absorption spectroscopy for various regions of the brain in cases restricted to non-neurologic disorders.
TL;DR: The tetrapeptide l-aspartyl- l-threonyl-l-histidyl-l -lysine was shown by titration, absorbance, and circular dichroism measurements to form an equimolar complex with copper(II) that has substantially the properties of the complex of peptide (1–24) containing 1 eq of copper( II) ion.
TL;DR: In this article, the relaxation and migration energies of adatoms and terrace vacancies on copper surfaces have been calculated for (100), (110) and (111) surface orientations.
TL;DR: In this paper, the atomic configuration around a vacancy in aluminium and copper and the interaction energy between two vacancies in these metals were calculated using a harmonic discrete face-centred cubic lattice with first and second-neighbour interactions.
Abstract: The method of lattice statics is used to calculate the atomic configuration around a vacancy in aluminium and copper and the interaction energy between two vacancies in these metals. The model used is a harmonic discrete face-centred cubic lattice with first and second-neighbour interactions. The force constants are chosen to fit the elastic constants and phonon dispersion data for both aluminium and copper.
TL;DR: Spectrophotometric titrations provide evidence that tyrosine residues also participate in copper binding, as well as in iron binding, and it seems probable, therefore, that the metal-binding sites of transferrin have available 4 nitrogen ligands and 2 or 3 oxygen ligands.
TL;DR: In this article, the magnetic properties of a series of discrete trinuclear transition-metal complexes derived from tetradentate Schiff bases have been investigated over the temperature range 80°-400°K.
Abstract: The magnetic properties of a series of discrete trinuclear transition‐metal complexes derived from tetradentate Schiff bases have been investigated over the temperature range 80°–400°K. The complexes contain the groupings of metals CuMCu where M is Cu(II), Ni(II), Co(II), Fe(II), and Mn(II), and the three metal atoms are linked by oxygen bridges. For each grouping of metals, the observed magnetic moments are subnormal, and decrease markedly with decreasing temperatures. These magnetic properties are explained in terms of antiferromagnetic interactions between the central metal atom M and the adjacent copper (II) atoms. The magnetic moments calculated on the basis of this model of discrete antiferromagnetism are found to be in good agreement with the experimental results. Mutual interactions between the terminal copper atoms apparently exist to only a small degree or not at all.
TL;DR: The trisodium salt of nitrilotriacetic acid (NTA) seems to be a promising “anti-pollutant”, to prevent fish-kills in case of short-term breakdown of normal pollution controls.
Abstract: COPPER and zinc are surprisingly widespread pollutants of water. In wilderness areas they may endanger fish in otherwise clean rivers as the result of mining operations1. In British industrial areas, they commonly contribute an average of 23 per cent of total toxicity of mixed pollution for fish, and in some rivers a much higher proportion2. Furthermore, trace concentrations, one-tenth to one-twentieth of accepted standards for drinking water, can be lethal for fish in regions where surface water is very soft1. In such circumstances, year-round prevention of “spills” of metal pollution can be difficult. The trisodium salt of nitrilotriacetic acid (NTA) seems to be a promising “anti-pollutant”, to prevent fish-kills in case of short-term breakdown of normal pollution controls.
TL;DR: In this paper, the wettability of sapphire single crystals by liquid copper which contained oxygen added as cupric oxide was investigated using the sessile drop technique in vacuum at 1230°C.
Abstract: The wettability of sapphire single crystals by liquid copper which contained oxygen added as cupric oxide was investigated using the sessile drop technique in vacuum at 1230°C. Additions of cupric oxide to copper, varying from 1 to 72% of copper weight, resulted in rapid chemical reaction at the solid-liquid interface with a significant reduction of the contact angle, the final value being dependent on the oxygen in the system. In all cases the interfacial product was CuAlO2. A linear relation between the fourth power of the basal radius of the molten drop and the amount of oxygen present was observed. The initial stage of the reaction could be explained by the formation of a Cu2O layer at the interface, followed by reaction between Cu2O and Al2O3 to form CuAlO2.