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  • copper  (21)
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  • Chemistry and Pharmacology  (21)
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  • Articles  (21)
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  • Springer  (21)
  • American Geophysical Union
  • Cell Press
  • Emerald
  • International Union of Crystallography
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  • 2000-2004
  • 1995-1999  (21)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 29 (1999), S. 1427-1438 
    ISSN: 1572-8838
    Keywords: anomalous oxidation ; copper ; electrocatalysis ; hydrous oxides ; mediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract There is increasing evidence, for example, from recently published surface enhanced Raman spectroscopy data, that copper, silver and gold electrode surfaces in base, may exist in an oxidized state at unusually low potentials. In the present work, which was carried out using electrochemical techniques, up to six oxide reduction peaks were recorded for copper in base in the region below 0.6 V vs RHE. One of these peaks, at about −0.6 V vs RHE, was particularly prominent; this occured at a potential 1.0 V more negative than the standard potential for the Cu/Cu2O electrode reaction in aqueous media. Such behaviour is rationalized in terms of the involvement of nonequilibrium (and hence unstable) active states of the metal surface; these states may be regarded as adatoms or minute clusters (the lowering of the redox potential being due to the unusually low lattice stabilization energy of these active metal atoms). Copper and its oxides, especially Cu2O, are of major interest from a catalytic, electrocatalytic, photocatalytic and microelectronics fabrication viewpoint and the involvement of the active states of the metal, as a key ingredient in several of these areas, is outlined.
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  • 2
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    Journal of applied electrochemistry 29 (1999), S. 393-402 
    ISSN: 1572-8838
    Keywords: copper ; cu–xNi alloys ; EDS ; localized pitting attack ; nickel ; SEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The anodic behaviour of Cu–xNi alloys and Cu and Ni metals was studied in slightly alkaline solutions containing Cl−-ions in the concentration range from 0.01 to 2.0moldm−3. The morphology and composition of the surface films formed by anodic polarization were analysed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). On the basis of quasi-potentiodynamic polarization data, Ec against cNaCl diagrams were constructed, where Ec is the critical pitting potential. These diagrams allow the determination of areas where the materials are susceptible to localized pitting attack. A critical chloride concentration (ccrit) exists below which the resistance to localized corrosion increases with decreasing nickel content and above which it increases with increasing nickel content. This effect is connected with the change in the corrosion resistance observed for the pure metal constituents, i.e., copper and nickel as a function of chloride concentration. The kinetic parameters of pitting corrosion of Cu–xNi alloys reflect the specific properties of both elements and suggest that an increase in Ni content above 40% would not have a significant effect on the corrosion resistance of Cu–xNi alloys.
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  • 3
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    Journal of applied electrochemistry 29 (1999), S. 585-591 
    ISSN: 1572-8838
    Keywords: copper ; electrochemical nucleation ; polycrystalline platinum ; thiourea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The influence of thiourea on the nucleation of copper from a 0.30 M CuSO4-1 M H2SO4 solution on polycrystalline platinum electrodes covered by a copper adlayer was investigated. In the case of diffusion controlled nucleation and growth the conditioning potential, that is, the potential of the electrode prior to the application of a large negative potential step, has a strong influence on the nucleation transients. This can result in either a promotion or an inhibition of the nucleation (which is characterized by a change in the nucleation rate constant and/or the site density) depending on the applied potential and the concentration of thiourea. In the region of mixed kinetics and for a fixed value of the conditioning potential (0.175 V vs Cu2+|Cu, that is, in the region of strongest inhibition), a new and rather unexpected effect was observed. Thus, after an induction period, which is proportional to the concentration of thiourea, the current increases sharply to a much higher value, but after reaching a maximum drops again to its original value. At present there is no ready explanation for this phenomenon, which has been called 'nucleation outbursts', but it deserves more investigation because the linearity between the induction time and the concentration of thiourea might have practical applications.
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  • 4
    ISSN: 1572-8773
    Keywords: capsule secondary structure ; exopolysaccharide ; bacterial cell surface ; copper ; mercury ; ytterbium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Escherichia coli K1 secretes a homopolymer capsular polysaccharide (CPS) consisting of alpha 2,8 linked N-acetylneuraminic acid (poly α2,8NeuNAc). Typically poly α2,8NeuNAc is arranged in low and high order alpha helices with carboxyl and hydroxyl groups extending from the helices. Several properties of CPS such as antigenicity and metal binding can be influenced by its structural conformation. We examined the influences of metal ions and temperature on the secondary structure of polyαa2,8NeuNAc. Conformation alteration was detected by ultraviolet (UV) spectroscopy and circular dichroism (CD). The majority of metal ions tested had no detectable influence on poly a2,8NeuNAc structure. In contrast, Yb3+., Hg2+, and Cu2+ ions greatly altered the UV and CD spectra, which suggests that these ions had disrupted the alpha helical structure of poly α2,8NeuNAc. These changes were influenced by the metal ion concentration. When poly α2,8NeuNAc was incubated at temperatures ranging from 20 - 60°C, alterations in its UV absorption spectra were also seen. The most significant change occurred between 35 and 40°C. In summary, this study suggests that the higher order structure and function of bacterial CPS may be influenced by environmental factors
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  • 5
    ISSN: 1572-8773
    Keywords: copper ; metal ions ; metallothionein ; yeast Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Copper-induced metallothionein (MT) synthesis in Saccharomyces cerevisiae was investigated in order to associate this exclusively with Cu2+ in vivo, when cultured in nutrient medium containing other heavy metal ions. Expression of the CUP1 promoter/lacZ fusion gene was inhibited by all heavy metal ions tested, especially Cd2+ and Mn2+. By adding Cd2+ and Mn2+ at 10 μM concentration, the β-galactosidase activity decreased by about 80% and 50% of the maximum induction observed with 1 mM CuSO4, respectively. Furthermore, cell growth was markedly inhibited by combinations of 1 mM-Cu2+ and 1 μM-Cd2+. Therefore, the yeast S. cerevisiae could not rely on MT synthesis as one of the copper-resistance mechanisms, when grown in a Cd2+ environment. In contrast, the presence of Mn2+ in the nutrient medium showed alleviation rather than growth inhibition by high concentrations of Cu2+. The recovery from growth inhibition by Mn2+ was due to decreased Cu2+ accumulation. Inhibitory concentrations of Co2+, Ni2+ and Zn2+ on expression of the CUP1p/lacZ fusion gene were at least one order of magnitude higher than that of Cd2+ and Mn2+. These results are discussed in relation to Cu2+ transport and Cu-induced MT synthesis in the copper-resistance mechanism of the yeast S. cerevisiae.
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  • 6
    ISSN: 1572-879X
    Keywords: hydrogen‐assisted dechlorination ; 1,2‐dichloroethane ; ethylene ; carbon ; platinum ; copper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of Pt–Cu/C catalyst composition on the activity and selectivity in the reaction of 1,2‐dichloroethane dechlorination in a H2‐containing atmosphere has been investigated. For monometallic Pt catalysts and those with Cu/Pt atomic ratio ⩽1, the reaction products are almost entirely ethane and monochloroethane. However, increasing the Cu/Pt ratio increases the selectivity towards ethylene. Approximately 90% selectivity towards ethylene is obtained for catalysts with Cu/Pt ratio ⩾9. Monometallic Cu/C produce only ethylene, but the activity is two orders of magnitude lower than that of other catalysts studied. With time on stream during the initial 2–30 h there is a continuous increase in selectivity towards ethylene at the expense of ethane. This behavior was rationalized in terms of equilibration of bimetallic particle surface composition exposed to the reaction mixture.
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  • 7
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    Catalysis letters 59 (1999), S. 15-20 
    ISSN: 1572-879X
    Keywords: propyne ; copper ; coupling ; intermediates ; benzene ; dienes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemistry of propyne on Cu{111} is very different from that of ethyne. Instead of trimerising, propyne undergoes coupling reactions in which two molecules react to yield either benzene, with elimination of hydrogen, or C6 dienes. These two processes occur with approximately equal probability. A plausible mechanism for benzene formation involves head-to-tail interaction of two propyne molecules. 1,4-cyclohexadiene is a likely intermediate in this process, its formation being rate determining. Propyne trimerisation is sterically inhibited by the methyl group. However, the first stage in this process does seem to occur, namely formation of a dimethyl-metallopentacycle intermediate. This may be ascribed to head-to-head coupling of two propyne molecules. This metallocycle undergoes either hydrogenation to C6 dienes or disproportionation to butadiene and ethyne.
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  • 8
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    Catalysis letters 58 (1999), S. 99-102 
    ISSN: 1572-879X
    Keywords: surface ; chemisorption ; methylamine ; oxygen ; methyl ; XPS ; copper ; migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The exposure of preadsorbed oxygen to monomethylamine or the coadsorption of a 2:1 monomethylamine (CH3NH2)/dioxygen mixture at a Cu(211) surface at room temperature results in the formation of a surface species characterised by C(1s) and N(1s) binding energies of 285.2 and 398.2 eV, respectively, with a calculated carbon to nitrogen ratio of 2:1. This species, which we assign to a chemisorbed dimethylamine ((CH3)2NHx(a)), is the only adsorbed product of the reaction and its formation must involve the breaking of a carbon–nitrogen bond and the intermolecular transfer of a methyl group.
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  • 9
    ISSN: 1572-879X
    Keywords: cerium oxides ; SO2 ; desulfurization ; copper ; X‐ray absorption spectroscopy ; photoemission and XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract CeO2 and Cu/CeO2 are effective catalysts/sorbents for the removal or destruction of SO2. Synchrotron‐based high‐resolution photoemission, X‐ray absorption near‐edge spectroscopy (XANES), and temperature‐programmed desorption (TPD) have been employed to study the reaction of SO2 with pure and reduced CeO2 powders, ceria films (CeO2, CeO2−x, Ce2O3+x) and model Cu/CeO2 catalysts. The results of XANES and photoemission provide evidence that SO4 was formed upon the adsorption of SO2 on pure powders or films of CeO2 at 300 K. The sulfate decomposed in the 390–670 K temperature range with mainly SO2 and some SO3 evolving into gas phase. At 670 K, there was still a significant amount of SO4 present on the CeO2 substrates. The introduction of O vacancies in the CeO2 powders or films favored the formation of SO3 instead of SO4. Ceria was able to fully dissociate SO2 to atomic S only if Ce atoms with a low oxidation state were available in the system. When Cu atoms were added to CeO2 new active sites for the destruction of SO2 were created improving the catalytic activity of the system. The surface chemistry of SO2 on the Cu‐promoted CeO2 was much richer than on pure CeO2. The behavior of ceria in several catalytic processes (oxidation of SO2 by O2, reduction of SO2 by CO, automobile exhaust converters) is discussed in light of these results.
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  • 10
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    Journal of applied electrochemistry 29 (1999), S. 239-244 
    ISSN: 1572-8838
    Keywords: acid solution ; copper ; corrosion potential ; cyanide ; electrodeposition ; zinc diecast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The corrosion potential and morphology of copper films deposited from a cyanide solution on zinc diecast were studied in acid solutions similar to those employed in industry for the deposition of a second copper layer. Open circuit potential measurements and gravimetric methods were employed to determine the influence of the copper electrodeposition variables on the corrosion potential. The influence of variables such as the presence or absence of additives, the current density and the copper or cyanide concentrations were studied. The corrosion potential decreased with increasing copper film thickness. Less protection was obtained when a thin copper layer was electrodeposited from a solution without additives. Higher protection for the same thickness was obtained from a solution with high cyanide content. This result is related to the strong interaction between cyanides and the metal surface during the electrodeposition. A smooth surface structure was observed by SEM under these conditions.
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  • 11
    ISSN: 1572-879X
    Keywords: scanning tunnelling microscopy ; copper ; chemisorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three distinct states of oxygen have been observed at a Cu(110) surface at 120 K by scanning tunnelling microscopy (STM): isolated oxygen adatoms; pairs or dimers, separated by about 6 Å and clusters of five or six atoms arranged anisotropically. There is also evidence for oxygen atoms undergoing ballistic motion as might be expected from “hot” oxygen atoms. Such states of oxygen have been central to the mechanistic models proposed earlier, and based on surface spectroscopic studies, for the oxidation of ammonia at copper surfaces under ammonia-rich conditions.
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  • 12
    ISSN: 1572-879X
    Keywords: hydrogen ; copper ; activation energy ; adsorption ; sticking probability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The coverage-dependent sticking probabilities of molecular hydrogen on polycrystalline copper supported on alumina have been determined in the temperature range 213–273 K by analysis of the hydrogen frontal adsorption line shape. In this temperature range the initial sticking probabilities increase from 8× 10−13 (213 K) to 1.3× 10−10 (273 K). The overall activation energy to adsorption has been found to be 42 kJ mol−1. The application of reactive frontal chromatography for the measurement of hydrogen sticking probabilities on copper is a novel variant of the N2O reactive frontal chromatographic method, developed for the measurement of copper surface areas. Its use here shows that reactive frontal chromatography may be applied generally to any adsorbate/adsorbent system involving activated adsorption and low sticking probabilities.
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  • 13
    ISSN: 1572-8773
    Keywords: particulate methane monooxygenase ; Methylosinus trichosporium OB3b ; iron ; copper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effect of iron ions on particulate methane monooxygenase was studied by using the EDTA-treated membranes from Methylosinus trichosporium OB3b. When the membrane was treated with EDTA the activity remained 82% of the as-isolated membranes, and the activity of the EDTA-treated membranes was strongly influenced by the addition of metal ions. Among the metal ions, ferric, ferrous and cupric ions stimulated the activity, indicating those ions were needed for the activity. When propargylamine was added, pMMO activity decreased and also the iron ESR signal decreased. As the ESR signal involves the ferrous nitrosyl complex in EDTA-treated membranes, the active site of pMMO may contain a mononuclear non-heme iron.
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  • 14
    ISSN: 1572-8773
    Keywords: copper ; mercury ; rat ; tooth fillings ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aim of this study was to measure the distribution of mercury, in tissues of rats exposed to amalgam over a two months period. Possible interaction of mercury with copper and zinc in organs was also evaluated. Rats were either exposed to mercury from 4 dental amalgams, or fed the diet containing powdered amalgam during two months. Mercury was measured in the kidney, liver and brain, copper in kidney and brain and zinc in kidney. The results showed significantly higher concentrations of mercury in the kidneys and the brains of rats in both exposed groups compared to control. Even after two months of exposure to mercury brain mercury concentration in rats with amalgam fillings was 8 times higher than in the control and 2 times higher than in rats exposed to amalgam supplemented diet. The highest mercury concentration in the latter group was found in the kidneys and it was 5 times higher than in the control group. We found no significant differences between mercury levels in exposed and control rat's liver. Exposure to mercury from dental amalgams did not alter the concentrations of copper and zinc in the tissues. Histopathological analyses of rats tissues did not show any pathological changes. These results support previously proposed nose-brain transport of mercury released from dental amalgam fillings.
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  • 15
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    Adsorption 5 (1999), S. 409-417 
    ISSN: 1572-8757
    Keywords: competitive sorption ; copper ; nickel ; peat ; isotherm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Bicomponent aqueous solutions of copper and nickel ions have been used to investigate the sorption of metal ions onto peat. Peat, a low cost sorbent, has shown a high capacity for the sorption of single component metal ions attributed to extensive carboxylic acids within its structure. Copper and nickel ions were selected as typical metals in the effluents of electroplating industries. The effects of competitive sorption in batch systems were studied at various metal ion concentrations. In this study the Butler and Ockrent model was modified using a coefficient, η. Two models were developed based on the interaction coefficient η. The first model incorporates a constant fixed η factor for each metal ion into the Butler-Ockrent equation. The second model incorporates a variable η factor into the Butler-Ockrent equation; this interaction factor varies as a function of sorbent surface coverage. Predicted equilibrium data are found to be in excellent agreement with experimental values using both modified models for various mole ratios of copper and nickel ions in competitive sorption.
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  • 16
    ISSN: 1572-879X
    Keywords: hydrogen ; desorption ; copper ; activation energy ; kinetics ; order of desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of desorption of hydrogen from the copper component of an alumina-supported polycrystalline copper catalyst has been studied in detail by temperature-programmed desorption (TPD). Line-shape analysis of the hydrogen TPD spectra shows: (i) that the desorption is second order, (ii) that the desorption activation energy is in the range 64–68 kJ mol−1 in the coverage range 7–44% of a monolayer, and (iii) that the desorption pre-exponential term has a value ∼10−5 cm2 s−1 atom−1 consistent with the desorption being second order, involving mobile adsorbates and a mobile desorption transition state.
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  • 17
    ISSN: 1436-5073
    Keywords: cobalt ; nickel ; copper ; soil ; sediment ; slurry ; electrothermal atomic absorption spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electrothermal atomic absorption procedures for the rapid determination of cobalt, nickel and copper in soil and sediment samples are presented. The samples are suspended in a hydrofluoric acid solution before being injected into the electrothermal atomizer. Prior mild heating in a microwave oven is recommended for nickel and copper determination. No modifier other than hydrofluoric acid is required. The conventional ashing step is unnecessary since the fast-heating programmes lead to well defined atomization profiles with low background levels that can be corrected using a common deuterium device. Calibration is performed directly using aqueous standards. The results obtained for six certified reference materials confirm the reliability of the procedures.
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  • 18
    ISSN: 1436-5073
    Keywords: ion chromatography ; series bulk acoustic wave ; copper ; human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract By using ion chromatography with series bulk acoustic wave detection, a method for the determination of copper in human blood plasma has been developed. The advantages of the good selectivity of ion chromatography and the highly sensitive response of SBAW have been combined to improve detection limit, accuracy and reproducibility. The detection limit (3σ) of the method to copper is 0.3 μg/ml. The relative standard deviation for the determination of 1.0 μg/ml of copper is 2.1% (n=7). For the IC analysis, the analytical column is a Shim-pack IC C1 column, and the mobile phase is 4.0 mM tartaric acid/2.0 mM ethylenediamine solution with pH 4.2. This system has been applied to the determination of Cu in blood plasma from healthy people or patients with renal failure.
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  • 19
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    Microchimica acta 130 (1999), S. 209-214 
    ISSN: 1436-5073
    Keywords: mercury ; copper ; acid urease ; ammonium optode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report on a quick and simple test based on enzyme inhibition for the detection of mercury and copper using free acid urease coupled to an optical sensor system. Lipophilized Nile Blue was incorporated in plasticized poly(vinyl chloride) (PVC) to produce an ammonium-sensitive layer with a thickness of around 4 μm. The layer was fixed on one side of a disposable cuvette. A solution of buffer, enzyme and heavy metals was placed into the thermostated cell. Enzymatic hydrolysis was started upon addition of urea and the formation of ammonium was monitored. Mercury and copper were the strongest inhibitors; for this reason the inhibitory efficiency of these metals was examined in citrate, acetate and trismaleate buffers. The cuvette test was most sensitive and selective for mercury in a citrate buffer. The limit of detection for mercury(II) ions was as low as 1 μg/L. Copper ions do not interfere because of complexation by citrate. The inhibitory effects of metal combinations on the activity of acid urease and the effects of optimum pH of the enzyme and the transducer on the dynamic range of the cuvette test are presented.
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  • 20
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    Journal of thermal analysis and calorimetry 56 (1999), S. 239-245 
    ISSN: 1572-8943
    Keywords: copper ; iron ; mechanical alloying ; Mössbauer spectroscopy ; thermomagnetometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mechanical alloying is a versatile technique for the solid state synthesis of many materials, including alloys such as iron-copper where the elements are immiscible under equilibrium conditions. The structural and magnetic state of these alloys, and their thermal stability, have been investigated by means of thermomagnetometry, DSC, X-ray diffraction and Mössbauer spectroscopy. Comparison of the thermomagnetometry curves for the various alloys together with analysis of intermediate reaction products enabled the individual thermal processes to be identified. The Curie temperature of the alloys was measured, and it was found that on heating the metastable alloys underwent phase segregation between 300-400°C.
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  • 21
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    Interface science 7 (1999), S. 147-158 
    ISSN: 1573-2746
    Keywords: intergranular fatigue cracking ; twin boundary ; bicrystal ; copper ; persistent slip band
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The criterion for occurrence of intergranular fatigue cracking in copper has been investigated from the view point of both the grain boundary (GB) character and the cyclic deformation property of constituent grains. The copper bicrystals were prepared to have several orientation relationships close to Σ3(1 1 1) coherent twin (Σ3 vicinal domain) so as to change the GB character rapidly with increasing deviation angles |Δθ| from the Σ3 relation. These bicrystals were shaped to single-edge-notched specimens in which a GB plane was perpendicular to the tensile axis. The fatigue crack propagation tests were carried out in air at room temperature. The specimens having deviation angles |Δθ| less than 3° involved no intergranular fatigue cracking. When the |Δθ| values were ranged from 3° to 5°, the ratio of the intergranular cracking increased. In the specimens having the |Δθ| values more than 9°, the intragranular cracking became predominate again. The increase in the intergranular cracking with increasing deviation angle at the |Δθ| values less than 5° could be understood in terms of the increasing GB susceptibility to the GB damage due to air environment. On the other hand, the intragranular cracking at the |Δθ| values more than 9° could be attributed to the formation of the persistent slip bands in the constituent grains and subsequent crack propagation preferentially along them.
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