Mixture Of Ag Research Articles

Organobismuth(V) complexes containing bifunctional ligands: hydrogen-bonded extended structures and stereoselectivity

New bismuth(V) complexes with the general formula of Bi V R 3 (O 2 CR′) 2 have been synthesized by the reaction of BiR 3 Cl 2 with Ag(O 2 CR′), where R is an aromatic ligand and R′ a substituent containing a hydroxyl group. The role of these new bismuth(V) complexes as building blocks to form hydrogen-bonded extended structures in the solid has been examined by single-crystal X-ray diffraction analyses. The bismuth atoms in these compounds adopt distorted trigonal-bipyramidal geometries. The hydrogen-bonding pattern and the extended structure displayed have been found to be highly dependent on the R and the R′ groups. Unusual hydrogen-bonded extended structures such as double strands and double layers have been observed. In an attempt to obtain chiral helical extended structures, the reactions of BiR 3 Cl 2 with several silver salts, Ag(O 2 CR*), where R* contains one chiral centre and a hydroxyl group, were examined. The bismuth(V) centre shows an unusual stereoselectivity towards the chiral ligand R*CO 2 - . When a racemic mixture of Ag(O 2 CR*) was used only the enantiomers (R,R)- and (S,S)-BiR 3 (O 2 CR*) 2 were obtained.

Specific Uphill Transport of Zinc as Zn(SCN)42− Ion using Na+‐Dicyclohexyl‐18‐Crown‐6 as Carrier

AbstractSodium‐dicyclohexyl‐ 18‐crown‐6 complex cation was used as carrier for the uphill transport of zinc as Zn(SCN)42− complex anion. By using L‐cysteine as a metal ion acceptor in the receiving phase at the optimized pH of 7.6, the amount of zinc transport through the liquid membrane after 90 min was 97.2 ± 1.0%. The selectivity and efficiency of zinc transport from aqueous solutions containing equimolar mixtures of Ag+, Cd2+ Co2+, Cu2+, Fe2+, Ni2+, Pb2+, Pd2+, Sr2+, Bi3+, Cr3+ and Fe3+ ions was investigated. In the presence of NH2OH.HCl as a suitable masking agent in the source phase, the interfering effect of Cu2+ and Pb2+ ions was diminished drastically.

Highly Selective and Efficient Membrane Transport of Copper as Cu(SCN)2−4Ion Using K+-Dicyclohexyl-18-crown-6 as Carrier

Abstract Potassium-Dicyclohexyl-18-Crown-6 Complex Was Used As A Highly Efficient Carrier For The Uphill Transport Of Copper As Cu(SCN)2− 4 Complex Ion Through A Chloroform Bulk Liquid Membrane. By Using Histidine As A Metal Ion Acceptor In The Receiving Phase At The Optimum Ph Of 7.4, The Amount Of Copper Transported Across The Liquid Membrane After 2 Hours Was 90.2 ± 1.0%. The Selectivity And Efficiency Of Copper Transport From Aqueous Solutions Containing Equimolar Mixtures Of Ag+, Cd2+, Zn2+, Ni2+, Fe2+, Co2+, Pb2+, Mn2+, Fe3+, Bi3+, And Cr3+ Ions Were Investigated. In The Presence Of Pyrophosphate As A Suitable Masking Agent In The Source Phase, The Interfering Effects Of Co2+, Zn2+, Pb2+, And Cd2+ Ions Were Completely Eliminated.

Anti-inflammatory properties of copper, gold and silver, individually and as mixtures.

It has been previously demonstrated that the mixture of Cu, Au and Ag impaired significantly the clinical and biochemical disorders induced by adjuvant arthritis in the rat. The efficiency of this mixture and of each component was tested on the same animal model. Treated rats were injected daily with either 22.8 micrograms of copper gluconate, 0.2 micrograms of gold thioglucose, 6.8 micrograms of silver proteinate or the blended solution over a period of 29 d. The treatment with the one component solutions was found to have a little or no effect on the plasma levels of fibrinogen, haptoglobin, ceruloplasmin, prostaglandin E2, thromboxane B2, total proteins, Zn, Cu, Mn, Se, Co and Ni, and no significant decrease was observed in the paw oedema resulting from the Freund's adjuvant injection. The treatment with the mixture had a significant preventive effect. Therefore it seems that the administration of low doses of each of the three trace elements have no anti-rheumatic property in the rat. The results indicate an enhanced effect of the metal mixture in the model studied.

Giant magnetoresistance at low fields in [(NixFe1−x)yAg1−y]/Ag multilayers prepared by molecular beam epitaxy (abstract)

The structural changes that accompany the development of GMR (giant magnetoresistance) at low (≲10 Oe) fields in annealed magnetic multilayers are of current interest because of potential applications of such structures in sensors. In this paper we report a study of the development of GMR in [111]-oriented multilayers comprising ferromagnetic films of a mixture of Ag and permalloy (NixFe1−x, x∼0.8) alternating with Ag spacer films. The multilayers were grown by molecular beam epitaxy (MBE) on Pt(111) seed films on sapphire (0001) substrates at temperatures in the range 20 to 200 °C. The structure of the multilayers was investigated using x-ray diffraction and electron microscopy. For a series of multilayers grown with nominally identical ferromagnetic and spacer layer thicknesses, the magnetoresistance is found to be strongly dependent on both growth temperature and subsequent annealing temperature. The multilayers exhibited a negative magnetoresistance in the as-grown state which more than doubled when the growth temperature was increased from 20 to 100 °C. However, the highest magnetoresistance (peak 5.6%; maximum slope 0.4% per Oe) was obtained by annealing (at 400 °C) multilayers grown at 100 °C. Transmission electron microscopy studies of such multilayers showed no evidence for discontinuities or penetration of the ferromagnetic films by Ag along grain boundaries. Thus, we conclude that discontinuous or granular multilayers with complete phase separation are not necessary for GMR with low saturation fields.

A study on the mechanism model of luminescence in fast neutron television converter

For a real time imaging technique using a fast neutron radiography (FNR), a fast neutron television system (FNR-TV) was studied using the fast neutron source reactor YAYOI at the University of Tokyo. In order to obtain a good quality image with the FNR-TV, it is essential to develop a high sensitive converter to detect fast neutrons. A sensitive prototype converter made of polypropylene (PP) resin and ZnS(Ag) mixture was recently developed. It was called a PP converter. In this paper, the mechanism models of luminescence for fast neutrons and gamma-rays in the PP converter are presented as well as the comparison with the experimental results. The analytical results agree well with the experimental results.

The stability of YBa2Cu3O7−x in contact with silver

The stability of YBa2Cu3O7−x (the 123 compound) in contact with silver (Ag) at temperatures below 900 °C was investigated by conducting SEM and EDX analyses on 123 agglomerates that were enclosed in a dense Ag matrix and subjected to various thermal treatments. The stability of the 123 agglomerates was found to depend heavily on the oxygen content in the Ag matrix. In the case of insufficient oxygen content in Ag, the 123 agglomerates, which were as large as 150 μm thick, decomposed readily at temperatures above 500 °C. The complete decomposition process can be summarized as continuous extraction of Ba from the 123 oxide into the surrounding Ag matrix and is proposed to be driven by high mutual solubilities between Ag and Ba under the oxygen-lean condition. Prolonged preoxygenation of the (123 + Ag) mixture powders at temperatures above 400 °C prevents the occurrence of 123 decomposition in compacted samples during subsequent heat treatment, suggesting that the critical oxygen content in Ag for stabilizing the 123 compound to be no higher than 10−3 at. % (the oxygen saturation solubility at 400 °C). The findings may have implications for the processing of other Ba-containing high-Tc superconducting oxides as well.

The molecular structures and conformational compositions of 1-bromo-3-chloropropane and 1,3-diiodopropane, as determined by gas-phase electron diffraction and molecular mechanics calculations

The molecular structures and conformational compositions of 1-bromo-3-chloropropane (BCP) and 1,3-diiodopropane (DIP) have been studied by gas-phase electron diffraction at 27 and 38°C, respectively. BCP was found to exist as a mixture of the following four conformers, with estimated mole fractions in brackets: AA (0.1), AG (0.3), GA (0.1) and GG (0.5). These estimated mole fractions correspond to the following relative conformational energies: ΔEAA = 0.5 kcal mol−1, ΔEAG = 0.3 kcal mol−1, ΔEGA = 0.9 kcal mol−1 and ΔEGG = 0.0 kcal mol−1. DIP was found to exist as a mixture of AA, AG and GG. The mole fractions and uncertainties estimated at 2σ were found to be 0.05(9), 0.40(21) and 0.55(24), respectively. This corresponds to the following relative conformational energies: ΔEAA ≈ 1.1 kcal mol−1, ΔEAG = 0.7(6) kcal mol−1 and ΔEGG = 0.0 kcal mol−1. In order to conduct a more detailed investigation of the conformational geometries, results from molecular mechanics (MM) calculations have been included in the analysis.

Synthesis and Crystal Structure Determination of (NH 4)Ag 2AsS 4, a Further Chalcopyrite-Type Compound

Crystals of (NH 4)Ag 2AsS 4 were synthesized from an approximately equimolar mixture of Ag, As 2S 3, and S in ammonia solution under hydrothermal conditions. The crystals are tetragonal: a = 6.780(1) Å, c = 8.277(1) Å, space group I4̄2 m, Z = 2. The structure was determined from a Patterson map (277 single crystal X-ray data) and refined to final residual parameters of R = 0.031 and R w = 0.028. In a first coordination sphere the atoms Ag and As as well as the NH 4 group are equidistant 4-coordinated to S atoms. The crystal structure represents a distorted chalcopyrite-type framework. The Ag-S bonds in the AgS 4 polyhedron of (NH 4)Ag 2AsS 4 exhibit a pronounced covalent character, deduced from the comparison of about twenty AgS 4 polyhedra mentioned in the literature.

Activity and corrosion of tungsten carbide recombination electrodes during lead/acid battery operation

The oxidation of the tungsten carbide (WC) catalyst in recombination electrodes partially immersed in H 2SO 4 solution was investigated when the electrodes operated in an atmosphere of oxygen and hydrogen. It has been established that after a long operation period (400 h) 60 to 70% of the catalysts, depending on the initial active surface of WC, may be oxidized to WO x, whereby the rate of recombination decreases about three times. It is assumed that the oxidation of WC is due to the H 2O 2 formed as an intermediate product of the recombination of hydrogen and oxygen. Silver accelerates the decomposition of H 2O 2 and hence the use of a WC—Ag mixture as catalyst in the recombination electrodes reduces strongly the carbide corrosion.

The forming phase and various properties of Au, Ag, Cu and Ga mixture in metal fired crowns : Yoshida T., Miyasaka T., Okamura H. et al. (1990) Jpn. J. Dent. Mater.9, 812–824

A new time-saving method has been developed to produce artificial crowns without using the casting process. Plastic mixtures of gallium and other metal particles are kneaded into desired shape and then heated for hardening. By this method, the time required for hardening and producing restorative materials has been shortened greatly. In the present experiment, gallium was triturated with powdered gold, silver and copper to make binary alloy samples. The dimensional change was measured between heat treatment. After heat treatment, the test piece was examined for compressive strength, compressive shrinkage, hardness, tarnishing and difference in phase. Non-heated and heated alloy specimens (Au-Ga, Ag-Ga, Cu-Ga) expanded to form the new phase. The ability of Au-Ga samples to bear compressive strength, when heated at 300 degrees C or more (AuGa2----AuGa), became 2.6 times greater than that of non-heat-treated specimens. The compressive strength of Ag-Ga samples dropped briefly at 350 degrees C (Ag0.72Ga0.28----Ag3Ga) but increased at 450 degrees C (Ag3Ga----AgGa). The strength of Cu-Ga pieces fell by half at 475 degrees C and upward (CuGa2----unknown phase). A compression test showed that the contraction percentage of Au and Ag specimens became large as a result of heat treatment, while that of Cu alloys remained almost unchanged. The results of a hardness test (HV) were comparable to those of the compressive strength test. The Au-Ga alloys increased in hardness after high-temperature treatment. In the Ag-Ga alloys, hardness declined at 350 degrees C and increased at 450 degrees C. There was no difference in hardness between Cu specimens after heat treatment and those allowed to stand at room temperature. A tarnishing test revealed that Au-Ga samples turned slightly yellowish. In the case of Ag-Ga samples, the reflectivity Y (%) dipped slightly but discoloration was not recognizable. However, the Cu-Ga samples which were heated at temperatures of up to 280 degrees C showed a slight drop in reflectivity, but those heated at temperatures higher than 280 degrees C decreased to 50-66% in reflectivity and turned black.

Regulation of the effector stages of experimental autoimmune encephalomyelitis via neuroantigen-specific tolerance induction. II. Fine specificity of effector T cell inhibition.

Ag-specific tolerance induced by the i.v. administration of splenocytes coupled with mouse spinal cord homogenate, containing a mixture of myelin Ag, dramatically inhibits development and expression of clinical and histologic signs of both active and adoptive forms of relapsing experimental autoimmune encephalomyelitis (R-EAE) in the SJL/J host. Here we examined the dose-dependency, route of tolerogen administration, and fine neuroantigen specificity of inhibition of adoptive R-EAE. Expression of clinical R-EAE induced by a polyclonal population of bovine myelin basic protein (MBP)-specific effector T cells was dramatically inhibited in a dose-dependent manner following the i.v., but not s.c. or i.p., injection of MBP-coupled splenocytes. The exquisite Ag specificity of the inhibition was evident by the observation that splenocytes coupled with intact bovine MBP or species variants of MBP homologous with bovine MBP within the major encephalitogenic region (amino acids 84-104), but not with proteolipid protein or mouse kidney homogenate, were able to suppress disease expression. Splenocytes coupled with the MBP84-104 peptide, containing a nested set of the major SJL/J encephalitogenic epitopes, completely inhibited peptide-specific T cell responses, but only partially inhibited the expression of disease transferred by T cells specific for intact MBP, suggesting the participation of T cell responses specific for additional MBP determinants in disease pathogenesis. However, splenocytes coupled with previously identified minor SJL/J encephalitogenic epitopes (MBP91-104 or MBP17-27), or with the Lewis rat major encephalitogenic epitope (MBP68-86), did not suppress disease expression. Collectively, the results demonstrate that MBP84-104-specific T cells and T cells specific for an as yet unidentified MBP epitope(s) contribute to the pathology of R-EAE. In addition, the results demonstrate that peptide-specific tolerance induction appears to have potential for the treatment of T cell-mediated inflammatory diseases.

Microstructure at the interface between AIN and a Ag–Cu–Ti braze alloy

The joining of aluminum nitride by active metal brazing with a Ag–Cu–Ti foil has been investigated in cross section by transmission electron microscopy. The reaction of AIN with the braze alloy results in the formation of continuous TiN and (Ti, Cu, Al)6N (η-phase) layers at the interface. AIN grains at the interface often display arrays of dislocations, presumably arising from thermal expansion mismatch between the AIN and the TiN (the coefficients of thermal expansion are 43 ⊠ 10−7/°C and 80 ⊠ 10−7/°C, respectively). The adjoining TiN contains small Cu precipitates and may also contain numerous defects. Titanium preferentially penetrates the AIN grain boundaries, resulting in finger-like TiN intrusions into the substrate, which sometimes cover entire AIN grains in a TiN shell. On the other side of the TiN, a continuous layer of equiaxed, defect-free η–nitride grains is found. Beyond this η–nitride layer is the remaining mixture of metallic Ag and Cu. High-resolution electron microscopy demonstrates that the AIN–TiN and TiN–η boundaries are abrupt and contain no additional crystalline or amorphous intervening phases. Particular orientation relationships are occasionally observed at the AIN–TiN interface; these are not always the ones that produce the minimum lattice mismatch. The implications of the observed morphology with respect to the reaction sequence, transitional phases, and structural integrity of the joint are discussed.

Local blood flow measured by fluorescence excitation of nonradioactive microspheres

An X-ray fluorescence system with low Compton background and high counting efficiency was developed to measure regional blood flow with nonradioactive microspheres. The performance of the system was tested in vitro by counting mixed aqueous solutions of either Mo, Ag, and I; Nb, Ag, and Ba; or Zr, Mo, Rh, Ag, Sn, I, and Ba, as well as a mixture of Ag and Ba nonradioactive microspheres. Mixtures containing 2-20 ppm of each element were counted for 10 min by the fluorescence system, and the individual elements in mixtures of three to seven nonradioactive elements were measured with high accuracy. The best counting statistics were obtained for Ag. For 10-min counts, the system measures as few as 120 Ag microspheres with 30% standard deviation but measures 800 Ag microspheres per sample with 3.6% standard deviation. We compared regional myocardial blood flows determined simultaneously by fluorescence and radioactive microsphere methods; the latter samples were counted by a 3-in. NaI (Tl) well detector and pulse-height analyzer. The radioactive and nonradioactive measurements showed good correlations.

The forming phase and various properties of Au, Ag, Cu and Ga mixture in metal fired crowns

A new time-saving method has been developed to produce artificial crowns without using the casting process. Plastic mixtures of gallium and other metal particles are kneaded into desired shape and then heated for hardening. By this method, the time required for hardening and producing restorative materials has been shortened greatly. In the present experiment, gallium was triturated with powdered gold, silver and copper to make binary alloy samples. The dimensional change was measured between heat treatment. After heat treatment, the test piece was examined for compressive strength, compressive shrinkage, hardness, tarnishing and difference in phase. Non-heated and heated alloy specimens (Au-Ga, Ag-Ga, Cu-Ga) expanded to form the new phase. The ability of Au-Ga samples to bear compressive strength, when heated at 300 degrees C or more (AuGa2----AuGa), became 2.6 times greater than that of non-heat-treated specimens. The compressive strength of Ag-Ga samples dropped briefly at 350 degrees C (Ag0.72Ga0.28----Ag3Ga) but increased at 450 degrees C (Ag3Ga----AgGa). The strength of Cu-Ga pieces fell by half at 475 degrees C and upward (CuGa2----unknown phase). A compression test showed that the contraction percentage of Au and Ag specimens became large as a result of heat treatment, while that of Cu alloys remained almost unchanged. The results of a hardness test (HV) were comparable to those of the compressive strength test. The Au-Ga alloys increased in hardness after high-temperature treatment. In the Ag-Ga alloys, hardness declined at 350 degrees C and increased at 450 degrees C. There was no difference in hardness between Cu specimens after heat treatment and those allowed to stand at room temperature. A tarnishing test revealed that Au-Ga samples turned slightly yellowish. In the case of Ag-Ga samples, the reflectivity Y (%) dipped slightly but discoloration was not recognizable. However, the Cu-Ga samples which were heated at temperatures of up to 280 degrees C showed a slight drop in reflectivity, but those heated at temperatures higher than 280 degrees C decreased to 50-66% in reflectivity and turned black.

Vaccination against murine cutaneous leishmaniasis by using Leishmania major antigen/liposomes. Optimization and assessment of the requirement for intravenous immunization.

Efficacy of vaccination against cutaneous leishmaniasis in highly susceptible BALB/c mice was assessed comparatively by using radiation-attenuated promastigotes and colloidal Ag mixtures generated from a mixed Leishmania major (LV39) isolate (SLV39) and from a virulent cloned line (SVJ2) derived from the Jericho 2 L. major isolate. Dehydration-rehydration vesicle (DRV) liposomes were used as adjuvants. In optimization experiments phospholipid composition of DRV was varied, and the distearoyl derivative (DSPC) (liquid-crystalline phase transition temperature (Tc) 54 degrees C) of egg lecithin L-alpha-phosphatidylcholine was found to be superior to the dipalmitoyl derivative (DPPC, Tc 41.5 degrees C) and underivatized L-alpha-phosphatidylcholine (Tc -10 degrees C). The criteria studied were in vivo priming for a secondary in vitro proliferative response and the prepatency of lesion onset after L. major challenge of mice immunized once i.v. A single s.c. immunization with SLV39 either free or entrapped within DSPC liposomes primed spleen cells to produce significant levels of IL-3 when stimulated with SLV39 in vitro. In contrast, the i.v. route of immunization with the same Ag preparations led to little or no IL-3 production by the spleen cells. Despite development of significant T cell activation, both SLV39 and SVJ2 administered s.c., either free or entrapped within liposomes, were not protective. However, i.v. immunization four times with SVJ2 entrapped within DSPC liposomes induced a level of resistance comparable with that of 2 x 10(7) gamma-irradiated promastigotes in the stringent BALB/c L. major model. Although significant, protection conferred after i.v. immunization with SLV39/DSPC liposomes was less effective. These data therefore show that DSPC/DRV liposomes, although a good adjuvant for inducing protective immunity to cutaneous leishmaniasis, are not able to overcome the requirement for an i.v. route of immunization with the leishmanial Ag preparation. Additionally, they demonstrate a correlation between IL-3 secretion and non-protection. They also suggest that SVJ2 represents a better source of protective Ag than SLV39.

Ａｇ２Ｏ混合酸化物超電導体の低抵抗接続端子

Low resistivity contacts to the bulk specimens of YBa2Cu3O7-y with Ag have been developed. In order to obtain homogeneous mixtures of YBa2Cu3O7-y and Ag we used Ag2O powder, The contact resistivity of 0.19μΩ·cm2 was obtained by annealing the specimen at 1, 100°C. The current versus voltage characteristic of the contact was found to be ohmic. The contact was made to the specimen which is exposed to air for 110 days; the contact resistivity after this period had elapsed was almost the same as the contact made to the fresh specimen. Using physical and chemical analysis it was found that all the Ag2O in YBa2Cu3O7-y was separated to Ag and that Ag existed in all voids.

High temperature stability of oxysulfides containing Ce 3+ and Y 3+ ions

Standard Gibbs energies of formation of oxysulfides of cerium and yttrium from their respective oxedes were determined using solid oxide galvanic cells incorporating calcia-stabilized zirconia as the electrolyte in the temperature range 870–1120 K. The sulfur potential over the electrode containing the oxide and oxysulfide was fixed by a buffer mixture of Ag + Ag 2S. A small amount of CaH 2 was added to the buffer to generate an equilibrium ratio of H 2S and H 2 species in a closed system containing the buffer and the electrode. The sulfur potential is transmitted to the electrode via the gas phase. The results can be summarized by the equations 2〈CeO 2〉+1/2(S 2)→〈Ce 2O 2S〉+(O 2) ΔG°=430600−109·7T(±400)J mol −1 〈Y 2O 3〉+1/2(S 2)→〈Y 2O 2S〉+1/2(O 2) ΔG°=114780−1·45T(±200)J mol −1 The values are compared with data reported in the literature. The stability field diagram for the CeOS system has been developed using the results of this study for Ce 2O 2S and data for other phases from the literature.

Quantitative Auger analysis of complex electrical contact alloy materials

Addition of elemental Auger spectra has been used to produced several series of Auger lineshapes versus composition for the ovelapping peaks resulting from mixtures of Cu, Pt, Pd or Ag in Au; S in Au or Pt, Cl in Au, Pt or Pd; C (both graphitic and carbidic) in Au, Pt, Ag or Pd. These assorted lineshapes series may be used to obtain semi-quantitative analysis of overlapping peaks by matching lineshapes, but have also been used to calibrate peak ratios versus composition in order to quantitatively separate contributions to overlapping Auger peaks. This procedure is illustrated by application to the quantitative analysis of tw electrical contact alloys - ASTM B541. Advantages and limitations of this procedure are B540 and ASTM B541. Advantages and limitations of this procedure are discussed.

ChemInform Abstract: New Quaternary Chalcogeno Halides.

AbstractAgHgSI (I), AgHgSBr (II), and CuHgSI (III) have been synthesized by annealing mixtures of Ag(Cu) halides and HgS.