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Silver
Terms modified by Silver Selected AbstractsComposite thin films of poly(phenylene oxide)/poly(styrene) and PPO/silver via vapor phase depositionPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2009I. S. Bayer Abstract We report fabrication of thin (100,300,nm) poly(phenylene oxide) (PPO) films and their composites with poly (styrene) (PS) and silver (Ag) nanoparticles using a one-step electron beam-assisted vapor phase co-deposition technique. Surface morphology and the structure of the deposited polymer thin film composites were characterized by FTIR, Raman, X-ray spectroscopy, and contact angle measurements. As-deposited PPO films and PPO/Ag composites were of porous nature and contrary to solvent casting techniques were free from nodular growth. In the case of PPO/PS thin film polymer composites, however, film morphology displayed nodular growth of PPO with nodule diameters of about ,200,nm and height of approximately 50,nm. Unique morphological changes on the porous PPO thin film surface were noticed at different Ag filling ratios. Further, the capacitance of PPO/Ag composites (<16 wt%) were measured under radio-frequency conditions and they were functional up to 100,MHz with an average capacitance density of about 2,nF/cm2. The fabricated PPO-based composite systems are discussed for their potential applications including embedded capacitor technology. Copyright © 2008 John Wiley & Sons, Ltd. [source] NEW APPROACHES ON THE ARCHAIC TRADE IN THE NORTH-EASTERN IBERIAN PENINSULA: EXPLOITATION AND CIRCULATION OF LEAD AND SILVEROXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2010NÚRIA RAFEL Summary A wide-ranging study based on compositional and isotopic analyses of minerals and manufactured objects from the north-eastern Iberian Peninsula and their respective archaeological and cultural contexts demonstrates significant lead mineral exploitation in the El Priorat area (Tarragona province) linked to Phoenician trade (seventh,sixth centuries BC). This exploitation continued, despite losing intensity, until the Romanization of the territory. Our project also aims to determine the nature and origin of the lead and silver supply in the northern Iberian territory surrounding the Phocaean enclave of Emporion, especially with regard to the demands of the colonial mint. The behaviour pattern of the circulation of lead, silver and copper in Catalonia in the period studied indicates a plurality of contemporary supply sources, although, at least from the fifth century BC onward, minerals and metals from the south-eastern Iberian Peninsula take on considerable importance. [source] Inalienable Commodities: The Production and Circulation of Silver and Patrimony in a Mexican Mining CooperativeCULTURAL ANTHROPOLOGY, Issue 3 2002Elizabeth Emma Ferry First page of article [source] Differential Pulse Anodic Stripping Voltammetric Simultaneous Determination of Copper(II) and Silver(I) with Bis(2-hydroxyacetophenone) Butane-2,3-dihydrazone Modified Carbon Paste ElectrodesELECTROANALYSIS, Issue 19 2010M. B. Gholivand Abstract The behavior of a modified carbon paste electrode (CPE) for simultaneous determination of copper(II) and silver(I) by anodic adsorptive stripping voltammetry (ASV) was studied. The electrode was built incorporating the bis(2-hydroxyacetophenone) butane-2,3-dihydrazone (BHAB) as a complexing agent to a Nujol-graphite base paste. The resulting electrode demonstrated linear responses over the range of Cu(II) and Ag(I) concentrations 0.1,20 and 0.01,2.0,µM respectively. The relative standard deviation (RSD) for the determination of 5.0,µM of both metal ions were 2.9 and 3.1,% for Cu(II) and Ag(I), respectively. The method has been applied to the analysis of copper in wheat and barley seed samples and silver in developed radiological film. [source] Silver Doped Poly(L -valine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Uric Acid, Ascorbic Acid and DopamineELECTROANALYSIS, Issue 5 2010Wenna Hu Abstract In this paper, a silver doped poly(L -valine) (Ag-PLV) modified glassy carbon electrode (GCE) was fabricated through electrochemical immobilization and was used to electrochemically detect uric acid (UA), dopamine (DA) and ascorbic acid (AA) by linear sweep voltammetry. In pH,4.0 PBS, at a scan rate of 100,mV/s, the modified electrode gave three separated oxidation peaks at 591,mV, 399,mV and 161,mV for UA, DA and AA, respectively. The peak potential differences were 238,mV and 192,mV. The electrochemical behaviors of them at the modified electrode were explored in detail with cyclic voltammetry. Under the optimum conditions, the linear ranges were 3.0×10,7 to 1.0×10,5,M for UA, 5.0×10,7 to 1.0×10,5,M for DA and 1.0×10,5 to 1.0×10,3,M for AA, respectively. The method was successfully applied for simultaneous determination of UA, DA and AA in human urine samples. [source] Novel Sensitive Voltammetric Detection of Trace Gallium(III) with Presence of Catechol Using Mercury Film Silver Based ElectrodeELECTROANALYSIS, Issue 16 2009Robert Piech Abstract A new adsorptive stripping voltammetric method for the determination of trace gallium(III) based on the adsorption of gallium(III)-catechol complex on the cyclic renewable mercury film silver based electrode (Hg(Ag)FE) is presented. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimized. The calibration graph is linear from 2,nM (0.14,,g L,1) to 100,nM (6.97,,g L,1) for a preconcentration time of 30,s, with correlation coefficient of 0.9993. For a Hg(Ag)FE with a surface area of 9.7,mm2 the detection limit for a preconcentration time of 90,s is as low as 7,ng L,1. The repeatability of the method at a concentration level of the analyte as low as 0.05,,g L,1, expressed as RSD is 3.6% (n=5). The proposed method was successfully applied by studying the natural samples and simultaneous recovery of Ga(III) from spiked water and sediment samples. [source] Differential Pulse Voltammetric Determination of Selected Nitro-Compounds on Silver, Solid Silver Composite, and Solid Graphite Composite ElectrodesELECTROANALYSIS, Issue 3-5 2009Navrátil Abstract Three different types of solid electrodes, namely silver electrode, silver composite electrode containing 20% (m/m) of silver powder, 20% (m/m) of graphite powder and 60% (m/m) of methacrylate resin and graphite composite electrode containing 30% (m/m) of graphite powder and 70% (m/m) of epoxy resin were tested for differential pulse voltammetric determination of selected genotoxic nitro-compounds using 2-nitronaphthalene, 6-nitroquinoline, and 5-nitrobenzimidazole as model compounds. It was found that all three electrodes can be used for the determination of micromolar concentrations of tested model substances, the limit of detection and other figures of merits being dependent both on the electrode used and the substance to be determined. [source] Silver(I)-Selective PVC Membrane Potentiometric Sensor Based on a Recently Synthesized Calix[4]areneELECTROANALYSIS, Issue 10 2006Ayça Demirel Abstract A new PVC membrane potentiometric sensor for Ag(I) ion based on a recently synthesized calix[4]arene compound of 5,11,17,23-tetra- tert -butyl-25,27-dihydroxy-calix[4]arene-thiacrown-4 is developed. The electrode exhibits a Nernstian response for Ag(I) ions over a wide concentration range (1.0×10,2,1.0×10,6 M) with a slope of 53.8±1.6,mV per decade. It has a relatively fast response time (5,10,s) and can be used for at least 2 months without any considerable divergence in potentials. The proposed electrode shows high selectivity towards Ag+ ions over Pb2+, Cd2+, Co2+, Zn2+, Cu2+, Ni2+, Sr2+, Mg2+, Ca2+, Li+, K+, Na+, NH4+ ions and can be used in a pH range of 2,6. Only interference of Hg2+ is found. It is successfully used as an indicator electrode in potentiometric titration of a mixture of chloride, bromide and iodide ions. [source] Catalytic Effect on Silver Electrodeposition of Gold Deposited on Carbon ElectrodesELECTROANALYSIS, Issue 19 2004Alfredo de, Escosura-Muñiz Abstract A new methodology, based on silver electrocatalytic deposition and designed to quantify gold deposited onto carbon paste electrode (CPE) and glassy carbon electrode (GCE), has been developed in this work. Silver (prepared in 1.0,M NH3) electrodeposition at ,0.13,V occurs only when gold is previously deposited at an adequate potential on the electrode surface for a fixed period of time. When a CPE is used as working electrode, an adequate oxidation of gold is necessary. This oxidation is carried out in both 0.1,M NaOH and 0.1,M H2SO4 at oxidation potentials. When a GCE is used as working electrode, the oxidation steps are not necessary. Moreover, a cleaning step in KCN, which removes gold from electrode surface, is included. To obtain reproducibility in the analytical signal, the surface of the electrodes must be suitably pretreated; this electrodic pretreatment depends on the kind of electrode used as working electrode. Low detection limits (5.0×10,10,M) for short gold deposition times (10,min for CPE and 5,min for GCE) were achieved with this novel methodology. Finally, sodium aurothiomalate can be quantified using silver electrocatalytic deposition and GCE as working electrode. Good linear relationship between silver anodic stripping peak and aurothiomalate concentration was found from 5.0×10,10,M to 1.0×10,8,M. [source] Protein-based electrochemical biosensor for detection of silver(I) ions,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2010Sona Krizkova Abstract Silver(I) ions are extremely toxic to aquatic animals. Hence, monitoring of these ions in the environment is needed. The aim of the present study was to suggest a simple biosensor for silver(I) ions detection. The suggested biosensor is based on the modification of a hanging mercury drop electrode (HMDE) by the heavy metal binding protein metallothionein (MT) for silver(I) ions detection. Metallothionein accumulated for 120 s onto the HMDE surface. After rinsing the electrode, the biosensor (MT modified HMDE) was prepared prior to detection of silver(I) ions. The biosensor was immersed in a solution containing silver(I) ions. These ions were bound to the MT structure. Furthermore, the electrode was rinsed and transferred to a pure supporting electrolyte solution, in which no interference was present. Under these experimental conditions, other signals relating to heavy metals naturally occurring in MT were not detected. This phenomenon confirms the strong affinity of silver(I) ions for MT. The suggested biosensor responded well to higher silver(I) ion concentrations. The relative standard deviation for measurements of concentrations higher than 50,µM was approximately 2% (n,=,8). In the case of concentrations lower than 10,µM, the relative standard deviation increased to 10% (n,=,8). The detection limit (3,signal/noise) for silver(I) ions was estimated as 500,nM. Environ. Toxicol. Chem. 2010;29:492,496. © 2009 SETAC [source] Association of heavy metals with metallothionein and other proteins in hepatic cytosol of marine mammals and seabirdsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2004Tokutaka Ikemoto Abstract Distribution of Cu, Zn, Cd, Ag, Hg, and Se were determined in hepatocytosol of northern fur seals (Callorhinus ursinus), black-footed albatrosses (Diomedea nigripes), and Dall's porpoises (Phocoenoides dalli). Copper, Zn, and Cd were accumulated preferentially in metallothionein (MT) fraction and their contents in MT fraction increased with the amounts in the hepatocytosol. Silver was bound to both high-molecular-weight substances (HMWS) and MT in the hepatocytosol for all three species, whereas the distribution of Ag in the cytosol was different among the three species. In northern fur seals, Ag mainly was bound to MT, whereas it mainly was associated with HMWS in Dall's porpoises. In contrast, Ag was distributed almost equally in both HMWS and MT for black-footed albatrosses. Mercury content in HMWS and Se content in HMWS and low-molecular-weight substances (LMWS) increased with their contents in hepatocytosol for all the three species. A significant positive correlation was found between Se and Hg contents in high-molecular weight (HMW) fraction in cytosol. The molar ratio of Hg and Se was close to unity in HMW fraction of the specimens with high Hg concentration in cytosol, implying that the Hg,Se complex was bound to the HMWS. Analysis of metals in the hepatocytosol by high-performance liquid chromatography/inductively coupled plasma,mass spectrometry (HPLC/ICP-MS) suggests that multiple isoforms of MT are present in hepatocytosol of the three species and that the metal profiles in hepatocytosols are different among the species. To our knowledge, this is the first report on the association of Ag with HMWS and MT in hepatocytosol of marine mammals and seabirds. Also, distribution and interaction of Hg and Se were investigated for the first time in hepatocytosol of the higher trophic marine animals. [source] Synthesis and Characterization of Linear Tetranuclear Silver(I) Complexes Bridged by Tetraphosphane LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2009Yukie Takemura Abstract Reactions of AgOTf with meso -bis[(diphenylphosphanylmethyl)phenylphosphanyl]methane (dpmppm) afforded[Ag4(OTf)2(,-OTf)(,-dpmppm)2{(CH3)2CO}](OTf) (1) and [Ag4(OTf)2(,-OTf)(,-dpmppm)2(RNC)2](OTf) {R = Xyl (2a), Mes (2b), tBu (2c)}. When AgOTf was treated with dpmppm in air in the presence of tBuNC, cleavage of the C,Cl and P,C bonds occurred to give [Ag4(,-Cl)(,-dpmppm)2(tBuNC)4](OTf)3 (3) and [Ag4(,-Ph2PO2)(,-dpmppm)2(tBuNC)3](OTf)3 (4). Reaction of AgOCOCF3 with dpmppm resulted in [Ag4(OCOCF3)2(,-OCOCF3)(,-dpmppm)2](CF3COO) (5). By treatment of AgPF6 with dpmppm, [Ag4(,-dpmppm)2(tBuNC)4](PF6)4 (6) and [Ag4(PO2F2)2(,-dpmppm)2(tBuNC)2] (PF6)2 (7) were obtained. Wheareas complexes 1,3 possess a {Ag4(,-dpmppm)2}4+ core in which the Ag4 strings are rather bent with two dpmppm ligands arranged in a syn fashion, complexes 4,7 have linear Ag4 strings supported by two dpmppm ligands arranged in an anti fashion. These results suggest that the dpmppm-supported tetrasilver(I) strings are quite flexible and labile and thus are potentially important in promoting organic reactions as a result of the multimetallic centers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Anion-Dependent Structural Diversity in Silver(I) Complexes of 4-Amino-3,5-diisopropyl-1,2,4-triazoleEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2007Guang Yang Abstract Reactions of silver salts with 4-amino-3,5-diisopropyl-1,2,4-triazole (L) afford dinuclear complex [Ag2L2(NO3)2(CH3CN)], triangular complex [Ag3L3](CF3SO3)3, and cyclic tetranuclear complexes [Ag4L6](BF4)4 and [Ag4L6](ClO4)4. On the basis of the X-ray analyses, anions are found to play an important role in determining the structures. Through coordination/noncoordination, anions can impart their influence on the coordination geometry of Ag atoms and the angles of N,Ag,N, which seems to be the main factor controlling the nuclearity of the reaction products in this system. 1H NMR and MS measurements suggest that these complexes probably retain their structural integrities in CH3CN solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis, Characterization and in Vitro Study of the Cytostatic and Antiviral Activity of New Polymeric Silver(I) Complexes with Ribbon Structures Derived from the Conjugated Heterocyclic Thioamide 2-Mercapto-3,4,5,6-tetra- hydropyrimidineEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2004Panagiotis C. Zachariadis Abstract Silver(I) bromide reacts with 2-mercapto-3,4,5,6-tetrahydropyrimidine (StpmH2, C4H8N2S) in DMSO with an excess of triethylamine to give a water-insoluble complex of formula [Ag6(,2 -Br)6(,2 -StpmH2)4(,3 -StpmH2)2]n (1), while the reaction of silver(I) nitrate with StpmH2 under the same conditions gives a water-insoluble complex of formula [{Ag4(,2 -StpmH2)6}(NO3)4]n (2). The products were characterized by elemental analyses, and FT-IR far-IR, UV/Vis, 1H and 13C NMR spectroscopy. Crystal structures of complexes 1 and 2 were determined by X-ray diffraction. Complex 1, C24H48Ag6N12S6, crystallizes in the triclinic system space group P , a = 8.041(1) Å, b = 12.838(4) Å, c = 13.281(2) Å, , = 68.40(1)°, , = 72.97(1)°, , = 87.80(2), Z = 2, forming a one-dimensional infinite ribbon structure by strong interatomic interactions of two ,2 -Br bonds with Ag(1). Complex 2, C24H48Ag4N16O12S6, crystallizes in the orthorhombic system, space group Cmc21, and a = 32.148(3) Å, b = 9.461(2) Å, c = 7.234(1) Å, , = , = , = 90°, Z = 8, forming infinite Ag,S,Ag chains which are bridged to each other by a sulfur atom of ,2 -StpmH2 ligands. Complexes 1 and 2 were studied for their cytostatic activity against murine leukemia (L1210) and human T-lymphocyte (Molt4/C8 and CEM) cells and for their antiviral activity against a wide variety of viruses. They are markedly cytostatic at 50% inhibitory concentration (IC50) values ranging from 3 to 17 ,g/mL. None of the compounds showed appreciable antiviral activity at subtoxic concentrations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] High Antibacterial and Antifungal Activity of Silver Monodispersed Nanoparticles Embedded in a Glassy Matrix,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Leticia Esteban-Tejeda Silver doped glass powders have been obtained starting from vitellinate/nAg and montmorillonite/nAg. These powders have shown a high biocide activity against the three different types of microorganisms studied: Escherichia coli (gram-negative bacteria), Micrococcus luteus (gram-positive-bacteria), and Issatchenkia orientalis (yeast). It was found that these glasses keep constant the silver concentration even below the cytotoxic limit. Therefore we interpret that silver doped glasses play the role of dosing devices. [source] C-Glycosidations of a 2-Ketohexosyl Bromide with Electrophilic, Radical, and Nucleophilic Anomeric CarbonsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2003Frieder W. Lichtenthaler Abstract The susceptibility of acylated 2-ketohexosyl halides to C-homologation is demonstrated with the easily accessible tri- O -benzoyl-,- D - arabino -hexos-ulosyl bromide 1 as the model compound. C-Glycosidation with an electrophilic anomeric carbon requires prior carbonyl protection, to avoid carbonyl addition by the C-nucleophile, for example, as the cyanohydrin. Silver triflate-promoted reaction with the silylenol ether of acetophenone then efficiently yields the ,-phenacyl product. With thermal (AIBN) or photochemical induction, 1 smoothly generates an anomeric radical , comparatively electrophilic, due to its capto-dative substitution , which exclusively traps hydrogen in the presence of tributyltin and electron-deficient alkenes. With allyltributylstannanes, however, it reacts with high stereoselectivity to afford ,- C -allyl glycosiduloses. The ,-bromoketone functionality in ulosyl bromide 1 is susceptible to Reformatsky conditions: treatment with zinc-copper couple readily generates the 1,2-enolate, a most simple anomeric nucleophile, which effectively adds to aldehydes to give ,- C -hydroxyalkyl glycosiduloses or ,- C -disaccharides (with sugar aldehydes) with a high degree of double stereoselection. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] A Concept in Bactericidal Materials: The Entrapment of Chlorhexidine within SilverADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Racheli Ben-Knaz Abstract A new concept in bactericidal agents is described: the entrapment of an organic biocidal agent within a bactericidal metal, which leads to synergism between the two components. Specifically this concept is demonstrated for the entrapment of chlorhexidine digluconate (CHD) within an aggregated silver matrix, a metal known for its own biocidal qualities, forming the CHD@silver composite. The bactericidal efficacy against E. coli is evaluated and compared with the separate components. While the bactericidal efficacy of the individual ingredients (CHD and metallic silver) is very low, CHD@silver exhibits a markedly enhanced efficacy. This enhanced bactericidal effect is partially attributed to the simultaneous release and presence of the active biocidal ingredients CHD and Ag+ in the solution. Detailed composite characterization is provided. [source] Silver (Ag+) reduces denitrification and induces enrichment of novel nirK genotypes in soilFEMS MICROBIOLOGY LETTERS, Issue 2 2007Ingela Noredal Throbäck Abstract The use of silver ions in industry to prevent microbial growth is increasing and silver is a new and an overlooked heavy-metal contaminant in sewage sludge-amended soil. The denitrifying community was the model used to assess the dose-dependent effects of silver ions on microorganisms overtime in soil microcosms. Silver caused a sigmoid dose-dependent reduction in denitrification activity, and no recovery was observed during 90 days. Dentrifiers with nirK, which encodes the copper nitrite reductase, were targeted to estimate abundance and community composition for some of the concentrations. The nirK copy number decreased by the highest addition (100 mg Ag kg,1 soil), but the nirK diversity increased. Treatment-specific sequences not clustering with any deposited nirK sequences were found, indicating that silver induces enrichment of novel nirK denitrifiers. [source] Nanoparticles: Investigations on the Structural Damage in Human Erythrocytes Exposed to Silver, Gold, and Platinum Nanoparticles (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Mater. [source] Investigations on the Structural Damage in Human Erythrocytes Exposed to Silver, Gold, and Platinum NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 8 2010P. V. Asharani Abstract Human erythrocytes or red blood cells (RBCs), which constitute 99% of blood cells, perform an important function of oxygen transport and can be exposed to nanoparticles (NPs) entering into the human body during therapeutical applications involving such NPs. Hence, the haemocompatibility of the Ag, Au, and Pt NPs on human RBCs is investigated. The parameters monitored include haemolysis, haemagglutination, erythrocyte sedimentation rate, membrane topography, and lipid peroxidation. The findings suggest that platinum and gold NPs are haemocompatible compared to Ag NPs. Erythrocytes exhibit significant lysis, haemagglutination, membrane damage, detrimental morphological variation, and cytoskeletal distortions following exposure to Ag NPs at a concentration of 100,µg,mL,1. Exposure of Ag+ to RBCs shows no lysis or deterioration, implying that the observed toxicity is solely due to NPs. The haemolyzed erythrocyte fraction has the ability to induce DNA damage in nucleated cells. Additionally, multiple pits and depressions are observed on RBC membrane following exposure to Ag NPs (50,µg,mL,1 onwards). Hence, it is apparent that Ag NPs exhibit toxicity on RBCs and on other cells that are exposed to NP-mediated haemolyzed fractions. [source] Polyaniline Entrapped in Silver: Structural Properties and Electrical ConductivityADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Guy Nesher Abstract By employing the new methodology of entrapment of organic molecules within metals, we demonstrate the ability to modify the conductivity of a metal by suitable polymer entrapment. Specifically, polyaniline (PANI) in two molecular weights was entrapped in silver at different concentrations and a comprehensive comparison was preformed for a range of the composite properties, characterized by XRD, SEM, BET, TGA, and density measurements. Pressed films were utilized to measure the electrical conductivity of the composites in order to study the PANI-silver interactions at the molecular level and to establish a correlation between the microscopic morphology and the film conduction. Such correlations have been identified, and are interpreted. This work extends the functional applications of the new metallic composites and offers insight on the polymer-metal molecular level interactions. [source] High-Dielectric-Constant Silver,Epoxy Composites as Embedded Dielectrics,ADVANCED MATERIALS, Issue 14 2005L. Qi The incorporation of organic-coated silver nanoparticles into an epoxy matrix (see Figure, a,f represent increasing Ag content) results in a flexible 0-3 type nanocomposite with a strikingly high dielectric constant (greater than 300). The composite retains the flexibility and other mechanical properties of the polymer matrix, and may be useful in applications where capacitors are embedded into printed circuit boards. [source] Axially Chiral Phosphine-Oxazoline Ligands in Silver(I)- Catalyzed Asymmetric Mannich Reaction of Aldimines with TrimethylsiloxyfuranADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Hong-Ping Deng Abstract A new asymmetric catalytic system for the Mannich reaction of aldimines with trimethylsiloxyfuran is described. The combination of an axially chiral phosphine-oxazoline ligand (S)-2-[(R)-2,-(diphenylphosphino)-1,1,-binaphthyl-2-yl]-4-phenyl-4,5-dihydrooxazole with silver acetate and 2,2,2-trifluoroacetic acid is a very effective catalytic system in the asymmetric Mannich reaction of various aldimines with trimethylsiloxyfuran in dichloromethane at ,78,°C, affording the corresponding adducts in up to 99% yield, 99:1 (dr) and 99% ee (major diastereoisomer) under mild conditions. [source] Asymmetric Aldol Reaction of Ketones with Alkenyl Trichloroacetates Catalyzed by Dibutyltin Dimethoxide and BINAP,Silver(I) Complex: Construction of a Chiral Tertiary Carbon CenterADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Akira Yanagisawa Abstract A novel aldol reaction of alkenyl trichloroacetates with ,-keto esters was realized by using dibutyltin dimethoxide as a catalyst, which was regenerated by the addition of methanol. The reaction was found to be remarkably accelerated by the addition of a catalytic amount of a bidentate phosphine,silver(I) complex. Use of the BINAP,silver triflate (AgOTf) complex as the chiral co-catalyst resulted in the formation of optically active aldol products possessing a chiral tertiary carbon with up to 93% ee. This catalytic method was further applied to the asymmetric reaction of diketene with methyl benzoylformate. [source] Ruthenium(II)-Catalyzed Regioselective Synthesis of Allyl Ketones from Alkynes and their Silver(I)-Catalyzed Hydroarylation into ,-Functionalized KetonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Min Zhang Abstract The regioselective synthesis of ,,,-unsaturated ketones from terminal alkynes is achieved by cooperative action of tris(acetonitrile)pentamethylcyclopentadieneruthenium hexafluorophosphate [Cp*Ru(NCMe)3+ PF6,] and para -toluenesulfonic acid catalysts. These allyl ketones undergo direct regioselective hydroarylation/Friedel,Crafts reaction to introduce an electron-rich aryl group at the ,-position in the presence of ligand-free silver triflate (AgOTf) catalyst. Both catalytic reactions take place with atom economy and provide an alternative to the synthesis of a variety of allyl ketones and , -arylated ketones. [source] Ligand-Free Silver(I)-Catalyzed Intramolecular Friedel,Crafts Alkylation of Arenes with Allylic AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Marco Bandini Abstract The silver-catalyzed direct activation of allylic alcohols as electrophilic partners for intramolecular Friedel,Crafts alkylation of arenes is described. Use of silver triflate (AgOTf; 10 mol%) enabled functionalized 1-vinyl-1,2,3,4-tetrahydronaphthalenes and a 4-vinyl-1,2,3,4-tetrahydroisoquinoline to be isolated in good yields with high levels of regiochemistry, under a ligand-free regime. [source] A Dramatic Substituent Effect in Silver(I)-Catalyzed Regioselective Cyclization of ortho -Alkynylaryl Aldehyde Oxime DerivativesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Hongyin Gao Abstract A dramatic substituent effect was found in the silver(I)-catalyzed cyclization reaction of ortho -alkynylaryl aldehyde oxime derivatives. When R is an alkyl group, the Ag(I)-catalyzed reaction in dimethylacetamide at 110,°C (conditions A) affords isoquinolines in good to excellent yields, in contrast, isoquinolin-1(2,H)-ones were produced in moderate to high yields under conditions B (dimethylformamide, room temperature) when R is an acetyl group. A plausible mechanism was proposed for this product selectivity control reaction (PSCR) by subtle structure modification. [source] ,Amsterdam is Standing on Norway' Part I: The Alchemy of Capital, Empire and Nature in the Diaspora of Silver, 1545,1648JOURNAL OF AGRARIAN CHANGE, Issue 1 2010JASON W. MOORE In the first of two essays in this Journal, I seek to unify the historical geography of early modern ,European expansion' (Iberia and Latin America) with the environmental history of the ,transition to capitalism' (northwestern Europe). The expansion of Europe's overseas empires and the transitions to capitalism within Europe were differentiated moments within the geographical expansion of commodity production and exchange , what I call the commodity frontier. This essay is developed in two movements. Beginning with a conceptual and methodological recasting of the historical geography of the rise of capitalism, I offer an analytical narrative that follows the early modern diaspora of silver. This account follows the political ecology of silver production and trade from the Andes to Spain in Braudel's ,second' sixteenth century (c. 1545,1648). In highlighting the Ibero-American moment of this process in the present essay, I contend that the spectacular reorganization of Andean space and the progressive dilapidation of Spain's real economy not only signified the rise and demise of a trans-Atlantic, Iberian ecological regime, but also generated the historically necessary conditions for the unprecedented concentration of accumulation and commodity production in the capitalist North Atlantic in the centuries that followed. [source] Tinctorial Properties of Zygomycosis in Cutaneous Biopsy SpecimensJOURNAL OF CUTANEOUS PATHOLOGY, Issue 1 2005A. Rubin It is a little known fact that the organisms causing Zygomycosis are often better visualized with routine Hematoxylin and Eosin (H and E) staining than Periodic Acid Schiff (PAS) staining. Experienced dermatopathologists, when evaluating histologic samples suspected of harboring deep fungal infection often rely more heavily on PAS staining to detect fungi. The diagnosis of Zygomycosis may be delayed or missed entirely if sufficient attention is not devoted to the H and E stained specimen. A review of multiple dermatopathology textbooks shows there is no universal agreement on the usefulness of routine H and E staining versus use of special stains for the detection of Zygomycosis. Grocott's Methanamine Silver (GMS) staining can give false negative results if background staining of reticulum fibers is enhanced. This can occur because of overexposure in silver solution, excessive heat during processing, or use of incorrectly titrated solutions. Three consecutive culture proven cases of cutaneous Zygomycosis infection were evaluated. In each case, organisms were clearly visualized on routine H and E sections while PAS staining was variable. Examples of false negative GMS staining are also shown. Recognition of these staining properties can help dermatopathologists better detect the agents of Zygomycosis. [source] Novel microfibrous-structured silver catalyst for high efficiency gas-phase oxidation of alcoholsAICHE JOURNAL, Issue 6 2010Jiping Mao Abstract Novel microfibrous-structured silver catalysts were developed for gas-phase selective oxidation of mono-/aromatic-/di-alcohols. Sinter-locked three-dimensional microfibrous networks consisting of 5 vol % 8-,m-Ni (or 12-,m-SS-316L) fibers and 95 vol % void volume were built up by the papermaking/sintering processes. Silver was then deposited onto the surface of the sinter-locked fibers by incipient wetness impregnation method. At relatively low temperatures (e.g., 380°C), the microfibrous-structured silver catalysts provided quite higher activity/selectivity compared to the electrolytic silver. The microfibrous Ag/Ni-fiber offered much better low-temperature activity than the Ag/SS-fiber. The interaction at Ag particles and Ni-fiber interface not only visibly increased the active/selective sites of Ag+ ions and Agn,+ clusters but also significantly promoted their low-temperature reducibility and ability for O2 activation. In addition, the microfibrous structure provided a unique combination of large void volume, entirely open structure, high thermal conductivity and high permeability. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] | ||||||||||||||||||||||||||||||||||||||||||||||