Determination of low sulphide and cyanide levels in biochemical and environmental control using a deposited-on-wire Ag-Ag2S electrode.
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Cyanides↗
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Turbidimetric determination of chloride in different types of water using a single sequential injection analysis system.
A sequential injection analysis system for the turbidimetric determination of chloride in different types of water is proposed. The determination is based on the reaction of chloride with silver ions and the subsequent measurement of the turbidity caused by silver chloride precipitation. In this method, the use of toxic reagents, such as mercury thiocyanate, commonly employed in most spectrophotometric techniques for chloride determination, is avoided. The main feature of the developed system is the use of a single configuration to carry out the determination over a wide concentration range (2-400 mg L(-1)) by changing only the aspirated sample volume. This characteristic allows the determination of chloride in ground, surface and wastewaters using the same manifold. In addition, a considerable saving of precipitating reagent is achieved due to non-continuous consumption. The results obtained with the developed system were statistically indistinguishable from those of the potentiometric titration reference method. Relative standard deviations for ten consecutive injections were lower than 3.7%, with a sampling frequency of between 55 and 57 determinations per hour.
Chemical Precipitation↗
Enhancement of facilitated olefin transport by amino acid in silver-polymer complex membranes.
Silver ions dissolved in a polymer matrix are additionally coordinated by carbonyl oxygens of asparagines and their counter anions interact with cationic sites, resulting in the enhanced activity of the silver ion as an olefin carrier for facilitated olefin transport.
Alkenes↗
Ultrafast nuclear dynamics induced by photodetachment of Ag2- and Ag2O2-: oxygen desorption from a molecular silver surface.
Femtosecond nuclear dynamics of mass-selected neutral Ag2 and Ag2O2 clusters are investigated with the 'negative ion-to neutral-to positive ion'(NeNePo) technique. For the bare silver dimer, wave packet dynamics occurring in the neutral electronic ground state and in the first excited triplet state are observed after photodetachment from the anion with 3.05 eV photon energy. While the dynamics in the ground state lead to an oscillatory structure in the NeNePo-pump-probe spectra with a vibrational constant of 185 cm-1, the dynamics in the triplet state are assigned to a bound-free transition leading to dissociation. Photodetachment from the Ag2O2- complex results in the desorption of O2. The experimental data clearly show the influence of the desorbing oxygen ligand on the nuclear dynamics of the silver dimer inducing a red shift in the vibrational frequency and an intensity enhancement of the oscillatory signal.
Adsorption↗
Homologous, long-chain alkyl dendrons form homologous thin films on silver oxide surfaces.
As suggested by X-ray crystal structures, homologous, long-chain alkyl dendrons with three carboxyl groups form thin films on silver oxide surfaces, which give reflection-absorption infrared spectra that show a linear increase in intensities of methylene C-H stretching absorptions.
Alkylation↗
Selective catalytic reduction of NO over supported silver catalysts--practical and mechanistic aspects.
Selective catalytic reduction of NO by hydrocarbons (HC-SCR) is one of the promising technologies for removal of NO in exhausts containing excess oxygen, such as diesel and lean burn gasoline engines. Supported Ag catalysts, especially Ag/Al2O3, are thought to be the promising candidates for use in diesel exhausts, as confirmed by several reports on engine bench tests. The HC-SCR performance of supported Ag catalysts is very sensitive to the reaction conditions, especially the type of hydrocarbons and the addition of H2. The control of reaction conditions would be key for practical use. The current research of supported Ag catalysts is reviewed from the viewpoints of practical use and the reaction mechanism, i.e., the reaction scheme, the role of surface adsorbed species, and the structure of active Ag species.
Catalysis↗
Optical transition process in AgOx super-resolution near-field structure.
A sandwiched 15 nm AgOx thin film of the super-resolution, near-field optical disk was studied using a confocal Z-scan system. Nonlinear optical properties of quartz glass/ZnS-SiO2 (170 nm)/AgOx (15 nm)/ZnS-SiO2 (40 nm) were measured using a Q-switch Nd : YAG pulse laser of wavelength 532 nm, pulse width 0.7 ns, and 15.79 kHz repetition rate. Transmittance and reflectance of the sandwiched AgOx thin film show important optical responses at the focused position of Z-scan. The dissociation processes of AgOx, recombination of the silver and oxygen, and the resonance of the localized surface plasmon of the nano-composites of the AgOx thin film are correlated to transmittance and reflectance at the focused position of the Z-scan for different input laser powers. An irreversible upper threshold intensity of 4.40 x 106 mW cm-2 at the focused position was found. A reversible working window of the focusing intensity between 1.86 x 106 and 4.40 x 106 mW cm-2 was measured with sandwiched AgOx thin film alone. The near-field interactions of the AgOx thin film and the recording layers of super-resolution near-field optical disk are also discussed.
Energy Transfer↗
Silver and fluoride ion release from metal-reinforced glass-ionomer filling materials.
This study was undertaken to examine whether a relationship exists between the composition of metal-containing glass-ionomer cements and ion release from these materials. Conflicting data on silver release from this type of material has been reported and it was felt that further investigation was desirable in view of the increasing use of these materials. In this study, the release of ions, particularly of silver and fluoride, into deionized water and artificial saliva was measured for up to one year. Low levels of silver and copper ions were found in both media. The amounts released from alloy-containing materials were dependent on the amount of alloy present; lesser amounts were leached from cermets. Fluoride ion release was less material-dependent but still lowest for cermets. The use of artificial saliva reduced ion release as did increasing the maturation time prior to immersion in either liquid.
Aluminum↗
Antibacterial temporary filling materials: the effect of adding various ratios of Ag-Zn-Zeolite.
The effect of a new type of antibacterial temporary filling material was evaluated. Ag-Zn-Zeolite (Bactekiller, Kanebo, Japan) and SiO2 filler were incorporated into urethane acrylate monomer paste in amounts of 5/55, 10/50, 20/40 and 30/30 wt%, respectively. The present study was designed to use a dye penetration test to measure direct inhibition of bacterial growth of four oral bacteria (Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Streptococcus sanguis). The amounts of silver and zinc ions released from these materials were measured by atomic absorption spectrophotometry. The results indicated that the occurrence of marginal leakage was low in all of these materials. These materials exhibited prominent in-vitro antibacterial activity against S. mutans and S. mitis. The Ag-Zn-Zeolite in these materials was able to release very small but detectable amounts of Ag and Zn even 4 weeks after the immersion started. The larger the amounts of Ag-Zn-Zeolite that were incorporated, the greater the release of silver and zinc. However, it appears that increasing antibacterial activity is not promoted by the higher ratio of Ag-Zn-Zeolite.
Acrylic Resins↗
Biodetoxification of silver-cyanide from electroplating industry wastewater.
A bacterial consortium capable of utilizing metal-cyanides as a source of nitrogen was used to develop a microbiological process for the detoxification of silver-cyanide from electroplating wastewater. When the treatment was carried out in a 27-l rotating biological contactor (R3C) in continuous mode, the system could achieve > 99.5% removal of 0.1 mmol l(-1) silver-cyanide (approximately 5 mg l(-1) cyanide and 10 mg l(-1) silver) in 10 h with sugarcane molasses (0.1 ml l(-1)) as carbon source. The silver ions set free during biodegradation were efficiently adsorbed by the bacterial biomass. The RBC-treated effluent was found to be safe for discharge into the environment, as confirmed by chemical analysis and fish bioassay studies.
Animals↗
Argyria in the ED.
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Administration, Oral↗
In vivo resistance to bacterial biofilm formation on tympanostomy tubes as a function of tube material.
Adherent bacterial biofilms have been implicated in the irreversible contamination of implanted medical devices. We evaluated the resistance of various tympanostomy (pressure equalization [PE]) tube materials to biofilm formation using an in vivo model. PE tubes of silicone, silver oxide-impregnated silicone, fluoroplastic, silver oxide-impregnated fluoroplastic, and ion-bombarded silicone were inserted into the tympanic membranes of 18 Hartley guinea pigs. Staphylococcus aureus was then inoculated into the middle ears. An additional 8 guinea pigs were used as controls; the PE tubes were inserted without middle ear inoculation. All PE tubes were removed on day 10 and analyzed for bacterial contamination using culture, immunofluorescence, and scanning electron microscopy (SEM). All infected ears developed otitis media with otorrhea, but none of the animal control ears drained. Fluorescence imaging of the animal control tubes showed large cellular components consistent with inflammation. The infected tubes showed heavy DNA fluorescence consistent with bacteria and inflammatory cells. All animal control tubes except the ion-bombarded silicone tubes showed adherent inflammatory film on SEM. Also, all tubes placed in infected ears except the ion-bombarded silicone tubes showed adherent bacterial and inflammatory films on SEM. Nonadherent surface properties such as the ion-bombarded silicone may be helpful in preventing chronic PE tube contamination.
Animals↗
Randomized multi-centre trial of the effects of a catheter coated with hydrogel and silver salts on the incidence of hospital-acquired urinary tract infections.
Catheters coated with hydrogel and silver salts have been proposed to prevent hospital-acquired urinary tract infections (UTI). We carried out a randomized, prospective, double-blind multi-centre trial to compare those catheters with classical urinary tract catheters. We included in the study 199 patients requiring urethral catheterization for more than three days: 109 in group 1 (classical catheter) and 90 in group 2 (catheter coated with hydrogel and silver salts). Urine from the patients was tested for 10 days after the insertion of the catheter (reactive dipsticks each day and diagnostic urinalysis every two days). The UTI associated with catheterization was defined on the basis of bacterial and cytological criteria (>10(5)cfu bacteria per mL and >10 leucocytes per mm(3)). Twenty-two UTIs were recorded: 13 in group 1 and nine in group 2. The cumulative incidence of UTI associated with catheterization was 11.1% overall, 11.9% for group 1 and 10% for group 2; the odds ratio was 0.82 (95% confidence interval: 0.30 to 2. 20); the cumulative incidence for UTI, calculated by the Kaplan-Meier method was 36.3 overall, 35.2 in group 1 and 36.0 in group 2; the overall incidence density was 19 per thousand days of catheterization, 21 in group 1 and 18 in group 2. The differences between the two groups were not significant. Overall, we feel that there is not enough evidence to conclude that catheters coated with silver salts and hydrogel give greater protection than classical catheters and to recommend widespread use.
Coated Materials, Biocompatible↗
Antibacterial properties of a silver chloride-coated nylon wound dressing.
OBJECTIVE: A silver chloride-coated nylon wound dressing (Ag-WD) was evaluated in vitro for antimicrobial activity against five common equine wound pathogens. STUDY DESIGN: Bacterial susceptibility study. SAMPLE POPULATION: Equine wound pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus equi subspecies zooepidemicus, and Staphylococcus aureus. METHODS: An inoculum of each pathogen was incubated directly with Ag-WD and quantitated after 24 to 48 hours of incubation. To determine if bactericidal activity of Ag-WD was contact dependent, an inoculum of E. coli and Staphylococcus aureus was incubated separately from Ag-WD by a filter and quantitated after 18 hours of incubation. Inductively coupled plasma emission spectrometry (ICP) determined the silver concentration of Mueller-Hinton broth containing Ag-WD after 24 hours of incubation. To establish if the rate of bacterial killing by Ag-WD differed from a constant silver concentration, pathogens were exposed to a silver concentration of 6.45 microg/mL and quantitated after 18 hours. RESULTS: Direct exposure to Ag-WD significantly reduced bacterial numbers after 15 minutes for K. pneumoniae, 30 minutes for E. coli, 1 hour for P. aeruginosa, and 2 hours for S. equi subspecies zooepidemicus and Staphylococcus aureus. Indirect exposure to Ag-WD resulted in > or =99.9% and > or =90% kill of the inoculum doses of E. coli at 2 hours and Staphylococcus aureus at 18 hours, respectively. Incubation of the pathogens at the constant silver concentration resulted in bacterial killing rates similar to those obtained by incubation with Ag-WD. CONCLUSIONS: In vitro, equine pathogens are effectively killed when exposed to Ag-WD, and the rate of bacterial killing by Ag-WD is similar to a constant silver concentration of 6.45 microg/mL. CLINICAL RELEVANCE: The in vitro antimicrobial properties of this silver-coated nylon wound dressing are promising for future prevention of equine wound infections.
Animals↗
New silver polypyridyl complexes: synthesis, characterization and biological activity on Leishmania mexicana.
Leishmania parasites are the causal agents of leishmaniasis that currently threatens 350 million people in 88 different countries, in the absence of an effective drug. In order to continue the development of transition metal complexes with planar ligands that show interactions with DNA and activity against Leishmania parasites, the synthesis of the complexes [Ag(dpq)2]NO3 (1) and [Ag(dppz)2]NO3 (2), which were obtained by the reaction of silver nitrate with dpq and dppz, respectively, in a 1:2 molar ratio is reported. These complexes were characterized by elemental analysis and 1H-NMR, IR, and UV-vis spectroscopies. The most probable structure for these complexes is tetrahedral, with two molecules of ligand coordinated to the silver atom and a nitrate as a counter ion. Affinity studies of DNA vs. bovine albumin were carried out, and a strong interaction of the complexes with DNA was observed. Bioassays were undertaken in vitro on promastigotes of Leishmania (L.) mexicana exposed to the silver complexes for 48 h. At 10 micromol/L complex 2 induced a leishmanicidal effect (LD23), whilst complex 1 reduced the parasites growth rate by 55% (LD55). These findings suggest that biological activity could be associated with the interaction of the complexes with the parasitic DNA.
Animals↗
[Comparison of gold-plated silver- and silver oxide-impregnated silastic tympanostomy tubes: a randomized, prospective clinical trial].
UNLABELLED: The insertion of tympanostomy tubes is the most common surgical procedure in the world. A major complication of chronic intubation is infectious otorrhea. The present study compares the rate of infectious otorrhea and survival rate of gold-plated silver tubes (GPR) vs. Silver Oxide-Impregnated Silastic Tubes (SPR). STUDY DESIGN: The prospective, randomized clincial trial was conducted with 116 children (59 female, 57 male) aged between 16 and 127 months (median: 51 months). Bilateral insertion of ventilation tubes was performed with SPR on one side and GPR on the other side in all children. The resulting data were compared using 2-tailed Wilcoxon-test. RESULTS: Out of 116 children, 11 left the study, 26 children finished the study by extrusion of both tubes, 32 children lost one tube and 47 children lost no tube. Total follow-up of GPR and SPR amounted to 703 and 949 months, respectively. Mean survival rate of SPR and GPR was 9.9 +/- 4.6 and 7.0 +/- 3.4 months, respectively (p < 0.001). During the first postoperative week, 13% of children suffered from otorrhea; after the first postoperative week until extrusion of the tubes, otorrhea was observed in 55% of children. The ratio otorrhea/months amounted to 0.046 and 0.05 in SPR and GPR, respectively (p: n. s.). CONCLUSIONS: Survival rate of SPR is significantly longer than compared to GPR. No differences in the otorrhea rate of SPR vs. GPR are detectable. The longer survival rate of SPR seems to be independent of the rate of infectious otorrhea but depends probably on other effects of biocompatibility.
Anti-Infective Agents↗
[Clinical use of a voice prosthesis with a flap valve containing silver oxide (Blom-Singer Advantage), biofilm formation, in-situ lifetime and indication].
BACKGROUND: Fungal growth and the resulting leakage through an indwelling voice prosthesis remains the most frequent reason of prosthesis failure and renewal. In some patients leakage caused by fungal growth occurs in very short intervals (below 12 weeks in-situ lifetime) and causes frequent treatments and high costs. METHODS: The Blom-Singer(R) Advantage voice prosthesis is a new prosthesis type with a modified flange design, a flap valve containing 7 % silver oxide in the silicon matrix and is expected to be resistant against biofilm formation and fungal growth. PATIENTS: In a clinical trial we used the Blom-Singer(R) Advantage prosthesis in 33 patients with short in-situ lifetimes of their voice prosthesis and analysed the effects on in-situ lifetime and complications statistically. RESULTS: The clinical use of the Blom-Singer(R) Advantage prosthesis was similar to other types of indwelling voice prosthesis (Provox(R) II, Blom-Singer Indwelling(R)) and did not cause any special problems. Prosthesis specific side effects (i. e. allergy against silver oxide) did not occur. Statistical analysis of the aquired data showed an interindividually changing, but significantly longer in-situ lifetime for the Blom-Singer(R) Advantage prosthesis. The mean device lifetime increased from 36 days (median 36 days) to a mean lifetime of 110 days (median 87 days) with the use of the Blom-Singer(R) Advantage prosthesis. CONCLUSIONS: Using a voice prosthesis with a valve containing silver oxide can normalize and even increase the in-situ lifetime in patients with frequent changing procedures caused by fungal growth on the valve. Therefore we recommend the use of this type of voice prosthesis for those patients as reduction of costs and effort results.
Aged↗
The effect of thermocycling on the fracture toughness and hardness of core buildup materials.
STATEMENT OF PROBLEM: Thermocycling has been shown to cause surface degradation of many dental materials, but its effect on the fracture toughness and hardness of direct core buildup materials is unknown. PURPOSE: This study was designed to determine the effect of thermocycling on the fracture toughness and hardness of 5 core buildup materials. MATERIAL AND METHODS: Fifteen specimens were prepared from each of the following materials: Fluorocore, VariGlass VLC, Valiant PhD, Vitremer, and Chelon-Silver. American Standard for Testing Materials guidelines for single-edge notch, bar-shaped specimens were used. Ten specimens of each material were thermocycled for 2000 cycles; the other 5 specimens were not thermocycled. All specimens were subjected to 3-point bending in a universal testing machine. The load at fracture was recorded, and the fracture toughness (K(IC)) was calculated. Barcol hardness values were also determined. Data were analyzed with 1-way analysis of variance and compared with the Tukey multiple range test (P<.05). Pearson's correlation coefficient was also calculated to measure the association between fracture toughness and hardness. RESULTS: Fluorocore had the highest thermocycled mean K(IC) and Valiant PhD the highest non-thermocycled K(IC). Chelon-Silver demonstrated the lowest mean K(IC) both before and after thermocycling. One-way analysis of variance demonstrated significant differences between conditions, and the Tukey test showed significant differences (P<.05) between materials for both conditions. Most specimens also showed significant hardness differences between conditions. Pearson's correlation coefficient indicated only a mild-to-moderate correlation between hardness and fracture toughness. CONCLUSION: Within the limitations of this study, the thermocycling process negatively affected the fracture toughness and hardness of the core buildup materials tested.
Acrylic Resins↗