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At least 631 records · Page 35Linked to original sources
PubMed2005

Single-file electrophoretic transport and counting of individual DNA molecules in surfactant nanotubes.

We demonstrate a complete nanotube electrophoresis system (nanotube radii in the range of 50 to 150 nm) based on lipid membranes, comprising DNA injection, single-molecule transport, and single-molecule detection. Using gel-capped electrodes, electrophoretic single-file transport of fluorescently labeled dsDNA molecules is observed inside nanotubes. The strong confinement to a channel of molecular dimensions ensures a detection efficiency close to unity and identification of DNA size from its linear relation to the integrated peak intensity. In addition to constituting a nanotechnological device for identification and quantification of single macromolecules or biopolymers, this system provides a method to study their conformational dynamics, reaction kinetics, and transport in cell-like environments.

Bacteriophage phi X 174↗
PubMed2001

Luis Simarro Lacabra [1851-1921]: from Golgi to Cajal through Simarro, via Ranvier?

Knowledge of cerebral structure and function in its modern form can be traced to the neurone doctrine based largely on the work of Santiago Ramón y Cajal [1852-1934] and his lifelong exploitation of the Golgi method. Cajal openly acknowledged his debt to the neuropsychiatrist Luis Simarro Lacabra [1851-1921] who introduced him to the method in 1887, and recalled that the sight of the silver-impregnated nerve cells was the turning point which led him to abandon general anatomy and concentrate on neurohistology. Simarro, who dissipated his free time in trying to improve not only the scientific but also the political world around him, was able to produce exciting Golgi preparations of the cerebral cortex after he returned from voluntary exile in Paris from 1880 to 1885. Certainly it was there that he learned the methods of experimental histology from Louis-Antoine Ranvier [1835-1922] whose laboratory exercises, in the guise of lectures, he attended assiduously.

Chromates↗
PubMed2005

Development and testing of a silver chloride-impregnated activated carbon for aqueous removal and sequestration of iodide.

Silver impregnated activated carbon (SIAC) can effectively remove iodide from water and sequester it in the form of AgI(s)). Given the extremely insoluble nature of AgI(s), the spent SIAC can be safely disposed of in land burial facilities. However, when the molar ratio of silver to iodide is greater than one, which is typical for waters contaminated with iodide, unreacted silver on the SIAC leached into solution with decreasing pH. To minimize silver leaching, a silver chloride impregnated activated carbon (SIAC-Cl) was produced from a SIAC. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-Ray Diffraction (XRD) analyses confirmed the presence of silver chloride on the SIAC-Cl. Batch isotherm experiments conducted at pH 5, 7 and 8 showed that the iodide uptakes of SIAC-Cl and SIAC were similar and independent of pH. SEM/EDX and XRD analyses after reaction with iodide indicated that chloride was exchanged with iodide to form AgI(s) on the SIAC-Cl. Batch leaching experiments demonstrated that leaching of silver from SIAC-Cl under acidic conditions was significantly lower than from SIAC. The performance of SIAC and SIAC-Cl for practical applications was evaluated by conducting column experiments using a radioactively contaminated groundwater that included 129I. SIAC and SIAC-Cl showed similar degrees of iodide uptake. However, a significant degree of silver leaching, about 50% of the total silver, occurred from the SIAC during the course of the column experiments, whereas silver leaching from SIAC-Cl was remarkably low (only 6% of the total silver). SIAC-Cl appears to be a suitable getter material to remove and sequester iodide from contaminated waste streams.

Adsorption↗
PubMed2002

A simulation method of the reduction of nitrogen oxides over a silver aluminate catalyst in static tests of combustion engines.

The paper presents a proposition of simulation studies of nitrogen oxide catalytic reduction. The method enables estimating the influence of catalytic reactors on ecological properties of engines in static bench tests (e.g., ECE R49, United Nations Economic Commission for Europe [UN/ECE], 2000; Standard No. ISO 8178-4:1996, International Organization for Standardization [ISO], 1996; Merkisz (1998). An algorithm of simulation studies is shown. A model catalytic reactor for selective catalytic reduction is described. Silver aluminate deposited on steel substrate covered with aluminium phosphate is used as a catalyst. Propene is used as a reductant. The results of reactor studies in a chemical lab are presented. A simulation of the influence of catalytic reactor properties on ecological properties of an engine was done. Unitary emission conversion coefficients of nitrogen oxide in a static test ECE R49 were determined.

Algorithms↗
PubMed2000

Healing of porcine donor sites covered with silver-coated dressings.

OBJECTIVE: To compare rates of healing of donor sites in pigs between those dressed with silver-coated dressings and those dressed with petrolatum-impregnated absorbent gauze. DESIGN: Open study with each animal acting as its own control. SETTING: University research facility, Canada. ANIMALS: 6 young specific-pathogen-free domestic pigs. INTERVENTIONS: A total of 72 wounds about 1 cm x 2 cm x 0.4 mm were made in rows of eight on each pig with a dermatome. They were divided into three groups of 24, and dressed with petrolatum gauze, or silver-coated dressings moistened with sterile water either once only or daily for 10 days. All dressings were secured in place with an elastic bandage. MAIN OUTCOME MEASURES: Erythema, infection, epidermal migration, and healing. RESULTS: Wounds dressed with moistened silver-coated dressings re-epithelialised significantly more quickly. This resulted in complete re-epithelialisation within 70% of the time taken by those wounds dressed with petrolatum gauze. CONCLUSION: Silver-coated dressings provide a moist environment for the healing wound combined with an effective antimicrobial agent, and this significantly accelerates healing compared with wounds dressed with traditional petrolatum gauze dressings.

Animals↗
PubMed2002

Biosensor for the enantioselective analysis of the thyroid hormones (+)-3,3',5-triiodo-L-thyronine (T3) and (+)-3,3',5,5'-tetraiodo-L-thyronine (T4).

An amperometric biosensor based on L-aminoacid oxidase is proposed for enantioselective assay of (+)-3,3',5-triiodo-L-thyronine (L-T3) and (+)-3,3',5,5'-tetraiodo-L-thyronine (L-T4), due to the fact that only the L enantiomer has the hormonal activity. The construction of the amperometric biosensor is simple and reproducible. The analytical information obtained from enantioselective analysis are reliable. The RSD <1% assured by using the amperometric biosensors for L enantiomers assay as raw materials, and from tablets, demonstrated their suitability for the analysis of T3 and T4 at ppb concentration levels.

Amino Acid Oxidoreductases↗
PubMed2006

Physical mechanism of the Schwarzschild effect in film dosimetry--theoretical model and comparison with experiments.

In consideration of the importance of film dosimetry for the dosimetric verification of IMRT treatment plans, the Schwarzschild effect or failure of the reciprocity law, i.e. the reduction of the net optical density under 'protraction' or 'fractionation' conditions at constant dose, has been experimentally studied for Kodak XOMAT-V (Martens et al 2002 Phys. Med. Biol. 47 2221-34) and EDR 2 dosimetry films (Djouguela et al 2005 Phys. Med. Biol. 50 N317-N321). It is known that this effect results from the competition between two solid-state physics reactions involved in the latent-image formation of the AgBr crystals, the aggregation of two Ag atoms freshly formed from Ag(+) ions near radiation-induced occupied electron traps and the spontaneous decomposition of the Ag atoms. In this paper, we are developing a mathematical model of this mechanism which shows that the interplay of the mean lifetime tau of the Ag atoms with the time pattern of the irradiation determines the magnitude of the observed effects of the temporal dose distribution on the net optical density. By comparing this theory with our previous protraction experiments and recent fractionation experiments in which the duration of the pause between fractions was varied, a value of the time constant tau of roughly 10 s at room temperature has been determined for EDR 2. The numerical magnitude of the Schwarzschild effect in dosimetry films under the conditions generally met in radiotherapy amounts to only a few per cent of the net optical density (net OD), so that it can frequently be neglected from the viewpoint of clinical applications. But knowledge of the solid-state physical mechanism and a description in terms of a mathematical model involving a typical time constant of about 10 s are now available to estimate the magnitude of the effect should the necessity arise, i.e. in cases of large fluctuations of the temporal pattern of film exposure.

Bromides↗
PubMed1992

Optimal electrolytic chloriding of silver ink electrodes for use in electrical impedance tomography.

The electrode-electrolyte interface impedance may be simplistically modelled by an equivalent circuit comprising a resistance, RTOTAL, in series with an empirical, constant phase angle impedance, ZCPA. This pseudo-capacitance can be thought of as representing empirically the non-faradaic, double layer capacitance in the presence of specific adsorption and surface roughness effects. RTOTAL is the sum of the lead and electrolyte resistances. Depositing a thin layer of silver chloride on silver electrodes can yield improved electrical performance characteristics (potential and impedance) when used in conjunction with a chloride gel. An electrolytically deposited AgCl layer tends to have a rough surface profile thus leading to an increase in the effective interface area. This gives rise to a decrease in RTOTAL and ZCPA, both of which are desirable. Unfortunately AgCl is a relatively poor conductor. Increasing layer thickness causes RTOTAL to increase, thus adversely affecting the inter-electrode impedance at high frequencies. Electrode systems for use in electrical impedance tomography therefore require only relatively thin layers of AgCl.

Electric Conductivity↗
PubMed2001

Study on acid resistance of human dental enamel and dentin irradiated by semiconductor laser with Ag(NH3)2F solution.

OBJECTIVE: The purpose of this study was to investigate the acquired acid resistance of human dental enamel and dentin treated by 38% diamine silver fluoride [Ag(NH3)2F] solution and semiconductor (diode) laser irradiation in vitro. BACKGROUND DATA: There have been no reports on the acid-resistant effect by combined use of fluoride and semiconductor laser. METHODS: Sixty crowns of extracted human molars were divided into two groups for enamel and dentin samples, and each group was subdivided into three subgroups of 10 each. Each subgroup of enamel and dentin samples served as a control; one was treated with Ag(NH3)2F and the other was treated with Ag(NH3)2F and semiconductor laser irradiation at 2 W for 30 sec. Then all samples were immersed in 5 ml of 0.1 M lactic acid (pH 4.8) at 37 degrees C for 24 h. The concentration of calcium ion (Ca2+) dissolved in the solution was measured by atomic absorption spectrophotometry, and the samples were observed by stereoscopy and scanning electron microscopy (SEM). RESULTS: In both enamel and dentin samples, dissolved Ca2+ concentration in Ag(NH3)2F- or Ag(NH3)2F- and laser-treated group was significantly decreased compared with that in the control (p < 0.01). SEM findings showed that numerous cubic particles ranging from 0.1 to 0.5 mcirom were observed only in the combined treated groups of both enamel and dentin samples. CONCLUSIONS: A significantly decreased solubility of human enamel and dentin was acquired after treatment by Ag(NH3)2F and semiconductor laser irradiation, which suggested that this combined use has the capability of a more efficient acid-resistant effect on human dental hard tissues.

Cariostatic Agents↗
PubMed1990

Prevention of catheter-associated urinary tract infection with a silver oxide-coated urinary catheter: clinical and microbiologic correlates.

In a prospective clinical trial involving 482 acutely hospitalized patients, the overall incidence of catheter-associated urinary tract infection (UTI; 10%) was similar in recipients of a silver oxide-coated urinary catheter (silver catheter) or a control silicone catheter. However, female sex and absence of antimicrobial use were independently associated with an increased risk of UTI. After stratification for these variables, the silver catheter reduced the incidence of UTI among women not receiving antimicrobial agents (19% for control catheter vs. 0 for silver catheter, P = .04; confidence interval for the difference in incidence, 0.4%-38%) but not in the other subgroups. Gram-positive UTI was associated with absence of antimicrobial use, the control catheter, and catheter care violations. Gram-negative and candidal UTIs were more common after 7 days of catheterization, and candidal UTI was associated with being female and antimicrobial use. These findings demonstrate that several clinical variables influenced the incidence and microbiology of catheter-associated UTI and that the silver catheter appeared to prevent UTI among women not receiving antimicrobials.

Adult↗
PubMed2006

Silver-containing dressings and the need for evidence.

The field of wound care has been inundated with "active" dressings--those that deliver biologically active substances to the wound site--and much attention has been given to those containing silver. Silver is a broad-spectrum agent: it is bactericidal to a large number of Gram-positive and Gram-negative microorganisms, many aerobes and anaerobes, and several antibiotic-resistant strains. More than 10 dressings containing pure silver are currently available; all claim to enhance wound healing through the antimicrobial activity of silver. But research findings on silver's antimicrobial efficacy are often inconclusive or contradictory. How, therefore, can clinicians decide which dressing is most appropriate for each patient? A grading system for reviewing the literature is presented.

Anti-Infective Agents↗
PubMedDate not supplied

Bladder volume measurement with electrical impedance analysis in spinal cord-injured patients.

The purpose of the study contained herein was to determine the usefulness of electrical impedance for measurement of bladder volume in spinal cord-injured patients, with an assessment of the relationship between electrical impedance and bladder volume exclusively. The study was performed during urodynamic studies to match the exact bladder volume. Thirteen patients with complete spinal cord injuries were recruited. We used silver-silver chloride compound electrodes composed of one pair of current and amplitude electrodes to minimize the influence of superficial skin impedance. Each compound electrode was attached on the lower abdomen bilaterally after skin cleansing. Constant current (60 kHz-1.0 mA), converted from 9 V of direct current, was applied, and corresponding electrical impedance (omega) was measured at "pre" (before urodynamic empty bladder), "full" (with a urodynamic filled bladder), and "post" (after urodynamic empty bladder) status. Electrical impedance at the full status was definitely lower than that at the pre and post statuses in all subjects, with a statistically significant difference (P < 0. 001). The correlation between electrical impedance and bladder volume was negative (r = -0.7988), and the fact of how much the variation in electrical impedance could be explained by variation in bladder volume was estimated (r2 = 0.6381). From these findings, we have determined that the electrical impedance analysis technique can be an alternative measure of bladder volume indirectly.

Adult↗
PubMed2003

Impact of oligon central venous catheters on catheter colonization and catheter-related bloodstream infection.

OBJECTIVE: To evaluate a new antimicrobial treatment for central venous catheters in comparison with a traditional treatment, by assessing the catheter colonization and catheter-related bloodstream infection rates in two groups of patients. DESIGN: Multiple-center, prospective randomized study. SETTING: The medical and surgical departments of ten institutions. PATIENTS: Patients requiring a central venous catheter for medical or surgical pathologies between June 2000 and November 2001. INTERVENTIONS: Patients in the control group received a conventional benzalkonium-treated double-lumen central venous catheter, while patients in the oligon group received an oligon-treated (polyurethane combined with silver, carbon, and platinum) catheter with the same characteristics. Data collection included demographics, preexisting clinical conditions, main pathology, catheter insertion, and management data. Catheter colonization was defined as the growth of > or = 15 colony-forming units in culture of catheter segments by the roll-plate method, or > or = 1000 colony-forming units for the sonication method, and catheter-related bloodstream infection was defined as isolation of the same organism from the colonized catheter and from the peripheral blood of a patient with clinical signs of bloodstream infection. MEASUREMENTS AND MAIN RESULTS: Data were obtained from 545 catheters. Of these, 132 catheters (24.2%) were positive for colonization. Patients in the oligon group demonstrated a lower risk for catheter colonization in the overall population (relative risk, 0.63; 95% confidence interval, 0.46-0.86; p = .003) and in the surgical subgroup (relative risk, 0.5; 95% confidence interval, 0.33-0.76;p = .001). Significant differences between groups were detected for coagulase-negative staphylococci and Gram-negative bacilli colonization rates. Twenty-one patients (3.8%) were positive for catheter-related bloodstream infection, without significant differences between control and oligon groups. CONCLUSIONS: Oligon treatment is effective in limiting the catheter colonization rate. Due to the limited amount of events, this study lacked the power to detect significant differences in terms of catheter-related bloodstream infection rate.

Actuarial Analysis↗