50,366 research outputs found
The Politics of Regulation: Adolescent Mothers and the Social Context of Resiliency
No full textThe experiences of adolescent mothers have too often been reduced to patterns of correlation linking teenage parenthood with low educational attainment, persistent poverty and continued welfare dependency. These analyses have reinforced representation of an "undeserving poor" and the tendency to "blame the victim" for her structural condition and her dependence on the state. Researchers in adolescent development have attempted to move beyond pathologizing frameworks by considering the "resiliency" of young mothers; yet their contributions have been limited by the tendency to reduce experience to the level of psychological coping mechanisms. In this article, I build upon more recent work as I explore the multifaceted ways in which resiliency can be interpreted. Drawing form the experiences of adolescent mothers within the care of the child welfare system, I illustrate empirically that resiliency is not an intrinsic, psychological characteristic but rather, shifts in relation to particular social contexts and policies.This article was published in Voices. The published version is available at: http://onlinelibrary.wiley.com/doi/10.1111/j.1548-7423.2008.tb00040.x/abstrac
Spaces of Encounter: Public Bureaucracy and the Making of Client Identities
No full textThis article was published in ETHOS: Journal of the Society for Psychological Anthropology. The published version is available at: http://onlinelibrary.wiley.com/doi/10.1111/j.1548-1352.2010.01145.x/abstrac
Minding the Gap: Adolescent Mothers Navigate Child Welfare
No full textThis article was published in Social Service Review. The published version is available at: http://www.jstor.org/stable/10.1086/59571
Silver City, Fourth of July Parade
No full textMoving north on Bullard Street between Broadway and Yankie. From far left: Borenstein Bros.; Silver City National Bank; Schiff’s Emporium; E. Cosgrove Hardware; M. F. Downes & Co. grocery; New Mexico Cigar Co.8 bit; 697 ppi; ScanMaker 9800X
Nanoscale silver: Thin-film structure and antimicrobial functionality
No full textSince antiquity, silver has been used as a material to reduce spoilage. Over the past decades, there has been an increasing scientific and commercial interest in developing silver surfaces due to the increasing number of drug resistant microorganisms. In this study, the effect of nanostructuring silver films as an antimicrobial against the bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was examined. Films consisting of 3 nm chromium adhesion layers and nominal 20 nm silver surfaces (assuming flat deposition) were deposited by thermal evaporation and nanostructuring was controlled by varying the incident angle of the silver onto the substrate. Four substrate angles were used including 0 °, 18 °, 40 ° and 70 ° to the horizontal. Examination by atomic force microscope, Rutherford backscattering and ellipsometry showed that as the incident angle of deposition increased, so did the nanostructuring and surface roughness. This was coupled with a decrease in film thickness. Incubation of the nanostructured thin-films in bacterial broths with E. coli and S. aureus showed that as the surface roughness increased the antimicrobial activity was enhanced – both in solution and for bacteria adhered to the thin-films. Inductively coupled plasma mass spectrometry was used to measure silver leaching from the thin-films and showed a negligible loss for all films, with corresponding low-levels of antimicrobial activity. Further indicating the enhancing effect of nanostructuring as an antimicrobial. All thin-films showed biological fouling after prolonged exposure to the bacterial solutions, which reduced antimicrobial activity. Cleaning the films with IPA showed that the films could be regenerated but with some loss of antimicrobial activity. The mechanism of thin-film antimicrobial activity is at this time unknown but it is speculated that nanostructuring is capable of penetrating the cell envelopes of bacteria, which enhances the antimicrobial activity of silver
Production of silver-loaded zeolites and investigation of their antimicrobial activity
No full textA thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of PhilosophyThe production of silver-loaded zeolites either by ion exchange method or by isomorphous substitution of silver ions into zeolites frameworks and their antimicrobial activity is presented. Silver-loaded zeolites produced by ion-exchange in this work include silver-exchanged zeolite X, silver-exchanged zeolite A and silver-exchanged high-alumina Phillipsite. Silver-doped Analcime was produced by isomorphous substitution of silver ions into the Analcime framework. The silver-loaded zeolites were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, particle size analysis and Fourier transformed infrared (FTIR) spectroscopy. Studies showed that the amount of silver ions loaded into the zeolites frameworks differed for each zeolite. XRD analysis showed little or no changes in the phase purity of all zeolites before and after ion exchange or before and after substitution of silver ions. SEM analysis and particle size analysis showed that the morphology of each zeolite particles was closely related before and after ion exchanged or before and after substitution of silver ions. The antimicrobial activity of these silver-loaded zeolites was investigated by exposing Escherichia coli K12W-T, Staphylococcus aureus NCIMB6571 and Pseudomonas aeruginosa NCIMB8295 suspended in tryptone soya broth (TSB) to the silver-loaded zeolites. The first stage of the investigation involved the exposure of the strains to silver-loaded zeolites in TSB for a duration of 24 hours at different concentration of silver-loaded zeolites. The second stage involved the exposure of the strains to silver-loaded zeolites in TSB over a period of two hours. The persistency of antimicrobial activity of silver-loaded zeolites was investigated by retrieving each silver-loaded zeolite from the first exposure cultures, washed copiously with de-ionised water and adding to fresh bacterial suspensions. To understand the mode of antimicrobial activity of the silver-loaded zeolites, the uptake of silver ions by the strains, composition of fatty acid, as well as the DNA content of Escherichia coli K12W-T was studied. The results obtained showed silver ions appeared to elute from the zeolites frameworks into the TSB in anomalous trend. All three microorganisms were completely inhibited within one hour with the silver-loaded zeolites retaining their antimicrobial activity. The release of silver ions from the zeolites frameworks followed first-order kinetics with varying rate constants and half-lives. The fatty acid composition of all strains as well as the DNA content of Escherichia coli K12W-T were affected by the action of silver ions
Effect of silver content on the structure and antibacterial activity of silver-doped phosphate-based glasses
No full textStaphylococcus aureus can cause a range of diseases, such as osteomyelitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of S. aureus biofilms. Silver was found to be an effective bactericidal agent against S. aureus biofilms, and the rate of silver ion release (0.42 to 1.22 µg·mm–2·h–1) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer (20 µm) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its +1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (+2 or +3). Analysis of the glasses by 31P nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat S. aureus biofilm infections
An investigation into the effect of fabrication parameter variation on the characteristics of screen printed thick film silver/silver chloride reference electrodes
No full textPurpose – the purpose of this paper is to show how the fabrication parameters of screen-printed thick-film reference electrodes have been experimentally varied and their effect on device characteristics investigated.Design/methodology/approach – the tested devices were fabricated as screen-printed planar structures consisting of a silver back contact, a silver/silver chloride interfacial layer and a final salt reservoir layer containing potassium chloride. The fabrication parameters varied included deposition method and thickness, salt concentration and binder type used for the final salt reservoir layer. Characterisation was achieved by monitoring the electrode potentials as a function of time following initial immersion in test fluids in order to ascertain initial hydration times, subsequent electrode drift rates and useful lifetime of the electrodes. Additionally, the effect of fabrication parameter variation on electrode stability and their response time in various test media was also investigated.Findings – results indicate that, although a trade-off exists between hydration times and drift rate that is dependent on device thickness, the initial salt concentration levels and binder type also have a significant bearing on the practical useful lifetime. Generally speaking, thicker devices take longer to hydrate but have longer useful lifetimes in a given range of chloride environments. However, the electrode stability and response time is also influenced by the type of binder material employed for the final salt reservoir layer.Originality/value – the reported results help to explain better the behaviour of thick-film reference electrodes and contribute towards the optimisation of their design and fabrication for use in solid-state chemical senso
In vitro evaluation of the impact of silver coating on Escherichia coli adherence to urinary catheters
No full textA silver-coated urinary catheter was compared to a non-silver-coated urinary catheter for the ability to reduce adherence of 6 isolates of Escherichia coli. Catheters were incubated with E. coli strains for 0, 24, 48, and 72 h. Broth was sampled at all time points to determine CFU/mL. Catheters were subjected to sonication to determine adhered bacteria at all time points, and scanning electron microscopy (SEM) to semi-quantitatively assess biofilm formation. Silver-coated catheters had significantly less adhered bacteria than non-silver-coated catheters at times 24, 48, and 72 h. Subjectively, silver-coated urinary catheters had less biofilm formation than non-silver-coated urinary catheters as assessed by SEM. Silver coating of catheters was associated with reduced adherence of E. coli in an in vitro evaluation. Testing of catheters in dogs in vivo is required to determine if there is a reduction in catheter-associated urinary tract infections.journal articleresearch support, non-u.s. gov't2015 Mayimporte
Persistence of recombinant bacteria to antimicrobial silver
No full textSilver, owing to its effective antimicrobial properties, has been used against a broad range of microorganisms. Silver is now utilized commonly in numerous consumer products, medical devices and clinical applications. However, the mechanism of action of the silver is not yet fully established and well-understood. In addition, it is also important to understand the biochemical and evolutionary pathways that give rise to resistance. Here, we report new genetic determinants for silver resistance in E. coli and explore aspects of their mechanism and laboratory evolution.
Initial exploration of the antimicrobial activity of silver showed that (1) antimicrobial ability of silver is time and dose-dependent; (2) Ag ions have much more antibiotic activity than silver nanoparticles (AgNPs) and (3) the antimicrobial ability of AgNPs is size-dependent. Further selection for resistance genes of E. coli using AgNO3 and AgNPs led to the identification of several candidates, including cysD and ycdB, which displayed cross-resistance to Ag ion and AgNPs as well as Cu+ and Cd2+. The genes cysD and ycdB conferred less resistance to metallic Ag(0) under anaerobic incubation than aerobic incubation. These results support that Ag+ ions are the main toxic agents of AgNPs. These novel anti-silver genes also endowed resistance to the antibiotics kanamycin and ampicillin; in these experiments, antibacterial synergy between kanamycin and silver, but not between ampicillin and silver, was also found. Quantification of oxygen radicals suggest that silver ion is bactericidal through production of reactive oxygen species and that silver-resistance genes prevent their generation.
The selected gene ycdB and control gene cueO, both of which led to increased silver resistance, encode Tat-dependent proteins, which are transported after folding from cytoplasm to periplasm. Chapter 2 focuses on several Tat-containing genes, which also gave more resistance to Ag ion. The 7 selected Tat sequence genes, including torA, yedY, sufI, ycdO and hybA, were recombinantly expressed in various truncated forms, showing that for ycdB and yedY deleting Tat sequences impaired export and silver-resistance ability, despite increased expression, but that for other Tat genes deleting Tat had little effect on either periplasmic translocation or resistance. In all cases, expression of the Tat export sequence alone or with the his-tag in absence of the gene led to suppression of resistance.
Finally, we explored the evolvability of selected genes, such as yeaO, ydgT, iscA and ycdB for silver-resistance. Evolved mutants of yeaO and ydgT were found that endowed increased resistance to silver compared to wildtypes. In these two cases, increased resistance to silver did not lead to increased antibiotic resistance. In short, several kinds of anti-silver genes were identified in our studies, showing various pathways rendering resistance to silver. Weak resistance functions for some genes were evolvable. Our studies provide a deeper insight into silver’s mechanism of action and of the possible resistance pathways in bacteria, which may in some cases lead also to cross-resistance to antibiotics
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