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Boulton and Fothergill silver.
No full textPhDThis thesis is about the silver business of Matthew Boulton and John
Fothergill at their Soho Manufactory near Birmingham. Their
partnership lasted from 1762 until 1782.
A rounded discussion of the topic is attempted. Within the contexts
of industry elsewhere and Soho's other activities, successive chapters
cover the early development, marketing, production, design, and later
decline of the partners' silver.
Silver plate was prestigious and, untypically for Boulton, he
concentrated on sales to the public rather than trade customers. To
attract orders he made modest charges. This was viable where mainly
machinery was used to make plate, even though sales were not high,
since the expense of machinery was substantially covered by the larger
sales of non-silver items. However, where Boulton relied to a
greater degree upon hand methods, he lacked technical means to
compensate for low profit-margins. Moreover, inefficiency and the
firm's lack of capital which led to substantial bankers' interest
charges on payment for bullion, particularly when customers paid late,
caused losses. These problems applied particularly to silver plate
and were mainly responsible for the decision to reduce production
drastically; however, the manufacture of a large range of small items
remained relatively consistent.
The thesis includes appendices. Some contain new information about
annual totals for the following aspects of the business: the volume of
assay silver; each type of article; pieces sold on commission; and
sterling silver supplies. Other appendices provide details about the
partners' silversmiths and extracts from a Soho inventory.
This thesis involves a more detailed use of sources than previous
studies of the topic. Apart from the silver itself (which is
selectively illustrated), the Matthew Boulton Papers and statistics
derived from The Birmingham Assay office provide the main sources.
Manuscripts covering silver production elsewhere provide contextual
material for understanding the partners' silver business
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
Cost-Effective Use of Silver Dressings for the Treatment of Hard-to-Heal Chronic Venous Leg Ulcers
No full textAim
To estimate the cost-effectiveness of silver dressings using a health economic model based on time-to-wound-healing in hard-to-heal chronic venous leg ulcers (VLUs).
Background
Chronic venous ulceration affects 1–3% of the adult population and typically has a protracted course of healing, resulting in considerable costs to the healthcare system. The pathogenesis of VLUs includes excessive and prolonged inflammation which is often related to critical colonisation and early infection. The use of silver dressings to control this bioburden and improve wound healing rates remains controversial.
Methods
A decision tree was constructed to evaluate the cost-effectiveness of treatment with silver compared with non-silver dressings for four weeks in a primary care setting. The outcomes: ‘Healed ulcer’, ‘Healing ulcer’ or ‘No improvement’ were developed, reflecting the relative reduction in ulcer area from baseline to four weeks of treatment. A data set from a recent meta-analysis, based on four RCTs, was applied to the model.
Results
Treatment with silver dressings for an initial four weeks was found to give a total cost saving (£141.57) compared with treatment with non-silver dressings. In addition, patients treated with silver dressings had a faster wound closure compared with those who had been treated with non-silver dressings.
Conclusion
The use of silver dressings improves healing time and can lead to overall cost savings. These results can be used to guide healthcare decision makers in evaluating the economic aspects of treatment with silver dressings in hard-to-heal chronic VLUs
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
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Inactivation of the antibacterial and cytotoxic properties of silver ions by biologically relevant compounds
No full textThere has been a recent surge in the use of silver as an antimicrobial agent in a wide range of domestic and clinical products, intended to prevent or treat bacterial infections and reduce bacterial colonization of surfaces. It has been reported that the antibacterial and cytotoxic properties of silver are affected by the assay conditions, particularly the type of growth media used in vitro. The toxicity of Ag+ to bacterial cells is comparable to that of human cells. We demonstrate that biologically relevant compounds such as glutathione, cysteine and human blood components significantly reduce the toxicity of silver ions to clinically relevant pathogenic bacteria and primary human dermal fibroblasts (skin cells). Bacteria are able to grow normally in the presence of silver nitrate at >20-fold the minimum inhibitory concentration (MIC) if Ag+ and thiols are added in a 1:1 ratio because the reaction of Ag+ with extracellular thiols prevents silver ions from interacting with cells. Extracellular thiols and human serum also significantly reduce the antimicrobial activity of silver wound dressings Aquacel-Ag (Convatec) and Acticoat (Smith & Nephew) to Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli in vitro. These results have important implications for the deployment of silver as an antimicrobial agent in environments exposed to biological tissue or secretions. Significant amounts of money and effort have been directed at the development of silver-coated medical devices (e.g. dressings, catheters, implants). We believe our findings are essential for the effective design and testing of antimicrobial silver coatings
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
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
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Silver inhibition on recombinant flavin reductase from Citrobacter freundii A1
No full textIn this study, the flavin reductase (Fre) of Citrobatter freundii A1 was expressed in E. coli DH5a host with 1 mM IPTG induction. This recombinant protein was fused to 6xHis-tag, thus promising easier IMAC purification of the expressed enzyme. Flavin reductase catalyzes the reduction of free flavin using NADH to produce free reduced flavin. The purity of recombinant flavin reductase was observed using 15 % SDS-PAGE and the molecular weight of the target protein was determined to be 27.04 kDa. In this study, flavin reductase activity was measured at 340 nm (e340 = 6.22 mM-1cm-1) due to the oxidation of NADH. The effect of silver ions from silver nitrate (AgNO3) on the activity of flavin reductase was determined. As the concentration of silver ions increased, the relative activity and velocity of flavin reductase reaction decreased over time. Silver ions may inhibit flavin reductase irreversibly via unspecific binding to different amino acids. In conclusion, silver ions could be a potent inhibitor of flavin reductase of C. freundii A1
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