Imaging and spectroscopy of laser-produced colliding plasmas

Laser-produced plasmas are formed when short pulse, high power lasers are focused onto a surface Applications range from VUV / X-ray sources for lithography, microscopy and radiography to X-ray lasers, thin him deposition, analytical spectroscopy and electron / ion beam generation A battery of particle and optical techniques are currently being used to fully characterise the properties of laserproduced plasmas. Over the past forty years much experimental and theoretical / computational work has focussed on the generation and expansion of LPP’s in vacuum Recently however, the dynamics of LPP’s expanding into background gasses has received increased interest This has been driven by the need to control the growth conditions of thin films produced using pulsed laser deposition The dynamics of LPP’s expanding into background gasses are very different from that of the vacuum case and leads to plume splitting and sharpening effects. Although much is known about the properties of laser-produced plasmas expanding in vacuum and into background gasses, very little is known about the expansion and interaction of a LPP into another LPP The aim of this project is the study of this system, colliding laser-produced plasmas Colliding plasma experiments may be cast as a model system for atmospheric and/or astrophysical colliding systems, for example when tracer elements are injected into supersonic winds at high altitude or collisionless plasma interaction in young supernova remnants Colliding plasmas have also been considered as a possible solution to the problem of particulate deposition in PLD. In order to study colliding plasmas m this work we have used, primarily, three diagnostic techniques VUV photoabsorption imaging was used in order to track the evolution of dark plume matter, or non-emitting plasma species residing m ground and metastable states We have also performed combined conventional gated CCD imaging and imaging spectroscopy to study excited species in the interaction region

Adherence mechanisms of Candida albicans

The yeast Candida albicans is an opportunistic fungal pathogen that is capable of inducing a range of superficial and systemic diseases in the immunocompromised host. Although it displays a variety of virulence factors, one--the ability to adhere to host tissue--is considered essential in the early stages of colonisation and tissue invasion. Adherence is achieved by a combination of specific (ligand-receptor interactions) and non-specific (electrostatic charge, van der Waals forces) mechanisms which allow the yeast to attach to a wide range of tissue types and inanimate surfaces. Conventional methods for treating disease cause by C. albicans rely upon the use of antifungal drugs designed to kill the yeast or arrest its growth. An alternative approach, aimed at disrupting the adherence of the yeast to host tissue in cases of superficial infection, may have potential for controlling disease, particularly in situations where the unattached fungal cell can be removed from the affected site, either by the flushing action of the oropharynx or by the production of mucus in the vagina

Histatins: antimicrobial peptides with therapeutic potential

Histatins are a group of antimicrobial peptides, found in the saliva of man and some higher primates, which possess antifungal properties. Histatins bind to a receptor on the fungal cell membrane and enter the cytoplasm where they target the mitochondrion. They induce the non-lytic loss of ATP from actively respiring cells, which can induce cell death. In addition, they have been shown to disrupt the cell cycle and lead to the generation of reactive oxygen species. Their mode of action is distinct from those exhibited by the conventional azole and polyene drugs, hence histatins may have applications in controlling drug-resistant fungal infections. The possibility of utilising histatins for the control of fungal infections of the oral cavity is being actively pursued with the antifungal properties of topical histatin preparations and histatin-impregnated denture acrylic being evaluated. Initial clinical studies are encouraging, having demonstrated the safety and efficacy of histatin preparations in blocking the adherence of the yeast Candida albicans to denture acrylic, retarding plaque formation and reducing the severity of gingivitis. Histatins may represent a new generation of antimicrobial compounds for the treatment of oral fungal infections and have the advantage, compared with conventional antifungal agents, of being a normal component of human saliva with no apparent adverse effects on host tissues and having a mode of action distinct to azole and polyene antifungals

Caspofungin primes the immune response of the larvae of Galleria mellonella and induces a non-specific antimicrobial response

The echinocandins (e.g. caspofungin) function by inhibiting the synthesis of 1,3-b-glucan in the fungal cell wall. While the potent antifungal activity of caspofungin has been well characterized in mammals, this study investigated the in vivo antifungal effect of caspofungin using larvae of the insect Galleria mellonella. Caspofungin was successful in increasing the survival of larvae that were inoculated with Candida albicans 1 h before the drug was administered, particularly when a concentration of 0.19 mg ml”1 was used. Pre-injecting larvae with caspofungin also increased their survival when they were inoculated with either Staphylococcus aureus or C. albicans. Caspofungin administration resulted in an increase in the number of circulating immune cells (haemocytes), an increase in the expression of the genes encoding IMPI and transferrin, and an increase in the expression of a number of proteins (identified by liquid chromatography–mass spectrometry) some of which have immune functions. This work indicates that administration of caspofungin can increase the survival of infected G. mellonella larvae, and this is due to the antifungal properties of caspofungin and also to the ability of caspofungin to prime the insect’s immune response

Adherence mechanisms of Candida albicans

The yeast Candida albicans is an opportunistic fungal pathogen that is capable of inducing a range of superficial and systemic diseases in the immunocompromised host. Although it displays a variety of virulence factors, one--the ability to adhere to host tissue--is considered essential in the early stages of colonisation and tissue invasion. Adherence is achieved by a combination of specific (ligand-receptor interactions) and non-specific (electrostatic charge, van der Waals forces) mechanisms which allow the yeast to attach to a wide range of tissue types and inanimate surfaces. Conventional methods for treating disease cause by C. albicans rely upon the use of antifungal drugs designed to kill the yeast or arrest its growth. An alternative approach, aimed at disrupting the adherence of the yeast to host tissue in cases of superficial infection, may have potential for controlling disease, particularly in situations where the unattached fungal cell can be removed from the affected site, either by the flushing action of the oropharynx or by the production of mucus in the vagina

Effect of pre-incubation temperature on susceptibility of Galleria mellonella larvae to infection by Candida albicans

The use of insects for evaluating the virulence of microbial pathogens and for determining the efficacy of antimicrobial drugs is increasing. When larvae of the greater wax moth Galleria mellonella were incubated at 4 or 37°C for 24 h. prior to infection, they manifested increased resistance to infection by the yeast Candida albicans compared to larvae that had been pre-incubated for 24 h at 30°C. Incubation at 4 or 37°C led to an increase in haemocyte density and the expression of genes coding for gallerimycin, transferrin, an inducible metalloproteinase inhibitor (IMPI) and galiomicin. Peak expression of these genes was recorded at approximately 24 h after the commencement of the 4 or 37°C incubation. These results indicate that exposure of larvae to mild thermal shock conditions induces a protective cellular and humoral immune response mediated by increased numbers of haemocytes and elevated expression of antimicrobial peptides

Raymond Williams and the limits of cultural materialism

Cultural materialism has become an influential discipline in recent years, particularly so in 'Renaissance' studies, but also more generally in 'English', as well as departments defined as practising 'cultural' or 'communications' studies. The phrase is usually linked with the name of Raymond Williams, but a cursory examination of Williams's own work quickly establishes that it is a phrase he rarely uses, and only schematically attempts to define. The thesis therefore takes the form of an investigation into the way cultural materialism has come to be understood, by examining in detail the trajectory of Raymond Williams's theoretical development, and how his own engagement with various theoretical positions has helped to set 'limits' on the meaning of cultural materialism. Chapters 1 and 2 deal with some of Williams's earliest work, particularly Reading and Criticism, as a way of investigating how reasonable it is to tag him as a 'Left-Leavisite', arguing that Leavis's undoubted influence is resisted (though not entirely rejected) from a very early stage. The first chapter considers in detail Leavis's work at Cambridge, the influence of Eliot, and the significance of the 'Organic Community'. Chapter 2, which is based around a comparative analysis of Williams's and Leavis's readings of Dickens, argues that Williams rejects the 'organic community' in favour of his 'knowable community'. Chapters 4 and 5 deal with specific 'theoretical' issues: the first, based around a reading of Terry Eagleton's critique of Williams's use of the Marxist metaphor of 'base and superstructure', shows some of the problems which arise from Williams's cultural model, as well as suggesting refinements; the second deals with the influence of Volosinov's theories on Williams. Chapter 6 comes out of Williams's readings of the 'Country-House' poems in The Country and the City, showing how his practice of literary criticism relies on an acceptance of 'ideology' apparently denied in his more 'theoretical' writings. This analysis is extended as a result of investigations into the 'De L'Isle' manuscripts relating to the Penshurst estate. Chapter 7 argues that it is possible to see the work of Fredric Jameson as developing Williams's cultural materialism into Jameson's debates on postmodernism. In the Introduction and Conclusion, I have taken the opportunity to look briefly at the activity of cultural materialism as it has developed since Raymond Williams's death in 1988. The Introduction emphasizes what I see to be important methodological differences between 'cultural materialism' and 'new historicism'; the Conclusion deals with the continuing debate over the value of a cultural materialist approach by considering the 'appropriation' of Shakespeare

Exploiting the potential of Insects for in vivo pathogenicity testing of Microbial pathogen

Conventional assays for quantifying the virulence of microbial pathogens and mutants have traditionally relied upon the use of a range of mammalian species. A number of workers have demonstrated that insects can be used for evaluating microbial pathogenicity and provide results comparable to those that can be obtained with mammals since one component of the vertebrate immune system, the innate immune response, remains similar to that found in insects. Larvae of the Greater Wax Moth Galleria mellonella have been used to evaluate the virulence of a range of bacterial and fungal pathogens and a correlation with the virulence of these microbes in mice has been established. This review highlights the similarities of the vertebrate and insect innate immune responses to infection and identifies the potential use of insects for the in vivo evaluation of the microbial pathogenicity

Exploiting the potential of Insects for in vivo pathogenicity testing of Microbial pathogen

Conventional assays for quantifying the virulence of microbial pathogens and mutants have traditionally relied upon the use of a range of mammalian species. A number of workers have demonstrated that insects can be used for evaluating microbial pathogenicity and provide results comparable to those that can be obtained with mammals since one component of the vertebrate immune system, the innate immune response, remains similar to that found in insects. Larvae of the Greater Wax Moth Galleria mellonella have been used to evaluate the virulence of a range of bacterial and fungal pathogens and a correlation with the virulence of these microbes in mice has been established. This review highlights the similarities of the vertebrate and insect innate immune responses to infection and identifies the potential use of insects for the in vivo evaluation of the microbial pathogenicity