Transport between edge states in multilayer integer quantum Hall systems: exact treatment of Coulomb interactions and disorder

A set of stacked two-dimensional electron systems in a perpendicular magnetic field exhibits a three-dimensional version of the quantum Hall effect if interlayer tunneling is not too strong. When such a sample is in a quantum Hall plateau, the edge states of each layer combine to form a chiral metal at the sample surface. We study the interplay of interactions and disorder in transport properties of the chiral metal, in the regime of weak interlayer tunneling. Our starting point is a system without interlayer tunneling, in which the only excitations are harmonic collective modes: surface magnetoplasmons. Using bosonization and working perturbatively in the interlayer tunneling amplitude, we express transport properties in terms of the spectrum for these collective modes, treating electron-electron interactions and impurity scattering exactly. We calculte the conductivity as a function of temperature, finding that it increases with increasing temperature as observed in recent experiments. We also calculate the autocorrelation function of mesoscopic conductance fluctuations induced by changes in a magnetic field component perpendicular to the sample surface, and its dependence on temperature. We show that conductance fluctuations are characterised by a dephasing length that varies inversely with temperature.Comment: 13 pages, 10 figures, minor changes made for publicatio

Pseudomonas aeruginosa Elastase Provides an Escape from Phagocytosis by Degrading the Pulmonary Surfactant Protein-A

Pseudomonas aeruginosa is an opportunistic pathogen that causes both acute pneumonitis in immunocompromised patients and chronic lung infections in individuals with cystic fibrosis and other bronchiectasis. Over 75% of clinical isolates of P. aeruginosa secrete elastase B (LasB), an elastolytic metalloproteinase that is encoded by the lasB gene. Previously, in vitro studies have demonstrated that LasB degrades a number of components in both the innate and adaptive immune systems. These include surfactant proteins, antibacterial peptides, cytokines, chemokines and immunoglobulins. However, the contribution of LasB to lung infection by P. aeruginosa and to inactivation of pulmonary innate immunity in vivo needs more clarification. In this study, we examined the mechanisms underlying enhanced clearance of the ΔlasB mutant in mouse lungs. The ΔlasB mutant was attenuated in virulence when compared to the wild-type strain PAO1 during lung infection in SP-A+/+ mice. However, the ΔlasB mutant was as virulent as PAO1 in the lungs of SP-A-/- mice. Detailed analysis showed that the ΔlasB mutant was more susceptible to SP-A-mediated opsonization but not membrane permeabilization. In vitroand in vivo phagocytosis experiments revealed that SP-A augmented the phagocytosis of ΔlasB mutant bacteria more efficiently than the isogenic wild-type PAO1. The ΔlasB mutant was found to have a severely reduced ability to degrade SP-A, consequently making it unable to evade opsonization by the collectin during phagocytosis. These results suggest that P. aeruginosa LasB protects against SP-A-mediated opsonization by degrading the collectin

Update on the management of chronic eczema: new approaches and emerging treatment options

Atopic dermatitis (AD) is a common disease with worldwide prevalence, affecting up to 20% of children and 3% of adults. Recent evidence regarding pathogenesis has implicated epidermal barrier defects deriving from filagrin mutations with resulting secondary inflammation. In this report, the authors comprehensively review the literature on atopic dermatitis therapy, including topical and systemic options. Most cases of AD will benefit from emollients to enhance the barrier function of skin. Topical corticosteroids are first-line therapy for most cases of AD. Topical calcineurin inhibitors (tacrolimus ointment, pimecrolimus cream) are considered second line therapy. Several novel barrier-enhancing prescription creams are also available. Moderate to severe cases inadequately controlled with topical therapy may require phototherapy or systemic therapy. The most commonly employed phototherapy modalites are narrow-band UVB, broadband UVB, and UVA1. Traditional systemic therapies include short-term corticosteroids, cyclosporine (considered to be the gold standard), methotrexate, azathioprine, mycophenolate mofetil, and most recently leflunamide. Biologic therapies include recombinant monoclonal antibodies acting on the immunoglobulin E / interleukin-5 pathway (omalizumab, mepolizumab), acting as tumor necrosis factor-α inhibitors (infliximab, etanercept, adalimumab), and acting as T-cell (alefacept) and B-cell (rituxumab) inhibitors, as well as interferon γ and intravenous immunoglobulin. Efficacy, safety, and tolerability are reviewed for each medication

A review of source tracking techniques for fine sediment within a catchment

Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments

Gene Therapy for Osteosarcoma : "In Vitro" Characterization of Five Tumor Cell Lines and Development of Treatment Models "In Vivo"

135 leaves. Advisor: Dean A. HogansonFour human osteosarcoma cell lines (MNNG, TE85, MG63, and G292) and a human-derived osteosarcoma metastatic to murine lung (MLM) were transduced "in vitro" using retroviral vectors containing the Herpes simplex thymidine kinase (HS-tk), human interleukin 2 (IL2). and B-galactosidase (BAG) genes. Each osteosarcoma cell line was stably transduced, and the HS-tk gene effectively conferred ganciclovir (GCV) susceptibility to transduced cells. Each cell line showed a bystander effect (whereby wild type tumor cells are killed by co-incubation with HS-tk positive tumor cells and GCV). MNNG cells were used to develop a series of experiments in athymic nude mice to investigate the utility of gene therapy for the treatment of experimental osteosarcomas. Subcutaneous implants of mixtures of tumor cells and HS-tk vector producer cells (vpc) resulted in the development of tumors which were completely cured upon administration of GCV. Subcutaneous implant of mixtures of transduced and wild-type cells resulted in a potent bystander effect upon administration of GCV, with complete tumor ablation when as little as ten percent of the cells were HS-tk positive. A significant anti-tumor response was seen against primary tumors comprised of unmodified cells when a secondary tumor of transduced cells was induced at a distance of one centimeter, which supports a soluble bystander factor model. The presence of IL2-transduced cells significantly improved the efficacy of treatment, suggesting a synergy between the HS-tk and IL2 gene products. A significant anti-tumor response was seen in the treatment of established osteosarcomas by the injection of HS-tk vpc

Kinetic and economic analysis of reactive capture of dilute carbon dioxide with Grignard reagents

Carbon Dioxide Utilisation (CDU) processes face significant challenges, especially in the energetic cost of carbon capture from flue gas and the uphill energy gradient for CO2 reduction. Both of these stumbling blocks can be addressed by using alkaline earth metal compounds, such as Grignard reagents, as sacrificial capture agents. We have investigated the performance of these reagents in their ability to both capture and activate CO2 directly from dried flue gas (essentially avoiding the costly capture process entirely) at room temperature and ambient pressures with high yield and selectivity. Naturally, to make the process sustainable, these reagents must then be recycled and regenerated. This would potentially be carried out using existing industrial processes and renewable electricity. This offers the possibility of creating a closed loop system whereby alcohols and certain hydrocarbons may be carboxylated with CO2 and renewable electricity to create higher-value products containing captured carbon. A preliminary Techno-Economic Analysis (TEA) of an example looped process has been carried out to identify the electrical and raw material supply demands and hence determine production costs. These have compared broadly favourably with existing market values