Anisotropic Response of Nanosized Bismuth Films Upon Femtosecond Laser Excitation Monitored by Ultrafast Electron Diffraction

The lattice response of 5 nm thick bismuth film to femtosecond laser excitation is probed by ultrafast electron diffraction. The transient decay time after laser excitation is greater for diffraction from (012) lattice planes compared to (110) planes and is reduced for both planes with the increased laser fluence. These results indicate that different energy coupling mechanisms to the lattice occur depending on the crystal direction. The behavior of the diffraction peak width indicates partial disorder of the film upon photoexcitation that increases together with the laser fluence. © 2011 American Institute of Physics. [doi:10.1063/1.3652919

Nonuniformity in Lattice Contraction of Bismuth Nanoclusters Heated Near Its Melting Point

The structural properties of bismuth nanoclusters were investigated with transmission high-energy electron diffraction from room temperature up to 525 ± 6 K. The Bi nanoclusters were fabricated by thermal evaporation at room temperature on transmission electron microscope grids coated with an ultrathin carbon film, followed by thermal and femtosecond laser annealing. The annealed sample had an average cluster size of ∼14 nm along the minor axis and ∼16 nm along the major axis. The Debye temperature of the annealed nanoclusters was found to be 53 ± 6 K along the [012] direction and 86 ± 9 K along the [110] direction. At T = 464 ± 6 K, the diffraction intensity started to deviate from Debye-Waller behavior due to increased lattice anharmonicity. The onset of the melting of the Bi nanoclusters was T ∼ 500 ± 6 K, as measured by the reduction of the nanocluster size through the formation of a liquid shell detected by the width of the diffraction rings. The thermal expansion coefficient of the Bi (012) and (110) planes is positive up to ∼ 499 11 K. However, the expansion coefficient of the Bi (012) planes showed a transition from a positive to a negative value that occurs over the temperature range Tc ∼ 499 ± 11 K to 511 ± 8 K. For the Bi (110) planes, the thermal expansion coefficient is positive up to their melting point, which is 525 ± 6 K. © 2011 American Institute of Physics. [doi:10.1063/1.3565028

Cell-mediated immunity in recent-onset type 1 diabetic children

Background: The ability to suppress an immune response makes regulatory T-cells (T-reg) an attractive candidate as a novel therapeutic agent for treating autoimmune diseases. The mechanisms involved in maintenance of peripheral tolerance include a specialized subset of regulatory-T-cells (Treg) within the T-cell population. The CD4+ CD25+ T-cells may be important in modulating the risk for autoimmunity. Auto-reactive cytotoxic T-cells recognize peptide epitopes displayed on the beta cells surface in the context of HLA class1 molecules. A population of CD8+ regulatory T-cells characterized by expression of CD25 and FOXP3 have been identified and induced in the human peripheral blood cells. The regulatory activity of these cells is on autologous, antigen-reactive CD4+ T-cells in a cell contactdependent manner. These findings provide an evidence for a new mechanism for induction of immune regulation in human. Objective: This study was aiming to assess the cellular immune parameters including the percentage of CD4+, CD8+, CD4+/CD8+ ratio,CD4+CD25+, CD8+ CD25+ lymphocytes, which may have its application in developing immune therapy based tools for halting disease progression. Methods: This study was conducted on 20 children of recent onset type 1 diabetes (disease duration 0.05) between the two groups. A significant inverse correlation was found between CD4+ CD25+ T-cells and HbA1c percentage among patients group (p < 0.05).Also a significant difference in the percentage of CD4+ CD25+ T-cells was found when patients with HbA1c8% (the latter group had significantly lower percentage of CD4+ CD8+ T-cells). Conclusion: Type 1diabetes is characterised at its onset by a lowered percentage of CD8+ and CD8+ CD25+ T-cells in peripheral blood, a normal percentage of CD4+ and CD4+ CD25+ T-cells. There may be an inverse correlation between percentage of CD4+ CD25+ T-cells at disease onset and HbA1c level after three months. These data support the hypothesis that a defect in function or deficiency in number of T- regulatory cells may affect the pathogenesis of type 1 diabetes.Keywords: Type 1 diabetes, cell-mediated immunity, childrenEgypt J Pediatr Allergy Immunol 2008; 6(2): 69-7

Coherent Phonons in Bismuth Film Observed by Ultrafast Electron Diffraction

The generation of coherent phonons in polycrystalline bismuth film excited with femtosecond laser pulse is observed by ultrafast time-resolved electron diffraction. The dynamics of the diffracted intensities from the (110), (202), and (024) lattice planes show pronounced oscillations at 130-150 GHz. The origin of these coherent acoustic phonons is discussed in view of optical phonon decay into two acoustic phonons. Different drop times in the intensity of the diffraction orders are observed and interpreted as anisotropy in the energy transfer rate of coherent optical phonons

Recent progress in understanding immune activation in the pathogenesis in HIV-TB coinfection

Purpose of review Tuberculosis is the leading infectious cause of death worldwide, and HIV-1 the best recognized risk factor for active TB. This review focuses on immune complex formation; the interplay of type I and II interferon signaling; and T-cell activation in HIV–TB pathogenesis. Recent findings Circulating immune complexes and complement, and Fcγ signaling in whole blood act as early markers of TB disease in HIV-1-infected persons. HIV-1 is associated with a type I interferon response in whole blood, reducing the specificity of TB biomarkers dependent on type I and II interferon genes. Type I and type II interferons are implicated in both protection and TB disease, a protective outcome may depend on modulating these pathways. Whilst M. tuberculosis-specific CD4 T cells are preferentially depleted during HIV-1 infection, activation markers on M. tuberculosis-specific CD4 T cells, in particular HLA-DR, reflect immune activation and have promise as biomarkers of M. tuberculosis disease activity in individuals with HIV-1. Summary TB pathogenesis in HIV-1 involves a complex interaction of underlying activation of both the innate and adaptive immune systems. Further research is required to understand whether biomarkers of activation could be used to predict or quantify TB disease in the context of HIV-1 infection

Expression of recombinant Streptokinase from local Egyptian Streptococcus sp. SalMarEg

Streptokinase (SK) is a therapeutically important thrombolytic agent. Cardiovascular disease is the first cause of adult death worldwide. In Egypt about 13% of the population die every year due to ischemic heart disease. In spite of this fact, there is no local production of cardiovascular therapeutics. We reported for the first time the expression of a recombinant SK from a local Streptococcus strain. When produced on industrial scale this r-SK may substantially contribute to reducing the costs of thrombolytic therapy in developing countries. In this study, a highly purified r-SK from Streptococcus sp. isolated from Egyptian pharyngitis patients was obtained. The isolated strain was partially identified using 16S rDNA sequencing and named Streptococcus sp. SalMarEg. It was found to be phylogenetically related to Streptococcus pyogenes. Analysis of the obtained sequence showed high similarity with other SK genes. The protein expression in a prokaryotic system obtained a 47-kDa SK protein that could be purified using a single-step his-tagged affinity purification chromatography, with nearly 80% recovery. The clot lytic activities of both recombinant and commercial SK were similar, thus giving the basis to scale up this SK product in order to evaluate the possibilities of its commercialization in local and/or regional markets.Key words: Streptokinase, Streptococcus SalMarEg, thrombolytic agent, heterologous expression

Food insecurity amongst older people in the UK

Purpose The purpose of this paper is to present findings from research into food insecurity amongst older people aged 50 years and older in the UK. Design/methodology/approach This paper uses secondary analysis of national-level survey data and semi-structured interviews with older people receiving emergency food from foodbanks. Findings There is a forgotten care gap in the UK where a substantial number of older people are living in food insecurity. Many older people live alone and in poverty, and increasing numbers are constrained in their spending on food and are skipping meals. Food insecurity amongst older people can be hidden. Within families a number of older people were trying to ensure that their children and grandchildren had enough to eat, but were reluctant to ask for help themselves. Research limitations/implications The broad categorisation of older people aged 50 and above comprises people in very different circumstances. The qualitative component of the research was undertaken across various sites in a single city in England. Despite these limitations, the analysis provides important insights into the experiences of the many older people enduring food insecurity. Practical implications An increased public and professional awareness of food insecurity amongst older people is needed. Increased routine screening for under-nutrition risk is a priority. Policy initiatives are needed that are multifaceted and which support older people across a range of age groups, particularly those living alone. Social implications Food insecurity amongst older people in the UK raises questions about the present policy approach and the responsibilities of the government. Originality/value The research provides important new insights into the experiences of the many older people experiencing food insecurity in the UK by drawing on survey data and interviews with older people using foodbanks

Extraction and characterization of Nanocellulose obtained from sugarcane bagasse as agro-waste

This study aimed to characterize nanocellulose extracted from sugarcane bagasse (SCB) by acid hydrolysis 60% (w/w) H2SO4 at 45 â—¦C. The effect of hydrolysis time (20, 30 and 40 min) on the structure and properties of the nanofibers was investigated. Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) results indicated that the hemicellulose and lignin were removed extensively in the cellulose whiskers. The morphology and dimensions of the fibers and acid-released cellulose nanowhisker (CNW) were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that SCB could be used as source to obtain cellulose whiskers and they had needle-like structures. Longer hydrolysis time produced a lower yield of nanofibers; whereas the degree of crystallinity increased from 38.22% to 65.37% with increasing hydrolysis time due to removal of amorphous cellulose