Radiation Effects in Ultraviolet Sensitive Pd/4H-SiC Schottky Detectors

9-154H-SiC, by virtue of its intrinsic properties, is a very promising semiconductor material for fabricating rad-hard UV detectors suitable for harsh radiation environments. This paper aims to investigate the radiation tolerance of indigenously developed Pd/4H-SiC Schottky detectors, in order to determine their feasibility for space applications. 4H-SiC detectors of active area 1 × 1 mm2 were irradiated with electrons of energy 10 MeV at fluence of 2×1013 e-/cm2 and gamma rays from a Co-60 source with a total dose of 1 Mrad. The impact of these irradiations on electro-optical characteristics of the devices was studied by analyzing the changes in electrical parameters like reverse saturation current (Is), ideality factor (n), barrier height (ɸB), effective doping concentration (Neff) derived from I-V and C-V characteristics as well as in the UV spectral responsivity (i.e., from 248 to 365 nm) of the irradiated detectors. The electron irradiated device showed negligible change in I-V and C-V characteristics whereas its UV spectral responsivity at the peak wavelength of 290 nm reduced by 48.7 %. Gamma irradiated device displayed a noticeable variation in its electrical characteristics and 15.8 % reduction in the spectral responsivity (optical characteristics) at the peak wavelength. The results show that the radiation hardness of 4H-SiC detectors is better than that of conventional semiconductor ones, making it a more appealing choice as radiation detectors in space systems

Estimating compensation payments for on-farm conservation of agricultural biodiversity in developing countries.

This paper examines the role of direct compensation payments for agrobiodiversity conservation, using minor millet landraces in India as an example. The cost of farmer participation in a hypothetical 'payments for agrobiodiversity conservation services' (PACS) scheme is estimated using a stated preference valuation approach. Significant inter-crop and inter-varietal differences are observed with respect to consumption values, upon which the compensation demanded by farm households is shown to primarily depend. Drawing on a categorisation of consumption values and farmer preferences, the paper points to the importance of simultaneously considering a range of potential interventions in order to conserve a priority portfolio of agrobiodiverse resources in predominantly subsistence-based agricultural systems

Changes in Culture Expanded Human Amniotic Epithelial Cells: Implications for Potential Therapeutic Applications

Human amniotic epithelial cells (hAEC) isolated from term placenta have stem cell-like properties, differentiate into tissue specific cells and reduce lung and liver inflammation and fibrosis following transplantation into disease models established in mice. These features together with their low immunogenicity and immunosuppressive properties make hAEC an attractive source of cells for potential therapeutic applications. However, generation of large cell numbers required for therapies through serial expansion in xenobiotic-free media may be a limiting factor. We investigated if hAEC could be expanded in xenobiotic-free media and if expansion altered their differentiation capacity, immunophenotype, immunosuppressive properties and production of immunomodulatory factors. Serial expansion in xenobiotic-free media was limited with cumulative cell numbers and population doubling times significantly lower than controls maintained in fetal calf serum. The epithelial morphology of primary hAEC changed into mesenchymal-stromal like cells by passage 4–5 (P4–P5) with down regulation of epithelial markers CK7, CD49f, EpCAM and E-cadherin and elevation of mesenchymal-stromal markers CD44, CD105, CD146 and vimentin. The P5 hAEC expanded in xenobiotic-free medium differentiated into osteocyte and alveolar epithelium-like cells, but not chondrocyte, hepatocyte, α- and β-pancreatic-like cells. Expression of HLA Class IA, Class II and co-stimulatory molecules CD80, CD86 and CD40 remained unaltered. The P5 hAEC suppressed mitogen stimulated T cell proliferation, but were less suppressive compared with primary hAEC at higher splenocyte ratios. Primary and P5 hAEC did not secrete the immunosuppressive factors IL-10 and HGF, whereas TGF-β1 and HLA-G were reduced and IL-6 elevated in P5 hAEC. These findings suggest that primary and expanded hAEC may be suitable for different cellular therapeutic applications

Human Amniotic Epithelial Cell Transplantation Induces Markers of Alternative Macrophage Activation and Reduces Established Hepatic Fibrosis

Chronic hepatic inflammation from multiple etiologies leads to a fibrogenic response that can progress to cirrhosis and liver failure. Transplantation of human amniotic epithelial cells (hAEC) from term delivered placenta has been shown to decrease mild to moderate hepatic fibrosis in a murine model. To model advanced human liver disease and assess the efficacy of hAEC therapy, we transplanted hAEC in mice with advanced hepatic fibrosis. Immunocompetent C57BL/6 mice were administered carbon tetrachloride (CCl4) twice weekly resulting in bridging fibrosis by 12 weeks. hAEC (2×106) were infused via the tail vein at week 8 or weeks 8 and 10 (single and double dose, respectively). Human cells were detected in mouse liver four weeks after transplantation showing hAEC engraftment. CCl4 treated mice receiving single or double hAEC doses showed a significant but similar decrease in liver fibrosis area associated with decreased activation of collagen-producing hepatic stellate cells and decreased hepatic protein levels of the pro-fibrogenic cytokine, transforming growth factor-beta1. CCl4 administration caused hepatic T cell infiltration that decreased significantly following hAEC transplantation. Hepatic macrophages play a crucial role in both fibrogenesis and fibrosis resolution. Mice exposed to CCl4 demonstrated increased numbers of hepatic macrophages compared to normal mice; the number of macrophages decreased significantly in CCl4 treated mice given hAEC. These mice had significantly lower hepatic protein levels of the chemokine monocyte chemoattractant protein-1 than mice given CCl4 alone. Alternatively activated M2 macrophages are associated with fibrosis resolution. CCl4 treated mice given hAEC showed increased expression of genes associated with M2 macrophages including YM-1, IL-10 and CD206. We provide novel data showing that hAEC transplantation induces a wound healing M2 macrophage phenotype associated with reduction of established hepatic fibrosis that justifies further investigation of this potential cell-based therapy for advanced hepatic fibrosis

Adoption and Outcomes of Hybrid Maize in the Marginal Areas of India

Smallholder maize cultivation is prevalent in the marginal areas of India, under diverse agro-climatic conditions. Abiotic stress tolerant maize cultivars are expected to be highly beneficial in reducing the production risks and enhancing farmer livelihoods, especially in the face of climate change. Nevertheless, the adoption and production risk implications of any of the crop varietal technologies in the marginal areas of India have not been widely examined. In this paper, we analyse the case of hybrid maize adoption, using data from a survey of 340 maize-growing households from three stressprone regions in India. Hybrid maize adoption varies from 33% to 99% in these locations. A probit model is used to assess the factors determining adoption. The outcomes of hybrid maize adoption are examined in terms of yield and profitability, employing mean-variance analysis. We find a clear superiority of the hybrid technology with respect to yield enhancement, per-unit cost reduction and risk reduction only in one of the study locations. Our findings indicate significant economic potentials for developing abiotic stress tolerant maize cultivars for India’s marginal environments

Radiation Effects in Ultraviolet Sensitive Pd/4H-SiC Schottky Detectors

4H-SiC, by virtue of its intrinsic properties, is a very promising semiconductor material for fabricating rad-hard UV detectors suitable for harsh radiation environments. This paper aims to investigate the radiation tolerance of indigenously developed Pd/4H-SiC Schottky detectors, in order to determine their feasibility for space applications. 4H-SiC detectors of active area 1 × 1 mm2 were irradiated with electrons of energy 10 MeV at fluence of 2×1013 e-/cm2 and gamma rays from a Co-60 source with a total dose of 1 Mrad. The impact of these irradiations on electro-optical characteristics of the devices was studied by analyzing the changes in electrical parameters like reverse saturation current (Is), ideality factor (n), barrier height (ɸB), effective doping concentration (Neff) derived from I-V and C-V characteristics as well as in the UV spectral responsivity (i.e., from 248 to 365 nm) of the irradiated detectors. The electron irradiated device showed negligible change in I-V and C-V characteristics whereas its UV spectral responsivity at the peak wavelength of 290 nm reduced by 48.7 %. Gamma irradiated device displayed a noticeable variation in its electrical characteristics and 15.8 % reduction in the spectral responsivity (optical characteristics) at the peak wavelength. The results show that the radiation hardness of 4H-SiC detectors is better than that of conventional semiconductor ones, making it a more appealing choice as radiation detectors in space systems