The systematic variations in the structural, optical, and electrical properties of polycrystalline Cu͑In, Ga͒Se 2 ͑CIGS͒ thin films with Na doping level were investigated. Precise control of the Na concentration in CIGS films was demonstrated using alkali-silicate glass thin layers of various thicknesses deposited on substrates prior to CIGS growth. The CIGS grain size was observed to decrease with increasing Na concentration, although the surface morphology became smoother and exhibited a stronger ͑112͒ texture, which has been demonstrated consequence of larger grain size. The Ga composition gradient in the CIGS films was found to become large due to the presence of Na during growth, which in turn led to a decrease in the nominal band gap energy. Variations in the photoluminescence spectra and electrical properties suggested that the formation of an acceptor energy state, which may originate from O Se point defects, was enhanced in the presence of Na. This result suggests that not only Na, but also the presence of O in combination with Na contributes to the compensation of point defects and enhances p-type conductivity in CIGS films.
Gut-derived lymphocytes transiently migrate through the peripheral circulation before homing back to mucosal sites and can be detected using an ELISPOT-based antibody secreting cell (ASC) assay. Alternatively, transiently circulating lymphocytes may be cultured in vitro, and culture supernatants may be assayed for antigen-specific responses (antibody in lymphocyte supernatant [ALS] assay). The ALS assay has not been validated extensively in natural mucosal infection, nor has the ALS response been compared to the ASC assay and other cholera-specific immunological responses. Accordingly, we examined immune responses in 30 adult patients with acute cholera in Bangladesh, compared with 10 healthy controls, measuring ALS-immunoglobulin A (IgA), ASC-IgA, and serum and fecal IgA responses to two potent Vibrio cholerae immunogens, the nontoxic B subunit of cholera toxin (CtxB) and lipopolysaccharide (LPS) and a weaker V. cholerae immunogen, the mannose-sensitive hemagglutinin (MSHA). We found significant increases of anti-CtxB, anti-LPS, and anti-MSHA IgA in supernatants of lymphocytes cultured 7 days after onset of cholera using the ALS assay. We found that ALS and ASC responses correlated extremely well; both had comparable sensitivities as the vibriocidal responses, and both procedures were more sensitive than fecal IgA measurements. An advantage of the ALS assay for studying mucosal immune responses is the ability to freeze antibodies in supernatants for subsequent evaluation; like the ASC assay, the ALS assay can distinguish recent from remote mucosal infection, a distinction that may be difficult to make in endemic settings using other procedures.
We present evidence for the production of photocurrent due to two-photon excitation in an intermediate band solar cell structure. The structure consists of an n-GaNAs intermediate band layer sandwiched between a p-AlGaAs emitter and an n-AlGaAs barrier layer with suitable doping level to block electron escaping from the intermediate band to the bottom n-GaAs substrate. Multi-band transitions observed in two-photon excitation experiments are explained using photo-modulated reflectance spectrum, and further support for intermediate band solar cell operation of this structure is given by current-voltage measurements.
Both Th1 and Th17 cells are important components of the immune response to Helicobacter pylori (Hp) in adults, but less is known about T cell responses to Hp during early childhood, when the infection is often acquired. We investigated Th1 and Th17 type responses to Hp in adults, children and infants in Bangladesh, where Hp is highly endemic. IL-17 and IFN-γ mRNA levels in gastric biopsies from Hp-infected Bangladeshi adults were analyzed and compared to levels in infected and uninfected Swedish controls. Since biopsies could not be collected from infants and children, cytokine responses in Bangladeshi infants (6–12 months), children (3–5 years) and adults (>19 years) were instead compared by stimulating peripheral blood mononuclear cells (PBMCs) with a Hp membrane preparation (MP) and analyzing culture supernatants by ELISA and cytometric bead array. We found significantly higher expression of IL-17 and IFN-γ mRNA in gastric mucosa of Hp-infected Bangladeshi and Swedish adults compared to uninfected Swedish controls. PBMCs from all age groups produced IL-17 and IFN-γ after MP stimulation, but little Th2 cytokines. IL-17 and IFN-γ were primarily produced by CD4+ T cells, since CD4+ T cell depleted PBMCs produced reduced amounts of these cytokines. Infant cells produced significantly more IL-17, but similar levels of IFN-γ, compared to adult cells after MP stimulation. In contrast, polyclonal stimulation induced lower levels IL-17 and IFN-γ in infant compared to adult PBMCs and CD4+ T cells. The strong IL-17 production in infants after MP stimulation was paralleled by significantly higher production of the IL-17 promoting cytokine IL-1β from infant compared to adult PBMCs and monocytes. In conclusion, these results show that T cells can produce high levels of IL-17 and IFN-γ in response to Hp from an early age and indicate a potential role for IL-1β in promoting Th17 responses to Hp during infancy.
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