| 1. |
- Zakaria, A. K. M., et al.
(författare)
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Cation distribution and crystallographic characterization of the spinel oxides MgCrxFe2-xO4 by neutron diffraction
- 2015
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 633, s. 115-119
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Tidskriftsartikel (refereegranskat)abstract
- The spinel system MgCrxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) has been prepared by solid state sintering method in air at 1573 K. X-ray and neutron powder diffraction experiments have been performed on the samples at room temperature for structural characterization. Rietveld refinement of the neutron diffraction data reveals that all the samples of the series possess cubic symmetry corresponding to the space group Fd-3m. The distribution of the three cations Mg, Fe and Cr over the two sublattices and other crystallographic parameters has been determined precisely. The results reveal that Cr has been substituted for Fe selectively. Cr ions invariably occupy the octahedral (B) site for all values of x. Mg and Fe ions are distributed over both A and B sites for all x values. With increasing x the occupation of Mg increases in the A site and decreases in the B site for all the samples, while the Fe ions gradually decreases in both the sites for all values of x. The lattice constant decreases with increasing Cr content in the system. The magnetic structure at room temperature was ferrimagnetic for all the samples.
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| 2. |
- Alam, M., et al.
(författare)
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Antigen-Specific Memory B-cell Responses to Enterotoxigenic Escherichia coli Infection in Bangladeshi Adults
- 2014
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Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Multiple infections with diverse enterotoxigenic E. coli (ETEC) strains lead to broad spectrum protection against ETEC diarrhea. However, the precise mechanism of protection against ETEC infection is still unknown. Therefore, memory B cell responses and affinity maturation of antibodies to the specific ETEC antigens might be important to understand the mechanism of protection. Methodology: In this study, we investigated the heat labile toxin B subunit (LTB) and colonization factor antigens (CFA/I and CS6) specific IgA and IgG memory B cell responses in Bangladeshi adults (n = 52) who were infected with ETEC. We also investigated the avidity of IgA and IgG antibodies that developed after infection to these antigens. Principal Findings: Patients infected with ETEC expressing LT or LT+heat stable toxin (ST) and CFA/I group or CS6 colonization factors developed LTB, CFA/I or CS6 specific memory B cell responses at day 30 after infection. Similarly, these patients developed high avidity IgA and IgG antibodies to LTB, CFA/I or CS6 at day 7 that remained significantly elevated at day 30 when compared to the avidity of these specific antibodies at the acute stage of infection (day 2). The memory B cell responses, antibody avidity and other immune responses to CFA/I not only developed in patients infected with ETEC expressing CFA/I but also in those infected with ETEC expressing CFA/I cross-reacting epitopes. We also detected a significant positive correlation of LTB, CFA/I and CS6 specific memory B cell responses with the corresponding increase in antibody avidity. Conclusion: This study demonstrates that natural infection with ETEC induces memory B cells and high avidity antibodies to LTB and colonization factor CFA/I and CS6 antigens that could mediate anamnestic responses on re-exposure to ETEC and may help in understanding the requirements to design an effective vaccination strategies.
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| 3. |
- Nandi, A., et al.
(författare)
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Accretion flow dynamics during 1999 outburst of XTE J1859+226—modeling of broadband spectra and constraining the source mass
- 2018
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Ingår i: Astrophysics and Space Science. - : Springer Netherlands. - 0004-640X .- 1572-946X. ; 363:5
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Tidskriftsartikel (refereegranskat)abstract
- We examine the dynamical behavior of accretion flow around XTE J1859+226 during the 1999 outburst by analyzing the entire outburst data (∼166 days) from RXTE Satellite. Towards this, we study the hysteresis behavior in the hardness intensity diagram (HID) based on the broadband (3–150 keV) spectral modeling, spectral signature of jet ejection and the evolution of Quasi-periodic Oscillation (QPO) frequencies using the two-component advective flow model around a black hole. We compute the flow parameters, namely Keplerian accretion rate (m˙ d), sub-Keplerian accretion rate (m˙ h), shock location (rs) and black hole mass (Mbh) from the spectral modeling and study their evolution along the q-diagram. Subsequently, the kinetic jet power is computed as Ljetobs∼3–6×1037ergs−1 during one of the observed radio flares which indicates that jet power corresponds to 8–16% mass outflow rate from the disc. This estimate of mass outflow rate is in close agreement with the change in total accretion rate (∼14%) required for spectral modeling before and during the flare. Finally, we provide a mass estimate of the source XTE J1859+226 based on the spectral modeling that lies in the range of 5.2–7.9 M⊙ with 90% confidence.
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