Transient reduction in erythrocyte membrane sialoglycoprotein associated with the presence of elliptocytes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73806/1/j.1365-2141.1988.00477.x.pd

Measurement of the GaAs/AlAs valence-band offset from a single quantum well near the Γ-X crossover

An iterative procedure which utilizes the type-I and type-II transitions of a GaAs/AlAs single quantum well is used to determine the GaAs/AlAs valence-band offset. The iteration is based on the fact that the confinement energy is not sensitive to the change of the barrier potential. It has the advantage that knowledge of the thickness of the quantum well is not necessary to determine the valence-band offset. Both the type-I and type-II transitions can be observed in the low-temperature photoluminescence spectrum if the GaAs is thin enough so that the lowest-energy level of the electron in the GaAs well is higher than the X-conduction-band minimum of the adjacent AlAs. We illustrate this procedure with a 35 Å GaAs/AlAs single quantum well, and the valence-band offset is found to be 36% of the Γ-gap difference

Photoluminescence measurements of tensile-strained GaAs/In0.07Al0.93As quantum wells

GaAs/In0.07Al0.93As tensile-strained quantum wells were grown on [001] GaAs substrates using molecular-beam epitaxy. The incorporation of tensile strain is made possible by preparing a 1-μm-thick In0.07Al0.93As relaxed buffer which is followed by the growth of quantum wells. The strain of the GaAs was measured using Raman spectroscopy and photoluminescence. The photoluminescence measurements from wells ranging in thickness from 25 to 100 Å reveal that the observed optical transition originates from the electron-light hole recombination for a 100 Å well and from the electron-heavy hole recombination if the well thickness is less than 40 Å. Therefore, a thick Al-rich InxAl1-x As relaxed buffer on the GaAs substrate can be used to engineer the relative energy position of the light and heavy holes for GaAs-based quantum wells

Mass spectrometry imaging identifies palmitoylcarnitine as an immunological mediator during Salmonella Typhimurium infection

Salmonella Typhimurium causes a self-limiting gastroenteritis that may lead to systemic disease. Bacteria invade the small intestine, crossing the intestinal epithelium from where they are transported to the mesenteric lymph nodes (MLNs) within migrating immune cells. MLNs are an important site at which the innate and adaptive immune responses converge but their architecture and function is severely disrupted during S. Typhimurium infection. To further understand host-pathogen interactions at this site, we used mass spectrometry imaging (MSI) to analyse MLN tissue from a murine model of S. Typhimurium infection. A molecule, identified as palmitoylcarnitine (PalC), was of particular interest due to its high abundance at loci of S. Typhimurium infection and MLN disruption. High levels of PalC localised to sites within the MLNs where B and T cells were absent and where the perimeter of CD169+ sub capsular sinus macrophages was disrupted. MLN cells cultured ex vivo and treated with PalC had reduced CD4+CD25+ T cells and an increased number of B220+CD19+ B cells. The reduction in CD4+CD25+ T cells was likely due to apoptosis driven by increased caspase-3/7 activity. These data indicate that PalC significantly alters the host response in the MLNs, acting as a decisive factor in infection outcome

DNA Methylation of the ABO Promoter Underlies Loss of ABO Allelic Expression in a Significant Proportion of Leukemic Patients

Background: Loss of A, B and H antigens from the red blood cells of patients with myeloid malignancies is a frequent occurrence. Previously, we have reported alterations in ABH antigens on the red blood cells of 55% of patients with myeloid malignancies. Methodology/Principal Findings: To determine the underlying molecular mechanisms of this loss, we assessed ABO allelic expression in 21 patients with ABH antigen loss previously identified by flow cytometric analysis as well as an additional 7 patients detected with ABH antigen changes by serology. When assessing ABO mRNA allelic expression, 6/12 (50%) patients with ABH antigen loss detected by flow cytometry and 5/7 (71%) of the patients with ABH antigen loss detected by serology had a corresponding ABO mRNA allelic loss of expression. We examined the ABO locus for copy number and DNA methylation alterations in 21 patients, 11 with loss of expression of one or both ABO alleles, and 10 patients with no detectable allelic loss of ABO mRNA expression. No loss of heterozygosity (LOH) at the ABO locus was observed in these patients. However in 8/11 (73%) patients with loss of ABO allelic expression, the ABO promoter was methylated compared with 2/10 (20%) of patients with no ABO allelic expression loss (P = 0.03). Conclusions/Significance: We have found that loss of ABH antigens in patients with hematological malignancies is associated with a corresponding loss of ABO allelic expression in a significant proportion of patients. Loss of ABO allelic expression was strongly associated with DNA methylation of the ABO promoter.Tina Bianco-Miotto, Damian J. Hussey, Tanya K. Day, Denise S. O'Keefe and Alexander Dobrovi

Growth and Characterization of MBE Parametric Variations Upon Polarization Independent Strained Films

This project was designed to comprehensively investigate the effects of molecular beam epitaxy (MBE) growth variations upon tensile-strained films. Using two dimensional (2-D) structures, such as quantum wells of variable configurations, we worked to observe the electro-optical response of polarization independence. The latter had been studied for compressively strained systems. However, the proof of principle for the feasibility of tensile-strained single and double quantum wells, particularly in the GaAs as opposed to the InP material system, had been much less investigated by comparison. The significance of this project, from a Basic Energy Sciences perspective, has been in its contribution to the understanding of how MBE parameters and sample design effect the physics of strained materials which themselves have been tailored to react with polarization insensitivity. Fundamental issues of materials structure control, growth parameter modifications, and characterization methods were investigated. Both single and double quantum well systems were used with both symmetric and asymmetric well widths for the latter. In this work, we essentially investigated both the growth of and potential applications for quantum based structures that use tensile strain to induce polarization independence

Engineering the I-V characteristics of an asymmetric double barrier device with variable period GaAs/AlAs superlattice injectors

This study represents a first-time examination of an asymmetric double barrier structure using variable period superlattice emitters. The layer thickness and period of the superlattices were systematically varied in order to define a unique emitter state in each structure grown. In each case, the emitter state was determined theoretically by calculating the miniband formation in the constituting superlattice. The relationship between the emitter state defined by the superlattice structure parameters and the current-voltage behavior of the diode at 77 K has been investigated here. © 1997 Elsevier Science S.A

Electrophoretic deposition of carbon nanotubes on 3-amino-propyl-triethoxysilane (Aptes) surface functionalized silicon substrates

Fabrication of uniform thin coatings of multi-walled carbon nanotubes (MWCNTs) by electrophoretic deposition (EPD) on semiconductor (silicon) substrates with 3-aminopropyl-triethoxysilane (APTES) surface functionalization has been studied extensively in this report. The gradual deposition and eventual CNT film formation on the organosilane treated silicon substrates is greatly assisted by the Coulombic force of attraction existing between the positively charged –NH2 surface groups of APTES and the acid treated, –COOH− functionalized negatively charged nanotubes migrating towards the anode (silicon) surface. The superior CNT coatings produced by EPD in comparison to the dip/immersion coating and the influence of isopropyl (IPA) based EPD suspension in the fabricated film quality have also been revealed in this study. The effect of varying APTES concentration (5%–100%) on the Raman spectroscopy and thickness of the deposited CNT film has been discussed in details, as well. The organosilane assisted deposition approach has eliminated the need of metal deposition in the EPD technique and has established an economical, fast and entirely room temperature solution-based fabrication strategy of CNT thin films for a wide range of next generation electronic applications