Theory of Electron Spin Relaxation in n-Doped Quantum Wells

Recent experiments have demonstrated long spin lifetimes in uniformly n-doped quantum wells. The spin dynamics of exciton, localized, and conduction spins are important for understanding these systems. We explain experimental behavior by invoking spin exchange between all spin species. By doing so we explain quantitatively and qualitatively the striking and unusual temperature dependence in (110)-GaAs quantum wells. We discuss possible future experiments to resolve the pertinent localized spin relaxation mechanisms. In addition, our analysis allows us to propose possible experimental scenarios that will optimize spin relaxation times in GaAs and CdTe quantum wells.Comment: Small corrections made. Accepted to Phys. Rev. B. 8 pages, 5 figure

Isogrid design handbook

Handbook has been published which presents information needed for design of isogrid triangular integral-stiffened structures. It develops equations, methods, and graphs to handle wide variety of loadings, materials, and geometry. Handbook is divided into seven sections. Handbook may be used by marine and civil engineers and by students and designers without access to computers

New laboratory methodologies to analyse the top of rail friction modifier performance across different test scales

Test methodologies originally developed for greases have been adapted to be used for top of rail friction modifiers (TORFMs). This has included: a small-scale benchtop tribometer to measure the tackiness of different TORFMs, attaching an applicator bar to a section of rail and rolling a scaled-wheel through the TORFM applied to the rail head to analyse the effect of different variables on pick-up, and applying TORFM to a full-scale test facility to analyse the scaling effects and the effect of slip, load and speed on pick-up. These methods can be used to measure the relative performance of different TORFMs with respect to how much product is picked up by the wheel. The results have shown that the relative ranking of different TORFMs is the same across the three test scales. This shows that these small-scale test methods that are more suitable for inclusion in test standards could be used to reduce the need for the more time-consuming and expensive larger scale tests, as the relative performance is the same

A Mechanistic Study in the Nephrotoxicity of p-Aminophenol

The acetaminophen metabolite, p-aminophenol (PAP), is a known nephrotoxicant. The current study is directed at understanding the mechanism of this nephrotoxicity. Renal cortical slices isolated from F344 rats were incubated with 0 – 0.5 mM PAP with or without pretreatments. Renal slices exposed to PAP showed toxicity as measured by increased lactate dehydrogenase leakage (LDH), decreased pyruvate-stimulated gluconeogenesis, and decreased total adenine nucleotides. There was, however, an increase in ATP as percent of total, implying maintained mitochondrial function. These data show that PAP is directly toxic to renal cortical slices. Pretreatment with EDTA or EGTA provided protection from PAP- induced LDH leakage, while EGTA-AM did not. These data show that PAP toxicity is dependent on extracellular calcium and independent of small increases in intracellular calcium. PAP exposure decreased total glutathione within 30 min, and marked depletion was evident at 120 min. At 60 min, PAP increased glutathione disulfide (GSSG) as percent of total glutathione (%GSSG). PAP exposure also increased 4-hydroxynonenal- adducted proteins. Pretreatment with ascorbate prevented PAP mediated increases in LDH, while reduced glutathione (GSH) or N-acetylcysteine did not prevent PAP toxicity. These data support the hypothesis that PAP induces oxidative stress, which cannot be prevented by exogenous sulfhydryl containing compounds. Administration of pyruvate protected against PAP-induced time- and concentration-dependent effects on LDH and adenine nucleotides. Finally, pyruvate caused an increase in cellular total glutathione and reduced PAP effects on total glutathione and %GSSG. These data imply that pyruvate protects from PAP toxicity through increasing the concentrations of total glutathione and recycling GSSG back to GSH. Pretreatment with glucose provided slight protection from LDH and increases in %GSSG. Finally, pyruvate but not glucose induced a significant increase in NADPH, confirming the hypothesis that pyruvate protects through NADPH-dependent recycling of glutathione. The greater degree of protection provided by pyruvate implies that pyruvate may provide a more readily available source for the prevention of oxidative stress. Pyruvate protection from oxidative stress of PAP may be expanded to other toxins with oxidant mechanisms of toxicity. These results could also be extrapolated to acetaminophen nephrotoxicity, and may provide the basis for future treatments

A Method for Determining Optimum Re-entry Trajectories

Determining optimum atmospheric reentry trajectories using Pontryagin maximum principl

Baptists, Catholics, and the Whole Church: Partners in the Pilgrimage to Unity

Within the whole church, Baptists and Catholics might seem to be ecclesiological and liturgical polar opposites. The two traditions are arguably more dissimilar from one another than each is from almost any other Christian tradition. Yet they share much in common that can enable them to travel together as fellow pilgrims on the journey toward a more visibly united church. Baptists, Catholics, and the Whole Church: Partners in the Pilgrimage to Unity, the book on which Steven R. Harmon (Professor of Historical Theology, Gardner-Webb University School of Divinity) worked during his Fall 2020 sabbatical research leave, challenges Baptists, Catholics, and other Christians to envision their own patterns of faith and practice as included in the convergences it presents and to dedicate themselves to deeper involvement in the quest for the unity Jesus prayed his followers would manifest.https://digitalcommons.gardner-webb.edu/sabbatical-presentations/1000/thumbnail.jp

KOI-1003: A new spotted, eclipsing RS CVn binary in the Kepler field

Using the high-precision photometry from the Kepler space telescope, thousands of stars with stellar and planetary companions have been observed. The characterization of stars with companions is not always straightforward and can be contaminated by systematic and stellar influences on the light curves. Here, through a detailed analysis of starspots and eclipses, we identify KOI-1003 as a new, active RS CVn star---the first identified with data from Kepler. The Kepler light curve of this close binary system exhibits the system's primary transit, secondary eclipse, and starspot evolution of two persistent active longitudes. The near equality of the system's orbital and rotation periods indicates the orbit and primary star's rotation are nearly synchronized ($P_\mathrm{orb} = 8.360613\pm0.000003$ days; $P_\mathrm{rot} \sim 8.23$ days). By assuming the secondary star is on the main sequence, we suggest the system consists of a $1.45^{+0.11}_{-0.19} \ M_\odot$ subgiant primary and a $0.59^{+0.03}_{-0.04} \ M_\odot$ main-sequence companion. Our work gives a distance of $4400 \pm 600$ pc and an age of $t = 3.0^{-0.5}_{+2.0}$ Gyr, parameters which are discrepant with previous studies that included the star as a member of the open cluster NGC 6791.Comment: 21 pages, 19 figures, accepted to Ap