Strain Effects on Point Defects and Chain-Oxygen Order-Disorder Transition in 123-Structure Cuprate Superconductors

The energetics of Schottky defects in 123 cuprate superconductor series, $\rm REBa_2Cu_3O_7$ (where RE = lanthandies) and $\rm YAE_2Cu_3O_7$ (AE = alkali-earths), were found to have unusual relations if one considers only the volumetric strain. Our calculations reveal the effect of non-uniform changes of interatomic distances within the RE-123 structures, introduced by doping homovalent elements, on the Schottky defect formation energy. The energy of formation of Frenkel Pair defects, which is an elementary disordering event, in 123 compounds can be substantially altered under both stress and chemical doping. Scaling the oxygen-oxygen short-range repulsive parameter using the calculated formation energy of Frenkel pair defects, the transition temperature between orthorhombic and tetragonal phases is computed by quasi-chemical approximations (QCA). The theoretical results illustrate the same trend as the experimental measurements in that the larger the ionic radius of RE, the lower the orthorhombic/tetragonal phase transition temperature. This study provides strong evidence of the strain effects on order-disorder transition due to oxygens in the CuO chain sites.Comment: In print Phys Rev B (2004

Cu Nuclear Quadrupole Resonance Study of Site-Disorder and Chemical Pressure Effects on Y(Ba1-xSrx)2Cu4O8

We report a zero-field Cu nuclear quadrupole resonance (NQR) study on the effects of nonmagnetic Sr substitution for high-Tc superconductors, Y(Ba1-xSrx)2Cu4O8 (Tc=82-80 K for x=0-0.4), using a spin-echo technique. The site-disordering and chemical pressure effects associated with doping Sr were observed in the broadened, shifted Cu NQR spectra. Nevertheless, the site disorder did not significantly affect the homogeneity of Cu electron spin dynamics, in contrast to the in-plane impurity. The peak shift of Cu NQR spectrum due to Sr was different between the chain- and the plane-Cu sites, more remarkably than those under a hydrostatic physical pressure, suggesting anisotropic or nonuniform local structural strains. The small decrease of Tc due to Sr can be traced back to either a cancellation effect on Tc between the disorder and the pressure, or an anisotropic or nonuniform chemical pressure effect on Tc.Comment: 4 pages, 5 figure

Synaptic dysfunction, memory deficits and hippocampal atrophy due to ablation of mitochondrial fission in adult forebrain neurons

Well-balanced mitochondrial fission and fusion processes are essential for nervous system development. Loss of function of the main mitochondrial fission mediator, dynamin-related protein 1 (Drp1), is lethal early during embryonic development or around birth, but the role of mitochondrial fission in adult neurons remains unclear. Here we show that inducible Drp1 ablation in neurons of the adult mouse forebrain results in progressive, neuronal subtype-specific alterations of mitochondrial morphology in the hippocampus that are marginally responsive to antioxidant treatment. Furthermore, DRP1 loss affects synaptic transmission and memory function. Although these changes culminate in hippocampal atrophy, they are not sufficient to cause neuronal cell death within 10 weeks of genetic Drp1 ablation. Collectively, our in vivo observations clarify the role of mitochondrial fission in neurons, demonstrating that Drp1 ablation in adult forebrain neurons compromises critical neuronal functions without causing overt neurodegeneration

HYPERVELOCITY PROJECTILE: EFFECTS OF A COMMON MUNITION IN MULTI-MISSION OPERATIONS

This project explored how a common hypervelocity projectile (HVP) munition could support Anti-Air Warfare (AAW), Anti-Surface Warfare (ASUW), and Naval Surface Fire Support (NSFS) missions by comparing the legacy munitions to the HVP fired from U.S. legacy weapon systems. This study examined the effects of HVPs in mission planning, logistics and use in multiple mission areas. The main objective question for the study was, “Will the use of HVP in legacy weapon systems provide equivalent offensive and defensive capability and improve logistic operations in mission planning?” Using model-based systems engineering and architecting, the project formalized the criteria needed to perform a quantitative systems analysis for the operational, or mission, flexibility inherent in the HVP system. An in-depth model was created that analyzes the performance of multiple variables in the scenario for both the inclusion and exclusion of the HVP munition, which provides information of the overall effectiveness. The results provide evidence of the benefit of incorporating the HVPs into the weapon systems load out. There are benefits in cost, resupply, and munitions available, while maintaining performance. Based upon the results of this modeling, the initial hypothesis was confirmed that the effectiveness of HVP munitions improve the overall mission success, as well as deliver a cost effective alternative to using only legacy weapon systems.Naval Research ProgramCivilian, Department of the NavyCivilian, Department of the NavyCivilian, Department of the NavyCivilian, Department of the NavyApproved for public release. Distribution is unlimited

Granulocytic sarcoma in a non-leukemic patient presenting with unusual cutaneous paraneoplastic syndrome.

40-year old man was admitted to our Institute because of an erythematous, exfoliative dermatitis, along with a gross right leg and scrotal edema. Histologic examination of the skin biopsy was consistent with a diagnosis of acquired ichthyosis (Figure 1). A total body computed tomography documented the presence of a voluminous mass in the right iliac fossa (Figure 2). Histologic, histochemical and immunohistochemical examinations of a CT-guided biopsy (Figures 3-4) were consistent with the diagnosis of granulocytic sarcoma.1 Support therapy was started, but after 8 days the patient die

Zn doping of YBCO and hall effect study in Y1Ba2(Cu1-xZnx)3O7-δ

Long-exposure photographs taken with a Guinier camera on powders of Zn doped YBCO indicate incomplete inclusion of Zn in YBCO for x>=0.05. The study of the temperature dependence of the Hall number in Zn doped YBCO ceramics shows no substantial change of the number of carriers but the presence of Zn provokes the flattening of Hall number vs T