Dielectric versus magnetic pairing mechanisms in high-temperature cuprate superconductors investigated using Raman scattering

We suggest, and demonstrate, a systematic approach to the study of cuprate superconductors, namely, progressive change of ion size in order to systematically alter the interaction strength and other key parameters. R(Ba,Sr)$_2$Cu$_3$O$_y$ (R={La, ... Lu,Y}) is such a system where potentially obscuring structural changes are minimal. We thereby systematically alter both dielectric and magnetic properties. Dielectric fluctuation is characterized by ionic polarizability while magnetic fluctuation is characterized by exchange interactions measurable by Raman scattering. The range of transition temperatures is 70 to 107 K and we find that these correlate only with the dielectric properties, a behavior which persists with external pressure. The ultimate significance may remain to be proven but it highlights the role of dielectric screening in the cuprates and adds support to a previously proposed novel pairing mechanism involving exchange of quantized waves of electronic polarization.Comment: Manuscript: 5 pages, 4 figures. Supplemental material included (9 pages, 5 figures

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

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

Prevalence and significance of psammoma bodies in cervicovaginal smears in a cervical cancer screening program with emphasis on a case of primary bilateral ovarian psammocarcinoma

<p>Abstract</p> <p>Background</p> <p>The purpose of our study was to determine the prevalence and significance of psammoma bodies (PBs) in the cervicovaginal smears of the screening population of Trento district (Italy), with the description of the cytological presentation of an asymptomatic bilateral ovarian psammocarcinoma.</p> <p>Methods</p> <p>From 1993 to 2006, women with PBs detected on consecutively screened cervical smears were identified from the computerized pathology database of Rovereto Hospital. The follow-up period was set from the time of cytological diagnosis to May 31^st, 2007. Clinical information was obtained from retrospective review of women's medical records. The source of PBs was identified with adequate diagnostic procedures.</p> <p>Results</p> <p>PBs were found in six of the 201,231 Papanicolaou screening smears (0.0029%). Benign conditions (intrauterine device, inclusion ovarian cysts and ovarian cystoadenofibroma with PBs) were found in four patients. In two cases, PBs were associated with malignant cells; a bilateral ovarian malignancy was diagnosed in both cases, a serous adenocarcinoma and a psammocarcinoma.</p> <p>Conclusion</p> <p>PBs in the cervicovaginal smears are a rare finding, associated more often with benign conditions than with malignancies. Moreover, to our knowledge, our case of primary ovarian psammocarcinoma is the first report in which the presence of malignant cells and PBs in the cervicovaginal and endometrial smears represents the first manifestation of disease.</p

Treating benign paroxysmal positional vertigo of the lateral semicircular canal with a shortened forced position

Benign paroxysmal positional vertigo (BPPV) is the peripheral vestibular disorder that is most frequently encountered in routine neuro-otological practice. Among the three semicircular canals, the lateral semicircular canal (LSC) is the second most frequently interested in the pathological process. In most cases, LSC BPPV is attributable to a canalithiasis or cupulolithiasis mechanism. The clinical picture of LSC BPPV is that of positional nystagmus and vertigo evoked by turning the head from the supine to the side lateral position. With such a movement, a horizontal positional (and often also paroxysmal) direction-changing nystagmus is generated. Depending on whether the pathogenetic mechanism is that of canalithiasis or cupulolithiasis and depending on where the dense particles are located, LSC BPPV direction-changing positional nystagmus is geotropic or apogeotropic on both lateral sides. Due to its mechanical nature, BPPV is effectively treated by means of physical therapy. In the case of a LSC BPPV, one of the most effective therapies is the forced prolonged position (FPP), in which the patient is invited to lie for 12 h on the lateral side on which vertigo and nystagmus are less intense, to move the canaliths out from the canal (or to shift them inside of the canal from one tract to another) exploiting the force of gravity. Despite its efficacy, FPP is not always well tolerated by every patient, and it cannot be done during the diagnostic session because of its duration. The present study aimed to verify the efficacy of a different forced position, shortened forced position (SFP), with respect to the original FPP. SFP treatment would allow patients to more easily bear the forced position and physicians to control the outcome almost immediately, possibly enabling them to dismiss patients without vertigo. After 1 h of lying on the side where vertigo and nystagmus are the less intense, 38 out of 53 (71.7%) patients treated with SFP were either healed or improved. Although the outcomes are not as satisfying as those of the original FPP, SFP should be considered as a therapeutic prospect, especially by those physicians who work in collaboration with emergency departments or otherwise encounter acute patients to cure them of vertigo as soon as possible

Magnetic study of the M-type doped barium ferrite nanocrystalline powders

We have studied the static magnetic properties of three different M‐type doped barium ferrite compounds prepared by the glass crystallization method. The zero‐field‐cooled (ZFC) and field‐cooled (FC) processes have been recorded at low field and they all show the typical features of a small particle system. The ZFC curves display a broad peak at a temperature TM, which depends on the distribution of particle volumes in the sample. Isothermal magnetization curves M(H) at several temperatures and saturation magnetization Ms as a function of temperature have been measured for the Co‐Ti sample (BaFe10.4Co0.8Ti0.8O19). The dependence on temperature of the macroscopic magnetic parameters has been analyzed. The distribution of blocking temperatures is studied from the derivative of the remanent‐to‐saturation magnetization ratio with respect to temperature and it is fitted to a lognormal distribution, leading to a mean blocking temperature 〈TB〉=(81±40) K. The distribution of volumes of the magnetic unit is also obtained from this fitting. The dependence on temperature of the coercive field follows a Tk‐law below 35 K. The value of the k exponent is discussed within the scope of two models: (i) the aligned case (k=0.5) and (ii) the random case (k=0.77)

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