Generation of Bulk HTS with Doped Tungstates

Doped tungstates exhibit superconductivity as indicated to occur mainly at the surface of the WO₃ grains present. To generate bulk 3D superconducting material of doped tungstates, it is proposed to employ the recently discovered UV-generated synthesis of complex oxides from mixed simple oxides by illuminating the mixture with ultraviolet light at modest temperatures, as found in Shengelaya’s group in Tbilisi, and to generate a percolating 3D network of 2D superconducting sheets using the smallest basis oxides as the starting material. The latter procedure was demonstrated recently to be very effective in a collaboration with the present author (Daraselia et al., J. Appl. Phys. 121, 145104, 2017). If this proposition is successful, it would establish the doped tungstates as a second group of HTS besides the copper oxides that could be chosen for certain applications.     

Cognitive training and strategy behavior: comparative evaluation of 2 cognitive training programs

Combining a non-comparative with a comparative evaluation, two modern programs for fostering inductive reasoning, namely the German version of the "Cognitive training for children" by Klauer and Phye (1994; Klauer 1989), and the "DenkMit" by Sydow and Meincke (1994), are compared to each other and to a control program which intends to enhance aspects of memory instead of inductive reasoning. The programs were performed with N = 49 children between six and eight years who had been postponed from regular school because of various reasons or who had been selected as especially in need for particular interventions from first classes. Besides the psychometric test often used for assessing inductive reasoning, i.e. three subtests of the German form of the Culture Fair Test by Cattell (Weiss a. Osterland 1980), tasks of concept formation were applied for assessing changes in strategic behavior of children--a type of task which has been used in connection with inductive reasoning since many years. Counter to expectations, the children whose memory was trained, showed changes in performance in the psychometric test in a similar size as the children whose inductive reasoning was trained. These effects are interpreted in terms of special attention directed to the children during the intervention situation. Moreover, it was found that despite the authors claim to the opposite the DenkMit did not cause any changes in visual perception. In contrast to the author's intentions, the "Cognitive Training for Children" did cause some substantive changes in the area of visual perception. The pattern of results with the concept formation tasks, however, overall indicates that the reasoning programs caused some changes in strategic behaviors of the children. Although these changes are not very impressive, they cannot be attributed to extraneous factors such as special attention.     

Energy gap distribution of HgBa2CuO4+δ investigated by scanning tunneling microscopy/spectroscopy

The superconducting energy gap distribution of poly crystalline HgBa₂CuO₄₊ samples of differing oxygen doping levels (T_c = 94 K and T_c = 96 K) is determined by scanning tunneling spectroscopy (STS) using a low temperature scanning tunneling microscope (STM). From histograms of energy gap values the presence of two distinct energy gaps is inferred (₁=8.5±1.6meV and ₂=15.1±1.4meV). We attribute the different gaps to different crystallographic faces, implying a non-BCS electron-electron pairing mechanism.     

Polarization-dependent angle-resolved photoemission of the layered cuprate Ba2Cu3O4Cl2

We report polarization-dependent angle-resolved photoemission studies of single crystalline Ba₂Cu₃O₄Cl₂. This antiferromagnet adopts a layered body-centered tetragonal structure related to that of the cuprates, but with anextra copper site resulting in a plane with Cu₃O₄ stoichiometry. For the -M direction of the Brillouin zone we observe a dispersive feature with a bandwidth of 400 ±80 meV, which approaches to within 0.9 eV of the Fermi level at (/2,/2). The magnitude of the observed dispersion and its polarization dependence are consistent with its origin as a purely antibonding combination of O2p_x,y and atomic orbitals from the cuprate-like CuO₂ sub-system, i.e. Zhang-Rice singlets.     

Scanning/friction force microscopy study of YBa2Cu3O7−δ single crystals grown in BaZrO3 crucibles

Very pure YBa₂Cu₃O_7– (YBCO) single crystals grown in BaZrO₃ crucibles are studied in the as-grown and the oxidized state by scanning force (SFM), friction force (FFM) and scanning tunneling microscopies (STM). The images show clean terraces with step-heights of one unit cell along YBCO(001), i.e. 1.2 nm. Only close to step edges is material contrast observed by FFM indicating traces af flux. Some crystal surfaces exhibit over-layer features, such as star-like, ribbon-like and checkerboard-like structures, which exhibit friction contrast implying the presence of different materials on the surface. Tunneling spectroscopy at 4.7 K in high vacuum reveals a superconducting energy gap of 2 26 me V.     

Long-term effects of continuous intrathecal opioid treatment in chronic pain of nonmalignant etiology

In the present retrospective investigation, the long-term effects of continuous intrathecal opioid therapy via implantable infusion pump systems were examined in 120 patients with chronic, nonmalignant pain syndromes. The follow-up period was 6 months to 5.7 years (mean 3.4 years +/- 1.3 standard error of the mean). Deafferentation pain and neuropathic pain showed the best long-term results, with 68% and 62% pain reduction (visual analog scale), respectively. The mean morphine dosage initially administered was 2.7 mg/day (range 0.3-12 mg/day); after an average of 3.4 years, it was 4.7 mg/day (range 0.3-12 mg/day). In a long-term observation of 28 patients who received intrathecal morphine for longer than 4 years. 18 patients (64.3%) had a constant dosage history and 10 patients (35.7%) showed an increase in morphine dosage to more than 6 mg/day 1 year after dosage determination. In seven cases, a tolerance developed: in four patients the tolerance was controlled by means of "drug holidays"; but in three patients it was necessary to remove the pump systems. Explantation of the pump system occurred in 22 additional cases for other reasons. Throughout the follow-up period, 74.2% of the patients profited from the intrathecal opiate therapy: the average pain reduction after 6 months was 67.4% and, as of the last follow-up examination, it was 58.1%. Ninety-two percent of the patients were satisfied with the therapy and 81% reported an improvement in their quality of life. The authors' 6-year experience with administration of intrathecal opioid medications for nonmalignant pain should encourage the use of this method in carefully selected patients.     

Learning short synfire chains by self-organization

A model of cortical neurons capable of sustaining a low level of spontaneous activity is investigated. Without learning the activity of the network is chaotic. We report on attempts to learn synfire chains in this type of network by introducing a Hebbian learning mechanism and exciting a small set of neurons at random intervals. We discuss the types of instabilities that can arise and prevent the formation of long synfire chains and also discuss various biologically plausible mechanisms which to some extent cure these instabilities.     

Adaptive isogeometric analysis by local h-refinement with T-splines

Isogeometric analysis based on non-uniform rational B-splines (NURBS) as basis functions preserves the exact geometry but suffers from the drawback of a rectangular grid of control points in the parameter space, which renders a purely local refinement impossible. This paper demonstrates how this difficulty can be overcome by using T-splines instead. T-splines allow the introduction of so-called T-junctions, which are related to hanging nodes in the standard FEM. Obeying a few straightforward rules, rectangular patches in the parameter space of the T-splines can be subdivided and thus a local refinement becomes feasible while still preserving the exact geometry. Furthermore, it is shown how state-of-the-art a posteriori error estimation techniques can be combined with refinement by T-splines. Numerical examples underline the potential of isogeometric analysis with T-splines and give hints for further developments.