A possible solution of the grain boundary problem for applications of high-Tc superconductors

It is shown that the critical current density of high-Tc wires can be greatly enhanced by using a threefold approach, which consists of grain alignment, doping, and optimization of the grain architecture. According to model calculations, current densities of 4x10^6 A/cm2 can be achieved for an average grain alignment of 10 degree at 77K. Based on this approach, a road to competitive high-Tc cables is proposed.Comment: 3 pages, 5 figure

Spatial homogeneity and doping dependence of quasiparticle tunneling spectra in cuprate superconductors

Scanning tunneling spectroscopy (STS) studies reveal long-range (similar to 100 nm) spatial homogeneity in optimally and underdoped superconducting YBa2Cu3O7-delta (YBCO) single crystals and thin films, and macroscopic spatial modulations in overdoped (Y0.7Ca0.3)BaCu3O7-delta (Ca-YBCO) epitaxial films. In contrast, STS on an optimally doped YBa2(Cu0.9934Zn0.0026Mg0.004)(3)O-6.9 single crystal exhibits strong spatial modulations and suppression of superconductivity over a microscopic scale near the Zn or Mg impurity sites, and the global pairing potential is also reduced relative to that of optimally doped YBCO, suggesting strong pair-breaking effects of the non-magnetic impurities. The spectral characteristics are consistent with d(x2-y2) pairing symmetry for the optimally and underdoped YBCO, and with (d(x2-y2) + s) for the overdoped Ca-YBCO. The doping-dependent pairing symmetry suggests interesting changes in the superconducting ground state, and is consistent with the presence of nodal quasiparticles for all doping levels. The maximum energy gap Delta (d) is non-monotonic with the doping level, while the (2 Delta (d)/k(B)T(c)) ratio increases with decreasing doping. The similarities and contrasts between the spectra of YBCO and of Bi2Sr2CaCu2O8+x are discussed

Xenon prevents cellular damage in differentiated PC-12 cells exposed to hypoxia

BACKGROUND: The neuroprotective effect of xenon has been demonstrated for glutamatergic neurons. In the present study it is investigated if dopaminergic neurons, i.e. nerve-growth-factor differentiated PC-12 cells, are protected as well against hypoxia-induced cell damage in the presence of xenon. RESULTS: Pheochromocytoma cells differentiated by addition of nerve growth factor were placed in a N(2)-saturated atmosphere, a treatment that induced release of dopamine, reaching a maximum after 30 min. By determining extracellular lactate dehydrogenase concentration as marker for concomitant cellular damage, a substantial increase of enzymatic activity was found for N(2)-treated cells. Replacement of N(2 )by xenon in such a hypoxic atmosphere resulted in complete protection against cellular damage and prevention of hypoxia-induced dopamine release. Intracellular buffering of Ca(2+ )using the Ca-chelator 1, 2-bis(2-Aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl) ester (BAPTA) reduced the neuroprotective effect of xenon indicating the essential participation of intracellular Ca(2+)-ions in the process of xenon-induced neuroprotection. CONCLUSIONS: The results presented demonstrate the outstanding property of xenon to protect neuron-like cells in a hypoxic situation

Impact of response evaluation for resectable esophageal adenocarcinoma – A retrospective cohort study

AbstractIntroduction: The standard treatment concept in patients with locally advanced adenocarcinoma of the esophagogastric junction is neoadjuvant chemotherapy, followed by tumor resection in curative intent. Response evaluation of neoadjuvant chemotherapy using histopathological tumor regression grade (TRG) has been shown to be a prognostic factor in patients with esophageal cancer. Methods: We assessed the impact of the various methods of response control and their value in correlation to established prognostic factors in a cohort of patients with adenocarcinoma at the gastroesophageal junction treated by neoadjuvant chemotherapy. Results: After neoadjuvant chemotherapy, in 56 consecutive patients with locally advanced (T2/3/4 and/or N0/N1) esophageal adenocarcinoma an oncologic tumor resection for curative intent was performed. Median follow-up was 44 months. Histopathological tumor stages were stage 0 in 10.7%, stage I in 17.9%, stage II in 21.4%, stage III in 41.1% and stage IV 8.9%. The 3-year overall survival (OS) rate was 30.3%. In univariate analysis, ypN-status, histopathological tumor stage and tumor regression grade correlated significantly with overall survival (p = 0.022, p = 0.001, p = 0.035 respectively). Clinical response evaluation could not predict response and overall survival (p = 0.556, p = 0.254 respectively). Conclusion: After preoperative chemotherapy, outcomes of esophageal carcinoma are best predicted utilizing pathological tumor stage and histologic tumor regression. Clinical response assessments were not useful for guidance of treatment

The discrete dipole approximation for periodic targets I. theory and tests

The discrete-dipole approximation (DDA) is a powerful method for calculating absorption and scattering by targets that have sizes smaller than or comparable to the wavelength of the incident radiation. The DDA can be extended to targets that are singly- or doubly-periodic. We generalize the scattering amplitude matrix and the 4 x 4 Mueller matrix to describe scattering by singly- and doubly-periodic targets, and show how these matrices can be calculated using the DDA. The accuracy of DDA calculations using the open-source code DDSCAT is demonstrated by comparison to exact results for infinite cylinders and infinite slabs. A method for using the DDA solution to obtain fields within and near the target is presented, with results shown for infinite slabs.Comment: 19 pages, 7 figures, submitted to J. Opt. Soc. Am.

Electronic Transport through YBCO Grain Boundary Interfaces between 4.2 K and 300 K

The current-induced dissipation in YBCO grain boundary tunnel junctions has been measured between 4.2 K and 300 K. It is found that the resistance of 45 degree (100)/(110) junctions decreases linearly by a factor of four when their temperature is increased from 100 K to 300 K. At the superconducting transition temperature Tc the grain boundary resistance of the normal state and of the superconducting state extrapolate to the same value.Comment: 14 pages, 4 figure

Flux flow of Abrikosov-Josephson vortices along grain boundaries in high-temperature superconductors

We show that low-angle grain boundaries (GB) in high-temperature superconductors exhibit intermediate Abrikosov vortices with Josephson cores, whose length $l$ along GB is smaller that the London penetration depth, but larger than the coherence length. We found an exact solution for a periodic vortex structure moving along GB in a magnetic field $H$ and calculated the flux flow resistivity $R_F(H)$, and the nonlinear voltage-current characteristics. The predicted $R_F(H)$ dependence describes well our experimental data on $7^{\circ}$ unirradiated and irradiated $YBa_2Cu_3O_7$ bicrystals, from which the core size $l(T)$, and the intrinsic depairing density $J_b(T)$ on nanoscales of few GB dislocations were measured for the first time. The observed temperature dependence of $J_b(T)=J_{b0}(1-T/T_c)^2$ indicates a significant order parameter suppression in current channels between GB dislocation cores.Comment: 5 pages 5 figures. Phys. Rev. Lett. (accepted

Evidence of Doping-Dependent Pairing Symmetry in Cuprate Superconductors

Scanning tunneling spectroscopy (STS) studies reveal long-range spatial homogeneity and predominantly $d_{x^2-y^2}$-pairing spectral characteristics in under- and optimally doped $\rm YBa_2Cu_3O_{7-\delta}$ superconductors, whereas STS on $\rm YBa_2(Cu_{0.9934}Zn_{0.0026}Mg_{0.004})_3O_{6.9}$ exhibits {\it microscopic} spatial modulations and strong scattering near the Zn or Mg impurity sites, together with global suppression of the pairing potential. In contrast, in overdoped $\rm (Y_{0.7}Ca_{0.3})Ba_2Cu_3O_{7-\delta}$, $(d_{x^2-y^2}+s)$-pairing symmetry is found, suggesting significant changes in the superconducting ground-state at a critical doping value.Comment: 4 pages, 4 figures. Published in Physical Review Letters. Corresponding author: Nai-Chang Yeh (e-mail address: [email protected]

Acute neurological care in north-east Germany with telemedicine support (ANNOTeM): protocol of a multi-center, controlled, open-label, two-arm intervention study

Background: Both diagnosis and treatment of neurological emergencies require neurological expertise and are time-sensitive. The lack of fast neurological expertise in regions with underserved infrastructure poses a major barrier for state-of-the-art care of patients with acute neurological diseases and leads to disparity in provision of health care. The main purpose of ANNOTeM (acute neurological care in North East Germany with telemedicine support) is to establish effective and sustainable support structures for evidence based treatments for stroke and other neurological emergencies and to improve outcome for acute neurological diseases in these rural regions. Methods: A “hub-and-spoke” network structure was implemented connecting three academic neurological centres (“hubs”) and rural hospitals (“spokes”) caring for neurological emergencies. The network structure includes (1) the establishment of a 24/7 telemedicine consultation service, (2) the implementation of standardized operating procedures (SOPs) in the network hospitals, (3) a multiprofessional training scheme, and (4) a quality management program. Data from three major health insurance companies as well as data from the quality management program are being collected and evaluated. Primary outcome is the composite of first time of receiving paid outpatient nursing care, first time of receiving care in a nursing home, or death within 90 days after hospital admission. Discussion: Beyond stroke only few studies have assessed the effects of telemedically supported networks on diagnosis and outcome of neurological emergencies. ANNOTeM will provide information whether this approach leads to improved outcome. In addition, a health economic analysis will be performed. Study registration: German Clinical Trials Register DRKS00013067, date of registration: November 16 th, 2017, URL: http://www.drks.de/DRKS0001306