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

Reference design and simulation framework of a multi-megawatt airborne wind energy system

In this paper, we present the design and computational model of a representative multi-megawatt airborne wind energy (AWE) system, together with a simulation framework that accounts for the flight dynamics of the fixed-wing aircraft and the sagging of the tether, combining this with flight control and optimisation strategies to derive the power curve of the system. The computational model is based on a point mass approximation of the aircraft, a discretisation of the tether by five elastic segments and a rotational degree of freedom of the winch. The aircraft has a wing surface area of 150 m2 and is operated in pumping cycles, alternating between crosswind flight manoeuvres during reel out of the tether, and rapid decent towards the ground station during reel in. To maximise the net cycle power, we keep the design parameters of the aircraft constant, while tuning the operational and controller parameters for different wind speeds and given contraints. We find that the presented design can generate a net cycle power of up to 3.8 megawatts

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

Permeation of electroactive solutes through ultrathin polymeric films on electrode surfaces

The rates of permeation of a series of electroactive solutes, bromide, ferrocene, benzoquinone, diquat, (Ru(bpy)2C12), [Fe(bpy)2 (CN) 2], and [Ru(bpy)2(py)Cl] have been measured through ultrathin, electrochemically polynerized films like poly-[Ru(vbpy)3 . The films are coated on Pt disk electrodes. The permeabilities, expressed as PDs pol , the product of a partition coefficient and a diffusion coefficient in the film, range from very fast (bromide, > 4 x 10" cm2 /sec.) to measurable and sensitive to solute size and charge (2 - 58 x 10" cm2/sec.) to immeasurably slow ([Ru(bpy)2(py)Cl] +, < 7 x 10 1 cm2/sec.). The permeation rates vary linearly with film thicknessthis and the molecular size discrimination rule out transport through larger-than-moleculardimensional channels and pinholes in the film. The film permeability process is described as membrane diffusion. Relatively pinhole-free films are preparable as thin as 20 - 40 A

Kite-Powered Design-to-Robotic-Production for Affordable Building on Demand

<p>Building technologies employed today in 2nd and 3rd world countries are imported, expensive, outdated and unsustainable. Highly developed countries, on the other hand, rapidly advance in developing affordable, numerically controlled and robotically supported material- and energy-efficient methods for building on demand. The research team proposes to close this gap by applying advanced design-to-robotic-production (D2RP) technologies developed at Technical University Delft (TUD) to construction problems in 2nd and 3rd world countries. The provided tool base uses refurbished robotic technology, which is retrofitted with state-ofthe-art open source control software, and by employing local approaches and available materials the dependency on imported materials and processes is drastically reduced. The D2RP unit is coupled with the electricity generating Kite Power (KP) system developed at TUD to create a mobile sustainable autarkic unit that can be deployed everywhere.</p

Generalization of the coupled dipole method to periodic structures

We present a generalization of the coupled dipole method to the scattering of light by arbitrary periodic structures. This new formulation of the coupled dipole method relies on the same direct-space discretization scheme that is widely used to study the scattering of light by finite objects. Therefore, all the knowledge acquired previously for finite systems can be transposed to the study of periodic structures.Comment: 5 pages, 2 figures, and 1 tabl

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]

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

Modulating endothelial adhesion and migration impacts stem cell therapies efficacy

Background: Limited knowledge of stem cell therapies‘ mechanisms of action hampers their sustainable implementation into the clinic. Specifically, the interactions of transplanted stem cells with the host vasculature and its implications for their therapeutic efficacy are not elucidated. We tested whether adhesion receptors and chemokine receptors on stem cells can be functionally modulated, and consequently if such modulation may substantially affect therapeutically relevant stem cell interactions with the host endothelium. Methods: We investigated the effects of cationic molecule polyethylenimine (PEI) treatment with or without nanoparticles on the functions of adhesion receptors and chemokine receptors of human bone marrow-derived Mesenchymal Stem Cells (MSC). Analyses included MSC functions in vitro, as well as homing and therapeutic efficacy in rodent models of central nervous system´s pathologies in vivo. Findings: PEI treatment did not affect viability, immunomodulation or differentiation potential of MSC, but increased the CCR4 expression and functionally blocked their adhesion receptors, thus decreasing their adhesion capacity in vitro. Intravenously applied in a rat model of brain injury, the homing rate of PEI-MSC in the brain was highly increased with decreased numbers of adherent PEI-MSC in the lung vasculature. Moreover, in comparison to untreated MSC, PEI-MSC featured increased tumour directed migration in a mouse glioblastoma model, and superior therapeutic efficacy in a murine model of stroke. Interpretation: Balanced stem cell adhesion and migration in different parts of the vasculature and tissues together with the local microenvironment impacts their therapeutic efficacy. Funding: Robert Bosch Stiftung, IZEPHA grant, EU grant 7 FP Healt