Heating in mesa structures

Analytic and computational methods are used to consider the e®ects of heating on IV mea- surements on commonly used mesa structures fabricated from single crystals of highly anisotropic superconductors. We address the time dependence of the temperature rise as well as its ultimate value and discuss the relative advantages for measurements of employing small mesa-size, short pulses and ns-to-¹s measurements

Quasiparticle tunnelling and field-dependent critical current in 2212-BSCCO

Intrinsic c-axis tunnelling in the superconducting state has been measured in zero and finite fields in small mesa structures fabricated on the surface of 2212-BSCCO single crystals. The temperature dependence of the zero-field critical current and quasi-particle conductance is related to microscopic d-wave models in the presence of impurity scattering. The strong field dependence of the c-axis critical current provides information on the correlation of flux pancakes across adjacent superconducting bi-layers. An instability in the IV characteristics is observed below 20K, which accounts for the apparent drop in critical current at low temperatures previously reported

Interlayer tunnelling in Bi2Sr2CaCu2O8+d single crystals

We present measurements of the intrinsic quasi-particle conductivity along the c-axis of 2212-BSCCO single-crystal mesa structures in the superconducting and normal states. Direct measurement of the mesa temperature enables corrections to be made for self-heating and permits the acquisition of reliable I-V characteristics over a wide range of temperatures and voltages. Unlike a conventional superconductor, there is no evidence for any change in the quasiparticle conductivity at Tc, consistent with precursor pairing of electrons in the normal state. At low temperatures the initial low-voltage linear conductivity exhibits a T2 dependence, approaching a limiting value at zero temperature

Intrinsic c-axis transport in 2212-BSCCO

We describe two experimental approaches to circumvent the problem of self-heating in IV measurements on small mesa samples of 2212-BSCCO. Simultaneous dc and temperature measurements have been performed, allowing corrections for heating to be made. Short pulse measurements have also been made, where the IV characteristics and the mesa temperature can be measured on a $\mu$s time-scale enabling intrinsic IV characteristics to be derived, even in the presence of appreciable self-heating. Self-heating leads to an appreciable depression of the apparent energy gap and also accounts, in major part, for the s-shaped characteristics often reported at high currents. By correcting for the temperature rise, we derive the intrinsic temperature dependence of the tunnelling characteristics for crystals with a range of doping. Results are compared with recent theoretical models for c-axis transport in d-wave superconductors

System for fast time-resolved measurements of c-axis quasiparticle conductivity in intrinsic Josephson junctions of 2212-BSCCO

A wide-band cryogenic ampli¯er measurement system for time-resolved 4-point VI-characteristic measurements on Bi2Sr2CaCu2O8+± mesa structures is described. We present measurements which demonstrate the importance of self-heating on » 50 ns time scales. Such heating is likely to have been very signi¯cant in many previously published measurements, where the reported nonlinear VI characteristics have been used to derive superconducting energy gaps

Efficacy of live B1 or Ulster 2C Newcastle disease vaccines simultaneously vaccinated with inactivated oil adjuvant vaccine for protection of Newcastle disease virus in broiler chickens

Two hundred, one-day-old broiler chicks were divided into groups 1, 2 and 3 containing 60, 70 and 70 chicks, respectively. The groups were divided into subgroups of 10 chicks that were vaccinated according to the following scheme: group 1 unvaccinated control, group 2 vaccinated subcutaneously at 1 day old with inactivated oil adjuvant vaccine (IOAV) in combination with live B1 vaccine. Group 3 was vaccinated in the same mode as group 2 with IOAV and live Ulster 2C vaccine. All birds were challenged when they were 28 days old. Mortality rate, body weight gain and feed conversion ratio (FCR) were monitored before and after challenge. All the chickens in group 1 died, indicating that there was no disease resistance of this unvaccinated control group of chickens. Conversely, the monitored disease resistance of chickens in groups 2 and 3 was 68.57% ± 18.64 and 88.57% ± 9.00, respectively (P < 0.05). The morbidity of chickens in groups 2 and 3 was 37.89% ± 14.36 and 14.76% ± 12.40, respectively (P < 0.05). The body weight gain, feed intake and FCR of group 3 were significantly better than those of group 2 (P < 0.05) during 1–42 days old. The simultaneous vaccination with B1 or Ulster 2C and IOAV of 1-day-old chicks gave some protection of 28-day-old broilers without a booster vaccination

Identifying and quantifying heterogeneity in high content analysis: Application of heterogeneity indices to drug discovery

One of the greatest challenges in biomedical research, drug discovery and diagnostics is understanding how seemingly identical cells can respond differently to perturbagens including drugs for disease treatment. Although heterogeneity has become an accepted characteristic of a population of cells, in drug discovery it is not routinely evaluated or reported. The standard practice for cell-based, high content assays has been to assume a normal distribution and to report a well-to-well average value with a standard deviation. To address this important issue we sought to define a method that could be readily implemented to identify, quantify and characterize heterogeneity in cellular and small organism assays to guide decisions during drug discovery and experimental cell/tissue profiling. Our study revealed that heterogeneity can be effectively identified and quantified with three indices that indicate diversity, non-normality and percent outliers. The indices were evaluated using the induction and inhibition of STAT3 activation in five cell lines where the systems response including sample preparation and instrument performance were well characterized and controlled. These heterogeneity indices provide a standardized method that can easily be integrated into small and large scale screening or profiling projects to guide interpretation of the biology, as well as the development of therapeutics and diagnostics. Understanding the heterogeneity in the response to perturbagens will become a critical factor in designing strategies for the development of therapeutics including targeted polypharmacology. © 2014 Gough et al

Evidence for a novel Kit adhesion domain mediating human mast cell adhesion to structural airway cells

Background: Human lung mast cells (HLMCs) infiltrate the airway epithelium and airway smooth muscle (ASM) in asthmatic airways. The mechanism of HLMC adhesion to both cell types is only partly defined, and adhesion is not inhibited by function-blocking anti-Kit and anti-stem cell factor (SCF) antibodies. Our aim was to identify adhesion molecules expressed by human mast cells that mediate adhesion to human ASM cells (HASMCs) and human airway epithelial cells. Methods: We used phage-display to isolate single chain Fv (scFv) antibodies with adhesion-blocking properties from rabbits immunised with HLMC and HMC-1 membrane proteins. Results: Post-immune rabbit serum labelled HLMCs in flow cytometry and inhibited their adhesion to human BEAS-2B epithelial cells. Mast cell-specific scFvs were identified which labelled mast cells but not Jurkat cells by flow cytometry. Of these, one scFv (A1) consistently inhibited mast cell adhesion to HASMCs and BEAS-2B epithelial cells by about 30 %. A1 immunoprecipitated Kit (CD117) from HMC-1 lysates and bound to a human Kit-expressing mouse mast cell line, but did not interfere with SCF-dependent Kit signalling. Conclusion: Kit contributes to human mast cell adhesion to human airway epithelial cells and HASMCs, but may utilise a previously unidentified adhesion domain that lies outside the SCF binding site. Targeting this adhesion pathway might offer a novel approach for the inhibition of mast cell interactions with structural airway cells, without detrimental effects on Kit signalling in other tissues

Integer and half-integer flux-quantum transitions in a niobium/iron-pnictide loop

The recent discovery of iron-based superconductors challenges the existing paradigm of high-temperature superconductivity. Owing to their unusual multi-orbital band structure, magnetism, and electron correlation, theories propose a unique sign reversed s-wave pairing state, with the order parameter changing sign between the electron and hole Fermi pockets. However, because of the complex Fermi surface topology and material related issues, the predicted sign reversal remains unconfirmed. Here we report a novel phase-sensitive technique for probing unconventional pairing symmetry in the polycrystalline iron-pnictides. Through the observation of both integer and half-integer flux-quantum transitions in composite niobium/iron-pnictide loops, we provide the first phase-sensitive evidence of the sign change of the order parameter in NdFeAsO0.88F0.12, lending strong support for microscopic models predicting unconventional s-wave pairing symmetry. These findings have important implications on the mechanism of pnictide superconductivity, and lay the groundwork for future studies of new physics arising from the exotic order in the FeAs-based superconductors.Comment: 23 pages, including 4 figures and supplementary informatio