d-wave pairing symmetry in cuprate superconductors

Phase-sensitive tests of pairing symmetry have provided strong evidence for predominantly d-wave pairing symmetry in both hole- and electron-doped high-Tc cuprate superconductors. Temperature dependent measurements in YBCO indicate that the d-wave pairing dominates, with little if any imaginary component, at all temperatures from 0.5K through Tc. In this article we review some of this evidence and discuss the implications of the universal d-wave pairing symmetry in the cuprates.Comment: 4 pages, M2S 2000 conference proceeding

Evidence for Thermally Activated Spontaneous Fluxoid Formation in Superconducting Thin-Film Rings

We have observed spontaneous fluxoid generation in thin-film rings of the amorphous superconductor Mo$_3$Si, cooled through the normal-superconducting transition, as a function of quench rate and externally applied magnetic field, using a variable sample temperature scanning SQUID microscope. Our results can be explained using a model of freezout of thermally activated fluxoids, mediated by the transport of bulk vortices across the ring walls. This mechanism is complementary to a mechanism proposed by Kibble and Zurek, which only relies on causality to produce a freezout of order parameter fluctuations.Comment: 4 pages, 3 figure

Electron localization effects on the low-temperature high-field magnetoresistivity of three-dimensional amorphous superconductors

he electrical resistivity ρ of three-dimensional amorphous superconducting films a-Mo3Si and a-Nb3Ge is measured in magnetic fields μ0H up to 30 T. At low temperatures and at magnetic fields above the upper critical field Hc2, ρ is temperature independent and decreases as a function of magnetic field. This field dependence is consistent with localization theory in the high-field limit [μ0H≫ħ/(4eLφ2), where Lφ is the phase-coherence length]. Above the superconducting transition temperature Tc, the temperature dependence of the conductivity is consistent with inelastic scattering processes which are destructive to the phase coherence for electron localization, thereby allowing estimates for Lφ(T). The Hall effect data on a-Mo3Si, in conjunction with the resistivity data, allow the determination of the carrier concentration and mean free path. The upper critical field is comparable to (in a-Mo3Si) and significantly larger than (in a-Nb3Ge) the Clogston-Chandrasekhar paramagnetic limit. This phenomenon is discussed in the context of electron localization

A Circle With Edges: How Story Time Privileges the Abled Learner

Takes a critical look at one of the commonplace features of early childhood classrooms—story time. In her essay, Melissa considers the ways in which story time reinforces unequal power dynamics for diverse learners by privileging the able-bodied learner. In response, Melissa creates and presents the SPHERE model, which promotes active engagement and shared dialogue through collaborative storytelling and nurtures an inclusive literacy-learning environment

Accuracy study of the Upper Atmosphere Research Satellite (UARS) definitive attitude determination

The Upper Atmosphere Research Satellite (UARS) has two definitive attitude determination requirements: the definitive attitude of the Modular Attitude Control Subsystem (MACS) and the definitive attitude of the gimbaled Solar-Stellar Pointing Platform (SSPP). The onboard computer (OBC) will compute the MACS attitude using a Kalman filter and will transform this attitude solution through the SSPP gimbals to calculate the SSPP attitude. The attitude ground support system (AGSS) will compute the MACS attitude using a batch least-squares differential corrector algorithm and will also transform this solution through the gimbals to obtain the SSPP attitude. This paper reports the results of a prelaunch study to predict the accuracy of the OBC attitude solutions and the accuracy of the AGSS attitude solutions. The OBC and AGSS solution accuracies are then compared to establish the relative quality. The effects of star observability, sensor noise, and sensor misalignment uncertainties on attitude determination accuracy are analyzed for each case

Protein engineering of the pH dependence and substrate specificity of glucoamylase from Aspergillus awamori

Glucoamylase (EC 3.2.1.3) (GA), an enzyme that catalyzes the release of [beta]-D-glucose from the nonreducing ends of starch and related oligo- and polysaccharides, is widely used in industry to produce high-glucose syrups. Site-directed mutagenesis was used to construct mutations to obtain mutant enzymes with industrially desired alterations in pH dependence and substrate specificity;An increased pH optimum for GA would be industrially desirable so that it could be used in process conditions more similar to that of other enzymatic steps in starch processing. Five mutations were designed to remove or weaken the hydrogen bond between Ser411 and Glu400 (the general catalytic base), in order to destabilize the carboxylate ion form of Glu400, and thereby raise its pK. All five mutations, Ser411→Cys, Ser411→Ala, Ser411→His, Ser411→Asp and Ser411→Gly, increased the optimal pH of GA. Ser411→Ala is the best performing pH mutant of GA isolated to date. Ser411→Ala GA increased the optimal pH by 0.84 units while maintaining a high level of catalytic activity (k cat) and catalytic efficiency ( kcat/Km);For substrate specificity, reducing isomaltose formation from glucose condensation would be industrially desirable so that the glucose yield in starch processing could be increased. The substrate specificity of ten single mutations and a double mutation were investigated. Compared to wild-type GA, Ser119→Glu, Ser119→Gly, Ser119→Trp, Tyr175→Phe, Arg241→Lys and Ser411→Gly GAs were highly active. Tyr116→Trp, Gly121→Ala, Ser411→Ala and Gly121→Ala/Ser411→Gly GAs had moderately decreased activity. Tyr48Phe49→Trp GA, however, had severely decreased activity. The ratio of the initial rate of isomaltose production (from glucose condensation reactions) to that of glucose production (from the hydrolysis of DE 10 maltodextrin) was used to represent the ability to synthesize isomaltose at a normalized level DE 10 maltodextrin hydrolytic activity. Compared to wild-type GA, mutant Ser119→Gly, Ser119→Trp, Gly121→Ala, Tyr175→Phe, Ser411→Ala, Ser411→Gly and Gly121→Ala/Ser411→Gly GAs showed a decrease in this ratio at 35°C. Only Tyr175→Phe, Ser411→Ala, Ser411→Gly and Gly121→Ala/Ser411→Gly GAs, however, showed a decrease in this ratio at 55°C. Mutant Tyr175→Phe, Ser411→Ala, and Ser411→Gly GAs have great potential for increasing the glucose yield in industrial starch processing applications

Effects of metformin on human monocytic THP-1 cells - Implications for type 2 diabetes mellitus

Metformin is an anti-hyperglycaemic agent widely prescribed for type 2 diabetes (T2D). Despite decades of clinical use, its exact pharmacological mechanism(s) is yet to be definitively determined. Accumulative data have shown its mild inhibitory effect on the complex 1 of the mitochondrial respiratory chain, which is thought to contribute to its anti-hyperglycaemic effect. Metformin is also thought to have a protective effect on cardiovascular disease (CVD), the most common complication in T2D. It is widely accepted that T2D is an inflammatory state thus it is not surprising that T2D patients have 2-4 times higher risk in developing CVD. Furthermore, the pathology of T2D has been proposed to involve dysfunctioning mitochondria, the organelle of energy sensing and production. The use of metformin, a mitochondria inhibitor, in cells under mitochondrial stress led us to speculate the physiological responses that ensue. To understand metformin‟s mode of action and its involvement in inflammation processes the human monocytic leukemia THP-1 cells were used in this study. Since studies of metformin on this cell type is scarce if not non-existence the first task was to determine its cytoxicity in this cell line. Next the mRNA and protein expressions of heat shock protein 60 (Hsp60), a mitochondrial stress marker, was determined in metformin-treated THP-1 cells. Further, various cell types have shown surface expressed Hsp60 under stress conditions. Thus the study here attempted to optimise the detection of surface Hsp60 in THP-1 cells, as human Hsp60 has been shown to induce innate immune response. Localisation of Hsp60 on the cell surface in metformin-treated cells may exacerbate the already-inflammed state of T2D. Lastly, metformin‟s effect on PMA-stimulated monocyte differentiation was determined by the mRNA expression of CD14, a surface receptor on macrophages. The results here agreed with published data that metformin at therapeutic concentrations are not cytotoxic and is a mild inhibitor of mitochondrial respiration. We also provide evidence that metformin up-regulated the mitochondria stress protein, Hsp60, in a time- and dose-dependent manner. In addition, live cell Hsp60 immunocytochemistry proved to be a promising method for surface Hsp60 detection in THP-1 cells. Finally, at the therapeutic concentration metformin caused a significant up-regulation in cd14 expression, which contradicts with much acclaimed protective effect of metformin in the literature

Quantifying VIO Uncertainty

We compute the uncertainty of XIVO, a monocular visual-inertial odometry system based on the Extended Kalman Filter, in the presence of Gaussian noise, drift, and attribution errors in the feature tracks in addition to Gaussian noise and drift in the IMU. Uncertainty is computed using Monte-Carlo simulations of a sufficiently exciting trajectory in the midst of a point cloud that bypass the typical image processing and feature tracking steps. We find that attribution errors have the largest detrimental effect on performance. Even with just small amounts of Gaussian noise and/or drift, however, the probability that XIVO's performance resembles the mean performance when noise and/or drift is artificially high is greater than 1 in 100

Probing the order parameter symmetry in the cuprate high temperature superconductors by SQUID microscopy

The orbital component of the order parameter in the cuprate high-Tc cuprate superconductors is now well established, in large part because of phase sensitive tests. Although it would be desirable to use such tests on other unconventional superconductors, there are a number of favorable factors associated with the properties of the cuprates, and a number of technical advances, that were required for these tests to be successful. In this review I will describe the development of phase sensitive pairing symmetry tests using SQUID microscopy, underlining the factors favoring these experiments in the cuprates and the technical advances that had to be made.Comment: 12 pages, 7 figure, invited review to be published in Comptes Rendus de l'Academie des Sciences (Comptes Rendus Physique