High-field measurements on YBCO

We have performed resistance measurements on thin films of the high-temperature superconductor YBa₂Cu₃O₇ (YBCO) in applied magnetic fields to above 200 T (2 MegaOersted) at temperatures as low as 2.5 K. The fields are produced by an explosively driven flux-compression system. We can see a particularly clear onset, without replotting the data, of the hydrodynamic flow of vortices probably because of the very fast increasing field. The low-temperature critical field for the field parallel to the c-axis of the sample is 135 T. Our data in the other direction are still preliminary. We discuss possible interpretation of our results.     

Semi-parametric Estimation Based on Second Order Parameter for Selecting Optimal Threshold of Extreme Rainfall Events

Analysis of extreme rainfall events can be performed using two main approaches; fitting Generalized Extreme Value distribution to the yearly peaks of events in the observation period or the annual maximum series, and fitting Generalized Pareto distribution to the peaks of events that exceed a given threshold or the partial duration series. Even though partial duration series are able to reduce sampling uncertainty and are useful for analyzing extreme values and tail asymmetries, the series require an optimal threshold. The objective of this study is to compare and determine the best method for selecting the optimal threshold of partial duration series using hourly, 12-hour and 24-hour data of rainfall time series in Peninsular Malaysia. Nine semi-parametric second order reduced-bias estimators are applied to estimate extreme value index and six estimators are used for the external estimation of the second order parameter. A semi-parametric bootstrap is used to estimate mean square error of the estimator at each threshold and the optimal threshold is then selected based on the smallest mean square error. Based on the plots of extreme value index and mean square error, several second order reduced-bias estimators behave reasonably well compared to Hill estimator, as indicated by their stable sample paths and flatter mean square errors.     

Participation rates in physics 12 in BC: Science teachers’ and students’ views

Abstract

In recent years, participation rates in the British Columbia (BC) provincial physics exams have been low, compared with chemistry and biology. A qualitative study employing questionnaire and interview methods sought the views of teachers and students of senior science courses on why this is the case. Data analysis revealed that students’ decisions about Physics 12 were influenced by their perceptions of the mathematical content of physics, the physics teachers’ personalities and teaching styles, the perceived difficulty of physics, and prior experience of physics. We conclude that enhancing student interest in taking physics at advanced high school levels may necessitate a wider, more articulated exposure to topics in physics, together with more careful attention to mathematical background and skills.     

Science studies,situatedness, and instructional design in science education: A summary and critique of the promise

Abstract

This article critically examines the claim that findings from the sociology of science (or science studies) literature may be used as benchmarks in designing authentic school science curricula. First, it argues that such instructional design claims are based on erroneous understandings of the concepts of situated learning and authenticity, which result from the historically evaluative orientation of education research. Second, it considers several specific claims about the success of designed environments from the science education literature (Roth & McGinn, 1998), and contrasts those claims with an alternative way of viewing students’ work in school science. The article concludes that science education could productively consider situated actions in school science settings as interesting and authentic phenomena in their own right, apart from measuring them against professional scientific activities.     

Revisiting the IISS Small‐Gain Theorem through Transient Plus ISS Small‐Gain Regulation

Recently, the small‐gain theorem for input‐to‐state stable (ISS) systems has been extended to the class of integral input‐to‐state stable (iISS) systems. Feedback connections of two iISS systems are robustly stable with respect to disturbance if an extended small‐gain condition is satisfied. It has been proved that at least one of the two iISS subsystems needs to be ISS for guaranteeing globally asymptotic stability and iISS of the overall system. Making use of this necessary condition for the stability, this paper gives a new interpretation to the iISS small gain theorem as transient plus ISS small‐gain regulation. The observation provides useful information for designing and analyzing nonlinear control systems based on the iISS small‐gain theorem.     

Sharing visual features for multiclass and multiview object detection

We consider the problem of detecting a large number of different classes of objects in cluttered scenes. Traditional approaches require applying a battery of different classifiers to the image, at multiple locations and scales. This can be slow and can require a lot of training data since each classifier requires the computation of many different image features. In particular, for independently trained detectors, the (runtime) computational complexity and the (training-time) sample complexity scale linearly with the number of classes to be detected. We present a multitask learning procedure, based on boosted decision stumps, that reduces the computational and sample complexity by finding common features that can be shared across the classes (and/or views). The detectors for each class are trained jointly, rather than independently. For a given performance level, the total number of features required and, therefore, the runtime cost of the classifier, is observed to scale approximately logarithmically with the number of classes. The features selected by joint training are generic edge-like features, whereas the features chosen by training each class separately tend to be more object-specific. The generic features generalize better and considerably reduce the computational cost of multiclass object detection     

Ozonolysis of Naphthalene Derivatives in Water and in Kerosene Films

In an aqueous solution of the water-soluble constituents of kerosene, naphthalenes were destroyed more quickly by ozone than alkylbenzenes at both pH 5 and pH 9. When a kerosene surface film was ozonized, selective attack on aromatic relative to aliphatic hydrocarbon constituents occurred. Alkylbenzoic acids were the major products. Other oxygenated products (aldehydes, alcohols, peroxides) also were detected at lower concentrations. When ozonized separately, naphthalene reacted to form 2-formylcinnamaldehyde, 1-methylnaphthalene produced methylated isomers of 2-formylcinnamaldehyde, and tetrahydronaphthalene formed 1-tetralone.     

X-ray photoelectron spectroscopy study on the photodegradation of copolyester model compounds

The photodegradation of irradiated PETG and PCCT model compounds namely Tm-CHDM-Tm and Tm-TMCD-Tm, where Tm refers to the methyl ester of terephthalic acid, CHDM refers to 1, 4-cyclohexanedimethanol, and TMCD refers to tetramethyl-1, 3-cyclobutanediol, was analyzed using X-ray photoelectron spectroscopy. Photodegradation products were characterized based on high resolution O_1s x-ray photoelectron spectroscopy (XPS) spectra and the spectra of irradiated model compounds showed a decrease in the relative intensity of C O compared to the CO peak. The percentage of CO formation in irradiated model compounds changed in proportion to irradiation time and showed that the model compound containing CHDM was slightly more UV stable than the TMCD based model compound. Photodegradation mechanisms for model compounds were proposed based on XPS spectra. In parallel studies, density functional theory calculations were performed as an approach to predict degradation products, to help interpreting the XPS spectra of model compounds and characterize the reactivity of model compounds.     

Input electrical impedance as signature for nondestructive evaluation of weld quality during ultrasonic welding of plastics

As a wide applied joining process of plastics with long history, ultrasonic welding of plastics could be helped by newer technologies in sensing, pattern recognition, etc. to improve production rate and weld quality. This paper introduces a new concept which allows in situ monitoring of an ultrasonic welding process in real time and assessing the resulted weld quality right after the completion of the process. In the method, the input voltage and current of a welding machine are first probed and processed to obtain the input electrical impedance during the whole welding period. Because there are no changes of the dynamic properties of the welding machine and fixtures during the process, the detected waveforms of the real and imaginary part of the impedance directly reflect the thermo-mechanical behavior of the plastic work-pieces at the joining point. By recognizing the patterns of these waveforms, the joining quality could then be properly evaluated. This new concept and the accordingly derived nondestructive evaluation method were investigated experimentally. The results show that the input electrical impedance is an effective signature and that the built system evaluates bonding quality of welds effectively and efficiently.     

Design,Synthesis and Evaluation of Oxazaborine Inhibitors of the NLRP3 Inflammasome

The NLRP3 inflammasome is an important regulator of the sterile inflammatory response, and its activation by host‐derived sterile molecules leads to the intracellular activation of caspase‐1, processing of the pro‐inflammatory cytokines interleukin‐1β (IL‐1β)/IL‐18, and pyroptotic cell death. Inappropriate activation of NLRP3 drives a chronic inflammatory response and is implicated in several non‐communicable diseases, including gout, atherosclerosis, type II diabetes and Alzheimer's disease. In this study, we report the design, synthesis and biological evaluation of novel boron compounds (NBCs) as NLRP3 inflammasome inhibitors. Structure–activity relationships (SAR) show that 4‐fluoro substituents on the phenyl rings retain NLRP3 inhibitory activity, whereas more steric and lipophilic substituents diminish activity. Loss of inhibitory activity is also observed if the CCl₃ group on the oxazaborine ring is replaced by a CF₃ group. These findings provide additional understanding of the NBC series and will aid in the development of these NLRP3 inhibitors as tool compounds or therapeutic candidates for sterile inflammatory diseases.