Multisample Data Acquisition System for Resistance Measurement of High-temperature Superconductors

The construction of a system for simultaneous multiple sample resistance measurement of high-temperature superconductors is reported. The data acquisition system uses the PCLD785B relay board controlled by parallel input-output 8255A PIA emulation through a PCL724B card to perform multisample measurements by signal switching. The system, which is controlled by a 80486 microcomputer, is able to log, store and plot temperature and resistance readings and can be modified to accommodate up to six samples per run. The temperature can be measured with a precision of 0.1 K and accuracy of ±1 K. The absolute-zero offset value is less than 0.1 K. The maximum switching voltage, maximum current and open channel isolation resistance are 125 V, 2 A and 100 MQ, respectively. The closed channe

Synthesis and Formation of T11223 and T1223 High-Tc Superconductors

The preparation methods of Tl2Ba2Ca2Cu30,o (T1l223) and Tlo.5Pbo.5Sr1.6Ca.4Cu30g (TI2223) superconductors using a variety of starting compositions and sintering temperatures are discussed. Single-phased Tl2223 with T, between 106 to 109 K can be prepared using T12Ba2C~Cu3010 and Tl1.6Ba2C~4Cu3010as starting compositions in a non-closed system by heating around 20 min at 910°C in flowing 02' Samples with Tl1223 major phase (- 70%) can be prepared from Tlo.5Pbo.5SrI.6C~.4Cu30gcomposition with the sample wrapped in gold foil and sintered in flowing oxygen at 940°C for 3 hours

Data Acquisition System for Resistance Measurement of High-temperature Superconductors

This paper discusses the design of a data acquisition system based on the 80486 microcomputer serving as a controller connected via a PC-Lab 848B card to digital multimeters and a temperature controller using IEEE 488 standard bus. The system is able to log, store and plot temperature versus resistance readings. Resistance measurement on YBa2Cu3074l) phase is reported and compared with previous results. Measurements on (YO.5 EUO.5)Ba2CuS07.S showed an increase in Tc onset and Tc zero; this was explained in terms of change in the internal pressure in the CuO planes due to partial substitution of larger Eu3+ in place of y3+. This data acquisition system is simple to use and very sensitive in detecting small variations in transition temperatures. The temperature can be measured with a precision of 0.1 K and accuracy of ± I K, which is the limit of the platinum resistor temperature sensor. The absolute-zero offset value is less than 0.1 K

Enhanced levitation force of partial melted (Y,Er)Ba2Cu3O7-8 superconductors with formation of minor 211 phase / Ahmad Kamal Yahya, Suzi Ahmad and Imad Hamadneh

Y0.5 Er 0.5 Ba2 Cu307-8 superconductors with Er2 O3 addition were prepared by partial melting and the effects of excess Er2 03 addition on the magnetic levitation force (MLF) of the partial-melted samples have been investigated. A non-linear relationship was observed between the MLF measured at 77 K and the amount of Er2 O3. It was found that the optimum amount of excess Er2 O3 for enhanced MLF is 10 wt.%. X-ray powder diffraction analysis showed formation of major 123 phase with minor 211 non-superconducting phase for all samples. The results were discussed in detail and the presence of 211 impurities is suggested to act as pinning centers in the 123 samples

Superconducting properties of bulk Bi1.6Pb0.4Sr2Ca2− xCdxCu3O10 system prepared via conventional solid state and coprecipitation methods

The effect of Cd doping on the superconducting properties of BSCCO system with nominal starting compositions of Bi1.6Pb0.4Sr2Ca2−xCdxCu3O10 (x = 0.00–0.10) was studied. The preparation methods used to prepare the samples are the conventional solid-state oxide powder (SSR) and the coprecipitation (COP) techniques. Resistivity versus temperature measurements (R–T) showed that all doped samples exhibited metallic behaviour. For the SSR samples, existence of a two step feature was observed at x = 0.07 indicating the presence a lower temperature 2212 phase together with the higher temperature 2223 phase. This behaviour resulted in the shifting of the TC(R=0) towards lower temperature. However, the COP samples showed better superconducting properties probably due to higher homogeneity resulted from mixing of sub-micron particles during sintering. The R–T curve did not display any two step features due to the single phase nature of the samples. This is confirmed by the XRD data where Bi-2212 phase was minor. In addition, small amount of doping (x = 0.02 in COP and SSR samples) enhanced the phase formation and TC(R=0)

Performance of Shariah vs Non-Shariah Firms: A Study of Manufacturing Sector in Malaysia

This research aims to examine the differences in the determinants of performance between Shariah-compliant and non-Shariah-compliant firms. The changes in the Shariah screening technique in Malaysia since 2013 have significantly affected how firms that comply with the Shariah principles, as opposed to non-compliant firms, leading to the motivation of this research being conducted. This research employs panel data regression analysis to test its hypotheses. Compiling data from 142 manufacturing firms (71 Shariah-compliant and 71 non-Shariah-compliant firms) from 2012 to 2021, this research found that Shariah-compliant firm performance is significantly influenced by firm size, leverage, tangibility and efficiency. In contrast, non-Shariah-compliant firm performance is significantly influenced by leverage, tangibility, working capital and efficiency. This research contributes to relevant parties, such as the manufacturing firms and policymakers, in providing insights on the most relevant indicators affecting firm performance, specifically those in the manufacturing sector

Changes in doping state of (Tl, Pb)Sr1212 superconductors with Yb substitution at Sr site

Samples with nominal starting compositions of Tl0.5Pb0.5Sr2−yYbyCaCu2O7 (y = 0–0.6) were synthesized using conventional solid-state synthesis method. Temperature dependent electrical resistance measurements on the series showed that the normal state behavior and superconducting properties can be controlled by adjusting Yb concentration to achieve maximum critical temperature (Tc). The best superconducting behavior for the series was observed for Tl0.5Pb0.5Sr1.8Yb0.2CaCu2O7 with onset critical temperature (Tc onset) of 105 K. Results of critical temperature (Tc) measurements, microstructure investigation using scanning electron microscope (SEM) and powder X-ray diffraction (XRD) analysis are presented. The effects of Yb substitutions are discussed in terms of Tc, Tl1212 phase formation and the concept of average Cu valence

Effects of concurrent TeO2 reduction and ZnO addition on elastic and structural properties of (90 − x)TeO2–10Nb2O5–(x)ZnO glass

Niobium-containing tellurite glass with starting composition of (90 − x)TeO2–10Nb2O5–(x)ZnO (x = 0–15 mol%) have been prepared by melt-quenching method and the effect of reduction of TeO2 with simultaneous increase in ZnO on elastic properties was studied. Ultrasonic longitudinal and shear velocity showed initial decrease of 3.52% and 2.37%, respectively, at x = 5 mol%. For x > 5 mol%, longitudinal velocity showed weak recovery but shear velocity showed steady recovery with ZnO and recorded 0.95% increase in value at x = 15 mol% compared to x = 0 sample. Shear and Young's moduli recorded similar drop at x = 5 mol% followed by strong recovery at x > 5 mol%, while longitudinal and Bulk modulus showed weak and no recovery, respectively, with x. Infrared (IR) absorption spectra showed increase in intensity of NbO6-assigned peak accompanied by increase in intensity of ZnO4 tetrahedra and TeO4 trigonal bipyramid (tbp) assigned peaks indicating formation of both non-bridging oxygen, NBO and bridging oxygen, BO, respectively, with addition of ZnO. The initial drop in ultrasonic velocity and related elastic moduli observed at x = 5 mol% indicates weakening of network rigidity of the glass system due to structural modification as a direct effect of TeO2 reduction and existence of NBO. However, further replacement of TeO2 by ZnO at x > 5 mol% contributed to increase in BO causing rigidity of the glass network to improve. In addition, hardness, H, was observed to increase with ZnO indicating increase in connectivity of the glass network while Poisson's ratio, σ, decreased indicating increase in cross-link density of the glass system. The combined results of ultrasonic velocity and IR absorption spectra suggest that the role of TeO2 is very critical in the ternary glass system as, although ZnO addition showed improved rigidity due to recovery of shear modulus, the weakening of longitudinal and Bulk moduli indicates ZnO is not fully effective as glass former in place of TeO2

Anomalous dielectric constant and AC conductivity in mixed transition-metal-ion xFe2O3-(20 - x)MnO2-80TeO2 glass system

Glasses with xFe2O3–(20−x)MnO2–80TeO2 (x=2, 5, 10, 15, and 20 mol%) composition were prepared by meltquenching technique to investigate the effects of mixed-transition metal ion Fe2 +/3 +//Mn3 +/4 + on AC conductivity and dielectric properties using impedance spectroscopy. Dielectric constant showed strong variation with Fe2O3 at a frequency ≥10 kHz, where έ decreased to a minimum value at x =10 mol% before increasing for x> 10%. The decrease in έ may be attributed to some form of hindrance effect on heavy dipoles caused by the mixed transition-ion effect (MTE). Meanwhile, variation of AC conductivity with Fe2O3 showed non-linear increase for x ≤ 10 mol% before dropping to a minimum at 15 mol% Fe2O3. This result was attributed to Anderson localization because of the disorder in the glass system. Conductivity analysis showed that the conduction mechanism at the dispersion region for x = 2 mol% followed the correlated barrier hopping (CBH) model, while the mechanism transformed to the overlapping large polaron tunnelling (OLPT) model at higher Fe2O3, content (x > 2 mol%). The electric modulus of the investigated samples showed asymmetric peak of the imaginary part of electric modulus (M¢¢), which reflected a non-Debye type relaxation

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London