Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound

We report on the comprehensive experimental and theoretical studies of magnetic and electronic structural properties of the Gd_0.4Tb_0.6Co₂ compound crystallization in the cubic Laves phase (C15). We present new results and compare them to those reported earlier. The magnetic study was completed with electronic structure investigations. Based on magnetic isotherms, magnetic entropy change (ΔS_M) was determined for many values of the magnetic field change (Δμ₀H), which varied from 0.1 to 7 T. In each case, the ΔS_M had a maximum around room temperature. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that the compound undergoes a magnetic phase transition of the second type. From the M(T) dependency, the exchange integrals between rare-earth R-R (J_RR), R-Co (J_RCo), and Co-Co (J_CoCo) atoms were evaluated within the mean-field theory approach. The electronic structure was determined using the X-ray photoelectron spectroscopy (XPS) method as well as by calculations using the density functional theory (DFT) based Full Potential Linearized Augmented Plane Waves (FP-LAPW) method. The comparison of results of ab initio calculations with the experimental data indicates that near T_C the XPS spectrum collects excitations of electrons from Co3d states with different values of exchange splitting. The values of the magnetic moment on Co atoms determined from magnetic measurements, estimated from the XPS spectra, and results from ab initio calculations are quantitatively consistent.     

Comparison of Properties of Hardfaced Layers Made by a Metal-Core-Covered Tubular Electrode with a Special Chemical Composition

In this article, the results of research on the metal-mineral-type abrasive wear of a wear-resistant plate made by a tubular electrode with a metallic core and an innovative chemical composition using the manual metal arc hardfacing process were presented. The properties of the new layer were compared to the results of eleven wear plates manufactured by global suppliers, including flux-cored arc welding gas-shielded (FCAW-GS, Deposition Process Reference Number: 138), flux-cored arc welding self-shielded (FCAW-SS, Deposition Process Reference Number: 114), automated hardfacing, and manual metal arc welding (MMAW, Deposition Process Reference Number: 111) hardfacing T Fe15 and T Fe16 alloys, according to EN 14700:2014. Characterization of the hardfaced layers was achieved by using hardness tests, optical microscopy, confocal microscopy, scanning electron microscopy, and EDS (Energy Dispersive Spectroscopy) and X-ray diffraction analyses. Based on wear resistance tests in laboratory conditions, in accordance with ASTM G65-00: Procedure A, and surface layer hardness tests, in accordance with PN-EN ISO 6508-1, the wear plates most suitable for use in metal-mineral conditions were chosen. The results demonstrated the high metal-mineral abrasive wear resistance of the deposit weld metal produced by the new covered tubular electrode. The tubular electrode demonstrated a high linear correlation between the surface wear resistance and the hardness of the metal matrix of the tested abrasive wear plates. In addition to hardness, size, shape, the dispersion of strengthening phases, and the base metal content, depending on hardfacing technology and technological parameters, impact wear resistance is represented by volumetric loss caused by effect-free or constrained dry abrasive medium contact. The presented results can be used in machine part material selection and wear planning for applications in inspection, conservation, and regeneration interval determination. The obtained results will be applied in a real-time wear rate prediction system based on the measurement of the working parameters.     

Verapamil prevents the effect of calcium-sensing receptor activation on the blood glucose and insulin levels in rats

BackgroundThe Ca²⁺ triggered insulin exocytosis in β cells of the pancreatic islets may be the result of Ca²⁺ influx through L-type voltage dependent calcium channels (VDCC) localized in the plasma membrane, as well as of liberation of Ca²⁺ from intracellular storages, induced by activation of the calcium receptor (CaR) coupled with the PLC enzyme present in the pancreatic islets. The present study was designated to determine, in in vivo experiments, the effects of CaR activation by R-568 and inhibition of the receptor by NPS 2143 on the plasma glucose and insulin levels in the presence of verapamil, a calcium channel blocker.MethodsWistar rats, after fasting for 14 h before the experiment, were anesthetized with inactin and loaded ip with 1 g/kg glucose.ResultsIn comparison to the control group, the verapamil-induced blockade of the calcium channels in glucose loaded animals increased the blood glucose level and decreased the insulin level, whereas CaR activation with R-568 induced opposite effects. However, in the presence of verapamil, R-568 did not change the concentration of glucose or insulin versus the control animals. Verapamil infusion did not alter elevated glucose concentration in the NPS 2143 animals. At the same time, verapamil reduced the plasma insulin level and potentiated the drop of insulin concentration induced by NPS 2143.ConclusionThe observations suggest that under the in vivo conditions, calcium channel blockade may prevent changes in the blood glucose and insulin concentrations induced by the CaR activation.     

Correlates of sedentary behaviour in Asian adults: A systematic review

The objective of this study is to systematically review the evidence on correlates of sedentary behaviour (SB) among Asian adults. We searched for studies that examined individual, environmental, and political/cultural correlates of total and domain‐specific SB (transport, occupation, leisure, and screen time) in Asian adults published from 2000 onwards in nine scientific databases. Two reviewers independently screened identified references. Following quality assessment of included studies, we performed narrative synthesis that considered differences based on SB measurements, regions, and population characteristics (PROSPERO: CRD42018095268). We identified 13 249 papers of which we included 49, from four regions and 12 countries. Researchers conducted cross‐sectional analyses and most relied on SB self‐report for SB measurement. Of the 118 correlates studied, the following associations were consistent: higher age, living in an urban area (East Asia), and lower mental health with higher total SB; higher education with higher total and occupational SB; higher income with higher leisure‐time SB; higher transit density with higher total SB in older East Asians; and being an unmarried women with higher SB in the Middle East. We encourage more research in non‐high‐income countries across regions, further exploration of important but neglected correlates using longitudinal designs and qualitative research, and the use of objective instruments to collect SB data.     

High Mortality in Late Octogenarians Undergoing Isolated Aortic Valve Replacement for Aortic Valve Stenosis: EuroSCORE Underestimates Mortality in this Cohort

Objectives Considering the expanding technology of catheter-based aortic valve implantation, high-risk patients who would not be suitable for conventional aortic valve replacement (AVR) should be identified.Methods From 1997 to April 2007, 190 patients aged from 80 and 89 years old received isolated AVR. Patients between 80 and 84 years old were categorized as the early octogenarians (n = 148) and patients between 85 and 89 years old were categorized as the late octogenarians (n = 42).Results Thirty days mortality in the early and late octogenarians were 6 and 21%, respectively (p = 0.003). The additive and logistic EuroSCORE were 8.0 ± 2.4 and 8.8 ± 1.8 in the early octogenarians and 13.2 ± 11.8 and 14.6 ± 8.7 in the late octogenarians. Multivariate analysis revealed the late octogenarians (OR 6.7, 95%CL 1.8-24.4, p = 0.004) and poor left ventricular function (OR 8.0, 95%CL 1.2-53.5, p = 0.032) as significant risk factors for 30 days mortality. Early octogenarians showed 1-year, 3-year, 5-year, and 8-year survival of 82.4, 67.6, 54.7, and 33%, respectively. Late octogenarians showed 1-year, 3-year, 5-year, and 8-year survivals of 69.0, 66.2, 41.6, 22.3%, respectively.Conclusions Mortality after AVR in the late octogenarians was very high, and was underestimated by EuroSCORE in this patients group. In late octogenarians, catheter-based aortic valve implantation despite relative low EuroSCORE level could be considered as a reasonable alternative.     

Cuantificación del área miocárdica en riesgo: validación de puntuaciones angiográficas coronarias con métodos de resonancia magnética cardiovascular

Introduction and objectives

Quantification of myocardial area-at-risk after acute myocardial infarction has major clinical implications and can be determined by cardiovascular magnetic resonance. The Bypass Angioplasty Revascularization Investigation Myocardial Jeopardy Index (BARI) and Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) angiographic scores have been widely used for rapid myocardial area-at-risk estimation but have not been directly validated. Our objective was to compare the myocardial area-at-risk estimated by BARI and APPROACH angiographic scores with those determined by cardiovascular magnetic resonance.

Methods

In a prospective study, cardiovascular magnetic resonance was performed in 70 patients with a first successfully-reperfused ST-segment elevation acute myocardial infarction in the first week after percutaneous coronary intervention. Myocardial area-at-risk was obtained both by analysis of T2-short tau inversion recovery sequences and calculation of infarct endocardial surface area with late enhancement sequences. These results were compared with those of BARI and APPROACH scores.

Results

BARI and APPROACH showed a statistically significant correlation with T2-short tau inversion recovery for myocardial area-at-risk estimation (BARI, intraclass correlation coefficient=0.72; P<.001; APPROACH, intraclass correlation coefficient=0.69; P<.001). Better correlations were observed for anterior acute myocardial infarction than for other locations (BARI, intraclass correlation coefficient=0.73 vs 0.63; APPROACH, intraclass correlation coefficient=0.68 vs 0.50). Infarct endocardial surface area showed a good correlation with both angiographic scores (BARI, intraclass correlation coefficient=0.72; P<.001; with APPROACH, intraclass correlation coefficient=0.70; P<.001).

Conclusions

BARI and APPROACH angiographic scores allow reliable estimation of myocardial area-at-risk in current clinical practice, particularly in anterior infarctions.Full English text available from:www.revespcardiol.org