First-principles calculations of exchange interactions, spin waves, and temperature dependence of magnetization in inverse-Heusler-based spin gapless semiconductors

Employing first principles electronic structure calculations in conjunction with the frozen-magnon method we calculate exchange interactions, spin-wave dispersion, and spin-wave stiffness constants in inverse-Heusler-based spin gapless semiconductor (SGS) compounds Mn$_2$CoAl, Ti$_2$MnAl, Cr$_2$ZnSi, Ti$_2$CoSi and Ti$_2$VAs. We find that their magnetic behavior is similar to the half-metallic ferromagnetic full-Heusler alloys, i.e., the intersublattice exchange interactions play an essential role in the formation of the magnetic ground state and in determining the Curie temperature, $T_\mathrm{c}$. All compounds, except Ti$_2$CoSi possess a ferrimagnetic ground state. Due to the finite energy gap in one spin channel, the exchange interactions decay sharply with the distance, and hence magnetism of these SGSs can be described considering only nearest and next-nearest neighbor exchange interactions. The calculated spin-wave dispersion curves are typical for ferrimagnets and ferromagnets. The spin-wave stiffness constants turn out to be larger than those of the elementary 3$d$-ferromagnets. Calculated exchange parameters are used as input to determine the temperature dependence of the magnetization and $T_\mathrm{c}$ of the SGSs. We find that the $T_\mathrm{c}$ of all compounds is much above the room temperature. The calculated magnetization curve for Mn$_2$CoAl as well as the Curie temperature are in very good agreement with available experimental data. The present study is expected to pave the way for a deeper understanding of the magnetic properties of the inverse-Heusler-based SGSs and enhance the interest in these materials for application in spintronic and magnetoelectronic devices.Comment: Accepted for publ;ication in Physical Review

Spin-polarized surface state of MnSb(0001)

Knowledge of the spin-dependent electronic structure at surfaces and interfaces plays an increasingly important role when assessing possible use of novel magnetic materials for spintronic applications. It is shown that spin- and angle-resolved photoelectron spectroscopy together with ab initio electronic structure methods provides a full characterization of the surface electronic structure of ferromagnetic MnSb(0 0 0 1). Two different surface reconstructions have been compared in spin- and angle-resolved valence-band photoemission. For annealing at elevated temperatures, the ( 1 x 1)-structure transforms into 2 x 2 and a majority-spin peak appears at - 1.7 eV inside a majority-spin bulk band gap at the surface Brillouin zone centre. Its sensitivity to oxygen supports an interpretation as magnetic compound surface state. Local spin density calculations predict at the same energy (- 1.75 eV) a prominent d(z)2 surface state of majority spin for ( 1 x 1)- Mn terminated MnSb(0 0 0 1) but no such feature for ( 1 x 1)-Sb termination. The calculation shows that neither the bulk nor the surface is half-metallic, in agreement with the expectation for the hexagonal NiAs structure

Factors associating with differences in the incidence of renal replacement therapy among elderly : data from the ERA-EDTA Registry

Background. The incidence of renal replacement therapy (RRT) in the general population >= 75 years of age varies considerably between countries and regions in Europe. Our aim was to study characteristics and survival of elderly RRT patients and to find explanations for differences in RRT incidence. Methods. Patients >= 75 years of age at the onset of RRT in 2010-2013 from 29 national or regional registries providing data to the European Renal Association-European Dialysis and Transplant Association Registry were included. Chi-square and Mann-Whitney U tests were used to assess variation in patient characteristics and linear regression was used to study the association between RRT incidence and various factors. Kaplan-Meier curves and Cox regression were employed for survival analyses. Results. The mean annual incidence of RRT in the age group >= 75 years of age ranged from 157 to 924 per million age-related population. The median age at the start of RRT was higher and comorbidities were less common in areas with higher RRT incidence, but overall the association between patient characteristics and RRT incidence was weak. The unadjusted survival was lower in high-incidence areas due to an older age at onset of RRT, but the adjusted survival was similar [relative risk 1.00 (95% confidence interval, 0.97-1.03)] in patients from low- and high-incidence areas. Conclusions. Variation in the incidence of RRT among the elderly across European countries and regions is remarkable and could not be explained by the available data. However, the survival of patients in low-and high-incidence areas was remarkably similar.Peer reviewe

Renal replacement therapy in Europe : A summary of the 2013 ERA-EDTA Registry Annual Report with a focus on diabetes mellitus

Publisher Copyright: © The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA.Background: This article provides a summary of the 2013 European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) Registry Annual Report (available at http://www.era-edta-reg.org), with a focus on patients with diabetes mellitus (DM) as the cause of end-stage renal disease (ESRD). Methods: In 2015, the ERA-EDTA Registry received data on renal replacement therapy (RRT) for ESRD from 49 national or regional renal registries in 34 countries in Europe and bordering the Mediterranean Sea. Individual patient datawere provided by 31 registries, while 18 registries provided aggregated data. The total population covered by the participating registries comprised 650 million people. Results: In total, 72 933 patients started RRT for ESRD within the countries and regions reporting to the ERA-EDTA Registry, resulting in an overall incidence of 112 per million population (pmp). The overall prevalence on 31 December 2013was 738 pmp (n = 478 990). Patients with DM as the cause of ESRD comprised 24% of the incident RRT patients (26 pmp) and 17% of the prevalent RRT patients (122 pmp).Whencompared with the USA, the incidence of patients starting RRTpmpsecondary toDMin Europe was five times lower and the incidence of RRT due to other causes of ESRD was two times lower. Overall, 19 426 kidney transplants were performed (30 pmp). The 5-year adjusted survival for all RRT patients was 60.9% [95% confidence interval (CI) 60.5-61.3] and 50.6% (95% CI 49.9-51.2) for patients with DM as the cause of ESRD.publishersversionPeer reviewe

Evaluation of calcium acetate/magnesium carbonate as a phosphate binder compared with sevelamer hydrochloride in haemodialysis patients: a controlled randomized study (CALMAG study) assessing efficacy and tolerability

Background. Phosphate binders are required to control serum phosphorus in dialysis patients. A phosphate binder combining calcium and magnesium offers an interesting therapeutic option

The European Renal Association - European Dialysis and Transplant Association Registry Annual Report 2014 : a summary

Background: This article summarizes the European Renal Association - European Dialysis and Transplant Association Registry's 2014 annual report. It describes the epidemiology of renal replacement therapy (RRT) for end-stage renal disease (ESRD) in 2014 within 35 countries. Methods: In 2016, the ERA-EDTA Registry received data on patients who in 2014 where undergoing RRT for ESRD, from 51 national or regional renal registries. Thirty-two registries provided individual patient level data and 19 provided aggregated patient level data. The incidence, prevalence and survival probabilities of these patients were determined. Results: In 2014, 70 953 individuals commenced RRT for ESRD, equating to an overall unadjusted incidence rate of 133 per million population (pmp). The incidence ranged by 10-fold; from 23 pmp in the Ukraine to 237 pmp in Portugal. Of the patients commencing RRT, almost two-thirds were men, over half were aged >= 65 years and a quarter had diabetes mellitus as their primary renal diagnosis. By day 91 of commencing RRT, 81% of patients were receiving haemodialysis. On 31 December 2014, 490 743 individuals were receiving RRT for ESRD, equating to an unadjusted prevalence of 924 pmp. This ranged throughout Europe by more than 10-fold, from 157 pmp in the Ukraine to 1794 pmp in Portugal. In 2014, 19 406 kidney transplantations were performed, equating to an overall unadjusted transplant rate of 36 pmp. Again this varied considerably throughout Europe. For patients commencing RRT during 2005-09, the 5-year-adjusted patient survival probabilities on all RRT modalities was 63.3% (95% confidence interval 63.0-63.6). The expected remaining lifetime of a 20-to 24-year-old patient with ESRD receiving dialysis or living with a kidney transplant was 21.9 and 44.0 years, respectively. This was substantially lower than the 61.8 years of expected remaining lifetime of a 20-year-old patient without ESRD.Peer reviewe