Grain alignment and its relationship with superconductivity and thermal transport of Ni-substituted Bi-2212 textured rods fabricated at two different growth rates

The microstructure, grain alignment, superconducting and thermal transport properties of Ni-substituted Bi-2212 rods grown at two different speeds (15 and 30 mm h−1) through the Laser Floating Zone method, have been evaluated. Significant variations in grain size, grain alignment, electrical and thermoelectric power properties have been observed for the rods depending on the growth and substitution rates. The highest aligned structure was obtained on unsubstituted rods grown at 15 mm h−1. Both increased substitution and growth rates degraded the grain alignment. The presence of Ni-based secondary phases showed that Ni is not totally incorporated into the crystal structure, which, in turn, caused a decrease on the average grain size of the rods. With increasing Ni concentration, peak values of thermoelectric power of the rods, which lie between 3.8 and 6.4 μVK−1, monotonically decreased while thermal conductivity values did not show any systematic change. The activation energy of flux motion, Uo, was calculated from the field dependent resistivity–temperature curves in a range of 0–8 T. Superconducting transition temperatures, Tconset and Tcoffset, and activation energy, Uo, were found to decrease with increasing Ni contents and applied magnetic field. It has been estimated from the magnetic field dependence of activation energy of the samples that plastic creep of the collective vortices is dominant in the rods.This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under 2214 International Doctoral Research Fellowship Program (M. Ozabaci). A. Sotelo and M.A. Madre acknowledge DGA (Consolidated research group T12) for financial support. M. A. Madre acknowledges MINECO-FEDER (Project MAT2011-22719) for funding.Peer Reviewe

Epidemiology of intra-abdominal infection and sepsis in critically ill patients: “AbSeS”, a multinational observational cohort study and ESICM Trials Group Project

Purpose: To describe the epidemiology of intra-abdominal infection in an international cohort of ICU patients according to a new system that classifies cases according to setting of infection acquisition (community-acquired, early onset hospital-acquired, and late-onset hospital-acquired), anatomical disruption (absent or present with localized or diffuse peritonitis), and severity of disease expression (infection, sepsis, and septic shock). Methods: We performed a multicenter (n = 309), observational, epidemiological study including adult ICU patients diagnosed with intra-abdominal infection. Risk factors for mortality were assessed by logistic regression analysis. Results: The cohort included 2621 patients. Setting of infection acquisition was community-acquired in 31.6%, early onset hospital-acquired in 25%, and late-onset hospital-acquired in 43.4% of patients. Overall prevalence of antimicrobial resistance was 26.3% and difficult-to-treat resistant Gram-negative bacteria 4.3%, with great variation according to geographic region. No difference in prevalence of antimicrobial resistance was observed according to setting of infection acquisition. Overall mortality was 29.1%. Independent risk factors for mortality included late-onset hospital-acquired infection, diffuse peritonitis, sepsis, septic shock, older age, malnutrition, liver failure, congestive heart failure, antimicrobial resistance (either methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase-producing Gram-negative bacteria, or carbapenem-resistant Gram-negative bacteria) and source control failure evidenced by either the need for surgical revision or persistent inflammation. Conclusion: This multinational, heterogeneous cohort of ICU patients with intra-abdominal infection revealed that setting of infection acquisition, anatomical disruption, and severity of disease expression are disease-specific phenotypic characteristics associated with outcome, irrespective of the type of infection. Antimicrobial resistance is equally common in community-acquired as in hospital-acquired infection

Intuitionistic Fuzzy Time Series Functions Approach for Time Series Forecasting

Fuzzy inference systems have been commonly used for time series forecasting in the literature. Adaptive network fuzzy inference system, fuzzy time series approaches and fuzzy regression functions approaches are popular among fuzzy inference systems. In recent years, intuitionistic fuzzy sets have been preferred in the fuzzy modeling and new fuzzy inference systems have been proposed based on intuitionistic fuzzy sets. In this paper, a new intuitionistic fuzzy regression functions approach is proposed based on intuitionistic fuzzy sets for forecasting purpose. This new inference system is called an intuitionistic fuzzy time series functions approach. The contribution of the paper is proposing a new intuitionistic fuzzy inference system. To evaluate the performance of intuitionistic fuzzy time series functions, twenty-three real-world time series data sets are analyzed. The results obtained from the intuitionistic fuzzy time series functions approach are compared with some other methods according to a root mean square error and mean absolute percentage error criteria. The proposed method has superior forecasting performance among all methods

Enhancement of magnetic relaxation behavior by texturing in Bi-2212 superconducting rods

Time decay of magnetization, known as magnetic relaxation, is crucial for both fundamental and applied point of view in bulk high temperature superconductors (HTS) by setting the limits to the HTS devices stability. Melt-processed BiSrCaCuGaO rods (Bi-2212, x=0, 0.1) were used to study the effect of both grain alignment and substitution on the samples critical current density, relaxation and pinning behavior. The magnetic field has been applied both perpendicular and parallel to the rods growth axis to determine the effect of grain alignment. It has been found that Ga substitution reduces grains orientation and sizes leading to lower magnetic properties. The peaks of the curves, which indicate the temperature dependence of the samples magnetic relaxation rate (S), have been observed in the 7-35 K temperature range. Characteristic pinning energy (U/k) of samples was determined using the formalism developed by Maley. The change of pinning energy as a function of magnetization has been found to be exponential between 3 and 60 K, which is in agreement with the collective creep theory.Peer Reviewe

Growth speed and substitution effects on alignment and thermal transport properties of Bi-2212 textured superconductors

Fe-substituted superconducting thin BiSrCaCuO rods with nominal compositions of Bi2Sr2Ca1Cu2−xFexO8+δ (x = 0, 0.01, 0.03, 0.05, and 0.1) were fabricated using the laser floating zone technique at two different growth speeds, 15 mm h−1 and 30 mm h−1. The influences of growth speed and Fe substitution on the grain alignment in the rods were evaluated by means of x-ray pole figure studies. The obtained results showed that both applied growth speed and Fe substitution play a crucial role on grain alignment, which is strongly connected with the current-carrying capacity of the rods. It was found that the rods grown at 15 mm h−1 (G15) have stronger orientation than the rods grown at 30 mm h−1 (G30). However, in contrast to the G15 rods, an increased substitution rate improved the orientation of the G30 rods. Another important observation is that the increase on the substitution caused a decrease on the grain size of all the rods. The decrease of critical temperature values of the rods upon substitution was ascribed to both grain size effect and formation of a nonsuperconducting Fe-rich phase detected in scanning electron microscope/energy-dispersive x-ray analyses. The thermal conductivity values of the G15 and G30 rods were found to be in the range of 0.9–1.9 and 1.1–1.18 W m−1 K−1 at 150 K, respectively. The higher values of figure of merit (ZT), at all temperature ranges, were obtained from the highest substituted rods (x = 0.1) for both of the applied growth speeds. In addition, it was observed that the ZT of G30 rods are up to three times higher than that of G15 ones.This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under 2214 International Doctoral Research Fellowship Program (M. Ozabaci). A. Sotelo and M.A. Madre acknowledge DGA (Consolidated research group T12) for financial support. M.A. Madre acknowledges MINECO-FEDER (Project MAT2011-22719) for funding.Peer Reviewe