Effect of (Ta/Nb) co-doping on the magnetoresistivity and flux pinning energy of the BPSCCO superconductors

In the present work, the effect of co-doping of Ta and Nb with nominal composition of (BiPb) 2 Ta x Sr 2 Ca 3 Cu 4-y Nb y O 12+? where x = 0.1 and y = 0.0, 0.025, 0.05, 0.075, and 0.1 were investigated. The samples were prepared by using the well-known conventional standard solid-state reaction method. The magnetoresistance measurements were studied for different values of the applied magnetic field. The activation energies, irreversibility fields (H irr ), upper critical fields (H c2 ) and coherence lengths at 0 K (?(0)) were calculated from the resistivity versus temperature (?-T) curves, under DC magnetic fields up to 6 T. The thermally activated flux flow (TAFF) model has been applied in order to calculate the flux pinning energies. The results have shown that the upper critical magnetic field, H c2 (0), and the flux pinning energies vary from ~113 to 74 T and ~384 to 101 meV at 0 T, with the Nb-content, respectively. © 2014 Springer Science+Business Media New York.Acknowledgments This work is supported by the Research Fund of C¸ ukurova University, Adana, Turkey, under Grant No. FEF2011BAP15

Effect of Yb-substitution on thermally activated flux creep in the Bi 2 Sr 2 Ca 1 Cu 2-x Yb x O y superconductors

In the present work, Bi 2 Sr 2 Ca 1 Cu 2-x Yb x O y (x = 0.0, 0.05, 0.1, and 0.25) superconductors were prepared by a polymer matrix route technique, and subsequently used as feed in a laser induced directional solidification (LFZ) process. The X-ray diffraction, DC magnetization and magnetoresistance measurements were studied. All samples consist mainly of the Bi-2212 phase which indicates the performed process is adequate. However, some impurity phases like CaCuO 2 were also detected. We have calculated the hole number using the relation given by Presland, and particle size, L hkl , using the XRD patterns results. From M-T results, the superconducting transition temperatures, T C , of the samples were found 93, 90, 87, and 85 K, respectively. The activation energies, irreversibility fields (H irr ), upper critical fields (H c2 ) and coherence lengths at 0 K (?(0)) were calculated from the resistivity versus temperature (R-T) curves, under DC magnetic fields up to 5 T. The thermally activated flux creep model has been studied in order to calculate the flux pinning energies. The results indicated that Hc2(0) varied from 132 to 30 T and the flux pinning energies varied from 650 to 400 meV at 0 T, with the content of Yb. © 2013 Springer Science+Business Media New York.MAT2011-22719 Gobierno de Aragón FEF 2011D21Acknowledgments This work is supported by Research Fund of Cukurova University, Adana, Turkey, under grant contracts no: FEF 2011D21. A. Sotelo and M. A. Madre wish to thank the Gobierno de Aragón (Research Group T12), for financial support. M. A. Madre also acknowledges the MINECO-FEDER (Project MAT2011-22719) for funding. The authors thank to Prof. Dr. Cabir Terziog^lu from Abant 'zzet Baysal University for his help during the magnetoresistance measurements

Hipotermiye Bağlı Ölümlerin Değerlendirilmesi

Amaç: Sistemik hipotermi terimi insan vücudunun 35° C’den daha aşağı düşecek kadar soğuduğunu belirtmek için kullanılır. Bu durum, vücudun ısı kaybının ısı yapımını aştığı zaman meydana gelir. Kaza sonucu meydana gelen hipoterminin en sık nedeni ısı derecesi düşük olan bir ortama maruz kalmadır. Hipotermi tehlikeli fizyolojik değişikliklere ve hatta ölüme neden olabilir. Bu çalışmada hipotermiye bağlı ölüm olgularının değerlendirilmesi amaçlanmıştır. Gereç ve Yöntem: 2000-2008 yılları arasında Konya Adli Tıp Şube Müdürlüğü tarafından ve Konya’ya bağlı ilçelerde adli tıp uzmanı tarafından otopsileri yapılan olgular retrospektif olarak taranmış ve ölümü hipotermiye bağlı olan olgular çalışma kapsamına alınmıştır. Bulgular: Çalışmaya dahil edilen dönemde 12 hipotermiye bağlı ölüm olgusu saptanmıştır. Olguların 11’i erkek, 1’i kadındır. Olguların yaşları 41 ile 85 arasında değişmekte olup, ortalama yaş 57.0±15.4 bulunmuştur. Ölümler en sık 5 olgu ile Ocak ayında meydana gelmiştir. Olguların 4’ü tarlada, 3’ü metruk binada bulunmuştur. 6 olguda psikiyatrik hastalık öyküsü mevcuttur. Histopatolojik incelemede 5 olguda enzimatik yağ nekrozu bulguları tespit edilmiştir. Sonuç: Hipotermiye bağlı ölümler, toplum sağlığı açısından önemli olduğu gibi, adli tıbbi açıdan da önemlidir. Bu tür olgularda, olay yeri incelemesi, olgunun tıbbi özgeçmişinin ayrıntılı bir şekilde incelenmesi, dikkatli bir şekilde yapılacak otopsi ve histopatolojik inceleme tanı konulmasını kolaylaştırı

Effect of tungsten (W) substitution on the physical properties of Bi-(2223) superconductors

The superconducting Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3-x W x O 10+y (x=0.00, 0.05, 0.10, 0.15) bulk samples were prepared by the solid-state reaction method. The effects of W substitution on the BSCCO system have been investigated by the electrical resistivity (?-T), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), magnetic hysteresis and critical current density measurements. It has been found that the Bi-(2212) low-T C phase is formed for all the substitution levels, together with the Bi-(2223) high-T C phase. The results obtained from the XRD data show that the Bi-(2223) phase gradually transforms into the Bi-(2212) phase with increasing W substituting for Cu. In addition, from the magnetization measurements at the temperatures below the zero resistance temperatures of the samples, we have observed that a decreasing in magnitude of |M| with the increasing measurement temperature and W concentration. Therefore, the decreasing of |M| related to superconducting volume seems to imply an existence of flux-pinning centers in our samples. © 2013 Springer Science+Business Media New York.FEF2011YL25Acknowledgements This work is supported by Research Fund of Çukurova University, Adana, Turkey, under grant contracts no: FEF2011YL25