[en] Electrical conductivity measurements show that Lnsub(1-x)Srsub(x)CoO₃ (Ln = Pr or Nd) undergoes a non-metal-metal transition when x approximately equals 0.3. The d.c. conductivity of compositions with 0 < x < 0.1 obeys the Tsup(-1/4) law up to 400 K and the a.c. conductivity data follow the ωsup(s) law with s in the range 0.66 - 0.8. Surprisingly, however, s seems to increase with increasing temperature. Thermopower measurements show clear evidence for a change in the mechanism of conduction (around 350 K) from variable range hopping to transport at Esub(c). All these transport properties suggest that Co⁴⁺ ions in Lnsub(1-x)Srsub(x)CoO₃ (0 < x < 0.1), considered as moving in a lattice of Co³⁺, form a degenerate gas and that the states at the Fermi energy are Anderson localized. (author)

[en] The two systems (a) and (b) for different values of x were synthesized. Their electron transport and magnetic properties show a change in behavior above a critical value of x. Unlike the system La/sub 1-x/Sr/sub x/CoO₃, itinerant electron ferromagnetism is not observed. This is explained on the basis of the absence of an itinerant band of Co⁴⁺ whose generation is restricted on account of substitution of Ti⁴⁺. Electron transport in these two systems is compared with that of LaCoO₃ or La/sub 1-x/Sr/sub x/CoO₃ and is discussed in view of the presence of different valence states of cobalt and change in crystal field splitting. Spin-state equilibria in these two systems are simiar to that in LaCoO₃

[en] Attempts have been made to prepare the solid-solution La/sub 1-x/Pb/sub x/Co/sub 1-x/O₃ for 0 < x < 1. X-ray diffraction indicates the formation of single-phase materials over the entire range. Compositions with 0 < x ≤ 0.20 are rhombohedral, those with x in the range 0.2 to 0.8 are cubic, and those with x ≥ 0.9 are tetragonal. Chemical analysis shows that all these samples are lead deficient. This is due to volatilization of PbO during preparation. Conduction is mainly due to 3d electrons of cobalt ions. All the samples except x = 0.05 show p-type conduction at and above 300 K. Samples with x ≥ 0.5 exhibit dielectric anomaly at a particular temperature which increases the increasing x

[en] To describe the clinical and laboratory features of hereditary hemochromatosis associated liver disease in a tertiary care hospital. Study Design: Observational study. Place and Duration of Study: The Aga Khan University Hospital, Karachi, from January 2002 to October 2012. Methodology: Charts of patients with Hereditary Hemochromatosis (HHC) were reviewed. Data collected and analyzed consisting of clinical presentations, liver function tests, serum ferritin, transferrin saturation, hepatic imaging and histology in patients with HHC. Results: A total of 22 patients were identified as having hemochromatosis. All subjects were men with a mean age of 53 ± 9.2 years at the time of diagnosis. The most common presentation was skin pigmentation seen in 17 (77%), followed by loss of libido/ impotence in 11 (50%) and then arthralgias in 10 (45%) and weakness in 6 (27%). Eleven (50%) subjects had diabetes mellitus and one subject had concomitant cardiac involvement. Patients with diabetes were diagnosed earlier as compared to those without it. Eighteen (81%) subjects had cirrhosis at the time of diagnosis. Serum iron was 164 ± 53 ug/dl, ferritin 3391 ± 1960 ug/L, TIBC 202 ± 61 ug/dl and transferrin saturation 76.8 ± 14%. Liver biopsy was done in 10 (45%) and using Pearls stain histopathological features were consistent with hemochromatosis and none had carcinoma. Only 3 (14%) patients had regular phlebotomy. Conclusion: Hemochromatosis is not a rare disease in Pakistan and should be looked in those subjects whose liver function tests are deranged. (author)

[en] This paper reports how surface area, linear shrinkage, and compressive strength measurements show that, with the help of neutron irradiation, sintering of high-purity alumina can be initiated at temperatures lower than 150 degrees C. Such radiation sintering might be beneficial to many other ceramics

[en] B/sub 2/O/sub 3/-Li/sub 2/O-LiCl glasses containing varying amounts of fine dispersion of silicon carbide and tin particulates have been prepared. Microstructural studies have been carried out using scanning electron microscope. Electrical conductivity measurements in the temperature range 300-575K show that initially the conductivity increases with addition of dispersed when the dispersed particles are uniformly distributed in the glassy matrix. Further addition of these in the glass leads to their agglomeration and the ionic conductivity decreases. This enhancement of ionic conductivity is similar to that of polycrystalline dispersed solid electrolytes

[en] Dielectric properties of the system (La_1-xPb_x) (Co_1-xTi_x)O₃ (0.50 ≤ x ≤ 0.90) are investigated as a function of temperature and frequency. All the samples exhibit diffuse phase transitions in the variation of their dielectric constant, ε, as a function of temperature. The variation of ε with temperature can be expressed by a quadratic law of the type ε^-1 = ε_max^-1 + C(T - T_C)² both above as well as below T_C over a considerable range of temperature where T_C is the temperature where ε shows the peak value ε_max and C is a constant. Dielectric parameters show a pronounced frequency dependence near T_C. This points to the contribution of relaxation polarisation to the observed dielectric behaviour. The observed dielectric behaviour is interpreted on the basis of microscopic chemical inhomogeneities present in the samples. (author)

[en] The system La/sub 1-x/Sr/sub x/Co/sub 1-y/Ti/sub y/O₃ for (a) x = 0 and (b) x = y is investigated through Moessbauer spectroscopy measurements carried out between 77 and 800 K. None of the Moessbauer spectra show hyperfine splitting even at 77 K as Ti⁴⁺ substitution restricts the generation of Co⁴⁺ which is primarily responsible for itinerant electron ferromagnetism in La/sub 1-x/Sr/sub x/CoO₃. In all the samples, two resonances are observed expect in the samples with y = 0.3 and 0.5 in the system (a) where three resonances are observed. Three resonances are assigned to low spin cobalt states (i.e. Co/sup II/, Co/sup III/ and Co/sup IV/), high spin Co³⁺ (t/sub 2g//sup 4/e/sub g//sup 2/) and high spin Co²⁺(t/sub 2g//sup 5/e/sub g//sup 2/) states, the first two being common in all the samples. The variation of the isomer shift and other data with temperature is discussed in the framework of spin-state and valence-state equilibria of cobalt ions in these materials. The difference in behaviour between the systems (a) and (b) is explained in terms of generation of different valence and spin states of cobalt with the increase in x and is further compared with the system La/sub 1-x/Sr/sub x/CoO₃. The susceptibility, electron transport, and other data reported earlier support the results obtained from Moessbauer studies. (author)

[en] Electrophysiological changes in cirrhosis are well known but least investigated especially in our country hence we wanted to see electrophysiological changes especially QT interval in cirrhotic patients. Methods: A cross-sectional study was conducted at Aga Khan University Hospital Karachi (AKUH) in which medical records (duration 2008-2010) of cirrhotic patients were reviewed. Results: Three hundred and eighty cirrhotic patients' charts were studied, 227 (59.7 percent) were male and mean age of this cohort was 52.8+-12.6 years. The most common cause for CLD was Hepatitis C (CHC) in 260 (68.4 percent), NBNC in 56(14.7 percent) and HBV in 51 (13.4 percent). Only 225 had complete ECG workup, the mean corrected QT interval was 0.44+-0.067 sec. Among the electrophysiological abnormalities, 79 (35 percent) had a prolonged corrected QT interval, 7 (3.1 percent) had a prolonged PR interval (>0.22s) and prolonged QRS duration was seen in 23 (10.4 percent) patients. QT prolongation was seen in 1 of the 5 patients with Child Class A (20 percent), 22 of the 73 patients with Child Class B (30.1 percent), and 25 of the 61 patients with Child Class C (41 percent). However, this difference however was not statistically significant. (p value=.331). Conclusion: We conclude that QT prolongation is more frequent in patients with liver cirrhosis especially when the disease is more advanced like in Child C hence these patients are more prone to sudden cardiac death. Moreover, this study shows that the risk associated with QT prolongation is present through all classes of liver cirrhosis. We recommend that routine cardiac screening with ECG of all cirrhotic patients be performed. (author)

[en] In the manganite La_1-xM_xMnO₃(M=Ca,Ba,Sr) the doping concentration introduces a mixed valency (Mn³⁺, Mn⁴⁺) which governs the magnetic and electrical properties of the compound. The perovskite oxides La_1-3xCa_xBa_xSr_xMnO₃ (x=0.00,0.05,0.10) were prepared by chemical method. Single-phase formation is confirmed by XRD studies. The electrical behavior of compositions with x=0.00, 0.05 and 0.10 in the system La_1-3xCa_xBa_xSr_xMnO₃ was studied in the temperature range 300-420 K. It is observed that conductivity decreases with increasing temperature as well as dopants concentration. Metallic behavior of these compositions decreases with increasing dopants concentration (x). The microstructures of these samples have been characterized using scanning electron microscopy (SEM). (copyright 2007 WILEY -VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)