Polycrystalline iron sulphide based semiconductors for solar energy conversion

Potentialities of iron sulphide semiconductors for solar energy conversion have been outlined. Iron sulphide semiconductors have been characterized with respect to their bulk (XRD, EDAX), surface (XPS) and electronic (UV-Vis reflectance spectroscopy) structure. Materials have been formed into electrodes by screenprinting and have been thermally activated under different conditions.Synthetic polycrystalline pyrite activated in air-hydrogen atmosphere showed the highest efficiency for solar energy conversion in polyiodide electrolyte. Distinguishing characteristics of these materials are due to the optimal absorption and charge transfer properties at the electrode-electrolyte interface. From parallel experiments carried out on pyrrhotite and natural pyrite-based semiconductors, it was derived that the latter characteristics are related to favourable substoichiometric surface sites and to the formation of an iron oxide bulk phase in the semiconductors.     

Electric,magnetic, and transport critical current density behavior of the 2201, 2212, and 2223 phases of ‘BSCCO’

We have studied the electrical properties of polycrystalline pellets of the high-T _c superconducting phases occurring in the Bi₂O₃-SrO-CaO-CuO (BSCCO) system, having nominal compositions Bi₂Sr₂Cu₁O_6+y, (2201 phase, withT _c = 10 K.) Bi₂Sr₂CaCu₂O_8+y (2212 phase, withT _c = 85 K), and Bi₂Sr₂Ca₂Cu₃O_10+y (2223 phase, withT _c = 110 K). Pellets containing the 2223 phase having zero resistance below 105 K were obtained. For the 2212 and 2223 phases, the transport critical current density was measured as a function of temperature and of the externally applied magnetic field. As previously found for YBa₂Cu₃O_7-x (YBCO), results are consistent with the occurrence of a weak superconducting coupling among the grains. Such coupling was, however, noticeably stronger for the 2223 phase than for the 2212 phase.     

Chondrocalcinosis is a feature of Gitelman's variant of Bartter's syndrome. A new look at the hypomagnesemia associated with calcium pyrophosphate dihydrate crystal deposition disease

The occurrence of chondrocalcinosis in patients with Bartter's syndrome has been reported as a typical example of hypomagnesemia-associated calcium pyrophosphate dihydrate crystal (CPPD) deposition disease. However, hypomagnesemia is a feature of Gitelman's variant of Bartter's syndrome, whereas serum magnesium levels are normal in Bartter's syndrome strictly speaking. We managed four patients with chondrocalcinosis and hypomagnesemia who met criteria for Gitelman's disease, including hypomagnesemia, hypokalemia with normal or high urinary potassium excretion, hypocalciuria, and normal blood pressure. Based on our experience with these patients, we argue that many cases of chondrocalcinosis and hypomagnesemia ascribed in previously published articles to Bartter's syndrome were due to Gitelman's syndrome.     

Effects of vasoactive agents in healthy and diseased human saphenous veins

In breast cancer, DNA amplification of the oncogene c-erbB-2, encoding for the p185 protein, is associated with a poor prognosis. A retrospective study on a population of 220 cases of primary breast cancer permitted a quantitative measure of p185 oncoprotein overexpression by an immunoenzymetric assay and the determination of c-erbB-2 amplification by the Southern blot method. A correlation existed between the two measurements (r=0.85) using the double cut-off: DNA 2 copies and p185 400 U/mg protein, and only 2.7% of the cases were discordant. 13.2% of the tumors showed p185 overexpression. The percentage of tumors overexpressing p185 was significantly different between the groups with amplified and non-amplified c-erbB-2. We observed a significant correlation between p185 levels and tumor grade (p=0.03), and an inverse correlation with hormonal receptors (p=0.0001). The p185 assay could be an additional prognostic factor to better define patient subgroups with node negative, grade II, and positive or negative hormonal receptors.     

Portal levels of the isoprostane F2 alpha-III, a marker of lipid peroxidation, do not correlate with increased portal pressure in cirrhotic patients

BACKGROUND: Isoprostane F2 alpha-III (iPF2 alpha-III), a recently described member of a family of prostaglandin F2 alpha isomers and a biologically active end-product of lipid peroxidation, has been reported to increase portal pressure in cirrhotic rats. We found that its urinary levels were elevated in cirrhotic patients. METHODS: To investigate whether portal levels of iPF2 alpha-III were elevated in cirrhotic patients and whether there was a relationship between these levels and the portal pressure in the same patients, peripheral and portal plasma from cirrhotic patients (n = 18) undergoing elective transjugular intrahepatic portosystemic shunt and appropriate controls (n = 18) were assayed for iPF2 alpha-III levels by using a gas chromatography/mass spectrometry assay. Portal pressure was measured in all cirrhotic patients. RESULTS: Cirrhotic patients had higher peripheral plasma levels of iPF2 alpha-III [78 (27-150) pg/mL] than controls [18(10-30)pg/mL] (P < 0.001). Portal iPF2 alpha-III levels were higher than plasma peripheral levels [129(50-375) pg/mL; P < 0.0001]. No correlation was found between peripheral and portal levels of iPF2 alpha-III (Rho = 0.17, P = 0.5). Portal levels of iPF2 alpha-III and portal pressure did not correlate (Rho = 0.17, P = 0.49). CONCLUSIONS: This study shows that peripheral and portal levels of iPF2 alpha-III, marker of in vivo lipid peroxidation, are elevated in liver cirrhosis. There is no correlation between iPF2 alpha-III portal levels and the portal pressure observed in these patients. These findings suggest that this biologically active isoprostane does not directly contribute to the portal hypertension observed in hepatic cirrhosis.     

Methanol electrooxidation on carbon-supported Pt-WO3−x electrodes in sulphuric acid electrolyte

Electrooxidation of methanol has been studied in sulphuric acid electrolyte at 60°C on carbon-supported Pt-WO_3–x electrodes employing varying amounts of WO_3–x . It is found that the electrodes containing (3:1) Pt-WO_3–x composite catalyst exhibit a higher catalytic activity towards methanol electrooxidation than platinized carbon electrodes without WO_3–x . In the light of the XPS and XRD data on the carbon-supported (3:1) Pt-WO _x sample, it is speculated that the WO _x is present in the form of an oxyhydroxide, which can promote surface oxy-species on platinum by proton transfer.     

Cortical Sensorimotor Interactions During the Expectancy of a Go/No-Go Task: Effects of Painful Stimuli.

The intent of this electroencephalography study was to investigate the competition between cortical nociceptive and cognitive-motor processes preceding sensorimotor interactions. Sensorimotor expectancy processes to painful stimulation and motor go/no-go demands were indexed over primary sensorimotor and midline cortical areas by contingent negative variation (CNV). Before the sensorimotor interaction, CNV was observed over midline posterior and bilateral central areas. Early expectancy of painful stimulation and the go/no-go task induced an evident midline posterior CNV. During the late expectancy period. CNV extended to the right central area contralateral to the stimulation. These findings suggest a sequential activation of midline posterior and primary sensorimotor areas contralateral to the painful stimulation as a reflection of the enhanced nociceptive processes preceding painful sensorimotor interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition by N omega-nitro-L-arginine methyl ester of the electrocortical arousal response in rats

In rats chronically implanted with cannulae into one lateral cerebral ventricle and recording electrodes onto the fronto-parietal cortex, the effects of systemic or intraventricular administration of the nitric oxide (NO) synthesis inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), on electrocortical (ECoG) arousal response evoked by sound stimulation were studied. In control animals, a single acoustic stimulation (80 dB for 15 s) produced a significant decrease in ECoG total voltage power lasting approximately 25 s. No tolerance developed after repeating the same sound stimulation at 15, 30, 60 min and 24 h intervals. Under these experimental conditions, pretreatment with L-NAME, given systemically (10 mg kg-1, i.p.) or intracerebroventricularly (300 micrograms), significantly reduced the sound-evoked arousal response 1 h and 15 min later, respectively. In conclusion, the present data are in favour of a physiological role of NO in the control of arousal mechanisms.