Authors:M. Armelin, M. Vasconcellos, E. Pereira, and F. Sircilli Neto
A radiochemical neutron activation analysis procedure is described for the determination of concentration levels of iridium in sedimentary rocks and in the geochemical standard PCC-1. After irradiation, the powdered rock samples and standard are dissolved with a mixture of HF, HNO3 and HClO4 in a teflon bomb. The final solution obtained, in dilute HCl, is passed through a column containing the cationic resin Bio Rad AG 50W-X8. The interfening radionuclides are sorbed by the resin. The effluent solution containing iridium is concentrated for counting by evaporation. Experiments with radioactive tracer for checking radiochemical separation yield are carried out. The accuracy of the method is evaluated by means of analysis of the USGS standard rock peridotite, PCC-1. The precision is about 25% in the ppb range. The method is used for the determination of iridium in 16 samples of sedimentary rocks collected at different depths in the Campos basin-RJ (BRAZIL).
Authors:György Koszta, Gábor Tihamér Sira, and Krisztina Béczy
A vérkészítményekhez való hozzáférés világszerte egyre korlátozottabbá válik. A
rendelkezésre álló források észszerű felhasználása emiatt is kiemelt jelentőségű
napjaink perioperatív betegellátásában. Az összes vérkészítmény-felhasználás
közel fele a cardiovascularis sebészetben történik. A jelen közleményben
összefoglaltuk a vérkészítmény-megtakarítás lehetséges módszereit a
szívsebészeti betegellátás kapcsán, kiemelve a súlyos perioperatív vérzés
kezelésével és megelőzésével kapcsolatos szempontokat. Orv Hetil. 2020; 161(37):
The initial activation energy at zero conversionEo of thermooxidative decomposition has been taken as a measure of thermal stability of polycarbonates (PC) andEo has been correlated with the relative hydrolysis raterh as a measure of their hydrolyse resistance. It is suggested that both decomposition processes are initiated by the same mechanism,
the attack of hydrolytic agent onto ester C−O bonds. The following values ofEo have been found:
187 (PC-M)>87 (PC-A)>43 (PC-C) kJ/mol, and they are correlated with values ofrh being 0.01 (PC-M)<1 (PC-A)<4.4 (PC-C). It has been found, using a computer modeling technique, that bothEo andrh depend on the minimized energy of conformations.
The possibilities of reactor induced (n, p) reactions as a tool for neutron activation analysis of titanium in geological samples are discussed. The interference of calcium and scandium is experimentally evaluated. Results for Ti, Ca and Sc in GSP-1 and PCC-1 standard rocks are presented. On the basis of the experimental values, it is concluded that the47Ti(n, p)47Sc reaction is the most favourable for titanium determination.
The (U. S.) National Bureau of Standards standard reference material 1633a (coal flyash) was standardized for the concentrations of 29 elements against chemical standards by instrumental neutron activation analysis. United States Geological Survey basalt standard BCR-1 was analyzed concurrently as a check. SRM 1633a is a good multielement comparator standard for geochemical analysis for 25 of the elements analyzed and is a better standard than rock-powder SRMs commonly used. Analytical data for USGS DTS-1, PCC-1, GSP-1, BIR-1, DNC-1, and W-2; NBS SRMs 278 and 688; and GIT-IWG (French) anorthosite AN-G are also presented.
A procedure is described for the determination of Pd, Au, Ir, and Pt in rocks at the ppb concentration level. After irradiation
with thermal neutrons, powdered rock samples are fused with carriers and Na2O2−NaOH. The fusion cake is dissolved in dilute HCl, and the activated noble metals and carriers are coprecipitated as a group
with Te, using Sn2+ as a reductant. Gamma and X-rays are counted on semi-conductor Ge deterctors. Yields are determined by reirradiation. Results
are given for several rocks, including U.S.G.S. standards PCC-1 and W-1.
Authors:Ágnes Vehovszky, A. Kovács, Henriette Szabó, J. Győri, and Anna Farkas
The responses of the snail central neurons (Helix pomatia, Lymnaea stagnalis) and the isolated Helix heart were characterized evoked by cyanobacterial extracts (Cylindrospermopsis raciborskii ACT strains) isolated from Lake Balaton (Hungary). The nicotinergic acetylcholine (ACh) receptors in the CNS (both excitatory and inhibitory) were blocked by the extracts of ACT 9502 and ACT 9505 strains and the anatoxin- a (homoanatoxin-a) producing reference strain of Oscillatoria sp. (PCC 6506), similar to the inhibitory effects of the pure anatoxin-a. The enhancement of the ACh responses by the ACT 9504 extract suggests additional, probably acetylcholine esterase inhibitory mechanisms. On the isolated Helix heart the crude ACT 9505 and PCC 6506 extracts evoked frequency increase and transient twitch contraction, opposite to the ACh evoked heart relaxation. Anatoxin-a similarly contracted the heart but did not increase its contration frequency. These data suggest the involvement of some non-cholinergic mechanisms, acting very likely by direct modulation of the electrical or contractile system of the isolated heart. Diversity of the effects evoked by the cyanobacterial extracts in the CNS and heart suggest pharmacologically different neuroactive components among the secondary metabolites of the cyanobacteria acting on both (anatoxin-a like) cholinergic and (unidentified) non-cholinergic receptors.
Authors:I. Demin, C. Shimshilashvili, N. Yur’eva, N. Naraykina, I. Goldenkova-Pavlova, D. Los, A. Nosov, and T. Trunova
The responses of plant leaves to chilling were studied in potato (Solanum tuberosum L., cv. Desnitsa) and in its transformants with the native desA gene that encodes the acyl-lipid Δ12-desaturase from the cyanobacterium Synechocystis sp. PCC 6803 and with the hybrid desA gene fused to the reporter gene of thermostable lichenase (licBM3) from Clostridium thermocellum. Cold stress caused a rapid and significant increase in superoxide production and lipid peroxidation (the content of conjugated dienes and malonic dialdehyde) in wild-type plants. By contrast no significant increase was detected in transformed plants under cold stress conditions. This can be attributed to the fact that the overexpression of the acyl-lipid Δ12-desaturase in transformed potato plants promotes fatty acid polyunsaturation and presumably averts the accelerated generation of the superoxide anion, thus suppressing lipid peroxidation under low-temperature stress