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101.
H. A. Ergül S. Topcuo?lu E. Ölmez Ç. K?rbaşo?lu 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(1):133-136
Summary Radionuclide (137Cs, 238U, 232Th and 40K) concentrations were determined in a sediment trap and bottom sediment samples collected from a station at the eastern Turkish
coast of the Black Sea. The specific activity of the 137Cs radionuclide in the settling particles ranged from 0.04±0.01 to 0.10±0.02 Bq. g-1dry weight. The calculated flux rate of the 137Cs was between 0.37 and 2.59 Bq. m-2. d-1in the sampling periods of 2002 and 2003. The 137Cs concentration in the bottom sediment profile were between 0.039±0.013-9.083±0.017 Bq. g-1dry weight in the same station. The vertical profile of the radionuclides suggests that they have little mobility during the
17 years after the Chernobyl accident. 相似文献
102.
The purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast-like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square-wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10−4 mol L−1; ammonium chloride buffer: 0.10 mol L−1 (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10−9 mol L−1 for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays. 相似文献
103.
104.
Jo?o L M Santos Arnaud Clausse José L F C Lima M L M F S Saraiva António O S Rangel 《Analytical sciences》2005,21(4):461-464
A new flow methodology exploiting the multi-pumping approach was developed for the spectrophotometric determination of ambroxol hydrochloride in pharmaceutical preparations. The flow manifold was implemented by using, exclusively, multiple solenoid-actuated micro-pumps, which acted simultaneously as sample insertion, solutions propelling and reagents commutation units. Linear calibration plots were obtained over an ambroxol concentration ranging from 10 to 200 mg l(-1) (r.s.d. < 0.5%, n = 15) and a sampling rate of about 60 samples per hour (flow rate = 1.92 ml min(-1), sample volume = 80 microl). 相似文献
105.
Summary A method is reported for the determination of dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT), and triphenyltin (TPhT)
species at the nanogram per litre concentration level in natural water samples. Analytes were isolated from samples by solid-phase
extraction and analysed both off-line and on-line by reversed-phase high-performance liquid chromatography with post-column
derivatization and fluorimetric detection. Several SPE cartridges and eluents were evaluated; C18 enrichment and elution with a mixture of methanol, acetic acid, and water was found most suitable. Preconcentration factors
up to 250 can be achieved when a 500-mL sample is processed. Detection limits, recovery rates, and the precision of the whole
process have been determined. The method has been applied to the determination of organotin species in spiked natural water
samples collected on the NW Mediterranean coast. Recovery rates range from 75 to 110% and detection limits are at the low
ng L−1 level (1–3 ng Sn L−1 for DPhT, DBT, and PhT and 40 ng Sn L−1 for TBT when 250 mL spiked sea water is processed.) 相似文献
106.
J. V. Kunzler W. Schreiner A. Bristoti D. E. BrandÃo 《Journal of Thermal Analysis and Calorimetry》1977,11(1):81-86
Saturation magnetization measurements as a function of temperature were performed on Cu2Mn(Al1–xSnx) Heusler alloys to study the existence of stable structures. The derivatograph was applied to study the thermal effects.
Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and Banco Nacional de Desenvolvimento Economico, Brasil. 相似文献
Zusammenfassung Sättigungsmagnetisierungsmessungen als Funktion der Temperatur sowie Derivatographie wurden an Heusler-Legierungen der Formel Cu2Mn(Al1–xSnx) zu Untersuchungen der Existenz einer stabilen Struktur vorgenommen.
Résumé Etude de l'existence d'une structure stable dans les alliages de Heusler Cu2Mn(Al1–xSnx), à l'aide d'un Derivatograph et par des mesures de magnétisation à saturation en fonction de la température.
XecnepaCu2Mn(Al1–xSnx), , , . .
Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and Banco Nacional de Desenvolvimento Economico, Brasil. 相似文献
107.
H. Langfelderová L'. Macášková K. Otrubová J. Gažo 《Journal of Thermal Analysis and Calorimetry》1986,31(5):1143-1151
The thermal decompositions of Cu(en)2(NCS)X. where X–=Cl–, Br–, NO
3
–
, BF
4
–
and ClO
4
–
, have been studied in comparison with the courses of Cu(en)2(SCN)2 and Cu(en)2X2 decomposition. It is shown that the presence of the thiocyanate group in the complexes Cu(en)2(NCS)X is the most important factor in the decomposition course, in agreement with the fact that the anions X– are not coordinated. or are only semicoordinated. Significant differences were found in the courses of thermal decomposition of two forms of Cu(en)2(NCS)(BF4) differing in the structure of their coordination polyhedra.
Zusammenfassung Die thermische Zersetzung von Cu(en)2(NCS)X (X=Cl Br, NO3, BF4 und ClO4) wurde untersucht und mit der von Cu(en2(SCN)2 und Cu(en)2X2 verglichem. Der den Verlauf der Zersetzung entscheidend bestimmende Faktor isi die Anw esenheit der Thiocyanat-Gruppe in den Cu(en)2(NCS)X-Komplexen, was in Übereinstimmung damit steht,. daß die Anionen X nicht oder nur teilweise koordiniert sind. Es wurden signifikante Unterschiedeim Verlauf der thermischen Zersetzung von zwei sich in der Struktur ihrer Kordinationspolyeder unter-, heidenden Formen von Cu(en)2(NCS)(BF4) gefunden.
Cu(en)2(NCS)X (X–=Cl–, Br–, NO 4 – , NO 3 – , BF4 ClO4, Cu(en)2(SCN)2 Cu(en)2(X)2. , Cu(en)2(NCS)X X Cu(en) (NCS)BF4 i .相似文献
108.
Guimarães KL Castro RH Gouvêa D 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11645-11650
The standard methods for obtaining adsorption isotherms on colloidal suspensions are usually very time consuming and involve a large number of steps and assumptions that increase the experimental errors. In this work, an alternative method is proposed to evaluate the adsorption behavior of electrosteric-stabilized systems based on electrokinetic sonic amplitude signal measurements. The new method, entitled "zeta-sorption", is noticeably less time-consuming when compared to conventional procedures but showed great precision and reliability confirmed by comparison with data obtained from conventional routes on alumina-polyacrylate and alumina-citric acid aqueous suspensions. The experimental conditions that restrict the applicability of the new method were identified and justified by discussing the possible ion exchanges. 相似文献
109.
The main features of transition structures associated with eight-electron electrocyclic reactions have been studied with Density Functional Theory. It is found that conrotatory electrocyclization reaction of (3Z,5Z)-octa-1,3,5,7-tetraenes takes place via M?bius aromatic transition structures of helical conformation. The reaction is completely periselective. In general, transition structures having outward substituents are preferred with respect to the inward transition structures, irrespective of the pi-donor or pi-acceptor character of the substituent. In contrast with four-electron thermal conrotatory electrocyclic reactions, there is no satisfactory correlation between the difference in energy of activation between inward and outward substituents and the Taft resonance sigma(R) parameter. 相似文献
110.
AurelioG. Cskÿ Rocío Medel M.Carmen Murcia Joaquín Plumet 《Helvetica chimica acta》2005,88(6):1387-1396
A new method for the synthesis of spiro‐β‐lactams tethered to tetrahydrofuran rings is described. The procedure is based on Ru‐catalyzed metathesis sequences with oxanorbornene precursors easily obtained by the Staudinger [2+2] cycloaddition of related imines. 相似文献