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111.
Eine der oft angewandten Möglichkeiten der Markierung fester Träger mit gasförmigen Tracern ist die Diffusionstechnik. Die mit dieser Technik hergestellten Träger wurden zu reaktionskinetischen und analytischen Bestimmungen herangezogen. Im vorliegenden Artikel werden die Grenzen und die Möglichkeiten der Anwendung dieser Träger anhand der in der früheren Mitteilung abgeleiteten allgemeinen Erwägungen theoretisch begründet. 相似文献
112.
Milan Jakubek Zdeněk Kejík Robert Kaplánek Hana Veselá David Sýkora Pavel Martásek 《Supramolecular chemistry》2018,30(3):218-226
Perimidine-based chelators 1 and 2 were prepared, and their structures were confirmed by 1H and 13C NMR, MS spectroscopy and elemental analysis. These compounds were studied as specific synthetic receptors for the recognition of transition metal ions. They exhibited high affinity and selectivity towards Cu(II) ions. The conditional binding constants, linear dynamic range and detection limit were determined by UV–vis spectroscopy. These parameters demonstrated high potential of the prepared synthetic receptors for the recognition and determination of Cu(II) ions. The minimum detectable concentrations of Cu(II) ions for the synthetic receptors 1 and 2 were 270 and 75 nM (R 2 = 0.9915 and 0.9964) in aqueous medium (water/DMSO; 99:1 (v/v)), respectively. 相似文献
113.
Using chemical separations and radiometric measurements medium-half-life irradiation products of molybdenum with 12.5 MeV deuterons were determined (90Nb, 92Nb, 95mNb, 95Nb, 96Nb, 99Mo, 95mTc, 96Tc, 99mTc) as well as thick target yields for some of them: 92Nb (0.22 μCi/μAh), 95Nb(0.05 μCi/μAh), 99Mo (64 μCi/μAh), 95mTc(0.76 μCi/μAh), 96Tc((62.5 μCi/μAh). Moreover isolation possibiities of radioactive preparations from removed worn-cut molybdenum parts of the U-120 cycletron are discussed. 相似文献
114.
Infinite tubular assemblies based on calix[4]arenes can be easily constructed using cation–π interactions of silver triflate with preorganised aromatic subunits (1,3-alternate or pinched cone conformations). X-ray crystallographic analysis shows that the overall self-assembly is held together by triflate anions playing the role of the bridges between the individual complexes. 相似文献
115.
E. Makrlík P. Vaňura P. Selucký 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):163-166
From extraction experiments and $ \gamma Accurate knowledge of the trace elemental concentrations in wheat and its products is of great importance from a nutritional point of view. In this study, six wheat samples were prepared from the agriculture research center of Arak named Sardari, Amir, MV-17, Batava, Karaj-2 and Alvand; they were analyzed by neutron activation method (NAA). In this method, Isfahan miniature reactor as a neutron source and relative NAA method has been used as the analysis type. In this design in order to record gamma spectrum the MCA system and high purity germanium detector were used. Finally, the concentration of the trace elements such as Br, K and Na value was determined for the Sardari, Amir, Alvand, MV-17, Batava, Karaj-2 wheat samples. The average concentration of trace elements in all wheat samples in the studied area are 2.41(0.8597?6.1175) mg kg?1 for Br, 13.42(8.7063?24.696) mg kg?1 for Na and 463.30(434.22?505.45) mg kg?1 for K, respectively. These were compared with other reports results. This study has been conducted as the first time for this region. 相似文献
116.
E. Makrlík P. Vaňura P. Selucký 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):2077-2081
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium C+(aq) + 1·Cs+(nb) ?1·C+ (nb) + Cs+(aq) taking place in the two–phase water–nitrobenzene system (C+ = methylammonium, ethylammonium, propylammonium, ethanolammonium, diethanolammonium, triethanolammonium, protonated tyramine, protonated dopamine, protonated DL–noradrenaline; 1 = hexaethyl p-tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the 1·C+ complex species in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: protonated tyramine < protonated dopamine < triethanolammonium < diethanolammonium < protonated DL-noradrenaline < propylammonium < ethanolammonium < ethylammonium < methylammonium. 相似文献
117.
Kristýna Urbánková Martin Moos Jiří Machát 《International journal of environmental analytical chemistry》2013,93(11):1077-1087
This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of 75As, 82Se, 121Sb and 125Te by ICP-MS for amounts less than 10?µg?L?1. Internal standards such as 72Ge and 209Bi were successfully used for the suppression of both influence of macro elements Na+, K+, Ca2+, Mg2+ or Al3+, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon? SGX C18, C8, CN, NH2, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5?µg?L?1) in the form of ion associates with cationic surfactants from 50–250?mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005?mol?L?1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7?±?0.2 and the mixture of acetone with ethanol in ratio 1?:?1 in the presence of 0.1?mol?L?1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon? SGX C18 and the above reagents were compared with the standard addition method. 相似文献
118.
Prof. Dr. Andrei V. Malkov Dr. Sigitas Stončius Dr. Mark Bell Dr. Fabiomassimo Castelluzzo Dr. Pedro Ramírez‐López Dr. Lada Biedermannová Prof. Dr. Vratislav Langer Dr. Lubomír Rulíšek Prof. Dr. Pavel Kočovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(28):9167-9185
Detailed kinetic and computational investigation of the enantio‐ and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5 , employing the pyridine N‐oxides METHOX ( 9 ) and QUINOX ( 10 ) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate‐ and selectivity‐determining step, which is supported by both experimental and computational data. 相似文献
119.
The paper deals with the classical fiber bundle model with brittle Weibull fibers and equal load sharing. This model is significant for the strength of fibrous materials and composites, and the generally random strength of quasi-brittle structures. The model is also relevant for the analysis of the reliability of various parallel systems (computer components, infrastructure etc.). An improved closed-form Gaussian approximation of the standard deviation of bundle strength is presented and compared with accurate solution calculated by recursive formula proposed by Daniels. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
120.
Martin Porubský Dr. Kristýna Vychodilová Dr. David Milićević Dr. Miloš Buděšinský Jarmila Stanková Dr. Petr Džubák Dr. Marián Hajdúch Prof. Jan Hlaváč 《ChemistryOpen》2021,10(11):1104-1110
The combination of cytotoxic amino-BODIPY dye and 2-phenyl-3-hydroxy-4(1H)-quinolinone (3-HQ) derivatives into one molecule gave rise to selective activity against lymphoblastic or myeloid leukemia and the simultaneous disappearance of the cytotoxicity against normal cells. Both species′ conjugation can be realized via a disulfide linker cleavable in the presence of glutathione characteristic for cancer cells. The cleavage liberating the free amino-BODIPY dye and 3-HQ derivative can be monitored by ratiometric fluorescence or by the OFF-ON effect of the amino-BODIPY dye. A similar cytotoxic activity is observed when the amino-BODIPY dye and 3-HQ derivative are connected through a non-cleavable maleimide linker. The work reports the synthesis of several conjugates, the study of their cleavage inside cells, and cytotoxic screening. 相似文献