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81.
István Gaál 《Acta Mathematica Hungarica》2005,106(1-2):41-51
Summary In the definition of semi-open sets and other kinds of generalized open sets, the role of the starting topology is given to a generalized topology. Some properties of the classes of sets so obtained is examined. 相似文献
82.
GC–MS Studies of Thiophenes in the Supercritical Fluid CO2 and Solvent Extracts of Tagetes patula L.
Szabolcs Szarka István Gyurján Miklós László Éva Héthelyi Inna N. Kuzovkina Éva Lemberkovics Éva Szőke 《Chromatographia》2010,71(11-12):1039-1047
The intact plant parts and genetically modified hairy root clone #TpA6 of Tagetes patula were extracted with supercritical fluid CO2 extraction (SFE) and a conventional solvent extraction. SFE optimization included the variation of fluid CO2 pressure, dynamic time, and the addition of methanol modifier co-solvent. The four characteristic thiophene metabolites, 5-(3-buten-1-ynyl)-2,2′-bithienyl (BBT), 2,2′:5′,2″-terthiophene (α-T), 5-(4-acetoxy-1-butynyl)-2,2′-bithienyl (BBTOAc), and 5-(3,4-diacetoxy-1-butynyl)-2,2′-bithienyl [BBT(OAc)2], were analysed by GC–MS. The proposed SFE method allowed the selective extraction of thiophenes in 60 min dynamic time with supercritical CO2 without modifier co-solvent, at 30 MPa and 40 °C. The SFE and the reference solvent extraction yielded similar results. The SFE of intact roots and flowers yielded 717 ± 31.3 and 480 ± 26.6 μg g?1 α-T, respectively, while the leaves did not contain considerable amounts of thiophenes. Remarkable amounts of BBT, BBTOAc, and BBT(OAc)2 were characteristic of the SFE of hairy root cultures. 相似文献
83.
The merits and limitations of gas-phase electron diffraction as a technique for determining accurately the structures of small
organic molecules are demonstrated by comparing the molecular structures of five benzene derivatives studied in two different
laboratories. The existence of many possible representations of the structure of a molecule (r
a, r
g, r
α, r
α0, r
e, …), implying differences in the physical meaning of geometrical parameters, is discussed in some detail as it may cause
difficulties in a comparison. Also illustrated are different ways of estimating and expressing uncertainties in the geometrical
parameters from a gas-phase electron diffraction study. 相似文献
84.
Mihály Molnár László Palcsu István Futó Éva Svingor Zoltán Major Mihály Veres Péter Ormai István Barnabás 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(3):745-750
To obtain reliable estimates of the quantities and rates of the gas production in L/ILW a series of measurements was carried
in the last 7 years in Hungary. The typical gas production rates were 0.05–0.2 STP litre gas/day for CO2 and CH4 generation, and less for H2. No explosive gas mixture was indicated in the L/ILW drums during the investigated storage period. Compositions of headspace
gases in closed L/ILW vaults were in agreement with gas generation processes observed in L/ILW drums. The stable carbon isotope
measurements show that the main source of the CO2 gas is the degradation of organic matter and indicates microbial degradation processes as the main sources of CH4. Typical tritium activity concentrations were <10 Bq/l gas in the drums and <1,000 Bq/l gas in the vaults. Typical 14C activity values of the headspace gases were <2.0 Bq/l gas in the drums and <1,000 Bq/l gas in the vaults. 相似文献
85.
Lajos Kovács Pál Herczegh Gyula Batta István Farkas 《Journal of carbohydrate chemistry》2013,32(5):585-599
ABSTRACT The reactivity of the title compounds has been studied toward different nucleophiles and electrophiles. Unlike other ketene dithioacetals, compounds 3-5 did not add nucleophiles to the double bond. Instead, in the presence of Lewis acids they underwent substitution reaction at position 3. If the nucleophile was not strong enough, formation of 6 and 7 were observed. With 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranose (18), a 3:1 mixture of 11 and 12 was formed from 4. These observations may be interpreted in terms of easy formation of the allylic carbocation I which gives diastereomers with nucleophiles. However, this allylic ether-like behaviour was ruled out by the fact that compounds 9 and 10 did not undergo [2,3] sigmatropic rearrangement with lithium diisopropylamide. With N-bromosuccinimide compound 3 gave the 2-bromo derivative 8. Compounds 3 and 8 resisted common mercury salt assisted demercaptalization procedures. 相似文献
86.
We have measured the variation of atmospheric pressure and of 222Rn activity concentration in the air of a wine cellar with an AlphaGAURD type ionization chamber radon monitor. We have found
that the 222Rn activity concentration varies inversely with pressure. To explain this behavior we have done model calculations. We have
compared the results of model calculations with the results of experimental measurements, and we have found that the model
is capable to reproduce some part of the variation of 222Rn activity concentration. 相似文献
87.
88.
István Hargittai 《Structural chemistry》2010,21(1):1-7
Linus Pauling, arguably the greatest chemist of the twentieth century, never publicly admitted that there was a race for the
determination of the structure of the most important biopolymers. But according to his competitors there was a race, in fact,
there were two, and Pauling won one and lost the other. He had a tremendous amount of ideas, many of them worthless, but a
few were spectacular. Not only did he make seminal discoveries, he was also a master of announcing them in a most dramatic
way. Eventually, Pauling shifted toward politics and controversial issues, but his science ensured him his place among the
greats. Here, we follow Pauling’s route to the discovery of the alpha-helix; the defeat of the star-studded British team in
the same quest; and a seemingly unrelated story about the fate of the theory of resonance that assured Pauling’s victory yet
at the same time it was excommunicated in the Soviet Union. 相似文献
89.
Unsigned book reviews are by the Book Review Editor. 相似文献
90.
Aart Blokhuis Győrgy Kiss István Kovács Aleksander Malnič Dragan Marušič János Ruff 《组合设计杂志》2007,15(6):491-501
Semiovals which are contained in the union of three concurrent lines are studied. The notion of a strong semioval is introduced, and a complete classification of these objects in PG(2,p) and PG(2,p2), p an odd prime, is given. © 2007 Wiley Periodicals, Inc. J Combin Designs 15: 491–501, 2007 相似文献