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41.
Bla Bollobs Istvan Simon 《Journal of Algorithms in Cognition, Informatics and Logic》1985,6(4):466-477
The average cost of inserting n elements into an initially empty heap is analyzed, under the assumption that the n! orders in which the n elements can be inserted are equally likely. It is proved that this average, expressed in number of exchanges per insertion, is bounded by a constant about 1.7645. 相似文献
42.
Istvan Hazai Alfredo Galvez-Sinibaldi R. Paul Philp 《Journal of separation science》1992,15(12):791-794
The development of tandem mass spectrometry (MS-MS) and its combination with gas chromatography (GC-MS-MS) has greatly enhanced our ability to analyze exceedingly complex mixtures from a wide variety of sources, including fossil fuels. This paper describes a comparison of the conventional electron impact (El) mass spectral fragmentation patterns, obtained in the MS-MS precursor – product mode, of three oleanane isomers and one ursene, all of which are used as indicators of higher plant input to the sedimentary environment Results show that El and collision-activated dissociation (CAD) spectra are most similar at collision energies between ?15 and ?20 eV.The presence of methyl substituents in these pentacyclic terpenes plays an important role in the process of ring fragmentation: the daughter spectra of the M – 15 fragments can be used to obtain structural information, such as the positions of the double bonds. 相似文献
43.
Semiempirical self-consistent-field molecular-orbital calculations are carried out for six iron-pentacyanide complexes and are used to interpret their experimental Mössbauer quadrupole splittings. Probable orientations are identified for the C6H 5 ? and NO 2 ? groups in Fe(CN)5NOC6H 5 ?3 and Fe(CN)5NO 2 ?4 . Calculations on Fe(CN)5NO?2 and Fe(CN)5NO?3 can simultaneously be brought into agreement with experiment by reparametrization to make the NO group more positively charged. All the calculations indicate the importance of including all the Fe 3d and 4p orbitals in the calculations and of considering neighboring-atom effects. 相似文献
44.
Measurements of nitrate in natural waters with a nitrate ion-selective electrode are seriously affected by the presence of humic substances. These can be removed quantitatively by a clean-up procedure with cheap disposable adsorption columns packed with chemically-bonded alkylamino silica. The method is applied to natural water samples with high contents of humic substances. The nitrate concentrations found were in good agreement with determination by ion chromatography. 相似文献
45.
Michael A. Baldwin Kevin J. Welham Istvan Toth William A. Gibbons 《Journal of mass spectrometry : JMS》1988,23(10):697-699
Under fast atom bombardment conditions, compounds having long alkyl chains may exhibit [M ? H]+ as the major quasimolecular ion species, which can lead to incorrect assignment of molecular masses. It is shown that for a long-chain ether the loss of the hydride occurs from the hydrocarbon chain remote from the oxygen. This effect may yield information concerning ionization mechanisms in fast atom bombardment/mass spectrometry. 相似文献
46.
Istvan Hargittai 《Structural chemistry》2017,28(5):1277-1277
47.
Tom X.-P. Zhao Hongbin Yu Istvan Laszlo William C. Conant 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(7):1162-1186
A two-step approach is proposed to derive component aerosol direct radiative forcing (ADRF) at the top of atmosphere (TOA) over global oceans from 60°S to 60°N for clear-sky condition by combining Terra CERES/MODIS-SSF shortwave (SW) flux and aerosol optical thickness (AOT) observations with the fractions of component AOTs from the GSFC/GOCART model. The derived global annual mean component ADRF is +0.08±0.17 W/m2 for black carbon, −0.52±0.24 W/m2 for organic carbon, −1.10±0.42 W/m2 for sulfate, −0.99±0.37 W/m2 for dust, −2.44±0.84 W/m2 for sea salt, and −4.98±1.67 W/m2 for total aerosols. The total ADRF has also been partitioned into anthropogenic and natural components with a value of −1.25±0.43 and −3.73±1.27 W/m2, respectively. The major sources of error in the estimates have also been discussed. The analysis adds an alternative technique to narrow the large difference between current model-based and observation-based global estimates of component ADRF by combining the satellite measurement with the model simulation. 相似文献
48.
Robert Ludmerczki Dr. Stefania Mura Prof. Carlo Maria Carbonaro Prof. Istvan M. Mandity Dr. Massimo Carraro Dr. Nina Senes Prof. Sebastiano Garroni Prof. Gaetano Granozzi Prof. Laura Calvillo Sergio Marras Prof. Luca Malfatti Prof. Plinio Innocenzi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11963-11974
Thermal decomposition of citric acid is one of the most common synthesis methods for fluorescent carbon dots; the reaction pathway is, however, quite complex and the details are still far from being understood. For instance, several intermediates form during the process and they also give rise to fluorescent species. In the present work, the formation of fluorescent C-dots from citric acid has been studied as a function of reaction time by coupling infrared analysis, X-ray photoelectron spectroscopy, liquid chromatography/mass spectroscopy (LC/MS) with the change of the optical properties, absorption and emission. The reaction intermediates, which have been identified at different stages, produce two main emissive species, in the green and blue, as also indicated by the decay time analysis. C-dots formed from the intermediates have also been synthesised by thermal decomposition, which gave an emission maximum around 450 nm. The citric acid C-dots in water show short temporal stability, but their functionalisation with 3-aminopropyltriethoxysilane reduces the quenching. The understanding of the citric acid thermal decomposition reaction is expected to improve the control and reproducibility of C-dots synthesis. 相似文献
49.
There were ideal conditions in 1982 at the NBS/NIST for the kind of exploratory research that led Dan Shechtman to the quasicrystal
discovery. Almost thirty years later, in 2011, Shechtman received the Nobel Prize for this achievement. What happened in between
these two dates has been covered quite extensively elsewhere. But it is intriguing to learn more about the very beginning.
Then, the festivities in Stockholm added to our seeing the story in a fuller perspective. 相似文献
50.
Emil Burzo Istvan Balasz Iosif Deac Romulus Tetean 《Journal of magnetism and magnetic materials》2010,322(9-12):1109-1112
Magnetic properties and magnetocaloric effects were studied in (GdxY1?x)3Co11B4 ferrimagnetic compounds. Rather high values of the entropy changes were shown in large temperature ranges. The ΔS values were correlated with high temperature dependences of resultant magnetizations determined mainly by the gadolinium sublattice one. Large relative cooling power was also shown. 相似文献