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751.
In this paper we introduce the concept of s-monotone index selection rule for linear programming problems. We show that several known anti-cycling pivot rules like the minimal index, Last-In–First-Out and the most-often-selected-variable pivot rules are s-monotone index selection rules. Furthermore, we show a possible way to define new s-monotone pivot rules. We prove that several known algorithms like the primal (dual) simplex, MBU-simplex algorithms and criss-cross algorithm with s-monotone pivot rules are finite methods. 相似文献
752.
Edit Farkas Gergely Kovcs Istvn Szilgyi Sndor Db Tibor Brces Ferenc Mrta 《国际化学动力学杂志》2006,38(1):32-37
The fast flow method with laser induced fluorescence detection of CH3C(O)CH2 was employed to obtain the rate constant of k1 (298 K) = (1.83 ± 0.12 (1σ)) × 1010 cm3 mol?1 s?1 for the reaction CH3C(O)CH2 + HBr ? CH3C(O)CH3 + Br (1, ?1). The observed reduced reactivity compared with n‐alkyl or alkoxyl radicals can be attributed to the partial resonance stabilization of the acetonyl radical. An application of k1 in a third law estimation provides ΔfH(CH3C(O)CH2) values of ?24 kJ mol?1 and ?28 kJ mol?1 depending on the rate constants available for reaction ( ‐1 ) from the literature. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 32–37, 2006 相似文献
753.
Bartók T Szécsi A Szekeres A Mesterházy A Bartók M 《Rapid communications in mass spectrometry : RCM》2006,20(16):2447-2462
Fumonisins were produced in a rice culture infected with Fusarium verticillioides. To decrease the possibility of the formation of artifacts, the fumonisins were analyzed by reversed-phase high-performance liquid chromatography with electrospray ionization ion trap tandem mass spectrometry (RP-HPLC/ESI-IT-MS2) immediately after the extraction of the culture material without any sample clean-up. In addition to already known fumonisins, numerous new fumonisin mycotoxins and fumonisin-like compounds were detected. On the basis of the IT-MS2 data, detailed fragmentation pathways including new mechanisms were proposed for the different series of fumonisins. The retention times, the masses of the protonated molecules and of the product ions including the backbones and the characteristic neutral mass losses from the protonated molecules of the new compounds suggested their structures (applying the well-known designation): iso-FA1a,b, iso-FB1a-d, iso-FB2,3a-e, PHFB2a-c, PHFB4a-d, FB5/iso-FB5a-d, FBK1 2TCA, FBK4 2TCA, FC2, iso-FC2,3, PHFC4, FD and FBX series. The relative quantities of fumonisins and fumonisin-like compounds found in the sample extract were expressed as percentages of FB1 (0.02-100%). The backbone of the compound denoted FD contained fewer carbon atoms than the well-known fumonisins with the C19 or C20 backbone and may well be a precursor of the longer compounds. For the compounds denoted FBX (12 compounds), one or two OH groups attached to the fumonisin backbone were esterified by carboxylic acids other than tricarballylic acid, such as cis-aconitic acid, oxalylsuccinic acid and oxalylfumaric acid. 相似文献
754.
A rapid liquid chromatography-atmospheric pressure photoionization mass spectrometry (LC-APPI-MS) method was developed for the determination of ergosterol in wheat grains. The effects of the dopants acetone, toluene and anisole on the ionization efficiency were studied. To identify the predominant ions, APPI-MS-MS studies were performed. Different LC and MS parameters were optimized to obtain maximum sensitivity. The effects of the mobile phase composition and of the flow rate were investigated. Additionally, the effects of the nebulizer gas pressure, the drying gas flow, the vaporizer temperature, the fragmentor voltage and the capillary voltage on the ionization efficiency were evaluated. The calibration curve exhibited good linearity and reproducibility. The detection limit (S/N=3) was 0.15 ng on column, which allows the determination of ergosterol in wheat at a concentration as low as 0.12 microg/g. Twenty wheat varieties artificially infected with Fusarium graminearum were investigated by this method. 相似文献
755.
Gilányi T Varga I Gilányi M Mészáros R 《Journal of colloid and interface science》2006,301(2):428-435
The adsorption of polyethylene oxide (PEO) homologues in a wide range of molecular weight (from M(PEO)=200 to 10(6)) at the air/aqueous solution interface was investigated by dynamic and static surface tension measurements. An approximate estimate for the lower limit of PEO concentration was given at which reliable equilibrium surface tension can be determined from static surface tension measurements. It was shown that the observed jump in the earlier published sigma-lg(c(PEO)) curves is attributable to the nonequilibrium surface tension values at low PEO concentrations. The adsorption behavior of short chain PEO molecules (M(PEO)1000) is similar to that of the ordinary surfactants. The estimated standard free energy of PEO adsorption, DeltaG(0), increases linearly with the PEO molecular weight until M(PEO)=1000. In this molecular weight range, DeltaG(0) was found to be approximately the fifth of the hydrophobic driving force related to the adsorption of a surfactant with the same number of methylene groups. In the case of the longer chain PEOs the driving force of adsorption is so high that the adsorption isotherm is near saturation in the experimentally available polymer concentration range. Above a critical molecular weight the PEO adsorption reveals universal features, e.g., the surface tension and the surface density of segments do not depend on the polymer molecular weight. 相似文献
756.
Lívia Budai Oliver Ozohanics Krisztina Ludányi László Drahos Tibor Kremmer Judit Krenyacz Károly Vékey 《Analytical and bioanalytical chemistry》2009,393(3):991-998
Genetic variants of human plasma alpha-1 acid glycoprotein (AGP) have been studied in cancer, compared with a group of healthy
control. AGP has four genetic variants: AGP F1, F2, and S variants correspond to the ORM1 gene whereas AGP A corresponds to
the ORM2 gene. The proportion of ORM1 and ORM2 variants were studied in plasma using a novel UPLC–MS method. Plasma total
AGP level was 0.5 ± 0.2 g L−1 and the proportions of the ORM1 and ORM2 variants were 76.3 ± 8.2% and 23.7 ± 8.2%, respectively. In cancer plasma AGP levels
increased fourfold and the proportion of ORM1 variants increased to 88.7 ± 6.8%. Changes in the proportion of genetic variants
due to cancer were clearly significant, as shown by statistical analysis. Three different cancer types have been studied,
lymphoma, melanoma, and ovarian cancer. The results did not show any difference depending on cancer type. The results indicate
that, in accordance with prior expectations, the ORM1 variant is predominantly responsible for the acute-phase property of
AGP. 相似文献
757.
758.
759.
Mrta Berkesi Kroly Hidas Tibor Guzmics Jean Dubessy Robert J. Bodnar Csaba Szab Balzs Vajna Toshiaki Tsunogae 《Journal of Raman spectroscopy : JRS》2009,40(11):1461-1463
Raman spectroscopic analysis at low (−100 °C) or high (100–200 °C) temperature is shown to be effective for detecting small amounts of H2O in CO2‐rich fluid inclusions from the deep lithosphere, which have previously been thought to be water‐free. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
760.
The fundamental aspects of PVC degradation and stabilization are discussed. The primary process of thermal degradation (initiation, zip-elimination of HCl and simultaneous formation of polyene sequences, and termination of unzipping) is reevaluated in the light of results obtained with PVCs containing increased concentrations of labile chlorines. The effect of these defects on thermooxidative stability of the resin is also discussed. It has been shown that results obtained in recent systematic stabilization studies cannot be explained by the widely accepted Frye-Horst mechanism, i.e., substitution of labile chlorines by stabilizers. A new mechanistic proposition, the reversible blocking mechanism, for the stabilization of PVC is presented, and the effect of stabilizing reactions on the main elementary events of thermal and thermooxidative degradation is described in a unified manner. 相似文献