排序方式: 共有36条查询结果,搜索用时 609 毫秒
1.
Zanin Gisella M. Neitzel Ivo De Moraes Flavio F. 《Applied biochemistry and biotechnology》1993,(1):477-489
The axial dispersion of a liquid fluidized bed of controlled pore silica (CPS) particles has been determined by the pulse
tracer method. The CPS used was the same as for enzyme immobilization, having an average diameter of 0.436 mm and mean pore
size of 37.5 nm. The fluidization liquid is α-amylase liquefied manioc starch, 30% w/v, 45°C pH=4.5. Nominal bed porosities
tested were 0.7 and 0.8. The results show that the axial dispersion coefficient increases with greater superficial liquid
velocities. Various available correlations tested disagree with each other to a large extent and are unable to represent collected
experimental data. 相似文献
2.
We are concerned with the discretization of semilinear parabolic optimization problems subject to constraints on the first derivative of the solution of the PDE. Constructing sequences of feasible controls for the dG(0)-cG(1) discretization of the problem and relying on a quadratric growth condtion, we show convergence orders as temporal and spatial mesh tends to zero. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
Neitzel R Seixas N Olson J Daniell W Goldman B 《The Journal of the Acoustical Society of America》2004,115(1):237-245
Efforts to characterize nonoccupational noise exposures have focused primarily on infrequent, episodic events. Few studies have assessed noise levels resulting from routine daily activities. In the current study, 112 construction workers wore datalogging noise dosimeters and simultaneously completed activity logs during two phases of data collection. The 81 subjects monitored in phase 1 received logs listing numerous preselected occupational and nonoccupational activities, while the 31 subjects monitored in phase 2 used free-field logs and reported nonoccupational activities in greater detail. Nearly all of the 221,439 1-min intervals of nonoccupational L(eq) level and activity reporting were below 70 dBA; only a small percentage exceeded 80 dBA. The primary contributor to nonoccupational noise exposure was traveling in a car or bus, while time at home contributed the least. One hundred seventy 24-h L(eq) levels were computed from the 1-min noise level data. The percentage of phase 2 workday L(eq(24)) levels which exceeded 80 dBA was higher than that of the nonworkday levels. The mean L(eq(24)) level of phase 2 workdays was higher than that of nonworkdays, and the difference was statistically significant. Routine nonoccupational noise exposures contributed much less to total noise dose than occupational exposures in the subjects evaluated. 相似文献
4.
5.
The selective catch and release of the synthetically useful (o-biphenyl)(t-butyl)2P from basic and non basic compounds, utilizing solid phase supported sulfonic acid sources is demonstrated. 相似文献
6.
H. Elias G. Gumbel S. Neitzel und H. Volz 《Fresenius' Journal of Analytical Chemistry》1981,306(4):240-244
Zusammenfassung Zur empirischen Beschreibung der Polarität binärer Lösungsmittelgemische wurden mit einem solvatochromen Betain-Farbstoff ET-Werte für folgende Systeme bestimmt: Methanol/Butanol-2, Methanol/2-Methylbutanol-2, Methanol/Pyridin, Methanol/Acetonitril, Methanol/Toluol und Ethanol/ 2,2,2-Trifluorethanol. In allen Systemen treten mehr oder weniger starke Abweichungen vom idealen Mischungsverhalten auf, was im einzelnen diskutiert wird. In den genannten Lösungsmittelgemischen wurde parallel die Kinetik der Ligandensubstitution an einem neutralen Kupfer(II)-bis-chelatkomplex vermessen. Die ET-Werte korrelieren mit den lnkWerten (k = Geschwindigkeitskonstante für den durch das Solvens induzierten Ligandenaustausch). Dies weist darauf hin, daß die Bildung des Übergangszustandes durch H-Brücken erleichtert wird.
Polarity of binary solvent mixtures: Determination of ET(30)-values and correlation with kinetic solvent effects
Summary The polarity of binary solvent mixtures is empirically described by ET-values as determined with a solvatochromic betaine dye. The following mixtures were studied: methanol/butanol-2, methanol/2-methylbutanol-2, methanol/pyridine, methanol/acetonitrile, methanol/toluene and ethanol/2,2,2-trifluoroethanol. All mixtures behave as more or less non-ideal systems which is discussed in detail. Parallel to the determination of ET-values the kinetics of ligand substitution in a neutral copper(II)-bis-chelate complex were studied in the same set of solvent mixtures. The ET-values correlate with the corresponding lnk-values (k = rate constant for solvent induced ligand substitution). This would mean that the formation of the transition state is facilitated by hydrogen bonding.
Für finanzielle Unterstützung bedanken wir uns bei der Deutschen Forschungsgemeinschaft und dem Verband der Chemischen Industrie e.V. Der verwendete Salicylaldehyd wurde uns von der Firma Bayer AG, Leverkusen, zur Verfügung gestellt. 相似文献
7.
Peter L. Neitzel Wolfgang Walther W. Nestler 《Analytical and bioanalytical chemistry》1998,361(3):318-323
Strongly polar organic substances like halogenated acetic acids have been analyzed in surface water and groundwater in the catchment area of the upper Elbe river in Saxony since 1992. Coming directly from anthropogenic sources like industry, agriculture and indirectly by rainfall, their concentrations can increase up to 100 μg/L in the aquatic environment of this catchment area. A new static headspace GC-MSD method without a manual pre-concentration step is presented to analyze the chlorinated acetic acids relevant to the Elbe river as their volatile methyl esters. Using an ion-pairing agent as modifier for the in-situ methylation of the analytes by dimethylsulfate, a minimal detection limit of 1 μg/L can be achieved. Problems like the thermal degradation of chlorinated acetic acids to halogenated hydrocarbons and changing reaction yields during the headspace methylation, could be effectively reduced. The method has been successfully applied to monitoring bank infiltrate, surface water, groundwater and water works pumped raw water according to health provision principles. 相似文献
8.
Dr. Luong Phong Ho Angelika Neitzel Dr. Thomas Bannenberg Prof. Dr. Matthias Tamm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202104139
The lithium salts of anionic N-heterocyclic thiones and selones [{(WCA-IDipp)E}Li(toluene)] ( 1 : E=S; 2 : E=Se; WCA=B(C6F5)3, IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene), which contain a weakly coordinating anionic (WCA) borate moiety in the imidazole backbone were reacted with Me3SiCl, to furnish the silylated adducts (WCA-IDipp)ESiMe3 ( 3 : E=S; 4 : E=Se). The reaction of the latter with [(η5-C5Me5)MCl2]2 (M=Rh, Ir) afforded the rhodium(III) and iridium(III) half-sandwich complexes [{(WCA-IDipp)E}MCl(η5-C5Me5)] ( 5 – 8 ). The direct reaction of the lithium salts 1 and 2 with a half or a full equivalent of [M(COD)Cl]2 (M=Rh, Ir) afforded the monometallic complexes [{(WCA-IDipp)E}M(COD)] ( 9 – 12 ) or the bimetallic complexes [μ2-{(WCA-IDipp)E}M2(COD)2(μ2-Cl)] ( 13 – 16 ), respectively. The bonding situation in these complexes has been investigated by means of density functional theory (DFT) calculations, revealing thiolate or selenolate ligand character with negligible metal-chalcogen π-interaction. 相似文献
9.
Novel accelerator applications favor free-surface liquid–metal flows, in which the liquid acts both as a target producing
secondary particles but also to remove efficiently the heat deposited. A crucial aspect for the operation is the continuous
monitoring of both shape and position of the liquid’s surface. This demands, in a nuclear environment, a non-intrusive measurement
technique with high temporal and spatial resolution. In this context, the double-layer projection (DLP) technique based on
geometric optics has been developed, allowing one to detect either point-wise or area-wise the shape and position of the nearly
totally reflecting liquid–metal surface. The DLP technique employs a laser beam projected through a coplanar glass plate to
the surface from which it is reflected to the plate again. Beam locations captured by means of a camera permit the position
and shape of the surface to be reconstructed. The parameters affecting the resolution and performance of the DLP technique
are discussed. Additionally, validation studies using static and moving objects of pre-defined shape are conducted, exhibiting
spatial and temporal resolutions of 300 μm and 100 Hz, respectively. Finally, the DLP system is applied to perform measurements
of a circular hydraulic jump (CHJ) in a liquid metal. The DLP system has proved the capability to measure the jump both qualitatively
and quantitatively. Additionally, the experiments identified, at high Reynolds numbers, the existence of a two-step jump.
The analysis of spectral data of the DLP surface measurements shows clearly that, at the outer radius, gravity waves occur.
Also, contributions from the pump oscillations were found, demonstrating the high performance of the DLP system. 相似文献
10.
We consider Lavrentiev regularization for a class of semilinear parabolic optimal control problems with control constraints and pointwise state constraints and review convergence results for local solutions under Slater type assumptions as well as quadratic growth conditions. Moreover, we state a local uniqueness result for local optima under the assumptions of strict separability of the active sets as well as a second order sufficient condition for the regularized solution. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献