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91.
A non-steady-state mathematical model system for the kinetics of adsorption and reduction of Cr(VI) by Escherichia coli (E. coli) biofilm on chitosan bead (EBCB) process was derived. The mechanisms in the model system included Cr(VI) adsorption by chitosan beads, Cr(VI) bioreduction by E. coli cells and Cr(VI) mass transport diffusion. Batch kinetic tests were performed to determine surface diffusivity of Cr(VI), adsorption parameters for Cr(VI) and biokinetic parameters of E. coli 33456. Experiments were conducted using an EBCB reactor system with high recycled rate to approximate a completely-mixed flow reactor for model verification. The experimental results indicated that E. coli biofilm bioregenerated the chitosan beads after E. coli biofilm has grown significantly. Cr(VI) reducing efficiency by E. coli was about 84% when Cr(VI) concentration in the influent was 5 mg/L at a steady-state condition. The concentration of suspended E. coli cells reached up to 10 mg/L while the thickness of attached E. coli cells was estimated to be 150 μm at a steady-state condition by model prediction. The comparisons of experimental data and model simulation show that EBCB model system for Cr(VI) adsorption and reduction can predict the experimental results well. 相似文献
92.
Following Jacobi's geometrization of Lagrange's least action principle, trajectories of classical mechanics can be characterized as geodesics on the configuration space M with respect to a suitable metric which is the conformal modification of the kinematic metric by the factor (U + h), where U and h are the potential function and the total energy, respectively. In the special case of 3-body motions with zero angular momentum, the global geometry of such trajectories can be reduced to that of their moduli curves, which record the change of size and shape, in the moduli space of oriented m-triangles, whose kinematic metric is, in fact, a Riemannian cone over the shape space M^*≌S^2 (1/2).
In this paper, it is shown that the moduli curve of such a motion is uniquely determined by its shape curve (which only records the change of shape) in the case of h≠0, while in the special case of h = 0 it is uniquely determined up to scaling. Thus, the study of the global geometry of such motions can be further reduced to that of the shape curves, which are time-parametrized curves on the 2-sphere characterized by a third order ODE. Moreover, these curves have two remarkable properties, namely the uniqueness of parametrization and the monotonieity, that constitute a solid foundation for a systematic study of their global geometry and naturally lead to the formulation of some pertinent problems. 相似文献
In this paper, it is shown that the moduli curve of such a motion is uniquely determined by its shape curve (which only records the change of shape) in the case of h≠0, while in the special case of h = 0 it is uniquely determined up to scaling. Thus, the study of the global geometry of such motions can be further reduced to that of the shape curves, which are time-parametrized curves on the 2-sphere characterized by a third order ODE. Moreover, these curves have two remarkable properties, namely the uniqueness of parametrization and the monotonieity, that constitute a solid foundation for a systematic study of their global geometry and naturally lead to the formulation of some pertinent problems. 相似文献
93.
Akihiro Furuta 《Tetrahedron letters》2008,49(1):110-113
A combination of a catalyst derived from ferrous acetate and sodium thiophene-2-carboxylate efficiently promoted hydrosilylation of aromatic and aliphatic ketones to give the corresponding secondary alcohols in high yields with extremely high selectivity. 相似文献
94.
The interaction of two charges moving in ℝ3 in a magnetic field B can be formulated as a Hamiltonian system with six degrees of freedom. Assuming that the magnetic field is uniform and the
interaction potential has rotation symmetry, we reduce this system to one with three degrees of freedom. For special values
of the conserved quantities, choices of parameters or restriction to the coplanar case, we obtain systems with two degrees
of freedom. Specialising to the case of Coulomb interaction, these reductions enable us to obtain many qualitative features
of the dynamics. For charges of the same sign, the gyrohelices either “bounce-back”, “pass-through”, or exceptionally converge
to coplanar solutions. For charges of opposite signs, we decompose the state space into “free” and “trapped” parts with transitions
only when the particles are coplanar. A scattering map is defined for those trajectories that come from and go to infinite
separation along the field direction. It determines the asymptotic parallel velocities, guiding centre field lines, magnetic
moments and gyrophases for large positive time from those for large negative time. In regimes where gyrophase averaging is
appropriate, the scattering map has a simple form, conserving the magnetic moments and parallel kinetic energies (in a frame
moving along the field with the centre of mass) and rotating or translating the guiding centre field lines. When the gyrofrequencies
are in low-order resonance, however, gyrophase averaging is not justified and transfer of perpendicular kinetic energy is
shown to occur. In the extreme case of equal gyrofrequencies, an additional integral helps us to analyse further and prove
that there is typically also transfer between perpendicular and parallel kinetic energy.
相似文献
95.
Combined neural network and reduced FRF techniques for slight damage detection using measured response data 总被引:2,自引:0,他引:2
Summary This paper deals with structural damage detection using measured frequency response functions (FRF) as input data to artificial
neural networks (ANN). A major obstacle, the impracticality of using full-size FRF data with ANNs, was circumvented by applying
a data-reduction technique based on principal component analysis (PCA). The compressed FRFs, represented by their projection
onto the most significant principal components, were used as the ANN input variables instead of the raw FRF data. The output
is a prediction of the actual state of the specimen, i.e. healthy or damaged. A further advantage of this particular approach
is its ability to deal with relatively high measurement noise, which is a common occurrence when dealing with industrial structures.
The methodology was applied to detect three different states of a space antenna: reference, slight mass damage and slight
stiffness damage. About 600 FRF measurements, each with 1024 spectral points, were included in the analysis. Six 2-hidden
layer networks, each with an individually-optimised architecture for a specific FRF reduction level, were used for damage
detection. The results showed that it was possible to distinguish between the three states of the antenna with good accuracy,
subject to using an adequate number of principal components together with a suitable neural network configuration. It was
also found that the quality of the raw FRF data remained a major consideration, though the method was able to filter out some
of the measurement noise. The convergence and detection properties of the networks were improved significantly by removing
those FRFs associated with measurement errors.
Received 9 March 2000; accepted for publication 12 December 2000 相似文献
96.
Boris Kruglikov 《Acta Appl Math》2008,101(1-3):145-161
Many methods for reducing and simplifying differential equations are known. They provide various generalizations of the original
symmetry approach of Sophus Lie. Plenty of relations between them have been noticed and in this note a unifying approach will
be discussed. It is rather close to the differential constraint method, but we make this rigorous basing on recent advances
in compatibility theory of non-linear overdetermined systems and homological methods for PDEs.
相似文献
97.
Paul Kosma Martina Strobl Andreas Hofinger Jens Ø. Duus Bent O. Petersen Klaus Bock Helmut Brade 《Monatshefte für Chemie / Chemical Monthly》2002,133(4):561-570
Summary. Methyl glycosides of Kdo and a (2→8)-linked Kdo disaccharide were prepared which contain a deuterium label at C-8 of the reducing unit. The label was introduced in fair
diastereoselectivity upon reduction of an aldehyde group using a chiral borane complex derived from N-benzyloxycarbonyl-(S)-proline which produced the 8-(S)-deuterated derivative as the major isomer. Further coupling with a Kdo bromide gave the α-(2→8)-linked disaccharide in good yield. The deprotected disaccharide serves as a model for NMR spectroscopic
studies on the side chain conformation of a carbohydrate epitope from the bacterial pathogen Chlamydia.
Received September 17, 2001. Accepted October 17, 2001 相似文献
98.
Aveline S.Y. Yim 《Tetrahedron》2005,61(33):7994-8004
A series of investigations into the use of amino acid derivatives for the asymmetric catalysis of the transfer hydrogenation of ketones are presented. Based on the results observed, a mechanistic suggestion for the origin of the enantioselective induction is proposed. 相似文献
99.
1 Introduction
Nowadays, green chemistry has received increased attention. The use of water and scCO2 as a solvent or reagent is an important field for organic reactions and green chemistry both in laboratory and industry. 相似文献
Nowadays, green chemistry has received increased attention. The use of water and scCO2 as a solvent or reagent is an important field for organic reactions and green chemistry both in laboratory and industry. 相似文献
100.
Klaus Müllen 《Angewandte Chemie (International ed. in English)》1987,26(3):204-217
The successive reduction of fully conjugated cyclic hydrocarbons leads to singly and multiply charged ions with unusual bonding. The charge distribution in these ions can be determined spectroscopically, and the information so obtained is then used in kinetically controlled trapping reactions for the regioselective introduction of electrophilic groups. When non-benzenoid substrates are used, syntheses become possible which can either not be carried out or can only be carried out with great difficulty in other ways. Examples of new preparative applications are cycloannelation and bridging reactions as well as polymerization reactions. The ion pair structure of the intermediate and the type of electrophile used are of paramount importance in controlling the mechanism of these reductive transformations. 相似文献