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排序方式: 共有107条查询结果,搜索用时 31 毫秒
71.
Andréa M. Salgado Rossana O. M. Folly Belkis Valdman Francisco Valero 《Applied biochemistry and biotechnology》2004,113(1-3):137-144
A software sensor for on-line determination of substrate was developed based on a model for fed-batch alcoholic fermentation
process and on-line measured signals of ethanol, biomass, and feed flow. The ethanol and biomass signals were obtained using
a colorimetric biosensor and an optical sensor developed in previous works that permitted determination of ethanol at a concentration
of 0–40 g/L and biomass of 0–60 g/L. The volume in the fermentor could be continuously calculated using the total measured
signal of the feed flow. The results obtained show that the model used is adequate for the proposed software sensor and determines
continuously the substrate concentration with efficiency and security during the fermentation process. 相似文献
72.
Elisabetta Alberico Ilenia Nieddu Rossana Taras Serafino Gladiali 《Helvetica chimica acta》2006,89(8):1716-1729
A range of α,β‐unsaturated acids and esters have been selectively reduced to the corresponding saturated acid derivatives by hydrogen transfer. As the reducing agent, formic acid was used in the presence of RhI complexes formed with the powerful chiral ligand Ph‐binepine ( 1 ), an axially chiral binaphthalene‐type monodentate P‐donor ligand. Very high stereoselectivities (up to 97% ee) were obtained in the case of itaconic acid ( 2a ). 相似文献
73.
Milián L Estellés R Abarca B Ballesteros R Sanz MJ Blázquez MA 《Chemical & pharmaceutical bulletin》2004,52(6):696-699
Four phenanthrene and one aporphine alkaloids semi-synthesized from boldine were evaluated for their inhibitory effect on reactive oxygen species (ROS) generation. ROS generation by neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine was inhibited in a concentration dependent manner. Alkaloids exerted similar inhibitory effect in the hypoxanthine-xanthine oxidase system than in stimulated neutrophils, which could be attributed to a direct ROS scavenging activity. None of the alkaloids assayed had any effect on xanthine oxidase activity. Therefore the synthesized alkaloids might constitute an alternative therapy in inflammation disorders in which ROS generation is involved. 相似文献
74.
Rossana Bonnaccorsi Eolo Scrocco Jacopo Tomasi Alberte Pullman 《Theoretical chemistry accounts》1975,36(4):339-344
The ab initio isopotential map of guanine is given and compared to that of adenine. It shows that in contrast to the situation in adenine, the most basic site of guanine is N7 with a secondary potential minimum at O6. These results as well as those concerning the secondary out-of-plane attractive regions over the NH2 group and C8 H bonds of the two molecules are discussed in connection with the available experimental knowledge concerning the bonding of alkylating carcinogens and mutagens. 相似文献
75.
Koller FO Reho R Schrader TE Moroder L Wachtveitl J Zinth W 《The journal of physical chemistry. B》2007,111(35):10481-10486
Infrared absorption experiments on light-triggered azobenzene peptides have been performed below and above the freezing point of the solvent dimethyl sulfoxide (DMSO). Even 20 K below the freezing point, illumination of the azobenzene chromophore resulted in IR absorption changes indicative of light-induced structural rearrangements of the peptide. In addition, new conformational states could be found at low temperature, which involve the formation of additional hydrogen bonds. In one sample the new low-temperature state survived melting and reheating and disappeared at 298 K only on the time scale of 10 min. The observations indicate that at low temperatures the peptide, together with traces of water present in the sample, forms a shell in the vicinity of the chromophore that facilitates internal motion even in the rigid cage of frozen DMSO. 相似文献
76.
Rossana Pasquino Fabio Nicodemi Veronica Vanzanella Roberta Alfani Nino Grizzuti 《Rheologica Acta》2013,52(5):395-401
A detailed rheological study of aqueous solutions of methylhydroxyethylcellulose has been carried out in the presence of different acrylate-based graft polymer used as additive contents. Both polymer components are used in cement formulations to improve the flow performances of the concretes, but no physicochemical studies can be easily found in the literature. The content of the graft polymer has been varied between 0.1 and 2.7 wt% in an aqueous solution with a fixed content of 6.5 wt% of methylhydroxyethylcellulose. Creep curves were performed at different stresses in order to build up the flow curves for the various solutions. We found that the addition of the graft polymer triggers a phase transition, which is made more dramatic by the presence of an external flow. A “flow-phase diagram” has been obtained, which could be used as a guide for determining the critical conditions for the onset of the flow-induced instability. 相似文献
77.
We illustrate the use of the recent approach by P. Albrecht to the derivation of order conditions for partitioned Runge-Kutta methods for ordinary differential equations. 相似文献
78.
Flow-induced structures in suspensions containing spheres in viscoelastic suspending media were investigated by microscopy
and rheo-optical methods. Suspensions of monodisperse polystyrene spheres with diameters ranging from 1.2 to 2.8 μm and dispersed
in aqueous solutions of hydroxypropylcellulose were studied in simple shear flows. Optical microscopy observations as well
as small-angle light-scattering (SALS) experiments were performed using a parallel plate geometry. In agreement with previous
work, necklaces of particles aligned in the flow direction were observed when shearing faster then a critical shear rate,
which was found to be independent of particle size. In contrast to earlier work, however, the role of particle migration was
found to be of prime importance. Particles were shown to migrate toward the plates where the particles assembled and aligned
in strings running in the flow direction. For the smallest particles (1 μm diameter), the formation of particle doublets or
short strings along the vorticity direction was observed at low shear rates, which flipped to an orientation into the flow
direction and grew into longer strings at higher shear rates. SALS experiments were used to quantify the degree of alignment
and its dependence on particle size, shear rate, and gap. For the system under investigation, the degree of alignment was
found to increase with increasing shear rate and particle size and with decreasing gap. The present results suggest that,
depending on the details of the suspending medium and the size and nature of the suspended particles, the formation of aligned
structures is affected by the relative magnitude of the colloidal and hydrodynamic forces and the kinetics of string formation
versus the kinetics of migration. 相似文献
79.
The stability of an equilibrium point of a dynamical system is determined by the position in the complex plane of the so-called characteristic values of the linearization around the equilibrium. This work presents an approach for the computation of characteristic values of partial differential equations of evolution involving time delay, based on a coupled pseudospectral-spectral method. Convergence of computed values is of infinite order with respect to the pseudospectral discretization and of finite order with respect to the spectral one. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
80.
Emilio Scamporrino Rossana Alicata Sebastiano Bazzano Daniele Vitalini Placido Mineo 《Macromolecular Symposia》2004,218(1):21-28
The synthesis of some poly(bisphenol-A)carbonates (PCs) containing hydrophilic porphyrin units as end groups, by thermal treatment of commercial PC and 5,10,15-tri{p[ω-methoxy-poly(oxyethylene)]phenyl}20(p-hydroxy phenyl)porphyrin (I) blends, is reported. A suitable choice of reaction temperature, molar composition and reaction time, allowing the extent of the outer-inner transesterification reactions, leads to a gradual insertion of porphyrin units in the polymer chains. The composition of the obtained materials was inferred by GPC and MALDI-TOF mass spectrometric analysis. 相似文献