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1.
Enzymatic production of alkyl esters through alcoholysis: A critical evaluation of lipases and alcohols 总被引:3,自引:1,他引:3
Li?Deng Xuebing?XuEmail author Gudmundur?G.?Haraldsson Tianwei?Tan Fang?Wang 《Journal of the American Oil Chemists' Society》2005,82(5):341-347
This paper focuses on a detailed evaluation of commercially available immobilized lipases and simple monohydric alcohols for
the production of alkyl esters from sunflower oil by enzymatic alcoholysis. Six lipases were tested with seven alcohols, including
straight and branched-chain primary and secondary alcohols. The reactions were conducted in a batch stirred reaction vessel
using stoichiometric amounts of substrates under solvent-free conditions. Dramatic differences in alcoholysis performance
were observed among the different lipases. For most of the alcohols, Novozym 435 produced the highest yield of FA alkyl esters,
with yields well over 90% for methanol, absolute ethanol, and 1-propanol. Overall, 96% ethanol was the preferred alcohol for
all lipases except Novozym 435, and ethanolysis reactions reached the maximal conversion efficiency. Increasing the water
content in the system resulted in an increased degree of conversion for all lipases except Novozym 435. The secondary alcohol
2-propanol significantly reduced the alcoholysis reaction with all lipases; however, the branch-chain isobutanol was more
advantageous than linear 1-butanol for Novozym 435, Lipozyme RMIM, and Lipase PS-C. Many commercial immobilized lipases are
highly efficient and promising for the production of alkyl esters, offering high reaction yields and a simple operation process. 相似文献
2.
Bottomley Stephen P.; Popplewell Andrew G.; Scawen Michael; Wan Tommy; Sutton Brian J.; Gore Michael G. 《Protein engineering, design & selection : PEDS》1994,7(12):1463-1470
The stability and unfolding of an immunoglobulin (Ig) G bindingprotein based upon the B domain of protein A (SpAB) from Staphylococcusaureus were studied by substituting tryptophan residues at strategiclocations within each of the three a-helical regions (al-a3)of the domain. The role of the C-terminal helix, a3, was investigatedby generating two protein constructs, one corresponding to thecomplete SpAB, the other lacking a part of ct3; the Trp substitutionswere made in both one-and two-domain versions of each of theseconstructs. The fluorescence properties of each of the single-tryptophanmutants were studied in the native state and as a function ofguanidine-HCl-mediated unfolding, and their IgG binding activitieswere determined by a competitive enzyme-linked immunosorbentassay. The free energies of folding and of binding to IgG foreach mutant were compared with those for the native domains.The effect of each substitution upon the overall structure andupon the IgG binding interface was modelled by molecular graphicsand energy minimization. These studies indicate that (i) 3 contributesto the overall stability of the domain and to the formationof the IgG binding site in l and 2, and (ii) al unfolds first,followed by 2 and 3 together. 相似文献
3.
Liu Xinke Kao Evan Haraldsson Henrik Ballweber Megan Martin Alastair Li Youxiang Wang Yuting Saloner David 《Magma (New York, N.Y.)》2021,34(5):659-666
Magnetic Resonance Materials in Physics, Biology and Medicine - To determine the intra-individual flow variation in serially acquired studies, and the influence of this variation on subsequent... 相似文献
4.
Robustness of ISS systems to inputs with limited moving average: Application to spacecraft formations 下载免费PDF全文
Esten Ingar Grøtli Elena Panteley Antoine Chaillet Jan Tommy Gravdahl 《国际强度与非线性控制杂志
》2016,26(4):816-833
》2016,26(4):816-833
We provide a theoretical framework that fits realistic challenges related to spacecraft formation with disturbances. We show that the input‐to‐state stability of such systems guarantees some robustness with respect to a class of signals with bounded average‐energy, which encompasses the typical disturbances acting on spacecraft formations. Solutions are shown to converge to the desired formation, up to an offset, which is somewhat proportional to the considered moving average of disturbances. In the presence of fast peaking perturbations, the approach provides a tighter evaluation of the disturbances' influence, which allows for the use of more parsimonious control gains. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
Michael Shneier Tommy Chang Tsai Hong Will Shackleford Roger Bostelman James S. Albus 《Autonomous Robots》2008,24(1):69-86
Autonomous mobile robots need to adapt their behavior to the terrain over which they drive, and to predict the traversability
of the terrain so that they can effectively plan their paths. Such robots usually make use of a set of sensors to investigate
the terrain around them and build up an internal representation that enables them to navigate. This paper addresses the question
of how to use sensor data to learn properties of the environment and use this knowledge to predict which regions of the environment
are traversable. The approach makes use of sensed information from range sensors (stereo or ladar), color cameras, and the
vehicle’s navigation sensors. Models of terrain regions are learned from subsets of pixels that are selected by projection
into a local occupancy grid. The models include color and texture as well as traversability information obtained from an analysis
of the range data associated with the pixels. The models are learned without supervision, deriving their properties from the
geometry and the appearance of the scene.
The models are used to classify color images and assign traversability costs to regions. The classification does not use the
range or position information, but only color images. Traversability determined during the model-building phase is stored
in the models. This enables classification of regions beyond the range of stereo or ladar using the information in the color
images. The paper describes how the models are constructed and maintained, how they are used to classify image regions, and
how the system adapts to changing environments. Examples are shown from the implementation of this algorithm in the DARPA
Learning Applied to Ground Robots (LAGR) program, and an evaluation of the algorithm against human-provided ground truth is
presented.
相似文献
James S. AlbusEmail: |
6.
Tommy W.S. Chow Haijun Zhang M.K.M. Rahman 《Expert systems with applications》2009,36(10):12023-12035
This paper presents a new document representation with vectorized multiple features including term frequency and term-connection-frequency. A document is represented by undirected and directed graph, respectively. Then terms and vectorized graph connectionists are extracted from the graphs by employing several feature extraction methods. This hybrid document feature representation more accurately reflects the underlying semantics that are difficult to achieve from the currently used term histograms, and it facilitates the matching of complex graph. In application level, we develop a document retrieval system based on self-organizing map (SOM) to speed up the retrieval process. We perform extensive experimental verification, and the results suggest that the proposed method is computationally efficient and accurate for document retrieval. 相似文献
7.
A novel approach of combining flexible molecular docking, GRID molecular interaction fields, analysis of ligand-protein hydrogen bond interactions, conformational energy penalties and 3D-QSAR analysis was used to propose a binding mode in the dimer interface of the iGluR2 receptor for the biarylpropylsulfonamide class of positive allosteric AMPA modulators. Possible binding poses were generated by flexible molecular docking. GRID molecular interaction fields of the binding site, ligand-protein hydrogen bonding interactions and conformational energy penalties were used to select the most likely binding mode. The selected binding poses were subjected to a 3D-QSAR analysis using previously published activity data. The resulting model (2 LVs, R2=0.89, q2=0.61) predicted the activities of the compounds in the test set with a standard deviation on error of prediction of 0.17. The proposed binding mode was validated by interpretation of the PLS-coefficient regions from the 3D-QSAR analysis in terms of interactions between the receptor and the modulators. 相似文献
8.
Dealing with high-dimensional data has always been a major problem in many pattern recognition and machine learning applications. Trace ratio criterion is a criterion that can be applicable to many dimensionality reduction methods as it directly reflects Euclidean distance between data points of within or between classes. In this paper, we analyze the trace ratio problem and propose a new efficient algorithm to find the optimal solution. Based on the proposed algorithm, we are able to derive an orthogonal constrained semi-supervised learning framework. The new algorithm incorporates unlabeled data into training procedure so that it is able to preserve the discriminative structure as well as geometrical structure embedded in the original dataset. Under such a framework, many existing semi-supervised dimensionality reduction methods such as SDA, Lap-LDA, SSDR, SSMMC, can be improved using our proposed framework, which can also be used to formulate a corresponding kernel framework for handling nonlinear problems. Theoretical analysis indicates that there are certain relationships between linear and nonlinear methods. Finally, extensive simulations on synthetic dataset and real world dataset are presented to show the effectiveness of our algorithms. The results demonstrate that our proposed algorithm can achieve great superiority to other state-of-art algorithms. 相似文献
9.
Onome Scott-Emuakpor Tommy George Todd Letcher M.-H. Herman Shen Charles Cross 《Journal of Failure Analysis and Prevention》2012,12(1):109-115
The proposed work analyzes the possibility of improving the capabilities of an energy-based fatigue life prediction method.
The improvement being addressed is regarding the variation of empirical monotonic strain energy density calculations and the
effects on the energy-based fatigue life prediction capability. Since the prediction method was developed from the concept
that the strain energy accumulated during both monotonic failure and an entire fatigue process are equal, meaning the strain
energy accumulated during monotonic failure is a physical damage quantity, it was important to understand the variation of
monotonic strain energy density. The process for incorporating this variation into the prediction method explores a probabilistic,
Three-Sigma analysis that is applicable for all deterministic methods of measuring experimental monotonic strain energy density.
The accuracy of the probabilistic energy-based lifing method was admirably assessed by comparison with experimental fatigue
life results, between 103 and 105 cycles, conducted on Titanium 6Al–4V specimens at room temperature. 相似文献
10.
Tae-Hyoung Tommy Gim 《Papers in Regional Science》2021,100(4):1055-1077
This study conceptually confirms and empirically tests the potential that the significance and magnitude of the compact land use–trip time relationship differ by the degree of compactness and trip time. Based on a quantile regression of about 25,000 commuters in Seoul, Korea, the empirical analysis suggests a significant level for each neighbourhood land use variable and a magnitude change within the level. Weekend trip and school densities are significant for shorter trip time commuters, population density is significant for longer trip time commuters, and pedestrian density is significant for all commuters. Wherever significant, the land use variables exert stronger effects as their values increase. 相似文献