It has been demonstrated using CD that ethanol induces importantsecondary structure changes of ß-lactoglobulin. CDspectra indicate that ß-lactoglobulin secondary structure,which is mainly composed of ß-strands, becomes mostly-helical under the influence of the solvent polarity changes.The midpoint of ß-strand/-helix transition in ß-lactoglobulinis observed at dielectric constant {small tilde}60 (35% ethanol;v/v). According to CD measurements, the ethanol-dependent secondarystructure changes are reversible. The alkylation of lysines-NH2 in ß-lactoglobulin weakens the central ß-barrelstructure, since the ß-strand/-helix transition midpointof alkylated ß-lactoglobulin is shifted to lower ethanolconcentration (25% ethanol; v/v). ß-Lactoglobulinstructural changes are triggering the dissociation of the ß-lactoglobulin- retinol complex as judged from complete quenching of its fluorescencein ethanol concentration >30% (v/v). However, in 20% ethanol(v/v), ß-lactoglobulin still retains most of its nativesecondary structure as shown by CD and, in this condition, oneß-lactoglobulin molecule binds an additional secondretinol molecule. This suggests that the highly populated speciesobserved around 20% ethanol (v/v) might represent an intermediatestate able to bind two molecules of retinol. 相似文献
New silane monomers with the pendant 4-(3-pyridine)butyl group have been synthesized by hydrosilation of 3-(3-butenyl)pyridine with MenSi(OEt)3-nH (n=0, 1) using a platinum catalyst. Only -addition products were observed. The products were characterized by elemental analysis, infrared,1H- and13C-NMR spectroscopy, and gas chromatography-mass spectrometry. Hydrolysis-polycondensation of the difunctional monomer with a basic catalyst, Me4NOH, gave a mixture of cyclic oligomers, principally cyclic tetramer, and linear homopolymer. Under similar reaction conditions, the trifunctional monomer gave crosslinked material which was soluble in common organic solvents. The linear homopolymer and crosslinked polymer were trimethylsilyl end-blocked with hexamethyldisilazane. The cyclic and end-blocked polymers were characterized by elemental analysis and spectroscopic methods. Molecular weights of the polymers were obtained by end-group analysis using1H-NMR spectral data, size exclusion chromatography, and direct insertion-probe mass spectrometry. The cyclic, linear, and crosslinked materials were N-oxidized withm-chloroperoxybenzoic acid and characterized by spectroscopic methods. The polymeric N-oxide derivatives were shown to be effective transacylation catalysts in the synthesis of mixed carboxylic acid anhydrides in immiscible solvents (H2O/CH2Cl2) under phase-transfer conditions. The implications of the results on the mechanism of catalysis are discussed. 相似文献
Pattern Analysis and Applications - Nearest neighbor search is a powerful abstraction for data access; however, data indexing is troublesome even for approximate indexes. For intrinsically... 相似文献
This paper investigates the flocking control of multi-agent systems with unknown nonlinear dynamics while the virtual leader information is heterogeneous. The uncertain nonlinearity in the virtual leader information is considered, and the weaker constraint on the velocity information measurements is assumed. In addition, a bounded assumption on the unknown nonlinear dynamics is also considered. It is weaker than the Lipschitz condition adopted in the most flocking control methods. To avoid fragmentation, we construct a new potential function based on the penalty idea when the initial network is disconnected. A dynamical control law including a adjust parameter is designed to achieve the stable flocking. It is proven that the velocities of all agents approach to consensus and no collision happens between the mobile agents. Finally, several simulations verify the effectiveness of the new design, and indicate that the proposed method has high convergence and the broader applicability in practical applications with more stringent restrictions.
Gold nanoparticles used in most experiments (1–10 nm) in gold catalysis show varying degrees of reactivity, with particles
below 5 nm generally being more reactive. The origin of this activity is a subject of a number of model experiments and theoretical
studies on either clusters of a few atoms in size or extended surfaces (smooth or stepped). In the work described here, a
classical theory for the variation of the metal workfunction with cluster size, Extended Hückel Theory (EHT) calculations
combined with DFT calculations, as well as a carbon monoxide (CO) chemisorption model are combined to develop a relationship
between metal particle size and the particle's reactivity towards CO. For gold, it is shown that while the contribution of
the d-band hybridization energy to the total CO chemisorption energy is unfavourable for bulk gold, this is not true for gold
particles below 5–6 nm. That is, the d-band hybridization energy is negative for small gold particles. This is believed to
be explanation of the onset of high reactivity for small gold particles. 相似文献
A discrete Laplace‐Beltrami operator is called perfect if it possesses all the important properties of its smooth counterpart. It is known which triangle meshes admit perfect Laplace operators and how to fix any other mesh by changing the combinatorics. We extend the characterization of meshes that admit perfect Laplacians to general polygon meshes. More importantly, we provide an algorithm that computes a perfect Laplace operator for any polygon mesh without changing the combinatorics, although, possibly changing the embedding. We evaluate this algorithm and demonstrate it at applications. 相似文献
This study develops a system framework and an enterprise IT solution for integrating gamification elements to efficiently implement and continuously perform Cost Engineering. Cost Engineering is a systematic approach to manage knowledge and competencies regarding costs reduction measures throughout the life cycle of products and is technology, resource and time intensive. Gamification as a non-monetary multidimensional incentive system holds great potential to implement and establish Cost Engineering in a novel and less resource demanding manner and stipulate knowledge sharing and dissemination. Building on a review of the relevant literature we conducted 20 interviews with experts from eight companies of the German and Austrian high-tech manufacturing industry to examine the system requirements from an organizational perspective. Analyzing the interviews, we found that companies need a flexible platform where the game elements help to align management objectives with concrete tasks, meet legislative regulations and have different evaluation methods. Our proposed system framework combines the organizational and IT requirements with gamification elements to efficiently steer Cost Engineering methods and best manage knowledge and competencies. 相似文献
“Creative development” and “creativity” have become important topics in the field of education research. The assessment of creativity is a key to understanding how instructional strategies influences the creative process and the output of learners. At present, most methods of assessing creativity are paper-and-pencil tests scored by individuals. Despite the professional training of evaluators, subjectivity in scoring assessments remains inevitable. Therefore, a completely objective tool of measurement is crucial for the progress of education to eliminate the subjectivity in manual grading. This paper presents at first place a review of the literature related to the development of creativity, the assessment of creativity, and further on the means of measuring creativity, particularly in a digital game environment. Our focus is on the application of computing technologies for the assessment of creativity, while exploring the possibility of using computerized systems such as fuzzy logic and hybrid methods to produce objective measurement results. The results of Pearson correlation coefficient between the fuzzy inference scores and the Williams CAP scores is 0.805, which shows the strong construct validity. Additionally, the fuzzy inference system can eliminate subjectivity in scoring and provide analysis results to enhance creativity, unlike paper-and-pencil scores provided without explanations. 相似文献
A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes. 相似文献