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121.
In this Account, we explore the role constant curvature structures play in amphiphilic small molecule crystals and extended coordination solids. A constant curvature structure is one in which there is a surface or interface that has the same curvature throughout its surface. Simple examples of such structures contain spheres (micelles), columns, or layers. Yet another family are cubic as is found in the gyroid topology. For amphiphilic systems, there are two domains, one generally hydrophobic and the other hydrophilic. We find that the interfaces between these two domains in small molecule structures resemble those in larger scale systems and adopt topologies related to constant curvature structures. The hydrophobic-to-total volume ratio, a molecular parameter, can be used to predict which type of constant curvature structure is adopted. In the case of three coordinate extended solids, constant curvature plays a role both in the extended net topology and in the hydrophobic-to-hydrophilic interface. 相似文献
122.
Extraction of Lipids from Municipal Wastewater Plant Microorganisms for Production of Biodiesel 总被引:2,自引:0,他引:2
Stephen Dufreche R. Hernandez T. French D. Sparks M. Zappi E. Alley 《Journal of the American Oil Chemists' Society》2007,84(2):181-187
Municipal wastewater treatment plants in the USA produce over 6.2 × 106 t of dried sewage sludge every year. This microorganism-rich sludge is often landfilled or used as fertilizer. Recent restrictions
on the use of sewage sludge, however, have resulted in increased disposal problems. Extraction of lipids from sludge yields
an untapped source of cheap feedstock for biodiesel production. Solvents used for extraction in this study include n-hexane, methanol, acetone, and supercritical CO2. The gravimetric yield of oil was low for nonpolar solvents, but use of polar solvents gave a considerably increased yield;
however, the percentage of saponifiable material was less. Extraction of lipids with a mixture of n-hexane, methanol, and acetone gave the largest conversion to biodiesel compared with other solvent systems, 4.41% based on
total dry weight of sludge. In situ transesterification of dried sludge resulted in a yield of 6.23%. If a 10% dry weight
yield of fatty acid methyl esters is assumed, the amount of biodiesel available for production in the USA is 1.4 × 106 m3/year. Outfitting 50% of municipal wastewater plants for lipid extraction and transesterification could result in enough biodiesel
production to replace 0.5% of the national petroleum diesel demand (0.7 × 106 m3). 相似文献
123.
Fei Yan Josef Kittler David Windridge William Christmas Krystian Mikolajczyk Stephen Cox Qiang Huang 《Image and vision computing》2014
Fully automatic annotation of tennis game using broadcast video is a task with a great potential but with enormous challenges. In this paper we describe our approach to this task, which integrates computer vision, machine listening, and machine learning. At the low level processing, we improve upon our previously proposed state-of-the-art tennis ball tracking algorithm and employ audio signal processing techniques to detect key events and construct features for classifying the events. At high level analysis, we model event classification as a sequence labelling problem, and investigate four machine learning techniques using simulated event sequences. Finally, we evaluate our proposed approach on three real world tennis games, and discuss the interplay between audio, vision and learning. To the best of our knowledge, our system is the only one that can annotate tennis game at such a detailed level. 相似文献
124.
An experimental study to determine the effect of copper (I) iodide (Cul) on the rate and product distribution of degradation of a model of an aliphatic–aromatic polyamide was carried out. N,N′-Dihexylisophthalamide (DHI) was reacted in both an inert argon atmosphere and a pure oxygen environment at 350°C with CuI added in amounts ranging from 0 to 20% by weight. The rate of disappearance of DHI was enhanced by an order of magnitude when 0.5% by weight of CuI was added and was an increasing function of increasing CuI loading. Reaction in pure O2 increased the rate of DHI degradation by two orders of magnitude over that for neat DHI pyrolysis. The rate of disappearance of DHI in O2 was relatively unchanged when 5% CuI by weight was added. The transformations of DHI and its products are organized in terms of a set of reaction rules. This “reaction operator” formalism allowed computer generation of the reaction network and facilitated estimation of kinetic parameters. © 1995 John Wiley & Sons, Inc. 相似文献
125.
A series of polyurethane (PU) films was prepared from chain-extended hydroxypropyl lignins (CEHPL). In appearance, these films ranged from brittle and dark brown to rubbery and bronze. The thermal, mechanical, and network properties of these PUs were investigated by DMTA and DSC analysis. All films exhibited single Tg's which varied between ?53° and 101°C, depending on lignin content. From swelling experiments, molecular weight between crosslinks (M c) was determined and found to vary over 2.5 orders of magnitude. The M c's were related to the change in Tg that accompanied network formation. Stress–strain experiments showed a variation in Young's modulus between 7 and 1300 MPa. Most of the variation in material properties was related to lignin content and to a lesser extent to diisocyanate type, hexamethylene diisocyanate, or toluene diisocyanate. The source of the CEHPL had no effect on the observed properties. From these results it was concluded that the properties of PUs can be controlled and engineered for a wide variety of practical uses. 相似文献
126.
Stephen Q. Zhou Liming Wang Xiugao Liao Georges Manuel William P. Weber 《Journal of Inorganic and Organometallic Polymers and Materials》1991,1(2):199-210
High molecular weight poly(1,1-dimethyl-1-germa-cis-pent-3-ene), poly(1,1-diphenyl-1-germa-cis-pent-3-ene), poly(1,1-dimethyl-1-sila-cis-pent-3-ene), and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) have been prepared. The thermal stability of these polymers is found to increase with their molecular weight. 相似文献
127.
Lo KM Zhang J Sun Y Morelli B Lan Y Lauder S Brunkhorst B Webster G Hallakou-Bozec S Doaré L Gillies SD 《Protein engineering, design & selection : PEDS》2005,18(1):1-10
Leptin plays a central role in the homeostasis of body weight through its regulatory effects on appetite and energy expenditure, yet in trials as a therapeutic agent for the treatment of obesity in humans it has been disappointing. The poor clinical efficacy of leptin results from its short circulating half-life, low potency and poor solubility, necessitating large and frequent doses to obtain even modest clinical benefit. Engineered Fc-leptin immunofusins, consisting of the Fc fragment of an immunoglobulin gamma chain followed by leptin, exhibit improved pharmacological properties with very consistent and potent biological activities. Furthermore, in extending the circulating half-life of the protein in vivo from a few minutes for leptin to many hours for Fc-leptin, these proteins have the potential to reduce drastically the dosage and frequency of administration required to obtain clinical benefit. The results of this study show that the engineered leptin immunofusins described here have significantly enhanced pharmacological properties in comparison with the recombinant leptin that was used in clinical trials. As such, they could represent an important step towards a therapeutically superior form of leptin if the disappointing performance of leptin in early clinical trials was due to its poor pharmacological properties rather than any conceptual weakness in the strategy of using leptin for the treatment of obesity and its related disorders. 相似文献
128.
This paper reviews the brittle fracture behavior of dielectric ceramics such as barium titanate, and describes some of the relationships between defects such as cracks and electrical degradation and failure of multilayer capacitors. Stresses arising from the ferroelectric phase transformation in these dielectric materials are shown to play a part as a driving force for crack growth. In addition, possible contributions to failure from stresses arising from thermal excursions in the capacitor are discussed. Low-voltage failures arising from a short between the electrodes in multilayer capacitors are shown to be related to the growth of cracks in the dielectric. A technique for predicting the onset of these types of failures based upon fracture mechanics techniques is described. Possible effects of the electric field itself in promoting or retarding the growth of cracks are discussed. 相似文献
129.
An elimination strategy for solving sparse linear systems in bordered triangular form is presented. This strategy is designed to exploit certain common structural properties of the borders of such a system. It may also be interpreted as a recursive application of block elimination. The technique is numerically efficient and provides significant reductions in fill-in compared to routine Gaussian elimination. It is applicable in the iterative solution of the large systems of nonlinear equations that arise in the equation-oriented approach to process simulation and design calculations, as well as in other problems of interest to the chemical engineer. 相似文献
130.
Michael J. Banach Stephen J. Clarson Gregory Beaucage Jason Benkoski Tom Mates Edward J. Kramer Richard A. Vaia 《应用聚合物科学杂志》2002,86(8):2021-2024
For many microelectronic and optoelectronic applications, polymer thin films require the addition of small molecules. However, the thin‐film geometry and associated processing techniques will influence the final morphology and compositional distribution of the constituents. It is therefore important that these be examined directly rather than inferred from bulk measurements. As an example system, the concentration and distribution of Disperse Red 1 (DR1) molecules in poly(methyl methacrylate) thin films were examined. Ultraviolet visibility spectroscopy and dynamic secondary ion mass spectrometry indicate that the composition of the molecules decreased dramatically with thermal treatment of the film. The sublimation of the chromophore was observed to occur at temperatures well below the melting point of the small molecule and the glass transition of the pure polymer; this solute loss manifested itself in changes in the glass transition temperature of the film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2021–2024, 2002 相似文献