A sample of high molecular weight poly(diethyl siloxane), [Si(C2H5)2-O-] x, (PDES) was separated into a series of fractions by means of liquid-liquid precipitations. Four of the fractions were studied by osmometry and viscometry in toluene at 25°C. The resulting values of the number-average mole-cular weight, second virial coefficient, and intrinsic viscosity indicate that the unperturbed dimen-sions of PDES are essentially the same as those of poly(dimethyl siloxane) (PDMS) of the same chain length. Thus, differences in intramolecular interactions between these two chains have little effect on their unperturbed dimensions. Most pertinent in this regard are interactions between the side chains, which are favourable in trans conformations in both PDES and PDMS. These favourable inter-actions in trans conformations would be enhanced in the case of the ethyl groups in PDES, but this effect is apparently offset by a comparable increase in favourable interactions between ethyl groups and oxygen atoms in the competing gauche conformations.

prototype shape that is maximally similar to that in the image. Results are presented for silhouettes, trademarks, handwritten digits and the COIL dataset.

A computer program that progressively evaluates the hydrophilicity and hydrophobicity of a protein along its amino acid sequence has been devised. For this purpose, a hydropathy scale has been composed wherein the hydrophilic and hydrophobic properties of each of the 20 amino acid side-chains is taken into consideration. The scale is based on an amalgam of experimental observations derived from the literature. The program uses a moving-segment approach that continuously determines the average hydropathy within a segment of predetermined length as it advances through the sequence. The consecutive scores are plotted from the amino to the carboxy terminus. At the same time, a midpoint line is printed that corresponds to the grand average of the hydropathy of the amino acid compositions found in most of the sequenced proteins. In the case of soluble, globular proteins there is a remarkable correspondence between the interior portions of their sequence and the regions appearing on the hydrophobic side of the midpoint line, as well as the exterior portions and the regions on the hydrophilic side. The correlation was demonstrated by comparisons between the plotted values and known structures determined by crystallography. In the case of membrane-bound proteins, the portions of their sequences that are located within the lipid bilayer are also clearly delineated by large uninterrupted areas on the hydrophobic side of the midpoint line. As such, the membrane-spanning segment’s of these proteins can be identified by this procedure. Although the method is not unique and embodies principles that have long been appreciated, its simplicity and its graphic nature make it a very useful tool for the evaluation of protein structures. 1.

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Scientists need new tools to explore and browse large collections of scholarly literature. Thanks to organizations such as JSTOR, which scan and index the original bound archives of many journals, modern scientists can search digital libraries spanning hundreds of years. A scientist, suddenly

Hypothetical scanning Monte Carlo (HSMC) is a method for calculating the absolute entropy, S and free energy, F from a given MC trajectory developed recently and applied to liquid argon, TIP3P water and peptides. In this paper HSMC is extended to random coil polymers by applying it to self

The BLAST programs are widely used tools for searching protein and DNA databases for sequence similarities. For protein comparisons, a variety of definitional, algorithmic and statistical refinements described here permits the execution time of the BLAST programs to be decreased substantially while enhancing their sensitivity to weak similarities. A new criterion for triggering the extension of word hits, combined with a new heuristic for generating gapped alignments, yields a gapped BLAST program that runs at approximately three times the speed of the original. In addition, a method is introduced for automatically combining statistically significant alignments produced by BLAST into a position-specific score matrix, and searching the database using this matrix. The resulting Position-Specific Iterated BLAST (PSIBLAST) program runs at approximately the same speed per iteration as gapped BLAST, but in many cases is much more sensitive to weak but biologically relevant sequence similarities. PSI-BLAST is used to uncover several new and interesting members of the BRCT superfamily.

Recently, methods based on local image features have shown promise for texture and object recognition tasks. This paper presents a large-scale evaluation of an approach that represents images as distributions (signatures or histograms) of features extracted from a sparse set of keypoint locations and learns a Support Vector Machine classifier with kernels based on two effective measures for comparing distributions, the Earth Mover’s Distance and the χ 2 distance. We first evaluate the performance of our approach with different keypoint detectors and descriptors, as well as different kernels and classifiers. We then conduct a comparative evaluation with several state-of-the-art recognition methods on four texture and five object databases. On most of these databases, our implementation exceeds the best reported results and achieves comparable performance on the rest. Finally, we investigate the influence of background correlations on recognition performance via extensive tests on the PASCAL database, for which ground-truth object localization information is available. Our experiments demonstrate that image representations based on distributions of local features are surprisingly effective for classification of texture and object images under challenging real-world conditions, including significant intra-class variations and substantial background clutter.

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Factors that affect he probability of genetic transformation f Escherichia coli by plasmids have been evaluated. A set of conditions is described under which about one in every 400 plasmid molecules produces a transformed cell. These conditions include cell growth in medium containing elevated levels of Mg 2+. and incubation of the cells at 0 ~ in a solution of Mn 2+, ("a 2+, Rb + or K +, dimethyl sulfoxide, dithiothreitol, and hexamine cobalt (III). Transibrmation efficiency declines linearly with increasing plasmid size. Relaxed and supercoiled plasmids transfol'm with similar probabilities. Non-transforming DNAs compete consistent with mass. No significant variation is observed between competing DNAs of difi~rent source, complexity, length or form. Competition with both transforming and non-transforming plasmids indicates that each cell is capable of taking up many DNA molecules, and that the establishment of a transformation event is neither helped nor hindered significantly by the presence of multiple plasmids. 1. Introduct ion Both gram-posit ive and gram-negative bacteria can take up and stably establish