Adsorption of alizarinate–micelle complexes on Na-montmorillonite

The adsorption on Na-montmorillonite of the monovalent anion alizarinate and its complexes with micelles of cationic surfactants was investigated. Micelles were prepared from octadecyltrimethylammonium (ODTMA) and benzyldimethylhexadecyl-ammonium (BDMHDA). Alizarinate–micelle complexes are much more efficient for the adsorption of the dye than alizarinate alone, e.g., from 0.05 mM alizarinate solution 12.5 mmol per 100 g clay was adsorbed in the presence of micelles, whereas only 4 mmol per 100 g clay was adsorbed in their absence. However, unlike the adsorption of alizarinate on the clay, where its adsorbed fraction increased with the concentration of the clay, in the presence of micelles, the concentration of the clay should be optimized for achieving maximal adsorption of alizarinate. This effect is due to monomer adsorption on excessive clay sites, which leads to the decomposition of micelles, and consequently, the adsorption of alizarinate is reduced.Visible spectra of alizarinate–micelle complexes in water and adsorbed on montmorillonite were recorded. The absorption band of alizarinate in aqueous solutions at 522 nm was red-shifted in the presence of ODTMA and BDMHDA micelles due to the effect of the micelle microenvironment. Further shifts were observed in the presence of montmorillonite indicating that the alizarinate–micelle complexes were adsorbed on the clay. Significant spectroscopic changes were observed after the adsorption of alizarinate–BDMHDA-micelle complex on the clay indicating that the adsorption leads to changes in the micelle. This observation suggests that the dye may serve as a probe in visible-spectroscopy study of the adsorption of micelles on clay minerals.     

The application of cryo-SEM techniques to the study of the symbiotic association in the Azolla leaf cavity

The preparation of frozen-hydrated samples for scanning electron microscopy to observe symbionts in Azolla is described and compared to the conventional method of chemical fixation followed by critical-point drying. The frozen-hydrated specimens preserve the structure of the associating symbionts and the liquid phase in the Azollaleaf cavity. The leaf cavity structure and the endosymbionts in the frozen-hydrated specimens were intact and unharmed throughout the fixation. The cyanobiont cells were distributed along the envelope of the leaf cavity, and did not aggregate around the hair cells, as reported for chemical fixation specimens. The mucilage layer removed by the chemical fixation could be observed in the cryo-fixation specimens, especially at the lower part of the cavity.     

Synthesis and Structures of Substrates for Investigation of Intramolecular Electronic Energy Transfer

A series of cyclic α-diketones incorporating a benzene ring (ortho, meta or para substituted) have been synthesized for studies of intramolecular energy transfer (intra-ET). The synthetic method involved acyloin cyclization of the corresponding dicarboxylic acid diesters followed by oxidation with DMSO-acetic anhydride reagent. All compounds were sufficiently flexible so that, even at temperatures in the range of −120°, only broadened lines were observed in their NMR spectra, consistent with observations on temperature dependence of the intra-ET process. The structure of one compound (P-4,4) was established by X-ray crystallographic analysis and of the remaining compounds by a combination of spectroscopic data and molecular mechanics calculations. The calculated structure of P-4,4 is essentially identical to the X-ray structure. In all compounds the methylene chains assume staggered conformations, the dicarbonyl torsion angle aproached 180°, and the molecule folds in such a way that, with one exception, the dicarbonyl moiety lies above (or below) the plane of the benzene ring. Distances between chromophores range from about 3.3 to 5.8 Å.     

Verification of distributed programs using representative interleaving sequences

Summary We present a formal proof method for distributed programs. The semantics used to justify the proof method explicitly identifies equivalence classes of execution sequences which are equivalent up to permuting commutative operations. Each equivalence class is called an interleaving set or a run. The proof rules allow concluding the correctness of certain classes of properties for all execution sequences, even though such properties are demonstrated directly only for a subset of the sequences. The subset used must include a representative sequence from each interleaving set, and the proof rules, when applicable, guarantee that this is the case. By choosing a subset with appropriate sequences, simpler intermediate assertions can be used than in previous formal approaches. The method employs proof lattices, and is expressed using the temporal logic ISTL. Shmuel Katz received his B.A. in Mathematics and English Literature from U.C.L.A., and his M.Sc. and Ph.D. in Computer Science (1976) from the Weizmann Institute in Rechovot, Israel. From 1976 to 1981 he was at the IBM Israel Scientific Center. Presently, he is on the faculty of the Computer Science Department at the Technion in Haifa, Israel. In 1977–1978 he visited for a year at the University of California, Berkeley, and in 1984–1985 was at the University of Texas at Austin. He has been a consultant and visitor at the MCC Software Technology Program, and in 1988–1989 was a visiting scientist at the I.B.M. Watson Research Center. His research interests include the methodology of programming, specification methods, program verification and semantics, distributed programming, data structures, and programming languages. Doron Peled was born in 1962 in Haifa. He received his B.Sc. and M.Sc. in Computer Science from the Technion, Israel in 1984 and 1987, respectively. Between 1987 and 1991 he did his military service. He also completed his D.Sc. degree in the Technion during these years. Dr. Peled was with the Computer Science department at Warwick University in 1991–1992. He is currently a member of the technical staff with AT & T Bell Laboratories. His main research interests are specification and verification of programs, especially as related to partial order models, fault-tolerance and real-time. He is also interested in semantics and topology.This research was carried out while the second author was at the Department of Computer Science, The Technion, Haifa 32000, Israel     

Organic sorbate-organoclay interactions in aqueous and hydrophobic environments: sorbate-water competition

Sorption of nitrobenzene, phenol, and m-nitrophenol from water and n-hexadecane was measured on Na-montmorillonite and organoclays in which 41 and 90% of the exchange capacity of the Na-clay was occupied by hexadecyltrimethylammonium. The strength of sorbate-sorbent interactions in n-hexadecane for all three sorbents was in the following order: nitrobenzene < phenol < m-nitrophenol. The magnitude of the distribution coefficients suggests that the contribution to solute uptake of partitioning between n-hexadecane and the organic pseudophase of the dried organoclays is minor, whereas the major contribution is from adsorptive sorbate-sorbent interactions. Sorption isotherms obtained in different solvents were compared using a sorbate activity scale. In the organoclays, the stronger the tendency of a sorbate to interact with sorption sites, the less pronounced is the reduction in the activity-based sorption due to competition with water. The order of this reduction for the different sorbates is nitrobenzene > phenol > m-nitrophenol. The weakening of sorbate-sorbent interactions resulting from water-sorbate competition might be mitigated by interaction between the organic sorbate and sorbed water molecules. Since the more strongly interacting organic compounds are less susceptible to suppression of sorption in the presence of water, hydrating organoclays may result in an increased differentiation between "weakly" and "strongly" interacting ("nonpolar" and "polar") compounds in the organoclay phase.     

Initial failures in distributed computations

We investigate the possibility of solving problems in completely asynchronous message passing systems where a number of processes may fail prior to execution. By using game-theoretical notions, necessary and sufficient conditions are provided for solving problems is such a model with an without a termination requirement. An upper bound on the message complexity for solving any problem in the model is given, as well as a simple design concept for constructing a solution to any solvable problem.Supported in part by the Guttwirth Fellowship, by the National Science Foundation under grant CCR-8405478, and by the Hebrew Technical Institute scholarship.Supported in part by Technion V.P.R. fund—C. Wellner Research fund.     

Efficient elections in chordal ring networks

We study the message complexity of the problem of distributively electing a leader in chordal rings. Such networks consist of a basic ring with additional links, the extreme cases being the oriented ring and the complete graph with a full sense of direction. We present a general election algorithm for these networks, and prove its optimality. As a corollary, we show thatO(logn) chords at each processor suffice to obtain an algorithm that uses at mostO(n) messages; this improves and extends a previous work, where an algorithm, also usingO(n) messages, was suggested for the case where alln-1 chords exist (the oriented complete network).The work of this author was supported in part by the Natural Sciences and Engineering Research Council of Canada under Grant No. A2415.The work of this author was supported in part by Technion Research Grant No. 120-0641.     

Constrained synthesis of textural motion for articulated characters

Obtaining high-quality, realistic motions of articulated characters is both time consuming and expensive, necessitating the development of easy-to-use and effective tools for motion editing and reuse. We propose a new simple technique for generating constrained variations of different lengths from an existing captured or otherwise animated motion. Our technique is applicable to textural motions, such as walking or dancing, where the motion sequence can be decomposed into shorter motion segments without an obvious temporal ordering among them. Inspired by previous work on texture synthesis and video textures, our method essentially produces a reordering of these shorter segments. Discontinuities are eliminated by carefully choosing the transition points and applying local adaptive smoothing in their vicinity, if necessary. The user is able to control the synthesis process by specifying a small number of simple constraints.     

Fast panoramic stereo matching using cylindrical maximum surfaces.

This paper presents a fast panoramic stereo matching algorithm using a cylindrical maximum surface technique. The disparity for a pair of panoramic images is found in a cylindrical shaped correlation coefficient volume by obtaining the maximum surface rather than simply choosing a position that gives the maximum correlation coefficient value. The use of our cylindrical maximum surface technique ensures that the disparities obtained at the left and the right columns of the panoramic stereo images are properly constrained. Typical running time for a pair of 1324 x 120 images is about 0.33 s on a 1.7-GHz PC. A variety of real images have been tested, and good results have been obtained.