Formation of solid-liquid interface in ferroelectric particle dispersion and its effect on the dispersion stability

A model has been proposed for the formation of the ferroelectric solid-liquid interface in the non-electrolyte dispersion system. Bulk properties as well as the surface properties of the dispersing solid could be a factor which was associated with various characters of the dispersion state. A qualitative investigation was carried out to see whether the continuum polarization process in solid-liquid interface due to the inhomogeneous field from the polar solid might affect the powder dispersion. The development of the polarized solid-liquid interface might depend on the polarity of solid particle and of liquid medium, shapes, mobility, and solubility of the molecules in the liquid phase, and temperature. Two possible effects of polarized solid-liquid interface on the dispersion stability have been discussed. Lastly, this model was applied to interpreting some experimental results of adhesion.     

Synthesis of 2-isoxazoline and alpha-hydroxy ketomethylene dipeptide isosteres

We have developed a simple and stereoselective method for synthesizing novel dipeptide isosteres using nitrile oxide cycloaddition as a key reaction. Employing this method, we have prepared efficiently various peptidomimetics containing 2-isoxazolines and alpha-hydroxy ketomethylene dipeptide isosteres.     

Synthesis and antitumor activity of 1-β-D-arabinofuranosylcytosine conjugates of optical isomers of ether and thioether lipids

Four 1-β-D-arabinofuranosylcytosine conjugates (ara-C) (1a, b and 2a, b) ofsn−1 andsn−3 isomers of 1-O-octadecyl-2-O-palmitoylglycerol and its 1-S-alkyl analogue have been synthesized, and their antitumor activity against L1210 lymphoid leukemia in mice were compared with those of the previous conjugates (3a, b) of racemates in order to determine the significance of chirality of the glycerol moieties for activity. Administration (i.p.) of a single dose (300 mg/kg) of conjugates ofsn−1 (1a),sn−3 (2a) andrac (3a) isomers of the ether lipid increased lifespan of i.p. implanted L1210 lymphoid leukemic DBA/2J mice by 169, 175 and 236%, respectively. Thesn−1 (1b),sn−3 (2b), andrac (3b) isomers of the thioether lipid with a single dose of 300 mg/kg produced an increase in lifespan values of 238, 263 and 250%, respectively. The results indicate that chirality of the glycerol moieties appears not to be critical for the activity, and racemates 3a and 3b are promising prodrugs of ara-C for further clinical investigations. This material was presented in part at the 81 st Annual Meeting of the American Association for Cancer Research in Washington, D.C., May, 1990 (Abstract No. 2493).     

A system for the analysis of seat support surfaces using surface shape control and simultaneous measurement of applied pressures

Chronic aspiration in the neurologically impaired child is associated with significant medical and social complications. Traditional surgical management has often relied on tracheotomy. This may well fail to control aspiration. The purpose of this retrospective study was to determine which neurologically impaired children would benefit from a laryngotracheal separation (LTS), as opposed to tracheotomy, as the primary surgical procedure to control chronic salivary aspiration. Patient selection was based on neurologic status, verbal communication ability, likelihood of neurologic recovery, and failure of previous treatments to control aspiration. Nineteen neurologically impaired children aged 8-172 months with chronic salivary aspiration underwent LTS. A total of 73.6% of these patients had prior tracheotomies, yet they continued to aspirate. Two early and three late complications were noted. No instances of fistula formation were noted. There were no deaths related to complications of the surgery or persistent aspiration. Follow-up 1-62 months after surgery demonstrated that complete control of the aspiration was achieved in all of these children. Two of the children who had achieved verbal communication prior to the procedure lost this ability. Improved general health and ability to resume oral intake was noted in all patients. This, combined with a decrease in the need of frequent suctioning, was felt by the families of these children to be a major improvement in the quality of life. Laryngotracheal separation appears to be a simple and effective means of controlling chronic aspiration. It should be considered as a primary treatment of aspiration in the properly selected child with neurologic disease.     

An adaptive control strategy for mechanical manipulators

This paper focuses on the study of an adaptive perturbation control which tracks a desired time-based trajectory as close as possible for all times over a wide range of manipulator motion and payloads. The proposed adaptive control is based on the linearized perturbation equations in the vicinity of a nominal trajectory. The controlled system is characterized by feedforward and feedback components which can be computed separately and simultaneously. The feedforward component computes the nominal torques from the Newton-Euler equations of motion to compensate all the interaction forces among the various joints. The feedback component consisting of recursive least-square identification and an optimal adaptive self-tuning control algorithm for the linearized system computes the perturbation torques which reduce the position and velocity errors of the manipulator along the nominal trajectory. A computer simulation study was conducted to evaluate the performance of the proposed adaptive control.     

Rapid characterization and modeling of pattern-dependent variationin chemical-mechanical polishing

Pattern-dependent effects are a key concern in chemical-mechanical polishing (CMP) processes. In oxide CMP, variation in the interlevel dielectric (ILD) thickness across each die and across the wafer can impact circuit performance and reduce yield. In this work, we present new test mask designs and associated measurement and analysis methods to efficiently characterize and model polishing behavior as a function of layout pattern factors-specifically area, pattern density, pitch, and perimeter/area effects. An important goal of this approach is rapid learning which requires rapid data collection. While the masks are applicable to a variety of CMP applications including back-end, shallow-trench, or damascene processes, in this study we focus on a typical interconnect oxide planarization process, and compare the pattern-dependent variation models for two different polishing pads. For the process and pads considered, we find that pattern density is a strongly dominant factor, while structure area, pitch, and perimeter/area (aspect ratio) play only a minor role     

A network model for the diffusion-convection equation

In the past network models have been used frequently to simulate the Laplace's, wave and diffusion equations. In this paper the application of the network model is further extended to include the diffusion-convection equation. the time-dependent diffusion-convection equation is first modelled by an RC electric network from which a set of ODEs is derived. Numerical experiments are then performed to compare the network model and the method of lines in solving the one-dimensional linear diffusion-convection equation and the Burgers' equation where highly non-linear network components are required. It is shown that, for the former problem, the network method has improved accuracy for low Peclet numbers. At high Peclet numbers the behaviour of the network method resembles that of the method of lines (MOL) with upstream-differencing. Spurious oscillations are absent. Computing time required to solve the network is slightly less than that for the MOL. For the Burgers' equation, the network method shows a substantial improvement over the MOL in terms of accuracy with no oscillations but requires longer computing time.     

Changes of volatile components of tomato fruits during ripening

Volatile components obtained by simultaneous steam distillation-extraction from two varieties of tomato fruits at various ripening stages and their artificially ripened tomato fruits were analyzed by GC and GC-MS using a glass capillary column. One hundred and thirty compounds were identified. Of these, quantitative changes in the major thirty-six compounds were investigated. Hexanal, trans-2-hexenal, 2-iso-butylthiazole, 2-methyl-2-hepten-6-one, geranylacetone and farnesylacetone, which were estimated to be important volatile components of fresh tomato aroma by the GC-Sniff method, increased with natural and artificial ripening. However, many volatile components showed complicated changes in the case of artificially ripened tomato fruits.     

Sound propagation,density, and viscosity in liquid3He

We have measured the temperature dependence of the velocity and the attenuation of sound in the range 60–700 mK. The maximum in the sound velocity observed by Abraham and Osborne is confirmed. The viscosity deduced from the attenuation measurements is in good agreement with that of Abel, Anderson, and Wheatley but differs from that of Betts, Keen, and Wilks. The sound velocity as a function of pressure at 150 mK was also measured and from this the low-temperature pressure dependence of the density was determined.Based on work performed under the auspices of the U.S. Atomic Energy Commission.     

Three-photon contributions in optically pumped lasers

A signal flow graph representation of the density matrix equations appropriate to a serial three-wave interaction is introduced, from which perturbation theory and AC Stark shift information may be extracted. The conditions for a large interaction cross section for the three-photon transition are deduced and applied to selected experimental situations with the main conclusion being that the effect may be present in a large number of CW and pulsed experiments.