Specialty polyurethane soft segments. III. Synthesis and characterization of N-isopropyl polyether polyamine oligomers containing backbone urea or amide moieties

Primary polyether polyamine oligomers containing preformed urea or amide moieties in their backbones were converted to the corresponding N-isopropyl polyether polyamine oligomers (secondary amines) by reaction with acetone and hydrogen in the presence of a catalyst. The best results were from reactions carried out at about 150°C using a supported platinium or palladium catalyst in a fixed bed. Reactants and products were monitored by quantitative carbon-13 NMR, size exclusion chromatography, and amine titration. Perchloric acid titration was used to quantify the number of urea moleties per molecule. Amide backbone materials gave very little backbone degradation. However, some backbone degradation was observed with urea backbone materials, leading to products with lower molecular weights. These polyether polyamine oligomers, containing urea or amide moieties in their backbones, are useful in urethane/urea polymer systems. The lower reactivity of these secondary amines (toward polyisocyanates) results in their utility in a broader range of polyurethane fabrication technologies. © 1992 John Wiley & Sons, Inc.     

Progressive spatial restriction of Sek-1 and Krox-20 gene expression during hindbrain segmentation

After segmentation of the vertebrate hindbrain, expression of the zinc-finger gene Krox-20 and the receptor tyrosine kinase gene Sek-1 is precisely restricted to rhombomeres (r) 3 and 5. This precise segmental expression is likely to reflect a critical requirement for these rhombomeres to acquire a distinct and homogeneous identity and raises the question as to how this relates to the intermingling and restriction of cell movement during segmentation. We have analysed Krox-20 and Sek-1 expression in the mouse and chick hindbrain at single-cell resolution using whole-mount in situ hybridisation and immunocytochemistry. We find that, in the mouse, the presumptive r3 and r5 expression domains each arise as narrow stripes that then broaden, suggestive of a recruitment of cells to an r3/r5 identity and/or a segmental regulation of cell proliferation. In addition, we find that expression of these genes initially occurs in fuzzy domains, and that these are progressively restricted to segmental domains, although occasional "violating" cells are observed even after segmentation. We propose that the establishment and maintenance of these segmental domains may involve both a dynamic regulation of r3/r5 identity and the restriction of cell movement across rhombomere boundaries.     

Chromatographic characterisation of aptamer-modified poly(EDMA-co-GMA) monolithic disk format for protein binding and separation

The introduction of aptameric ligands onto disk-monolithic adsorbent, representing a unique strategy for convective isolation of target molecules with high specificity and selectivity, is investigated for the first time. Experimental results showed that the disk monolith possessed a good permeability of 1.67 ± 0.05 × 10^–14 m² (RSD = 3.2%). The aptameric ligand density for the aptamer-modified disk monolith was 480 pmol/uL. Chromatographic analysis of the aptamer disk-monolith efficiency showed an optimum linear velocity of 126 cm/min (≈0.25 mL/min) at room temperatures 25 ± 2°C. The theoretical number of plates corresponding to the optimum linear velocity was 128.2 with an height equivalent to the theoretical plate of 0.022 mm. The disk aptamer-immobilised monolithic system demonstrated good selectivity and isolation of thrombin from non-targets.     

Gel–water relationships in hydrophilic polymers: Thermodynamics of sorption of water vapor

A thermodynamic study was conducted of water vapor adsorption on four hydrophilic polymers (agar, carboxymethyl cellulose, gelatin, and maize starch) at 12 and 25°C. Monolayer coverage amounted, after correction for crystallinity, respectively, to 0.93, 1.46, 0.51, and 0.77 mol water/mol monomer. Evidence is adduced from the Bradley equation and thermodynamic data to indicate that at least during coverage with the second layer of water, the energy of adsorption is greater than that due to condensation alone. Differences in the amount of sorption and in the trend of values of ΔS?° and ΔH?° with the amount of sorbed water are related with differences in the strength of intermolecular association as affected by steric hindrances.     

1H MAS NMR (magic-angle spinning nuclear magnetic resonance) techniques for the quantitative determination of hydrogen types in solid catalysts and supports

Distinct hydrogen species are present in important inorganic solids such as zeolites, silicoaluminophosphates (SAPOs), mesoporous materials, amorphous silicas, and aluminas. These H species include hydrogens associated with acidic sites such as Al(OH)Si, non-framework aluminum sites, silanols, and surface functionalities. Direct and quantitative methodology to identify, measure, and monitor these hydrogen species are key to monitoring catalyst activity, optimizing synthesis conditions, tracking post-synthesis structural modifications, and in the preparation of novel catalytic materials. Many workers have developed several techniques to address these issues, including 1H MAS NMR (magic-angle spinning nuclear magnetic resonance). 1H MAS NMR offers many potential advantages over other techniques, but care is needed in recognizing experimental limitations and developing sample handling and NMR methodology to obtain quantitatively reliable data. A simplified approach is described that permits vacuum dehydration of multiple samples simultaneously and directly in the MAS rotor without the need for epoxy, flame sealing, or extensive glovebox use. We have found that careful optimization of important NMR conditions, such as magnetic field homogeneity and magic angle setting are necessary to acquire quantitative, high-resolution spectra that accurately measure the concentrations of the different hydrogen species present. Details of this 1H MAS NMR methodology with representative applications to zeolites, SAPOs, M41S, and silicas as a function of synthesis conditions and post-synthesis treatments (i.e., steaming, thermal dehydroxylation, and functionalization) are presented.     

Optimization of the Second-Order Logarithmic Machining Economics Problem by Extended Geometric Programming Part II: Posynomial Constraints

An algorithm is presented for solution of the machining economics problem with a Quadratic Posylognomial (QPL) objective function and single term posynomial constraints, meeting certain sufficient conditions. The algorithm applies to minimum cost or maximum productivity when the tool-life equation is a single term QPL and the removal rate is a single-term posynomial. A peripheral end-milling example, using the same tool-life equation and cost parameters as Part I, with the addition of experimentally derived constraints, is solved to illustrate the computational aspects of the algorithm. The QPL and posynomial (Taylor) formulations of the constrained machining problem are compared using the same experimental tool-life data. The QPL formulation is based on a quadratic logarithmic model whereas the posynomial formulation is based on a linear logarithmic tool-life model. An optimum without active constraints is possible using the QPL formulation in several independent machining variables, such as feed, speed, and depth, whereas the posynomial optimum, by nature, requires active constraints for more than one independent variable. This is tantamount to having additional “degrees of freedom” for optimization, as illustrated by the example problem.     

The role of soft computing in intelligent machines

An intelligent machine relies on computational intelligence in generating its intelligent behaviour. This requires a knowledge system in which representation and processing of knowledge are central functions. Approximation is a 'soft' concept, and the capability to approximate for the purposes of comparison, pattern recognition, reasoning, and decision making is a manifestation of intelligence. This paper examines the use of soft computing in intelligent machines. Soft computing is an important branch of computational intelligence, where fuzzy logic, probability theory, neural networks, and genetic algorithms are synergistically used to mimic the reasoning and decision making of a human. This paper explores several important characteristics and capabilities of machines that exhibit intelligent behaviour. Approaches that are useful in the development of an intelligent machine are introduced. The paper presents a general structure for an intelligent machine, giving particular emphasis to its primary components, such as sensors, actuators, controllers, and the communication backbone, and their interaction. The role of soft computing within the overall system is discussed. Common techniques and approaches that will be useful in the development of an intelligent machine are introduced, and the main steps in the development of an intelligent machine for practical use are given. An industrial machine, which employs the concepts of soft computing in its operation, is presented, and one aspect of intelligent tuning, which is incorporated into the machine, is illustrated.     

Project Change Management System

Changes in projects are common and may be deleterious or beneficial—whether you see a change as a conflict or a valuable lesson depends only on your prospective. Project changes affect the cost, the scheduling, and the duration of projects, both directly and indirectly. Despite many articles and much discussion in practice and academic literature, there is a lack of information about systematic approaches to manage project change. This paper introduces a comprehensive project change management system that is founded on five principles: (1) promote a balanced change culture; (2) recognize change; (3) evaluate change; (4) implement change; and (5) continuously improve from lessons learned. By applying this project change management system, project participants can minimize deleterious change and promote beneficial change.     

Solvent extraction successfully applied

Summary Extraction efficiency clearly points to counter-current extraction and with the other requirements indicates continuous operation. So our investigations and plant experience together with consideration of modern production methods have led us to the firm conclusion that the future of large scale solvent extraction of vegetable oils lies in continuous counter-current extraction. Presented at Fourth Annual Fall Meeting of the American Oil Chemsits' Society, Chicago, Nov. 13, 1930. Prosco Oils Corporation.