Acrylonitrile-based copolymers: Synthesis,characterization, and formation of ultrafiltration membranes utilized for the immobilization of proteins

Various high molecular weight copolymers of acrylonitrile and a vinyl comonomer containing an aryl amine, a pyridine, or an aliphatic hydroxyl group were synthesized via slurry polymerization techniques so as to contain from 1 to 15 mol % functional comonomer. The comonomer content was quantitated by ultraviolet absorbance, base titration of acid polymer salts, and/or relative chemical reactivity with trichloro-s-triazine. Thin films were cast from copolymer solutions, coagulated into unsupported ultrafiltration membrances, and characterized with respect to both water permeability and pore size distribution. Analysis by size exclusion chromatography of the membrane permeate of a pool of dextran fractions yielded a continuous distribution curve for membrane pore size over the range 1.5 to 70 nm. The ultrafiltration membranes were used for protein immobilization after appropriate chemical activation. The three distinct types of functional copolymers gave comparable results for α-chymotrypsin, with protein weight loadings of 6–12% and 40–65% retention of enzymatic specific activity.     

Introduction to the special section on neuropsychology and rehabilitation: The view from New York University.

30 yrs prior to this article, psychologists at the New York University Medical Center addressed issues at the interface of clinical neuropsychology and rehabilitation. The work gave rise to programs for interventions with people with cognitive deficits after brain damage, stroke, and traumatic brain injury. The expansion of this early work is discussed in reference to articles about instrument development, cognitive remediation programs, issues of program outcome, and problems in delivering neuropsychological services to individuals with brain trauma. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adsorption of dissolved organics from industrial effluents on to activated carbon

Industrial effluents usually include multicomponent organic solutes. The optimum pH for adsorption of a specific industrial effluent on activated carbon should be determined experimentally because, in general, more than one mechanism is involved. A series of experiments was conducted to establish the influence of the initial hydrogen ion concentration on carbon adsorption of organic solutes. For these studies, powdered activated carbon was used, and the water systems studied included both single component pure organic compounds as well as multicomponent organic wastes. Results indicate that the pH effect upon the effectiveness of carbon adsorption mainly depends upon the nature of the adsorbed substance. In general, the degree of ionisation is the controlling factor for adsorption of ionic organic solutes on activated carbon. Adsorption reaches a maximum at the point of least ionisation of the adsorbate. As the organic compounds become more complex (i.e. longer hydrocarbon chains, higher molecular weights, increased branching), the electrical adsorption forces between activated carbon and ionic organic solutes will govern. Anionic surfactants meet with decreased electronegative repulsive forces at low pH levels, which increase the effectiveness of carbon adsorption. However, the adsorption of a cationic surfactant is increased by an increase in the electronegative carbon surface at high pH levels. When ionic organic solutes become much more complex, like a polymer, the effects of both ionisation and electrical adsorption forces become less important. Instead, the adsorption rate will be controlled by the extent of hydrolysis caused by the pH adjustment. For non-ionic organic solutes, chemical reaction(s) between the adsorbate and the added chemical (acid or base) for pH adjustment is an important controlling factor. Again, hydrolysis is responsible for the breakdown of larger size molecules to smaller sizes. Then an increase in adsorption rate with decreasing molecular weight of adsorbate is expected.     

Preparation of lot samples of nut meats for mycotoxin assay

A procedure has been devised for preparing lot samples of mycotoxin-contaminated nut meats so that a representative analytical sample may be removed. The sample is rapidly reduced to coarse size. A relatively large portion (about 1/10 of total sample) of subsample is then split out and further comminuted to a fine particle size with the aid of a fat solvent (meat-solvent, w/v, 3:2). The analytical sample is removed from this mixture. The procedure was tested with shelled almonds and shelled walnuts using radioactive nuts to simulate the mycotoxin contamination and provide a simple, precise measure of the contaminated nut meat distribution. The pooled coefficient of variation was 18% for the subsamples and 4.4% for the analytical samples. Considering the dilution factors used (1.50 and 2.14 contaminated nuts/10⁴ nuts) and the low degree of reliability of the lot sample, the sample preparation methods tested appear to be practical and reliable.     

Chemical modification of hemp,sisal, jute,and kapok fibers by alkalization

Plant fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of surface impurities and the large amount of hydroxyl groups make plant fibers less attractive for reinforcement of polymeric materials. Hemp, sisal, jute, and kapok fibers were subjected to alkalization by using sodium hydroxide. The thermal characteristics, crystallinity index, reactivity, and surface morphology of untreated and chemically modified fibers have been studied using differential scanning calorimetry (DSC), X‐ray diffraction (WAXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively. Following alkalization the DSC showed a rapid degradation of the cellulose between 0.8 and 8% NaOH, beyond which degradation was found to be marginal. There was a marginal drop in the crystallinity index of hemp fiber while sisal, jute, and kapok fibers showed a slight increase in crystallinity at caustic soda concentration of 0.8–30%. FTIR showed that kapok fiber was found to be the most reactive followed by jute, sisal, and then hemp fiber. SEM showed a relatively smooth surface for all the untreated fibers; however, after alkalization, all the fibers showed uneven surfaces. These results show that alkalization modifies plant fibers promoting the development of fiber–resin adhesion, which then will result in increased interfacial energy and, hence, improvement in the mechanical and thermal stability of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2222–2234, 2002     

Equilibrium bulk polymerization of 1,3-dioxolan

Cationic bulk polymerization of 1,3-dioxolan has been carried out in sealed ampoules using a high vacuum technique. The polymerization is initiated with triethyl oxonium hexafluorophosphate and the equilibrium between monomer and active polymer is attained within a few hours. Specific volumes of pure monomer and polymer in solution of its own monomer have been measured. Equilibrium measurements have been performed in the 40° to 141·4°C temperature range and the ceiling temperature is estimated to be 144° ± 2°C. The effect of short polymer chains on the equilibrium is discussed briefly. Values of ΔG_lc, the free energy of polymerization of one mole of pure liquid monomer to one base-mole of amorphous polymer, are computed making allowance for the non-ideal mixing. Respective values of ?17.5 ± 0.8 kJ/mol and ?47.9 ± 2.2JK^?1mol^?1 are deduced for the corresponding ΔH_lc and ΔS_lc. ΔG_lc is also computed from published data on equilibrium polymerization of 1,3-dioxolan in various solvents and the combined results for both types of polymerization yield ΔH_lc = ?16.7 ± 0.5kJ/mol and ΔS_lc = ?45.8 ± 1.5JK^?1mol^?1 for the 20° to 140°C range.     

确保管道运输的泄漏检测技术

保证所有管道中石油从一端流向另一端不泄漏要比它的探测更加困难。比较图中的3个系统,可以看到这项技术在40多年来是如何逐步发展的。     

2D space–time wave-digital multi-fan filter banks for signals consisting of multiple plane waves

Two dimensional space–time fan filters may be used for the highly-selective enhancement of spatio-temporal plane-waves on the basis of their directions of arrival. Unlike uniform bandwidth beam filters, ideal fan filters transmit passband signals over a range of directions of arrival that is independent of their 1D temporal spectrum. In this work, closed-form 2D wave-digital filter design equations and corresponding hardware architectures are proposed for realizing M independent fan-shaped passbands having independently steerable directionality and selectivity. A design method based on LCR ladder networks is proposed and implemented using a 2D time-multiplexed raster-scanned architecture that is suitable for low frequency applications such as audio, multimedia, seismic and ultrasonic beamforming. The architectures are designed, simulated, physically realized and tested on FPGA-based prototypes. Examples of 2D IIR M-fan filterbanks with FPGA implementations, together with measured results from on-chip hardware verifications, show the successful design and hardware realization. The filterbanks and hardware architectures are shown to be suitable for real-time sensor-array beamforming applications using custom VLSI circuits.     

Practitioner's Insight: Learning to Manage Emerging Technologies

New management techniques and policies need to be developed in order for more effective commercialization of emerging technologies.     

Probabilistic model of fatigue fracture of carbon nanostructures

Presented evaluation of risk of fatigue fracture of carbon nanostructures (CN) is based on: (a) the criterion of the threshold of the dissipated energy of tensile stresses, and (b) simulation of stochastic character of fracture by the failures in queueing system. The assessments of probability of fatigue fracture of CN in conditions of uniaxial tension, plane torsion and uniaxial compression are done.