Impact modification of lactic acid based poly(ester-urethanes) by blending

Branched biodegradable poly(ester-urethane)(PEU) was blended with two elastic biodegradable copolymers in proportions 5, 10, 15, and 20 wt % to investigate their effect on this hard and brittle polymer. Copolymer of L-lactide and ϵ-caprolactone, P(L-LA50/CL50), was synthesized by ring-opening polymerization and the other elastic poly(L-lactic acid-co-ϵ-caprolactone)urethane, P(LA50/CL50)U, was prepared by direct polycondensation of L-lactic acid and ϵ-caprolactone, followed with urethane bonding. In addition, four elastic biodegradable copolymers, three of them P(L-LA/CL) and one P(LA/CL)U, were blended with linear PEU to investigate their modifying effect on PEU. These compositions studied were 10, 15, and 20 wt % of P(L-LA40/CL60), P(L-LA60/CL40), P(L-LA80/CL20), and P(LA40/CL60)U in PEU. Blending was done in a batch mixer. PEU became more ductile when blended with P(L-LA/CL) and P(LA/CL)U, and its impact resistance improved markedly. In general, an addition of 15 wt % of copolymer appeared to give the most desirable mechanical properties. Moreover, the more L-lactide in the P(L-LA/CL) copolymer, the better was the miscibility of the blends, as shown by dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). One P(L-LA/CL) was also blended with poly(DL-lactide) (PDLLA) to see if the dispersion of rubbery copolymer particles was the same in PDLLA and PEU. A well-known commercial nonbiodegradable rubber [styrene/ethylene/butylene copolymer (SEBS)] was blended with linear PEU to compare its effect on impact strength. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1335–1343, 1997     

Differentiation of Frozen and Unfrozen Beef Using Near-Infrared Spectroscopy

Freezing and thawing affects the quality of meat. The present paper focuses on using near-infrared (NIR) diffuse reflectance spectroscopy to detect whether beef has been frozen and thawed. Intact beef and drip or centrifuged meat juice of M longissimus dorsi slices from 40 cattle were used as samples. The meat juices were analysed using dry extract spectroscopy by infrared reflection (DESIR). From centrifuged juice 80 samples were classified 100% correctly, using crossvalidation, into frozen or unfrozen beef by the K nearest neighbours method. This was obtained by high-order principal components from 400–2500 nm spectra. Other multivariate techniques, smaller wavelength ranges and detecting refrozen, thawed beef also gave results between 90 and 100%. Analyses of drip loss, exudative properties, water-holding capacity and dry matter of meat juice supported the interpretation of the NIR measurements. The results showed that NIR might be used as a screening method to differentiate unfrozen and frozen beef. © 1997 SCI.     

DNA Computing Based on Splicing: The Existence of Universal Computers

We prove that splicing systems with finite components and certain controls on their work are computationally complete (they can simulate any Turing Machine); moreover, there are universal splicing systems (systems with all components fixed which can simulate any given splicing system, when an encoding of the particular system is added—as a program—to the universal system). Splicing systems are based on the splicing operation which is a model for DNA recombination. Informally, a prefix of a word is catenated to a suffix of another word, thus yielding a (possibly) new word. Cutting occurs at specific sites which correspond to specific sequences in DNA strands as they can be recognized by restriction enzymes. When no additional control is assumed, splicing systems with finitely many starting words (axioms) and finitely many splicing rules are known to characterize only regular languages (those recognized by finite automata ). However, when a splicing rule is allowed to be used (1)\hskip .5em only in the presence of certain symbols (``catalyst') or (2)\hskip .5em only in the absence of certain symbols (``inhibitors'), then we can characterize the recursively enumerable languages (recognized by Turing Machines ); the same result is obtained when counting the number of copies of (some of) the words used. From the proofs, we also infer the existence of universal (hence programmable) splicing systems. Received August 1997, and in final form March 1998.     

Adsorption of metal cations from aqueous solutions onto the pH responsive poly(vinylidene fluoride grafted poly(acrylic acid) (PVDF-PAA) membrane

This study investigated the influence of pH of adsorption medium and co-adsorptive metal cations for the adsorption of potassium (K⁺) and magnesium (Mg²⁺) ions onto poly (vinylidene fluoride) grafted poly(acrylic acid) (PAA-PVDF) membrane. At pH 4.8, the adsorption of potassium and magnesium was minimal, because of nearly non-dissociated carboxylic acid groups of PAA-chains, but adsorption increased with increasing ion concentration. The interaction of the studied cations between PVDF-PAA membranes increased considerably at pH 7.0 the dissociation of carboxylic acid groups of PAA. The addition of ionic substances (calcium (Ca²⁺) and sodium (Na⁺) to the adsorption medium reduced the adsorption of potassium and magnesium onto the membrane, because of co-adsorption. Divalent calcium reduced more effectively than univalent sodium the adsorption of potassium and magnesium onto the membrane. In conclusion, co-adsorbing ions reduced the adsorbed amount of potassium and magnesium ions due to binding competition. The percentual adsorbed values suggest that adsorption affinity of studied ions onto the PVDF-PAA membrane followed the order Na⁺ < K⁺ < Mg²⁺ < Ca²⁺. The effect of metal cations on drug adsorption from biological fluids needs research in the future, because e.g. PVDF-PAA membrane has been used in drug separation processes.     

Lower Efficacy in the Utilization of Dietary ALA as Compared to Preformed EPA + DHA on Long Chain n-3 PUFA Levels in Rats

We made a comparative analysis of the uptake, tissue deposition and conversion of dietary α-linolenic acid (ALA) to its long chain metabolites eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with preformed EPA + DHA. Diets containing linseed oil [with ALA at ~2.5 (4 g/kg diet), 5 (8 g/kg diet), 10 (16 g/kg diet), 25% (40 g/kg diet)] or fish oil [with EPA + DHA at ~1 (1.65 g/kg diet), 2.5 (4.12 g/kg diet), 5% (8.25 g/kg diet)] or groundnut oil without n-3 polyunsaturated fatty acids (n-3 PUFA) were fed to rats for 60 days. ALA and EPA + DHA in serum, liver, heart and brain increased with increments in the dietary ALA level. When preformed EPA + DHA were fed, the tissue EPA + DHA increased significantly compared to those given ALA. Normalized values from dietary n-3 PUFA to tissue EPA + DHA indicated that 100 mg of dietary ALA lead to accumulation of EPA + DHA at 2.04, 0.70, 1.91 and 1.64% of total fatty acids respectively in liver, heart, brain and serum. Similarly 100 mg of preformed dietary EPA + DHA resulted in 25.4, 23.8, 15.9 and 14.9% of total fatty acids in liver, heart, brain and serum respectively. To maintain a given level of EPA + DHA, the dietary ALA required is 12.5, 33.5, 8.3 and 9.1 times higher than the dietary EPA + DHA for liver, heart, brain and serum respectively. Hence the efficacy of precursor ALA is lower compared to preformed EPA + DHA in elevating serum and tissue long chain n-3 PUFA levels.     

Computational fractal geometry with WFA

We define two measures of “fractalness” of gray-tone images: the degree of self-similarity and the gray-tone fractal dimension as a generalization of Minkovski dimension of compact sets. We show how to compute both these measures from the WFA-representation of a gray-tone image. Since we have developed a WFA-inference algorithm which computes a good approximation of any gray-tone image we can compute a close approximation of both our measures of fractalness for any gray-tone image. Received: 15 November 1994 / 6 October 1995     

Hydrochloric acid extractable protein patterns of Pectinatus cerevisiophilus strains

Pectinatus cerevisiophilus strains were subjected to mild hydrochloric acid extraction. Electron microscopic examination revealed that the bacterial cells still retained their original form. The extract contained vesicles, derived mostly from the outer membranes of the bacteria. The extracted material from ten isolates was studied by SDS polyacrylamide gel electrophoresis and a number of different protein patterns were found. These allowed two main groups and four subgroups to be distinguished among the isolates. The molecular weights of the major proteins varied between 13 and 62 kilodaltons. The mild hydrochloric acid extractable protein patterns provide a useful tool for typing different strains.     

Challenging the Traditional Counter‐Current Water Circulation System Case: Washing of Soap in a Kraft Pulp Fibreline

Would it be possible to challenge the traditional counter‐current water circulation system in a way that enables better soap washability, and thus improves process runnability in the kraft pulp fibreline? New water circulation alternatives were simulated in order to find ways to modify dissolved solids contents in the liquors and thus to improve soap washability. An application of using different fractions of liquors in dilution washing proved to be an interesting alternative. The presented modification principles should be applicable also in other branches of the chemical industry, especially when solubility is a limiting factor in washing.     

Chlorinated aromatic hydrocarbons in fish from an area polluted by industrial effluents

The content of chlorinated fat-soluble aromatic hydrocarbons was determined in fish from an area polluted by industrial effluents. The fish species investigated were selected among those used for human consumption. For some samples, both the fillet and liver were investigated. For others the whole fish was used. The following compounds were analysed and quantified: Trichlorobenzene, tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, heptachlorostyrene, octachlorostyrene and polychlorinated biphenyls. The results indicate an appreciable accumulation in fish of the higher chlorinated compounds as pentachlorobenzene, hexachlorobenzene, heptachlorostyrene and octachlorostyrene.Other chlorinated hydrocarbons as decachlorobiphenyl, pentachloronaphthalene, hexachloronaphthalene and hexachlorostyrene were identified, but not quantified. The total content of fat-soluble chlorine was determined in some samples before and after sulphuric acid treatment. The content of chlorine in the identified and quantified compounds accounted for between 40 and 100 per cent of the total amount of chlorine present in the samples as persistent (sulphuric acid resistant) compounds.     

OFDM for broadcasting in presence of analogue co-channelinterference

This paper treats the problems of digital TV terrestrial broadcasting in presence of co-channel interference from analogue TV services. The channel capacity is calculated for the optimum distribution of the transmitted power. An OFDM scheme is presented which is designed to be robust to the analogue TV interference. Power and number of bits per symbol are assigned to each OFDM channel to give the maximum data rate for a given signal to interference ratio. Simulations of the proposed scheme, for 8 MHz bandwidth and interference from a system G PAL signal, show that acceptable error rate can be achieved for e.g. 27 Mbit/s and 39 Mbit/s at signal to interference ratios of -6 dB and 0 dB, respectively. The proposed scheme is suitable for the next generation terrestrial TV networks which are going to coexist with the current analogue systems