bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractionation of oligosaccharides by nanofiltration
Authors: Goulas Athanasios K , Grandison Alistair S , Rastall Robert A
Published: April 2003

Two loose nanofiltration membranes (NF‐CA‐50 and NF‐TFC‐50) and one dense ultrafiltration membrane (UF‐CA‐1) were used to fractionate commercial oligosaccharide mixtures by applying diafiltration in a ‘dead‐end’ filtration cell at 40 bar constant pressure with a maximum volume concentration ratio (VCR) of 6 at each fractionation. The rejections of a monosaccharide (glucose) and a disaccharide (lactose) were determined for each membrane; the results indicated that fractionation between these two sugars was possible using the two nanofiltration membranes. During the nanofiltration purification of a commercial oligosaccharide mixture, yields of 19% (w/w) for monosaccharides and 88% (w/w) for di‐ and oligosaccharides were obtained with the NF‐TFC‐50 membrane after four filtration steps, indicating that removal of the monosaccharides is possible with only minor losses of the oligosaccharide content of the mixture. The ultrafiltration membrane, at the same time, gave purification levels similar to the NF‐TFC‐50 membrane with fewer diafiltration steps but with higher losses of di‐ and oligosaccharides (12% (w/w) for monosaccharides and 53% (w/w) for di‐ and oligosaccharides on the third run).

© 2003 Society of Chemical Industry
Effect of cutting and storage on sensory traits of cantaloupe melon cultivars with extended postharvest shelf life
Authors: Lamikanra Olusola , Juaraez Benito , Watson Michael A , Richard Olga A
Published: April 2003

Fresh cut cantaloupe melons (Cucumis meloL varreticulatus) from fruits with extended postharvest shelf life were analysed for changes in their volatile aroma compounds and polygalacturonase activity during storage. The total volatile aroma contents and the number of volatile compounds in fruits with extended shelf life were significantly less than those present in the traditional shelf life cultivarMission. Esters were the major volatile compounds present in the fruits, and their concentrations decreased considerably with storage of the cut fruit for 24 h at 4 °C. Polygalacturonase activity was detected from measurements of the hydrolytic release of reducing groups after storage of the cut fruit for 3 days. Enzymatic activity decreased thereafter in all fruits. The results indicate a lack of correlation between the postharvest shelf life of whole cantaloupe and that of fresh cut fruit.

© 2003 Society of Chemical Industry
The effect of cellulose crystallinity on the in vitro digestibility and fermentation kinetics of meadow hay and barley, wheat and rice straws
Authors: Rodrigues M A M , Cone J W , Gelder A H van , Sequeira J C , Fonseca A M , Ferreira L M M , Sequeira C A
Published: April 2003

The effect of cellulose crystallinity on in vitro digestibility (IVD) and fermentation kinetics was investigated in samples of meadow hay and barley, wheat and rice straws. A saturated solution of potassium permanganate was used to isolate the celluloses, and their crystallinity was evaluated in a Fourier transform infrared spectrometer as the ratio of the observed transmittance at two distinct wave frequencies ${\bf (\alpha_{1372 \ cm}^{-1}/\alpha_{2900 \ cm}^{-1})}$. IVD was determined after 48 h of incubation, and the kinetics of fermentation was studied with fully automated gas production equipment. Despite significant differences (P < 0.05), crystallinity showed low variation (0.30–0.42) among celluloses and correlated positively with IVD (P < 0.05). Although positively correlated with maximal gas production (r = 0.91) and rates of fermentation, IVD (averaging 784 g kg−1 organic matter (OM)) was also low for all samples as compared with the usually referred values for isolated celluloses. The lowest means were observed for meadow hay and rice straw. The cumulative gas production profiles were well described by a monophasic model (r2 = 0.997, RSD (residual standard deviation) = 8.367), but all the curves had a lag phase varying from 3 to 6 h. Cellulose isolated from rice straw showed the lowest maximal gas production (366 ml g−1 OM) and highest times to reach half of the maximal gas production and maximal rate. Transmission electron microscopy (TEM) of two cellulose samples showing considerable gas production at highest rates as compared with cellulose isolated from rice straw that provided the lowest gas production at the lowest rate revealed generalised bacterial colonisation, the presence of glycocalyx fibres and cell erosion in all samples. Although samples collected after 12 h of fermentation appeared to present lower microbial attack as compared with those incubated for 24 h, TEM did not explain the observed differences in the data. Since crystallinity, IVD, gas production and rates of fermentation were shown to be associated with the nutritional availability of cellulose, further research dealing with extreme values of cellulose crystallinity may be important.

© 2003 Society of Chemical Industry
The apparent ileal digestibility, determined with young broilers, of amino acids in near‐isogenic lines of peas (Pisum sativum L) differing in trypsin inhibitor activity
Authors: Wiseman Julian , Al‐Mazooqi Waleed , Welham Tracey , Domoney Claire
Published: April 2003

Two pairs of near‐isogenic lines of peas were developed to have high and low concentrations of seed trypsin inhibitor. HA5 and LA5 contained 8.73 ± 0.19 and 1.45 ± 0.19 trypsin inhibitor units per mg dry weight respectively, whereas HB5 and LB5 contained 7.40 ± 0.65 and 1.78 ± 0.15 trypsin inhibitor units per mg dry weight respectively. The four pea samples were included in semi‐synthetic diets and evaluated in a poultry metabolism experiment, using birds aged 3 weeks, to determine the coefficient of apparent ileal amino acid digestibility (CAID). There was a significant difference in CAID for the amino acids reported that correlated with pea genotype. Thus, for example, CAID for cystine was 0.738 ± 0.0196 and 0.812 ± 0.0128 for HA5 and LA5 respectively and 0.721 ± 0.0139 and 0.804 ± 0.0178 for HB5 and LB5 respectively. Corresponding data for methionine, the other main nutritionally deficient amino acid in peas, were 0.887 ± 0.0103, 0.930 ± 0.0089, 0.885 ± 0.0083 and 0.929 ± 0.0125 respectively. Other amino acids followed similar patterns. These data provide information on the nutritional consequences of variation in trypsin inhibitor content of pea seeds in near‐isogenic backgrounds. Plant breeding for low trypsin inhibitor activity in seeds accordingly offers potential for improving nutritional value.

© 2003 Society of Chemical Industry
Mineral content and electrical conductivity of the honeys produced in Northwest Morocco and their contribution to the characterisation of unifloral honeys
Authors: Terrab Anass , González A Gustavo , Díez María J , Heredia Francisco J
Published: April 2003

In this study the mineral content, ash content and electrical conductivity of 98 honey samples from Northwest Morocco were studied. Using inductively coupled plasma atomic emission spectrometry (ICP‐AES), six minerals were identified and quantified: K, Mg, Mn, Cu, Fe and Zn. Potassium was the predominant mineral (accounting for 80% of the total minerals quantified), followed by Mg and Fe (9 and 3% respectively). The ash content values were lower than 0.6% in 95 of the samples. The higher electrical conductivity values corresponded to the honeydew honeys (
x = 1734 µS cm−1). In addition, characterisation of the main unifloral honeys by principal component analysis (PCA), linear discriminant analysis (LDA) and multilayer perceptrons (MLP) was carried out. The PCA showed that the cumulative variance was approximately 67%. On the other hand, the LDA and MLP allowed perfect classification of the honeydew (100% correct classification) and Eucalyptus (92%) honeys.

© 2003 Society of Chemical Industry
Antioxidant capacity of tomato juice functionalised with enzymatically synthesised hydroxytyrosol
Authors: Larrosa Mar , Espín Juan Carlos , Tomás‐Barberán Francisco A
Published: April 2003

The antioxidant hydroxytyrosol has been enzymatically synthesised in order to functionalise tomato juice. The antioxidant capacity significantly increased in the functionalised juice according to a set of in vitro antioxidant assays (ie ferric thiocyanate method, inhibition of oxygen consumption, and scavenging of both DPPH· and ABTS·+ free radicals). In addition, hydroxytyrosol was stable within the tomato juice matrix under extreme storage conditions (room temperature and light exposure) for 48 days. Sensory properties (flavour and colour) of the tomato juice were not affected by functionalisation with hydroxytyrosol concentrations of up to 1 mg ml−1. Therefore this functional tomato juice could be a promising source of health‐beneficial properties, beyond basic nutrition, taking into account both the high activity and bioavailability of hydroxytyrosol.

© 2003 Society of Chemical Industry
Relation between bioactive compounds and free radical‐scavenging capacity in berry fruits during frozen storage
Authors: González Eva M , de Ancos Begoña , Cano M Pilar
Published: April 2003

In this work the correlation between the free radical‐scavenging capacity and bioactive compounds (anthocyanins, ellagic acid, total phenolics and vitamin C) in four Spanish raspberry cultivars (Heritage, Autumn Bliss, Zeva and Rubi) and Spanish wild blackberry as affected by freezing and frozen storage was evaluated. From this mathematical study a significant correlation was obtained between the radical‐scavenging capacity and the anthocyanin and total phenolic contents in both raspberry (r = 0.85 and 0.83 respectively) and blackberry (r = 0.84 and 0.68 respectively) fruits, but no correlation was found between this parameter and the ellagic acid and vitamin C contents. A key objective of this study was to select the raspberry cultivar most suitable for freezing preservation in terms of the stability of its health‐promoting constituents. A two‐dimensional principal component analysis (PCA) of the raspberry cultivars explained 82% of the total variance of the factors mentioned above. The early raspberry cultivars (Heritage and Autumn Bliss) showed a lower content of bioactive compounds and lower radical‐scavenging capacity, while the late cultivars (Zeva and Rubi) showed higher values, and these differences were clearly displayed by the PCA.

© 2003 Society of Chemical Industry
Determination of fat in live farmed Atlantic salmon using non‐invasive NIR techniques
Authors: Solberg Christel , Saugen Esten , Swenson Lars‐Petter , Bruun Lars , Isaksson Tomas
Published: April 2003

Non‐destructive near‐infrared (NIR) measurements were performed on 100 live, anaesthetised farmed Atlantic salmon, whole weight 1–11 kg, using two different NIR instruments: a grating monochromator instrument equipped with a fibre optic interactance probe, and a diode array instrument measuring diffuse reflectance in a non‐contact mode. Crude fat content was determined using partial least squares (PLS) regression. Full cross‐validation was used to evaluate the performance of the calibration models, expressed as the root mean square error of prediction (RMSEP). For the fibre optic instrument the wavelength range from 800 to 1098 nm resulted in a correlation coefficient of 0.90 and an RMSEP equal to 14 g kg−1 fat. The diode array instrument using the wavelength range from 900 to 1700 nm gave results of the same accuracy. The measurement times were 21 and 3 s respectively. It is concluded that either instrument could be used to determine the crude fat content in live Atlantic salmon, with good accuracy.

© 2003 Society of Chemical Industry
Hydrolytic enzyme activities as indicators of fungal spoilage in bakery products
Authors: Marín Sonia , Guynot M Elena , Sanchis Vicente , J Ramos Antonio
Published: April 2003

Cake analogues were prepared at different aw (0.80, 0.85 and 0.90) and pH (6 and 7.5) levels and inoculated with a range of seven representative moulds of spoilage mycoflora of bakery products. The responses recorded were colony radii after 1, 2, 3 and 4 weeks as well as microbial counts and total and specific activities of six hydrolytic enzymes after 4 weeks. Multivariate analysis was applied in order to determine correlations among the responses and thus assess the suitability of using enzyme activities as estimators for fungal growth. The results showed that enzyme activities correlated with growth parameters for Aspergillus and Penicillium isolates, although the useful enzymes were not the same for the three isolates tested. The correlation was poor, however, for Eurotium isolates. In general, specific activities of some enzymes showed better correlation with growth parameters, with α‐D‐galactosidase, β‐D‐galactosidase, β‐D‐glucosidase and N‐acetyl‐β‐D‐glucosaminidase being the more useful enzymes among those assayed.

© 2003 Society of Chemical Industry
Evaluation of (E)‐2′‐deoxy‐2′‐(fluoromethylene)cytidine on the 9L rat brain tumor model using MRI
Authors: Ross Brian D. , Chenevert Thomas L. , Garwood Michael , Kim Boklye , Stegman Lauren D. , Ben‐Yoseph Oded , Zwolshen John , Rehemtulla Alnawaz , Sunkara Prasad S.
Published: April 2003

(E)‐2′‐deoxy‐2′‐(fluoromethylene)cytidine (FMdC), was evaluated as a potential treatment for malignant gliomas using the rat 9L brain tumor model. FMdC was shown to be an effective inhibitor of cell proliferation in cultured 9L cells with an EC50 of 40 ng/ml. In vitro studies also revealed that this compound significantly inhibited incorporation of [3H]thymidine in 9L cells. In vivo therapeutic efficacy of FMdC was evaluated in rats harboring intracerebral 9L tumors which were treated daily with 15 mg/kg, i.p. Treatment response was quantified from changes in tumor growth rates as assessed from sequential magnetic resonance imaging (MRI) tumor volume measurements. In vivo tumor cell kill in individual animals was calculated by fitting tumor volume data with an iterative computer routine. It was estimated that therapeutically responsive rats treated with FMdC daily produced a ≥ 0.1 log kill per therapeutic dose which resulted in a significant reduction in tumor growth rate. In addition, localized 1H‐MRS of intracerebral 9L tumors revealed changes in metabolite levels which correlated with therapeutic response. These results provide evidence supporting the use of FMdC in clinical trials for the treatment of malignant gliomas and reveals that MR can play an important role in the pre‐clinical evaluation of novel compounds using orthotopic tumor models. Copyright © 2003 John Wiley & Sons, Ltd.
Diffusion tensor imaging in fixed brain tissue at 7.0 T
Authors: Guilfoyle David N. , Helpern Joseph A. , Lim Kelvin O.
Published: April 2003

The purpose of this work is to assess the feasibility of performing quantitative in vitro brain tissue diffusion tensor imaging (DTI) measurements and to examine their comparability to in vivo measurements. DTI of fixed tissue at high field strength is potentially a very valuable investigative tool as very high spatial resolution can be achieved. DTI was applied to human and mouse brain fixed tissue samples as well as in vivo measurements of the mouse brain. T1 and T2 relaxography of the fixed tissue samples was also performed to provide further characterization of the tissue. All experiments were performed at 7 T. The fractional anisotropy (FA) of the human fixed brain tissue samples is found to be higher in the corpus callosum than in the occipital white matter region, consistent with in vivo measurements reported in the literature. Our FA measurements of the corpus callosum of a mouse brain are also found to be the same both in vitro and in vivo. This preliminary work supports the use of DTI in both fixed human and fixed animal brain tissue as a valid investigative tool. With the increased availability of brain banks in different brain disorders, DTI in fixed tissue may prove to be a very useful method for the study of white matter abnormalities. Copyright © 2003 John Wiley & Sons, Ltd.
Manganese ions as intracellular contrast agents: proton relaxation and calcium interactions in rat myocardium
Authors: Nordhøy Wibeke , Anthonsen Henrik W. , Bruvold Morten , Jynge Per , Krane Jostein , Brurok Heidi
Published: April 2003

Paramagnetic manganese (Mn) ions (Mn2+) are taken up into cardiomyocytes where they are retained for hours. Mn content and relaxation parameters, T1 and T2, were measured in right plus left ventricular myocardium excised from isolated perfused rat hearts. In the experiments 5 min wash‐in of MnCl2 were followed by 15 min wash‐out to remove extracellular (ec) Mn2+ MnCl2, 25 and 100 µM, elevated tissue Mn content to six and 12 times the level of control (0 µM MnCl2). Variations in perfusate calcium (Ca2+) during wash‐in of MnCl2 and experiments including nifedipine showed that myocardial slow Ca2+ channels are the main pathway for Mn2+ uptake and that Mn2+ acts as a pure Ca2+ competitor and a preferred substrate for slow Ca2+ channel entry. Inversion recovery analysis at 20 MHz revealed two components for longitudinal relaxation: a short T1 − 1 and a longer T1 − 2. Approximate values for control and Mn‐treated hearts were in the range 600–125 ms for T1 − 1 and 2200–750 ms for T1 − 2. The population fractions were about 59 and 41% for the short and the long component, respectively. The intracellular (ic) R1 − 1 and R2 − 1 correlated best with tissue Mn content. Applying two‐site exchange analyses on the obtained T1 data yielded results in parallel to, but also differing from, results reported with an ec contrast agent. The calculated lifetime of ic water (τic) of about 10 s is compatible with a slow water exchange in the present excised cardiac tissue. The longitudinal relaxivity of Mn ions in ic water [60 (s mM)−1] was about one order of magnitude higher than that of MnCl2 in water in vitro [6.9 (s mM)−1], indicating that ic Mn‐protein binding is an important potentiating factor in relaxation enhancement. Copyright © 2003 John Wiley & Sons, Ltd.
A spline strip kernel particle method and its application to two‐dimensional elasticity problems
Authors: Liew K. M. , Zou G. P. , Rajendran S.
Published: April 2003

In this paper we present a novel spline strip kernel particle method (SSKPM) that has been developed for solving a class of two‐dimensional (2D) elasticity problems. This new approach combines the concepts of the mesh‐free methods and the spline strip method. For the interpolation of the assumed displacement field, we employed the kernel particle shape functions in the transverse direction, and the B3‐spline function in the longitudinal direction. The formulation is validated on several beam and semi‐infinite plate problems. The numerical results of these test problems are then compared with the existing solutions obtained by the exact or numerical methods. From this study we conclude that the SSKPM is a potential alternative to the classical finite strip method (FSM). Copyright © 2003 John Wiley & Sons, Ltd.
Three‐dimensional viscous flow over rotating periodic structures
Authors: Kim Kyu‐Tae , Khayat Roger E. , Pollet Anthony
Published: April 2003

The three‐dimensional Stokes flow in a periodic domain is examined in this study. The problem corresponds closely to the flow inside internal mixers, where the flow is driven by the movement of a rotating screw; the outer barrel remaining at rest. A hybrid spectral/finite‐difference approach is proposed for the general expansion of the flow field and the solution of the expansion coefficients. The method is used to determine the flow field between the screw and barrel. The regions of elongation and shear are closely examined. These are the two mechanisms responsible for mixing. Besides its practical importance, the study also allows the assessment of the validity of the various assumptions usually adopted in mixing and lubrication problems. Copyright © 2003 John Wiley & Sons, Ltd.
Study of non‐Fickian diffusion problems with the potential field in the cylindrical co‐ordinate system
Authors: Chen Han‐Taw , Liu Kuo‐Chi
Published: April 2003

The present study applies a hybrid numerical scheme of the Laplace transform technique and the control volume method in conjunction with the hyperbolic shape functions to investigate the effect of a potential field on the one‐dimensional non‐Fickian diffusion problems in the cylindrical co‐ordinate system. The Laplace transform method is used to remove the time‐dependent terms in the governing differential equation and the boundary conditions, and then the resulting equations are discretized by the control volume scheme. The primary difficulty in dealing with the present problem is the suppression of numerical oscillations in the vicinity of sharp discontinuities. Results show that the present numerical results do not exhibit numerical oscillations and the potential field plays an important role in the present problem. The strength of the jump discontinuity can be reduced by increasing the value of the potential gradient. The propagation speed of mass wave is independent of the potential gradient and the boundary condition. Copyright © 2003 John Wiley & Sons, Ltd.
Fatigue control of thin‐walled structures
Authors: Tesar Alexander
Published: April 2003

The control of the ultimate fatigue behaviour of slender thin‐walled structures is treated in the paper. A macro‐ and micromechanical simulation model adopting the neural network approach is used for the numerical analysis of the problem. The numerical treatment of the non‐linear problems is made using the updated Lagrangian formulation of motion combined with the pseudo‐force technique in the FETM‐approach. Each step of the iteration approaches the solution of the linear problem and the feasibility of the parallel processing and neural network numerical techniques is established. The application on the actual slender bridge is made in order to demonstrate the efficiency of the procedures suggested. Copyright © 2003 John Wiley & Sons, Ltd.
An algorithm using co‐ordinate transformation for free vibration analysis of fully incompressible materials
Authors: Kohsetsu Yuji
Published: April 2003

This paper presents an algorithm for conducting eigenvalue analysis of fully incompressible isotropic materials (a Poisson's ratio of exactly 0.5). This algorithm is based on the concept of co‐ordinate transformation defined by eigenvectors with positive eigenvalues of the system stiffness matrix. The transformation to the new co‐ordinates of orthogonal bases in the system potential energy can reduce the size of the system equations. The original eigenvalue problem is reduced to a smaller one that can be solved. This algorithm possesses two drawbacks. One is the increase of system degrees of freedom (DOF) due to the mixed method for incompressible problems; the other is due to additional eigenvalue calculation. However, the present algorithm is inherently able to compensate for the above two drawbacks by reducing the DOF. Numerical demonstrations indicate that the exact transformation yields accurate results that converge to analytical results. They also indicate that an approximated transformation retaining only several per cent of all the eigenvectors produces accurate results in the lower frequency range that is generally of interest in engineering analyses. Therefore, the proposed algorithm is judged to be an efficient procedure for eigenvalue problems of fully incompressible materials. This co‐ordinate‐transformation scheme, derived from the system stiffness matrix, will be applicable to static incompressible problems. Copyright © 2003 John Wiley & Sons, Ltd.
An approach to verifying and debugging simulation models governed by ordinary differential equations: Part 1. Methodology for residual generation
Authors: Yuan Zhiguo , Graham Malcolm L. , Lennox James A.
Published: April 2003

For dynamic simulations to be credible, verification of the computer code must be an integral part of the modelling process. This two‐part paper describes a novel approach to verification through program testing and debugging. In Part 1, a methodology is presented for detecting and isolating coding errors using back‐to‐back testing. Residuals are generated by comparing the output of two independent implementations, in response to identical inputs. The key feature of the methodology is that a specially modified observer is created using one of the implementations, so as to impose an error‐dependent structure on these residuals. Each error can be associated with a fixed and known subspace, permitting errors to be isolated to specific equations in the code. It is shown that the geometric properties extend to multiple errors in either one of the two implementations. Copyright © 2003 John Wiley & Sons, Ltd.
An approach to verifying and debugging simulation models governed by ordinary differential equations: Part 2. Residuals analysis and a case study
Authors: Lennox James A. , Yuan Zhiguo
Published: April 2003

In Part 1 of this paper a methodology for back‐to‐back testing of simulation software was described. Residuals with error‐dependent geometric properties were generated. A set of potential coding errors was enumerated, along with a corresponding set of feature matrices, which describe the geometric properties imposed on the residuals by each of the errors. In this part of the paper, an algorithm is developed to isolate the coding errors present by analysing the residuals. A set of errors is isolated when the subspace spanned by their combined feature matrices corresponds to that of the residuals. Individual feature matrices are compared to the residuals and classified as ‘definite’, ‘possible’ or ‘impossible’. The status of ‘possible’ errors is resolved using a dynamic subset testing algorithm. To demonstrate and validate the testing methodology presented in Part 1 and the isolation algorithm presented in Part 2, a case study is presented using a model for biological wastewater treatment. Both single and simultaneous errors that are deliberately introduced into the simulation code are correctly detected and isolated. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling topology optimization problems as linear mixed 0–1 programs
Authors: Stolpe M. , Svanberg K.
Published: April 2003

This paper deals with topology optimization of discretized continuum structures. It is shown that a large class of non‐linear 0–1 topology optimization problems, including stress‐ and displacement‐constrained minimum weight problems, can equivalently be modelled as linear mixed 0–1 programs. The modelling approach is applied to some test problems which are solved to global optimality. Copyright © 2003 John Wiley & Sons, Ltd.
Engaging youth in philanthropy
Authors: Tice Karin E.
Published: April 2003

A brief history and overview of youth involvement in philanthropy is followed by a description of a range of models for involving young people. These models can be implemented by community foundations, schools, nonprofits, and governmental organizations.
Understanding how organizations affect the civic engagement of adolescent participants
Authors: Kirlin Mary K.
Published: April 2003

This chapter examines what we know about the predictors of civic engagement, the required elements for adults to be civically engaged, and the role that adolescent extracurricular activities play in creating civically engaged adults.
A developmental study of the Bonner Foundation's scholarship recipients: Impact of a four‐year, cocurricular service‐learning model
Authors: Keen Cheryl , Keen James P.
Published: April 2003

Preliminary research findings indicate that a four‐year, cocurricular service‐learning model supports an exemplary group of low‐income students in sustaining and deepening their commitments to service. It also provides skills germane to life success as well as unique opportunities for experience and reflection.
Youth and philanthropy: Legal issues, practical consequences
Authors: Allen Paula
Published: April 2003

Incorporating youth as decision makers in a nonprofit organization presents certain legal questions about their status, particularly if they serve on boards of directors.
Claiming youth: A new paradigm in youth policy
Authors: Calhoun John A.
Published: April 2003

Youth involved in youth in philanthropy programs have changed their communities, changed policy and practice, and in the process transformed their own lives. The author calls for an asset‐based public policy approach that invites all youth to be partners in creating positive change in their communities.
Involving youth: The last divide
Authors: Kendall Kathryn
Published: April 2003

A unique opportunity exists to engage youth, who are seeking meaning and purpose, in the enterprise of public service and decision making. Young people offer a unique perspective to well‐rounded discussions, and their vital participation will provide our communities and nation with a brighter future.
An analysis of the swelling equilibrium of an ionic polymer network in a binary liquid mixture
Authors: Iwatsubo Takashi , Masuoka Toshio , Mizoguchi Kensaku
Published: April 2003

An equation which represents the swelling equilibrium of an ionic polymer network in a binary liquid mixture is introduced and evaluated numerically. Discontinuous volume changes are obtained with pertinent values of the parameters. From two types of dependence of the degree of ionic dissociation on the composition of a liquid mixture, two types of volume transitions of an ionic gel are illustrated. One is the transition typically seen in acrylamide gels, and the other is a re‐entrant transition typical of isopropylacrylamide gels. The selective dissolution factor of two liquids into a swollen polymer network also becomes discontinuous in accordance with the discontinuous volume change. Transition points and the spinodal line are calculated from a generalized form of the free energy change of the swollen gel system. © 1994 John Wiley & Sons, Inc.
Compatibilizing effect of polyarylate‐polystyrene block copolymer in polyarylate/polystyrene blends
Authors: Ahn Tae Oan , Kim Jung Ho , Jeong Han Mo , Lee Sang Won , Park Lee Soon
Published: April 2003

The compatibilizing effect of polyarylate‐polystyrene (PAR‐PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view‐points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed‐domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR‐PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc.
FTIR Investigation of ion‐dipole interaction in styrene ionomer/poly(ethylene oxide) blends
Authors: Lim Jong‐Chul , Park Jung‐Ki , Song Hae‐Young
Published: April 2003

Fourier‐transform infrared (FTIR) spectroscopy was used to examine specific interactions contributing to the partial miscibility in blends of styrene‐sodium methacrylate copolymer (S‐NaMA) and poly(ethylene oxide) (PEO). From the shifts of carboxylatelon and ether group stretching bands, an important specific interaction was found involving ion‐dipole bonding between the ionic group in styrene ionomer and the ether group in PEO. The asymmetric stretching vibration frequency of the carboxylate ion group increases as the fractional amount of PEO in the blend is increased, while the symmetric stretching frequency is decreased. The transition value of the fraction of PEO, above which both vibration frequencies of the carboxylate ion mentioned above remained almost unchanged, increases as the concentration of ionic groups in ionomer is increased. The ether group stretching band shifts to higher frequencies as the PEO content in the ionomer/PEO blend is increased. From the differential scanning calorimetry (DSC) and FTIR studies, we find that the iondipole interaction is the important mechanism that determines the miscibility of S‐NaMA/PEO blends. © 1994 John Wiley & Sons, Inc.
ESR and magnetic properties of electrically conducting metallophthalocyanine polymers
Authors: Venkatachalam S. , Rao K. V. C. , Manoharan P. T.
Published: April 2003

Polymeric metallophthalocyanines of Cu, Ni, Co in which benzene rings are shared in common with the macrocyclic phthalocyanine rings containing peripheral carboxylic groups have been synthesized and their electrical conductivities are shown to increase from 5 to 8 orders of magnitude by thermal treatment. The cobalt polymer exhibits greater conductivity than its nickel or copper analogs. The heated polymers show very broad electron spin resonance (ESR) signals and large paramagnetic susceptibilities. The bulk magnetic susceptibility of these polymers shows Curie‐like behavior when the samples are heated from room temperature to 473 K. This is explained on the basis of coexistence of fixed mobile and conduction electron spins in the system and the interaction of the soliton type defects present in these polymers with the polymeric network to give dipolar charge carriers. This is also supported by the decrease in ESR intensity with increasing temperature when the samples are heated in the ESR cavity. The effect of the presence of unpaired electrons on the d shell of the central metal atoms on the line width and the line shape of the ESR spectra is also explained. © 1994 John Wiley & Sons, Inc.
Permeability relationships of polyimide copolymers
Authors: Zoia G. , Stern S. A. , St. Clair A. K. , Pratt J. R.
Published: April 2003

The permeability of the homopolymers 6FDA‐3BDAF and 6FDA‐4BDAF and of the copolymers 6FDA‐4/2BDAF, 6FDA‐4/3BDAF, and 6FDA‐4/3/2BDAF to He, CO2, and CH4 was measured at 35.0°C and at pressures up to 10 atm. The experimental values of the permeability coefficients for the copolymers are in satisfactory agreement with the values estimated from the permeability coefficients for the constituent homopolymers and their weight fractions. The synthesis of the fluorine‐containing diamine 2BDAF is reported for the first time. © 1994 John Wiley & Sons, Inc.
Thermal conductivity of poly(vinyl chloride)/polycaprolactone blends
Authors: Agari Y. , Ueda A.
Published: April 2003

Thermal diffusivity, heat capacity, and density of polyvinyl chloride/polycaprolactone (PVC/PCL) blends were measured by the laser flash method, DSC, and pycnometry, respectively. The thermal conductivity of the PVC/PCL blends was determined from the results. The miscibility of the blend and crystallinity of PCL were determined by DSC. The effect of blend structure on thermal conductivity is discussed. The phase compositions of the PVC/PCL blends are of three types depending on PCL content: i.e., up to 33%, from 33 to 70%, and above 70% PCL by weight. Thermal conductivity, thermal diffusivity, and heat capacity of the PVC/PCL blends are strongly affected by the phase composition of the blend, which changes in a complicated way with PCL content. © 1994 John Wiley & Sons, Inc.
Light scattering studies of copolymers. 1. Soluble hemoglobin‐‐dextran complexes
Authors: Nordmeier Eckhard , Rad Darush
Published: April 2003

Complexes between dextrans of different molar mass and bovine hemoglobin were synthesized by two different methods. In the alkylation method three and in the dialdehyde method, two hemoglobins are coupled on average to one dextran molecule. In both cases, the soluble hemoglobin‐dextran complexes reversibly bind and release oxygen; the oxygen affinity is greater than that of free hemoglobin. Static and dynamic light scattering was used to determine the average molar mass Mu, the radius of gyration 〈S〉, and the hydrodynamic radius Rh of both the complexes and the single dextrans. Interpretation of these data is complicated due to the fact that the complexes are copolymers. When appropriate approximations are made, the results indicate that the complexes have a spherical shape and an internal structure of a multiple‐chain network, where several dextrans are linked together by the hemoglobins. The number of single dextrans per complex increases as the molar mass of the single dextrans is decreased. The increment is greater in the dialdehyde than in the alkylation method. The probable reason is that in the dialdehyde method one hemoglobin can connect many dextrans simultaneously while in the alkylation method a hemoglobin is able to link maximally two dextrans. The ratio of the radius of gyration to the hydrodynamic radius decreases as the temperature is increased. This suggests a decrease of the solvent penetration length for the complexes and can be interpreted on the basis of the Deutsch‐Felderhof theory for porous spheres. © 1994 John Wiley & Sons, Inc.
Pulsed NMR study of the structure of poly(vinyl alcohol)‐poly(sodium acrylate) composite hydrogel
Authors: Shiga T. , Fukumori K. , Hirose Y. , Okada A. , Kurauchi T.
Published: April 2003

The heterogeneous structure of poly(vinyl alcohol)‐poly(sodium acrylate) composite hydrogels (PVA‐PAA gels), prepared by repeatedly freezing and thawing mixed aqueous solutions of PVA and PAA, has been studied using pulsed NMR. The free induction decay (FID) signals of the transverse magnetization for the PVA‐PAA gels were measured by both Carr‐Purcell‐Meiboom‐Gill and solid‐echo pulse sequences. The FID signal was decomposed into two or three decaying signals with various spin‐spin relaxation times, based upon differences in the molecular mobility that reflected structural heterogeneity. The structural heterogeneity of the PVA‐PAA gel is quite different from that of PVA gel free of PAA. We have made observations on “crosslinked” domains in the PVA‐PAA gels. They are formed by PVA solid chains, probably phase‐separated in the freezing‐thawing process. The formation of crosslinked domains is influenced by the number of freezing‐thawing cycles. © 1994 John Wiley & Sons, Inc.
Interaction of water with poly(vinyl methyl ether) in aqueous solution
Authors: Maeda Hideatsu
Published: April 2003

Near‐infrared, viscometric, and calorimetric measurements were made on aqueous poly(vinyl methyl ether) (PVME) solutions at temperatures between 15 and 43°C. We found a hydrogen‐bonded structure of water around the polymer chain (a polymer‐water complex), which is characterized by two distinct hydration numbers (i.e., 2.7 and 5.0 water molecules on each monomer unit of the chain) by analyzing the concentration dependence of endothermic enthalpies at a cloud point temperature, ca. 35°C. In particular, the 2.7 water‐polymer complex has been suggested to be cooperatively formed by using data of the near‐infrared (nir) absorption spectrum around 1930 nm. Furthermore, the peak‐wavelength of the nir spectrum has been observed to change drastically at the cloud point when the temperature is raised. This can be interpreted as a cooperative collapse of the hydrogen‐bonded water structure to free water, resulting in the aggregation of the polymer chains due to the exposure of their hydrophobic groups at the cloud point. © 1994 John Wiley & Sons, Inc.
Structural aspects of suspension poly(vinyl chloride): Influence of temperature on the macro‐ and microstructure
Authors: Scherrenberg R. L. , Reynaers H. , Gondard C. , Booij M.
Published: April 2003

The structural aspects of rigid suspension poly(vinyl chloride), PVC, have been investigated on the basis of two independent series of suspension PVC samples, polymerized at temperatures between 26 and 84°C. The reproducibility of the suspension polymerization process and the importance of the polymerization temperature with respect to the macro‐ and microstructure is demonstrated. Quantitative examination of the grain structure by small angle neutron scattering, Brunauer‐Emmett‐Teller absorption technique, and mercury porosimetry clarifies the gradual increase of the specific surface on lowering the polymerization temperature. A detailed WAXS study shows an increasing degree of crystallinity on lowering the polymerization temperature, which can be associated with the corresponding increase of the syndiotacticity. Furthermore, the presence of a polymerization history in the PVC powders with respect to the crystallinity is evidenced. This effect seems to be related to chain mobility restrictions during the polymerization process and is determined by the difference between the polymerization temperature and the glass‐transition temperature (Tg) of rigid PVC. This so‐called Tg effect is indicative of the fact that no appreciable swelling of PVC by its monomer occurs. © 1994 John Wiley & Sons, Inc.
Structural aspects of suspension poly(vinyl chloride): The thermal aspects of rigid suspension PVC
Authors: Scherrenberg R. L. , Reynaers H. , Gondard C. , Steeman P. A. M.
Published: April 2003

The thermal aspects of a series of suspension PVC samples, polymerized at different temperatures, have been investigated using DSC, WAXS, and dielectric measurements. The observed thermal behavior, extending over a wide temperature range, is in line with the presence of ordered entities, having a wide distribution of size and perfection. The importance of small variations of the syndiotacticity on the crystallizability is demonstrated by cooling experiments. © 1994 John Wiley & Sons, Inc.
Phase morphology of blends of polycarbonate with poly(methyl methacrylate‐co‐cyclohexyl methacrylate), and of polycarbonate with poly(methyl methacrylate) by solid state nuclear magnetic resonance, differential scanning calorimetry, and transmission electron microscopy
Authors: Hung C.‐C. , Carson W. G. , Bohan S. P.
Published: April 2003

The miscibility of polycarbonate (PC) with poly(methyl methacrylate‐co‐cyclohexyl methacrylate) (PMCHM) and with poly(methyl methacrylate) (PMMA) was studied by nuclear magnetic resonance (NMR) 1H spin‐lattice relaxation time in the rotating frame (1H T1p), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). A blend of PC/PMCHM (50/50 wt/wt) with the acrylic component PMCHM, a copolymer of PMMA and poly(cyclohexyl methacrylate) (80/20 wt/wt), shows only one T1p value, which indicates high miscibility in this blend. A blend of PC/PMMA (50/50 wt/wt) shows two 1H T1p values, which are similar to those of the homopolymers PC and PMMA. These results indicate high immiscibility. The “domain size” calculated from NMR results of the miscible blend PC/PMCHM is approximately 40 Å. The results of DSC and TEM are similar to the NMR results. However, TEM results show the presence of 3% PC domains in the PC/PMCHM blend, which are not seen by NMR or DSC. Those PC domains are approximately 500 Å. A strong intramolecular repulsion in the copolymer PMCHM and specific intermolecular interactions between PC and PMMA may explain the miscibility in the PC/PMCHM system. © 1994 John Wiley & Sons, Inc.
Infrared spectroscopic studies of CO2 sorbed in glassy and rubbery polymeric membranes
Authors: Higuchi Akon , Nakagawa Tsutomu
Published: April 2003

Infrared spectra of CO2 sorbed in rubbery and glassy polymers were measured to examine the relationships between the spectroscopic data and physical properties of the polymeric membranes. The “V‐shape” tendency in the plot of W1 [i.e., half‐width of CO2 peak sorbed in the membranes] vs glass‐transition temperature (Tg) is observed, and has exactly the same tendency that is widely known from the plot of log D (diffusion coefficient) vs Tg. It is suggested that the membranes having a wider W1 give a faster diffusion coefficient, since W1 is inversely related to the moment of inertia of CO2 in the membranes. Two distinct peaks of CO2 were not observed in the infrared spectra of CO2 sorbed in the glassy polymers. This suggests that the states of CO2 in the Henry mode and Langmuir mode in the glassy polymers are similar in the spectroscopic measurements. © 1994 John Wiley & Sons, Inc.
Phase behavior, morphology, and mechanical properties of polyethylene‐copolymer blends
Authors: Rhee J. , Crist B.
Published: April 2003

Binary blends of unbranched polyethylene (PE) and 5‐10% model ethylene‐butene random copolymers are used to determine the effects of composition heterogeneity on phase separation in the melt, semicrystalline morphology, plane strain fracture toughness JC and tensile modulus and yield strength. Slowly cooled samples of melt‐miscible blends are appreciably tougher (JC = 5.2 kJ/m2) than unblended PE (JC = 2.7 kJ/m2). A blend with the same average short chain branch concentration, but which is phase separated in the melt state, has JC= 3.3 kJ/m2; dispersed domains of amorphous polymer have little effect on toughness. Enhanced toughness is associated with nonuniform morphology formed on slow cooling “one phase” melts composed of chains with different amounts of branching. The relative number of chemically different chains, as opposed to absolute branch concentrations, seems most important. Tensile properties are relatively unaffected by blending at these levels. Results from these model blends are used to consider the properties of compositionally heterogeneous ethylene copolymers. © 1994 John Wiley & Sons, Inc.
Association of hydrophobic counterions in aqueous solution of poly(allylammonium) chloride: Comparison between p‐n‐propylbenzenesulfonate and p‐iso‐propylbenzenesulfonate ions
Authors: Itaya Tomoyuki , Ochiai Hiroshi , Aoyama Tsuyoshi , Ueda Kazuyoshi , Imamura Akira
Published: April 2003

The hydrophobic association behavior of p‐propylbenzenesulfonate ions (n‐PBS− and iso‐PBS−) around poly(allylammonium) cation (PAAH+ was studied by absorption and 1H nuclear magnetic resonance (NMR) spectroscopy. In the presence of PAAH+Cl−, the broadening (hypochromism) of absorption band of PBS− were observed. In addition, all 1H NMR signals of PBS− exhibited up‐field shift which resulted from the intermolecular ring current shift. These results indicate the hydrophobic association of negative PBS− around PAAH+. The hydrophobic association arises from the accumulation of counterions around the polyion, and is stabilized by the hydrophobic interaction between propyl groups and the stacking interaction between benzene rings. The association of iso‐PBS− ions is rather weaker than that of n‐PBS−, suggesting that the steric hindrance of isopropyl groups prevents an effective association of hydrophobic counterions. Furthermore, through viscosity and Cl− activity measurements, it was found that the binding of associated PBS−,s to PAAH+ causes the change of its surroundings to hydrophobic character and its conformation. © 1994 John Wiley & Sons, Inc.
Refractive index and nonlinear optical properties of polyaniline derivatives
Authors: Chen Wen‐Chang , Jenekhe Samson A. , Meth Jeffrey S. , Vanherzeele Hermann
Published: April 2003

An investigation of the refractive index and third‐order nonlinear optical susceptibility χ(3)of two polypernigraniline derivatives, poly (4,4'‐diphenylimine methine) (PDPIM) and poly (4,4'‐diphenylimine p‐heptyloxybenzylidene) (PDPIHB) reveals effects of molecular structure on the linear optical and nonlinear optical properties of conjugated polymers. The χ(3)(−3ωω,ω,ω) of PDPIM was found to decrease relative to polypernigraniline, reflecting the observed decrease of the oscillator strength of the 2.2 eV absorption band when a methine carbon replaces one of the nitrogen atoms of pernigraniline repeat unti. The alkoxyphenylene side group substitution at the methine carbon in PDPIHB, however, significantly enhances the nonlinear optical response of PDPIHB while reducing the refractive index compared to PDPIM and polypernigraniline. The present results suggest that structural changes in conjugated polymers can be made in such a way as to enhance the nonlinear optical properties while modulating the linear optical properties. © 1994 John Wiley & Sons, Inc.