bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of environmental temperature on composition of lipids in edible flesh of rainbow trout (Oncorhynchus mykiss)
Authors: Calabretti Antonella , Cateni Francesca , Procida Giuseppe , Favretto Luciana Gabrielli 
Published: October 2003

AbstractThe adaptative changes in the fatty acid composition of the main lipid classes in rainbow trout (Oncorhynchus mykiss) edible flesh in response to environmental variation in water temperature were investigated. The research was carried out on intensively farmed trout sampled at different times of the year. Neutral lipids (NL), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were separated using flash chromatography. Compared with summer acclimatisation, a decrease in neutral lipids of about 19% was observed in winter, accompanied by increases in phosphatidylethanolamine and phosphatidylcholine of about 41 and 29%, respectively. The metabolic adjustment in cold adaptation caused an increase in the levels of unsaturated fatty acids and monoenes of the oleic acid ω9 family and an increase in the levels of unsaturated fatty acids of the linoleic acid ω3 family. At the same time a reduction in the levels of saturated and monounsaturated fatty acids of the oleic acid ω9 family was observed. This pattern turned out to be particularly evident in phosphatidylcholine. The net result of these changes in composition was a significant increase in the polyunsaturated/saturated and polyunsaturated/monoenic fatty acid ratios in the edible flesh. Copyright © 2003 Society of Chemical Industry
Antioxidant efficiency of oregano during frying and storage of potato chips
Authors: Houhoula Dimitra P , Oreopoulou Vassiliki , Tzia Constantina 
Published: October 2003

AbstractThe effect of oregano on the oxidative stability of cottonseed oil during frying of potato chips and on the storage stability of the produced chips was studied. The ground spice or an ethanol‐derived extract thereof was added to the oil at a concentration of 2 g l−1 (dry basis) before frying. The results showed that both ground oregano and its ethanol‐derived extract decreased the rates of accumulation of conjugated dienes, polar compounds, polymerised triglycerides, dimeric triglycerides as well as p‐anisidine value (p‐AV) of the frying oil. The major decrease was observed in the accumulation of polymerised and dimeric triglycerides. The accumulation of oxidised triglycerides showed a low decrease with the addition of oregano, while the hydrolytic compounds formed during frying were not affected. No significant difference (at 95% significance level) between ground oregano and its ethanol‐derived extract was observed. The storage stability of potato chips removed from the fryer at various time intervals was estimated by the rates of increase in peroxide value and conjugated dienes of the oil absorbed in the chips. Both rates were depressed when oregano was added to the frying oil; the protective action of oregano extract was considerably greater (at 95% significance level) than that of ground oregano. Copyright © 2003 Society of Chemical Industry
Phenolic compound contents in edible parts of broccoli inflorescences after domestic cooking
Authors: Vallejo F , Tomás‐Barberán FA , García‐Viguera C 
Published: October 2003

AbstractTotal flavonoid and individual hydroxycinnamoyl derivative (sinapic and caffeoyl‐quinic acid derivative) contents were evaluated in the edible portions of freshly harvested broccoli (cv Marathon inflorescences) before and after cooking and in the cooking water. High‐pressure boiling, low‐pressure boiling (conventional), steaming and microwaving were the four domestic cooking processes used in this work. The predominant sinapic acid derivatives were identified as 1,2,2′‐trisinapoylgentiobiose and 1,2′‐disinapoyl‐2‐feruloylgentiobiose. In addition 1,2‐diferuloylgentiobiose and 1‐sinapoyl‐2,2′‐diferuloylgentiobiose were also identified in broccoli inflorescences. The results showed large differences among the four treatments in their influence on flavonoid and hydroxycinnamoyl derivative contents in broccoli. Clear disadvantages were detected when broccoli was microwaved, namely high losses of flavonoids (97%), sinapic acid derivatives (74%) and caffeoyl‐quinic acid derivatives (87%). Conventional boiling led to a significant loss of flavonoids (66%) from fresh raw broccoli, while high‐pressure boiling caused considerable leaching (47%) of caffeoyl‐quinic acid derivatives into the cooking water. On the other hand, steaming had minimal effects, in terms of loss, on both flavonoid and hydroxycinnamoyl derivative contents. Therefore we can conclude that a greater quantity of phenolic compounds will be provided by consumption of steamed broccoli as compared with broccoli prepared by other cooking processes. Copyright © 2003 Society of Chemical Industry
Effect of nitrogen fertiliser rates and defoliation regimes on the vertical structure and composition (crude protein content and digestibility) of a grass sward
Authors: Duru M 
Published: October 2003

AbstractThe vertical sward structure (proportions of lamina and sheath) and sward composition (crude protein and digestibility) have an effect on animal behaviour and performance, but their variation through management is not well known. We studied the effect of defoliation regime and nitrogen supply on these sward characteristics. There were six treatments, two nitrogen fertiliser rates combined with three defoliation regimes. Two of the latter mimicked a long growth duration (up to 7 weeks) and one mimicked a short period of regrowth (2 weeks). The swards were cut 7 cm from ground level. We found that there was a single relationship between sheath length and sward height, regardless of treatment and sampling date. For the treatments which mimicked a long growth duration, crude protein and digestibility decreased linearly from the top to the base of the sward when these decreases were expressed per unit of herbage mass. Conversely, for the treatments which mimicked a short growth duration, crude protein and digestibility fell quickly between the upper layers and those close to the ground. This discontinuity was the result of a smaller number of laminae per tiller than for the other treatments, whereas the composition of the sheath was the same. For resting periods longer than 20 days a model was proposed to simulate the effect of sward defoliation depth on the chemical composition of the diet selected by grazing animals according to available herbage mass before and during grazing. From a practical point of view the sward height alone could not be used to predict the sward composition from the top to the base of the sward and its effect on diet selection by grazers. The length of the resting period needs to be known in addition to the residual sward height. Copyright © 2003 Society of Chemical Industry
Lipase‐catalysed biosynthesis of hexyl butyrate by direct esterification: optimisation by response surface methodology
Authors: Shaw Jei‐Fu , Chang Shu‐Wei , Liao Hui‐Fen , Shieh Chwen‐Jen 
Published: October 2003

AbstractThe ability of immobilised lipase from Rhizomucor miehei (Lipozyme IM‐77) to catalyse the direct esterification of hexanol and butyric acid was investigated. Response surface methodology (RSM) and a four‐factor/five‐level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters such as reaction time (2–10 h), temperature (25–65 °C), substrate molar ratio of hexanol to butyric acid (1:1–3:1) and enzyme amount (10–50%; 0.24–1.18 BAUN) on the percentage molar conversion of hexyl butyrate by direct esterification. All the parameters had significant effects on the percentage molar conversion. Based on ridge maximum analysis, the optimal conditions for synthesis were: reaction time 8.0 h, temperature 46.9 °C, substrate molar ratio 1:1.2 and enzyme amount 36.4% (0.87 BAUN). The predicted value was 100% and the actual experimental value 98.2% molar conversion. Copyright © 2003 Society of Chemical Industry
Blanching and long‐term freezing affect various bioactive compounds of vegetables in different ways
Authors: Puupponen‐Pimiä Riitta , Häkkinen Suvi T , Aarni Marjukka , Suortti Tapani , Lampi Anna‐Maija , Eurola Merja , Piironen Vieno , Nuutila Anna Maria , Oksman‐Caldentey Kirsi‐Marja 
Published: October 2003

AbstractAn extensive study on the effects of blanching/freezing and long‐term freezer storage on various bioactive compounds of more than 20 commonly used vegetables was performed. Effects were strongly plant species‐dependent. Contents of dietary fibre components either were not affected or increased slightly. Minerals in general were also stable, but some losses of soluble minerals by leaching were observed. Phenolic antioxidants and vitamins were clearly more sensitive. Significant losses (20–30%) of antioxidant activity and total phenolics were detected in many vegetables. A qualitative HPLC profiling method for phenolic antioxidants was developed which proved to be very useful when evaluating the complex behaviour of phenolics during food processing. Up to one‐third of vitamin C contents were lost during blanching, and further slight losses were detected during storage. Folic acid turned out to be very sensitive to blanching, with more than half of the vitamin being lost, but was stable during freezer storage. Carotenoids and sterols were not affected by blanching or freezer storage. The usefulness of the applied screening methods for evaluation of the effects of processing on vegetables is shown. Copyright © 2003 Society of Chemical Industry
Synthesis of Polyphenylene Ether Derivatives: Estimation of Their Dielectric Constants
Authors: Seike Yuusuke , Okude Yuriko , Iwakura Izumi , Chiba Ikuka , Ikeno Taketo , Yamada Tohru 
Published: October 2003

AbstractA series of poly(2‐alkyl‐6‐phenylphenylene ether)s were prepared by the oxidative polymerization of 2‐alkyl‐6‐phenylphenols. Their dielectric constants were approximately 2.5, whereas it was found that the phenyl group at the 6‐position clearly increased the Q factor of the polymer compared with poly(2,6‐dimethylphenylene ether), PPE. These values were qualitatively predicted from the polarizability and the molar volume calculated by the theoretical analysis of the unit structure at the HF/6‐31G* level.magnified image
Effect of the Structure of Reactor Poly(propylene‐co‐ethylene) Blends on the Diffusion Coefficient and Activation Energy of a Conventional Antioxidant
Authors: Bertoldo Monica , Ciardelli Francesco , Ferrara Giuseppe , Scoponi Marco 
Published: October 2003

AbstractThe diffusion of a thermal stabilizer, i.e., Irganox 1010, has been studied in three different reactor poly(propylene‐co‐ethylene) blends, namely HecoQ, ExpSS, and Super Soft. The diffusion experiments were carried out by using Roe's method based on a stack of several polymer films where each of them had 60–70 μm thickness. The concentration profile of the stabilizer in every film has been monitored by the absorbance at 282 nm of the recorded UV spectra. Under our experimental conditions, the diffusion of Irganox 1010 for all polymer materials can be correctly interpreted by using Fick's second law resolved under certain boundary conditions. Best‐fitting the experimental data with the equation model also allows calculation of the diffusion coefficient, D, for these polymer materials at 40, 70 and 80 °C. By applying an Arrhenius‐type equation to the calculated D coefficients, an estimation of activation energies of the diffusion process has been achieved. An interpretation, in terms of free volume theory, has been applied to explain the observed variation of D which depends mostly on the amount of amorphous phase of the blends.Arrhenius plots of ln D versus 1/(RT) for the polymers given in legend.magnified imageArrhenius plots of ln D versus 1/(RT) for the polymers given in legend.
Regioselective Synthesis and Structures of (+)‐Catechin‐Aldehyde Polycondensates
Authors: Kim Young‐Jin , Chung Joo Eun , Kurisawa Motoichi , Uyama Hiroshi , Kobayashi Shiro 
Published: October 2003

AbstractThe polymerization of (+)‐catechin with various aldehydes has been performed in the presence of an acid catalyst to produce catechin‐aldehyde polycondensates in high yields. NMR analysis of the product showed that the polymerization regioselectively proceeded to form the polymer linked by an ethyl bridge through C‐6 and C‐8 positions of catechin A ring. Specific rotation and CD measurements of the polymer showed the change of chemical bonding and conformation at near chiral center. The direction of specific rotation was changed from dextrorotatory (+) to levorotatory (−) and a new chiral center was formed on the bridge moiety between the catechin units. Computer simulation suggests the coiled interactions in the polymer by hydrogen bonds between hydroxyl groups and pyranic oxygens.
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Mechanical and Chemical Analysis of Gelatin‐Based Hydrogel Degradation
Authors: Martínez‐Díaz Gabriel J. , Nelson Darceé , Crone Wendy C. , Kao Weiyuan John 
Published: October 2003

AbstractThe interrelated effect of environmental pH and temperature, gelatin backbone modification and content on the tensile and degradative property of interpenetrating networks (IPNs) containing gelatin and poly(ethylene glycol) diacrylate (PEGdA) was examined. Either increasing the PEGdA content or modifying the gelatin backbone with PEG‐monoacetate ester and/or polyanions decreased the IPN elasticity at ambient room temperature (rt). Under an aqueous environment of varying pH levels and elevated temperature, the degradation of IPN tensile properties was further accelerated. IPNs showed an enhanced elasticity and strength when compared to glutaraldehyde‐fixed gelatin hydrogels. Under an aqueous condition, IPNs showed a wider range of degradation products than hydrogels cross‐linked with glutaraldehyde, as characterized with gel permeation chromatography. The nature of IPN degradation products was independent of the type of gelatin backbone modification. The presence of loaded drug, chlorohexidine digluconate, which was found to interact with PEG‐monoacetate esters of the modified gelatin backbone, resulted in unique degradation products. The tensile and chemical degradation of IPNs is a complex interrelationship of the environmental condition, time, and material modification.Stress‐strain curves of some IPNs studied here.magnified imageStress‐strain curves of some IPNs studied here.
Syntheses and Characterization of Luminescent Polymers Containing Rhenium(I) Pyridinyl‐Carbonyl Complexes
Authors: Bignozzi Carlo A. , Ferri Violetta , Scoponi Marco 
Published: October 2003

AbstractThe syntheses of methacrylate‐ and styrene‐based monomers containing substituted pyridine ligands are reported. The preparation of the corresponding homopolymers has been performed by free radical polymerization by using 2,2′‐azoisobutyronitrile (AIBN) at 60 °C. The high molecular weights, up to 119 000 g · mol−1, and low glass transition (Tg) values (< −43 °C) have been obtained by the copolymerization reaction with butyl acrylate. The free metal homopolymer and copolymer were subsequently metalated by reaction with Re[phen(CO)3(acetone)]+. All polymer materials have been characterized by conventional experimental techniques, such as gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). UV‐Vis and fluorescence spectroscopy have been used to investigate the optical and photophysical properties of the polymers in solid‐state films and in solution. 1H NMR spectra confirmed the structure of the synthesized polymers and contributed to the estimate of the monomer sequences in the copolymer chains. Time‐resolved and emission‐quenching experiments in diluted solutions and on the solid films suggest application of the polymeric materials as oxygen sensors. The morphological aspects of some polymers containing a low amount of rhenium metal complexes have been investigated by scanning electron microscopy (SEM).One of the Re complex‐containing copolymers synthesized here.magnified imageOne of the Re complex‐containing copolymers synthesized here.
Crystal Growth in Poly(L‐lactide) Thin Film Revealed by in situ Atomic Force Microscopy
Authors: Kikkawa Yoshihiro , Abe Hideki , Fujita Masahiro , Iwata Tadahisa , Inoue Yoshio , Doi Yoshiharu 
Published: October 2003

AbstractDirect visualization of crystal growth in poly(L‐lactide) thin films was carried out by using a temperature‐controlled atomic force microscopy (AFM). At the initial stage of crystallization, edge‐on lamellar crystals have nucleated and elongated. Subsequently, the edge‐on lamellar crystals showed S‐shaped morphology and changed their orientation from edge‐on manner to flat‐on one. The curvature of edge‐on lamellar crystal has been discussed in terms of inclination and distortion of polymer chains in the crystal. In addition, mechanism on the formation of flat‐on crystal from edge‐on lamellae was proposed as derivative growth on the basis of in situ AFM observation of crystal growth and enzymatic degradation.
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Functionalisation of Polyolefins: Grafting of Phenol Groups on Olefin/5,7‐Dimethylocta‐1,6‐diene Copolymers
Authors: Dolatkhani Marc , Cramail Henri , Deffieux Alain , Santos Jorge Moniz , Ribeiro Maria Rosário , Bordado João M. 
Published: October 2003

AbstractThe grafting of phenol groups on ethylene/5,7‐dimethylocta‐1,6‐diene copolymers and on ethylene/propylene/5,7‐dimethylocta‐1,6‐diene terpolymers was performed, using two different modification procedures. An indirect route involving hydrochlorination followed by phenol insertion was found to be very effective for the terpolymers, and lead to a grafting phenol rate higher than 75%. However, if the phenol grafting is performed directly on a non‐modified terpolymer, lower rates are obtained. When applied to the copolymers the procedures used were revealed to be less efficient. This fact might be related to the lower solubility of the ethylene/5,7‐dimethylocta‐1,6‐diene copolymers (related to a higher crystallinity and a smaller diene content) when compared with the corresponding terpolymers. Although incomplete, the addition of a hindered phenol to the copolymer gave rise to a polymer that, when compared to polyethylene, presents a higher thermal‐oxidative stability.Grafting of phenol on a hydrochlorinated ethylene/propylene/5,7‐DMO terpolymer.magnified imageGrafting of phenol on a hydrochlorinated ethylene/propylene/5,7‐DMO terpolymer.
Enthalpy Relaxation of Layered Silicate‐Epoxy Nanocomposites
Authors: Lu Hongbin , Nutt Steven 
Published: October 2003

AbstractUsing standard and temperature‐modulated differential scanning calorimetry, we have studied the segmental relaxation behavior of montmorillonite‐epoxy nanocomposites. The experimental results showed that the incorporation of clay particles caused the epoxy network to exhibit slower relaxation dynamics compared with the neat epoxy resin. Analysis based on the Tool‐Narayanaswamy‐Moynihan (TNM) model indicated that the nanocomposite systems had greater nonlinearity, higher apparent activation energy, and broader relaxation time distribution than the neat epoxy resin. Further analysis based on the Adam‐Gibbs model indicated that the presence of clay nanoparticles decreased the macroscopic configurational entropy of the epoxy network, and increased the size of the cooperative rearrangement region as well as the fundamental energy barrier. The peculiar relaxation behavior observed in the present experiments was attributed to the confinement effect of nanoparticles on molecular entities during the segmental relaxation. This confinement effect led to a stronger temperature dependence of the relaxation behavior near the glass transition temperature, or greater fragility. An inverse correlation between nonexponentiality and fragility was also observed, which is consistent with the results reported in the literature.The original MDSC curves: complex heat capacity (C_{\rm P}^*) versus temperature; the inset shows the nonexponentiality parameters (β) for all the samples.magnified imageThe original MDSC curves: complex heat capacity (C_{\rm P}^*) versus temperature; the inset shows the nonexponentiality parameters (β) for all the samples.
Reactivities of ω‐Unsaturated Methacrylate Oligomers toward tert‐Butoxy Radicals: Investigation of the Effect of Degree of Polymerization and Ester Alkyl Group
Authors: Sato Eriko , Zetterlund Per B. , Yamada Bunichiro , Busfield W. Ken , Jenkins Ian D. 
Published: October 2003

AbstractThe reactivities of ω‐unsaturated methacrylate oligomers (RMA‐n; n = 2–5) toward tert‐butoxy radicals (t‐BuO·) as a model of the addition step in addition‐fragmentation chain transfer (AFCT) have been investigated by the nitroxide trapping technique in combination with HPLC and electrospray ionization mass spectrometry. The ratio of the rate coefficients for the addition of ω‐unsaturated methyl methacrylate oligomers (MMA‐n) to t‐BuO· to the β‐fragmentation of t‐BuO· (kadd/kβ), where kβ can be treated as a constant, has been shown to decrease with increasing n due to increased steric hindrance of the α‐substituents. However, the value of kadd/kβ reaches a constant value at n = 3–4, and the greatest extent of suppression of the addition rate compared with MMA is less than a factor of four. Comparison of the values of kadd/kβ for ω‐unsaturated cyclohexyl methacrylate oligomers (CHMA‐n; n = 2 and 3) with MMA‐n revealed that the extent of suppression increased with increasing n without regard to the ester alkyl group. Hydrogen abstraction by t‐BuO· from RMA‐n appears to occur mainly at the ester alkyl groups, and the extent is much greater from CHMA‐n than from MMA‐n.
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Novel Route to Immobilize Metallocenes within Silica‐Based Supports: Investigation of a Nonhydrolytic Sol–Gel Process
Authors: Dever Cédric , Deffieux Alain , Cramail Henri , Mastroianni Sergio 
Published: October 2003

AbstractA novel approach to metallocene catalyst heterogenization is presented. Supported metallocenes are obtained by metallation of indenyl‐modified silica produced by a nonhydrolytic sol–gel process. The catalytic activities for ethylene polymerization are rather high for supported systems and may reach 190 grams of polyethylene per gram of catalyst per hour per bar. The influence of the preparation and composition of these supported metallocene systems on ethylene polymerization and polyethylene characteristics are reported.Possible structure of the indenyl‐modified silicas.magnified imagePossible structure of the indenyl‐modified silicas.
Preparation of Binary Conductive Polymer Composites with Very Low Percolation Threshold by Latex Blending
Authors: Hu Ji Wen , Li Ming Wei , Zhang Ming Qiu , Xiao Ding Shu , Cheng Gen Shui , Rong Min Zhi 
Published: October 2003

AbstractThe communication reports a way to prepare carbon black (CB)/waterborne polyurethane conducting composites with percolation thresholds as low as 0.2 vol.‐% through conventional latex blending. CB particles in the composites appear segregated in their distribution and are located in the two‐dimensional interstices among the polymer domains. The intimate filler/matrix interaction also improves the tensile strength of the matrix at the CB content corresponding to the electrical percolation threshold.Room temperature conductivity, σ, and tensile strength as a function of carbon black (CB) concentration of the waterborne‐polyurethane‐based composites prepared by latex blending.magnified imageRoom temperature conductivity, σ, and tensile strength as a function of carbon black (CB) concentration of the waterborne‐polyurethane‐based composites prepared by latex blending.