bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure–property relationship and influences of phenolic compounds on the mechanical and thermomechanical properties of UV‐cured acrylic resin networks
Authors: Yin S. , Merlin A. , Pizzi A. , Deglise X. , George B. , Sylla M. 
Published: March 2004

AbstractTrimethylolpropane triacrylate (TMPTA) resin was cured under UV radiation, with 2,2‐dimethoxy‐2‐phenylacetophenon (DMPA) and a mixture of benzophenone and methyl‐diethanolamine (BP/MDEA) as initiators and three phenolic compounds as inhibitors, respectively. For each formulation, the curing enthalpy was measured by photocalorimetry and the modulus of elasticity (MOE) of cured resin films by thermomechanical analysis. The DMPA resulted in networks with higher rigidity that was slightly reduced by the addition of a phenolic compound; while the networks were more flexible and the effects in reducing the MOE by the phenols were much more pronounced when the BP/MDEA was used as an initiator. For the three phenolic compounds, their importance in reducing the MOE can be ranked in the order of eugenol > dimethoxyphenol > phenol. Three equations are proposed to model the structure–property relationship of TMPTA networks. These models suggest that 1) the MOE increases with the crosslinking density, which is proportional to the conversion degree to a power of about 1/3, indicating that cyclization becomes progressively more important as the photopolymerization advances; 2) the decrease of the MOE with temperature is mainly due to relaxation of pending chains and chain segments, and the activation energy needed to overcome such an energy barrier is greater for a less crosslinked network than for a more crosslinked one; and 3) the overall contribution of the crosslinking and the interactions between pending chains (secondary forces) can be expressed by a simple equation in which the network rigidity (MOE) is a function of the degree of conversion, the activation energy and the temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3499–3507, 2004
Step‐strain stress relaxation of carbon black‐loaded natural rubber vulcanizates
Authors: Madkour Tarek M. 
Published: March 2004

AbstractStep‐strain stress relaxation experiments were performed on natural rubber vulcanizates of various carbon black (HAF) concentrations by subjecting the samples to a very rapid strain and fixing its length at the deformed state. Time–temperature superposition in the viscoelastic region was evaluated to investigate the effect of temperature on the relaxation times of the rubbery composites. Remarkably, it was observed that, at higher HAF concentrations, increasing the temperature had a lesser effect on decreasing the overall stress values. That was attributed to the lower number of elastomeric chains per unit volume due to the agglomeration of the carbon black particles. The energy barrier resulting from the adsorption of the rubbery chains on the filler particles was insufficient to drastically reduce the diffusion and rearrangement of the polymer chains. The activation energy of the rubber‐like deformation calculated from the time–temperature superposition was shown to be independent of temperature. Interestingly, the viscosity coefficients showed a large increase with a modest addition of the carbon black. This is due to the long‐range nature of the temporary bonds formed between the polymer molecules and the surface‐active carbon black. The stress–strain of the rubbery composites was shown to behave in a Gaussian manner in accordance with the Mooney–Rivlin relationship. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3387–3393, 2004
Compatibility of poly(butadiene‐co‐acrylonitrile) with poly(L‐lactide) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)
Authors: Park Eun‐Soo , Kim Hye Kyung , Shim Jae Hun , Kim Hun Sik , Jang Lee Wook , Yoon Jin‐San 
Published: March 2004

AbstractPoly(L‐lactide) (PLLA) and poly(3‐hydrobutyrate‐co‐3‐hydroxyvalerate) (PHBV) were blended with poly(butadiene‐co‐acrylonitrile) (NBR). Both PLLA/NBR and PHBV/NBR blends exhibited higher tensile properties as the content of acrylonitrile unit (AN) of NBR increased from 22 to 50 wt %. However, two separate glass transition temperatures (Tg) appeared in PLLA/NBR blends irrespective of the content of NBR, revealing that PLLA was incompatible with NBR. In contrast, a single Tg, which shifted along with the blend composition, was observed for PHBV/NBR50 blends. Moreover NBR50 suppressed the crystallization of PHBV, indicating that PHBV was compatible with NBR50. Decrease of both elongation modulus and stress at maximum load was less significant and increase of elongation at break was more pronounced in PHBV/NBR50 blends than in PLLA/NBR50 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3508–3513, 2004
Distinct composite structure and properties of Eu(phen)2Cl3(H2O)2 in poly(methyl methacrylate) and polyvinylpyrrolidone
Authors: Liu Hong‐Guo , Lee Yong‐Ill , Qin Wei‐Ping , Jang Kiwan , Kim Sangsu , Feng Xu‐Sheng 
Published: March 2004

AbstractThe luminescent europium complex Eu(phen)2 Cl3(H2O)2 (phen refers to 1,10‐phenanthroline) was doped in poly(methyl methacrylate) (PMMA) and polyvinylpyrrolidone (PVP), respectively. The formed composite systems with different molar ratios of CO groups in polymers and Eu ions were characterized by X‐ray diffractometry (XRD), FTIR, and photoluminescent (PL) spectroscopy and lifetime measurement. The XRD diffractograms show that the composites of PMMA/Eu(phen)2Cl3(H2O)2 and PVP/Eu (phen)2Cl3(H2O)2 have crystalline and amorphous structures, respectively, arising from different interactions between the polymers and the complex, as revealed by FTIR spectra. This leads to distinct luminescent characteristics arising from the 5D0→7FJ transitions of Eu(III) ion (J = 0–4). For the composite systems of PMMA/complex, the characteristics of the emission lines change with decreasing molar ratios of CO/Eu and approach that of the pure complex; whereas the composite systems of PVP/complex have similar spectral features, regardless of the molar ratios, differing from that of the pure complex. The polymer matrices have a substantial influence on the structure and properties of the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3524–3530, 2004
Use of epoxidized rubber seed oil as a coupling agent and a plasticizer in silica‐filled natural rubber compounds
Authors: Joseph Reethamma , Alex Rosamma , Madhusoodanan K. N. , Premalatha C. K. , Kuriakose Baby 
Published: March 2004

AbstractTo obtain good reinforcement by silica filler in nonpolar rubbers, it is almost essential to use coupling agents, such as bis(triethoxy silyl propyl) tetrasulfane (TESPT). Chemicals that can interact with the silanol groups on the silica particles and reduce their network formation are also expected to enhance reinforcement. We made a comparative evaluation of TESPT, epoxidized rubber seed oil (ERSO), and their combination as a coupling agent and a plasticizer in silica‐filled natural rubber compounds. The results indicate that compounds containing ERSO showed physical and mechanical properties between that of TESPT and naphthenic oil. The action of ERSO in the improvement of the properties was expected to be bifunctional and similar to that of TESPT; that is, it caused the hydrophobation of silica, which increased its degree of dispersion and the formation of chemical bonds with the rubber, thereby ensuring strong polymer–filler interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3531–3536, 2004
Preparation and properties of polyimide–clay nanocomposite materials for anticorrosion application
Authors: Yu Yuan‐Hsiang , Yeh Jui‐Ming , Liou Shir‐Joe , Chen Chi‐Lun , Liaw Der‐Jang , Lu Hsin‐Yi 
Published: March 2004

AbstractA series of polymer–clay nanocomposite (PCN) materials that consist of organosoluble polyimide and layered montmorillonite clay were prepared by the solution dispersion technique. The organosoluble polyimide containing non‐coplanar moiety in diamine monomer and flexible bridging linkages in dianhydride monomer was synthesized by chemical imidization. The as‐synthesized PCN materials were characterized by infrared spectroscopy, wide‐angle powder X‐ray diffraction, and transmission electron microscopy. The organosoluble polyimide showed better corrosion resistance compared to polyaniline, poly(o‐ethoxyaniline) and poly(methyl methacrylate) by using a series of standard electrochemical corrosion measurements of corrosion potential, polarization resistance, and corrosion current in 5 wt % aqueous NaCl electrolyte. Polyimide–clay nanocomposite materials incorporated with low loading of clay were found to further improve corrosion inhibition over pure polyimide. Effects of the material composition on the O2/H2O molecular permeability, optical clarity, and thermal properties of polyimide–clay nanocomposite materials were studied by molecular permeability analysis, UV–visible transmission spectra, thermogravimetric analysis, and differential scanning calorimetry, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3573–3582, 2004
Theoretical morphology of developmental asymmetries
Authors: Rasskin‐Gutman Diego , Izpisúa‐Belmonte Juan Carlos 
Published: March 2004

AbstractMorphospaces are theoretical tools to explore the morphological organization of living and fossil organisms. They have been used mostly by the paleontological community in an effort to get the most out of one of the only pieces of evidence that fossil material usually provide: the morphology of hard parts. The expectation with the establishment of theoretical morphospaces is that, by abstracting and modeling the fundamental parts of form, the multiple processes that generate the phenotypes of embryonic and adult structures will be better understood. In this essay, we suggest that ontogenetic trajectories can be used as the generative functions that build morphospaces, and propose approaches to build theoretical models for the establishment of left–right asymmetries during vertebrate heart embryogenesis. BioEssays 26:405–412, 2004. © 2004 Wiley Periodicals, Inc.
Kinetic proofreading by the cavity system of myoglobin: protection from poisoning
Authors: Radding Wilson , Phillips George N. 
Published: March 2004

AbstractThroughout its matrix of atoms, myoglobin has a network of cavities that are inhabited for short lengths of time by ligands released by photolysis from the myoglobin heme. The purpose or effect of this cavity network is not clear. A recently published kinetic scheme that fits data from many native and mutant myoglobin oxygen photolysis experiments can be modified easily into a kinetic scheme that includes kinetic proofreading. Proofreading would provide protection against contaminants and, specifically, might help protect the cell from carbon monoxide poisoning. Here we present a two‐part model: (1) myoglobin represented by a kinetic description, which includes proofreading reactions associated with the cavities, and (2) a reaction–diffusion description of a myocyte model in which the part 1 myoglobin acts as a mobile buffer in simultaneous carbon monoxide and oxygen gradients. The non‐equilibrium nature of part 2 should promote the proofreading function of part 1. A simulation using the model demonstrates that the cavity system can in principle proofread, reducing mitochondrial enzyme contamination. BioEssays 26:422–433, 2004. © 2004 Wiley Periodicals, Inc.
Synaptophysin: leading actor or walk‐on role in synaptic vesicle exocytosis?
Authors: Valtorta Flavia , Pennuto Maria , Bonanomi Dario , Benfenati Fabio 
Published: March 2004

AbstractSynaptophysin (Syp) was the first synaptic vesicle (SV) protein to be cloned. Since its discovery in 1985, it has been used by us and by many laboratories around the world as an invaluable marker to study the distribution of synapses in the brain and to uncover the basic features of the life cycle of SVs. Although single gene ablation of Syp does not lead to an overt phenotype, a large body of experimental data both in vitro and in vivo indicate that Syp (alone or in association with homologous proteins) is involved in multiple, important aspects of SV exo‐endocytosis, including regulation of SNARE assembly into the fusion core complex, formation of the fusion pore initiating neurotransmitter release, activation of SV endocytosis and SV biogenesis. In this article, we summarise the main results of the studies on Syp carried out by our and other laboratories, and explain why we believe that Syp plays a major role in SV trafficking. BioEssays 26:445–453, 2004. © 2004 Wiley Periodicals, Inc.
The evolutionary origins and significance of vertebrate left–right organisation
Authors: Cooke Jonathan 
Published: March 2004

AbstractIn the last few years, an understanding has emerged of the developmental mechanism for the consistent internal left–right structure, termed situs, that characterises vertebrate anatomy. This involves largely vertebrate‐conserved (i.e. ‘phylotypic’) gene expression cascades that encode ‘leftness’ and ‘rightness’ in appropriate tissues either side of the embryo's midline soon after gastrulation. Recent evidence indicates that the initial, directional symmetry breaking that initiates these cascades utilises mechanisms that are conserved or at least closely related in different vertebrate types. I describe a scenario whereby the capacity for directional modification of an otherwise bilateral body plan can be viewed as an adaptive innovation rather closely connected with vertebrate origins, enabling optimal ‘design’ for very active lifestyles. But an alternative scenario, while retaining the view that situs and indeed other vertebrate functional lateralisations are deeply adaptive, proposes that they originated in the co‐optation of left–right developmental information inherited from a very early stage in metazoan diversification. It is proposed that a remote chordate ancestor lost its original or ‘ur‐bilaterian’ symmetry to pass through an altogether non‐symmetrical stage, and that the vertebrate dorsoventral midline plane is not descended from that original one. I review the considerable evidence in favour of this scenario, and discuss its wider implications for directional asymmetries across the Metazoa. BioEssays 26:413–421, 2004. © 2004 Wiley Periodicals, Inc.
It's time to flower: the genetic control of flowering time
Authors: Putterill Jo , Laurie Rebecca , Macknight Richard 
Published: March 2004

AbstractIn plants, successful sexual reproduction and the ensuing development of seeds and fruits depend on flowering at the right time. This involves coordinating flowering with the appropriate season and with the developmental history of the plant. Genetic and molecular analysis in the small cruciform weed, Arabidopsis, has revealed distinct but linked pathways that are responsible for detecting the major seasonal cues of day length and cold temperature, as well as other local environmental and internal signals. The balance of signals from these pathways is integrated by a common set of genes to determine when flowering occurs. Excitingly, it has been discovered that many of these same genes regulate flowering in other plants, such as rice. This review focuses on recent advances in how three of the signalling pathways (the day‐length, vernalisation and autonomous pathways) function to control flowering. BioEssays 26:363–373, 2004. © 2004 Wiley‐Liss, Inc.
Morphological evolution in sea urchin development: hybrids provide insights into the pace of evolution
Authors: Byrne Maria , Voltzow Janice 
Published: March 2004

AbstractHybridisations between related species with divergent ontogenies can provide insights into the bases for evolutionary change in development. One example of such hybridisations involves sea urchin species that exhibit either standard larval (pluteal) stages or those that develop directly from embryo to adult without an intervening feeding larval stage. In such crosses, pluteal features were found to be restored in fertilisations of the eggs of some direct developing sea urchins (Heliocidaris erythrogramma) with the sperm of closely (Heliocidaris tuberculata) and distantly (Pseudoboletia maculata) related species with feeding larvae. Such results can be argued to support the punctuated equilibrium model—conservation in pluteal regulatory systems and a comparatively rapid switch to direct development in evolution.1,2 Generation of hybrids between distantly related direct developers may, however, indicate evolutionary convergence. The ‘rescue’ of pluteal features by paternal genomes may require maternal factors from H. erythrogramma because the larva of this species has pluteal features. In contrast, pluteal features were not restored in hybridisations with the eggs of Holopneustes purpurescens, which lacks pluteal features. How much of pluteal development can be lost before it cannot be rescued in such crosses? The answer awaits hybridisations among indirect and direct developing sea urchins differing in developmental phenotype, in parallel with investigations of the genetic programs involved. BioEssays 26:343–347, 2004. © 2004 Wiley Periodicals, Inc.
On the stability of different experimental dimeric structures of the SL1 sequence from the genomic RNA of HIV‐1 in solution: A molecular dynamics simulation and electrophoresis study
Authors: Aci S. , Gangneux L. , Paoletti J. , Genest D. 
Published: March 2004

AbstractSL1 is a stem–loop RNA sequence from the genome of HIV‐1 thought to be the initiation site for the dimerization of the retroviral genomic RNA. The aim of this study is to check the stability in solution of different experimental dimeric structures available in the literature. Two kinds of dimer have been evidenced: an extended duplex looking like a double helix with two internal bulges and a kissing complex in which the monomers with a stem/loop conformation are linked by intermolecular loop–loop interactions. Two divergent experimental structures of the kissing complex from the Lai isolate are reported in the literature, one obtained from NMR (Mujeeb et al., Nature Structural Biology, 1998, Vol. 5, pp. 432–436) and the other one from x‐ray crystallography (Ennifar et al., Nature Structural Biology, 2001, Vol. 8, pp. 1064–1068). A crystallographic structure of the Mal isolate was also reported (Ennifar et al., Nature Structure Biology, 2001, Vol. 8, pp. 1064–1068). Concerning the extended duplex, a NMR structure is available for Lai (Girard et al., Journal of Biomolecular Structure and Dynamics, 1999, Vol. 16, pp. 1145–1157) and a crystallographic structure for Mal (Ennifar et al., Structure, 1999, Vol. 7, pp. 1439–1449). Using a molecular dynamics technique, all these experimental structures have been simulated in solution with explicit water and counterions. We show that both extended duplex structures are stable. On the contrary, the crystallographic structures of the Lai and Mal kissing complexes are rapidly destabilized in aqueous environment. Finally, the NMR structure of the Lai loop–loop kissing complex remains globally stable over a 20 ns MD simulation, although large rearrangements occur at the level of the stem/loop junctions that are flexible, as shown from free energy calculations. These results are compared to electrophoresis experiments on dimer formation. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Methanol induction optimization for scFv antibody fragment production in Pichia pastoris
Authors: Cunha A. E. , Clemente J. J. , Gomes R. , Pinto F. , Thomaz M. , Miranda S. , Pinto R. , Moosmayer D. , Donner P. , Carrondo M. J. T. 
Published: March 2004

AbstractFibronectin splice variant ED B (extracellular domain B) is a promising marker for angiogenesis in growing solid tumors. Currently, recombinant antibodies against ED B are being investigated concerning their potential use, for either therapeutic or diagnostic purposes. Single‐chain antibody fragments directed against the ED B can be efficiently expressed in Pichia pastoris; thus, a recombinant strain of the methylotropic yeast P. pastoris was used for this work. Three different forms of scFv antibody fragment are found in the supernatant from this fermentation: covalent homodimer, associative homodimer, and monomer. Both homodimeric forms can be converted to the monomeric form (under reducing conditions) and be efficiently radiolabeled, whereas the monomeric form of scFv already present in the supernatant cannot. It was also found that the fraction of protein in the monomeric form is highly dependent on the mode of induction rather than scFv concentration. This suggests that the monomeric form of the scFv present in the supernatant might be a result of events occurring at the expression, secretion, or folding level. A high cell density fermentation protocol was developed by optimizing methanol induction, yielding the highest scFv antibody fragment production rate and product quality; cell concentration at the induction point and specific methanol uptake rate were found to be the most important control variables. A decrease in specific methanol uptake rate led to a higher specific production rate for the scFv antibody fragment (5.4 μg gcell h−1). Product quality, i.e., percentage of product in a homodimeric form, also increased with the decrease in methanol uptake rate. Furthermore, the volumetric productivity depended on cell concentration at the induction point, increasing with the increase of cell concentration up to 320 g L−1 wet cell weight (WCW). The reduction of the methanol feeding rate for induction, and consequently of the oxygen uptake rate, have important consequences for optimizing product titers and quality and thus on the scale‐up of this production process; hence one of the major limitations upon high cell density cultivation in bioreactors is keeping the high oxygen transfer rate required. From the results obtained, a scale‐up strategy was developed based on the available oxygen transfer rates at larger scales, allowing the definition of the optimum biomass concentration for induction and methanol feeding strategy for maximization of product titer and quality. © 2004 Wiley Periodicals, Inc.
Combined discrete particle and continuum model predicting solid‐state fermentation in a drum fermentor
Authors: Schutyser M. A. I. , Briels W. J. , Boom R. M. , Rinzema A. 
Published: March 2004

AbstractThe development of mathematical models facilitates industrial (large‐scale) application of solid‐state fermentation (SSF). In this study, a two‐phase model of a drum fermentor is developed that consists of a discrete particle model (solid phase) and a continuum model (gas phase). The continuum model describes the distribution of air in the bed injected via an aeration pipe. The discrete particle model describes the solid phase. In previous work, mixing during SSF was predicted with the discrete particle model, although mixing simulations were not carried out in the current work. Heat and mass transfer between the two phases and biomass growth were implemented in the two‐phase model. Validation experiments were conducted in a 28‐dm3 drum fermentor. In this fermentor, sufficient aeration was provided to control the temperatures near the optimum value for growth during the first 45–50 hours. Several simulations were also conducted for different fermentor scales. Forced aeration via a single pipe in the drum fermentors did not provide homogeneous cooling in the substrate bed. Due to large temperature gradients, biomass yield decreased severely with increasing size of the fermentor. Improvement of air distribution would be required to avoid the need for frequent mixing events, during which growth is hampered. From these results, it was concluded that the two‐phase model developed is a powerful tool to investigate design and scale‐up of aerated (mixed) SSF fermentors. © 2004 Wiley Periodicals, Inc.