bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology and properties of isotactic polypropylene modified with hydrocarbon resin MBG273. I. Binary blends
Authors: Cimmino S. , Silvestre C. , della Vecchia G.
Published: March 2004

We investigated a system formed of isotactic polypropylene (iPP) and hydrogenated hydrocarbon resin MBG273 (up to 30 wt % resin) to study the influence of the composition on the morphology, structure, and properties of its blends and derived films. All the blends, after the mixing of the components in the melt and cooling at room temperature, were formed by a crystalline phase of iPP and by one homogeneous phase formed by amorphous iPP and the MBG273 resin. The presence of MBG273 did not influence the crystalline structure of iPP, which remained, for every blend, α‐monoclinic, but it reduced the crystallization temperature and nucleation density of iPP. Differential scanning calorimetry and dynamic mechanical thermal analysis showed an increase in the glass‐transition temperature with the resin content, confirming the formation of one amorphous phase. Tensile property analysis indicated an increase in Young's modulus and a decrease in the elongation at break of films as a function of the resin content in the blends. The water vapor permeability and tensile mechanical properties were related to an increase in the glass transition with the addition of MBG273. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3454–3465, 2004
Rice husk powder–filled polystyrene/styrene butadiene rubber blends
Authors: Zurina M. , Ismail H. , Bakar A. A.
Published: March 2004

Natural fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of large amounts of hydroxyl groups makes natural fibers less attractive for reinforcement of polymeric materials. Composites made from polystyrene (PS)/styrene butadiene rubber (SBR) blend and treated rice husk powder (RHP) were prepared. The RHP was treated by esterification and acetylation. A similar series of composites was also prepared using maleic anhydride–polypropylene (MA–PP) as a coupling agent. The processing behavior, mechanical properties, effect of thermooxidative ageing, and surface morphology of untreated and chemically modified RHP were studied. There was a decrease in tensile strength (except MA–PP composites), elongation at break, and Young's modulus in chemically treated RHP composites. The postreaction process during thermooxidative ageing enhanced the tensile strength and Young's modulus of the esterified and MA–PP composites. Acetylation treatment was effective in reducing the percentage of water absorption in RHP/PS–SBR composites. In general chemically treated RHP/PS–SBR composites and MA–PP showed a better matrix phase and filler distribution. However, the degree of filler–matrix interaction was mainly responsible for the improvement of mechanical properties in the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3320–3332, 2004
Poly(N‐isopropylacrylamide) grafted to a strongly charged backbone: Thermoresponsive behavior in aqueous solution
Authors: Chourdakis N. , Bokias G. , Staikos G.
Published: March 2004

The thermoresponsive properties in aqueous solution of the graft copolymer poly(acrylic acid‐co‐2‐acrylamido‐2‐methyl propane sulfonic acid)‐g‐poly(N‐isopropylacrylamide) [P(AA‐co‐AMPSA)‐g‐PNIPAM] were studied and compared to the corresponding behavior of the poly(acrylic acid)‐g‐poly(N‐isopropylacrylamide) (PAA‐g‐PNIPAM) graft product. Both products contain about 40% (w/w) of PNIPAM, whereas the backbone, P(AA‐co‐AMPSA), of the first copolymer contains about 40% of AMPSA mole units. The strongly charged P(AA‐co‐AMPSA)‐g‐PNIPAM graft copolymer was water soluble over the whole pH range, whereas the PAA‐g‐PNIPAM copolymer precipitated out from water at pH < 4. As a result, the first product exhibited a temperature‐sensitive behavior in a wide pH range, extended in the acidic region, whereas in semidilute aqueous solutions, an important thermothickening behavior was observed, even at low pH (pH = 3.0). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3466–3470, 2004
Synthesis of aliphatic polyesters by a chain‐extending reaction with octamethylcyclotetrasilazane and hexaphenylcyclotrisilazane as chain extenders
Authors: Zhao Jing‐Bo , Wu Xiao‐Feng , Yang Wan‐Tai
Published: March 2004

Aliphatic HO‐terminated polyesters such as poly(diethylene glycol adipate) (PDEGA), poly(ethylene adipate) (PEA), and poly(butylene succinate) (PBS) with molecular weight from 1247 to 1948 were synthesized through condensation polymerization from adipic acid or butanedioic acid with excess diethylene glycol, ethylene glycol, or butylene glycol. From the HO‐terminated polyesters, polyesters with high molecular weight were synthesized by a chain‐extending reaction with octamethylcyclotetrasilazane (OMCT) or hexaphenylcyclotrisilazane (HPCT) as chain‐extenders. Gel permeation chromatography (GPC) characterization shows that the Mn of chain‐extended PDEGA is from 12,644 to 32,870, Mw is from 22,786 to 70,048; Mn of chain‐extended PEA is 11,368, Mw is 19,877; and the Mn of chain‐extended PBS is from 9823 to 39,873, Mw is from 18,823 to 137,192. The chain‐extended polyesters were also characterized by 1H‐NMR spectrum, IR spectra, and DSC spectra. The multiple peaks at 7.37 and 7.67 ppm in the 1H‐NMR spectrum of chain‐extended PDEGA and peaks at 3051.1 and 1593.4 cm−1 in the IR spectrum of the chain‐extended PBS show the evidence of the SiPh2 structure in the polyesters obtained from the chain‐extending reaction. DSC study shows that the bulky SiPh2 units introduced by the chain‐extending reaction lower the regularity of the polyester chains, so the melting point of the chain‐extended PBS and PEA decreases compared to that of the original HO‐terminated PBS and PEA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3333–3337, 2004
Dyeing of wool with antibiotics to develop novel infection resistance materials for extracorporeal end use
Authors: Choi Hyung‐Min , Bide Martin , Phaneuf Matthew , Quist William , LoGerfo Frank
Published: March 2004

Two antibiotics, doxycycline (Doxy) and ciprofloxacin (Cipro), were applied under a variety of conditions to wool and to hydrolyzed wool at 40°C. Nylon was used as a synthetic control. Sorption of Doxy was much higher in wool than in nylon, whereas sorption of Cipro was similar in both fibers. FTIR spectroscopy confirmed that a drastic increase in sorption of antibiotics by hydrolyzed wool was attributed to an increase in polar functional groups by peptide scission and in oxidized sulfur groups by cystine oxidation. Both sorption and zone of inhibition (ZOI) values were improved by hydrolysis of wool. Wool hydrolyzed for 20 or 40 min at 40°C and dyed with Doxy at 45°C for 3.5 h maintained around 30 mm of ZOI after 24 h of challenge by a simulated flow of blood. Wool hydrolyzed for 60 min at 40°C and dyed with Cipro at 45°C for 3.5 h also maintained its antibiotic activity for an extended time. For the most part, ZOI values for nylon dyed by both antibiotics were zero within 24 h. This technique produced infection‐resistant biomaterials of potential use in extra‐corporeal biomedical and biological applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3343–3354, 2004
Binding of methyl orange or ethyl orange dyes by some dioxolane copolymers: Synthesis of the copolymers and thermodynamics of the dye–copolymer interactions
Authors: Ceylan Nilgun Nese , Ilter Zulfiye
Published: March 2004

The extent of binding of methyl orange or ethyl orange by (2‐phenyl‐1,3‐dioxolane‐4‐yl) methyl methacrylate (PDMMA), 2‐hydroxyethyl methacrylate (HEMA), and vinyl‐pyrrolidone (VPy) copolymers has been investigated by the equilibrium dialysis method. The dialysis experiments have been carried out in a Tris (hydroxy methyl) aminomethane buffer (pH = 7) and at the temperatures of 15, 25, and 35°C. The PDMMA‐co‐HEMA and PDMMA‐co‐VPy copolymers have been prepared in the laboratory by using the related monomers in different ratios. The synthesized products were analyzed by Fourier Transform‐infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) spectroscopy, differential thermal analysis (DTA), and differential scanning calorimetry (DSC) techniques. The binding extent of the dyes by the copolymers was determined by ultraviolet (UV) absorbance measurements. The results indicate that the extent of binding is relatively higher for ethyl orange than that for methyl orange under identical conditions. The binding slightly decrease with increasing temperature, and it is accompanied with favorable free energy, and exothermic enthalpy change within the temperature range studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3355–3361, 2004
Determination of monomer reactivity ratios in styrene/2‐ethylhexylacrylate copolymer
Authors: Kavousian A. , Ziaee F. , Nekoomanesh M. H. , Leamen M. J. , Penlidis A.
Published: March 2004

The monomer reactivity ratios for styrene/2‐ethylhexylacrylate in bulk at 80°C were investigated by studying the resulting copolymer composition via 1H‐NMR. Composition results were summarized and various methods were employed to estimate the reactivity ratios including the use of the Error‐in‐Variables‐Model (EVM) approach by using the Mayo–Lewis model. The estimates of the reactivity ratios from the EVM method are found to be rs = 0.979 and rEHA = 0.292. The resulting copolymer has a tendency toward alternation with an azeotrope of f(styrene) = 0.972. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3368–3370, 2004
Enantioselective esterification reaction using immobilized Candida rugosa lipase on poly(N‐vinyl‐2‐pyrrolidone‐co‐styrene) hydrogel
Authors: Harun A. , Basri M. , Ahmad M. B. , Salleh A. B.
Published: March 2004

Lipase from Candida rugosa was immobilized on poly(N‐vinyl‐2‐pyrrolidone‐co‐styrene) hydrogel (poly‐(VP‐co‐ST)) with ethylene dimethacrylate and α,α'‐azoisobutyronitrile, which act as crosslinker and initiator, respectively. Three different compositions of monomers were used, namely VP(%):ST(%), 10:90, 50:50, and 70:30 (wt(%)/wt(%)). The immobilized lipases were used in the enantioselective esterification of (R,S)‐2‐(4‐chlorophenoxy)‐propanoic acid with n‐tetradecanol. The optimum reaction condition of the enantioselective esterification for the native lipase and the poly(VP‐co‐ST) hydrogel immobilized lipases was determined with respect to temperature, solvents, and initial water activity (aw). The optimum temperature obtained was 40°C, with the poly(VP‐co‐ST) hydrogel immobilized lipase VP(%)/ST(%):10:90 showing the highest enantiomeric excess. In the solvent effect studies, the best solvents for high enantioselectivity were chloroform and carbon tetrachloride. In the aw studies, optimum αw for NL, VP(%):ST(%), 10:90, and 50:50 was 0.328, while for VP(%):ST(%), 70:30, it was 0.55. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3381–3386, 2004
Synthesis of novel block copolymers containing polyamide4 segments and control of their biodegradability
Authors: Hashimoto Kazuhiko , Sudo Mie , Sugimura Takayuki , Inagaki Yoshiki
Published: March 2004

Different novel copolymers, ABA‐type block copolymers composed of polyamide4 as outer segments and polyoxyethylene as an inner segment and AB‐ and ABA‐type block copolyamides containing polyamide4 and another hydrophilic polyamide derived from a bicyclic lactam, were synthesized by the anionic ring‐opening polymerization of 2‐pyrrolidone using the corresponding acyllactam‐type macromolecular activators. The degradation rate of both block copolymers containing polyamide4 segments in a composted soil was found to decrease with increasing content of the second segments, although they were also hydrophilic and/or biodegradable. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3492–3498, 2004
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

Trimethylolpropane 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

Step‐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

Poly(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

The 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

To 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

A 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

Morphospaces 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

Throughout 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

Synaptophysin (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

In 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

In 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

Hybridisations 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

SL1 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

Fibronectin 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

The 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.
Making a difference? Bringing children's and young people's views into policy‐making
Authors: Tisdall E. Kay M. , Davis John
Published: March 2004

As the participation of children and young people in policy decision‐making has spread in the UK, participation work is facing hard questions on its translation from principle to effective practice. The participation literature has been largely self‐referential in its consideration of policy influence. This paper considers the potential usefulness of the UK literature on policy networks, which categorises the relationships between government actors and other interests in policy‐making. A brief introduction is given to this literature. Then a participatory project is examined in light of certain key concepts within the policy network literature. The paper concludes by considering how both the participation and the policy networks literature might learn from each other in future conceptual and empirical work.
Participation in practice: making it meaningful, effective and sustainable
Authors: Sinclair Ruth
Published: March 2004

Children's participation in decision‐making is complex: it is undertaken for different purposes and is reflected in different levels of involvement, different contexts and different activities. This paper reviews the current state of participation and, drawing on practice and research literature, highlights several aspects of practice where further consideration is needed if participation is to develop positively. This suggests that, if participation is to be more meaningful to children and effective in influencing change, it is necessary to move beyond one‐off or isolated participation and consider how participation becomes embedded as an integral part of our relationship with children.
Children's participation in the policy process: some thoughts on policy evaluation based on the Irish National Children's Strategy
Authors: Pinkerton John
Published: March 2004

Prompted by Article 12 of the UN Convention on the Rights of the Child, there is a growing number of examples of children and young people being involved in the policy process. To date this had not been matched by evaluation of the practice. This situation needs to change to ensure that existing experience provides learning for more widespread and more effective involvement. Using the development of the Irish National Children's Strategy for illustration, this article argues that the evaluation required must be more than monitoring. There is a need to get below the formal documented surface of participatory initiatives through developing analysis based in a critical perspective on both policy and evaluation.
Children's participation in ethnographic research: Issues of power and representation
Authors: Christensen Pia Haudrup
Published: March 2004

The recognition of children's social agency and active participation in research has significantly changed children's position within the human and social sciences and led to a weakening of taken‐for‐granted assumptions found in more conventional approaches to child research. In order to hear the voices of children in the representation of their own lives it is important to employ research practices such as reflexivity and dialogue. These enable researchers to enter into children's ‘cultures of communication’. Drawing on detailed examples from an ethnographic study on child health and self‐care, the article examines issues of power, voice and representation central to the discussion of children's participation.
Kontinuierliche Nitratreduktion mit immobilisierten Mikroorganismen
Authors: Rathjen A. , Hasch M.
Published: March 2004

No abstracts.
Kinetic Models of Complex Biochemical Reactions and Biological Processes
Authors: Peleg M. , Corradini M. G. , Normand M. D.
Published: March 2004

The momentary rate of complex biochemical reactions and biological processes may depend not only on temperature (or an equivalent factor like pH or moisture contents) but also on the system's momentary state. Also, complex reactions and processes need not have a single ‘energy of activation’ and their ‘kinetic order’ is not always clearly defined. Thus, the progress of such a reaction or process is governed by time dependent kinetics whose description requires a departure from the traditional models, which are based on an analogy to simple chemical reactions. A general model that takes these considerations into account is demonstrated with simulated biochemical reactions under monotonic temperature increase and decrease and under regular and irregular temperature fluctuations. Its potential application to microbial growth and growth followed by decay is also demonstrated. The model is in the form of a cumbersome differential equation, which, nevertheless, can be solved by standard mathematical software. In certain cases, the same software can also be used to determine the process's basic kinetic parameters, and their temperature dependence, from experimental data obtained under non‐isothermal conditions. This could simplify the study of fast reactions and processes, where shortening the come up and cooling times to insignificance, as required by the traditional isothermal analyses, is not a viable option.
Methoden zur Beurteilung des Befeuchtungs‐ und Dispergierverhaltens von Pulvern
Authors: Hogekamp S. , Pohl M.
Published: March 2004

Pulverförmige Produkte müssen in den meisten Fällen vor ihrer endgültigen Verwendung wieder in einer Flüssigkeit dispergiert werden. Idealerweise erlaubt ein Pulver das schnelle Eindringen von Flüssigkeit, sinkt bei Aufgeben auf eine Flüssigkeitsoberfläche schnell ein und kann mit geringem Aufwand dispergiert werden. Reale Pulver zeigen derartig ideales Verhalten häufig nicht, so dass Messverfahren zur Kontrolle ihrer Eigenschaften erforderlich sind. In diesem Artikel werden Verfahren zur Beurteilung des Befeuchtungs‐ und Dispergierverhaltens vorgestellt. Einfache Methoden zur Bestimmung des Befeuchtungsver‐haltens eignen sich vorzugsweise für die Qualitätskontrolle von Produkten. Aufwändigere Verfahren erlauben einen besseren Einblick in das Verhalten eines Produkts und die Bestimmung von Stoffeigenschaften. Die Beschreibung des Dispergierverhaltens eines Produkts erfordert den höchsten experimentellen Aufwand.
Emulgieren: Mehr als nur Zerkleinern
Authors: Schuchmann H. P. , Danner T.
Published: March 2004

Emulsionen begleiten uns als industrielle Zwischenprodukte oder formulierte Produkte für Endverbraucher durch das tägliche Leben. Mikrostrukturell sind Emulsionen disperse Mehrphasensysteme aus mindestens zwei nahezu ineinander unlöslichen Flüssigkeiten. Zur Produktgestaltung müssen Eigenschafts‐ und Prozessfunktionen bekannt sein. In diesem Übersichtsartikel werden die Grundlagen des Emulgierens mit den Teilschritten Tropfenzerkleinerung und Koaleszenz dargestellt, typische Emulgiermaschinen und ‐apparate beschrieben sowie Prozess‐ und Eigenschaftsfunktionen aufgezeigt. Neben praxisrelevanten typischen Anwendungen des Emulgierens wird auch alternativ der Einsatz eines Emulgierschrittes zur Herstellung von feinsten Feststoffen mit modifizierten Produkteigenschaften diskutiert.
Loss of Gli3 and Shh function disrupts olfactory axon trajectories
Authors: Balmer Curtis William , LaMantia Anthony‐Samuel
Published: March 2004

The transcriptional regulator Gli3 and the secreted signal Shh influence induction, patterning, and differentiation at several sites of mesenchymal/epithelial (M/E) interaction including the limbs, heart, face, and forebrain. We asked whether loss of function of these two genes has specific consequences for early differentiation of the primary olfactory pathway—which comprises both craniofacial and forebrain structures and depends on M/E induction during initial stages of development. Loss of Gli3 or Shh function does not compromise several aspects of olfactory receptor neuron (ORN) and olfactory ensheathing cell maturation; however, directed outgrowth of ORN axons and their initial targeting to the telencephalon is altered. In Gli3 mutant extra toes‐Jackson (XtJXtJ) embryos, ORN axons defasciculate and project aberrantly near the forebrain. They rarely enter the central nervous system, and their association with mesenchymal laminin is disrupted. In Shh−/−embryos, ORN axons exit a single olfactory epithelium (OE) that develops centrally within an altered mesenchymal environment in a dysmorphic proboscis. These axons project as a single nerve toward the mutant forebrain; however, their trajectory varies according to the position of the proboscis relative to the forebrain. These alterations in axon outgrowth probably reflect compromised inductive interactions in the olfactory primordia because neither Gli3 nor Shh are expressed in olfactory neurons. Thus, two genes that influence induction and subsequent differentiation of craniofacial structures and the forebrain have distinct consequences for ORN axon growth during the initial genesis of the olfactory pathway. J. Comp. Neurol. 472:292–307, 2004. © 2004 Wiley‐Liss, Inc.
Effects of prolonged exposure to an augmented acoustic environment on the auditory system of middle‐aged C57BL/6J mice: Cochlear and central histology and sex differences
Authors: Willott James F. , Bross Lori
Published: March 2004

Genetic progressive sensorineural hearing loss in mice of the C57BL/6J (B6) inbred strain begins at high frequencies during young adulthood and is severe by 12 months (middle age). Nightly treatment with an augmented acoustic environment (AAE)—12‐hour periods of exposure to repetitive noise bursts of moderate intensity, begun at age 25 days—resulted in less severe hearing loss compared with control mice. Cochlear histopathological correlates of AAE treatment, assessed at 12–14 months of age, included lessened severity of progressive loss of outer hair cells in both sexes as well as small savings of spiral ganglion cells in females and inner hair cells in males. AAE effects on the number of surviving neurons (age 12–14 months) in the anterior ventral cochlear nucleus (AVCN) depended on sex. Compared with controls, the loss of AVCN neurons that typically accompanies the initial period of hearing loss (between 2 and 7 months of age) was not significantly affected by AAE treatment in females. In contrast, males treated with the AAE exhibited more severe loss of neurons in the dorsal and ventral extremes of the AVCN than male controls of the same age. AAE treatment begun at age 3–5 months resulted in significant but less severe loss of AVCN neurons in 1‐year‐old male mice. J. Comp. Neurol. 472:358–370, 2004. © 2004 Wiley‐Liss, Inc.
Development of oculomotor axon projections in the chick embryo
Authors: Chilton John Kevin , Guthrie Sarah
Published: March 2004

The pattern of innervation of the extraocular muscles is highly conserved across higher vertebrate species and mediates sophisticated visuomotor processes. Defects in oculomotor development often lead to strabismus, a misalignment of the eyes that can cause partial blindness. Although it has been intensively studied from a clinical perspective, relatively little is known about how the system develops embryonically. We have therefore mapped the development of the oculomotor nerve (OMN) in chick embryos by using confocal microscopy. We show that OMN development follows a series of stereotyped steps that are tightly regulated in space and time. The OMN initially grows past three of its targets to innervate its distal target, the ventral oblique muscle, only later forming branches to the more proximal muscles. We have also investigated spatiotemporal aspects of the unusual contralateral migration of a subpopulation of oculomotor neurons by using molecular markers and have found the semaphorin axon guidance molecules and their receptors, the neuropilins, to be expressed in discrete subnuclei during this migration. Finally, we have created an embryological model of Duane retraction syndrome (DRS), a form of strabismus in which the OMN is believed to innervate aberrantly the lateral rectus, the normal target of the abducens nerve. By ablating rhombomeres 5 and 6 and hence the abducens, we have mimicked a proposed oculomotor deficit occurring in DRS. We find that the absence of the abducens nerve is not sufficient to produce this inappropriate innervation, so other factors are required to explain DRS. J. Comp. Neurol. 472:308–317, 2004. © 2004 Wiley‐Liss, Inc.