bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbohydrate‐based amphiphilic diblock copolymers: Synthesis, characterization, and aqueous properties
Authors: Suriano Fabian , Coulembier Olivier , Degée Philippe , Dubois Philippe 
Published: April 2008

AbstractAmphiphilic poly(ε‐caprolactone)‐b‐poly[(methacrylate‐graft‐poly(ethylene oxide))‐co‐6‐O‐methacryloyl‐D‐galactopyranose] (PCL‐b‐P(MAPEO‐co‐GaMa)) with various compositions and molecular weights were synthesized via a controlled four‐step strategy. The first step involves the synthesis of functionalized poly(ε‐caprolactone) macroinitiator by ring‐opening polymerization (ROP) of ε‐caprolactone (CL) as initiated by aluminum triisopropoxide (Al(OiPr)3). After selective bromination of the hydroxyl end‐group of the resulting α‐isopropoxy, ω‐hydroxy poly(ε‐caprolactone) by using 2‐bromoisobutyryl bromide, the controlled radical copolymerization of α‐methoxy, ω‐methacrylate poly(ethylene oxide) (MAPEO) with 6‐O‐methacryloyl‐1,2;3,4‐di‐O‐isopropylidene‐D‐galactopyranose (DIGaMa) was performed by atom transfer radical polymerization (ATRP) in THF at 60 °C using CuBr ligated with 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as catalytic complex. In the final step, isopropylidene protective functions were selectively removed using an aqueous formic acid solution leading to the expected amphiphilic graft copolymers. The molecular characterization of those copolymers was performed by 1H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self‐assembly of the copolymers into micellar aggregates as well as the related critical micellization concentration (CMC) in aqueous media were determined by dynamic light scattering (DLS) and fluorescence spectroscopy, respectively. In parallel, the morphology of the solid deposits of micellar aggregates was examined with atomic force microscopy (AFM). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3662–3672, 2008
Thermally latent reaction of hemiacetal ester with epoxide catalyzed by recyclable polymeric catalyst consisting of salen‐zinc complex and polyurethane main chain
Authors: Komatsu Hiroyuki , Ochiai Bungo , Endo Takeshi 
Published: April 2008

AbstractThis article describes the synthesis of and catalysis with a polymeric catalyst (Zn/1NHCOO) carrying salen‐zinc complex structure in the main chain prepared from polyaddition of zinc/bis(4‐hydroxy)salicylidene‐1,2‐diiminoethane and 4,4′‐diphenylmethane diisocyanate. Poly(Zn/1NHCOO) promoted the reaction of glycidyl phenyl ether (2) with 1‐propoxyethyl‐2‐ethylhexanoate (3) only at moderately elevated temperatures. Poly(Zn/1NHCOO) can be recycled by simple filtration from the reaction mixtures, and the recycled polymer is as active as the freshly prepared one. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3673–3681, 2008
Thermally latent synthesis of networked polymers from multifunctional hemiacetal ester and diepoxide catalyzed by Schiff‐base‐zinc chloride complex
Authors: Komatsu Hiroyuki , Ochiai Bungo , Endo Takeshi 
Published: April 2008

AbstractThermally latent reaction of a copolymer (P1) bearing hemiacetal ester and n‐butyl methacrylate moieties and glycidyl phenyl ether (2) was catalyzed by bis(p‐methoxybenzylidene)‐1,2‐diiminoethane/zinc chloride complex (ZnCl2/3) at 30–150 °C for 6 h. No reaction of P1 and 2 took place below 70 °C, and it smoothly proceeded above 120 °C. The latencies and activities mean that ZnCl2/3 meets both the high latencies at ambient conditions and the high activities at desired temperatures. Thermal crosslinking reaction employing multifunctional derivatives was carried out using ZnCl2/3 at 140 °C for 6 h to afford a networked polymer in high yields. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3682–3689, 2008
Homogeneous anionic PPE hybrids with silica gel
Authors: Kokado Kenta , Chujo Yoshiki 
Published: April 2008

AbstractAnionic poly(p‐phenylene‐ethynylene) (PPE) incorporated polymer hybrids were synthesized from the PPE and tetramethoxysilane together with the organic polymers such as poly(vinylpyrrolidone) via a sol–gel method. Up to 10 wt % of the anionic PPE could be dispersed homogeneously in the resulting polymer hybrid matrix. The obtained polymer hybrids exhibited controllable photoluminescence properties by the modification of the internal environment of organic–inorganic polymer hybrids by changing the organic/inorganic ratios. The photoluminescence of the anionic PPE surrounded by the polymer hybrid matrix was reinforced against the thermal irradiation. Moreover, the photoluminescence of the obtained organic–inorganic polymer hybrids was also tuned by utilizing ionic interactions between the anionic PPE and the inorganic matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3749–3755, 2008
Photopolymerization kinetics of tributylmethylammonium‐based (meth)acrylate ionic liquids and the effect of water
Authors: Zhou Hui , Jiménez Zulma , Pojman John A. , Paley Mark S. , Hoyle Charles E. 
Published: April 2008

AbstractPolymerizable ionic liquids were synthesized from the neutralization reaction between tributylmethylammonium hydroxide and methacrylic or acrylic acid, and their photopolymerization kinetics have been determined. The acrylate monomer polymerization rate exhibited a profound dependence on the water content as follows: the monomer viscosity was a strong function of the water content, increasing substantially as the water content increased from less than 5 to 30%. For the tributylmethylammonium acrylate with less than 5% water, the viscosity was 2000 times greater than that of butyl acrylate. The high viscosity is proposed to reduce both the propagation and termination steps. Both monomers exhibited an increase in rate with temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3766–3773, 2008
Synthesis and characterization of polycyanurate/montmorillonite nanocomposites
Authors: Anthoulis George I. , Kontou Evagelia , Fainleib Alexander , Bei Irina , Gomza Yurii 
Published: April 2008

AbstractThe advantages of cyanate esters (CEs) versus competitor systems such as epoxies and polyimides, as well as the great reinforcing potential of organoclays properly dispersed into a polymeric matrix, have been examined in a series of polycyanurate (PCN)/montmorillonite (MMT) nanocomposites prepared under appropriate polymerization conditions. The curing schedule applied resulted in gradual propagation of polymerization. Through this procedure, the intragallery curing rate becomes comparable to the extragallery one, allowing intercalation before gelation. Systems with clay loadings from 1 to 3% per weight were synthesized, and their morphology and mechanical properties were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X‐ray scattering (WAXS), dynamic mechanical analysis (DMA), and tensile tests. Microscopy investigations revealed better dispersion for the 3 wt % system compared to smaller concentrations, in which aggregation and, in some cases, agglomeration were the conspicuous features. Roughness and area analyses revealed more homogeneous dispersion for this nanocomposite. Topology and 3D‐phase images further suggested considerable reduction of the average particle diameters. WAXS analysis showed that the interlayer spacing of nanocomposites was increased compared to pristine MMT, indicating the formation of intercalated structures. On the other hand, tensile strength and elongation at break values displayed abrupt diminution with MMT addition, while Young's modulus exhibited a slight but systematic increment with MMT content. The decreasing glass transition tendency observed for small clay loadings was reversed in the case of 3 wt %, while secondary transitions were practically unaffected by the presence of MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1036–1049, 2008
Filler size effects on the conductivity of polymer nanocomposites: Semiconductive phthalocyanine nanoparticles in epoxy matrices
Authors: Yuan Ming , Brokken‐Zijp José C. M. , Huijbregts Laura J. , De With Gijsbertus 
Published: April 2008

AbstractThree Cobalt(III) phthalocyanine (Phthalcon) powders with different particle sizes and chemical compositions, but almost equal XRD spectra and powder conductivity were synthesized and used as conductive fillers in crosslinked epoxy matrices. Two of these Phthalcons are new compounds. The relation between the conductivity of the composites and the type and amount of filler used was determined. The influence of particle size and chemical composition on this relation appeared to be minimal. These composites had a percolation threshold of 0.9 vol % and a maximum volume conductivity of 10−7 S/cm. Detailed analysis showed that the particle networks have very similar fractal structures and that they are likely to be formed by diffusion limited cluster‐cluster aggregation during processing. Evidence is presented that these particle networks are formed at an early stage of crosslinking and that the charge transfer between particles in the networks is neither limited by the Phthalcon particle size, nor by the presence of polymer matrix between the particles. The maximum volume conductivity of these composites is likely to be limited by the amount of filler used, the crystal structure defects on the particle surface, and the fractality and the imperfection of the particle networks. The impact of these findings on the conductivity of other polymer nanocomposites is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1079–1093, 2008
Predicting functional residues inPlasmodium falciparumplasmepsins by combining sequence and structural analysis with molecular dynamics simulations
Authors: Valiente Pedro A. , Batista Paulo R. , Pupo Amaury , Pons Tirso , Valencia Alfonso , Pascutti Pedro G. 
Published: April 2008

AbstractPlasmepsins are aspartic proteases involved in the initial steps of the hemoglobin degradation pathway, a critical stage in thePlasmodium falciparumlife cycle during human infection. Thus, they are attractive targets for novel therapeutic compounds to treat malaria, which remains one of the world's biggest health problems. The three‐dimensional structures available forP. falciparumplasmepsins II and IV make structure‐based drug design of antimalarial compounds that focus on inhibiting plasmepsins possible. However, the structural flexibility of the plasmepsin active site cavity combined with insufficient knowledge of the functional residues and of those determining the specificity of parasitic enzymes is a drawback when designing specific inhibitors. In this study, we have combined a sequence and structural analysis with molecular dynamics simulations to predict the functional residues inP. falciparumplasmepsins. The careful analysis of X‐ray structures and 3D models carried out here suggests that residues Y17, V105, T108, L191, L242, Q275, and T298 are important for plasmepsin function. These seven amino acids are conserved across the malarial strains but not in human aspartic proteases. Residues V105 and T108 are localized in a flap of an interior pocket and they only establish contacts with a specific non‐peptide achiral inhibitor. We also observed a rapid conformational change in the L3 region of plasmepsins that closes the active site of the enzyme, which explains earlier experimental findings. These results shed light on the role of V105 and T108 residues in plasmepsin specificities, and they should be useful in structure‐based design of novel, selective inhibitors that may serve as antimalarial drugs. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Development and evaluation of active packaging for sliced mozzarella preservation
Authors: dos Santos Pires Ana Clarissa , de Fátima Ferreira Soares Nilda , de Andrade Nélio José , da Silva Luís Henrique Mendes , Camilloto Geany Peruch , Bernardes Patrícia Campos 
Published: April 2008

AbstractAntimicrobial films were formed by the incorporation of nisin (NI), natamycin (NA) and a combination of both (NI + NA) into cellulose polymer. Film efficacies were evaluated in vitro against Staphylococcus aureus ATCC 6538, Listeria monocytogenes ATCC 15313, Penicillium sp. and Geotrichum sp. The films were also evaluated on sliced mozzarella cheese against moulds and yeasts, Staphylococcus sp. and psychrotrophic bacteria. Mechanical and microscopic properties of the films and the diffusion of the antimicrobial agents from the film to the cheese were also evaluated. Films containing NI showed an antimicrobial effect in vitro against S. aureus and L. monocytogenes, while films containing NA were effective in vitro against Penicillium sp. and Geotrichum sp. By the ninth day of storage at 12 ± 2°C, the count of yeasts and moulds on cheese covered with films containing NA decreased 2 log10 units compared with the count on cheese with control films. NI film did not show an effect against Staphylococcus sp., but it was effective against psychrotrophic bacteria for 6 days of storage of the cheese. The incorporation of antimicrobial compounds decreased the resistance and elongation of the films and caused changes in their molecular conformation. NI diffusion from the films to the cheese was not detected; however, time‐dependent diffusion of NA from the film containing NI + NA was measured. The incorporation of NI and NA together in the films did not show an effect. The film containing NA showed potential for application as active food packaging for sliced mozzarella cheese. Copyright © 2008 John Wiley & Sons, Ltd.
Diffusion technique for 15N and inorganic N analysis of low‐N aqueous solutions and Kjeldahl digests
Authors: Chen Rui Rui , Dittert Klaus 
Published: April 2008

AbstractDiffusion of ammonia is a common sample preparation method for the stable isotope analysis of inorganic nitrogen in aqueous solution. Classical diffusion methods usually require 6–12 days of diffusion and often focus on 15N/14N analysis only. More recent studies have discussed whether complete N recovery was necessary for the precise analysis of stable N isotope ratios. In this paper we present a newly revised diffusion technique that allows correct and simultaneous determination of total N and 15N at% from aqueous solutions and Kjeldahl digests, with N concentrations down to sub‐0.5‐mg N L−1 levels, and it is tested under different conditions of 15N isotope labelling. With the modification described, the diffusion time was reduced to 72 h, while the ratios of measured and expected 15N at% were greater than 99% and the simultaneous recovery of total N was >95%. Analysis of soil microbial biomass N and its 15N/14N ratio is one of the most important applications of this diffusion technique. An experiment with soil extracts spiked with 15N‐labelled yeast showed that predigestion was necessary to prevent serious N loss during Kjeldahl digestion of aqueous samples (i.e. soil extracts). The whole method of soil microbial biomass N preparation for 15N/14N analysis included chloroform fumigation, predigestion, Kjeldahl digestion and diffusion. An experiment with soil spiked with 15N‐labelled yeast was carried out to evaluate the method. Results showed a highly significant correlation of recovered and added N, with the same recovery rate (0.21) of both total N and 15N. A kN value of 0.25 was obtained based on the data. In conclusion, the diffusion method works for soil extracts and microbial biomass N determination and hence could be useful in many types of soil/water studies. Copyright © 2008 John Wiley & Sons, Ltd.
Factors affecting 13C‐natural abundance measurement of breath carbon dioxide during surgery: absorption of carbon dioxide during endoscopic procedures
Authors: Eaton Simon , Pacilli Maurizio , Wood James , McHoney Merrill , Corizia Lucia , Kingsley Charlotte , Curry Joseph I. , Herod Jane , Cohen Ralph , Pierro Agostino 
Published: April 2008

AbstractThe aim of this paper is to review the factors which may affect breath 13CO2/12CO2 natural abundance in patients undergoing surgery or intensive care. Intravenous glucose administration is a major determinant of the 13CO2/12CO2 of breath as intravenous glucose preparations are almost all derived from cornstarch. In addition, the oxidation of endogenous substrates can affect the 13CO2/12CO2 ratio. During many endoscopic procedures, such as laparoscopic surgery, carbon dioxide insufflation is used to provide a working space. As medical CO2 is relatively depleted in 13CO2 compared with endogenous and exogenous metabolic CO2 sources, breath 13CO2/12CO2 measurements can be used to estimate CO2 absorption during these procedures. However, all these factors may also be affected by the bicarbonate pool, making a definitive attribution of changes in breath 13CO2/12CO2 to a single factor problematic. Copyright © 2008 John Wiley & Sons, Ltd.
The application of isotope ratio mass spectrometry for discrimination and comparison of adhesive tapes
Authors: Horacek Micha , Min Ji‐Sook , Heo Sangcheol , Park Jongseo , Papesch Wolfgang 
Published: April 2008

AbstractForensic scientists are frequently requested to differentiate between, or compare, adhesive tapes from a suspect or a crime scene. The most common polymers used to back packaging tape are polypropylene and polyvinyl chloride. Much of the oriented polypropylene (OPP) needed to produce packaging tapes, regardless of the tape brand, is supplied by just a few polymer manufacturers. Consequently, the composition of the backing material varies little. Therefore, the discriminating power of classical methods (physical fit, tape dimensions, colour, morphology, FTIR, PyGC/MS, etc.) is limited. Analysis of stable isotopes using isotope ratio mass spectrometry (IRMS) has been applied in the broad area of forensics and it has been reported that isotope analysis is a valuable tool for the identification of adhesive tapes. We have tested the usefulness of this method by distinguishing different South Korean adhesive tapes produced by just a few manufacturers in the small South Korean market. Korean adhesive tapes were collected and analysed for their isotope signatures. The glue of the tapes was separated from the backing material and these sub‐samples were analysed for their H‐ and C‐isotope composition. The result shows the possibility for discriminating most tape samples, even from the same brand. Variations within single rolls have also been investigated, where no variations in H‐ and C‐isotope composition significantly exceeding the standard deviation were found. Copyright © 2008 John Wiley & Sons, Ltd.
Optimized multi‐stage designs controlling the false discovery or the family‐wise error rate
Authors: Zehetmayer Sonja , Bauer Peter , Posch Martin 
Published: April 2008

AbstractWhen a large number of hypotheses are investigated, we propose multi‐stage designs where in each interim analysis promising hypotheses are screened, which are investigated in further stages. Given a fixed overall number of observations, this allows one to spend more observations for promising hypotheses than with single‐stage designs, where the observations are equally distributed among all considered hypotheses. We propose multi‐stage procedures controlling either the family‐wise error rate (FWER) or the false discovery rate (FDR) and derive asymptotically optimal stopping boundaries and sample size allocations (across stages) to maximize the power of the procedure. Optimized two‐stage designs lead to a considerable increase in power compared with the classical single‐stage design. Going from two to three stages additionally leads to a distinctive increase in power. Adding a fourth stage leads to a further improvement, which is, however, less pronounced. Surprisingly, we found only small differences in power between optimized integrated designs, where the data of all stages are used in the final test statistics, and optimized pilot designs where only the data from the final stage are used for testing. However, the integrated design controlling the FDR appeared to be more robust against misspecifications in the planning phase. Additionally, we found that with increasing number of stages the drop in power when controlling the FWER instead of the FDR becomes negligible.Our investigations show that the crucial point is not the choice of the error rate or the type of design, but the sequential nature of the trial where non‐promising hypotheses are dropped in the early phases of the experiment. Copyright © 2008 John Wiley & Sons, Ltd.
Phytotoxicity of chlorinated benzenes to Typha angustifolia and Phragmites communis
Authors: Ma Xingmao , Havelka Megan M. 
Published: April 2008

AbstractHealthy growth of plants is a prerequisite for successful application of phytoremediation technologies. Typha angustifolia and Phragmites communis are common wetland plants and have shown potential for phytoremediation of hexachlorobenzene (HCB). However, the lack of phytotoxicity data impedes their application in field sites. This study investigated the phytotoxicity of HCB, and its two metabolites: 1,3,5‐trichlorobenzene (1,3,5‐TCB) and 1,4‐dichlorobenzene (1,4‐DCB) to Typha and the phytotoxicity of 1,3,5‐TCB to Phragmites. The phytotoxicity of 1,3,5‐TCB is species‐dependent, with Typha demonstrating significantly higher tolerance than Phragmites. The concentration of 1,3,5‐TCB causing zero growth of Phragmites was determined to be 1575 mg TCB/kg dry sediment. The concentration has to be doubled to completely inhibit the growth of Typha. Adverse effects of chlorinated benzenes in sediments on Typha increased with decreasing chlorine atoms. The concentrations causing zero growth of Typha are 5765 mg HCB/kg dry soil, 3157 mg 1,3,5‐TCB/kg dry soil, and 1325 mg 1,4‐DCB/kg dry soil. The higher toxicity of 1,4‐DCB than 1,3,5‐TCB and HCB in sediment was ascribed to its higher availability and easiness to be taken up by plants. The conclusion was supported by both growth rate calculations and plant height measurements. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
Agronomic and nutritional characteristics of fourteen Ghanaian groundnut varieties
Authors: Frimpong A , Johnson P‐N T , Baidoo E 
Published: April 2008

AbstractThe growth and yield parameters of 14 groundnut varieties were evaluated at three locations in Ghana, and key physical and nutritional characteristics of the grains were measured and compared. Kernel yields ranged from 940 kg ha−1 to 1463 kg ha−1. Grain length and 100‐grain mass were not consistently and strongly correlated, and the inconsistency may be partly due to differences in oil content, which has implications for processing of the different varieties. The protein content of the varieties ranged from 25.6% to 29.6% and many of the varieties would be suitable for dietary protein supplementation. No variety scored consistently highly for all characteristics, but varieties CSTV404MB and CS‐49 grew very well, and had high protein contents and moderately high oil contents, so they can be recommended for oil extraction and protein supplementation of local diets low in protein. Copyright © 2008 John Wiley & Sons, Ltd