bluuebunny/crossref_metadata_2025_split huggingface dataset:
SEC‐MALS study of dynamic structuring of natural rubber: Comparative study of two Hevea brasiliensis genotypes
Authors: Wisunthorn Suwaluk , Liengprayoon Siriluck , Vaysse Laurent , Beuve Jerome Sainte , Bonfils Frederic 
Published: October 2011

AbstractThe dynamic structuring of natural rubber (NR) was studied selecting two specific Hevea brasiliensis genotypes (RRIM600 and PB235) to prepare model samples. The mesostructure (macromolecular structure + aggregates or gel) of NR samples was studied by SEC‐MALS. The NR samples were analyzed after (i) slow structuring (18 months' storage at room temperature) and (ii) fast structuring (stored for 24 h on P2O5 at 60°C). This study showed that the macromolecular structure, especially Mn, and the total gel rates were dramatically modified after fast structuring. For genotype RRIM600, the aggregates formed during fast structuring were essentially macroaggregates, whereas for genotype PB235 mostly microaggregates were formed. These results indicate that the dynamic structuring of NR is dependent on genotype. Depending on the genotype, for extreme conditions (fast structuring), it can be assumed there was percolation between elementary bricks, probably microaggregates, or no percolation. Although the mechanisms of dynamic structuring are quite complex and should be multifactors dependent, on the basis of our results, the degree of percolation seems to be partly dependent on the quantity of short polyisoprene chains initially present in the NR samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Cellulose nanofibres and cellulose nanowhiskers based natural rubber composites: Diffusion, sorption, and permeation of aromatic organic solvents
Authors: Visakh P. M. , Thomas Sabu , Oksman Kristiina , Mathew Aji P. 
Published: October 2011

AbstractThis article investigates the transport behavior of three aromatic organic solvents, viz. benzene, toluene, and p‐xylene in natural rubber nanocomposite membranes containing cellulose nanofibres (CNFs) and cellulose nanowhiskers (CNWs) isolated from bamboo pulp. The solvent molecules act as molecular probes to study the diffusion, sorption, and permeation through the nanocomposites, and provide information on the nanocomposite structure and matrix–filler interactions. Both the nanocelluloses were found to decrease the uptake of aromatic solvents in nanocomposite membranes, but the effect was more significant in the case on nanofibers compared to nanowhiskers. Furthermore, the uptake decreased with increased penetrant size; being the highest for benzene and the lowest for p‐xylene. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated. Comparison of the experimental values of equilibrium solvent uptake with the predicted values indicated that both the nanocelluloses have restricted the molecular mobility at the interphase and thereby decreased the transport of solvents through the materials; being more significant for nanofibers. The results showed that both the used cellulosic nanomaterials act as functional additives capable of manipulating and tailoring the transport of organic solvents through elastomeric membranes, even at concentrations as low as 2.5 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Synthesis of (3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl) propionate derivatives and their thermal antioxidation behavior for POM
Authors: Park Dongkyung , Kobayashi Daisuke , Suh Hongsuk , Cho Youngki , Lee Areum 
Published: October 2011

AbstractPolyoxymethylene (POM) has been widely utilized in industry due to its light weight properties in engineering plastics. At present, POM applications are expanding into the car industry, especially in fuel tanks. Hindered alkyl phenol derivatives have been used as antioxidants for POM; however, these compounds are easily extracted by solvents. Two antioxidants with new structures (N,N′‐triethylenedioxy‐bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylhydrocinnamamide) and N,N′,N′‐tris[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyl‐3‐oxapentyl]melamine) were synthesized and characterized, and their performance as antioxidants for POM was investigated in the present study. The results revealed that N,N′‐triethylenedioxy‐bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylhydrocinnamamide) has good heat aging resistance compared to existing antioxidants for POM, and N,N′,N′‐tris[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyl‐3‐oxa‐pentyl]melamine has good extraction resistance against solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Copolymerizations of tetrafluoroethylene and perfluoropropylvinyl ether in supercritical carbon dioxide: Polymer synthesis, characterization, and thermal properties
Authors: Xu Anhou , Yuan Wang Zhang , Zhao Junhong , Li Hong , Zhang Heng , Zhang Yongming 
Published: October 2011

AbstractTetrafluoroethylene (TFE) and perfluoropropylvinyl ether (PPVE) were copolymerized in supercritical carbon dioxide (sc‐CO2) with a perfluorodiacyl initiator bis(perfluoro‐2‐n‐propoxypropionyl) peroxide (BPPP). The resultant copolymers with stable perfluoroalkyl end groups were obtained, avoiding the decomposition during processing and applications. Reactivity ratios of TFE and PPVE were first reported. The rTFE and rPPVE values are about 8 and 0.08, respectively. Such parameters are significant for the modification of PTFE through copolymerization of TFE and PPVE. It is found that through increasing the reaction pressure from 8.5 to 25 MPa, while rTFE increases by 12.0%, rPPVE decreases by 9.0%, which should be ascribed to the enhancement of the polarity of CO2 under high pressures. Because the reactivity of TFE is by two orders of magnitude higher than that of PPVE; on one hand, the copolymerization rate falls rapidly with the decrease of TFE feed ratio; on the other hand, TFE content in the copolymer decreases with the reaction time. All copolymers containing different fractions of PPVE enjoy outstanding thermal stability. The DSC result indicates that there exist two forms of crystals with highly regular molecular arrangement or less ordered chain packing which is disturbed by perfluoropropyl pendants. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Atom transfer radical polymerization of methylmethacrylate and styrene initiated by 3,5‐bis(perfluorobenzyloxy)benzyl 2‐bromopropanoate
Authors: Çanak Tuba Çakır , Selçukoğlu Mukaddes , Hamuryudan Esin , Serhatlı İ. Ersin 
Published: October 2011

AbstractThe synthesis of polymethylmethacrylate (pMMA) and polystyrene (pSt) were realized with newly synthesized initiator, 3,5‐bis(perfluorobenzyloxy)benzyl 2‐bromopropanoate (FBr) in the presence of copper bromide (CuBr) and N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) by using atom transfer radical polymerization (ATRP). The perfluorinated aromatic group containing initiator was prepared by esterification of the (3,5‐bis[(perfluorobenzyl)oxy]‐phenyl alcohol. Both initiator and polymers were characterized by 1H‐NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP was supported by an increase in the molecular weight of the forming polymers and also by their monomodal molecular weight distribution. Contact angle measurements of water and ethylene glycol on films of synthesized polymers indicated higher degree of hydrophobicity than that of pure pMMA and pure pSt. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Quantitative analysis of interfacial tension effect on the impact strength of organic flame retardants and acrylonitrile‐butadiene‐styrene blends
Authors: Jia Lina , Li Bin , Shi Baoli , Zhang Hongjie , Lan Yongqiang , Zhang Xin , Wang Yue , Wang Lili 
Published: October 2011

AbstractFor a polymeric blend containing powder additive, quantitative analysis of its mechanical performances with interfacial tension methodology is generally a difficult work because it needs at least two groups of consistent and comparable surface tension data, either for the polymer matrix or for the powder additive, to calculate their interfacial tension. In this article, to quantitatively analyze the effect of interfacial tension on the impact strength of acrylonitrile‐butadiene‐styrene/flame retardants (ABS/FR) blends, the surface tension components (STC) of three organic flame retardant powders, FR‐245 (2,4,6‐tris(2,4,6‐tribromophenoxy)‐1,3,5 triazine), decabromodiphenyl oxide, and charringefoaming agent were measured through the combination of contact angle (CA) and inverse gas chromatography technique. The relationship of the STC measured from CA between ABS resin and its homopolymer components (polyacrylonitrile, polybutadiene, and polystyrene) was also researched. Then, the interfacial tension between the three FR and ABS was calculated. It was found that the impact strength of the ABS/FR blends decreased almost linearly with the increase of the interfacial tension, and the linear correlation degree reached a very high value, 0.9969. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Synthesis and characterization of LDHs/PMMA nanocomposites: Effect of two different intercalated anions on the mechanical and thermal properties
Authors: Nogueira Telma , Botan Rodrigo , Wypych Fernando , Lona Liliane 
Published: October 2011

AbstractPoly(methyl methacrylate) (PMMA)/layered double hydroxides (LDH) nanocomposites were synthesized by in situ bulk polymerization. The LDHs were synthesized by coprecipitation method. Eight LDHs having different compositions were produced, varying the divalent/trivalent cations (Zn/Al, Mg/Fe), the ratio between these cations (2: 1 and 4: 1) and the LDH intercalated anions (dodecyl sulfate and laurate). The LDH percentage (wt %) in the PMMA was fixed at 1%. The thermal properties of the nanocomposites were evaluated by thermal analysis (thermogravimetric—TGA and differential scanning calorimetry—DSC). Most of the nanocomposites presented higher thermal resistance than PMMA and the best results were presented by the following nanocomposites: PMMA/(Zn/Al 2: 1 laurate) and PMMA/(Zn/Al 4: 1 laurate). The dynamic mechanical properties of the nanocomposites were investigated and compared to those obtained for PMMA. It was noticed that PMMA/(Mg/Fe 4: 1 laurate) nanocomposite presented an elastic modulus 2.2 times higher than PMMA at 40°C. This investigation demonstrated that the addition of low concentrations of selected LDHs can enhance some desired properties of PMMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
The significance of shore height in intertidal macrobenthic seagrass ecology and conservation
Authors: Barnes R. S. K. , Ellwood M. D. F. 
Published: October 2011

ABSTRACT

Benthic faunal assemblages of an intertidal seagrass bed were sampled at three shore heights (LWN, MLW, LWS) at the mouth, mid‐point and head of the Steenbok Channel in South Africa's premier seagrass site, the warm‐temperate Knysna estuarine bay, Garden Route National Park.
Faunal abundance, species richness, species diversity, and proportion of rare species were relatively uniform along the Channel, as were faunal abundance, species diversity and proportion of rare species down the shore. Overall species richness per station, however, was significantly lower at LWN than at either MLW or LWS, although the distribution of species richness over the shore did not depart from random at one of the three sites. Overall faunal abundance and those of individual component species were dispersed patchily through the bed.
The nature of the faunal assemblages present, however, varied significantly throughout the bed, both along the Channel at each shore‐height horizon, and down the shore at each site. LWN assemblages formed a unit distinct from those at MLW and LWS. Overall, the shore‐height axis accounted for 47% and the along‐shore axis 28% of total assemblage variation.
Faunal assemblages were randomly structured at each nodal intersection point of the down‐shore and along‐shore axes, but were significantly non‐randomly assembled down the shore at each site and along the Channel at each shore‐height horizon except at the LWN level.
Components of total assemblage variance were largest at the smallest scale investigated (1 m).

Higher seagrass horizons are not just progressively more impoverished versions of lower ones and although macrofaunal assemblage composition is heavily influenced by shore height much of the ecological structure of faunal assemblages seems little affected by tidal horizon. These findings are discussed in relation to conservation of the vulnerable seagrass Nanozostera capensis at Knysna, a system affected by subsistence exploitation of its intertidal benthic invertebrates.
Copyright © 2011 John Wiley & Sons, Ltd.
Historical Tracks and Trail Resources as Delineated by Near‐field Ground‐penetrating Radar: Two Case Studies
Authors: Weissling Blake P. 
Published: October 2011

ABSTRACTThe information content of the near‐field coupling‐wave zone of ground‐penetrating radar is explored in the context of cultural resource investigations at two archaeological sites in Washington State and New Mexico. While the coupling‐wave zone is frequently assumed to be information‐poor in the context of very shallow resources, and routinely filtered out for the benefit of accentuating deeper resources, this study advocates careful inspection of this data zone. In both case studies, cultural resources most likely related to animal/human/vehicular trails or trackways were detected in unprocessed (raw) horizontal amplitude slices. The ability of radar to ‘see’ these resources is conjectured to be related to soil or sediment compaction. Copyright © 2011 John Wiley & Sons, Ltd.
Marginal structural models for estimating principal stratum direct effects under the monotonicity assumption
Authors: Chiba Yasutaka 
Published: October 2011

AbstractIn epidemiological and clinical research, investigators are frequently interested in estimating the direct effect of a treatment on an outcome that is not relayed by intermediate variables. In 2009, VanderWeele presented marginal structural models (MSMs) for estimating direct effects based on interventions on the mediator. This paper focuses on direct effects based on principal stratification, i.e. principal stratum direct effects (PSDEs), which are causal effects within latent subgroups of subjects where the mediator is constant, regardless of the exposure status. We propose MSMs for estimating PSDEs. We demonstrate that the PSDE can be estimated readily using MSMs under the monotonicity assumption.
Metabolic ensemble modeling for strain engineers
Authors: Tan Yikun , Liao James C. 
Published: October 2011

AbstractPrevious mathematical modeling efforts have made significant contributions to the development of systems biology for predicting biological behavior quantitatively. However, dynamic metabolic model construction remains challenging due to uncertainties in mechanistic structures and parameters. In addition, parameter estimation and model validation often require designated experiments conducted only for purpose of modeling. Such difficulties have hampered the progress of modeling in biology and biotechnology. To circumvent these problems, ensemble approaches have been used to account for uncertainties in model structure and parameters. Specifically, this review focuses on approaches that utilize readily available fermentation data for parameter screening and model validation. Time course data for metabolite measurements, if available, can further calibrate the model. The basis for this approach is explained in non‐mathematical terms accessible to experimentalists. Information gained from such an approach has been shown to be useful in designing Escherichia coli strains for metabolic engineering and synthetic biology.
Three‐reaction model for the anaerobic digestion of microalgae
Authors: Mairet Francis , Bernard Olivier , Cameron Elliot , Ras Monique , Lardon Laurent , Steyer Jean‐Philippe , Chachuat Benoît 
Published: October 2011

AbstractCoupling an anaerobic digester to a microalgal culture has received increasing attention as an alternative process for combined bioenergy production and depollution. In this article, a dynamic model for anaerobic digestion of microalgae is developed with the aim of improving the management of such a coupled system. This model describes the dynamics of inorganic nitrogen and volatile fatty acids since both can lead to inhibition and therefore process instability. Three reactions are considered: Two hydrolysis–acidogenesis steps in parallel for sugars/lipids and for proteins, followed by a methanogenesis step. The proposed model accurately reproduces experimental data for anaerobic digestion of the freshwater microalgae Chlorella vulgaris with an organic loading rate of 1 gCOD L−1 d−1. In particular, the three‐reaction pathway allows to adequately represent the observed decoupling between biogas production and nitrogen release. The reduced complexity of this model makes it suitable for developing advanced, model‐based control and monitoring strategies. Biotechnol. Bioeng. 2012; 109:415–425. © 2011 Wiley Periodicals, Inc.
Clinical significance of liver ischaemia after pancreatic resection
Authors: Hackert T , Stampfl U , Schulz H , Strobel O , Büchler M W , Werner J 
Published: October 2011

Abstract

Background
Liver ischaemia after pancreatic resection is a rare but potentially serious complication. The aim of this study was to determine the impact of postoperative liver ischaemia after pancreatic resection.

Methods
All consecutive patients undergoing pancreatic resection between January 2007 and August 2008 in the Department of Surgery in Heidelberg were identified retrospectively from a prospectively collected database and analysed with a focus on postoperative hepatic perfusion failure. Laboratory data, computed tomography (CT) findings, symptoms, therapy and outcome were recorded.

Results
A total of 762 patients underwent pancreatic resection in the study period. Seventeen patients (2·2 per cent) with a postoperative increase in liver enzymes underwent contrast-enhanced CT for suspected liver perfusion failure. The types of perfusion failure were hypoperfusion without occlusion of major hepatic vessels (6 patients) and ischaemia with arterial (5) and/or portal vein (6) involvement. The overall mortality rate was 29 per cent (5 of 17 patients). Therapy included conservative treatment (7), radiological or surgical revascularization and necrosectomy or resection of necrotic liver tissue (10). Outcome varied from full recovery (4 patients) to moderate systemic complications (6) and severe complications (7) including death. Simultaneous involvement of the portal vein and hepatic artery was always fatal.

Conclusion
Postoperative liver perfusion failure is a rare but potentially severe complication following pancreatic surgery requiring immediate recognition and, if necessary, radiological or surgical intervention.
Assessment of haemorrhoidal artery network using colour duplex imaging and clinical implications
Authors: Ratto C , Parello A , Donisi L , Litta F , Zaccone G , Doglietto G B 
Published: October 2011

Abstract

Background
Dearterialization should reduce arterial overflow to haemorrhoids. The purpose of this study was to assess the topography of haemorrhoidal arteries.

Methods
Fifty patients with haemorrhoidal disease were studied. Using endorectal ultrasonography, six sectors were identified within the lower rectal circumference. Starting from the highest level (6 cm above the anorectal junction), the same procedure was repeated every 1 cm until the lowest level was reached (1 cm above the anorectal junction). Colour duplex imaging examinations identified haemorrhoidal arteries related to the rectal wall layers, and the arterial depth was calculated.

Results
Haemorrhoidal arteries were detected in 64·3, 66·0, 66·0, 98·3, 99·3 and 99·7 per cent of the sectors 6, 5, 4, 3, 2 and 1 cm above the anorectal junction respectively (P &lt; 0·001). Most of the haemorrhoidal arteries were external to the rectal wall at 6 and 5 cm (97·9 and 90·9 per cent), intramuscular at 4 cm (55·0 per cent), and within the submucosa at 3, 2 and 1 cm above the anorectal junction (67·1, 96·6 and 100 per cent) (P &lt; 0·001). The mean arterial depth decreased significantly from 8·3 mm at 6 cm to 1·9 mm at 1 cm above the anorectal junction (P &lt; 0·001).

Conclusion
This study demonstrated that the vast majority of haemorrhoidal arteries lie within the rectal submucosa at the lowest 2 cm above the anorectal junction. This should therefore be the best site for performing haemorrhoidal dearterialization. Copyright © 2011 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.
Aptamers can Discriminate Alkaline Proteins with High Specificity
Authors: Yu Hanyang , Jiang Bing , Chaput John C. 
Published: October 2011

AbstractAptamers are single‐stranded nucleic acids that fold into stable three‐dimensional structures with ligand binding sites that are complementary in shape and charge to a desired target. Aptamers are generated by an iterative process known as in vitro selection, which permits their isolation from pools of random sequences. While aptamers have been selected to bind a wide range of targets, it is generally thought that these molecules are incapable of discriminating strongly alkaline proteins due to the attractive forces that govern oppositely charged polymers (e.g., polyelectrolyte effect). Histones, eukaryotic proteins that make up the core structure of nucleosomes are attractive targets for exploring the binding properties of aptamers because these proteins have positively charged surfaces that bind DNA through noncovalent sequence‐independent interactions. Previous selections by our lab and others have yielded DNA aptamers with high affinity but low specificity to individual histone proteins. Whether this is a general limitation of aptamers is an interesting question with important practical implications in the future development of protein affinity reagents. Here we report the in vitro selection of a DNA aptamer that binds to histone H4 with a Kd of 13 nM and distinguishes other core histone proteins with 100 to 480‐fold selectivity, which corresponds to a ΔΔG of up to 3.4 kcal mol−1. This result extends our fundamental understanding of aptamers and their ability to fold into shapes that selectively bind alkaline proteins.
A Novel Synthesis of Bioactive Catechols by Layer‐by‐Layer Immobilized Tyrosinase in an Organic Solvent Medium
Authors: Guazzaroni Melissa , Pasqualini Marina , Botta Giorgia , Saladino Raffaele 
Published: October 2011

AbstractCommercial and extracted mushroom tyrosinases were supported on Eupergit C 250 L and protected by a coating of oppositely charged polyelectrolytes by means of the layer‐by‐layer technique. The kinetic parameters (Km, Vmax, and Vmax/Km) of these novel biocatalysts in both organic and aqueous media were evaluated, showing tyrosinase to be more reactive in organic solvent than in buffer solution. Heterogeneous tyrosinase systems were used for the oxidation of a large group of phenol derivatives to the corresponding catechols. Different enzyme reactivities were found depending on the substrate structure. The catalyst activity was retained for successive runs. Catechols are difficult to synthesize through traditional chemical methods under environmentally friendly conditions; the use of immobilized tyrosinase opens a novel synthetic alternative to this interesting biologically active family of substances.