bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soft Nanostructured Films with an Ultra‐Low Volume Fraction of Percolating Hard Phase
Authors: Chenal Marion , Rieger Jutta , Véchambre Cyril , Chenal Jean‐Marc , Chazeau Laurent , Creton Costantino , Bouteiller Laurent 
Published: August 2013

In this study, aqueous emulsion polymerization of n‐butyl acrylate is performed in batch conditions without surfactants using a poly(acrylic acid)‐trithiocarbonate macro‐RAFT agent to control the polymerization and to stabilize the emulsion. According to the polymerization‐induced self‐assembly (PISA) approach, well‐defined amphiphilic PAA‐b‐PBA diblock copolymers form and self‐assemble during synthesis to yield highly stable core–shell particles with an extremely thin hard PAA shell. For the first time, we report here the specific properties of films obtained from these particular latexes. After drying the aqueous dispersion, tough and transparent films are obtained. Although the films are not chemically cross‐linked, they do not dissolve in good solvents for PBA. Moreover, they remain transparent even after immersion in water. Rheology shows that the films are both stiff and ductile, thanks to the nanostructured but very low volume fraction (less than 3 wt%) of PAA forming a percolating network in the soft PBA. Compared with conventional core–shell‐based films, this approach affords for the first time a route to a thin percolating honeycomb nanostructure with a sharp and strong interface between the two phases. The versatility of the synthetic procedure opens perspectives for a large range of functional materials.
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Cobalt Replacement in Unsaturated Polyester Resins; Going for Sustainable Composites
Authors: Jansen Johan F.G.A. , Hilker Iris , Kleuskens Engelien , Hensen Guido , Kraeger Ivo , Posthumus Willem 
Published: August 2013

SummaryAs alternative to cobalt based catalysts, various other catalysts based on manganese, iron and/or copper were developed for curing unsaturated polyesters in styrene with a hydroperoxide. This development is based on the simultaneous tuning of the redox chemistry taking place on the transition metal as well as on the ligand. From a mechanical point of view, based on DMA, these systems behave as drop‐ins. Employing these systems, unsaturated polyesters diluted in vinyl esters can also be cured. This makes cobalt‐free and styrene‐ free unsaturated polyesters possible.
Influence of Photopolymerization Characteristics on Thermo‐Mechanical Properties of Nanocomposites Utilizing Polymerizable Organoclays in Thiol‐Acrylate Systems
Authors: Kim Soon Ki , Baguenard Céline , Guymon C. Allan 
Published: August 2013

SummaryTo produce clay nanocomposites, photopolymerizable organoclays can react with monomers and incorporate into polymer matrices during the UV curing process. This research investigates the effects of polymerizable organoclays on the reaction behavior as well as the ultimate composite properties based on in‐situ thiol‐ene photopolymerization. To this end, different types of polymerizable organoclays, prepared by changing the functional group structure, were examined in various thiol‐acrylate systems. Small angle X‐ray diffraction was used to examine the degree of clay exfoliation. Photopolymerization behavior was characterized using real time infrared spectroscopy. Dynamic mechanical analysis was used for analyzing both mechanical and thermal properties. With sufficient clay exfoliation, the incorporation of thiol groups on the clay surfaces significantly increases the photopolymerization rate and final thiol conversion, whereas acrylate group conversion does not change significantly. While increasing monomer functionality does decrease final thiol conversion, the increase of thiol functionality of organoclays enhances thiol‐ene step growth reaction. Dark curing results suggest that the structure of propagating radicals on the clay surface varies by the type of polymerizable organoclays, changing the reaction behavior of the system. In accordance with the reaction behavior, the incorporation of acrylated organoclays significantly increases the storage modulus by inducing dominant acrylate homopolymerization. Addition of thiolated organoclays, on the other hand, makes more flexible polymer chains due to increased thio‐ether linkages.
Synthesis of Model Network Hydrogels via Tetrazine‐Olefin Inverse Electron Demand Diels‐Alder Cycloaddition
Authors: Cok Alexandra M. , Zhou Huaxing , Johnson Jeremiah A. 
Published: August 2013

SummaryThe formation of poly(etheylene glycol) (PEG) model network hydrogels via an A2 + B3 inverse‐electron‐demand tetrazine‐olefin Diels‐Alder cycloaddition is reported. This method provides an efficient, additive‐free, colorimetric gelation reaction that will complement other “click chemistry” approaches to model network synthesis.
Tuning Mechanical Properties of Chondroitin Sulfate‐Based Double‐Network Hydrogels
Authors: Suekama Tiffany C. , Hu Jian , Kurokawa Takayuki , Gong Jian Ping , Gehrke Stevin H. 
Published: August 2013

SummaryHigh strength double‐network (DN) biopolymer‐based hydrogels were created using copolymers of methacrylated chondroitin sulfate (MCS) and poly(ethylene glycol) diacrylate (PEGDA) as the first network and polyacrylamide (PAAm) as the second network. The concentration and cross‐linking of the networks were adjusted to control the mechanical properties including the failure stress, failure strain, Young's modulus, and yielding behavior. First, we increased the cross‐linking of the first network both by increasing the MCS concentration from 13 to 20 wt% and by copolymerizing MCS with 2 to 6 wt% PEGDA. The additional cross‐linking increased the Young's modulus as much as five times, reaching 3.3 MPa, and the failure stress up as much as four times, reaching 2.9 MPa. However, this also reduced failure strain from a high of 2.9 mm/mm to a low of 0.12 mm/mm and diminished the yielding region. Changes in the concentrations of acrylamide or its cross‐linking with N,N′‐methylenebisacrylamide (BIS) in the second network had a lesser effect on the DN properties. We hypothesized that to obtain a yielding region which results in high toughness, we need to alter the cross‐linking of the first network such that the yield stress of the MCS‐PEGDA/PAAm DN does not exceed the failure stress of PAAm network. Because of the wide range of mechanical properties achieved in these DNs with limited changes in the swelling degrees, unlike conventional single‐network gels, the DN approach allows attainment of a much greater range of mechanical behavior than is possible with single networks.
Homogeneous Copolymers of Ethylene with α‐olefins Synthesized with Metallocene Catalysts and Their Use as Standards for TREF Calibration
Authors: Cossoul Emilie , Baverel Laetitia , Martigny Elsa , Macko Tibor , Boisson Christophe , Boyron Olivier 
Published: August 2013

SummaryA range of crystalline copolymers of ethylene with α‐olefins (propene, hexene, octene and octadecene) were prepared using the complexes Et(Ind)2ZrCl2 and (nBuCp)2ZrCl2 activated with MAO. The average composition of the copolymers was measured using 1H‐ and 13C‐NMR. Then the samples were characterized by High Temperature SEC and DSC. These investigations showed that polymers are homogeneous in composition and consequently were suitable to be used as standards for TREF. This work provided calibrations curves for TREF that can be used on a wide range of α‐olefin contents. Finally, these calibrations curves were used to characterize heterogeneous copolymers of ethylene/hexene synthesized using a conventional Ziegler‐Natta catalyst.
Poly(propylene) Heterophasic Copolymers: Molecular Structure Analysis through Fractionation Techniques
Authors: Liberman Susana , de Azeredo Ana Paula , Dos Santos Francisco P. , da Silva Marco A. , Monrabal Benjamin , Mayo Nuria 
Published: August 2013

SummaryHeterophasic poly(propylene) copolymers obtained by sequential polymerization are multi‐component products formed by a crystalline matrix of poly(propylene) and an ethylene‐propylene rubber phase. Some crystalline polyethylene and poly(ethylene‐co‐propylene) are formed in the rubber synthesis step by copolymerization of ethylene and propylene. These multi‐component systems present a complicated microstructure and heterophasic morphology. In this study, two heterophasic copolymers with the same total amount of rubber but different composition and molecular weight, were thoroughly analyzed. The morphology was evaluated by SEM and AFM techniques. The complexity of the system required some attention in the fractionation methodology to perform an accurate interpretation of results and different methodologies of fractionation, especially for obtaining PE fractions as free of PP as possible, were performed in order to better characterize the crystalline polyethylene fractions in the copolymers. Preparative TREF was used to obtain fractions for further analysis by 13C‐NMR, DSC and GPC. Also samples were submitted to Cross Fractionation Chromatography (CFC). Results obtained by the different methodologies were compared.
The Influence of the Cooling Rate on the Nucleation Efficiency of Isotactic Poly(propylene) with Bis(3,4‐dimethylbenzylidene)sorbitol
Authors: Meijer‐Vissers Tamara , Goossens Han 
Published: August 2013

SummaryThe phase behavior of isotactic poly(propylene) (i‐PP) and 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS) was studied by using differential scanning calorimetry (DSC), rheology and optical microscopy and can be characterized by a simple binary monotectic phase diagram. DMDBS is a well‐known nucleating and clarifying agent for i‐PP that forms a fibrillar network upon cooling from a homogeneous melt within a specific concentration range. The influence of the cooling rate and the residence time in regime II of the phase diagram on the formation of the fibrillar network and the ratio between the α‐ and mesophase is investigated. This shows that DMDBS is actually a better nucleation agent for i‐PP when it is given less time for gelation, since the formation of a ‘secondary’ structure, in which the thin elementary nano‐fibrils form bundles of thicker fibrils, results in a decrease of the surface area that is available for nucleation.
Mathematical Model of Dynamic Crystallization of Ethylene/1‐Octene Copolymers
Authors: Chokputtanawuttilerd Nuttawat , Anantawaraskul Siripon , Soares João B. P. 
Published: August 2013

SummaryDynamic crystallization (DC) is a fractionation technique to enhance physical separation of polymers with different chain crystallizabilities by crystallizing polymer chains from solution in a column under a constant flow rate. In this work, a mathematical model for describing fractionation mechanism of dynamic crystallization based on the concept of population balance, crystallization kinetic, and dispersion models is proposed by the first time. The model was validated with experimental DC analysis of three ethylene/1‐octene copolymers. The simulated DC profiles were found to describe experimental results well.
Cellulose and Soy Proteins Based Membrane Networks
Authors: Zhu Yidan , Douglass Eugene , Theyson Tom , Hogan Robina , Kotek Richard 
Published: August 2013

SummaryUsing the novel ethylenediamine/potassium thiocyanate (ED/KSCN) solvent system developed in our labs, a simpler, environmentally friendlier method was developed to produce membranes using cellulose, proteins, and other polymers. In contrast to current industrial methods that use processes that are relatively expensive with toxic or dangerous solvents, the new system eliminated majority of those concerns. In this study, soy protein concentrate and cellulose was used to develop a nonporous composite membrane with good physical properties. Glutaraldehyde was applied as the crosslinking agent to stabilize the molecular network structure of the blended membranes. Results showed that nonporous membranes were produced that were strong, flexible, and the exposure to the crosslinking agent shown structural and thermal improvement of the network membranes. This resulting blend of biopolymer membranes with improved physical abilities can be useful for food packaging, filtration systems, or even medical applications.
Effect of Multiple Extrusion on Impact Fracture of Three Poly(propylene) Impact Copolymers
Authors: Jancar J. , Tochacek J. 
Published: August 2013

SummaryThe effect of structural changes induced by multiple extrusion on the impact fracture behavior of three reactor poly(propylene) impact‐copolymers (ICPPs) was investigated. The morphogenesis of the complex ICPP structure was controlled by the competition between the intraspherulitic phase separation and crystallization. The rubbery inclusion size was controlled by the rate of spinodal decomposition at the onset of crystallization. The following fast spherulite growth fixed the size and spatial distribution of these inclusions. The Charpy notched impact strength (ak) and critical strain energy release rate (Gc) measured under impact loading decreased significantly with the number of extruder passes. A measurable reduction of the size of the crack tip plastic zone (Rp) with the number of extruder passes was observed using high speed digital camera. While the melt flow index (MFI) dependence of ak exhibited ICPP specific shape, the MFI dependences of Gc fell on a single master curve at both 23 and −20 °C.
Modeling of Free Radical Styrene/Divinylbenzene Copolymerization with the Numerical Fractionation Technique
Authors: Nikitin Anatoly N. , Wulkow Michael , Schütte Christof 
Published: August 2013

AbstractThe modeling approach called “numerical fractionation” has been incorporated into a PREDICI model to simulate crosslinking copolymerization. In order to take inhomogeneities of the considered copolymerization into account, the kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. Using this approach the chain‐length dependence of the termination has been incorporated into the model so that even the method of moments could be applied to study crosslinking copolymerization. The styrene/m‐divinylbenzene crosslinking copolymerization at low crosslinker content has been simulated. The chain‐length dependence of the termination has been found to accelerate the gel point in monovinyl/divinyl copolymerization and must be taken into account for a correct description of the gel points.
Automatic assignment of 1H‐NMR spectra of small molecules
Authors: Cobas C. , Seoane F. , Vaz E. , Bernstein M. A. , Dominguez S. , Pérez M. , Sýkora S. 
Published: August 2013

AbstractA novel data‐evaluation procedure for the automatic atom to peak or multiplet assignment of 1H‐NMR spectra of small molecules has been developed using a fast and robust expert system. The applicability and reliability of the method are demonstrated by comparison of a manually assigned database of 1H‐NMR spectra with the assignments produced by the automatic procedure. The results of this analysis show an excellent success ratio, indicating that this new algorithm can have a major impact as a time saving tool for the organic chemist. A new graphical feature used to illustrate both the stability and quality of the elementary assignments is also introduced. Copyright © 2013 John Wiley & Sons, Ltd.
Management of cognitive radio ad hoc networks using a congestion‐based metric
Authors: Potier Paul , Qian Lijun 
Published: August 2013

SUMMARYIn this paper, we propose a new network management protocol to address the unique challenges of managing cognitive radio ad hoc networks that have distributed, multihop architectures with dynamic spectrum availability. We focus on performance management for these networks, and address the problem of network congestion for secondary users, because of its significant impact on data throughput. Specifically, we define a performance metric, the average congestion level of the network, and derive it analytically as a function of the primary users’ activities and the secondary users’ strategy. For practical implementation, we further propose a cluster‐based management architecture that utilizes a designated central manager and cluster heads that function as distributed managers. The cluster heads collect information from multiple layers of the protocol stack using new MIB (management information base) variables to capture the characteristics of cognitive radio ad hoc networks, such as the location‐dependent spectrum availability. The objective of the management action is to utilize a network‐level view of the congestion situation in the network by directing the secondary users to select the highest‐quality links available and avoid congested clusters. This hierarchical networkmanagement design allows us to take advantage of its scalability to achieve near‐real‐time management. Numerical results demonstrate the effectiveness of the proposed scheme. Copyright © 2013 John Wiley & Sons, Ltd.
Outcome of patients with stage II/favorable histology wilms tumor with and without local tumor spill: A report from the National Wilms Tumor Study Group
Authors: Green Daniel M. , Breslow Norman E. , D'Angio Giulio J. , Malogolowkin Marcio H. , Ritchey Michael L. , Evans Audrey E. , Beckwith J. Bruce , Perlman Elizabeth J. , Shamberger Robert C. , Peterson Susan , Grundy Paul E. , Dome Jeffrey S. , Thomas Patrick R.M. , Kalapurakal John A. 
Published: August 2013

AbstractBackgroundIntra‐operative tumor spill increases the risk of local recurrence of Wilms tumor, and adversely impacts relapse‐free (RFS) and overall survival (OS) rates.MethodsSurgical checklists, operative notes, institutional pathology reports, central pathology review and flow sheets of 602 patients registered between August 1986 and September 1994 on National Wilms Tumor Study—4 as randomized, followed or switched and coded as Final Stage II, favorable histology (FH) were reviewed. RFS and OS were estimated using the Kaplan–Meier method. Hazard ratios (HRs) were estimated using the Cox model and tested for statistical significance by the log‐rank test.ResultsFour hundred ninety‐nine patients were found after review to have Stage II, FH Wilms tumor. The 8‐year RFS percentages were 85.0% (95% confidence interval (CI): 81.1%, 88.1%) for those with no spill compared to 75.7% (65.8%, 83.2%) for those with spill. The 8‐year OS percentages were 95.6% (93.1%, 97.3%) for those with no spill compared to 90.3% (82.2%, 94.9%) for those with spill. The HR for relapse among those with spill was 1.55 ((95%CI: 0.97,2.51),P = 0.067) and the HR for death was 1.94 ((0.92,4.09),P = 0.077).ConclusionsRFS and OS were lower for patients who had intra‐operative tumor spill. The majority of NWTS Stage II, FH patients with intra‐operative tumor spill have an overall excellent outcome when treated with two drug chemotherapy (vincristine and actinomycin D) and no abdominal irradiation. Pediatr Blood Cancer 2014;61:134–139. © 2013 Wiley Periodicals, Inc.
Malformations, genetic abnormalities, and wilms tumor
Authors: Dumoucel S. , Gauthier‐Villars M. , Stoppa‐Lyonnet D. , Parisot P. , Brisse H. , Philippe‐Chomette P. , Sarnacki S. , Boccon‐Gibod L. , Rossignol S. , Baumann C. , Aerts I. , Bourdeaut F. , Doz F. , Orbach D. , Pacquement H. , Michon J. , Schleiermacher G. 
Published: August 2013

AbstractBackgroundWilms Tumor (WT) can occur in association with tumor predisposition syndromes and/or with clinical malformations. These associations have not been fully characterized at a clinical and molecular genetic level. This study aims to describe clinical malformations, genetic abnormalities, and tumor predisposition syndromes in patients with WT and to propose guidelines regarding indications for clinical and molecular genetic explorations.ProcedureThis retrospective study analyzed clinical abnormalities and predisposition syndromes among 295 patients treated for WT between 1986 and 2009 in a single pediatric oncological center.ResultsClinically identified malformations and predisposition syndromes were observed in 52/295 patients (17.6%). Genetically proven tumor predisposition syndromes (n = 14) frequently observed were syndromes associated with alterations of the chromosome WT1 region such as WAGR (n = 6) and Denys–Drash syndromes (n = 3), syndromes associated with alterations of the WT2 region (Beckwith–Wiedeman syndrome, n = 3), and Fanconi anemia (n = 2). Hemihypertrophy and genito‐urinary malformations (n = 12 and n = 16, respectively) were the most frequently identified malformations. Other different syndromes or malformations (n = 10) were less frequent. Median age of WT diagnosis was significantly earlier for children with malformations than those without (27 months vs. 37 months, P = 0.0009). There was no significant difference in terms of 5‐year EFS and OS between WT patients without or with malformations.ConclusionsThe frequency of malformations observed in patients with WT underline the need of genetic counseling and molecular genetic explorations for a better follow‐up of these patients, with a frequently good outcome. A decisional tree, based on clinical observations of patients with WT, is proposed to guide clinicians for further molecular genetic explorations. Pediatr Blood Cancer 2014;61:140–144. © 2013 Wiley Periodicals, Inc.
Placenta membranacea with placenta accreta: radiologic diagnosis and clinical implications
Authors: Pereira Nigel , Yao Ruofan , Guilfoil Daniel S. , Richard Scott D. , Plante Lauren A. 
Published: August 2013

What's already known about this topic?

Placenta membranacea is a rare developmental abnormality of the human placenta associated with abnormal placental adherence.
This placental abnormality is usually diagnosed after post‐delivery pathologic examination of the placenta.What does this study add?

We highlight the utility of magnetic resonance imaging as an adjunct to ultrasonography in the antenatal diagnosis of placenta membranacea.
Magnetic resonance imaging can optimize the diagnosis of abnormal placental adherence in the presence of placenta membranacea, thereby influencing antenatal management, as well as the timing and route of delivery.