bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and characterization of a novel thermostable lectin from the wild edible mushroom Agaricus arvensis
Authors: Zhao J. K. , Zhao Y. C. , Li S. H. , Wang H. X. , Ng T. B.
Published: February 2011

A thermostable novel lectin with a molecular weight of 30.4 kDa was isolated from dried fruiting bodies of Agaricus arvensis. It was a dimer made up of two 15.2 kDa subunits. The lectin was unadsorbed on DEAE‐cellulose in 10 mM phosphate buffer (pH 7.5), subsequently adsorbed on CM‐cellulose in 10 mM NaAc buffer (pH 4.6) and then on SP‐Sepharose in 10 mM NaAc buffer (pH 4.6), and finally purified by fast protein liquid chromatography‐gel filtration on Superdex 75. The hemagglutinating activity of the lectin was stable at temperatures up to 90 °C. The activity was preserved in concentrations of NaOH solution up to 50 mM, but was sensitive to HCl and declined to 12.5% in 12.5 mM HCl. The activity was unaffected by Ca2+, Mn2+, Zn2+and Mg2+ ions, but was activated by Al3+ and Fe3+ ions. Among the carbohydrates tested, only inulin could inhibit the hemagglutinating activity of the lectin. It did not exhibit anti‐HIV reverse transcriptase activity. Proliferation of HepG2 and MCF7 tumor cells was inhibited by the lectin with an IC50of 1.64 and 0.82 μM, respectively. The lectin was devoid of antifungal activity. The lectin has a remarkable thermostablity and a unique N‐terminal amino acid sequence, TYAVLNFVYG. The present report is the first report on a lectin from wild mushroom Agaricus arvensis. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The paf gene product modulates asexual development in Penicillium chrysogenum
Authors: Hegedüs Nikoletta , Sigl Claudia , Zadra Ivo , Pócsi Istvan , Marx Florentine
Published: February 2011

Penicillium chrysogenum secretes a low molecular weight, cationic and cysteine‐rich protein (PAF). It has growth inhibitory activity against the model organism Aspergillus nidulans and numerous zoo‐ and phytopathogenic fungi but shows only minimal conditional antifungal activity against the producing organism itself.

In this study we provide evidence for an additional function of PAF which is distinct from the antifungal activity against putative ecologically concurrent microorganisms. Our data indicate that PAF enhances conidiation in P. chrysogenum by modulating the expression of brlA, the central regulatory gene for mitospore development. A paf deletion strain showed a significant impairment of mitospore formation which sustains our hypothesis that PAF plays an important role in balancing asexual differentiation in P. chrysogenum. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective removal of human DNA from metagenomic DNA samples extracted from dental plaque
Authors: Hunter Stephanie J. , Easton Samantha , Booth Veronica , Henderson Brian , Wade William G. , Ward John M.
Published: February 2011

Metagenomic techniques are used to analyse bacterial communities allowing both culturable and unculturable species to be represented. However, the screening of oral metagenomic samples can be hindered by high animal host DNA content. This study evaluated methods for the reduction of human DNA concentrations within oral metagenomic samples.

Plaque samples were collected from 27 patients presenting with periodontal disease and treated to remove human DNA using either selective lysis of eukaryotic cells at several buffer concentrations or differential centrifugation after treatment with trypsin and/or detergents. Human and bacterial DNA levels were determined by quantitative polymerase chain reaction (qPCR).

The human DNA content of plaque extracts was significantly reduced by all treatments compared with an untreated control (P < 0.05). However, differential centrifugation simultaneously reduced the bacterial DNA content unless samples were pretreated with a detergent. Observations of Gram stained samples that were processed using differential centrifugation without detergent suggest that many bacteria remain adhered to human cells. An approach that uses differential centrifugation in parallel with selective lysis is recommended to fully represent the oral microbiota in metagenomic samples, including those tightly adhered to human cells and more delicate bacteria such as Mycoplasma. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wheat gluten‐based materials plasticised with glycerol and water by thermoplastic mixing and thermomoulding
Authors: Zárate‐Ramírez Lidia S , Martínez Inmaculada , Romero Alberto , Partal Pedro , Guerrero Antonio
Published: February 2011

BACKGROUND: Gluten has been investigated as a source for biodegradable polymeric materials because it is a renewable, available and low‐cost raw material. The aim of this study was to evaluate the influence of some variables involved in the two stages of protein/plasticiser thermo‐mechanical processing, where a mixture of glycerol and water was used as the plasticiser.

RESULTS: Gluten/glycerol/water blends mixed under different thermal conditions (adiabatic starting at 25 °C and isothermal at 60 and 90 °C) exhibited shear thinning capillary flow behaviour, where a marked increase in flow properties was obtained at the highest temperature. Two thermal events, glass transitions related to the plasticiser blend and gluten, were detected by Modulated Differential Scanning Calorimetry (MDSC) and Dynamic Mechanical Analysis (DMA) tests. Moderate moulding temperature led to less resistant materials showing higher ductility, whereas higher mixing and moulding temperatures led to bioplastics with higher mechanical properties.

CONCLUSION: A moulding temperature of 130 °C (close to the denaturation temperature) was found to be suitable for the thermomoulding process. In addition, the use of moderate mixing temperature seems to be convenient for those applications that required materials exhibiting high water absorption behaviour and suitable mechanical properties. Protein extractability results reflect the benefits of combining high shear and high temperature during processing to improve cross‐linking reactions. Copyright © 2010 Society of Chemical Industry
The impact of 3d virtual haptics in marketing
Authors: Jin Seung‐A Annie
Published: February 2011

Tactile input plays a key role in consumers' evaluation of products' substance properties. Utilization of haptic interfaces and force feedback devices that enable consumers to feel and manipulate three‐dimensional (3D) virtual products is a promising but under‐explored area in marketing and consumer behavior research. This study investigated 3D virtual touch created by Novint Falcon haptic interfaces and its impacts on consumer behavior in the interactive marketing of automobiles. It was hypothesized that consumers' instrumental Need for Touch (NFT) plays a significant moderating role in haptic interfaces. Results from a 2 (nature of tactile stimuli: haptic input with force feedback versus no force feedback) × 2 (haptic orientation: high NFT versus low NFT) full factorial between‐subjects experiment indicated that consumers high in instrumental NFT evaluate products more positively, enjoy the test‐driving experience more, and show stronger brand–self connection when there are force feedback haptic stimuli as opposed to when there is no force feedback. Theoretical and managerial implications of the study are discussed. © 2011 Wiley Periodicals, Inc.
To touch or not to touch; that is the question. Should consumers always be encouraged to touch products, and does it always alter product perception?
Authors: Marlow Nigel , Jansson‐Boyd Cathrine V.
Published: February 2011

It has previously been suggested that consumers' product evaluations are positively affected by tactile interaction. However, it is not known if it is applicable to products that people usually touch for brief periods of time. This study sets out to explore whether it is possible to influence consumers' tactile perception of fast‐moving consumer goods by altering the surface texture. In this study individual tactile sensing and visual appreciation were compared with the combined visual and tactile sensing of surface textures for two types of products (soap and biscuits). Three types of textures on the outside of either a soap or biscuit box and three separate sample swatches of the textures used on the boxes were used in the study. The three soap or biscuit boxes were visually presented to the participants. This was followed by a blind haptic evaluation of the three textures, and then by a combined visual and tactile evaluation of three differently textured boxes (either soap or biscuit boxes). The results suggest that a consumer's perception of the packaging of fast‐moving consumer goods is affected more by vision than by touch, which raises some questions with regard to when marketers should encourage consumers to engage in extensive tactile interaction prior to purchase. © 2011 Wiley Periodicals, Inc.
Multisensory design: Reaching out to touch the consumer
Authors: Spence Charles , Gallace Alberto
Published: February 2011

Touch plays an important, if often underacknowledged, role in our evaluation/appreciation of many different products. It is unsurprising, therefore, that there has been such a recent growth of interest in “tactile branding” and tactile marketing. This article reviews the evidence from the fields of marketing, psychology, and cognitive neuroscience, demonstrating just how important the feel of a product, not to mention the feel of its packaging, can be in determining people's overall product evaluation. Problems for tactile design associated with the growth of the aging population, and the growth of Internet‐based shopping, are highlighted. The critical role that touch can play in multisensory product design, appreciation, and marketing is also discussed, as is the increasingly frequent use by marketers of synesthetic correspondences to evoke tactile sensations via the visual and auditory modalities. We put forward the argument that tactile stimulation may influence multisensory product evaluation by means of affective ventriloquism: Our suggestion is that the hedonic attributes of a product perceived via one modality (such as touch) can “pull” (or bias) a person's estimates of the quality and pleasantness of the product derived from other sensory modalities into alignment, and by so doing, modulate a person's overall (multisensory) product experience. What is more, powerful mathematical modeling approaches now exist to predict the magnitude of this kind of intersensory (or crossmodal) interaction effect, hence offering the promise of a more scientific approach to tactile design/marketing in the coming years. © 2011 Wiley Periodicals, Inc.
Effects of the Temperature and UV Radiation on the Antimicrobial Action of Bactericidal Wood Polymer Composite (BWPC)
Authors: Júnior Jair Fiori , Piletti Raquel , Barichello Tatiana , Quadri Mara G.N. , Riella Humberto G. , Angioletto Elídio , da Silva Luciano , Paula Marcos M. S. , Fiori Márcio A.
Published: February 2011

This paper presents an investigation of the influences of temperature and UV radiation on the antimicrobial properties of Bactericide Wood Polymer Composite (BWPC). The composite was formulated with polypropylene (PP), wood flour from Pinus elliotis and a triclosan compound. The BWPC was exposed to different time periods and to UV radiation at 100 °C. Microbiological tests were conducted with Escherichia coli and Staphylococcus aureus bacteria. These results showed that the bactericide action is strongly affected by the time of exposure of the composite to high temperature and UV radiation.
Characterization of Natural and Modified Clays to the Development of Polymeric Nanocomposites
Authors: Jarek Flavia , Reis Dayane M. , Mauler Raquel S. , Barbosa Ronilson V. , Kloss Juliana R.
Published: February 2011

Bentonite is a technical term applied to layered silicates of very thin granulation, mainly composed by minerals of the smectites group. Montmorillonite, a phylossilicate with layers as thick as 1 nm, is the most common structure in the bentonite clay. The polarity of these materials is incompatible with most of the usual polymers and in order to overcome this problem, chemical modifications are often necessary. The purpose of this work is to evaluate the chemical and physical characteristics of different bentonites by comparing their product data sheets, their performance in the water Foster swelling and their response to chemical modifications of their surfaces structures. The samples were characterized by infrared spectroscopy and X‐ray diffraction analysis. All bentonite samples showed effective intercalations of the modifying agent on their surface structures. This behavior showed the possibility of usage of these materials in the polymer layered silicates nanocomposites preparations.
Enzymatic Treatment as a Pre‐Step to Remove Cellulose Films from Sensors
Authors: Silva Deusanilde J. , Rojas Orlando J. , Hubbe Martin A. , Park Song W.
Published: February 2011

In this work an enzymatic treatment is proposed as a preparative, cleaning protocol to remove cellulose films from resonators and sensors. Quartz crystal and surface plasmon gold sensors, coated with ultrathin films of cellulose are used in studies of molecular (for example, polymer and surfactant) adsorption. The sensors are usually recycled after removal of the film, with limited success, after one of two treatments, either hot acid or ammoniac solutions. In the proposed, improved protocol a mixture of cellulases from Aspergillus species, are used as a pre‐treatment to facilitate the release of the cellulose film from the surfaces of the sensors. Two concentrations of NaCl solutions were considered in the enzymatic treatment, 1 and 10 mM, at given enzyme solution concentration, temperature and pH. It was found that after 80 min, the water contact angle after treatment with both salt concentration conditions reached a plateau. The average water contact angle after integration of the enzymatic and ammoniac treatments was found to be low enough, between 6.4 and 7.1 deg to allow reuse the sensors. It is concluded that the use of the ammoniac cleaning solution after the enzymatic treatment is a very convenient, safe and less time consuming way to remove the cellulose films from the sensors to be recycled.
Oxidation and N‐Alkylation at the C‐6 Position of Galactomannan Extracted from Caesalpinia ferrea var. ferrea Seeds
Authors: de Souza Clayton F. , Lucyszyn Neoli , Ferraz Fernando A. , Sierakowski Maria Rita
Published: February 2011

Carboxyl (GMOX) and carboxyl‐aminoalkylated derivatives (GMOXD) of galactomannan (GM), extracted from the seeds of Caesalpinia ferrea (Pau‐ferro; Brazilian Ironwood), were synthesised by selective modification of the polysaccharide at the C‐6 position in the presence of TEMPO reagent (2,2,6,6‐tetramethylpiperidine‐1‐oxyl) and dodecylamine, with high yields (77 and 94% for GMOX and GMOXD, respectively). The chemical modifications were confirmed by Fourier‐transform infrared (FTIR) and nuclear magnetic resonance (13C‐NMR) spectroscopy. Analysis by gel permeation chromatography (GPC) coupled to refractive index (RI), light‐scattering (LS) and viscometer detectors revealed a decrease in molar‐mass values and the intrinsic viscosity and an increase in polydispersity. Modification of galactomannan with a primary amine led to an interesting anionic water‐soluble polymeric surfactant, as determined by interfacial tension values at 24 °C. The critical aggregation and micellar concentration values of amphiphilic GMOXD were determined to be 0.48 and 0.89% (w/v), respectively. The development of polyelectrolyte and amphiphilic derivatives of GM and their physicochemical characterisation can contribute to numerous product applications such as nano‐structured films, cosmetics and pharmaceuticals.
Bulk Ring Opening Polymerization of L‐Lactide with Calcium methoxide
Authors: Dias Marcos Lopes , Palermo Luiz Carlos , Silvino Alexandre C.
Published: February 2011

Summary: Bulk ring opening polymerization (ROP) of L‐lactide (LA) initiated by calcium methoxide (Ca(OMe)2) was investigated in LA/Ca molar ratio from 100 to 5000 and reaction times up to 3h at 180 °C. Ca(OMe)2 showed good activity as ROP catalyst, particularly at high catalyst concentration. The polymerization shows a linear relationship between $\overline {{\rm M}} $n and reaction time, typical of a controlled process. The increase of LA/Ca molar ratio decreases the conversion which was maximum (66%) when the polymerization was carried out at 180 °C and LA/Ca = 100. Semicrystalline poly(L‐lactic acid) (PLLA) with moderate $\overline {{\rm M}} $n varying from 8,500 to 19,500 and polydispersities from 1.20 to 1.44 were obtained. The increase of LA/Ca molar ratio decreased $\overline {{\rm M}} $n, increased the degree of crystallinity and decreased racemization processes which can be controlled by the polymerization condition. Racemization could be reduced by using low catalyst concentration.
Preparation and Characterization of PVC/Natural Filler Composites
Authors: Iulianelli Gisele Cristina V. , Maciel Paula de M.C. , Tavares Maria Inês B.
Published: February 2011

The main purpose of the present work is to use a renewable material obtained from fruit seed to prepare a reinforced polymer composite with poly(vinyl chloride) (PVC). The characterization of the composites was based on the determination of the molecular motion and of mechanical and thermal properties. The thermal properties were characterized through thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The mechanical properties were characterized through tensile tests. The molecular dynamic behavior of the polymer matrix was studied by proton spin‐lattice relaxation, using low field nuclear magnetic resonance (NMR). It is shown that the thermal properties do not depend on the filler content, although mechanical properties are improved with the addition of filler. Despite that, no strong interaction between the filler and the PVC matrix could be detected.
Effectiveness of the Transesterification Catalyst on the Thermal, Dynamic‐Mechanical and Rheological Properties of PET/PC Reactive Melting Blends
Authors: Mendes Luis C. , Pereira Patrícia S. C. , Ramos Valéria D.
Published: February 2011

Reactive poly(ethylene terephthalate) / polycarbonate (PET/PC) melting blends were prepared with different cobalt catalyst and polymer compositions. The presence of catalyst increased the miscibility of the 20/80 (wt%) blend, according to differential scanning calorimetry (DSC) and dynamic‐mechanical analyses (DMA). The catalyst also promoted the amorphisation of the PET chains. Besides, the catalyst caused drastic lowering of both moduli (storage and loss) and melt flow rate (MFR) of some blends. The best mechanical and processing properties were achieved for blends without catalyst, indicating that transesterification reactions prejudice mechanical properties.
Development of Maleated Starches Using an Internal Mixer
Authors: Dias Fernanda T.G. , Souza Roberta C.R. , Andrade Cristina T.
Published: February 2011

Summary: Novel maleated starches (MSt) were prepared by chemical modification of cornstarch with maleic anhydride (MA), using an internal mixer as a reactor. Benzoyl peroxide (BPO) was chosen as initiator. Physico‐chemical parameters were given by the process, recorded at different MA contents, under the same reaction conditions. Processing was carried out at 50 °C, 30 rpm for 8 min. Torque developed during processing was given by the digital display of the rheometer, and the total specific mechanical energy (SME) input was estimated. FTIR measurements confirmed the successful incorporation of MA into the starch backbone. X‐ray diffractograms obtained for the products revealed disruption of the crystalline structure of native starch. The results indicated that the MA content had a significant effect on the characteristics of the resulting modified starches.
Thermal and Rheological Properties of Polyethylene Composites Based on Poly(diphenylsiloxanes)/Organoclay Hybrids Obtained from Two Different Silanes
Authors: Monasterio Fernanda , Pita Victor Rodriguez , Dias Marcos Lopes , Erdmann Eleonora , Destéfanis Hugo
Published: February 2011

Poly(diphenylsiloxanes) (PDPhS) were synthesized in presence of organophilic clay in order to modify its nanostructure. Two silane monomers were used: dimethoxydiphenylsilane and dichlorodiphenylsilane. The following characterizations were performed for all clays: XRD, FTIR, TG/DTG and SEM. These siloxane‐modified clays were more hydrophobic and had enhanced thermal stability. Solvent extraction was carried out in the siloxane‐modified clays and the PDPhS soluble fraction analyzed according the molecular weight via GPC. The presence of free and grafted oligomers on clay surface was identified. The modified clays were added to high density polyethylene (HDPE) by melt processing to obtain HDPE/hybrid clay composites which exhibited marked differences on macroscopic properties when compared with neat HDPE.
In‐Reactor Stabilization of Poly(propylene) with Natural Antioxidants
Authors: Oliveira Renato J.B. , Forrester Amanda M.S. , Marques Maria F.V.
Published: February 2011

Poly(propylene) is one the polymers with the widest range of commercial applications, though as all polymers, it is susceptible to degradation reactions. The addition of antioxidants to polymers is the main way to prevent or retard the degradation process. Extrusion is the most used industrial process to mix additives to the polymer, but this technique involves processing under high temperatures and shear, which causes polypropylene to degrade. Therefore, a Ziegler‐Natta catalyst system based on MgCl2/TiCl4 was prepared with morphology control and the antioxidant was added directly in the polymerization medium, thereby producing spherical and stabilized PP.
Effect of Essential Oils in the Properties of Cellulosic Active Packaging
Authors: Espitia Paula J.P. , Soares Nilda De F.F. , Botti Laura C.M. , Silva Washington A.
Published: February 2011

The use of essential oils (EO) as antifungal agents is an alternative to synthetic fungicides. In the present work, active packaging in the form of cellulosic films and paper coated with a cellulosic emulsion incorporated with 20% cinnamon, oregano or lemongrass EO was developed. The mechanical properties (maximum load‐at‐break and elongation at break), the water‐vapor‐barrier properties and the microscopic characterization of the packaging materials were evaluated. The EO added to the packages significantly affected the maximum load at break of the active films and their elongation at break. The EO incorporated in the films and coated paper did not affect the water‐vapor barrier. However, this parameter was significantly modified when the uncoated paper and coated paper with and without EO were evaluated. The incorporation of EO altered the microstructures of the active films and coated paper.
Development of an Alternative Route for Production of Glassy Polymeric Carbon Electrodes in Laboratorial Scale
Authors: Oiye Érica Naomi , de Andrade José Fernando , Balbo Valdir Roberto , dos Santos André Luiz , de Oliveira Marcelo Firmino
Published: February 2011

A complete alternative and cheaper route for production of glassy polymeric carbon electrodes in laboratorial scale is described. Two kinds of polyphenolic resins were synthesized by mixing the precursors phenol and formaldehyde with 1) ammonium or 2) sodium hydroxide as catalyst. A shorter treatment time of 3.5 days (from 25 to 1000 °C) was employed for preparation of the electrodic material compared with the 5–7 day period proposed in the literature. The obtained materials were inserted into conventional hollow plastic bodies and electrically contacted with copper wire. After proper polishing, the electrodic materials were tested as working electrodes by cyclic voltammetry technique. The data demonstrated that the use of sodium hydroxide causes peculiar problems such as alkaline residues in the electrodic materials and subsequent fading of final product. On the other hand, the materials obtained by the ammonium hydroxide route presented good results in terms of mechanical resistance, glassy appearance, conductivity and voltammetric response, allowing for application of such materials in electrochemistry.
Surface Modification of Synthetic Polymers Using UV Photochemistry in the Presence of Reactive Vapours
Authors: Rajajeyaganthan Ramanathan , Kessler Felipe , de Mour Leal Pedro Henrique , Kühn Sidiney , Weibel Daniel Eduardo
Published: February 2011

Polystyrene (PS), Polyurethane (PU), Polysulfone (PSU) and Polypropylene (PP) were surface modified using UV assisted treatment in the presence of acrylic acid (AA) vapour. In this context, PU and PSU were also modified using vapour of trimethoxy propyl silane (TMPSi). The surface changes were characterized by water contact angle measurement, Fourier transform infrared spectroscopy – Attenuated total reflection and X‐ray photoelectron spectroscopy. Permanent hydrophilic surface was obtained by UV assisted treatment in the presence of AA vapour on all polymers studied. After 65 days of treatment, the polymer surfaces had the original degree of hydrophilicity as obtained immediately after treatment. By using vapour of TMPSi with UV radiation, the surface hydrophobicity of PU and PSU was increased after thermal treatment. The surface modification methodology used was simple and did not require any extensive set‐up compared to traditional surface modification techniques.
Synthesis of Poly(propylene)/Graphite Nanocomposites by in Situ Polymerization
Authors: Montagna Larissa Stieven , Fim Fabiana de Carvalho , Galland Griselda Barrera , Basso Nara Regina de Souza
Published: February 2011

This work presents the synthesis of polypropylene/graphite nanocomposites by in situ polymerization using the catalytic system C20H16Cl2Zr (rac‐ethylenebis (indenyl)zirconium(IV)) dichloride/Methyoluminoxane (MAO). 60 nm graphite nanosheets (GNS) were obtained by means of the chemical exfoliation, thermal and ultrasound treatment. GNS previously treated with MAO were added into the reactor at percentages of 0.3, 1.0 and 2.2% (w/w) in relation to nanocomposite yields. The morphology of graphite nanosheets and nanocomposites was studied by Scanning Electron Microscopy (SEM). Moreover, the structural properties of natural graphite flake (NGF), graphite nanosheets (GNS) and nanocomposites were observed through the X‐Ray diffraction (XRD) analysis and by Transmission Electron Microscopy (TEM).
Polyaniline/Graphite Nanocomposites: Synthesis and Characterization
Authors: Gheno Grasiela , de Souza Basso Nara Regina , Hübler Roberto
Published: February 2011

Graphite nanosheet (GNS) was prepared by physical/chemical method. The polyaniline (PANI)/graphite nanocomposites were synthesized by in situ polymerization of aniline monomer using different amounts (1 to 5 wt%) of graphite nanosheets. The formation of graphite nanosheets was confirmed by Transmission Electron Microscope (TEM) and X‐ray Diffraction (XRD). The surface morphology of exfoliated graphite and PANI/GNS nanocomposites were studied by the Scanning Electronic Microscopy (SEM). A device for electrical conductivity measurements was developed in this work and the results show that the conductivity of PANI/GNS is dependent of the GNS contents.
PEX Synthesized via Peroxide for Oil Pipes, Starting from Different Commercial Polyethylenes: Influence of Comonomer and Catalyst Type
Authors: de Melo Renato P. , Marques Maria F.V.
Published: February 2011

In the present work, crosslinked polyethylene (PEX) was obtained by adding dicumyl peroxide (DCP) to polyethylene. High‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE) were used as starting polymers, synthesized by Ziegler‐Natta or metallocene catalysts. Also, the effect of the comonomer type (butene or hexane) in the LLDPE was investigated. Materials were processed with increasing amounts of dicumyl peroxide (DCP). Samples were pressed with suitable amounts of these components. The efficiency of the crosslinking reaction was evaluated by gel content and thermal properties, and the melting temperature and degree of crystallinity were evaluated using differential scanning calorimetry (DSC). The microstructure of the starting polyethylene was correlated with the effectiveness of crosslinking and the resultant thermal and mechanical properties of the PEX. A new crosslinking coagent was also evaluated, along with the resistance of PEX samples in oil.
Incorporation of PMMA and PS in Styrene and Methyl methacrylate Miniemulsion Homopolymerization
Authors: Colmán M. Magdalena E. , Moreira Rodrigo P. Muniz , Amaral Marcelo do , Araújo Pedro H.H. , Sayer Claudia
Published: February 2011

In this work, the effect of adding different polymer types, such as polystyrene (PS) and poly(methyl methacrylate) (PMMA), with different molecular weight and variable concentrations on the kinetics and the nucleation mechanisms of styrene and methyl methacrylate miniemulsion homopolymerizations was evaluated. Results showed that higher amounts of predissolved polymer increases the fraction of blend (PMMA and PS) particles formed, indicating that it favors the mechanism of droplet nucleation. However, there is a limit to the incorporation of predissolved polymers as very high viscosities of the organic phase lead to poor dispersion of monomer droplets. It was also noted that other nucleation mechanisms besides monomer droplets nucleation were less important in the miniemulsion homopolymerization of methyl methacrylate than in the styrene homopolymerization.
In‐Line Monitoring of Vinyl Acetate/Acrylic Acid Batch Copolymerizations through Near Infrared Spectroscopy
Authors: Pereira Helder Luciano , Machado Fabricio , Lima Enrique Luis , Pinto José Carlos
Published: February 2011

Near infrared spectroscopy (NIRS) is widely used for determination of polymer properties through in line and real time monitoring of polymerization reactions. Experimental runs were performed to evaluate whether NIRS can be used to monitor vinyl acetate/acrylic acid (VAc/AA) copolymerizations carried out in suspension reactors. It is shown that NIRS can be used successfully to monitor the evolution of VAc/AA suspension copolymerizations and that very good calibration models can be developed for monitoring of composition trajectories along the batch. Therefore, NIRS can be employed for real time monitoring and control of copolymer composition in VAc/AA copolymerizations performed in suspension reactors.
Synthesis of Spherical Core‐Shell PVAc‐co‐PMMA/PVA Particles for Use in Vascular Embolization
Authors: Peixoto Luciana S. , Cordeiro Felipe B. , Melo Príamo A. , Nele Márcio , Pinto José Carlos
Published: February 2011

Previous published works described suspension polymerization processes for the production of spherical core‐shell poly(vinyl acetate)/poly(vinyl alcohol) (PVAc/PVA) particles with regular morphology for use as embolic agents in vascular embolization procedures. Although the clinical performance of the produced particles was regarded as excellent, the produced PVAc/PVA particles were prone to agglomeration during storage. For this reason, methyl methacrylate is now used as comonomer in order to increase the glass transition temperature of the final product and prevent agglomeration of polymer particles. The final expansion of particles, intended to control the density of the polymer beads, also exerts a beneficial effect on the rate of particle agglomeration. Therefore, a methodology to obtain spherical poly(vinyl acetate)‐co‐poly(methyl methacrylate)/poly(vinyl alcohol) (PVAc‐co‐PMMA/PVA) particles with core‐shell structure is presented in this work.
Effects of Accelerated Ageing in a PTFE Matrix Polymer Composite
Authors: Martins Silvana , Borges Lavinia , D'Almeida José Roberto
Published: February 2011

The objective of this work is to present a comparative study of the behaviour of a polymer composite before and after accelerated ageing with exposure to UVB radiation and water vapour. The goal is to propose a methodology to characterise material ageing by observing its phenomenological behaviour without taking into account chemical or physical changes that result from ageing. With this objective, tensile and creep tests were performed and the experimental results were used in an inverse approach to identify the material parameters in a three‐parameter rheological model. A silica‐polytetrafluoroethylene (PTFE) matrix reinforced composite was investigated. It was verified that significant differences in the composite behaviour only occurred after a long time. In particular, the strength of the composite increased significantly.
Nanoanalytische Methoden und ihre Anwendungsfelder
Authors: Albers Peter
Published: February 2011

Die Funktion feinteiliger Produkte wie Verstärkerfüllstoffe für Autoreifen und die Leistungsfähigkeit technischer Katalysatoren ist durch Morphologie und chemische Zusammensetzung bis in den Subnanometerbereich bestimmt. Diese Eigenschaften zu kontrollieren und zu optimieren, setzt verlässliche nanoanalytische Messdaten voraus.
Eine Chemikalie scheidet die Geister
Authors: Osterath Brigitte
Published: February 2011

Die einen sehen Gefahren: Bisphenol A gehöre stark eingeschränkt. Die anderen verweisen auf die wissenschaftlichen Beweise, dass die Substanz in den vorherrschenden Mengen für den Menschen harmlos sei. Diese Ansicht hat die europäische Behörde für Lebensmittelsicherheit Ende September 2010 erneut bestätigt. Trotzdem verbietet die EU‐Kommission ab Juni Bisphenol A in Babyflaschen.
Die Seltenheit der Selten‐Erd‐Exporte
Authors: Wildemann Kathrin
Published: February 2011

Kein Handy, kein LCD‐Bildschirm, kein Hybridauto kommt ohne Seltene Erden aus. Fast den gesamten Weltbedarf deckt China — aber es schränkt die Exporte immer stärker ein.
Als Chemiker beim Umweltbundesamt
Authors: Pritzsche Marc
Published: February 2011

Direkt nach meiner Promotion habe ich beim Umweltbundesamt eine Stelle im Fachgebiet Chemikalien angenommen. Meinen Kollegen an der Universität hatten teilweise nur wenig Verständnis dafür: Warum die Forschung verlassen und in einen vermeintlich trockenen Behördenjob wechseln? Heute, zwei Jahre später, weiß ich: Ich habe mich richtig entschieden.
Systemchemie — interdisziplinär und komplex
Authors: Dieckmann Arne
Published: February 2011

Mehrere Variablen gleichzeitig und nicht nur isoliert voneinander zu studieren, ist bei komplexen chemischen Reaktionssystemen unabdingbar. Um die erhaltenen Daten zu analysieren, muss ein Chemiker oft auch Programmierer sein.
Probing the growth of β‐FeSi2 nanoparticles for photovoltaic applications: a combined imaging and spectroscopy study using transmission electron microscopy
Authors: Wong A.S.W. , Ho G.W. , Liew S.L. , Chua K.C. , Chi D.Z.
Published: February 2011

The microstructure of β‐FeSi2 nanoparticles grown using magnetron sputtering on Si has been examined using various electron microscopy techniques. FeSi2 nanoparticles as small as ∼4 nm are found embedded in Si after growth using co‐sputtering of FeSi2 and Si, followed by rapid thermal annealing (RTA). The formation of nanoparticles and its variation in density with Fe content is discussed in terms of phase separation. Our study shows that the size and density of the nanoparticles as well as the extent of Fe diffusion into sputtered Si and substrate can be controlled by controlling the Fe content in the co‐sputtered film. Copyright © 2011 John Wiley & Sons, Ltd.
Photoluminescence study of Ge containing crystal defects
Authors: Kittler Martin , Arguirov Tzanimir , Oehme Michael , Yamamoto Yuji , Tillack Bernd , Abrosimov Nikolai V.
Published: February 2011

Multi‐crystalline Ge (mc‐Ge) and Ge layers on Si substrate grown by MBE and CVD are studied. The photoluminescence (PL) spectra are analysed by comparison with those obtained for bulk Ge. We present a scheme which explains the temperature dependence of the peak positions of the direct and indirect lines observed in the PL spectra. The complex fine structure of the indirect band, consisting of different sub‐peaks, can be understood in terms of phonon assisted processes. Around 80 K emission of longitudinal acoustic (LA) phonons is the decisive process whereas at room temperature absorption of LA phonons dominates. Moreover, PL spectra measured in material with crystal defects suggest that multi‐phonon absorption is involved in the formation of the indirect sub‐peaks. As compared to mono‐Ge the overall luminescence intensity of MBE and CVD grown Ge layers on Si substrate is strongly reduced. In the CVD grown Ge layers the direct line dominates at room temperature whereas in the MBE grown layers the indirect lines are found to be decisive. A shift of the peak positions for the Ge layers to lower energy (10 meV and more) is caused by tensile strain. In the Ge layers on Si and in mc‐Ge, respectively, at 300 or 80 K several lines are observed, ranging roughly between 0.45 and 0.6 eV, which are originated by crystal defects/dislocations.
Enhanced Field Emission and Improved Supercapacitor Obtained from Plasma‐Modified Bucky Paper
Authors: Roy Soumyendu , Bajpai Reeti , Soin Navneet , Bajpai Preeti , Hazra Kiran S. , Kulshrestha Neha , Roy Susanta Sinha , McLaughlin James A. , Misra D. S.
Published: February 2011

The surface morphology of bucky papers (BPs) made from single‐walled carbon nanotubes (CNTs) is modified by plasma treatment resulting in the formation of vertical microstructures on the surface. The shapes of these structures are either pillarlike or conelike depending on whether the gas used during plasma treatment is Ar or CH4. A complex interplay between different factors, such as the electric field within the plasma sheath, polarization of the CNT, intertubular cohesive forces, and ion bombardment, result in the formation of these structures. The roles played by these factors are quantitatively and qualitatively analyzed. The final material is flexible, substrate‐free, composite‐free, made only of CNTs, and has discrete vertically aligned structures on its surface. It shows enhanced field emission and electrochemical charge‐storage capabilities. The field enhancement factor is increased by 6.8 times, and the turn‐on field drops by 3.5 times from an initial value of 0.35 to 0.1 V μm−1 as a result of the treatment. The increase in Brunauer–Emmett–Teller surface area results in about a fourfold improvement in the specific capacitance of the BP electrodes. Capacitance values before and after the treatments are 75 and 290 F g−1, respectively. It is predicted that this controlled surface modification technique could be put to good use in several applications based on macroscopic CNT films.
Application of wavelength dispersive X‐ray spectroscopy to improve detection limits in X‐ray analysis
Authors: Kavčič M. , Žitnik M. , Bučar K. , Szlachetko J.
Published: February 2011

In this work, a Johansson‐type crystal spectrometer was employed to record the high‐resolution L X‐ray emission spectra of pure Ag, Pd and Cd target in order to determine minimum detection limits (MDL) for trace amounts of Pd and Cd in silver. The X‐ray emission was induced by a 3 MeV proton beam as well as by monochromatic synchrotron radiation with excitation energy tuned just below the Ag L3 edge. As a direct consequence of extremely high spectrometer resolution reaching below the natural line widths of the measured L X‐ray lines, detection limits of a few tens of parts per million were reached in case of proton excitation. These limits were additionally lowered by an order of magnitude using energy‐selective photoexcitation with synchrotron radiation as the signal from the resonant Raman scattering (RRS) was completely separated from the Pd signal. The method presented in this work can be used in general to substantially improve detection limits in case of trace elements with atomic number in the close vicinity of the atomic number of the target matrix element. Copyright © 2011 John Wiley & Sons, Ltd.
Theoretical basis for the experimental determination of the intrinsic resolution of a strip detector
Authors: Samedov Victor V.
Published: February 2011

The principal contribution to the peak broadening is the broadening determined by the intrinsic particles' (iparticles) statistics. Iparticles are particles which are generated in the detector's absorber by incident X‐rays and cause signals at the detector's output. Detectors of this type are superconducting and scintillation detectors with quasiparticles and light photons as iparticles, correspondingly. In this work, the theory of branching cascade processes is applied to the description of signal formation in a detector with a single iparticles absorber and several outputs for soft X‐rays. From this theory, it follows the new method of experimental determination of the Fano factor. It is shown that the covariance between two signals of a strip detector depends on the fundamental combination of the Fano factor and the effective energy of the intrinsic particle creation in the absorber material. Independent determination of the effective energy of the intrinsic particle creation allows determining the value of the Fano factor. The important advantage of the proposed method is its independence from the sensors' electronic gains and noise. Copyright © 2011 John Wiley & Sons, Ltd.
Medical Student Surgery Elective in Rural Haiti: A Novel Approach to Satisfying Clerkship Requirements While Providing Surgical Care to an Underserved Population
Authors: Chin‐Quee Anthony , White Laura , Leeds Ira , MacLeod Jana , Master Viraj A.
Published: February 2011

Background

The addition of global health programs to medical school training results in graduates with enhanced clinical skills and increased sensitivity to cost issues. Funding from U.S. medical schools has been unable to meet student demand, and therefore it is often a critical limiting factor to the lack of development of these programs. We describe an alternative approach for global health surgical training for medical students.

Methods

Emory University medical students and faculty, in collaboration with Project Medishare for Haiti, planned, raised funds, and executed a successful short‐term surgical camp to supplement available surgical services in rural Haiti. Learning objectives that satisfied Emory University School of Medicine surgery clerkship requirements were crafted, and third‐year students received medical school credit for the trip.

Results

In the absence of house staff and placed in an under‐resourced, foreign clinical environment, the surgical elective described here succeeded in meeting learning objectives for a typical third‐year surgical clerkship. Objectives were met through a determined effort to ensure that home institution requirements were aligned properly with learning activities while students were abroad and through a close collaboration between medical students, faculty members, and the administration.

Conclusions

Emory University’s international surgery elective for medical students demonstrates that opportunities for supervised, independent student‐learning and global health service can be integrated into a traditional surgical clerkship. These opportunities can be organized to meet the requirements and expectations for third‐year surgery clerkships at other medical colleges. This work also identifies how such trips can be planned and executed in a manner that does not burden strained academic budgets with further demands on resources.
Prognostic Role of Carcinoembryonic Antigen is Influenced by Microsatellite Instability Genotype and Stage in Locally Advanced Colorectal Cancers
Authors: Søreide Kjetil , Søreide Jon Arne , Kørner Hartwig
Published: February 2011

Background

Carcinoembryonic antigen (CEA) is the most frequently used marker for colorectal cancer (CRC). Influence of genetic instability on tumor marker expression is not known. The aim of this study was to investigate microsatellite instability (MSI) of CEA serum levels in locally advanced CRC.

Methods

The observational cohort consisted of stage II–III CRC patients (n = 131) 75 years old or youngerwho underwent surgery with curative intent. CEA serum levels were measured before (preCEA) and immediately after surgery (postCEA). DNA from the extracted tumors was investigated for MSI. Survival was analyzed in univariate and multivariate analyses.

Results

The median preCEA was 3 U/ml (IQR = 1–3, range = 1–136 U/ml). Stage III cancers with MSI had an elevated preCEA more often than those without MSI (25% vs. 0%; p = 0.026). A preCEA >10 U/ml was significantly associated with elevated postCEA (CEA >1 U/ml; odds ratio [OR] = 5.4, 95% CI = 2.1‐14.2; p < 0.001). Survival wasnot significantly different between those with postCEA <10 U/ml vs. postCEA ≥10 U/ml or when stratified by MSI status. A cutoff of postCEA ≤1 U/ml conferred significantly improved survival compared to higher CEA levels. Stratified for MSI status, this difference was significant for microsatellite stable (MSS) cancers only (p = 0.021). In multivariate analysis, postCEA >1 U/ml (hazard ratio [HR] = 3.5, 95% CI = 1.7–7.3, p = 0.001) and stage III (HR = 6.7, 95% CI = 3.0–14.9; p < 0.001) were predictors of decreased survival.

Conclusions

Preoperative CEA levels were significantly higher in stage III cancers with the MSI genotype, and high preoperative CEA was associated with increased postoperative CEA. Absent postoperative CEA in serum conferred improved long‐term survival.
Life‐history and demographic variation in an alpine specialist at the latitudinal extremes of the range
Authors: Wilson Scott , Martin Kathy
Published: February 2011

Alpine environments are unique systems to examine variation in life‐history strategies because temperature and seasonality are similar across broad latitudinal gradients. We studied the life‐history strategies, demography and population growth of white‐tailed ptarmigan Lagopus leucura, an alpine specialist, at the latitudinal extremes of the range in the Yukon (YK, studied from 2004 to 2008) and Colorado (CO, 1987–1996). The two populations were separated by 2,400 km of latitude, and the Yukon site was approximately 2,000 m lower in elevation than the Colorado site. Yukon females bred on average 9 days earlier than those in Colorado, but the latter study was conducted 15 years earlier and breeding dates may have advanced over this period. The length of the breeding season was similar between the two populations, and females had comparable probabilities of re‐nesting after failure. The two populations differed in how they allocated effort to the first clutch as Yukon females laid larger clutches (7.1 vs. 5.9 eggs) but smaller eggs (18.8 vs. 20.5 g) than those in Colorado. Demographic rates also differed; nest survival was higher in the Yukon (0.40) than in Colorado (0.24), and the resultant annual fecundity was nearly twice as high in the Yukon (3.92 vs. 1.77 chicks/female). In contrast, annual adult survival was higher in Colorado although the confidence intervals overlapped (females: YK = 0.35, CO = 0.44; males: YK = 0.48, CO = 0.59). Estimates of annual population growth (λ) indicated both populations were declining, especially in Colorado (λYK = 0.83, λCO = 0.66), and thus, dispersal movements are likely key to long‐term persistence in both cases. Our findings suggest that breeding‐season temperature and seasonality affect measures related to timing of reproduction, but not the costs and benefits of clutch and egg size.