bluuebunny/crossref_metadata_2025 huggingface dataset:
On compactness of the velocity field in the incompressible limit of the full Navier–Stokes–Fourier system on large domains
Authors: Feireisl Eduard , Poul Lukáš
Published: November 2008

The incompressible limit for the full Navier–Stokes–Fourier system is studied on a family of domains containing balls of the radius growing with a speed that dominates the inverse of the Mach number. It is shown that the velocity field converges strongly to its limit locally in space, in particular, the effect of the sound waves is eliminated by means of the local decay estimates for the acoustic wave equation. Copyright © 2008 John Wiley & Sons, Ltd.
Characterization of high molecular weight coffee fractions and their fermentation by human intestinal microbiota
Authors: Reichardt Nicole , Gniechwitz Diana , Steinhart Hans , Bunzel Mirko , Blaut Michael
Published: November 2008

To investigate the structure and fermentability of high Mr components of coffee brews by human gut bacteria Arabica coffee samples of three different degrees of roast (light, medium, and dark) were used for drip brew preparations and fractionation by ultrafiltration with different Mr cut‐offs. Total carbohydrates of the fractions ranged from 28.6 g/100 g to 56.7 g/100 g. Galactomannans and arabinogalactans were the main polysaccharides and made up between one‐fourth and one‐half of the respective coffee fraction. After 24 h of incubation with a human fecal suspension the polysaccharides of all fractions were extensively degraded. A decrease in the absorbance values at 405 and 280 nm, respectively, indicated that also chemically noncharacterized UV‐active components such as Maillard reaction products, had been partially degraded or modified by the human gut bacteria. The remainder after 24 h of fermentation still showed antioxidant activity. Bacterial cells belonging to the Bacteroides–Prevotella group increased 2‐ to 40‐fold during fermentation depending on the Mr range of the fraction and the degree of roast. The production of high amounts of acetate and propionate is in accordance with a role of these bacteria in the degradation of high Mr components from coffee.
1H and 13C spectral assignment of substituted 5H‐[1,3]thiazolo[2,3‐b]quinazolin‐5‐one and 12H‐[1,3]benzothiazolo[2,3‐b] quinazolin‐12‐one
Authors: Docampo Palacios Maite L. , Fascio Mirta L. , Villalobo Anais Fernández , Pellón Rolando F.
Published: November 2008

1H and 13C spectroscopic data for 5H‐[1,3]thiazolo[2,3‐b]quinazolin‐5‐one and 12H‐[1,3]benzothiazolo[2,3‐b]quinazolin‐12‐one derivatives were fully assigned by combination of one‐ and two‐dimensional experiments (DEPT, HMBC and HMQC). Both heterocyclic systems show similar spectroscopic properties with some remarkable differences. Copyright © 2008 John Wiley & Sons, Ltd.
Screening of Different Titanium (IV) Catalysts in the Synthesis of Poly(ethylene terephthalate)
Authors: Ahmadnian Fatemeh , Velasquez Fernanda , Reichert Karl‐Heinz
Published: November 2008

The polycondensation of bis(hydroxyethylene) terephthalate and its oligomers to PET catalyzed by different chelated and non‐chelated titanium catalysts in a lab‐scale stirred‐tank reactor and differential scanning calorimeter were investigated. Different titanium compounds showed different activity and selectivity. The nature of catalyst ligands plays an important role in catalyst efficiency. Non‐chelated titanium derivatives were more active and less selective. Reaction progress is characterized by an initial inhibition period depending on the type of catalyst. The original titanium compounds used are precursors and are probably activated by a ligand exchange reaction.

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Transport and Reaction Characteristics of Reconstructed Polyolefin Particles
Authors: Seda Libor , Zubov Alexandr , Bobak Marek , Kosek Juraj , Kantzas Apostolos
Published: November 2008

The 3D spatial structure of porous polyethylene particles was reconstructed from their X‐ray micro‐tomography images. Several polyolefin particles with an artificial granular structure were generated. Transport in reconstructed particles was calculated for the case of a monomer diffusing through both the pores and the polymer. The calculated degassing characteristics of reconstructed polyolefin particles can be compared to experiments. Monomer mass transport limitations are important not only in the early stage of particle growth, but also in fully‐developed polyolefin particles. The problems and limitations of the developed method are discussed. The method developed allows prediction of the effect of particle structure on mass transport limitations for real particle structures.

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Effect of Reaction Temperature on the Gel Content of Acrylic Latexes
Authors: Kohut‐Svelko Nicolas , Pirri Rosangela , Asua José M. , Leiza Jose R.
Published: November 2008

The effect of reaction temperature on the kinetics and the microstructure properties of polyacrylates produced by seeded semicontinuous emulsion homopolymerization of two acrylate monomers (butyl acrylate and 2‐ethylhexyl acrylate) initiated by a thermal initiator was investigated. Contrary to what has been reported at higher temperatures (75–95 °C), increasing reaction temperature (from 60 to 80 °C) led to a decrease of the amount of gel content produced in the semicontinuous polymerizations. These results were analyzed by means of a Monte‐Carlo model of the process.

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The lattice Boltzmann method and the finite volume method applied to conduction–radiation problems with heat flux boundary conditions
Authors: Mondal Bittagopal , Mishra Subhash C.
Published: November 2008

This article deals with the implementation of the lattice Boltzmann method (LBM) in conjunction with the finite volume method (FVM) for the solution of conduction–radiation problems with heat flux and temperature boundary conditions. Problems in 1‐D planar and 2‐D rectangular geometries have been considered. The radiating–conducting participating medium is absorbing, emitting and scattering. In the 1‐D planar geometry, the south boundary is subjected to constant heat flux, while in the 2‐D geometry the south and/or the north boundary is at constant heat flux condition. The remaining boundaries are at prescribed temperatures. The energy equation is solved using the LBM and the radiative information for the same is computed using the FVM. In the direct method, by prescribing temperatures at the boundaries, the temperature profile and heat flux are calculated. The computed heat flux values are imposed at the boundaries to establish the correctness of the numerical code in the inverse method. Effects of various parameters such as the extinction coefficient, the scattering albedo, the conduction–radiation parameter, the boundary emissivity and the total heat flux and boundary temperatures are studied on the distributions of temperature, radiative and conductive heat fluxes. The results of the LBM in conjunction with the FVM have been found to compare very well with those available in the literature. Copyright © 2008 John Wiley & Sons, Ltd.
Purpose and regulation of stem cells: a systems‐biology view from the Caenorhabditis elegans germ line
Authors: Cinquin Olivier
Published: November 2008

Stem cells are expected to play a key role in the development and maintenance of organisms, and hold great therapeutic promises. However, a number of questions must be answered to achieve an understanding of stem cells and put them to use. Here I review some of these questions, and how they relate to the model system provided by the Caenorhabditis elegans germ line, which is exceptional in its thorough genetic characterization and experimental accessibility under in vivo conditions. A fundamental question is how to define a stem cell; different definitions can be adopted that capture different features of interest. In the C. elegans germ line, stem cells can be defined by cell lineage or by cell commitment (‘commitment’ must itself be carefully defined). These definitions are associated with two other important questions about stem cells: their functions (which must be addressed following a systems approach, based on an evolutionary perspective) and their regulation. I review possible functions and their evolutionary groundings, including genome maintenance and powerful regulation of cell proliferation and differentiation, and possible regulatory mechanisms, including asymmetrical division and control of transit amplification by a developmental timer. I draw parallels between Drosophila and C. elegans germline stem cells; such parallels raise intriguing questions about Drosophila stem cells. I conclude by showing that the C. elegans germ line bears similarities with a number of other stem cell systems, which underscores its relevance to the understanding of stem cells. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Parental needs for information related to neurocognitive late effects from pediatric cancer and its treatment
Authors: Trask Christine L. , Welch Jennifer J. Greene , Manley Peter , Jelalian Elissa , Schwartz Cindy L.
Published: November 2008

Background

Parents' needs for information about neurocognitive late effects (NCLE) associated with cancer treatment may differ as to the preferred source, format, timing, and amount of information about potential NCLE from treatment. Parental characteristics, treatment variables, and other risk factors may also modulate the needs for information about NCLE.

Procedure

A total of 90 parents completed a series of questionnaires related to their perceived knowledge of NCLE and need for further information about NCLE, coping style, stress, perceived risk for NCLE, and information related to their child's diagnosis and treatment.

Results

These findings indicate that although parents report feeling knowledgeable about NCLE, they continue to have a need for further information. Many parents would prefer multi‐modal presentation of this material, but they do not have a clear consensus about the optimal time to first discuss this risk. Parents who reported higher levels of emotional distress expressed a preference to receive information earlier. Stepwise regression analyses revealed that parents of children who received cranial radiation reported being well informed about NCLE, whereas parents of children who received chemotherapy reported wanting more information about NCLE.

Conclusions

It is important to recognize the high level of need for information about potential NCLE in caregivers of children with cancer. Further research is needed to understand how to tailor the timing and mode of presentation to individual families. Pediatr Blood Cancer 2009;52:273–279. © 2008 Wiley‐Liss, Inc.
Positron emission tomography in subcutaneous panniculitis‐like T‐cell lymphoma
Authors: Rodriguez Victor R. , Joshi Aparna , Peng Fangyu , Rabah Raja M. , Stockmann Paul T. , Savaşan Süreyya
Published: November 2008

Subcutaneous panniculitis‐like T‐cell lymphoma (SPTCL), an uncommon disorder, was diagnosed in a 17‐year‐old female when she presented with multiple hard subcutaneous masses that developed over 3 years. She was treated on chemotherapy consisting of cyclophosphamide, doxorubicin, vincristine, and prednisone. Pre‐ and post‐treatment positron emission tomography study demonstrated dramatic resolution of the subcutaneous lesions indicating its usefulness in SPTCL staging and treatment response monitoring. Pediatr Blood Cancer 2009;52:406–408. © 2008 Wiley‐Liss, Inc.
Aprepitant in adolescent patients for prevention of chemotherapy‐induced nausea and vomiting: A randomized, double‐blind, placebo‐controlled study of efficacy and tolerability
Authors: Gore Lia , Chawla Sant , Petrilli Antonio , Hemenway Molly , Schissel Debra , Chua Vickey , Carides Alexandra D. , Taylor Arlene , DeVandry Suzanne , Valentine Jack , Evans Judith K. , Oxenius Bettina ,   for the Adolescent Aprepitant in Cancer Study Group
Published: November 2008

Background

The neurokinin‐1 receptor antagonist aprepitant, plus a 5HT3 antagonist and corticosteroid is well‐tolerated and effective in preventing chemotherapy‐induced nausea and vomiting in adults but has not been formally assessed in adolescents.

Procedure

Patients age 11–19 years old receiving emetogenic chemotherapy were randomized 2:1 to aprepitant triple therapy (aprepitant [A] 125 mg p.o., dexamethasone [D] 8 mg p.o., and ondansetron [O] 0.15 mg/kg i.v. t.i.d. day 1; A 80 mg, D 4 mg, and O 0.15 mg/kg t.i.d. day 2; A 80 mg and D 4 mg day 3; and D 4 mg day 4) or a control regimen (D 16 mg and O 0.15 mg/kg t.i.d. day 1; D 8 mg and O 0.15 mg/kg t.i.d. day 2; and D 8 mg days 3 and 4). The primary endpoint was the difference in drug‐related adverse events during and for 14 days following treatment. Efficacy and aprepitant pharmacokinetics were assessed.

Results

Baseline characteristics were similar between aprepitant (N = 28) and control (N = 18) groups. Febrile neutropenia was more frequent in the aprepitant group (25% vs. 11.1%). Complete response (CR) rates were 35.7% for aprepitant triple therapy versus 5.6% for the control group. Mean plasma aprepitant AUC0–24 hr and Cmax on day 1 and mean trough concentrations on days 2 and 3 were consistently lower compared to historical data obtained from healthy adults; however, the differences were not clinically significant.

Conclusion

Aprepitant triple therapy was generally well tolerated; CR were greater with aprepitant, although not statistically significant. Pharmacokinetics suggest that the adult dosing regimen is appropriate for adolescents. Pediatr Blood Cancer 2009;52:242–247. © 2008 Wiley‐Liss, Inc.
Intensive chemotherapy for systemic anaplastic large cell lymphoma in children and adolescents: Final results of children's cancer group study 5941
Authors: Lowe Eric J. , Sposto Richard , Perkins Sherrie L. , Gross Thomas G. , Finlay Jonathan , Zwick David , Abromowitch Minnie
Published: November 2008

Background

Anaplastic large cell lymphoma (ALCL) is characterized by advanced disease at presentation (70–80% of pediatric cases) and accounts for 10–15% of all childhood lymphomas. Treatment strategies for pediatric ALCL vary from short pulse B‐NHL chemotherapy to prolonged leukemia like therapy. The optimal treatment strategy is unknown.

Methods

CCG‐5941 used a compressed aggressive multiagent T‐cell lineage chemotherapy regimen consisting of a 3‐week induction therapy (vincristine, prednisone, cyclophosphamide, daunomycin, asparaginase) followed by a 3‐week consolidation period (vincristine, prednisone, etoposide, 6‐thioguanine, cytarabine, asparaginase, methotrexate) followed by six courses of maintenance chemotherapy at 7‐week intervals (cyclophosphamide, 6‐thioguanine, vincristine, prednisone, doxorubicin, asparaginase, methotrexate etoposide, cytarabine). Total therapy was 48 weeks.

Results

Eighty‐six children (male 56%, female 44%) with non‐localized ALCL (CD30+) were treated. The majority of tumors were positive for ALK (90%) and of T lineage (83%). Extranodal disease was common (mediastinum 35%, skin 15%, lung 14%, bone 12%, bone marrow 13%, liver 6%, and other viscera 17%). Grade 4 neutropenia occurred in 82% of patients. The 5‐year EFS was 68% (95% CI of 57–78%) and the 5‐year OS was 80% (95% CI of 69–87%). There were 21 relapses and 4 toxic deaths as first events. Relapse occurred early with 17 (81%) relapses occurring within 2 years of diagnosis and 12 (57%) while receiving therapy. Univariate analysis for risk factors only identified bone marrow involvement predicting lower EFS (P = 0.03).

Conclusions

CCG‐5941 demonstrated efficacy similar to previously reported regimens but with significant hematologic toxicity. Pediatr Blood Cancer 2009;52:335–339. © 2008 Wiley‐Liss, Inc.
Small cell undifferentiated variant of hepatoblastoma: Adverse clinical and molecular features similar to rhabdoid tumors
Authors: Trobaugh‐Lotrario Angela D. , Tomlinson Gail E. , Finegold Milton J. , Gore Lia , Feusner James H.
Published: November 2008

Background

Small cell undifferentiated (SCU) histology in patients with stage I hepatoblastoma (HB) predicts an increased risk of relapse. We sought to determine the significance of SCU histology in patients with unresectable HB.

Procedure

Patients enrolled on the pediatric Intergroup (INT0098) trial for HB and patients from the personal consultation files of two of the authors (MF, LG) were reviewed for cases with SCU histology. These patients were compared with SCU HB patients identified by literature review.

Results

Eleven patients were studied. All patients with reported AFP results exhibited normal or minimally increased serum AFP levels. None of the patients survived: 10 died of disease progression, and 1 died from treatment complications. Immunostaining revealed that tumors from six of six patients tested were INI1 negative. Cytogenetic and molecular abnormalities in one patient (and two patients from the literature review) were similar to those described in rhabdoid tumors. Comparison with patients from the literature review revealed similar results except that 4 of 29 patients survived without evidence of disease.

Conclusions

SCU histology in HB patients is associated with an adverse outcome. These tumors appear to be biologically different from non‐SCU HB. Evaluation of patient characteristics and outcomes for children with SCU HB and/or those with low AFP levels should be determined from large cooperative group studies. In the meantime, we suggest patients with unresectable HB containing SCU elements have careful cytogenetic, molecular, and immunohistochemical evaluation to ascertain rhabdoid features and receive treatment that differs from that provided for other HB patients. Pediatr Blood Cancer 2009;52:328–334. © 2008 Wiley‐Liss, Inc.
Viscoelastic behavior of a polyester resin concrete reinforced with nonmetallic bars under bending loads
Authors: San‐José J. Tomás , Aguado Antonio , Manso Juan M.
Published: November 2008

This article deals with the study of a highly durable polyester polymer concrete reinforced with glass fiber polymer rebars. It describes the specific properties of the concrete, which were tested using different experimental techniques such as porosimetry, scanning electron microscopy, and petrography. Likewise, characterization on a macroscale was carried out to define the mechanical properties of the material (modulus of elasticity, stress–strain curve, ultimate strength, and bond). Having defined these properties, the article then presents a relatively simple calculation method to estimate the ultimate bearing capacity of beams under bending load, which is then verified by testing both beams and full‐scale elements. Bearing in mind the viscoelastic nature of the polymer, several considerations are advanced on the identification of safety factors connected with permanent load (deferred deformations) and live load. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Self‐lubricating and self‐protecting properties of polymer composites for wear and friction applications
Authors: Quintelier J. , Samyn P. , De Doncker L. , Vermeulen J. , Tuzolana T. , Cardon L. , Ragaert K. , De Baets P. , Degrieck J.
Published: November 2008

Based on the well‐known pin‐on‐disc test rig, a new test setup has been developed for online measuring of the wear and friction behavior of polymer matrix composites. Contrasting with a traditional friction and wear test rig, a steel pin and composite disc are presently used to study the influence of wear debris and fiber orientation. This test setup has a main influence on the results. The polymer materials, a thermoset polyester, and a thermoplastic polyphenylene sulfide were reinforced with glass and carbon fibers, respectively. The results show two different promising aspects of “new” materials for wear and friction applications and more specific to different machine components, namely self‐lubricating and self‐protecting ability. The self‐lubricating ability exists from creating a polymer film on the surface which reduces the coefficient of friction, and the self‐protecting behavior is because of the creation of a protecting carbon film on the surface. The self‐lubricating ability depends on the test parameters, while the self‐protecting ability was due to the material and the structure. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Covalent addition of diethyltoluenediamines onto carbon nanotubes for composite application
Authors: Wang Shiren , Liang Richard , Wang Ben , Zhang Chuck
Published: November 2008

Diethyltoluenediamines (DETDA) was grafted to single‐walled carbon nanotubes (SWNTs) through diazonium‐based addition for improving dispersion and interfacial bonding in SWNT/epoxy nanocomposites. Characterization results of Fourier Transformed Infrared spectroscopy and Raman spectroscopy validated covalent bonding between DETDA and carbon nanotubes. The degree of functionalization was about 4% based on thermo‐gravimetric analysis. Interfacial bonding strength was computed in the presence of chemical bonding and the computation results indicated that the interfacial shear strength in the presence of functionalized carbon nanotubes was significantly enhanced. The experimental test revealed that the tensile strength of nanocomposites was enhanced about 23% and Young's modulus about 25%, with 0.5 wt% loading of functionalized‐nanotubes. These considerable improvements further verified the load‐transfer enhancement in the functionalized‐SWNTs/epoxy nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Role of fillers on three‐body abrasive wear behavior of glass fabric reinforced epoxy composites
Authors: Suresha B. , Chandramohan G. , Mohanram P.V.
Published: November 2008

The article summarizes an experimental study on the abrasive wear behavior of particulate filled glass‐epoxy (G‐E) composites. The two fillers investigated were graphite and alumina. The wear behavior was assessed by rubber wheel abrasion tests. The tests were carried out for 270, 540, 810, and 1080 m abrading distances at 22 and 32 N loads. The worn surfaces were examined using scanning electron microscopy (SEM). The results showed varied responses under different abrading distance because of the addition of fillers in G‐E composites. Graphite filler, however, performed poorly resulting in significant deterioration in wear performance while the alumina filled G‐E composite showed improved abrasion resistance. Selected mechanical properties such as hardness, tensile strength, and elongation at fracture were analyzed for investigating wear property correlations. The SEM studies indicate the reasons for failure of composites and influencing parameters. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Tapioca starch‐poly(lactic acid)‐Cloisite 30B nanocomposite foams
Authors: Lee Siew Yoong , Hanna Milford A.
Published: November 2008

Tapioca starch (TS), poly(lactic acid) (PLA), and Cloisite 30B nanocomposite foams, with four clay contents of 1, 3, 5, 7 wt%, were prepared by a melt‐intercalation method. Selected structural, thermal, physical, and mechanical properties were characterized using X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine, respectively. XRD results indicated that intercalation of TS/PLA into the nanoclay layers occurred in all four nanocomposite foams. At the same time, tactoid structures were observed in all nanocomposite foams but to a lesser extend with 1 and 3 wt% clay contents. Effect of clay content on melting temperature (Tm), onset degradation temperature, radial expansion ratio, unit density, bulk compressibility and bulk spring index of the nanocomposites were investigated. Among the four nanocomposites, 3 wt% clay content produced significantly different (p < 0.05) properties. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Modification of carbon nanotubes and its effect on properties of carbon nanotube/epoxy nanocomposites
Authors: Špitalský Zdenko , Matějka Libor , Šlouf Miroslav , Konyushenko Elena N. , Kovářová Jana , Zemek Josef , Kotek Jiří
Published: November 2008

We have studied an effect of three types of modifications of carbon nanotubes (CNTs) on dispersion and mechanical properties of final epoxy‐amine based nanocomposites. First approach includes end‐walled covalent chemical modification at the ends of nanotubes. The second one is side‐walled covalent chemical modification along the whole length of nanotubes. The third procedure is noncovalent, physical modification done by the CNT surface coating with polyaniline. The modification of nanotubes was determined by X‐ray photoelectron spectroscopy. The prepared epoxy‐amine nanocomposites were characterized by dynamic‐mechanical analysis, tensile testing, light microscopy, transmission electron microscopy, and thermogravimetry. We observed an improvement of the mechanical properties and the thermal stability by addition of the carbon nanotubes to the epoxy matrix. The strong interactions between the nanotube and the polymer matrix were discovered in the nanocomposites with physically modified nanotubes. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Preparation and characterization of high permittivity and low loss PTFE/CaTiO3 microwave laminates
Authors: Rajesh S. , Murali K.P. , Ratheesh R.
Published: November 2008

This article discusses the preparation and characterization of CaTiO3 filled PTFE flexible laminates for microwave substrate applications. Single phase CaTiO3 filler composition was prepared through solid‐state ceramic route. Phase formation was confirmed by powder X‐ray diffraction studies. Morphology and filler distribution of the composites were studied using scanning electron microscopic technique. Permittivity and loss tangent of the composite substrates were measured at X‐band frequency region (8.2–12.4 GHz) using waveguide cavity perturbation technique. Effective permittivity of the composites was compared with theoretically predicted values. Temperature coefficient of permittivity (τεr) of the composites was also measured in the 0–100°C temperature range. PTFE/CaTiO3 composite has an effective permittivity of 11.8 and a loss tangent of 0.0036 at optimum filler loading. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Nonlinear optical properties of poly‐ortho‐toluidine films implantated by N+ ions with different energy
Authors: Shaolin Yan , Hongcai Wu , Song Gao
Published: November 2008

This article reports experimental work on the effect of N+ ion implantation on third‐order nonlinear optical properties of POT films. Using K2Cr2O7 as oxidizing agent, poly‐ortho‐toluidine (POT) was synthesized in 1 M hydrochloric. The POT films were prepared by spin‐coating method and then implantated by N+ ions (15–30 KeV) at a dose 1.9 × 1016 ions/cm2. The films were characterized by FT‐IR spectroscopy, visible spectroscopy and SEM, their third‐order nonlinear optical susceptibility (χ(3)) were also examined by a degenerate four‐wave mixing (DFWM) system at 532nm. Compared to pristine POT films, the optical band gap obtained from visible spectra decreased from 3.58 to 3.48 eV when the energy was 30 KeV. Also, The χ(3) value of implantated POT films increased from 3.31 × 10−10 esu to 4.04 × 10−9 esu when the implantated energy was 25 KeV. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Preparation and characterization of sepiolite‐poly(ethyl methacrylate) and poly(2‐hydroxyethyl methacrylate) nanocomposites
Authors: Benlikaya Ruhan , Alkan Mahir , Kaya İsmet
Published: November 2008

Poly(ethyl methacrylate) (PEMA) and poly(2‐hydroxyethyl methacrylate) (PHEMA) nanocomposites with sepiolite in pristine and silylated form were prepared using the solution intercalation method and characterized by the measurements of XRD, TEM, FTIR‐ATR, TG/DTG, and DSC. The TEM analysis indicated that the volume fraction of fibers in sepiolite decreased and the fiber bundles dispersed in PEMA and PHEMA at a nanometer scale. These results regarding TEM micrographs were in agreement with the data obtained by XRD. The increase in thermal stability of nanocomposites of PEMA is higher than that of PHEMA according to the data obtained from TG curves. The DTG analysis revealed that sepiolite/modified sepiolite caused some changes, as confirmed by FTIR in the thermal degradation mechanism of the polymers. Tg temperatures of PEMA and PHEMA usually increased upon the addition of sepiolite/modified sepiolite. In addition, modification of sepiolite with 3‐APTS had a slight influence on thermal properties of the nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Viscoplastic analysis of fiber reinforced polymer matrix composites under various loading conditions
Authors: Guedes R.M.
Published: November 2008

The present study aims modeling the viscoplastic behavior of polymer matrix composite laminates under different loading conditions. The adopted model is based on the one‐parameter plasticity model employed to predict the plastic part of the recognized nonlinear behavior of fiber composites [C.T. Sun and J.L. Chen, J. Compos. Mater., 23, 1009 (1989)]. This model evolved to a three‐parameter constitutive viscoplastic model used to describe successfully the strain‐rate dependent mechanical behavior. Based on this model, designated as 3PV, a numerical implementation was made, based on the Classical Laminate Theory (CTL), to simulate non‐linear behavior of general laminates. The validation of this numerical implementation was performed using experimental data reported in literature. The first step was to assess the model predictions under high strain rates. The model was able to model high strain rate mechanical response, of an epoxy system reinforced with glass fibers, between 10 and 2,500 s−1. Furthermore the model proved to be reasonable accurate to simulate creep, stress relaxation and constant strain rate loading of the same material system under high temperatures. Following the experimental observations of vsicoplasticity strain evaluation during load and unloading made by Kim and Tsai [J. Compos. Mater. 36(6), 745 (2002)], a simple model modification is suggested. This modified model proved accurate enough to simulate relaxation successfully of a composite during loading and unloading. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Biodegradability, antibacterial properties, and ultraviolet protection of polyvinyl alcohol‐natural polyphenol blends
Authors: Xu Xiang‐Ju , Huang Shao‐Ming , Zhang Li‐Hua
Published: November 2008

Polymer films of tea polyphenol (TP)/polyvinyl alcohol (PVA) were prepared by a solution casting. The films were studies for intermolecular interactions by Fourier transform infrared spectroscopy, the shifts in the major signals of IR for OH and CO absorption, and with varied intensities in the Fourier transform infrared spectroscopy spectra indicated intermolecular hydrogen bonded interaction between PVA and TP. The biodegradability of the PVA/TP blends is measured by soil burial test, the percentage weight loss of the PVA/TP blends increased with increasing TP content. And the antibacterial activity of PVA/TP blends was determined by shake flask test and three kinds of bacteria used were as follows: Staphylcoccus aures, Escherichia coli, and Proteus valgaris. The blends exhibit strong antibacterial activity against the three kinds of bacteria. According to the Australia/New Zealand standard, AS/NZS 4399:1996, the ultraviolet protective properties of the PVA/TP blends were evaluated and the result shows that the capacity of the ultraviolet protection for blends was extremely increased by adding TP to PVA. And all blends reach the highest level (50+) of the standard. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Uniformity of silicon microcrystallinity in large area RF capacitive reactors
Authors: Strahm Benjamin , Hollenstein Christoph , Howling Alan A.
Published: November 2008

In this work, a controlled, nonuniform RF power distribution is produced across a large area PECVD reactor. The effect of the RF power distribution on the crystallinity of silicon thin films deposited from silane‐hydrogen discharges is studied. Results show that, even with a strongly nonuniform RF distribution (70%), uniform crystallinity can still be achieved for films deposited at the limit between amorphous and microcrystalline silicon provided that the input silane concentration is sufficiently low (nominal concentration lower than ≈︂1˙2%). This work shows that to deposit silicon with a uniform microcrystallinity over large area using high silane concentration, the reactor design must guarantee a highly uniform power distribution. Copyright © 2008 John Wiley & Sons, Ltd.
Redox reactions of copper(II) upon electrospray ionization in the presence of acridine ligands with an amide side chain
Authors: Tintaru Aura , Charles Laurence , Milko Petr , Roithová Jana , Schröder Detlef
Published: November 2008

The complexation of copper(II) to acridine derivatives has been studied by means of electrospray ionization (ESI) mass spectrometry. Under soft conditions of ionization, the ESI mass spectra of methanolic solutions of copper(II) chloride and the acridine ligands show abundant signals of the mononuclear complexes formed from the metal and ligand. Depending on the position of the N‐benzoylamino substituent in the acridinic heterocycle, however, the copper atom involved in the complexation process adopts different oxidation states in the resulting cations. Hence, the metal is reduced to copper(I) in the monocationic complex with the compound substituted in position 2, whereas it keeps its divalent state in the monocation formed with the compound substituted in position 4. As a consequence, the regioisomers lead to monocations with different masses in the ESI spectra. In order to understand this unusual behavior of two isomeric compounds, additional experiments have been performed with quinoline as a model. Copyright © 2008 John Wiley & Sons, Ltd.
Investigating the binding of β‐1,4‐galactan to Bacillus licheniformis β‐1,4‐galactanase by crystallography and computational modeling
Authors: Le Nours Jérôme , De Maria Leonardo , Welner Ditte , Jørgensen Christel T. , Christensen Lars L. H. , Borchert Torben V. , Larsen Sine , Lo Leggio Leila
Published: November 2008

Microbial β‐1,4‐galactanases are glycoside hydrolases belonging to family 53, which degrade galactan and arabinogalactan side chains in the hairy regions of pectin, a major plant cell wall component. They belong to the larger clan GH‐A of glycoside hydrolases, which cover many different poly‐ and oligosaccharidase specificities. Crystallographic complexes of Bacillus licheniformis β‐1,4‐galactanase and its inactive nucleophile mutant have been obtained with methyl‐β(1→4)‐galactotetraoside, providing, for the first time, information on substrate binding to the aglycone side of the β‐1,4‐galactanase substrate binding groove. Using the experimentally determined subsites as a starting point, a β(1→4)‐galactononaose was built into the structure and subjected to molecular dynamics simulations giving further insight into the residues involved in the binding of the polysaccharide from subsite −4 to +5. In particular, this analysis newly identified a conserved β‐turn, which contributes to subsites −2 to +3. This β‐turn is unique to family 53 β‐1,4‐galactanases among all clan GH‐A families that have been structurally characterized and thus might be a structural signature for endo‐β‐1,4‐galactanase specificity. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Intrinsic structural disorder of mouse proNGF
Authors: Paoletti Francesca , Covaceuszach Sonia , Konarev Peter V. , Gonfloni Stefania , Malerba Francesca , Schwarz Elisabeth , Svergun Dmitri I. , Cattaneo Antonino , Lamba Doriano
Published: November 2008

The unprocessed precursor of the Nerve Growth Factor (NGF), proNGF, has additional functions, besides its initially described role as a chaperone for NGF folding. The precursor protein endows apoptotic and/or neurotrophic properties, in contrast to the mature part. The structural and molecular basis for such distinct activities are presently unknown. Aiming to gain insights into the specific molecular interactions that govern rm‐proNGF biological activities versus those of its mature counterpart, a structural study by synchrotron small angle X‐ray scattering (SAXS) in solution was carried out. The different binding properties of the two proteins were investigated by surface plasmon resonance (SPR) using, as structural probes, a panel of anti‐NGF antibodies and the soluble forms of TrkA and p75NTR receptors. SAXS measurements revealed the rm‐proNGF to be dimeric and anisometric, with the propeptide domain being intrinsically unstructured. Ab initio reconstructions assuming twofold symmetry generated two types of structural models, a globular “crab‐like” and an elongated shape that resulted in equally good fits of the scattering data. A novel method accounting for possible coexistence of different conformations contributing to the experimental scattering pattern, with no symmetry constraints, suggests the “crab‐like” to be a more likely proNGF conformation. To exploit the potential of chemical stabilizers affecting the existing conformational protein populations, SAXS data were also collected in the presence of ammonium sulphate. An increase of the proNGF compactness was observed. SPR data pinpoints that the propeptide of proNGF may act as an intrinsically unstructured protein domain, characterized by a molecular promiscuity in the interaction/binding to multiple partners (TrkA and p75NTR receptors and a panel of neutralizing anti‐NGF antibodies) depending on the physiological conditions of the cell. These data provide a first insight into the structural basis for the selectivity of mouse short proNGF, versus NGF, towards its binding partners. Proteins 2009. © 2008 Wiley‐Liss, Inc.
All‐atom chain‐building by optimizing MODELLER energy function using conformational space annealing
Authors: Joo Keehyoung , Lee Jinwoo , Seo Joo‐Hyun , Lee Kyoungrim , Kim Byung‐Gee , Lee Jooyoung
Published: November 2008

We have investigated the effect of rigorous optimization of the MODELLER energy function for possible improvement in protein all‐atom chain‐building. For this we applied the global optimization method called conformational space annealing (CSA) to the standard MODELLER procedure to achieve better energy optimization than what MODELLER provides. The method, which we call MODELLERCSA, is tested on two benchmark sets. The first is the 298 proteins taken from the HOMSTRAD multiple alignment set. By simply optimizing the MODELLER energy function, we observe significant improvement in side‐chain modeling, where MODELLERCSA provides about 10.7% (14.5%) improvement for χ1 (χ1 + χ2) accuracy compared to the standard MODELLER modeling. The improvement of backbone accuracy by MODELLERCSA is shown to be less prominent, and a similar improvement can be achieved by simply generating many standard MODELLER models and selecting lowest energy models. However, the level of side‐chain modeling accuracy by MODELLERCSA could not be matched either by extensive MODELLER strategies, side‐chain remodeling by SCWRL3, or copying unmutated rotamers. The identical procedure was successfully applied to 100 CASP7 template base modeling domains during the prediction season in a blind fashion, and the results are included here for comparison. From this study, we observe a good correlation between the MODELLER energy and the side‐chain accuracy. Our findings indicate that, when a good alignment between a target protein and its templates is provided, thorough optimization of the MODELLER energy function leads to accurate all‐atom models. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Mechanical unfolding pathway and origin of mechanical stability of proteins of ubiquitin family: An investigation by steered molecular dynamics simulation
Authors: Das Atanu , Mukhopadhyay Chaitali
Published: November 2008

Like the muscle protein Titin, proteins of the ubiquitin family exhibit a parallel strand arrangement, but otherwise having a distinctly different fold and not involved in an obvious load‐bearing function, exhibit high resistance to mechanical unfolding. We have applied all‐atom molecular dynamics simulation technique in implicit solvent to present a deep insight into the force‐induced unfolding pathway of three proteins—ubiquitin, NEDD8, and SUMO‐2—all having almost similar structural features. Two intermediates evolve in the unfolding pathway of each of the three proteins. The first intermediate, which has already been identified in case of ubiquitin by earlier simulation results, is similar for ubiquitin and NEDD8, but different in SUMO‐2. We have found a new intermediate with β3–β4 hairpin and some residual α‐helical character; and this intermediate is common for all the three proteins. Thus, proteins of the ubiquitin family pass through a well‐defined conformation in their force‐induced unfolding pathway. Reason behind the higher mechanical stability of the proteins with parallel strand structures like Titin has also been identified. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Domain motions of hyaluronan lyase underlying processive hyaluronan translocation
Authors: Joshi Harshad V. , Jedrzejas Mark J. , de Groot Bert L.
Published: November 2008

Hyaluronan lyase (Hyal) is a surface enzyme occurring in many bacterial organisms including members of Streptococcus species. Streptococcal Hyal primarily degrades hyaluronan‐substrate (HA) of the extracellular matrix. This degradation appears to facilitate the spread of this bacterium throughout host tissues. Unlike purely endolytic degradation of its other substrates, unsulfated chondroitin or some chondroitin sulfates, the degradation of HA by Hyal proceeds by processive exolytic cleavage of one disaccharide at a time following an initial endolytic cut. Molecular dynamics (MD) studies of Hyal from Streptococcus pneumoniae are presented that address the enzyme's molecular mechanism of action and the role of domain motions for processive functionality. The analysis of extensive sub‐microsecond MD simulations of this enzyme action on HA‐substrates of different lengths and the connection between the domain dynamics of Hyal and the translocation of the HA‐substrate reveals that opening/closing and twisting domain motions of the Hyal are intimately linked to processive HA degradation. Enforced simulations confirmed this finding as the domain motions in SpnHyal were found to be induced by enforced substrate translocation. These results establish the dynamic interplay between Hyal flexibility and substrate translocation and provide insight into the processive mechanism of Hyal. Proteins 2009. © 2008 Wiley‐Liss, Inc.
A comparison of polycrystalline elastic properties computed by analytic homogenization schemes and FEM
Authors: Counts W. A. , Friák M. , Battaile C. C. , Raabe D. , Neugebauer J.
Published: November 2008

Body‐center‐cubic (BCC) magnesium–lithium alloys are a promising light‐weight structural material. As a first step in a theoretically guided materials design strategy single crystal elastic coefficients for BCC magnesium‐lithium alloys with different compositions were computed using ab initio methods. These single crystal elastic coefficients were then used to predict the corresponding polycrystalline elastic properties using various analytic homogenization techniques (Voigt, Reuss, and a self‐consistent approach) as well as the finite element method. As expected, the Voigt and Reuss bounds form the upper and lower bounds on the polycrystalline elastic properties, which the predicted values of the self‐consistent approach and finite element approaches fall in between. Additionally, the difference between the polycrystalline elastic properties derived from the self‐consistent approach and the finite element method is small illustrating the power and value of the self‐consistent approach for non‐textured materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fault‐tolerant procedures for redundant computer systems
Authors: Samet Refik
Published: November 2008

Real‐time computer systems deployed in life‐critical control applications must be designed to meet stringent reliability specifications. The minimum acceptable degree of reliability for systems of this type is ‘7 nines’, which is not generally achieved. This paper aims at contributing to the achievement of that degree of reliability. To this end, this paper proposes a classification scheme of the fault‐tolerant procedures for redundant computer systems (RCSs). The proposed classification scheme is developed on the basis of the number of counteracted fault types. Table I is created to relate the characteristics of the RCSs to the characteristics of the fault‐tolerant procedures. A selection algorithm is proposed, which allows designers to select the optimal type of fault‐tolerant procedures according to the system characteristics and capabilities. The fault‐tolerant procedure, which is selected by this algorithm, provides the required degree of reliability for a given RCS. According to the proposed graphical model only a part of the fault‐tolerant procedure is executed depending on the absence or presence (type and sort) of faults. The proposed methods allow designers to counteract Byzantine and non‐Byzantine fault types during degradation of RCSs fromNto 3, and only the non‐Byzantine fault type during degradation from 3 to 1 with optimal checkpoint time period. Copyright © 2008 John Wiley & Sons, Ltd.
Prediction variance and G‐criterion location for split‐plot designs
Authors: Wesley Wayne R. , Simpson James R. , Parker Peter A. , Pignatiello Joseph J.
Published: November 2008

Prediction variance properties for completely randomized designs (CRD) are fairly well covered in the response surface literature for both spherical and cuboidal designs. This paper evaluates the impact of changes in the variance ratio on the prediction properties of second‐order split‐plot designs (SPD). It is shown that the variance ratio not only influences the value of the G‐criterion but also its location, in contrast with the G‐criterion tendencies in CRD. An analytical method, rather than a heuristic optimization algorithm, is used to compute the prediction variance properties, which include the maximum, minimum and integrated variances for second‐order SPD. The analytical equations are functions of the design parameters, radius and variance ratio. As a result, the exact values for these quantities are reported along with the location of the maximum prediction variance used in the G‐criterion. The two design spaces of the whole plot and the subplot are studied and as a result, relative efficiency values for these distinct spaces are suggested. Copyright © 2008 John Wiley & Sons, Ltd.
An improved run‐to‐run process control scheme for categorical observations with misclassification errors
Authors: Shang Yanfen , Wang Kaibo , Tsung Fugee
Published: November 2008

When product quality characteristics are evaluated and assigned to exclusive categories, measurement errors (misclassification of products) always exist unless a perfect measurement system is used to identify the categories. In run‐to‐run (R2R) process control, a categorical controller has been developed for process adjustments with categorical variables. However, if process outputs are misclassified, an adjustment bias will be introduced by the controller. In this study, an improved categorical R2R controller that utilizes the misclassification probabilities to decrease process deviation is proposed. Simulation results show that the proposed controller exhibits better performance when misclassification exists. Copyright © 2008 John Wiley & Sons, Ltd.