bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of hydroxyapatite/poly(vinyl alcohol phosphate) nanocomposite and its characterization
Authors: Pramanik Nabakumar , Mohapatra Sasmita , Alam Sarfaraz , Pramanik Panchanan 
Published: February 2008

AbstractHydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared using a solution‐based method varying HAp from 10 to 60% (w/w). X‐ray diffraction, Fourier transform infrared absorption spectra (FTIR), and thermal analysis have indicated the presence of bonding between HAp particles and PVAP matrix. Transmission electron microscope analysis shows the needle‐like crystals of HAp powder having a diameter of 6–10 nm and a length of 26–38 nm. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. Particle size distribution analysis shows the narrow distribution of hydrodynamic particles in the polymer matrix. The tensile stress–strain curves show the improvement in mechanical properties of the composites with increase in amount of HAp particles loading. The composites along with polymer are highly hemocompatible. The use of PVAP promotes the homogeneous distribution of particles on the polymer matrix along with strong particle–polymer interfacial bonding, which has supported the improvement in mechanical properties of the composites. The prepared HAp/PVAP composite with uniform microstructure would be effective to act as a potential biomaterial. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Preparation of polystyrene/clay nanocomposite by suspension and emulsion polymerization
Authors: Yang Wei‐Ta , Ko Tzu‐Heng , Wang Shu‐Chun , Shih Ping‐I , Chang Ming‐Jen , Jiang George J. 
Published: February 2008

AbstractOrganophilic montmorillonite was prepared using ion‐exchange method between sodium ions in clay layers and four kind of quaternary ammonium salt. The montmorillonite has the largest d001‐spacing, as determined by X‐ray diffraction in modified by di(hydrogenated tallowalkyl) dimethyl ammonium chloride. Polystyrene montmorillonite nanocomposites were obtained by suspension and emulsion polymerization of styrene in the dispersed organophilic montmorillonite. The d001‐spacing of clay was determined by X‐ray diffraction (XRD). The thermal stability of organophilic montmorillonite was investigated by thermogravimetric analysis (TGA). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
The preparation of composites of poly(N‐isopropylacrylamide) with silica and its application in HPLC for separating naphthalene derivatives
Authors: Zhu Y. , Ni C.H. , Shao D. , Jiang X. 
Published: February 2008

AbstractIn this study thermosensitive composites were prepared through grafting copolymerization of N‐isopropylacrylamide (NIPAM) with [3‐(methacryloyloxy) propyl] trimethoxysilane (MOPT, a silicon coupling agent) coupled on the surface of ultrafine silica beads. The effects of some synthetic conditions such as stabilizers, solvents, initiator, feed ratio on the grafting yields were investigated. The structures of the composites were characterized by infrared spectra, differential scanning calorimetry, and scanning electron microscope. The thermosensitive composite was used as a packing material in high performance liquid chromatography for separating naphthalene derivatives. The result indicated that satisfactory separation was achieved by controlling temperature of the column. As a comparison the packing material of silica‐MOPT has no this separating efficiency due to absence of thermosensitivety. The mechanism for the temperature‐controlled separation is attributed to polarity change of the poly(N‐isopropylacrylamide) (PNIPAM) on silica surface when PNIPAM undergoes volume phase transition. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Modeling and analysis of thickness gradient and variations in vacuum‐assisted resin transfer molding process
Authors: Li Jing , Zhang Chuck , Liang Richard , Wang Ben , Walsh Shawn 
Published: February 2008

AbstractAs vacuum‐assisted resin transfer molding (VARTM) is being increasingly used in aerospace applications, the thickness gradient and variation issues are gaining more attention. Typically, thickness gradient and variations result from the infusion pressure gradient during the process and material variations. Pressure gradient is the driving force for resin flow and the main source of thickness variation. After infusion, an amount of pressure gradient is frozen into the preform, which primarily contributes to the thickness variation. This study investigates the mechanism of the thickness variation dynamic change during the infusion and relaxing/curing processes. A numerical model was developed to track the thickness change of the bagging film free surface. A time‐dependent permeability model as a function of compaction pressure was incorporated into an existing resin transfer molding (RTM) code for obtaining the initial conditions for relaxing/curing process. Control volume (CV) and volume of fluid (VOF) methods were combined to solve the free surface problem. Experiments were conducted to verify the simulation results. The proposed model was illustrated with a relatively complex part. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Synthesis and characterization of bis(4‐cyanato 3,5‐dimethylphenyl) naphthyl methane/epoxy/glass fiber composites
Authors: Jayakumari L.S. , Thulasiraman V. , Sarojadevi M. 
Published: February 2008

AbstractBis(4‐cyanato 3,5‐dimethylphenyl) naphthylmethane was prepared by treating CNBr with bis(4‐hydroxy 3,5‐dimethylphenyl) naphthylmethane in the presence of triethylamine at −5 to 5°C. The dicyanate was characterized by FT‐IR and NMR techniques. The prepared dicyanate was blended with commercial epoxy resin in different ratios and cured at 120°C for 1 hr, 180°C for 1 hr, and post cured at 220°C for 1 hr using diamino diphenyl methane (DDM) as curing agent. Castings of neat resin and blends were prepared and characterized by FT‐IR technique. The morphology of the blends was evaluated by SEM analysis. The composite laminates were also fabricated from the same composition using glass fiber. The mechanical properties like tensile strength, flexural strength, and fracture toughness were measured as per ASTMD 3039, D 790, and D 5528, respectively. The tensile strength increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m2 for neat epoxy resin to 0.8615 kJ/m2 for 9% cyanate ester epoxy modified system. The thermal properties were also studied. The 10% weight loss temperature of pure epoxy is 358°C and it increased to 398°C with incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% loading level does not affect the Tg to a very great extent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Synergistic effects of carbon fillers in electrically and thermally conductive liquid crystal polymer based resins
Authors: King Julia A. , Barton Rodwick L. , Hauser Rebecca A. , Keith Jason M. 
Published: February 2008

AbstractAdding conductive carbon fillers to insulating thermoplastic resins increases composite electrical and thermal conductivity. Often, as much of a single type of carbon filler is added to achieve the desired conductivity, while still allowing the material to be molded into a bipolar plate for a fuel cell. In this study, varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX Liquid Crystal Polymer. The resulting single filler composites were tested for electrical resistivity (1/electrical conductivity) and thermal conductivity. In addition, the effects of single fillers and combinations of two different carbon fillers were studied via a factorial design. The results indicated that for the composites containing only single fillers, synthetic graphite, followed by carbon fiber, cause a statistically significant decrease in composite electrical resistivity. Composites containing only synthetic graphite, followed by carbon black, and then carbon fiber cause a statistically significant increase in thermal conductivity. For the combinations of two different fillers, the composites containing carbon black/synthetic graphite and synthetic graphite/carbon fiber had a statistically significant and positive effect on thermal conductivity. It is possible that thermally conductive pathways are formed that “link” these carbon fillers, which results in increased composite thermal conductivity. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Rheological and thermal behavior of starch/LDPE blends containing EAA
Authors: Yin Qin , Dong Aiqin , Wang Jinling , Yin Yeping 
Published: February 2008

AbstractThe composite casts were prepared from native corn starch and low density polyethylene. Ethylene‐arylic acid copolymer (EAA) was added as compabilizer and glycerol was added as plasticizer in the formulation. Their rheological and thermal properties were evaluated by capillary rheometry, differential scanning calorimerty, and thermogravimetry analysis. The results show that the viscosity of the blend has an Arrhenius dependence on temperature and a power law dependence on shear rate. The power law exponents (around 0.5) are less than unity, indicating that the melts are shear thinning. The thermal behavior of these materials is evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The water evaporation process observed by DSC in starch is also observed in the blends. Degradation mechanisms of the blends are identified by means of TGA, being assigned to the mass loss due to the plasticizer leaching, and to the degradation of the starch and synthetic polymer fractions. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Comparison of mechanical properties of epoxy composites reinforced with stitched glass and carbon fabrics: Characterization of mechanical anisotropy in composites and investigation on the interaction between fiber and epoxy matrix
Authors: Çeçen Volkan , Sarikanat Mehmet , Yildiz Hasan , Tavman Ismail H. 
Published: February 2008

AbstractThe primary purpose of the study is to evaluate and compare the mechanical properties of epoxy‐based composites having different fiber reinforcements. Glass and carbon fiber composite laminates were manufactured by vacuum infusion of epoxy resin into two commonly used noncrimp stitched fabric (NCF) types: unidirectional and biaxial fabrics. The effects of geometric variables on composite structural integrity and strength were illustrated. Hence, tensile and three‐point bending flexural tests were conducted up to failure on specimens strengthened with different layouts of fibrous plies in NCF. In this article, an important practical problem in fibrous composites, interlaminar shear strength as measured in short beam shear test, is discussed. The fabric composites were tested in three directions: at 0°, 45°, and 90°. In addition to the extensive efforts in elucidating the variation in the mechanical properties of noncrimp glass and carbon fabric reinforced laminates, the work presented here focuses, also, on the type of interactions that are established between fiber and epoxy matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, were interpreted in an attempt to explain the failure mechanisms in the composite laminates broken in tension. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Water soluble poly(ethylene oxide) functionalized norbornene polymers
Authors: Alfred Sterling F. , Al‐Badri Zoha M. , Madkour Ahmad E. , Lienkamp Karen , Tew Gregory N. 
Published: February 2008

AbstractThe synthesis of three different poly(ethylene oxide) macromonomers with a norbornene and oxanorbornene end group is presented. The macromonomers were polymerized to comb‐polymers by ring‐opening metathesis polymerization (ROMP) using Grubbs' Catalyst G3 to produce water soluble polymers with polydispersities between 1.04 and 1.30 and molecular weights between 14,000 and 50,000 g/mol. Characterization by static and dynamic light scattering reveals that the comb‐polymers with norbornene backbone are molecularly disperse in aqueous solution, while the oxanorbornene‐backbone polymers form small water‐soluble aggregates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2640–2648, 2008
Integrating soil conservation practices and glyphosate‐resistant crops: impacts on soil
Authors: Locke Martin A , Zablotowicz Robert M , Reddy Krishna N 
Published: February 2008

AbstractBACKGROUND: Conservation practices often associated with glyphosate‐resistant crops, e.g. limited tillage and crop cover, improve soil conditions, but only limited research has evaluated their effects on soil in combination with glyphosate‐resistant crops. It is assumed that conservation practices have similar benefits to soil whether or not glyphosate‐resistant crops are used. This paper reviews the impact on soil of conservation practices and glyphosate‐resistant crops, and presents data from a Mississippi field trial comparing glyphosate‐resistant and non‐glyphosate‐resistant maize (Zea mays L.) and cotton (Gossypium hirsutum L.) under limited tillage management.RESULTS: Results from the reduced‐tillage study indicate differences in soil biological and chemical properties owing to glyphosate‐resistant crops. Under continuous glyphosate‐resistant maize, soils maintained greater soil organic carbon and nitrogen as compared with continuous non‐glyphosate‐resistant maize, but no differences were measured in continuous cotton or in cotton rotated with maize. Soil microbial community structure based on total fatty acid methyl ester analysis indicated a significant effect of glyphosate‐resistant crop following 5 years of continuous glyphosate‐resistant crop as compared with the non‐glyphosate‐resistant crop system. Results from this study, as well as the literature review, indicate differences attributable to the interaction of conservation practices and glyphosate‐resistant crop, but many are transient and benign for the soil ecosystem.CONCLUSIONS: Glyphosate use may result in minor effects on soil biological/chemical properties. However, enhanced organic carbon and plant residues in surface soils under conservation practices may buffer potential effects of glyphosate. Long‐term field research established under various cropping systems and ecological regions is needed for critical assessment of glyphosate‐resistant crop and conservation practice interactions. Published in 2008 by John Wiley & Sons, Ltd.
Effects of ligands or substrate of insulin‐regulated aminopeptidase (IRAP) on trophoblast invasion
Authors: Cohen Marie , Wuillemin Christine , Chai Siew Yeen , Bischof Paul 
Published: February 2008

AbstractInsulin‐regulated aminopeptidase (IRAP) activity increases during placentation and in the invasive tumor cell of trophoblast suggesting a role for this peptidase in the invasiveness of normal and malignant trophoblast. To investigate this hypothesis, we studied the effects of substrate (OT) and inhibitors (angiotensin peptides and LVV‐H7) of IRAP on the first trimester trophoblast proliferation and invasion. Addition of these peptides in the culture medium of trophoblastic cells significantly decreased metalloproteinase‐9 activity and cellular invasiveness while no effect was observed on cell proliferation. The peptide IRAP inhibitors could exert their effect on cytotrophoblastic cell invasiveness by inhibition of its enzymatic activity, and thus increasing half life of the known placental peptide substrate of IRAP, OT. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Coupling of non‐aqueous electrokinetic chromatography using cationic cyclodextrins with electrospray ionization mass spectrometry
Authors: Mol Roelof , de Jong Gerhardus J. , Somsen Govert W. 
Published: February 2008

AbstractNon‐aqueous electrokinetic chromatography (NAEKC) using cationic cyclodextrins (CDs) was coupled to electrospray ionization mass spectrometry (ESI‐MS). A methanolic background electrolyte (BGE) was used which contained the hydrochloride salts of the single‐isomer derivative cyclodextrins 6‐monodeoxy‐6‐mono(2‐hydroxy)propylamino‐β‐cyclodextrin (IPA‐β‐CD) or 6‐monodeoxy‐6‐mono(3‐hydroxy)propylamino‐β‐cyclodextrin (PA‐β‐CD). Applying a reversed capillary electrophoresis (CE) polarity (−30 kV), efficient separation of negatively charged compounds was achieved with plate numbers of up to 190 000. PA‐β‐CD appeared to be the most suitable for the separation of various acidic drugs while also providing a high chiral selectivity. Analyte detection was achieved by ESI‐MS in the negative‐ion mode using a sheath‐liquid interface. In order to prevent current drops caused by the cathodic electroosmotic flow, a pressure of 15 mbar was applied on the inlet vial during NAEKC/MS analysis. The effect of the cationic CDs on the MS signal intensities of acidic test drugs was thoroughly studied. When a voltage is applied across the CE capillary, the overall mobility of the cationic CDs is towards the inlet vial so that no CD molecules enter the ion source. The chloride counter ions of the CDs, which migrated towards the capillary outlet, were found to cause ionization suppression, although significant analyte signals could still be detected. Depending on the CD concentration in the BGE, limits of detection for acidic drugs were in the 50–400 ng/mL range in full‐scan mode. Copyright © 2008 John Wiley & Sons, Ltd.
A selected ion flow tube mass spectrometry study of ammonia in mouth‐ and nose‐exhaled breath and in the oral cavity
Authors: Smith David , Wang Tianshu , Pysanenko Andriy , Španěl Patrik 
Published: February 2008

AbstractA study has been carried out, involving three healthy volunteers, of the ammonia levels in breath exhaled via the mouth and via the nose and in the static oral cavity using on‐line, selected ion flow tube mass spectrometry (SIFT‐MS), obviating the problems associated with sample collection of ammonia. The unequivocal conclusion drawn is that the ammonia appearing in the mouth‐exhaled breath of the three volunteers is largely generated in the oral cavity and that the ammonia originating at the alveolar interface in the lungs is typically at levels less than about 100 parts‐per‐billion, which is a small fraction of the total breath ammonia. This leads to the recommendation that exhaled breath analyses should focus on nose‐exhaled breath if the objective is to use breath analysis to investigate systemic, metabolic disease. Copyright © 2008 John Wiley & Sons, Ltd.
Enhanced electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry of long‐chain polysaccharides
Authors: Perdivara Irina , Sisu Eugen , Sisu Ioana , Dinca Nicolae , Tomer Kenneth B. , Przybylski Michael , Zamfir Alina D. 
Published: February 2008

AbstractA novel strategy was developed to extend the application of electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) to the analysis of long‐chain polysaccharides. High molecular weight polydisperse maltodextrins (poly‐α(1‐4) glucose) and dextrans (poly‐α(1‐6) glucose) were chosen as model compounds in the present study. Increased ionization efficiency of these mixtures in the positive ion mode was achieved upon modification of their reducing end with nitrogen‐containing groups. The derivatization method is based on the formation of a new CN bond between 1,6‐hexamethylenediamine (HMD) and the reducing end of the polysaccharide, which exists in solution as an equilibrium between the hemiacetal and the open‐ring aldehyde form. To achieve the chemical modification of the reducing end, two synthetic pathways were developed: (i) coupling of HMD by reductive amination and (ii) oxidation of the hemiacetal to lactone, followed by ring opening by HMD to yield the maltodextrin lactonamide of 1,6‐hexanediamine (HMMD). Amino‐functionalized polysaccharides were analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR‐MS) in the positive ion mode by direct flow injection. The hexamethylenediamine (HMD) and maltodextrin lactonamide of 1,6‐hexanediamine (HMMD) moieties provide increased proton affinities which dramatically improve the detection of the long‐chain polysaccharides by FTICR‐MS. The present approach allowed for identification of single components in mixtures with prominent heterogeneity in the degree of polymerization (DP), without the need for chromatographic separation prior to MS. The high mass accuracy was essential for the unambiguous characterization of the species observed in the analyzed mixtures. Furthermore, molecular components containing up to 42 glucose residues were detected, representing the largest polysaccharide chains analyzed so far by ESI FTICR‐MS. Copyright © 2008 John Wiley & Sons, Ltd.
Ductus venosus Doppler velocimetry in the first trimester: a new finding
Authors: Teixeira L. S. , Leite J. , Viegas M. J. B. C. , Faria M. M. L. , Chaves A. S. , Teixeira R. C. , Pires M. C. , Pettersen H. 
Published: February 2008

AbstractObjectivesTo establish reference curves for ductus venosus blood flow velocities during the first trimester and compare them with previously published curves.MethodsThis was a cross‐sectional and retrospective study performed between January 1998 and January 2003. The following inclusion criteria were used: singleton pregnancy, velocity measurements taken when the crown–rump length (CRL) was between 34 and 84 mm, absence of fetal anomalies, full‐term pregnancy and newborn birth weight appropriate for gestational age. The following variables of the ductus venosus were measured: peak velocity during ventricular systole (S‐wave) and diastole (D‐wave), nadir during atrial contraction in late diastole (A‐wave), time‐averaged maximum velocity (TAMXV) and pulsatility index for veins (PIV).ResultsA total of 843 fetuses were included. The mean CRL was 62 (range, 34–84) mm. The S‐wave, D‐wave, TAMXV and PIV were normally distributed, and logarithmic transformation was performed to achieve a normal distribution for the A‐wave. S‐wave, D‐wave and A‐wave and TAMXV increased with CRL. PIV increased up to a CRL of 63 mm and decreased thereafter. Regression analysis revealed a significant quadratic relationship between PIV and CRL.ConclusionsS‐wave, D‐wave, A‐wave velocities and TAMXV in the ductus venosus increase with CRL between 34 and 84 mm. The reference range for PIV has a biphasic pattern, with an initial non‐significant increase up to a CRL of 63 mm and a fall thereafter. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.