bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of MOD16 algorithm using MODIS and ground observational data in winter wheat field in North China Plain
Authors: Sun Zhigang , Wang Qinxue , Ouyang Zhu , Watanabe Masataka , Matsushita Bunkei , Fukushima Takehiko
Published: April 2007

Evapotranspiration (ET) is an important factor for understanding hydrological processes and climate dynamics. Remote sensing is considered as the most promising tool for estimation of ET over a large spatial scale. The purpose of this study is to analyse and evaluate the MOD16 algorithm, developed by Nishida et al. (2003a,b), in winter wheat fields by using MODIS land products, MOD11‐land surface temperature and MOD13‐standard normalized difference vegetation index (NDVI), as well as observations at the Yucheng Experimental Station, China in 2002. The original MOD16 is a dual‐source ET model in which the evaporation fraction (EF) for bare soil surface is estimated using the VI‐Ts diagram method, and EF for vegetation is determined by a function of canopy resistance, aerodynamic resistance and air temperature. We analysed a radiation budget sub‐model and found that the estimate for solar radiation is acceptable only on cloud‐free days. We also found that, in the original MOD16, seasonal variations of minimum canopy resistance and physiological temperatures are not considered, which results in overestimation of canopy resistance when leaf area index (LAI) is less than 2·5. Because the strong unstable thermal stratification over the dry bare soil surface is ignored in the original algorithm, wind speed is overestimated and aerodynamic resistance above the vegetation surface is underestimated. We then modified the original MOD16 algorithm. The result shows that both EF and ET for vegetation estimated with the modified algorithm are in consistent with both the observations of an eddy covariance system and the calculations using the Penman‐Monteith method. Copyright © 2007 John Wiley & Sons, Ltd.
A two‐dimensional hydrodynamic model for flood inundation simulation: a case study in the lower Mekong river basin
Authors: Dutta Dushmanta , Alam Jahangir , Umeda Kazuo , Hayashi Masayoshi , Hironaka Sadayuki
Published: April 2007

The lower Mekong basin is frequently affected by floods. Prolonged floods disrupt daily activities and cause huge socio‐economic damage almost every year. An advanced flood warning system could provide achievable non‐structural measures for reducing such damages. With a view to developing an advanced flood warning system, a distributed hydrodynamic modelling approach has been adopted for simulating a flood inundation phenomenon in the lower Mekong basin. A modelling system with a one‐dimensional (1‐D) river flow model and a two‐dimensional (2‐D) surface flow model has been used for simulating flood inundation. In the model, exchange of flows between the river and surface floodplain is calculated through established links, which determine the overflow from river nodes to surface grids or vice versa. These occur due to overtopping or failure of the levee when water height surpasses levee height. The model has incorporated detailed information about urban terrain features like embankments, roads, bridges, culverts, etc. in the simulation. A geographical information system (GIS)‐based comprehensive raster database of different spatial data layers is prepared and used in the model development. An explicit solution scheme is used for numerical computation, which considerably reduces the run time and makes the model suitable for use as a flood warning system in a large river basin. The model simulated results in the lower Mekong basin have shown close alignment with the observed data in terms of water level and discharge in various river gauging stations and flood extents in the floodplain and from the results it can be inferred that the model can predict the magnitude and duration of flood inundation to a reasonable level of accuracy. Copyright © 2007 John Wiley & Sons, Ltd.
Citrinin and endosulfan induced maternal toxicity in pregnant Wistar rats: pathomorphological study
Authors: Singh Nittin D. , Sharma Anil K. , Dwivedi Prabhaker , Patil Rajendra D. , Kumar Manoj
Published: April 2007

Dietary exposures to environmental food pollutants such as mycotoxin(s) or pesticide(s) have gained immense significance due to their adverse effects on production and reproduction in animal and human populations. The present investigation was conducted to evaluate the maternal toxicity of citrinin (CIT) and endosulfan administered per os either alone or in combination in pregnant rats during gestational days 6–20. CIT (group I, 10 mg kg−1 feed, through diet) and endosulfan (group II, 1 mg kg−1 body weight, by oral intubation) when administered either alone or in combination (group III) in Wistar rats caused clinical signs of toxicity and pathomorphological changes in all the toxin treated groups, the severity being more pronounced in the combination treatment compared with that observed in the control (group IV). The rate of fetal resorptions was highest (22.22%) in the combination treatment followed by endosulfan (16.48%) and CIT (12.50%) treatment groups compared with the control group (3.86%). The histopathological changes such as engorged vasculature, vacuolar degeneration and karyomegaly in liver; congestion, tubular degeneration and cast formation in kidneys; vascular changes and hemosiderosis in uterus and lymphocytic depletion and apoptosis in the lymphoid organs were recorded in the animals of the toxin treated groups. The lesions were consistent and more severe in the combination treatment group compared with the individual treatment groups, suggesting an additive interaction of CIT and endosulfan in inducing maternal toxicity in Wistar rats. Copyright © 2007 John Wiley & Sons, Ltd.
Toxicogenomics: a pivotal piece in the puzzle of toxicological research
Authors: Gatzidou Elisavet T. , Zira Athina N. , Theocharis Stamatios E.
Published: April 2007

Toxicogenomics, resulting from the merge of conventional toxicology with functional genomics, being the scientific field studying the complex interactions between the cellular genome, toxic agents in the environment, organ dysfunction and disease state. When an organism is exposed to a toxic agent the cells respond by altering the pattern of gene expression. Genes are transcribed into mRNA, which in turn is translated into proteins that serve in a variety of cellular functions. Toxicogenomics through microarray technology, offers large‐scale detection and quantification of mRNA transcripts, related to alterations in mRNA stability or gene regulation. This may prove advantageous in toxicological research. In the present review, the applications of toxicogenomics, especially to mechanistic and predictive toxicology are reported. The limitations arising from the use of this technology are also discussed. Additionally, a brief report of other approaches, using other ‐omic technologies (proteomics and metabonomics) that overcome limitations and give global information related to toxicity, is included. Copyright © 2007 John Wiley & Sons, Ltd.
Directing endothelial differentiation of human embryonic stem cells via transduction with an adenoviral vector expressing the VEGF165 gene
Authors: Rufaihah Abdul Jalil , Haider Husnain Khawaja , Heng Boon Chin , Ye Lei , Toh Wei Seong , Tian Xian Feng , Lu Kai , Sim Eugene Kwang‐Wei , Cao Tong
Published: April 2007

Endothelial progenitors derived from human embryonic stem cells (hESCs) hold much promise in clinical therapy. Conventionally, lineage‐specific differentiation of hESCs is achieved through supplementation of various cytokines and chemical factors within the culture milieu. Nevertheless, this is a highly inefficient approach that is often limited by poor replicability. An alternative is through genetic modulation with recombinant DNA. Hence, this study investigated whether transduction of hESCs with an adenoviral vector expressing the human VEGF165 gene (Ad‐hVEGF165) can enhance endothelial‐lineage differentiation. The hESCs were induced to form embryoid bodies (EBs) by culturing them within low‐attachment plates for 7 days, and were subsequently trypsinized into single cells, prior to transduction with Ad‐hVEGF165. Optimal transduction efficiency with high cell viability was achieved by 4‐h exposure of the differentiating hESCs to viral particles at a ratio of 1 : 500 for three consecutive days. ELISA results showed that Ad‐hVEGF165‐transduced cells secreted human vascular endothelial growth factor (hVEGF) for more than 30 days post‐transduction, peaking on day 8, and the conditioned medium from the transduced cells stimulated extensive proliferation of HUVEC. Real‐time PCR analysis showed positive upregulation of VEGF, Ang‐1, Flt‐1, Tie‐2, CD34, CD31, CD133 and Flk‐1 gene expression in Ad‐hVEGF165‐transduced cells. Additionally, flow cytometric analysis of CD133 cell surface marker revealed an approximately 5‐fold increase in CD133 marker expression in Ad‐hVEGF165‐transduced cells compared to the non‐transduced control. Hence, this study demonstrated that transduction of differentiating hESCs with Ad‐hVEGF165 facilitated expression of the VEGF transgene, which in turn significantly enhanced endothelial differentiation of hESCs. Copyright © 2007 John Wiley & Sons, Ltd.
Joseph Jastrow, the psychology of deception, and the racial economy of observation
Authors: Pettit Michael
Published: April 2007

This article reconstructs the recurring themes in the career of Joseph Jastrow, both inside and outside the laboratory. His psychology of deception provides the bridge between his experimental and popular pursuits. Furthermore, Jastrow's career illustrates the complex ways in which scientific psychology and pragmatist philosophy operated within the constraints of a moral economy deeply marked by notions of “race.” Psychological investigations of deception were grafted onto two of the human sciences' leading tools: the evolutionary narrative and the statistical analysis of populations. Such associations abetted the racialization of the acts of deceiving and being deceived. These connections also were used to craft moral lessons about how individuals ought to behave in relationship to the aggregate population and natural selection's endowment. © 2007 Wiley Periodicals, Inc.
Experimental metamorphosis of Halisarca dujardini larvae (Demospongiae, Halisarcida): Evidence of flagellated cell totipotentiality
Authors: Ereskovsky Alexander V. , Konjukov Paul , Willenz Philippe
Published: April 2007

The potency of flagellated cells of Halisarca dujardini (Halisarcida, Demospongiae) larvae from the White Sea (Arctic) was investigated experimentally during metamorphosis. Two types of experiments were conducted. First, larvae were maintained in Ca2+ free seawater (CFSW) until the internal cells were released outside through the opening of the posterior pole. These larvae that only composed of flagellated cells (epithelial larvae) were then returned to sea water (SW) to observe their metamorphosis. The posterior aperture closed before they settled on a substratum and started a metamorphosis similar to intact larvae. Secondly, epithelial larvae were, first, further treated in CFSW and then mechanically dissociated. Separated cells or groups of cells were returned to SW, where they constituted large friable conglomerates. After 12–17 h in SW, flagellated cells showed the first steps of dedifferentiation, and regional differentiation was noticeable within conglomerates after approximately 24–36 h. External cells differentiated into pinacocytes while internal cells kept their flagella and became united in a layer. Within 48–72 h, internal cells of the conglomerates formed spherical or ovoid clusters with an internal cavity bearing flagella. These clusters further fused together in a rhagon containing one or two large choanocyte chambers. The sequence of cellular processes in epithelial larvae and in flagellated cell conglomerates was similar. Previous observations indicating the totipotentiality of larval flagellated cells during normal metamorphosis of H. dujardini are thus confirmed. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
Coherent laser spectroscopy of molecular motions in liquids in the maser range
Authors: Bunkin A. F. , Pershin S. M. , Nurmatov A. A. , Gorchakov A. P.
Published: April 2007

The terahertz and subterahertz four‐photon spectroscopy of liquids gives the opportunity to study large volume samples in native conditions. We present the experimental measurements by this technique of the low‐wavenumber molecular motion in water and some aqueous solution. In fact, the coherent librations of H2O molecules in liquid water as well as aqueous solutions of H2O2 and a protein in the microwave range (0.1–100 cm−1) are observed. A satisfactory correlation of the observed resonances with the rotational spectra of H2O molecule in the gas phase is found. Moreover the lines of ortho‐ and para‐isomers of H2O molecule were identified. We have found that the protein molecules in water interact selectively with the spin isomers of H2O. There is a strong suppression of the rotational motion of the para‐isomers and their respective line intensities, with a corresponding magnification by a factor of 8 by the ortho species. Copyright © 2007 John Wiley & Sons, Ltd.
Raman scattering characterization of nanopowders and nanowires (rods)
Authors: Popović Z. V. , Dohčević‐Mitrović Z. , Konstantinović M. J. , Šćepanović M.
Published: April 2007

We study nanograin size confinement effects, the effect of the increase of local temperature and strain, and substitutional and nonstoichiometry effects on the Raman spectra in Ce(Ba,Nd,Gd)O2 nanopowders obtained by self‐propagating, room‐temperature synthesis, and silicon nanowires obtained by the electrochemical etching process. The local temperature was monitored by measuring the Stokes/anti‐Stokes peak ratio. We found large wavenumber shifts, up to 10 (30) cm−1, and broadenings, up to 40 (20) cm−1, of the first‐order Raman‐active modes of Ce(M)O2 (n‐Si), which we attribute to confinement and strain effects (laser heating). The phonon softening and phonon linewidth are calculated using a phenomenological model, which takes into account disorder effects through the breakdown of the k = 0 Raman‐scattering selection rule, and also anharmonicity, which is incorporated through the three‐ and four‐phonon anharmonic processes. Very good agreement with experimental data is obtained for the calculated spectra of CeO2 with nanograin sizes of about 7 nm, taking into account particle size distribution, as well as an increase in the anisotropy constants with respect to those of bulk materials. Copyright © 2007 John Wiley & Sons, Ltd.
Four‐photon laser spectroscopy of fused quartz and crown glass at 0–60 GHz
Authors: Bunkin A. , Pershin S. , Nurmatov A. , Luk'yanchenko V.
Published: April 2007

The low wavenumber spectra of fused quartz and crown glass K8 in the range 0.1–2 cm−1 at room temperature were measured by the four‐wave mixing technique. The experimental scheme is based on using both second harmonics of a neodynium‐doped yttrium aluminium garnet (Nd:YAG) pulsed laser and dye laser as a tuning source. The pulse‐to‐pulse deviation of the dye laser frequency is used to obtain the derivative spectra as an additional data source. It was established that the spectra contain a number of narrow (⩽0.1 cm−1) lines. The data could be fitted only by assuming that the Brillouin resonances on longitudinal and transverse sound, as well as the distinct resonances at ∼1.5 cm−1, which can be attributed to hydroxyl (OH) molecular rotations, were involved in the four‐photon scattering process. The fine structure of the Rayleigh wing scattering in fused quartz was observed for the first time. The detected lines, 0.165 cm−1 and 0.26 cm−1 (5.0 and 7.8 GHz, respectively), are attributed to the spheroidal modes ν20 and ν30 of SiO2 spheres with a diameter 880 ± 30 nm. The closely lying eigen modes ν00, ν10 and ν12 are unresolved with a central peak at ± 0.1 cm−1. The 0.4 cm−1 resonance lines in crown glass is attributed to be a manifestation of four‐photon scattering from a second sound phonon. Copyright © 2007 John Wiley & Sons, Ltd.
Raman and X‐ray investigations of the incorporation of Ca2+ and Cd2+ in the ZrO2 structure
Authors: Gazzoli Delia , Mattei Giorgio , Valigi Mario
Published: April 2007

The formation of solid solution and ZrO2 phase stabilization were investigated by Raman spectroscopy and X‐ray diffraction (XRD) in calcium‐containing and cadmium‐containing zirconium oxide samples heated at 1073 K in air. The adopted preparation procedure led to the incorporation of calcium and cadmium in solid solution into the zirconia structure. The solid solution favored the tetragonal and cubic zirconia phases at the expense of the thermodynamically stable monoclinic modification. Combined macro‐ and micro‐Raman spectroscopy disclosed that instead of forming a homogeneous phase t″, intermediate between the tetragonal t′ and the cubic phase, the tetragonal and cubic phases coexisted in the range 9.49–13.89 mol% for Ca and 11.88–17.23 mol% for Cd. At higher dopant contents the cubic form stabilized. The impurity content necessary to stabilize the high‐symmetry phases was defined. Copyright © 2007 John Wiley & Sons, Ltd.
Self‐assembled monolayers of mercaptosuccinic acid on silver and gold surfaces designed for protein binding. Part I: structure of the monolayer
Authors: Królikowska Agata , Bukowska Jolanta
Published: April 2007

Structure of the monolayers of mercaptosuccinic acid (MSA) on silver and gold electrodes, grown from aqueous solution, has been studied using surface enhanced Raman scattering (SERS) spectroscopy. It was found that MSA chemisorbs via both sulfur atom and one carboxylic group (more close to the sulfur atom) dissociated on the Ag and Au at natural pH (slightly acidic). The influence of the type of the substrate, pH of the solution and time of incubation of the thiol monolayer have been investigated. SERS results show that acidity of one carboxylic group of MSA (more close to the sulfur) decreases on both substrates with simultaneous increase of acidity of the second COOH group, in comparison to the solution. For silver substrate, longer time of incubation is necessary to form a stable monolayer, whereas the structure of monolayer on gold does not exhibit temporal evolution. Copyright © 2007 John Wiley & Sons, Ltd.
HPLC analysis and pharmacokinetics of icariin in rats
Authors: Cheng Shan , Qiu Feng , Wang Shuhui , He Junqi
Published: April 2007

As a prerequisite to the determination of pharmacokinetic parameters of icariin in rats, an HPLC method using UV detection was developed and validated. Icariin and the internal standard, quercetin, were extracted from plasma samples using ethyl acetate after acidification with 0.05 mol/L NaH2PO4 solution (pH 5.0). Chromatographic separation was achieved on an Agilent XDB C18 column (250×4.6 mm id, 5 μm) equipped with a Shim‐pack GVP‐ODS C18 guard column (10×4.6 mm id, 5 μm) using a mobile phase of ACN/water/acetic acid (31:69:0.4 v/v/v) at a flow rate of 1.0 mL/min. Detection was at 277 nm. The calibration curve was linear from 0.05 to 100.0 μg/mL with 0.05 μg/mL as the lower LOQ (LLOQ) in plasma. The intra‐ and interday precisions in terms of RSD were lower than 5.7 and 7.8% in rat plasma, respectively. The accuracy in terms of relative error (RE) ranged from –1.6 to 3.2%. The extraction recoveries of icariin and quercetin were 87.6 and 80.1%, respectively. The main pharmacokinetic parameters for rats were determined after a single intravenous administration of 10 mg/kg icariin: t1/2, 0.562 ± 0.200 h; AUC0–∞, 8.73 ± 2.23 μg·h/mL; CLTOT, 20.10 ± 5.80 L/kg·h; VZ, 1.037 ± 0.631 L/kg; MRT0–∞, 0.134 ± 0.040 h; and Vss, 0.170 ± 0.097 L/kg.
Mediators of control beliefs, stressful life events, and adaptive behavior in school age children: The role of appraisal and social support
Authors: Jackson Yo , Kim Kerri L. , Delap Chris
Published: April 2007

The authors examine the role of appraisal and social support as mediators of the relation between control beliefs and adaptive behavioral outcome. Using the responses from 297 children, ages 8 to 12 years old, the results suggest two significant mediational pathways. Social support was a mediator of the relation between unknown control for negative events and adaptive behavior and the relation between unknown control for positive events and adaptive behavior. Negative appraisal demonstrated no mediation relations. The role of social support and negative appraisal in the display of adaptive behavior and the implications for further model testing are discussed.
Randomized clinical trial for treatment of chronic nightmares in trauma‐exposed adults
Authors: Davis Joanne L. , Wright David C.
Published: April 2007

Nightmares and sleep disturbance are fundamental concerns for victims of trauma. This study examined the efficacy of a manualized cognitive–behavioral treatment (CBT) for chronic nightmares in trauma‐exposed individuals via a randomized clinical trial. Participants were randomly assigned to a treatment group or wait‐list control group, with 27 participants completing the treatment. At the 6‐month follow‐up assessment, 84% of treated participants reported an absence of nightmares in the previous week. Significant decreases were also reported in symptoms of depression and posttraumatic stress, fear of sleep, and number of sleep problems, while sleep quality and quantity improved. The present study adds to the growing literature indicating this brief CBT as a first‐line treatment for trauma‐exposed individuals with chronic nightmares.
A novel compact side-pumped bonded slab microchip laser
Authors: Yin C , Huang L , Gong M , Yan P , Liu Q , He F
Published: April 2007

Diode end-pumped microchip passively Q-switched Nd:YAG laser is widely used in many application fields. But the most important defect of the structure is that its poor thermal characteristic limits the output power and working reliability. In this paper, a novel compact side-pumped bonded slab microchip laser is put forward to solve the critical thermal problem. We use a commercial laser bar as pump source and a piece of bonded slab YAG as laser crystal to construct the compact microchip laser. Based on this compact structure, we have achieved 4.75 W output power and 43.9 kW peak power with 9 kHz repetition rate and 12 ns pulse width. Comparing with end-pumped structure, heat distribution in this structure is much more uniform. Experimental results indicate that this compact microchip slab laser can achieve high output power with excellent thermal characteristics.
Bacterial Translocation During Liver Transplantation
Authors: Abdala Edson , Baía Carlos Eduardo Sandoli , Mies Sérgio , Massarollo Paulo Celso Bosco , de Paula Cavalheiro Norma , Baía Vania Regina Mollo , Inácio Conceição Aparecida Félix , Sef Henry Corazza , Barone Antonio Alci
Published: April 2007

The aim of this study was to evaluate the bacterial translocation in liver transplantation (LT), comparing the conventional and the piggyback methods. A total of 32 patients were randomized into the 2 groups. Samples of blood were collected from the radial artery, portal vein (PV) and hepatic vein (HV), in up to 120 minutes postreperfusion. The samples were sent for endotoxin level, as well as samples up to 2 minutes post-perfusion were sent to culture. Hepatic artery and PV blood flows were measured at postreperfusion collection times. The results analyzed were: endotoxin concentration, its quantity, and hepatic clearance. The statistical treatment consisted of analyzing each group's mean profile. The analysis for endotoxin concentration in the radial artery was the deviation related to presurgery measure, and in the PV the deviation related to preclamping (PC) measure. The overall mean level of endotoxin concentration was 0.99 EU/mL in the artery, 1.30 EU/mL in the PV, and 1.22 EU/mL in the HV. The deviation was significant in the portal (P = 0.0031), but not in the artery samples (P = 0.2092). We detected a significant quantity of endotoxin in the artery and in the portal and the HVs (P < 0.001). There was no difference between the 2 groups and no hepatic clearance of endotoxin was detected either (P = 0.1515). All the cultures were negative. In conclusion, the study detected a significant translocation of endotoxin, but not of bacteria. The study also detected the absence of endotoxin hepatic clearance in both the piggyback and the conventional methods without any difference between them. Liver Transpl 13:488–496, 2007. © 2007 AASLD.
Biotechnological Production of Spider‐Silk Proteins Enables New Applications
Authors: Vendrely Charlotte , Scheibel Thomas
Published: April 2007

The outstanding mechanical properties of spider silks have motivated many researchers to establish biotechnological production techniques which are necessary to provide sufficient amounts of silk proteins for industrial applications. Based on recent developments in genetic engineering, two strategies for the recombinant production of spider‐silk proteins have been established which are discussed in detail. Further, protein‐design strategies are described, enabling the combination of silk properties with additional biological, chemical, or technical features. We highlight the potential of engineered and recombinantly‐produced spider‐silk proteins to provide the basis for a new generation of biomaterials.

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A New Network Composite Material Based on Soy Dreg Modified with Polyurethane Prepolymer
Authors: Chen Yun , Zhang Lina , Deng Rui , Cui Yejian
Published: April 2007

A series of biodegradable, soy‐protein‐based, composite materials was prepared by introducing castor‐oil‐based polyurethane prepolymer (PUP) into soy dreg (SD) without the addition of plasticizers, via extrusion and a compression‐molding process. The effects of the NCO/OH molar ratio and the PUP content on the structure and properties of the resulting materials were studied by Fourier‐transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, tensile testing, swelling experiments, and biodegradability testing. The results revealed that the NCO group in the PUP played a vital role in improving the compatibility and elasticity, as a result of the formation of a cross‐linking network structure with the NH2, NH, and OH groups in SD containing protein and cellulose. Increasing the NCO/OH molar ratio to 2.0 resulted in an enhancement of the degree of cross‐linking, leading to a higher tensile strength (24 MPa), glass‐transition temperature (52 °C) and water‐resistivity of the composite materials. The unreacted SD also served as a filler in the cross‐linked networks and enhanced the tensile strength of the composites. The biodegradation testing showed that the composites exhibited biodegradability under the condition of fungus culture.

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Polymeric Nanocomposites for Tribological Applications
Authors: Burris David L. , Boesl Benjamin , Bourne Gerald R. , Sawyer W. Gregory
Published: April 2007

Polymer nanocomposites operate in applications where fluid and grease lubricants fail, and have superior tribological performance to traditional polymer composites. Nanoparticle fillers have been a part of notable reductions in the wear rate of the polymer matrix at very low loadings. Despite instances of remarkable wear reductions at unprecedented loadings (3 000 times at 0.5% loading in one case), there is a lack of general agreement within the literature on the mechanisms of wear resistance in these nanocomposites. In addition, results appear to vary widely from study to study with only subtle changes of the filler material or blending technique. The apparent wide variation in tribological results is likely a result of processing and experimental differences. Tribology is inherently complex with no governing laws for dry sliding friction or wear, and the state of the art in polymeric nanocomposites tribology includes many qualitative descriptors of important system parameters, such as particle dispersion, bulk mechanical properties, debris morphology, and transfer film adhesion, morphology, composition, and chemistry. The coupling of inherent tribological complexities with the complicated mechanics of poorly characterized nanocomposites makes interpretation of experimental results and the state of the field extremely difficult. This paper reviews the state of the art in polymeric nanocomposites tribology and highlights the need for more quantitative studies. Examples of such quantitative measurements are given from recent studies, which mostly involve investigation of polytetrafluoroethylene matrix nanocomposites.

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Influence of Cure Regime on the Strain Development in an Epoxy Resin as Monitored by a Fiber Bragg Grating Sensor
Authors: Harsch Margit , Karger‐Kocsis József , Herzog Florian
Published: April 2007

In this paper, the effects of different cure regimes on the strain development in an anhydride‐cured epoxy resin were investigated by fiber optical measurements. The course of the strain signal was detected by an embedded fiber Bragg grating sensor in the unconstrainedly curing epoxy. The build‐up of strain was detected for various cure regimes differing in the dwelling times of the first isothermal step, heating rates to the cure temperature, and final curing temperatures, respectively. Characteristic points (gelation, vitrification) of the cure regimes were identified by conversion‐ and Tg‐determinations via DSC and assigned to changes of the FBG signal. The fiber Bragg sensing technique allowed us to find those variables of the cure regimes which mostly affect the strain development and thus, the level of the residual strain. It was established that the dwelling time and heating rate to the cure temperature influence markedly the residual strain whereas the cure temperature affects this value to a lesser extent for the selected cure regimes. So, the above parameters should be selected properly for an optimum cure regime characterized by the build‐up of a minimum residual strain.

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Exponential attractor for a planar shear‐thinning flow
Authors: Pražák Dalibor
Published: April 2007

We study the dynamics of an incompressible, homogeneous fluid of a power‐law type, with the stress tensor T = ν(1 + µ|Dv|)p−2Dv, where Dv is a symmetric velocity gradient. We consider the two‐dimensional problem with periodic boundary conditions and p ∈ (1, 2). Under these assumptions, we estimate the fractal dimension of the exponential attractor, using the so‐called method of 𝓁‐trajectories. Copyright © 2007 John Wiley & Sons, Ltd.
Apple polyphenols diminish the phosphorylation of the epidermal growth factor receptor in HT29 colon carcinoma cells
Authors: Fridrich Diana , Kern Melanie , Pahlke Gudrun , Volz Nadine , Will Frank , Dietrich Helmut , Marko Doris
Published: April 2007

Previously, we showed that an apple juice extract (AE) potently inhibits the protein tyrosine kinase (PTK) activity of the epidermal growth factor receptor (EGFR). In the present study, an apple pomace extract (APE) was found to exceed the EGFR inhibitory properties of AE in a cell‐free system. The impact of the extracts on the phosphorylation status of the EGFR in intact cells (HT29) was sensitive to catalase, added to suppress the accumulation of hydrogen peroxide. In the absence of catalase, the formation of hydrogen peroxide was observed, achieving 1.1 ± 0.1 μM (AE) and 1.5 ± 0.1 μM (APE) after 45 min of incubation. In the presence of catalase, suppressing the hydrogen peroxide level to the solvent control, APE effectively suppressed EGFR phosphorylation, even exceeding the effects of AE. Both extracts inhibited the growth of HT29 cells, albeit the enhanced EGFR inhibitory properties of APE compared to AE were not reflected by a higher growth inhibitory potential. The results clearly show that the effect of apple extracts on the EGFR and cell growth are not simply artefacts of hydrogen peroxide formation. However, the formation of hydrogen peroxide has to be considered to modulate and/or mask cellular responses to apple extracts.
Hyperstructured polyacetylene
Authors: Akagi Kazuo
Published: April 2007

Current progress in the synthesis and properties of conjugated polymers is presented by focusing on recently put forward hyperstructured helical polyacetylene. Interfacial polymerization of acetylene has been carried out in an asymmetric reaction field consisting of chiral nematic liquid crystal (N*‐LC) and Ziegler–Natta catalyst. Since the chiral nematic liquid crystal is composed of nematic liquid crystal and a chiral compound such as axially chiral binaphthyl derivative with R‐ or S‐configuration, the screw directions of the polyacetylene chain and fibril bundle and even the spiral morphology are rigorously controlled by selecting the chirality of the chiral compound. Surprisingly, the screw directions of the fibril and the bundle of fibrils in helical polyacetylene were found to be opposite to that of N*‐LC. It is worthwhile to emphasize that the hierarchical spiral morphology involving the primary to higher order structure is generated in a synthetic polymer such as polyacetylene by using N*‐LC as an asymmetric polymerization solvent. Copyright © 2007 Society of Chemical Industry
Anionic synthesis of dimethylamino‐functionalized polystyrenes and poly (methyl methacrylates) using 1 ‐ (4‐dimethylaminophenyl) ‐ 1 ‐ phenylethylene
Authors: Quirk Roderic P. , Zhu Lin‐Fang
Published: April 2007

ω‐Dimethylaminopolystyrenes can be synthesized in quantitative yields by reacting poly(styryl)lithium with 1‐(4‐dimethylaminophenyl)‐1 ‐phenylethylene (1). The resulting polymeric dimethylamino‐substituted 1,1‐diphenylalkyllithium was terminated with methanol or reacted with butadiene to form a diblock copolymer, poly(styrene‐b‐butadiene), with the dimethylamino group at the interface between the blocks. α‐Dimethylaminopolystyrene and α‐dimethylaminopoly‐(methyl methacrylate) were synthesized by using the adduct of 1 with sec‐butyllithium as initiator, α,ω‐Bis(dimethylamino)polystyrene was prepared by using the functionalized initiator and then terminating the resulting dimethylaminopoly‐(styryl)lithium with 1. The amine‐functionalized polymers were characterized by end‐group titration, size exclusion chromatography, thin‐layer chromatography, vapor phase osmometry, elemental analysis and both 1H and 13C NMR spectroscopy. All experimental evidence is consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative.
Synthesis and viscoelastic properties of α,ω‐diquaternary ammonium polybutadiene lonomers
Authors: Roberts Caroline , Lindsell W. Edward , Soutar Ian
Published: April 2007

Telechelic ionomeric elastomers with quaternary ammonium groups (Me2RN+) attached terminally to polybutadiene (M̄n ∼ 2.7 × 103; M̄w/M̄n = 1.27; containing 62% 1,4‐linkages) have been synthesised by an anionic technique using a functionalised initiator and terminator, followed by quaternisation of the resulting α,ω‐bis(dimethylamino)polybutadiene. By using differing alkyl halides for quaternisation and by ion exchange chromatography, a series of dialkylated telechelic cationomers has been produced containing alkyl groups, R = Me, Et, n‐Pr, n‐Bu or n‐C5H11 with counter anions X = I−, Br−, PF or SO. The glass transition temperatures, Tg, of these cationomers are c. 6°C higher than for the precursor, non‐quaternised polymer but are essentially unchanged with variations in groups R or anions X. Dynamic mechanical thermal analyses of the cationomers have been carried out and a secondary transition, Ti, associated with relaxation of ionic cross‐linking interactions, observed. Values of Ti decrease as the size of R increases from C1 to C5, and as the anion X is changed from Br− to I− to PF or SO to PF.

Activation energies can be derived from the frequency dependence of Ti values or from the temperature dependence of shift parameters, obtained from the master curves of the dependence on frequency of the shear storage (G') and loss (G') moduli; these activation energies are dependent on the nature of the counter anion, being greatest for the polymer containing the dinegative SO, but are essentially unchanged by the variations in alkyl group, R, implemented in this study. Other results of the dynamic mechanical analyses on the cationomeric elastomers are discussed in relation to their ionic cross‐linking.
Polymerization and copolymerization using high intensity ultrasound
Authors: Price Gareth J. , Daw Melanie R. , Newcombe Nicholas J. , Smith Paul F.
Published: April 2007

Abstract: High intensity ultrasound has been used to prepare homopolymers and copolymers of styrene, methyl methacrylate and n‐butyl methacrylate. High molecular weight homopolymers are formed rapidly during sonication and are then subjected to a degradation process. The copolymers prepared by this method have similar structure and properties to those prepared using AIBN as an initiator.
Reaction of the epoxide groups of the copolymer trimethylolpropane trimethacrylate‐glycidyl methacrylate with aliphatic amino compounds
Authors: Walenius Maria , Flodin Per
Published: April 2007

Functional macroporous polymers have been synthesized from copolymers of trimethylolpropane trimethacrylate (TRIM) and glycidyl methacrylate (GMA). The accessibility of the epoxy groups has been investigated by reaction with dialkylamines and diamines of different chain lengths. The obtained yield of reacted amine was approximately 80% for small molecules. The yield, and accessibility, decreased when the chain length or bulkiness of the reagent increased. The swelling ability in water of the functional polymers increased compared with the original copolymer.
Modelling of urethane formation
Authors: Jönsson Kersti , Flodin Per
Published: April 2007

The formation of polyurethanes has been followed by in‐situ 1H NMR. The experimental data have been used in a mathematical model. The model was found to be representative for a major part of the reaction. The Arrhenius preexponential factors and activation energies for the formation reactions were calculated based on the model.
Approaches to the synthesis of novel photoactive side chain liquid crystalline polymers containing analogues of the cinnamate ester group
Authors: Whitcombe Michael J. , Gilbert Andrew , Mitchell Geoffrey R.
Published: April 2007

A series of chain liquid crystalline copolymers of 4‐cyanophenyl 4′‐(6‐methacryloyloxyhexyloxy)benzoate and 2‐methacryloyloxyethyl β‐(1‐naphthyl)‐propenoate were prepared by free radical polymerization. The corresponding polyacrylates could not be prepared in the same way and an alternative method was used for their preparation involving the synthesis of copolymers of the mesogenic monomer and 2‐hydroxyethyl acrylate followed by treatment of the resulting polymers with β‐(1‐naphthyl)propenoyl chloride. The materials are of interest as photoactive liquid crystalline polymers. The effect of introducing a bulky nonmesogenic group into a liquid crystalline copolymer generally lowers the clearing temperature and raises Tg but also gives rise to contrasting phase behaviour in these two series of polymers. Polymethacrylates which show mesomorphism have sharp transitions and continue to exhibit a highly ordered smectic phase over the bulk of their liquid crystal range. Polyacrylates, on the other hand, exhibit a weakening and broadening‐out of their thermal transitions consistent with a lowering of order. These results emphasize the effect of the polymer backbone on phase behaviour.
New self‐crosslinkable polyethers
Authors: Eldin Sameer H.
Published: April 2007

New alkylene‐polyethers, OPh(CH2)nPhOPhXPh with X = SO2, CO are described that undergo an unexpected crosslinking reaction at temperatures ≧ 250°C. HNMR indicates the participitation of methylene groups in the vicinity of the aromatic ring and of the phenyl rings of the diarylsulphone moiety in this crosslinking reaction.

The crosslink density can be regulated via copolyaddition with bisphenol A. Polyethers of the general structure OPhRPhOPhXPh with R = (CH2)6 + C(CH3)2, X = SO2, CO are easily processable, impact and solvent resistant. ESR measurements correlate with the HNMR findings and identify the crosslinking as a radical reaction.

A crosslink mechanism is proposed and substantiated by the synthesis of specific model polymers.
Effect of reaction conditions on poly (methyl methacrylate) molecular weight as polymerized in aqueous media by the redox system Ce(IV)‐isobutyl alcohol
Authors: Fernández M. D. , Fernández M. J. , Guzmán G. M.
Published: April 2007

Polymerization of methyl methacrylate initiated by ceric ammonium nitrate in combination with isobutyl alcohol has been investigated in aqueous nitric acid. The effects of conversion, isobutyl alcohol, Ce(IV) and monomer concentrations, as well as temperature on polymer molecular weight have been studied. Molecular weight distributions obtained by size exclusion chromatography showed several shoulders and a high dispersity index which seemed to be related to the fact that the polymer precipitated continuously during the reaction. Average molecular weights increased initially as conversion increased, while an increase in the isobutyl alcohol and Ce(IV) concentrations up to a certain value caused the molecular weight to decrease. The average molecular weights increased with increasing monomer concentration, but decreased with a rise in temperature. These effects are in agreement with a reaction mechanism involving the oxidation of isobutyl alcohol by Ce(IV) via complex formation, decomposition of the complex giving rise to a primary radical, initiation, propagation, and bimolecular termination of the polymeric radicals and oxidative termination of the primary radical by Ce(IV).
Mechanical properties and dynamic mechanical relaxations of ethylene/alpha‐olefin copolymers
Authors: Benavente Rosario , Pereá José M. , Bello Antonio , Pérez Ernesto , Martínez Carmen , Aguilar Carmelo
Published: April 2007

The tensile drawing behaviour and the viscoelastic relaxations of three different copolymers of ethylene, containing 1‐butene, 1‐hexene and 4‐methyl‐1‐pentene as comonomer, have been studied. The composition of the copolymers is increasingly poorer in comonomer following the above order. However, they show similar mechanical properties, both large‐strain and small‐strain dynamic mechanical, because the minor differences which have been found can generally be explained by the thermal and mechanical histories of the samples. Thus, it seems that the higher disrupting effect produced in the copolymer structure by the comonomers of greater size and volume is counterbalanced by the corresponding smaller concentration, and that only thermal treatment produces appreciable differences in properties.
Thermal and mechanical properties of aryl ketone polymers and their composites
Authors: Barton J. M. , Lloyd J. R. , Goodwin A. A. , Hay J. N.
Published: April 2007

Carbon fibre composites of polyaryletheretherketone (PEEK), APC‐2, have been extracted with mixed solvents in order to separate the polymer matrix. A comparison of the crystallisation behaviour of this material with standard PEEK has been made. Nucleation by carbon fibre was only observed after the samples were sheared and this was attributed to stress‐induced nucleation. On allowing to relax in the melt, and in the absence of residual stresses, no surface nucleation by the carbon fibres was observed.

The fracture toughness and flexural modulus of the composite are discussed in terms of thermal history, as well as the dynamic mechanical thermal behaviour.
Thermal behaviour and morphology of copolyterephthalates derived from trimethylene glycols
Authors: González César C. , Bello Antonio , Pereña José M. , Pérez Ernesto
Published: April 2007

The thermal behaviour and the morphology of four polyterephthalate samples have been studied. Two of these samples are the pure homopolymers poly(trimethylene terephthalate) (PTMT) and poly(oxyditrimethylene terephthalate) (PTMTMT), while the other two are copolymers of both polyesters with 13 and 33% by weight of PTMTMT. It was found that the insertion of units of PTMTMT in the copolymers derived from PTMT produces a depression of the glass transition and melting temperatures as a consequence of the higher flexibility of the former units, and several equations have been tested to fit that depression. Moreover, the crystallization rate of PTMTMT was found to be very slow, and the need for higher supercoolings to crystallize the samples in a reasonable time, as the PTMTMT content increases, implies the formation of a greater number of nuclei, with subsequent inconvenience when trying to follow the evolution of the radii of the observed spherulites. On the other hand, well developed spherulites were obtained for the samples rich in PTMT, and two different kinds of this superstructure were observed, depending on the crystallization temperature.
Influence of resin structure on the addition of ethanol to isobutene in the vapour phase
Authors: Iborra Montserrat , Tejero Javier , Izquierdo José F. , Cunill Fidel
Published: April 2007

The addition of ethanol to isobutene in the vapour phase has been studied on four commercial macroporous resins. The acid group content of the resins used was about 5 meq g−1, and their degrees of crosslinking were 12, 16, 18 and 20%. Differential conversions were measured for ethanol‐isobutene‐nitrogen feeds at 53–78.5°C and atmospheric pressure, far from limitation by chemical equilibrium. The rate data showed that isobutene has an enhancing effect on the reaction, whereas ethanol has a strong inhibitory effect in the range studied. The four catalysts showed similar behaviour. At the lower temperatures explored all the resins have similar catalytic activity, but at the highest temperature the resin with 18% divinylbenzene showed the highest activity. This maximum activity can be explained by a greater accessibility to the acid groups, which is in agreement with the literature.
Spin‐labelling studies of the conformation of poly(vinyl alcohol) derivatives
Authors: Tenhu Heikki , Sundholm Franciska
Published: April 2007

Poly(vinyl acetate‐co‐vinyl alcohol‐co‐vinyl cinnamate) containing 12% residual acetate groups and 2% cinnamate groups has been studied in aqueous solution with a spin‐label covalently bound in the polymer chain. The polymer undergoes a conformational change around room temperature. In addition, it is suggested that the change in conformation is followed by a change in the aggregation state of the polymer molecules.
DSC study of the interaction of 2‐mercaptobenzothiazole, sulphur, ZnO and stearic acid in the absence of rubber
Authors: Luyt Adriaan S. , McGill William J. , Shillington David
Published: April 2007

The interactions between mixtures of 2‐mercaptobenzothiazole (MBT), sulphur, ZnO and stearic acid were studied by DSC in the absence of rubber. MBT was thermally stable up to its melting point of 174°C, but molten MBT reacted with ZnO as well as with molten zinc stearate, to form zinc mercaptobenzothiazole (ZMBT). The reactions did not go to completion, presumably as further reaction was hindered by solid ZMBT which was thermally stable up to its melting point of 330°C. MBT dissolved in molten sulphur and no thermal events that could be attributed to MBT/sulphur interaction were detected. A mixture of MBT/sulphur/ZnO heated to 190°C yielded ZMBT, together with residual MBT and sulphur (residual ZnO was not measured). In a mixture of MBT/ZnO/stearic acid, the formation of zinc stearate occurred at a lower temperature than in the absence of MBT and preceded the formation of ZMBT.