bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Adenosine Receptor Agonists in Regulation of Hematopoiesis
Authors: Hofer Michal , Pospisil Milan , Weiterova Lenka , Hoferova Zuzana
Published: January 2011

The review summarizes data evaluating the role of adenosine receptor signaling in murine hematopoietic functions. The studies carried out utilized either non-selective activation of adenosine receptors induced by elevation of extracellular adenosine or by administration of synthetic adenosine analogs having various proportions of selectivity for a particular receptor. Numerous studies have described stimulatory effects of non-selective activation of adenosine receptors, manifested as enhancement of proliferation of cells at various levels of the hematopoietic hierarchy. Subsequent experimental approaches, considering the hematopoiesis-modulating action of adenosine receptor agonists with a high level of selectivity to individual adenosine receptor subtypes, have revealed differential effects of various adenosine analogs. Whereas selective activation of A1 receptors has resulted in suppression of proliferation of hematopoietic progenitor and precursor cells, that of A3 receptors has led to stimulated cell proliferation in these cell compartments. Thus, A1 and A3 receptors have been found to play a homeostatic role in suppressed and regenerating hematopoiesis. Selective activation of adenosine A3 receptors has been found to act curatively under conditions of drug- and radiation-induced myelosuppression. The findings in these and further research areas will be summarized and mechanisms of hematopoiesis-modulating action of adenosine receptor agonists will be discussed.
Data-Centric Multiobjective QoS-Aware Routing Protocol for Body Sensor Networks
Authors: Razzaque Md. Abdur , Hong Choong Seon , Lee Sungwon
Published: January 2011

In this paper, we address Quality-of-Service (QoS)-aware routing issue for Body Sensor Networks (BSNs) in delay and reliability domains. We propose a data-centric multiobjective QoS-Aware routing protocol, called DMQoS, which facilitates the system to achieve customized QoS services for each traffic category differentiated according to the generated data types. It uses modular design architecture wherein different units operate in coordination to provide multiple QoS services. Their operation exploits geographic locations and QoS performance of the neighbor nodes and implements a localized hop-by-hop routing. Moreover, the protocol ensures (almost) a homogeneous energy dissipation rate for all routing nodes in the network through a multiobjective Lexicographic Optimization-based geographic forwarding. We have performed extensive simulations of the proposed protocol, and the results show that DMQoS has significant performance improvements over several state-of-the-art approaches.
Characterization of Carbonyl Compounds in the Ambient Air of an Industrial City in Korea
Authors: Seo Young-Kyo , Baek Sung-Ok
Published: January 2011

The purpose of this study was to characterize spatial and temporal variations of carbonyl compounds in Gumi city, where a number of large electronic-industrial complexes are located. Carbonyl samples were collected at five sites in the Gumi area: three industrial, one commercial, and one residential area. Sampling was carried out throughout a year from December 2003 to November 2004. At one industrial site, samples were taken every six days, while those of the other sites were for seven consecutive days in every season. Each sample was collected for 150 minutes and at intervals of three times a day (morning, afternoon, and evening). A total of 476 samples were analyzed to determine 15 carbonyl compounds by the USEPA TO-11A (DNPH-cartridge/HPLC) method. In general, acetaldehyde appeared to be the most abundant compound, followed by formaldehyde, and acetone+acrolein. Mean concentrations of acetaldehyde were two to three times higher in the industrial sites than in the other sites, with its maximum of 77.7 ppb. In contrast, ambient levels of formaldehyde did not show any significant difference between the industrial and non-industrial groups. Its concentrations peaked in summer probably due to the enhanced volatilization and photochemical reactivity. These results indicate significant emission sources of acetaldehyde in the Gumi industrial complexes. Mean concentrations of organic solvents (such as acetone+acrolein and methyl ethyl ketone) were also significantly high in industrial areas. In conclusion, major sources of carbonyl compounds, including acetaldehyde, are strongly associated with industrial activities in the Gumi city area.
Asp295 Stabilizes the Active-Site Loop Structure of Pyruvate Dehydrogenase, Facilitating Phosphorylation of Ser292 by Pyruvate Dehydrogenase-Kinase
Authors: Hirani Tripty A. , Tovar-Méndez Alejandro , Miernyk Ján A. , Randall Douglas D.
Published: January 2011

We have developed anin vitrosystem for detailed analysis of reversible phosphorylation of the plant mitochondrial pyruvate dehydrogenase complex, comprising recombinantArabidopsis thalianaα2β2-heterotetrameric pyruvate dehydrogenase (E1) plusA. thalianaE1-kinase (AtPDK). Upon addition of MgATP, Ser292, which is located within the active-site loop structure of E1α, is phosphorylated. In addition to Ser292, Asp295 and Gly297 are highly conserved in the E1α active-site loop sequences. Mutation of Asp295 to Ala, Asn, or Leu greatly reduced phosphorylation of Ser292, while mutation of Gly297 had relatively little effect. Quantitative two-hybrid analysis was used to show that mutation of Asp295 did not substantially affect binding of AtPDK to E1α. When using pyruvate as a variable substrate, the Asp295 mutant proteins had modest changes inkcat,Km, andkcat/Kmvalues. Therefore, we propose that Asp295 plays an important role in stabilizing the active-site loop structure, facilitating transfer of the γ-phosphate from ATP to the Ser residue at regulatory site one of E1α.
An Observational, Prospective Survey Assessing the Control of Atrial Fibrillation in Asia Pacific: Rationale and Design of the RecordAF-AP Registry
Authors: Amerena John , Chen Shih-Ann , Sriratanasathavorn Charn , Cho Jeong-Gwan , Dejia Huang , Omar Razali , Fat Tse Hung , King Anthony
Published: January 2011

Background

The literature suggests that the prevalence of atrial fibrillation (AF) may be lower in Asian countries than in Western countries. Nevertheless, AF remains a significant public health problem in the region. The burden of AF, the experiences of previous trials and the lack of data on AF and its management in Asia Pacific highlight the need for a comprehensive prospective study of AF management.

Methods

The REgistry on Cardiac rhythm disORDers assessing the control of Atrial Fibrillation Asia Pacific (RecordAF-AP) is a prospective, observational survey of the management of recently diagnosed AF patients with 1-year follow-up in 8 countries across Asia Pacific. Eligible patients presenting with AF, treated or not, will be included in the registry and data will be recorded prospectively during follow-up visits at 6 and 12 months.

Results

RecordAF-AP will recruit more than 3000 patients. Study recruitment commenced in April 2009 and the final results anticipated at the end of 2011.

Conclusions

RecordAF-AP will assess the real-life management of AF patients in Asia Pacific, including a comparison of clinical outcomes in rhythm versus rate control strategies, providing much needed insight into the costs, treatment choices and clinical outcomes of AF patients in this region.
Using measurements for evaluation of black carbon modeling
Authors: Gilardoni S. , Vignati E. , Wilson J.
Published: January 2011

Abstract. The ever increasing use of air quality and climate model assessments to underpin economic, public health, and environmental policy decisions makes effective model evaluation critical. This paper discusses the properties of black carbon and light attenuation and absorption observations that are the key to a reliable evaluation of black carbon model and compares parametric and nonparametric statistical tools for the quantification of the agreement between models and observations. Black carbon concentrations are simulated with TM5/M7 global model from July 2002 to June 2003 at four remote sites (Alert, Jungfraujoch, Mace Head, and Trinidad Head) and two regional background sites (Bondville and Ispra). Equivalent black carbon (EBC) concentrations are calculated using light attenuation measurements from January 2000 to December 2005. Seasonal trends in the measurements are determined by fitting sinusoidal functions and the representativeness of the period simulated by the model is verified based on the scatter of the experimental values relative to the fit curves. When the resolution of the model grid is larger than 1° × 1°, it is recommended to verify that the measurement site is representative of the grid cell. For this purpose, equivalent black carbon measurements at Alert, Bondville and Trinidad Head are compared to light absorption and elemental carbon measurements performed at different sites inside the same model grid cells. Comparison of these equivalent black carbon and elemental carbon measurements indicates that uncertainties in black carbon optical properties can compromise the comparison between model and observations. During model evaluation it is important to examine the extent to which a model is able to simulate the variability in the observations over different integration periods as this will help to identify the most appropriate timescales. The agreement between model and observation is accurately described by the overlap of probability distribution (PD) curves. Simple monthly median comparisons, the Student's t-test, and the Mann-Whitney test are discussed as alternative statistical tools to evaluate the model performance. The agreement measured by the Student's t-test, when applied to the logarithm of EBC concentrations, overestimates the higher PD agreements and underestimates the lower PD agreements; the Mann-Whitney test can be employed to evaluate model performance on a relative scale when the shape of model and experimental distributions are similar.
Transport of dust particles from the Bodélé region to the monsoon layer – AMMA case study of the 9–14 June 2006 period
Authors: Crumeyrolle S. , Tulet P. , Gomes L. , Garcia-Carreras L. , Flamant C. , Parker D. J. , Matsuki A. , Formenti P. , Schwarzenboeck A.
Published: January 2011

Abstract. Aerosol properties were measured during an airborne campaign experiment that took place in June 2006 in West Africa within the framework of the African Monsoon Multidisciplinary Analyses (AMMA). The goal of the present study was to investigate a dynamical mechanism able to facilitate the sedimentation of dust particles from the Saharan Air Layer (SAL) into the boundary layer. A significant change in the dust particle concentration measured along the meridian between Niamey (Niger) and Cotonou (Benin) was found in the boundary layer (~700 m), where the dust particle concentration increased in a zone where local emission is not possible. Moreover, the boundary layer top observed with the dropsondes launched with the F-F20 shows a strong relationship with the surface cover anomalies, with higher Boundary Layer (BL) tops over the warmer surfaces, such as croplands, as opposed to adjacent forest. A mesoscale atmospheric model with a new on-line dust parameterization, resulting from the Alfaro and Gomes (2001) parametrisation and AMMA observations, was used to interpret the impact of vegetation anomalies on dust particle sedimentation. The results of the simulation are consistent with the observations, with higher dust concentration over the warm surface cover anomalies.
The role of the QBO in the inter-hemispheric coupling of summer mesospheric temperatures
Authors: Espy P. J. , Ochoa Fernández S. , Forkman P. , Murtagh D. , Stegman J.
Published: January 2011

Abstract. Inter-hemispheric coupling between the polar summer mesosphere and planetary-wave activity in the extra-tropical winter stratosphere has recently been inferred using Polar Mesospheric Cloud (PMC) properties as a proxy for mesospheric temperature (Karlsson et al., 2007). Here we confirm these results using a ten-year time series of July mesospheric temperatures near 60° N derived from the hydroxyl (OH) nightglow. In addition, we show that the time-lagged correlation between these summer mesospheric temperatures and the ECMWF winter stratospheric temperatures displays a strong Quasi-Biennial Oscillation (QBO). The sign and phase of the correlation is consistent with the QBO modulation of the extra-tropical stratospheric dynamics in the Southern Hemisphere via the Holton-Tan mechanism (Holton and Tan, 1980). This lends strength to the identification of synoptic and planetary waves as the driver of the inter-hemispheric coupling, and results in a strong QBO modulation of the polar summer mesospheric temperatures.
A spectral method for retrieving cloud optical thickness and effective radius from surface-based transmittance measurements
Authors: McBride P. J. , Schmidt K. S. , Pilewskie P. , Kittelman A. S. , Wolfe D. E.
Published: January 2011

Abstract. We introduce a new multispectral method for the retrieval of optical thickness and effective radius from cloud transmittance, which is less sensitive to effective radius than cloud reflectance. Based on data from the moderate spectral resolution observations of the Solar Spectral Flux Radiometer (SSFR) and Shortwave Spectroradiometer (SWS), we use the spectral shape of transmitted radiance as a means of retrieving effective radius from cloud transmittance. The observations were taken during the International Chemistry Experiment in the Arctic Lower Troposphere and at the Southern Great Plains (SGP) site of the Atmospheric Radiation Measurement (ARM) Climate Research Facility. The spectral shape was quantified by fitting a slope to the normalized transmittance between 1565 nm and 1634 nm. The retrieval was performed by comparing the observed slope at 1565 nm and the transmittance at 515 nm with a pre-calculated library (lookup table). An estimate of the retrieval uncertainty was provided by propagating the uncertainty of the observations through the best-fit algorithm. We compare the new retrieval with an algorithm that uses transmittance at two wavelengths, a method often used with cloud reflectance. The liquid water path (LWP) is derived from the retrieved optical thickness and effective radius, assuming a cloud with effective radius varying linearly with altitude above cloud base, and compared to the retrieved liquid water path from a microwave radiometer. Retrievals from two MODIS overpasses of the SGP were also compared. The data taken from the SGP was under thicker cloud than the case used from ICEALOT, with average optical thickness of 44 and 22, respectively. For the time period with the thicker clouds, the dual-wavelength method and the slope method retrieved nearly indistinguishable results. The dual-wavelength method, however, resulted in slightly higher average relative effective radius uncertainty of 12.9 μm±12.8%, as compared to 12.8 μm±8.9% from the slope method. The thinner cloud case resulted in a significant difference between the dual-wavelength and slope algorithms with average retrieved effective radius and uncertainties of 12.5 μm±8.4% and 17.0 μm±21.0% for the slope and dual-wavelength methods, respectively. The retrieved optical thickness values for this case were nearly identical. The average derived LWP was within 12.5% and 20% of the MWR LWP for the ARM and ICEALOT data. For a homogeneous cloud case, the MODIS retrievals (optical depth, effective radius, and LWP) were within the uncertainty of the SWS retrievals. Inhomogeneous clouds resulted in lesser agreement between the MODIS and SWS retrievals.
Development and characterization of the CU ground MAX-DOAS instrument: lowering RMS noise and first measurements of BrO, IO, and CHOCHO near Pensacola, FL
Authors: Coburn S. , Dix B. , Sinreich R. , Volkamer R.
Published: January 2011

Abstract. We designed and assembled the University of Colorado Ground Multi AXis Differential Optical Absorption Spectroscopy (CU GMAX-DOAS) instrument to retrieve bromine oxide (BrO), iodine oxide (IO), formaldehyde (HCHO), glyoxal (CHOCHO), nitrogen dioxide (NO2) and the oxygen dimer O4 in the coastal atmosphere of the Gulf of Mexico. The detection sensitivity of DOAS measurements is directly proportional to the root mean square (RMS) of the residual spectrum that remains after all absorbers have been subtracted. Here we describe the CU GMAX-DOAS instrument and demonstrate that the hardware is capable of attaining RMS values of ~6 × 10-6 without apparent limitations other than photon shot noise. Laboratory tests revealed two factors that, in practice, limit the RMS: (1) detector non-linearity noise, RMSNLin, and (2) temperature fluctuations that cause variations in optical resolution (full width at half the maximum, FWHM, of atomic emission lines) and give rise to optical resolution noise, RMSFWHM. The non-linearity of our detector is low (~10−3) yet – unless actively controlled – is sufficiently large to create a RMSNLin limit of up to 1.4 × 10-4. The optical resolution is sensitive to temperature changes (0.03 detector pixels/°C at 334 nm), and temperature variations of 0.1 °C can cause residual RMSFWHM of ~1 × 10-4. Both factors were actively addressed in the design of the CU GMAX-DOAS instrument. The CU GMAX-DOAS was set up at a coastal site near Pensacola, FL, where we detected BrO, IO and CHOCHO in the marine boundary layer (MBL), with daytime average tropospheric vertical column densities, VCDs, of ~2 × 1013 molec cm−2, 8 × 1012 molec cm−2 and 4 × 1014 molec cm−2, respectively. HCHO and NO2 were also detected with typical MBL VCDs of 1 × 1016 and 3 × 1015. These are the first measurements of BrO, IO and CHOCHO over the Gulf of Mexico. The atmospheric implications of these observations for elevated mercury wet deposition rates in this area are briefly discussed. The CU GMAX-DOAS has great potential to investigate RMS-limited problems, like the abundance and variability of trace gases in the MBL and possibly the free troposphere (FT).
A millennial multi-proxy reconstruction of summer PDSI for Southern South America
Authors: Boucher É. , Guiot J. , Chapron E.
Published: January 2011

Abstract. We present the first highly resolved millennial reconstruction of the summer (DJF) Palmer Drought Severity Index (PDSI) for the Southern Hemisphere. Our multi-proxy reconstruction focuses on Southern South-America (SSA, south of 20° S) and is based on a novel spectral analogue method that aims at reconstructing the low frequencies of PDSI series independently from higher frequencies. The analysis of past regimes and long-term fluctuations in the PDSI reveals considerable geographical and temporal variations over the last millennia in SSA. Hence, recent changes, although some were very significant, were rarely exceptional over the last thousand years. However, from the point of view of extremes, recent PDSI values associated to extreme droughts (e.g. in the Andes) or wet spells (e.g. in the Pampas) were unequalled over the last thousand years. A major feature of our reconstruction is that it highlights that low frequency water availability fluctuations in Patagonia were generally in antiphase with those found on the rest of the sub-continent. We show that such antiphases within SSA's hydroclimate could be attributed the Antarctic Oscillation (AAO). The AAO was an important climatic driver during the calibration period (1930–1993) in SSA, and possibly over the last millennia as well. ENSO and PDO signals are also embedded, to a lesser extent, within the PDSI series, but the influence of these forcings has considerably varied through time and space over the last thousand years. Our results therefore highlight the complexity of water-availability fluctuations in SSA and their important dependence on external ocean-atmospheric forcings.
Influence of cross-shelf water transport on nutrients and phytoplankton in the East China Sea: a model study
Authors: Zhao L. , Guo X.
Published: January 2011

Abstract. A three dimensional coupled biophysical model was used to examine the supply of oceanic nutrients to the shelf of the East China Sea (ECS) and its role in primary production over the shelf. The model consisted of two parts: the hydrodynamic module was based on a nested model with a horizontal resolution of 1/18 degree, whereas the biological module was a lower trophic level ecosystem model including two types of phytoplankton, three elements of nutrients, and biogenic organic material. The model results suggested that seasonal variations occurred in the distribution of nutrients and chlorophyll a over the shelf of the ECS. After comparison with available observed nutrients and chlorophyll a data, the model results were used to calculate volume and nutrients fluxes across the shelf break. The annual mean total fluxes were 1.53 Sv for volume, 9.4 kmol s−1 for DIN, 0.7 kmol s−1 for DIP, and 18.2 kmol s−1 for silicate. Two areas, northeast of Taiwan and southwest of Kyushu, were found to be major source regions of oceanic nutrients to the shelf. Although the onshore fluxes of nutrients and volume both had apparent seasonal variations, the seasonal variation of the onshore nutrient flux did not exactly follow that of the onshore volume flux. Additional calculations in which the concentration of nutrients in Kuroshio water was artificially increased suggested that the oceanic nutrients were distributed in the bottom layer from the shelf break to the region offshore of the Changjiang estuary from spring to summer and appeared in the surface layer from autumn to winter. The calculations also implied that the supply of oceanic nutrients to the shelf can change the consumption of pre-existing nutrients from rivers. The response of primary production over the shelf to the oceanic nutrients was confirmed not only in the surface layer (mainly at the outer shelf and shelf break in winter and in the region offshore of the Changjiang estuary in summer) but also in the subsurface layer over the shelf from spring to autumn.
Theoretical and experimental study of the melting process of high‐density polyethylene for multidimensional vibration equipment
Authors: Zeng Guang‐Sheng , Qu Jin‐Ping , Liu Yue‐Jun
Published: January 2011

A model for investigating the melting process under a vibration force field is presented. The key parameters of this model are as follows: the rotation of the screw and heat are supplied by the vibration force field for the material phase conversion. A multidimensional vibration desk (DWZD‐500) and low‐density polyethylene material were used to investigate the effect of the vibration parameters on the melting process. A comparison of the derived model and experimental results revealed that increasing the vibration parameters increased the melting mass. This study will serve as the theoretical basis to optimize the parameters of vibration extruders' processing polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Recycling of Poly(phenylene ether) Blends
Authors: Nerkar Manoj , Bandyopadhyay Sumanda , Kamalakaran Radha , Gupta Samik , Guo Hua
Published: January 2011

The effects of postindustry recycling of polymer blends composed of poly(phenylene ether) (PPE) on the properties of the PPE blends were investigated by simulated recycling with multiple molding cycles. Two compositions with different concentrations of PPE were reprocessed with an injection‐molding machine. Mechanical, thermal, rheological, and morphological characterizations were carried out on as‐produced and reprocessed samples to examine the influence of the number of molding cycles on the two specific PPE blends. Efforts were made to determine the effect of each molding cycle on the specific properties of the two PPE blends, including the Elastic (E), modulus, stress at break, strain at break, multiaxial impact, and melt viscosity. The results are discussed in detail. The retention of the properties correlated well with the unperturbed morphology of the compositions before and after recycling, as observed by transmission electron microscopy analyses on fractured tensile samples. However, more in‐depth microanalyses are required to identify the effect of recycling on the individual components present in the studied compositions. In this study, we aimed to establish structure–property relations upon recycling using several characterization techniques. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Formation of blisters in kapton polymer by the effect of 1.25 MeV gamma irradiation
Authors: Siddhartha  , Aarya Suveda , Mishra Monika , Srivastava A. K. , Wahab M. A.
Published: January 2011

The surface morphology, chemical, optical, and structural response of 1.25 MeV gamma rays irradiation at various doses ranging from 16 to 300 kGy on Kapton polymer samples were studied by using scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), ultraviolet/visible absorption (UV/VIS) and X‐ray diffraction (XRD). The morphology study shows the blisters formation on the Kapton polymer surface due to 1.25 MeV gamma rays irradiation at ambient temperature. This observation provides a basis for the quantitative evaluation of FTIR results obtained for thermally stable polymer on the chemical bond deterioration with increasing gamma irradiation. The blistering mechanism is correlated with the internal gases (CO, H2) released due to gamma radiation induced damages. The recorded UV–VIS spectrum shows a maximum absorption around the wavelength 540 nm. However, the nature of the spectra does not change due to gamma irradiation but a shift in absorption edge towards the higher wavelength side has been observed with increasing dose. The optical data shows an increase in the calculated band gap at the highest dose. The diffraction pattern of virgin sample shows that polymer is semicrystalline, but due to irradiation, a decrease in the peak intensity and FWHM and an increase in the crystallite size at the highest dose level of 300 kGy have been observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Bacterial cellulose/collagen composite: Characterization and first evaluation of cytocompatibility
Authors: Zhijiang Cai , Guang Yang
Published: January 2011

The novel bacterial cellulose (BC)/collagen composites were prepared by immersing wet BC pellicle excreted by Acetobacter xylinum in collagen solution followed by freeze‐drying process. The product looks like a foam structure. The morphology of BC/collagen composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images showed that collagen molecules was not only coated on the BC fibrils surface but also could penetrate inside BC and hydrogen bond interactions were formed between BC and collagen. The prepared BC/collagen composite was also characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and mechanical test. With the incorporation of collagen in the BC, no changes happened in the crystal structure but the thermal stability was improved. Tensile test results indicate that the Young's Modulus and tensile strength have a big increase while the elongation at break has a slight decrease. The cytocompatibility of composite was preliminarily evaluated by cell adhesion studies. The tests were carried out using 3T3 fibroblast cells. The cells incubated with BC/collagen scaffolds for 48 h were capable of forming cell adhesion and proliferation. It showed much better cytocompatibility than pure BC. So, the prepared BC/collagen scaffolds are bioactive and may be suitable for cell adhesion/attachment suggesting that these scaffolds can be used for wound dressing or tissue‐engineering scaffolds. Therefore, these results suggest that these novel BC/collagen scaffolds may have the potential to be sued for some biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermogravimetric and resistivity study of Ex situ and In situ poly(methyl methacrylate)/carboxylic acid group functionalized multiwall carbon nanotubes composites
Authors: Das Mahuya , Ray Dipa , Bandyopadhyay Sri , Banerjee Sourish , Bandyopadhyay Nil R. , Basumallik Amitava
Published: January 2011

Polymer composites based on poly(methyl methacrylate) (PMMA)/carboxylic acid group functionalized multiwall carbon nanotubes (MWCNT) were prepared by the ex situ and in situ techniques with 0.05% loading by weight. Composite films were fabricated by solvent casting method. Electrical conductivity of the composites as well as of the neat PMMA polymer was measured in the temperature range 333 K to 423 K. Neat PMMA samples prepared by the same method showed complete insulating behavior. Ex situ technique leads to a lower value of percolation threshold. Infrared spectroscopy was used to analyze the effect of functionalization of MWCNT on the interfacial bonding of PMMA and MWCNT. Thermogravimetric analysis revealed that the maximum degradation temperature has been shifted to higher region for in situ composites compared to PMMA itself—and the ex situ composites indicated better thermal stability. X‐ray diffraction study of composites also indicates that in situ composites functionalization incorporated MWCNT particles in the polymer chain. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Microwave‐induced devulcanization for poly(ethylene–propylene–diene) recycling
Authors: Bani Alberto , Polacco Giovanni , Gallone Giuseppe
Published: January 2011

The production of high quantities of end‐of‐life rubbers is an environmental problem of growing importance. Because of their crosslinked nature, such rubbers cannot be easily reprocessed, and actually, they are mainly wasted or reused after a simple mechanical grinding. In this study, a microwave (MW)‐induced thermal treatment at temperatures above 300°C was proposed to obtain partial devulcanization of a poly(ethylene–propylene–diene) (EPDM) rubber filled with carbon black. The use of MWs showed to be a very fast and simple technique, which allowed the production of a treated rubber with a relatively low degree of crosslinking, a slight revulcanization ability, and suitability for reuse in conjunction with virgin rubber. Preliminary mechanical characterization, performed on the revulcanized samples, indicated that the virgin and treated rubber were able to establish a good interface adhesion, which led to performances better than those of similar materials where the recycled part was made of ground untreated EPDM. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Characterization of monodisperse copolymer submicrospheres with branched structures and different glass‐transition temperatures prepared by soap‐free emulsion polymerization
Authors: Liu Yi‐Yu , Lo Ming‐Yu , Chen Hui
Published: January 2011

This study was focused on the synthesis of monodisperse poly(n‐butyl methacrylate‐co‐methyl methacrylate) submicrospheres via soap‐free emulsion polymerization and on their characterization. The glass‐transition temperatures of poly(n‐butyl methacrylate) and poly(methyl methacrylate) were approximately 25 and 110°C, respectively. Therefore, submicrospheres with different glass‐transition temperatures could be obtained through the variation of the copolymer composition. In addition, relationships between the monomer feed concentration (M0) and the Mark–Houwink constant (α) for the copolymer submicrospheres were proposed. The molecular weights of the copolymer submicrospheres decreased sharply with an increase in the weight fraction of n‐butyl methacrylate. On the contrary, the particle diameter increased linearly from 277 to 335 nm with an increase in the weight fraction of n‐butyl methacrylate. The α values decreased with an increase in M0, and this indicated that the branched structures of the copolymer submicrospheres were easily obtained when M0 was higher than 0.11 g/mL of water. Consequently, the results of this study are expected to provide useful information for the synthesis of monodisperse copolymer submicrospheres by soap‐free emulsion polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and characterization of novel crosslinked poly[glycidyl methacrylate–poly(ethylene glycol) methyl ether methacrylate] as gel polymer electrolytes
Authors: Luo Dan , Li Yang , Yang Mujie
Published: January 2011

In this study, glycidyl methacrylate was copolymerized with poly(ethylene glycol) methyl ether methacrylate to obtain a copolymer {poly[glycidyl methacrylate–poly(ethylene glycol) methyl ether methacrylate] [P(GMA–PEGMA)]}, which was crosslinked with α,ω‐diamino poly(propylene oxide) (Jeffamine) at various weight ratios and molecular weights to form novel gel polymer electrolytes (GPEs). The crosslinked copolymers were characterized by Fourier transform infrared spectroscopy and thermal analysis. The crosslinked polymers were amorphous in the pristine state and became crystallized after they were doped with lithium electrolyte. Furthermore, the crosslinking degree of the crosslinked polymers increased with increasing weight ratio of Jeffamine, and both the swelling properties and mechanical behaviors of the crosslinked polymers were heavily affected by the weight ratio and molecular weight of Jeffamine. The ionic conductivity (σ) of the GPEs from the crosslinked copolymers was determined by alternating‐current impedance spectroscopy. A higher molecular weight and increased weight ratio of Jeffamine resulted in a higher σ. The GPE based on P(GMA–PEGMA) crosslinked with an equal weight of Jeffamine D2000 exhibited the highest σ of 8.29 × 10−4 S/cm at 25°C and had a moderate mechanical strength. These crosslinked copolymers could be potential candidates for the construction of rechargeable lithium batteries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Synthesis, characterization, and properties of degradable poly(l‐lactic acid)/poly(butylene terephthalate) copolyesters containing 1,4‐cyclohexanedimethanol
Authors: Wang Bingtao , Zhang Yan , Song Pingan , Guo Zhenghong , Cheng Jie , Fang Zhengping
Published: January 2011

High‐molecular‐weight copolyesters based on poly(butylene terephthalate) as rigid aromatic segments and poly(l‐lactic acid) (PLLA) as degradable aliphatic segments were synthesized via the polycondensation of terephthalic acid, 1,4‐butanediol (BDO), 1,4‐cyclohexanedimethanol (CHDM), and PLLA oligomer. By tailoring the molar ratio of diols (BDO and CHDM), we investigated in detail the effects of the CHDM rigid hexacyclic ring on the synthesis, mechanical properties, thermal stabilities, and degradation behaviors of the copolyesters. With increasing CHDM content, the initial decomposition temperature increased from 282.5 to 322.2°C, and the tensile strength improved by nearly four times, from 5.4 to 19 MPa. When the molar ratio of BDO/CHDM was 95/5, the weight‐average molecular weight of the copolyester was 89,400 g/mol with a polydispersity of 1.96. In addition, hydrolytic degradation results in phosphate buffer solution indicate that the degradation rate of the copolyesters displayed a strong dependency on the temperature and CHDM composition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Viscoelastic relaxation of styrene–butadiene–styrene block copolymers with different topological structures
Authors: Du Miao , Yu Qiuming , Lu Yi , Zheng Qiang
Published: January 2011

The viscoelastic relaxation of linear styrene–butadiene–styrene triblock copolymer (l‐SBS) and star styrene–butadiene–styrene triblock copolymer (s‐SBS) with four arms were investigated with differential scanning calorimetry and dynamic rheological measurements. Three characteristic viscoelastic responses of l‐SBS and s‐SBS in the plot of the loss tangent (tan δ) and temperature at different frequencies (ω's), which corresponded to the relaxation of the polybutadiene (PB) block (peak I), the glass transition of the polystyrene (PS) phase (peak II), and the mutual diffusion between the PB blocks and PS blocks (peak III), respectively, were observed in the experimental range. Although ω was 0.1 rad/s, a noticeable peak III was gained for both l‐SBS and s‐SBS. The dynamic storage modulus (G′) of l‐SBS showed two distinct types of behavior, depending on the temperature. At temperature (T) < T2 (where T2 is the temperature corresponding to peak II), G′ of l‐SBS displayed a very weak ω dependency. In contrast, at T > T2, G′ decayed much more rapidly. However, G′ of s‐SBS displayed a very weak ω dependency at both T < T2 and T > T2. Only near T2 did s‐SBS decay with ω a little sharply. These indicated, in contrast to l‐SBS, that s‐SBS still exhibited more elasticity even at T > T2 because of its crosslinking point between the PB blocks (the star structure). In the lower ω range, l‐SBS exhibited a stronger peak III than s‐SBS despite the same styrene content for l‐SBS and s‐SBS. The high tan δ value of peak III for l‐SBS was considered to be related to the internal friction among the PB blocks or the whole l‐SBS chain, not the PS blocks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
The effect of pH on the removal of anionic dyes from colored textile wastewater using a biosorbent
Authors: Mahmoodi Niyaz Mohammad , Arami Mokhtar , Bahrami Hajir , Khorramfar Shooka
Published: January 2011

The effect of pH on equilibrium and kinetics of dye adsorption onto canola hull as a biosorbent was studied. Reactive Red 198 (RR198), Reactive Blue 19 (RB19), Direct Red 79 (DR79), and Direct Red 80 (DR80) were used as model textile dyes. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and UV–vis spectroscopy were used. The presence of functional groups onto canola hull was investigated using FTIR spectroscopy. The pseudo first‐order, pseudo second‐order and intraparticle diffusion kinetics models were examined to evaluate the kinetics data. The Langmuir, Freundlich, and Tempkin adsorption isotherm models were applied to describe the equilibrium isotherms. The FTIR spectrum proved the presence of functional groups such as hydroxyl and amino groups in canola hull surface. The results showed that the adsorption of RR198, RB19, DR79, and DR80 onto canola hull followed Tempkin isotherm. Adsorption kinetic of dyes followed pseudo second‐order kinetics. Desorption tests showed maximum dye releasing of 88% for RR198, 86% for RB19, 91% for DR79, and 95% for DR80 at pH 12. Data showed that canola hull could be used as a novel natural material for the removal of anionic dyes from wastewater. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and characterization of hydrophilic, spectroscopic, and kinetic properties of hydrogels based on polyacrylamide and methylcellulose polysaccharide
Authors: Aouada Fauze Ahmad , Moura Márcia Regina de , Lopes da Silva Wilson Tadeu , Muniz Edvani Curti , Mattoso Luiz Henrique Capparelli
Published: January 2011

Hydrogels with potential technological applications has been prepared using polyacrylamide (PAAm) and methylcellulose (MC) polymers by free radical polymerization reaction. The spectroscopic, morphological, swelling, and kinetic properties were investigated by solid state 13C VACP‐MAS nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water uptake (WU) measurements, respectively. FTIR and NMR analysis confirmed the formation of semi‐IPN structured hydrogel. Data from WU and SEM revealed that the addition of MC into the solution‐forming hydrogel leads to increase in average pore size and hydrophilicity. By varying of AAm, MC, pH and ionic‐strength of swelling medium, it was possible to obtain hydrogels with hydrophilic properties controlled and optimized. The water uptake mechanism is dependent of the AAm concentration, which can follow the Fickian diffusion and anomalous transport process. In this way, PAAm‐MC hydrogels are promising materials for technological applications, such as agricultural field. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Electrical conductivity and major mechanical and thermal properties of carbon nanotube‐filled polyurethane foams
Authors: Yan Ding‐Xiang , Dai Kun , Xiang Zhi‐Dong , Li Zhong‐Ming , Ji Xu , Zhang Wei‐Qin
Published: January 2011

The carbon nanotubes (CNTs)/rigid polyurethane (PU) foam composites with a low percolation threshold of ∼ 1.2 wt % were prepared by constructing effective conductive paths with homogeneous dispersion of the CNTs in both the cell walls and struts of the PU foam. The conductive foam presented excellent electrical stability under various temperature fields, highlighting the potential applications for a long‐term use over a wide temperature range from 20 to 180°C. Compression measurements and dynamical mechanical analysis indicated 31% improvement in compression properties and 50% increase in storage modulus at room temperature in the presence of CNTs (2.0 wt %). Additionally, the incorporation of only 0.5 wt % CNTs induced remarkable thermal stabilization of the matrix, with the degradation temperature increasing from 450 to 499°C at the 50% weight loss. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
New Poly(azomethine‐urethane)s including melamine derivatives in the main chain: Synthesis and thermal characterization
Authors: Kaya İsmet , Yıldırım Mehmet , Kamacı Musa , Avcı Ali
Published: January 2011

Up to date, only a few kinds of poly (azomethine‐urethane)s (PAMUs) derived from aromatic hydroxy compounds were obtained and studied with thermal degradation steps. Novel PAMUs were prepared using the hydroxy‐functionalized Schiff bases derived from melamine and toluene‐2,4‐diisocyanate. Schiff base prepolymers were synthesized by the condensation reaction of melamine with 4‐hydroxybenzaldehyde and 2‐hydroxy‐1‐naphtaldehyde. Characterization was made by UV–Vis, FTIR, NMR, and SEC techniques. Thermal characterizations of the novel PAMUs were carried out by TG‐DTA and DSC techniques. Thermal decomposition steps at various temperatures were also clarified and the physical changes of the synthesized PAMUs with exposing to the thermal degradation steps were displayed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Studies on electrically conductive composites of ethylene propylene diene monomer rubber and steel fibers
Authors: Athawale Anjali A. , Joshi Aparna M.
Published: January 2011

Electrically conductive composites comprised of ethylene propylene diene monomer (EPDM) rubber and steel fibers were prepared by an open mill mixing method. Fibers of two distinctly different lengths (5 mm and several meters) were used and the influence of these fibers on electrical conductivity, mechanical, thermal, and physical properties of the composites was investigated. Composites with different compositions were prepared by varying the loading levels of fibers from 20–100 phr (parts per hundred parts of rubber). Homogeneity of the composites was determined using scanning electron microscopy. Further analysis included the measurement of resistance, hardness, tensile strength, tear strength, rebound resilience, etc. The results of the analysis revealed that the addition of steel fibers rendered conductivity to the otherwise insulating EPDM rubber even at small loading levels, however, the length appears to have negligible effect on conductivity. In case of short fibers, the resistance of composites was observed to decrease from > 40 MΩ (Initial value of EPDM rubber) to 25 KΩ at a loading level of 20 phr with a further significant decrease of the order of 103, that is around 18 Ω at 100 phr. Composites with long fibers exhibited resistance in the range of 15 kΩ–70 Ω at loading levels between 30 and 100 phr. The conductivity of the sample is observed to be altered negligibly on ageing. Mechanical properties such as hardness, tensile, and tear strength were observed to be enhanced in case of composites except resilience which decreased by 29 % in comparison to EPDM rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Swelling and drug release profile of poly(2‐ethyl‐2‐oxazoline)‐based hydrogels prepared by gamma radiation‐induced copolymerization
Authors: El‐Hag Ali A. , AlArifi A. S.
Published: January 2011

Poly(2‐ethyl‐2‐oxazoline) and acrylic acid were copolymerized in different compositions using γ‐rays‐induced polymerization and cross‐linking to obtain a series of pH‐sensitive hydrogels. The preparation parameters that may affect the copolymerization process such as the feed solution composition and irradiation dose were optimized. Swelling characteristics of the obtained polymeric hydrogels were evaluated. The results show the significant effects of the hydrogel composition, soaking time, and pH on the swelling equilibrium. The diffusion parameters obtained at pH 1 and 7 show the possibility of using the prepared hydrogels in the field of colon‐specific drug delivery systems. Ibuprofen as a model drug was loaded into (poly(2‐ethyl‐2‐oxazoline)/acrylic acid) copolymer hydrogel to investigate their drug release behavior at different pH values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Biocompatible/bioabsorbable silver nanocomposite coatings
Authors: Qureshi Ammar T. , Monroe W. Todd , Lopez Mandi J. , Janes Marlene E. , Dasa Vinod , Park Sunggook , Amirsadeghi Alborz , Hayes Daniel J.
Published: January 2011

A novel biomass‐mediated method to synthesize cellulose‐stabilized silver nanoparticles (SNPs) and incorporate them into biocompatible/bioabsorbable poly‐L‐lactic acid (PLLA) for producing SNP–PLLA nanocomposite thin films was developed and the antimicrobial efficacy and biocompatibility of the SNP–PLLA films were studied. The formation and coating morphology of SNPs were characterized with UV–visible spectrophotometry and transmission electron microscopy (TEM), and the release rate of silver ion from the SNP–PLLA films was determined by inductively coupled plasma‐optical emission spectrometry. Antimicrobial testing of the SNP–PLLA films performed with Staphylococcus aureus and Escherichia coli according to ISO 22196 standards demonstrated that the SNP–PLLA nanocomposite films with a SNP concentration of 700 ppm reduced colonies forming unit (CFU) counts by 99.8 and 99.99%, respectively. Despite the significant antimicrobial activity, the nanocomposite films with the same SNP concentration had little effect on the viability of human HeLa cells. This strategy that has been developed for the synthesis of nanoparticles and the formation of composite films demonstrates promise for reducing perioperative surgical site infections associated with indwelling devices. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and characterization of low density polyethylene/ethylene methyl acrylate glycidyl methacrylate/organoclay nanocomposites
Authors: Coskunses Fatma Isik , Yilmazer Ulku
Published: January 2011

The effects of organoclay type, compatibilizer, and the addition order of components during melt‐blending process on the morphology and thermal, mechanical, and flow properties of ternary nanocomposites based on low‐density polyethylene (LDPE) were investigated. As a compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate (E‐MA‐GMA), as organoclays Cloisites® 15A, 25A, and 30B were used. All samples were prepared by a corotating twin screw extruder, followed by injection molding. The highest increase of the basal spacing for ternary nanocomposites was obtained in LDPE/E‐MA‐GMA/Cloisite® 30B nanocomposites with interlayer spacing of 59.2 Å. Organoclay and compatibilizer addition did not influence the melting/crystallization behavior of the compositions, and both compatibilizer and organoclays had no significant nucleation activity in LDPE. Among the ternary nanocomposites, the maximum increase in tensile strength and tensile modulus values was observed for nanocomposites containing organoclay Cloisite® 15A. The improvement with respect to neat LDPE was 43% for tensile strength and 44% for tensile modulus. According to the mechanical analysis, the best sequence of component addition was the one in which LDPE, organoclay, and compatibilizer were simultaneously fed to the extruder in the first run, and the product of the first run was extruded once more. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011