bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimized process for the inclusion of carbon nanotubes in elastomers with improved thermal and mechanical properties
Authors: Cadambi Rahul M. , Ghassemieh Elaheh 
Published: December 2011

AbstractThe effects of addition of reinforcing carbon nanotubes (CNTs) into hydrogenated nitrile–butadiene rubber (HNBR) matrix on the mechanical, dynamic viscoelastic, and permeability properties were studied in this investigation. Different techniques of incorporating nanotubes in HNBR were investigated in this research. The techniques considered were more suitable for industrial preparation of rubber composites. The nanotubes were modified with different surfactants and dispersion agents to improve the compatibility and adhesion of nanotubes on the HNBR matrix. The effects of the surface modification of the nanotubes on various properties were examined in detail. The amount of CNTs was varied from 2.5 to 10 phr in different formulations prepared to identify the optimum CNT levels. A detailed analysis was made to investigate the morphological structure and mechanical behavior at room temperature. The viscoelastic behavior of the nanotube filler elastomer was studied by dynamic mechanical thermal analysis (DMTA). Morphological analysis indicated a very good dispersion of the CNTs for a low nanotube loading of 3.5 phr. A significant improvement in the mechanical properties was observed with the addition of nanotubes. DMTA studies revealed an increase in the storage modulus and a reduction in the glass‐transition temperature after the incorporation of the nanotubes. Further, the HNBR/CNT nanocomposites were subjected to permeability studies. The studies showed a significant reduction in the permeability of nitrogen gas. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
A polymer–drug conjugate for doxorubicin: Synthesis and biological evaluation of pluronic F127‐doxorubicin amide conjugates
Authors: Gao Qihe , Han Xuelian , Zhu Jin , Chen Renjie , Sun Baiwang 
Published: December 2011

AbstractHigher molecular weight of the polymer carrier is the basis for enhanced accumulation of the pro‐drug in a solid tumor tissue due to a tumor‐related phenomenon described as the enhanced permeability and retention (EPR) effect. The anticancer drug doxorubicin was covalently bound to F127 through amide group susceptible to lysosomal hydrolysis. The in vitro and in vivo properties of F127‐DOX amide conjugates were studied. F127‐DOX amide conjugates (Mw: 13,400) were stable in neutral circumstance and showed the potency and mechanism of action of the released drug. In the in vivo experiment, results showed that F127‐DOX amide conjugates prolonged blood circulation and lowered in vivo toxicity than corresponding DOX, which illustrated the importance of molecular weight. The results demonstrated that F127‐DOX amide conjugates may be very promising and clinically suitable candidates for anticancer therapy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Salinity effects on the degree of hydrophobicity and longevity for superhydrophobic fibrous coatings
Authors: Ochanda Fredrick O. , Samaha Mohamed A. , Tafreshi Hooman Vahedi , Tepper Gary C. , Gad‐el‐Hak Mohamed 
Published: December 2011

AbstractPrevious studies on submerged superhydrophobic surfaces focused on performance variables such as drag reduction and longevity. However, to use such surfaces for practical applications, environmental factors such as water salinity must be investigated and understood. In this work, experiments were carried out to investigate the impact of salt (sodium chloride, NaCl) concentrations in aqueous solutions on the hydrophobicity and longevity of polystyrene (PS) fibrous coatings. Rheological studies using salt water as a test fluid were performed to determine the effect of salt concentration on drag reduction. Contact‐angle measurements were used to validate the results from the rheometer. In situ noninvasive optical reflection was used to measure the longevity of the coating—time‐dependent loss of entrapped air within the coating—as a function of salinity. The superhydrophobic coating used herein consisted of PS fibers that were deposited using DC‐biased AC‐electrospinning. Electrospinning is scalable and far less expensive than conventional methods (e.g., microfabrication), bringing the technology closer to large‐scale submerged bodies such as submarines and ships. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Toughness enhancement of poly(lactic acid) by melt blending with natural rubber
Authors: Jaratrotkamjorn Ruedee , Khaokong Chuanpit , Tanrattanakul Varaporn 
Published: December 2011

AbstractRubber toughened poly(lactic acid) (PLA) was prepared by blending with natural rubber (NR)‐based polymers. The blends contained 10 wt % of rubber and melt blended with a twin screw extruder. Enhancement of impact strength of PLA was primarily concernced. This study was focused on the effect of rubber polarity, rubber viscosity and molecular weight on mechanical properties of the blends. Three types of rubbers were used: NR, epoxidized natural rubber (ENR25 and ENR50), and natural rubber grafted with poly(methyl methacrylate) (NR‐g‐PMMA). Effect of viscosity and molecular weight of NR, rubber mastication with a two‐roll mill was investigated. It was found that all blends showed higher impact strength than PLA and NR became the best toughening agent. Viscosity and molecular weight of NR decreased with increasing number of mastication. Impact strength of PLA/NR blends increased after applying NR mastication due to appropriate particle size. DMTA and DSC characterization were determined as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thiolated chitosans: In vitro comparison of mucoadhesive properties
Authors: Mueller Christiane , Verroken Andrea , Iqbal Javed , Bernkop‐Schnuerch Andreas 
Published: December 2011

AbstractThe aim of this study was to compare the mucoadhesive properties of thiolated chitosans with regard to their molecular mass and type of immobilized thiol ligand. Mediated by a carbodiimide, aromatic‐ and aliphatic‐thiol‐bearing compounds were covalently attached to low‐ and medium‐molecular‐mass chitosan. All synthesized conjugates displayed on average 320 ± 50 μmol of immobilized free thiol groups per gram of polymer. The rheological synergy was observed by the mixture of equal volumes of polymer with mucin solution. Because of the increase in viscosity of the conjugate/mucin mixture, the self‐crosslinking properties and the interaction of thiomers with the mucus layer could be confirmed. Further mucoadhesion of the chitosan conjugates was evaluated in vitro with the rotating cylinder method and tensile studies on excised porcine intestinal mucosa. The results show a significantly enhanced residence time (p < 0.05) on the mucosa of all thiolated chitosans compared to the unmodified polymer. Among all of the conjugates tested, the following rank order of mucoadhesion could be determined: Chitosan–thiobutylamidine > Chitosan–4‐mercaptobenzoic acid > Chitosan–glutathione > Chitosan–6‐mercaptonicotinic acid > Chitosan–N‐acetyl cysteine > Chitosan–thioglycolic acid > Unmodified chitosan. The charge, pKa, and reactivity of the attached compounds were found to be important factors influencing the mucoadhesive potential of the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Vulcanization behavior and mechanical properties of organoclay fluoroelastomer nanocomposites
Authors: Lakshminarayanan Sriram , Gelves Genaro A. , Sundararaj Uttandaraman 
Published: December 2011

AbstractThe vulcanization behavior and mechanical properties of clay/fluoroelastomer nanocomposites produced by melt‐mixing of Dyneon FPO 3741 (a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene) with 10 phr of unmodified montmorillonite (CloisiteNA) or di(hydrogenated tallow‐alkyl) dimethyl ammonium‐modified montmorillonites (Cloisite15A and Cloisite20A) were studied. The properties of clay/FKM nanocomposites were compared with composites prepared using 10 and 30 phr of carbon black. The effects of clay surfactant and surfactant concentration on the vulcanization behavior, mechanical, and dynamical properties of peroxide cured composites were studied. XRD results of cured composites showed a decrease in d‐spacing and indicated deintercalation of the clays after the vulcanization process. It was also found that organoclays retard the FKM peroxide vulcanization process. Significantly, higher maximum torque on vulcanization was obtained with organoclays versus unmodified clay and carbon black. Although the morphologies of organoclay/FKM nanocomposites studied by XRD and TEM suggest similar intercalated/exfoliated structures, the organoclay with the lowest concentration of surfactant (95 meq/100 g clay) resulted in the highest increase in torque, modulus, hardness, and tear strength in the clay/FKM nanocomposites. It was also found that organoclays can increase both the hydrodynamic reinforcement and hysteresis loss of FKM nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Poly(N‐isopropylacrylamide) hydrogel: Effect of hydrophilicity on controlled release of ibuprofen at different pH
Authors: Francis Raju , Baby Deepa K. , Kumar D. Sakthi 
Published: December 2011

AbstractStimuli‐sensitive drug delivery systems (DDSs) have attracted considerable attention in medical and pharmaceutical fields; thermo‐sensitive DDS dealing with poly(N‐isopropylacrylamide) (PNIPAM) have been widely studied. Hydrogels composed of temperature‐sensitive NIPAM and biocompatible and pH‐sensitive maleic acid (MAc) were synthesized by sedimentation polymerization. Experiments on drug release from the crosslinked NIPAM‐co‐MAc hydrogel loaded with ibuprofen into different pH buffer solutions were successfully carried out at temperature swing between 25 and 40°C. The in vitro release studies have showed that the release rate depended on acidity or basicity (polarity) of the medium and the gel and swelling ratio of the gel network as a function of the environmental pH and temperature. The SEM image of the dry bead gave more insight into the surface architecture and the thermal studies shine light on the decomposition pattern and glass transition temperature of the gel. The mechanism of the drug release was discussed in relation to the diffusion rate and the abrupt change in the pH of the medium. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Removal of pyridine from water by pervaporation using crosslinked and filled natural rubber membranes
Authors: Singha N. R. , Ray S. K. 
Published: December 2011

AbstractNatural rubber (NR) of grade RSS4 was efficiently cured (crosslinked) by using sulfur: accelerator weight ratio of 1 : 4. This was further compounded with high abrasion grade carbon black filler (grade N330) with three different doses, that is, 5, 10, and 20 wt % of rubber to form three different filled and crosslinked membranes designated as NR5, NR10, and NR20, respectively. These filled rubber membranes and one unfilled but efficiently cured membrane, that is, NR0, were used for pervaporative removal of low concentration of pyridine from water. The filled membranes were found to show higher pyridine selectivity but lower flux than the unfilled membrane. All of these membranes showed reasonably good range of flux and pyridine selectivity. Among all of the used membranes, NR5‐filled membrane yielded high pyridine selectivity (122) with reasonable thickness normalized flux (2.2 kg m−2 h−1 mμ) at 40°C for 0.5 wt % of pyridine in water. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Association between systemic antipsoriatic drugs and cardiovascular risk in patients with psoriasis with or without psoriatic arthritis: A nationwide cohort study
Authors: Chen Yi‐Ju , Chang Yun‐Ting , Shen Jui‐Lung , Chen Tzu‐Ting , Wang Chang‐Bi , Chen Chuan‐Mu , Wu Chun‐Ying 
Published: December 2011

AbstractObjectivePsoriasis is associated with ischemic heart disease (IHD). Results of prior studies have suggested that methotrexate (MTX) may improve vascular disease in patients with psoriasis and rheumatoid arthritis. The aim of this study was to assess the risk of new‐onset IHDs in psoriasis patients, comparing those taking MTX with those taking other nonbiologic antipsoriatic drugs.MethodsIn this retrospective cohort study, we utilized claims data from the National Health Insurance Research Database of Taiwan to identify 179,200 subjects who had received a diagnosis of psoriasis, with or without psoriatic arthritis, on at least 3 visits. The risk of hospitalization for new‐onset IHD was compared between psoriasis patients taking MTX monotherapy (n = 6,578; MTX case cohort) and psoriasis patients taking other nonbiologic antipsoriatic drugs (n = 5,471; reference control cohort) between January 1996 and December 2008. Additional adjustments were made for cardiovascular risk factors, number of hospital visits, Charlson comorbidity score, and use of other antiinflammatory drugs.ResultsThe incidence rates of IHD were 666 cases per 100,000 person‐years in the MTX case cohort and 830 cases per 100,000 person‐years in the reference control cohort (unadjusted P = 0.027). Increasing age, male sex, presence of hypertension, presence of diabetes, Charlson comorbidity score, and use of phototherapies were independent risk factors for hospitalization related to a new IHD in the study cohorts. However, the multivariate‐adjusted hazard ratio for IHD‐related hospitalizations among patients receiving MTX, in comparison with those receiving other nonbiologic antipsoriatic drugs, was 0.97 (95% confidence interval 0.79–1.19), after adjustment for age, sex, comorbidity score, number of hospital visits, and other antiinflammatory treatments for psoriasis.ConclusionIn patients with psoriasis with or without coexisting psoriatic arthritis, the adjusted risk of hospitalization for an IHD among individuals receiving MTX was comparable with that among individuals receiving other nonbiologic antipsoriatic drugs.
Magnetic chemically peculiar stars: Results of CCD magnetic field measurements with the 6‐m telescope
Authors: Romanyuk I.I. 
Published: December 2011

AbstractWe present a survey of observational data on the magnetic fields and physical parameters of chemically peculiar (CP) stars for the past 15–20 years. It appears that the traditional notions on chemically peculiar stars as very stable objects with frozen atmospheres are in need of revision. Analysis of new high‐precision observational data allows to detect such subtle phenomena as pulsations of brightness and radial velocities of stars, and the vertical stratification of chemical elements in their atmospheres. A relationship was found between weak anomalies in the energy distribution in the continuum and the magnetic field strength. An analysis of the Stokes Q and U parameter line profiles of some stars has shown that these observations can be described under the assumption of the field of complex topology, which can not be represented in the form of low‐order multipoles. We found large vertical gradients from lines formed at different optical depths in the stellar atmospheres. These facts indicate much more complex atmospheric structures in chemically peculiar stars than was considered only 20 years ago (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
General Magnetic Field of the Sun as a star (GMF): Variability of the frequency spectrum from cycle to cycle
Authors: Plachinda S. , Pankov N. , Baklanova D. 
Published: December 2011

AbstractDuring 42 years of observations the General Magnetic Field of the Sun as a star demonstrates a stable picture of variability with the activity cycle: during maximum activity GMF reaches ∼2 G, and during minimum it reaches ∼0.2 G. The frequencies of prominent peaks in the power spectrum of GMF significantly vary from one cycle of activity to another one. All data folded in phase with the equatorial synodic period ∼26.d9 shows a specific phase curve similar to a dipole with amplitude ∼0.2 G and the absolute ratio of positive to negative magnetic flux ∼0.9. That is, during four decades of observations the excess of the positive magnetic flux is concentrated on the one side of the Sun, the excess of the negative flux is concentrated on the opposite side, and this magnetic field does not reverse its polarity with the 22‐year Hale solar cycle. In the case, when poloidal dipole axis coincides with rotation axis one can see a more complex picture of variability: the power spectrum for GMF values obtained at four minima of activity between 20 and 24 sunspot cycles demonstrates a large difference in relative amplitude of frequencies from the power spectrum for total GMF array and indicates the presence of the quadrupole component. Rough empirical estimation of the upper limit of the mean velocity of the poloidal dipole sign reverse for the Hale cycles from 1749 to 1997 gives 〈V 〉 ≈ 6.85 ± 0.05 m s–1. We suppose the presence of additional weak large‐scale magnetic field on the Sun. The axis of the field lies near the equatorial plane. This weak large‐scale magnetic field reflects properties of the stationary global magnetic field of the solar radiative interior on the surface of the Sun, which appears to be a third large‐scale component of the magnetic field along with known toroidal and poloidal fields (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct observation of magnetic cycles in Sun‐like stars
Authors: Morgenthaler A. , Petit P. , Morin J. , Aurière M. , Dintrans B. , Konstantinova‐Antova R. , Marsden S. 
Published: December 2011

AbstractA sample of 19 solar‐type stars, probing masses between 0.6 and 1.4 solar masses and rotation periods between 3.4 and 43 days, was regularly observed using the NARVAL spectropolarimeter at Telescope Bernard Lyot (Pic du Midi, France) between 2007 and 2011. The Zeeman‐Doppler Imaging technique is employed to reconstruct the large‐scale photospheric magnetic field structure of the targets and investigate its long‐term temporal evolution. We present here the first results of this project with the observation of short magnetic cycles in several stars, showing up a succession of polarity reversals over the timespan of our monitoring. Preliminary trends suggest that short cycles are more frequent for stellar periods below a dozen days and for stellar masses above about one solar mass. The cycles lengths unveiled by the direct tracking of polarity switches are significantly shorter than those derived from previous studies based on chromospheric activity monitoring, suggesting the coexistence of several magnetic timescales in a same star (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New magnetic CP stars found at the 6‐m telescope
Authors: Kudryavtsev D.O. , Romanyuk I.I. , Semenko E.A. , Yakunin I.A. 
Published: December 2011

AbstractWe present 23 new magnetic and 4 probably magnetic chemically peculiar (CP) stars found with the analyser of circular polarization at the Russian 6‐m telescope in 2006–2011. These new data continue our observing program of searching for magnetic stars (Kudryavtsev et al. 2006) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical composition of AY Ceti: A flaring, spotted star with a white dwarf companion
Authors: Tautvaišienė G. , Barisevičius G. , Berdyugina S. , Ilyin I. , Chorniy Y. 
Published: December 2011

AbstractThe detailed chemical composition of the atmosphere AY Cet (HD 7672) is determined from a high‐resolution spectrum in the optical region. The main atmospheric parameters and the abundances of 22 chemical elements, including key species such as 12C, 13C, N, and O, are determined. A differential line analysis gives Teff = 5080 K, log g = 3.0, [Fe/H] = –0.33, [C/Fe] = –0.17, [N/Fe] = 0.17, [O/Fe] = 0.05, C/N = 1.58, and 12C/13C = 21. Despite the high chromospheric activity, the optical spectrum of AY Cet provides a chemical composition typical for first ascent giants after the first dredge‐up (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of three cool CP stars with strong fields
Authors: Semenko E.A. , Kichigina L.A. , Kuchaeva E.Yu. 
Published: December 2011

AbstractThe study of magnetic fields of cool chemically peculiar stars with effective temperatures less than 10 000 K is very important to understand the nature of their magnetism. We present new results of a long‐term spectroscopic monitoring of the well‐known magnetic star HD 178892. The analysis of spectra taken with the Russian 6‐m telescope has revealed a periodic variation of the surface magnetic field from 17 to 23 kG. A revised rotational period of HD 178892 was extracted from the mean longitudinal field: 8.2549 days. We have continued the study of the components of the magnetic binary BD +40°175 started by V. Elkin at SAO RAS. Our measurements of magnetically splitted lines in the spectra of each component show the presence of strong magnetic fields in both components. The surface field in the case of the component A was about 14 kG at three different epochs. The component B possesses a slightly weaker field: Bs varies from 9 to 11 kG. A preliminary analysis of the chemical abundances allows us to make an assumption about the roAp nature of both components of BD +40°175 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards a 3D dynamo model of the PMS star BP Tau
Authors: Bessolaz N. , Brun A.S. 
Published: December 2011

AbstractStudying how convective and magnetic properties of pre‐main sequence stars change during their evolution towards the zero‐age main sequence is a growing area of research triggered by the development of efficient spectropolarimeters. 3D simulations can help to identify the key parameters to understand the diversity (strength, topology) of magnetic fields observed. We present results of a dynamo computation done with the ASH code for a 0.7 M⊙ pre‐main sequence star with a 7.6 day rotation period which is nearly fully convective, using a realistic stratification contrast to resolve 90 % of the convective zone. This star corresponds to the target star BP Tau already observed with spectropolarimetry (Donati et al. 2008). We particularly compare the magnetic field properties found in our simulation with the observational constraints (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spot activity of II Peg
Authors: Hackman T. , Mantere M.J. , Jetsu L. , Ilyin I. , Kajatkari P. , Kochukhov O. , Lehtinen J. , Lindborg M. , Piskunov N. , Tuominen I. 
Published: December 2011

AbstractWe have studied the long‐term spot activity of the RS CVn star II Peg by means of Doppler imaging based on spectroscopy and time series analysis of photometry. We present 28 Doppler imaging temperature maps spanning the years 1994–2010, of which 14 were calculated for the present study. The longitudinal spot distribution, derived from the surface temperature maps, is compared with epochs of the light curve minima, derived from photometric observations. We detect a longitudinal drift in the major spot structure during 1995–2003. After this there is a clear decrease in the activity level and no clear drift can be seen. We conclude that the variations could be caused by a cyclic behaviour of the underlying magnetic dynamo (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)