bluuebunny/crossref_metadata_2025 huggingface dataset:
Large surface wave of the 2004 Sumatra-Andaman earthquake captured by the very long baseline kinematic analysis of 1-Hz GPS data
Authors: Ohta Yusaku , Meilano Irwan , Sagiya Takeshi , Kimata Fumiaki , Hirahara Kazuro
Published: August 2014

The 26 December 2004 Sumatra-Andaman great earthquake had a −1500 km long rupture of more than 600 seconds duration, and may have involved a complex rupture process including slow slip. We processed International GNSS Service (IGS) 1-Hz Global Positioning System (GPS) data using kinematic analysis to investigate ground motion caused by this large earthquake. Since there are few 1-Hz stations, we had to process long baseline up to several thousand kilometers long. Long baselines degrade the GPS carrier phase ambiguity resolution. Nevertheless, clear seismic surface waves of the earthquake are recorded in our longdistance kinematic GPS solutions, which are in good agreement with response-corrected broadband seismic record. Our long baseline kinematic GPS solutions clearly indicated directivity of the seismic wave associated by rupture process of this earthquake. Also at the GPS stations that are 2,000 km away from the epicenter, dynamic displacements exceeding 5–10 cm were detected. In contrast, short baseline kinematic analysis shows large strain change caused by passage of surface wave, which reaches 6 × 10-6. Based on the comparison with seismometer and spectrum analysis of GPS results, it is difficult to discuss for very long time period displacement such as with a period more than 600 seconds in this study.
GPS detection of total electron content variations over Indonesia and Thailand following the 26 December 2004 earthquake
Authors: Otsuka Y. , Kotake N. , Tsugawa T. , Shiokawa K. , Ogawa T. , Effendy  , Saito S. , Kawamura M. , Maruyama T. , Hemmakorn N. , Komolmis T.
Published: August 2014

We report the response of the ionosphere to the large earthquake that occurred in West Sumatra, Indonesia, at 0058 UT on December 26, 2004. We have analyzed Global Positioning System (GPS) data obtained at two sites in Sumatra and at three sites in Thailand to investigate total electron content (TEC) variations. Between 14 and 40 min after the earthquake, TEC enhancements of 1.6–6.9 TEC units (TECU) were observed at subionospheric points located 360–2000 km north of the epicenter. From the time delays of the observed TEC enhancements, we find that the TEC enhancements propagated northward from the epicenter. The time delays between the earthquake and rapid increases in TEC, which occurred near the epicenter, are consistent with the idea that acoustic waves generated by the earthquake propagated into the ionosphere at the speed of sound to cause the TEC variations. A small TEC enhancement of 0.6 TECU was observed south of the epicenter, while no TEC enhancements were seen east of the epicenter. From a model calculation, we find that this directivity of the TEC variations with respect to the azimuth from the epicenter could be caused partially by the directivity in the response of the electron density variation to the acoustic waves in the neutral atmosphere.
Changes in groundwater levels or pressures associated with the 2004 earthquake off the west coast of northern Sumatra (M9.0)
Authors: Kitagawa Yuichi , Koizumi Naoji , Takahashi Makoto , Matsumoto Norio , Sato Tsutomu
Published: August 2014

Associated with the 2004 earthquake off the west coast of northern Sumatra, changes in groundwater levels or pressures were observed at many observation stations in Japan which are more than 5000 km from the hypocenter. At 38 of the 45 observation stations, there were changes in groundwater levels or pressures. At the 10 observation stations in which the Ishii-type borehole strain instruments were established, changes in crustal strains were also observed. A major part of the changes in crustal strains and groundwater levels or pressures were dynamic oscillations due to a seismic wave. At some stations, coseismic or postseismic rises or drops were also observed. At five stations where both crustal stain and groundwater levels or pressures were observed, postseismic changes in groundwater levels or pressures were consistent with coseismic static steps in crustal strains. At the other five stations, postseismic changes in groundwater levels or pressures did not agree with the coseismic static steps. At two stations of these five stations, it is anticipated that the pore water pressure change in each aquifer locally occurred independently of the change in crustal strain. At another station, postseismic changes in groundwater level possessed the same characteristics as a model removing the temporary deposition. At the last two stations, the causes of the changes are unknown.
Well water level changes in Fairbanks, Alaska, due to the great Sumatra-Andaman earthquake
Authors: Sil Samik , Freymueller Jeffrey T.
Published: August 2014

The Mw 9.3 great Sumatra-Andaman earthquake of December 26, 2004 induced water level changes in Fairbanks, Alaska, at an epicentral distance of 10,800 km. Spike like water level changes followed by a step of water level rise were observed in at least four wells. We modeled the timing and magnitude of the water level rise using a combination of a linear trend and a step function. We calculated the misfit between the observed water level rises and our model by systematically shifting the timing of occurrence of step in water level. The minimum value of cumulative misfit suggested the timing of occurrence of steps. A previous study showed persistent water level rises in all these wells from the 2002 Denali fault earthquake and it’s major aftershocks. From those observations, we developed an empirical relationship between water level changes, epicentral distances and earthquake magnitude. This relationship attributed water level changes in the wells to ground shaking by seismic waves. The estimated average water level changes due to the Sumatra earthquake using that relationship was in agreement with the observed water level changes. Thus we concluded that ground shaking in Fairbanks, induced by surface waves from the Sumatra earthquake was sufficient to change water levels.
Dominant periods of the 2004 Sumatra tsunami and the estimated source size
Authors: Abe Kuniaki
Published: August 2014

Dominant periods determined from tide gauge records of the 2004 Sumatra tsunami were used to estimate the size of the tsunami source. A period of 40 minutes dominates the initial motions and spectra are consistent with a fault width of 110 km for a sea depth of 1000 m. Another dominant period of 140 minutes in the spectra observed at the direction of fault azimuth can be explained using a fault length of 1200 km. These values taken together are consistent with source formation on the continental slope with width of 110 km and length of 1200 km along Nicobar and Andaman Islands.
Geoelectric structure in the Andaman Islands using magnetotelluric studies
Authors: Gokarn S. G. , Gupta Gautam , Dutta Shipra , Hazarika Nitu
Published: August 2014

Magnetotelluric studies over the Middle Andaman islands have delineated a NNE-SSW trending suture, along which the Andaman flysch and the underlying Igneous crust subduct eastwards along a high angle thrust with a dip angle of about 60°. The Andaman flysch, which have thickness varying between 4 and 10 km are delineated up to depth of about 17 km along the observed thrust. The crust to the west of the suture has a high resistivity of more than 10000 Ω-m, as against a moderate resistivity of about 1000 Ω-m observed in the eastern part. The complex variations in its thickness and resistivity are indicative of the intense tectonic activity that this juvenile crust has experienced since the Cretaceous. The crust is underlain by a low resistivity, which could be due to the presence of fluids generated by the metamorphosis of the subducting crust and also expelled from the rocks at deeper levels. However the earthquake focal depths, extending up to about 150 km suggest that the lithosphere may be sufficiently solidified to permit strain accumulation at this depth. Thus the extent of the partial melt may be limited to about 1%.
Citrate anticoagulation versus systemic heparinisation in continuous venovenous hemofiltration in critically ill patients with acute kidney injury: a multi-center randomized clinical trial
Authors: Schilder Louise , Nurmohamed S Azam , Bosch Frank H , Purmer Ilse M , den Boer Sylvia S , Kleppe Cynthia G , Vervloet Marc G , Beishuizen Albertus , Girbes Armand RJ , ter Wee Pieter M , Groeneveld AB Johan
Published: August 2014

Introduction

Because of ongoing controversy, renal and vital outcomes are compared between systemically administered unfractionated heparin and regional anticoagulation with citrate-buffered replacement solution in predilution mode, during continuous venovenous hemofiltration (CVVH) in critically ill patients with acute kidney injury (AKI).

Methods

In this multi-center randomized controlled trial, patients admitted to the intensive care unit requiring CVVH and meeting inclusion criteria, were randomly assigned to citrate or heparin. Primary endpoints were mortality and renal outcome in intention-to-treat analysis. Secondary endpoints were safety and efficacy. Safety was defined as absence of any adverse event necessitating discontinuation of the assigned anticoagulant. For efficacy, among other parameters, survival times of the first hemofilter were studied.

Results

Of the 139 patients enrolled, 66 were randomized to citrate and 73 to heparin. Mortality rates at 28 and 90 days did not differ between groups: 22/66 (33%) of citrate-treated patients died versus 25/72 (35%) of heparin-treated patients at 28 days, and 27/65 (42%) of citrate-treated patients died versus 29/69 (42%) of heparin-treated patients at 90 days (P = 1.00 for both). Renal outcome, i.e. independency of renal replacement therapy 28 days after initiation of CVVH in surviving patients, did not differ between groups: 29/43 (67%) in the citrate-treated patients versus 33/47 (70%) in heparin-treated patients (P = 0.82). Heparin was discontinued in 24/73 (33%) of patients whereas citrate was discontinued in 5/66 (8%) of patients (P < 0.001). Filter survival times were superior for citrate (median 46 versus 32 hours, P = 0.02), as were the number of filters used (P = 0.002) and the off time within 72 hours (P = 0.002). The costs during the first 72 hours of prescribed CVVH were lower in citrate-based CVVH.

Conclusions

Renal outcome and patient mortality were similar for citrate and heparin anticoagulation during CVVH in the critically ill patient with AKI. However, citrate was superior in terms of safety, efficacy and costs.

Trial registration

Clinicaltrials.gov NCT00209378. Registered 13th September 2005.
Metabolic syndrome and pregnancy
Authors: Khromilev A V
Published: August 2014

Metabolic syndrome (MS) is a major problem of public health and health care system, with rising prevalence in the world. There is evidence that obesity, as the main component of MS, is strongly associated with the presence of gestational complications: fetal growth retardation, fetal macrosomia, gestational diabetes, preeclampsia, preterm delivery, stillbirth and perinatal death. The underlying mechanisms of this association are actively investigated nowadays. The importance of MS in pregnancy is also determined by the increase of the risk of venous trombosis.
Morphological and molecular studies on topotype material of Neoralfsia expansa (Phaeophyceae) reveal that Asian specimens assigned to this taxon are genetically distinct
Authors: León-Álvarez Daniel , Núñez-Resendiz Maria L. , Wynne Michael J.
Published: August 2014

The genus Neoralfsia was newly described by P.-E. Lim and Kawai on the basis of rbcL sequence data from specimens from Japan and Malaysia identified as Neoralfsia expansa, and N. expansa [Myrionema (?) expansum] from Mexico was designated as the type species. Our maximum likelihood and Bayesian analyses show that specimens of N. expansa from the type locality are grouped into a new, not previously described, clade in Neoralfsiaceae, distant from that of the putative specimens attributed to N. expansa from Japan and Malaysia. We show that genuine “expansa” does not include Asian material. The distribution of the species is not as wide as has been previously recorded.
e-Polymers: The new European electronic journal
Authors: Jung Bernd
Published: August 2014

e-Polymers has been founded under the auspices of the European Polymer Federation. It is a peer-reviewed internet journal in the area of polymer science and engineering. Its aim is to promote exchange of know-how concerning fundamental polymer science and technology, basically free of charge, for all researchers and engineers in academia and industry in Europe. Besides scientific and technical publications, this journal aims to mature into a discussion platform to promote joint research programmes and job mobility of notably young scientists within and outside of the EU.
Lipase-catalyzed synthesis of aliphatic polyesters in supercritical carbon dioxide
Authors: Takamoto Tetsufumi , Uyama Hiroshi , Kobayashi Shiro
Published: August 2014

Synthesis of aliphatic polyesters has been examined using Candidaantarctica lipase in supercritical carbon dioxide (scCO2). The enzymatic ring-opening polymerization of ε-caprolactone (ε-CL) proceeded in scCO2 to give a polymer with molecular weight higher than 104. Effects of reaction parameters such as the monomer concentration, enzyme amount and pressure have been systematically investigated. Copolymerization of ε-CL with 12-docecanolide afforded the random copolymer. The enzymatic polycondensation of divinyl adipate and 1,4-butanediol also proceeded in scCO2 to produce the corresponding polyester.
Methacrylic polymers bearing side-chain permanent dipole azobenzene chromophores spaced from the main chain by chiral moieties
Authors: Angiolini Luigi , Caretti Daniele , Giorgini Loris , Salatelli Elisabetta
Published: August 2014

Optically active photochromic copolymers, deriving from methyl methacrylate (MMA) and the methacrylic ester of (S)-3-hydroxypyrrolidine linked through the nitrogen atom to the highly conjugated photochromic 4'-(β-cyano-β- (methylsulfonyl)vinyl)-4-azobenzene moiety, have been prepared and characterized with the aim to evaluate the effect on their chiro-optical and thermal properties exerted by the insertion of inactive MMA groups along the main chain. The results indicate that these properties are still remarkable at a content of photochromic units as low as 26 mol-%.
Biodegradable copolymers based on poly(ethylene oxide), polylactide and polydepsipeptide sequences with functional groups
Authors: Feng Yakai , Klee Doris , Höcker Hartwig
Published: August 2014

For the purpose of increasing the hydrophilicity of polylactide, new block copolymers with protected functional groups, poly(lactide-co-(S)-b-benzyl aspartate)-poly(ethylene oxide)-poly(lactide-co-(S)- b-benzyl aspartate), were synthesized via ring-opening polymerization of D,L-lactide and (3S, 6R,S)-3- [(benzyloxycarbonyl)methyl]-6-methylmorpholine-2,5-dione in the presence of hydroxyltelechelic poly(ethylene oxide) (PEO) as an initiator at 140 °C for 24 h. The benzyl protective groups of the block copolymers were completely removed to give poly(lactide-co-(S)-aspartic acid)-PEO-poly(lactide-co-(S)-aspartic acid), (poly(DLLA-co-Asp)-b-PEO-b-poly(DLLA-co-Asp)). This shows lower crystallization and melting temperature compared with the polymers before deprotection. Poly(DLLA-co-Asp)-b-PEO-b-poly(DLLA-co-Asp) with 55.6 wt.-% of PEO is more hydrophilic, shows higher water absorption and is degraded faster than with 39.5 wt.-% of PEO.
Effects of finite chain extensibility on segmental orientation and stress in biaxially deformed polymers
Authors: Jarecki Leszek , Ziabicki Andrzej
Published: August 2014

Development of biaxial segmental orientation and stresses in flexible chain polymers subjected to affine deformation of end-to-end vectors or to steady biaxial extensional flow is discussed. A closed-formula theory with non-Gaussian chain statistics and a Padè approximation of the inverse Langevin function is considered. The approach accounts for finite chain extensibility and is free from the problems of weak convergence of series-expansion expressions at higher molecular deformations. Average orientation tensor, global anisotropy tensor, and axial orientation factors characterise segmental orientation. Axial orientation factors and normal stress differences, in the deformation and normal planes, are discussed for biaxial affine deformation and steady biaxial elongational flow in a wide range of molecular deformations using inverse Langevin chain statistics. Orientation characteristics predicted for biaxial flow deformation are higher, and change in a wider range, than those in affine biaxial stretch. Also sensitivity to transversal deformation is different in both types of deformation.
Development of thermal stability of polymer crystals during isothermal crystallisation
Authors: Wurm Andreas , Schick Christoph
Published: August 2014

In classic theories of polymer crystallisation, it is assumed that only the nuclei are in thermodynamic equilibrium with the melt. In Strobl's model of polymer crystallisation, a multi-step process is discussed. At the first intermediate states, the growing lamellar crystallites are assumed to be in equilibrium with the melt. After a stabilisation step, the lamella gains final stability. We have studied the stability of growing polymer lamellae by applying short temperature pulses. Changes in morphology were detected by simultaneous shear modulus measurements. The highest temperature reached during such temperature pulses was always below the final melting temperature. For poly(ε-caprolactone) (PCL) at 331 K it was found that temperature pulses of 4 K height and 300 s duration every 1 800 s prevented crystallisation totally. Lower pulses only slow down the crystallisation process. For syndiotactic polypropylene at 403 K, pulses of 14 K every 7 200 s were necessary to prevent crystallization. For PCL the kinetics of the crystallisation and stabilisation processes has been determined. A temperature pulse of 4 K height after 10 000 s isothermal crystallisation at 331 K totally destroys the already formed crystalline structures although the degree of crystallisation at this time is already 17%. With ongoing annealing time, the crystalline structure becomes more stable and the impact of the pulses decreases. After main crystallisation, when the crystallinity is basically constant, the amount of stable lamellae continuously increases. This indicates the occurrence of a significant stabilisation step after formation of the lamellae in PCL.
Synthesis and properties of novel poly(p-xylylene)s with aliphatic substituents
Authors: Ishaque Michael , Agarwal Seema , Greiner Andreas
Published: August 2014

Poly(p-xylylene)s (PPX) with aliphatic substituents at the alpha position were synthesized by chemical vapor deposition (CVD) via vapor phase pyrolysis of α-chloro-1,4-xylenes, or by base-induced dehydrohalogenation of α-chloro-1,4- xylenes (Gilch route). These PPXs are soluble under ambient conditions in organic solvents. The glass transition temperature of the tert-butyl substituted PPX is remarkably high. Good thermal stability under nitrogen was observed for the trifluoromethyl substituted PPX. A functionalized compound suitable for polymer analogous reactions is the norbornenyl substituted PPX.
Optical properties of the three polymorphic forms of isotactic polypropylene
Authors: Nedkov Emanuel , Dobreva Tatyana
Published: August 2014

A review of the results obtained for the birefringence of different supermolecular structures of three polymorphic forms of polypropylene is presented. All known lamellar super-molecular formations of the monoclinic, hexagonal and triclinic phases are included. The observed morphology varies among negative hedrite and oval structures with axial symmetry, spherulites and typical dendrites. An attempt to explain the observed variety of the various structures’ birefringence is made in terms of the mutual orientation of the polarizability ellipsoid and crystallographic axes in the lamellar surfaces.

For the α phase, the orientation of the axes of the polarizability ellipsoid relative to the orientation of the unit cell is determined. The axis Nm coincides with the a axis, the fastest growth direction. The hedritic structures, grown by branching homoepitaxy, have negative birefringence. The spherulites differ in intensity and sign of birefringence because of cross-hatching.

For the β phase, the crystallographic axis b coincides with Ne, the short axis of the rotational polarizability ellipsoid. The hedritic structures can grow by the screw dislocation mechanism. Spherulites grow by an epitaxy mechanism. Both structures show negative birefringence.

The long axis Ng of the polarizability ellipsoid of the γ phase coincides with the b axis. The short molecules of the γ phase are inclined 40° towards the lamellar surface. The a and b axes do not lie in the lamellar surface. The axes of the polarizability ellipsoid are also inclined towards the lamellar surface. The preferred fast growth direction of the branching lamellae is the b* direction which coincides with Ng', the longest axis in the projection of the optical indicatrix on the lamellar surface. Thus the positive birefringence of the branching lamellae in the mixed α-γ spherulites increases more than in the monoclinic positive spherulites.
Thermodegradable polycarbonates: Effect of substituents on the degradation temperature
Authors: Martelé Yves , Van Speybroeck Veronique , Waroquier Michel , Schacht Etienne
Published: August 2014

The thermal degradation process of some new polycarbonates is investigated from an experimental and theoretical point of view, in order to obtain insight into the microscopic aspects that influence the reaction mechanism and the process of thermolysis. In particular, attention is focussed on the influence of the type of substituents in the polymer chain on the degradation temperature. A series of novel polycarbonates were designed differing from each other by the groups attached at the α and β carbon atoms. Thermal behavior was characterized by thermogravimetrical analyses. The polymers undergo rapid and complete thermolysis at different degradation temperatures depending on the structure. The degradation products were separated by gas chromatography and analyzed by mass spectroscopy. The ratio of formed dienes in the product distribution depends on the heating rate. Furthermore, density functional theory calculations were performed on a series of model compound systems for the polycarbonates under study, in particular carbonate systems differing by the groups attached at the α and β carbons. The study proves that the thermal degradation route can be controlled by tailoring the polymer backbone structure. Moreover, ab initio calculations provide further insight into the microscopic ingredients that govern the degradation process and associated reaction rates.
Statistical approach to model discrimination for the radical copolymerization of methyl methacrylate and styrene from a posteriori data of composition
Authors: Kaim Andrzej , Oracz Paweł
Published: August 2014

The multiresponse maximum likelihood (MML) method and statistical tests - the F-test, the t-Student test, and the sign changes test - were compared with respect to their power of discrimination between two kinetic models, the terminal and the penultimate model, for the radical copolymerization of the styrene - methyl methacrylate monomer system in bulk. The results indicate that the investigated statistical methods (except the sign changes test) are suitable for kinetic-model discrimination when they are applied to a posteriori data of copolymer composition. Although the MML method was shown to be more demanding in the error estimation of experimental data, it can serve as a proper tool for kinetic-model discrimination in copolymerization, provided the correct estimates of the ratio between errors in measured copolymer composition data are known. The main steps of the calculating scheme are given.
Determination of the degree of randomness in condensation copolymers containing both symmetrical and unsymmetrical monomer units: a theoretical study
Authors: Tessier Martine , Fradet Alain
Published: August 2014

Expressions for the degree of randomness, B, and for the number- and weight-average block lengths of condensation copolymers containing both symmetrical (AA + BB) and unsymmetrical (AB) monomer units are established through an approach based on functional group probabilities. Several parameters introduced in literature to characterize randomness in AA + BB condensation copolymers are also calculated using this approach and compared to B, showing that they are simple linear or rational functions of B. A method for calculating functional group probabilities from the dyad and triad number-fractions determined by NMR spectroscopy is described for poly(ethylene terephthalate)-poly(ε-caprolactone) copolyesters. This method obviously applies to any AA + BB + AB polycondensation and is easily generalizable to other types of condensation copolymers.
Micro-thermal field-flow fractionation in the characterization of macromolecules and particles: Effect of the steric exclusion mechanism
Authors: Janča Josef , Ananieva Irina A.
Published: August 2014

The influence of the steric exclusion mechanism on the dependence of the retention on the thickness of the micro-TFFF channel was studied theoretically. A good agreement of theory with experimental data was found. In order to preserve the use of micro-TFFF within an extended range of molar masses and particle sizes, the thickness of the channel cannot be reduced without taking into account a possible deterioration of the separation due to the contribution of steric exclusion to the separation mechanism.
Methacrylic polymers bearing side-chain permanent dipole azobenzene chromophores spaced from the main chain by chiral moieties, 3 a Synthesis and chiroptical properties of the homopolymer of (R)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)- pyrrolidine and of copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)- pyrrolidine
Authors: Angiolini Luigi , Giorgini Loris , Salatelli Elisabetta
Published: August 2014

The optically active photochromic homopolymer deriving from radical polymerization of the monomer (R)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)- pyrrolidine, containing a chiral group of one prevailing configuration interposed between the methacrylic moiety and the photochromic azoaromatic chromophore, has been synthesized and characterized. Copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)pyrrolidine have also been prepared in order to evaluate the effect on the overall optical activity of side chain chiral groups of opposite configuration in various ratios. The spectroscopic and chiroptical properties in solution of the polymeric derivatives have been assessed.
Interfacial interactions-controlled thermoelastic behaviour of synthetic rubber/organoclay nanocomposites
Authors: Privalko Valery P. , Ponomarenko Sergiy M. , Privalko Eleonora G. , Schön Frank , Gronski Wolfram
Published: August 2014

Thermoelastic measurements of synthetic rubber/organoclay nanocomposites provided the first experimental evidence for the dramatic dependence on interfacial interactions of the scale of nanoparticle displacements within filler aggregates of synthetic rubber/organoclay nanocomposites at high uniaxial extensions.
Synthesis and characterization of a polyurethane prepared by frontal polymerization
Authors: Mariani Alberto , Bidali Simone , Fiori Stefano , Malucelli Giulio , Sanna Ester
Published: August 2014

Frontal polymerization (FP) has been successfully applied to the preparation of a polyurethane (PU) having practical interest. By comparing the classical PU synthetic route with FP, the latter allowed for the obtainment of both higher molecular weights and yields. Furthermore, reaction times have been significantly reduced. Eventually, FP materials are characterized by higher glass transition temperature and lower melting point than their batch counterparts.
Synthesis, characterisation and properties of aramid copolymers prepared from AB and AB2 monomers
Authors: Monticelli Orietta , Fiori Stefano , Mariani Alberto , Russo Saverio , Komber Hartmut
Published: August 2014

Aromatic polyamide (aramid) copolymers having a highly branched architecture were prepared by direct polycondensation of an AB2 monomer (5-(4-aminobenzoylamino) isophthalic acid) with an AB monomer (N-(4-aminophenyl)terephthalamic acid). Two synthetic routes have been followed for copolymer preparation, differing from each other in the overall monomer content and the type of salts added to the reaction medium (LiCl or LiCl + CaCl2). Otherwise, both methods used the same conditions and the same condensing agent (triphenyl phosphite). The feed ratio of the monomers affected the copolymer solubility in aprotic polar solvents such as N,N-dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide. Only high AB2/AB monomer ratios allowed obtaining completely soluble polymers in the above media. Also copolymer intrinsic viscosity was influenced by that ratio as well as by the polymerisation routes. IR measurements gave an indication of polymer structure evolution as a function of the monomer feed ratio, while 1H NMR experiments verified the actual monomer composition in the synthesized polymers. The monomer feed ratio turned out to influence polymer properties, such as degree of crystallinity, thermal degradation temperature and liquid crystalline behaviour. Some of the characterisation techniques we used (1H and 31P NMR, IR, SEM-EDS) revealed the presence of phosphorus derivatives in the copolymers, despite extensive sample purification. This presence is coming from derivatives of the condensing agent, and is directly related to the content of AB2-type structures present in the copolymers.
Optical and thermal properties of novel diazine-based oligo(phenylene vinylene)s
Authors: Mainil Michaël , Pascal Laurent , Vanden Eynde Jean-Jacques , Van Haverbeke Yves , Dubois Philippe
Published: August 2014

New electro-conjugated diazine-based oligo(phenylene vinylene) derivatives with some interesting optical and thermal properties have been synthesised and characterised. These conjugated systems are built up on two benzenic cycles linked to a central diazine, either pyrimidine or pyrazine, through a carbon-carbon double bond. Both benzenic rings are substituted by one or two alkoxy chains. The length, the position and the number of alkoxy chains per benzenic ring have been varied and have proved to modulate both optical and thermal properties. Optical properties have been studied by UV-visible absorption spectroscopy as well as emission spectroscopy. Differential scanning calorimetry, wide-angle X-ray scattering and optical microscopy under crossed polarizers have been applied for characterising the thermal transitions and crystalline changes occurring in these conjugated systems.
On the kinetics of nematic ordering in solutions of semiflexible macromolecules: a Monte Carlo simulation
Authors: Stukan Mikhail R. , Ivanov Viktor A. , Müller Marcus , Paul Wolfgang , Binder Kurt
Published: August 2014

The occurrence of nematic liquid-crystalline ordering in semidilute and concentrated solutions of semiflexible macromolecules has been studied by means of grand canonical Monte Carlo computer simulations using the bond fluctuation model and the configurational bias scheme. Chain length was equal to 20 monomer units, while the persistence length was about 5 monomer units. We used an intramolecular stiffness potential depending on the angle between successive bonds along the chain and on the bond length, and an attractive interaction between monomer units to model variable solvent quality. We have monitored the processes of appearance and destruction of monodomain and multidomain nematic configurations. Our findings are that the first stages of both the ordering and disordering processes occur upon sufficient oversaturation through the spinodal ordering scenario. Possible screening of nucleation processes and the applicability of our model to real kinetics are discussed. Results of our simulations are visualized in six movies.
Metallo-celluloses, 2 Synthesis of cellulose derivatives bearing lateral bis-terpyridine ruthenium(II) complexes
Authors: Laube Bettina , Schmelz Oliver , Rehahn Matthias , Wunderlich Winfried
Published: August 2014

An efficient method is described for the simultaneous introduction of 4’-p-benzyl-2,2’:6’,2’’-terpyridine and benzyl side groups into cellulose. For this purpose, cellulose triacetate was treated in dimethyl sulfoxide/NaOH solution with mixtures of 4’-p-bromomethylphenyl-2,2’:6’,2’’-terpyridine and benzyl bromide. An almost quantitative conversion of the cellulose hydroxyl groups was reached when less than one terpyridine substituent was attached to the cellulose repeating units on average. At higher degrees of terpyridine substitution, some of the cellulose hydroxyl groups seem to remain unsubstituted. This conclusion has been drawn on the basis of NMR, IR and solubility measurements. We assume that steric hindrance of the bulky side groups is responsible for incomplete conversion. In a final step, the terpyridine substituents of the cellulose derivatives could be converted quantitatively into ruthenium(II) complexes via treatment with activated [Ru(tpy)Cl3] in N,N-dimethylacetamide/1-butanol (tpy: 2,2’:6’,2’’-terpyridine).
Reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in fluid CO2
Authors: Arita Toshihiko , Beuermann Sabine , Buback Michael , Vana Philipp
Published: August 2014

Reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene in fluid CO2 have been carried out at 80°C and 300 bar using cumyl dithiobenzoate as the controlling agent in the concentration range of 3.5·10-3 to 2.1·10-2 mol/L. This is the first report on RAFT polymerization in fluid CO2. The polymerization rates were retarded depending on the employed RAFT agent concentration with no significant difference between the RAFT polymerization performed in fluid CO2 and in toluene. Full chain length distributions were analyzed with respect to peak molecular weights, indicating the successful control of radical polymerization in fluid CO2. A characterization of the peak widths may suggest a minor influence of fluid CO2 on the addition reaction of macroradicals on the dithiobenzoate group.
Determination of wear of surfaces by scratch testing
Authors: Brostow Witold , Darmarla Gowrisankar , Howe Juliet , Pietkiewicz Dorota
Published: August 2014

We have formulated a quantitative definition of wear different from the current imprecise definitions. Wear is defined as the unwanted loss of solid material from solid surfaces due to mechanical interaction. The debris method currently used to quantify wear produces results strongly dependent on conditions. We have performed multiple scratch tests for a variety of polymer samples: polypropylene, polytetrafluoroethylene and a polyester. In each of the materials studied, the scratch penetration depths reach a constant value at a given force after 8 scratches or so. Similarly, the scratch recovery (final, healing) depths for a fixed force reach a plateau after a dozen or so scratch tests. Thus, strain hardening by repetitive scratching takes place. A likely explanation is formation of a more ordered phase - as seen before in mechanical tests by Siegmann, Aharoni, Faitelson et al. Given these results we define a measure of wear W(F) for a given indenter geometry and force F as W(F) = limn→∞ Rh(F) where n is the number of tests performed and Rh is the final (residual, healing) depth after viscoelastic recovery. The present results confirm also our earlier ones that scratch recovery is another useful way to characterize viscoelasticity.
Interfacial irregularity induced by hydrogen bonds at the interface in immiscible polymer blends
Authors: Kobori Yuka , Yasumitsu Rei , Akiba Isamu , Akiyama Saburo , Sano Hironari
Published: August 2014

Effects of interactions at the interface on the morphologies of immiscible polymer blends were investigated using linear low-density polyethylene/poly(4- vinylphenol) (LLDPE/PVPh) and LLDPE/poly(methyl methacrylate) (LLDPE/PMMA) blends containing polyethylene-block-PMMA (PE-b-PMMA). In the case of LLDPE/ PMMA/PE-b-PMMA blends, in which there is no specific interaction at the interface, shapes of dispersed droplets were maintained and sizes were simply diminished with increasing PE-b-PMMA content. On the other hand, in the case of LLDPE/ PVPh/PE-b-PMMA, in which hydrogen bonds are formed between PVPh and PMMA blocks at the interface, we found irregularly undulated phase boundaries.
Hydrogels from chitosan crosslinked with poly(ethylene glycol) diacid as bone regeneration materials
Authors: Mincheva Rosica , Manolova Nevena , Sabov Rumen , Kjurkchiev Galen , Rashkov Iliya
Published: August 2014

A simple method to covalently crosslink chitosan using poly(ethylene glycol) diacid as crosslinking agent is proposed. Networks net-chitosan-ι- PEG(COOH)2 were obtained by heating chitosan in aqueous PEG600(COOH)2 solutions at a temperature higher than 60°C. IR spectroscopy revealed the formation of amide bonds. It is shown that the obtained chemical networks are pH-sensitive hydrogels with enhanced hydrophilicity. The equilibrium degree of swelling of the hydrogels is determined by the conditions of their preparation - heating temperature and mole ratio between chitosan and the crosslinker. The ability of the polymer networks to facilitate bone regeneration processes was shown by in vivo implantation experiments.
Novel silicone-based capacitive pressure sensors with high sensitivity for biomedical applications
Authors: Arshak Khalil , Morris Deirdre , Korostynska Olga , Jafer Essa , Arshak Arousian , Harris John , Clifford Seamus , Lyons Gerard
Published: August 2014

In this work, an investigation of the pressure-sensing properties of a silicone rubber was conducted. Small amounts of carbon black were added to the silicone during fabrication and the effect on the sensitivity was explored. A full investigation of the mechanical and electrical properties of each composition shows that adding carbon black to the material greatly increases its sensitivity to pressure. This increase in sensitivity appears to be related to improvements in the material’s permittivity, which increases with carbon loading.
Turbulent drag reduction characteristics of amylopectin and its derivative
Authors: Lim Sung Taek , Choi Hyoung Jin , Biswal Diptirani , Singh Ram Prakash
Published: August 2014

Using amylopectin (AP) and a derivative, we systematically investigated their turbulent drag reduction characteristics and shear stability. The expected shear stability of polysaccharides as drag reducing and flocculating agents triggered our study on structural modification of AP. For this purpose, we prepared a derivative of AP, viz. AP grafted with polyacrylamide (GA), in which the granular form of AP powder (≈10 μm) changed into a mixture of larger fibrils and lumps. Using a rotating-disk apparatus, we measured the shaft torque and calculated the turbulent drag reduction (DR) efficiency under various experimental conditions, i.e., different polymer concentration, rotation speed, and temperature. Contrary to AP, GA showed relatively high DR efficiencies (27%) and very strong shear resistance.
Electrospun poly(vinyl alcohol)/poly(acrylic acid) fibres with excellent water-stability
Authors: Zeng Jun , Hou Haoqing , Wendorff Joachim H. , Greiner Andreas
Published: August 2014

The water stability of electrospun poly(vinyl alcohol) (PVA) nanofibres was improved significantly by annealing with poly(acrylic acid) (PAA). Effects of annealing were tested on solution-cast PVA/PAA films by measurement of the swelling degree. The influence of PVA/PAA ratio, annealing temperature and period, molecular weight of PAA, and addition of esterification catalyst was investigated. The results were verified by a significant improvement of the water-stability of electrospun PVA/PAA composite nanofibres.
Wear of thermoplastics determined by multiple scratching
Authors: Bermúdez M. Dolores , Brostow Witold , Carrión-Vilches Francisco J. , Cervantes Juan J. , Pietkiewicz Dorota
Published: August 2014

We studied wear resistance in sliding by multiple scratching along the same groove for a variety of thermoplastics: polystyrene, styrene-acrylonitrile, polyamide 6 and polysulfone. Constant-load experiments were carried out with a micro scratch tester for several loads between 2.5 and 15 N; each time 15 scratches were performed. Except for polystyrene, all materials show an asymptotic residual depth as a function of the number of scratch tests performed. In contrast to other materials, polystyrene exhibits brittleness and debris formation. Scanning electron microscopy and scanning probe microscopy were used to characterize the deformation and wear mechanisms and were connected to the wear data obtained by multiple scratching. At 15 N we found a viscoelastic recovery for polystyrene of 27.8% while for polyamide 6 the corresponding value is 80.2%.
Carbon composite material and polysulfone modified by nano-hydroxyapatite
Authors: Szaraniec Barbara , Rosół Patrycja , Chłopek Jan
Published: August 2014

This paper reports on mechanical and biological properties of carboncarbon1 composites and polysulfone modified by hydroxyapatite (HAP), both natural (nano-particles) and synthetic (micro-particles) minerals. Results show that carbon-HAP composites have mechanical properties similar to carbon-carbon composites, while addition of HAP to polysulfone causes advantageous growth of Young’s modulus and limitation of creep, and disadvantageous decrease of tensile strength. Tests performed in simulated body fluid for carbon-HAP and polysulfone- HAP composites prove that the process of hydroxyapatite build-up becomes most intensive in the case of composites with nano-particles originating from natural hydroxyapatite.
Cyclodextrin in polymer chemistry: Kinetic studies on the free-radical polymerization of cyclodextrin-complexed styrene from homogeneous aqueous solution
Authors: Ritter Helmut , Steffens Christopher , Storsberg Joachim
Published: August 2014

Styrene was encapsulated by an equimolar amount of randomly methylated β-cyclodextrin (CD) in water resulting in a water-soluble CD complex. Polymerization of this complex was carried out at 50°C using different amounts of the water-soluble azo-initiator 2,2’-azobis[N,N’-dimethyleneisobutyramidine] dihydrochloride. Unthreading of CD during polymerization led to water-insoluble polystyrene. Analysis of the polymers obtained showed that the polymerization from homogenous aqueous solution can be described by an equation similar to the classical polymerization in solution (number-average degree of polymerization vs. initiator concentration: Pn -1 ~ [I]0.5).
Self-ignition of polymerization fronts with convection: the ‘rainstorm effect’
Authors: Bidali Simone , Ducrot Arnaud , Mariani Alberto , Rustici Mauro
Published: August 2014

This work is devoted to an experimental and numerical study on the influence of natural convection on the ignition of polymerization reaction fronts. Numerical simulations confirm experimental findings. Indeed, it has been observed that under the same initial and boundary conditions the front ignition can occur either in the centre of the reactor or at the top. The difference between these two cases is determined by the viscosity of the medium and by other parameters that can influence the convective motion of a liquid monomer. If the viscosity is low, weak convective motion in the beginning of the development of the reaction will lead to the accumulation of the hotter monomer at the top of the reactor. In this case, front ignition occurs at the top and propagates downwards (rainstorm effect). If the viscosity is sufficiently high, the convective motion does not essentially change the position of the emerging hot spot; the front appears at the centre of the reactor and propagates almost spherically outwards.
A new approach to multiblock copolymers using atom transfer radical coupling
Authors: Nagelsdiek René , Keul Helmut , Höcker Hartwig
Published: August 2014

Atom transfer radical coupling (ATRC) is a method for chain extension of styrene homopolymers prepared by atom transfer radical polymerization (ATRP). This concept is used to produce multiblock copolymers from block copolymers prepared via ATRP of styrene using various macroinitiators. ATRC comprises the reactivation of the dormant species at the chain ends. In the absence of monomer, the active radical species recombine to give chain extension (from polystyrene, PS) or multiblock copolymers (from block copolymers). The application of ATRC to PSblock- poly(bisphenol A carbonate)-block-PS (PS-b-PC-b-PS) was not successful because chain degradation of the PC block occurs. However, poly(phenylene oxide)-block-PS (PPO-b-PS) and PS-b-PPO-b-PS were successfully transformed into tri- and multiblock copolymers by ATRC, although the coupling efficiency is not as high as observed for PS oligomers under similar conditions.
Silica-coating of fluorescent polystyrene microspheres by a modified Stöber method and their stability against photobleaching
Authors: Kobayashi Yoshio , Misawa Kiyoto , Kobayashi Masaki , Takeda Motohiro , Konno Mikio , Satake Masanobu , Kawazoe Yoshiyuki , Ohuchi Noriaki , Kasuya Atsuo
Published: August 2014

Submicron-sized polystyrene spheres incorporating fluorescence dyes (fluorescent microspheres) were coated with silica by means of a seeded polymerization technique based on the Stöber method. Silica-coating of the fluorescent microspheres with a size of 100 nm was performed in the presence of 0 - 10 g/l polyvinylpyrrolidone (PVP), 1 - 13 mol/l water, 0 - 0.8 mol/l aq. ammonia and 0.00038 - 0.2 mol/l tetraethoxyorthosilicate (TEOS). The addition of PVP was found to suppress the generation of free silica particles and produced no shell-free fluorescent microspheres improving the uniformity of shell thickness of silicacoated fluorescent microspheres. Silica shell thickness increased from 11 to 63 nm with increasing TEOS concentration at 10 g/l PVP, 0.4 mol/l aq. ammonia and 11 mol/l water. Silica-coated fluorescent microspheres showed more stable fluorescence to laser-irradiation than uncoated fluorescent microspheres.
Plasma-bonding of poly(dimethylsiloxane) to glass
Authors: Katzenberg Frank
Published: August 2014

For the purpose of bonding poly(dimethylsiloxane) (PDMS) to glass, both components’ surfaces were treated with low-pressure oxygen plasma, indirect corona or simply with an oxygen-rich butane gas flame. In the case of low-pressure oxygen plasma treatment, the process parameters were varied and optimized with the consequence that the achieved adhesion between PDMS and the glass substrate was so strong that the PDMS could not be peeled off the glass slide without damaging the elastomer.
Hybrid Microgels Containing Gold Nanoparticles
Authors: Pich Andrij , Karak Arpita , Lu Yan , Ghosh Anup K. , Adler Hans-Juergen P.
Published: August 2014

In present paper we report on a preparation of hybrid microgels filled with gold nano-particles (AuNPs). Temperature-sensitive VCL/AAEM microgels have been used as containers for deposition of Au by in situ formation of gold nano-particles. Synthesis of AuNPs has been performed by two methods: a) reduction of chloroauric acid with sodium borhydride and b) reduction of chloroauric acid by sodium citrate under ultrasonic agitation. In both cases AuNPs were deposited directly into microgels leading to formation of composite particles which exhibit temperature-sensitive properties, tunable gold contents and high colloidal stability. The influence of Au load on microgel size, morphology, swellingdeswelling behaviour and stability is discussed.