bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Thermal Aging of Polyamide 4,6 by1H Solid‐State NMR
Authors: Demco Dan E. , Litvinov Victor M. , Rata Gabriel , Popescu Crisan , Phan Kim‐Hô , Schmidt Angelika , Blümich Bernhard 
Published: August 2007

AbstractThe thermal aging of polyamide 4,6 was investigated by DSC, SEM, WAXS, and1H solid‐state NMR. Phase composition, chain mobility, morphology, and domain sizes were determined as a function of aging time. Proton transverse magnetization relaxation was measured at low resonance frequency,1H wide‐line NMR spectra and1H spin‐diffusion experiments were made at high resonance frequency. The NMR investigation shows that the aging process affects the rigid (crystalline), semi‐rigid (crystalline/amorphous interface), and the mobile (amorphous) fraction of polyamide 4,6. The amount of rigid (crystalline) fraction increases by about 10% upon aging at 200 °C for 1 000 h at the expense of the interfacial fraction. Chain mobility in crystalline phase is reduced upon aging suggesting perfections of the crystalline order.magnified image
Hydroformylation with Dendritic‐Polymer‐Stabilized Rhodium Colloids as Catalyst Precursors
Authors: Tuchbreiter Lydie , Mecking Stefan 
Published: August 2007

AbstractHydroformylation of 1‐hexene with rhodium colloids stabilized by poly(ethylene imine) amides with a hyperbranched polyamine core and a lipophilic periphery is reported. The catalyst selectivity for aldehydes increases with increasing temperature or pressure. The ratio of linear to branched aldehydes decreases with increasing temperature. At 80 °C and 90 atm, 1‐hexene is converted completely with 96% selectivity for aldehydes, with a ratio of linear/branched aldehydes of 58:42. Turnover numbers up to 3 × 104 (calculated with respect to the entire amount of Rh present) were observed. The results indicate that the catalyst precursor colloids serve as a reservoir for the formation of soluble Rh(I) complexes as the active species.magnified image
Polymers with Side Chain N‐Alkoxy Pyridinium Ions as Precursors for Photoinduced Grafting and Modification Processes
Authors: Durmaz Yasemin Yuksel , Yilmaz Gorkem , Yagci Yusuf 
Published: August 2007

AbstractA combination of NMP and photoinitiated polymerization is suggested as a new strategy for the synthesis of graft copolymers. First, P(S‐co‐CMS) copolymer backbones with different chloromethyl content are prepared by NMP. The chloro functions are then converted into photosensitive 4‐phenyl pyridinium‐N‐oxide ion functions. Finally, these photoactive polymers are irradiated in the presence of MMA to obtain the graft copolymers. They and their precursors at various stages are characterized by spectroscopy and GPC. It is demonstrated that the irradiation of photoactive polymers in the presence of a hydrogen donors such as THF facilitates the conversion of pyridinium ions to hydroxyl groups.magnified image
The frequency and size of price adjustment: microeconomic evidence
Authors: Rátfai Attila 
Published: August 2007

AbstractThis paper presents direct, non‐parametric microeconomic evidence on pricing behavior and evaluates the findings in light of theories of nominal price rigidity. The main issues examined include the durability of price quotations and the size of price changes. The analysis is based on a unique high‐frequency panel data set of consumer prices recorded in 1993–1996 in Hungary. The results indicate that price adjustment patterns in the sample are primarily consistent with implications of two‐sided (S,s) pricing models. Copyright © 2007 John Wiley & Sons, Ltd.
Sustained relief of dystonia following cessation of deep brain stimulation
Authors: Hebb Matthew O. , Chiasson Paula , Lang Anthony E. , Brownstone Robert M. , Mendez Ivar 
Published: August 2007

AbstractWe describe the unusual clinical course of a patient with cranial dystonia (i.e., Meige syndrome) and additional upper limb involvement, who developed sustained relief of motor symptoms following cessation of a prolonged course of bilateral pallidal deep brain stimulation (DBS). Early response to therapy proved titratable and reversible; however, the patient gained independence from DBS in the fifth postoperative year and has since been more than a year without treatment or exacerbation of motor symptoms. Among the potential explanations for these neurological benefits lies the intriguing possibility that DBS therapy may have the capacity to induce plastic change that lessens or obviates the need for further treatment in susceptible patients. © 2007 Movement Disorder Society
Myoclonus or tremor in orthostatism: An under‐recognized cause of unsteadiness in Parkinson's disease
Authors: Leu‐Semenescu Smaranda , Roze Emmanuel , Vidailhet Marie , Legrand André‐Pierre , Trocello Jean‐Marc , Cochen Valérie , Sangla Sophie , Apartis Emmanuelle 
Published: August 2007

AbstractPatients with Parkinson's disease (PD) often complain of unsteadiness. This can occur as the result of various neurological dysfunctions, including changes in postural adjustments, loss of postural reflexes, axial akinesia and rigidity, freezing and/or postural hypotension. In some cases these symptoms remain unexplained, and rare cases of unsteadiness have been attributed to tremor on standing. To delineate this condition, we investigated 11 consecutive PD patients with unexplained unsteadiness because of tremor on standing, seen in our department over a 6‐year period. All the patients had detailed clinical and electrophysiological investigations based on surface polygraphic electromyographic recordings. Four patients had fast orthostatic tremor (13–18 Hz), one had intermediate orthostatic tremor (8–9 Hz), and three had slow orthostatic tremor (4–6 Hz). The remaining 3 patients had orthostatic myoclonus, a condition that has not previously been reported in PD. Patients with fast tremor improved on clonazepam. Patients with slow tremor and myoclonus improved on levodopa and sometimes benefited further when clonazepam was added. These observations show the usefulness of neurophysiological investigations for diagnosing and treating unexplained unsteadiness in Parkinson's disease. © 2007 Movement Disorder Society
Partial Noether operators and first integrals via partial Lagrangians
Authors: Kara A. H. , Mahomed F. M. , Naeem I. , Wafo Soh C. 
Published: August 2007

AbstractThe notions of partial Lagrangians, partial Noether operators and partial Euler–Lagrange equations are used in the construction of first integrals for ordinary differential equations that need not be derivable from variational principles. We obtain a Noether‐like theorem that provides the first integral by means of a formula which has the same structure as the Noether integral. However, the invariance
condition for the determination of the partial Noether operators is different as we have a partial Lagrangian and as a result partial Euler–Lagrange equations. Applications given include those that admit a standard Lagrangian such as the harmonic oscillator, modified Emden and Ermakov–Pinney equations and systems of two second‐order equations that do not have standard Lagrangians. Copyright © 2007 John Wiley & Sons, Ltd.
An improved perturbation method for stochastic finite element model updating
Authors: Hua X. G. , Ni Y. Q. , Chen Z. Q. , Ko J. M. 
Published: August 2007

AbstractIn this paper, an improved perturbation method is developed for the statistical identification of structural parameters by using the measured modal parameters with randomness. On the basis of the first‐order perturbation method and sensitivity‐based finite element (FE) model updating, two recursive systems of equations are derived for
estimating the first two moments of random structural parameters from the statistics of the measured modal parameters. Regularization technique is introduced to alleviate the ill‐conditioning in solving the equations. The numerical studies of stochastic FE model updating of a truss bridge are presented to verify the improved perturbation method under three different types of uncertainties, namely natural randomness, measurement noise, and the combination of the two. The results obtained using the perturbation method are in good agreement with, although less accurate than, those obtained using the Monte Carlo simulation (MCS) method. It is also revealed that neglecting the correlation of the measured modal parameters may result in an unreliable estimation of the covariance matrix of updating parameters. The statistically updated FE model enables structural design and analysis, damage detection, condition assessment, and evaluation in the framework of probability and statistics. Copyright © 2007 John Wiley & Sons, Ltd.
Comparison of molecular determinants of angiogenesis and lymphangiogenesis in lymph node metastases and in primary tumours of patients with breast cancer
Authors: Van den Eynden GG , Van der Auwera I , Van Laere SJ , Trinh XB , Colpaert CG , van Dam P , Dirix LY , Vermeulen PB , Van Marck EA 
Published: August 2007

AbstractAngiogenesis and lymphangiogenesis are complex processes, driven by multiple factors. In primary breast tumours (PTs), VEGFA, ‐C and ‐D are the most important (lymph)angiogenic factors. The induction of lymphangiogenesis in axillary lymph node (LN) metastases of patients with breast cancer was described recently. To compare the molecular determinants of (lymph)angiogenesis in LN metastases and PTs of breast cancer patients, RNA was isolated from formalin‐fixed, paraffin‐embedded tissue sections of a metastatically involved and uninvolved LN and the PT from 26 lymph node‐positive patients. The expression of 12 (lymph)angiogenic markers was measured by qRT–PCR. Expression was correlated with tumour cell proliferation, angiogenesis and lymphangiogenesis, quantified by tumour cell proliferation fraction (TCP%) and (lymphatic) endothelial cell proliferation fraction [(L)ECP%]. TCP%, ECP% and LECP% were assessed on immunohistochemical double stains for CD34/Ki‐67 and D2‐40/Ki‐67, respectively. In involved LNs, the relative gene expression levels of PROX1 (p < 0.001) and FGF2 (p = 0.008) were decreased and the expression levels of VEGFA (p = 0.01) and PDGFB (p = 0.002) were increased compared to uninvolved LNs. The expression of most markers was increased in PTs compared to involved LNs. In metastatically involved LNs, the expression of VEGFA correlated with ECP% (r = 0.54, p = 0.009) and LECP% (r = 0.76, p < 0.001). In PTs, VEGFA correlated only with ECP% (r = 0.74, p < 0.001). VEGFD correlated with peritumoural LECP% (r = 0.61, p = 0.001) and with VEGFC (r = 0.78, p < 0.001). Linear regression analysis confirmed the expression of VEGFA as an independent predictor of ECP% in both PTs and LN metastases and of LECP% in LN metastases. The expression of VEGFD, but not of VEGFA, independently predicted peritumoural LECP% in PTs. Our results confirm existing data that, in PTs, angiogenesis and lymphangiogenesis are respectively driven by VEGFA and VEGFD. In contrast, in LN metastases, both processes seem to be driven by VEGFA. Lymphangiogenesis in PTs and in LN metastases might thus be driven by different factors. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Effect of a poly(dimethylsiloxane) modified polyolefin additive on the processing and surface properties of LLDPE
Authors: Zhu S.‐H. , McManus N.T. , Tzoganakis C. , Penlidis A. 
Published: August 2007

AbstractA polydimethylsiloxane (PDMS) modified polyolefin (obtained by reacting an ethylene‐ethyl acrylate‐maleic anhydride (EEAMA) copolymer with an amine terminated PDMS in the melt phase) was used as a processing aid to facilitate the extrusion of linear low density polyethylene (LLDPE). In blends of LLDPE and PDMS modified polyolefin (PMPO), apparent viscosity and shear stress at the die wall are reduced in comparison to pure LLDPE, and extrusion instabilities are delayed as evidenced by the fact that extrudate surface roughness only occurs at higher shear rates when the additive is present. A higher PDMS content in the PMPO leads to a more pronounced delay of extrusion instabilities. Single‐screw extrusion of LLDPE compounds with a PMPO results in nearly doubled throughput per unit input energy. The reduction of viscosity and improvements in extrudate quality are attributed to the decreasing surface free energy of the PMPO with an increasing PDMS content, as determined by contact angle measurements. Chemical composition analysis of the extrudate surface and cross‐section reveals silicon enrichment at the surface. The friction coefficients of pure PMPO and PMPO/LLDPE blends are measured and found to decrease as a result of the presence of PDMS. POLYM. ENG. SCI., 47:1309–1316, 2007. © 2007 Society of Plastics Engineers
Processability of LLDPE/LDPE blends: Capillary extrusion studies
Authors: Delgadillo‐Velázquez O. , Hatzikiriakos S.G. 
Published: August 2007

AbstractThe processing behavior of a number of linear low‐density polyethylenes/low density polyethylene (LLDPE/ LDPE) blends with emphasis on the effects of long chain branches is presented. A Ziegler‐Natta linear low‐density polyethylene was blended with four low‐density polyethylene LDPE's having distinctly different molecular weights. The weight fractions of the LDPEs used in the blends were 1, 5, 10, 20, 50, and 75 wt%. Capillary extrusion reveals that the onset of sharkskin and gross melt fracture are slightly influenced with the addition of LDPE into LLDPE. However, the amplitude of the oscillations in the stick‐slip flow regime was found to scale well with the weight fraction of LDPE. Amounts as low as 1 wt% LDPE have a significant effect on the amplitude of pressure oscillations. These effects are clearly due to the presence of long chain branching (LCB); furthermore, it was observed that the onset of this flow regime was shifted to higher shear rates with increase of LDPE content. On the other hand, shear rheology is not sensitive to detect addition of small levels of LDPE up to 20 wt%. Extensional rheology can detect levels of LDPE as small as 1 wt% only at high Hencky strain rates (typically greater than 5s−1) and only for certain blends, typically those that contain LDPE of high molecular weight. It is suggested that the magnitude of oscillations in the oscillating melt fracture flow regime is a sensitive method capable of detecting low levels of LCB. POLYM. ENG. SCI., 47:1317–1326, 2007. © 2007 Society of Plastics Engineers
Effects of a tert‐butylphenylene substituent on the structure and optical, fluorescent and thermal properties of the poly(p‐phenylenevinylene) derivatives
Authors: Chang Hung‐Te , Lee Hsun‐Tsing , Chang En‐Chiuan , Yeh Mou‐Yung 
Published: August 2007

AbstractTwo soluble fluorescent polymers, poly(2‐decyloxy‐5‐(4′‐tert‐butylphenyl)‐1,4‐phenylenevinylene) (DtBP‐PPV) and poly(2‐decyloxy‐1,4‐phenylenevinylene) (DO‐PPV), were prepared by a method similar to the Gilch procedure. The DtBP‐PPV and DO‐PPV have a same chemical structure except for the conjugated tert‐bytulphenyl substituents in the former. The polymers are characterized by using 1H NMR, FTIR, UV–vis, photoluminescence (PL), and electroluminescence (EL) spectroscopies and thermogravimetric analysis (TGA). The 1H NMR spectra show no tolane‐bis‐benzyl (TBB) structure defects in DtBP‐PPV but some in DO‐PPV. Both UV–vis absorption and PL emission peaks of the DtBP‐PPV exhibit a red‐shift phenomenon as compared with those of the DO‐PPV. Moreover, with the DtBP‐PPV and DO‐PPV acting as light‐emitting polymers separately, EL devices were fabricated with a sequential lamination of ITO/PEDOT/DtBP‐PPV (or DO‐PPV)/Ca/Ag. The DtBP‐PPV‐based device shows a lower turn‐on voltage, a longer EL emission wavelength, and a higher brightness than the DO‐PPV‐based device. The maximum brightness of DtBP‐PPV‐based device is 57 cd/m2 at an applied voltage of 12 V. POLYM. ENG. SCI., 47:1380–1387, 2007. © 2007 Society of Plastics Engineers
Carrageenan‐g‐poly(acrylamide)/poly(vinylsulfonic acid, sodium salt) as a novel semi‐IPN hydrogel: Synthesis, characterization, and swelling behavior
Authors: Pourjavadi Ali , Ghasemzadeh Hossein 
Published: August 2007

AbstractA semi‐interpenetrating polymer network (semi‐IPN) hydrogel based on kappa‐carrageenan (κC) and poly (vinylsulfonic acid, sodium salt) (PVSA) was prepared by graft copolymerization of acrylamide (AAm) using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. FTIR spectroscopy was used for confirming the structure of the final product. It was found that the chemical composition of the Semi‐IPN hydrogel is equal to the initial homopolymers and monomer feed compositions. The swelling capacity of the hydrogel was shown to be affected by the MBA, APS, and AAm concentration as well as κC/PVSA weight ratio. The swelling behavior of the hydrogel was also investigated in various pHs and salt solutions. Since the highly swelling biopolymer‐based hydrogel exhibits low salt‐sensitivity, it may be referred to as an anti‐salt superabsorbent hydrogel. The swelling kinetics of the superabsorbent hydrogels was studied as well. POLYM. ENG. SCI., 47:1388–1395, 2007. © 2007 Society of Plastics Engineers
Mechanical, dielectric, and magnetic properties of the silicone elastomer with multi‐walled carbon nanotubes as a nanofiller
Authors: Park Il‐Seok , Kim Kwang J. , Nam Jae‐Do , Lee Joonsoo , Yim Woosoon 
Published: August 2007

AbstractSilicone elastomer and multi‐walled carbon nanotubes (MWCNTs) composites, applicable as actuators and controllable dampers, were studied. Dynamic mechanical analysis (DMA) and vibrating sample magnetometry (VSM) were used to investigate the mechanical and magnetic properties of silicone elastomers and MWCNTs composites. Also, measurement of their dielectric property was conducted. The addition of MWCNT was able to tailor the damping and dielectric properties of the silicone elastomer. In this study, a 0.7 wt% of MWCNT composite demonstrated an attractive condition for the damping and the dielectric property. Exceedingly, the modulus increased with the application of a magnetic field. The good filler effect with the small addition of the MWCNTs content is caused by their unique structure, catalytic effect, and magnetic property. POLYM. ENG. SCI., 47:1396–1405, 2007. © 2007 Society of Plastics Engineers
Correlation between different microstructural parameters and tensile modulus of various polyethylene blown films
Authors: Fatahi Shokoh , Ajji Abdellah , Lafleur Pierre G. 
Published: August 2007

AbstractThe objective in this study is to establish a model for the prediction of tensile properties using various types of polyethylene films (LLDPE, HDPE, and LDPE). A series of blown films were produced by varying three process parameters: take‐up ratio, blow‐up ratio, and frost line height. The tensile properties of the resulting films were investigated in relation to their microstructural characteristics. The microstructural parameters were determined by differential scanning calorimetry, wide angle X‐ray diffraction (WAXD) pole figures, SAXS (small angle X‐ray diffraction), and birefringence measurements. The orientation parameters of the films were measured by WAXD and birefringence. They were determined for both crystalline and amorphous phases. The crystalline content, lamellar thickness, and crystal sizes were obtained from DSC and WAXD. The SAXS technique was used to find the average length of the crystalline and amorphous layers. A model for the tensile modulus is proposed and correlated to some structural parameters including crystallinity, orientation factors for crystalline c‐axis and amorphous phase, lamellar thickness, crystal size, the average length of the crystal layer, and long spacing period. The measured modulus and the calculated one were compared and a reasonable agreement was found between them for all series of films. POLYM. ENG. SCI., 47:1430–1440, 2007. © 2007 Society of Plastics Engineers
The effect of density profile on the flexural properties of structural foams
Authors: Barzegari M. Reza , Rodrigue Denis 
Published: August 2007

AbstractIn this study, a comparison is made on the models available to predict the flexural modulus of structural polymer foams. Skin thickness and density profile in the core zone are taken into account to better relate foam morphology with mechanical response. It was found that including skin thickness is not sufficient to predict flexural moduli with high levels of precision and thus a transition zone between the skin and the core must be included. To this end, a single continuous equation is proposed to represent the complete density profile, which enabled us to predict our experimental data within 3%. POLYM. ENG. SCI., 47:1459–1468, 2007. © 2007 Society of Plastics Engineers
Temperature and pressure dependence of the free volume in the perfluorinated polymer glass CYTOP: A positron lifetime and pressure‐volume‐temperature study
Authors: Dlubek G. , Pionteck J. , Sniegocka M. , Hassan E. M. , Krause‐Rehberg R. 
Published: August 2007

AbstractThe microstructure of the free volume was studied for an amorphous perfluorinated polymer (Tg = 378 K). To this aim we employed pressure–volume–temperature experiments (PVT) and positron annihilation lifetime spectroscopy (PALS). Using the Simha‐Somcynsky equation of state the hole free volume fraction h and the specific free and occupied volumes, Vf = hV and Vocc = (1 − h)V, were determined. Their expansivities and compressibilities were calculated from fits of the Tait equation to the volume data. It was found that in the glass Vocc has a particular high compressibility, while the compressibility of Vf is rather low, although h (300 K) = 0.108 is large. In the rubbery state the free volume dominates the total compressibility. From the PALS spectra the hole size distribution, its mean, 〈vh〉, and mean dispersion, σh, were calculated. From a comparison of 〈vh〉 with Vf a constant hole density of Nh′ = 0.25 × 1021 g−1 was estimated. The volume of the smallest representative freely fluctuating subsystem, 〈VSV〉 ∝ 1/σh2, is unusually small. This was explained by an inherent topologic disorder of this polymer. 〈vh〉 and σh show an exponential‐like decrease with increasing pressure P at 298 K. The hole density, calculated from Nh′ = Vf/〈vh〉, seems to show an increase with P which is unexpected. This was explained by the compression of holes in the glass in two, rather than three, dimensions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2519–2534, 2007
Charge transport properties in carbon black/polymer composites
Authors: Psarras G. C. 
Published: August 2007

AbstractThe charge transport properties of polymer matrix–carbon black composites are investigated in this study. Direct current conductivity is examined with varying parameters: the temperature and the conductive filler content. Conductivity data are analyzed by means of percolation theory, and both percolation threshold and critical exponent are determined at each of the examined temperatures. The temperature dependence of conductivity and the agreement of experimental results with the variable range hopping model reveal hopping conduction as the predominant transport mechanism, below and in the vicinity of the critical concentration of carbon black particles. At higher concentrations, the contribution of hopping transport to the overall conductivity is reduced and a balance between hopping and conduction via geometrical contact occurs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2535–2545, 2007