bluuebunny/crossref_metadata_2025 huggingface dataset:
Gait analysis in patients with Parkinson's disease and motor fluctuations: Influence of levodopa and comparison with other measures of motor function
Authors: O'Sullivan John D. , Said Catherine M. , Dillon Louise C. , Hoffman Marion , Hughes Andrew J.
Published: May 2005

Although clinical rating scales and simple timed tests of motor function are widely used to assess motor response to therapy, gait analysis may provide an alternative measure of this response. We studied 15 patients with PD complicated by motor fluctuations, first to determine changes in temporal and spatial gait parameters following levodopa, secondly to assess the stability of repeated gait measures and timed tests in “off” and “on” states, and thirdly to determine the use of gait analysis in the assessment of the dopaminergic response. Gait analysis (velocity, stride length, cadence, and double limb support), clinical rating scales (modified Webster scale and Hoehn and Yahr stage), and timed tests of motor function (hand tapping and stand‐walk‐sit time) were performed before (“off”) and after (“on”) a levodopa challenge. Stride length and gait velocity increased following medication whereas cadence and double limb support did not. Most gait measures and the stand‐walk‐sit time were stable over three consecutive trials in both “off” and “on” states. Of the gait measures, only cadence in the “off” state changed significantly whereas the tapping count improved with repeated trials in both “off” and “on” states. Changes in stride length, gait velocity, and tapping count following levodopa correlated with changes in clinical rating scales following treatment. Measurement of gait parameters provides a reliable, objective alternative to rating scales and timed tests in assessing the dopaminergic response in patients with PD and motor fluctuations.
Treatment of tremor in Parkinson's disease by subthalamic nucleus stimulation
Authors: Krack P. , Benazzouz Abdelhamid , Pollak Pierre , Limousin Patricia , Piallat Brigitte , Hoffmann Dominique , Xie Jing , Benabid Alim‐Louis
Published: May 2005

The recent resurgent interest in functional surgery for the treatment of Parkinson's disease (PD) has focused on the effects on akinesia and levodopa‐induced dyskinesia. Stimulation of the subthalamic nucleus (STN) improves akinesia and rigidity but its effects on tremor have not been studied. The objective of this study was to assess the efficacy of STN stimulation on tremor in patients with the complete parkinsonian triad with motor fluctuations. Of 27 consecutive patients with STN stimulation (26 bilateral), 15 exhibited tremor rated at least 2/4 according to item 20 (rest tremor) of the Unified Parkinson's Disease Rating Scale (UPDRS) in at least one limb. The mean preoperative tremor score was 11.3 ± 5.6 in off‐drug and 1.2 ± 2.4 in on‐drug conditions. The postoperative tremor scores at the last follow up (from 1–12 months) were 2.2 ± 2.2 off‐drug/on‐stimulation and 0.2 ± 0.4 on‐drug/on‐stimulation. Both rest and action tremors were improved in all patients. The UPDRS tremor score was reduced by 80%, rigidity score by 65%, and akinesia score by 51% on average. For the three symptoms, the stimulation effect was close to that induced before surgery by a suprathreshold dose of levodopa given in the morning. STN stimulation can be considered an interesting alternative to thalamic or internal pallidal surgery even in PD patients with severe high‐amplitude tremor. In keeping with electrophysiological data in monkeys rendered parkinsonian by MPTP injections, our results emphasize the importance of the oscillation of a neuronal loop involving the STN in the pathophysiology of parkinsonian tremor.
Neurophysiological abnormalities in the westphal variant of Huntington's disease
Authors: Töpper Rudolf , Schwarz Michael , Lange Herwig W. , Hefter Harald , Noth Johannes
Published: May 2005

The Westphal variant of Huntington's disease (HD) is a distinct clinical entity of HD characterized by a rigid‐hypokinetic syndrome and is often associated with a juvenile onset of disease. Definite genetic differences between the subtypes of HD have not been delineated so far. Here we present the results of a battery of neurophysiological tests including somatosensory‐evoked potentials, blink reflexes, longlatency reflexes, and measurement of saccadic velocities in a Westphal HD patient. Although quantitative assessment of his motor performance showed a severe hypokinetic syndrome resembling Parkinson's disease, the results of somatosensoryevoked potentials and blink reflexes were indistinguishable from results obtained in hyperkinetic HD patients. Longlatency reflexes, however, which are typically absent in hyperkinetic HD patients, were retained in this patient. It is concluded that neurophysiology in HD patients is not a mere reflection of the patient's symptomatology but can give insight into the underlying pathophysiological process.
Tardive blepharospasm
Authors: Sachdev Perminder
Published: May 2005

I report on five patients with tardive blepharospasm seen in a movement disorders clinic, out of 25 tardive dystonia patients. They were young (aged 25–50 yrs); four were men and three had a schizophrenic disorder. The onset was gradual while on maintenance neuroleptics in four and on withdrawal in the fifth. There were no significant antecedent events precipitating the disorder. The disorder was bilateral but asymmetric in two cases. Dyskinetic blinking was often an initial feature and tended to persist after the resolution of the blepharospasm. Orolingual dyskinesia was present in one case and tardive akathisia in two other cases. The symptoms fluctuated in severity with a number of exacerbating and relieving factors. Reduction of neuroleptic dose led to improvement with complete reversal in one of two patients who could be withdrawn off neuroleptic medication. These reports suggest that TB, although uncommon, can be a disabling disorder that may improve considerably with the cessation or dose reduction of the neuroleptic drugs. Its treatment and longitudinal course should be further examined.
Gait in patients with cerebellar ataxia
Authors: Palliyath Sarala , Hallett Mark , Thomas Sherry L. , Lebiedowska Maria K.
Published: May 2005

The gait pattern in 10 patients with cerebellar degenerations was studied and the results were compared with 10 matched normal subjects, seeking the principal patterns in this disorder. Gait at natural speed was studied in a biomechanics laboratory using a video‐based kinematic data acquisition system for measuring body movements. Patients showed a reduced step and stride length with a trend to reduced cadence. Heel off time, toe off time, and time of peak flexion of the knee in swing were all delayed. Range of motion of ankle, knee, and hip were all reduced, but only ankle range of motion reached significance. Multijoint coordination was impaired, as indicated by a relatively greater delay of plantar flexion of the ankle compared with flexion of the knee and a relatively late knee flexion compared with hip flexion at the onset of swing. The patients also showed increased variability of almost all measures. Although some of the deviations from normal were simply the result of slowness of walking, the gait pattern of patients with cerebellar degeneration shows incoordination similar to that previously described for their multijoint limb motion.
EPR study of bridgehead‐substituted bicyclo [2.2.2]oct‐1‐yl and triptycyl radicals
Authors: Binmore Gavin T. , Walton John C. , Adcock William , Clark Christopher I. , Kristic Alexander R.
Published: May 2005

4‐Substituted bicyclo [2.2.2] oct‐1‐yl radicals were generated by bromine atom abstraction from the corresponding 1‐bromobicyclo [2.2.2] octanes and observed in solution by EPR spectroscopy. A tendency towards lower a(Hβ) and a(Hγ) values for inductively electron‐withdrawing substituents such as OMe and F and towards higher values for electron‐releasing groups such as Me3Ge and Me3Sn was observed. For a series of bridgehead radicals, the hfs of β‐hydrogens showed a monotonic increase as the extent of flattening at the bridgehead increased. The EPR data indicated that 4‐substitutents exercised a significant effect at the radical centre, mainly by a through‐bond mechanism. 10‐Substituted triptycl radicals were generated in a similar way but showed no hfs from magnetic nuclei of the substituents. Thus, the triptycyl cage transmitted spin density much less effectively than the bicyclo [2.2.2] octyl cage. Bicyclo [2.2.2] oct‐1‐yl and adamant‐1‐yl radicals added to benzene, tert‐butylbenzene and 1,3‐di‐tert‐butylbenzene to give cyclohexadienyl radicals which were characterized by EPR spectroscopy. Triptycyl radicals and strained bridgehead radicals such as cubyl and bicyclo [1.1.1] pent‐1‐yl gave no detectable cyclohexadienyl radicals under similar conditions. Both bicyclo [2.2.2] oct‐1‐yl and adamant‐1‐yl radicals generated in tert‐butylbenzene showed exclusive meta addition with formation of the corresponding 1‐polycyclo‐3‐tert‐butylcyclohexadienyl radical.
ESR and ENDOR study on the radical ions of two non—alternant hydrocarbons: 1,3,5,7‐tetra‐tert‐butyl‐s‐indacene and 2,7‐di‐tert‐butyldicyclopenta [a,e] cyclooctene
Authors: Bachmann Rainer , Gerson Fabian , Gescheidt Georg , Hafner Klaus
Published: May 2005

The radical anions and radical cations of two alkyl‐substituted non‐alternant hydrocarbons, 1,3,5,7‐tetra‐tert‐butyl‐s‐indacene and 2,7‐di‐tert‐butyldicyclopenta [a,e] cyclooctene, were characterized by their proton coupling constants with the use of ESR and, in part, ENDOR spectroscopy. Considering the unusual electronic structures of the π‐systems in question, these values agree fairly well with those predicted by simple MO theory. Also reported are the proton hyperfine data for the radical ions of the likewise alkyl‐substituted non‐alternant 8,16‐diisopropyl‐s‐indaceno [1,2,3‐cd:5,6,7‐c′ d′] diphenalene.
EPR study of alkali metal atoms in hydrocarbon matrices
Authors: Jones Ruth , Howard J. Anthony , Joly Helen A. , Edwards Peter P. , Singer Richard J.
Published: May 2005

A rotating cryostat was used to trap the Group 1 metal atoms in adamantane and cyclohexane matrices at 77 K. Electron paramagnetic resonance spectra of matrix‐isolated atoms were obtained in adamantane at X‐ and Q‐band frequencies. The magnetic parameters were calculated from exact solutions of the Breit‐Rabi equation and compared with values in the gas phase and in rare gas matrices. The EPR spectra show no evidence for g and/or hyperfine anisotropy. Consequently, there is no evidence for the dipolar state of these atoms. Furthermore, trimers, pentamers and/or septamers are not formed from Rb and Cs under experimental conditions that have led to the formation of Li3, Li5, Na3 and K7. Group 1 atoms in a solid cyclohexane matrix give only colloidal metal particles with an average diameter of less than 102 Å.
Evaluation of nitroxides for the study of myocardial metabolism and oxygenation
Authors: Kuppusamy Periannan , Wang Penghai , Zweier Jay L.
Published: May 2005

Electron paramagnetic resonance spectroscopy at the L‐band (1.2 GHz) was used to investigate the redox metabolism and oxygenation within ischemic rat hearts loaded with a variety of six‐ and five‐membered carbocyclic nitroxide spin labels. Both cardiopleged and non‐cardiopleged hearts were studied at room temperature and at physiological temperatures. The results indicate that nitroxides that have greater intracellular partitioning are reduced faster than those that are extracellular. In addition, the six‐membered rings are metabolized much faster than the five‐membered rings. Increased nitroxide radical metabolism was observed in non‐cardiopleged compared with cardiopleged hearts. The oxygen utilization in the ischemic hearts was studied by using the oxygen‐dependent broadening of the nitroxide signals that occurs due to Heisenberg spin exchange. These structurally different nitroxides were evaluated for their sensitivity and suitability as probes of myocardial redox metabolism and oxygenation in the heart.
Spin trapping chemistry of acyl radicals
Authors: Janzen Edward G. , Davis Edward R. , DuBose Coit M.
Published: May 2005

The EPR spectra of a variety of different acyl radical adducts of PBN (C‐phenyl N‐tert‐butyl nitrone) and MNP (2‐methyl‐2‐nitrosopropane) were measured and their hyperfine splitting constants determined. Included are benzoyl, acetyl and other alkylacyl, alkoxyacyl, aminoacyl and alkylaminoacyl adducts. All examples gave relatively large β‐hydrogen hyperfine splittings ranging from 2.71 to 5.93 G in the PBN spin adducts. Long‐range hyperfine splitting was found to both nitrogen and amino‐hydrogen atoms in the aminoacyl adducts, indicating specific preferred conformations of the spin adducts. The MNP adducts have the well known 7‐8 G nitrogen hyperfine splitting with little else. The existence of hydrogen atom abstraction from benzaldehyde by nitroxides was established, indicating that nitroxides cannot be considered as inert reagents when sent to probe systems containing aldehydes. For example, the EPR signal due to a nitronyl nitroxide was rapidly quenched in the presence of benzaldehyde in benzene. Also, a surprising increase in intensity of benzoyl PBN adduct was noted after photolysis when the light was turned off. Double acyl adduct formation is proposed.
Rubber‐modified epoxies: III. Influence of the rubber molecular weight on the phase separation process
Authors: Chen Dong , Pascault Jean Pierre , Sautereau Henry , Ruseckaite Roxane A. , Williams Roberto J. J.
Published: May 2005

The effect of varying the rubber molecular weight on the reaction induced phase separation taking place in rubber‐modified epoxies is reported. Three butadiene–acrylonitrile copolymers with number‐average molecular weights of 2030, 3600 and 6050 g mol−1 were used. The thermosetting polymer was an epoxy based on diglycidylether of bisphenol‐A cured with a cycloaliphatic diamine. Increasing the rubber molecular weight showed the following effects: (i) a decrease in the conversion at the cloud point; (ii) a corresponding decrease in the viscosity at the cloud point; (iii) a primary morphology of a low concentration of particles with a large size; (iv) a more complete segregation of the rubber from the matrix leading to a smaller decrease of the glass transition temperature of the system; (v) a decrease in the toughening. The Flory–Huggins lattice model may be used as a simple approximation to describe the phase separation process when varying the rubber molecular weight.
Rubber‐modified epoxies: IV. Role of chain ends on the morphologies and properties
Authors: Chen Dong , Pascault Jean Pierre , Sautereau Henry
Published: May 2005

Four reactive liquid rubbers with different end‐groups but the same main chain (carboxyl‐, epoxy‐, amino‐terminated and non‐functional butadiene–acrylonitrile random copolymers) were employed in the same epoxy system, the diglycidyl ether of bisphenol A and 4,4′‐diamino‐3,3′‐dimethyldicyclohexyl methane cured at 50°C. The effects of the end‐groups of the liquid rubber on the morphology, phase compositions, sub‐structure inside the particles, interface between the phases and the mechanical properties were determined. The effects were related to the reactivity and the miscibility of the additive.
DSC studies on states of water in crosslinked poly(methyl methacrylate‐co‐n‐vinyl‐2‐pyrrolidone) hydrogels
Authors: Ahmad Mansor B. , Huglin Malcolm B.
Published: May 2005

Mixtures of methyl methacrylate (MMA) with N‐vinyl‐2‐pyrrolidone (VP) of various composition in the presence of fixed concentration of ethylene glycol dimethacrylate (EDMA) have been copolymerized to 100% conversion by γ‐irradiation. The resultant solid xerogels were swollen in water to yield hydrogels of equilibrium water contents ranging from 15 to 76wt%. The state of water in the poly(MMA‐co‐VP) hydrogels has been studied by differential scanning calorimetry (DSC) and the percentages of free freezing, freezable bound and nonfreezing water were found to vary with the xerogel composition, i.e. the degree of hydration of the hydrogels. At low equilibrium swelling, most of the water exists as a non‐freezing type, whereas at higher equilibrium swelling the majority of water exists as free freezing water. The maximum number of non‐freezing water molecules per VP unit in the hydrogel is about 7.5.
DSC analysis of ethylene/1‐butene copolymers obtained with different ziegler–natta catalysts
Authors: Bruni Cosimo , Pracella Mariano , Masi Francesco , Menconi Francesco , Ciardelli Francesco
Published: May 2005

The crystallization and melting behaviour of two sets of ethylene/1‐butene copolymers have been analysed by DSC. The samples, with comonomer content in the range from 0 to 21.5 mol%, were obtained by industrial processes using both Mg/Ti‐based catalyst systems. The composition dependences of melting and crystallization temperatures were found to be strictly affected by the catalyst type. Moreover, logarithmic plots of the melting and crystallization enthalpy as a function of the ethylene content (mol%) in the copolymers fitted linear relationships whose slopes have been related to the critical sequence length of crystallizable ethylene units, depending on the catalytic system. These results are compared with those reported in the literature for ethylene/1‐butene copolymers synthesized by other catalysts and are accounted for by a different distribution of the comonomer units in the macromolecules of the two sets of samples.
Molecular motions in poly(vinyl acetate) revisited. A thermally stimulated current study
Authors: Dias Ana B. , Correia Natália T. , Moura‐Ramos Joaquim J. , Fernandes Anabela C.
Published: May 2005

The dipolar relaxation mechanisms in poly(vinyl acetate) have been studied in detail using the technique of thermally stimulated currents. The papers published in the literature about this subject are very contradictory, particularly with respect to the assignment of the observed discharges to the corresponding motions at the molecular level. This work aims at clarifying these problems. We detected and characterised three different relaxation mechanisms: (1) a low temperature one (around −140°C) which was attributed to local internal rotations in the acetate side‐groups; (2) a relaxation whose maximum occurs at 42°C, which corresponds to the glass transition relaxation, and shows a compensation behaviour; (3) an upper glass transition relaxation whose maximum appears at 87°C and was attributed to a liquid‐liquid transition. These assignments have been made on the basis of the analysis of the behaviour of the samples when submitted to different thermal and electrical treatments.
Kinetic behaviour of adsorption of gelatin at solid–liquid interface
Authors: Bajpai A. K.
Published: May 2005

The kinetics of adsorption of gelatin from its aqueous solution on to silica has been studied at room temperature. The adsorption isotherms were found to be of the Langmuir type. From the adsorption isotherms, the adsorption coefficient, surface coverage and rate constants for adsorption and desorption were evaluated. The rate of adsorption was found to be maximum at the isoelectric point of gelatin and decreased with increase in pH of the adsorption medium. The increased ionic strength of the medium also caused an increase in the rate and amount of adsorption.
Effect of accelerated aging on the properties of some writing paper sheets
Authors: El‐Din Nabil M. Safy , Fahmy A. M.
Published: May 2005

Writing papers made from kraft softwood pulp and bagasse dissolving pulp were subjected to thermal aging for different time intervals (24, 48, 72, 96 and 120h) and the resulting changes in their chemical, physical and submicroscopic properties were investigated. The crystallinity changes in these pulps during thermal aging were studied by X‐ray diffractograms. The carboxyl content of the kraft softwood pulp increased with time of thermal aging up to 96h and then decreased with increasing aging time, while the carboxyl content of bagasse dissolving pulp increased during thermal aging up to 72h and then decreased after this time. The crystallinity of kraft softwood pulp increased gradually during thermal aging. However, in the case of bagasse dissolving pulp the crystallinity increased up to 72h and then decreased. All pulps were characterized by a reduction in the degree of whiteness and chain depolymerization during the time of thermal aging.
Morphology of fibers from poly(phenylene sulfide) and its liquid crystallinity
Authors: Xiao Weiwei , Xu Xi
Published: May 2005

Fresh poly(phenylene sulfide) (PPS) fibers have pleated surface morphology and banded texture. These structural features are similar to those of poly(phenylene terephthalamide) fiber (Kevlar), whereas some unique morphologies were observed for the long‐term stored PPS fibers, which have not been found with liquid crystalline polymer fibers including Kevlar. The long‐term stored PPS fibers show a decreased Tg and a decreased onset temperature of melting, compared with their fresh counterparts, which is attributed to stress relaxation and resulting disorientation in the amorphous region of the fibers. Combination of the observed typical morphologies with polarized optical microscopy and X‐ray diffraction analysis suggests that PPS possesses liquid crystalline nature.
Investigation of the molecular transport of aliphatic and aromatic esters into engineering polymer membranes
Authors: Aminabhavi Tejraj M. , Munnolli Ravindra S.
Published: May 2005

Molecular transport as manifested by sorption and diffusion of organic esters into engineering polymer membranes, viz. nitrile butadiene rubber, styrene butadiene rubber, ethylene propylene diene terpolymer, neoprene and natural rubber, has been investigated in the temperature range 25–60°C by the sorption gravimetric technique. The sorption equilibrium for ethylene propylene diene terpolymer was lower than those of the other polymers with all the liquids. Diffusion and permeation coefficients were obtained for the polymer‐solvent systems and these follow Arrhenius type behaviour in the temperature range investigated.
Copolymerization of zinc acrylate with acrylonitrile initiated by As2S3–styrene complex
Authors: Agrawal B. P. , Srivastava A. K.
Published: May 2005

Radical copolymerization of zinc acrylate (ZnA2) with acrylonitrile (AN), initiated by As2S3–styrene complex(I), in dimethyl Sulphoxide (DMSO) at 90 ± 0.1°C for 1.0h under inert atmosphere, yields non‐alternating copolymers. The kinetic expression is Rp ∝ [I]0.33 [ZnA2]0.25 [AN]0.44, i.e. the system follows non‐ideal kinetics, which is due to primary radical termination as well as degradative chain transfer reactions. The values for activation energy (E) and k2p/kt are 128kJ mol−1 and 8.57 × 10−7 litre mol−1 s−1, respectively. Thermal stability, solubility in different solvents, and IR and NMR spectra have been evaluated.
Structure and electrical properties of polypyrrole–thermoplastic elastomer blends
Authors: Radhakrishnan S. , Saini D. R.
Published: May 2005

Conducting thermoplastic elastomer blends have been synthesised by deposition of polypyrrole in styrene–butadiene–styrene (SBS) block copolymers containing various amounts of ferric chloride (FeCl3). These blends have phasesegregated morphology with preferenatial deposition of polypyrrole in one of the domains as confirmed by structural investigations using optical microscopy, X‐ray diffraction and infrared spectroscopy. The electrical resistivity (ρ) for these blends shows a sharp transition in the region of 273 K and is sensitive to small mechanical deformations both in compressions and extension modes. The dependence of ρ on mechanical stress (P) follows a power law of the type ρ ∝ Pn, where n has a value between 3 and 4. These various findings have been explained on the basis of a phase‐segregated morphology having highly conducting domains separated by a semiconducting/insulating matrix, together with non‐linear conduction processes for charge transport in such heterogeneous materials.
Interpenetrating polymer networks from castor oil‐based polyurethanes and polystyrene, XXV
Authors: Suthar Bhikhu , Jadav Kanak , Dave Mayank
Published: May 2005

Interpenetrating polymer networks (IPNs) of castor oil‐based polyurethanes and polystyrene were prepared by simultaneous polymerization. The liquid prepolyurethanes were formed by reacting the hydroxyl functionality of castor oil with isophorone diisocyanate using different stoichiometric NCO/OH ratios. These prepolyurethanes were mixed with styrene monomer and subsequently polymerized by free radical polymerization initiated by benzoyl peroxide in the presence of the crosslinker 1,4‐divinyl benzene. The interpenetrating polymer networks. PU/PS IPNs, were obtained as tough and transparent films by the transfer moulding technique. These IPNs were characterized by the static mechanical properties (tensile strength, Young's modulus and % elongation), thermal properties and morphology. The dielectric relaxation properties (σ, E′, E″ and tanδ) of the IPNs at different temperatures were studied.
Vinyl polymerization initiated by ceric ion–methyl cellosolve redox system in aqueous nitric acid
Authors: Reddy G. Venkataramana , Umamaheswari M. V. , Vidya V. , Krishnaswamy V.
Published: May 2005

Polymerizations of methyl methacrylate (MMA) and acrylonitrile (AN) were carried out in aqueous nitric acid at 30°C with the redox initiator system ammonium ceric nitrate–methyl cellosolve (MC). A short induction period was observed, as well as the attainment of a limiting conversion for polymerization reactions. The consumption of ceric ion was first order with respect to Ce(IV) concentration in the concentration range (0.5–3.0) × 10−3 M Ce(IV), and the point at higher concentration deviated from the graph. Plots of the inverse of the pseudo‐first order rate constant for ceric ion consumption, [k′]−1, versus [MC]−1 gave straight lines with non‐zero intercepts for both monomer systems, suggesting complex formation between Ce(IV) and MC. Complex formation between Ce(IV) and reducing agent was also detected by a shift in the absorption maximum of Ce(IV), using a Beckman spectrophotometer. The rates of polymerizations increased with increase in Ce(IV), MC and monomer concentrations; however, at higher concentration of AN (0.2187 M) a steep fall in Rp was observed for AN polymerization. The orders with respect to Ce(IV), MC and monomer for MMA polymerization were found to be 0.22, 0.35 and 1.73 respectively. The orders with respect to Ce(IV), MC and monomer for AN polymerization were found to be 0.56, 0.30 and 1.30 respectively. Maintaining constant nitrate ion in the reaction medium did not significantly change the rate of polymerization with [Ce(IV)], but a fall in RCe was observed. A kinetic scheme involving oxidation of MC by Ce(IV) via complex formation, whose decomposition gives rise to a primary radical, initiation, propagation, and termination of the polymeric radicals by bimolecular interaction, is proposed. An oxidative termination of primary radicals by Ce(IV) is also included.
Studies on the transesterification of polycarbonate/poly(ethylene terephthalate) blends. I: Mechanisms and extent of reaction
Authors: Zheng Wen‐ge , Wan Ze‐hong , Qi Zong‐neng , Wang Fu‐song
Published: May 2005

Transesterification of polycarbonate/poly(ethylene‐terephthalate) (PC/PET) blends and the reaction extent were investigated by DSC, FTIR, 1H NMR and Soxhlet extraction. A new characteristic peak appeared in the FTIR spectrum of PC/PET blends after heat treatment, which indicates that new copolymers were formed in the transesterification of the PC/PET blends. The reaction extent was characterized by the absorbance ratios of the FTIR characteristic bands. The reaction extent was associated not only with the reaction conditions but also with the composition of the blends. These results were confirmed by chemical analysis of the extracted products in CH2Cl2 solvent and FTIR analysis. For all the blends studied, the blend with 50/50 wt% had the highest reaction extent. The reaction mechanisms and extent were also confirmed by 1H NMR analysis.
Viscoelastic properties of polystyrene–poly(vinyl methyl ether) blends in oscillatory and steady shear flows near the phase separation temperature
Authors: Takahashi Yoshiaki , Suzuki Hirokazu , Nakagawa Yoshiki , Noda Ichiro
Published: May 2005

Viscoelastic properties of a polystyrene‐poly(vinyl methyl ether) blend were measured in oscillatory and steady shear flows near the phase separation temperature. In the one‐phase region, the viscoelastic properties are independent of the type of flow and flow geometry, and their shear and frequency dependences are the same as those of homopolymers. When phase separation occurred, a change in viscoelastic properties was observed in all types of flow and flow geometries, and they are different in the different types of flow and/or different flow geometries in the two‐phase region.

In the shear rate dependence of viscosity of the polymer blend in the two‐phase region at quiescence, a plateau region was observed, in which the shear viscosity can be regarded as the zero shear viscosity of the homogenized polymer blend at that temperature.
Influence of ZnCl2 on the structure and mechanical properties of polyacrylonitrile fibers
Authors: Cho Seo Hyun , Park Jong Su , Jo Seong Mu , Chung In Jae
Published: May 2005

The structure and mechanical properties of polyacrylonitrile fibers containing small amounts of Zn2+ were investigated. It is possible to interpret the influence of ZnCl2 on the fibers by diffusion. Fibers spun from spinning dope containing ZnCl2 may have a denser and finer structure because ZnCl2 in the spinning dope retards the coagulation rate. The tensile strength and modulus of the fibers are much improved because of the retardation of coagulation. It is probable that the complexation between Zn2+ and CN groups does not contribute to the improvement of the mechanical properties because the amount of ZnCl2 added in a spinning dope is extremely small.
Preparation and morphological characterization of microscopic composite particles
Authors: Shen S. , El‐Aasser M. S. , Dimonie V. L. , Vanderhoff J. W. , Sudol E. D.
Published: May 2005

Monodisperse microscopic poly (methyl methacrylate)/polystyrene composite particles of 1–10 μm diameter were prepared by seeded emulsion polymerization of styrene in poly (methyl methacrylate) seed particles which were initially prepared by dispersion polymerization. The resulting composite particles were characterized by transmission and scanning electron microscopy. The unique morphology of the composite particles comprised three types of polystyrene domains embedded in a continuous poly (methyl methacrylate) matrix: the dispersed “internal” domains in the interior, the interconnected “subsurface” domains that from a crust beneath the surface, and the separated “surface” domains at the surface. In addition to thermodynamics and kinetics, the phase separation in composite particles is affected by polymerization mechanism. The complicated particle morphology found is attributed to the coexistence of bulk polymerization and emulsion polymerization (radical absorption and desorption) mechanisms. An explanation of the formation of the observed morphology is proposed. With varying poly (methyl methacrylate)/styrene ratio, the internal viscosity and the competition between the two polymerization mechanisms resulted in a series of interesting morphologies.
Ethynyl‐terminated polyethers from new end‐capping agents. II. End‐chain functionalization through nitro displacement
Authors: Lucotte Georges , Cormier Laurent , Delfort Bruno
Published: May 2005

Ethynyl‐terminated polysulfones and ethynyl‐terminated polyether‐ketones were prepared in a one‐step polyetherification reaction using new end‐capping agents, respectively 4‐ethynyl‐3′‐nitrodiphenylsulfone and 4‐ethynyl‐4′‐nitrobenzophenone. These reagents were prepared according to a three‐step route each. End‐capping of the polymers involve the nitro displacement by a phenoxide ion. The nitro group was found to be more reactive than the fluoro one as a leaving group. Due to the thermally induced reaction of their ethynyl end‐groups, the polymers lead to materials with improved glass transition temperatures and good thermostability.
Effect of thermal oxidation on the spherulitic morphology of high‐density polyethylene
Authors: Scheirs John , Bigger Stephen W. , Delatycki Oskar
Published: May 2005

The supermolecular structure of high‐density polyethylene (HDPE) at various stages of oxidation was studied using polarized optical microscopy and small‐angle x‐ray scattering (SAXS). Samples of HDPE crystallized isothermally at 123°C show a pronounced change in their spherulitic structure with progressive thermal oxidation. Polarized optical micrographs and SAXS data indicate that the average lamellar thickness decreases concomitantly with thermal treatment. Solid‐state oxidative scission occurs preferentially at the chain folds where the polymer molecules are strained. This process increases the level of crystallinity of the polymer due to the more efficient packing of crystallites formed by the shorter cleaved chains. The morphological changes are related to the polymer melt flow index, molecular weight distribution, crystallinity and peak melting temperature. A model is proposed to account for the changes in the spherulitic morphology.
Relating microhardness of poly(ethylene terephthalate) to microstructure
Authors: Cruz C. Santa , Calleja F. J. Baltá , Zachmann H. G. , Stribeck N. , Asano T.
Published: May 2005

The microhardness (H) of poly(ethylene terephthalate) (PET) containing catalysts, as well as of PET without catalysts has been investigated. Two types of morphologies have been examined: (a) structures where spherulitic growth is incomplete, resulting from a primary crystallization from the glassy state and (b) samples in which spherulitic crystallization is completed. It is shown that for the former materials,His an increasing linear function of the volume of the spherulites and depends on annealing time and catalyst content. For the latter materials,His nearly constant with increasing annealing temperature (TA). Results are discussed in the light of three principal structural factors which determine the microhardness behavior: (1) the volume content of spherulites within the material; (2) the value of crystallinity within the stacks of the lamella, which turns out to be a constant; (3) the average thickness of the crystals, which increases slightly withTAafter crystallization is completed. An expression which takes into account the above parameters and offers a description of theHof polyethylene terephthalate is proposed.
Calculation of the Electrical Field within an Electrical Sensing Zone Counter
Authors: Wilson R.
Published: May 2005

Iterative numerical analysis methods, similar to those used for ray tracing in electron and ion guns, have been employed to calculate the electrical potential distribution in the vicinity of the orifice of an electrical sensing zone (esz) instrument. In particular, the electrical potential across the mouth of the orifice is considered and the effects of numerically bevelling the sharp peripheral edge are demonstrated.

The results support the empirical equation:

for the axial component of the potential gradient, dϕ/dx, at the mouth of the orifice expressed as a function of the radial distance, r, from the centre of the orifice of radius R; α′ and β′ are empirical constants. This equation was derived from previously reported experimental data on relative shifts and heights of artefact peaks apparent on the coarse side of size distributions measured via the esz method on a series of latex copolymers.
Photometric Determination of Respirable Dust Concentration without Elutriation of coarse particles
Authors: Armbruster Lorenz , Breuer Hans , Gebhart Josef , Neulinger Gerold
Published: May 2005

The principle of an instantaneous reading, respirable dust, photometer and its application are described. The instrument measures the infrared light (940 nm wavelength) scattered on airborne particles under a mean scattering angle of 70°. Its open measuring chamber, which is insensitive to daylight, is filled with total dust. The photometer reading, however, is calibrated in terms of mass concentration of respirable dust by means of a gravimetric respirable dust sampler. Experiments carried out with monodisperse test aerosols and with real dusts confirm the instrument's principle. The photometer values obtained for real dusts can be linearly converted into mass values of respirable dust as long as ultra‐fine or ultra‐coarse dusts are excluded. In several practical cases an increased flux of scattered light is compensated for by a higher density of the dust material.
Experimental Investigation of the Tensile Strength of a Powder bed by split cell type tensile testers
Authors: Jimbo Genji , Hatano Shigenobu
Published: May 2005

New types of equipment for measuring the tensile strength of a powder bed, based on the Warren Spring type of split cell, have been developed by the authors and are reported in this paper. The main modification is an extension of the range of the porosity of the powder bed to be tested by improving the sliding mechanism of the split cell. Three versions of the modified equipment are introduced and explained, and the reduction of the sliding friction and the stability of the split cell at a high compression range are shown. The results obtained with beds of a wide porosity range are presented in a new equation for the adhesion force of a powder bed.
Electrochemical Properties of Constituent Minerals of Manganese Nodules
Authors: Nonaka Michio , Uchio Takayasu
Published: May 2005

Deep‐sea manganese nodules must be potentially valuable one of the most mineral resources containing several economically valuable metal elements. Manganese minerals in the nodules are regarded principally as todorokite and δ‐MnO2. The todorokite phase is porous and enriched in copper and nickel, while the porous δ‐MnO2 phase is enriched in cobalt. Porosity and adsorption as well as dissolution characteristics have been observed for each constituent mineral. Furthermore the pore diffusion coefficient has been calculated. Moreover, the zeta potential of each constituent mineral has been measured in order to evaluate the electrochemical property. This has been applied successfully to the selective concentration of copper and nickel bearing or cobalt bearing minerals in deep‐sea manganese nodules.
Laser Diffraction Spectrometers/Experience in Particle Size Analysis
Authors: Bürkholz Armin , Polke Reinhard
Published: May 2005

Over the past few years, laser diffraction spectrometry has become a very important method of particle size analysis. Typical features include the large measuring range, the simplicity of operation and the speed with which analyses can be carried out. The principle of measurement and the set‐up of three commerical instruments are described.

The following points are discussed, with reference to examples:

–Relevant parameters, such as particle shape, shape of distribution curve or dispersion, bution curve or dispersion,

–reproducibility, comparison of the results obtained with different types of apparatus between one another and with other, analytical methods, and

–on‐line use of the instruments for the measurement of dynamic processes, eg. flocculation and dispersion processes.

Operating experience gained with six instruments over a number of years is discussed.

The measuring method which is described here is in a stage of rapid development and dissemination. It is for this reason that recent improvements and new developments cannot be dealt with here. For example, an apparatus named Helos from Sympatec GmbH, Remlingen, has appeared on the market. The external appearance of the instruments marketed by the Malvern and Leeds and Northrup companies has changed somewhat.

The author's practical experience (in some instances extremely wide‐ranging) with these devices is presented here in summary form.
Minimum Sintering Temperatures of Fluidizable Particles
Authors: Compo Peter , Tardos Gabriel I. , Mazzone Dominick , Pfeffer Robert
Published: May 2005

Experimental methods to determine minimum sintering temperatures of a variety of granules such as polymers, glass, coal, inorganic salts, etc. are presented. These methods include the use of a dilatometer in which the contraction‐dilation characteristics of a small sample is measured, a differential scanning calorimeter test and an Instron machine by which yield strengths are measured. It is clearly shown that for the majority of materials studied, the different methods give similar values for the minimum sintering temperature but that the dilatometer experiment is the simplest as well as the most reliable method. Since the minimum sintering temperature is always less than the solid's melting point, an efficient method of measuring this temperature is very important for all fluidizable granules subjected to high temperatures. The danger of agglomeration during fluidization increases tremendously at temperatures higher than minimum sintering and therefore special precautions must be taken to avoid defluidization under these conditions.
Quality Control in Solids Process Engineering
Authors: Polke Reinhard , Scholz Norbert
Published: May 2005

Product quality is influenced by the properties of feedstocks and by production parameters. In contrast to gases and liquids, the quality of solids is also affected by the particle properties, such as size, specific surface area, structure and shape. These are the properties which are primarily changed in solids process engineering.

The accuracy and cost of possible methods for the measurement of the particle properties of feedstocks, intermediates and end products are discussed. Examples of the methods discussed are laser diffraction spectrometry, quantitative image analysis and photon correlation spectroscopy.

The measuring techniques required for monitoring production processes in solids process engineering are illustrated by simple examples. In the field of process control in particular, there is still room for improvement, since there is a lack of suitable sensors and models. Process monitoring is necessary in order to ensure that product quality meets requirements which are constantly increasing.
Approximate Mathematical Description of Particle‐Size Distributions – Possibilities and limitations as to the assessment of comminution and classification processes
Authors: Zisselmar Raimund , Kellerwessel Hans
Published: May 2005

Disperse materials are often characterized by their particle‐size distributions which can be determined by different measuring methods. Frequently the quantitative portions of the particle size classes obtained by way of experiment are considered insufficient and one strives for approximating the measured values by an analytic function. This can be reached, more or less satisfactorily, by power, exponential, or normal distribution functions which may include two, three, or four parameters.

Publications as well as common practice have proved again and again that due to very rough or incorrect approximations wrong conclusions are derived from test and operating results, so that it appears expedient to investigate – when such an approximation would actually be advisable and – which function would be expedient in the specific case.

Application of distriction functions will always be justified then when there is an actual need for utilizing the advantages connected with an approximation. Evaluation of a great number of measuring results revealed that the two‐parameter functions in most cases only permit an utmost rough approximation which might give rise to wrong conclusions. Carefully classified products, however, mostly require three‐ or four‐parameter functions for making an appropriate approximation.

The functions, which appear appropriate for certain types of products, are set out in Table 1.

In order to make the tabulated individual results accessible to a practical utilization a systematization was attempted. The outcome is a graph which is meant as an assistance for the practician and which presents the possibility of a quick selection of function type.
Dynamic Shape Factors for Particle Shape Characterization
Authors: Dressel Martina
Published: May 2005

The need for particle shape characterization has been internationally recognised and has resulted in a number of publications proposing a variety of methods for particle shape analysis and shape description. Though very important in chemical engineering, correlations between shape parameters and bulk properties are still rare.

This paper describes theoretical and experimental investigations of dynamic shape factors for use when calculating the settling velocity of a particle. For this purpose a study of the settling velocities of particles of various shapes has been made. A correlation is developed from the data with which to quantify the effect of shape on settling velocity for particles falling freely in a fluid in the laminar flow range.
Comparison of Light Scattering with other Techniques for Particle Size Measurement
Authors: Tüzün Ug̈ur , Farhadpour Farhad A.
Published: May 2005

The forward‐light scattering technique was compared with three other well known size analysis techniques in determining the size distribution of a crystalline adsorbent, Silicalite (1–10 μm) in a dilute aqueous suspension. The commercial light scattering equipment Malvern was found to produce size distributions within ± 10% agreement with those obtained by scanning electron microscopy (SEM), electronic image analysis (Quantimet) and the electrical sensing zone method (Coulter Counter).

This rather surprising accuracy of the light scattering technique with crystal sizes quite close to the wavelength of the incident light is explained by considering the relative refractive index and the light absorbancy of the crystals in the “anamolous diffraction” regime. The theoretical analysis shows quite clearly that the calculation of a “unique” size distribution from a given set of scattering data is possible only when independently measured values of the optical properties are used.

The commercial equipment (Malvern) which is currently in use does not require a priori knowledge of the optical properties. The exceptional accuracy obtained with Silicalite crystals using the Fraunhofer approximation in the anamolous diffraction regime is demonstrated with the aid of the light scattering theory to be due to a rather fortunate combination of the light absorptive nature and the polydispersity of the crystals.
Measurement of the Flow Behaviour of Aerated and Fluidised Powders using a rotating viscometer
Authors: Hobbel Erik F. , Scarlett Brian
Published: May 2005

The rheological behaviour of a fluidised bed of alumina powder was determined using a specially designed form of rotating viscometer. Several different geometries of the inner and outer cylinder were tested. In the machine the two cylinders can be rotated independently, in either direction, which enables both their relative velocity and absolute velocity to be varied. Thus, the torque on the inner cylinder, strain‐rate and the absolute velocity have been chosen as the consistency variables. Some examples of the derived consistency surface are given. The characteristics of these surfaces could be explained by assuming different states of structure, to which a certain mobility can be ascribed. It is proposed that any state of structure which can exist in the bed is an intermediate of two extremes the first being the immobile state which is elastic and has a yield value and the second being the dynamic state which behaves like a Newtonian fluid.