bluuebunny/crossref_metadata_2025 huggingface dataset:
Postural finger tremor exhibited by Parkinson patients and age‐matched subjects
Authors: Palmer Suzanne S. , Hutton J. Thomas
Published: December 2004

Physiological correlates of postural tremor of the finger seen in Parkinson's disease patients are different from those seen in age‐matched control subjects. A significant correlation between the spectral peak of acceleration and the spectral peak of rectified electromyographic activity from the muscle responsible for finger extension was found in Parkinson's disease patients. This correlation was not seen in age‐matched control subjects. Any neural drive imposed on the motoneuron pool from supraspinal levels would enhance the electromyographic activity. Likewise, any feedback effects via spinal stretch reflexes or supraspinal stretch responses would be mediated through the motoneuron pool and electromyographic activity. The results of this research support the theory that Parkinson tremor is a centrally driven rhythm that may be influenced by feedback effects, whereas physiological tremor is due to a complex interaction of central, feedback, and mechanical effects.
A clinical and pharmacokinetic case study of an interaction of levodopa and antituberculous therapy in Parkinson's disease
Authors: Wenning G. K. , O'Connell M. T. , Patsalos P. N. , Quinn N. P.
Published: December 2004

We studied the relationship between levodopa response and antituberculous treatment in a patient with idiopathic Parkinson's disease whose parkinsonism deteriorated when treatment with rifampicin and isoniazid (Rifinah) for pulmonary tuberculosis was started. A levodopa challenge test with regular recording of motor function was performed during, and again after stopping, antituberculous treatment. Plasma levodopa and levodopa metabolite pharmacokinetic profiles were determined using standard techniques. “On” period duration was 75% longer after antituberculous treatment had been stopped. These clinical findings correlated with a 37% increase in area under the concentration versus time curve (AUC), a 103% increase in apparent elimination half‐life (t1/2), a 41% increase in time to maximum concentration (Tmax), and a 33% decrease in maximum concentration (Cmax) of levodopa. A concurrent increase in plasma 3‐O‐methyldopa (3‐OMD) and a decrease in plasma 3,4‐dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), the three major metabolites of levodopa, suggests an inhibition of the enzyme dopa decarboxylase, probably by isoniazid.
Iron in parkinsonian and control substantia nigra—A mössbauer spectroscopy study
Authors: Gała̧zka‐Friedman J. , Bauminger E. R. , Friedman A. , Barcikowska M. , Hechel D. , Nowik I.
Published: December 2004

We used Mössbauer spectroscopy to study the iron content, the redox state, and the binding site of iron in substantia nigra (SN) from parkinsonian (PD) and control brains. Measurements performed on fresh‐frozen, formalin‐fixed, and lyophilized samples demonstrated the presence of ferric (Fe3+) iron only, both in PD and control SN. Ferrous iron, if present at all, may represent at most 5% of the total iron. We found no difference in the total amount of iron in SN between PD and control brains. The Mössbauer spectra observed at 4.1 K in fresh (frozen or lyophilized) samples were different from those obtained in formalin‐fixed (frozen or lyophilized) samples. In the fresh samples, only ferritin‐like iron was observed, whereas in the samples frozen or lyophilized from formalin, non‐ferritin iron was detected.
Quantification of essential tremor in writing and drawing
Authors: Elble Rodger J. , Brilliant Mikhail , Leffler Keith , Higgins Constance
Published: December 2004

Eighty‐seven patients, aged 15–84 years (mean, 61.8 ± 16.2 SD), with essential tremor wrote two series of cursive e's and cursive l's on a standard sheet of ruled paper that was mounted on a commercially available digitizing tablet. Forty patients also drew an Archimedes spiral. Postural wrist tremor was measured with a triaxial accelerometer on the dorsum of the horizontally extended hand. The digitizing tablet was sufficiently sensitive to measure sustained visible tremor. Very severe tremor could not be recorded when it prevented a patient from keeping the ballpoint pen on the tablet. The intertrial variability of the handwriting data was such that a 36.0% change in mean acceleration amplitude (cm/s2) and an 8.3% change in mean tremor frequency (Hz) could be detected in a hypothetical population of 30 patients (paired‐sample t test, p = 0.01, power = 90%). The intertrial changes detectable with accelerometry were 35.9% (amplitude) and 7.8% (frequency). The correlations between wrist tremor and writing tremor were <0.60 for amplitude and <0.25 for frequency. Significant correlations between patient age and tremor frequency and between tremor amplitude and frequency existed for postural tremor but not for writing or drawing tremor. Standard digitizing tablets for personal computers are useful in the quantitative assessment of writing tremor. The amplitude and frequency characteristics of tremor in posture, writing, and drawing may differ significantly.
Perioperative use of botulinum toxin for movement disorder–induced cervical spine disease
Authors: Adler Charles H. , Zimmerman Richard S. , Lyons Mark K. , Simeone Fred , Brin Mitchell F.
Published: December 2004

Patients with cervical dystonia or tics of the nuchal muscles can develop serious cervical spine disease. We report a series of four patients who received botulinum toxin injections to control their movement disorders prior to their required surgery. One patient with cervical tic–induced radiculomyelopathy required botulinum toxin injection postoperatively to facilitate stabilization of the cervical fusion. Two patients with torticollis‐induced cervical radiculomyelopathy, and one patient with dystonia‐induced C5 fracture, had botulinum toxin injected pre‐operatively to facilitate postoperative recovery. Botulinum toxin appears to be a useful adjunct in the treatment of cervical movement disorders prior to or following surgery for associated cervical spine disease.
Essential myoclonus and myoclonus dystonia
Authors: Quinn Niall P.
Published: December 2004

This review explores the history and use of the terms essential myoclonus and myoclonie dystonia. In addition, the review proposes that herediatry essential myoclonus and dominantly inherited myoclonic dystonia, with lightning jerks and dramatic response to alcohol, are the same disease, although proof of this hypothesis must come from ongoing genetic studies.
Core assessment program for intracerebral transplantation in Huntington's disease (CAPIT‐HD)
Authors: Quinn Niall , Brown Richard , Craufurd David , Goldman Serge , Hodges John , Kieburtz Karl , Lindvall Olle , MacMillan John , Roos Raymund
Published: December 2004

Studies in Parkinson's disease using the Core Assessment Program for Intracerebral Transplantation (CAPIT) protocol have demonstrated that grafts of embryonic mesencephalic cells into striatum can survive, grow, and exert useful clinical effects. Attention is now being directed toward neural grafting in other conditions, such as Huntington's disease. As a precondition for grafting of embryonic striatal cells into diseased striatum in this complex motor and psychiatric disorder, not only is further basic research needed, but also a thorough and wide‐ranging assessment protocol is essential. This article presents such a CAPIT‐HD assessment protocol.
Proton magnetic resonance spectroscopy in Huntington's disease: Evidence in favour of the glutamate excitotoxic theory?
Authors: Taylor‐Robinson S. D. , Weeks R. A. , Bryant D. J. , Sargentoni J. , Marcus C. D. , Harding A. E. , Brooks D. J.
Published: December 2004

The gene responsible for Huntington's disease (HD) has been located, but its action and the pathophysiology of HD remain unclear. Glutamate excitotoxicity may contribute to the striatal neurodegeneration seen in HD. We used localised proton magnetic resonance spectroscopy (MRS) of the brain to investigate five patients with early HD, one symptom‐free gene carrier, and 14 healthy volunteers. Peak area ratios of choline‐containing compounds (Cho), glutamine and glutamate (Glx), and N‐acetyl moieties including N‐acetylaspartate (NAx), relative to creatine (Cr), were calculated. Spectra were analysed from the striatum and the occipital and the temporal cortex. The HD patients all had an elevated Glx/Cr in spectra localised to the striatum, compared with healthy controls, and one patient also had an elevated thalamic Glx/Cr. The mean Glx/Cr was unaltered in the cortical spectra of HD patients. The asymptomatic gene carrier displayed no spectral abnormalities. Our findings suggest disordered striatal glutamate metabolism and may support the theory of glutamate excitotoxicity in HD.
Basal ganglia iron content in Parkinson's disease measured with magnetic resonance
Authors: Ye Frank Q. , Allen Peter S. , Martin W. R. Wayne
Published: December 2004

The possibility of using magnetic resonance (MR) to evaluate the severity of the pathological changes of Parkinson's disease (PD) is suggested by the known accumulation of iron in the basal ganglia in PD and the reduced signal evident from this area with conventional reduced signal evident from this area with conventional T2‐weighted MR imaging. To improve the specificity of MR for the measurement of tissue iron content, we have developed a method that quantifies the effects of paramagnetic centers sequestered inside cellular membranes, based on the echo time dependence of the decay of transverse magnetization caused by the local field inhomogeneities which are due to intracellular iron. This method enables an index of local tissue iron content to be calculated for structures of the basal ganglia. We report here the application of this method to a series of patients with PD (n = 12) and of normal, age‐matched controls (n = 13). Our objective was to determine whether this measurement of basal ganglia iron concentration correlates with the presence and severity of PD. We observed a significant increase in iron content in both the putamen and pallidum in PD as well as a correlation with the severity of clinical symptomatology. More severely affected patients had a higher iron content in both of these structures. Our results suggest that this MR measurement may provide a noninvasive method of measuring the severity of the pathological changes underlying PD.
Influence of dopaminergic medication on automatic postural responses and balance impairment in Parkinson's disease
Authors: Bloem Bastiaan R. , Beckley Dennis J. , van Dijk J. Gert , Zwinderman Aeilko H. , Remler Michael P. , Roos Raymund A. C.
Published: December 2004

It is still unclear why balance impairment in Parkinson's disease (PD) often responds insufficiently to dopaminergic medication. We have studied this issue in 23 patients with idiopathic PD and 24 healthy controls. Our specific purposes were (a) to investigate the contribution of abnormal automatic postural responses to balance impairment in PD and (b) to assess the influence of dopaminergic medication on abnormal automatic postural responses and balance impairment. Standing subjects received 4° “toe‐up” rotational perturbations of a supporting forceplate. We bilaterally recorded posturally destabilizing medium latency (ML) responses from the stretched gastrocnemius muscles and functionally corrective long latency (LL) responses from the shortened tibialis anterior (TA) muscles. We also assessed changes in the center of foot pressure (CFP) and the center of gravity (COG). All patients were tested “off” and “on” phase. All controls were tested and retested after 1 h. During the off phase, we found enlarged ML amplitudes and diminished LL amplitudes in patients, together with a markedly increased posterior displacement of the COG. The abnormal ML and LL responses were partially responsible for the increased body sway in patients because the initial forward (destabilizing) displacement of the CFP was increased, while the subsequent backward displacement of the CFP (a measure of the corrective braking action of LL responses) was delayed. Abnormal late automatic or possibly more voluntary postural corrections also contributed substantially to the increased body sway. During the on phase, ML amplitudes were reduced in patients but remained increased compared with controls. LL amplitudes no longer differed between both groups due to a modest, possibly dopamine‐related in crease in patients and a simultaneous decrease in controls. The abnormal CFP displacement was only partially improved by dopaminergic medication. The later postural corrections were not improved at all. Consequently, the increased posterior COG displacement was not ameliorated during the on phase. We conclude that (a) a combination of abnormal automatic and perhaps more voluntary postural corrections contributes to increased body sway in PD and (b) dopaminergic medication fails to improve balance impairment in PD because early automatic postural responses are only partially corrected, while later occurring postural corrections are not improved at all. These electrophysiological results support clinical observations and suggest that nondopaminergic lesions play a significant role in the pathophysiology of postural abnormalities in PD.
Hashimoto's myoclonic encephalopathy: An underdiagnosed treatable condition?
Authors: Ghika‐Schmid F. , Ghika J. , Regli F. , Dworak N. , Bogousslavsky J. , Städler C. , Portmann L. , Despland P. A.
Published: December 2004

We report two patients with subacute diffuse encephalopathy characterized by confusion, myoclonic encephalopathy, and mild akineto‐rigid extrapyramidal signs in one case and by apathy, memory deficit, and partial complex seizures in the other. Hashimoto's thyroiditis with high titers of antithyroglobulin antibodies was diagnosed in both patients, who were unresponsive to anticonvulsant medication, but showed rapid neurological improvement following steroid treatment. On neuropsychological examination, predominant frontotemporal dysfunction was noted. Electroencephalographic activity was remarkable for its rhythmical delta activity, unresponsive to, or even paradoxically increased by, anticonvulsant treatment. On magnetic resonance imaging, atrophy with temporal predominance was found. These observations support the idea that this potentially treatable dementia and movement disorder should be classified as a separate clinical entity.
Postencephalitic stereotyped involuntary movements responsive to L‐Dopa
Authors: Picard F. , de Saint‐Martin A. , Salmon E. , Hirsch E. , Marescaux C.
Published: December 2004

In 1954, at the age of 5 years, our patient had an encephalitic syndrome associated with a prolonged lethargic state. After this episode, he developed a severe parkinsonian syndrome that, after a few years, was associated with axial dystonia and stereotyped abnormal movements of the upper limbs. This complex and progressive extrapyramidal syndrome had many similarities to the encephalitis lethargica as described by von Economo. Results of cerebral computed tomography and magnetic resonance imaging were normal. Fluorodopa positron emission tomography showed a significant bilateral reduction of tracer accumulation in both putamen, similar to that observed in patients with idiopathic Parkinson's disease. However, in this patient, treatment with L‐Dopa suppressed all akinetic, dystonic and dyskinetic symptoms. The effectiveness of L‐Dopa was abolished by administration of a D2 antagonist and was fully reproduced by a D2 agonist. In conclusion, this patient presented a complex postencephalitic, extrapyramidal syndrome, with akinetic symptoms and involuntary movements. These symptoms appeared to be related to a limited lesion of the dopaminergic neurons of the zona compacta of the substantia nigra.
Striatal interneurons in Huntington's disease: Selective increase in the density of calretinin‐immunoreactive medium‐sized neurons
Authors: Cicchetti Francesca , Parent André
Published: December 2004

The marked atrophy of the striatum seen in Huntington's disease (HD) is largely due to a massive neuronal loss that affects the striatal projection neurons more severely than the local circuit neurons. We recently reported the existence of a new class of interneurons characterized by their immunoreactivity for the calciumbinding protein calretinin in the human striatum. In the present immunohistochemical study, we compared the distribution and relative density of the calretininexpressing interneurons in the striata of four normal individuals and four patients with HD (grade 1 to 3). The population of calretinin‐containing interneurons comprised (a) a small subset of large (17‐to 44‐μm), multipo‐ lar neurons with five to seven long, aspiny, and highly branched dendrites and (b) a large number of medium‐ sized (8‐to 18‐μm), round‐to‐oval neurons with two to three long, varicose, and poorly branched dendrites. Both types of chemospecific neurons occurred throughout the striatum in all specimens examined, but the density of the medium‐sized neurons was much higher in patients with HD than in controls. A quantitative analysis showed a significant (p < 0.01) twofold increase in the density of the striatal medium‐sized neurons and a similar decrease in the density of the large neurons in patients with HD compared with controls. This differential effect on the densities of the two types of interneurons suggests that calretinin may protect the medium‐sized but not the large neurons against neurodegeneration in HD.
Effects of diminished and conflicting sensory information on balance in patients with cerebellar deficits
Authors: Gatev Plamen , Thomas Sherry , Lou Jau‐Shin , Lim Meerana , Hallett Mark
Published: December 2004

We studied the effects of altered sensory information on standing balance in 25 patients with cortical cerebellar atrophy (CCA), nine patients with olivopontocerebellar atrophy (OPCA), and 10 normal subjects. The total sway path and its components, the antroposterior (AP) sway path and the lateral sway path, were measured under six conditions: (1) standing on a fixed platform with the eyes open and visual surroundings fixed, (2) standing on a fixed platform with the eyes closed, (3) standing on a fixed platform with the eyes open and visual surroundings AP sway referenced, (4) standing on an AP sway‐referenced platform with the eyes open and visual surroundings fixed, (5) standing on an AP sway‐referenced platform with the eyes closed, and (6) standing on an AP sway‐referenced platform with the eyes open and visual surroundings AP sway referenced. Patients swayed more than normal subjects during normal stance (condition 1), when the visual information was absent (condition 2) or distorted (condition 3), and when the proprioceptive information from the ankles was distorted (condition 4). Patients swayed much more than normal, and most fell, when two sensory modalities were affected under condition 5 (proprioceptive information distorted and visual information absent) and condition 6 (both proprioceptive information and visual information distorted). When the patients' sway was normalized to that of the first condition, however, only their lateral sway was greater than the sway in normal subjects. Unlike in normal subjects, the patients' lateral sway varied with the AP sway to approximately the same degree in each condition for conditions 1–5. Clinical ratings of gait and balance were highly correlated with the sway measures. Quantitative testing of standing balance with altered sensory information has better sensitivity than normal stance testing.
Sleep‐related periodic leg movements associated with spinal cord lesions
Authors: Lee M. S. , Choi Y. C. , Lee S. H. , Lee S. B.
Published: December 2004

We describe three patients who developed progressive paraparesis and sleep‐related periodic leg movements (SRPLM) associated with thoracic spinal cord lesions; one patient had a schwannoma and two had intramedullary lesions. The patients showed periodic repetitive involuntary movements involving one or both lower limbs. The involuntary movements consisted of a single rapid dorsiflexion of the great toe or ankle, two to four repetitive dorsiflexions of the toes and ankle, and a mixture of repetitive jerks and prolonged spasms causing flexion of the hip and knee and dorsiflexion of the ankle and toes. In the patient with a schwannoma, paraparesis and SRPLM improved completely after surgical removal of the mass lesion. In one patient the SRPLM associated with an intramedullary lesion improved markedly after levodopa treatment. We suspect that thoracic spinal lesions partially disinhibit the lumbosacral generator. Such disinhibition seems to be enhanced by the activation of the neuronal systems related to periodic somatic and vegetative phenomena during sleep.
Chorea caused by lithium intoxication: A case report and literature review
Authors: Podskalny Gerald D. , Factor Stewart A.
Published: December 2004

We report a patient who developed an acute, reversble, generalized choreiform disorder from lithium (Li) intoxication. This medication was prescribed for manic‐depressive disorder, and serum levels became elevated after the addition of a diuretic for the treatment of hypertension. There were no other apparent causes for the movement disorder, and it was associated with other known features of Li intoxication, including ataxia and encephalopathy. There was a delay between the intial symptoms of Li intoxication and the onset of chorea. The chorea improved as serum Li levels diminished, with some lag time. This represents the eleventh case report of Li‐induced chorea, but only the sixth in a patient without concomitant neuroleptic therapy, and the first presented with videotape confirmation. A review of these other cases is included, and possible mechanisms are discussed.
A double‐blind, placebo‐controlled study of intranasal apomorphine spray as a rescue agent for off‐states in Parkinson's disease
Authors: Dewey Richard B. , Maraganore Demetrius M. , Ahlskog J. Eric , Matsumoto Joseph Y.
Published: December 2004

Nine patients with advanced levodopa‐responsive Parkinson's disease were enrolled in a double‐blind, placebocontrolled crossover trial of intranasal apomorphine as rescue therapy for parkinsonian off‐states. Patients were assigned in random order to each of four possible combinations of apomorphine, trimethobenzamide antiemetic, and their matched placebos and received detailed in‐office motor scoring during each of the four study periods. Patients also completed diaries describing the effectiveness of the nasal spray for reversing off‐states. A statistically significant reduction in the Unified Parkinson's Disease Rating Scale (UPDRS) motor score was seen following active apomorphine during in‐office evaluation visits but not following placebo nasal spray. Patient diaries revealed that active apomorphine had a latency to onset of 11 minutes and a duration of 50 minutes. Significant nausea from apomorphine spray was seen in only one patient whereas nasal irritation was disabling in three and mild in two. We conclude that intranasal apomorphine is an effective rescue agent for parkinsonian off‐states although nasal irritation is a limiting factor.
Total structural assignment and absolute configuration of terreinol by 13C and 1H NMR
Authors: de Macedo Fernando César , Marsaioli Anita Jocelyne
Published: December 2004

The carbon–carbon connectivity of terreinol, a new metabolite isolated from Aspergillus terreus, and its previous 13C assignments were confirmed by a two‐dimensional INADEQUATE experiment using a few milligrams of the compound with natural 13C abundance. The carbon–carbon correlations were determined by computational analysis (with >99% probability) of this experiment. Additionally, the absolute configuration of terreinol was achieved indirectly via its corresponding secondary alcohol by the modified Mosher method allied to conformational analysis. The shielding effect of the phenyl group of methoxytrifluoromethylphenylacetic acid (MTPA) on the substituents of the carbonylic centre gave a fully regular ΔδSR sign distribution, allowing reliable assignment of the R configuration for terreinol. Copyright © 2004 John Wiley & Sons, Ltd.
Proton MR CSF analysis and a new software as predictors for the differentiation of meningitis in children
Authors: Subramanian Arunachalam , Gupta Abhishek , Saxena Swapnil , Gupta Ashish , Kumar Raj , Nigam Anjali , Kumar Rashmi , Mandal Sudhir K. , Roy Raja
Published: December 2004

This article describes proton MR spectroscopic analysis of cerebrospinal fluid of 167 children suffering from meningitis and 24 control cases. Quantification of 12 well‐separated and commonly observed cerebrospinal fluid metabolites viz., β‐hydroxybutyrate, lactate, alanine, acetate, acetone, acetoacetate, pyruvate, glutamine, citrate, creatine/creatinine, glucose (total) and urea was carried out using Bruker's NMRQUANT software with respect to a known concentration of sodium‐3‐(trimethylsilyl)‐2,2,3,3‐d4‐propionate (TSP), serving as an external reference. The assignment of urea in CSF is reported for the first time by NMR. The presence of cyclopropane, observed for the first time in tuberculous meningitis overall in 85.1% of cases, acts as a finger‐print marker for the differential diagnosis. Multivariate discriminant function analysis was carried out for the proton MR‐detected metabolite information and the clinical symptoms data of the meningitis and control cases to find the important descriptors for classification, followed by a re‐validation of the entire database. It was found that the control could be differentiated from the disease group with a success rate of 96.4%, followed by the differential diagnosis of tuberculous meningitis with a corresponding value of 77.2%. Excluding the presence of cyclopropane, bacterial meningitis could be classified 84.4% correct and viral meningitis with a rate of 83.3%. It is proposed that the NMR spectroscopic information, along with other routine clinical features, may serve as an additional diagnostic tool for the differential diagnosis of meningitis in children. Copyright © 2004 John Wiley & Sons, Ltd.
Effect of hydrostatic pressure on polyethylene melt rheology
Authors: Westover R. F.
Published: December 2004

A description is given of the procedure and equipment used for the purpose of studying the effect of hydrostatic pressure upon the capillary flow properties of polymer melts. Flow properties are reported for a low density polyethylene over a wide range of temperatures, die sizes, different pressures and hydrostatic pressures.
An empirical method for … The prediction of liquid permeation in polyethylene and related polymers
Authors: Salame Morris
Published: December 2004

Permeability properties depend on the size, shape and polarity of the permeating molecule. Permeability of organic liquids, polar or non‐polar, can be quite accurately predicted if the chemical composition of the permeant is known. By the choice of an arbitrary value (unity) as an indicator for the carbon atom, numbers specific to each structural element of the permeating molecule can be computed from previous experimental data. These numbers, herein called “Permachor” values (π), then combine by simple addition to relate the logarithm of a liquid's permeation in polyethylene.
A study of the finish mechanism: Glass to finish, finish thickness and finish to resin
Authors: Eakins William J.
Published: December 2004

A solution of substituted alkyl alkoxy silanes was applied to E‐glass filament strands before forming glass‐resin composite hoops, which were tested to relate changes in hoop physical properties to the nature of the coupling agent‐size application. Continuously heat cleaning E‐glass in oxygen‐enriched air gives a strand that, when properly coated with size and laminated, makes a hoop with superior strength and modulus properties.
Transitions in polymers by nuclear magnetic resonance¨ a study ¨
Authors: Woodward A. E.
Published: December 2004

The principles of nuclear magnetic resonance, NMR, are briefly reviewed and the use of proton resonance for the study of segmental motion in solid high polymers is outlined. Studies of the temperature dependence of NMR spectra have shown that both completely amorphous and partially crystalline polymers exhibit NMR line narrowing processes at temperatures near the respective glass transition temperature due to increased segmental motion. The presence of small molecules, such as H2O or D2O in the polyamides, or a change of tacticity to a greater isotatic content, such as for poly(methyl methacrylate), is found to lower this line narrowing process on the temperature scale. Heating of polyethylene single crystal aggregates at temperatures somewhat below the melting point also leads to a decrease in temperature for this line narrowing process, presumeably due to the introduction of defects in the polymer crystals. In the ⩽ 77°K to 200°K region numerous polymers having methyl and methyl group containing side chains are found to exhibit line width and second moment dispersions, attributed to methyl group rotation. If the methyl group is attached to a phenyl or ester side chain, methyl rotation takes place at 77° K and below.
Olefin–substituted silicas as active fillers for polymers
Authors: Neimark I. E. , Chuiko A. A. , Slinyakova I. B.
Published: December 2004

Silicas have been synthesized of which the OH groups have been substituted for organic radicals with double bonds. The methanol, benzene and heptane sorption isotherms of the olefin‐substituted silica specimens have been determined. It has been shown that the sorption of the vapors decreases with increasing substitution of the OH group by the organic radicals. The organosubstituted silicas were used as fillers of polymethylmethacrylate.
The use of microscopy to aid surface coating evaluation
Authors: Lindquist J. A. , Widmer V. E. , McKinley G. G.
Published: December 2004

By observing the surface and internal portions of a film with an electron microscope, information is obtained about the binder structure, pigment distribution and compatibility of the plasticizer. On a larger scale the light microscope can detect imperfections in vortex cells, which can be eliminated by proper solvent formulation, and crystalline bloom which is influenced by plasticizer and light polymer migration. When plasticizer exudes to the surface the durability of the coating is lowered in the two types of exposure, the difference of which can be determined by plasticizer migration.
Chromatographic fractionation of polyolefins
Authors: Guillet J. E. , Combs R. L. , Slonaker D. F. , Summers J. T. , Coover H. W.
Published: December 2004

The results compare favorably with those obtained by careful refractionation of fractions isolated by the precipitation method. A convenient parameter, U, related to the breadth of the molecular weight distribution can be calculated from the slope of the log‐probability plot. When the plot is linear, U, is numerically equal to the ratio Mw/Mn. Values of U obtained for a number of commercial and experimental polypropylenes indicate that, with a given type of polypropylene, the breadth of the distribution increases as the average molecular weight of the sample increases, and that wide differences in distribution can be expected from polymers made by different processes.
Evaluation of brittle failures of polyethylene by subjection to biaxial stress
Authors: McFedries R. , Brown W. E. , McGarry F. J.
Published: December 2004

First and second order effects of density and melt index were found to be significant with stress level a significant factor in determining failure time using Maltese Cross shaped specimens. Stress and temperature had the greater influence on failure. Influence of temperature‐viscosity interaction is of concern along with transition in the mode of failure from ductile to brittle type. Reduction in the effect of melt index with increasing density is in accord with new theories on polyethylene crystal structure. It was also shown that higher modulus materials fail more rapidly.
An evaluation of polypropylene by dynamic mechanical tests
Authors: Maxwell Bryce , Heider James E.
Published: December 2004

The loss factor ratio is dependent upon temperature and the rate of change of mechanical load or frequency of the oscillatory loading. The limit of linear viscoelastic response is another variable which occurs at the break in the stress‐strain curve. If storage modulus varies slightly, with magnitude of stress or strain, the data is considered linear viscoelastic. The only true test is in the limit of zero strain and independent modulus. Polypropylene's dynamic properties are most dependent on test temperature. The loss factor peak which can be controlled by temperature and pressure history during crystallization is an indication of the ductile‐brittle transition point.
Physical properties of ethylene‐1‐olefin copolymers
Authors: Folt V. L.
Published: December 2004

With the advent of the newer catalyst systems it is now possible to prepare copolymers of ethylene and 1‐olefins possessing useful physical properties. A wide range of physical properties is readily achieved through variations in the concentration and type of 1‐olefin used as the comonomer. The era of tailor‐making ethylene type polymers to fit any specification regarding stiffness, strength and melt flow properties is now at hand. A comparison of physical properties of ethylene/1‐olefin copolymers with those of the corresponding polyethylene/poly (1‐olefin) blends indicates true copolymers are formed.

Decrease in crystallinity of copolymers is due to the number of branch sites introduced into the main chain rather than to the bulk of the comonomer or the length of side chain.
The relative stability of cation impurities and silica fiber surfaces
Authors: Eakins William J.
Published: December 2004

The effects of heat soaking and leaching with HCl at pH 6.0, 5.0 and 4.0 of five fiber glass formulations are investigated. Silane coupling agents are applied and acid titration is used to determine the specific ions reacting and the approximate quantity reacted. Fiber glass surfaces are largely uncovered, and bare glass reactivity can be determined if a non‐ionic alkoxy silane is applied. While aqueous applications of a silane covers only a proportion of the silica sites, a vapor phase application covers a proportion of all reactive cation sites. With nonporous silica a large propotion of the amphoteric and alkali impurities are on the surface.
Anomalous flow behavior of high density polyethylene melts
Authors: Metzger A. P. , Hamilton C. W. , Merz E. H.
Published: December 2004

Attempts to operate plastic processing equipment at higher production rates is often accompanied by erratic flow behavior of the polymer melts. In order to study this problem, a constant‐rate, capillary rheometer was used to study the melt flow over a wide range of shear rates. These data demonstrate that many high‐density polyethylenes exhibit a discontinuous shear‐stress shear‐rate curve; that is, under certain conditions the observed load oscillates “between two values differing by about 15%”. This region of unstable melt flow is not necessarily allied with melt fracture although it is dependent on molecular weight and melt temperature. Unstable melt flow occurs at lower shear rates with a decrease in the melt index (increase in molecular weight) or melt temperature.
Some bonding characteristics of nitrile‐phenolic liquid adhesives
Authors: Rice Rip G. , Hay Wallace S. , Bell Landon , Toothaker Wallis L. , Perkins Dee M.
Published: December 2004

It is demonstrated that the bonding characteristics of commercial liquid adhesive primers made from nitrile rubbers and phenol‐formaldehyde polymers, cured by means of hexamethylenetetramine can be quite sensitive to the presence of small amounts of excess water and ammonia. The added water partially decomposes the hexamethylenetetramine to formaldehyde and ammonia, the concentration of the latter thus increasing to such a point as to promote a lower temperature curing of the phenolic resin. Restoration of the original adhesive properties can be attained by the addition of reagents which remove either the water or the ammonia, or both, from the adhesive. Examples of such reagents are certain organic acids, anhydrides and peroxides. The addition of these reagents has been found to reactivate and increase greatly the useful lives of nitrile‐phenolic liquid adhesive primers containing hexamethylenetetramine.
Progress in high polymer science and technology
Authors: Melville H. W.
Published: December 2004

Thoughts on the development of theoretical approaches that would help make progress more certain in the polymer field are developed by a British polymer scientist of international reputation.
Structure property relationships of chlorinated polyethylene
Authors: Oswald H. J. , Kubu E. T.
Published: December 2004

Resin structures available from chlorinated polyethylene have been determined by studies of the infrared absorption spectra, and have been related to the glass transition temperatures and degree of crystallinity of the products. The relationships between chlorine content, molecular weight, glass transition temperature and a number of mechanical and rheological properties are described. Data are presented on the effect of blends of various resins in this series on glass transition phenomena. The stability of the resins to dehydrochlorination is discussed.
Polymers and telomers of 4‐chloroperfluoroheptadiene‐1,6
Authors: Fearn James E. , Wall Leo A.
Published: December 2004

The polymer was prepared by pyrolyzing the sodium salt of 3,5,7,8,‐tetrachloroperfluoro‐octanoic acid and subsequent dechlorination of the resulting heptene with activated zinc. The heptadiene was separated from other dechlorination products and brought to a high degree of purity through use of vapor phase chromatography and polymerized in bulk utilizing gamma rays at room temperature, 100°C and 150°C, and utilizing ultraviolet light at 150°C. The properties of these brittle and glossy polymers were determined. Also the purified 4‐chloroperfluoroheptadiene‐1,6 was telomerized with dibromodifluoromethane yielding a cycle, clear, colorless, liquid telomer.
Evaluation methods for ablative plastics. A review of the techniques used
Authors: Schmidt Donald L. , Schwartz Herbert S.
Published: December 2004

A determination of the performance indices of ablative plastics is indeed a formidable task because of the severity of the high‐temperature test environment, nonstandard test methods, limitations of available evaluation facilities and the complex interrelationship between materials performance and environmental parameters. In spite of these difficulties, considerable progress has been made in establishing new test methods for evaluating very high‐temperature (ablative) plastics. This article describes the test facilities and measurement techniques available for obtaining research and design data on ablative plastics.
Properties of high density polyethylenes with bimodal molecular weight distribution
Authors: Zabusky H. H. , Heitmiller R. F.
Published: December 2004

The effect of a bimodal molecular weight distribution on the flow properties and stress crack resistance of polyethylene is investigated. It is found that the melt viscosity of a bimodal polyethylene is less shear dependent at high shear rates than a log normal distribution of equivalent weight average molecular weight and ratio of weight average to number average molecular weight. Spiral mold studies indicate that the bimodal polymer flows more readily under injection molding conditions. The stress crack resistance of the bimodal polymer is shown to be superior to other polyethylenes of the same weight average molecular weight.
The transparency of crystalline polymers
Authors: Pritchard Ruth
Published: December 2004

Much past confusion has originated from attempts to describe the complete optical properties of a plastic in terms of a few ill‐defined parameters. Simple light‐scattering theory and studies of morphology have been combined in this article to suggest the causes of polymer opacity; methods cited for the improvement of transparency and properties of reflectance have been re‐examined in this light. It is concluded that the optical properties displayed by a polymer which is allowed to crystallize without external stress depend on fundamental molecular and morphological parameters. The extent to which these inherent characteristics can be modified depends on such widely different factors as the Tg of the polymer and the physical form of the desired article.
The interface microscopy of crystalline linear high polymers
Authors: Sullivan P. , Wunderlich B.
Published: December 2004

Solution‐grown crystals of polyethylene may reach lateral dimensions large enough for optical microscopy. Interference microscopy represents, in this case, a suitable method of observation of morphology and defects as well as quantitative determinations. The double‐beam interference method used in the Baker type microscope has been applied to determine refractive indices and lamellar thicknesses. The Nomarski double‐beam interferometer has been used for hot‐stage experiments. Multiple‐beam techniques involving silvering of crystal surfaces and using an ordinary light microscope for observation have been developed. The applicability of the different types of interference microscopy to polymer research is illustrated in a series of representative photomicrographs of polyethylene.
Theoretical aspects of polymer morphology— crystallization from solution
Authors: Price Fraser P.
Published: December 2004

Investigation of the crystallography of the thin platelike polymer crystals precipitated from dilute solution has led to the concept of chain folding in polymer crystallization. This unexpected and unusual phenomenon has produced much speculation about both its origin and its implications concerning the morphology of the polymer crystals. The theories which have been proposed to account for the observed effects fall into two categories: (a) equilibrium theories; and (b) kinetic theories. At the moment the kinetic theories appear to be the more successful in explaining the observed morphology and behavior of the polymer crystals. Essentially it is proposed that the plate‐like habit of the crystals results from the formation of crystal uncleii from single polymer molecules followed by a growth process whose rate is controlled by nucleation of new crystal layers on existing completed crystal faces. Quantitative observations of crystal growth rates and of the influence of supercooling on the thickness of the crystals are consistent with the predictions of these theories.
Structural interpretations of mechanical properties of polycrystalline polymers
Authors: Stein R. S.
Published: December 2004

Structural changes are considered in light of the two differing views of the structure of crystalline polymers involving either a two phase structure or a single phase structure involving detects. A compromise picture is proposed which appears consistent with existing experimental evidence. Optical methods are described for analyzing structural changes accompanying deformation of these polymers. These include x‐ray diffraction, static and dynamic birefringence measurements and dynamic light scattering studies. The results are consistent with a two stage deformation process involving first the elastic deformation of a spherulitic or crystalline structure followed by an internal rearrangement of crystals within this structure, taking place by a number of mechanisms such as recrystallization, defect migration, plastic flow and crystal rotation. The time dependence of some of these processes is studied and related to structural features.
How to improve glass cloth laminates
Authors: Oswald R. C.
Published: December 2004

The combination fo dicyandiamide and diaminodiphenyl sulfone in the presence of a tertiary amine, like 2,4,6‐tris (dimethyl amino methyl) phenol, will crosslink liquid epoxy resins (E.E.W. 180‐200) of diglycidyl ether of Bisphenol A type, or brominated resins, and if used to impregnate glass cloth will produce printed circuit laminated boards combining interlaminar bond and flexural strength retention of NEMA‐G‐10 and G‐11 grades.
Auxiliary stabilizers for plasticized polyvinyl chloride
Authors: Barnes W. A. , Franke N. W.
Published: December 2004

More than seventy materials were examined for their ability to improve the performance of DTDP plasticized PVC wire formulation in a modified 105°C wire oven aging test. Twenty of these were as effective as the widely used Bisphenol A, four of which were effective at a lower concentration.
Plastics processing and fabricating problems involving membranes and rotational symmetry
Authors: Alfrey Turner
Published: December 2004

Equations of equilibrium can be used as tools to convert observations of plastic processing operations into a complete process analysis, including the interpretation of simulated fabrication experiments. If material properties of the plastic are known under the fabrication conditions, a predictive process analysis can be made, yielding such data (in the case of extrusion) as membrane thickness and radial velocity. Such predictive analyses also may be used to develop valuable insights into thermoforming operations by means of simulation experiments.
Heat‐resistant epoxy‐boroxine foams for high temperature applications
Authors: Chen H. H. , Nixon A. C.
Published: December 2004

Foams are produced by mixing an epoxy resin, a primary polyamine and a trialkoxyboroxine without applied heat. The reaction heat evolved, predominantly from the reaction between the boroxine and the amine, speeds up the gelation of the epoxy resin and simultaneously evaporates methanol, a by‐product, to form the foam, leading to the formation of a highly crosslinked polymer. A theory for the mechanism involves the chemical properties of intermediates, the basicity of the nitrogens, the acidity of the borons, and the mode of curing of the epoxy resin. The physical properties can be varied using different epoxies, amines and boroxines and different proportions. With a typical mixture, the foams produced have densities and thermal conductivities similar to polystyrene foam but have heat resistance up to 300°C. Adhesion to various substrates is excellent. Compression strengths are low but can be increased by the addition of fillers. The foams are self‐extinguishing. Potential applications and method of dispensing the foams are suggested.
“Dynamic mechanical properties of polymers‥ a review”
Authors: Silberberg Melvin
Published: December 2004

There has been a marked increase in the interest shown in the field of characterization of polymeric materials via dynamic techniques, so much so that symposia devoted exclusively to “dynamic” properties of materials are now commonplace (1, 2). This article provides both a frame of reference with regard to the wide variety of “dynamic” test techniques now in use, and…as well…dynamic test data for a wide range of polymers. Particular emphasis will be placed upon the difference in function of varying test techniques and the applicability of data obtained for specific R & D vs engineering applications. For the purposes of the presentation an arbitrary distinction will be made between “dynamic” tests of the cyclic type and “dynamic” tests of the unidirectional type.
Thermal degradation of polytetrafluoroethylene in a closed system. Effect of the nature of the surface of the reaction vessel wall
Authors: Jellinek H. H. G. , Kachi H.
Published: December 2004

The thermal degradation of polytetrafluoroethylene has been investigated in a closed system as a function of the nature of the surface of the reaction vessel wall. Reproducible results cannot be obtained in a stainless steel vessel as metal fluoride is continuously formed and a stable fluoride is not formed on the wall. Quartz spoon reaction vessels coated with calcium fluoride give a few reproducible runs, before the coating has to be renewed. If the dimerization of the monomer, which takes place very rapidly around 600°C, is considered, first order rates are obtained up to about 75% monomer formation. The kinetics is briefly discussed on the basis of random initiation followed by depropagation with a relatively short kinetic chain length and disproportionation as termination reaction.