bluuebunny/crossref_metadata_2025 huggingface dataset:
Association of the muscarinic cholinergic 2 receptor (CHRM2) gene with major depression in women
Authors: Comings David E. , Wu Sujihan , Rostamkhani M. , McGue Matt , Iacono William G. , MacMurray James P.
Published: October 2002

Cholinergic neurons have been implicated in depression and in the disorders of REM sleep in depression. We examined a common A‐> T 1890 polymorphism in the 3′ UTR of the cholinergic muscarinic receptor 2 (CHRM2) gene. There was a significant increase in the frequency of 11 homozygotes in 126 women with major depression (43.7%) compared to 304 women without major depression (25.7%), P = .001. There was no increase in the frequency of 11 homozygotes in 52 men with depression (26.9%) compared to 278 men without depression (27.7%). Regression analysis, scoring subjects with the 11 genotype as 1, and those with other genotypes as 0, showed that in women r2 = .030, F = 13.37, P = .0003. By contrast, in men r2 = .00001, F = 0.002, P = .96. These results are consistent with a gender‐specific role of the CHRM2 gene in depression in women. © 2002 Wiley‐Liss, Inc.
Predicting the risk of cystic fibrosis with abnormal ultrasound signs of fetal bowel: Results of a French molecular collaborative study based on 641 prospective cases
Authors: Muller F. , Simon‐Bouy B. , Girodon E. , Monnier N. , Malinge M.C. , Serre J.L. ,   and the French Collaborative Group
Published: October 2002

Hyperechogenic fetal bowel is prenatally detected by ultrasound during the second trimester of pregnancy in 0.1–1.8% of fetuses. It has been described as a normal variant but has often been associated with severe diseases, notably cystic fibrosis (CF). The aim of our study was to determine the risk of CF in a prospective study of 641 fetuses with ultrasonographically abnormal fetal bowel and the residual risk when only one mutation is detected in the fetus. Fetal cells and/or parental blood cells were screened for CFTR mutations. Two screening steps were used, the first covering the mutations most frequently observed in French CF patients (mutation detection rate of 70–90%) and, when a CF mutation was detected, a DGGE‐sequencing strategy. We observed a 3.1% risk of CF when a digestive tract anomaly was prenatally observed at routine ultrasound examination. The risk was higher when hyperechogenicity was associated with bowel dilatation (5/29; 17%) or with the absence of gall bladder (2/8; 25%). The residual risk of CF was 11% when only one CF mutation was detected by the first screening step, thereby justifying in‐depth screening. Mutations associated with severe CF (ΔF508 mutation) were more frequently observed in these ultrasonographically and prenatally detected CF cases. However, the frequency of heterozygous cases was that observed in the normal population, which demonstrates that heterozygous carriers of CF mutations are not at increased risk for hyperechogenic bowel. In conclusion, fetal bowel anomalies indicate a risk of severe cystic fibrosis and justify careful CFTR molecular analysis. © 2002 Wiley‐Liss, Inc.
Heterogeneity for congenital generalized lipodystrophy in seventeen patients from Oman
Authors: Rajab Anna , Heathcote Kirsten , Joshi Surendra , Jeffery Steve , Patton Michael
Published: October 2002

Seventeen children with congenital generalized lipodystrophy or Berardinelli‐Seip Congenital Lipodystrophy (BSCL) from 12 consanguineous sibships were observed in Oman. All children had widespread absence of adipose tissue from infancy together with apparent muscle hypertrophy and hepatomegaly. They did not appear to represent a single homogenous entity, and it was possible to subclassify the cases into two distinct groups. In the first group of seven cases, the features were similar to other published cases with acanthosis nigricans, raised insulin levels, and insulin resistance. In this group, there was an association between the degree of acanthosis nigricans and the severity of the disorder. Molecular analysis of these cases showed homozygosity at the BSCL2 locus on chromosome 11q13 in four of the seven cases. In the second group of ten cases, there were striking abnormalities in both skeletal and nonskeletal muscle. Reduced exercise tolerance and percussion myoxedema were observed in skeletal muscle, while infantile hypertrophic pyloric stenosis, prominent veins (phlebomegaly), disturbance of cardiac rhythm, and cardiomyopathy were observed in nonskeletal muscle. There was evidence against homozygosity in some cases for the known loci for BSCL, and this group may represent a new clinical syndrome with lipodystrophy at a different genetic location. © 2002 Wiley‐Liss, Inc.
No evidence for phenotypic variation between probands in case‐control versus family‐based association studies of schizophrenia
Authors: Malhotra Anil K. , Bates John A. , Jaeger Judith , Petrides Georgios , Robinson Delbert G. , Bilder Robert M. , Nassauer Katharine W.
Published: October 2002

Traditional case‐control genetic association studies utilizing unrelated probands are often used interchangeably with family‐based designs to detect genes for complex psychiatric disorders. This strategy may be limited, however, if significant phenotypic variation exists between probands enrolled in these two types of studies. The present study compared 37 probands enrolled in a case‐control study of schizophrenia with 37 age‐, sex‐, and ethnically matched probands enrolled in a family‐based study of schizophrenia. Age of onset of illness was compared as well as performance on a battery of cognitive tests assessing attention, working memory, executive function, and verbal memory. Results revealed no significant differences in age of onset between the two groups or on any measure of cognitive performance. These data do not support reports of significant phenotypic variation between probands in case‐control and family‐based studies, and suggest that studies utilizing family‐based approaches may be used to replicate reports of association made with case‐control designs in schizophrenia. © 2002 Wiley‐Liss, Inc.
Severe lymphedema, intestinal lymphangiectasia, seizures and mild mental retardation: Further case of Hennekam syndrome with a severe phenotype
Authors: Forzano F. , Faravelli F. , Loy A. , Di Rocco M.
Published: October 2002

We report on an Italian patient affected by severe lymphedema of lower limbs, genitalia and face, intestinal lymphangiectasia, seizures, and moderate mental retardation. He has a flat face, flat nasal bridge, and hypertelorism. We propose that he presents with a severe form of Hennekam syndrome. © 2002 Wiley‐Liss, Inc.
Genome‐wide linkage analysis of families with obsessive‐compulsive disorder ascertained through pediatric probands
Authors: Hanna Gregory L. , Veenstra‐VanderWeele Jeremy , Cox Nancy J. , Boehnke Michael , Himle Joseph A. , Curtis George C. , Leventhal Bennett L. , Cook Edwin H.
Published: October 2002

The goal of this study was to identify chromosomal regions likely to contain susceptibility alleles for early‐onset obsessive‐compulsive disorder (OCD). A genome scan was done in 56 individuals from seven families ascertained through pediatric OCD probands; 27 of the 56 subjects had a lifetime diagnosis of definite OCD. Denser mapping of regions on chromosomes 2, 9, and 16 was subsequently done with those subjects and ten additional subjects from the largest family in the study. Direct interviews were completed with 65 of the 66 genotyped individuals. Relatives were interviewed blind to proband status. Of the 65 interviewed individuals, 32 had a lifetime diagnosis of definite OCD. Three of the seven probands had a history of Tourette disorder. Two of the 25 relatives with OCD had a tic history, whereas none of the 33 relatives without OCD had tics. The genome scan consisted of 349 microsatellite markers with an average between‐marker distance of 11.3 centiMorgan (cM). Fine mapping was done with 24 additional markers at an average spacing of 1.6 cM. Parametric and nonparametric linkage analyses were conducted using GENEHUNTER+. The maximum multipoint LOD score with a dominant model was 2.25 on 9p. However, with fine mapping and additional subjects, that LOD score decreased to 1.97. The maximum multipoint nonparametric LOD* score was 1.73 on 19q. The maximum multipoint LOD score with a recessive model was 1.40 on 6p. The results provide suggestive evidence for linkage on 9p and identify regions requiring further study with much larger samples. © 2002 Wiley‐Liss, Inc.
Familial childhood onset neuropathy and cirrhosis with the 4977bp mitochondrial DNA deletion
Authors: McDonald D.G.M. , McMenamin J.B. , Farrell M.A. , Droogan O. , Green A.J.
Published: October 2002

The common 4977 base pair mitochondrial deletion has been identified in association with a number of distinct clinical phenotypes. These include the Kearns‐Sayre syndrome, the Pearson marrow‐pancreas syndrome, and chronic progressive external ophthalmoplegia. We report the clinical and pathological findings in two siblings in whom the 4977 base pair mitochondrial DNA deletion was identified in muscle‐derived mitochondrial DNA. One sibling manifested early onset liver and renal failure, and both developed prominent peripheral sensorimotor neuropathy. These clinical findings have not been previously described in association with the 4977bp mtDNA deletion and thus represent a further expansion of the spectrum of mitochondrial disease. © 2002 Wiley‐Liss, Inc.
Further delineation of cardiac abnormalities in Costello syndrome
Authors: Lin Angela E. , Grossfeld Paul D. , Hamilton Robert M. , Smoot Leslie , Gripp Karen W. , Proud Virginia , Weksberg Rosanna , Wheeler Patricia , Picker Jonathan , Irons Mira , Zackai Elaine , Marino Bradley , Scott Charles I. , Nicholson Linda
Published: October 2002

We review the cardiac abnormalities in 94 patients (27 new, 67 literature) with Costello syndrome, an increasingly recognized syndrome consisting of increased birth weight, postnatal growth retardation, and distinctive facial, skin, and musculoskeletal features (MIM 218040). A cardiac abnormality was found in 59 (63%) patients, with each of three categories occurring in approximately one‐third of patients. A cardiovascular malformation (CVM) was noted in 30%, typically pulmonic stenosis (46% of those with a CVM). Cardiac hypertrophy was reported in 34%, which involved the left ventricle in 50% and was usually consistent with classic hypertrophic cardiomyopathy (HCM). A variety of rhythm disturbances were reported in 33%. Most (74%) were atrial tachycardia that was reported as supraventricular, chaotic, multifocal, or ectopic. Of 31 patients with a rhythm abnormality, 22 (68%) had an additional abnormality, i.e., CVM (4), cardiac hypertrophy (12), or both (6). Nine patients had isolated dysrhythmia, five (56%) of whom died. All of the 12 (13%) patients who died had a cardiac abnormality. One patient died of embryonal rhabdomyosarcoma, but in the remainder, a cardiac cause of death could not be disproved. All patients with Costello syndrome need a baseline cardiology evaluation with echocardiography and Holter monitoring. Additional prospective evaluations, even in patients without apparent cardiac abnormalities, would be prudent, although data are insufficient to propose a specific schedule. © 2002 Wiley‐Liss, Inc.
Linkage of chromosome 13q32 to schizophrenia in a large veterans affairs cooperative study sample
Authors: Faraone Stephen V. , Skol Andrew D. , Tsuang Debby W. , Bingham Stephen , Young Keith A. , Prabhudesai Sarita , Haverstock Susan L. , Mena Felicitas , Menon Aerath Sri Kumar , Bisset Darren , Pepple John , Sautter Fred , Baldwin Charlene , Weiss David , Collins Joseph , Keith Tim , Boehnke Michael , Tsuang Ming T. , Schellenberg G.D.
Published: October 2002

Several prior reports have suggested that chromosomal region 13q32 may harbor a schizophrenia susceptibility gene. In an attempt to replicate this finding, we assessed linkage between chromosome 13 markers and schizophrenia in 166 families, each with two or more affected members. The families, assembled from multiple centers by the Department of Veterans Affairs Cooperative Studies Program, included 392 sampled affected subjects and 216 affected sib pairs. By DSM‐III‐R criteria, 360 subjects (91.8%) had a diagnosis of schizophrenia and 32 (8.2%) were classified as schizoaffective disorder, depressed. The families had mixed ethnic backgrounds. The majority were northern European‐American families (n = 62, 37%), but a substantial proportion were African‐American kindreds (n = 60, 36%). Chromosome 13 markers, spaced at intervals of approximately 10 cM over the entire chromosome and 2–5 cM for the 13q32 region were genotyped and the data analyzed using semi‐parametric affected only linkage analysis. For the combined sample (with race broadly defined and schizophrenia narrowly defined) the maximum LOD score was 1.43 (Z‐score of 2.57; P = 0.01) at 79.0 cM between markers D13S1241 (76.3 cM) and D13S159 (79.5 cM). Both ethnic groups showed a peak in this region. The peak is within 3 cM of the peak reported by Brzustowicz et al. [1999: Am J Hum Genet 65:1096–1103]. © 2002 Wiley‐Liss, Inc.
DRD4 and novelty seeking: Results of meta‐analyses
Authors: Schinka J.A. , Letsch E.A. , Crawford F.C.
Published: October 2002

Studies of the association between polymorphisms within and near the dopamine D4 receptor (DRD4) gene and novelty seeking (NS) have produced inconsistent results, raising questions about the strength of the relationship and the methodological conditions under which the relationship holds. We conducted three meta‐analyses of existing studies to provide formal statistical measures of the strength of the DRD4‐NS relationship. Results provided no support for a relationship between NS and the presence of the 7‐repeat allele of the VNTR polymorphism. A small positive effect, however, was found for long repeats of the same polymorphism. The most promising findings were obtained for the relationship with the −521 C/T promoter polymorphism, for which the analysis showed an effect size of 0.32. The positive findings are consistent with a polygenic model of influence on fundamental personality dimensions. © 2002 Wiley‐Liss, Inc.
Mitochondria, oxygen free radicals, and apoptosis
Authors: Raha Sandeep , Robinson Brian H.
Published: October 2002

Reactive oxygen species (ROS) generated by mitochondria are produced as by‐products of normal oxidative metabolism. The fate of these species is governed by a number of factors that vary from tissue to tissue in mammals and may be involved in the pathogenesis of disease. Reactive oxygen species are also invoked as agents that are important in the processes which become active in cells undergoing apoptosis. Integration of knowledge surrounding these different aspects of ROS generation is difficult and reveals considerable gaps in our understanding. © 2001 Wiley‐Liss, Inc.
Genetic drift and gene flow in a prehistoric population of the Azapa valley and coast, Chile
Authors: Varela Héctor Hugo , Cocilovo Jose Alberto
Published: October 2002

The present paper studies the evolutionary process operating on prehistoric groups from the Azapa valley and coast (northern Chile). The sample consists of 237 crania from the Archaic Late, Early Intermediate, Middle, Late Intermediate, and Late periods. Six metric variables were used, which were transformed to eliminate the special environmental component and to increase the proportion of genetic variance. Population structure was assessed using a method based on quantitative genetic theory, which predicts a lineal relationship between average within‐group phenotypic variance and group distance to the population centroid. Results indicate that 17.5% of the total variance accounts for special environmental variance. An excess in extraregional genetic flow is observed in the population corresponding to the Early Intermediate period in the valley. A reduced differentiation is observed between Archaic and Early Intermediate coastal groups, as well as between the latter and the inhabitants of the valley in the same period. Genetic differences between both areas increased substantially since the Middle period. Evidence indicates that long‐range gene flow was lower on the coast than in the valley, the lowest estimated Fst being 0.0199 for the total population (coast and valley), 0.0111 for the coastal population, and 0.0057 for the valley. Results are discussed in terms of regional archeological and ethnohistorical evidence, and a microevolutionary model is presented to account for the biological history of the population. Am J Phys Anthropol 118:259–267, 2002. © 2002 Wiley‐Liss, Inc.
Alzheimer's neurofibrillary pathology and the spectrum of cognitive function: Findings from the Nun Study
Authors: Riley Kathryn P. , Snowdon David A. , Markesbery William R.
Published: October 2002

The development of interventions designed to delay the onset of dementia highlights the need to determine the neuropathologic characteristics of individuals whose cognitive function ranges from intact to demented, including those with mild cognitive impairments. We used the Braak method of staging Alzheimer's disease pathology in 130 women ages 76–102 years who were participants in the Nun Study, a longitudinal study of aging and Alzheimer's disease. All participants had complete autopsy data and were free from neuropathologic conditions other than Alzheimer's disease lesions that could affect cognitive function. Findings showed a strong relationship between Braak stage and cognitive state. The presence of memory impairment was associated with more severe Alzheimer's disease pathology and higher incidence of conversion to dementia in the groups classified as having mild or global cognitive impairments. In addition to Braak stage, atrophy of the neocortex was significantly related to the presence of dementia. Our data indicate that Alzheimer's neurofibrillary pathology is one of the neuropathologic substrates of mild cognitive impairments. Additional studies are needed to help explain the variability in neuropathologic findings seen in individuals whose cognitive performance falls between intact function and dementia.
A novel D104G mutation in the adenine nucleotide translocator 1 gene in autosomal dominant progressive external ophthalmoplegia patients with mitochondrial DNA with multiple deletions
Authors: Komaki Hirofumi , Fukazawa Toshiyuki , Houzen Hideki , Yoshida Kazuto , Nonaka Ikuya , Goto Yu‐Ichi
Published: October 2002

Autosomal dominant progressive external ophthalmoplegia is a mitochondrial disorder characterized by multiple large deletions of mitochondrial DNA. A recent study showed pathogenic heterozygous missense mutations in the heart/skeletal muscle isoform of the adenine nucleotide translocator 1 gene in autosomal dominant progressive external ophthalmoplegia patients. In one Japanese autosomal dominant progressive external ophthalmoplegia family, we found a novel A‐to‐G heterozygous mutation at nucleotide 311 of the adenine nucleotide translocator 1 gene, which segregated with affected individuals and could not be detected in the genomic DNA sequence of 120 normal controls. This mutation converted a highly conserved aspartic acid into a glycine at codon 104. Polymerase chain reaction analysis of single muscle fibers showed the presence of one type of deletion in each fiber, suggesting clonal expansion of mitochondrial DNA with deletions. These findings support the pathogenesis of the adenine nucleotide translocator 1 gene mutation in human disease.
Focal cortical dysplasia of Taylor's balloon cell type: Mutational analysis of the TSC1 gene indicates a pathogenic relationship to tuberous sclerosis
Authors: Becker Albert J. , Urbach Horst , Scheffler Björn , Baden Thomas , Normann Sabine , Lahl Rainer , Pannek Heinz W. , Tuxhorn Ingrid , Elger Christian E. , Schramm Johannes , Wiestler Otmar D. , Blümcke Ingmar
Published: October 2002

Focal cortical dysplasia (FCD) is characterized by a localized malformation of the neocortex and underlying white matter. Balloon cells, similar to those observed in tuberous sclerosis, are present in many cases (FCDbc). In these patients, a hyperintense funnel‐shaped subcortical lesion tapering toward the lateral ventricle was the characteristic finding on fluid‐attenuated inversion recovery magnetic resonance imaging scans. Surgical lesionectomy results in complete seizure relief. Although the pathogenesis of FCDbc remains uncertain, histopathological similarities indicate that FCDbc may be related pathogenetically to tuberous sclerosis. Here, we studied alterations of the TSC1 and TSC2 genes in a cohort of patients with chronic, focal epilepsy and histologically documented FCDbc (n = 48). DNA was obtained after microdissection and laser‐assisted isolation of balloon cells, dysplastic neurons, and nonlesional cells from adjacent normal brain tissue. Sequence alterations resulting in amino acid exchange of the TSC1 gene product affecting exons 5 and 17 and silent base exchanges in exons 14 and 22 were increased in patients with FCDbc compared with 200 control individuals (exon 5, 2.3% FCDbc vs 0% C; exon 17, 35% FCDbc vs 1.0% C; exon 14, 37.8% FCDbc vs 15% C; exon 22, 45% FCDbc vs 23.8% C). Sequence alterations could be detected in FCDbc and in adjacent normal cells. In 24 patients, DNA was suitable to study loss of heterozygosity at the TSC1 gene locus in microdissected FCDbc samples compared with control tissue. Eleven FCDbc cases exhibited loss of heterozygosity. In the TSC2 gene, only silent polymorphisms were detected at similar frequencies as in controls. Our findings indicate that FCDbc constitutes a clinicopathological entity with distinct neuroradiological, neuropathological, and molecular genetic features. These data also suggest a role of the TSC1 gene in the development of FCDbc and point toward a pathogenic relationship between FCDbc and the tuberous sclerosis complex.
Pallidal stimulation for Parkinsonism: Improved brain activation during sequence learning
Authors: Fukuda Masafumi , Ghilardi Maria Felice , Carbon Maren , Dhawan Vijay , Ma Yilong , Feigin Andrew , Mentis Marc J. , Ghez Claude , Eidelberg David
Published: October 2002

We used 15O‐labeled water and positron emission tomography to assess the effect of deep brain stimulation of the internal globus pallidus on motor sequence learning in Parkinson's disease. Seven right‐handed patients were scanned on and off stimulation while they were performing a motor sequence learning task and a kinematically matched motor execution reference task. The scans were performed after a 12‐hour medication washout. Stimulation parameters were adjusted for maximal motor improvement; experimental task parameters were held constant across stimulation conditions. Internal globus pallidus stimulation improved motor ratings by 37% (p < 0.01). During the sequence learning task, stimulation improved performance as measured by several correct anticipatory movements (p < 0.01) and by verbal report (p < 0.001). Concurrent positron emission tomography imaging during learning demonstrated significant (p < 0.01) increases in brain activation with stimulation in the left dorsolateral prefrontal cortex, bilaterally in premotor cortex, and in posterior parietal and occipital association areas. Stimulation did not affect the activity of these regions during the performance of the motor execution reference task. These findings suggest that internal globus pallidus deep brain stimulation can enhance the activity of prefrontal cortico‐striato‐pallidothalamic loops and related transcortical pathways. Improved sequence learning with stimulation may be directly related to these functional changes.
Early inflammation and dementia: A 25‐year follow‐up of the Honolulu‐Asia aging study
Authors: Schmidt Reinhold , Schmidt Helena , Curb J. David , Masaki Kamal , White Lon R. , Launer Lenore J.
Published: October 2002

Inflammatory responses are associated with cardiovascular disease and may be associated with dementing disease. We evaluated the long‐term prospective association between dementia and high‐sensitivity C‐reactive protein, a nonspecific marker of inflammation. Data are from the cohort of Japanese American men who were seen in the second examination of the Honolulu Heart Program (1968–1970) and subsequently were reexamined 25 years later for dementia in the Honolulu‐Asia Aging Study (1991–1996). In a random subsample of 1,050 Honolulu‐Asia Aging Study cases and noncases, high‐sensitivity C‐reactive protein concentrations were measured from serum taken at the second examination; dementia was assessed in a clinical examination that included neuroimaging and neuropsychological testing and was evaluated using international criteria. Compared with men in the lowest quartile (<0.34mg/L) of high‐sensitivity C‐reactive protein, men in the upper three quartiles had a 3‐fold significantly increased risk for all dementias combined, Alzheimer's disease, and vascular dementia. For vascular dementia, the risk increased with increasing quartile. These relations were independent of cardiovascular risk factors and disease. These data support the view that inflammatory markers may reflect not only peripheral disease, but also cerebral disease mechanisms related to dementia, and that these processes are measurable long before clinical symptoms appear.
Cortical control of spatial memory in humans: The visuooculomotor model
Authors: Pierrot‐Deseilligny Charles , Müri René M. , Rivaud‐Pechoux Sophie , Gaymard Bertrand , Ploner Christoph J.
Published: October 2002

We review current knowledge of the cortical control of spatial memory, studied using visuooculomotor paradigms. Spatial memory is an essential cognitive process that can be involved in preparing motor responses. Our knowledge of spatial memory in humans recently has progressed thanks to the use of ocular saccades as a convenient model of motor behavior. Accuracy of memory‐guided saccades, made to the remembered locations of visual targets, is a reflection of spatial memory. For the performance of memory‐guided saccades with brief delays (up to 15–20 seconds), that is, involving short‐term spatial memory, lesion studies have shown that the posterior parietal cortex, the dorsolateral prefrontal cortex, and the frontal eye field play significant roles. Studies of memory‐guided saccades using transcranial magnetic stimulation have suggested that the right posterior parietal cortex is involved at the initial stage (<300 milliseconds) of visuospatial integration, whereas the dorsolateral prefrontal cortex in both hemispheres controls the following phase of short‐term memorization, the frontal eye field mainly serving to trigger saccades. The new concept of a medium‐term spatial memory has emerged from a behavioral study of memory‐guided saccades in normal subjects, showing a paradoxical spontaneous improvement of spatial memory after delays of approximately 20 seconds. Lesion studies have shown that the parahippocampal cortex could specifically control this medium‐term spatial memory. Last, different experimental and clinical arguments suggest that, after a few minutes, the hippocampal formation finally takes over the control of spatial memory for long‐term spatial memorization. Therefore, spatial memory involved in the memorization of visual items could be successively controlled by the dorsolateral prefrontal cortex (short‐term spatial memory), the parahippocampal cortex (medium‐term spatial memory), and the hippocampal formation (long‐term spatial memory), depending on specific periods of times. The applicability of this simple visuooculomotor model of spatial memory to other types of stimuli and general motoricity has yet to be confirmed.
Miscibility and morphology of poly(vinylidene fluoride)/poly[(vinylidene fluoride)‐ran‐trifluorethylene] blends
Authors: Gregorio Rinaldo , Chaud Matheus Rigobelo , Nunes Dos Santos Wilson , Baldo João Baptista
Published: October 2002

This study presents an investigation of the effect of the different crystalline phases of each blend component on miscibility when blending poly(vinylidene fluoride) (PVDF) and its copolymer poly[(vinylidene fluoride)‐ran‐trifluorethylene] [P(VDF–TrFE)] containing 72 mol % of VDF. It was found that, when both components crystallized in their ferroelectric phase, the PVDF showed a strong effect on the crystallinity and phase‐transition temperature of the copolymer, indicating partial miscibility in the crystalline state. On the other hand, immiscibility was observed when both components, after melting, were crystallized in their paraelectric phase. In this case, however, a decrease in crystallization temperatures suggested a strong interaction between monomers in the liquid state. Blend morphologies indicated that, in spite of the lack of miscibility in the crystalline state, there is at least miscibility between PVDF and P(VDF–TrFE) in the liquid state, and that a very intimate mixture of the two phases on the lamellar level can be maintained upon crystallization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1362–1369, 2002
Preparation and characterization of polystyrene–clay nanocomposites by free‐radical polymerization
Authors: Tseng Chen‐Rui , Wu Jeng‐Yue , Lee Hsin‐Yi , Chang Feng‐Chih
Published: October 2002

The polymerizable cationic surfactant, vinylbenzyldimethylethanolammouium chloride (VBDEAC), was synthesized to functionalize montmorillonite (MMT) clay and used to prepare exfoliated polystyrene–clay nanocomposites. The organophilic MMT was prepared by Na+ exchanged montmorillonite and ammonium cations of the VBDEAC in an aqueous medium. Polystyrene–clay nanocomposites were prepared by free‐radical polymerization of the styrene containing intercalated organophilic MMT. Dispersion of the intercalated montmorillonite in the polystyrene matrix determined by X‐ray diffraction reveals that the basal spacing is higher than 17.6 nm. These nanocomposites were characterized by differential scanning calorimetry (DSC), transmission electron micrograph (TEM), thermal gravimetric analysis (TGA), and mechanical properties. The exfoliated nanocomposites have higher thermal stability and better mechanical properties than the pure polystyrene. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1370–1377, 2002
Effect of radiation on the crosslinking and branching of polypropylene
Authors: Gao Jianming , Lu Yujie , Wei Genshuan , Zhang Xiaohong , Liu Yiqun , Qiao Jinliang
Published: October 2002

To make crosslinked polypropylene (PP) and PP with high melting strengths, we studied the effects of radiation on the crosslinking and branching of PP in detail with the Charlesby–Pinner (C–P) equation. We studied the radiation crosslinking and branching behavior of homopolypropylene (HPP), impact copolypropylene (IPP), and random copolypropylene (RPP) and used the C–P equation for some parameter calculations. We found that (1) the C–P equation seemed applicable when PP with a multifunctional crosslinking agent was irradiated within a certain dose range in air and (2) IPP had the highest gel dose value, crosslinking G value/scission G value, and gel fraction after irradiation among HPP, RPP, and IPP; therefore, IPP is the best material for making radiation crosslinking and radiation branching PP among HPP, RPP, and IPP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1758–1764, 2002
Adhesion of electrochemically formed polypyrrole coatings to low carbon steel
Authors: Iroh Jude O. , Su Wencheng
Published: October 2002

The lap shear strength of polypyrrole coatings formed on low carbon steel (∼ 23 MPa) is shown to be significantly higher (by ∼ 60%) than that obtained using uncoated steel as the adherend. The lap shear (adhesion) strength of polypyrrole‐coated steel varied with the pH of the monomer–electrolyte solution and the applied current. The low carbon steel‐containing polypyrrole coatings formed at low pH (pH ≤ 2.4) have higher adhesion strength than those coated with polypyrrole at higher pH (pH ≥ 6.0). However, poly(N‐methyl pyrrole)‐coated steel showed significantly lower adhesion strength. Increasing the applied current density decreased the adhesion strength. The surface free energies of polypyrrole coatings, ∼ 49–53 mJ/m2 are similar to that obtained for uncoated low carbon steel, ∼ 53 mJ/m2, indicating that polypyrrole will effectively wet low
rbon steel. The extent of wetting of low carbon steel by the coatings was additionally confirmed by an interaction parameter, ϕ, of unity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2757–2763, 2002
Synthesis and properties of high oil‐absorbent 4‐tert‐butylstyrene‐EPDM‐divinylbenzene graft terpolymer
Authors: Zhou Mei Hua , Cho Won‐Jei
Published: October 2002

The graft crosslinking polymerization of 4‐tert‐butylstyrene (tBS) and divinylbenzene (DVB) onto ethylene–propylene–diene (EPDM) was carried out in toluene by using benzoyl peroxide (BPO) as an initiator. The synthesized graft terpolymer, tBS‐EPDM‐DVB (PBED), was extracted with tetrahydrofuran (THF) into gel (called as PBED I) and sol, and then they were identified by infrared (IR) spectroscopy. The effects of solvent amount, molar ratio of DVB to tBS, EPDM content, initiator concentration, reaction temperature, and reaction time on the graft crosslinking polymerization were examined. Among them, solvent amount and molar ratio of DVB to tBS were the important factors for this reaction system. Maximum oil absorbency of PBED I was 84.0 g/g but its oil‐absorption kinetic rate was very low. Sol PBED can be reused as oil absorbent (named as PBED II) through photocrosslinking by ultraviolet light irradiation. Although the oil absorbencies of PBED II were lower than those of PBED I in most cases, their oil absorption kinetic rates were higher than oil absorbencies of PBED I. The highest value of oil absorbency of PBED II was 56.0 g/g. The thermal stability of PBED I was studied by TGA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2119–2129, 2002
Friction of linerboard based on recycled fiber
Authors: Garoff Niklas , Nilvebrant Nils‐Olof , Fellers Christer
Published: October 2002

The purpose of this investigation was to study the origin of the differences in paper‐to‐paper friction of linerboards based on old corrugated containers (OCC). The sheets were subjected to two extraction stages and analyzed with respect to, surface roughness, and their content of low‐molecular‐mass lipophilic compounds (LLC). Friction was measured using a friction tester based on the horizontal plane principle. The surface roughness was measured using a Perthometer profiler and the low molecular mass lipophilic constituent of the paper sheets was determined by gas chromatography‐mass spectroscopy. The sheets were imaged using environmental scanning electron microscopy (ESEM), and the relative compositions of inorganic ions on the paper surfaces were determined by energy dispersive X‐ray spectroscopy (EDS). The results showed that a high amount of LLC in the sheets lead to low friction, due to lubrication. It was also observed that large CaCO3 particles on the surface had a friction‐increasing effect, and that there was no relationship between the surface roughness and the friction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1511–1520, 2002
Crystallization and melting characteristics of metallocene isotactic polypropylenes
Authors: Fujiyama Mitsuyoshi , Inata Hitoshi
Published: October 2002

The measurement of crystallization and melting behaviors under constant rates of cooling and heating and the Avrami's analysis of isothermal crystallization were carried out for various metallocene‐ (MET‐PP) and Ziegler‐ Natta‐catalyzed (ZN‐PP) random polypropylene copolymers with various ethylene contents. Both the melting pointTmand the crystallization temperatureTcdecrease with increasing ethylene content. Compared at the same ethylene content, both are lower for MET‐ PP because of the higher uniformities of stereoirregular bonds and copolymerization bonds.TmandTcshow a linear correlation, and compared at the sameTc,Tmof MET‐PP is lower than that of ZN‐PP. This is because MET‐PP has narrower distributions of isotactic sequence length and hence of lamellar thickness than ZN‐PP. The heat of fusion and the latent heat of crystallization decrease with ethylene content. At the same ethylene content, both are lower for MET‐PP, owing also to the higher uniformities of stereoirregular bonds and copolymerization bonds. From the Avrami's analysis, it is assumed that there is little difference in crystallization modes of both catalyst PPs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1851–1857, 2002
Dynamic mechanical properties of dental base material reinforced with glass fiber
Authors: Karacaer Özgül , Doğan Arife , Doğan Orhan Murat , Usanmaz Ali
Published: October 2002

Dynamic mechanical properties of poly(methyl methacrylate) (PMMA) reinforced with glass fibers were investigated. The composite used as dental base material contained other additives for different purposes to give the same appearance as natural dentals. The fiber–polymer bonding and orientation of fibers in polymer matrix are very important in the application of the product. To see that, the fibers were treated with silane and compared with untreated fibers. The commercial polymer and monomer used were the heat‐cured type. However, in addition to heat curing, γ‐radiation was also used in curing. This gives much improved material in terms of mechanical properties. The voids, which cause mechanical failure in the material, will be minimal in number with irradiation curing. The results showed that the orientation of all fibers were not regular. This could be observed from the micrographs and DMA behaviors of samples. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1683–1697, 2002
Flow behavior of enhanced oil recovery Alcoflood polymers
Authors: Ghannam Mamdouh , Esmail Nabil
Published: October 2002

Flow behavior in terms of shear stress and viscosity versus shear rate is investigated for aqueous solutions of Alcoflood polymer materials. Rheostress RS100 is employed for operating, measuring, and analyzing this experimental investigation. Polymer concentration in the range of 100–10,000 ppm was covered. Fitting analysis is carried out for all the examined polymer solutions. Casson and Ostwald‐de‐Waele correlations can be employed for predicting flow behavior, depending upon polymer type. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2896–2904, 2002
Effect of meta‐dihydroxy benzene as a surface modifier on filler–filler and filler–polymer interaction of carbon black polymer composite
Authors: Ganguly S. , Chakraborty S. , Banerjee A. N. , Bhattacharya P.
Published: October 2002

In the present context an attempt was made to use polyhydroxybenzene on rubber‐grade carbon black to suitably modify the surface morphology and hence to achieve improved thermomechanical and mechanical dynamic properties. FTIR studies clearly point out the presence of excess hydroxyl group in the modified black. The improvement in mechanical properties is attributed to higher crosslink density through hydrogen bonding and oxygen bridge participation during the covulcanization reaction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2025–2033, 2002
Electrical properties of poly(propylene terephthalate)
Authors: Motori Antonio , Saccani Andrea , Sisti Laura
Published: October 2002

Direct current (dc) and alternating current (ac) electrical behavior of a laboratory‐synthesized semicrystalline poly(propylene terephthalate) is investigated. The dc charging/discharging currents and electrical conductivity are studied as a function of temperature and time of applied voltage. The conduction mechanisms are pointed out and related to the structural characteristics of the polymer. The ac properties (dielectric constant and loss factor) are investigated over a wide temperature and frequency range. The relaxation processes, which take place in the material, are disclosed and their origin is analyzed. The electrical behavior of poly(propylene terephthalate) is finally related to that shown by other thermoplastic polyesters. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2271–2275, 2002
Influence of centrifugal field on free‐radical polymerization kinetics
Authors: Boodhoo K. V. K. , Dunk W. A. E. , Jachuck R. J.
Published: October 2002

It has been observed that when a prepolymer mix of styrene, poly(styrene), toluene, and benzoyl peroxide is transferred from a conventional stirred tank reactor (STR) to a spinning disc reactor (SDR), the rate of polymerization is substantially increased. Furthermore, the molecular weight and the molecular weight distribution of the polymer formed at conversions up to about 80% in the SDR is virtually unchanged from that of the polymer formed at 60% conversion in the STR. These results seem to indicate that the increase in polymerization rate is not the result of the well‐known Trommsdorff–Norrish effect, which would be expected to lead to an increase in polydispersity. We believe that shear and centrifugal forces experienced by the film provide intense mixing and extension flow effects, which are responsible for the above‐described observations. In this report an explanation has been put forward to describe the observed effects. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2283–2286, 2002
Synthesis and structure of the poly(methyl methacrylate) microlatex
Authors: Dan Yi , Yang Yunhua , Chen Sanyu
Published: October 2002

Microemulsion polymerization is a new approach for preparing nanosize polymer materials. In this article, a nanosize poly(methyl methacrylate) (PMMA) was prepared by a novel microemulsion polymerization. The kinetics of the polymerization and the effects of the temperature, the monomer, and emulsifier/water ratio on the polymerization were investigated by means of the conversion, the transmittance, and the refractive index measurements. The structure of the obtained PMMA microlatex was studied through transmission electron microscopy (TEM), nuclear magnetic resonance (1H‐NMR), and differential scanning calorimetry (DSC). The results show that the polymerization exhibits typical kinetic characteristics of a microemulsion polymerization, i.e., there only exists two rate stages: a stage of increasing rate, and a stage of decreasing rate, and no constant rate stage is observed during the polymerization. The obtained PMMA microparticles are very uniform, regular, and small, being about 17–33 nm in the number‐average diameter. The polymer has higher molecular weight (1.71 × 106 viscosity average molecular weight), higher tacticity (51% syndiotacticity), and higher glass transition temperature (127°C), much different from the commercial PMMA. Experimentally, a stable and transparent PMMA microlatex with higher polymer content (30–40 wt %), lower weight ratio of emulsifier to water (E/W ≤ 0.03) and emulsifier to monomer (E/M ≤ 0.05) as well as smaller particle size (dp < 40 nm), has been prepared, which is very important for the industrialization of the microemulsion polymerization technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2839–2844, 2002
Controlled release of biocides in solid wood. I. Efficacy against brown rot wood decay fungus (Gloeophyllum trabeum)
Authors: Liu Y. , Laks P. , Heiden P.
Published: October 2002

Nanoparticles containing the fungicides tebuconazole or chlorothalonil were prepared with median diameters of ∼ 100–250 nm. The nanoparticle matrices were polyvinylpyridine (PVP), copolymers of PVP and styrene (PVP‐co‐St), and blends of PVP and hyperbranched polyesters (HBPs). The isolated nanoparticles were resuspended in water to yield suspensions able to deliver 0.1, 0.2, 0.4, and 0.8 kg fungicide/m3 of wood. Southern yellow pine (SYP) was treated with these suspensions using conventional vacuum‐pressure treatments. Less concentrated suspensions delivered the nanoparticles quantitatively into the SYP while suspensions capable of delivering up to 0.8 kg of the fungicide (the active ingredient or AI) per cubic meter of SYP delivered 0.4–0.7 kg AI/m3, depending on the nanoparticle matrix. The SYP lost less than 5% of its mass after 55 days of exposure to Gloeophyllum trabeum when the tebuconazole content in the SYP reached 0.2 kg/m3, and the matrix identity had little effect on the results. The SYP lost between 3 and 6% of its mass after 55 days of exposure to G. trabeum when the AI was chlorothalonil at a level of ∼ 0.6 kg AI/m3 of wood and was introduced into SYP in nanoparticles with a PVP/HBP matrix, but it lost ∼ 11% of its mass at the same AI levels when the nanoparticle matrix was PVP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 596–607, 2002
Solid state polymerization (SSP) of low molecular weight poly(ethylene terephthalate) (PET) copolyesters compared to conventional SSP of PET
Authors: Schiavone Robert J.
Published: October 2002

SSP, starting from very low molecular weight (MW) poly(ethylene terephthalate) (PET) precursors, is claimed to offer significant production cost advantages over conventional PET production. However, as the intrinsic viscosity (IV) of the PET precursor is reduced, there is a significant change in the crystallization behavior of PET and morphology that affects reactivity in SSP. Using small particle size PET to significantly reduce the effects of diffusion so that SSP is under chemical reaction control and using a kinetic model that describes an overall SSP rate, the effect of ethylene isophthalate substitution on the SSP rate from low MW PET precursor was determined. As the ethylene isophthalate comonomer content increases, the rate of SSP for low MW PET increases. The activation energy for SSP of low MW PET decreases with an increase in the ethylene isophthalate content. For the low MW PET copolyesters in this study, the SSP activation energy is comparable to conventional process when the comonomer content of the low MW polyester is around 7 mol % and the conventional precursor is around 3 mol %. However, even though the activation energy is reduced through the use of higher comonomer content, the overall rate of SSP for the low MW copolyesters studied is significantly slower than conventional SSP. This reduction in rate is explained by differences in crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 230–238, 2002
A fluorine gas monitoring system for the direct oxy‐fluorination of polyethylene sheets
Authors: Kasai Toshi , Aya Tetsuya , Ohara Hidehiko
Published: October 2002

A new technique is presented to measure the concentration of fluorine in a reaction gas consisting of fluorine, nitrogen, and oxygen in a reaction chamber. The method is described as follows: The gas is directly taken from the chamber using a peristaltic pump and dissolved in a TISAB (total ionic strength adjusted buffer) solution. The concentration of fluorine ion is measured using the selected fluorine ion electrode, the output voltage of which is monitored. The concentration of the fluorine ion and the output voltage follow the Nernst relation so that the measurement of the output voltage of the system enables us to know the concentration of fluorine gas. This technique was applied to monitor the concentration of fluorine gas in the chamber in which a sheet of polyethylene nonwoven fabric was continuously oxy‐fluorinated. The monitored concentration of the fluorine gas as a function of time coincided with the variation of the incorporated fluorine in the sheet measured by X‐ray fluorescence (XRF) spectroscopy after the treatment. This technique can be best used for process control of the continuous oxy‐fluorination of polymeric materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 684–691, 2002