bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple model adaptive control with safe switching
Authors: Anderson Brian D. O. , Brinsmead Thomas , Liberzon Daniel , Stephen Morse A.
Published: September 2002

The purpose of this paper is to marry the two concepts of multiple model adaptive control and safe adaptive control. In its simplest form, multiple model adaptive control involves a supervisor switching among one of a finite number of controllers as more is learnt about the plant, until one of the controllers is finally selected and remains unchanged. Safe adaptive control is concerned with ensuring that when the controller is changed in an adaptive control algorithm, the frozen plant–controller combination is never (closed‐loop) unstable. This is a non‐trivial task since by definition of an adaptive control problem, the plant is not fully known. The proposed solution method involves a frequency‐dependent performance measure and employs the Vinnicombe metric. The resulting safe switching guarantees depend on the extent to which a closed‐loop transfer function can be accurately identified. Copyright © 2001 John Wiley & Sons, Ltd.
A genetic search approach to unfalsified PI control design for a weigh belt feeder
Authors: Collins Emmanuel G. , Zhao Yanan , Millett Richard
Published: September 2002

This paper proposes and experimentally demonstrates an approach to automated PI tuning for an industrial weigh belt feeder that is based on unfalsified control concepts. Unfalsified control is used here as a means of using either open‐ or closed‐loop test data to identify a subset of controllers (from an initial set) that is not proved to violate the multiple objectives specified by the control engineer. A novel feature of the unfalsified approach is that it allows controllers to be eliminated from consideration by predicting their performance without actually inserting the controllers in the loop. In addition, this methodology does not require an explicit model. However, in practice, it does require some closed‐loop experimentation to determine the cost functions used to perform the unfalsification. When the unfalsified PI autotuning approach is applied to the industrial weigh belt feeder, it is able to successfully identify a subset of PI control laws that meets the performance specs. A key feature of this paper is the use of a genetic search algorithm to reduce the computational requirements of unfalsified control, especially when the initial set of controllers is large. Copyright © 2001 John Wiley & Sons, Ltd.
Experimental investigation of polymer pellets melting mechanisms in corotating twin‐screw extrusion
Authors: Zhu Linjie , Geng Xiaozheng
Published: September 2002

With the visualization corotating twin‐screw extruder, the melting of HDPE pellets under different screw configurations and operational conditions was investigated on‐line. It is shown that the melting progression of polymer pellets in corotating twin‐screw extruders is different from that in single‐screw extruders. Screw configuration, screw speed, and feed rate are three decisive factors in polymer melting. Based on the melting phenomena, a new melting mechanism, island‐sea melting model, was defined. It was found that island‐sea melting model is an important mechanism to realize high efficiency melting progression. The state of polymer, the degree of fill, and the structure of kneading blocks are factors in determining the energy consumption of kneading blocks in melting zone. The conveying of polymer pellets in kneading blocks, in which pellets were compressed and deformed, consumed much more energy than the conveying of polymer melt. This indicates that the control of the deformation of polymer pellets in corotating twin‐screw extrusion is a useful concept in developing new screw elements for high efficiency polymer melting. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 188–200, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10021
Leukemia in relation to occupational exposures to benzene and other agents: A case‐control study nested in a cohort of gas and electric utility workers
Authors: Guénel Pascal , Imbernon Ellen , Chevalier Anne , Crinquand‐Calastreng Anne , Goldberg Marcel
Published: September 2002

Background

Many occupational and environmental exposures have been implicated in the etiology of leukemia, but only a few, such as benzene, are well‐established leukemogens. The risk of leukemia in a large cohort of gas and electricity utility workers with exposures to several suspected or confirmed carcinogens was investigated.

Methods

A case‐control study nested within the cohort was conducted, with 72 leukemia cases identified among male workers, and 285 controls matched to the cases by year of birth. Only cases, and their matched controls, active in the company at the date of diagnosis were included. Exposure assessment was based on a job‐exposure matrix (JEM) developed from expert judgment using a standardized procedure.

Results

The risk of leukemia was increased in workers with an estimated cumulative exposure to benzene ≥ 16.8 ppm‐years (OR = 3.6; 95% CI 1.1–11.7), and there was an indication of a dose‐response relation (OR = 1.2; 95% CI 1.0–1.5 per 10 ppm‐years increase in exposure). The link with benzene was more pronounced for acute leukemia than for chronic leukemia, but no association with a particular leukemia cell type was apparent. The risk of leukemia remained elevated for latency periods of 2, 5, or 10 years.

Conclusions

From our evaluation, it could be estimated that the median TWA exposure to benzene among exposed workers was 0.16 ppm, i.e., within concentration ranges where an increased leukemia risk was usually not apparent in previous epidemiological studies. Although an increased leukemia risk may be real, it may also be related to other occupational factors not totally controlled for in the analysis, or to benzene exposures actually higher than expected. Am. J. Ind. Med. 42:87–97, 2002. © 2002 Wiley‐Liss, Inc.
Injury risks in children of California migrant Hispanic farm worker families
Authors: McCurdy Stephen A. , Samuels Steven J. , Carroll Daniel J. , Beaumont James J. , Morrin Lynne A.
Published: September 2002

Background

Few data are available addressing occupational and other injury risks among children of migrant Hispanic farm workers.

Methods

We conducted the U.C. Davis Farm Worker Injury Study (UCD‐FWIS), a longitudinal follow‐up study of injury among migrant Hispanic farm worker families living in six Northern California Migrant Housing Centers (MHCs). Nine hundred forty‐one children (age < 18 years) were interviewed through parental proxy.

Results

Fifty‐one injuries resulting in medical care or at least one‐half day of lost or restricted work or school time occurred among 49 children (3.8 injuries/100 person‐years). Open wounds (31.4%) and fractures (29.4%) were most common. Falls comprised over one‐third of the cases, followed by being struck and bicycle injuries. Over three‐quarters of subjects never use a helmet when riding a bicycle. Seventy‐eight (8.3%) children reported employment in the preceding year, typically involving manual agricultural tasks. Two injury cases were occupational and involved agricultural work.

Conclusions

Occupational injury was uncommon in this group of children in migrant Hispanic farm worker families. Injury prevention in this population should include a focus on the home and surrounding environment as well as the work place. Am. J. Ind. Med. 42:124–133, 2002. © 2002 Wiley‐Liss, Inc.
Occupational risks and injuries in non‐agricultural immigrant Latino workers
Authors: Pransky Glenn , Moshenberg Daniel , Benjamin Katy , Portillo Silvia , Thackrey Jeffrey Lee , Hill‐Fotouhi Carolyn
Published: September 2002

Background

To investigate occupational health in urban immigrant Latino workers, using a community‐based method.

Methods

A survey was administered through consecutively selected door‐to‐door interviews.

Results

Response rate was 80% (n = 427). Average time in the US was 7.6 years, and average job tenure was 2.8 years. Twenty‐five reported exposures to over 10 different hazards, and 18% thought these hazards had harmed their health. Only 31% received any job safety training; 55% had no workers' compensation coverage. Of the 47 (11%) with a work injury in the past 3 years, 27% reported difficulty obtaining treatment, 91% lost time from work (median = 13 days) and 29% had to change jobs because of the injury. The annual occupational injury rate was 12.2/100 full‐time workers, compared to an expected rate of 7.1.

Conclusions

Urban immigrant workers have increased risk of occupational injuries, with adverse outcomes. Am. J. Ind. Med. 42:117–123, 2002. © 2002 Wiley‐Liss, Inc.
Carpal tunnel syndrome among apprentice construction workers
Authors: Rosecrance John C. , Cook Thomas M. , Anton Dan C. , Merlino Linda A.
Published: September 2002

Background

In terms of lost‐work time and restricted workdays, surgery, and rehabilitation, one of the most costly occupational musculoskeletal disorders is carpal tunnel syndrome (CTS). The purpose of this study was to determine the prevalence of CTS among apprentice construction workers.

Methods

This cross‐sectional study included apprentices from four construction trades. Apprentices completed a self‐administered questionnaire and received electrophysiologic studies assessing median nerve function across the carpal tunnel. A surveillance case definition for CTS was based on characteristic hand symptoms and the presence of median mononeuropathy across the carpal tunnel.

Results

Of the 1,325 eligible apprentices, 1,142 (86.2%) participated in the study. The prevalence of CTS among apprentices was 8.2%; sheet metal workers had the highest rate (9.2%). In operating engineers, the prevalence of CTS was significantly higher (OR = 6.9; 95% CI = 2.6–18.2) among the heavy equipment mechanics than the drivers of those vehicles. Body mass index, age, and self‐reports of working overhead were associated with prevalent CTS. Less than 15% of the apprentices with CTS sought medical attention for their disorder.

Conclusions

Many construction workers begin developing CTS before or during their apprenticeship. Few apprentices seek medical attention for hand symptoms characteristic of CTS. The results of this study indicate a public health need for the implementation of prevention strategies for CTS in the construction industry. Am. J. Ind. Med. 42:107–116, 2002. © 2002 Wiley‐Liss, Inc.
Development of quantitative exposure data for a pooled exposure‐response analysis of 10 silica cohorts
Authors: 't Mannetje Andrea , Steenland Kyle , Checkoway Harvey , Koskela Riitta‐Sisko , Koponen Matti , Attfield Michael , Chen Jingqiong , Hnizdo Eva , DeKlerk Nicholas , Dosemeci Mustafa
Published: September 2002

Background

Comprehensive quantitative silica exposure estimates over time, measured in the same units across a number of cohorts, would make possible a pooled exposure‐response analysis for lung cancer. Such an analysis would help clarify the continuing controversy regarding whether silica causes lung cancer.

Methods

Existing quantitative exposure data for 10 silica‐exposed cohorts were retrieved from the original investigators. Occupation‐ and time‐specific exposure estimates were either adopted/adapted or developed for each cohort, and converted to milligram per cubic meter (mg/m3) respirable crystalline silica.

Results

Quantitative exposure assignments were typically based on a large number (thousands) of raw measurements, or otherwise consisted of exposure estimates by experts (for two cohorts). Median exposure level of the cohorts ranged between 0.04 and 0.59 mg/m3 respirable crystalline silica. Exposure estimates were partially validated via their successful prediction of silicosis in these cohorts.

Conclusions

Existing data were successfully adopted or modified to create comparable quantitative exposure estimates over time for 10 silica‐exposed cohorts, permitting a pooled exposure‐response analysis. The difficulties encountered in deriving common exposure estimates across cohorts are discussed. Am. J. Ind. Med. 42:73–86, 2002. © 2002 Wiley‐Liss, Inc.
Cohort mortality study of Philadelphia firefighters
Authors: Baris Dalsu , Garrity Thomas J. , Telles Joel Leon , Heineman Ellen F. , Olshan Andrew , Zahm Shelia Hoar
Published: September 2002

Background

Fire fighters are exposed to a wide variety of toxic chemicals. Previous studies have reported excess risk of some cancers but have been limited by small numbers or little information on employment characteristics.

Methods

We conducted a retrospective cohort mortality study among 7,789 Philadelphia firefighters employed between 1925 and 1986. For each cause of death, the standardized mortality ratios (SMRs) and 95% confidence intervals were estimated. We also compared mortality among groups of firefighters defined by the estimated number of career runs and potential for diesel exposure.

Results

In comparison with U.S. white men, the firefighters had similar mortality from all causes of death combined (SMR = 0.96) and all cancers (SMR = 1.10). There were statistically significant deficits of deaths from nervous system diseases (SMR = 0.47), cerebrovascular diseases (SMR = 0.83), respiratory diseases (SMR = 0.67), genitourinary diseases (SMR = 0.54), all accidents (SMR = 0.72), and suicide (SMR = 0.66). Statistically significant excess risks were observed for colon cancer (SMR = 1.51) and ischemic heart disease (SMR = 1.09). The risks of mortality from colon cancer (SMR = 1.68), kidney cancer (SMR = 2.20), non‐Hodgkin's lymphoma (SMR = 1.72), multiple myeloma (SMR = 2.31), and benign neoplasms (SMR = 2.54) were increased among firefighters with at least 20 years of service.

Conclusions

Our study found no significant increase in overall mortality among Philadelphia firefighters. However, we observed increased mortality for cancers of the colon and kidney, non‐Hodgkin's lymphoma and multiple myeloma. There was insufficient follow‐up since the introduction of diesel equipment to adequately assess risk. Am. J. Ind. Med. 39:463–476, 2001. Published 2001 Wiley‐Liss, Inc.
An application of hierarchical regression in the investigation of multiple paternal occupational exposures and neuroblastoma in offspring*
Authors: De Roos Anneclaire J. , Poole Charles , Teschke Kay , Olshan Andrew F.
Published: September 2002

Background

We used hierarchical regression to study the effects of 46 paternal occupational exposures on the incidence of neuroblastoma in offspring.

Methods

The study population included 405 cases and 302 controls. The effect of each exposure was estimated using both conventional maximum likelihood and hierarchical regression.

Results

Using hierarchical regression, overall precision was greatly enhanced compared to the conventional analysis. In addition, adjustment of effect estimates based on prespecified prior distributions of the true effect parameters allowed a more consistent interpretation across the entire panel of exposures. Estimates for several metals and solvents were shrunk close to the null value, whereas estimates for several thinner solvents, diesel fuel, solders, wood dust, and grain dust remained moderately elevated.

Conclusions

Hierarchical regression may mitigate some of the problems of the conventional approach by controlling for correlated exposures, enhancing the precision of estimates, and providing some adjustment of estimates based on prior knowledge. Am. J. Ind. Med. 39:477–486, 2001. © 2001 Wiley‐Liss, Inc.
Methyl‐tertiary‐butyl‐ether (MTBE) misclassified
Authors: Mehlman Myron A.
Published: September 2002

Methyl‐tertiary‐butyl‐ether (MTBE) was introduced into motor fuels in 1992 to reduce carbon monoxide automotive emissions in areas where the National Ambient Air Quality Standards for CO were exceeded.

At a meeting of the National Toxicology Program's Board of Scientific Counselors (2–3 December 1998), data were presented showing that exposure to MTBE caused increased incidence of liver tumors, renal adenomas, carcinomas and interstitial cell adenomas of the testes in male, and lymphomas and leukemia in female CD1 mice [National Toxicology Program, 1998]. Despite this evidence, the NTP Board defeated a motion to list MTBE as “Reasonably anticipated to be a human carcinogen” by a vote of 6 to 5. This decision directly contravenes rules and procedures previously established by NTP for assessing carcinogenicity of chemical compounds.

Good public health policy dictates that the NTP Board conduct another review of MTBE with proper consideration of the criteria that have been established for listing agents as carcinogens. Millions of Americans who are exposed daily to this chemical deserve an unbiased evaluation of carcinogenic agents being introduced into the environment. Am. J. Ind. Med. 39:505–508, 2001. © 2001 Wiley‐Liss, Inc.
Occupation and leukemia: A population‐based case—control study in Iowa and Minnesota†
Authors: Blair A. , Zheng T. , Linos A. , Stewart P.A. , Zhang Y.W. , Cantor K.P.
Published: September 2002

Background

Studies have suggested that risk of leukemia may be associated with occupational or industrial exposures and risk may vary by the histological type of the disease.

Methods

A population‐based case—control study was conducted in Iowa and Minnesota to evaluate the association between various occupations, industries, and occupational exposures and leukemia risk. A total of 513 cases and 1,087 controls was included in the study. A lifetime occupational history and other risk factor information were collected through in‐person interviews, and a job‐exposure matrix was used to assess possible risks associated with specific exposures.

Results

A significantly increased risk of leukemia was observed among agricultural service industries and among nursing and healthcare workers. Janitors, cleaners, and light truck drivers also experienced increased risk. Those employed in plumbing, heating and air conditioning industries, and sales of nondurable goods (such as paints and varnishes) had an increased risk. Printers, painters, and workers in the food and metal industries had a nonsignificantly increased risk of leukemia. Analyses by specific exposures and histology of leukemia showed that risk of leukemia associated with occupational or industrial exposures may vary by histological type of the disease.

Conclusions

An increased risk of leukemia among workers employed in agricultural industries, nursing and healthcare workers, and in a few occupations with possible exposure to solvents is consistent with earlier studies. Associations of risk with occupations not observed previously deserve further assessment. Am. J. Ind. Med. 40:3–14, 2001. Published 2001 Wiley‐Liss, Inc.
Respiratory symptoms and lung function in workers in heavy and highway construction: A cross‐sectional study*
Authors: Oliver L. Christine , Miracle‐McMahill Heidi , Littman Andrew B. , Oakes J. Michael , Gaita Raymond R.
Published: September 2002

Background

Occupational exposures for workers in heavy and highway (HH) construction include cement‐containing dusts and diesel exhaust (DE). To investigate possible health effects, respiratory symptoms and lung function were examined in laborers, tunnel workers (TW), and operating engineers (OE) in HH and tunnel construction. The principal outcome of interest was airways disease.

Methods

Subjects were recruited through their unions. Medical and occupational histories and flow‐volume loops were obtained. Based on self‐report, asthma and chronic bronchitis were categorized as (1) physician‐diagnosed or (2) for asthma, undiagnosed likely, and (3) for chronic bronchitis, symptomatic. Trade and time in the union were used as surrogates of exposure. Prevalence of asthma and chronic bronchitis, lung function outcome, and relationships with exposure variables were examined.

Results

Data were obtained on 389 workers: 186 laborers, 45 TWs, and 158 OEs. Prevalence of asthma was 13 and 11.4% for laborers (including TW) and OEs, respectively, and of symptomatic chronic bronchitis, 6.5 and 1.9%, respectively. Odds ratios (OR) for undiagnosed asthma likely were significantly elevated in TWs compared to OEs, and marginally elevated for chronic bronchitis. Inverse relationships were observed between time in the union, and risk for asthma and chronic bronchitis. Asthma (physician‐diagnosed or undiagnosed likely) predicted lower FEV1. Current cigarette use was associated with chronic bronchitis but not asthma.

Conclusions

TWs, laborers, and OEs in HH construction are at increased risk for asthma. TWs also appear to be at increased risk for chronic bronchitis. Our data suggest that symptomatic workers are self‐selecting out of their trade. Asthma was associated with lower lung function in those affected. Am. J. Ind. Med. 40:73–86, 2001. © 2001 Wiley‐Liss, Inc.
Peripheral neuropathy in workers exposed to nitromethane†
Authors: Page Elena H. , Pajeau Aurora K. , Arnold Thomas C. , Fincher Allene R. , Goddard Mark J.
Published: September 2002

Background

Two workers from a headlight subassembly plant developed severe peripheral neuropathy. These workers had extensive, but brief (1–2 months) dermal and inhalational exposure to nitromethane, a solvent.

Methods

Environmental sampling was performed for nitromethane and ethyl cyanoacrylate. Medical records, including electrodiagnostic studies, were reviewed. Literature on nitromethane, ethyl cyanoacrylate, and other exposures in the workplace was reviewed.

Results

Electromyography and nerve conduction studies performed on these patients were consistent with a severe, axonal neuropathy. No etiology was discovered despite an extensive medical evaluation. Environmental sampling revealed exposure to nitromethane at the threshold limit value.

Conclusions

The history of acute onset of severe peripheral neuropathy temporally associated with exposure to nitromethane is suggestive of a toxic neuropathy. While it cannot be definitively concluded that these two workers developed peripheral neuropathy secondary to exposures at work, occupational exposure to nitromethane appears to be the most likely etiology. Am. J. Ind. Med. 40:107–113, 2001. © 2001 Wiley‐Liss, Inc.
Brain size and the human cranial base: A prenatal perspective
Authors: Jeffery Nathan , Spoor Fred
Published: September 2002

Pivotally positioned as the interface between the neurocranium and the face, the cranial base has long been recognized as a key area to our understanding of the origins of modern human skull form. Compared with other primates, modern humans have more coronally orientated petrous bones and a higher degree of basicranial flexion, resulting in a deeper and wider posterior cranial fossa. It has been argued that this derived condition results from a phylogenetic increase in the size of the brain and its subcomponents (infra‐ and supratentorial volumes) relative to corresponding lengths of the cranial base (posterior and anterior, respectively). The purpose of this study was to test such evolutionary hypotheses in a prenatal ontogenetic context. We measured the degree of basicranial flexion, petrous reorientation, base lengths, and endocranial volumes from high‐resolution magnetic resonance images (hrMRI) of 46 human fetuses ranging from 10–29 weeks of gestation. Bivariate comparisons with age revealed a number of temporal trends during the period investigated, most notable of which were coronal rotation of the petrous bones and basicranial retroflexion (flattening). Importantly, the results reveal significant increases of relative endocranial sizes across the sample, and the hypotheses therefore predict correlated variations of cranial base flexion and petrous orientation in accordance with these increases. Statistical analyses did not yield results as predicted by the hypotheses. Thus, the propositions that base flexion and petrous reorientation are due to increases of relative endocranial sizes were not corroborated by the findings of this study, at least for the period investigated. Am J Phys Anthropol 118:324–340, 2002. © 2002 Wiley‐Liss, Inc.
Evolutionary significance of cranial variation in Asian Homo erectus
Authors: Antón Susan C.
Published: September 2002

Homo erectus inhabited a wide geographic area of Asia, ranging from 40° north latitude in China to 8° south latitude in island Southeast Asia. Yet variation within Asian H. erectus and its relation to ecological and temporal parameters have been little studied. I synthesize the revised radiometric chronologies for hominid sites in Asia and their relation to new oxygen isotope curves (proxies for climatic fluctuations and landbridge connections). These data suggest substantial opportunities in the later Pleistocene for both regional isolation and gene flow between hominids in mainland and Southeast Asia. They also suggest that the most northerly located Chinese sites (Zhoukoudian and Nanjing) may have been occupied during sequential, interglacial periods. Probably reflecting these periods of isolation, nonmetric features and principal components analysis (PCA) of calvarial shape suggest regional differentiation between northern Asian and Southeast Asian H. erectus. The most recent Southeast Asian fossils (e.g., Ngandong) conform to the Southeast Asian pattern. Except perhaps in brain size, there is no evidence that the temporally intermediate Chinese fossils are intermediate in morphology between older and younger Indonesian fossils. In fact, northern Chinese calvaria are easier to exclude from the larger Asian H. erectus hypodigm than are the Ngandong fossils. The Chinese specimens differ from the others based on their narrower occipitals and frontals for their cranial size. The Chinese sample from Zhoukoudian alone is thus not a good proxy for the morphology and variation seen within Asian H. erectus. Both the Chinese and late Indonesian samples exhibit less variation than does the early Indonesian sample; this along with their shared morphological bauplan suggests a common origin and no more than subspecific differentiation. This shared morphology, despite regional differences, was likely maintained by the increasing intensity of multiple glaciations (and longer‐lasting land bridge connections) between mainland and island Southeast Asia during the last million years. Am J Phys Anthropol 118:301–323, 2002. © 2002 Wiley‐Liss, Inc.
Normal neuroanatomical variation in the human brain: An MRI‐volumetric study
Authors: Allen John S. , Damasio Hanna , Grabowski Thomas J.
Published: September 2002

Normative data on the in vivo size of the human brain and its major anatomically defined subdivisions are not readily available. In this study, high‐resolution magnetic resonance imaging was used to measure regional brain volumes in 46 normal, right‐handed adults (23 men, 23 women) between the ages of 22–49 years. Parcellation of the brain was based on neuroanatomical landmarks. The following brain regions were measured: the cerebral hemispheres, frontal lobe, temporal lobe, parietal lobe, occipital lobe, cingulate gyrus, insula, cerebellum, corpus callosum, and lateral ventricles. Males tend to be significantly larger than females, for the whole brain and for nearly all of its major subdivisions, including the corpus callosum. However, the proportional sizes of regions relative to total volume of the hemisphere are remarkably similar in males and females. Variation in size of region is always greater than variation in proportional representation. Asymmetries in brain regions are not profound, with the exception of the cingulate gyrus, which is larger in the left hemisphere. Brain regions are highly correlated in size, with the exception of the lateral ventricles. After controlling for hemisphere size, the volumes of the frontal and parietal lobes are significantly negatively correlated. The occipital lobe tends to be less sexually dimorphic than other major lobes, and less correlated with other brain regions for volume. These results have implications for understanding whether or not certain sectors of the brain have shown relative expansion over the course of hominid and hominoid evolution. Am J Phys Anthropol 118:341–358, 2002. © 2002 Wiley‐Liss, Inc.
Dichloroacetate exerts therapeutic effects in transgenic mouse models of Huntington's disease
Authors: Andreassen Ole A. , Ferrante Robert J. , Huang Hsueh‐Meei , Dedeoglu Alpaslan , Park Larry , Ferrante Kimberly L. , Kwon Jennifer , Borchelt David R. , Ross Christopher A. , Gibson Gary E. , Beal M. Flint
Published: September 2002

Dichloroacetate (DCA) stimulates pyruvate dehydrogenase complex (PDHC) activity and lowers cerebral lactate concentrations. In the R6/2 and N171‐82Q transgenic mouse models of Huntington's disease (HD), DCA significantly increased survival, improved motor function, delayed loss of body weight, attenuated the development of striatal neuron atrophy, and prevented diabetes. The percentage of PDHC in the active form was significantly reduced in R6/2 mice at 12 weeks of age, and DCA ameliorated the deficit. These results provide further evidence for a role of energy dysfunction in HD pathogenesis and suggest that DCA may exert therapeutic benefits in HD.
Effects of the fractionated components of the seaweed Hizikia fusiforme Okam. on arsenic metabolism in rats administered a large dose of arsenate
Authors: Katayama Masayuki , Kouya Yukie , Furusawa Chiduru , Sakiyama Chie , Kaise Toshikazu , Sugawa‐Katayama Yohko
Published: September 2002

To investigate factors in the seaweed Hijiki affecting arsenic metabolism in rats, we extracted pulverized Hijiki samples with hot 0.1 M NaOH, and neutralized the extract with HCl. After centrifugation at 10 000 rpm for 30 min, the supernatants and the residues were lyophilized, mixed with cellulose, and added to the standard diet for rats. The rats were divided into three groups as follows: (1) group C, fed the standard diet, (2) group H‐sup, fed a diet containing the extracted soluble fraction, and (3) group H‐rsd, fed a diet containing the residues. After feeding the diets for 12 days, the respective groups were divided into two sub‐groups; one of them was administered a large oral single dose (40% of the LD50) of an aqueous solution of sodium arsenate, Na2AsHO4·7H2O, 24 h before sacrifice. Samples of urine were gathered before and after the administration of arsenate. Arsenic compounds in the urine and serum were analyzed by high‐performance liquid chromatography–inductively coupled plasma mass spectrometry system. The patterns of the arsenic compounds suggested that some Hijiki components accelerated arsenic metabolism, e.g. methylation, in rats. Copyright © 2002 John Wiley & Sons, Ltd.
Accumulation of arsenic by Traustochytrium sp. CHN‐1 from Seto Inland Sea
Authors: Yamaoka Yukiho , Carmona Marvelisa L. , Naganuma Tuyoshi , Jin Kazuo
Published: September 2002

The accumulation of arsenic by Traustochytrium sp. CHN‐1 (Labyrinthulids) was examined by using a medium [2% (w/v) glucose, 0.1% (w/v) yeast extract, 0.1% (w/v) peptone in a half salt concentration of sea water] containing arsenic as As(V), As(III). Traustochytrium sp. CHN‐1 was grown in 1/2 sea water medium [2% (w/v) glucose, 0.1% (w/v) yeast extract, 0.1% (w/v) peptone] containing an arsenate (As(V)) at up to 1000 mg dm−3 and arsenite (As(III)) at up to 50 mg dm3. The cells died even at [As(III)]‐100 mg dm−3. These results suggested that the order of growth inhibition of Traustochytrium sp. CHN‐1 by arsenic was As(III) > As(V). The biomass of Traustochytrium sp. CHN‐1 decreased with an increase of the surrounding arsenic concentration. On the other hand, the arsenic concentration in cells increased with an increase of the surrounding arsenic concentration. Arsenic compounds were extracted with methanol/water (1:1) from a freeze‐dried sample of Traustochytrium sp. CHN‐1. The extracts were analyzed by high‐performance liquid chromatography, with an inductively coupled plasma mass spectrometer serving as an arsenic‐specific detector. Arsenite, arsenate, monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA) and arsenosugar were identified in Traustochytrium sp. CHN‐1. The order of arsenic species in Traustochytrium sp. CHN‐1 was As(V) > DMAA > As(III) > MMAA > arsenosugar at [As]‐10 mg dm−3 in the medium. Detoxification of arsenic by cells was probably achieved by methylation. Copyright © 2002 John Wiley & Sons, Ltd.
Study of in vitro cytotoxicity of arsenocholine, a trimethyl arsenic compound in seafood
Authors: Sakurai Teruaki , Ochiai Masayuki , Kojima Chikara , Kumata Hidetoshi , Fujiwara Kitao
Published: September 2002

We examined the in vitro cytotoxic effects of an organic arsenic compound contained in seafood, viz. the trimethyl (2‐hydroxyethyl)‐arsonium cation, or arsenocholine (AsCho), on some murine immune effector cells, such as splenocytes, thymocytes, Peyer's patch lymphocytes, peritoneal macrophages and bone marrow (BM) cells using synthesized pure material. We found that AsCho had no cytotoxicity on most immune effector cells, even at concentrations over 10 mmol dm−3, and it slightly but significantly enhanced the viability of BM cells at doses over 100 µmol dm−3. This biological effect of AsCho on BM cells might be direct rather than due to autocrine mechanisms mediating some factors secreted by AsCho‐stimulated BM cells, because the culture supernatants of BM cells pre‐stimulated with AsCho did not influence the viability of other fresh BM cells. It is interesting that this unique biological effect was found in AsCho, an organic arsenic compound contained in some marine animals that are ingested daily as seafood in many countries. Copyright © 2002 John Wiley & Sons, Ltd.
Arsenic speciation in whelks, Buccinum undatum
Authors: Lai Vivian W.‐M. , Beach Anda S. , Cullen William R. , Ray Sankar , Reimer Kenneth J.
Published: September 2002

The arsenic species present in the foot muscle of whelks, Buccinum undatum, collected from Newfoundland, Canada, were characterized by using high‐performance liquid chromatography–inductively coupled plasma mass spectrometry. All samples contain high amounts of arsenic, mostly over 100 µg g−1 (as arsenic, dry weight basis), and one sample contained up to 1360 µg g−1. These values are considerably higher than those reported in other gastropods. Speciation studies of representative samples revealed arsenobetaine as the major water‐soluble arsenic compound, together with trace amounts of an arsenosugar. No inorganic arsenic species were detected in the sample extracts, indicating that consumption of the whelks poses little human risk. Copyright © 2002 John Wiley & Sons, Ltd.
Fracture behavior of NR and SBR vulcanizates filled with ground rubber having uniform particle size
Authors: Han Seung‐Cheol , Han Min‐Hyeon
Published: September 2002

The use of recycled rubber including ground scrap vulcanizates in rubber compounds was studied. When ground rubber was incorporated into rubber compounds, the physical properties, especially the tensile strength, were deteriorated compared to the virgin rubber compound. Also, incorporating ground rubber caused a change of the cure behavior via migration of sulfur or an accelerator between the virgin rubber matrix and the ground rubber vulcanizate. In this study, the fracture behavior and abrasion property of carbon black‐filled SBR and NR compounds containing ground rubber vulcanizate were investigated. Also, the effect of the particle size or loading volume of ground rubber powder on those properties was studied. Four different sizes, 420–600, 177–250, 125–150, and 75–88 μm, of ambient ground rubber powder recycled from waste tire were selected and used in the compounding. The loading amounts of ground rubber powder were 10, 30, and 50 phr. The flex crack growth of SBR‐ and NR‐based compounds was altered by the addition of ground rubber particles. More delayed crack growth was observed with an increasing loading volume and decreasing particle size of the ground rubber powders, and this behavior was more prominent in SBR than in NR compounds. Tangent delta, a direct measure of internal energy dissipation, increased with an increasing loading volume of the ground rubber particles. The abrasion rate of ground rubber‐filled compounds was more dependent on the size of the abrasion pattern than on the loading level or particle size of the ground rubber powders. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2491–2500, 2002
Mechanical properties of poly(N‐isopropyl‐acrylamide‐co‐itaconic acid) hydrogels
Authors: Quintana José R. , Valderruten Nora E. , Katime Issa
Published: September 2002

Hydrogels of N‐isopropylacrylamide and itaconic acid were synthesized with different monomer ratios and with two crosslinking agent concentrations. The different xerogels were immersed in water and the swelling process was conducted up to equilibrium conditions at two temperatures (22 and 37°C). These temperatures are lower and higher than the transition temperature shown by PNIPA hydrogels. The mechanical properties of the different solvated hydrogels were examined by oscillatory shear measurements at 22 and 37°C. The copolymer volume fraction and the elastic storage modulus of the hydrogels decreased as the itaconic acid percentage in the copolymer increased. This behavior was attributed to the higher hydrophilic character of the itaconic acid comonomer. Effective crosslinking density, molar mass between crosslinks, and the polymer–solvent interaction parameter were determined from the experimental values of the elastic storage moduli and the copolymer volume fractions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2540–2545, 2002
Poly(1,2‐diaminobenzene) and poly(1,3‐diaminobenzene): Synthesis, characterization, and properties
Authors: Sánchez C. O. , Rivas B. L.
Published: September 2002

Poly(1,2‐diaminobenzene) (1,2‐DAB) and poly(1,3‐diaminobenzene) (1,3‐DAB) have been synthesized by using ammonium persulfate as oxidizing agent in the presence and in the absence of the following metal ion salts: CuCl2, NiCl2, and CoCl2 with different HCl concentrations. The products showed a different content of the metal ion depending on the HCl concentration. The polymers were characterized by Fourier transform infrared (FTIR), ultraviolet‐visible (UV‐Vis) spectroscopy, thermal analysis, and electrical conductivity. The polymerization yield depended on the presence of metal ions that can react as oxidizing reagents and/or catalysts. The polymerization mechanism depended on the position of the substituent. For poly(1,2‐DAB) a ladder‐type structure was obtained, and for poly(1,3‐DAB) one similar to that of polyaniline. The thermal stability increased as the metal ion content in the polymer matrix increased. The electrical conductivity of the polymer did not depend on the metal ion content in the polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2564–2572, 2002
Eucalyptus Kraft pulp fibers as an alternative reinforcement of silicone composites. I. Characterization and chemical modification of Eucalyptus fibers with organosilane coupling agent
Authors: Redondo S. U. A. , Radovanovic E. , Gonçalves M. C. , Yoshida I. V. P.
Published: September 2002

In this study, bleached Eucalyptus fibers obtained by a Kraft pulping process were characterized prior to and after chemical modification with a silane coupling agent, vinyltriethoxysilane, for use as an alternative additive in composites based on silicone. The presence of a silane coating on the fiber surface was observed by infrared, energy dispersive, and X‐ray photoelectron spectroscopies. The morphology of the fibers was investigated by field emission scanning electron microscopy. The untreated fibers were ribbon‐shaped and had a rough surface, due to the presence of fibrils. The coating reaction conducted in ethanol gave rise to loose fibrils and a more rough surface compared with those of untreated fibers. A smoother surface was observed when fibers were modified in tetrahydrofuran. The surface topography of the fibers was also examined by atomic force microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2573–2579, 2002
Fracture behavior of vinylester resin matrix composites reinforced with alkali‐treated jute fibers
Authors: Ray Dipa , Sarkar B. K. , Rana A. K.
Published: September 2002

Jute fibers were treated with 5% NaOH solution for 4 and 8 h, respectively, to study the mechanical and impact fatigue properties of jute‐reinforced vinylester resin matrix composites. Mechanical properties were enhanced in case of fiber composites treated for 4 h, where improved interfacial bonding (as evident from scanning electron microscopy [SEM]) and increased fiber strength properties contributed effectively in load transfer from the matrix to the fiber; but their superior mechanical property was not retained with fatigue, as they showed poor impact fatigue behavior. The fracture surfaces produced under a three‐point bend test and repeated impact loading were examined under SEM to study the nature of failure in the composites. In case of untreated fiber composites, interfacial debonding and extensive fiber pullout were observed, which lowered the mechanical property of the composites but improved their impact fatigue behavior. In composites treated for 4 h under repeated impact loading, interfacial debonding occurred, followed by fiber breakage, producing a sawlike structure at the fracture surface, which lowered the fatigue resistance property of the composites. The composites with fibers treated with alkali for 8 h showed maximum impact fatigue resistance. Here, interfacial debonding was at a minimum, and the fibers, being much stronger and stiffer owing to their increased crystallinity, suffered catastrophic fracture along with some microfibrillar pullout (as evident from the SEM micrographs), absorbing a lot of energy in the process, which increased the fatigue resistance property of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2588–2593, 2002
Study of the thermal behavior of alkali‐treated jute fibers
Authors: Ray Dipa , Sarkar B. K. , Basak R. K. , Rana A. K.
Published: September 2002

Jute fibers were treated with 5% NaOH solution for 2, 4, 6, and 8 h to study the performance of the fibers as a reinforcing material in the composites. Thermal analysis of the fibers was done by the DTG and DSC technique. The moisture desorption was observed at a lower temperature in the case of all the treated fibers, which might be a result of the increased fineness of the fibers, which provides more surface area for moisture evaporation. The decrease in percentage moisture loss for the fibers treated with alkali for 6 and 8 h could be the result of the increased crystallinity of the fibers. The percentage degradation of the hemicellulose decreased considerably in all the treated fibers, conforming to the fact that the hemicellulose content was lowered on alkali treatment. The decomposition temperature for α‐cellulose was lowered to 348°C from 362.2°C for all the treated fibers, and the residual char formation increased to a significant extent. The enthalpy for the thermal degradation of α‐cellulose showed a decreasing trend for the fibers treated for 2 and 4 h, which could be caused by the initial loosening of the structure, followed by an increase in the enthalpy value in the case of the 6‐ and 8‐h‐alkali‐treated fibers resulting from increased crystallinity, as evident from the X‐ray diffraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2594–2599, 2002
Use of amidoximated acrylonitrile/N‐vinyl 2‐pyrrolidone interpenetrating polymer networks for uranyl ion adsorption from aqueous systems
Authors: Pekel Nursel , Şahiner Nurettin , Güven Olgun
Published: September 2002

Poly(N‐vinyl 2‐pyrrolidone) (PVP)/acrylonitrile (AN) interpenetrating polymer networks (IPNs) were synthesized and amidoximated for the purpose of uranyl ion adsorption. The adsorption of amidoximated IPNs was studied from different uranyl ion solutions (850, 1000, 1200, 1400, and 1600 ppm). The result of all our adsorption studies showed that the bonding between UO‐amidoxime groups complied with the Langmuir‐type isotherm. The adsorption capacity was found as 0.75 g UO/g dry amidoximated IPN. In order to increase the UO ion adsorption capacity the amidoximated IPN was treated with alkali, but no significant increase could be observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2324–2329, 2001
Comparison of thermal degradation characteristics of poly(arylene sulfone)s using thermogravimetric analysis/mass spectrometry
Authors: Perng Li‐Hsiang
Published: September 2002

Thermal degradation of poly(arylene sulfone)s had been studied by the combination of thermogravimetric analysis/mass spectrometry (TG/MS) with pyrolysis/gas chromatography/mass spectrometry (Py‐GC/MS) techniques. Through these two methods, the pyrolysates from poly(ether sulfone) (PES) and polysulfone (PSF) were identified in 11 and 21 sets of evolution curves, respectively, from room temperature to 900 °C. Among these pyrolysates, 12 products from PES and 25 products from PSF were obtained. The major mechanism for both PES and PSF was one‐stage pyrolysis involving main chain random scission and carbonization with evolution of SO2 and phenol as major products. Although the initial thermal stability of PES was lower than that of PSF, the formation of sulfide groups in the condensed phase from PES, through reduction of sulfone group by hydrogen radicals, increased the fire retardation behavior of PES. In PES, the ether and sulfone groups showed similar thermal stability. The thermal stability of functional groups in PSF were in the order of sulfone < ether < isopropylidene group. The scission of the ether group in PSF, with evolution of phenol as the major product, reached maximum evolution amount at the temperature of the maximum thermogravimetry loss of TG (Tmax). The scission of isopropylidene groups at high temperature (>580 °C) evolved higher mass derivatives that lower the fire retardancy of PSF. By using a simplified kinetic model, PES showed maximum activation energy with a conversion ratio of 0.2–0.3, which implies a high fire retardant effect of sulfide formation in PES. A comparative study with the proposed model and experimental data showed the theoretical pyrolysis curves to be in agreement with the experimental curves for PES and PSF pyrolysis, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2387–2398, 2001
Corona discharge treatments of plastified PVC samples used in biological environment
Authors: Dumitrascu N. , Borcia G. , Popa G.
Published: September 2002

The effects of the plasticizer content and of the treatments by corona discharge in helium on the morphology and on some physico‐chemical properties of the PVC surface were investigated by scanning electron microscopy (SEM), IR spectroscopy, and contact angle measurements. A biological test of adsorption of some ions (calcium, potassium, and sodium) from human serum sanguine on the surface of PVC was also performed. After corona discharge treatment, the surface morphology presents a cleaning of oligomers and an increase in porosity, depending on the treatment time and on the content of the plasticizer. Surface energy considerably increases and functionalization of the surface is observed after treatment by corona discharge in helium. This functionalization does not change the electrolitical equilibrium of some ions from the serum sanguine, a convenient result that controls the stability of the blood‐PVC sample interface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2419–2425, 2001
Collagen‐based new biomedicial films: Synthesis, property, and cell adhesion
Authors: Harada Osamu , Kadota Kazushige , Yamamoto Tohei
Published: September 2002

Grafted‐collagen films with poly(methyl methacrylate), poly(butyl methacrylate), and poly(styrene) were prepared by photoirradiation of the collagen films in the presence of respective monomers. Cell adhesion onto the films was investigated, and the amount of cells adhered onto every grafted films was almost the same as that onto the collagen film crosslinked with glutaraldehyde. Because the swollen grafted films are stronger than the collagen film, they are expected to be good biomedical materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2433–2438, 2001