bluuebunny/crossref_metadata_2025 huggingface dataset:
The bedding of laboratory animals as a source of airborne contaminants
Authors: Kaliste E. , Linnainmaa M. , Meklin T. , Torvinen E. , Nevalainen A.
Published: January 2004

In work environments with laboratory animals, the bedding of animals binds the excreta as well as other compounds originating from the animals and their environment. These may be generated into the ambient air when the personnel handle bedding in different procedures. This study compares the dustiness of different types of six clean and four soiled beddings from rat or mouse cages. The dust generation of clean bedding varied from <1 to 25 mg/m3. When used in the cages of rats or mice for 4 days, the dust concentration of the beddings decreased, increased or stayed the same, depending on the type of bedding and animal species. A decrease in dustiness was, however, more common. The levels in the soiled beddings varied from <1 to 8.6 mg/m3. In the case of the aspen chip bedding, the contents of bedding used in mouse, rat or rabbit cages were analysed for mesophilic bacteria and fungi, mycobacteria and endotoxins. All of these contaminants were variably found in the bedding samples, the maximal concentrations for bacteria were >6 500 000 colony-forming units (cfu)/g, for fungi 212 000 cfu/g, and for endotoxins 6500 ng/g (81 000 EU/g). The results showed that the bedding of laboratory animals may contain biologically effective compounds, and that these may be distributed into the ambient air depending on the characteristics of the bedding material. The dustiness of different bedding types is an important factor affecting the amount and quality of the occupational exposure of the personnel to airborne contaminants.
Does preoperative administration of metamizol (Novalgin®) affect postoperative body weight and duration of recovery from ketamine-xylazine anaesthesia in mice undergoing embryo transfer: A preliminary report
Authors: Dorsch M. M. , Otto K. , Hedrich H. J.
Published: January 2004

Thirty-two female mice used for embryo transfer or as controls received either metamizol or equal volumes of normal saline administered subcutaneously following induction of anaesthesia with ketamine–xylazine. Body weight was measured immediately before surgery, after 24 and after 48 h. The duration of the surgical anaesthesia was recorded and postoperative behavioural responses were measured. Comparison of the treatment groups revealed no significant differences in body weight and recovery times, nor were other signs of discomfort detected in either treatment group. It was concluded that administration of metamizol did not provide additional analgesia following embryo transfer in mice anaesthetized with ketamine–xylazine.
Exposure to warmer postoperative temperatures reduces hypothermia caused by anaesthesia and significantly increases the implantation rate of transferred embryos in the mouse
Authors: Bagis H. , Odaman Mercan H. , Dinnyes A.
Published: January 2004

Embryo transfer (ET) is among the key factors determining the overall efficiency of transgenic technology in the mouse. A successful ET depends among other factors on the quality of the transferred embryos, foster mothers and anaesthetic reagents and on the transfer techniques. Anaesthesia-caused deaths and suboptimal ET procedures are factors which reduce the success of transgenic experiments and mouse colony maintenance. Here we compared the effects of two anaesthetic reagents—a ketamine/xylazine combination, and tribromoethanol (Avertin)—on the rates of implantation and development to term of mouse zygotes transferred into the oviducts of CD-1 foster mothers, and evaluated whether hypothermia caused by anaesthetics after the ET operation could be overcome by postoperative incubation of the foster mothers. We established two experimental groups of fosters, one of which was kept at room temperature (RT, 21°C) with the other in an incubator (33°C) overnight after ET. Rates of implantation, resorption and development to normal fetuses were evaluated by sacrificing the foster mothers on the 15th day of their pregnancy. Our results showed that regardless of the anaesthetic reagents used, the rates of implantation and of development to normal fetuses can be significantly improved by exposing the foster mothers to warmer temperatures (33°C) immediately after the ET operation. These results may have important implications in increasing the success rate of ET with micromanipulated embryos.
A comparison of a forced-air warming system to traditional thermal support for rodent microenvironments
Authors: Rembert M. S. , Smith J. A. , Hosgood G.
Published: January 2004

Thermal homeostasis is important for the well-being of laboratory rodents during experimental investigations involving chemical restraint. Anaesthesia-induced hypothermia may alter physiological processes, prolong recovery times, or result in death. Therefore, active warming may be needed to prevent excess heat loss from the rodent to the environment. Three methods of active warming were evaluated in typical rodent procedural areas and recovery cages: a forced-air warming system, infra-red heat emitter and circulating-water blanket. The first experiment involved recording the temperature of the immediate environment of the three devices, with and/or without the accompanying plastic drape, to simulate a surgical situation. In the second experiment, temperatures were recorded within cages that simulated a recovery situation with the same modalities. Forced-air warmer blankets (FAWB) were either wrapped around or placed underneath standard polycarbonate rodent cages and the results were compared with cage temperatures warmed by the heat emitter and circulating-water blanket. Temperatures were recorded at 0, 20, 40, and 60 min for each warming treatment, to determine mean temperature (± SEM) and the magnitude of increase (± SEM) between 0 and 60 min. All three devices showed an increase in temperature, but the FAWB with a plastic drape heated the procedural area microenvironment (Experiment 1) quickly and to a final temperature of 38.6°C (101.5°F) at 60 min, compared with 25°C (77°F) for the heat emitter and 28°C (82.4°F) for the circulating-water blanket. The magnitude of increase was significantly different for each treatment, but the FAWB with a plastic drape climbed 16.3°C (29.3°F) in 60 min. In Experiment 2, the FAWB wrapped around a cage, covered with a plastic drape, heated recovery cages to 32.5°C (90.5°F) compared to the heat emitter 26.4°C (79.5°F) and circulating-water blanket with drape 26.3°C (79.3°F). The magnitude of increase in the microenvironmental temperature was significantly higher for the FAWB, with the plastic drape wrapped around the recovery cage, compared to the other treatments. In both experiments, forced-air warming proved superior to the more traditional thermal support treatments in heating the microenvironments quickly and to an optimum ambient temperature. Forced-air warming devices should be considered when thermal support is required for rodent procedural areas and recovery cages.
Pentobarbital versus medetomidine-ketamine-fentanyl anaesthesia: effects on haemodynamics and the incidence of ischaemia-induced ventricular fibrillation in swine
Authors: Grund F. , Tjomsland O. , Sjaastad I. , Ilebekk A. , Kirkebøen K. A.
Published: January 2004

The present study was performed to compare haemodynamic variables at baseline and the incidence of ventricular fibrillation during the early phase of ischaemia in swine during pentobarbital or medetomidine-ketamine-fentanyl anaesthesia. Twenty-two swine (mean ± SD: 29± 3 kg) were anaesthetized with sodium pentobarbital (induction with 36 mg/kg intraperitoneally, and maintenance with 5-20 mg/kg/h intravenously [i.v.]) and 6 swine (27± 3 kg) were anaesthetized with ketamine and fentanyl (premedicated with medetomidine 0.1 mg/kg and ketamine 10 mg/kg intramuscularly, induction with ketamine 20 mg/kg and fentanyl 0.025 mg/kg i.v., and maintenance with ketamine 20 mg/kg/h and fentanyl 0.025 mg/kg/h i.v.). After a stabilization period of 30 min, the left anterior descending coronary artery (LAD) was occluded for 10 min. Haemodynamic data and occurrence of ventricular fibrillation were recorded. The ischaemic area was measured by fluorescing microspheres. Swine anaesthetized with medetomidine-ketamine-fentanyl had significantly lower heart rate, myocardial contractility, peak left ventricular pressure, arterial blood pressure, aortic blood flow, myocardial blood flow and cardiac index at baseline, than swine anaesthetized with pentobarbital. Whereas none of the swine anaesthetized with pentobarbital fibrillated during the LAD occlusion, ventricular fibrillation occurred in 83% of the animals anaesthetized with medetomidine-ketamine-fentanyl ( P< 0.001). No significant difference was found in size of ischaemic area between the two groups. Thus, we show a depression in haemodynamic variables at baseline and a higher incidence of ventricular fibrillation during the early phase of ischaemia in swine anaesthetized with medetomidine-ketamine-fentanyl compared to swine anaesthetized with pentobarbital.
Renal epithelial proliferation and its clinical expression in Brown Norway (BN) rats
Authors: Stub C. , Thon R. , Ritskes-Hoitinga M. , Hansen A. K.
Published: January 2004

Renal epithelial proliferation has previously been found to be a common condition in a colony of Lewis × Brown Norway (BN) F2 hybrid rats. The aim of this study was to investigate the prevalence and clinical consequences of this condition in pure inbred BN and Lewis rats. Renal epithelial proliferation was found in 29 of 49 BN rats (59%) examined and in four of 50 Lewis rats (8%) examined. Serum creatinine and serum corticosterone was not influenced by the condition. Haematuria was more common in BN rats with (74%) than without renal papillary proliferation (35%, P < 0.05), but it may not be used to diagnose renal epithelial proliferation, as we found rats having renal epithelial proliferation without showing haematuria and rats showing haematuria without having renal epithelial proliferation. Haematuria was also common in Lewis rats (16-56% dependent of age and gender), in which renal epithelial proliferation were found in only 8%. Fluctuating asymmetry, which was used as a measure of developmental instability, was found to be increased in rats with renal epithelial proliferation ( P < 0.05). Haematuria was also found to be related to the degree of fluctuating asymmetry ( P < 0.01). Although the prevalence of renal epithelial proliferation is clearly higher in BN rats than in Lewis rats ( P < 0.01), and although in previous reports the condition was found in F2 BN × Lewis hybrids and not in F1 BN × Lewis hybrids it cannot clearly be defined as having been caused by a single Mendelian gene, as we found it in both inbred strains. Futhermore, we found that morphologically the proliferations could be placed on the papillary as well as the medullary wall of the renal pelvis, while previously it has only been described on the papillary wall.
Slope seeking: a generalization of extremum seeking
Authors: Ariyur Kartik B. , Krstić Miroslav
Published: January 2004

This work introduces slope seeking, a new idea for non‐model based adaptive control. It involves driving the output of a plant to a value corresponding to a commanded slope of its reference‐to‐output map. To achieve this objective, we introduce a slope reference input into a sinusoidal perturbation‐based extremum seeking scheme; derive a stability test for single parameter slope seeking, and then develop a systematic design algorithm based on standard linear SISO control methods to satisfy the stability test. We then extend the results to the multivariable case of gradient seeking. Finally, we illustrate near‐optimal compressor operation under slope seeking feedback through a simulation study upon the well‐known Moore–Greitzer model of compressor instability. Copyright © 2003 John Wiley & Sons, Ltd.
Optimality for the linear quadratic non‐Gaussian problem via the asymmetric Kalman filter
Authors: Romera Rosario
Published: January 2004

In the linear non‐Gaussian case, the classical solution of the linear quadratic Gaussian (LQG) control problem is known to provide the best solution in the class of linear transformations of the plant output if optimality refers to classical least‐squares minimization criteria. In this paper, the adaptive linear quadratic control problem is solved with optimality based on asymmetric least‐squares approach, which includes least‐squares criteria as a special case. Our main result gives explicit solutions for this optimal quadratic control problem for partially observable dynamic linear systems with asymmetric observation errors. The main difficulty is to find the optimal state estimate. For this purpose, an asymmetric version of the Kalman filter based on asymmetric least‐squares estimation is used. We illustrate the applicability of our approach with numerical results. Copyright © 2004 John Wiley & Sons, Ltd.
Performance characterization of a non‐linear system as both an adaptive notch filter and a phase‐locked loop
Authors: Karimi‐Ghartemani M. , Ziarani A. K.
Published: January 2004

The behaviour of a non‐linear dynamical system is described. The system may be characterized as an adaptive notch filter, or alternatively, as a phase‐locked loop. Either way, the system has the inherent capability of directly providing estimates of the parameters of the extracted sinusoidal component of its input signal, namely its amplitude, phase and frequency. The structure and mathematical properties of the system are presented for two cases of fixed‐frequency and varying‐frequency operation. The effects of parameter setting of the system on its performance are studied in detail using computer simulations. Transient and steady‐state behaviour of the system are studied in the presence of noise. Simplicity of structure, high noise immunity and robustness and the capability of direct estimation of amplitude, phase and frequency are the salient features of the system when envisaged as an adaptive notch filter or a phase‐locked loop. Copyright © 2004 John Wiley & Sons, Ltd.
Sensor network design for fault tolerant estimation
Authors: Staroswiecki M. , Hoblos G. , Aitouche A.
Published: January 2004

This paper addresses the problem of fault tolerant estimation and the design of fault tolerant sensor networks. Fault tolerance is defined with respect to a given estimation objective, namely a given functional of the system state should remain observable when sensor failures occur. Redundant and minimal sensor sets are defined and organized into an automaton which contains all the subsets of sensors such that the estimation objective can be achieved. Three criteria, which evaluate the system fault tolerance with respect to sensor failures when a reconfiguration strategy is used, are introduced: (strong and weak) redundancy degrees (RD), sensor network reliability (R), and mean time to non‐observability (MTTNO). Sensor networks are designed by finding redundant sensor sets whose RD and/or R and/or MTTNO are larger than some specified values. A ship boiler example is developed for illustration. Copyright © 2004 John Wiley & Sons, Ltd.
Plutonium‐related work and cause‐specific mortality at the United States Department of Energy Hanford Site
Authors: Wing Steve , Richardson David , Wolf Susanne , Mihlan Gary
Published: January 2004

Background

Health effects of working with plutonium remain unclear. Plutonium workers at the United States Department of Energy (US‐DOE) Hanford Site in Washington State, USA were evaluated for increased risks of cancer and non‐cancer mortality.

Methods

Periods of employment in jobs with routine or non‐routine potential for plutonium exposure were identified for 26,389 workers hired between 1944 and 1978. Life table regression was used to examine associations of length of employment in plutonium jobs with confirmed plutonium deposition and with cause specific mortality through 1994.

Results

Incidence of confirmed internal plutonium deposition in all plutonium workers was 15.4 times greater than in other Hanford jobs. Plutonium workers had low death rates compared to other workers, particularly for cancer causes. Mortality for several causes was positively associated with length of employment in routine plutonium jobs, especially for employment at older ages. At ages 50 and above, death rates for non‐external causes of death, all cancers, cancers of tissues where plutonium deposits, and lung cancer, increased 2.0 ± 1.1%, 2.6 ± 2.0%, 4.9 ± 3.3%, and 7.1 ± 3.4% (±SE) per year of employment in routine plutonium jobs, respectively.

Conclusions

Workers employed in jobs with routine potential for plutonium exposure have low mortality rates compared to other Hanford workers even with adjustment for demographic, socioeconomic, and employment factors. This may be due, in part, to medical screening. Associations between duration of employment in jobs with routine potential for plutonium exposure and mortality may indicate occupational exposure effects. Am. J. Ind. Med. 45:153–164, 2004. © 2004 Wiley‐Liss, Inc.
Effectiveness of the HomeSafe Pilot Program in reducing injury rates among residential construction workers, 1994–1998
Authors: Darragh Amy Rowntree , Stallones Lorann , Bigelow Phillip L. , Keefe Thomas J.
Published: January 2004

Background

The construction industry typically has one of the highest fatal and non‐fatal injury rates compared with other industries. Residential construction workers are at particular risk of injury (work is in remote sites with small crews, there are often many subcontractors, and they have limited access to safety programs). Difficulty accessing information specific to this group has made research more challenging, therefore, there are few studies. This study evaluated the effectiveness of the HomeSafe Pilot Program, a safety education and training program designed to reduce injuries among residential construction workers.

Methods

Researchers evaluated whether overall and severe injury incidence rates declined during the intervention period. Data were analyzed using incidence rates and Poisson regression to control for the effect of antecedent secular trend.

Results

Injury incidence rates declined significantly following HomeSafe; however, this effect was not statistically significant once temporal variation was controlled.

Conclusions

The decline in injury rates following HomeSafe cannot be attributed solely to HomeSafe, however, programmatic and methodologic limitations contributed to the inconclusive results. Further research into the hazards faced by residential construction workers is needed. Am. J. Ind. Med. 45:210–217, 2004. © 2004 Wiley‐Liss, Inc.
Quantitative exposure‐response for silica dust and lung cancer in Vermont granite workers
Authors: Attfield Michael D. , Costello Joseph
Published: January 2004

Background

Excess lung cancer mortality among the exposed Vermont granite workers has been reported. These studies were based on job and tenure surrogates, with the potential for misclassification and inability to evaluate quantitative exposure‐response.

Methods

Industrial hygiene data collected from 1924 to 1977 was analyzed in conjunction with mortality data to examine quantitative exposure‐response for silica, lung cancer, and other lung diseases. A person‐years analysis was undertaken by cumulative exposure group, including lagged and unlagged tabulations. Poisson models were fitted to untransformed and log transformed exposure.

Results

The results indicated a clear relationship of lung cancer, tuberculosis, pneumoconiosis, non‐malignant lung disease, and kidney cancer with cumulative exposure. An exposure to 0.05 mg/m3 from age 20 to 64 was associated with a lifetime excess risk of lung cancer for white males of 27/1,000.

Conclusions

The results of this study of workers exposed almost exclusively to silica and no other major occupational confounding exposures indicate a clear exposure‐response for lung cancer. Am. J. Ind. Med. 45:129–138, 2004. Published 2004 Wiley‐Liss, Inc.
Mortality patterns among workers exposed to styrene in the reinforced plastic boatbuilding industry: An update
Authors: Ruder Avima M. , Ward Elizabeth M. , Dong Maxia , Okun Andrea H. , Davis‐King Karen
Published: January 2004

Background

Mortality was updated through 1998 for 5,204 workers exposed to styrene between 1959 and 1978 at two reinforced plastic boatbuilding plants. The a priori hypothesis: leukemia and lymphoma excesses would be found.

Methods

Standardized mortality ratios (SMR) and 95% confidence intervals (CI) used Washington State and U.S. rates.

Results

Overall, 860 deaths occurred (SMR 1.09, CI 1.02–1.17), with excess mortality for esophageal cancer (n = 12, SMR 2.30, CI 1.19–4.02), prostate cancer (n = 24, SMR 1.71, CI 1.09–2.54), and accidents (n = 99, SMR 1.26, CI 1.02–1.53). Among 2,062 highly exposed workers, urinary tract cancer (n = 6, SMR 3.44, CI 1.26–7.50) and respiratory disease (n = 12, SMR 2.54, CI 1.31–4.44) rates were elevated. Urinary tract cancer SMR increased with duration of employment.

Conclusions

We found no excess leukemia or lymphoma mortality. Unanticipated excess urinary tract cancer and respiratory disease mortality, possibly associated with styrene exposure, are difficult to interpret and could be chance findings. Am. J. Ind. Med. 45:165–176, 2004. Published 2004 Wiley‐Liss, Inc.
Concentration of hydroxyproline in blood: A biological marker in occupational exposure to asbestos and its relationship with Pi*Z and Pi*S polymorphism in the alpha‐1 antitrypsin gene
Authors: Mas S. , Casterad X. , Laso N. , Lafuente M.J. , Panades R. , Calleja A. , Hernandez S. , Turuguet D. , Deulofeu R. , Ballesta A. , Ascaso C. , Lafuente A.
Published: January 2004

Background

Hydroxyproline (OHP) is one of the most abundant amino acids in collagen and, in general, it provides a good measure of overall collagen catabolism.

Methods

Asbestos workers suffering from asbestosis (cases n = 85); asbestos exposed workers without asbestosis (exposed controls, EC, n = 86), and non‐exposed population (non‐exposed controls, NEC, n = 122) were studied. The concentration of free OHP in whole blood was measured following the Pico‐Tag procedure.

Results

Concentration of OHP in blood was significantly different in the three groups studied (P < 0.001), being higher in cases (19.8 ± 14.7 μmol/L) than in EC (16 ± 12.4) and NEC (13.5 ± 6.7). When all individuals were grouped and stratified by the Pi*S and Pi*Z polymorphisms in the alpha‐1‐antitrypsin gene, the highest OHP levels were detected in the Pi*S homozygotes, one of the asbestosis‐at risk‐genotypes (Pi*S homozygotes, x = 24.5 ± 11.7; Pi*S heterozygotes, x = 16.6 ± 10.0; wild type, wt, x = 15.9 ± 11.8).

Conclusions

Blood OHP concentration could be used for monitoring human exposure to asbestos, either as a marker for occupational monitoring or as an additional clinical parameter in diagnostic exploration of asbestosis. Am. J. Ind. Med. 45:186–193, 2004. © 2004 Wiley‐Liss, Inc.
Structural development in cycloolefin copolymers under uniaxial elongational flow
Authors: Maiti Pralay , Okamoto Masami
Published: January 2004

Development of structures in new cycloolefin copolymers (COCs) of ethylene–norbornene (E–NB) and ethylene–tetracyclododecene (E–TD) of different NB/TD compositions were investigated under uniaxial elongational flow. For E–NB copolymer, which has multiblock sequences, a shoulder in WAXD at 0.76 nm was evident besides its amorphous halo, and the relative intensity of the peak increased with increasing comonomer content (NB). The appearance of a new peak for E–TD copolymer, and a relatively higher intense peak for E–NB copolymer at the same position of 0.76 nm, indicated that local ordering of the segments occurred when the COC was subjected to uniaxial flow. A lower comonomer composition of elongated COC, at a constant Hencky strain rate, exhibited two Tg values, whereas a higher composition showed a single Tg. Both local ordering and segmentization occurred in low comonomer content COCs but only local ordering occurred in higher comonomer content COCs. Both the shear viscosity and roll processing experiments exhibited similar phenomena of segregation. A model is proposed to illustrate the structure of COC after uniaxial elongation/deformation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3421–3427, 2004
Cobalt (II), nickel (II), and copper (II) complexes of polystyrene‐supported Schiff bases
Authors: Suja N. R. , Yusuff K. K. Mohammed
Published: January 2004

Two novel polystyrene‐supported Schiff bases, PSOPD and PSHQAD, were synthesized. A polymer‐bound aldehyde was condensed with o‐phenylenediamine to prepare the Schiff base PSOPD, and a polymer‐bound amine was condensed with 3‐hydroxyquinoxaline‐2‐carboxaldehyde to prepare the Schiff base PSHQAD. This article addresses the study of cobalt (II), nickel (II), and copper (II) complexes of these polymer‐bound Schiff bases. All the complexes were characterized, and the probable geometry was suggested using elemental analysis, diffuse reflectance ultraviolet, Fourier transform infrared spectroscopy, thermal studies, surface area studies, and magnetic measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3710–3719, 2004
Network formation during cocure of phenolic resins with vinyl‐ester and epoxy‐amine systems for use in multifunctional composites
Authors: Singh K. P. , Palmese G. R.
Published: January 2004

Traditionally, multilayered composites have been manufactured in multiple steps that involve the fabrication of each layer separately and the bonding them together by using adhesives or secondary bonding. More recently, manufacturing techniques have been developed that enable the manufacture of multilayered hybrid composite parts in a single step. In one such technique known as coinjection resin transfer molding (CIRTM), two or more resins are simultaneously injected into a mold filled with a stationary fiber bed. This method not only cuts down manufacturing costs and time, but also offers the potential of cocure of the adjacent thermosetting resins inside the mold, which could aid in the formation of a tougher interphase between the layers and improve long‐term durability. The advantages offered by coinjection are, however, dependent on the successful cocure of the resins involved, and hence, there exists a need to determine compatible resin systems for coinjection. By compatible, it is meant that the resins must cure when in contact with each other, have compatible cure cycles (i.e., cure temperature, cure time, etc.), and result in acceptable physical and mechanical properties. The most commonly used matrix resins are vinyl‐ester resins. The cure of vinyl‐ester resin was found to be severely limited by contact with phenolic resin. This necessitates an impermeable separation layer between phenolic and vinyl‐ester resins in CIRTM manufacture. A possible candidate for this separation layer was epoxy‐amine‐based prepregs or adhesive layers. Thus, the cocure of mixtures of phenolic with epoxy‐amine was studied, and it was found that phenolic resin significantly affects the cure of epoxy‐amines. A model to quantify the effect of phenolic resin on the cure of epoxy‐amines has been proposed. By using this model, the fraction of primary amine consumed by the phenolic can be estimated. It was found that increasing the initial amine concentration in the cocure reaction mixture leads to an increase in the epoxy conversion as well as the Tg of the material. Therefore, it is recommended that, in cocure of epoxy‐amine and phenolic resins, the initial concentration of amine must be greater than the stoichiometric amount to compensate for the loss of amine to the phenolic resin. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3107–3119, 2004
The effects of polymer‐nanofiller interactions on the dynamical mechanical properties of PMMA/CaCO3 composites prepared by microemulsion template
Authors: Qiang Xi , Chunfang Zhao , JianZun Yuan , Yuan Cheng Shi
Published: January 2004

We prepared novel poly(methyl methacrylate) (PMMA)/CaCO3 nanocomposites by using reverse micelle as a template. The nanoparticles of CaCO3 were prepared by the reverse microemulsion with functional monomer, methyl methacrylate (MMA) as oily phase, and the PMMA/CaCO3 nanocomposite was obtained via polymerization of MMA monomer. The SEM image showed that the nanoparticles of CaCO3 were dispersed in the polymer matrix. Dynamic mechanical analysis (DMTA) was performed to investigate the interaction between the nanoparticles and the polymer chains. In the low‐temperature ripening process, two tan δ peaks were observed in the nanocomposite, corresponding to the glass transitions of the matrix and the interface layer. In the high‐temperature ripening process, only one tan δ peak was observed, suggesting that the interface layer forms a continuous phase. The nanoparticles behave as a physical crosslinker in the interface layer. Modification of the surface of nanoparticles with polyacrylamide and poly(N,N′‐methylenedisacrylamide) in the nanocomposite did not show an appreciable effect on the interaction of nanoparticles with the matrix. Upon removal of the aqueous phase around the nanoparticles, we obtained surface‐capped nanoparticles by using an improved reverse microemulsion technique. Another PMMA/CaCO3 nanocomposite was also obtained with these modified nanoparticles. DMTA analysis of this nanocomposite demonstrated that the aqueous phase layer around the nanoparticles does not significantly affect the interaction between the nanoparticles and the polymer chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2739–2749, 2004
A novel approach for evaluation of polymeric interface materials for chemical sensors using alternate indirect methods
Authors: Dubey Vinita , Saxena Chhaya , Pandey Lokesh Kumar
Published: January 2004

The heart of a chemical sensor based on bulk or surface acoustic wave devices is a polymer‐coated piezoelectric substrate that selectively sorbs and concentrates the target analyte vapors. The development of such sensors often necessitates the screening and evaluation of suitable polymeric interface materials meeting the specified sensitivity and selectivity toward the analytes of interest. The magnitude and dynamics of sorption–desorption of the vapors in the polymer and the extent of polymer–vapor interactions largely determine the performance of a sensor. The standard protocol used for the purpose is rather tedious, involving the generation and calibration of individual analyte vapors, with stringent control on temperature, humidity, and test parameters. This article outlines four different alternative techniques based on mass uptake of the analyte vapors, on its partitioning in polymers, or both, which in combination can determine the characteristics of an interface material used for coating a piezoelectric substrate in acoustic wave‐based chemical sensors. These methods were applied to poly(ethylene maleate), a representative interface material. The analytes ranged from volatile organic chemicals to sarin—a chemical warfare agent—and its simulant, dimethyl methylphosphonate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3428–3432, 2004
Efficient method for recycling poly(ethylene terephthalate) to poly(butylene terephthalate) using transesterification reaction
Authors: Kulkarni Neeta G. , Avadhani C. V. , Sivaram S.
Published: January 2004

A method of recycling postconsumer poly(ethylene terephthalate (PET) using transesterification was studied. Shredded flakes of postconsumer PET waste were transesterified with higher diols, such as 1,4‐butanediol, 1,4‐cyclohexane dimethanol, and 1,6‐hexanediol, to yield copolyesters in the presence of Ti(iPrO)4 and Sb2O3 as catalysts. The extent of the formation of undesirable tetrahydrofuran side products was dependent on the molar ratio of PET to1,4‐butanediol and the time of reflux during transesterification. Quantitative insertion of the butylene moiety into PET could be achieved under appropriate reaction conditions. The mechanical properties of PBT obtained by a transesterification reaction of PET with 1,4‐butanediol were comparable to those of virgin PBT (obtained by direct reaction of dimethyl terephathalate with 1,4‐butanediol). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3720–3729, 2004
Cephazoline sodium release from poly(N‐isopropyl acrylamide‐co‐N,N‐dimethylacrylamide) hydrogels
Authors: Escobar J. L. , García D. , Valerino A. , Zaldívar D. , Hernáez E. , Katime Issa
Published: January 2004

Hydrogels are hydrophilic polymers that swell to an equilibrium volume in the presence of water, preserving their shape. The dynamic swelling behavior of poly(N‐isopropylacrylamide‐co‐N,N‐dimethylacrylamide) [poly(NIPA‐co‐DMA)] copolymers at 37°C was investigated. It was observed that the swelling degree in the copolymers decreases with the N‐isopropylacrylamide content. In addition, the liberation mechanism was found to be Fickian. Diffusion coefficients according to Fick′s law as a function of the N‐isopropylacrylamide concentration and results of the release process are reported. The kinetics of cephazoline sodium release from poly(NIPA‐co‐DMA) hydrogels with different compositions was studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3433–3437, 2004
Preparation and properties of heterocyclically conjugated poly(3‐hexylthiophene)–clay nanocomposite materials
Authors: Yu Yuan‐Hsiang , Jen Chien‐Chih , Huang Hsiu‐Ying , Wu Pei‐Chi , Huang Chao‐Cheng , Yeh Jui‐Ming
Published: January 2004

A series of heterocyclically conjugated polymer–clay nanocomposite (PCN) materials that consisted of organic poly(3‐hexylthiophene) (P3HT) and inorganic montmorillonite (MMT) clay platelets were prepared byin situoxidative polymerization with FeCl3as an oxidant. The as‐synthesized PCN materials were characterized by Fourier transform infrared (FTIR) spectroscopy, wide‐angle powder X‐ray diffraction (WAXRD), and transmission electron microscopy (TEM). The effects of the material composition on the anticorrosion, gas barrier, thermal stability, flammability, mechanical strength, and electrical conductivity properties of the P3HT and PCN materials were studied by electrochemical corrosion measurements, gas‐permeability analysis (GPA), thermogrametric analysis (TGA), limiting oxygen index (LOI) measurements, dynamic mechanical analysis (DMA), and a four‐point probe technique, respectively. The molecular weights of extracted and bulk P3HT were determined by gel permeation chromatography (GPC) with THF as an eluant. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3438–3446, 2004
Novel V‐shaped negative temperature coefficient of conductivity thermistors and electromagnetic interference shielding effectiveness from butyl rubber–loaded boron carbide ceramic composites
Authors: El‐Tantawy Farid , Dishovsky Nikolay
Published: January 2004

The presentation of a new conductive composite with good effective applications like negative and positive temperature coefficient of conductivity thermistors (i.e., V‐shaped thermistors) and electromagnetic interference shielding effectiveness (EMI) was the aim of this study. The effect of boron carbide (B4C) contents on the vulcanization characteristics and network structure of butyl rubber (IIR) composites were analyzed in detail. The prediction of the type of crosslinks based on the affine and phantom network theory was also analyzed. The influence of the volume fraction of B4C on the dc conductivity and thermoelectric power was investigated. The electrical and dielectric properties of IIR composites were investigated. The results suggest that the conduction occurs by a tunneling mechanism and behaves as a p‐type semiconductor. Isothermal resistance at different temperatures, as a function of B4C content, was displayed. The current–voltage characteristics showed properties of switches, which were explained by coulombic repulsive force. For practical applications, as self‐electrical heating the temperature–time cycles were investigated under certain applied power. It was found that increasing the B4C content increases the thermal stability of the composite. However, the theoretical modeling of the current–voltage characteristic is very useful for planning groups in industrial applications of conducting polymer composites. Furthermore, the endurance test under applied power indicates that the proposed composites could be useful as temperature sensors with good reliability. Specific heat as a function of B4C contents was evaluated by experimental and various energy balance models. Furthermore, the temperature dependency of thermal conductivity and thermal diffusivity were investigated. Finally, the standing wave ratio, reflection coefficient, return loss, and attenuation of IIR/B4C composites were studied in the 1‐ to 4‐GHz frequency range. The resulting values of electromagnetic interference shielding effectiveness were compared with theoretical models. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2756–2770, 2004
Electrical and mechanical properties of expanded graphite‐reinforced high‐density polyethylene
Authors: Zheng Wenge , Lu Xuehong , Wong Shing‐Chung
Published: January 2004

High‐density polyethylene (HDPE) was reinforced with expanded and untreated graphite in a melt‐compounding process. Viscosity increased upon addition of graphite phase, with the expanded graphite (EG) showing more dramatic rise than the untreated graphite (UG) in viscosity. The increase in viscosity was attributed to the increased surface‐to‐volume ratio for the EG filler after acid treatment. Electrical conductivity also increased from that pertaining to an insulator to one characteristic of a semiconductor. The EG system showed a lower percolation threshold for transition in conductivity compared to that in the UG system. DSC results indicated that the fillers acted as a nucleating agent in inducing the crystallization of HDPE in the composites. However, the overall degree of crystallinity and melting temperature of HDPE decreased with the addition of EG and UG. Mechanical properties improved as a function of filler content but the overall enhancement was not impressive. It was conjectured that the filler–matrix interface was not optimized in the melt‐mixing process. However, the role of EG as a reinforcement phase for both electrical and mechanical properties was unambiguously established. The EG composites demonstrated potentially useful attributes for antistatic, barrier, mechanical, electrical, and cost‐effective applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2781–2788, 2004
Structure and mechanical properties of uniaxially oriented films of syndiotactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends
Authors: Dikshit A. K. , Kaito A.
Published: January 2004

The structure and mechanical properties of highly oriented films of a miscible blend of syndiotactic polystyrene and poly(2,6‐dimethylphenylene‐1,4‐oxide) (sPS/PPO) were studied in the composition range of sPS/PPO = 10/0 to 5/5. The oriented films were prepared by stretching the amorphous films of the blends. Wide‐angle X‐ray diffraction and polarized FTIR spectroscopy were used to analyze the amount of mesophase and molecular orientation. Drawing of the amorphous films of sPS and sPS/PPO blend induced a highly oriented mesophase. The mesophase content increases with increasing draw ratio and becomes nearly constant above a draw ratio of 3. Under the same draw ratio, the mesophase content decreases with increasing PPO content. The orientation function in the mesophase is as high as 0.95–0.99 irrespective of the composition and draw ratio. On the other hand, the orientation of molecular chains in the amorphous phase and mesophase increases with increasing draw ratio, and it decreases with increasing PPO content. The drawn films of pure sPS show high strength and high modulus in the drawing direction, but exhibit low strength in the direction perpendicular to the drawing. In the case of sPS/PPO = 7/3 blend, however, the ultimate strength in the perpendicular direction was dramatically improved compared with that of pure sPS and the ultimate strength in the parallel direction was similar to that for the oriented pure sPS. The improved mechanical properties in the sPS/PPO blends were discussed in relation to the structural characteristics of the sPS/PPO blend system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2789–2797, 2004
Viscoelastic and conductive characteristics of titanium carbide/polyethylene composites in relation to their structural parameters
Authors: Kataoka Mitsuhiro , Masuko Toru
Published: January 2004

Titanium carbide (TiC)/polyethylene (PE) composite is a candidate for a positive‐temperature coefficient resistor, which is used for a self‐recoverable element that provides protection from overcurrents in many kinds of electrical devices. In the present study, the PE‐based composites containing various volume fractions (ϕ) of TiC were prepared, after which their viscoelastic characteristics were investigated compared against their electric conductivity as a function of temperature. When the value of ϕ exceeded 0.39, the resistivities of the sample decreased steeply with increasing TiC content. The resistivity of the specimen maintained a constant value of about 0.1 Ωcm in the range of ϕ values > 0.52. Alternatively, the changes in the storage moduli at room temperature with various ϕ values of the samples could be expressed by a modified Kerner equation with the maximum ϕ value of 0.67. Melting behaviors of the samples were also examined and discussed in terms of their morphological features. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3134–3139, 2004
Molecular weight distribution of poly(dimethyl diallyl ammonium chloride): Analysis within the framework of irreversible aggregation models
Authors: G. V. Koslov , Yu A. Malkanduev , G. E. Zaikov
Published: January 2004

The results of the present study have shown that the molecular weight distribution of polydimethyldiallyl ammonium chloride is simulatable and predictable within the framework of the irreversible cluster–cluster aggregation model. The shape and position of a curve of molecular weight distributiion are influenced by a number of factors, for example, by macromolecular coil structure, stochastic contribution of a coil environment to polymerization intensity, and level of coil destruction during polymerization. These factors can be linked by simple relationships to technical characteristics of the polymerization process, which is especially important for fractal applictions of the proposed theoretical model. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3144–3147, 2004
Reaction kinetics modeling and thermal properties of epoxy–amines as measured by modulated‐temperature DSC. II. Network‐forming DGEBA + MDA
Authors: Swier Steven , Van Assche Guy , Van Mele Bruno
Published: January 2004

Reaction‐induced vitrification takes place in the network‐forming epoxy–amine system diglycidyl ether of bisphenol A (DGEBA) + methylenedianiline (MDA) when the glass‐transition temperature (Tg) rises above the cure temperature (Tcure). This chemorheological transition results in diffusion‐controlled reaction and can be followed simultaneously with the reaction rate in modulated‐temperature DSC (MTDSC). To predict the effect of Tcure and the NH/epoxy molar mixing ratio (r) on the reaction rate in chemically controlled conditions, a mechanistic approach was used based on the nonreversing heat flow and heat capacity MTDSC signals, in which the reaction steps of primary (E1OH = 44 kJ mol−1) and secondary amine (E2OH = 48 kJ mol−1) with the epoxy–hydroxyl complex predominating. The diffusion factor DF as defined by the Rabinowitch approach expresses whether the chemical reaction rate or the diffusion rate determines the overall reaction rate. A model based on the free volume theory together with an Arrhenius temperature dependency was used to calculate the diffusion rate constant in DF as a function of conversion (x) and Tcure. The relation between x, r, and Tg, needed in this model, can be predicted with the Couchman equation. An experimental approximation for DF is the mobility factor DF* obtained from the heat capacity signal at a modulation frequency of 1/60 Hz, normalized for the effect of the reaction heat capacity in the liquid state and the change in Cp in the glassy region with x and Tcure. In this way, an optimized set of diffusion parameters was obtained that, together with the optimized kinetic parameters set, can predict the reaction rate for different cure schedules and for stoichiometric and off‐stoichiometric mixtures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2814–2833, 2004
Modification of acrylonitrile‐butadiene‐styrene terpolymer by graft copolymerization with maleic anhydride in the melt. II. Properties and phase behavior
Authors: Qi Rongrong , Qian Junling , Chen Zhefeng , Jin Xing , Zhou Chixing
Published: January 2004

The graft copolymerization of maleic anhydride (MAH) onto acrylonitrile‐butadiene‐styrene terpolymer (ABS) using dicumyl peroxide and benzoyl peroxide as the binary initiator and styrene as the comonomer in the molten state was described. The properties and phase morphologies of the modified products (ABS‐g‐MAH) were studied. The results indicate that the melt flow index (MFI) of ABS‐g‐MAH increases with the increase of MAH content, the initiator concentration, and the screw speed, whereas the MFI decreases with the increase of temperature. The impact strength and the percentage elongation of ABS‐g‐MAH both decreased and the tensile strength of ABS‐g‐MAH increased slightly as the grafting degree increased. The phase inversion behavior of the modified product was observed by transmission electron microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2834–2839, 2004
Binder fiber distribution and tensile properties of thermally point bonded cotton‐based nonwovens
Authors: Rong Haoming , Bhat Gajanan S.
Published: January 2004

Cotton‐based nonwovens are generally produced by carding and then bonding. One of the most important characteristics of nonwoven materials is the uniformity of their structure and properties. However, the carded webs always have irregularities caused by processing and material variables. The binder fiber distribution in carded cotton‐based nonwoven fabrics was analyzed based on the crystallization behavior of one of the components of the binder fibers by DSC. The effects of process parameters, such as bonding temperature and binder fiber component, on the uniformity were discussed in detail in this article. Also, the relationship of binder fiber distribution and the strip tensile property and single‐bond tensile strength were investigated. The results showed that if the binder fibers were not well distributed in the fabric, it would be hard to get the same trend of temperature effect on tensile property for the strip and single‐bond tests. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3148–3155, 2004