bluuebunny/crossref_metadata_2025 huggingface dataset:
Recurring features of local tertiary structural elements in RNA molecules exemplified by hepatitis D virus RNA
Authors: CIRCLE DAVID A , LYONS ALITA J. , NEEL OLIVIA D. , ROBERTSON HUGH D.
Published: February 2003

Elements of local tertiary structure in RNA molecules are important in understanding structure–function relationships. The loop E motif, first identified in several eukaryotic RNAs at functional sites which share an exceptional propensity for UV crosslinking between specific bases, was subsequently shown to have a characteristic tertiary structure. Common sequences and secondary structures have allowed other examples of the E-loop motif to be recognized in a number of RNAs at sites of protein binding or other biological function. We would like to know if more elements of local tertiary structure, in addition to the E-loop, can be identified by such common features. The highly structured circular RNA genome of the hepatitis D virus (HDV) provides an ideal test molecule because it has extensive internal structure, a UV-crosslinkable tertiary element, and specific sites for functional interactions with proteins including host PKR. We have now found a UV-crosslinkable element of local tertiary structure in antigenomic HDV RNA which, although differing from the E-loop, has a very similar pattern of sequence and secondary structure to the UV-crosslinkable element found in the genomic strand. Despite the fact that the two structures map close to one another, the sequences comprising them are not the templates for each other. Instead, the template regions for each element are additional sites for potential higher order structure on their respective complementary strands. This wealth of recurring sequences interspersed with base-paired stems provides a context to examine other RNA species for such features and their correlations with biological function.
A uniform system for microRNA annotation
Authors: AMBROS VICTOR , BARTEL BONNIE , BARTEL DAVID P. , BURGE CHRISTOPHER B. , CARRINGTON JAMES C. , CHEN XUEMEI , DREYFUSS GIDEON , EDDY SEAN R , GRIFFITHS-JONES SAM , MARSHALL MHAIRI , MATZKE MARJORI , RUVKUN GARY , TUSCHL THOMAS
Published: February 2003

MicroRNAs (miRNAs) are small noncoding RNA gene products about 22 nt long that are processed by Dicer from precursors with a characteristic hairpin secondary structure. Guidelines are presented for the identification and annotation of new miRNAs from diverse organisms, particularly so that miRNAs can be reliably distinguished from other RNAs such as small interfering RNAs. We describe specific criteria for the experimental verification of miRNAs, and conventions for naming miRNAs and miRNA genes. Finally, an online clearinghouse for miRNA gene name assignments is provided by the Rfam database of RNA families.
Coordination of editing and splicing of glutamate receptor pre-mRNA
Authors: BRATT EVA , ÖHMAN MARIE
Published: February 2003

Adenosine deaminase that acts on RNA, ADAR, catalyzes the conversion of adenosine into inosine within double-stranded RNA. This type of editing has mainly been found in genes involved in neurotransmission. Site-specific A to I modifications often require intronic sequences to create the double-stranded structure necessary for editing. A system was developed to investigate if editing and splicing of pre-mRNA are coordinated. We have focused on a selectively edited site (R/G) in the glutamate receptor subunit B pre-mRNA. This editing site is situated in close proximity to a 5′ splice site. To ensure efficient splicing, the editing site, together with its natural 5′ splice site, was fused to a 3′ splice site of the major late transcript from adenovirus. In vitro, on a premade transcript, ADAR2 editing and splicing were found to interfere with each other. The stable stem-loop required for ADAR2 editing had a negative effect on in vitro splicing, possibly by sequestering the 5′ splice site. Further, RNA helicase A was shown to overcome the splicing inhibition caused by ADAR2. In vivo, allowing cotranscriptional processing, the same construct was found to efficiently edit and splice without interference, suggesting that the two RNA processing events are coordinated.
Laser Shadow Analysis of Particle-Size Distribution of Montmorillonites in Aqueous Suspensions
Authors: Yariv S. , Lapides I.
Published: February 2003

Particle-size analysis (obtained by Galai CIS 1) was used to determine the following statistical parameters of aqueous suspensions of Na-, Ca- and Mn-montmorillonite: the size distributions, the diameters of the largest and of the median and mean particles, and the percentage of particles with diameters <1.5 µm. Dilution or shaking had almost no effect on the particle-size distribution curves and statistical parameters of Ca- and Mn-montmorillonites but the curves and the statistical parameters of Na-montmorillonite were very much affected by these treatments. The median and mean diameters of Na-montmorillonite range from 0.8 to 10.5 µm and 0.8 to 11.6 µm, respectively, the median and mean diameters of Ca-montmorillonite range from 1.5 to 3.6 µm and 2.12 to 4.2 µm, respectively, and those for Mn-montmorillonite from 1.2 to 2.3 µm and 1.5 to 2.5 µm, respectively. The presence of large particles of Na-montmorillonite was attributed to the extensive swelling of this clay in aqueous suspensions by osmotic water adsorption. The median and mean diameters of aged Na-montmorillonite suspensions indicate that swelling increases with dilution. The swelling of Ca- and Mn-montmorillonite, on the other hand, is limited and their particle size does not increase with dilution.
Firefighting and risk of testicular cancer: Results from a German population‐based case‐control study
Authors: Stang Andreas , Jöckel Karl‐Heinz , Baumgardt‐Elms Cornelia , Ahrens Wolfgang
Published: February 2003

Background

There is some evidence of an elevated risk for testicular cancer among firefighters.

Methods

We performed a population‐based case–control study including 269 testicular cancer cases and 797 controls matching on age and region with a special focus on occupational exposures. Job tasks were coded according to the International Standard Classification of Occupations (ISCO 68). We used conditional logistic regression to calculate odds ratios (OR).

Results

Three controls (0.4%) and four cases (1.5%) ever worked as firefighters. Firefighters showed an increased odds of testicular cancer in the matched evaluation (OR = 4.3, 95% confidence interval (95% CI) 0.7–30.5). The adjustment for a history of cryptorchidism or family history of testicular cancer did not alter our results.

Conclusion

Although the association between firefighting and testicular cancer risk is based on only small numbers of exposed subjects in our study, the finding is consistent with a recent cohort study from New Zealand. Occupational hazards experienced by firefighters may increase the risk of testicular cancer. Am. J. Ind. Med. 43:291–294, 2003. © 2003 Wiley‐Liss, Inc.
Role of underlying pulmonary obstruction in short‐term airway response to metal working fluid exposure: A reanalysis
Authors: Zeka Ariana , Kriebel David , Kennedy Susan M. , Wegman David H.
Published: February 2003

Background

Among epidemiologic studies that found evidence for associations between exposures to metal working fluids (MWF) and pulmonary function impairments, one found effects restricted to workers with fixed obstruction at baseline. We reanalyzed a previously published study on MWF exposure and cross‐shift pulmonary function to further evaluate this finding.

Methods

Pulmonary function was measured cross‐shift on Monday and Friday in 131 male automotive workers. Quantitative personal MWF exposure data were available. Those with an FEV1/FVC ratio of ≤0.72 were considered obstructed.

Results

There was a trend towards increasing incidence of cross‐shift decrement in FEV1 as MWF exposure increased in the full cohort as well as when the results were restricted to the 19 (14.5%) who were obstructed. Those with obstruction were slightly more likely to show decrements in FEV1 on Fridays. Removing the obstructed subgroup did not appear to substantially weaken the exposure–response relation.

Conclusions

No important differences were found in cross‐shift effects of MWF between obstructed and non‐obstructed workers. Am. J. Ind. Med. 43:286–290, 2003. © 2003 Wiley‐Liss, Inc.
Using respirators and goggles to control exposure to air pollutants in an anatomy laboratory
Authors: Akbar‐Khanzadeh Farhang , Pulido Edgar V.
Published: February 2003

Background

Engineering or administrative methods are often insufficient or impractical to control exposure to chemicals in anatomy laboratories. This study explored the feasibility of wearing one or a combination of respirators and goggles used as personal protective equipment (PPE) to control exposure in one such laboratory.

Methods

A group of 28 subjects were briefly trained in wearing PPE, fit‐tested, and asked to complete a questionnaire regarding their subjective reaction after wearing the assigned PPE ensemble while working in the laboratory. The subjects' exposure to formaldehyde was also measured and generally exceeded the recommended limits.

Results

When a full‐face respirator or the combination of a half‐mask respirator and goggles was worn, a majority of subjects reported no odor problem and no irritation to eyes or upper respiratory system. Subjects accepted the PPE to certain degrees, but those using respirators encountered difficulties communicating with others.

Conclusions

The combination of a half‐mask respirator and goggles was the most feasible ensemble to control exposure to air pollutants in an anatomy laboratory. Am. J. Ind. Med. 43:326–331, 2003. © 2003 Wiley‐Liss, Inc.
Cancer mortality in a cohort of male German iron foundry workers
Authors: Adzersen Karl‐Heinrich , Becker Nikolaus , Steindorf Karen , Frentzel‐Beyme Rainer
Published: February 2003

Background

Observations of an increased incidence of cancers of the upper aero‐digestive tract (pharynx, esophagus, larynx, lung) among workers of local German foundries gave rise to concern about a potentially elevated occupational risk of those cancer sites. The purpose of the study was to examine whether occupational exposure in iron foundries increases the risk of cancer.

Methods

A historical cohort study of 17,708 male German production workers in 37 iron foundries who were first employed in 1950–1985 with a minimum employment period of 1 year was initiated. Employment and occupational histories were collected. Mortality was compared with that of the German general population during 1950–1993 using a new method for computing the SMR when not all causes of death are available (called SMR*).

Results

Mortality from all causes was elevated to SMR = 115.4 (95% confidence interval (CI) = 111.9–119.1), as was for total cancer (SMR* = 123.8, CI = 102.1–152.6), especially cancers of the lung (SMR* = 163.9, CI = 123.9–223.0) and liver (SMR* = 322.5, CI = 149.5–844.8), and diseases of the respiratory system (SMR* = 147.6, CI = 100.4–221.5). Non‐significant elevations of mortality were also found for cancers of the mouth and pharynx (SMR* = 153.5, CI = 82.3–359.8) and larynx (SMR* = 173.1, CI = 85.5–550.5). Mortality from various causes of death was higher among workers with shorter exposure periods than among long‐term employees. The elevated mortality persisted for years and decades after termination of employment.

Conclusions

The results provide further evidence for an increased risk of lung cancer and possibly other cancers of the upper aero‐digestive tract among foundry workers. Special attention should be paid to the strongly increased mortality from liver cancer and the mortality pattern among employees having terminated work. Am. J. Ind. Med. 43:295–305, 2003. © 2003 Wiley‐Liss, Inc.
Work injuries among Finnish farmers: A National Register Linkage study 1996–1997
Authors: Virtanen Simo V. , Notkola Veijo , Luukkonen Ritva , Eskola Erkki , Kurppa Kari
Published: February 2003

Background

Farming is one of the most injury‐prone occupations in Finland as it is in other countries. Our goals were to describe work injuries of Finnish farmers and to compare occupational injury rates between various subgroups.

Methods

A national cohort of 69,629 full‐time farmers and their 11,657 compensated injuries were identified from an insurance company database. Cohort data were merged with a population census and farm register. Relative incidence rates were calculated using Poisson regression.

Results

Men had higher injury rates than women, except with regard to injuries caused by animals. Dairy and hog farming were the riskiest activities, and injury rates increased with the number of dairy cows.

Conclusions

One‐half of insured farmers in Finland are full‐time farmers, which may have lead to underestimation of risk in Finnish injury statistics. Dairy farming is of particular concern because it is both common and has a high injury rate. Am. J. Ind. Med. 43:314–325, 2003. © 2003 Wiley‐Liss, Inc.
Factors associated with women's risk of rape in the military environment
Authors: Sadler Anne G. , Booth Brenda M. , Cook Brian L. , Doebbeling Bradley N.
Published: February 2003

Background

Health hazards specific to women workers have not been adequately documented. This study assessed military environmental factors associated with rape occurring during military service, while controlling for pre‐military trauma experiences.

Methods

A national cross‐sectional survey of 558 women veterans serving in Vietnam or in subsequent eras was obtained through structured telephone interviews.

Results

Rape was reported by 28% (n = 151) of participants, with consistent rates found across eras. Military environmental factors were associated with increased likelihood of rape, including: sexual harassment allowed by officers (P < 0.0001), unwanted sexual advances on‐duty (P < 0.0001) and in sleeping quarters (P < 0.0001).

Conclusion

Violence towards military women has identifiable risk factors. Work and living environments where unwanted sexual behaviors occurred were associated with increased odds of rape. Officer leadership played an important role in the military environment and safety of women. Assailant alcohol and/or drug abuse at time of rape was notable. Interventions and policies based on modifiable environmental risk factors are needed to increase protection for women in the workplace. Am. J. Ind. Med. 43:262–273, 2003. Published 2003 Wiley‐Liss, Inc.
Asphalt—A continuing challenge
Authors: Melius James
Published: February 2003

Assessing the health risks of complex mixtures of polynuclear aromatic hydrocarbons such as diesel fumes and asphalt or bitumen continues to be a major challenge for occupational and environmental health scientists. The special Asphalt issue of the American Journal of Industrial Medicine (Cancer Mortality Among European Asphalt Workers (Am.J.Ind.Med. Volume 43, Number 1, 2003) presented the results of a major multi‐country epidemiological study of a group of workers exposed to one common commercial PAH mixture, asphalt or bitumen.
Taxonomic affinities of the Eppelsheim femur
Authors: Köhler Meike , Alba David M. , Solà Salvador Moyà , MacLatchy Laura
Published: February 2003

The taxonomic affinities of the Eppelsheim femur, known as Paidopithex, have been unclear for more than a century. Over the years, due to similarities with Pliopithecus, some authors have considered it a large pliopithecid, while others refer to it as Dryopithecus. The issue could not be resolved, because no definitive Dryopithecus femora were available. With the discovery of the Dryopithecus laietanus skeleton from Can Llobateres (CLl 18800), it has become possible to test the attribution of the Eppelsheim femur to Dryopithecus on the basis of direct morphological and metrical comparisons. By means of allometric techniques, we show that the Eppelsheim and D. laietanus femora fit different hindlimb morphologies with regard to relative length and relative head/neck size, with Paidopithex significantly differing from Dryopithecus, but more closely resembling Pliopithecus. Paidopithex also differs from Dryopithecus in other important aspects, such as its lower neck/shaft angle, lack of elevation of the femoral head above the greater trochanter, more posteriorly oriented lesser trochanter, and proximal shaft diameter thicker anteroposteriorly than mediolaterally. In these features, Paidopithex most closely resembles Pliopithecus in spite of differences in body mass (ca. 22 kg vs. ca. 10 kg, respectively). These features suggest that Paidopithex used a primitive locomotor pattern associated with arboreal quadrupedalism, instead of the more derived pattern displayed by Dryopithecus. Currently available evidence confirms that the attribution of Paidopithex to Dryopithecus can be rejected. Paidopithex could be a large and otherwise unknown pliopithecid, but the possibility cannot be ruled out that it represents a third kind of catarrhine. Am J Phys Anthropol 119:297–304, 2002. © 2002 Wiley‐Liss, Inc.
Mechanical properties of short sisal fiber‐reinforced polypropylene composites: Comparison of experimental data with theoretical predictions
Authors: Joseph P. V. , Mathew G. , Joseph K. , Thomas S. , Pradeep P.
Published: February 2003

Sisal fibers were used for the reinforcement of a polypropylene (pp) matrix. Composites consisting of polypropylene reinforced with short sisal fibers were prepared by melt‐mixing and solution‐mixing methods. A large amount of fiber breakage was observed during melt mixing. The fiber breakage analysis during composite preparation by melt mixing was carried out using optical microscopy. A polynomial equation was used to model the fiber‐length distribution during melt mixing. The experimental mechanical properties of sisal/PP composites were compared with existing theoretical models such as the modified rule of mixtures, parallel and series models, the Hirsch model, and the Bowyer–Baders model. The dependence of the tensile strength on the angle of measurement with respect to fiber orientation also was modeled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 602–611, 2003
Mechanical and thermal properties of polyurethane elastomers based on hydroxyl‐terminated polybutadienes and biopitch
Authors: Araújo Renata Costa Silva , Pasa Vânya Márcia Duarte
Published: February 2003

Biopitch is a renewable source of polyol obtained from Eucalyptus tar distillation, which was studied as an active component of polyurethane (PU). The polymerization occurred in one step, with a mixture of biopitch and hydroxyl‐terminated polybutadiene polyols reacted with 4‐4′‐diphenyl methane diisocyanate in the presence of dibutyltin dilaurate. Solid‐state 13C‐NMR, IR spectroscopy, elemental analysis, and thermal analysis [thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)] were used to characterize the biopitch. The biopitch sample showed an aromatic and oxygenated structure with great thermal stability at high temperatures. Multiphasic PUs were synthesized and characterized by IR spectroscopy (attenuated total reflectance), elemental analysis, thermal analysis (TGA and DSC), mechanical assays (tensile strength, elongation at break, toughness, hardness, and resilience), and water absorption resistance (ASTM D 570‐81). In a comparative study of the synthesized elastomers, biopitch content increased tensile strength and hardness and decreased thermal stability, elongation at break, and water absorption. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 759–766, 2003
Biodegradable extruded starch blends
Authors: You Xiudong , Li Li , Gao Jianping , Yu Jiugao , Zhao Zhuxuan
Published: February 2003

We prepared biodegradable extruded starch blends by first mixing starch with additives and then processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, solubility, biodegradability, rheological properties, molecular weight, and glass‐transition temperature of the extruded blends were studied. Glycerol and urea, to some extent, could both decrease the tensile strength and increase the percentage elongation at break because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. The extruded starch blends showed thermoplasticity, and their melts behaved as pseudoplastic liquids at a comparatively low shear rate. The biodegradability of the extruded starch was slightly higher than that of native starch. The molecular weight of starch displayed a decreasing tendency after extruding modification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 627–635, 2003
Spin‐on‐glass (SOG) for the trilayer imaging process
Authors: Sugita Hikaru , Saito Akio , Konno Keiji , Hayasui Akihiro , Nishiyama Satoru , Ebisawa Masahiko , Nishikawa Michinori , Ohta Yoshihisa , Tominaga Tetsuo
Published: February 2003

Maleic acid catalyzed hydrolysis and condensation of tetramethoxysilane was carried out in 1‐propoxy‐2‐propanol to prepare a spin‐on‐glass (SOG) material for the trilayer imaging process. The material was found to be stable enough for industry use. Minor amounts of methylsilsesquioxane and photoacid generators were introduced into the material. Thin resist (top layer) patterns were imaged on the SOG film (intermediate layer), which was coated on a hard‐baked i‐line resist (bottom layer). The SOG film showed sufficient adhesion to the resist patterns, and superior resist profiles were imaged on the film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 636–640, 2003
Prediction of nonlinear long‐term tensile creep of heterogeneous blends: Rubber‐toughened polypropylene–poly(styrene‐co‐acrylonitrile)
Authors: Kolařík Jan , Pegoretti Alessandro , Fambri Luca , Penati Amabile
Published: February 2003

The proposed predictive format for the tensile compliance, Db(t), of polymer blends is based on (1) a two‐parameter equivalent box model (EBM) and (2) calculations of the phase continuity of components in blends by using modified equations of the percolation theory. The input data encompass (1) selected parameters characterizing the creep of parent polymers and (2) critical volume fractions v1cr and v2cr of constituents in blends (delimiting the interval of phase cocontinuity). To describe the effects of time and stress on tensile compliance, a routinely used empirical equation was found suitable. Parameters characterizing the creep of parent polymers and their blends were extracted from generalized dependencies obtained through the superposition of time dependencies of tensile compliance assessed for a series of applied stresses and reconstructed with regard to the strain‐induced free‐volume expansion. Reconstructed dependencies can be approximated by a straight line, which simplifies the predictive format. The comparison of experimental and calculated compliance dependencies shows that the proposed format plausibly predicts the blend creep behavior over the studied interval of 0.1–10,000 min. The upswing in blend compliance after a long period of creeping is attributed to the redistribution of stresses acting on the constituents in the course of the creep under a constant load. This format is believed to have allowed the researchers in this study to anticipate (at least semiquantitatively) the creep behavior of intended blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 641–651, 2003
Electrical conduction and dielectric properties of poly(methyl methacrylate)/perylene solar concentrators
Authors: El‐Shaarawy M. G. , Mansour A. F. , El‐Bashir S. M. , El‐Mansy M. K. , Hammam M.
Published: February 2003

Poly(methyl methacrylate) doped with fluorescent perylene dye was prepared by both radical polymerization of methyl methacrylate and solvent casting from polymer solutions. The samples were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, electrical conductivity, and dielectric properties. Both conductivity and dielectric properties were measured in the temperature range 303–433 K and the frequency range 103to 5 × 106Hz. The results show that the direct‐current electrical conductivity increased by increasing dye content in solvent‐cast samples, whereas it decreased radically polymerized samples. The results of alternating‐current conductivity suggest electron hopping between filled and empty localized states. The study of dielectric properties showed two relaxation peaks corresponding to the dipole segmental and dipole group losses. Explanations based on the polymer free volume and acid–base interactions were proposed to examine the influence of the sample preparation and perylene dye concentration on the glass‐transition temperature and dielectric relaxation of the samples. The obtained results recommend the thermal and molecular stability of luminescent solar concentrator (LSC) matrices prepared by radical polymerization over those prepared by solvent casting. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 793–805, 2003
Studies on morphology, mechanical, thermal, and rheological behavior of extrusion‐blended polypropylene and thermotropic liquid crystalline polymer
Authors: Mandal P. K. , Bandyopadhyay D. , Chakrabarty D.
Published: February 2003

Polypropylene (PP) was melt‐blended in a single‐screw extruder with a thermotropic Vectra B‐950 liquid crystalline polymer (LCP) in different proportions. The mechanical properties of such blends were compared in respect of their Young's moduli, ultimate tensile strength (UTS), percent elongation at break, and toughness to those of pure PP. The thermal properties of these blends were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphology was studied by using a polarizing light microscope (PLM) and a scanning electron microscope (SEM) while the rheological aspects of the blends and the pure PP were studied by a Haake Rheowin equipment. Mechanical analysis (tensile properties) of the blends showed pronounced improvement in the moduli and the UTS of the PP matrix in the presence of 2–10% of LCP incorporation. TGA of all the blends showed an increase in the thermal stability for all the blends with respect to the matrix polymer PP, even at a temperature of 410°C, while PP itself undergoes drastic degradation at this temperature. DSC studies indicated an increase in the softening range of the blends over that of PP. Morphological studies showed limited mixing and elongated fibril formation by the dispersed LCP phase within the base matrix (PP) at the lower ranges of LCP incorporation while exhibiting a tendency to undergo gross phase separation at higher concentrations of LCP, which forms mostly agglomerated fibrils and large droplets. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 767–774, 2003
Effect of fillers and additives on the properties of SBR vulcanizates
Authors: Yin Dehui , Zhang Yong , Peng Zonglin , Zhang Yinxi
Published: February 2003

Methacrylic acid (MAA) and methyl methacrylate (MMA) were used as additives for peroxide‐cured styrene–butadiene rubber (SBR) filled with three inorganic fillers with different particle sizes and surface activity, for example, MgO, Mg(OH)2, and BaSO4. The experimental results show that the introduction of MAA can improve the mechanical properties of SBR vulcanizates filled with MgO, Mg(OH)2, or BaSO4. A small amount of MAA leads to significant increases in the modulus, tensile strength, and tear strength. MMA has little effect on the mechanical properties of the SBR vulcanizates. The SEM micrographs show that MAA can improve the interfacial bonding between SBR and the three kinds of fillers. The SBR–filler interaction was studied by Kraus plots. The relationship between the SBR–filler interaction and the mechanical properties was explored. m, a characteristic constant of a filler–SBR matrix, represents the interfacial bonding between fillers and SBR and the accumulated structure of the fillers. At a given ϕ, a high value of m means a strong interaction between SBR and the filler and, therefore, strong mechanical properties. The Payne effect of the SBR vulcanizates was observed, and the vulcanizates have low storage moduli at high strains and high storage moduli at low strains, and the moduli are nonlinear and increase the nonlinearity as the filler content increases. The loss moduli and loss factor reach their maximums at moderate and high strain amplitudes, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 775–782, 2003
Mechanical properties of ethylene–vinyl acetate/polystyrene blends studied by in situ polymerization
Authors: Cheng Shih‐Kai , Chen Po‐Tsun , Wang Cheng‐Chien , Chen Chuh‐Yung
Published: February 2003

This study examined ethylene–vinyl acetate (EVA)‐toughened polystyrene (PS). EVA is well‐known to be incompatible with PS; thus, the PS graft to the EVA backbone (EVA‐g‐PS) was used as a compatibilizer and provided good adhesion at the interface of PS and EVA. In addition, the mechanical properties and impact resistance of the PS matrix were obviously improved by EVA‐g‐PS and by EVA itself. Meanwhile, differential scanning calorimetry results showed that the grafted PS chain influenced the crystallization of EVA; for example, the melting temperature, the crystallization temperature, and the percentage crystallinity related to EVA were reduced. Moreover, the addition of 10% EVA increased the impact strength by a factor of five but reduced the modulus by the same factor. Additionally, a lower number‐average molecular weight EVA delayed phase inversion and resulted in poor mechanical properties. A fracture surface photograph revealed that the major mechanism of EVA‐toughened PS was craze and local matrix deformation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 699–705, 2003
Adhesion properties of phosphate‐ and siloxane‐containing polyurethane dispersions to steel: An analysis of the metal–coating interface
Authors: Mequanint K. , Sanderson R. , Pasch H.
Published: February 2003

Polyurethane dispersions containing phosphate and siloxane groups in the main chain were investigated as possible self‐assembling metal coatings. Improved adhesion of the polymer to the metal was observed because of the formation of an insoluble metal phosphate layer at the metal–coating interface. The neutralizing amine of the dispersions affected the formation of this metal phosphate, and the metal phosphate formation was dependent on the curing temperature and boiling point of the amine used for neutralization. A crosscut comparative study of adhesion proved that the phosphate‐containing coatings had better adhesion because of the formation of ionic bonds at the metal–coating interface. A solid‐state adhesion prediction method based on thermodynamic considerations was used. The results of the solid‐state adhesion method correlated well with that obtained from the crosscut adhesion test method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 900–907, 2003
Preparation and characterization of soy protein isolate–carboxymethylated konjac glucomannan blend films
Authors: Tang Rupei , Du Yumin , Zheng Hua , Fan Lihong
Published: February 2003

To improve the mechanical and water vapor barrier properties of soy protein films, the transparent films were prepared by blending 5 wt % soy protein isolate (SPI) alkaline water solution with 2 wt % carboxymethylated konjac glucomannan (CMKGM) aqueous solution and drying at 30 °C. The structure and properties of the blend films were studied by infrared spectroscopy, wide‐angle X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and measurements of mechanical properties and water vapor transmission. The results demonstrated a strong interaction and good miscibility between SPI and CMKGM due to intermolecular hydrogen bonding. The thermostability and mechanical and water vapor barrier properties of blend films were greatly enhanced due to the strong intermolecular hydrogen bonding between SPI and CMKGM. The tensile strength and breaking elongation of blend films increased with the increase of CMKGM content: the maximum values achieved were 54.6 MPa and 37%, respectively, when the CMKGM content was 70 wt %. The water vapor transmission of blend films decreased with the increase of CMKGM content: the lowest value achieved was 74.8 mg · cm−2 · d−1 when the CMKGM content was 70 wt %. The SPI–CMKGM blend films provide promising applications to fresh food packaging. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1095–1099, 2003
Aqueous polyurethane dispersions: A comparative study of polymerization processes
Authors: Barni Anita , Levi Marinella
Published: February 2003

Restrictions on volatile organic compounds have forced the producers of solvent‐based polymers to develop safer products. Water dispersions of polyurethanes are successfully replacing solvent‐borne products in the coating industry, but relatively little systematic work has been reported that compares polyurethanes obtained by different processes. In this study, polyurethanes were produced with three polymerization processes: in a solution, in a dispersion with the acetone process, and in a dispersion with the prepolymer mixing process. The same prepolymer was synthesized in all cases, and the reaction was concluded under the conditions required by the three different methods. In the first phase, nonextended polyurethanes were prepared with different functional group ratios (NCO/OH), and an evaluation of the quality of the dispersions and solutions and of the morphology of the dry polymers was made by a comparison of the products from the three preparation routes. Second, the growth of the molecular weight in water was studied for the prepolymer mixing process. NCO‐terminated prepolymers were dispersed in water and then extended by aliphatic diamines. The extender was added in different percentages that referred to the NCO equivalents of the prepolymer. This led to an evaluation of the effect of the dispersing medium on chain extension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 716–723, 2003
Antimicrobial protection of cotton and cotton/polyester fabrics by radiation and thermal treatments. I. Effect of ZnO formulation on the mechanical and dyeing properties
Authors: El‐Naggar A. M. , Zohdy M. H. , Hassan M. S. , Khalil E. M.
Published: February 2003

Cotton and cotton/polyester fabrics were treated against microbial attack by applying a formulation based essentially on ZnO under high‐energy radiation and thermal curing. To achieve the homogeneity and the reactivity of the treating formulation, a binder (Impron MTP) and a dispersing agent (Setamol WS) were used with ZnO. The antimicrobial property of the fabrics was evaluated, in terms of mechanical properties, by a soil burial test. Moreover, the effect of antimicrobial finishing on the dyeing properties in terms of color strength was investigated. It was found that the best composition that affords the best antimicrobial protection to cotton fabrics contains 2% ZnO, 2% binder, and 1% dispersing agents. For the cotton/polyester blend, the best results were achieved at the same conditions except the ZnO was 1%. It was found that the treatment under the effect of electron‐beam irradiation is better than that of gamma irradiation and thermal curing. The results showed that when the finishing process was carried out before dyeing with a reactive dye, it affects the color strength rather than performing the finishing after the dyeing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1129–1137, 2003
Molecular transport of esters, aldehydes, aromatic liquids, and a ketone into fluoroelastomer membrane at 30, 40, and 50°C
Authors: Kariduraganavar Mahadevappa Y. , Kulkarni Sangeeta B. , Aminabhavi Tejraj M.
Published: February 2003

Molecular transport of esters, aldehydes, substituted aromatic liquids, and a ketone through a fluoroelastomer (FC‐2120) membrane sample was studied at 30, 40, and 50°C. Sorption results were obtained by using a gravimetric method and concentration‐independent diffusion coefficients were calculated using Fick's diffusion equation. Permeability coefficients were calculated from sorption and diffusion data. Concentration profiles of the liquid penetrants were calculated by solving the Fick's equation under appropriate initial and boundary conditions and these plots are displayed to show the variations in liquid concentrations with reference to the nature of liquids chosen, membrane thickness, as well as the time of polymer immersion in the liquids. Arrhenius activation parameters were also estimated from a temperature dependence of diffusion and sorption coefficients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 840–847, 2003
Immobilization of lipase on a polymeric microsphere with an epoxy group prepared by radiation‐induced polymerization
Authors: Choi Seong‐Ho , Lee Kwang‐Pill , Kang Hee‐Dong
Published: February 2003

A polymeric microsphere (PM) with an epoxy group was prepared by the radiation‐induced polymerization of glycidyl methacrylate and diethylene glycol dimethacrylate in reaction conditions with variations in solvents, irradiation dose, and monomer composition. The epoxy group of the PM was analyzed by solid‐state 13C‐NMR, Fourier transform infrared spectroscopy (FTIR), Fourier transform Raman spectroscopy, and elemental analysis (EA) after amination. In EA after amination, the epoxy group content was in the range 0.20–0.50 mmol/g. The lipase was immobilized to the epoxy group of the PM in experimental conditions with variations in the pH and the epoxy group content. The activity of the lipase‐immobilized PM was in the range 148–342 unit/mg min. The activity of lipase‐immobilized PM increased in accordance with the epoxy group content. The lipase‐immobilized PM was also characterized by FTIR and EA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1153–1161, 2003
Recycling of unfilled polyurethane rubber using high‐power ultrasound
Authors: Ghose Sayata , Isayev A. I.
Published: February 2003

This investigation deals with the recycling of polyurethane rubber by the application of high‐power ultrasound in a continuous ultrasonic coaxial reactor. The cured rubber has been devulcanized at various feed rates and various gap sizes and then revulcanized again with certain adjustments in the curing recipe. The die pressure and the total power consumption have been recorded as a function of the processing conditions. The rheological and mechanical properties, hardness, gel fraction, and crosslink density of the original, devulcanized, and revulcanized samples have been measured and compared in an attempt to determine the optimum condition for devulcanization. Gel permeation chromatography (GPC) has been carried out with the sol part of the devulcanized samples to study the devulcanization and degradation. The results show that at low flow rates and narrow gaps, the material is degraded very quickly and, therefore, exhibits very poor mechanical properties. However, increasing the feed rate results in an improvement of the mechanical properties. Measured values of the crosslink densities and gel fractions indicate the processing conditions under which greater devulcanization and degradation of the samples take place. The lower molecular weights of the sol, extracted from the devulcanized samples, obtained in the GPC experiments in comparison with polyurethane gum indicate a breakdown of the polymeric chains as a result of devulcanization. The devulcanized samples show a higher activation energy of viscous flow, possibly because of the formation of branched structures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 980–989, 2003
Use of silica from rice husk ash as an antiblocking agent in low‐density polyethylene film
Authors: Chuayjuljit S. , Kunsawat C. , Potiyaraj P.
Published: February 2003

In packaging applications, blocking is always found in low‐density polyethylene (LDPE) films. Practically, such problems can be solved by incorporation of antiblocking agents, for example, silica and talc. The objective of this research was to explore the possibility of using silica from rice husk ash (RHA silica) as an antiblocking agent in LDPE film. Properties of RHA silica were compared with commercial silica, Sylo‐1. The appropriate amount of silica to be used as an antiblocking agent in LDPE film was also investigated. The results indicate that RHA silica has a smaller particle size and a higher specific surface area but a higher bulk density than those of Sylo‐1 silica. In the plastic film industry, 500–1000 ppm of silica is added in LDPE films as an antiblocking agent. It was also found that LDPE film with 2000–3000 ppm RHA silica showed similar properties to LDPE film filled with commercial silica in terms of its blocking behavior, mechanical strength, and film clarity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 848–852, 2003
Morphology and electrical properties of carbon‐black‐filled poly(ϵ‐caprolactone)/poly(vinyl butyral) nanocomposites
Authors: Wu Tzong‐Ming , Cheng Jen‐Chih
Published: February 2003

The morphology of poly(ε‐caprolactone) (PCL)/poly(vinyl butyral) (PVB)/clay nanocomposites was studied as a function of a small amount of amorphous PVB by polarized optical microscopy. The band spacings of PCL spherulites in PCL/PVB/clay nanocomposites decreased with increasing PVB content, and this indicated that increasing the PVB content shortened the period of lamellar twisting. The electrical properties of PCL/PVB/clay nanocomposites containing carbon black (CB) were also measured as a function of the PVB content. For samples with the same CB content, the intensity of the positive temperature coefficient (defined as the ratio of the peak resistivity to the resistivity at room temperature) of the nanocomposites increased as the PVB content increased. The change in the positive temperature coefficient was related to the morphological differences (i.e., the period of lamellar twisting) in the nanocomposites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1022–1031, 2003
Synthesis and characterization of maleated poly(3‐hydroxybutyrate)
Authors: Chen Cheng , Peng Shuwen , Fei Bin , Zhuang Yugang , Dong Lisong , Feng Zhiliu , Chen Shan , Xia Hongmei
Published: February 2003

Graft copolymerization of maleic anhydride (MA) onto poly(3‐hydroxybutyrate) (PHB) was carried out by use of benzoyl peroxide as initiator. The effects of various polymerization conditions on graft degree were investigated, including solvents, monomer and initiator concentrations, reaction temperature, and time. The monomer and initiator concentrations played an important role in graft copolymerization, and graft degree could be controlled in the range from 0.2 to 0.85% by changing the reaction conditions. The crystallization behavior and the thermal stability of PHB and maleated PHB were studied by DSC, WAXD, optical microscopy, and TGA. The results showed that, after grafting MA, the crystallization behavior of PHB was obviously changed. The cold crystallization temperature from the glass state increased, the crystallization temperature from the melted state decreased, and the growth rate of spherulite decreased. With the increase in graft degree, the banding texture of spherulites became more distinct and orderly. Moreover, the thermal stability of maleated PHB was obviously improved, compared with that of pure PHB. Its thermal decomposition temperature was enhanced by about 20°C. In addition, the introduction of the MA group promoted the biodegradability of PHB. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 659–668, 2003
Photoinitiation systems and thermal decomposition of photodefinable sacrificial materials
Authors: Wu Xiaoqun , Reed Hollie A. , Rhodes Larry F. , Elce Ed , Ravikiran R. , Shick Robert A. , Henderson Clifford L. , Allen Sue Ann Bidstrup , Kohl Paul A.
Published: February 2003

The exposure characteristics of norbornene‐based photosensitive sacrificial materials as functions of the photoinitiator have been investigated. The results show that the initiator, bis(2,4,6‐trimethylbenzoyl)‐phenylphosphine oxide, provides high photosensitivity and an adjustable contrast factor. The kinetics of the thermal decomposition of the polymers have been investigated with dynamic and isothermal thermogravimetric analysis to determine the most appropriate conditions for the thermal decomposition of the sacrificial polymers. The reaction is slightly higher than first‐order, and a single mechanism can account for the decomposition throughout the process. The dependence of the kinetic parameters on the composition of the copolymers has been studied, and the reaction order remains unchanged; however, the activation energy is lower when the alkenyl‐substituted norbornene content is increased in the copolymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1186–1195, 2003
Mechanical properties of a cryogenically mechanically alloyed polycarbonate–poly(aryl ether ether ketone) system
Authors: Martin Julie P. , Kander Ronald G.
Published: February 2003

The processing–property relationship of a model cryogenically mechanically alloyed polymer–polymer system [polycarbonate (PC) and poly(aryl ether ether ketone) (PEEK)] was investigated. PC and PEEK powders were cryogenically mechanically alloyed for 10 h, and the resulting two‐phase powder particles were processed into testable coupons with a miniature ram‐injection molder. The bulk mechanical properties of the coupons made from the mechanically alloyed powders and nonmechanically alloyed powders were investigated as a function of mechanical alloying and injection‐molding parameters. The injection‐molded coupons were mechanically tested in the three‐point‐bending mode. The results demonstrated that no measurable improvement was achieved in the energy to break, strain at failure, or failure strength in the coupons made from the mechanically alloyed materials in comparison with those of the coupons made from the nonmechanically alloyed powders. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1196–1202, 2003
Synthesis and properties of new polyurethane ionomers. I. Photosensitive cationomers with triazene units
Authors: Buruiana Emil C. , Niculescu Violeta , Buruiana Tinca
Published: February 2003

New bifunctional triazene compounds 1‐(m‐ hydroxymethyl)phenyl‐3‐(2‐hydroxyethyl)‐3‐methyltriaz(1)ene and l‐p‐nitrophenyl‐3,3‐di(2‐hydroxyethyl)triaz(1)ene as intermediates in polyurethane synthesis were prepared. Photosensitive polyetherurethane cationomers based on poly(tetramethylene oxide) diol of 2,000 average molecular weight, tolylene‐2,4‐diisocyanate, and N‐methyldiethanolamine/triazene diols, as cochain extender, followed by a quaternization with benzyl chloride, were synthesized and characterized. Upon UV irradiation, feniltriazene chromophore in monomer and both polymers (ionomeric or nonionomeric type) is irreversibly cleaved, as evidenced in photolytic and kinetic studies. The rate constant of photolysis in ionomer film was lower than for the corresponding nonionic film. A positive pattern can then be developed by treatment with CHCl3 that dissolves the exposed zone, while the unexposed area remains resistant and insoluble. By incorporating side nitrofeniltriazene groups, photostable polyurethanes were obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1203–1210, 2003