bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical modification of chitosan: Synthesis and characterization of chitosan‐crown ethers
Authors: Changhong Peng , Weijun Yang , Motang Tang 
Published: January 2003

AbstractFour novel Schiff‐type chitosan (CTS)‐crown ethers were synthesized through a reaction between NH2 in CTS or crosslinked chitosan (CCTS) and CHO in 4′‐formylbenzo‐crown ethers, and four secondary‐amino‐type CTS‐crown ethers were prepared through the reduced reaction of NaBH4, respectively. Their structures were characterized by elemental analysis, Fourier transform infrared (FTIR) spectra analysis, solid‐state 13C‐NMR analysis, and X‐ray diffraction (XRD) analysis. The elemental analysis results showed that the percentage of nitrogen in all CTS‐crown ethers were lower than that of CTS or CCTS. From the FTIR data of CTS, CCTS, and CTS‐crown ethers I–VIII, we saw that the characteristic peaks of CN, NH, and Ar appeared and that the characteristic peaks of pyranoside in the chain of CTS or CCTS were not destroyed. The XRD spectra demonstrated that CTS‐crown ethers I–VIII gave lower crystallinities than CTS or CCTS, which indicated that these compounds were considerably more amorphous than CTS or CCTS. In the solid‐state 13C‐NMR spectra, all of these CTS‐crown ethers had a particular peak of aromatic at 128 or 129 ppm, and the greatest difference between Schiff‐type CTS‐crown ethers and secondary‐amino‐type CTS‐crown ethers was that the Schiff‐type CTS‐crown ethers had the particular peak of CN, which disappeared in secondary‐type CTS‐crown ethers. All these facts confirmed that the structures of CTS‐crown ethers I–VIII were as expected. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2221–2225, 2003
Some features of phenolic inhibitor consumption in oxidized polypropylene in the presence of synergists–hydroperoxide decomposers
Authors: Shanina E. L. , Zaikov G. E. , Mukmeneva N. A. 
Published: January 2003

AbstractThe influence of sulfur and phosphors containing substances, hydroperoxide decomposers, on the kinetics of the consumption of two phenolic antioxidants in polypropylene (PP) was studied. The induction periods of PP autoxidation at 130°C were measured in the presence of inhibiting compositions that consisted of phenolic inhibitors and decomposers of hydroperoxide. The obtained results indicated that the influence of the hydroperoxide decomposer became significant when the concentration of the phenolic antioxidant became close to a critical value. It was shown also that the influence of the hydroperoxide decomposer significantly depended on the mechanism of the phenolic inhibitor transformation: first of all, on the nature of its transformation products. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2226–2229, 2003
Synthesis of new free‐radical initiators for polymerization
Authors: Gawdzik B. , Ksiȩżopolski J. , Matynia T. 
Published: January 2003

AbstractSynthesis and properties of new initiating systems formed from commercially available ketones, glycols, and hydrogen peroxide (60%) are presented. In preparation of free radical initiators methyl ethyl ketone, which was oxidized by hydrogen peroxide, was used. Reaction was carried out in etanodiol or 1,4‐butanodiol as diluent. The obtained initiators with cobalt octoate as a promotor were applied for crosslinking of the commercially available unsaturated polyester resin. Properties of the resin were compared with those obtained while it was hardened by the typical curing system containing methyl ethyl ketone hydroperoxide and cobalt octoate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2238–2243, 2003
Studies on the structure of activated carbon fibers activated by phosphoric acid
Authors: Fu Ruowen , Liu Ling , Huang Wenqiang , Sun Pingchun 
Published: January 2003

AbstractBy solid‐state 13C‐ and 31P‐NMR, XPS, and FTIR, the chemical structure of activated carbon fiber–P (ACF‐P) and its reaction with phosphoric acid were studied. Even when activated at low temperatures, these fibers developed a graphitelike carbon structure with a certain amount of phenol groups as well as acetal (or methylenedioxy) carbon. As expected, the oxygen‐containing groups were greatly reduced at high activation temperatures. Different from the ACF‐W, metaphosphoric acid (or polyphosphates) and a small amount of phosphorus exist on ACF‐P. The original ACF‐P activated at low temperature contained a lot of phosphoric acid, so it had to be washed with water to expose the large surface area. The washing process can be omitted for ACF‐P activated at high temperature because most phosphorus compounds in fiber have volatilized. The ACF‐P activated at lower temperature possessed a large amount of oxygen‐containing surface groups and had enhanced adsorption ability for polar adsorbates. The remaining of metaphosphoric acid enhanced the adsorption of silver ion. The experimental results showed that the peaks of 31P‐NMR, P2p‐XPS, and FTIR at 1620 cm−1 shifted with the increase of activated temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2253–2261, 2003
Study on swelling behavior and pervaporation properties of AA–MMA–BA copolymers for separation of methanol/MTBE/C5 mixtures
Authors: Zhang Lin , Chen Huan‐Lin , Pan Zu‐Ren 
Published: January 2003

AbstractIn this study, the copolymers with different ratios of AA(acrylic acid)–MMA(methyl methacrylate)–BA (butyl acrylate) are synthesized to prepare pervaporation membrane for the separation of methanol/MTBE (methyl tert‐butyl ether)/C5 mixtures. Swelling experiment of these copolymers in pure methanol, MTBE, C5, and methanol/MTBE mixtures are carried out, respectively. The results show that there is a strong interaction between MTBE and copolymer with high content of BA. The pervaporation characteristics of the membranes prepared with different copolymer are measured in the separation of methanol/MTBE mixture. The experimental results show that the pervaporation ability changes with swelling degree in the same direction. The copolymers are characterized by FTIR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2267–2271, 2003
New fluoro‐modified thermoplastic polyurethanes
Authors: Tonelli Claudio , Ajroldi Giuseppe 
Published: January 2003

AbstractNew fluoro‐modified thermoplastic polyurethanes containing perfluoropolyether (PFPE) blocks were synthesized by the reaction of a fluorinated macrodiol with a hydrogenated prepolymer based on poly(tetramethylene glycol) and 4,4′‐methylene‐bis‐phenylisocyanate, followed by subsequent chain extension with 1,4‐n‐butanediol. This multistep bulk process opened the way for a new family of polymeric materials whose tensile properties appear to be excellent and unchanged in comparison with the corresponding unmodified hydrogenated polymers. Dynamic mechanical analysis and differential scanning calorimetry revealed peculiar characteristics. These polymers showed an unusual multiphase structure in which not only the hard and the hydrogenated soft segments were self‐organized, but also a second soft phase, constituted by the PFPE segments, was present. Moreover, an easier hard‐phase segregation and self‐organization were observed, as was evidenced by the higher melting temperatures of the semicrystalline phase. This unique characteristic combined with a selective enrichment of PFPE segments to the surface, as indicated by the unusually low coefficient of friction data and superior chemical resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2279–2294, 2003
Determination of refractive index profile of partially and highly oriented fibers using double refracting interference microscopy
Authors: El‐Bakary Mohammed A. 
Published: January 2003

AbstractDouble refracting polarizing interference microscope designed by Pluta is used with a suggested method to determine the refractive index profile and birefringence profile of partially and highly oriented fibers. The application of this method depends on using Pluta polarizing interference microscope in two positions (crossed position for the duplicated images and subtractive position for the nonduplicated image of the fiber). The mathematical representation of the suggested method is given. The refraction of the light beam inside the fibers is taken into consideration while measuring the fringe shift profile. The refractive index profiles of polypropylene fiber with draw ratio 3.5 are determined using the conventional method. The results are compared with those obtained with the suggested method and found to be in good agreement. The suggested method is applied to determine the refractive index profile of poly(aryl ether ether ketone) partially oriented fiber and poly(ethylene terephthalate) highly oriented fiber. The diffraction of He–Ne laser beam is used to determine the average diameters of these fibers. Microinterferograms are given for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2341–2347, 2003
Polyurethane‐infiltrated carbon foams: A coupling of thermal and mechanical properties
Authors: Bunning Timothy J. , Jeon Hong G. , Roy Ajit K. , Kearns Kristen M. , Farmer Barry L. , Adams Walter W. 
Published: January 2003

AbstractThe thermal and mechanical properties of polyurethane‐infiltrated carbon foam of various densities were investigated. By combining the high thermal conductivity of the carbon foam with the mechanical toughness of the pure polyurethane, a mechanically tough composite (relative to the unfilled foam) that could be used at higher temperatures than the polyurethane's degradation was formed. Both the tensile strength and the modulus increased by an order of magnitude for the composites compared to unfilled foam, while the compressive and shear strengths and moduli of the composites approached values exhibited by pure polyurethane. At both 300 and 400°C, the rectangular blocks of pure polyurethane lost their mechanical integrity due to decomposition in air. Thermogravimetric analysis confirms substantial initial weight loss above 290°C. Filled carbon foam blocks, however, maintain their mechanical integrity at both 300 and 400°C indefinitely, although the bulk of the rectangular block mass is polyurethane. Three different carbon foam densities are examined. As expected, the higher density foams show greater heat transfer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2348–2355, 2003
Natural weathering, artificial photo‐oxidation, and thermal aging of low density polyethylene: Grafting of acrylic acid onto aged polyethylene films
Authors: El‐Awady M. M. 
Published: January 2003

AbstractThe photo‐oxidation and thermal initiation changes of commercial low density polyethylene (LDPE) films used in greenhouse covering, in the presence or absence of ultraviolet (UV) stabilizer, were monitored by infrared (IR) spectroscopy, by mechanical tests and by applying the grafting of acrylic acid onto the aged films. It was found that the resistance of PE films to UV irradiation and heat initiation as proved by tensile strength and elongation at break % was better for stabilized PE films compared with the unstabilized ones. A simple correlation was not observed between the fall in mechanical properties and the rate of film oxidation. On the other hand, an almost linear relation was obviously noticed between the degree of PE oxidation (CO) measured by IR spectroscopy and the grafting level. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2365–2371, 2003
Sulfation of silk fibroin by sulfuric acid and anticoagulant activity
Authors: Tamada Yasushi 
Published: January 2003

AbstractSilk fibroin (Bombyx mori) was sulfated with an aqueous sulfuric acid solution. The sulfated fibroin was characterized by Fourier transform infrared spectroscopy (FTIR), amino acid analysis, and gel filtration chromatography (GFC). Maximum yield was obtained at around 2–4 h, and it decreased at 6 h and more. The molecular size decreased and dispersed with sulfation, and the molecular weight was estimated at around 10,000 by GFC using protein standards. The amino acid composition indicated that the crystal region of the fibroin molecule remained in sulfated fibroin until a sulfation reaction time of 4 h. The incorporation of sulfate groups was confirmed by FTIR and the amount of sulfate groups introduced for 4 h sulfation was estimated in 0.3 mmol/g by acidimetric titration. The efficiency of sulfation was calculated at 15.7%. Blood coagulation was prevented by 20 mg of sulfated fibroin in 1 mL of blood, while original fibroin did not show the effect. This result indicates that sulfate group introduction results in addition of anticoagulant function to silk fibroin. Although a variety of polymer backbones have been used for synthesis of sulfated polymers as anticoagulant materials, no reports are available concerning a sulfated polymer based on a protein backbone. Sulfated fibroin is a new type of anticoagulant material having a protein backbone. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2377–2382, 2003
Development of new concepts for the control of polymerization processes: Multiobjective optimization and decision engineering. I. Application to emulsion homopolymerization of styrene
Authors: Massebeuf Silvère , Fonteix Christian , Hoppe Sandrine , Pla Fernand 
Published: January 2003

AbstractThis article deals with the development of a multicriteria analysis, and its application to the optimization of batch emulsion polymerization processes. This new approach in the domain of polymer reaction engineering illustrates how a multiobjective optimization aided by a genetic algorithm and using the Pareto concept of domination is useful. In this process (emulsion homopolymerization of styrene), several objectives were simultaneously required, e.g., a high quality of the resulting products together with a high productivity. The aim of this study was to find the optimal experimental conditions to obtain simultaneously the minimum reaction time and designed values for both average molecular weights and particles size. To do that, an adapted mathematical model, able to describe all the process physicochemical phenomena, was been first elaborated. The multicriteria analysis then gave a set of nondominated points with conflicting criteria. A decision support system was then developed and applied to rank the Pareto solutions set and to propose some good solutions by taking into account the decision maker's preferences. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2383–2396, 2003
Hydrophobic association and temperature and pH sensitivity of hydrophobically modified poly(N‐isopropylacrylamide/acrylic acid) gels
Authors: Tian Qin , Zhao Xian , Tang Xiaozhen , Zhang Yunxiang 
Published: January 2003

AbstractHydrophobically modified poly(acrylic acid/N‐isopropylacrylamide) gels were synthesized by the radical copolymerization of acrylic acid/N‐isopropylacrylamide with a small amount of the hydrophobic comonomer 2‐(N‐ethylperfluorooctanesulfoamido)ethyl acrylate, stearyl acrylate, or lauryl acrylate in tert‐butanol with ethylene glycol dimethacrylate as a crosslinker. Swelling kinetics and fluorescence measurements showed that the hydrophobic association ability of fluorocarbon groups was stronger than that of hydrocarbon analogues in modified hydrogels that contained both physical and chemical crosslinking networks. The effects of the fractions and the species of the hydrophobe on the gel swelling and pH and temperature sensitivity were studied. The results indicated that the swelling behavior and pH and temperature sensitivity of the gels were affected by the degree of hydrophobic modification. A hydrogel with a suitable 2‐(N‐ethylperfluorooctanesulfoamido)ethyl acrylate content (0.349 mol %) showed good pH and temperature sensitivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2406–2413, 2003
Dynamic mechanical study on the thermal aging of a hydroxyl‐terminated polybutadiene‐based energetic composite
Authors: Fuente José Luis de la , Rodríguez Olga 
Published: January 2003

AbstractIn an attempt to determine the aging behavior of hydroxyl‐terminated polybutadiene‐based composite solid propellants, viscoelastic measurements were used to study the effect of thermal aging on this kind of energetic material. Accelerated‐aging tests at 40, 60, and 80°C were performed for 5000 h. The changes in the dynamic mechanical properties, including the storage modulus (E′) and loss factor or damping efficiency (tan δ), with time and temperature were measured to determine the aging rate and likely mechanisms occurring during this process. An Arrhenius analysis based on the determination of relative rate constants showed a linear tendency from tan δ values, whereas a significant curvature was found from E′ values. In addition, the effects of external (surface) and internal (core) sampling in the intensification of the aging process were analyzed. The results confirmed dynamic mechanical analysis as a powerful tool for determining the aging characteristics of composite propellants. This technique allows the evaluation of the actual state of a propellant grain with a small sample and a straightforward measurement. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2397–2405, 2003
Molecular genetics of aging in the fly: Is this the end of the beginning?
Authors: Helfand Stephen L. , Rogina Blanka 
Published: January 2003

AbstractHow we age and what we can do about it have been uppermost in human thought since antiquity. The many false starts have frustrated experimentalists and theoretical arguments pronouncing the inevitability of the process have created a nihilistic climate among scientists and the public. The identification of single gene alterations that substantially extend life span in nematodes and flies however, have begun to reinvigorate the field. Drosophila's long history of contributions to aging research, rich storehouse of genetic information, and powerful molecular techniques make it an excellent system for studying the molecular mechanisms underlying the process of aging. In recent years, Drosophila has been used to test current theories on aging and explore new directions of potential importance to the biology of aging. One such example is the surprising finding that, as opposed to the commonly held assumption that adult life is a period of random passive decline in which all things are thought to fall apart, the molecular life of the adult fly appears to be a state of dynamic well‐regulated change. In the fly, the level of expression of many different genes changes in an invariant, often age‐dependent, manner. These as well as other molecular genetic studies and demographic analyses using the fly have begun to challenge widely held ideas about aging providing evidence that aging may be a much more dynamic and malleable process than anticipated. With the enormous success that Drosophila molecular genetics has demonstrated in helping understand complex biological phenomena such as development there is much optimism that similar approaches can be adapted to assist in understanding the process of aging. BioEssays 25:134–141, 2003. © 2003 Wiley Periodicals, Inc.
Levels of polymorphism on the sex‐limited chromosome: a clue to Y from W?
Authors: Ellegren Hans 
Published: January 2003

AbstractNucleotide diversity of the human Y chromosome is much lower than that in the rest of the genome. A new hypothesis postulates that this invariance may result from mutations in maternally inherited mitochondrial DNA (mtDNA), leading to impaired reproduction among males and lowered male effective population size. If correct, we should expect to see low levels of polymorphism in the male‐specific Y chromosome of many organisms but not necessarily in the female‐specific W chromosome in organisms with female heterogamety. However, recent observations from birds suggest that the avian W chromosome is very low in nucleotide diversity. This indicates that mtDNA mutations cannot broadly explain the evolution of the sex‐limited chromosome. Other work has suggested that sexual selection at loci involved in sex determination or secondary sexual characteristics might reduce levels of genetic variability on Y through hitch‐hiking effects. Although the W chromosome does not seen to play a dominant role for sex determination in birds, it cannot be excluded that selective sweeps arising from natural or sexual selection contribute to the low levels of genetic variability seen on this chromosome. BioEssays 25:163–167, 2003. © 2003 Wiley Periodicals, Inc.
Stem cells, telomerase and dyskeratosis congenita
Authors: Mason Philip J. 
Published: January 2003

AbstractDyskeratosis congenita is a rare skin and bone marrow failure syndrome caused by defective telomere maintenance in stem cells. The major X‐linked form of the disease is due to mutations in a nucleolar protein, dyskerin, that is part of small nucleolar ribonucleoprotein particles that are involved in processing ribosomal RNA. It is also found in the telomerase complex, pointing to an unexpected link between these two processes. An autosomal dominant form is due to mutations in the RNA component of telomerase (hTR). Patients with this form of the disease are more severely affected in later generations that carry the mutations, possibly due to the inheritance of shortened telomeres, disguising the inherited nature of the disease in some cases classified as aplastic anemia. Because of the importance of telomerase in tumour formation and aging, study of this disease may provide important clues about these fundamental processes. BioEssays 25:126–133, 2003. © 2003 Wiley Periodicals, Inc.
Detection of unpaired DNA at meiosis results in RNA‐mediated silencing
Authors: Hynes Michael J. , Todd Richard B. 
Published: January 2003

AbstractDuring meiosis, homologous chromosomes must pair in order to permit recombination and correct chromosome segregation to occur. Two recent papers1,2 show that meiotic pairing is also important for correct gene expression during meiosis. They describe data for the filamentous fungus Neurospora crassa that show that a lack of pairing generated by ectopic integration of genes can result in silencing of genes expressed during meiosis. This can result in aberrant meioses whose defects are specific to the function of the unpaired gene. Furthermore, mutations affecting the silencing mechanism have been selected in a gene encoding a putative RNA‐dependent RNA polymerase. This finding indicates the involvement of a meiotic specific post‐transcriptional gene silencing mechanism (PTGS) similar to that observed in vegetative cells in N. crassa and other organisms. Finally, this gene product is essential for normal meiosis, suggesting that RNA‐dependent processes are fundamental to the sexual cycle. BioEssays 25:99–103, 2003. © 2003 Wiley Periodicals, Inc.
A new faculty orientation program: Building a core of new faculty to shape the future of the college
Authors: Welch Gerry F. 
Published: January 2003

AbstractSt. Louis Community College leadership recognized that a new large cohort of faculty hired to replace retiring instructors would shape the college over the next quarter century and beyond. The college challenged its staff development team to create a program that would integrate new faculty into the college and prepare them for the vital role they would play.
Web‐based faculty development using Time‐Revealed Scenarios
Authors: Nellis Patrick , Hosman David , King Jeffrey M. , Armstead Cathleen 
Published: January 2003

AbstractJust as community colleges are making course work available to their students through a variety of delivery systems, so, too, are staff developers creating on‐line means of providing activities for their faculty. The on‐line faculty development programs at Valencia Community College, Orlando, Florida, and the Art Institute of Dallas use the Time‐Revealed Scenarios software program as the basis of their on‐line approach.
Recent advances in retreats: Adapting the Great Teachers Seminar model to serve an entire college
Authors: Bergeron Pam , McHargue Mike 
Published: January 2003

AbstractDespite the advanced technology on today's community college campuses, the need for sit‐around‐the‐campfire human interaction endures. One way to bring this interesting dichotomy together is through a retreat based on the Great Teachers Seminar model.