bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acculturation, social support and academic achievement of Mexican and Mexican American high school students: An exploratory study
Authors: López Eric J. , Ehly Stewart , García‐Vásquez Enedina 
Published: August 2002

AbstractConcerns about the high dropout rate among Mexican American high school students has led researchers and educators to determine which variables affect academic success. The study investigated two factors associated with academic achievement: acculturation and social support. The sample consisted of 60 ninth‐grade students of Mexican decent in a southwestern school district. Results indicated that students identified as highly integrated and strongly Anglo‐oriented bicultural tended to have higher academic achievement. In addition, the sample as a whole perceived social support from all four sources. Although no generational effects were identified, females tended to have higher GPAs, and perceive more social support, while the males, interestingly, were slightly more acculturated. © 2002 Wiley Periodicals, Inc.
Designing effective interventions for children at‐risk for antisocial behavior: An integrated model of components necessary for making valid inferences
Authors: Lane Kathleen L. , Beebe‐Frankenberger Margaret E. , Lambros Katina M. , Pierson Melinda 
Published: August 2002

AbstractChildren demonstrating antisocial behavior patterns are at‐risk for a host of negative outcomes including school failure, peer and teacher rejection, academic difficulties, and future delinquency. These children are undoubtedly in need of effective and appropriate interventions to address problem areas in both behavioral and academic domains. To ensure that academic and sociobehavioral interventions will be more successful, three main components: (a) social validity, (b) treatment integrity, and (c) generalization and maintenance must be addressed when designing the interventions. The purpose of this article is to (a) describe the pertinent characteristics (e.g., definition, application, and assessment issues) of each of these components as they relate to school‐based interventions, and (b) introduce an integrated model that illustrates the interrelatedness of these essential intervention components. © 2001 John Wiley & Sons, Inc.
Model reaction for the synthesis of polyhydroxyurethanes from cyclic carbonates with amines: Substituent effect on the reactivity and selectivity of ring‐opening direction in the reaction of five‐membered cyclic carbonates with amine
Authors: Tomita Hidetoshi , Sanda Fumio , Endo Takeshi 
Published: August 2002

AbstractThis article focuses on the substituent effect on the reactivity and selectivity of the ring‐opening direction in the reaction of five‐membered cyclic carbonates with n‐hexylamine. The reactivity of the cyclic carbonate and the formation selectivity of the adduct with a secondary hydroxyl group increased as a stronger electron‐withdrawing group was introduced at the α‐methylene of the cyclic carbonate. These results are discussed on the basis of the stability of intermediates, primary and secondary alcoholate anions, Mulliken charges on carbonyl carbon, and the bond lengths and orders of the OCO single bond. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3678–3685, 2001
Synthesis and thermal behavior of poly(ethylene oxide) poly(N‐substituted urethane)
Authors: Kweon Jung‐Ohk , Lee Yong‐Kuen , Noh Si‐Tae 
Published: August 2002

AbstractPoly(N‐substituted urethane)s with an alkyl or ligo(ethylene oxide) monomethyl ether side chain were synthesized by the reaction operating in the following two‐step process: first, by metalation of the starting polymer with potassium tertiary butoxide (t‐BuOK) and then by treatment of the obtained urethane polyanion with tosylate in dimethyl sulfoxide. The thermal properties of poly(ethylene oxide) poly(N‐substituted urethane) (N‐sub PEOPU) were investigated in view of the N‐substitution degree and properties of the substituent. The chemical structures were characterized by Fourier transform infrared, 1H NMR, and 13C NMR spectroscopies. DSC and thermogravimetric analysis (TGA) were used to investigate the thermal properties of N‐sub PEOPUs. As the degree of N‐methylation increased, the glass‐transition temperature (Tg) of the N‐sub PEOPUs linearly decreased from 6 to −29 °C, and the weight‐loss temperature of 5% (T) from TGA in air increased from 278 to 360 °C. In the fully N‐substituted PEOPUs, the behavior of the thermal decomposition of the PEOPU that was processed in two stages was changed to one‐step decomposition in the temperature range of 360–440 °C. The Tg was shifted to a lower temperature with an increasing length of the substituent in N‐sub PEOPU. Improvement of the thermal stability by N‐substitution was more significant in N‐alkyl PEOPU than in N‐ethoxylate PEOPU. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4129–4138, 2001
Polyaddition of bis(seven‐membered cyclic carbonate) with diamines: A novel and efficient synthetic method for polyhydroxyurethanes
Authors: Tomita Hidetoshi , Sanda Fumio , Endo Takeshi 
Published: August 2002

AbstractThis article deals with the polyaddition of a novel bis(seven‐membered cyclic carbonate), 1,2‐bis[3‐(1,3‐dioxepan‐2‐one‐5‐yl)‐propylthio]ethane, with the diamines 4,9‐dioxa‐1,12‐dodecanediamine and p‐xylylenediamine. The polyaddition was carried out at 30–70 °C for 6–24 h in dimethyl sulfoxide to obtain the corresponding polyhydroxyurethanes with number‐average molecular weights of 10,900–35,700 in good yields. The reaction of a monofunctional seven‐membered cyclic carbonate, 5‐allyl‐1,3‐dioxepan‐2‐one (7CC), with monoamines was also carried out to examine the reactivity in comparison with that of six‐ and five‐membered cyclic carbonates. The reaction rate constants of 7CC with n‐hexylamine and benzylamine were estimated to be 48.5 and 11.0 L/mol · h, respectively, in dimethyl sulfoxide‐d6 (initial reagent concentration = 1 M) at 30 °C. The seven‐membered cyclic carbonate ring was 2.98 and 5.82 kcal/mol more strained than those of the six‐ and five‐membered cyclic carbonates, respectively, according to a semiempirical molecular orbital calculation with the PM3 Hamiltonian. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4091–4100, 2001
Highly biodegradable copolymers composed of chiral depsipeptide and L‐lactide units with favorable physical properties
Authors: Shirahama Hiroyuki , Tanaka Akira , Yasuda Hajime 
Published: August 2002

AbstractSyntheses of copolymers composed of optically active depsipeptides (3,6‐dimethyl‐2,5‐morphorinedione) and L‐lactide—poly(L‐3,L‐6‐dimethyl‐2,5‐morphorinedione‐co‐L‐lactide), poly(L‐3,DL‐6‐dimethyl‐2,5‐morphorinedione‐co‐L‐lactide), and poly(L‐3,D‐6‐dimethyl‐2,5‐morphorinedione‐co‐L‐lactide)—were examined in an effort to improve the biodegradability and physical properties of homopoly(L‐lactide). In degradation tests, the copolymers composed of 3,6‐dimethyl‐2,5‐morphorinedione and lactide in the ratios 10/90 to 13/87 exhibited high biodegradability toward proteinase K, whereas a homopolymer, poly(L‐lactide), exhibited very poor biodegradability (only 50% after 200 h). These polymers composed of 3,6‐dimethyl‐2,5‐morphorinedione/L‐lactide in 11/89 to 13/87 ratios also degrades rapidly after being in compost for 30 days. The resulting copolymers, however, showed relatively low elongation properties. Therefore, ternary copolymerizations of L‐3,DL‐6‐dimethyl‐2,5‐morphorinedione, ϵ‐caprolactone, and L‐lactide were explored in an effort to improve their mechanical properties, especially the elongation, and sufficient results were obtained with an approximate ratio of 3/11/86. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 302–316, 2002
Solid polymer electrolytes III: Preparation, characterization, and ionic conductivity of new gelled polymer electrolytes based on segmented, perfluoropolyether‐modified polyurethane
Authors: Chen Chi‐Chang , Liang Wuu‐Jyh , Kuo Ping‐Lin 
Published: August 2002

AbstractNew segmented polyurethanes with perfluoropolyether (PFPE) and poly(ethylene oxide) blocks were synthesized from a fluorinated macrodiol mixed with poly(ethylene glycol) (PEG) in different ratios as a soft segment, 2,4‐toluene diisocyanate as a hard segment, and ethylene glycol as a chain extender. Fourier transform infrared, NMR, and thermal analysis [differential scanning calorimetry and thermogravimetric analysis (TGA)] were used to characterize the structures of these copolymers. The copolymer films were immersed in a liquid electrolyte (1 M LiClO4/propylene carbonate) to form gel‐type electrolytes. The ionic conductivities of these polymer electrolytes were investigated through changes in the copolymer composition and content of the liquid electrolyte. The relative molar ratio of PFPE and PEG in the copolymer played an important role in the conductivity and the capacity to retain the liquid electrolyte solution. The copolymer with a 50/50 PFPE/PEG ratio, having the lowest decomposition temperature shown by TGA, exhibited the highest ionic conductivity and lowest activation energy for ion transportation. The conductivities of these systems were about 10−3 S cm−1 at room temperature and 10−2 S cm−1 at 70 °C; the films immersed in the liquid electrolyte with an increase of 70 wt % were homogenous with good mechanical properties. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 486–495, 2002; DOI 10.1002/pola.10119
Staff‐type dendrimer: End functionalization of the dendronized siloxane polymer Me3SiO(MeSiHO)nSiMe3
Authors: Kim Chungkyun , Kwark Kyongran 
Published: August 2002

AbstractA staff‐type dendritic carbosilane was synthesized with the siloxane polymer Me3SiO[MeSi(H)O]nSiMe3 as the core. Through hydrosilation and alcoholysis, the polymeric core grew to the second generation, which contained three, six, and nine allyloxy end groups on each siloxane unit backbone, respectively. The reaction of the monofunctionalized second‐parent generation, which had three SiCl groups on the peripheral layer of the unit backbone, with allylalcohol, cholesterol, 8‐hydroxyquinoline, 5‐(2‐hydroxyl)‐4‐methylthiazole, 4‐pyridinepropanol, and 4‐pyridinealdoxime in the presence of 1,1,2,2‐tetramethyethylenediamine, produced end‐functionalized, staff‐type dendrimers. The characterization of the dendritic polymers was carried out with NMR spectroscopy and gel permeation chromatography as well as elemental analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 976–982, 2002
Synthesis and characterization of temperature‐ and pH‐sensitive hydrogels based on poly(2‐ethyl‐2‐oxazoline) and poly(D,L‐lactide)
Authors: Wang Chau‐Hui , Hsiue Ging‐Ho 
Published: August 2002

AbstractA novel series of temperature‐ and pH‐sensitive hydrogels based on poly(2‐ethyl‐2‐oxazoline) and three‐arm poly(D,L‐lactide) were synthesized via photocopolymerization. For the creation of polymeric networks, two types of macromers terminated with methacrylate groups were prepared: poly(2‐ethyl‐2‐oxazoline) dimethacrylate and three‐arm poly(D,L‐lactide) trimethacrylate. The chemical structures were analyzed with 1H NMR and Fourier transform infrared techniques. The thermal behaviors, morphologies, and swelling properties were measured for the characterization of the polymeric networks. All the poly(2‐ethyl‐2‐oxazoline)/three‐arm poly(D,L‐lactide)hydrogels provided high water retention capacity and exhibited reversible swelling–shrinking behavior in response to temperature and pH variations. The hydrogels with higher poly(2‐ethyl‐2‐oxazoline) dimethacrylate contents were more effective in raising the swelling ratio and temperature and pH sensitivity. However, higher contents of three‐arm poly(D,L‐lactide) trimethacrylate produced larger particles and pore sizes in the hydrogels. This study effectively proves that this unique combination of water swellability and biodegradability provides hydrogels with a much wider range of applications in biomedical fields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1112–1121, 2002
Syntheses and characterizations of thermally degradable epoxy resins. III
Authors: Li Haiying , Wang Lejun , Jacob Karl , Wong C. P. 
Published: August 2002

AbstractIn flip‐chip technology, the development of reworkable underfill materials has been one of the keys to the recovery of highly integrated and expensive board assembly designs through the replacement of defective chips. This article reports the syntheses, formulations, and characterizations of two new diepoxides, one containing secondary ester linkages and the other containing tertiary ester linkages, that are thermally degradable below 300 °C. The secondary and tertiary ester diepoxides were synthesized in three and two steps, respectively. Both compounds were characterized with NMR and Fourier transform infrared spectroscopy and formulated into underfill materials with an anhydride as the hardener and an imidazole as the catalyst. A dual‐epoxy system was also formulated containing the tertiary ester diepoxide and a conventional aliphatic diepoxide, 3,4‐epoxy cyclohexyl methyl‐3,4‐epoxycyclohexyl carboxylate (ERL‐4221E), with the same hardener and catalyst. The curing kinetics of the formulas were studied with differential scanning calorimetry (DSC). Thermal properties of cured samples were characterized with DSC, thermogravimetric analysis, and thermomechanical analysis. The dual‐epoxy system showed a viscosity of 18.7 and 0.87 P at 25 and 100 °C, respectively. The cured secondary, tertiary, and dual‐epoxy formulas showed decomposition temperatures around 265, 190, and 220 °C, glass‐transition temperatures around 120–140, 110–157, and 140–157 °C, and coefficients of thermal expansion of 70, 72, and 64 ppm/°C below their glass‐transition temperatures, respectively. The shear strength of the cured dual‐epoxy system decreased quickly with aging at 230 °C. The reworkability test showed that the removal of a chip underfilled with this material from the board was quite easy, and the residue on the board could be thoroughly removed with a mechanical brush without obvious damage to the solder mask. In summary, the synthesized tertiary epoxide can be used as a reworkable underfill for flip‐chip applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1796–1807, 2002
Copolymerization of dodecyl‐4‐vinyl benzoate and dodecyl acrylate by conventional, atom transfer, and nitroxide‐mediated free‐radical polymerization
Authors: Bisht H. S. , Ray S. S. , Pandey D. , Sharma C. D. , Chatterjee A. K. 
Published: August 2002

Abstractn‐Dodecyl acrylate (DA) and dodecyl‐4‐vinyl benzoate (DVB) were copolymerized by conventional free‐radical polymerization (CFRP); atom transfer radical polymerization (ATRP), and nitroxide‐mediated living free‐radical polymerization (NMLFRP) with benzoyl peroxide, 1‐phenyl ethyl chloride/cuprous chloride/2,2′‐bipyridine, and benzoyl peroxide/2,2,6,6‐tetramethylpiperidinyl‐1‐oxy initiator systems, respectively. In CFRP and NMLFRP, toluene and xylene were used as solvents, whereas ATRP was performed in bulk. Mayo–Lewis, Kelen–Tüdös, and Fineman–Ross methods were used for the determination of the monomer reactivity ratios (r1 and r2). They all gave nearly the same values of r1 and r2. The reactivity ratios of the two monomers in CFRP, ATRP, and NMLFRP were 0.17 ≤ r1 ≤ 0.4 (DA) and 1.0 ≤ r2 ≤ 1.24 (DVB). The side‐chain crystallinity of the copolymers decreased with an increasing DVB molar fraction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1818–1830, 2002
Synthesis of polyquinoline ether and its optical sensor property in the presence of metal cations
Authors: Seung Lee Taek , Yang Changduk , Kim Jong Lae , Lee Jin‐Kyun , Park Won Ho , Won Youjip 
Published: August 2002

AbstractSemirigid polyquinoline with a flexible ether linkage was prepared via Friedländer quinoline synthesis, of which monomer was obtained through a five‐step synthesis. We investigated the polymer as a fluorescent sensor toward ferric ion that used a quinoline unit as a fluoroionophore group. The polymer solution in dimethylformamide/tetrahydrofuran showed the hyperchromic shift of the absorption maximum upon addition of metal ions exhibiting that the effect was clearly manifested upon exposure to ferric ion. A fluorescence quenching was observed in the presence of ferric ion corresponding to an interaction of the ferric cation to the polyquinoline ether, which results in a photoinduced electron‐transfer quenching pathway showing a Stern–Volmer constant (KSV) of 7.17 × 103 (M−1). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1831–1837, 2002
Hydrogen effects in propylene polymerization reactions with titanium‐based Ziegler–Natta catalysts. II. Mechanism of the chain‐transfer reaction
Authors: Kissin Yury V. , Rishina Laura A. , Vizen Elizabeth I. 
Published: August 2002

AbstractHydrogen is a very effective chain‐transfer agent in propylene polymerization reactions with Ti‐based Ziegler–Natta catalysts. However, measurements of the hydrogen concentration effect on the molecular weight of polypropylene prepared with a supported TiCl4/dibutyl phthalate/MgCl2 catalyst show a peculiar effect: hydrogen efficiency in the chain transfer significantly decreases with concentration, and at very high concentrations, hydrogen no longer affects the molecular weight of polypropylene. A detailed analysis of kinetic features of chain‐transfer reactions for different types of active centers in the catalyst suggests that chain transfer with hydrogen is not merely the hydrogenolysis reaction of the TiC bond in an active center but proceeds with the participation of a coordinated propylene molecule. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1899–1911, 2002
Unique dual function of La(C5Me5)[CH(SiMe3)2]2(THF) for polymerizations of both nonpolar and polar monomers
Authors: Tanaka Kohji , Furo Masahito , Ihara Eiji , Yasuda Hajime 
Published: August 2002

AbstractA half‐metallocene‐type complex, La(C5Me5)[CH(SiMe3)2]2tetrahydrofuran (THF) 1, showed the dual function of performing the controlled polymerizations of nonpolar monomers such as ethylene and styrene as well as polar monomers like methyl methacrylate, hexyl isocyanate, and acrylonitrile in high yields. On the other hand, the metallocene‐type rare‐earth metal complexes, [(C5H4SiMe3)2Y(μ‐Me)]2 2 and (C5Me5)2YMe(THF) 3, showed relatively low catalytic activity. The structure of complex 2 was characterized by X‐ray analysis. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1382–1390, 2001
Stereocontrol during the free‐radical polymerization of methacrylates with Lewis acids
Authors: Isobe Yutaka , Nakano Tamaki , Okamoto Yoshio 
Published: August 2002

AbstractThe free‐radical polymerizations of methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, and 2‐methoxyethyl methacrylate were carried out in the presence of various Lewis acids. The MMA polymerization in the presence of scandium trifluoromethanesulfonate [Sc(OTf)3] in toluene or CHCl3 produced a polymer with a higher isotacticity and heterotacticity than that produced in the absence of Sc(OTf)3. Similar effects were observed during the polymerization of the other monomers. ScCl3, Yb(OTf)3, Er(OTf)3, HfCl4, HfBr4, and In(OTf)3 also increased the isotacticity and heterotacticity of the polymers. The effects of the Lewis acids were greater in a solvent with a lower polarity and were negligible in tetrahydrofuran and N,N‐dimethylformamide. Sc(OTf)3 was also found to accelerate the polymerization of MMA. On the basis of an NMR analysis of a mixture of Sc(OTf)3, MMA, and poly(methyl methacrylate), the monomer–Sc(OTf)3 interaction seems to be involved in the stereochemical mechanism of the polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1463–1471, 2001
Preparation of antimicrobial sodium alginate with chito‐oligosaccharide side chains
Authors: Song Jae Wook , Ghim Han Do , Choi Jin Hyun , Ko Sohk‐Won , Lyoo Won Seok 
Published: August 2002

AbstractTo provide sodium alginate (SA) with an antimicrobial property, we introduced chito‐oligosaccharide (COS) via chemical bonding in a two‐step procedure. We reacted COS with N‐methylol acrylamide (NMA) with N‐methylol groups to prepare acrylamidomethyl chito‐oligosaccharide (COS–NMA). SA with COS side chains (SA–COS) was produced through a subsequent reaction of SA with COS–NMA. The chemical structure of SA–COS was confirmed by IR spectroscopy and 1H NMR spectroscopy. With a two‐step method, we successfully prevented insoluble‐complex formation due to electrostatic attraction between chitosan and alginate. SA–COS showed excellent antimicrobial activity, with the growth of microorganisms completely suppressed by a small amount of COS (1.8 wt %). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1810–1816, 2001
The effect of rise in mean annual temperature on the stability of rock slopes containing ice‐filled discontinuities
Authors: Davies Michael C. R. , Hamza Omar , Harris Charles 
Published: August 2002

AbstractDirect shear box tests have revealed that the stiffness and strength of an ice‐filled joint are a function of both normal stress and temperature. Comparison of these data with the results of similar experiments conducted on unfrozen joints indicates that at low temperatures and normal stresses the strength of an ice‐filled joint can be significantly higher than that of an unfrozen joint. However, in the absence of sufficient closure pressure, the strength of an ice‐filled joint can be significantly less than that of an unfrozen joint. This implies that if the stability of a slope is maintained by ice‐filled joints, its factor of safety will reduce with temperature rise. This hypothesis suggests that a jointed rock slope that is stable when there is no ice in the joints and is also stable when ice in the joints is at low temperatures will become unstable as the ice warms. Results from the model tests have confirmed this hypothesis. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉDes tests de cisaillement directs ont révélés que la rigidité et la résistance d'un joint rempli de glace est fonction à la fois de la contrainte normale et de la température (Davies et al., 2000). La comparaison de ces données avec les résultats d'expériences semblables conduites sur des joints non gelés indique qu'à basse température et pour des contraintes normales identiques, la résistance d'un joint rempli de glace peut être plus élevée d'une manière significative que celle d'un joint non gelé. Toutefois, en l'absence d'une pression de fermeture suffisante, la résistance d'un tel joint rempli de glace peut être significativement moindre que celle d'une fissure non gelée. Ceci implique que si la stabilité de la pente est maintenue par des joints remplis de glace, son facteur de sécurité sera réduit avec l'augmentation de la température. Cette hypothèse suggère qu'une pente de roches fissurées qui est stable quand il n'y a pas de glace dans les joints et est aussi stable quand la glace dans les joints est à basse température, deviendra instable quand la glace s'échauffe. Des résultats obtenus par des tests ont confirmé ce résultat. Copyright © 2001 John Wiley & Sons, Ltd.
The thermal regime of soils in the north of Western Siberia
Authors: Pavlov A. V. , Moskalenko N. G. 
Published: August 2002

AbstractThe results of long‐term stationary observations upon the thermal regime of soils in natural and anthropogenically‐disturbed tundra and northern taiga landscapes in the north of Western Siberia are discussed. Quantitative assessments of the heating effect of snow cover and the cooling effect of surface organic layer on soil temperatures in both winter and summer seasons are given. Spatial and temporal variations in the depth of seasonal thaw and soil temperatures in the tundra and taiga zones are outlined. Data on changes in soil temperature regimes following disturbance of surface organic layers are presented. Contemporary tendencies in permafrost degradation induced by climatic warming, changes in the snow cover depth, and anthropogenic impacts are shown. Copyright © 2002 John Wiley & Sons, Ltd.