bluuebunny/crossref_metadata_2025_split huggingface dataset:
Block copolyesters of poly(pentamethylene p,p′‐bibenzoate) and poly(tetramethylene adipate)
Authors: Tsai Ruey‐Shi , Lee Yu‐Der , Tsai Hong‐Bing 
Published: October 2002

AbstractHydroxy‐terminated poly(pentamethylene p,p′‐bibenzoate) oligomers with different molecular weights were prepared. The poly(pentamethylene p,p′‐bibenzoate) oligomers showed rather high crystallinity, and some of them exhibited a monotropic smectic phase. Block copolyesters with hard segments of poly(pentamethylene p,p′‐bibenzoate) and soft segments of poly(tetramethylene adipate) were prepared by coupling the poly(pentamethylene p,p′‐bibenzoate) oligomer and a poly(tetramethylene adipate)glycol with methylene‐4,4′‐diphenylene diisocyanate in solution. The block copolyesters were characterized by IR, 1H NMR, differential scanning calorimetry, a polarized microscope, and X‐ray diffraction. The thermal transitions of the block copolyesters were dependent on the composition and the molecular weight of the poly(pentamethylene p,p′‐bibenzoate) oligomer used. The hard segments in the block copolyesters showed no liquid crystallinity and exhibited rather low crystallinity or were even amorphous. The molecular weight of the poly(pentamethylene p,p′‐bibenzoate) oligomer used influences the glass‐transition temperature and crystalline properties of the soft segments in the block copolyesters significantly. The effect on the glass‐transition temperature of the soft segments is described as the difference in miscibility between the hard and soft segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2626–2636, 2002
Facile synthesis of comb, star, and graft polymers via reversible addition–fragmentation chain transfer (RAFT) polymerization
Authors: Quinn John F. , Chaplin Rodney P. , Davis Thomas P. 
Published: October 2002

AbstractReversible addition–fragmentation chain transfer (RAFT) polymerization has been shown to be a facile means of synthesizing comb, star, and graft polymers of styrene. The precursors required for these reactions were synthesized readily from RAFT‐prepared poly(vinylbenzyl chloride) and poly(styrene‐co‐vinylbenzyl chloride), which gave intrinsically well‐defined star and comb precursors. Substitution of the chlorine atom in the vinylbenzyl chloride moiety with a dithiobenzoate group proceeded readily, with a minor detriment to the molecular weight distribution. The kinetics of the reaction were consistent with a living polymerization mechanism, except that for highly crowded systems, there were deviations from linearity early in the reaction due to steric hindrance and late in the reaction due to chain entanglement and autoacceleration. A crosslinked polymer‐supported RAFT agent was also prepared, and this was used in the preparation of graft polymers with pendant polystyrene chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2956–2966, 2002
Structure‐property relationships for a series of amorphous partially aliphatic polyimides
Authors: Eichstadt Amy E. , Ward Thomas C. , Bagwell Melanie D. , Farr Isaac V. , Dunson Debra L. , McGrath James E. 
Published: October 2002

AbstractHigh molecular weight, soluble, amorphous, partially aliphatic polyimides were successfully synthesized using an ester acid high‐temperature solution imidization route, which allows one to control desired glass‐transition (Tg) and processing temperatures. This method involves the prereaction of aromatic dianhydrides with ethanol and a tertiary amine catalyst to form ester acids, followed by the addition of diamines. Subsequent thermal reaction forms fully cyclized polyimides. This reaction pathway eliminates the need for anhydrous solvents and overcomes the problem of salt formation commonly observed for nucleophilic, more‐basic aliphatic amines when utilizing the traditional polyamic acid synthesis route. The molar ratio of aromatic‐to‐aliphatic diamines was varied to generate a series of copolyimides with the chosen dianhydride and tailor the physical properties for specific adhesive applications. This series of copolyimides was characterized by their molecular weight, Tg, thermal stability, coefficient of thermal expansion, refractive index, and dielectric constant. Structure‐property relationships were established. The γ and β sub‐Tg viscoelastic properties were researched to understand their molecular origins. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1503–1512, 2002
Gel polymer electrolytes prepared with porous membranes based on an acrylonitrile/methyl methacrylate copolymer
Authors: Min Hyo‐Sik , Kang Dong‐Wan , Lee Doo‐Yeon , Kim Dong‐Won 
Published: October 2002

AbstractPorous membranes based on acrylonitrile/methyl methacrylate copolymer were prepared by a phase‐inversion method. Microstructures of the porous membranes were controlled through the variation of the evaporation drying time before immersion in a nonsolvent bath. Gel polymer electrolytes were prepared from these porous membranes via soaking in an organic electrolyte solution. They encapsulated the electrolyte solution well without solvent leakage and maintained good mechanical properties that allowed the preparation of thin films (∼23 μm). These systems showed acceptable ionic conductivity values (>6.0 × 10−4 S/cm) at room temperature and sufficient electrochemical stability over 4.4 V that allowed applications in lithium‐ion polymer batteries. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1496–1502, 2002
Information exchange in oncology outpatient clinics: source, valence and uncertainty
Authors: Rogers Margaret , Todd Chris 
Published: October 2002

AbstractA large literature of doctor–patient communication exists, yet little is known about how symptom information is communicated in cancer care. This qualitative study explores the exchange of symptom and clinical information between cancer patients and oncologists in outpatient clinics of a regional teaching hospital. Verbatim transcripts of consultations between 14 doctors and 43 post‐treatment follow‐up patients from eight consultants' clinics were subjected to analytic induction and microinteractional analysis techniques. Findings from these analyses indicate that information about patients was accorded varying relevance by doctors depending upon its source, valence and certainty. Doctors' requests for information was contingent upon certainty of clinical information. Symptom information was elicited from patients only when clinical information with high certainty was unavailable. If negative patient information was volunteered, it was not addressed when positive clinical information was present and cancer treatment was not indicated. It appears that information in outpatient oncology consultations is organised according to a hierarchy and is used to make treatment decisions and not primarily for symptom management. Copyright © 2002 John Wiley & Sons, Ltd.
Unusual cause of chronic cough in a four‐year‐old cured by uvulectomy
Authors: Najada Abdelhamid , Weinberger Miles 
Published: October 2002

AbstractA 4‐year‐old boy had a history of persistent barking cough unresponsive to medical treatment since infancy. He described a feeling of something in his throat. When investigated by flexible fiberoptic bronchoscopy, the only abnormality was the uvula resting in contact with the epiglottis. The cough was no longer present after uvulectomy. Pediatr Pulmonol. 2002; 34:144–146. © 2002 Wiley‐Liss, Inc.
Hormones and prostate cancer: Current perspectives and future directions
Authors: Hsing Ann W. , Reichardt Juergen K.V. , Stanczyk Frank Z. 
Published: October 2002

AbstractProstate cancer is the most commonly diagnosed non‐skin cancer in men in most western countries. Despite the high morbidity and mortality from prostate cancer, its etiology remains obscure. Although compelling laboratory data suggest a role for androgens in prostate carcinogenesis, most epidemiologic data on humans are inconclusive. To provide insights and directions for future epidemiologic research on hormones and prostate cancer, this review focuses on current perspectives of serum‐based studies and polymorphisms in relevant hormone‐related genes. We highlight the importance of methodologic studies and investigations of hormone levels in the prostatic tissue to help clarify the often‐contradictory data on serologic studies. We recommend careful analysis and cautious interpretation of studies of genetic markers, including repeats and single nucleotide polymorphisms (SNPs), as false positive and negative results may arise in many current and future studies with limited statistical power and non‐representative samples from the population. The review also highlights the reasons to perform functional analyses of SNPs, a critical and often under‐appreciated component of molecular epidemiologic investigations.The time is ripe for large‐scale multidisciplinary investigations that incorporate molecular genetics, biochemistry, histopathology, and endocrinology into traditional epidemiologic studies. Such collaboration will lead to a deeper understanding of the etiologic pathways of prostate cancer, ultimately yielding better preventive, diagnostic, and therapeutic strategies. Prostate 52:213–235, 2002. Published 2002 Wiley‐Liss, Inc.
Pathway heterogeneity in protein folding
Authors: Fernández Ariel , Colubri Andrés 
Published: October 2002

AbstractWe generate ab initio folding pathways in two single‐domain proteins, hyperthermophile variant of protein G domain (1gb4) and ubiquitin (1ubi), both presumed to be two‐state folders. Both proteins are endowed with the same topology but, as shown in this work, rely to a different extent on large‐scale context to find their native folds. First, we demonstrate a generic feature of two‐state folders: A downsizing of structural fluctuations is achieved only when the protein reaches a stationary plateau maximizing the number of highly protected hydrogen bonds. This enables us to identify the folding nucleus and show that folding does not become expeditious until a topology is generated that is able to protect intramolecular hydrogen bonds from water attack. Pathway heterogeneity is shown to be dependent on the extent to which the protein relies on large‐scale context to fold, rather than on contact order: Proteins that can only stabilize native secondary structure by packing it against scaffolding hydrophobic moieties are meant to have a heterogeneous transition‐state ensemble if they are to become successful folders (otherwise, successful folding would be too fortuitous an event.) We estimate mutational Φ values as ensemble averages and deconvolute individual‐route contributions to the averaged two‐state kinetic picture. Our results find experimental corroboration in the well‐studied chymotrypsin inhibitor (CI2), while leading to verifiable predictions for the other two study cases. Proteins 2002;48:293–310. © 2002 Wiley‐Liss, Inc.
Identification of the N‐terminal functional domains of Cdk5 by molecular truncation and computer modeling
Authors: Zhang Jianwen , Luan Chi‐Hao , Chou Kuo‐Chen , Johnson Gail V.W. 
Published: October 2002

AbstractCyclin dependent kinase (Cdk) 5, an atypical member of the Cdk family, plays a fundamental role in the development of the nervous system, and may also be involved in the pathogenesis of certain neurodegenerative diseases. Further, Cdk5 is activated by the specific regulatory proteins p39, p35, or p25 rather than cyclins, and in contrast to other members of the Cdk family is not involved in the progression of the cell cycle. A three‐dimensional computer model of Cdk5‐p25‐ATP has been generated previously [Chou et al., Biochem Biophys Res Commun 1999;259:420–428], providing a structural basis for the study of the mechanisms of Cdk5 activation. To assess the predicted ATP and p25 binding domains at the N‐terminal of Cdk5, two mutants of Cdk5 were prepared in which amino acids 9–15 (Δ9–15) or 9–47 (Δ9–47) were deleted. The results of these studies clearly demonstrate that an N‐terminal loop and the PSSALRE helix are indispensable for Cdk5‐p25 interactions, and amino acids 9–15 are necessary for ATP binding but are not involved in Cdk5‐p25 interactions. Predicted models of Δ9‐15 Cdk5 and Δ9‐47 Cdk5 were generated, and were used to interpret the experimental data. The experimental and molecular modeling results confirm and extend specific aspects of the original predicted computer model, and may provide useful information for the design of highly selective inhibitors of Cdk5, which could be used in the treatment of certain neurodegenerative conditions. Proteins 2002;48:447–453. © 2002 Wiley‐Liss, Inc.
Studies on heat processing and storage of seer fish curry in retort pouches
Authors: Shankar C. N. Ravi , Gopal T. K. Srinivasa , Vijayan P. K. 
Published: October 2002

AbstractSeer fish in curry medium packed in locally manufactured retort pouches, having a three‐layer configuration of thickness 12.5 µm polyester/12.5 µm aluminium foil/80 µm cast polypropylene was processed in a steam/air mixture over a pressure retort. About 210 g fish curry, having 110 g fish slices, was packed in a retort pouch of size 17 cm × 15.5 cm, each fitted with a thermocouple. Time–temperature data were collected during heat processing using an Ellab data recorder FO and cook value integrator. The heat penetration characteristics were determined using a mathematical method. The fh value was 25 min with a FO value of 11.5 and cook value of 95 min. These samples remained in good condition for up to 24 months at room temperature. Copyright © 2002 John Wiley & Sons, Ltd.
Theoretical study of insoluble polymer monolayers
Authors: Ivanova A. , Tadjer A. , Radoev B. 
Published: October 2002

AbstractSeveral oligomers of biodegradable polymers (polycaprolactone and polylactic acid) were theoretically investigated at the gas–water interface. A combined Monte Carlo–semiempirical computational scheme was suggested. It proved to reproduce successfully the most essential properties of the monolayer, such as dipole moment and area/monomer. These calculations were used for prediction of the most probable molecular conformation at the interface. Moreover, an effective normal component of the monolayer dielectric constant was estimated and can be used for description of the dielectric behavior of different insoluble monolayers. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Vibronic polarons: Self‐trapping, local rotation, and band features
Authors: Andreev A. G. , Ivanovich M. D. , Georgiev M. 
Published: October 2002

AbstractWe revisit basic theoretical concepts of local and itinerant vibronic polarons in crystals. The following results may be regarded as novel: (1) The electron self‐trapping rate to a small polaron is calculated via the reaction rate method; subsequently, self‐trapped on‐center small polarons relax to an off‐center vibronic polaron state. (2) The general vibronic Hamiltonian is redefined so as to incorporate both local and itinerant behavior and pairing into bipolarons or Cooper pairs. (3) The planar rotation and diametral tunneling of an off‐center polaron around and across its centrosymmetrical site are dealt with to adiabatic approximation. (4) Variational calculations are made for vibronic polarons itinerant along 1‐D chains by means of a two‐band extension of Merrifield's ansatz. This investigation of vibronic polarons is undertaken in view of their presumed role in high‐temperature superconductivity and colossal magnetoresistance. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Relaxation of quantum hydrodynamic modes
Authors: Bittner Eric R. , Maddox Jeremy B. , Burghardt Irene 
Published: October 2002

AbstractIn this article, we develop a series of hierarchical mode‐coupling equations for the momentum cumulants and moments of the density matrix for a mixed quantum system. Working in the Lagrange representation, we show how these can be used to compute quantum trajectories for dissipative and nondissipative systems. This approach is complementary to the de Broglie–Bohm approach in that the moments evolve along hydrodynamic/Lagrangian paths. In the limit of no dissipation, the paths are the Bohmian paths. However, the “quantum force” in our case is represented in terms of momentum fluctuations and an osmotic pressure. Representative calculations for the relaxation of a harmonic system are presented to illustrate the rapid convergence of the cumulant expansion in the presence of a dissipative environment. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Improved embedded molecular cluster model
Authors: Shidlovskaya E. K. 
Published: October 2002

AbstractWe demonstrate that boundary effects (i.e., displacements of the cluster boundary atoms from their lattice sites and the difference between effective charges of the perfect crystal atoms and those of the cluster atoms in the case of a cluster with no point defect in it) in an embedded molecular cluster (EMC) model can be radically reduced. A new embedding scheme is proposed. It includes search for the structural elements (SE) of which perfect crystal is composed, use of corresponding to these SE expression for the total energy, and application of the degree of localization of equations consistent with the wave functions of the cluster. To get equations for the cluster wave functions, the problem of varied subsystem in the field of the frozen remaining part of the whole electron system” is investigated in the framework of a one‐electron approximation. The consideration is general for every task of this type. Homogeneous equations resulting directly from variation of the total energy expression are obtained and transformed to the eigenvalue problem equations. Orthogonality constraints are not imposed during variation. A particular case of the equations describing mutually orthogonal one‐electron wave functions of the cluster staying nonorthogonal to those of the remaining crystal is found. A proposed embedding scheme is realized in the CLUSTER code based on the calculation scheme of the semiempirical INDO method. Boundary effects both in the standard (cluster in the field of the infinite lattice of nonpoint spherical charges) and new embedding scheme are investigated, calculating the clusters of LiF, MgO, NaCl, KCl, and AgCl crystals. Significant reduction of the boundary effects in the new embedding scheme is achieved. Reasons for the boundary effects are discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Numerical method to solve chemical differential‐algebraic equations
Authors: Çelik Ercan , Karaduman Erdal , Bayram Mustafa 
Published: October 2002

AbstractIn this article, the solution of a chemical differential‐algebraic equation model of general type F(y, y′, x) = 0 has been done using MAPLE computer algebra systems. The MAPLE program is given in the Appendix. First we calculate the Power series of the given equations system, then we transform it into Padé series form, which gives an arbitrary order for solving chemical differential‐algebraic equation numerically. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Quantitative determination of polar and ionic compounds in petroleum fractions by atmospheric pressure chemical ionization and electrospray ionization mass spectrometry
Authors: Roussis Stilianos G. , Fedora James W. 
Published: October 2002

AbstractThe capabilities of atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) methods for quantitative analysis of polar and ionic compounds in petroleum fractions have been examined. The requirements of the analysis for sensitivity, linear dynamic range, and structural characterization have been discussed. ESI was found to be approximately two orders of magnitude more sensitive than APCI and is most suitable for the detection of analytes in weak concentrations. Equivalent relative linear dynamic ranges were observed by the two methods (at least three orders of magnitude). For the relatively high analyte concentrations examined here (e.g., 1–100 ppm or higher), the absolute area counts increased linearly with the analyte amount only in APCI, making this method more attractive for quantitative liquid chromatography/mass spectrometry (LC/MS) applications. Nevertheless, a wider range of ionic compounds can be detected by ESI than by APCI. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of estrogenic contaminants in river water using liquid chromatography coupled to ion trap based mass spectrometry
Authors: Benijts Tom , Dams Riet , Günther Wolfgang , Lambert Willy , Leenheer André De 
Published: October 2002

AbstractA precise and reliable method, using liquid chromatography combined with ion trap based mass spectrometry, for the determination of three endogenous estrogens, namely, estrone, estradiol, and estriol, and two synthetic estrogens, ethinyl estradiol and diethylstilbestrol, in environmental water samples was developed. Optimization of the parameter settings of the ion source and mass analyzer as well as evaluation of solvent composition were carried out by continuous introduction of standards through a syringe pump. In negative ion mode the electrospray ionization source gave acceptable results. The optimum solvent used consisted of water/acetonitrile, with no volatile bases or buffers added. A simple, off‐line, manual solid‐phase extraction method was developed for sample preparation of environmental water samples. Recoveries were over 86% for all compounds. The method was validated and found to be linear, selective, and robust. For analysis of a 50‐mL sample, the limit of detection (LOD) ranged from 3.2 to 10.6 ng/L for all compounds, and the limit of quantitation (LOQ) from 10.6 to 35.0 ng/L. Within‐day (n = 5) and total (n = 5) reproducibility were investigated at three different concentration levels and ranged from 6.2 to 9.5% and 9.4 to 12.1%, respectively. Finally, the method was applied to real‐world samples. Copyright © 2002 John Wiley & Sons, Ltd.
Direct surface analysis of fungal species by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Valentine Nancy B. , Wahl Jon H. , Kingsley Mark T. , Wahl Karen L. 
Published: October 2002

AbstractIn this study various methods of sample preparation and matrices were investigated to determine optimum collection and analysis criteria for fungal analysis by matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS). Intact spores and/or hyphae of Aspergillus niger, Rhizopus oryzae, Trichoderma reesei and Phanerochaete chrysosporium were analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). The fungal samples were applied to the MALDI sample target as untreated, sonicated, or acid/heat treated samples, or blotted directly from the fungal culture with double‐stick tape. Ferulic acid or sinapinic acid matrix solution was layered over the dried samples and analyzed by MALDI‐MS. Statistical analysis showed that simply using double‐stick tape to collect and transfer to a MALDI sample plate typically worked as well as the other preparation methods, and required the least sample handling. Copyright © 2002 John Wiley & Sons, Ltd.