bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of optically active alicyclic polyimides from a chiral, nonracemic dianhydride
Authors: Kudo Kazuaki , Nonokawa Daigo , Li Jun , Shiraishi Shinsaku 
Published: October 2002

AbstractOptically active alicyclic polyimides were prepared for the first time from (−)‐[1S*,5R*,6S*]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐ 2′,5′‐dione) [(−)‐DAn] via polycondensation with diamines and subsequent chemical or thermal imidization. The dianhydride (−)‐DAn was synthesized by an asymmetric Diels–Alder reaction of a chiral itaconic acid derivative as a key step. Colorless or slightly yellow flexible films were obtained for the (−)‐DAn‐derived polyimides {PI[(−)‐DAn]s}. PI[(−)‐DAn]s showed good solubility toward dipolar aprotic solvents and pyridine. For 1,4‐dioxane and chloroform, the optically active polyimides showed slightly better solubility than the corresponding polyimides prepared from rac‐DAn [PI(rac‐DAn)s]. PI[(−)‐DAn]s showed glass‐transition temperatures of 267–268 °C and 10% weight‐loss temperatures of 416–424 °C in nitrogen. These values were almost identical to those of PI(rac‐DAn)s. The circular dichroism spectra of PI[(−)‐DAn]s showed exciton coupling patterns indicating that to some extent these polyimides had a higher order structure in solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4038–4044, 2002
Controlling the mechanical properties of poly(L‐lactide– ε‐caprolactone) monofilament sutures by an acetone/water treatment
Authors: Uddin Ahmed Jalal , Katayama Norihiro , Ohkoshi Yutaka , Gotoh Yasuo , Nagura Masanobu 
Published: October 2002

AbstractFor monofilament biodegradable sutures fabricated from the L‐lactide–ε‐caprolactone (75/25) copolymer [P(LLA/CL)], there have been some concerns regarding their mechanical properties, such as the knot‐pull strength and stiffness. This article demonstrates the further potentiality of these sutures through improvements in those properties. With the aim of diminishing the molecular orientation, particularly in the suture surface region, we adopted an expedient method to treat P(LLA/CL) sutures with an acetone/water mixture, using different times and time patterns. The changes in the molecular orientation distributions across the suture cross sections were characterized by the specific index of birefringence measured with an interference microscope. The crystal orientations, knot‐pull strengths, tensile strengths, and bending rigidity were measured. The conformational changes in suture breaking during knot‐pull tests were analyzed with high‐speed‐video observations. Morphological analyses of the fractural surfaces were performed with scanning electron microscopy. The knot‐pull strength tended to rise, in comparison with that of untreated samples, up to a certain treatment time and was accompanied by a minimal decrement of the tensile strength. The knot‐pull strength did not show an increasing trend with further treatment, whereas the tensile strength declined remarkably. The birefringence, crystal orientation, bending rigidity, fractured surface analysis, and high‐speed‐video observations revealed molecular disorientation mainly in the filament outer layers for that particular treatment causing the sutures to be considerably softer. The suture softness played a role in changing the deformation behavior of the knot when a load was applied and caused the knot‐pull strength to rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2449–2462, 2002
Effect of structural characteristic on physical properties of copolyesters from poly(ethylene terephthalate) oligomer and polycaprolactone
Authors: Lim Kyung Yul , Kim Byoung Chul , Yoon Kee Jong 
Published: October 2002

AbstractA series of poly(ethylene terephthalate/polycaprolactone) (PET/PCL) copolyesters were prepared by adding PCL with a weight‐average molecular weight of 40,000 to the PET oligomer during polycondensation, and the composition and physical properties of the copolymers were investigated. In the case of copolyesters containing caprolactone (CL) units less than 26 mol %, the melting and crystallization temperatures were decreased with increasing CL content. They exhibited wide‐angle X‐ray diffraction (WAXD) patterns similar to PET. However, the variation of d‐spacing on the WAXD pattern suggested that a small amount of CL could be included into the crystal of ethylene (ET) because of strong hydrogen bonding between crystallizable ET blocks. In the copolyesters containing CL components higher than 38 mol %, they exhibited thermal behavior and WAXD patterns typical of amorphous random copolymers. The copolyester composition has a decisive effect on the rheological properties. The copolyesters with CL contents higher than 38 mol % exhibited a viscosity behavior similar to Bingham fluid, although the copolyesters with CL contents lower than 26 mol % exhibited a Newtonian flow behavior similar to PET. In addition, the value of the loss tangent of the copolyester melts notably decreased with an increasing CL content, and the bulk exhibited rubberlike behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2552–2560, 2002
Studies on the equilibrium among poly(sodium 4‐styrenesulfonate), Cu2+, and iminodiacetic acid by ultrafiltration at constant ionic strength
Authors: Moreno‐Villoslada I. , Muñoz C. , Rivas B. L. 
Published: October 2002

AbstractThe ultrafiltration technique evaluates the interactions of water‐soluble polymers with metal ions. Aqueous solutions containing poly(sodium 4‐styrenesulfonate) (PSS), Cu(NO3)2, NaNO3, and iminodiacetic acid (IDAA) are examined by this technique. Cu2+ undergoes complex formation with IDAA and intreracts electrostatically with PSS. On the other hand, Na+ ions are in competition with Cu2+ for the electrostatic binding to PSS. The solutions are ultrafiltered keeping the ionic strength constant, so their compositions are allowed to change continuously. The concentration of Cu2+ bound to the polymer showed an exponential decay during filtration. The concentration of Cu2+ bound to the polymer before ultrafiltration is calculated by extrapolation. The concentration of the different species in solution is proposed as a function of the filtration factor. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2587–2593, 2002
Relaxation behavior of poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6‐dicarboxylate) blends prepared by cryogenic blending
Authors: Denchev Z. , Ezquerra T. A. , Nogales A. , Ŝics I. , Alvarez C. , Broza G. , Schulte K. 
Published: October 2002

AbstractA method including cryogenic grinding, melt pressing from the molten state, and quenching was used to prepare blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) in which the two phases were highly dispersed. The effect of melt‐pressing times on the thermal properties and relaxation behavior of PET/PEN films were characterized with differential scanning calorimetry and dielectric spectroscopy. For short melt‐pressing times, two glass‐transition, two crystallization, and two melting peaks were observed, indicating the presence of PET‐rich and PEN‐rich phases in these blends. Longer melt‐pressing times revealed a single glass transition and a single α‐relaxation process, showing that PET–PEN block copolymers were likely to be formed during the melt pressing. The experimental findings were examined in terms of the transesterification reactions between the blend components, as revealed by 1H NMR measurements. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2570–2578, 2002
Invasive mechanical ventilation for acute respiratory failure in children with cystic fibrosis: Outcome analysis and case‐control study
Authors: Berlinski Ariel , Fan Leland L. , Kozinetz Claudia A. , Oermann Christopher M. 
Published: October 2002

AbstractThe outcome for cystic fibrosis (CF) patients requiring intubation and invasive mechanical ventilation (IMV) due to acute respiratory failure (ARF) has been poor. Mortality rates have been reported as high as 60–90%. However, a review of mortality in children has not been published in 20 years. Our objectives were to study outcomes in CF patients requiring IMV due to ARF between 1988–1998, compare recent outcomes with those previously reported, and identify risk factors associated with poor outcome. We additionally attempted to identify factors suggesting an increased risk of developing ARF requiring IMV. A retrospective cohort study design was used, comparing IMV survivors and nonsurvivors with a nested case‐control study to identify risk factors for ARF leading to IMV. All patients cared for at our Center who required IMV for ARF between 1988–1998 were identified. Outcome, age, steroid use, forced vital capacity (FVC), forced expired volume in 1 sec (FEV1), microbiology, nutritional status, CF‐related diabetes (CFRD), liver dysfunction, and history of major hemoptysis (HEM) or pneumothorax (PTX) were recorded. Cases were matched for gender and age with CF controls identified through a clinical database.Thirty‐eight episodes of IMV due to ARF were reported in 33 patients. Three subjects underwent IMV on two or more occasions, but only the first episode was included in analysis. Older age was the only factor that was significantly associated with mortality: 9 subjects were <5 years of age (mortality, 22%), while 24 were 5–34 years old (mortality, 75%) (P = 0.013). There was an increased risk of having an episode of ARF requiring IMV in malnourished subjects (OR = 4.2; 95% CI = 1.66–10.51) and in those with a history of HEM (OR = 6.3; 95% CI = 1.75–22.65).Infants and young children with CF requiring IMV due to ARF have a favorable prognosis, whereas those ≥5 years of age suffer significantly higher mortality. Malnutrition and a history of HEM are important risk factors for having an episode of ARF requiring IMV. Pediatr Pulmonol. 2002; 34:297–303. © 2002 Wiley‐Liss, Inc.
Influence of lipopolysaccharide exposure on airway function and allergic responses in developing mice
Authors: Cochran John R. , Khan Amir M. , Elidemir Okan , Xue Hasen , Cua Beatrize , Fullmer Jason , Larsen Gary L. , Colasurdo Giuseppe N. 
Published: October 2002

AbstractExposure to endotoxin has been associated with an exacerbation of asthmatic responses in humans and animal models. However, recent evidence suggests that microbial exposure in early life may protect from the development of asthma and atopy. In this study, we sought to evaluate the effects of lipopolysaccaride (LPS) on airway function in developing mice. In addition, we evaluated the influence of LPS on subsequent allergen sensitization and challenge. Under light anesthesia, 2–3‐week‐old Balb/c mice received a single intranasal instillation of LPS or sterile physiologic saline. Measurements of airway function were obtained in unrestrained animals, using whole‐body plethysmography. Airway responsiveness was expressed in terms of % enhanced pause (Penh) increase from baseline to aerosolized methacholine (Mch). In additional studies, we assessed the functional and cellular responses to ovalbumin sensitization and challenge following prior exposure to LPS.We found that exposure to LPS induced transient airway hyperresponsiveness to Mch. These functional changes were associated with the recruitment of neutrophils and lymphocytes into the bronchoalveolar lavage (BAL) fluid. Airway responsiveness after allergen sensitization and challenge was decreased by prior exposure to LPS. The analysis of BAL cells and cytokines (interferon‐γ and interleukin‐4) did not reveal alterations in the overall Th1/Th2 balance.Our findings suggest that LPS leads to airway hyperresponsiveness in developing mice, and may protect against the development of allergen‐driven airway dysfunction. Pediatr Pulmonol. 2002; 34:267–277. © 2002 Wiley‐Liss, Inc.
Inhibition of orthotopic growth and metastasis of androgen‐sensitive human prostate tumors in mice by bioactive soybean components
Authors: Zhou Jin‐Rong , Yu Lunyin , Zhong Ying , Nassr Rena L. , Franke Adrian A. , Gaston Sandra M. , Blackburn George L. 
Published: October 2002

AbstractBACKGROUNDSystematic analysis of the influence of diet on the initiation and progression of prostate cancer is often difficult in human populations, for which dietary variables overlap a diversity of genetic backgrounds and social behaviors. Animal models that emulate human prostate cancer allow experimental analysis of the mechanisms of action of nutritional agents that show anti‐prostate cancer activity.METHODSWe have used an orthotopic implant model to characterize the in vivo response of androgen‐sensitive LNCaP prostate tumors to three well‐characterized soy dietary supplements: isoflavone depleted soy protein, soy phytochemical concentrate (SPC), and genistin.RESULTSIn male SCID mice orthotopically implanted with the androgen‐sensitive human prostate cell line LNCaP, dietary supplements of soy protein, genistin, and SPC reduced primary tumor weight by 42% (P = 0.07), 57% (P < 0.05) and 70% (P < 0.005), respectively. All three soy supplements significantly increased tumor apoptosis and decrease microvessel density, with no significant change in tumor proliferation. Each supplement produced a distinct serum androgen response, with genistin producing the greatest decrease in total serum testosterone and dihydrotestosterone (DHT) (P < 0.05) and the greatest increase in testosterone to DHT ratio (P < 0.05) and soy protein the greatest decrease in bioactive androgen (P < 0.05). Only SPC significantly inhibited metastases to lymph nodes and lungs, and only SPC produced a significant increase in tumor p53 expression.CONCLUSIONTaken together, these data suggest that the anti‐prostate cancer activity of dietary soy protein, soy phytochemicals, and genistin use different molecular pathways. In addition, we have demonstrated that this animal model can be used in the design of dietary strategies for prostate cancer prevention and therapy. Prostate 53: 143–153, 2002. © 2002 Wiley‐Liss, Inc.
Rebuilt 3D structure of the chloroplast f1 ATPase–tentoxin complex
Authors: Minoletti Claire , Santolini Jérôme , Haraux Francis , Pothier Joël , André François 
Published: October 2002

AbstractThe F1 part of the chloroplast H+ adenosine triphosphate (ATP)‐synthase (CF1) strongly interacts with tentoxin, a natural fungous cyclic tetrapeptide known to inhibit the chloroplast enzyme and not the mammalian mitochondrial enzyme. Whereas the synthesis or the hydrolysis of ATP requires the stepwise rotation of the protein rotor γ within the (αβ)3 crown, only one molecule of tentoxin is needed to fully inhibit the complex. With the help of an original homology modeling technique, based on robust distance geometry protocols, we built a tridimensional model of the α3β3γ CF1 subcomplex (3200 residues), in which we introduced three different nucleotide occupancies to check their possible influence on the tentoxin binding site. Simultaneous comparison of three available high‐resolution X‐ray structures of F1, performed with a local structural alignment search tool, led to characterizing common structural blocks and the distorsions experienced by the complex during the catalytic turnover. The common structural blocks were used as a starting point of the spinach CF1 structure rebuilding. Finally, tentoxin was docked into its putative binding site of the reconstructed structure. The docking method was initially validated in the mitochondrial enzyme by its ability to relocate nucleotides into their original position in the crystal. Tentoxin binding was found possible to the two α/β interfaces associated with the empty and adenosine diphosphate (ADP)‐loaded catalytic sites, but not to the one associated with the ATP‐loaded site. These results suggest a mechanism of CF1 inhibition by one molecule of tentoxin, by the impossibility of the α/β interface bearing tentoxin to pass through the ATP‐loaded state. Proteins 2002;49:302–320. © 2002 Wiley‐Liss, Inc.
Effect of quercetin on plasma extravasation in rat CNS and dura mater by ACE and NEP inhibition
Authors: Cyrino Luiz A. R. , Cardoso Ronie C. F. , Hackl Luciane P. N. , Nicolau Mauro 
Published: October 2002

AbstractThe effects of quercetin on substance P‐induced plasma protein extravasation (PE) in the rat dura mater, cerebellum, olfactory bulb and cortex and also its modulation by endopeptidases, angiotensin‐converting enzyme (ACE) and neutral endopeptidase (NEP) were studied. PE was assessed by photometric measurement of extravasated Evans blue. Substance P (SP) and NEP or ACE inhibitors increased the PE in dura mater. Pretreatment with captopril or phosphoramidon potentiated PE induced by SP in the dura mater and cerebellum, respectively. Quercetin increased the PE in the dura mater, cerebellum and cortex. Further results suggested that the PE induced by SP in the dura mater was enhanced by pretreatment with quercetin, similar to that observed with selective peptidase inhibitors. Quercetin‐stimulated extravasation in all tissues was abolished by NK‐1 receptor blockade. These results suggest that quercetin increases PE in the dura mater and CNS tissues by inhibiting NEP and/or ACE, showing that the effect induced in the dura mater, cerebellum and cortex occurs through endogenous SP accumulation. Copyright © 2002 John Wiley & Sons, Ltd.
Antimicrobial activity of some species of the family Combretaceae
Authors: Elegami A. A. , El‐Nima E. I. , Tohami M. S. El , Muddathir A. K. 
Published: October 2002

AbstractForty eight extracts of four plants of the family Combretaceae were screened for antibacterial activity against standard organisms as well as clinical isolates. The extracts in different solvent systems showed high activity against both standard organisms and clinical isolates. Phytochemical screening revealed that the plants were very rich in tannins to which antibacterial activity may be attributed. Copyright © 2002 John Wiley & Sons, Ltd.
Self‐energy operator and self‐energy fields in many‐body systems: Liouvillian approach
Authors: Bochicchio Roberto C. , Grinberg Horacio 
Published: October 2002

AbstractAn explicit definition for the self‐energy field operator and the self‐energy fields obtained from an average of the associated operator within the algebraic formalism of superoperators is presented. It stems from the formal expansion of the many‐body propagator equations of motion hierachy in quantum many‐body systems within the scenario of the Liouvillian decoupling scheme developed in previous works. An essential theoretical property of such fields for the complete expansion of the propagator to any order in the interaction potential is shown. This states that the interaction potential to a given order only depends on one q‐reduced density matrix. The contraction order q of the density matrix depends on both the nature of the operators defining the propagator and the actual order of the expansion. This result is rigorous regarding infinite summation of the irreducible terms of the self‐energy fields and provides a direct way to estimate the extent to which many‐body effects are involved in successive approximations, i.e., truncation of the excitation level given by the reference state throughout the reduced density matrix and the expansion of the propagator. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Conformations of the S and S homocyclic radical cations
Authors: Cioslowski Jerzy , Szarecka Agnieszka , Moncrieff David 
Published: October 2002

AbstractAccording to both UB3LYP/6‐311G* and UMP2/6‐311G* calculations, the S homocyclic radical cation exists in only one conformer of Cs symmetry that undergoes a facile pseudorotation through a C2 transition state. A structure with D3d symmetry is predicted to be the global minimum for the S species. The current study uncovers the gradual transition from the conformational simplicity of smaller homocyclic sulfur cations, for which the rigidity of the rings apparently translates into a relatively weak influence of electron correlation effects on their relative energetics and geometries, to the conformational complexity of larger species, for which significant discrepancies between the predictions of different electronic structure methods are observed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
An ab initio/Rice–Ramsperger–Kassel–Marcus study of photodissociation of carbonyl cyanide
Authors: Lee H. Y. , Mebel A. M. , Lin S. H. 
Published: October 2002

AbstractThe geometries and vibrational frequencies of the parent molecule, intermediates, transition state, and products involved in the photochemical decay of carbonyl cyanide NC–C(O)–CN have been studied by ab initio calculations at the MP2/6‐311G* level. The energies of various species have been refined using the modified Gaussian‐2 [G2M(MP2)] method. The molecular parameters and energetics derived from the ab initio calculations were used to compute microcanonical rate constants of all possible reaction steps of photodissociation of the carbonyl cyanide employing the conventional and variational RRKM theory and to obtain the product branching ratios. The results show that the radical decay, CO(CN)2+ hν→OCCN/OCNC+CN, is dominant (86.14% and 13.85% for OCCN and OCNC, respectively), while the molecular decay, CO(CN)2→CO+NCCN, gives only a trace amount of the products. Whereas the computed radical product yields qualitatively agree with those measured in experiment (Scheld, H. A., et al. J Chem Phys 1999, 111, 923), the calculated branching ratio for the molecular decay channel underestimates the experimental value of ∼6%. This deviation may be attributed to the deficiencies in the variational RRKM treatment of the radical decay rate constants and/or to some nonstatistical behavior of the system which enhances the molecular decay. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Use of fast Fourier transform computational methods in electron scattering
Authors: Ritchie Burke , Riley Merle E. 
Published: October 2002

AbstractTwo methods are studied for elastic electron–atom and electron–molecule elastic scattering. The first is a numerical solution of the time‐dependent Schrödinger equation suitable for continuum states; the second is a convergent modified Born series of the time‐independent integral Schrödinger (Lippmann–Schwinger) equation. Both methods make use of fast Fourier transform (FFT) computational methods in order to bring the free‐electron Green's function into diagonal form. A large advantage of this methodology is the ability to describe scattering from targets of any geometry and at any collision energy by using 3D FFTs to accomplish the labor of evaluating spatially complex collision kernels. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002