bluuebunny/crossref_metadata_2025 huggingface dataset:
Prenatal identification of esophageal atresia: the role of ultrasonography for evaluation of functional anatomy
Authors: Shulman Adrian , Mazkereth Rami , Zalel Yaron , Kuint Jacob , Lipitz Shlomo , Avigad Itamar , Achiron Reuwen
Published: October 2002

Objective

To suggest a new ultrasonographic approach for prenatal diagnosis of esophageal atresia (EA).

Methods

Since 1995, whenever EA is suspected, we perform a systematic multiplanar ultrasonographic scanning of the fetal upper body in order to demonstrate an esophageal pouch. This includes three image plans of the neck and upper chest: coronal, sagittal and axial views in the cephalic direction. The scan time is 20–30 min.

Results

Twenty‐five pregnant patients were referred during the period under study for prenatal examinations due to polyhydramnios and/or absent or small stomach. In six fetuses an esophageal pouch was demonstrated at ultrasonography in utero, thus a definitive diagnosis of EA was obtained. All six were confirmed with EA postpartum. In 19 fetuses an esophageal pouch was not demonstrated and all delivered normal neonates. During the same period two additional newborns, who were not included in the referred patients because amniotic fluid volume and stomach size were normal, were diagnosed postpartum with EA. The earliest gestational age of pouch visualization was at 23 weeks. The sagittal view was the best for visualizing a low‐level pouch, and the coronal view was optimal for revealing a high pouch.

Conclusions

Our three‐sectional view of the neck and upper chest is useful for in utero detection of esophageal pouch that may enhance the prenatal diagnosis of EA. The positive predictive value for prenatal ultrasound for detecting EA is 100% with a sensitivity of 80%. Copyright © 2002 John Wiley & Sons, Ltd.
Prenatal diagnosis and intrafamilial clinical heterogeneity of Fraser syndrome
Authors: Rousseau Thierry , Laurent Nicole , Thauvin‐Robinet Christel , Lionnais Stéphanie , Durand Christine , Faivre Laurence , Sagot Paul
Published: October 2002

Fraser syndrome (MIM 219000) is a rare disorder of autosomal recessive inheritance, characterized by the association of cryptophthalmos, syndactyly and genital abnormalities. Here we report on two cases of Fraser syndrome (cryptophthalmos syndrome) in a non‐consanguineous couple, with variable expression in echographic, clinical and autopsy findings. Furthermore, we highlight the difficulties in prenatal diagnosis of Fraser syndrome. Copyright © 2002 John Wiley & Sons, Ltd.
Outcome of prenatally diagnosed trisomy 6 mosaicism
Authors: Wallerstein Robert , Oh Tracey , Durcan Judy , Abdelhak Yaakov , Clachko Mark , Aviv Hana
Published: October 2002

We report the prenatal diagnosis of trisomy 6 mosaicism via amniocentesis, in which trisomy 6 cells were identified in three of five culture vessels with 33% (5/15) of colonies showing trisomic cells. The pregnancy was electively terminated and examination revealed minor abnormalities (shortening of the femurs, micrognathia, posterior malrotation of the ears, and bilateral camptomelia of the second digit of the hands and fifth digits of the feet). Cytogenetic analysis of the placenta showed trisomy 6 in 100% of 20 cells studied. Karyotype was 46,XX in 100 cells examined from fetal skin. There are relatively few prenatally diagnosed cases of mosaic trisomy 6 at amniocentesis. Confined placental mosaicism (CPM) has been postulated in other cases where follow‐up cytogenetic studies were not available. The present case differs from those previously reported, as it appears to represent CPM of chromosome 6 with phenotypic effects to the fetus. Copyright © 2002 John Wiley & Sons, Ltd.
What should we do about the obesity epidemic?
Authors: Barth Julian H.
Published: October 2002

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The current increase in obesity is occurring despite increasing awareness by the population at large of the benefits of healthy eating and exercise. Although weight gain is the direct result of a mismatch in energy balance, it is important to realise that there is a complex interplay between the environment and individual biology and behaviour. Management of obesity whether in a primary or secondary care setting requires a multi‐disciplinary team to produce an individualised approach to embrace food, exercise and behavioural change. The prevention of obesity requires a three‐level approach. First, there needs to be a co‐ordinated public health policy at national level to create an environment where it is easy to make healthy choices for physical activity and food. Second, there needs to be a policy that targets those individuals who are at risk of becoming obese and those who have lost weight to help prevent weight regain. Finally, there needs to be a systematic uptake of the established protocols for the management of individuals with obesity and its co‐morbidities. The challenge in the UK is to build imaginative networks that integrate all available resources both within the NHS and without, such as sports centres, fitness clubs and slimming clubs. Copyright © 2002 John Wiley & Sons, Ltd.
Thermoreversible gelation of a polystyrene–poly(ethylene/butylene)–polystyrene triblock copolymer in n‐octane/4‐methyl‐2‐pentanone solutions
Authors: Quintana Jose R , Hernáez Estíbaliz , Katime Issa
Published: October 2002

The thermoreversible gelation of a triblock copolymer polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene in n‐octane and two solvent mixtures of n‐octane and 4‐methyl‐2‐pentanone with a high n‐octane content has been studied. n‐Octane and 4‐methyl‐2‐pentanone are selective solvents for the middle poly(ethylene/butylene) block and the end polystyrene blocks, respectively. The influence of the solvent composition on the sol–gel transition and the mechanical properties of the gels was studied. The gel formation temperature increased with the copolymer concentration and the n‐octane content in the solvent system. The mechanical properties of the different gels were studied through oscillatory shear measurements. The concentration dependence of the elastic storage modulus showed an exponent close to that expected for gels in good solvents (2.25) that possess a structure similar to those of chemical networks.

© 2002 Society of Chemical Industry
On the ‘curiosity’ of electrical self‐heating, static charge and electromagnetic shielding effectiveness from carbon black/aluminium flakes reinforced epoxy‐resin composites
Authors: El‐Tantawy Farid , Kamada K , Ohnabe H
Published: October 2002

This paper shows the wide application range (such as electrical self‐heating and electromagnetic shielding effectiveness) of composites consisting of conductive carbon black/aluminum flakes (CBA) filler and epoxy insulative matrix. The effect of CBA content on the network structure of epoxy matrix was investigated in detail. Static electrical conductivity increases linearly with the increase of filler concentration at the interface in epoxy composites. The large decrease of the conductivity as a function of the temperature is analyzed in terms of the negative temperature coefficient of conductivity (NTCC) effect. The influence of viscosity, surface energy and barrier highest energy on the NTCC behaviour in the composite is also considered. Based on these results, a new interpretation is proposed to explain the NTCC phenomena by computing the swelling force among conductive phases. The correlations of conductivity during the temperature cycling and activation energy were analyzed. The effects of dynamic ageing at various temperatures on the resistivity are reported. Current–voltage–temperature characteristics for epoxy with different contents of CBA were examined in detail. A model based on the law of energy conservation is proposed to calculate the specific heat and amount of heat dissipation. The static charge of the epoxy–CBA composites was estimated. The correlation between electromagnetic wave‐shielding effectiveness (EMS), conductivity and frequency of epoxy composites with different filler contents is also discussed. Furthermore, the effect of annealing on EMS of epoxy composites was examined.

© 2002 Society of Chemical Industry
Direct observation of the fringed micelles structure of cellulose molecules solvated in dimethylacetamide/LiCl system
Authors: Yan Lifeng , Zhu Qingshi
Published: October 2002

A dilute solution of cellulose in dimethylacetamide/LiCl was deposited on the surface of freshly cleaved mica, and the resulting morphologies of cellulose aggregates were observed by atomic force microscopy. It was found that cellulose molecules aggregated together following the fringed micelles model, and that the fringed micelles aggregated together to form larger fractal structures.

© 2002 Society of Chemical Industry
Teacher and child variables as predictors of academic engagement among low‐income African American children
Authors: Tucker Carolyn M. , Zayco Rose A. , Herman Keith C. , Reinke Wendy M. , Trujillo Mark , Carraway Kirsten , Wallack Cory , Ivery Phyllis D.
Published: October 2002

A causal model for understanding the complex interplay between student‐reported teacher behaviors, student self‐systems, and student engagement was tested. One hundred seventeen African American students in grades 1 through 12 completed a comprehensive questionnaire regarding teacher context, self, and engagement variables. A series of hierarchical regression analyses were conducted to test the hypothesized mediation models and to construct a path model. Most hypotheses were supported. Student self‐system variables (perceived competency and autonomy) mediated relations between teacher context (structure and autonomy support), and engagement. Contrary to predictions, however, teacher involvement exerted a strong and direct effect on student engagement even when controlling for grade level and self‐system variables. Given existing research showing that African American students are at risk for low teacher involvement and that engagement is critical for academic success, research and intervention strategies are urgently needed to promote teacher involvement with these students. © 2002 Wiley Periodicals, Inc.
Adolescent suicide: An ecological approach
Authors: Ayyash‐Abdo Huda
Published: October 2002

Adolescent suicide, which has been ranked among the top 10 causes of death in the world, is an issue of increasing concern to school psychologists, educators, and parents. Here an ecological approach is proposed to enhance our understanding of how personal, interpersonal, and sociocultural factors contribute to the increased risk for suicide among adolescents. The ecological approach allows exploration of how adolescent suicide is determined by multiple factors related to the adolescent's personal history or ontogenic development (e.g., depression), the influences of those individuals with whom adolescents have immediate contact with, or the microsystems (e.g., family and school), the larger social units, or the exosystems, that indirectly influence adolescents (e.g., media), and the larger culture or macrosystems (e.g., cultural differences in attitudes about suicide). In this article the interaction of several factors within and between the permeable boundaries of each of the layers of the ecological paradigm is also highlighted. Finally, examples of intervention and prevention strategies at each level of the system are set forth. © 2002 Wiley Periodicals, Inc.
Recognition of protonated aliphatic α,ω‐diamines by coproporphyrin I tetraanion in water
Authors: Flores‐Villalobos Alejandro , Morales‐Rojas Hugo , Escalante‐Tovar Sigfrido , Yatsimirsky Anatoly K.
Published: October 2002

Interactions of aliphatic α,ω‐diamines [H2N(CH2)
nNH2, 2 ≤ n ≤ 8] with coproporphyrin I tetraanion (CP) were studied by spectrophotometry, fluorimetry and 1H NMR spectroscopy in the pH range 7–10 and ionic strengths 0.01–0.1 M. Diprotonated diammonium cations induce dimerization of CP by forming 1:1 complexes with CP which undergo much stronger self‐aggregation than free CP tetraanions. On increasing the number of methylene units n connecting the ammonium groups, the binding constants for the complex formation with monomeric CP (KL) increase but the dimerization constants of the resulting complexes decrease. A hydrophobic contribution to the binding free energy of −1.6 ± 0.2 kJ mol−1 per methylene unit was obtained from the linear correlation of logKL values extrapolated to zero ionic strength vs the number of methylene units (n = 2–6). A model for diammonium‐induced porphyrin dimerization is proposed, which involves complexation of diammonium cations with CP monomer via a combination of electrostatic and hydrophobic interactions and subsequent formation of porphyrin face‐to‐face dimers in which diammonium cations serve as the stabilizing bridges via ion pairing to carboxylate groups of two CP monomeric units. Copyright © 2001 John Wiley & Sons, Ltd.
Kinetics and mechanism of the oxidation of substituted benzylamines by hexamethylenetetramine‐bromine
Authors: Dubey Rashmi , Kothari Seema , Banerji Kalyan K.
Published: October 2002

The oxidation of substituted benzylamines by hexamethylenetetramine‐bromine (HABR) to the corresponding aldimines is first order with respect to each the amine and HABR. It is proposed that HABR itself is the reactive oxidizing species. The oxidation of deuterated benzylamine (PhCD2NH2) indicated a substantial kinetic isotope effect (kH/kD = 5.60 at 293 K). This confirmed the cleavage of an α‐C—H bond in the rate‐determining step. Correlation analyses of the rates of oxidation of 20 monosubstituted benzylamines were performed with various single‐ and multi‐parametric equations. The rates of the oxidation showed excellent correlations in terms of the Yukawa–Tsuno and Brown equations. The polar reaction constants were negative. The oxidation exhibited extensive cross‐conjugation, in the transition state, between the electron‐donating substituents and the reaction centre. A mechanism involving a hydride ion transfer from the amine to HABR, in the rate‐determining step, is proposed. Copyright © 2001 John Wiley & Sons, Ltd.
Rate constants for the CH3O + NO → CH3ONO reaction by classical trajectory and canonical variational transition state theory calculations
Authors: Martínez‐Núñez Emilio , Borges Itamar , Vázquez S. A.
Published: October 2002

Classical trajectory and canonical variational transition state theory (CVTST) calculations were performed on the CH3O + NO → CH3ONO recombination reaction for the temperature range 300–1000 K to study theoretically this reaction for the first time. The dynamics calculations employ our previously reported potential energy surface for the dissociation and elimination reactions of methyl nitrite (Martínez‐Núñez E, Vázquez SA. J. Chem. Phys. 1998; 109: 8907). In the present work this surface was conveniently modified to reproduce more accurately the experimental CH3ONO dissociation energy and to obtain more reliable rate constants for both the dissociation and the recombination reactions. The recombination rate constants calculated with this modified version of the original potential energy surface agree better with the experimental results than do the rates obtained with the original one. Copyright © 2001 John Wiley & Sons, Ltd.
Mechanism and dynamics of organic reactions: 1,2‐H shift in methylchlorocarbene
Authors: Kraka Elfi , Cremer Dieter
Published: October 2002

The unified reaction valley approach (URVA) was used to investigate the mechanism of the rearrangement of methylchlorocarbene to chloroethene [reaction(1)] in the gas phase with special emphasis on the role of H tunneling. The reaction valley of (1) was explored using different methods (HF, MP2 and DFT/B3LYP) and different basis sets [6–31G(d), 6–31G(d,p) and cc‐pVTZ]. Results were analyzed characterizing normal modes, reaction path vector and curvature vector in terms of generalized adiabatic modes associated with internal parameters that are used to describe the reaction complex. For reaction (1), H tunneling plays a significant role even at room temperature, but does not explain the strongly curved Arrhenius correlations observed experimentally. The probability of H tunneling can be directly related to the curvature of the reaction path and the associated curvature couplings. The reaction is preceeded in the forward and reverse direction by energy‐consuming conformational changes that prepare the reactant for the actual 1,2‐H shift, which requires only little energy. The effective energy needed for CH bond breaking is just 6 kcal mol−1 for (1). The gas‐phase and the solution‐phase mechanisms of (1) differ considerably, which is reflected by the activation enthalpies: 11.4 (gas, calculated) and 4.3 kcal mol−1 (solution, measured). Stabilizing interactions with solvent molecules take place in the latter case and reduce the importance of H tunneling. The non‐linearity of the measured Arrhenius correlations most likely results from bimolecular reactions of the carbene becoming more important at lower temperatures. Copyright © 2002 John Wiley & Sons, Ltd.
Theoretical study of the ring‐opening reactions of 2H‐azirines—a classification of substituent effects
Authors: Klessinger Martin , Bornemann Christian
Published: October 2002

Based on CASSCF and CASPT2 calculations, the mechanisms of the photoreactions of 2H‐azirines are discussed. A general classification of substituent effects on non‐adiabatic singlet photoreactions is presented, and the effect of phenyl substituents on the photochemistry of 2H‐azirine, including the wavelength dependence of the photochemistry of 3‐phenyl‐2H‐azirine, is discussed in detail. Copyright © 2002 John Wiley & Sons, Ltd.
4‐Alkylbenzopyrylium perchlorates as C—H Acidic compounds
Authors: Grummt U.‐W. , Czerney P.
Published: October 2002

7‐Alkyl‐5,6‐dihydro‐3‐methoxy(naphtho[1,2b]‐1‐benzopyrylium) compounds are acidochromic due to CH acidity of the 7‐alkyl substituent. Their acidity exponents are 4 < pKa < 5 and 1 < pKa < 3 regardless of whether the carbocation generated by deprotonation is resonance stabilized by a phenyl substituent or not. The thermodynamic equilibrium data were obtained via UV–vis spectroscopy. The activation parameters for protonation and deprotonation reactions were derived from rapid mixing experiments. Ab initio calculations with model compounds are presented in order to rationalize the experimental findings. The title compounds are useful objects to study the kinetics of proton‐transfer kinetics to and from carbon. Copyright © 2002 John Wiley & Sons, Ltd.
Bivariate distribution in copolymers: A new model
Authors: Montaudo Maurizio S. , Adamus Grażyna , Kowalczuk Marek
Published: October 2002

A new model for the bivariate distribution of chain sizes and composition in copolymers is presented. The model combines the sum of a two‐bivariate distribution, and it replaces the previous model that consists of a single entity. The compositional distribution histogram was obtained by summation of the sections of the bivariate distribution that belong to a narrow compositional range. The predictions of the model were compared with mass spectrometric data relative to a block copolymer sample containing structural units of pivalolactone and 3‐hydroxybutyrate with some literature data, namely, mass spectrometric data concerning a random copolymer sample reacted at high conversion containing units of styrene and methyl methacrylate as well as a block copolymer sample containing units of α‐methyl styrene and methyl methacrylate. The new model gives better results than the previous model because it fits better with the experimental compositional distribution histogram of the copolymer samples. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2442–2448, 2002
Synthesis and characterization of new poly(aryl ether)s with isolated fluorophores
Authors: Hwang Shiao‐Wen , Chen Shinn‐Horng , Chen Yun
Published: October 2002

Four novel poly(aryl ether)s (P1–P4) consisting of alternate isolated electron‐transporting (3,3″′‐bis‐trifluoromethyl‐p‐quaterphenyl for P1, P3 or 3,3″′‐dicyano‐p‐quaterphenyl for P2, P4) and hole‐transporting fluorophores [N‐(2‐ethylhexyl)‐3,6‐bis(styryl)carbazole for P1, P2 or 9,9‐dihexyl‐2,7‐bis(styryl)fluorene for P3, P4] were synthesized and characterized. These poly(aryl ether)s can be dissolved in organic solvents and exhibited good thermal stability with 5% weight‐loss temperature above 500 °C in nitrogen atmosphere. The photoluminescent (PL) spectra of the films of these polymers showed maximum peaks at around 442–452 nm. The PL spectral results revealed that the emission of polymers was dominated by the fluorophores with longer emissive wavelength via the energy transfer from p‐quaterphenyl to 3,6‐bis(styryl)carbazole or 2,7‐bis(styryl)fluorene segments. Therefore, the p‐quaterphenyl segments function only as the electron‐transporting/hole‐blocking units in these polymers, and the other segments are the emissive centers and hole‐transporting units. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy levels of these polymers were measured by cyclic voltammetry. The electron‐donating nitrogen atom on carbazole resulted in the higher HOMO energy levels of P1 and P2 than those of P3 and P4. The single‐layer light‐emitting diodes (LED) of Al/poly(aryl ether)s (P1–P4)/ITO glass were fabricated. P1, P2, and P4 revealed blue electroluminescence, but P3 emitted yellow light as a result of the excimer emission. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2215–2224, 2002
Peroxide‐mediated crosslinking of poly(ethylene oxide)
Authors: Emami Shahriar H. , Salovey Ronald , Hogen‐Esch Thieo E.
Published: October 2002

The crosslinking of poly(ethylene oxide) (PEO) with a difunctional peroxide such as 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (Luperox 101) may proceed through at least two different pathways. Thus, the thermally formed alkoxy radicals abstract hydrogen from PEO, and the resulting PEO radicals may combine or react with the peroxide radicals to give ether or acetal crosslinks. However, these reactions also produce noncrosslinking acetals and vinyl ethers. The acetals may react further with peroxy or other radicals and yield orthoesters and ketene acetals. These and similar groups, in the presence of dilute acids, are susceptible to acid hydrolysis, leading to the disintegration of the gels. The gels, upon swelling in dilute acids, undergo a slow degradation process that is not observed for unmodified PEO. The acid hydrolysis is confirmed by a combination of size exclusion chromatography and dynamic mechanical analysis. IR analysis shows the presence of hydroxyl end groups and the presence of carboxylates rather than aldehyde groups, this is consistent with orthoesters and ketene acetal intermediates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3021–3026, 2002
Radical polymerization behavior of ethyl ortho‐(4‐phenyl‐1,3‐dioxolan‐2‐yl)phenyl fumarate
Authors: Seno Makiko , Sunagawa Seigo , Sato Tsuneyuki
Published: October 2002

The polymerization of ethyl ortho‐(4‐phenyl‐1,3‐dioxolan‐2‐yl)phenyl fumarate (EPDPF) with dimethyl 2,2′‐azobisisobutyrate (MAIB) was kinetically investigated in benzene. The polymerization rate (Rp) at 60 °C was presented by Rp = k[MAIB]1.1[EPDPF]0.8. The number‐average molecular weight of poly(EPDPF) was in the range of 2500–3500. Analysis of 1H and 13C NMR spectra of the resulting polymers suggested that the radical polymerization of EPDPF proceeds in a complicated manner involving vinyl addition, intramolecular hydrogen abstraction, and ring opening of the cyclic acetal. The polymerization system involved electron spin resonance (ESR)‐observable poly(EPDPF) radicals under the practical polymerization conditions. ESR‐determined apparent rate constants (2.0–8.5 L/mol s) of propagation increased with increasing initiator concentration and decreasing monomer concentration. The apparent rate constants (0.68–6.6 × l06 L/mol s) of termination decreased with the monomer concentration and slightly increased with the initiator concentration. The activation energies of initiation (Ei), propagation (Ep), and termination (Et) were calculated as Ei = 158, Ep = 41, and Et = 30 kJ/mol, respectively. Radical copolymerization of EPDPF with styrene was also examined at 70 °C in benzene. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2945–2955, 2002
Phthalide as an activating group for the synthesis of poly(aryl ether phthalide)s by nucleophilic aromatic substitution
Authors: Knauss Daniel M. , Bender Jack T.
Published: October 2002

The phthalide ring was examined as an activating group for nucleophilic aromatic substitution. The proposed mechanism by which activation occurs is through a ring opening of the phthalide ring to form a Meisenheimer‐like σ complex. 3,3‐Bis(4‐fluorophenyl)phthalide was synthesized and examined under different reaction conditions to determine its suitability for polymer formation. Semiempirical calculations at the PM3 level suggested that 3,3‐bis(4‐fluorophenyl)phthalide is only moderately activated, whereas 1H, 13C, and 19F NMR spectroscopy suggested that the monomer was not sufficiently activated for nucleophilic aromatic substitution. However, low‐molecular‐weight polymers (number‐average molecular weight < 7000 g/mol) were produced from bisphenol A, hydroquinone, and phenolphthalein. The polymers were characterized by gel permeation chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, NMR spectroscopy, and differential scanning calorimetry. The polymers displayed relatively high glass‐transition temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3046–3054, 2002
Synthesis and characterization of a fluorinated polyanhydride
Authors: Kaur Sarjit , Doerr Allison , Thompson Adrienne , Dalby Charlie
Published: October 2002

A fluorinated aromatic polyanhydride (B) was synthesized from the melt condensation of mixed anhydrides of 4,4′‐(hexafluoroisopropylidene)bis benzoic acid. Although the mixed anhydride from acetic anhydride yielded only a mixture of oligomers (weight‐average molecular weight < 2000), higher weight‐average molecular weight materials in the range of 15,000–18,000 were obtained with trifluoroacetic anhydride. Polymer B was soluble in chloroform and tetrahydrofuran, had a relatively high glass‐transition temperature of 176 °C with no melting point detected to 310 °C, and showed excellent thermal stability (5% weight loss observed at 380 °C by thermogravimetric analysis). The hydrolytic degradation of the fluorinated polyanhydride in a 0.1 M phosphate buffer of pH 7.4 at 37 °C was initially zero‐order, with 35% degradation occurring in 10 days. Loss of film integrity following that led to accelerated degradation, and almost complete dissolution was observed by the 16th day. The stability of the fluorinated polyanhydride in the solid state and in the solvent tetrahydrofuran was also evaluated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3027–3036, 2002
Poly(acrylamide) grafts on spherical bead polymers for extremely selective removal of mercuric ions from aqueous solutions
Authors: Sonmez H. Bulbul , Senkal B. F. , Bicak N.
Published: October 2002

Poly(acrylamide) grafted from solid polymer particles provides a simple solution for extremely selective removal of mercuric ions from aqueous solutions. The grafting of polyacrylamide has been performed, in high yields (164%), by redox initiation from iminoacetic acid groups created on crosslinked spherical beads (210–420 μm) of glycidyl methacrylate/methyl methacrylate/ethylene glycol dimethacrylate terpolymer. In the grafting, homopolymer formation has been reduced greatly (22%) by the treatment of the bead polymer with ceric ammonium nitrate before the addition of acrylamide monomer. The mobility of the graft chains provides nearly homogeneous reaction conditions and rapid mercury binding ability, as for low molecular weight amides [mercury sorption by a 0.105‐g polymer sample from 105 mL of a 7.74 × 10−4 mol L−1 (∼155 ppm) Hg(II) solution shows first‐order kinetics with respect to the Hg(II) concentration, k = 1.1 × 10−3 s−1]. The mercury sorption capacity under nonbuffered conditions is around 3.6 mmol g−1 (i.e., 720 g of mercury/kg) and mostly occurs with the formation of diamido–mercury linkages, which result in the crosslinking of polyacrylamide brushes outside the spherical beads. The crosslinks can be destroyed by treatment with hot acetic acid, without hydrolysis of the amide groups. This process allows a complete elution of the mercury as mercury acetate, and the overall result is reversible crosslinking of the outer shell by mercuric ions. The material presented is efficient in the removal of mercury at concentrations measured in parts per million, and the mercury sorption is extremely selective over some foreign ions, such as Fe(III), Cd(II), Zn(II), and Pb(II). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3068–3078, 2002
Scratching behavior of elastomeric poly(dimethylsiloxane) coatings
Authors: Zhang S. L. , Tsou A. H. , Li J. C. M.
Published: October 2002

Scratch testing has been performed on elastomeric poly(dimethylsiloxane) (PDMS) coatings on stainless steel with a spherical indenter. The friction coefficient (horizontal‐to‐normal force ratio) during scratching decreases with increasing normal load. This result can be explained by assuming that during scratching the contact area is determined by elastic deformation and the horizontal force is proportional to the contact area. With increasing driving speed, the friction coefficient increases, but the rate of increase decreases; this suggests that the scratching of the PDMS coating is a rate process and that the viscoelastic property of the coating influences its frictional behavior. Below a critical normal load, which increases with the coating thickness, the PDMS coating recovers elastically after being scratched so that there are no scratch marks left behind. Above the critical normal load, the coating is damaged by a combination of delamination at the coating/substrate interface and through‐thickness cracking. When the coating is damaged, there is an increase in the friction coefficient, and the friction force displays significant fluctuations. Furthermore, the critical normal load increases with the driving speed; this implies that time is needed to nucleate damage. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1530–1537, 2002
Luminescence of monolayer thin films of the fully conjugated rigid‐rod polymer poly(p‐phenylenebenzobisthiazole)
Authors: Bai S. J. , Wu C. C. , Tu L. W. , Lee K. H.
Published: October 2002

Poly(p‐phenylenebenzobisthiazole) (PBT) is a heterocyclic, aromatic rigid‐rod polymer with a fully conjugated backbone and excellent dimensional, thermo‐oxidative, and solvent stabilities. A PBT polymer with an intrinsic viscosity of 18.0 dL/g was dissolved in methanesulfonic acid or Lewis acid. The PBT solution was spin‐coated and doctor‐bladed for freestanding films or onto an indium tin oxide (ITO) substrate. The acid was removed via coagulation. Scanning electron microscopy determined that the resultant film thicknesses were about 340 and 60 nm for PBT freestanding films and films on the ITO substrate, respectively. X‐ray scattering demonstrated that the freestanding films were in‐plane isotropic without long‐range order. The freestanding films were excited with a He‐Cd laser at 325 nm for photoluminescence (PL) response. PL spectra showed a distinct intensity maximum at 580 nm, regardless of the film‐forming conditions. After the films cooled to 67 K, the PL maximum shifted to 566 nm with enhanced intensity. Aluminum was evaporated onto the monolayer PBT thin film on the ITO substrate as an electron injector for electroluminescence (EL) response. Diodic electric behavior was observed for all monolayer PBT EL devices for the first time. A threshold voltage as low as 4 V was achieved for the monolayer EL devices. In addition, PBT EL spectra were tunable, with a maximum intensity at 570 nm at a bias voltage of 4.5 V changing to 496 nm at 7.5 V (i.e., a blueshift) with greatly increased intensity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1760–1767, 2002
Miscibility and hydrogen‐bonding interactions in blends of carbon dioxide/epoxy propane copolymer with poly(p‐vinylphenol)
Authors: Zhang Zhihao , Mo Zhishen , Zhang Hongfang , Zhang Ying , Na Tianhai , An Yuxian , Wang Xianhong , Zhao Xiaojiang
Published: October 2002

The miscibility and hydrogen‐bonding interactions of carbon dioxide and epoxy propane copolymer to poly(propylene carbonate) (PPC)/poly(p‐vinylphenol) (PVPh) blends were investigated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). The single glass‐transition temperature for each composition showed miscibility over the entire composition range. FTIR indicates the presence of strong hydrogen‐bonding interassociation between the hydroxyl groups of PVPh and the oxygen functional groups of PPC as a function of composition and temperature. XPS results testify to intermolecular hydrogen‐bonding interactions between the oxygen atoms of carbon–oxygen single bonds and carbon–oxygen double bonds in carbonate groups of PPC and the hydroxyl groups of PVPh by the shift of C1s peaks and the evolution of three novel O1s peaks in the blends, which supports the suggestion from FTIR analyses. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1957–1964, 2002
Toughening of a propylene‐b‐(ethylene‐co‐propylene) copolymer by a plastomer
Authors: Arranz‐Andrés Javier , Benavente Rosario , Peña Begoña , Pérez Ernesto , Cerrada María L.
Published: October 2002

Several blends, covering the entire range of compositions, of a metallocenic ethylene‐1‐octene copolymer (CEO) with a multiphasic block copolymer, propylene‐b‐(ethylene‐co‐propylene) (CPE) [composed of semicrystalline isotactic polypropylene (iPP) and amorphous ethylene‐co‐propylene segments], have been prepared and analyzed by differential scanning calorimetry, X‐ray diffraction, optical microscopy, stress‐strain and microhardness measurements, and dynamic mechanical thermal analysis. The results show that for high CEO contents, the crystallization of the iPP component is inhibited and slowed down in such a way that it crystallizes at much lower temperatures, simultaneously with the crystallization of the CEO crystals. The mechanical results suggest very clearly the toughening effect of CEO as its content increases in the blends, although it is accompanied by a decrease in stiffness. The analysis of the viscoelastic relaxations displays, first, the glass transition of the amorphous blocks of CPE appearing at around 223 K, which is responsible for the initial toughening of the plain CPE copolymer in relation to iPP homopolymer. Moreover, the additional toughening due to the addition of CEO in the blends is explained by the presence of the β relaxation of CEO that appears at about 223 K. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1869–1880, 2002
Dornase alfa in early cystic fibrosis lung disease
Authors: Robinson Philip J.
Published: October 2002

Leukocytes that infiltrate cystic fibrosis (CF) sputum as a result of infection have long been known to liberate large amounts of DNA, which increases sputum viscosity and promotes the cycle of chronic lung infection and inflammation that ultimately leads to respiratory failure and death. It was only recently recognized that this vicious cycle begins in infancy, and that archi‐tectural damage to CF lungs is detectable even in children with normal pulmonary function tests.

Dornase alfa cleaves DNA and improves sputum viscosity in CF. Although its efficacy in reducing the risk of acute infectious exacerbations and improving pulmonary function has been recognized for a decade, there is growing interest in its potential for long‐term benefit in young patients with mild lung function abnormalities.

The Pulmozyme Early Intervention Trial (PEIT) study demonstrated that dornase alfa reduces the risk of pulmonary exacerbations requiring i.v. antibiotic treatment by 34% and improves forced expiratory flow at 25–75% of forced vital capacity (FEF25–75), mid‐expiratory flow at 50% of forced vital capacity (MEF), and forced expired volume in 1 sec (FEV1) over a 2‐year period in CF patients with almost normal lung function. A post hoc subgroup analysis suggests that the magnitude of pulmonary function test (PFT) changes may vary, depending on the initial degree of lung function impairment, but that the reduction in exacerbations appears to be a consistent benefit.

These results support the current view that CF patients benefit from intervention early in the course of their lung disease. Pediatr Pulmonol. 2002; 34:237–241. © 2002 Wiley‐Liss, Inc.
Evidence‐based medicine in cystic fibrosis: How should practice change?
Authors: Conway Steven P.
Published: October 2002

This critical review of current practice and research in some aspects of cystic fibrosis (CF) concludes that, despite recent success in prolonging life expectancy, there is still room for improvement in terms of earlier diagnosis and earlier intervention in some of its complications. Specifically, the body of evidence implies that neonatal diagnosis; early attention to nutrition, staphylococcal and pseudomonal infection, and diabetes mellitus; and early treatment with dornase alfa can all be expected to improve patients' quality and quantity of life. Pediatr Pulmonol. 2002; 34:242–247. © 2002 Wiley‐Liss, Inc.
Prevalence of asthma and asthma‐like symptoms in inner‐city elementary schoolchildren
Authors: Webber Mayris P. , Carpiniello Kelly E. , Oruwariye Tosan , Appel David K.
Published: October 2002

American inner‐city children are disproportionately affected by asthma. During the 1999–2000 school year, we conducted a survey of 6 Bronx, New York City elementary schools to assess the prevalence of asthma and asthma‐like symptoms as reported by parents. Children with probable asthma had symptoms within the last 12 months and parents who indicated that their child had asthma. Children with possible asthma had symptoms within the last 12 months but lacked a diagnosis.

Overall, 74% (4,775/6,433) of parents returned completed surveys, identifying 20% (949/4,775) of children as probable asthmatics, and 12% (589/4,775) as possible asthmatics. In multivariate analyses, probable asthma was associated with: Puerto Rican, Black, and white race/ethnicity, male gender, having health insurance, and registration at the poorest school. Possible asthma was associated with lack of health insurance and female gender, but was not associated with any specific race/ethnicity.

Our findings support the effectiveness of school‐based surveys to identify children at high risk for asthma. The challenge remains to engage children and families in appropriate follow‐up care and to manage their illness, either through the use of school‐based health centers or stronger links to community services.Pediatr Pulmonol. 2002; 34:105–111. © 2002 Wiley‐Liss, Inc.
Mechanisms of constitutive NF‐κB activation in human prostate cancer cells
Authors: Suh Junghan , Payvandi Faribourz , Edelstein Leonard C. , Amenta Peter S. , Zong Wei‐Xing , Gélinas Céline , Rabson Arnold B.
Published: October 2002

BACKGROUND

Activation of the NF‐κB transcription factor has been previously demonstrated in two androgen receptor negative prostate cancer cell lines. We wished to extend this work to additional prostate cancer cells and to characterize the mechanisms responsible for constitutive NF‐κB activation.

METHODS

Electrophoretic mobility shift assays were performed to measure NF‐κB DNA‐binding activity in prostate cancer cell lines, and immunohistochemistry was performed to detect nuclear localization of NF‐κB in prostate cancer tissues. Western blot analysis was used to study the status of IκBα. Transient transfection assays were employed to characterize the contributions of IκB kinase (IKK), MAPK kinase kinases (MAPKKKs), androgen receptor (AR), and tyrosine phosphorylation to the constitutive activation of NF‐κB in the prostate cancer cell lines.

RESULTS

Constitutive NF‐κB activity was observed in AR‐negative cell lines as well as in the prostate cancer patient samples, but was not present in AR positive cells. A “super‐repressor” IκBα, as well as dominant negative forms of IKKβ and NF‐κB‐inducing kinase (NIK), and tyrosine kinase inhibition were able to suppress NF‐κB activity in the cells with constitutive activation.

CONCLUSIONS

The constitutive activation of NF‐κB observed in prostate cancer cells is likely due to a signal transduction pathway involving tyrosine kinases, NIK, and IKK activation. Prostate 52:183–200, 2002. © 2002 Wiley‐Liss, Inc.
Folding and stretching in a Go‐like model of titin
Authors: Cieplak Marek , Hoang Trinh Xuan , Robbins Mark O.
Published: October 2002

Mechanical stretching of the I27 domain of titin and of its double and triple repeats are studied through molecular dynamics simulations of a Go‐like model with Lennard‐Jones contact interactions. We provide a thorough characterization of the system and correlate the sequencing of the folding and unraveling events with each other and with the contact order. The roles of cantilever stiffness and pulling rate are studied. Unraveling of tandem titin structures has a serial nature. The force‐displacement curves in this coarse‐grained model are similar to those obtained through all atom calculations. Proteins 2002;49:114–124. © 2002 Wiley‐Liss, Inc.
Prediction of protein secondary structures from conformational biases
Authors: Hoang Trinh Xuan , Cieplak Marek , Banavar Jayanth R. , Maritan Amos
Published: October 2002

We use LINUS (the “Local Independently Nucleated Units of Structure”), a procedure developed by Srinivasan and Rose, to provide a physical interpretation of and predict the secondary structures of proteins. The secondary structure type at a given site is identified by the largest conformational bias during short simulations. We examine the rate of successful prediction as a function of temperature and the interaction window. At high temperatures, there is a large propensity for the establishment of β‐strands whereas α‐helices appear only when the temperature is lower than a certain threshold value. It is found that there exists an optimal temperature at which the correct secondary structures are predicted most accurately. We find that this temperature is close to the peak temperature of the specific heat. Changing the interaction window or carrying out longer simulations approaching equilibrium lead to little change in the optimal success rate. Our findings are in accord with the observation by Srinivasan and Rose that the secondary structures are mainly determined by local interactions and appear in the early stage of folding. Proteins 2002;48:558–565. © 2002 Wiley‐Liss, Inc.
Role of stabilization centers in 4 helix bundle proteins
Authors: Fuxreiter M. , Simon I.
Published: October 2002

Stabilization centers (SCs) were shown to play an important role in preventing decay of three‐dimensional protein structures. These residue clusters, stabilized by cooperative long‐range interactions, were proposed to serve as anchoring points for arranging secondary structure elements. In all‐α proteins, SC elements appear less frequently than in all‐β, α/β, and α+β proteins suggesting that tertiary structure formation of all‐α proteins is governed by different principles than in other protein classes. Here we analyzed the relation between the formation of stabilization centers and the inter‐axial angles (Ω) of α‐helices in 4 helix bundle proteins. In the distance range, where dipoles have dominant effect on the helix pair arrangement, those helix pairs, where residues from both helices participate in SC elements, appear as parallel more frequently than those helices where no SC elements are present. For SC containing helix pairs, the energetic difference between the parallel and anti‐parallel states decreases considerably from 1.1 kcal/mol to 0.4 kcal/mol. Although the observed effect is weak for more distant helices, a competition between the SC element formation and the optimal dipole–dipole interaction of α‐helices is proposed as a mechanism for tertiary structure formation in 4 helix bundle proteins. The SC‐forming potential of different arrangements as well as the pitfalls of the SC definition are also discussed. Proteins 2002;48:320–326. © 2002 Wiley‐Liss, Inc.
Quantitative structure–transformation relationships of sulfonylurea herbicides
Authors: Berger Bernhard M , Müller Martin , Eing Andreas
Published: October 2002

Model development to predict transformation of sulfonylureas in different matrices was carried out using multiple linear regression. Descriptors for lipophilicity and molecular topology, as well as quantum chemical descriptors for energy, geometry, polarity, charges and reactivity using MOPAC with three different Hamiltonians, AM1, PM3 and MNDO, were calculated. In addition, experimental descriptors were measured and taken from the literature. End‐points were transformation rates of twelve sulfonylurea herbicides in buffers at different pH (4, 7 and 10), in sterile and native sediments, and in sterile and native soil. Inter‐correlation of reaction rates indicated four different groups of transformation types, for which sum parameters were calculated. (1) Hydrolysis at pH 4 could be estimated with pKa and charges at a specific atom of the heterocycle. (2) Hydrolysis at pH 7 and 10, as well as transformation in sterile sediments and soil, could be described with descriptors for reactivity (polarisability and superdelocalisability) at specific atoms of the molecules. (3) For transformation in native sediments different models could be found, all based on descriptors for polarisability, superdelocalisability and charges at specific atoms. (4) Modelling of biotransformation in native soil led to diverse models with a variety of descriptors reflecting electronic properties and lipophilicity. Models confirmed previous findings on reaction mechanisms and thereby prove valuable not only for quantitative prediction of reaction rates, but also for studies on transformation pathways.

© 2002 Society of Chemical Industry
Cytotoxic flavonoids from the stem bark of Lonchocarpus aff. fluvialis
Authors: Blatt Cecília T. T. , Chávez Daniel , Chai Heebyung , Graham James G. , Cabieses Fernando , Farnsworth Norman R. , Cordell Geoffrey A. , Pezzuto John M. , Kinghorn A. Douglas
Published: October 2002

Activity‐guided fractionation of a chloroform‐soluble extract of Lonchocarpus aff. fluvialis stem bark using a human epidermoid (KB) tumour cell line as a monitor afforded five rotenoids, one pterocarpan, one chalcone, three flavanones, one flavone and one triterpenoid. All of the compounds isolated proved to be of previously known structure. Among them, the rotenoids (−)‐sumatrol and (±)‐villosinol, the dibenzoylmethane derivative (+)‐3,4‐methylenedioxy‐2′‐methoxy‐[2″,3″:4′,3′]‐furanodibenzoylmethane, and the flavanones (−)‐isoglabrachromene and (−)‐candidone have been shown to exhibit significant cytotoxic activity against human cancer cells for the first time. This is the first report of the chemical constituents of this species, and the profile of compounds obtained was in accordance with the established chemosystematic patterns of species in the tribe Tephrosieae (Leguminosae, Papilionoideae). Copyright © 2002 John Wiley & Sons, Ltd.
Standard Operating Procedures for Clinical Research Personnel ‐ part 13
Authors: Bohaychuk Wendy , Ball Graham
Published: October 2002

This is the 13th in a series of articles containing proposals for wording and content of standard operating procedures (SOPs) for clinical research activities conducted by sponsors and Contract Research Organisations (CROs). The procedures include those required by the International Conference on Harmonisation (ICH), the Food and Drug Administration (FDA), many other guidelines and regulations, and ‘best practice’ observed by the authors. The model forms require modification for actual use. In this article, SOPs are presented for initiation activities: study site initiation visits (SOP 328); and study startup meetings for multicentre studies ( SOP 329). (The full text of all 101 SOPs is available from the authors.) Copyright © 2002 John Wiley & Sons, Ltd.