bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differences and hormone influences on tyrosine hydroxylase immunoreactive cells in the leopard frog
Authors: Wilczynski Walter , Yang Eun‐Jin , Simmons Diana
Published: May 2003

We examined sex differences in tyrosine hydroxylase immunoreactive (TH‐ir) cell populations in the preoptic area (POA), suprachiasmatic nucleus (SCN), posterior tuberculum (TP), and caudal hypothalamus (Hy) in the leopard frog (Rana pipiens), in addition to the effects of natural variation in sex steroid hormones on these same populations in both sexes. All four of these populations have been shown to be dopaminergic. Gonadal sex, androgens, and estrogen all influenced TH‐ir cell numbers, but in a complicated pattern of interactions. After factoring out the effects of sex steroids by multiple regression, TH‐ir cell numbers in all four areas differed between the sexes, with males having a greater number of TH‐ir cells. The influence of androgens and estrogen differed by region and sex of the animals. Androgens were the main influence on TH‐ir cell numbers in the POA and SCN. Plasma androgen concentrations were positively correlated with TH‐ir cell numbers in both areas in males. In females, androgen concentration was negatively correlated with TH‐ir cell numbers in the POA; there was no significant relationship in the SCN in females. In the more caudal populations, estrogen (E2) levels were positively correlated with TH‐ir cell numbers in the TP of both males and females. In the caudal hypothalamus, E2 levels were positively correlated with TH‐ir cell numbers in females, but there was no significant correlation in males. The results indicate that gonadal sex imposes a baseline sex difference in the four TH‐ir (dopamine) populations, resulting in a higher number of such cells in males. Individual and sex‐linked differences in gonadal steroid hormones lead to variation around this baseline condition, with androgens having a greater influence on rostral populations and estrogen on caudal populations. Last, an individual's gonadal sex determines the effect that androgens and estrogen have on each population. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 54–65, 2003
Operator trigonometry of preconditioning, domain decomposition, sparse approximate inverses, successive overrelaxation, minimum residual schemes
Authors: Gustafson Karl
Published: May 2003

This paper extends the relationship between the author's operator trigonometry and convergence rates and other properties of important iterative methods. A new interesting trigonometric preconditioning lemma is given. The general relationship between domain decomposition methods and the operator trigonometry is established. A new basic conceptual link between sparse approximate inverse algorithms and the operator trigonometry is observed. A new underlying fundamental inherent trigonometry of the classical successive over‐relaxation scheme is exposed. Some improved trigonometric interpretations of minimum residual schemes are mentioned. Copyright © 2002 John Wiley & Sons, Ltd.
A note on bound for norms of Cauchy–Hankel matrices
Authors: Solak Süleyman , Bozkurt Durmuş
Published: May 2003

We determine bounds for the spectral and 𝓁p norm of Cauchy–Hankel matrices of the form Hn=[1/(g+h(i+j))]ni,j=1≡ ([1/(g+kh)]ni,j=1), k=0, 1,…, n –1, where k is defined by i+j=k (mod n). Copyright © 2002 John Wiley & Sons, Ltd.
An increasing‐angle property of the conjugate gradient method and the implementation of large‐scale minimization algorithms with line searches
Authors: Dai Yu‐Hong , Martínez José Mario , Yuan Jin‐Yun
Published: May 2003

The search direction in unconstrained minimization algorithms for large‐scale problems is usually computed as an iterate of the preconditioned) conjugate gradient method applied to the minimization of a local quadratic model. In line‐search procedures this direction is required to satisfy an angle condition that says that the angle between the negative gradient at the current point and the direction is bounded away from π/2. In this paper, it is shown that the angle between conjugate gradient iterates and the negative gradient strictly increases as far as the conjugate gradient algorithm proceeds. Therefore, the interruption of the conjugate gradient sub‐algorithm when the angle condition does not hold is theoretically justified. Copyright © 2002 John Wiley & Sons, Ltd.
Application of the Lanczos algorithm for solving the linear systems that occur in continuation problems
Authors: Chien C.‐S. , Chang S.‐L.
Published: May 2003

We study the Lanczos method for solving symmetric linear systems with multiple right‐hand sides. First, we propose a numerical method of implementing the Lanczos method, which can provide all approximations to the solution vectors of the remaining linear systems. We also seek possible application of this algorithm for solving the linear systems that occur in continuation problems. Sample numerical results are reported. Copyright © 2002 John Wiley & Sons, Ltd.
A nodal coupling of finite and boundary elements
Authors: Sayas Francisco‐Javier
Published: May 2003

This article presents and analyzes a simple method for the exterior Laplace equation through the coupling of finite and boundary element methods. The main novelty is the use of a smooth parametric artificial boundary where boundary elements fit without effort together with a straight approximate triangulation in the bounded area, with the coupling done only in nodes. A numerically integrated version of the algorithm is also analyzed. Finally, an isoparametric variant with higher order is proposed. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 555–570, 2003
Mass‐lumping or not mass‐lumping for eigenvalue problems
Authors: Armentano María G. , Durán Ricardo G.
Published: May 2003

In this article we analyze the effect of mass‐lumping in the linear triangular finite element approximation of second‐order elliptic eigenvalue problems. We prove that the eigenvalue obtained by using mass‐lumping is always below the one obtained with exact integration. For singular eigenfunctions, as those arising in non convex polygons, we prove that the eigenvalue obtained with mass‐lumping is above the exact eigenvalue when the mesh size is small enough. So, we conclude that the use of mass‐lumping is convenient in the singular case. When the eigenfunction is smooth several numerical experiments suggest that the eigenvalue computed with mass‐lumping is below the exact one if the mesh is not too coarse. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 653–664, 2003
A second‐order linearized difference scheme on nonuniform meshes for nonlinear parabolic systems with Dirichlet boundary value conditions
Authors: Zhang Ling‐Yun , Sun Zhi‐Zhong
Published: May 2003

A linearized three‐level difference scheme on nonuniform meshes is derived by the method of the reduction of order for the Dirichlet boundary value problem of the nonlinear parabolic systems. It is proved that the difference scheme is uniquely solvable and second order convergent in L∞‐norm. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 638–652, 2003
Stimuli‐sensitive behaviour of novel betaine‐type polyampholytes
Authors: Didukh Alexander G , Koizhaiganova Raushan B , Khamitzhanova Gulzhan , Bimendina Larisa A , Kudaibergenov Sarkyt E
Published: May 2003

Novel linear and crosslinked polyampholytes of betaine structure based on acrylic acid and ethyl 3‐aminocrotonate (ethyl ester of 3‐amino‐2‐butenoic acid) have been synthesized by Michael addition reaction followed by radical copolymerization. The mechanism of formation of monomer and polymer betaines is discussed. The linear polyampholyte has been characterized by potentiometric titration, IR, NMR and GPC. Crosslinked polymeric betaines were synthesized in the presence of N,N′‐methylenebisacrylamide. The stimuli‐sensitive properties of amphoteric gels have been studied as a function of pH, ionic strength, water–organic mixture composition, electric, and combined electric and magnetic fields. The isoelectric points of linear and crosslinked polymeric betaines correspond to pH 2.0–2.1. The effect of ionic strength on the solution and gel properties of polybetaine has been interpreted on the basis of destruction of inter‐chain, intra‐chain and intra‐group salt bonds. Water–acetone, water–ethanol or water–DMF mixtures cause the shrinking of amphoteric gel due to change of the dielectric constant of the medium and decrease of the osmotic pressure. Electrocollapse is observed under the action of DC electric field. Simultaneously cross action of electric and magnetic fields enhances the collapsing rate. Appearance of pH gradient within the volume of polyampholyte gel under the externally imposed DC electric field has been observed. Copyright © 2003 Society of Chemical Industry
Synthesis and properties of poly(methyl methacrylate)/montmorillonite (PMMA/MMT) nanocomposites
Authors: Li Yan , Zhao Bin , Xie Shaobo , Zhang Shimin
Published: May 2003

PMMA/MMT nanocomposites were successfully synthesized via in situ intercalative polymerization, and characterized by means of wide‐angle X‐ray diffractometry, transmission electron microscopy, thermal gravimetric analysis, dynamic mechanical analysis and Fourier‐transform infrared analysis. The nanocomposites possess partially exfoliated and partially intercalated structure, in which the silicate layers are exfoliated into nanometre secondary particles with thickness of less than 20 nm and uniformly dispersed in the polymer matrix. In comparison with pure PMMA, the thermal stability, glass transition temperature, and mechanical properties of the polymer are notably improved by the presence of the nanometric silicate layers. It was found that part of the PMMA chains in the nanocomposites are well immobilized inside and/or onto the layered silicates and, therefore, the unique properties of the nanocomposites result from the strong interactions between the nanometric silicate layers and the polymer chains. Copyright © 2003 Society of Chemical Industry
Evaluation of bis(2‐pyridinal)ethylenediimine as ligand for atom transfer radical polymerization of methyl methacrylate: influence of polar solvents
Authors: Iovu Mihaela C , Maithufi Norah G , Mapolie Selwyn F
Published: May 2003

Bis(2‐pyridinal)ethylenediimine was used as a ligand for copper‐mediated atom transfer radical polymerization (ATRP) of methyl methacrylate. Reactions were performed at molar ratios of monomer:initiator:catalyst of 100:1:0.5 and catalyst:ligand ratios of 1:1 and 1:2. Polymerization reactions were performed in bulk as well as in the presence of polar solvents such as dimethylformamide and acetonitrile. Reactions carried out in bulk resulted in polymerizations with poor control due to the low solubility of the copper complex in the monomer. The control was however improved by carrying out the reactions in solution using either dimethylformamide or acetonitrile as solvent. Copyright © 2003 Society of Chemical Industry
Studies on the curing and thermal behaviour of DGEBA in the presence of bis(4‐carboxyphenyl) dimethyl silane
Authors: Khurana Parveen , Aggarwal S , Narula AK , Choudhary Veena
Published: May 2003

The curing behaviour of diglycidyl ether of bisphenol‐A (DGEBA) was investigated by differential scanning calorimetry using bis(4‐carboxyphenyl) dimethyl silane (CPA) as a crosslinking agent and imidazole as a catalyst. Two exotherms were observed in the absence of catalyst in the temperature range 166–328 °C. A significant decrease in the curing temperature was observed when 0.1% imidazole was used as catalyst. Further increase in the concentration of imidazole resulted in a decrease in the peak exotherm temperature. The effect of stoichiometry of functional groups on the curing behaviour of DGEBA was investigated by taking varying mole ratios of CPA, ranging from 1 to 2.5, keeping the concentration of imidazole as 0.1% w/w. The heat of polymerization (ΔH) was found to be maximum at a molar ratio of 1:1.75 (DGEBA:CPA). Mixtures of diaminodiphenyl sulfone (DDS and CPA or phthalic anhydride (PA) and CPA in ratios of 1:0, 0.25:0.75, 0.5:0.5, 0.75:0.25) were also used to investigate the curing behaviour of DGEBA. A significant decrease in curing temperature of DGEBA/DDS was observed on partially replacing DDS with CPA, whereas marginal change in the curing temperatures was observed on replacing phthalic anhydride with CPA. The thermal stability of epoxy resin, cured isothermally, was evaluated by recording thermogravimetry/dynamic thermogravimetry traces in nitrogen atmosphere. The percentage char yield was highest for the sample cured using 1.75 mole of CPA. Copyright © 2003 Society of Chemical Industry
Thermoreversible gelation of poly(vinylidene fluoride)/poly(methyl acrylate) blends in diethyl azelate: a thermodynamic investigation
Authors: Dikshit Asok K , Jana Tushar , Malik Sudip , Nandi Arun K
Published: May 2003

The thermodynamic behaviour of poly(vinylidene fluoride) (PVF2)/poly(methyl acrylate) (PMA) blend gels in diethyl azelate (DEAZ) was studied by differential scanning calorimetry at three different blend compositions (x (weight fraction of PVF2 in the blend) = 0.75, 0.5 and 0.25). Transmission electron microscopy together with optical microscopy indicate the presence of fibrillar network morphology in the gels. The quasi‐binary phase diagrams drawn from both the heating and cooling processes are almost similar, with a hysteresis of 50–60 °C. The possibility of polymer–solvent compound formation in the blend gels have been explored from the composition dependency of enthalpy of gel fusion and enthalpy of gel formation data. Extending the procedure of the pure PVF2/DEAZ gel systems to blend gels, it has been surmised that polymer–solvent compound formation also occurs in blend gels, but the stoichiometry of the complexes varies with blend composition. The shapes of the quasi‐binary phase diagrams of the blend gels are different in some cases from that of pure PVF2/DEAZ, gel indicating that the polymer–solvent compounds are incongruent or singular type depending on the blend compositions. A possible explanation for this behaviour has been offered from entropic and enthalpic viewpoints. Copyright © 2003 Society of Chemical Industry
Thermal and mechanical properties of biodegradable blends of poly(L‐lactic acid) and lignin
Authors: Li Jianchun , He Yong , Inoue Yoshio
Published: May 2003

The thermal and mechanical properties of the biodegradable blends of poly(L‐lactic acid) (PLLA) and lignin prepared by manual mixing have been investigated. Both the results of DSC and FTIR spectral analyses indicated the existence of intermolecular interaction between PLLA and lignin. Furthermore, FTIR elucidated the existence of an intermolecular hydrogen‐bonding interaction. Study of the mechanical properties of the blends indicated that the maximum strength and the elongation of the material decreased and the Young's modulus remained almost constant when the lignin content reached 20%. Thermogravimetry indicated that lignin would accelerate the thermal degradation of PLLA when the content of lignin was more than 20%. Compared with some other biodegradable polymers, the blend of PLLA and lignin is thought to be a promising material, because the material properties, as well as the price, are at an acceptable level when the content of lignin is less than about 20%. Copyright © 2003 Society of Chemical Industry
Synthesis of styrene–maleic anhydride random copolymer and its compatibilization to poly(2,6‐dimethyl‐1,4‐phenylene ether)/brominated epoxy resin
Authors: Liang Guozheng , Meng Jiru , Zhao Lei
Published: May 2003

Styrene–maleic anhydride random copolymer (R‐SMA7.5), with a low content of maleic anhydride (MAH) of about 7.5 mol%, has been prepared, and the copolymer was characterized by fourier‐transform infrared (FTIR) and 13C NMR techniques showing that the product contained only random copolymer without blocks. The miscibility between poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and R‐SMA, was investigated by differential scanning calorimetry (DSC), showing that PPE was miscible with R‐SMA synthesized in our laboratory over the entire composition with low MAH content. A blend of R‐SMA18 (MAH content is about 18 mol%) and PPE was also studied by DSC, which showed that PPE was immiscible when R‐SMA was the major component, although it was miscible with limited composition. FTIR investigation showed that R‐SMA could react with bromide epoxy (BEP) resin at high temperature (180°). The heat‐resistance and mechanical properties of R‐SMA/PPE/BEP systems were tested and analyzed, and results indicated that R‐SMA could improve the miscibility of PPE and BEP with increasing Tg of the BEP phase and decreasing the Tg of the PPE slightly, improving the breaking elongation and breaking energy, which resulted from good miscibility between PPE and BEP with R‐SMA as the compatibilizer. Finally, the properties of the composites (copper clad laminate) with R‐SMA7.5 are studied and discussed. Copyright © 2003 Society of Chemical Industry
Effect of the nature and degree of crosslinking on Rose Bengal binding by DVB‐, NNMBA‐, HDODA‐ and TTEGDA‐crosslinked poly(N‐vinylpyrrolidone)s
Authors: Gigimol MG , Mathew Beena
Published: May 2003

Poly(N‐vinylpyrrolidone)s with 2–20 mol% DVB, NNMBA, HDODA and TTEGDA crosslinkings were prepared by suspension polymerisation. The binding of Rose Bengal by these poly(N‐vinylpyrrolidone)s was followed by a batch equilibration method. In order to optimise the conditions of dye binding, the effect of the concentration of Rose Bengal solutions, temperature and pH were followed. Kinetic studies showed that the binding of Rose Bengal by poly(N‐vinylpyrrolidone)s is a phase boundary process followed by a three‐dimensional diffusion. Copyright © 2003 Society of Chemical Industry
The influence of interphase on nylon‐6/nano‐SiO2 composite materials obtained from in situ polymerization
Authors: Li Ying , Yu Jian , Guo Zhao‐Xia
Published: May 2003

Three commercially available silane, titanate and aluminate based coupling agents were used to pretreat nano‐SiO2 for the preparation of nylon‐6/nano–SiO2 composites via in situ polymerization. The interphases formed in different composite systems and their influence on material properties were investigated. Results indicated that the interfacial interactions differed between composite systems, whereas rigidity and toughness of composites were all improved by addition of pretreated silicas at an optimal content of 4.3 wt%. The presence of pretreated silicas did not have a distinct influence in the non‐isothermal crystallization behaviour of the nylon matrix. The composites containing pretreated silicas had slightly higher dynamic viscosities and superior storage moduli at high frequency, compared with neat nylon‐6. Copyright © 2003 Society of Chemical Industry
The influence of wax content on the physical properties of low‐density polyethylene–wax blends
Authors: Djoković V , Mtshali TN , Luyt AS
Published: May 2003

The influence of wax content on the thermal, mechanical and viscoelastic properties of low‐density polyethylene (LDPE)–oxidized wax miscible blends have been investigated. It was found that small concentrations of wax improved physical properties such as thermal stability, elastic modulus and yield stress. At higher concentrations, however, due to crystal phase separation, wax deteriorates the thermal as well as the mechanical properties. It was also shown that a formerly established two‐process model for the stress relaxation in semicrystalline polymers could be used for the explanation of the viscoelastic behaviour of the blends. Copyright © 2003 Society of Chemical Industry
Ring‐opening polymerization of lactones initiated by diphenylzinc–coinitiator systems
Authors: Vivas M , Mejías N , Contreras J
Published: May 2003

Diphenylzinc, alone or in combination with water and butanone as coinitiators, was used as a polymerization initiator system for a variety of lactones at varying temperatures. The resulting data indicate that the course of the polymerization is greatly influenced by the lactone structure, as well as by the molar ratio of coinitiator to diphenylzinc. When used alone, diphenylzinc exhibited high activity as an initiator in δ‐valerolactone polymerizations, although it was less efficient when used in the β‐butyrolactone and the β‐propiolactone polymerizations. Activity in the polymerization of β‐lactones was increased by adding small amounts of butanone or water. It was also observed that the diphenylzinc–butanone combination was more effective than the diphenylzinc–water mixture in the polymerizations of β‐butyrolactone and β‐propiolactone. Copyright © 2003 Society of Chemical Industry
Thermal degradation of flame‐retarded polyethylene/magnesium hydroxide/poly(ethylene‐co‐propylene) elastomer composites
Authors: Wang Zhengzhou , Hu Keliang , Hu Yuan , Gui Zhou
Published: May 2003

Magnesium hydroxide‐based halogen‐free flame retarded linear low‐density polyethylene (LLDPE) composites containing poly(ethylene‐co‐propylene) (EP) elastomer were prepared by a melt process and subsequently vulcanized thermally. The thermal degradation of the composites was studied using thermogravimetric (TG) analysis and real‐time Fourier transform infrared (RT‐FTIR) spectroscopy. The combustion residues from the composites were characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS). The results from TG and RT‐FTIR tests show that the incorporation of a suitable amount of the elastomer into polyethylene/magnesium hydroxide composites after vulcanization increases the thermal stability. A graphite‐like char was found for the composites with EP elastomer, from Raman spectroscopy studies. XPS results indicate that there are several forms of carbon present in the combustion residues of the composites with EP elastomer, compared with only one form of carbon in the residues of the composites without the elastomer. Copyright © 2003 Society of Chemical Industry
The chain extension of anionic prepolymers in the preparation of aqueous poly(urethane–urea) dispersions
Authors: Lahtinen Mika , Pinfield Rachel K , Price Colin
Published: May 2003

Anionic polyurethane prepolymers end‐capped with isocyanate groups were dispersed and chain‐extended in aqueous media using three different extension agents: hydrazine, 1,2‐ethylene diamine (EDA) and 1,2‐propylene diamine (PDA). Two types of prepolymer were used. The first was prepared from isophorone diisocyanate (IPDI), α,α‐dimethylol propionic acid (DMPA) and poly(propylene oxide) diol (PPO) and the second from α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate (m‐TMXDI), poly(caprolactone) diol (PCL) and DMPA. The colloidal particles which formed in the dispersion process and the constituent poly(urethane–urea) chains were characterised by a combination of dynamic and static light scattering, gel permeation chromatography and FTIR spectroscopy. Using EDA as the extender, a study was made of how the degree of extension depended on the molar ratio of amine to isocyanate groups, [NH2]/[NCO] (= RA, I). It was found that using a stoichiometric balance of isocyanate and amine groups did not lead to high degree of extension, and better chain extension was obtained at lower RA, I values. In a comparative study using stoichiometric balances of isocyanate and amine groups, the degrees of extension obtained using PDA and EDA were approximately the same, while hydrazine was the least effective. Force–extension studies were carried out on samples prepared from films cast from the aqueous poly(urethane–urea) dispersions in order to assess the influence of chain‐extender type and stoichiometry on bulk properties; values of Young's modulus, tensile strength and maximum extension are reported. Copyright © 2003 Society of Chemical Industry
The influence of layered compounds on the properties of starch/layered compound composites
Authors: Wilhelm Helena‐M , Sierakowski Maria‐R , Souza Gabriel P , Wypych Fernando
Published: May 2003

Glycerol‐plasticized starch films were modified by addition of various layered compounds as fillers, two being of natural origin (kaolinite, a neutral mineral clay, and hectorite, a cationic exchanger mineral clay) and two synthetic (layered double hydroxide, LDH, an anionic exchanger, and brucite, having a neutral structure). The effects of the filler type and the plasticizer were analyzed by X‐ray diffraction, dynamic mechanical analysis and thermogravimetry. The storage modulus was higher for kaolinite > brucite > hectorite than for LDH starch composites. However, only the hectorite filler presented a shift of the interplanar basal distance to higher values, which represents the intercalation of glycerol molecules between the clay layers. The glycerol intercalation is minimized in plasticized–oxidized starch films where the oxidized starch chains are preferentially intercalated. Copyright © 2003 Society of Chemical Industry
Crosslinking of elastomers upon ageing: a kinetic approach based on crystallinity changes followed by DSC
Authors: Baba Mohamed , George Soney , Gardette Jean Luc , Lacoste Jacques
Published: May 2003

It was observed that crosslinking reactions resulting both from peroxide decomposition or photoageing at wavelengths longer than 300 nm involve a drastic decrease of the crystallinity of some dienic elastomers, such as polybutadienes (rich in cis 1,4 and 1,2 microstructures) and polycyclo‐octene. By comparing precisely the rate of decomposition of dicumyl peroxide and that of the crystallinity decrease, it was possible to show that the kinetics of crystallinity loss observed upon ageing can be identified with that of the crosslinking of elastomers. The results indicate that the crosslinking process can be followed directly by DSC measurement of the crystallization/melting cycle.

© 2003 Society of Chemical Industry
Micellar solutions of amphipathic copolymers based on carboxymethyl cellulose
Authors: Cao Ya , Li Huilin
Published: May 2003

A novel family of amphipathic copolymers based on carboxymethyl cellulose (CM‐cellulose) has been synthesized through ultrasonic irradiation. Their micellar conformation in aqueous solution was studied by dynamic laser scattering, environmental scanning electron microscopy and gel permeation chromatography. The results show that conformation of copolymer molecules is totally different from that of CM‐cellulose because of the introduction of the surface active macromonomers. Due to the influence of hydrophobic character and molecular weight, different amphipathic copolymers have different micellar conformations, such as cylindrical, spheroidal or ellipsoidal micelles. In the range of concentration tested, the normalized first‐order autocorrelation function g(1)(τ) of a copolymer of CM‐cellulose and poly(ethylene oxide) dodecyl ether acrylate does not fit a single‐exponential decay, indicating a polydisperse system and the existence of species of different shapes and size. At different concentrations, the hydrodynamic radii of micelles (R) almost distribute into two regions of smaller and larger size. With increasing copolymer concentration, the region of smaller R remains in the range 30–100 nm and is considered to represent monomolecular micelles, while the larger R region increases gradually with concentration, which means that polymolecular micelles increase in size.

© 2003 Society of Chemical Industry
Synthesis of liquid crystalline–amorphous block copolymers by the combination of atom transfer and photoinduced radical polymerization mechanisms
Authors: Serhatli I. E. , Kacar T. , Önen A.
Published: May 2003

The synthesis of ABA‐type block copolymers, involving liquid‐crystalline 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate (LC6) and styrene (St) monomer with copper‐based atom transfer radical polymerization (ATRP) and photoinduced radical polymerization (PIRP), was studied. First, photoactive α‐methylol benzoin methyl ether was esterified with 2‐bromopropionyl bromide, and it was subsequently used for ATRP of LC6 in diphenylether in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst. The obtained photoactive functional liquid‐crystalline polymer, poly[6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate] (PLC6), was used as an initiator in PIRP of St. Similarly, photoactive polystyrenes were also synthesized and employed for the block copolymerization of LC6 in the second stage. The spectral, thermal, and optical measurements confirmed a full combination of ATRP and PIRP, which resulted in the formation of ABA‐type block copolymers with very narrow polydispersities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1892–1903, 2003
Supramolecular discotic liquid crystals from wedge‐shaped diacetylenes and their polymerization
Authors: Hwang In Ho , Lee Seung Ju , Chang Ji Young
Published: May 2003

Wedge‐shaped diacetylenic compounds were synthesized by the amidation reaction between the linear diacetylenic side groups and 5‐acetamidoisophthalic acid. The compounds showed enantiotropic transitions. In the liquid‐crystalline states, they were dimerized via hydrogen bonding of acetamide groups, forming disklike supramolecules and had rectangular columnar phases. Polymerization was carried out by UV irradiation and thermal annealing at their mesophase temperatures, giving polydiacetylenes. After polymerization, the compounds became dark red, but their textures were still birefringent. The IR and ultraviolet–visible study demonstrated that the polymerization proceeded topochemically by 1,4‐addition. X‐ray analysis showed that the UV‐polymerized samples maintained rectangular columnar phases. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1881–1891, 2003
Pore size modification of macroporous crosslinked poly(dicyclopentadiene)
Authors: Della Martina Alberto , Garamszegi László , Hilborn Jöns G.
Published: May 2003

This article describes the pore size modification and in situ surface functionalization of macroporous crosslinked poly(dicyclopentadiene), produced by chemically induced phase separation, with norbornene‐functionalized poly(ethylene glycol) telechelic oligomers. The microstructure of the open porosity materials produced with this technique consisted of agglomerated particles. The incorporation of these telechelic oligomers allowed a substantial decrease in the pore size and a related increase in the internal surface area. These functionalized oligomers acted as stabilizers around the primary particles produced by phase separation and blocked their growth so that the materials resulting from the agglomeration of these smaller particles showed finer microstructures. The resulting porous materials were characterized by scanning electron microscopy, density measurements, nitrogen adsorption, and mercury porosimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2036–2046, 2003
Synthesis and characterization of multiblock copolymers based on L‐lactic acid, citric acid, and poly(ethylene glycol)
Authors: Yao Fanglian , Bai Yun , Zhou Yutao , Liu Chang , Wang Hao , Yao Kangde
Published: May 2003

Because poly(L‐lactic acid) (PLLA) is a biodegradable polyester with low immunogenicity and good biocompatibility, it is used as a biomaterial. However, hydrophobic PLLA does not have any reactive groups. Thus, its application is limited. To increase the hydrophilicity of PLLA and accelerate its degradation rate, functionalized pendant groups and blocks were introduced through copolymerization with citric acid and poly(ethylene glycol) (PEG), respectively. This article describes the synthesis and characterization of poly(L‐lactic‐co‐citric acid) (PLCA)‐PLLA and PLCA‐PEG multiblock copolymers. The results indicated that the hydrolysis rate was enhanced, and the hydrophilicity was improved because of the incorporation of carboxyl groups in PLCA‐PLLA. The joining of the PEG block led to improved hydrophilicity of PLCA, and the degradation rate of PLCA‐PEG accelerated as compared with that of PLCA‐PLLA. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2073–2081, 2003
Ring‐opening metathesis polymerization as a route to controlled copolymers of ethylene and polar monomers: Synthesis of ethylene–vinyl chloride‐like copolymers
Authors: Yang Hongli , Islam Manirul , Budde Charles , Rowan Stuart J.
Published: May 2003

A series of ethylene–vinyl chloride‐like copolymers were prepared by ring‐opening metathesis polymerization (ROMP). The route to these materials included the bulk polymerization of 5‐chlorocyclooctene and 5,6‐dichlorocyclooctene with the first‐generation Grubbs' catalyst, followed by diimide hydrogenation of the resulting unsaturated polymers. In addition, the amount of chlorine in these materials was varied by the copolymerization of 5‐chlorocyclooctene with cyclooctene. These materials were fully characterized by NMR (1H and 13C), gel permeation chromatography, and Fourier transform infrared spectroscopy. Finally, hydroboration was carried out on the ROMP product of 5‐chlorocyclooctene to yield a polymer, which was effectively a vinyl alcohol–vinyl chloride–ethylene terpolymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2107–2116, 2003
Kinetics of the ring‐opening metathesis polymerization of a 7‐oxanorbornene derivative by Grubbs' catalyst
Authors: Holland Marium G. , Griffith Veronica E. , France Marcia B. , Desjardins Steven G.
Published: May 2003

The kinetics of the initiation and propagation of the ring‐opening metathesis polymerization of exo,exo‐5,6‐bis(methoxycarbonyl)‐7‐oxabicyclo[2.2.1]hept‐2‐ene catalyzed by Grubbs' catalyst (Cl2(PCy3)2RuCHPh) were measured by ultraviolet–visible and 1H NMR spectroscopy, respectively. Activation parameters for these processes were also determined. Although the ratio of the rate constant of initiation to the rate constant of propagation was determined to be less than 1 for this system, this polymerization showed many of the characteristics of a living system, including low polydispersities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2125–2131, 2003
Subcutaneous emphysema secondary to foreign‐body aspiration
Authors: Findlay C.A. , Morrissey S. , Paton J.Y.
Published: May 2003

Pneumomediastinum is uncommon in pediatric medical practice, outside the neonatal period. While asthma or respiratory infections are the most frequent underlying causes, it is important not to forget the possibility of foreign body aspiration, particularly after the clinical presentation. Pediatr Pulmonol. 2003; 36:81–82. © 2003 Wiley‐Liss, Inc.
Granulomatous pulmonary disease in a child: An unusual presentation of Crohn's disease
Authors: Al‐Binali Ali M. , Scott Brent , Al‐Garni A. , Montgomery Mark , Robertson Marli
Published: May 2003

Crohn's disease (CD) is a chronic inflammatory disorder of the bowel which may be associated with an extensive list of extraintestinal manifestations involving almost every organ system. The most common organs involved are the eyes, skin, joints, and liver. Symptomatic bronchopulmonary disorders have been reported only rarely in pediatric CD. We report on an 11‐year‐old child who had a recurrent cough and increasing dyspnea with exercise for 8 months before developing any gastrointestinal symptoms. He was demonstrated to have granulomatous inflammation of the lung, as well as of the gastrointestinal tract. Similarities between CD and sarcoidosis are discussed. Pediatr Pulmonol. 2003; 36:76–80. © 2003 Wiley‐Liss, Inc.
Sputum induction as a diagnostic tool for community‐acquired pneumonia in infants and young children from a high HIV prevalence area
Authors: Zar H.J. , Tannenbaum E. , Hanslo D. , Hussey G.
Published: May 2003

Sputum induction is a standard diagnostic procedure to identify pathogens in lower respiratory tract secretions in adults with pneumonia, but has rarely been studied or used in infants and young children. Our aim was to determine the usefulness of induced sputum (IS) as a diagnostic method for infants and children hospitalized with community‐acquired pneumonia (CAP) in a high HIV prevalence area. Children hospitalized for CAP were prospectively enrolled over a year. IS was obtained by nebulization with hypertonic (5%) saline, physiotherapy, and suctioning. Sputum was submitted for bacterial and mycobacterial culture and P. carinii detection. Gastric lavages (GLs) were done for M. tuberculosis culture; a nasopharyngeal aspirate (NPA) was obtained for bacterial culture and P. carinii detection. IS was obtained in 210 children (median age, 7 (25th to 75th percentile, 3–18) months); 138 (66%) were HIV‐infected; 148 (70%) were receiving supplemental oxygen. Bacteria were isolated from 101 (50%) IS and 141 (70%) NPA paired specimens (P < 0.001). A significantly higher rate of S. aureus, H. influenzae, M. catarrhalis, and S. pneumoniae was found in NPAs compared to IS; this pattern was particularly evident in HIV‐infected children. M. tuberculosis was cultured from sputum in 19 patients (9%); GLs performed in 142 children were positive in only 9 (6%). The difference (95% confidence interval) between yields for M. tuberculosis from culture of IS compared to GL was 4.3% (95% CI, 0–5.6%; P = 0.08). P. carinii was identified from IS in 12 (5.7%) children; all corresponding NPAs were negative. Seven (3%) children could not tolerate sputum induction. Side effects included increased coughing in 4%, epistaxis in 3%, and wheezing responsive to bronchodilators in 1%. In conclusion, induced sputum is a useful and safe diagnostic procedure in infants and children with CAP from a high HIV prevalence area. Pediatr Pulmonol. 2003; 36:58–62. © 2003 Wiley‐Liss, Inc.
Role of budesonide as maintenance therapy for children with asthma
Authors: Szefler Stanley , Pedersen Søren
Published: May 2003

Asthma is a chronic inflammatory disease of the airways. Inhaled corticosteroids are recognized as the preferred long‐term control medication for persistent asthma based on their anti‐inflammatory properties and significant evidence of efficacy. Inhaled budesonide is the most carefully characterized inhaled corticosteroid for childhood asthma. It is available for administration in children down to six months of age and to date has an excellent safety profile. Pediatr Pulmonol. 2003; 36:13–21. © 2003 Wiley‐Liss, Inc.
Hospital readmissions for asthma in children and young adults in Canada
Authors: Chen Yue , Dales Robert , Stewart Paula , Johansen Helen , Scott Geoffroy , Taylor Gregory
Published: May 2003

To examine the incidence rate of hospital readmission for asthma in relation to sex and age among Canadian children and young adults, we used data from 86,863 subjects under age 20 years when they had a first admission for asthma as 1 of first 5 diagnoses in Canada between April 1, 1994 and March 31, 1997. We calculated age‐ and sex‐specific incidence rates, and used the Cox proportional hazards model for multivariate analysis. Of these subjects, 20,277 (23.3%) were readmitted to hospital for asthma during the study period. After adjusting for length of stay for first admission and province, the rate ratio for females vs. males was 0.86 for those under age 1 year, and close to unity for the 1–4‐year and 5–9‐year age groups, whereas it was 1.47 and 1.35 for the 10–14‐year and 15–19‐year age groups, respectively. The data showed similar trends for rehospitalization asthma as a primary diagnosis. The incidence rate of rehospitalization showed little sex difference between ages 1–9 years, but was markedly higher in females than in males 10–19 years of age. Airway size, female hormonal changes, increased use of cosmetic products, and cigarette smoking among adolescent girls may contribute to the age‐ and sex‐differences in adolescence. Pediatr Pulmonol. 2003; 36:22–26. © 2003 Wiley‐Liss, Inc.
Exercise‐induced bronchospasm in children: Comparison of FEV1 and FEF25–75% responses
Authors: Fonseca‐Guedes Cristina H.F. , Cabral Anna Lúcia B. , Martins Milton A.
Published: May 2003

The response of asthmatic children to exercise has usually been evaluated by forced expiratory volume in 1 sec (FEV1). We reasoned that other respiratory indexes derived from the forced vital capacity manuever such as forced expiratory flow between 25–75% of vital capacity (FEF25–75%) would add significant information in the evaluation of the relationship between asthma severity and response to exercise. We studied 164 children with intermittent (n = 63), mild persistent (n = 30), moderate persistent (n = 40), and severe persistent asthma (n = 31). Subjects exercised for 6 min on a cycle ergometer at 80% of their maximum heart rate, and spirometry was performed before and 5, 10, and 20 min after exercise. There was good correlation between changes in FEV1 and FEF25–75% after exercise (r = 0.60, P < 0.001 for intermittent asthma and r = 0.80, P < 0.001 for severe persistent asthma). The presence of a fall in both FEV1 (≥10%) and in FEF25–75% (≥26%) when compared to a decrease in only one of these two indexes was significantly greater in children with more severe asthma (60.0% for intermittent asthma and 94.4% for severe persistent asthma, P = 0.022). FEF25–75% can decrease in response to exercise without changes in FEV1, mainly in children with mild asthma. In the evaluation of the response to exercise in children with different asthma severities, more than one maximum expiratory flow‐volume parameter should be used. Pediatr Pulmonol. 2003; 36:49–54. © 2003 Wiley‐Liss, Inc.
Expression and function of pro‐inflammatory interleukin IL‐17 and IL‐17 receptor in normal, benign hyperplastic, and malignant prostate
Authors: Steiner Georg E. , Newman Martin E. , Paikl Doris , Stix Ursula , Memaran‐Dagda Nima , Lee Chung , Marberger Michael J.
Published: May 2003

INTRODUCTION AND OBJECTIVES

To investigate factors involved in inflammation of the prostate besides IL‐15, we screened prostatic cells and tissues for IL‐17 and IL‐17 receptor expression.

METHODS

Normal prostate (n = 1), BPH (n = 19), and carcinoma (CaP, n = 12) specimens were screened for IL‐17, IL‐17 receptor, CD45, IL‐6, and IL‐8 mRNA expression. The carcinoma cell lines DU145, PC3, LNCaP, and BPH‐epithelial (EC), stromal cell (SC) preparations, and BPH‐T‐cell lines were analyzed for IL‐17 production by RT‐PCR and ELISA. The effect of IL‐17 on IL‐6, IL‐8, TGF‐β1, and fibroblast growth factor (FGF‐2) mRNA expression and/or release of SC was analyzed using real‐time PCR and/or ELISA. Immunohistochemistry was used to localize both IL‐17 and IL‐17 receptor.

RESULTS

In the normal prostate, IL‐17 expression was very weak and restricted to lymphocytes. In 79% of BPH and 58% of CaP specimens, IL‐17 mRNA and protein expression was increased. IL‐17 mRNA expression could be shown for activated BPH‐T‐cells and to some extend for BPH‐EC. Expression of IL‐17 receptor was ubiquitous. Release of IL‐17 was shown only for activated BPH‐T‐cells. IL‐17 stimulated expression of IL‐6 (13‐fold) and IL‐8 (26‐fold) by prostatic BPH‐SC. In situ, however, the amount of IL‐17mRNA in BPH‐tissue did not correlate with the amount of IL‐6 and IL‐8 mRNA. In CaP tissue, significant correlation was found only between the amount of IL‐6 and IL‐8 mRNA.

CONCLUSIONS

Activated BPH‐T‐cells abundantly express IL‐17. The increase of IL‐17 in BPH‐tissues goes hand in hand with elevated levels of IL‐15, a pro‐inflammatory cytokine with T‐cell growth factor properties. A clinical relevance of increased IL‐17 expression under pathological conditions is suggested by the demonstration of significant upregulation of IL‐6 and IL‐8 production of prostatic SC by IL‐17. Prostate 56: 171–182, 2003. © 2003 Wiley‐Liss, Inc.
Recombinant prostate specific antigen inhibits angiogenesis in vitro and in vivo
Authors: Fortier A.H. , Holaday J.W. , Liang H. , Dey C. , Grella D.K. , Holland‐Linn J. , Vu H. , Plum S.M. , Nelson B.J.
Published: May 2003

BACKGROUND

Prostate specific antigen (PSA) is a kallikrein family member with serine protease activity commonly used as a diagnostic marker for prostate cancer. We recently described anti‐angiogenic properties of PSA [Fortier et al.: JNCI 91:1635–1640].

METHODS

Two forms of PSA were cloned and expressed in Pichia pastoris: one, an intact PSA with an N‐terminus of IVGGVS…; the second, an N‐1 PSA variant. The recombinant proteins were tested for serine protease activity and for anti‐angiogenic activity in vitro and in vivo.

RESULTS

The rate of substrate hydrolysis by the intact recombinant PSA was similar to that of PSA isolated and purified from human seminal plasma. In contrast, the N‐1 PSA variant lacked serine protease activity. In an endothelial cell migration assay, the concentration that resulted in 50% inhibition (IC50) was: 0.5 μM for native PSA, 0.5 μM for intact recombinant protein, and 0.1 μM for the N‐1 variant PSA. Both the intact recombinant and the N‐1 recombinant PSA inhibited angiogenesis in vivo.

CONCLUSIONS

Purified recombinant PSA inhibits angiogenesis, proving the concept that PSA is an anti‐angiogenic, and serine protease activity, as determined by synthetic substrate hydrolysis, is distinct from the anti‐angiogenic properties of PSA. Prostate 56: 212–219, 2003. © 2003 Wiley‐Liss, Inc.
Sample preparation effects in matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry of partially depolymerised carboxymethyl cellulose
Authors: Momcilovic Dane , Wittgren Bengt , Wahlund Karl‐Gustav , Karlsson Johan , Brinkmalm Gunnar
Published: May 2003

Sample preparation effects in matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS) of partially depolymerised carboxymethyl cellulose (CMC) have been investigated. The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised CMC were collected from size‐exclusion chromatography (SEC) and further investigated by MALDI‐TOFMS. 2,5‐Dihydroxybenzoic acid was used as matrix, dissolved in H2O due to the poor solubility of CMC in suitable organic solvents. The samples were dried by two methods, in ambient atmosphere and at reduced pressure. Under reduced pressure the sample spot homogeneity increased. This drying method, however, produced additional adduct peaks in the mass spectra originating from ion exchange on the CMC oligomers. Analysis of CMC could be performed in both negative and positive ion modes. Mass discrimination and variation in ionisation efficiency were demonstrated by comparing mass spectra with SEC data. Measurements of the degree of substitution (DS) were performed on three CMCs with different DS values, which were depolymerised in trifluoroacetic acid. The three CMCs were easily distinguished from one another, but the obtained DS values deviated from the values supplied by the manufacturer. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of urinary nucleosides. III. Identification of 5′‐deoxycytidine in urine of a patient with head and neck cancer
Authors: Dudley Edward , Lemiere Filip , Van Dongen Walter , Langridge James I. , El‐Sharkawi Salah , Games David E. , Esmans Eddy L. , Newton Russell P.
Published: May 2003

Modified nucleosides in the urine have been postulated to be diagnostic indices of disease, particularly of cancer. The urine of a patient with terminal head and neck cancer has been found to contain a modified nucleoside with a protonated molecule of m/z 228. By means of high‐performance liquid chromatography/ion trap mass spectrometry (HPLC/ITMS) and capillary liquid chromatography/triple quadruple mass spectrometry (CapLC/TQMS) we have identified the compound as 5′‐deoxycytidine. This is the first report of 5′‐deoxycytidine in man: in addition to the elucidation of its structure, its possible origins and the potential significance of its occurrence are discussed. Copyright © 2003 John Wiley & Sons, Ltd.