bluuebunny/crossref_metadata_2025 huggingface dataset:
The behaviour of poly(2,3‐epoxypropyl methacrylate) in dilute solution
Authors: Mrkvičková Libuše , Kálal Jaroslav , Bednář Bohumil , Janča Josef
Published: April 2003

Homopolymers of 2,3‐epoxypropyl methacrylate with various molecular masses were prepared by solution polymerization with 2,2′‐azoisobutyronitrile as initiator. The effect of polymerization conditions on the molecular parameters (weight‐ and number‐average molecular masses MW and Mn intrinsic viscosity [η]) and the tacticity of the resulting poly (2,3‐epoxypropyl methacrylate)s was investigated. For unfractionated polymers, the constants of the Mark‐Houwink equation for 1,4‐dioxane and tetrahydrofuran were determined. Gel permeation chromatography was tested as a tool for the determination of the Mw and Mn values.
Melting behaviour of native 1,4‐trans‐isotactic‐polypentadiene obtained by inclusion polymerization in perhydrotriphenylene
Authors: Farina Mario , Silvestro Giuseppe Di
Published: April 2003

The extrapolated melting point of native 1,4‐trans‐isotactic‐polypentadiene obtained by inclusion polymerization in pre‐irradiated perhydrotriphenylene is 104°C, 10 K higher than that of a long‐annealed conventional polymer. The WAXS spectrum corresponds to that of the already known paracrystalline structure; this notwithstanding, its heat of melting is 20–70% higher than that of polypentadiene crystallized from solution or from the melt. The native polymer shows noteworthy superheating phenomena and is not able to induce crystallization of high‐melting crystals from the melt. This behaviour is consistent with that predicted for extended‐chain polymeric crystals. This conclusion is supported by the absence of definite peaks in the SAXS spectrum of the native polymer.
Autoxidation reactions of polystyrene derivatives
Authors: Ohkatsu Yasukazu , Tanaka Tetsuo , Tsuruta Teiji
Published: April 2003

p‐Isopropylstyrene was homopolymerized or copolymerized with styrene using AIBN as initiator in benzene at 50°C. The resulting polymers were easily oxidized by oxygen to produce polymers having hydroperoxy groups. The oxidized polymer was found to have considerably different solubility from the original polymer. Kinetic evaluation of the oxidation reactions of poly(p‐isopropylstyrene) showed that the tertiary hydrogen of the isopropyl group present at the pendant aromatic ring was more susceptible to the oxidation reaction than the main chain methine hydrogen. The rate constants of these two oxidation reactions were found to be 4,0 · 10−4 mol−1/2 · l1/2 · sAutoxidation reactions of polystyrene derivatives1/2 and 2,5 · 10−4 mol−1/2 · l1/2 · s−1/2, respectively. These values were much smaller than that for the tertiary hydrogen atom of the isopropyl group of cumene (3,21 · 10−3 mol−1/2 · l1/2 · s−1/2, at 68°C), a low molecular weight model compound.
Disordering of helix of oxidized L‐methionine containing copolypeptides
Authors: Aiba Sei‐ichi , Minoura Norihiko , Fujiwara Yukihiko
Published: April 2003

The solid‐state conformation of copolymers of oxidized L‐methionine [L‐Met(O)] with L‐methionine (L‐Met) and/or L‐alanine (L‐Ala) was studied by IR spectroscopy and circular dichroism (CD). The results from the IR spectra in the region of 900−330 cm−1 are compared with data obtained by CD experiments. A film cast from the solution of a copolymer containing L‐Met(O) had a new trough between 205 and 210 nm in the solid‐state CD spectra and new IR absorption bands at 815 and 680 cm−1, while oxidizing the film of an L‐Met containing copolymer after casting did not induce a significant change in IR and CD spectra. It seems that the film cast from the solution of an L‐Met(O) containing copolymer exhibits the feature of a random coil as well as of an α‐helix. From the CD spectra of the film on immersion in water, it was deduced that the helix of the film became gradually disordered and hence the film was dissolved in water.
Metalloesters, 8. Esters of diacids and oligo(carboxylic acid)s (oligomers of methyl methacrylate) substituted in α‐position with an alkali metal. Their stability and IR Spectra
Authors: Lochmann Lubomír , Trekoval Jiří
Published: April 2003

Esters of diacids and oligo(carboxylic acid)s substituted in α‐position with Li, Na, or K (models of the propagation site in the anionic polymerization of methyl methacrylate (MMA)) were prepared, and their IR spectra were recorded. In the range 1600 – 1800 cm−1, their absorption of the Mt+ group in benzene solution was reflected in a band between 1630 and 1645 cm−1, depending on the counterion. In the presence of THF or of tert‐butoxide of the same alkali metal this band appears between 1626 and 1660 cm−1. Coordination of the more remote alkoxycarbonyl group (e.g., in γ‐position) to the counterion is demonstrated by a band near 1712 cm−1; its absorbance is much lower in the presence of THF. In solution, the metalloesters undergo autocondensation, the rate of which increases dramatically with the number of monomeric units. Thus, in benzene at 25 °C ethyl 2‐lithioisobutyrate is stable for more than a week, whereas the half life of dimethyl 2‐lithio‐2,4,4‐trimethylglutarate (Li‐dimer, 3b) is <24 h, and the Li‐trimer (5a), Li‐tetramer (5b), and Li‐pentamer (5c) completely decompose in less than 4 min under these conditions. The decomposition may be slowed down by adding tert‐butoxide of the same alkali metal. In THF the decomposition proceeds much more quickly. The properties of models used in this study are compared with those of the propagation site in the anionic polymerization of MMA.
Synthesis of a polyvinyl‐polyamino acid graft copolymer
Authors: Kimura Masatoshi , Egashira Toshiro , Nishimura Takao , Maeda Mizuo , Inoue Shohei
Published: April 2003

A copolymer having reactive primary amino groups was synthesized by the copolymerization of styrene and N‐methyl‐N‐(4‐vinylphenethyl)ethylenediamine (1). Polymerization of N‐carboxy amino acid anhydrides (NCA's) of L‐alanine, γ‐benzyl‐L‐glutamate, or β‐benzyl‐L‐aspartate was initiated by the primary amino groups of this copolymer to give a novel polyvinyl‐polyamino acid graft copolymer.
13C NMR spectra of polymers made by ring‐opening polymerization of optically active and racemic 5,5‐dimethylbicyclo[2.2.1]hept‐2‐ene using metathesis catalysts
Authors: Ho Huu Thoi , Ivin Kenneth J. , Rooney John J.
Published: April 2003

Ring‐opened polymers of racemic and optically active 5,5‐dimethylbicyclo[2.2.1]hept‐2‐ene (6) (5,5‐dimethylnorbornene), with cis double bond contents of 0–100%, were prepared using various Mo‐, W‐, Re‐, Os‐, Ru‐, and Ir‐based olefin metathesis catalysts. The 13C NMR spectra of these polymers are interpreted in terms of TH, TT, HH, HT structures (T = tail, H = head, referring to the orientation of the methyl groups), also tt, tc, ct, cc structures (t = trans, c = cis double bonds), and m, r dyads (m = meso, r = racemic, referring to the relative configuration of adjacent cyclopentane rings in the chains). m/r splitting is observed for both the olefinic carbon (C3) and the adjacent ring carbon (C4) in the HH structures of the all‐trans polymer made from racemic monomer using RuCl3 as catalyst. All‐cis polymers are fully syndiotactic while all‐trans polymers have 58% isotactic (m) and 42% syndiotactic (r) dyads. A consistent set of substitution parameters is derived, the effect of two methyl substituents on the 13C chemical shifts being generally a little less than the sum of the effects of the individual substituents.
Triphenylphosphine catalyzed polymerization of maleic anhydride
Authors: Sahu Uma S. , Bhadani Suraj N.
Published: April 2003

The polymerization of maleic anhydride initiated by triphenylphosphine was investigated in acetic anhydride as well as in dimethylformamide. It was found that the polymer conversion increases with the increase of the concentration of monomer and initiator and the reaction temperature. It was also found that the rate of polymerization is higher in dimethylformamide than in acetic anhydride under the same set of experimental conditions. The apparent overall activation energy was found to be about 26,4kJ · mol‐1 and 39,8 kJ · mol‐1 in acetic anhydride and dimethylformamide, respectively. The polymerization rate depends upon the basicity of the initiator as well as on the dielectric constant of the solvent.
Constitution and properties of the coatings formed in situ by anodic oxidation of azophenols
Authors: Musiani Macro M. , Mengoli Giuliano , Pelli Beatrice , Folonari Carlo
Published: April 2003

Three different azophenols were oxidized by both the system CuCl/O2 in pyridine and electrochemically (as coherent films) on Fe and Cu anodes in water/methanol mixtures. Products of the chemical and anodic oxidative coupling process are in any case very near each other. Poly(oxy‐4‐phenylazo‐1,2‐phenylene) and its 3‐allyl derivative are obtained from 4‐hydroxyazobenzene (1) and 3‐allyl‐4‐hydroxyazobenzene (2), respectively. The polymerization of 4‐hydroxy‐3,5‐dimethylazobenzene (3) mainly proceeds through elimination of the phenylazo group and formation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene). By oxidation of 2 at Cu anodes thin, adherent films having very good protective features are obtained in short electrolysis times.
Studies on syntheses and permeabilities of special polymer membranes, 52. Syntheses of p‐aminostyrene derivatives
Authors: Uragami Tadashi , Hachiya Hitoshi , Sugihara Mizuho
Published: April 2003

Four kinds of p‐aminostyrene derivatives, i. e., methyl 4‐vinylsuccinanilate (9), ethyl 4‐vinyl‐sebacanilate (10), 4‐vinylsuccinanilic acid (11), and 4‐vinylsebacanilic acid (12), were synthesized and purely isolated. Their structures were identified by elementary analysis and by IR and 1H NMR spectroscopy.
Poly(organophosphazenes). Some aspects of synthesis, catalysis and characterization
Authors: Devadoss Eswaran , Nair Chethrappilly P. Reghunadhan
Published: April 2003

The catalytic effects of three typical metal salts, HgCl2, Hgl2, and ZnCl2, on the ringopening polymerization of (PNCl2)3/(PNCl2)4 in terms of the hard/soft concept for acids and bases were studied. The influence of the nature and the concentration of the initiators on the onset of gelation, the extent of polymerization, and on the polymer molecular weight is described. A new technique to follow the substitution reaction of chlorine in poly(dichlorophosphazene) by the 4‐methylphenoxy group is proposed.
Polymerization of lactams, 52. Anionic polymerization of 2‐pyrrolidone accelerated with CO2, part 1
Authors: Daniel Ladislav , Brožek Jiří , Roda Jan , Kŕlíček Jaroslav
Published: April 2003

The polymerization of 2‐pyrrolidone (1) initiated with its potassium salt (2‐oxo‐1‐pyrrolidinylpotassium) (2) and accelerated by the presence of CO2, was investigated. For the optimal concentration of 2 (≈5 mol‐%) and 0,5 mol‐% CO2, the most suitable polymerization temperature was found to the range between 45 and 55°C. The variation of CO2 concentration, 0,5 < [CO2] < 3 mol‐%, does not affect the polymerization yield under the optimal conditions. The similarity of the course of polymerization in the presence of CO2 directly introduced into the reaction mixture with that in the presence of isolated carboxylate of 1, is considered as a proof that CO2 is transformed into the active potassium carboxylate of 1. The order of polymerization reaction with respect to initiator was found to be ≈0,8 indicating the complexity of the reaction mechanism.
Oxydation du polypropylène atactique photocatalysée par des oxydes de zinc
Authors: Penot Gilles , Arnaud René , Lemaire Jacques
Published: April 2003

The chemical modification of atactic polypropylene samples by ZnO‐photocatalysed oxidation were investigated by IR spectrophotometry, chemical titration, and kinetic measurements, using different types of ZnO as photocatalysts. It was found that in pigmented samples, the formation and disappearance of the primary hydroperoxides are enhanced by the oxides. The inner filter effect of the pigment is antagonized by its photocatalytic effect. However, higher photostationary concentrations of hydroperoxides were observed in presence of ZnO. The main feature of the photocatalytic oxidation was found to be complete inhibition of Norrish type I and type II processes of the ketonic groups observed with type A and “active” ZnO; ketones and lactones accumulate in the matrix without any formation of acidic or unsaturated groups.
Anionic polymerization and copolymerization of 1,3‐ and 1,4‐diisopropenylbenzene
Authors: Lutz Pierre , Beinert Gérard , Rempp Paul
Published: April 2003

The anionic polymerization of 1,3 and 1,4‐diisopropenylbenzene (DIB) was found to be characterized by a rather low ceiling temperature and by rather strong differences in reactivity between the two double bonds. At low degrees of conversion the polymers formed are essentially linear and carry one pendant double bond per monomeric unit. Branching and crosslinking can occur only at higher conversion. 1,3‐DIB can be copolymerized anionically with α‐methylstyrene. Grafting reactions were carried out on polymer backbones with pendant unsaturated groups, using two different pathways. The occurence of coupling reaction can be avoided by a proper choice of experimental conditions.
Phase distribution chromatography (PDC) as a method for the investigation of polymers in solution, 3. Determination of narrow molecular weight distributions
Authors: Greschner Georg S.
Published: April 2003

Phase distribution chromatography (PDC) is demonstrated to be a powerful method for the correct determination of narrow molecular weight distributions. This is shown by comparing the molecular weight distributions (MWD) of polystyrenes obtained from PDC measurements with those obtained by Baker‐Williams fractionation and by gel permeation chromatography. Four problems are formulated and analyzed which are closely connected with the calculation of the MWD from a measured PDC‐elution curve at temperatures below the theta point of the system. Thus, the theory of PDC outlined previously is tested.
Polymerization of lactams, 54. Anionic polymerization of 2‐pyrrolidone accelerated with CO2, part 3
Authors: Roda Jan , Brožek Jiří , Králíček Jaroslav , Tuzar Zdeněk
Published: April 2003

Intrinsic viscosities in m‐cresol and weight average molecular weights, M̄w, were measured for samples of high molecular weight poly(2‐pyrrolidone) (poly (1)) prepared by anionic polymerization of 2‐pyrrolidone (1) accelerated with CO2. It was proved that the earlier found relationship [η] = 4 · 10−2 · M0,77 (in cm3 · g−1) holds for M̄Mw up to 8 · 105 g. mol−1. The probable reason for the formation of poly (1) with an exceptionally high molecular weight is discussed.
Light scattering from aqueous solutions of poly(acrylamide‐co‐maleic anhydride)
Authors: Ionescu Livia Maria , Petrea Ion , Bujor Ingrid Ionescu , Demetrescu Ioana
Published: April 2003

Light scattering measurements from aqueous solutions for two samples of poly(acrylamide‐co‐maleic anhydride) in the presence of salt are conducted. One of the samples exhibits a negative initial slope and a minimum in the plot of the conventional reciprocal scattered intensity function of sin2 (θ/2). The explanation for this anomaly is a large optical anisotropy of the segment. A correction for this effect of segmental anisotropy is made. The behaviour of the other sample of this copolymer is typical for a polyelectrolyte. By analysing the disymmetry of the scattered light, the influence of the salt concentration on the polyion is evidenced by the determination of the macromolecular dimensions. Light scattering data allow the evaluation of the Mark‐Kuhn‐Houwink exponent a for various degrees of dissociation of the polyion; a correlation between the variation of a and the shape of the macromolecule is observed.
High temperature demixing of poly(decyl methacrylate) solutions in isooctane and its pressure dependence
Authors: Maderek Eugeniusz , Schulz G. V. , Wolf B. A.
Published: April 2003

Solutions of poly (decyl methacrylate) in isooctane (2,2, 4‐trimethylpentane) show lower critical solution temperatures (LCST) that lie well below the thermal degradation of the polymer. The corresponding exothermal theta‐temperature (from the Shultz‐Flory plot) amounts to 210°C. The increase in solvent quality by pressure turns out to be very pronounced (d Tc/dp ≈ +1 K/bar). With solutions of the polymer in motor oils, high temperature demixing is unlikely to occur below their boiling point. The theoretical evaluation of published experimental data for 11 different systems exhibiting LCSTs demonstrates the following: Under the equilibrium vapour pressure of the solution high temperature demixing is generally observed withing the temperature interval between Tb, the boiling point of the pure solvent (1 bar), and 1,5 Tb. As Tc ‐ Tb increases, the heats of mixing and the pressure influence on Tc increase, too.
Polymers containing enzymatically degradable bonds, 7. Design of oligopeptide side‐chains in poly[N‐(2‐hydroxypropyl)methacrylamide] copolymers to promote efficient degradation by lysosomal enzymes
Authors: Duncan Ruth , Cable Hazel C. , Lloyd John B. , Rejmanová Pavla , Kopeček Jindřich
Published: April 2003

N‐(2‐Hydroxypropyl)methacrylamide copolymers are considered to be a potential drug delivery system. To fulfil this role the drug‐polymer linkage must be susceptible to intralysosomal hydrolysis. Taking p‐nitroanilide as a drug analogue, copolymers were synthesized bearing oligopeptidyl‐p‐nitroanilide side‐chains designed to match known specificities of the lysosomal enzymes cathepsin L or cathepsin D. Degradation of side‐chains by rat liver lysosomal enzymes (measured by monitoring terminal p‐nitroaniline release) occurred only in the presence of reduced glutathione (5 mmol/l) and was effectively inhibited by leupeptin, indicating the involvement of thiol‐proteinases in every case. Depending on side‐chain composition, between 20 and more than 50% of the terminal p‐nitroaniline residues were liberated during a 5 h incubation. It has also been shown that 1) a polymer molecule may contain side‐chains of a single type that are nevertheless differentially susceptible to lysosomal hydrolysis; 2) two of the side‐chains studied liberate only a p‐nitroaniline residue, whereas the others also release amino‐acyl‐p‐nitroanilides; 3) the cleavage of all side‐chains displays a broad pH optimum pH 5 to pH 7; 4) the Michaelis‐Menten constant Km for side‐chain cleavage varied between 26,1 and 143,2 mg/ml, depending on the amino acid sequence of the side‐chain.
End groups in poly(vinyl chloride) and their influence on the thermal stability
Authors: Jurriaan C. , Van den Heuvel M. , Weber Anton J. M.
Published: April 2003

End groups in a low molecular weight fraction of a commercial suspension poly(vinylchloride) were analysed by means of 1H NMR and IR spectroscopy and by size exclusion chromatography. The following groups were identified and quantified: ethoxycarbonyloxy (1), 1,2‐dichloroethyl (2), trans‐ and cis‐4‐chloro‐2‐butenyl (3 and 4), 2‐chloroethyl (5), and 2‐chloroethylidene (6). The influence of these groups on the degradation at 180°C was determined.
Hypoglycaemic and hypolipidaemic action of alcohol extract of Tinospora cordifolia roots in chemical induced diabetes in rats
Authors: Stanely Mainzen Prince P. , Menon Venugopal P.
Published: April 2003

The present investigation was undertaken to evaluate the hypoglycaemic and hypolipidaemic effects of an alcohol extract of Tinospora cordifolia roots, an indigenous plant used in Ayurvedic medicine in India. Oral administration of the extract of Tinospora cordifolia (TCREt) roots for 6 weeks resulted in a signiﬁcant reduction in blood and urine glucose and in lipids in serum and tissues in alloxan diabetic rats. The extract also prevented a decrease in body weight. Thus our study clearly shows that an alcohol TCREt has a hypoglycaemic and hypolipidaemic action. Copyright © 2003 John Wiley & Sons, Ltd.
Inhibition of arginase by in alveolar macrophages: implications for the utilization of l‐arginine for nitric oxide synthesis
Authors: Hecker Markus , Nematollahi Heideh , Hey Claudia , Busse Rudi , Racké Kurt
Published: April 2003

The hypothesis was investigated that the nitric oxide (NO) synthase intermediate, (HOArg), is an arginase inhibitor in rabbit or rat alveolar macrophages. Exogenously applied HOArg strongly inhibited the arginase activity present in these cells (IC50 ≥ 15 μM), and attenuated l‐[3H]arginine transport (IC50 ≥ 500 μM) in rabbit alveolar macrophages. Moreover, up to 37 μM HOArg were detected in the conditioned medium, but not in the lysate, of rat alveolar macrophages exposed to bacterial lipopolysaccharide for 18 h. HOArg may thus be a potent endogenous arginase inhibitor in these cells which increases the availability of l‐arginine for NO biosynthesis.
Systemic production of foreign peptides on the particle surface of tobacco mosaic virus
Authors: Sugiyama Yoshinori , Hamamoto Hiroshi , Takemoto Shizume , Watanabe Yuichiro , Okada Yoshimi
Published: April 2003

By using a new tobacco mosaic virus (TMV) vector [Hamamoto, H., et al. (1993) Bio/Technology, 11, 930–932], we have constructed TMV particles which present three different kinds of epitopes, two of them from influenza virus hemagglutinin (HA), and one from human immunodeficiency virus type I (HIV‐I) envelope protein, on the surface of the particles. Each of these TMV particles reacted with each anti‐peptide antiserum. These results suggest that this TMV vector can be used as an antigen presentation system.
The Tetrahymena chaperonin subunit CCTη gene is coexpressed with CCTγ gene during cilia biogenesis and cell sexual reproduction
Authors: Cyrne Luisa , Guerreiro Paulo , Cardoso Ana Cristina , Rodrigues-Pousada Claudina , Soares Helena
Published: April 2003

We report here the cloning and the characterization of the T. pyriformis CCTη gene (TpCCTη) and also a partial sequence of the corresponding T. thermophila gene (TtCCTη). The TpCCTη gene encodes a protein sharing a 60.3% identity with the mouse CCTη. We have studied the expression of these genes in Tetrahymena exponentially growing cells, cells regenerating their cilia for different periods and during different stages of the cell sexual reproduction. These genes have similar patterns of expression to those of the previously identified TpCCTγ gene. Indeed, the Tetrahymena CCTη and CCTγ genes are upregulated at 60–120 min of cilia recovery, and in conjugation when vegetative growth was resumed and cell division took place. Our results seem to indicate that both CCT subunits play an important role in the biogenesis of the newly synthesized cilia of Tetrahymena and during its cell division.
A revenue management approach to demand management and order booking in assemble‐to‐order manufacturing
Authors: Harris Frederick H. deB. , Pinder Jonathan P.
Published: April 2003

Revenue management is an order acceptance and refusal process that employs differential pricing strategies and stop sales tactics to reallocate capacity, enhance delivery reliability and speed, and realize revenue from change order responsiveness in order to maximize the revenue from pre‐existing capacity. While previously considered primarily as a tool of service operations, revenue management has considerable potential for assemble to order (ATO) manufacturing environments. Increasing demand for customer responsiveness has created service‐oriented manufacturing environments suitable for the application of revenue management methods. This paper applies revenue management concepts and techniques to ATO manufacturing environments and presents models for optimal pricing and capacity decisions.
Morphological distribution of MBP‐like immunoreactivity in the brain during development
Authors: Bjelke B. , Seiger Å.
Published: April 2003

Myelin‐basic protein (MBP)‐like immunoreactivity was studied during development from postnatal day 1 to day 21 as a marker for the myelination process in the rat brain. Using monoclonal MBP antibodies, the caudo‐rostral successive progression of MBP immunoreactivity was mapped in 1‐, 7‐, 14‐, and 21‐day‐old animals using fluorescence microscopy of both coronal and sagittal sections. At 1 day of age, MBP‐immunoreactive single fibers were seen in the lower brain stem, especially in formatio reticularis, whereas the rest of the brain was negative. In 1‐week‐old animals, MBP‐positive fibers extended all the way into frontal cortex, but still in sparse arrays of single fibers with the largest number at the brain stem level. The 2‐week stage showed a dramatic increase in the number of MBP‐immunoreactive fibers. At the brain stem level, MBP‐positive fiber plexuses were mixed with MBP‐positive longitudinal axonal pathways. In cerebellar cortex, positive fibers began to radiate out from the white matter into the grey matter. A dense network of MBP‐positive fibers was located in thalamus, and dense fluorescent fiber bundles were seen in capsula interna piercing through striatum. In cerebral cortex positive radiating fibers were considerably more numerous than at the previous stage. At the age of 3 weeks, MBP‐immunoreactive fibers could be seen in networks and bundles in all parts of the brain. In the brain stem, a dense plexus of positive fibers filled formatio reticularis. In cortex cerebelli and cortex cerebri, a high density of radiating positive fibers was found. In striatum, a sparse distribution of single fibers was found in the neuropil surrounding the now strongly positive bundles of capsula interna.

MBP‐like immunoreactivity was followed during postnatal rat brain development and seemed to serve as a good indicator of progression of the myelinization process. With the excellent signal‐to‐noise ratio and the detailed morphological description of the distribution of MBP‐like immunoreactivity, the present report can serve as a reference for studies of pathological disturbances of myelination in CNS as they relate to mechanical, chemical or hormonal perturbations.
Patterns of ethanol‐induced cell death in the developing nervous system of mice; Neural fold states through the time of anterior neural tube closure
Authors: Kotch Lori E. , Sulik Kathleen K.
Published: April 2003

Vital staining and routine histological analyses of mouse embryos 12 h after acute maternal ethanol administration (2.9 g/kg) illustrated that selected neuronal cell populations are killed. At the time of treatment, embryos had 5–15 somite pairs, corresponding to the developmental stages occurring in humans during the fourth week of post‐fertilization; i.e. when neural folds are present and neural tube fusion begins. Affected cell populations in embryos having 6–26 somite pairs (up to the stage of anterior neuropore closure) were in discrete locations in the alar and basal plates of the rhombencephalon, in the otic placode/vesicle, and in the regions of the epibranchial placodes, olfactory placodes and trigeminal ganglion. The potential basis for the vulnerability of these cell populations to ethanol‐induced cell death is discussed. Our understanding of the scope of ethanol‐induced CNS damage is dependent upon further defining ethanol‐sensitive cell populations at all stages of CNS development.
Cognitive deficits in long‐term survivors of childhood medulloblastoma and other noncortical tumors: Age‐dependent effects of whole brain radiation
Authors: Radcliffe Jerilynn , Bunin Greta R. , Sutton Leslie N. , Goldwein Joel W. , Phillips∥ Peter C.
Published: April 2003

Twenty‐four children, aged 1.5–20 yr at diagnosis, with noncortical brain tumors, primarily medulloblastoma, have been followed for 3–4 yr for intellectual status. All the children received craniospinal irradiation, and 19 of 24 received chemotherapy as well. For the group as a whole, Full Scale IQ fell from 104 at baseline to 91 at final follow‐up. Children younger than 7 yr at diagnosis showed a significant decrease in IQ as early as year 1, and all changes from baseline to years 3 and 4 were significant. In contrast, children older than 7 yr at diagnosis did not show a significant IQ change from baseline to year 3 or 4. The Spearman correlation coefficient between IQ change and age at diagnosis from baseline to year 4 was 0.57 (P=0.003).

This study supports the hypothesis that children treated with whole brain radiation at a younger age have more severe cognitive impairment than those treated at a later age. Limitations in sample size and duration of observations do not permit us to identify whether a true plateau occurs 2–4 yr after irradiation versus a continued progressive decline in intellectual performance. Moreover, we cannot at this time distinguish between a true dementing process versus failure to acquire new cognitive skills at a rate comparable to age‐matched peers.
Muscarinic cholinergic receptor regulation and acetylcholinesterase inhibition in response to insecticide exposure during development
Authors: Dvergsten C. , Meeker R.B.
Published: April 2003

Neonatal rats were exposed to parathion, an acetylcholinesterase inhibiting organophosphorus pesticide, during a rapid phase of cholinergic receptor development. Rats were given subcutaneous injections of 1.5 mg/kg/day from postnatal days 8–20. The immediate effects of subchronic developmental exposure were assessed in 21‐day‐old animals and more persistent effects assessed in 36‐day‐old animals. There was a 61% inhibition of acetylcholinesterase and a 27% decrease of muscarinic receptor density in 21‐day‐old treated rats. The reduction in receptor density was dose‐dependent and a significant correlation was found between the level of acetylcholinesterase inhibition produced by parathion and the reduction in receptor density. It was estimated that a minimum of at least 15% prolonged inhibition of forebrain acetylcholinesterase by parathion was necessary to reduce receptor density. Regional analyses of receptor autoradiograms of 21‐day‐old animals indicated muscarinic receptors in the cortex and hippocampus were preferentially lost. The anterior thalamus was notable in having a high density of cholinergic receptors which were unaffected by parathion treatment. No changes were found in the affinity of [3H]QNB for the receptor or in the binding of the agonist, acetylcholine, in competition binding studies. AChE activity and muscarinic receptor density returned to normal after a 16 day recovery period. Parathion treated animals were growth inhibited but, growth retardation induced by undernutrition did not alter receptor density or affinity of QNB for muscarinic receptors. Thus, the transient decrease in receptor density in parathion exposed animals was similar to the response previously observed in adults and was not secondary to growth retardation or undernutrition. Receptor densities and acetylcholinesterase levels were regulated back to normal values after a 16 day recovery period in spite of the perturbation of cholinergic function during cholinergic synapse and receptor development.
The effect of workload control (WLC) on performance in make‐to‐order companies
Authors: Hendry L.C. , Kingsman B.G. , Cheung P.
Published: April 2003

Workload control (WLC) concepts are a new group of production planning and control methods designed to control queues in a job shop manufacturing environment. Their importance lies in the need to maintain this type of flexible manufacturing environment in make‐to‐order (MTO) companies, which manufacture different products for different customers. There have been several well‐developed WLC concepts presented in the literature that address two major decision levels in MTO firms, the job entry level and the job release level. At the job entry level, customer enquiries are processed, and delivery dates (DDs) and prices are quoted to customers. At the job release level, decisions are made regarding which jobs should be released to the shop floor so that processing can commence. The effectiveness of WLC concepts at these two decision levels has been explored in the literature but is still inconclusive, especially in terms of the ability of the job entry level to address one of the most important objectives of WLC ‐ the control of manufacturing lead times. This paper presents a simulation model designed to test the effectiveness of one of the most comprehensive WLC concepts presented in the literature. The model enables the effect of various control parameters within this WLC concept to be explored, including those used at the job entry level to control manufacturing lead times. Experimental results are presented, indicating that this particular concept can lead to lower manufacturing lead times when compared with an environment of no control, even when the same total workload is processed by the shop.
5‐Hydroxytryptamine7 (5‐HT7) receptor immunoreactivity‐positive ‘stigmoid body’‐like structure in developing rat brains
Authors: Muneoka Katsumasa T. , Takigawa Morikuni
Published: April 2003

We examined the expression of 5‐hydroxytryptamine7 (5‐HT7) receptor protein in developing and adult rats with immunohistochemical technique. In adult male rats, 5‐HT7 receptor immunoreactivity was detected in the septum, striatum, indusium griseum, tenia tecta, thalamus, hippocampus and hypothalamus in the forebrain as well as the pons and cerebellum. In brains of 1, 7, 15 and 21 days old male rats but not of adult ones, 5‐HT7 receptor immunoreactivity‐positive dot‐like structures were detected. The dot‐like structures were visualized in hypothalamus, hippocampus, frontal cortex, brainstem and cerebellum at 1 day old male rats. In 7 days old male rats, the dot‐like structures were found in the hypothalamus, medial preoptic area (MPA), bed nucleus of the stria terminalis (BST), amygdaloid nucleus and brainstem reticular formation. In 15 and 21 days old male and female rats, 5‐HT7 receptor immunoreactive dots were most clearly detected in MPA, hypothalamus, raphe pallidus, raphe magnus and brainstem reticular formation. The 5‐HT7 receptor immunoreactivity‐positive dot‐like structures were shown in the cytoplasm and they were less than 1 μm in diameter in 1 and 7 days old rats and became larger to 1–3 μm in 15 and 21 days old rats. From the distribution and morphologic features, the 5‐HT7 receptor immunoreactivity‐positive dot‐like structure found in developing rat brains is considered to be identical to a cytoplasmic inclusion named ‘stigmoid body’.
GVS‐111 prevents oxidative damage and apoptosis in normal and Down's syndrome human cortical neurons
Authors: Pelsman Alejandra , Hoyo‐Vadillo Carlos , Gudasheva Tatiana A. , Seredenin Sergei B. , Ostrovskaya Rita U. , Busciglio Jorge
Published: April 2003

The neuroprotective activity of a novel N‐acylprolyl‐containing dipeptide analog of the nootropic 2‐oxo‐1‐pyrrolidine acetamide (Piracetam) designated as GVS‐111 (DVD‐111/Noopept) was tested in two in vitro models of neuronal degeneration mediated by oxidative stress: normal human cortical neurons treated with H2O2, and Down's syndrome (DS) cortical neurons. Incubation of normal cortical neurons with 50 μM H2O2 for 1 h resulted in morphological and structural changes consistent with neuronal apoptosis and in the degeneration of more than 60% of the neurons present in the culture. GVS‐111 significantly increased neuronal survival after H2O2‐treatment displaying a dose‐dependent neuroprotective activity from 10 nM to 100 μM, and an IC50 value of 1.21±0.07 μM. GVS‐111 inhibited the accumulation of intracellular free radicals and lipid peroxidation damage in neurons treated with H2O2 or FeSO4, suggesting an antioxidant mechanism of action. GVS‐111 exhibited significantly higher neuroprotection compared to the standard cognition enhancer Piracetam, or to the antioxidants Vitamin E, propyl gallate and N‐tert‐butyl‐2‐sulpho‐phenylnitrone (s‐PBN). In DS cortical cultures, chronic treatment with GVS‐111 significantly reduced the appearance of degenerative changes and enhanced neuronal survival. The results suggest that the neuroprotective effect of GVS‐111 against oxidative damage and its potential nootropic activity may present a valuable therapeutic combination for the treatment of mental retardation and chronic neurodegenerative disorders.
Sexual behavior and sexual problems among patients with severe chronic psychoses
Authors: Raja Michele , Azzoni Antonella
Published: April 2003

The aim of the present study was to investigate sexual behavior in a population of psychiatric patients affected by schizophrenia, schizoaffective disorder or bipolar disorder by means of an ad hoc questionnaire designed to explore the three phases of the sexual response: desire (or interest), arousal, and performance. The study assessed patients’ attitude toward sexuality, several aspects of their sexual behavior, including patients’ awareness of the risk of sexually transmitted diseases (STD), contraceptive strategy preferred by patients, and sexual effects of psychotropic medication. Patients reported a high frequency of sexual dysfunction, in particular, hyposexuality. Schizophrenia diagnosis and female gender were associated with lower levels of sexual performance. The impact of psychotropic drugs on patients’ sexuality was significant, with both positive and negative effects. Although 65.8% of patients reported to be concerned about the risk of contracting infections during sexual intercourse, most of them engaged in sexual behavior at high risk for acquisition and transmission of STD. Patients’ compliance with contraceptive measures was poor.
The modular architecture of Cellvibrio japonicus mannanases in glycoside hydrolase families 5 and 26 points to differences in their role in mannan degradation
Authors: HOGG Deborah , PELL Gavin , DUPREE Paul , GOUBET Florence , MARTÍN-ORÚE Susana M. , ARMAND Sylvie , GILBERT Harry J.
Published: April 2003

β-1,4-Mannanases (mannanases), which hydrolyse mannans and glucomannans, are located in glycoside hydrolase families (GHs) 5 and 26. To investigate whether there are fundamental differences in the molecular architecture and biochemical properties of GH5 and GH26 mannanases, four genes encoding these enzymes were isolated from Cellvibrio japonicus and the encoded glycoside hydrolases were characterized. The four genes, man5A, man5B, man5C and man26B, encode the mannanases Man5A, Man5B, Man5C and Man26B, respectively. Man26B consists of an N-terminal signal peptide linked via an extended serine-rich region to a GH26 catalytic domain. Man5A, Man5B and Man5C contain GH5 catalytic domains and non-catalytic carbohydrate-binding modules (CBMs) belonging to families 2a, 5 and 10; Man5C in addition contains a module defined as X4 of unknown function. The family 10 and 2a CBMs bound to crystalline cellulose and ivory nut crystalline mannan, displaying very similar properties to the corresponding family 10 and 2a CBMs from Cellvibrio cellulases and xylanases. CBM5 bound weakly to these crystalline polysaccharides. The catalytic domains of Man5A, Man5B and Man26B hydrolysed galactomannan and glucomannan, but displayed no activity against crystalline mannan or cellulosic substrates. Although Man5C was less active against glucomannan and galactomannan than the other mannanases, it did attack crystalline ivory nut mannan. All the enzymes exhibited classic endo-activity producing a mixture of oligosaccharides during the initial phase of the reaction, although their mode of action against manno-oligosaccharides and glucomannan indicated differences in the topology of the respective substrate-binding sites. This report points to a different role for GH5 and GH26 mannanases from C. japonicus. We propose that as the GH5 enzymes contain CBMs that bind crystalline polysaccharides, these enzymes are likely to target mannans that are integral to the plant cell wall, while GH26 mannanases, which lack CBMs and rapidly release mannose from polysaccharides and oligosaccharides, target the storage polysaccharide galactomannan and manno-oligosaccharides.
On lithium walls and the performance of magnetic fusion devices
Authors: Krasheninnikov S. I. , Zakharov L. E. , Pereverzev G. V.
Published: April 2003

It is shown that lithium walls resulting in zero-recycling regimes at the edge of magnetic fusion device can cause dramatic improvements of core plasma performance. The plasma temperature at the wall in these regimes is much larger than in conventional tokamaks. It reduces the core temperature gradient and, thus, related anomalous transport, allowing an increase in the achievable beta to the level ∼20%, due to wall stabilization and second stability core. Fusion relevant plasma temperature over entire core and high beta results in a strong enhancement of fusion power density. Modeling of the International Thermonuclear Experimental Reactor performance in zero-recycling regimes shows so significant improvement that fusion power increases with no apparent limits due to elimination of the strong core temperature gradient and associated turbulent transport and due to expansion of the burning zone to the entire cross section.
Effect of shock proximity on Richtmyer–Meshkov growth
Authors: Glendinning S. G. , Bolstad J. , Braun D. G. , Edwards M. J. , Hsing W. W. , Lasinski B. F. , Louis H. , Miles A. , Moreno J. , Peyser T. A. , Remington B. A. , Robey H. F. , Turano E. J. , Verdon C. P. , Zhou Y.
Published: April 2003

Experiments conducted on the Omega laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] and simulations show reduced Richtmyer–Meshkov growth rates in a strongly shocked system with initial amplitudes kη0⩽0.9. The growth rate at early time is less than half the impulsive model prediction, rising at later time to near the impulsive prediction. An analytical model that accounts for shock proximity agrees with the results.
Flux cancellation and coronal mass ejections
Authors: Linker Jon A. , Mikić Zoran , Lionello Roberto , Riley Pete , Amari Tahar , Odstrcil Dusan
Published: April 2003

Time dependent magnetohydrodynamic computations of the flux cancellation mechanism are presented. Previous authors have discussed this mechanism as a possible cause for the formation of prominences and the trigger for prominence eruptions and coronal mass ejections (CMEs). This paper shows that flux cancellation in an energized two-and-one-half-dimensional helmet streamer configuration first leads to the formation of stable flux rope structures. When a critical threshold of flux reduction is exceeded, the configuration erupts violently. Significant amounts of stored magnetic energy are released through magnetic reconnection. The ejected flux rope propagates out into the solar wind and forms an interplanetary shock wave. A similar eruption occurs for a three-dimensional calculation where the ends of the flux rope field lines are anchored to the Sun. The flux cancellation mechanism unifies the processes of prominence formation, prominence eruption, and CME initiation, and thus provides an attractive hypothesis for explaining the cause of these dynamic events.
The quasilinear behavior of convective turbulence with sheared flows
Authors: Bian N. , Benkadda S. , Garcia O. E. , Paulsen J.-V. , Garbet X.
Published: April 2003

In the present contribution, the quasilinear dynamics of convective turbulence is studied. In essence, and contrary to the “frozen gradient” assumption, the quasilinear approach takes into account the back-reaction of the convective flux on the mean gradient driving the instability. The dynamical regulation of convective transport by a sheared mean flows is also included. Close to the instability threshold it naturally gives rise to a transition from low to high confinement modes. Further away, regular relaxation oscillations are sustained. In this time-dependent state, each transient maximum of the convective flux activity triggers a ballistic transport event observed on the mean profile. The period of the oscillations is not controlled by the nonlinearity but by the dissipation on the mean flow. A “Dimits-shift” regime is thus identified in the limit of zero damping on the mean flow. This infinite period cycle corresponds to a single ballistic transport event triggered before the system settles into its diffusive state. Far away from the threshold, relaxation oscillations are still sustained in the presence of mean flow dissipation, but are superimposed on high-frequency fluctuations. This particular behavior makes the convective transport to follow exponential statistics when measured at a local probe.
Efficient blue light-emitting diodes with InGaN/GaN triangular shaped multiple quantum wells
Authors: Choi R. J. , Hahn Y. B. , Shim H. W. , Han M. S. , Suh E. K. , Lee H. J.
Published: April 2003

InGaN/GaN triangular shaped multiple quantum wells (QWs) grown by grading In composition with time were adopted as an active layer of blue light-emitting diodes (LEDs). Compared to the LEDs with conventional rectangular QW structures, the triangular QW LEDs showed a higher intensity and a narrower linewidth of electrical luminescence (EL), a lower operation voltage, and a stronger light-output power. EL spectra of the triangular-QW-based LEDs also showed that the peak energy is nearly independent of the injection current and temperature, indicating that the triangular QW LED is more efficient and stable than the rectangular one.
Inhibition of plaque neovascularization reduces macrophage accumulation and progression of advanced atherosclerosis
Authors: Moulton Karen S. , Vakili Khashayar , Zurakowski David , Soliman Mohsin , Butterfield Catherine , Sylvin Erik , Lo Kin-Ming , Gillies Stephen , Javaherian Kashi , Folkman Judah
Published: April 2003

Plaque angiogenesis promotes the growth of atheromas, but the functions of plaque capillaries are not fully determined. Neovascularization may act as a conduit for the entry of leukocytes into sites of chronic inflammation. We observe vasa vasorum density correlates highly with the extent of inflammatory cells, not the size of atheromas in apolipoprotein E-deficient mice. We show atherosclerotic aortas contain activities that promote angiogenesis. The angiogenesis inhibitor angiostatin reduces plaque angiogenesis and inhibits atherosclerosis. Macrophages in the plaque and around vasa vasorum are reduced, but we detect no direct effect of angiostatin on monocytes. After angiogenesis blockade
in vivo
, the angiogenic potential of atherosclerotic tissue is suppressed. Activated macrophages stimulate angiogenesis that can further recruit inflammatory cells and more angiogenesis. Our findings demonstrate that late-stage inhibition of angiogenesis can interrupt this positive feedback cycle. Inhibition of plaque angiogenesis and the secondary reduction of macrophages may have beneficial effects on plaque stability.
Chemical synaptic activity modulates nearby electrical synapses
Authors: Smith Mackenzie , Pereda Alberto E.
Published: April 2003

Most electrically coupled neurons also receive numerous chemical synaptic inputs. Whereas chemical synapses are known to be highly dynamic, gap junction-mediated electrical transmission often is considered to be less modifiable and variable. By using simultaneous pre- and postsynaptic recordings, we demonstrate at single mixed electrical and chemical synapses that fast chemical transmission interacts with gap junctions within the same ending to regulate their conductance. Such localized interaction is activity-dependent and could account for the large variation in strength of electrical coupling at auditory afferent synapses terminating on the Mauthner cell lateral dendrite. Thus, interactions between chemical and electrical synapses can regulate the degree of electrical coupling, making it possible for a given neuron to independently modify coupling at different electrical synapses with its neighbors.