bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic process in the rat (Rattus norvegicus): Influence of methodology on results
Authors: Martínez‐Flores I. , Cabero LL. , Egozcue J. , Garcia M. 
Published: February 2003

AbstractSynaptonemal complex (SC) analysis is a widely used method for assessing the effects of genotoxic agents in germ cells. Although the evolution of the SCs and their related annexed structures, such as nucleoli, has been well established, sometimes it is difficult to assess whether the abnormal features observed correspond to genotoxic effects or to an artefact related to the method used to obtain the SC preparations. In this article, we describe a new method of obtaining SC preparations for electron microscopy, as well as the results of a study of the first meiotic prophase in oocytes and spermatocytes of the rat (Rattus norvegicus Sprague Dawley) in which we analysed how the methodology used can influence the results. Besides important sex‐specific differences, mainly during desynapsis (diplotene), a relationship between several bivalents and nucleolar structures, that in some cases could disturb the synaptic process, was observed in oocytes. At the same time, the characteristic SC fragmentation in oocytes was verified, but this fragmentation, in addition to a sex‐specific component, was influenced by the method itself. By reducing to a minimum the artefacts produced by the method, it is possible to optimise the analysis of SCs as a method of testing genotoxic effects in the germ line. Microsc. Res. Tech. 60:450–457, 2003. © 2003 Wiley‐Liss, Inc.
Molecular structure of the adelite group of minerals—a Raman spectroscopic study
Authors: Martens Wayde , Frost Ray L. , Williams Peter A. 
Published: February 2003

AbstractThe application of Raman microscopy to the study of closely related mineral phases of the adelite group has allowed their molecular characterization. The adelite group of minerals are orthorhombic arsenates and vanadates of general formula AB2+(XO4)(OH), where X may be As5+or V5+, cation A may be Ca or Pb and cation B may be Co or Cu and others. Raman spectroscopy has proven most powerful for the identification of these minerals. In particular, the position of the hydroxyl stretching vibrations and most of the arsenate bands have been identified. The two minerals tangeite and calciovolborthite have previously been identified as the same mineral. Raman spectroscopy has proven that the minerals are not identical and have different structures. The application of Raman spectroscopy to the study of these minerals shows that increased distortion of the arsenate anion occurs as the cationic substitution from conichalcite to austinite to duftite occurs. Copyright © 2003 John Wiley & Sons, Ltd.
Spectral investigations on 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone and 2,3‐bis(chloromethyl)‐1,4‐naphthoquinone under laser excitation
Authors: Umadevi M. , Vanelle P. , Terme T. , Ramakrishnan V. 
Published: February 2003

AbstractSolvent effects on 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone and 2,3‐bis(chloromethyl)‐1,4‐naphtho‐ quinone were investigated using optical absorption and fluorescence emission techniques and the orientation of 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone on a silver surface was studied by surface‐enhanced Raman scattering (SERS). The observed spectral shift and the bandwidth of the optical absorption spectrum reveal the changes in dipole moment and the solvent reorganization energy in the excited state. The observed fluorescence quantum yield influences the weak intermolecular hydrogen bond and the dipole–dipole interaction in the excited state. Fluorescence polarization measurements provide the faster rotational relaxation of 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone and 2,3‐bis(chloromethyl)‐1,4‐naphthoquinone in the excited state. SERS studies suggest that the orientation of 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone on a silver surface is stand‐on. Copyright © 2003 John Wiley & Sons, Ltd.
Validation of a quantitative assay using GC/MS for trace determination of free and conjugated estrogens in environmental water samples
Authors: Mouatassim‐Souali Asmaa , Tamisier‐Karolak Sara L. , Perdiz Daniel , Cargouet Maëlle , Levi Yves 
Published: February 2003

AbstractIt has been shown that sewage effluent can discharge human hormones and pharmaceuticals, particularly estrogens and synthetic chemicals, which are able to disrupt animal and human endocrine systems into surface waters. Since many surface waters receive sewage effluent and are subsequently used to produce drinking water, it is of principal interest to assess their contamination level and thereby their possible public health and environmental impact. To date, no data concerning the occurrence of estrogens present in the French aquatic environment are available. We therefore developed and validated an analytical procedure, which allows simultaneous quantitative determination of three natural estrogens, 17β‐estradiol, estriol, and estrone and one of the synthetic estrogens most widely used in contraception, ethinylestradiol, in water. Water samples are extracted using solid‐phase extraction (SPE) and then separated by gas‐chromatography coupled with mass spectrometric detection. Under our conditions, detection limits of estrogens reached the pg range of injected sample, i. e. less than 0.1 ng L–1. Conjugated estrogens were also investigated using the same procedure as described above but with a enzymatic hydrolysis preliminary step before extraction. The analysis of samples collected from four wastewater treatment plants and from surface water showed significant concentrations of estrogens ranging from 2 to 18 ng L–1 and from 0.5 to 3 ng L–1, respectively. Furthermore, no estrogen conjugated forms were detected in the water samples.
Thermal modulator array for analyte modulation and comprehensive two‐dimensional gas chromatography
Authors: Burger Ben V. , Snyman Tertia , Burger Wina J. G. , van Rooyen Willie F. 
Published: February 2003

AbstractSegmented thermal modulators were fabricated for the modulation of column effluent in one‐dimensional gas chromatography, comprehensive two‐dimensional gas chromatography, and as sample introduction devices in other analytical techniques. Thermal desorption of analytes from the modulator was achieved by computer‐controlled application of large DC currents at low voltages sequentially to consecutive segments or stages of the modulator heaters for periods between 100 and 400 ms per segment. This procedure produced sharply focussed analyte peaks. Unsegmented heaters and heaters having 2, 4, 6, 8, and 10 segments or stages were compared with respect to their focusing efficiency. The 10‐stage heater was found to give sharper focusing than heaters with a smaller number of segments. Analyte pulses with peak widths at half‐height of ca. 150 ms were generated by the 10‐stage heater. The application of a 10‐stage modulator in a comprehensive two‐dimensional analysis of a light petroleum condensate gave results of acceptable quality.
Impedance measurements on oxide films on aluminium obtained by pulsed tensions
Authors: Belmokre K. , Azzouz N. , Hannani A. , Pagetti J. 
Published: February 2003

AbstractWe have performed this study on oxide films sealed or not in boiling water. The films are first obtained on type 1050 A aluminium substrat by pulsed tensions anodizing technique, in a sulfuric acid solution.Afterwards the, Electrochemical Impedance Spectroscopy (EIS) is employed to appreciate the films behaviour in a neutral solution of 3.5% K2SO4, in which the interface processes interest only the ageing phenomenon of the oxide films and not their corrosion. We have also attempted a correlation between pulse parameters of anodization and the electrical parameters characterizing these films. The sealing influence on ageing has been studied as well. For all films, ageing is appreciated using impedance diagrams evolution versus time.The results show:– the existence of two capacitive loops confirming the presence of two oxide layers characteristic of oxide films obtained in a sulfuric acid medium. The first loop, at high frequencies, is related to the external porous layer and the second one, at lower freqencies, is related to the internal barrier layer.– the thickness of the barrier layer varies between 25 and 40 nm in relation with the electrical pulse parameters.– the sealing acts favorably against anodic oxide films ageing.
Flow‐accelerated corrosion behavior of SA106 Gr. C weldment
Authors: Kim J. H. , Kim I. S. , Zheng Y. G. 
Published: February 2003

AbstractChemical and geometrical effects of weld on flow‐accelerated corrosion (FAC) of SA106 Gr.C low alloy steel pipe was investigated using rotating cylinder electrode in 3.5‐wt% sodium chloride solution and simulated feedwater of nuclear power plants. Polarization tests and weight loss tests were conducted at rotating speed of 2000 rpm (3.14 m/s) with variation of chemical and geometric parameters. The results showed that the chemical effects were relatively larger than the geometrical effects, and the welded parts became local anode and preferentially corroded, which was explained by the differences between microstructural and compositional parameters. On the other hand, under active corrosion conditions, the heat affected zone was severely corroded and microstructural effects were dominant.
Dielectric Response of Aramid Fiber‐Reinforced PEEK
Authors: Korbakov Nina , Harel Hannah , Feldman Yuri , Marom Gad 
Published: February 2003

AbstractDielectric spectroscopy was applied for the first time to aramid fiber‐reinforced PEEK, wherein the effect of the fiber on the dielectric response was examined for both amorphous and crystalline poly(ether ether ketone) (PEEK) over wide temperature and frequency ranges. Whereas the temperature behavior of the dielectric losses of the materials exhibited the typical α and β processes of PEEK, the specific effect of the fibers in the crystalline PEEK was revealed in shifting the α process to a higher temperature. The unique effect of the fibers was expressed by a significantly higher activation energy and lower dielectric strength for the α relaxation, reflecting a higher constraint level that is imposed by the fiber. It is proposed that this additional constraint is associated with fiber generated transcrystallinity.
Scanning electron micrograph of transverse fracture surface of crystallized unidirectional aramid fiber‐reinforced PEEK.magnified imageScanning electron micrograph of transverse fracture surface of crystallized unidirectional aramid fiber‐reinforced PEEK.
Dynamic Light Scattering of Semi‐Dilute Hydrophobically Modified Alkali‐Soluble Emulsion Solutions with Varying Length of Hydrophobic Alkyl Chains
Authors: Dai S. , Tam K. C. , Jenkins R. D. 
Published: February 2003

AbstractDynamic light scattering as well as rheological technique was used to study the semi‐dilute hydrophobically modified alkali‐soluble emulsion (HASE) solutions. The solution viscosity increases dramatically, when the overlap concentrationC*is exceeded. Two diffusional modes are evident from the decay time distributions of light scattering and they are related to the hydrodynamic correlation length and the apparent hydrodynamic radius of the HASE clusters. The hydrodynamic correlation lengths, as determined from the fast diffusion mode decrease in proportion to the polymer concentrations but increase with increasing the hydrophobicity of the hydrophobes of the macromonomers. The apparent hydrodynamic radii of the clusters, as determined from the slow diffusion mode, increase with increasing polymer concentrations. When the carbon number of the hydrophobes is increased from C1to C8, both the viscosities and diffusion coefficients of the slow mode remain almost unchanged. However, they are strongly dependent on the carbon chain length when the carbon number exceeds C12, especially for the polymer with C20alkyl chains. The solution viscosities decrease and diffusion coefficients of the slow mode increase with increasing temperatures, however, the parameters ofDη/Tremain constant.Comparison of microstructures of semi‐dilute HASE solutions with (a) short hydrophobic alkyl groups and (b) long hydrophobic alkyl groups was made. For (a) with small hydrophobes, the aggregation number per association junction is smaller and there are more aggregation junctions in the network cluster. The hydrodynamic correlation length,ξh, which is the averaged distance between two aggregation junctions, is shorter. As for (b) with larger hydrophobes, the aggregation number is larger with fewer aggregation junctions in the network cluster. The hydrodynamic correlation length is longer.magnified imageComparison of microstructures of semi‐dilute HASE solutions with (a) short hydrophobic alkyl groups and (b) long hydrophobic alkyl groups was made. For (a) with small hydrophobes, the aggregation number per association junction is smaller and there are more aggregation junctions in the network cluster. The hydrodynamic correlation length,ξh, which is the averaged distance between two aggregation junctions, is shorter. As for (b) with larger hydrophobes, the aggregation number is larger with fewer aggregation junctions in the network cluster. The hydrodynamic correlation length is longer.
Synthesis of Well‐Defined Poly(methyl methacrylate) by a Normal Atom‐Transfer Radical Polymerization Procedure with a New Catalyst, Cuprous N,N‐Diethyldithiocarbamate
Authors: Li Peng , Qiu Kun‐Yuan 
Published: February 2003

AbstractCuprous N,N‐Diethyldithiocarbamate, Cu(S2CNEt2), was successfully used as a catalyst in p‐toluenesulfonyl chloride initiating atom‐transfer radical polymerization of methyl methacrylate in both bulk and solution in a heterogeneous system with 2,2′‐bipyridine as the ligand. The polymerization was controlled under various concentration ratios of the monomer to initiator, the molecular weight matched the predetermined value, and the molecular weight distribution of resulting polymers was quite low (Mw/Mn < 1.10). Solvents with different polarity had no significant effect on the living nature of this process. Well‐defined poly(methyl methacrylate) with α‐p‐toluenesulfonyl and ω‐diethylthiocarbamoylthiyl group was obtained. That the polymer chain was capped with an ultraviolet light sensitive group was confirmed by chain extension reactions.
Dependence of Mn and Mw/Mn on the monomer conversion of bulk polymerization of MMA at 80 °C with p‐TsCl/Cu(S2CNEt2)/bpy initiation system. Conditions the same as in Figure 5.magnified imageDependence of Mn and Mw/Mn on the monomer conversion of bulk polymerization of MMA at 80 °C with p‐TsCl/Cu(S2CNEt2)/bpy initiation system. Conditions the same as in Figure 5.
Hydrogen Bonding Interaction and Miscibilization of Ternary Blends of Poly(2‐vinylpyridine), Poly(N‐vinyl‐2‐pyrrolidone), and 4,4′‐(1,4‐Phenylenediisopropylidene)bisphenol
Authors: Li Xue‐Dong , Goh Suat H. 
Published: February 2003

AbstractThe interaction energy densities of poly(2‐vinylpyridine) (P2VPy)/4,4′‐(1,4‐phenylenediisopropylidene)bisphenol (PDIPBP) blend and poly(N‐vinyl‐2‐pyrrolidone) (PVP)/PDIPBP blend were determined using melting point depression method. The interaction between PVP and PDIPBP is stronger than that between P2VPy and PDIPBP. Wide‐angle X‐ray diffraction study revealed that PDIPBP crystallizes out from the polymer/PDIPBP blends at high PDIPBP contents. The phase equilibrium calculation supports that the single‐Tg behavior is a result of miscibilization rather than an overlap of two close Tg's of two separated phases. The critical miscibilization content of PDIPBP obtained from spinodal phase boundary calculation is lower than the saturation content, and therefore, there is enough PDIPBP in the amorphous phase to miscibilize P2VPy and PVP. Scanning electron microscopy showed a drastic reduction in domain size in single‐Tg blends.
Ternary phase diagram of P2VPy/PVP/PDIPBP blends. (○) miscible blends; (•) immiscible blends; (— × —) calculated phase boundary (Coordinate in volume fraction).magnified imageTernary phase diagram of P2VPy/PVP/PDIPBP blends. (○) miscible blends; (•) immiscible blends; (— × —) calculated phase boundary (Coordinate in volume fraction).
Novel Fluorinated Hybrid Polymer by Radical Polyaddition of Bis(α‐trifluoromethyl‐β,β‐difluorovinyl) Terephthalate onto Dialkoxydialkylsilanes
Authors: Fujiwara Hirotada , Narita Tadashi , Hamana Hiroshi , Horie Naohiro 
Published: February 2003

AbstractTo develop the radical polyaddition of bisperfluoroisopropenyl esters, the reactions of bis(α‐trifluoromethyl‐β,β‐difluorovinyl) terephthalate [CF2C(CF3)OCOC6H4COOC(CF3)CF2] (BFP) with dialkoxydialkylsilane were examined to prepare fluorinated hybrid polymers bearing dialkylsilyl groups in the main chain. Prior to polyaddition, the radical addition reaction of 2‐benzoyloxypentafluoropropene [CF2C(CF3)OCOC6H5] (BPFP) has been investigated to afford the results that diethoxydimethylsilane (DEOMS) or dimethoxydimethylsilane with BPFP initiated by oxo radical are the best combination for the preparation of polymers. The mechanism of the addition reaction was proposed. Radical polyaddition of BFP with DEOMS initiated by benzoyl peroxide or di‐tert‐butyl peroxide has yielded polymers of up to molecular weight 1 × 106 with rather broad molecular weight distribution. A mechanism for the polyaddition reaction is proposed based on the radical addition reaction between BPFP and DEOMS. The step‐growth polymerization is initiated by hydrogen abstraction of DEOMS to add a perfluoroisopropenyl group, followed by a 1,7‐shift of the radical in the intermediate. The relationship between addition reaction mechanism and polyaddition mechanism was also discussed.
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Two‐Photon Pattern Bleaching for Characterizing Structural Changes in Polymer Films
Authors: Van Keuren Edward , Schrof Wolfgang 
Published: February 2003

AbstractUsing two‐photon absorption, an array of spots in a dye‐doped polymer film can be bleached, creating a three‐dimensional structure that can be imaged with two‐photon or confocal microscopy. Microscopic deformations resulting from various treatments to the film can be characterized, for example, swelling or shrinking. This technique is demonstrated on dye‐doped poly(vinyl alcohol), in which the effect of swelling with the addition of water to the film is shown.
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An Infrared Approach toward Measuring the Thickness of Polyelectrolyte Films
Authors: Montrel Michael M. , Stroustrup Nicholas 
Published: February 2003

AbstractIR spectroscopy is applied to study polyelectrolyte films of 0.1–5 μm thickness. This approach permits to obtain not only the usual chemical information about polymer conformation, chemical bonds, interacting groups, and molecular/ionic state, but also important structural parameters of the film, such as total thickness, average thickness of each layer, and sparseness of polymer packing. All these information can be obtained from one single sample.
IR cell for thickness measurements of a polyelectrolyte film. The pathlength d of the cell is measured twice: before and after film deposition. The film thickness, Δd = de − df, can be calculated using the interference maxima that determine values de and df.magnified imageIR cell for thickness measurements of a polyelectrolyte film. The pathlength d of the cell is measured twice: before and after film deposition. The film thickness, Δd = de − df, can be calculated using the interference maxima that determine values de and df.
SANS from adsorbed polymer layers
Authors: King Stephen , Griffiths Peter , Hone John , Cosgrove Terence 
Published: February 2003

AbstractOne of the areas in which small‐angle neutron scattering (SANS) has had a profound impact over the last twenty years is the investigation of polymers and surfactants adsorbed at the solid/liquid and liquid/liquid interfaces. This is of course also an area of considerable commercial importance. Control of the structure of an adsorbed layer is thus a key priority of the colloid scientist. Equally important, however, is the ability to probe the arrangement of the adsorbed polymer molecules and to extract quantitative information from what might well be a complex, multicomponent system. SANS in combination with the principle of deuterium contrast variation is uniquely placed to provide this information.
A few remarks on classic problems of scattering by polymer solutions and mixtures
Authors: Benoît Henri , Jannink Gérard 
Published: February 2003

AbstractThe problem of scattering by multicomponent systems has been the object of many papers. Here it will be shown that the scattering can be split into two terms, one corresponding to the compressibility of the system and the other depending only on fluctuations of the number of molecules of different constituents. In neutron scattering on samples far from critical conditions, the compressibility term is negligible. In the second part, a simple demonstration of the random phase approximation theorem is proposed, which makes the theorem more understandable for nonspecialists.
Linear, branched and hyperbranched macromolecules in dilute solution
Authors: Ganazzoli Fabio 
Published: February 2003

AbstractWe report some theoretical results obtained for star polymers and dendrimers under different solvent conditions using the Gaussian self‐consistent approach. The focus is mainly on the model assumptions and approximations, and on the results. We discuss the Θ state in terms of both the Θ temperature and the molecular size, and then we consider the good‐solvent conditions also through the intramolecular dynamics.
The crystallization and melting of linear polyethylene studied by temperature‐modulated SAXS and WAXD
Authors: Goderis Bart , Reynaers Harry , Koch Michel H.J. 
Published: February 2003

AbstractTemperature‐reversible and ‐irreversible morphological events could be separated in the case of linear polyethylene during quasi‐isothermal crystallization by using simultaneous temperature‐modulated synchrotron SAXS and WAXD. Crystallization and subsequent annealing was followed at 126 °C for 90 min while applying a temperature modulation with an amplitude of 1 °C and a period of 2 min. The crystal growth rate associated with the irreversible part of the crystallization decreases with increasing temperature in a cycle. The crystalline lamellae irreversibly thicken with time. The actual crystallite thickness, however, exhibits a superimposed modulation out of phase with that of the temperature modulation. Melting was studied during heating at 1 °C/min after cooling at 10 °C/min. A temperature modulation was superimposed with an amplitude of 2 °C and a period of 3 min. Once again temperature‐reversible crystal thickness changes and irreversible crystal thickening could be observed.