bluuebunny/crossref_metadata_2025 huggingface dataset:
Plastic Hinge Lengths of Normal and High-Strength Concrete in Flexure
Authors: Mendis P.
Published: January 2003

Full-range analysis methods are becoming popular in design of reinforced concrete structures. These methods require a knowledge of the behaviour of plastic hinges up to advanced curvatures. Concrete sections characteristically soften beyond the plastic phase. To analyse a strain-softening structure, many researchers have used a finite hinge length. In this paper, existing formulae are re-examined and the effects of different variables on hinge length are discussed. Experimentally measured values are compared with the values predicted by using these formulae. It is shown that the upper and lower bounds suggested by the ACI committee 428 provide reliable estimates of hinge lengths for both normal and high-strength concrete flexural hinges up to 80 MPa.
Large Amplitude Vibration of a Cantilever Beam with Tip Mass under Random Base Excitation
Authors: Cheng Guangfeng , Mei Chuh , Lee Raymond Y. Y.
Published: January 2003

Nonlinear large amplitude random vibration of cantilever beam with lumped mass and rotary inertia under zero mean, stationary, Gaussian random base excitation is studied, using the inextensional beam theory. Single-mode approximation is employed to discretize the Lagrange's equation. The resulting nonlinear governing modal equation of motion is solved with application of the stochastic linearization method. Two examples, a cantilever beam with/without tip mass, are analyzed as application of the developed methodology. Effects of mass and rotary inertia variation on system response are investigated in detail. Results showed that increasing rotary inertia could reduce the random response of the beam structure and the random response of the structure is quite sensitive to the tip mass variation. The nonlinearities of the inextensional beam vibration result in a spring hardening system.
Bifurcation Analyses of Steel and Concrete with Rate-Dependent Properties Part One: Model Formulation and Verification
Authors: Liu Yuxing , Shen Luming , Chen Zhen
Published: January 2003

Department of Civil and Environmental Engineering, University of Missouri-Columbia, Columbia MO 65211–2200, U.S.A. The effects of strain rate on the mechanical properties of carbon steel and plain concrete are investigated through a rate-dependent elasto-plasticity model and rate-dependent elasto-damage model, respectively. Continuum tangent stiffness tensors are derived for both models so that bifurcation analyses can be performed to identify the onset of material failure. Three-dimensional constitutive model solvers are designed and the numerical results are compared with the experimental data to verify the proposed models.
Bifurcation Analyses of Steel and Concrete with Rate-Dependent Properties Part Two: Bifurcation Analyses and Demonstration
Authors: Shen Luming , Liu Yuxing , Chen Zhen
Published: January 2003

Based on the continuum tangent stiffness tensors derived in part one for steel and concrete, bifurcation analyses of rate-dependent elasto-plasticity and elasto-damage are performed in (-(and (-(spaces of Mohr, respectively. Localization ellipse osculating Mohr's circle enables us to determine the critical state and failure angle. It is shown that strain rate has no effect on the failure angle, and that the parameters in rate-dependent damage model are restricted by the results of bifurcation analysis.
An Exact Theory for Curved Beams with Any Thin-Walled Open Sections
Authors: Tong Genshu , Xu Qiang
Published: January 2003

Currently available theories for thin-walled curved beams lack rigorous theoretical development. This paper provides a detailed derivation of an exact theory for biaxial bending and torsion of thin-walled circularly curved beams with any open profile. The derivation is based on two well-accepted assumptions in the theory of thin-walled members. Exact expressions for longitudinal displacement, longitudinal normal stress and shear stress and their resultants are presented. Simplified theories are also given for practical applications.
Interaction between Flexure and Shear on the Debonding of RC Beams Retrofitted with Compression Face Plates
Authors: Ali M.S. Mohamed , Oehlers D.J. , Bradford M.A.
Published: January 2003

Steel and FRP plating reinforced concrete structures is increasingly being used for retrofitting. Plates can be bonded to any surface of a beam or slab, although it is common practice to adhesively bond plates to the tension faces. The addition of these tension face plates reduces the sectional ductility of the beam. Furthermore, these tension face plates are prone to premature debonding because the stress concentrations induced by these plates overlap with those induced by the tension reinforcing bars adjacent to the plate. Solutions to these two problems, which are the subject of this paper, consist of: adhesively bonding plates to the compression faces to counterbalance the tension face plates and, hence, improve the beam sectional ductility; and to extend the tension face plates, in continuous beams, past the points of contraflexure so that they terminate in a compression face. In this paper, eleven new tests on 340 mm deep beams are presented that show that compression face plates are less prone to debonding than tension face plates.
Large-Scale Testing of Steel Portal Frames Comprising Tapered Beams and Columns
Authors: Li Jin-Jun , Li Guo-Qiang
Published: January 2003

Advanced analysis and design of steel frames can directly and exactly determine the ultimate system capacity without resort to simplified elastic methods of analysis and semi-empirical interaction equations (Chen, 1993). However, the application of advanced analysis methods has previously been based on steel frames comprising prismatic members. A research project has been conducted with the aim of developing concentrated plasticity methods suitable for practical advanced analysis and reliability-based design of steel portal frames with tapered members (Li, 2001). Two large-scale realistic tests were performed in order to provide experimental results for verification of the new analytical models, and to examine the important nonlinear effects that should be added in further theoretical research. Tested frames are identical in dimensions and with tapered beams and columns. One was subjected to incremental vertical loads and the other to simultaneous constant vertical loads and incremental horizontal loads. The details of the test program including the test frames, test rig and instrumentation, test procedure and results are given in this paper. Comparisons between design and analytical results are presented and discussed.
A New Time Domain Formulation for Broadband Noise Predictions
Authors: Casper J. , Farassat F.
Published: January 2003

A new analytic result in acoustics called “Formulation 1B,” proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is analytically specied from a result based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B and to demonstrate its equivalence to Formulation 1A of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous, isotropic turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.
An Aeroacoustic Study of a Leading EDGE Slat Configuration
Authors: Mendoza J.M. , Brooks T.F. , Humphreys W.M.
Published: January 2003

Aeroacoustic evaluations of high-lift devices have been carried out in the Quiet Flow Facility of the NASA Langley Research Center. The present paper describes detailed flow and acoustic measurements that have been made in order to better understand the noise generated from airflow over a wing leading edge slat configuration, and to possibly predict and reduce this noise source. The acoustic database is obtained by a moveable Small Aperture Directional Array of microphones designed to electronically steer to different portions of models under study. The slat is shown to be a uniform distributed noise source. The data was processed such that spectra and directivity were determined with respect to a one-foot span of slat. The spectra are normalized in various fashions to demonstrate slat noise character. In order to equate portions of the spectra to different slat noise components, trailing edge noise predictions using measured slat boundary layer parameters as inputs are compared to the measured slat noise spectra.
Low-Speed Fan Noise Reduction with Trailing EDGE Blowing
Authors: Sutliff D.L. , Tweedt D.L. , Fite E.B. , Envia E.
Published: January 2003

An experimental proof-of-concept test was conducted to demonstrate rotor-stator interaction tone noise reduction through rotor trailing edge blowing. The velocity deficit from the viscous wake of the rotor blades was reduced by injecting air into the wake from a trailing edge slot. Composite hollow rotor blades with internal flow passages were designed based on Computational Fluid Dynamics codes modeling the internal flow. The hollow blade with interior guide vanes creates flow channels through which externally supplied air flows from the root of the blade to the trailing edge. The impact of the rotor wake-stator interaction on the acoustics was also predicted analytically.

The Active Noise Control Fan, located at the NASA Glenn Research Center, was used as the proof-of-concept test bed. In-duct mode and farfield directivity acoustic data were acquired at blowing rates (defined as mass flow supplied to trailing edge blowing system divided by fan mass flow) ranging from 0.5% to 2.0%. The first three blade passing frequency harmonics at fan rotational speeds of 1700 to 1900 rpm were analyzed. The acoustic tone mode power levels (PWL) in the inlet and exhaust were reduced 11.5&–0.1, 7.2&11.4, 11.8&19.1 PWL dB, respectively. The farfield tone power levels at the first three harmonics were reduced 5.4, 10.6, & 12.4 dB PWL. At selected conditions, two-component hotwire and stator vane unsteady surface pressures were acquired. These measurements show the modification of the rotor wake due to trailing edge blowing and its effect on the stator vane to illustrate the physics behind the noise reduction.
Development of Three-Dimensional PML Boundary Conditions for Aeroacoustics Applications
Authors: Dietiker J-F. , Hoffmann K.A. , Papadakis M. , Agarwal R.
Published: January 2003

Perfectly Matched Layer (PML) boundary conditions are derived in generalized curvilinear coordinates for three-dimensional aeroacoustic applications. The resulting governing equations are solved numerically by a four-stage Runge-Kutta scheme, with 4th/6th order compact finite difference formulation. The PML equations are programmed in a subroutine, which is easily incorporated to the main program LINEULER (Linearized Euler's equation solver). Two and three-dimensional benchmarks problems are solved to investigate the efficiency and accuracy of the PML boundary conditions. Investigations on the PML parameters have been conducted to determine the optimum combination of parameters used in the computations.
Crystallographic report: 1,3‐Bis[(trimethylsilylmethyl)dichlorostannyl]propane, [(Me3SiCH2)Cl2Sn]2(CH2)3
Authors: Dakternieks Dainis , Kuan Fong Sheen , Duthie Andrew , Tiekink Edward R. T.
Published: January 2003

The dinuclear molecule of [(Me3SiCH2)Cl2Sn]2(CH2)3 adopts an extended conformation and features distorted tetrahedral tin centres, with the greatest distortion manifested in the CSnC angles of approximately 128 °. The distortions are ascribed to the influence of intermolecular Sn···Cl interactions. Copyright © 2002 John Wiley & Sons, Ltd.
Crystallographic report: 1,4‐Bis(triphenylstannylmethyldimethylsilyl)benzene, p‐(Ph3SnCH2SiMe2)2C6H4
Authors: Dakternieks Dainis , Zobel Bernhard , Tiekink Edward R. T.
Published: January 2003

The dinuclear molecule of p‐(Ph3SnCH2SiMe2)2C6H4 adopts an ‘S’ conformation in the solid state, which is stabilized by CH···π interactions. Distorted tetrahedra defined by C4 donor sets are found for the tin atoms. Copyright © 2002 John Wiley & Sons, Ltd.
Crystallographic report: 1,4‐Bis[(phenyldichlorostannyl)ethyl]benzene, p‐(Cl2PhSnCH2CH2)2C6H4
Authors: Dakternieks Dainis , Duthie Andrew , Tiekink Edward R. T.
Published: January 2003

An ‘S’ conformation, stabilized by intramolecular CH···π interactions, is found in centrosymmetric p‐(Cl2PhSnCH2CH2)2C6H4. The dinuclear species features distorted tetrahedral tin centres, with the greatest distortion manifested in the CSnC angle of 134.32(16) °. Copyright © 2002 John Wiley & Sons, Ltd.
The cholesterol pathway of Trypanosoma congolense could be a target for triphenyltinsalicylate and triphenylsiliconsalicylate inhibition
Authors: Nok Andrew J. , Nock Ishaya H. , Bonire Josiah J.
Published: January 2003

The organometallic compounds triphenyltinsalicylate (TPTS) and triphenylsiliconsalicylate (TPSS) were found to be trypanocidal against culture forms of Trypanosoma congolense. Both compounds at 0.4–5 µmol ml−1 completely killed the parasites in vitro within 3‐8 min after incubation. A dosage of 1.5 µmol ml−1 TPTS killed at least 50% of the parasite population, which was preceded by a cluster effect as observed under phase contrast microscopy. Also, 3.5 µg ml−1 of TPSS was required to kill 50% of the T. congolense cells. At a low dosage of 2–10 µg ml−1, it was feasible to monitor the effect and mode of action of the organometallic compounds. There was a 50% reduction in the amount of synthesized cholesterols in the presence of 6 µg ml−1 and 10 µg ml−1 of TPTS and TPSS respectively. TPTS and TPSS also non‐competitively inhibited pyrophosphatase from lysed T. congolense with Ki values of 3.6 µM and 8.5 µM respectively. In the in vivo experiments, TPTS cured T. congolense infected mice at a dosage of 2–10 mg kg day−1 for 4 days. TPSS was, however, completely inactive in vivo. The use of organometallic compounds in the design of trypanocides is discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Review: Chemistry of the phosphinophosphinidene tBu2PP, a novel π‐electron ligand
Authors: Olkowska‐Oetzel Jolanta , Pikies Jerzy
Published: January 2003

In reactions with transition metal compounds, tBu2PPP(X)tBu2 (X = Br, Me) acts mainly as a precursor of the tBu2PP ligand, whereas tBu(Me3Si)PPP(Me)tBu2 acts as a precursor of the (Me3Si)PPtBu ligand. Up to now, only Pt(0) d10 ML2 metal centres were found to be able to stabilize the tBu2PP group in ‘pure form’ by means of η2‐coordination (side on). Several compounds of the [{η2 − tBu2PP}Pt(PR3)2] type were sufficiently stable to be isolated and characterized; however, not all of them gave single crystals suitable for X‐ray structure determinations. The X‐ray structures of these compounds and of [{µ − (1,2:2 − η − tBu2PP)Pt(PR3)2} {M(CO)5}] strongly suggest the ethene‐like form of 1,1‐di‐tert‐butyldiphosphene in these complexes. Such a form is also in agreement with RI DFT calculations with SVP basis for free tBu2PP. However, in trapping experiments with cyclic olefins and cyclic dienes tBu2PP exhibits, to some extent, electrophilic ‘singlet carbene’ properties. Copyright © 2002 John Wiley & Sons, Ltd.
Organotin(IV) complexes of ethylsarcosine hydrochloride: synthesis, characterization and in vitro cytotoxic activity
Authors: Ronconi L. , Marzano C. , Russo U. , Sitran S. , Graziani R. , Fregona D.
Published: January 2003

The synthesis and characterization of new coordination compounds of some organotin(IV) chlorides with ethylsarcosine hydrochloride (N‐methylglycine ethyl ester hydrochloride) is reported; the ligand molecules appear to be bound to the tin atoms through the carbonyl oxygen atoms by means of dative bonds. As single crystals were not obtained, a number of experimental techniques were used to accomplish a definitive characterization and determination of their structure. The results obtained by 1H, 13C, 119Sn NMR, FT‐IR and 119mSn Mössbauer spectroscopy and thermogravimetric analysis suggested pentacoordination for the 1:1 (Sn:ligand (ESH)) derivatives, [R2SnCl2(ESH)]+Cl−, in a trigonal bipyramidal (TBP) structure, and hexacoordination for the 1:2 complexes, [R2SnCl2(ESH)2]2+2Cl−, in an octahedral structure (R = Me, n‐Bu, Ph; ESH = protonated ethylsarcosine, CH3CH2O(O)CCH2N(CH3)H2+). The triphenyltin(IV) chloride ethylsarcosine hydrochloride derivative exists only as a 1:1 pentacoordinated adduct in a strongly distorted TBP structure. Finally, the compounds have been tested for in vitro cytotoxic activity against human adenocarcinoma HeLa cells, showing, in some cases, a high potency, even at low concentration. Copyright © 2002 John Wiley & Sons, Ltd.
Electrochemically generated tungsten‐based active species as catalysts for metathesis‐related reactions: 1. Acyclic diene metathesis polymerization of 1,9‐decadiene
Authors: Dereli Okan , Düz Bülent , Zümreoğlu‐Karan Birgül , İmamoğlu Yavuz
Published: January 2003

The application of the WCl6–e−–Al–CH2Cl2 system to acyclic diene metathesis polymerization of 1,9‐decadiene is reported. The polyoctenamer formed is of a weight‐average molecular weight of 9000 with a polydispersity of 1.92. IR and NMR spectral analyses indicate the retention of the double bonds in the polymer structure with high trans content as expected from a step condensation reaction. This relatively stable catalytic system, however, also activates the competing vinyl addition reactions while being inactive in ring‐closure metathesis reactions. Copyright © 2002 John Wiley & Sons, Ltd.
Novel synthesis of polyimides of the third‐order optical nonlinearities by microwave assistance
Authors: Lu Jian‐Mei , Ji Shun‐Jun , Chen Nai‐Yong , Zhang Zheng‐Biao , Sun Zhen‐Rong , Zhu Xiu‐Lin , Shi Wei‐Ping
Published: January 2003

The third‐order optical nonlinearities and time responses of three new polymeric materials, which were prepared by polymerization of benzoguanamine (BGA) and pyromellitic dianhydride (PMDA), m,m′‐diaminobenzophenone (m,m′‐DABP) and PMDA, BGA, and 2,4‐tolylenediisocyanate (TDI) under microwave radiation, were measured by a picosecond forward three‐dimensional degenerate four‐wave mixing technique. The experimental results showed that nonresonant optical nonlinearity [χ(3)] of the three polymers is larger by microwave than by heating and that third‐order optical nonlinearities were not only affected by the length of polymer chain, but also by the polymer chain structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1739–1747, 2003
Study of electrical properties for albumin/ poly(vinyl alcohol) blends
Authors: Ragab H. S. , Abo Ellil M. S. , Shehap A. , Abd El‐ Kader F. H.
Published: January 2003

Thermally stimulated depolarization current (TSDC), d.c. electrical conductivity (σ), and current–time characteristic techniques were used to study electrical polarization and conduction mechanisms for pure poly(vinyl alcohol) (PVA) and 2.5, 5, 10, 12, 15, and 20 wt % albumin content in PVA thin films. The TSDC spectrum for PVA revealed the existence of two broad peaks, while the blend samples show only one broad peak with a shoulder in the high‐temperature side. The existence of this current maximum was analyzed and discussed in terms of dipole‐orientation and space‐charge phenomena. Quantitative analysis was carried out to determine the thermal activation energies of the conduction process, drift mobility, and carrier concentration. The crystallinty of the PVA matrix was enhanced by the addition of albumin, as indicated by X‐ray diffraction and differential scanning calorimetry (DSC) measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1748–1757, 2003
Miscibility study on blend of thermotropic liquid crystalline polymers and polyester
Authors: Park Dae Soon , Kim Seong Hun
Published: January 2003

The miscibility of thermotropic liquid crystalline polymers (TLCPs) and polyester blends was investigated with thermal and morphological analyses, as well as transesterification. TLCPs composed of 80 mol % para‐hydroxybenzoate (PHB) and 20 mol % poly(ethylene terephthalate) (PET) or 60 mol % PHB and 40 mol % PET, and polyesters such as PET and poly(ethylene 2,6‐naphthalate) (PEN) were melt blended in an internal mixer. DSC analyses were performed to investigate the thermal transition behavior and to obtain thermodynamic parameters. All the blends showed only a single glass‐transition temperature, which means they are partially miscible in the molten state. The Flory–Huggins interaction parameter was calculated employing the Nishi–Wang approach, and negative values were obtained except for the P(HB8‐ET2)/PEN blends. Transesterification was investigated using 1H‐NMR, and the change of chemical shift compared to pure PET or P(HB‐ET)s was observed in the P(HB‐ET)/PET blends. An intermediate chemical shift value (4.83 ppm) was observed in the P(HB6‐ET4)/PEN blends, which indicates transesterification occurred. The fractured surface morphology of scanning electron micrographs showed that the interfaces between the LC droplets and matrix were not distinct. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1842–1851, 2003
Improvement of silicone endothelialization by treatment with allylamine and/or acrylic acid low‐pressure plasma
Authors: Monge Sophie , Mas André , Hamzaoui Amina , Kassis Camille M. , Desimone Joseph M. , Schué François
Published: January 2003

Plasma polymerization of allylamine, acrylic acid, and an allylamine/acrylic acid mixture on Silastic® silicone rubber led to a strong increase in the silicone rubber's hydrophilicity and surface energy. Analysis of the deposited layer by X‐ray photoelectron spectroscopy with 20° and 70° takeoff angles showed segregation of the atoms according to the depth and the incorporation of amino groups, oxygenated groups, and both. The endothelialization of untreated and treated samples was evaluated by the seeding and growth of aorta epithelial cells from pigs in cellular adherence (%), doubling time (in hours), and confluent density (104 cells/cm2). The best results were obtained with the allylamine/acrylic acid mixture treatment, which brought a biocompatibility to Silastic® similar to classic tissue culture on polystyrene plates. The interpretation was based on the presence of NH/CO2− microareas in the deposited layer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1794–1802, 2003
Preparation and characterization of nanofiltration membranes fabricated from poly(amidesulfonamide), and their application in water–oil separation
Authors: Chan Wing‐Hong , Tsao Sai‐Cheong
Published: January 2003

Nanofiltration membranes prepared from selected types of poly(amidesulfonamide) (PASA) targeted to retain either sucrose, raffinose, or β‐cyclodextrin were fabricated in conditions deduced from a chemometric method. Membrane performance was characterized by the permeation of solutions containing 1000 ppm carbohydrates and metal ions. To demonstrate the dependence of the membrane properties on the polymer structure, the separation characteristics of a series of four PASA homopolymers and four PASA copolymers were established. The results allowed us to screen out several promising PASA materials for the NF separation process. In addition, the superiority of the PASA materials, characterized by excellent retention and high flux rate, was evident from the results of a study comparing it with polysulfonamide, poly(ether amide), and commercially available regenerated cellulose. As a means of pollution control, the PASA NF membranes have been proven to be effective in removing oil from oily wastewater. Under an operating pressure of 2–3 psi, a constant flux of 5 L m−2 h−1 and 99.6% retention of a solution of 5000 ppm olive oil could be achieved with the PASA membranes over a period of 430 h. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1803–1810, 2003
Preparation of conductive polyaniline/nanosilica particle composites through ultrasonic irradiation
Authors: Xia Hesheng , Wang Qi
Published: January 2003

Polyaniline/nano‐SiO2 particle composites were prepared through ultrasonic irradiation. Polymerization of aniline was conducted under ultrasonic irradiation in the presence of two types of nano‐SiO2: porous nanosilica and spherical nanosilica. The stability of the colloid dispersion, UV–vis spectra, composition, interaction, conductivity, and other characteristics of the composites were examined. It was found that the aggregation of nano‐SiO2 could be reduced under ultrasonic irradiation and that nanoparticles were redispersed in the aqueous solution. The formed polyaniline deposited on the surface of the nanoparticle, which led to a core–shell structure. Two particle morphologies, threadlike aggregates with a few spherical nanoparticles for porous nanosilica and spherical particles with a few sandwichlike particles for spherical nanosilica, were observed. X‐ray photoelectron spectroscopy showed that for two types of composites the ratio of Si atoms to N atoms (Si:N) on the surface was much higher than that in the bulk. The UV–vis spectra of the diluted colloid dispersion of polyaniline/nano‐SiO2 composite particles were similar to those of the polyaniline system. Fourier transform infrared spectroscopy suggested strong interaction between polyaniline and nano‐SiO2. The conductivity of the polyaniline/porous nanosilica (23.1 wt % polyaniline) and polyaniline/spherical nanosilica (20.6 wt % polyaniline) composites was 2.9 and 0.2 S/cm, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1811–1817, 2003
Grafting mechanisms in hybrid miniemulsion polymerization
Authors: Tsavalas John G. , Luo Yingwu , Schork F. Joseph
Published: January 2003

The ultimate objective of hybrid miniemulsion polymerization is to produce a water‐based crosslinkable coating through in situ grafting of a free radical growing acrylic polymer with an unsaturated resin. Certain authors have reported low grafting while others have reported higher. This article explores the factors that influence the grafting tendencies of these systems. Methacrylates such as methyl methacrylate (MMA) have a sterically hindered radical center that lowers its reactivity toward unsaturated resin. This steric hindrance from the methyl group forces grafting of this type of monomer to occur by abstraction of a hydrogen allylic to a resinous double bond. This chain transfer produces a relatively inactive radical on the resin that reduces the grafting efficiency. The transfer process also inherently produces some degree of terminated PMMA polymer within the particle. Grafting occurs in this type of system through termination of living PMMA chains with that radical produced on the resin. For relatively water‐soluble monomers such as MMA, grafting efficiency is further lessened by homogeneous nucleation resulting from the monomer hydrophilicity. These newly created particles cannot contain alkyd due to its hydrophobicity and thus inability to transport across the aqueous phase, and hence cannot produce grafted polymer. Nonetheless, degree of grafting of nearly 50% was observed in these systems. For hybrid systems involving an acrylate monomer such as butyl acrylate (BA), virtually complete grafting with alkyd was observed. This is due to the uninhibited BA radical center allowing the molecule to add directly through a resin double bond. This process offers the possibility for complete grafting. Homogeneous nucleation is not involved in this system due to the insolubility of BA in the aqueous phase. Resin double bond content and degree of conjugation also play an integral role in the grafting process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1825–1836, 2003
The essential oil composition of Salvia brachyodon Vandas
Authors: Tzakou O. , Couladis M. , Slavkovska V. , Mimica‐Dukic N. , Jancic R.
Published: January 2003

The essential oils of Salvia brachyodon (samples A and B), collected from Montenegro, were analysed by GC–MS. Fifty‐four constituents were identified. The oil was characterized by a high content of oxygenated monoterpenes. The major constituents were 1,8‐cineole (23.0–17.2%), bornyl acetate (9.8–10.5%) and β‐pinene (8.8–9.4%). Copyright © 2002 John Wiley & Sons, Ltd.
Essential oils of Ocimum basilicum L., O. basilicum. var. minimum L. and O. basilicum. var. purpurascens Benth. grown in north‐eastern Brazil
Authors: de Vasconcelos Silva Maria Goretti , de Abreu Matos Francisco José , Lacerda Machado Maria Iracema , Craveiro Afrânio Aragão
Published: January 2003

Ocimum basilicum L. occurs everywhere in several forms, varieties and chemotypes whose essential oils presents marked variation on chemical composition. A new analysis of O. basilicum, O. basilicum var. minimum L. and O. basilicum var. purpuracens Benth. growing in north‐eastern Brazil showed that O. basilicum var. minimum represented a true estragole chemotype, while the other two species analysed may be considered linalool chemotypes. Copyright © 2002 John Wiley & Sons, Ltd.
Volatile components of the rhizomes of Cirsium japonicum DC
Authors: Miyazawa Mitsuo , Yamafuji Chikako , Kurose Kohsuke , Ishikawa Yukio
Published: January 2003

The chemical composition of the essential oils from the rhizomes of Cirsium japonicum DC. has been investigated by GC and GC–MS. Sixty‐seven components were identified in the essential oil, with palmitic acid (14.42%), caryophyllene oxide (12.57%), khusinol (6.31%), pentadecanoic acid (6.28%) and myristic acid (4.66%) as the major components. Terpenoids accounted for about 45.22%, especially sesquiterpenoids, which comprised 42.17% of the essential oil. Copyright © 2002 John Wiley & Sons, Ltd.
Volatile constituents of Cymbopogon nardus (Linn.) Rendle
Authors: Mahalwal Vijender S. , Ali Mohd.
Published: January 2003

The steam‐distilled volatile oil obtained from partially dried grass (citronella grass) Cymbopogon nardus (Linn.) Rendle (Syn. Andropogon nardus Linn.), cultivated in the Nilgiri Hills at Ooty, India, was analysed by capillary GC and GC–MS. The partially dried grass contained 35 components, of which 29 constituents, comprising 92.7% of the oil, were completely identified. The oil contains 16 monoterpenes (79.8%), nine sesquiterpenes (11.5%) and four non‐terpenic compounds (1.4%). The prominent monoterpenes were citronellal (29.7%), geraniol (24.2%), γ‐terpineol (9.2%) and cis‐sabinene hydrate (3.8%). The predominant sesquiterpenes were (E)‐nerolidol (4.8%), β‐caryophyllene (2.2%) and germacren‐4‐ol (1.5%). Copyright © 2002 John Wiley & Sons, Ltd.
Essential oil composition of Achillea santolina L. and Achillea biebersteinii Afan. collected in Jordan
Authors: Bader Ammar , Flamini Guido , Cioni Pier Luigi , Morelli Ivano
Published: January 2003

The essential oils of Achillea santolina L. and A. biebersteinii Afan., collected in Jordan, have been studied. The former has never been previously investigated, while the latter evidenced from a literature survey a high variability. The two oils were quite different: A. santolina oil showed mainly 1,8‐cineole, camphor, 4‐terpineol and trans‐carveol, while A. biebersteinii oil contained cis‐ascaridole, p‐cymene, carvenone oxide and camphor among its principal constituents. This is the second report of carvenone oxide from a natural source. Copyright © 2002 John Wiley & Sons, Ltd.
Composition and antimicrobial activity of the essential oils of Helichrysum kraussii Sch. Bip. and H. rugulosum Less. from South Africa
Authors: Bougatsos C. , Meyer J. J. M. , Magiatis P. , Vagias C. , Chinou I. B.
Published: January 2003

The chemical compositions of the essential oils obtained from the aerial parts of Helichrysum kraussii and H. rugulosum were analysed by GC and GC–MS. From the 39 identified constituents, representing 85.1% and 92.9% of the two oils, respectively, β‐caryophyllene (30.7%, 12.6%), α‐pinene (12.1%,−), β‐caryophyllene oxide (−, 8.8%), cis‐α‐bisabolene (−, 22.7%), β‐bisabolene (−, 4.7%) and α‐humulene (9.8%, −) were found to be the main components. Furthermore, the oils were tested against six Gram‐positive or ‐negative bacteria and three pathogenic fungi. It was found that oils from both plants, and especially that of H. rugulosum, exhibited interesting antibacterial activity. Copyright © 2002 John Wiley & Sons, Ltd.
Reduction of cis‐ and trans‐1,2‐epithio‐p‐menth‐8‐ene: preparation of new fragrant terpenoid thiols
Authors: Candela Karine , Fellous Roland , Joulain Daniel , Faure Robert
Published: January 2003

The synthesis of 2‐mercapto‐p‐menth‐8‐ene (3) and 1‐mercapto‐p‐menth‐8‐ene (4) are described, starting, respectively, from thioepoxydation of (+)‐trans‐limonene 1,2‐epoxide (1a) and (+)‐cis‐limonene 1,2‐epoxide (1b) via hydride reduction of episulphides 2a and 2b. Structural determination of these sulphur‐containing terpenoids was achieved by one‐ and two‐dimensional NMR spectroscopy. The odours of these two new monoterpene thiols were described, respectively, as reminescent of grapefruit juice and as being typically alliaceous. Copyright © 2002 John Wiley & Sons, Ltd.
A simple method for compressible multiphase mixtures and interfaces
Authors: Andrianov Nikolai , Saurel Richard , Warnecke Gerald
Published: January 2003

We develop a Godunov‐type scheme for a non‐conservative, unconditional hyperbolic multiphase model. It involves a set of seven partial differential equations and has the ability to solve interface problems between pure materials as well as compressible multiphase mixtures with two velocities and non‐equilibrium thermodynamics (two pressures, two temperatures, two densities, etc.).Its numerical resolution poses several difficulties. The model possesses a large number of acoustic and convective waves (seven waves) and it is not easy to upwind all these waves accurately and simply. Also, the system is non‐conservative, and the numerical approximations of the corresponding terms need to be provided. In this paper, we focus on a method, based on a characteristic decomposition which solves these problems in a simple way and with good accuracy. The robustness, accuracy and versatility of the method is clearly demonstrated on several test problems with exact solutions. Copyright © 2003 John Wiley & Sons, Ltd.
Positivity‐preserving, flux‐limited finite‐difference and finite‐element methods for reactive transport
Authors: MacKinnon Robert J. , Carey Graham F.
Published: January 2003

A new class of positivity‐preserving, flux‐limited finite‐difference and Petrov–Galerkin (PG) finite‐element methods are devised for reactive transport problems.The methods are similar to classical TVD flux‐limited schemes with the main difference being that the flux‐limiter constraint is designed to preserve positivity for problems involving diffusion and reaction. In the finite‐element formulation, we also consider the effect of numerical quadrature in the lumped and consistent mass matrix forms on the positivity‐preserving property. Analysis of the latter scheme shows that positivity‐preserving solutions of the resulting difference equations can only be guaranteed if the flux‐limited scheme is both implicit and satisfies an additional lower‐bound condition on time‐step size. We show that this condition also applies to standard Galerkin linear finite‐element approximations to the linear diffusion equation. Numerical experiments are provided to demonstrate the behavior of the methods and confirm the theoretical conditions on time‐step size, mesh spacing, and flux limiting for transport problems with and without nonlinear reaction. Copyright © 2003 John Wiley & Sons, Ltd.
Temporal specific patterns of semaphorin gene expression in rat brain after kainic acid‐induced status epilepticus
Authors: Barnes Gregory , Puranam Ram S. , Luo Yuling , McNamara James O.
Published: January 2003

Mossy fiber sprouting and other forms of synaptic reorganization may form the basis for a recurrent excitatory network in epileptic foci. Four major classes of axon guidance molecules—the ephrins, netrins, slits, and semaphorins—provide targeting information to outgrowing axons along predetermined pathways during development. These molecules may also play a role in synaptic reorganization in the adult brain and thereby promote epileptogenesis. We studied semaphorin gene expression, as assessed by in situ hybridization, using riboprobes generated from rat cDNA in an adult model of synaptic reorganization, kainic acid (KA)‐induced status epilepticus (SE). Within the first week after KA‐induced SE, semaphorin 3C, a class III semaphorin, mRNA content is decreased in the CA1 area of the hippocampus and is increased in the upper layers of cerebral cortex. Another class III semaphorin, semaphorin 3F, is also decreased in CA1 and CA3 of hippocampus within the first week after KA‐SE. These changes in gene expression are principally confined to neurons. By contrast, there was little change in the semaphorin 4C mRNA content of CA1 neurons at this time. No changes in expression of semaphorin 3A and 4C genes were detected 28 days after KA‐induced SE. Regulation of semaphorin gene expression after KA‐induced SE suggests that neurons may regulate the expression of axonal guidance molecules and thereby contribute to synaptic reorganization after injury of the mature brain. The anatomic locale of the altered semaphorin gene expression may serve as a marker for specific networks undergoing synaptic reorganization in the epileptic brain. Hippocampus 2003;13:1–20. © 2003 Wiley‐Liss, Inc.
The role of NMDA glutamate receptors, PKA, MAPK, and CAMKII in the hippocampus in extinction of conditioned fear
Authors: Szapiro German , Vianna Monica R.M. , McGaugh James L. , Medina Jorge H. , Izquierdo Ivan
Published: January 2003

Pavlovian conditioning involves the association of initially neutral conditioned stimuli (CS) with unconditioned stimuli (US) that elicit a response. In contextual fear conditioning in rodents, the CS is the context of a training apparatus and the US is a foot shock. Retrieval of memory of the training is tested by presenting the CS alone. But a retrieval test also initiates extinction of the conditioned response. That is, presentation of the CS alone results in new learning, i.e., the CS no longer predicts the US. Here we report that extinction is triggered by two hippocampal signaling pathways underlying retrieval (the cAMP‐dependent protein kinase and the mitogen‐activated protein kinase pathways) and two other mechanisms that become activated at the same time and are not necessary for retrieval (N‐methyl‐D‐aspartate glutamatergic receptors and the calcium/calmodulin‐dependent protein kinase II signaling pathway). Thus, the molecular mechanisms underlying acquisition and/or consolidation of the memory for extinction are similar to those described for the acquisition and/or consolidation of the original contextual fear. Hippocampus 2003;13:53–58. © 2003 Wiley‐Liss, Inc.
Effect of halothane on type 2 immobility‐related hippocampal theta field activity and theta‐on/theta‐off cell discharges
Authors: Bland Brian H. , Bland Cheryl E. , Colom Luis V. , Roth Sheldon H. , DeClerk Shandra , Dypvik Audny , Bird Jenn , Deliyannides Alexandra
Published: January 2003

Rats were studied in acute and chronic (freely moving) recording conditions during exposure to different levels of the volatile anesthetic halothane, in order to assess effects on hippocampal theta field activity in the chronic condition and on theta‐related cellular discharges in the acute condition. Previous work has shown that the generation of hippocampal type 2 theta depends on the coactivation of cholinergic and GABAergic inputs from the medial septum. Based on these data and recent findings that halothane acts on interneuron GABAA receptors, we predicted that exposure of rats to subanesthetic levels would result in the induction of type 2 theta field activity. In the chronic condition, exposure to subanesthetic levels of halothane (0.5–1.0 vol %) was found to induce theta field activity during periods of immobility (type 2 theta) with a mean increase of 39% in amplitude (mV) compared to control levels during movement. The total percentage of signal power (V2) associated with peak theta frequencies (80% compared to control levels of 47%) was also increased by halothane. Over the whole range of administered halothane concentrations, theta field frequency progressively declined from a mean peak frequency of 6.5 ± 0.8 Hz at 0.5 vol % halothane to a mean peak frequency of 4.0 ± 1.8 Hz at 2.0 vol % halothane. Subsequent administration of a muscarinic cholinergic antagonist, atropine sulfate, selectively abolished all type 2 immobility‐related theta field activity, while type 1 movement‐related theta was still intact. At anesthetic levels (1.5–2.0 vol %) in acute experiments, hippocampal field activity spontaneously cycled between theta and large‐amplitude irregular activity. Analysis of depth profiles in four experiments revealed they were identical to those previously described for rats under urethane anesthesia conditions. In addition, the discharge properties of 31 theta‐related cells, classified as tonic and phasic theta‐on and tonic and phasic theta‐off cells, did not differ significantly from those described previously in rats anesthetized with urethane. These data provide further support for an involvement of GABAA receptors in the generation of hippocampal theta. Hippocampus 2003;13:38–47. © 2003 Wiley‐Liss, Inc.
Type II glucocorticoid receptor immunoreactivity in the mossy cells of the rat and the mouse hippocampus
Authors: Patel Anisha , Bulloch Karen
Published: January 2003

Hippocampal principal neurons, granule and pyramidal cells, are known to express type II glucocorticoid receptors (GR) and it is believed that glucocorticoids (GC) mediate at least some of their effects through GR. Under conditions of severe stress and trauma, these principal cells are vulnerable to damage and this mechanism may be exacerbated by GR. The mossy cell, an excitatory dentate gyrus neuron, is also damaged following trauma, with over 50% reported loss in rats after kainate‐induced seizures. However, it has not been determined if GC play any role in protecting or exacerbating damage to this important hippocampal cell type. In the present study, we have undertaken an evaluation of the presence of GR in mossy cells of the rat and mouse utilizing an immunocytochemical double‐labeling technique. To identify mossy cells in the rat, we utilized an antibody to the glutamate receptor subunit 2/3 (GluR2/3). In addition to GluR2/3 antibodies, in the mouse, an antibody to the calcium‐binding protein, calretinin (CR), to identify mossy cells was also employed. Our results show that GR immunoreactivity (IR) was colocalized with GluR2/3‐IR in approximately 90% of the rat and the mouse mossy cells. In addition, GR‐IR was identified in the CR‐IR mossy cells in the mouse hippocampus, whereas the CR‐IR interneurons of rat and mouse were negative for GR‐IR. The presence of GR on mossy cells may indicate the ability of GC to mediate cellular activity of these cells. Hippocampus 2003;13:59–66. © 2003 Wiley‐Liss, Inc.
Theta‐ and movement velocity‐related firing of hippocampal neurons is disrupted by lesions centered on the perirhinal cortex
Authors: Muir Gary M. , Bilkey David K.
Published: January 2003

The hippocampus is critically involved in spatial memory and navigation. It has previously been proposed that, as part of this process, the hippocampus might have access to self‐motion information. The possibility that some of this information may originate from the perirhinal cortex, a region involved in high‐order multimodal processing, was tested in the present study by recording the responses of hippocampal complex‐spike (place cells) and theta cells (putative interneurons) to movement velocity and to the movement‐related theta rhythm EEG while rats with bilateral ibotenic acid lesions centered on the perirhinal cortex (n = 5), or control surgeries (n = 5), foraged in a rectangular environment. Perirhinal cortex lesions altered several characteristics of place and theta cell firing. First, the proportion of theta cells recorded was significantly lower in perirhinal lesion animals (8/39 units) compared to controls (22/53 units). Second, the firing of place cells recorded from lesion animals was phase‐shifted so as to occur significantly earlier during the theta rhythm cycle than in place cells from controls (mean difference = 48.73°). Third, the firing rates of a significantly lower proportion of place cells from lesion animals were modulated by the movement velocity of the animal compared to place cells from controls. These results indicate that the perirhinal cortex contributes to the responses of hippocampal CA1 place cells by providing information about self‐movement and by controlling the timing of firing of these cells. This information may normally be utilized by the hippocampus during spatial memory and navigation processes. Hippocampus 2003;13:93–108. © 2003 Wiley‐Liss, Inc.
Reward value invariant place responses and reward site associated activity in hippocampal neurons of behaving rats
Authors: Tabuchi E. , Mulder A.B. , Wiener S.I.
Published: January 2003

To investigate the involvement of the hippocampal‐accumbens system in goal‐oriented displacement behaviors, hippocampal neuronal activity was recorded in rats learning and recalling new distributions of different volumes of liquid reward among the arms of a plus maze. Each arm had a reward box containing a water trough and identical visual cues that could be illuminated independently. As the water‐restricted rat successively visited the respective boxes, it received 7, 5, and 3 drops of water, and then 1 drop, provided at 1‐s intervals. (Reward distributions were reassigned daily and mid‐session.) In the training phase, reward boxes were lit individually. In the recall phase, the lamps on all arms were lit and then turned off as the rat visited the boxes in order of descending value. Neuronal firing rates were analyzed for changes related to reward value or to shifts between learning and recall phases. The principal finding is that place responses remained unchanged after these manipulations and that these neurons showed no evidence of explicit coding of reward value. In addition, two other types of responses appeared while the rat was stationary at the reward boxes awaiting multiple rewards. These were observed primarily in neurons within the dentate gyrus, but also in CA1. Position‐selective reward site responses were regular at 20–60 impulses per second, while position‐independent discharges bursted irregularly at about 5 impulses per second. Such responses could explain controversial reports of reward dependence in hippocampal neurons. The higher incidence of the latter responses in the temporal (“ventral”) hippocampus is consistent with the distinctive anatomical and functional properties of this subregion. Hippocampus 2003;13:117–132. © 2003 Wiley‐Liss, Inc.