bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of binary aqueous‐organic solvents on the reaction of phenacyl bromide with nitrobenzoic acid(s) in the presence of triethylamine
Authors: Nallu M. , Subramanian M. , Vembu N. , Akber Hussain A.
Published: May 2004

Second‐order rate constants (k2) of the reaction between phenacyl bromide and equimolar mixture of nitrobenzoic acid(s)–triethylamine have been determined in dimethylformamide (DMF)/acetonitrile (ACN)/acetone and aqueous mixtures of these solvents by conductometric method at 30°C. The rates of nitrobenzoic acids are found to be in the order: 4‐NO2 > 3‐NO2 > 3,5‐(NO2)2. Changes in the rate just by the addition of water (1% (v/v)) into organic component is rationalized. Decrease in the values of k2 on increasing water content in organic solvent is explained on the basis of preferential solvation phenomenon. Single and dual regression analysis using the various solvent parameters of aqueous mixtures (ET(30), Z, π*, β, α, and Y) resulted in π* and α as the best parameters to explain solvation of nitrobenzoates. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 401–409, 2004
Study of the base‐catalyzed nitrito–nitro isomerization reaction ([(NH3)5Co‐ONO]2+ → [(NH3)5Co‐NO2]2+) in mixed solvents
Authors: Jiménez R. , Villar M. , Cueto M. , Grueso E. , Illanes J. , Cobrian J. I. , Cantón F. , Villa I. , Sánchez J. M. , Maza S. , Muñoz J. M. , Muñoz C. , Prado‐Gotor R.
Published: May 2004

The base‐catalyzed linkage isomerization of [Co(NH3)5‐ONO]2+ to the nitro [(NH3)5Co‐NO2]2+ form is studied in various isodielectric water–cosolvent mixtures (methanol, ethanol, tert‐butyl alcohol, and 2‐propanol) at 298 K. In all cases, except for methanol–water mixtures, the rate constants increase with the proportion of cosolvent. Medium effects have been rationalized by using a multiparameter regression of solvent parameters which rationalizes the results obtained, including water–methanol mixtures. The experimental data, k2, in fact, are well correlated through the following equation:

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where A, B, and Gexc are the acidity parameter, the basicity parameter, and the excess Gibbs free energy of the mixture, respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 410–415, 2004
Kinetics and mechanism of oxidation of a ternary complex involving dipicolinatochromium(III) and DL‐aspartic acid by N‐bromosuccinimide
Authors: Ewais Hassan A. , Ahmed Ahmed E. , Abdel‐Khalek Ahmed A.
Published: May 2004

The kinetics of oxidation of [CrIII(Dpc)(Asp)(H2O)2] (Dpc = dipicolinic acid and Asp = DL‐aspartic acid) by N‐bromosuccinimide (NBS) in aqueous solution have been found to obey the equation:

equation image

where k2 is the rate constant for the electron transfer process, K1 is the equilibrium constant for deprotonation of [CrIII(Dpc)(Asp)(H2O)2], K2 and K3 are the pre‐equilibrium formation constants of precursor complexes [CrIII(Dpc)(Asp)(H2O)(NBS)] and [CrIII(Dpc)(Asp)(H2O)(OH)(NBS)]−. Values of k2 = 4.85 × 10−2 s−1, K1 = 1.85 × 10−7 mol dm−3, and K2 = 78.2 mol−1 dm3 have been obtained at 30°C and I = 0.1 mol dm−3. The experimental rate law is consistent with a mechanism in which the deprotonated [CrIII(Dpc)(Asp)(H2O)(OH)]− is considered to be the most reactive species compared to its conjugate acid. It is assumed that electron transfer takes place via an inner‐sphere mechanism. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 394–400, 2004
Binding of the Bioactive Component Daphnetin to Human Serum Albumin Demonstrated Using Tryptophan Fluorescence Quenching
Authors: Liu Jiaqin , Tian Jianniao , Li Ying , Yao Xiaojun , Hu Zhide , Chen Xingguo
Published: May 2004

Summary: Daphnetin (7,8‐dihydroxycoumarin), one of the major bioactive components isolated from Daphne koreane Nakai, has been used in traditional Chinese medicine for the treatment of coagulation disorders. It is also a chelator, an antioxidant and a protein kinase inhibitor. In this paper, a combination of intrinsic fluorescence, Fourier transform infrared (FT‐IR) spectroscopy and circular dichroic (CD) spectroscopy has been used to characterize the binding between daphnetin and human serum albumin (HSA) under physiological conditions with drug concentrations of 6.7 × 10−6 − 2.3 × 10−5 mol · L−1, and a HSA concentration of 1.5 × 10−6 mol · L−1. Changes in the CD spectra and FT‐IR spectra were observed upon ligand binding, and the degree of tryptophan fluorescence quenching did change significantly in the complexes. These data have proved the change in protein secondary structure accompanying ligand binding. The change in tryptophan fluorescence intensity was used to determine the binding constants. The thermodynamic parameters, the enthalpy change (ΔH) and the entropy change (ΔS) were calculated to be −12.45 kJ · mol−1and 52.48 J · mol−1 · K‐1 according to the van't Hoff equation, which indicated that hydrophobic and electrostatic interactions played the main role in the binding of daphnetin to HSA, in accordance with the results of calculations performed on a Silicon Graphics Ocatane2 workstation. In addition, the binding distance between daphnetin and HSA was obtained (4.02 nm) based on the Förster energy transfer theory.

The binding mode between daphnetin and HSA.

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The binding mode between daphnetin and HSA.
Butyl Acrylate/Vinyl Acetate Miniemulsion Polymerization: A Study on Compartmentalization
Authors: Jovanovic Renata , Dubé Marc A.
Published: May 2004

Summary: A series of butyl acrylate/vinyl acetate miniemulsions were investigated. Two procedures were used to prepare the miniemulsions: one in which the monomers were mixed together, sonicated, and polymerized, and the other, in which the individual monomers were sonicated prior to mixing and then polymerized. Kinetic and final properties of the obtained polymers were compared. The two procedures offer interesting insights into monomer compartmentalization in miniemulsions. In most cases, there were no differences in monomer conversion, copolymer composition, particle size or average molecular weights between the two procedures. ATR‐FTIR spectroscopy was used to assess possible monomer transfer. The spectra obtained from each polymerization procedure were compared and no evidence of compartmentalization was found. Both procedures yielded similar spectra indicating that monomer transfer between particles occurred. In addition, adhesive properties of the obtained latexes were investigated. Due to the fact that relatively large amounts of CTA were used, adhesive performance was poor.

Comparison of the spectra of miniemulsion polymerizations obtained by two different procedures (BA/VAc 85/15 wt/wt).

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Comparison of the spectra of miniemulsion polymerizations obtained by two different procedures (BA/VAc 85/15 wt/wt).
Determination of the Kinetic Constants of the Telomerization of 10‐Undecenol with Alkyl Hydrogenphosphonate
Authors: Senhaji Omar , Robin Jean Jacques , Achoubi Mohammed , Boutevin Bernard
Published: May 2004

Summary: The telomerization of 10‐undecenol with alkyl hydrogenphosphonate was studied in order to synthesize telomers of different molecular weights. The study showed that telomers from 10‐undecenol could be obtained despite the fact that the double bond has a low reactivity. The kinetic constant Kp2/KTe was determined to be 7 × 10−4 l · mol−1 · s−1 at 135 °C and the transfer constant CT was 0.057. These values are normal for a low activity telogen such as hydrogenphosphonate and for slightly reactive monomers like 10‐undecenol.

SEC chromatogram of telomers obtained in the reaction of 10‐undecenol addition.

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SEC chromatogram of telomers obtained in the reaction of 10‐undecenol addition.
Primary Amine‐Initiated Polymerizations of Alanine‐NCA and Sarcosine‐NCA
Authors: Kricheldorf Hans R. , von Lossow Colin , Schwarz Gert
Published: May 2004

Summary: Sarcosine‐N‐carboxyanhydride (Sar‐NCA), L‐alanine‐NCA and D,L‐alanine‐NCA were polymerized with benzylamine as initiator in three different solvents: dichloromethane (CH2Cl2), 1,4‐dioxane and dimethylformamide (DMF). The isolated polyaminoacids were characterized by 1H NMR spectroscopy and MALDI‐TOF mass spectrometry. High conversions and degrees of polymerization $\overline {DP}$s close to the monomer‐initiator (M/I) ratios were found for all polypeptides. For polysarcosine which was soluble under the given reaction conditions a narrow monomodal frequency distribution was found. In contrast, a broad frequency distribution was observed, when L‐alanine NCA was polymerized in dioxane and DMF. These results were attributed to a partial precipitation of oligopeptides in the β‐sheet structure, which reduces the reactivity of endgroups for steric reasons. The polymerizations of D,L‐alanine‐NCA showed features in between the extremes of Sar‐NCA and L‐Ala‐NCA.

Schematic illustration of the secondary structures formed in a primary amine initiated polymerization of L‐Ala‐NCA.

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Schematic illustration of the secondary structures formed in a primary amine initiated polymerization of L‐Ala‐NCA.
Scaling of Yield Stress of Polythiophene Suspensions under Electric Field
Authors: Chotpattananont Datchanee , Sirivat Anuvat , Jamieson Alexander M.
Published: May 2004

Summary: Electrorheological properties in steady shear of perchloric acid doped poly(3‐thiopheneacetic acid), PTAA, particles in silicone oil were investigated to determine the effects of field strength, particle concentration, doping degree (conductivity values), operating temperature and nonionic surfactant. The PTAA/silicone oil suspensions show the typical ER response of Bingham flow behavior upon the application of electric field. The yield stress increases with electric field strength, E, and particle volume fraction, ϕ, according to a scaling law of the form, τy ∝ Eα · ϕγ. The scaling exponent α approaches the value of 2, predicted by the polarization model, as the particle volume fraction decreases and when the doping level of the particles decreases. The scaling exponent γ tends to unity, as predicted by the polarization model, when the electric field strength is low. The yield stress under electric field initially increases with temperature up to 25 °C, and then levels off. At electric fields above of 1.5 kV/mm, the yield stress increases significantly by up to 50% on addition of small amounts of a nonionic surfactant.

Effect of switching the applied electric field on the viscosity of a 20 wt.‐% highly HClO4 doped polythiophene suspensions during stress sweep test.

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Effect of switching the applied electric field on the viscosity of a 20 wt.‐% highly HClO4 doped polythiophene suspensions during stress sweep test.
Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion‐Based Pressure‐Sensitive Adhesives
Authors: Jovanovic Renata , McKenna Timothy F. , Dubé Marc A.
Published: May 2004

Summary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi‐batch mode. The objective was to generate polymers with properties favoring their application as pressure‐sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (Tg), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three‐component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. Tg, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration.

Shear strength contour lines over the investigated region.

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Shear strength contour lines over the investigated region.
Location of the Catalytic Site in Supported Atom Transfer Radical Polymerization
Authors: Faucher Santiago , Zhu Shiping
Published: May 2004

Summary: A supported and highly recyclable catalyst complex, CuBr/HMTETA physically adsorbed to silica gel, was used for the ATRP of MMA to elucidate the nature of the catalytic site. In some polymerizations, the reaction solutions were filtered and compared with their unfiltered references for catalytic activity. The filtered systems had high catalyst activity indicating the presence of active catalyst sites in solution. These sites are the primary catalytic contributors.

Conversion versus time and first‐order kinetic plot for the control and filtered polymerizations.

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Conversion versus time and first‐order kinetic plot for the control and filtered polymerizations.
Free‐Radical Termination Kinetics Studied Using a Novel SP‐PLP‐ESR Technique
Authors: Buback Michael , Egorov Mark , Junkers Tanja , Panchenko Elena
Published: May 2004

Summary: A novel method for measuring termination rate coefficients, kt, in free‐radical polymerization is presented. A single laser pulse is used to instantaneously produce photoinitiator‐derived radicals. During subsequent polymerization, radical concentration is monitored by time‐resolved electron spin resonance (ESR) spectroscopy. The size of the free radicals, which exhibits a narrow distribution increases linearly with time t, which allows the chain‐length dependence of kt to be deduced. The method will be illustrated using dodecyl methacrylate polymerization as an example.

Two straight lines provide a very satisfactory representation of the chain‐length dependence of kt over the entire chain‐length region (cR = radical concentration).

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Two straight lines provide a very satisfactory representation of the chain‐length dependence of kt over the entire chain‐length region (cR = radical concentration).
Temperature‐sensitive poly(vinyl methyl ether) hydrogel beads
Authors: Theiss Daniel , Schmidt Thomas , Arndt Karl‐Friedrich
Published: May 2004

Temperature‐sensitive hydrogel beads were prepared by radiation crosslinking of poly(vinyl methyl ether) PVME spheres wrapped in Ca‐alginate. The obtained gel beads have diameters in the sub‐millimeter or millimeter range (depending on the PVME concentration). They were characterized by sol‐gel analysis, swelling measurements, and differential scanning calorimetry.

The gel content g increases with increasing radiation dose D. The swelling degree Qv decreases with increasing PVME concentration cp and increasing D. In comparison to PVME bulkgels the phase‐transition temperature of the synthesized PVME gel beads is a little decreased.
Separation of polyelectrolyte chain dynamics and dynamics of counterion attachment by EPR spectroscopy
Authors: Hinderberger Dariush , Spiess Hans Wolfgang , Jeschke Gunnar
Published: May 2004

Rotational dynamics and local enrichment of counterions close to polyelectrolyte chains were studied by EPR spectroscopy in solvents of different viscosity. The results confirm previous findings (D. Hinderberger, G. Jeschke, and H. W. Spiess, Macromolecules 2002, 35, 9698) that electrostatic attachment of counterions to the chains is dynamic with lifetimes of contact ion pairs shorter than 1 ns. While in low‐viscosity solvents linewidths for a dianionic nitroxide probe and their dependence on polyelectrolyte concentration are dominated by the gradient of local concentration in the vicinity of the chain, they are more strongly influenced by changes in rotational dynamics in a glycerol/water mixture. The slowdown of dynamics at higher viscosity strongly depends on polyelectrolyte concentration, suggesting that the lifetime of the attached state increases. The linewidths of trianionic triarylmethyl probes and of the center line of the nitroxide probes are dominated by local counterion enrichment both at low and high viscosity. Comparison of these linewidths and of the extent to which the lineshapes are non‐Lorentzian indicates build‐up of larger concentration gradients at higher viscosity.
The stability of polyelectrolyte complex systems of poly(diallydimethyl‐ammonium chloride) with different polyanions
Authors: Mende Mandy , Buchhammer Heide‐Marie , Schwarz Simona , Petzold Gudrun , Jaeger Werner
Published: May 2004

Polyelectrolyte complex (PEC) dispersions formed by fast ionic exchange reaction between polyelectrolytes (PELs) bearing oppositely charged groups have been characterized by turbidity and dynamic light scattering. The stability of the formed PEC dispersions, the average hydrodynamic particle size dh and the also determined polydispersity index PI of the PEC particles were of special interest. In this study poly(diallyldimethylammonium chloride) (PD) of different molar mass is used in combination with copolymers of maleic acid and α‐methylstyrene (P(MS‐αMeSty)) as well as propene (P(MS‐P)), with a copolymer of acrylamide and sodium acrylate (PR2540UD) and poly(styrene‐p‐sodium sulfonate) (NaPSS).

A strong dependence of the PEC stability on the molar charge ratio n−/n+, the mixing conditions and especially on the chemical structures of the used polyanions was found. If the employed polyanion (PA) have a π‐system (phenyl‐) in the polymer chain a higher tendency to instability results. The average hydrodynamic particle sizes dh and the polydispersity indices PIs of the formed stable PEC dispersions determined by dynamic light scattering were strongly influenced by the mixing conditions of the PECs. If we are able to prepare stable complexes where the isoelectric point is exceeded during complex formation which is possible for PD/P(MS‐P) and PD/PR2540UD systems a distinct increase of dh and decrease of PI is observed. The polymer concentration CP and the chain length L of the used PELs have a minor effect on dh and PI.
Aggregation phenomena in polyelectrolyte multilayers made from polyelectrolytes bearing bulky functional, hydrophobic fragments
Authors: Laschewsky André , Mallwitz Frank , Baussard Jean‐François , Cochin Didier , Fischer Peter , Habib Jiwan Jean‐Louis , Wischerhoff Erik
Published: May 2004

The functionalization of polyelectrolyte multilayers often implies the use of bulky functional fragments, attached to a standard polyelectrolyte matrix. Despite of the high density of non‐charged, often hydrophobic substituents, regular film growth by sequential adsorption proceeds easily when an appropriate polyelectrolyte counter ion is chosen. However, the functional fragments may cluster or aggregate. This complication is particularly evident when using chromophores and fluorophores as bulky pendant groups. Attention has to be paid to this phenomenon for the design of functional polyelectrolyte films, as aggregation may modify crucially the properties. The use of charged spacer groups does not necessarily suppress the aggregation of functional side groups. Still, clustering and aggregation depend on the detailed system employed, and are not obligatory. In the case of cationic poly(acrylamide)s labeled with naphthalene and pyrene fluorophores, for instance, the polymers form intramolecular hydrophobic associates in solution, as indicated by strong excimer formation. But the polymers can undergo a conformational rearrangement upon adsorption so that they are decoiled in the adsorbed films. Analogous observations are made for polyanions bearing mesogenic biphenyls fragments. In contrast, polycations functionalized with the dye coumarin 343 show little aggregation in solution, but a marked aggregation in the ESA films.
Sporadic case of dentatorubral pallidoluysian atrophy with no CAG repeat expansion and no intranuclear inclusions
Authors: Munhoz Renato P. , Bergeron Catherine , Lang Anthony E.
Published: May 2004

We present a patient with a 14‐year course beginning at the age of 44 years with hemidystonia followed by generalized choreoathetosis, behavioral, and oculomotor disturbances. Family history and genetic testing were unrevealing. Neuropathological findings were identical to genetic dentatorubral pallidoluysian (DRPLA) except for the lack of intranuclear inclusions. © 2003 Movement Disorder Society
Neuronal globus pallidus activity in patients with generalised dystonia
Authors: Merello Marcelo , Cerquetti Daniel , Cammarota Angel , Tenca Eduardo , Artes Carlos , Antico Julio , Leiguarda Ramon
Published: May 2004

We studied 516 globus pallidus neurons in dystonic patients. The firing rate was analysed. We classified the burst activity into tonic, burst, and pause patterns. Mean ± SD firing rates and tonicity score for internal globus pallidus (GPi) and external globus pallidus (GPe) were 54.6 ± 28.6; 58.01 ± 39.1 and 1.18 ± 0.55; 0.95 ± 0.43, respectively. Differences in percentage appearance of tonic, burst, or paused neurons were not statistically significant for GPi versus GPe. GPi firing features in dystonic patients were closely similar to those of GPe. This could suggest that the abnormally patterned output from GPi would not result from increased differential inhibitory/excitatory input arising from the direct/indirect pathway but rather be transmitted from GPe, striatum, or either centromedian nucleus. © 2003 Movement Disorder Society
Dystonia as a presenting sign of spinocerebellar ataxia type 1
Authors: Wu Yih‐Ru , Lee‐Chen Guey‐Jen , Lang Anthony E. , Chen Chiung‐Mei , Lin Hsuan‐Yuan , Chen Sien‐Tsong
Published: May 2004

We report on a 39‐year‐old man who presented initially with marked blepharospasm, oromandibular dystonia and retrocollis and one year later developed mild ataxia. Our findings suggest that dystonia can be a disabling presenting sign of SCA1 and support the clinical heterogeneity of SCA1, highlighting the importance of considering this entity in patients combining dystonia and cerebellar ataxia. © 2004 Movement Disorder Society
SCA2 presenting as levodopa‐responsive parkinsonism in a young patient from the United Kingdom: A case report
Authors: Wilkins Alastair , Brown Jerry M. , Barker Roger A.
Published: May 2004

We report on a young woman from the United Kingdom with L‐dopa–responsive parkinsonism with a trinucleotide repeat expansion in her spinocerebellar ataxia 2 (SCA2) gene. The case further extends the phenotype of SCA2 and emphasizes the importance of SCA screening in young‐onset parkinsonism, irrespective of ethnic origin. © 2004 Movement Disorder Society
Multifrequency microwave tomography between boreholes
Authors: Tarnus R. , Dérobert X. , Pichot Ch.
Published: May 2004

In order to detect 2D underground heterogeneity between boreholes, a microwave‐imaging technique is presented along with numerical and experimental comparisons. The proposed technique is based on a spectral diffraction tomography technique which enables heterogeneities from the polarized currents induced by the incident field of a simple dipole antenna to be located. Numerical results in both a transverse‐magnetic (TM) and transverse‐electric (TE) modes are compared with a reduced‐scale physical model composed of a water tank with some immersed cylindrical heterogeneities. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 4–8, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20190
Distortion of a square pulse wave with finite rise time in edge‐coupled microstrip lines on LTCC substrate
Authors: Kang Kai , Li Le‐Wei , Yin Wen‐Yan
Published: May 2004

The distortion of a square pulse wave with a finite rise time in edge‐coupled microstrip lines is investigated. These microstrip lines are assumed to be fabricated on a single‐layer low‐temperature co‐fired ceramic (LTCC) substrate which has excellent high‐frequency performance. Parametric studies are performed to show the effects of different physical parameters of the strips and LTCC substrate on the distortion of the propagated pulse waveform, where the effects of the substrate as well as ohmic losses on the pulse‐wave propagation are treated appropriately. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 8–13, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20191
Periodic bandpass filter with near‐ideal filter response based on Sagnac loop interferometer
Authors: Wei Li , Mao Qinghe , Lit John W. Y.
Published: May 2004

In this paper, an analytical analysis is made on a periodic bandpass filter formed by a two‐cavity etalon incorporated into a Sagnac loop interferometer. The general optimum conditions for a quasi‐flat‐top spectrum and a ripple‐free group‐delay response are derived. Our results show that by properly choosing the reflectance of the mirrors, the filter can be designed with a quasi‐flat‐top spectral response that is also free from group‐delay ripples. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 17–21, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20194
A novel design technique for control of defect frequencies of an electromagnetic bandgap (EBG) superstrate for dual‐band directivity enhancement
Authors: Lee Young Ju , Yeo Junho , Ko Kyoung Dae , Mittra Raj , Lee Yoonjae , Park Wee Sang
Published: May 2004

In this paper, we propose a novel design technique to control the defect frequencies of an electromagnetic bandgap (EBG) superstrate with the objective of enhancing the directivity of a patch antenna at two frequencies. Two different defect configurations, the first of which is introduced by the ground plane of the antenna while the other is produced by a row of rods with dissimilar dielectric constants in the EBG structure, are examined in detail in order to achieve dual‐band operation. We begin by investigating the EBG structure and varying several of its parameters to determine the locations of the bandgap and defect frequencies, as well as their controllability. Finally, the promising designs for the EBG superstrates, which provide enhanced directivities for the EBG antenna, are evaluated to validate the proposed design scheme. It is demonstrated that the directivity of the antenna with a 12 × 3 EBG superstrate increases to 18 and 18.5 dBi, respectively, at the two design frequency bands, as compared to that of the antenna alone (maximum 10 dBi) without the superstrate. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 25–31, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20196
Characteristics analysis of a multiband wide‐aperture‐coupled microstrip antenna
Authors: Jang Yong‐Woong , Shin H. S. , Lee C. A.
Published: May 2004

In this paper, we study a rectangular microstripline‐fed wide aperture‐coupled microstrip antenna backed by a ground plane. In this case, a rectangular microstrip feed line and a wide slot lead to good impedance matching in a wide‐frequency band. The 2.0 VSWR impedance bandwidth of the lower mode is 0.29 GHz (0.83–1.12 GHz, 32.2% at the center frequency of 0.9 GHz) and covers the cellular and GSM bands; the band of the upper mode reaches 0.93 GHz (1.69–2.62 GHz, 46.5% at the center frequency of 2.0 GHz) and covers the PCS, IMT‐2000, WLL, and UMTS bands, in respectively. The results obtained for VSWR exhibit multiband characteristic. The peak antenna gain is 7.6 and 10.5 dBi for the lower (Cellular, GSM) and upper (DCS, PCS, IMT‐2000, WLL) operations, respectively. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 37–40, 2004; Published online Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20199
MicroPhotonic reconfigurable RF signal processor
Authors: Alameh Kamal E. , Zheng Rong , Ahderom Selam , Raisi Mehrdad , Eshraghian Kamran
Published: May 2004

In this paper, we present a novel MicroPhotonic RF signal processor that integrates fibre collimators, opto‐VLSI processors, and a WDM combiner within an optical substrate to control various fibre Bragg grating cavities, thus achieving adaptive RF filtering. Results show that a reconfigurable 64‐cavity MicroPhotonic RF processor can generate arbitrary RF responses. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 54–58, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20205
A parallel analysis of the scattering from inhomogeneous dielectric bodies by the volume integral equation and the precorrected‐FFT algorithm
Authors: Wang Yao‐Jun , Nie Xiao‐Chun , Li Le‐Wei , Li Er‐Ping
Published: May 2004

In this paper, a parallel implementation of the precorrected fast Fourier transform (FFT) algorithm is presented to efficiently solve the volume‐integral equation for scattering from inhomogeneous dielectric objects. Several examples are given to demonstrate the efficiency and correctness of the message‐passing interface (MPI)‐based parallelization algorithm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 77–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20214
Stepped‐impedance resonator bandpass diplexers with over‐coupling structures
Authors: Weng Min‐Hung , Pan Chi‐Shiang , Shao Chih‐Wei , Wu Hung‐Wei
Published: May 2004

A stepped‐impedance resonator (SIR) bandpass diplexer using over‐coupling structures and tapped input/output (I/O) has been presented. The advantages of this construction are simple design and suppression of spurious response at twice the center frequency (2f0). The tapped I/O creates an extra transmission zero in each filter of the duplexer in order to improve stopband attenuation. The diplexer, designed at 0.9 and 1.8 GHz, is suitable for mobile communication and is easily fabricated in the packing surface. Experimental results of the designed duplexer are in good agreement with the theoretical predictions and simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 79–82, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20215
A mitochondrial DNA mutation in a patient with an extensive family history of Duchenne muscular dystrophy
Authors: Wong Lee‐Jun C. , Wladyka Christopher , Mardach‐Verdon Rebecca
Published: May 2004

One challenge in the molecular diagnosis of mitochondrial DNA (mtDNA) disorders is detection of a low percentage of mutant heteroplasmy. We report a patient who had a delayed molecular diagnosis of mitochondrial encephalopathy, lactic acidosis, and stroke‐like episodes (MELAS) syndrome due to the complication of an extensive family history of another neuromuscular disease, Duchenne muscular dystrophy, and the failure to detect a low proportion of mutant A3243G mtDNA with a polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP)/ethidium bromide detection method. Using an improved, more sensitive allele‐specific oligonucleotide (ASO) radioactive dot‐blot hybridization method, a low degree of A3243G heteroplasmy was detected in several tissues from this patient. This case underscores the importance of a sensitive mutation detection method and the need for a search for mtDNA mutations if the patient's clinical symptoms suggest a mitochondrial disorder despite the family background of another neuromuscular disease. Muscle Nerve 30: 118–122, 2004
Treadmill training–induced adaptations in muscle phenotype in persons with incomplete spinal cord injury
Authors: Stewart Brian G. , Tarnopolsky Mark A. , Hicks Audrey L. , McCartney Neil , Mahoney Douglas J. , Staron Robert S. , Phillips Stuart M.
Published: May 2004

Body weight–supported treadmill (BWST) training has been shown to improve ambulatory capacity in persons with a spinal cord injury (SCI); however, the effect that BWST training has on skeletal muscle phenotype is unknown. We aimed to determine whether 6 months (three sessions/week) of BWST training in neurologically stable persons with a traumatic spinal cord injury (ASIA C) alters skeletal muscle phenotype, ambulatory capacity, and blood lipid profile. Externally supported body weight decreased, and walking velocity and duration of the training sessions increased (all P < 0.05) as a result of training. Muscle biopsies revealed increases in the mean muscle‐fiber area of type I and IIa fibers. Training induced a reduction in type IIax/IIx fibers, as well as a decrease in IIX myosin heavy chain, and an increase in type IIa fibers. Maximal citrate synthase and 3‐hydroxy‐acyl‐CoA dehydrogenase activity also increased following training. BWST training brought about reductions in plasma total (−11%) and low‐density lipoprotein (−13%) cholesterol. We conclude that, in patients with a spinal cord injury, BWST training is able to induce an increase in muscle fiber size and bring about increases in muscle oxidative capacity. In addition, BWST training can bring about improvements in ambulatory capacity and antiatherogenic changes in blood lipid profile. Muscle Nerve 30: 61–68, 2004
Primal–dual Newton interior point methods in shape and topology optimization
Authors: Hoppe R. H. W. , Petrova S. I.
Published: May 2004

We consider non‐linear minimization problems with both equality and inequality constraints on the state variables and design parameters as they typically arise in shape and topology optimization. In particular, the state variables are subject to a partial differential equation or systems of partial differential equations describing the operating behaviour of the device or system to be optimized. For the numerical solution of the appropriately discretized problems we emphasize the use of all‐in‐one approaches where the numerical solution of the discretized state equations is an integral part of the optimization routine. Such an approach is given by primal–dual Newton interior point methods which we present combined with a suitable steplength selection and a watchdog strategy for convergence monitoring. As applications, we deal with the topology optimization of electric drives for high power electromotors and with the shape optimization of biotemplated microcellular biomorphic ceramics based on homogenization modelling. Copyright © 2004 John Wiley & Sons, Ltd.
Interior‐point method for non‐linear non‐convex optimization
Authors: Lukšan Ladislav , Matonoha Ctirad , Vlček Jan
Published: May 2004

In this paper, we propose an algorithm for solving non‐linear non‐convex programming problems, which is based on the interior point approach. Main theoretical results concern direction determination and step‐length selection. We split inequality constraints into active and inactive to overcome problems with stability. Inactive constraints are eliminated directly while active constraints are used to define symmetric indefinite linear system. Inexact solution of this system is obtained iteratively using indefinitely preconditioned conjugate gradient method. Theorems confirming efficiency of several indefinite preconditioners are proved. Furthermore, new merit function is defined, which includes effect of possible regularization. This regularization can be used to overcome problems with near linear dependence of active constraints. The algorithm was implemented in the interactive system for universal functional optimization UFO. Results of extensive numerical experiments are reported. Copyright © 2004 John Wiley & Sons, Ltd.
Scalable FETI with optimal dual penalty for a variational inequality
Authors: Dostál Zdeněk , Horák David
Published: May 2004

The FETI method with the natural coarse grid is combined with the penalty method to develop an efficient solver for elliptic variational inequalities. A proof is given that a prescribed bound on the norm of feasibility of solution may be achieved with a value of the penalty parameter that does not depend on the discretization parameter and that an approximate solution with the prescribed bound on violation of the Karush–Kuhn–Tucker conditions may be found in a number of steps that does not depend on the discretization parameter. Results of numerical experiments with parallel solution of a model problem discretized by up to more than eight million of nodal variables are in agreement with the theory and demonstrate numerically both optimality of the penalty and scalability of the algorithm presented. Copyright © 2004 John Wiley & Sons, Ltd.
Fourier two‐level analysis for discontinuous Galerkin discretization with linear elements
Authors: Hemker P. W. , Hoffmann W. , van Raalte M. H.
Published: May 2004

In this paper we study the convergence of a multigrid method for the solution of a linear second‐order elliptic equation, discretized by discontinuous Galerkin (DG) methods, and we give a detailed analysis of the convergence for different block‐relaxation strategies. To complement an earlier paper where higher‐order methods were studied, here we restrict ourselves to methods using piecewise linear approximations. It is well known that these methods are unstable if no additional interior penalty is applied.

As for the higher‐order methods, we find that point‐wise block‐relaxations give much better results than the classical cell‐wise relaxations. Both for the Baumann–Oden and for the symmetric DG method, with a sufficient interior penalty, the block‐relaxation methods studied (Jacobi, Gauss–Seidel and symmetric Gauss–Seidel) all make excellent smoothing procedures in a classical multigrid setting. Independent of the mesh size, simple MG cycles give convergence factors 0.2–0.4 per iteration sweep for the different discretizations studied. Copyright © 2004 John Wiley & Sons, Ltd.
A preconditioner for the equations of linear elasticity discretized by the PEERS element
Authors: Klawonn Axel , Starke Gerhard
Published: May 2004

Block diagonal preconditioners for the mixed finite element formulation of planar linear elasticity using the PEERS element by Arnold et al. (Jpn. J. Ind. Appl. Math. 1984; 1:347–367) are studied. This mixed finite element approach treats the stress tensor, the displacement field and the anti‐symmetric part of the strain tensor as independent variables. The resulting linear system of equations is symmetric but indefinite due to its saddle‐point structure. The validity of an inf–sup condition with respect to the H (div,Ω)2 × L2(Ω)2 × L2(Ω) norm suggests an optimal block diagonal preconditioner for the MINRES iterative method. Equivalent preconditioning of the blocks associated with stresses, displacements and anti‐symmetric part leads to convergence rates of the block diagonal preconditioner uniformly bounded with respect to the refinement level and the Lamé parameter λ which determines the compressibility of the material. While the L2(Ω) blocks can simply be preconditioned by its diagonal parts, a multilevel technique is employed for the H(div,Ω) block. The smoothing iteration for this technique is based on the discrete Helmholtz decomposition of the underlying finite element space similar to the approach by Hiptmair (Electron. Trans. Numer. Anal. 1997; 6:133–152). Numerical tests for a benchmark problem of planar linear elasticity illustrate the efficiency of this preconditioner, in particular, its level independence and uniform convergence in the incompressible limit. Copyright © 2004 John Wiley & Sons, Ltd.
Eigenvalue analysis of the SIMPLE preconditioning for incompressible flow
Authors: Li C. , Vuik C.
Published: May 2004

In this paper, an eigenvalue analysis of the SIMPLE preconditioning for incompressible flow is presented. Some formulations have been set up to characterize the spectrum of the preconditioned matrix. This leads to a generalized eigenvalue problem. The generalized eigenvalue problem is investigated. Some eigenvalue bounds and the estimation for the spectral condition number in the symmetric case are given. Numerical tests are reported to illustrate the theoretical discussions. Copyright © 2004 John Wiley & Sons, Ltd.
Truncated Newton type solver with application to grid untangling problem
Authors: Garanzha V. , Kaporin I. , Konshin I.
Published: May 2004

A practical stopping criterion for inner conjugate gradient iterations in the truncated Newton type unconstrained optimization method is proposed. Numerical results are given for a family of large‐scale geometrical optimization problems. The comparison with the standard residual norm stopping rule demonstrates an essential gain in efficiency. Copyright © 2004 John Wiley & Sons, Ltd.
Generalizations to discrete and analytical Crouzeix–Velte decompositions
Authors: Stoyan G. , Strauber G. , Baran Á.
Published: May 2004

In this paper, the Crouzeix–Velte decomposition is generalized with respect to boundary conditions and boundary value problems, moreover, in the discrete case, the gap between the first‐order staggered grid approximation and the high‐order Scott–Vogelius elements (which was the only finite element family until now for which such a decomposition was known) is filled by proving that the (second‐order) Fortin–Soulie elements also admit such a decomposition—which is of advantage when iteratively solving the corresponding boundary value problems (Stokes, linear elasticity) and for long‐term calculations. Copyright © 2004 John Wiley & Sons, Ltd.
On the computation of the multivariate structured total least squares estimator
Authors: Markovsky Ivan , Huffel Sabine Van , Kukush Alexander
Published: May 2004

A multivariate structured total least squares problem is considered, in which the extended data matrix is partitioned into blocks and each of the blocks is Toeplitz/Hankel structured, unstructured, or noise free. Two types of numerical solution methods for this problem are proposed: (i) standard local optimization methods in combination with efficient evaluation of the cost function and its first derivative, and (ii) an iterative procedure proposed originally for the element‐wise weighted total least squares problem. The computational efficiency of the proposed methods is compared with this of alternative methods. Copyright © 2004 John Wiley & Sons, Ltd.
Structured weighted low rank approximation
Authors: Schuermans M. , Lemmerling P. , Van Huffel S.
Published: May 2004

This paper extends the weighted low rank approximation (WLRA) approach towards linearly structured matrices. In the case of Hankel matrices an equivalent unconstrained optimization problem is derived and an algorithm for solving it is proposed. The correctness of the latter algorithm is verified on a benchmark problem. Finally the statistical accuracy and numerical efficiency of the proposed algorithm is compared with that of STLNB, a previously proposed algorithm for solving Hankel WLRA problems. Copyright © 2004 John Wiley & Sons, Ltd.
Variational principles in grid generation and geometric modelling: theoretical justifications and open problems
Authors: Garanzha V. A.
Published: May 2004

The paper is devoted to analysis of variational principles for construction of mappings with prescribed properties in grid generation and geometric modelling. An attempt is made to formulate general requirements which should be satisfied by the variational principle. Theoretical justification is considered along with review of unsolved problems and fundamental mathematical difficulties. Copyright © 2004 John Wiley & Sons, Ltd.
Generalized polynomial chaos and random oscillators
Authors: Lucor D. , Su C.‐H. , Karniadakis G. E.
Published: May 2004

We present a new approach to obtain solutions for general random oscillators using a broad class of polynomial chaos expansions, which are more efficient than the classical Wiener–Hermite expansions. The approach is general but here we present results for linear oscillators only with random forcing or random coefficients. In this context, we are able to obtain relatively sharp error estimates in the representation of the stochastic input as well as the solution. We have also performed computational comparisons with Monte Carlo simulations which show that the new approach can be orders of magnitude faster, especially for compact distributions. Copyright © 2004 John Wiley & Sons, Ltd.
Anisotropic mesh adaption by metric‐driven optimization
Authors: Bottasso Carlo L.
Published: May 2004

We describe a Gauss–Seidel algorithm for optimizing a three‐dimensional unstructured grid so as to conform to a given metric. The objective function for the optimization process is based on the maximum value of an elemental residual measuring the distance of any simplex in the grid to the local target metric. We analyse different possible choices for the objective function, and we highlight their relative merits and deficiencies. Alternative strategies for conducting the optimization are compared and contrasted in terms of resulting grid quality and computational costs. Numerical simulations are used for demonstrating the features of the proposed methodology, and for studying some of its characteristics. Copyright © 2004 John Wiley & Sons, Ltd.
Adaptive embedded unstructured grid methods
Authors: Löhner Rainald , Baum Joseph D. , Mestreau Eric , Sharov Dmitri , Charman Charles , Pelessone Daniele
Published: May 2004

A simple embedded domain method for node‐based unstructured grid solvers is presented. The key modification of the original, edge‐based solver is to remove all geometry‐parameters (essentially the normals) belonging to edges cut by embedded surface faces. Several techniques to improve the treatment of boundary points close to the immersed surfaces are explored. Alternatively, higher‐order boundary conditions are achieved by duplicating crossed edges and their endpoints. Adaptive mesh refinement based on proximity to or the curvature of the embedded CSD surfaces is used to enhance the accuracy of the solution. User‐defined or automatic deactivation for the regions inside immersed solid bodies is employed to avoid unnecessary work. Several examples are included that show the viability of this approach for inviscid and viscous, compressible and incompressible, steady and unsteady flows, as well as coupled fluid–structure problems. Copyright © 2004 John Wiley & Sons, Ltd.
Prediction of stress–strain relation using cone indentation: effect of friction
Authors: DiCarlo Anthony , Yang Henry T. Y. , Chandrasekar Srinivasan
Published: May 2004

Atkins and Tabor's approach (J. Mech. Phys. Solids 1965; 13: 149) for predicting uniaxial stress–strain relation of metals from cone indentation tests has been studied using numerical (finite element) simulation of cone indentation. Two indentation parameters, namely representative strain and constraint factor, which are central to the prediction approach, have been estimated using the simulation for cone indenters of different apical angles. The effect of specimen–indenter interface friction on these parameters has been characterized. It is shown that uncertainty in our knowledge of this friction condition has an important bearing on the prediction of the stress–strain curve. However, a good estimate of the stress–strain curve can be obtained by making reasonable assumptions about the nature of the friction at the specimen–indenter interface. The simulation results are found to agree well with those reported in the experimental study of Atkins and Tabor, when a coefficient of friction value typical for the specimen–indenter interface is used. Copyright © 2004 John Wiley & Sons, Ltd.
Geometry independence for a meshing engine for 2D manifolds
Authors: Simpson R. B.
Published: May 2004

The ‘meshing engine’ of the title is a software component that generates unstructured triangular meshes of two‐dimensional triangles for a variety of contexts. The mesh generation is based on the well‐known technique of iterative Delaunay refinement, for which the Euclidean metric is intrinsic. The meshing engine is to be connected to applications specific host programs which can use a geometry that is different from the intrinsic geometry of the mesh, i.e. locally, the Euclidean plane. An application may require a surface mesh for embedding in a three‐dimensional geometry, or it might use a Riemannian metric to specify a required anisotropy in the mesh, or both.

We focus on how the meshing engine can be designed to be independent of the embedding geometry of a host program but conveniently linked to it. A crucial tool for these goals is the use of an appropriate local co‐ordinate system for the triangles as seen by the meshing engine. We refer to it as the longest edge co‐ordinate system. Our reference to ‘linking’ the meshing engine and host system is both general and technical in the sense that the example meshes provided in the paper have all been generated by the same object code of a prototype of such a meshing engine linked to host programs defining different embedding geometries. Copyright © 2004 John Wiley & Sons, Ltd.