bluuebunny/crossref_metadata_2025 huggingface dataset:
The structural instabilities of ferronematic based on liquid crystal with low negative magnetic susceptibility
Authors: Kopčanský P. , Potočová I. , Koneracká M. , Timko M. , Jadzyn J. , Czechowski G. , A. M. G. Jansen
Published: March 2003

The Fredericksz transition in ferronematic based on liquid crystal ZLI 1695 (extremely low anisotropy of diamagnetic susceptibility χa = –3 × 10–8) was studied. The decrease of the Fredericksz transition critical magnetic fields BFN with increasing magnetic particles volume concentration was found. The surface density of anchoring energy of liquid crystal molecules on magnetic particles surfaces was experimentally estimated falling into the range (0.3–5.2) × 10–6. These estimations confirm the soft‐anchoring considered within the Burylov and Raikher's theory.
Neutron diffraction study of crystal and magnetic structure of (La0.7Ca0.3)1–xMn1+xO3 (x = 0, 0.1) systems
Authors: Bażela W. , Dyakonov V. , Pashchenko V. , Penc B. , Szymczak H. , Hernandez‐Velasco J. H. , Szytuła A.
Published: March 2003

The evolution of crystal and magnetic structures of (La0.7Ca0.3)1–xMn1+xO3 (x = 0, 0.1) as a function of temperature was determined. For both compounds the crystal structure is orthorhombic (space group Pnma) with the following sequence of the lattice constants: b/√2< a < c for x = 0 and c < a < b/√2 for x = 0.1. The para‐ferromagnetic transitions at Tc = 265 K for x = 0 and 260 K for x = 0.1 are accompanied by structural distortions. For x = 0 the ferromagnetic ordering of the Mn moments equal to 3.57(10)μB and parallel to the b‐axis is stable in the temperature range from 1.5 K to Tc. For x = 0.1 at 1.5 K the magnetic order has two components: the ferromagnetic one with the magnetic moment μ = 3.46(12)μB parallel to the b‐axis and the antiferromagnetic one with μ = 0.66(23)μB parallel to the c‐axis. This order is stable up to Tt = 45 K. Then the ferromagnetic order only exists up to Tc = 260 K. These results correlate well with macroscopic magnetic data. At Tc and Tt the anomalies in the thermal dependence of Mn–O bond lengths and Mn–O–Mn bond angles are observed.
Two‐step mean‐field renormalization group results for the large square Ising clusters
Authors: Kamieniarz G. , Musiał G. , Tomecka D.
Published: March 2003

A transfer matrix approach has been worked out to test the predictions of the improved three‐step mean‐field renormalization group approach to square Ising clusters with linear size up to L = 11. Performing the asymptotic analysis, the convergence of the finite‐size critical couplings and the critical exponents towards the exact values is shown.
Ferromagnetism in diluted magnetic semiconductors at low carrier density
Authors: Dugaev V. K. , Litvinov V. I. , Barnaś J. , Slobodskyy A. H. , Dobrowolski W. , Vieira M.
Published: March 2003

We present a general approach to the problem of a ferromagnetic phase transition in diluted magnetic semiconductors with free carriers. The Curie temperature of ferromagnetic transition is calculated in the mean field approximation. The approach allows to analyze the effects of magnetic fluctuations and disorder on the Curie temperature. We also propose a new mechanism of exchange interaction between magnetic impurities at vanishing concentration of free carriers.
Marginal synchronization of spin‐wave amplitudes in a model for chaos in parallel pumping
Authors: Krawiecki A. , Sukiennicki A.
Published: March 2003

A model for chaos in high‐power parallel pumping is considered, based on nonlinear interactions of two groups of parametric spin wave pairs. If spin wave pairs within each group have identical damping, frequencies, and interaction coefficients with other pairs, all of them are excited in the chaotic regime and marginal synchronization of amplitudes of spin wave pairs belonging to the same group is observed. In the case of small differences between spin wave pairs only a low number of pairs from each group is excited. On the basis of this result, possible explanation of the origin of low dimensional chaos usually observed experimentally in parallel pumping is proposed.
Spin waves in La2CuO4: band structure and correlation effects
Authors: Peres N. M. R. , Araújo M. A. N.
Published: March 2003

We calculate the antiferromagnetic spin wave dispersion in the half‐filled (electronic density n = 1) Hubbard model for a two‐dimensional square lattice, using the random phase approximation (RPA) in a broken symmetry (spin density wave) ground state. Our results for the spin wave dispersion, ω (q), are compared with high‐resolution inelastic neutron scattering performed on La2CuO4. The effects of different band structures and different values of the on‐site Coulomb interaction on the spin wave spectrum are studied. Particular attention is put on the high energy dispersion values ω (π/2, π/2) and ω (0, π).
Properties of the UFe5Sn compound: electronic structureand X‐ray photoemission
Authors: Szajek A. , Malinowski W. L.
Published: March 2003

The UFe5Sn compound crystallizes in the orthorhombic CeCu5Au‐type structure having the Pnma space group with iron atoms located in four inequivalent sites. The electronic structure UFe5Sn compound has been studied using spin‐polarized tight binding version of the linear muffin‐tin orbital method in the atomic sphere approximation (TB LMTO ASA). The calculations showed that the magnetic moments on uranium atoms are antiparallel to the moments formed on Fe atoms, whose values depend on local environments. The X‐ray photoemission spectra were calculated.
Frontier orbital and density functional study of the variation of the hard–soft behavior of monoborane (BH3) and boron trifluoride (BF3) as a function of angles of reorganization from planar (D3h) to pyramidal (C3v) shape
Authors: Ghosh Dulal C. , Jana Jibanananda
Published: March 2003

In chemical response the BH3 and BF3 molecules undergo the physical process of planar (D3h) to pyramidal (C3v) reorganization in shape as the condition precedent to the event of chemical reaction under the requirement of symmetry. A frontier orbital and density functional study of the variation of the stability of electronic structures and chemical reactivity of associated with the physical process of D3h to C3v geometry reorganization has been performed. The theoretical parameters viz. eigenvalues of HOMO and LUMO, the HOMO and LUMO energy gap, the global hardness and global softness, the chemical potential, the condensed Fukui function, and local softness of B atom, the reaction site, have been computed over a wide range of ∠XBX angles. The nature of variation in the intrinsic chemical reactivity, global and local, of the molecules associated with their geometry reorganization during the chemical event of charge transfer interaction involving their frontier molecular orbitals has been quantitatively explored. The hardness profiles as a function of reaction coordinates are consistent with the principle of maximum hardness (PMH). Results demonstrate that the hardness and softness are not a static and invariable property of molecules but a dynamic and variable function of molecular structure. The hardness parameters and the HOMO–LUMO gap of the molecules are so modified with the distortion of molecular geometry that, after a certain stage of molecular deformation, the profiles of such parameters of the molecules intersect and cross each other, signifying that the relative order of the intrinsic hardness of their equilibrium geometry is reversed. The intrinsically hard molecule BF3 becomes softer than the intrinsically soft molecule BH3 as a consequence of structural distortion. The increase in chemical reactivity computed in terms of density functional parameters are transparent and justified in terms of the profiles of the eigenvalues of the frontier orbitals. The profiles of chemical potential reveal the inherent difference in the tendency of backdonation from two molecules. The computed values of Fukui functions and local softness parameters of the B atom site demonstrate that the concept of local softness can be exploited for a theoretical analysis and understanding of the characteristic chemical events of the molecules under consideration. The profiles of the Fukui functions and local softness parameters of the two molecules seem to reflect and reveal their intrinsic difference in the tendency of receiving donation in the LUMO (electrophilicity) and that of backdonation from the HOMO (nucleophilicity) and the inherent difference of overall reactivity of the two molecules by a simultaneous operation of two opposing processes of charge transfer. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Application of the electron localization function to radical systems
Authors: Melin Junia , Fuentealba P.
Published: March 2003

An application of the topological electron localization function (ELF) analysis to free radical systems is presented. A separation of the ELF function into its α‐spin and β‐spin contributions has been performed. Methyl and phenyl radicals, ortho‐, meta‐, and para‐benzyne biradicals, and their corresponding radical anions have been chosen with the aim to validate the new ELFα and ELFβ proposed functions. The results show that the ELF separation yields complementary information about the localization of the unpaired electron. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Coupled harmonic oscillator systems: Improved algebraic decoupling approach
Authors: Burrows B. L. , Cohen M. , Feldmann Tova
Published: March 2003

We present a novel explicit decoupling procedure that leads to exact solutions of the Schrödinger equation forNharmonic oscillators in the presence of general bilinear perturbing potentials. This generalizes previous work, which was restricted toorthogonaltransformations with conditions imposed on the perturbing terms. It is shown that the formalism is sufficiently general to embrace bothstationary‐stateandresonance‐stateproblems and, in particular, we include exact model calculations of a free electron interacting with a lattice and a discussion of an application to an ideal ion trap. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Conformational and electronic study ofN‐phenylalkyl‐3,4‐dichloromaleimides: Ab initio and DFT study
Authors: Zamora Miguel A. , Masman Marcelo F. , Bombasaro José A. , Freile Mónica L. , Filho Valdir Cechinel , López Silvia N. , Zacchino Susana A. , Enriz Ricardo D.
Published: March 2003

A conformational and electronic study onN‐phenylalkyl‐3,4‐dichloromaleimides, a new series of antifungal compounds, was carried out. In this study ab initio [RHF/3‐21G and RHF/6‐31G(d)] and density functional theory (B3LYP/6‐31G(d)) calculations were performed. The effect of solvent (water) was taken into account by performing calculations with the isodensity polarizable continuum model method. The electronic study of the compounds was carried out using molecular electrostatic potentials. The presence of two symmetrical aromatic systems reduces notably the conformational possibilities of these maleimides. The results permit the recognition of the minimal structural requirements for the production of the antifungal response; a 3,4‐dichloroimido ring and a benzene ring appear to be indispensable. Also, theoretical calculations suggest that the optimum interatomic distance between these moieties is about 3.5–5.0 Å. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Ionic matrices for matrix‐assisted laser desorption/ionization time‐of‐flight detection of DNA oligomers
Authors: Carda‐Broch Samuel , Berthod Alain , Armstrong Daniel W.
Published: March 2003

Salts with low melting points, also termed room‐temperature ionic liquids, can be used as matrices in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF). They have great vacuum stability, and can dissolve polar and apolar solutes including carbohydrates, biological oligomers and proteins. The ionic liquids give much more homogeneous sample solutions compared with solid matrices. We demonstrate the usefulness of using ionic matrices to determine the molecular weight of DNA oligomers by direct TOF mass spectrometric analysis. Three oligonucleotides were tested, (d(pT)10, d(pC)11, and d(pC)12), with several ionic matrices synthesized from different bases associated to two acids (3‐hydroxypicolinic acid and 2,5‐dihydroxybenzoic acid). The results obtained show that the best ionic matrices enhance the ion peak intensity of the oligonucleotides with respect to conventional molecular matrices under our experimental conditions. In one case, an ionic matrix provided a signal‐to‐noise ratio ten times higher than the corresponding molecular matrix. Several of the tested ionic matrices were liquids. However, all working ionic matrices were solids. Copyright © 2003 John Wiley & Sons, Ltd.
Liquid chromatography with electrospray ion‐trap mass spectrometry for the determination of anatoxins in cyanobacteria and drinking water
Authors: Furey Ambrose , Crowley Janet , Lehane Mary , James Kevin J.
Published: March 2003

Anatoxin‐a (AN) and homoanatoxin‐a (HMAN) are potent neurotoxins produced by a number of cyanobacterial species. A new, sensitive liquid chromatography/multiple tandem mass spectrometry (LC/MSn) method has been developed for the determination of these neurotoxins. The LC system was coupled, via an electrospray ionisation (ESI) source, to an ion‐trap mass spectrometer in positive ion mode. The [M+H]+ ions at m/z 166 (anatoxin‐a) and m/z 180 (homoanatoxin‐a) were used as the precursor ions for multiple MS experiments. MS2MS4 spectra displayed major fragment ions at m/z 149 (AN), 163 (HMAN), assigned to [MNH3+H]+; m/z 131 (AN), 145 (HMAN), assigned to [MNH3H2O+H]+, and m/z 91 [C7H7]+. Although the chromatographic separation of these neurotoxins is problematic, reversed‐phase LC, using a C18 Luna column, proved successful. Calibration data for anatoxin‐a using spiked water samples (10 mL) in LC/MSn modes were: LC/MS (25–1000 μg/L), r2 = 0.998; LC/MS2 (5–1000(μg/L), r2 = 0.9993; LC/MS3 (2.5–1000 μg/L), r2 = 0.9997. Reproducibility data (% RSD, N = 3) for each LC/MSn mode ranged between 2.0 at 500 μg/L and 7.0 at 10 μg/L. The detection limit (S/N = 3) for AN was better than 0.03 ng (on‐column) for LC/MS3 which corresponded to 0.6 μg/L. Copyright © 2003 John Wiley & Sons, Ltd.
Differentiation of isomeric sulfur heterocycles by electron ionization mass spectrometry: 1,4‐dithiins, 1,4‐dithiafulvenes and their analogues tetrathianaphthalenes, tetrathiafulvalenes and tetrathiapentalenes
Authors: Garín Javier , Orduna Jesús , Royo José María , Quéré Anne‐Marie Le , Müller Harald
Published: March 2003

The electron ionization mass spectra of the title compounds have been studied along with the product ion spectra of their metastable or collisionally activated molecular ions. The relative abundances of ions in the spectra allow unambiguous isomer differentiation. Isomerization of the molecular ions was observed in the metastable ion spectra of tetrathianaphthalenes and tetrathiafulvalenes. This isomerization reaction parallels the electrochemical or base‐induced isomerization observed in solution. The studied tetrathiapentalene derivative does not rearrange to the corresponding tetrathiafulvalene or tetrathianaphthalene isomers. Copyright © 2003 John Wiley & Sons, Ltd.
Enantioselective trace analysis of amphetamine in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry
Authors: Leis Hans‐Jörg , Rechberger Gerald N. , Fauler Günter , Windischhofer Werner
Published: March 2003

A method for the quantitative enantioselective analysis of amphetamine in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry (GC/NICI‐MS) is presented. Five‐fold deuterated analogues of both enantiomers were used as internal standard. Plasma sample preparation was performed by a rapid liquid–liquid extraction using n‐hexane. Derivatization with (S)‐(−)‐N‐(heptafluorobutyryl)prolyl chloride was accomplished directly in the n‐hexane extract to avoid loss of amphetamine during sample concentration. The method was validated in the expected concentration range of 0.006 for a pharmacokinetic study. Calibration curves were linear within a range 0.006–50 ng/mL plasma. Precision and accuracy were acceptable over the entire calibration range. Baseline separation of the enantiomers was easily achieved on a 15‐m nonchiral apolar column. The method is simple and robust, and has been applied to the batch analysis of amphetamine enantiomers. Copyright © 2003 John Wiley & Sons, Ltd.
SWI/SNF chromatin remodelling complex and retroviral gene silencing
Authors: Iba Hideo , Mizutani Taketoshi , Ito Taiji
Published: March 2003

Because of the unique infectious cycle of retroviruses which involves the integration of the retroviral genome into the host chromosome, many cellular chromosomal proteins are used by the virus to maintain its gene expression. At the same time, cellular mechanisms for the surveillance and exclusion of non‐self expression by such intragenomic parasites operate as an important host defence system in the cellular nuclei. Retroviruses have strategies for escaping from host defence systems, such as by maintaining or reactivating viral expression in specific host cell types. Understanding such epigenetical regulation would be essential for progress in retroviral virology. In this review, we emphasise the importance of the chromatin remodelling factor SWI/SNF complex as one of the key players in epigenetic regulation of host and viral gene expression. An understanding of these mechanisms will surely lead to new ideas on the pathogenicity of this virus, on the latent infection observed in many other viruses, and further forward the design of unique retroviral vectors for long‐term transgene expression, providing strong tools for human gene therapy and regenerative medicine. Copyright © 2003 John Wiley & Sons, Ltd.
Dynamics and Coupling Actuation of Elastic Underactuated Manipulators
Authors: Zhao Tie Shi , Dai Jian S.
Published: March 2003

This paper investigates the constraint and coupling characteristics of underactuated manipulators by proposing an elastic model of the manipulator and examining the second order constraint equation. A dynamic model and a coupling constraint equation are developed from a Jacobian matrix and the Newton‐Euler formulation. The inertia matrix and the Christoffel tensor are analyzed and decomposed into the part concerning actuated joints and the part concerning passive joints. This decomposition is further extended to the dynamic coupling equation and generates an actuation coupling matrix and a dynamic coupling tensor. Two new dynamic coupling indices are hence identified. One is related to an actuation input and the other is related to centrifugal and Coriolis forces. The former reveals the dynamic coupling between the input and the acceleration of passive joints and gives the actuation effect on the passive joints. The latter reveals the dynamic coupling between the centrifugal and Coriolis forces and the acceleration of passive joints and provides the centrifugal and Coriolis effect on the acceleration of passive joints. The study reveals the coupling characteristics of an underactuated manipulator. This is then demonstrated in a three‐link manipulator and extended to a serial manipulator with passive prismatic joint. © 2003 Wiley Periodicals, Inc.
AgentSalon: Facilitating face‐to‐face knowledge exchange by conversations of personal agents
Authors: Sumi Yasuyuki , Mase Kenji
Published: March 2003

This paper introduces a system called AgentSalon, intended to promote the acquaintance and dialogue of people meeting face to face at a place where people share an interest, a hobby, and a situation, such as a museum, the street, a school, an office, or a conference event. AgentSalon has a large display, which can be shared by multiple users. The personal agents belonging to each user are displayed as character animations, which start the conversation automatically. The personal agent usually operates on the portable guide system called PalmGuide, and provides a personal guide service, while managing the personal interests of the user and the behavior history. When the user connects PalmGuide to AgentSalon by infrared, the personal agent is transferred to AgentSalon together with the personal data. Then the agents start the conversation automatically. The content of the conversation is the interests and the behavior history of the users. The agents exchange views based on experience or make recommendations representing the user. The users listening to the conversation find common topics of interest, as if their minds are connected. Thus, a more valuable conversation should be realized, as if absorbed into the conversation of the agents. In this study, AgentSalon is implemented as a service to the participants of an actual conference. The principles of operation and evaluation are presented. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(4): 21–33, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10117
Automatic heart wall contour extraction from MR images using active contour models: Initial contour setting based on principal component analysis
Authors: Yuasa Mayumi , Watanabe Mutsumi , Nishiura Masahide , Yamaguchi Kojiro , Kondo Takeshi , Anno Hirofumi , Muto Kouichi
Published: March 2003

For the problem of initial value setting, which will become a problem in contour extraction using active contour models, we propose in this paper a scheme for effectively inputting the initial values by facilitating user input with statistical models of the contour shapes of the heart wall. We also describe a scheme for extracting and tracking the left ventricular contour of the heart from the MR images by the edge detection method adapted to low‐contrast images. Moreover, we will show the validity of the proposed scheme by comparison with the manually traced results of physicians. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(4): 72–82, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1202
Signal Processing Architectures for Chemical Sensing Microsystems
Authors: Wilson D. M. , Roppel T.
Published: March 2003

This paper reviews several levels of signal processing and associated architectures for chemical sensing microsystems that use either arrays of optical or of physical sensors. Many chemical sensors, because of their interaction and vulnerability to the environment, have been eliminated from inclusion in sensing systems that require high precision and accuracy. This discussion evaluates parametric vs. nonparametric techniques and linear vs. nonlinear signal processing approaches for addressing chemical classification problems using imperfect sensing technologies. Hardware implementations of signal processing and biologically inspired signal processing are also reviewed. Future research into the development of more accurate chemical classification systems demands the customization of current approaches, so that underlying principles of chemical sensors and associated interfering influences do not overburden the computational space, thereby allowing higher accuracy rates.
CMOS Single Chip Gas Detection Systems — Part I
Authors: Hagleitner C. , Hierlemann A. , Brand O. , Baltes H.
Published: March 2003

The current trend to control indoor air‐quality and to monitor environmental pollution has created a strong demand for miniaturized and inexpensive gas sensors for volatile organic compounds (VOCs). Gas sensor arrays based on industrial CMOS‐processes combined with post‐CMOS micromachining (CMOS MEMS) are a promising approach to low‐cost sensor devices. In this article, the state of research of CMOS‐based gas sensor systems is reviewed, and a platform technology is described, which provides the possibility of monolithically integrating several different transducers on a single chip. A design environment, batch‐fabrication processes, and fast testing procedures were developed to realize an example single‐chip gas detection system. The chip includes the transducers, their biasing circuitry, reference elements, a digital interface, and a temperature sensor. The three polymer‐based transducers and their interface electronics will be detailed in the second part of this article [1].
MEMS in RF Filter Applications: Thin‐film Bulk Acoustic Wave Technology
Authors: Aigner R.
Published: March 2003

RF‐MEMS filters will replace conventional filters in mobile communication as they offer better performance at lower cost. Requirements and key performance parameters for filters in next‐generation mobile applications are reviewed in detail. The fundamentals of RF‐MEMS filters — and in particular thin‐film bulk acoustic wave (BAW) filters — are summarized in a comprehensive form. The state‐of‐the‐art in BAW filters and future trends are presented. Supplementary information covers manufacturing and commercialization issues.
Real‐time lock‐in energy loss imaging with a novel high‐speed image processing CCD video camera
Authors: Nishikata Kentarou , Shimazaki Yusuke , Kimura Yoshihide , Takai Yoshizo , Ikuta Takashi , Yumen Hideji
Published: March 2003

We have developed a high‐speed image processing CCD video camera for real‐time energy‐loss imaging using a conventional electron microscope with an energy‐loss imaging facility. As an initial demonstration of real‐time lock‐in energy‐loss imaging, a background‐subtracted energy‐loss image was observed by attaching the high‐speed image processing CCD video camera to an analytical electron microscope equipped with a floating‐type energy‐loss imaging analyser. Copyright © 2003 John Wiley & Sons, Ltd.
Surface modification of PVC endotracheal tubes by oxygen glow discharge to reduce bacterial adhesion
Authors: Balazs D. J. , Triandafillu K. , Chevolot Y. , Aronsson B.‐O. , Harms H. , Descouts P. , Mathieu H. J.
Published: March 2003

A d.c. oxygen glow discharge was used to modify medical‐grade poly(vinyl chloride) (PVC) to study how surface chemistry and hydrophilicity influence Pseudomonas aeruginosa adhesion. The effects of plasma exposure time on the resulting surface, including chemical composition, wettability and roughness, were assessed using x‐ray photoelectron spectroscopy, contact angle measurements and atomic force microscopy analysis. A significant alteration in the hydrophilicity of the native PVC surface was observed after oxygen glow discharge treatment. The water contact angle decreased from ∼80° to 8–20°, with a weak dependence of the exposure time used. The change in surface wettability resulted from the incorporation of oxygenated functional groups, including esters, ketones and acids, as indicated by XPS analysis. The amount of oxygen incorporation was shown to be essentially independent of plasma exposure time. However, prolonged plasma exposure resulted in increased surface roughness. Bacterial adhesion efficiency was evaluated for PVC modified by 120 s of plasma exposure, because this exposure time was determined to yield the maximum decrease in contact angle. Oxygen plasma treatment of native PVC was found to yield a 70% reduction in bacterial adhesion for the four strains of Pseudomonas aeruginosa tested. Copyright © 2003 John Wiley & Sons, Ltd.
ToF‐SIMS and XPS surface characterization of novel perfluoropolyether–urethane ionomers from aqueous dispersions
Authors: Canteri R. , Speranza G. , Anderle M. , Turri S. , Radice S.
Published: March 2003

In this work a new class of ionomeric block perfluropolyether (PFPE) polyurethanes are presented; these polymers are obtained in the form of aqueous dispersions due to the presence of hydrophilic sites (ionomeric groups such as acetates or trialkylammonium salts) along the macromolecular chain, offering the chance to combine PFPEs in a variety of possible structures for coating or surface treatments with an environmentally friendly use. X‐ray photoelectron spectroscopy analysis at two different sampling depths, as well as time‐of‐flight secondary ion mass spectrometry analysis modelled by the use of principal component analysis (PCA), were used to investigate the first nanometres of the surface samples. It resulted in a clear surface enrichment in fluorine, and the different extent of the fluorine stratification will be discussed in relation to the ionic character, film‐forming from water and cross‐linking. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of associations with change in a multivariate outcome variable when baseline is subject to measurement error
Authors: Chambless Lloyd E. , Davis Vicki
Published: March 2003

A simple general algorithm is described for correcting for bias caused by measurement error in independent variables in multivariate linear regression. This algorithm, using standard software, is then applied to several approaches to the analysis of change from baseline as a function of baseline value of the outcome measure plus other covariates, any of which might have measurement error. The algorithm may also be used when the independent variables differ by component of the multivariate independent variable. Simulations indicate that under various conditions bias is much reduced, as is mean squared error, and coverage of 95 per cent confidence intervals is good. Copyright © 2003 John Wiley & Sons, Ltd.
An EM‐based semi‐parametric mixture model approach to the regression analysis of competing‐risks data
Authors: Ng S. K. , McLachlan G. J.
Published: March 2003

We consider a mixture model approach to the regression analysis of competing‐risks data. Attention is focused on inference concerning the effects of factors on both the probability of occurrence and the hazard rate conditional on each of the failure types. These two quantities are specified in the mixture model using the logistic model and the proportional hazards model, respectively. We propose a semi‐parametric mixture method to estimate the logistic and regression coefficients jointly, whereby the component‐baseline hazard functions are completely unspecified. Estimation is based on maximum likelihood on the basis of the full likelihood, implemented via an expectation‐conditional maximization (ECM) algorithm. Simulation studies are performed to compare the performance of the proposed semi‐parametric method with a fully parametric mixture approach. The results show that when the component‐baseline hazard is monotonic increasing, the semi‐parametric and fully parametric mixture approaches are comparable for mildly and moderately censored samples. When the component‐baseline hazard is not monotonic increasing, the semi‐parametric method consistently provides less biased estimates than a fully parametric approach and is comparable in efficiency in the estimation of the parameters for all levels of censoring. The methods are illustrated using a real data set of prostate cancer patients treated with different dosages of the drug diethylstilbestrol. Copyright © 2003 John Wiley & Sons, Ltd.
Regression analysis of incomplete medical cost data
Authors: Lin D. Y.
Published: March 2003

The accumulation of medical cost over time for each subject is an increasing stochastic process defined up to the instant of death. The stochastic structure of this process is complex. In most applications, the process can only be observed at a limited number of time points. Furthermore, the process is subject to right censoring so that it is unobservable after the censoring time. These special features of the medical cost data, especially the presence of death and censoring, pose major challenges in the construction of plausible statistical models and the development of the corresponding inference procedures. In this paper, we propose several classes of regression models which formulate the effects of possibly time‐dependent covariates on the marginal mean of cost accumulation in the presence of death or on the conditional means of cost accumulation given specific survival patterns. We then develop estimating equations for these models by combining the approach of generalized estimating equations for longitudinal data with the inverse probability of censoring weighting technique. The resultant estimators are shown to be consistent and asymptotically normal with simple variance estimators. Simulation studies indicate that the proposed inference procedures behave well in practical situations. An application to data taken from a large cancer study reveals that the Medicare enrollees who are diagnosed with less aggressive ovarian cancer tend to accumulate medical cost at lower rates than those with more aggressive disease, but tend to have higher lifetime costs because they live longer. Copyright © 2003 John Wiley & Sons, Ltd.
Truncated negative binomial mixed regression modelling of ischaemic stroke hospitalizations
Authors: Lee Andy H. , Wang K. , Yau Kelvin K. W. , Somerford Peter J.
Published: March 2003

A zero‐truncated negative binomial mixed regression model is presented to analyse overdispersed positive count data. The study is motivated by the determination of pertinent risk factors associated with ischaemic stroke hospitalizations. Random effects are incorporated in the linear predictor to adjust for inter‐hospital variations and the dependency of clustered observations using the generalized linear mixed model approach. The method assists hospital administrators and clinicians to estimate the number of subsequent readmissions based on characteristics of the patient at the index stroke. The findings have important implications on resource usage, rehabilitation planning and management of acute stroke care. Copyright © 2003 John Wiley & Sons, Ltd.
An illustration of the modelling of cost and efficacy data from a clinical trial
Authors: Hahn Seokyung , Whitehead Anne
Published: March 2003

Health care providers, purchasers and policy makers need to make informed decisions regarding the provision of cost‐effective care. When a new health care intervention is to be compared with the current standard, an economic evaluation alongside an evaluation of health benefits provides useful information for the decision making process. We consider the information on cost‐effectiveness which arises from an individual clinical trial comparing the two interventions. Recent methods for conducting a cost‐effectiveness analysis for a clinical trial have focused on the net benefit parameter. The net benefit parameter, a function of costs and health benefits, is positive if the new intervention is cost‐effective compared with the standard. In this paper we describe frequentist and Bayesian approaches to cost‐effectiveness analysis which have been suggested in the literature and apply them to data from a clinical trial comparing laparoscopic surgery with open mesh surgery for the repair of inguinal hernias. We extend the Bayesian model to allow the total cost to be divided into a number of different components. The advantages and disadvantages of the different approaches are discussed. In January 2001, NICE issued guidance on the type of surgery to be used for inguinal hernia repair. We discuss our example in the light of this information. Copyright © 2003 John Wiley & Sons, Ltd.
Regression analysis with multiplicative and time‐varying additive regression coefficients with examples from breast and colon cancer
Authors: Zahl Per‐Henrik
Published: March 2003

Regression analysis may be used to simplify the representation of mortality rates when there are many significant prognostic covariates or to adjust for confounding effects. The principal request of the regression model in this range of use is to have unbiased parameter estimates. A model with constant multiplicative and time‐varying additive regression coefficients is discussed. The model allows some covariate effects to be multiplicative while allowing others to have a time‐varying additive effect. Thus, it is a mix of classical Cox regression and Aalen's additive risk model. A major characteristic of cancer mortality rates, in contrast to general mortality rates, is that hazard rates, after a potentially initial increase, decrease, although not always tending to zero. Cancer diseases, like breast and colon cancer, have significantly increased cause‐specific mortality rates even 20 years after diagnosis. Another major feature in cancer survival analysis is that many covariate effects are time‐varying. Some covariate effects, like age at diagnosis, may only be significant for a limited time after diagnosis. Furthermore, some treatment procedures may initially decrease the mortality, while the long‐term effect may be opposite. A third issue is that average covariate effects are very often not multiplicative. Estimation is carried out iteratively; the cumulative additive regression functions are estimated non‐parametrically using a least‐squares method and the multiplicative parameters are estimated from the partial likelihood. The method is applied on 3201 female breast cancer and 1372 male colon cancer patients. Copyright © 2003 John Wiley & Sons, Ltd.
Integrating science and management through collaborative learning and better information management
Authors: Bosch O. J. H. , Ross A. H. , Beeton R. J. S.
Published: March 2003

Achieving more sustainable land and water use depends on high‐quality information and its improved use. In other words, better linkages are needed between science and management. Since many stakeholders with different relationships to the natural resources are inevitably involved, we suggest that collaborative learning environments and improved information management are prerequisites for integrating science and management. Case studies that deal with resource management issues are presented that illustrate the creation of collaborative learning environments through systems analyses with communities, and an integration of scientific and experiential knowledge of components of the system. This new knowledge needs to be captured and made accessible through innovative information management systems designed collaboratively with users, in forms which fit the users' ‘mental models’ of how their systems work. A model for linking science and resource management more effectively is suggested. This model entails systems thinking in a collaborative learning environment, and processes to help convergence of views and value systems, and make scientists and different kinds of managers aware of their interdependence. Adaptive management provides a mechanism for applying and refining scientists' and managers' knowledge. Copyright © 2003 John Wiley & Sons, Ltd.
Dopamine transporter gene, response to methylphenidate and cerebral blood flow in attention‐deficit/hyperactivity disorder: A pilot study
Authors: Rohde Luis A. , Roman Tatiana , Szobot Claudia , Cunha Renato D. , Hutz Mara H. , Biederman Joseph
Published: March 2003

The homozygosity of the 10‐repeat allele at dopamine transporter gene (DAT1) seems to be associated with a poor response to methylphenidate (MPH) in children with attention‐deficit/hyperactivity disorder (ADHD). This pilot study aimed to simultaneously assess polymorphisms at DAT1, response to MPH, and neuroimaging. Only ADHD children with at least a moderate response to MPH were included. Significantly higher regional cerebral blood flows assessed by single photon emission computerized tomography (SPECT) were detected in medial frontal and left basal ganglia areas in children with homozygosity for the 10‐repeat allele at DAT1 gene (n = 4) than in children without this genotype (n = 4) (P < 0.05). These findings provide a preliminary connection between pharmacogenetics and neurobiological investigations on stimulant treatment of ADHD. Synapse 48:87–89, 2003. © 2003 Wiley‐Liss, Inc.
Behavioral and subthalamic effects of combining a fetal ventral mesencephalic transplant in striatum with an electrolytic lesion of the entopeduncular nucleus in the rat with a unilateral 6‐OHDA lesion of substantia nigra
Authors: Olds M.E. , Jacques D.B. , Kopyov O.
Published: March 2003

Behavioral and electrophysiological methods were used to determine whether a transplant of dopamine‐rich fetal tissue in striatum combined with an electrolytic lesion of the entopeduncular nucleus have additive effects in the unilaterally lesioned rat model for Parkinson's disease. The subjects were rats with the left substantia nigra lesioned with 6‐hydroxydopamine (6‐OHDA) and responding to systemic amphetamine with rotation toward the side of the lesion (ipsilateral rotation). The motor response to amphetamine was fractionated into six aspects, half reflecting the unilateral deafferentation in striatum and half representing those aspects of the response evoked in normal rats. After collection of baseline values, 25 rotators received a transplant of fetal ventral mesencephalic tissue in the left striatum and 20 received a transplant and, at the same time, an electrolytic lesion of the left entopeduncular nucleus. Testing for the motor response to amphetamine resumed after 4 weeks of recovery and continued at weekly intervals for 5 weeks. Upon completion of these tests, each rotator was implanted with multiple electrodes in the subthalamic nucleus. After recovery, multiunit responses to amphetamine and apomorphine were recorded from several electrodes in parallel during the motor response to the drugs. In rotators with transplant only, treatment with amphetamine evoked oral stereotypy and an attenuated ipsilateral rotation response. In rotators with combined transplant and entopeduncular lesion, ipsilateral rotation did not change or increased. Subthalamic responses to amphetamine and apomorphine were larger in rotators with combined transplant and entopeduncular lesion than in rotators with transplant alone. These findings indicate that the combination of transplant and pallidotomy in the 6‐OHDA rat model for parkinsonism does not lead to additive benefits, an effect that may have been due to the nonselectivity of the electrolytic damage and/or of the lesion extending beyond the entopeduncular nucleus into the lateral hypothalamus. Synapse 48:90–99, 2003. © 2003 Wiley‐Liss, Inc.
Differential effects of atypical and typical antipsychotic drugs on N‐methyl‐D‐aspartate‐ and electrically evoked responses in the pyramidal cells of the rat medial prefrontal cortex
Authors: Ninan Ipe , Jardemark Kent E. , Wang Rex Y.
Published: March 2003

In the present study, we have demonstrated that atypical antipsychotic drugs (APDs, e.g., clozapine, olanzapine, risperidone, and quetiapine) and atypical APD candidates (e.g., M100907 and Y‐931) share a common property in facilitating responses evoked by electrical stimulation of the forceps minor and by N‐methyl‐D‐aspartate (NMDA), but not (±)‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA), in pyramidal cells of the medial prefrontal cortex (mPFC). The concentrations of these drugs to exert their action are in a clinically relevant range. Although haloperidol has shown a considerably smaller potentiation of NMDA‐evoked current at 50 and 100 nM, it consistently depressed the AMPA‐induced current. Chlorpromazine and loxapine failed to modulate significantly NMDA‐ or AMPA‐induced current in the pyramidal cells. Moreover, haloperidol and loxapine demonstrated depression of excitatory postsynaptic currents, whereas chlorpromazine did not show any effect. These findings combined indicate that atypical, but not typical, APDs augment glutamatergic neurotransmission in pyramidal cells of the mPFC. We propose that the beneficial effect of atypical APDs in cognitive dysfunction and negative symptoms in schizophrenia is due to their ability to enhance glutamatergic neurotransmission in the PFC and functionally related limbic structures. Our results further suggest the possible use of glutamatergic neurotransmission in the mPFC as a model for screening and studying the action of potential atypical APDs. Synapse 48:66–79, 2003. © 2003 Wiley‐Liss, Inc.
Different brain kinetics of two sigma1 receptor ligands, [3H](+)‐pentazocine and [11C]SA4503, by P‐glycoprotein modulation
Authors: Kawamura Kazunori , Kobayashi Tadayuki , Matsuno Kiyoshi , Ishiwata Kiichi
Published: March 2003

We compared the brain kinetics of radiolabeled (+)‐pentazocine and SA4503, which have a high and selective affinity for sigma1 receptors. Brain uptake of [11C]SA4503 was high after intravenous injection followed by a gradual decrease in mice, whereas that of [3H](+)‐pentazocine rapidly decreased. The brain uptake of the two radioligands was dose‐dependently reduced, but the reduction of [3H](+)‐pentazocine was found at higher doses. Percentages of the saturable binding of [3H](+)‐pentazocine was much lower than that of [11C]SA4503. The brain uptake of [3H](+)‐pentazocine was greatly blocked by SA4503 at a dose of 2 μmol/kg, while that of [11C]SA4503 was blocked by (+)‐pentazocine at a dose of 20 μmol/kg and over. When mice were treated with cyclosporin A, a P‐glycoprotein modulator, the uptake of [3H](+)‐pentazocine was enhanced, but that of [11C]SA4503 was not. Under control and P‐glycoprotein‐modulated conditions, the brain uptake of both radioligands was reduced by haloperidol, another representative sigma receptor ligand, to a different extent. We concluded that the P‐glycoprotein modulation resulted in the different brain kinetics of the two radioligands. The radiolabeled SA4503 is suitable as an in vivo probe, but radiolabeled (+)‐pentazocine is not. Synapse 48:80–86, 2003. © 2003 Wiley‐Liss, Inc.
Country factor differentials as determinants of FDI flow to China
Authors: Zhao Hongxin
Published: March 2003

Given the large size and rapid growth of foreign direct investment (FDI) in China, a systematic
analysis of the connection between FDI and the characteristics of source countries provides clearer insights
into the roles of home‐country factors in the vast but still fast‐growing foreign investment in
China. Unlike the existing mainstream studies of FDI in China, this analysis focuses on the effects of
country‐factor differentials (between investing countries and China) on the FDI flow to China.
Based on data from 21 source countries over a period of 17 years, this paper examines the impacts of eight
variables in three sets of country factors, namely market conditions, risk, and financial factors. The
statistical results show that, while the market‐condition variables and the high values of source country
currencies positively influenced the flow of FDI to China, the relatively high costs of capital borrowing and
political and operational risks in China inhibited the flow of FDI. © 2003 Wiley Periodicals, Inc.