bluuebunny/crossref_metadata_2025 huggingface dataset:
Aromaticity/antiaromaticity in cyclic conjugated hydrocarbons
Authors: Ichikawa Hiroshi , Sakata Ken
Published: August 2002

The physical reason for aromaticity/antiaromaticity was determined. The conclusion was reached after interpreting Hobey's mathematical results that were given in the study of the energy difference between the one‐dimensional linear and cyclic particles‐in‐a‐box models. We first revealed that the Hückel theory and particles‐in‐a‐box model are simply different ways of solving the same Schrödinger equation. Then, we pointed out that appearance of the zero‐kinetic energy orbital as the lowest one in a cyclic conjugated system is the determining factor of aromaticity/antiaromaticity. Thirdly, reasons of such appearance, double degeneracy in the higher ones, and their splitting by changing into the linear system were discussed. Finally, it was ascertained that what happens in the cyclic particles‐in‐a‐box model really takes place in actual π orbitals obtained by an ab initio molecular orbital (MO) method in cyclobutadiene and benzene. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Analytic evaluation of two‐center STO electron repulsion integrals via ellipsoidal expansion
Authors: Harris Frank E.
Published: August 2002

Extant analytic methods for evaluating two‐center electron repulsion integrals in a Slater‐type orbital (STO) basis using ellipsoidal coordinates and the Neumann expansion of 1/r12 have problems of numerical stability that are analyzed in detail using computer‐assisted algebraic techniques. Some of these problems can be eliminated by use of procedures known in this field 40 years ago but seemingly forgotten now. Others can be removed by use of a formulation suitable for small values of the STO screening parameter. A recent attempt at such a formulation is corrected and extended in a way permitting its practical use. The main functions encountered in the integrations over the ellipsoidal coordinate of the range 1 … ∞ are Bessel functions or generalizations thereof, as pointed out here for the first time. This fact is used to motivate the derivation of recurrence relations additional to those previously known. Novel techniques were devised for using these recurrence relations, thereby providing new ways of calculating the quantities that enter the ellipsoidal expansion. The convergence rate of this expansion and the numerical characteristics of several computational strategies are reported in enough detail to identify the ranges where various schemes can be used. This information shows that recent discussions of the “convergence characteristics of [the] ellipsoidal coordinate expansion” are in fact not that, but are instead discussions of an inability to make accurate calculations of the individual terms of the expansion. It is also seen that the parameter range suitable for use of Kotani's well‐known recursive scheme is more limited than seems generally believed. The procedures discussed in this work are capable of yielding accurate two‐center electron repulsion integrals by the ellipsoidal expansion method for all reasonable STO screening parameters, and have been implemented in illustrative public‐domain computer programs. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Hybrid molecular mechanics: For effective crystal field method for modeling potential energy surfaces of transition metal complexes
Authors: Darhovskii M. B. , Razumov M. G. , Pletnev I. V. , Tchougréeff A. L.
Published: August 2002

The effective crystal field (ECF) methodology previously developed for description of the electronic structure of transition metal complexes (TMCs) is combined with molecular mechanics (MM) formalism. In this way, a new method for calculations of potential energy surfaces of the Werner‐type TMC is developed. It is based on a combined quantum mechanics (QM)–MM approach with the ECF method taking part of the QM and advanced MM package MMPC developed for the metal ion complex computations and based on the CHARMM organic force field. The MM region consists of ligand atoms and metal ion coordination sphere, leaving out effects of d‐shell, while the QM region is limited to metal ion d‐shell. Crystal field matrix for the d‐shell is calculated with use of the local ECF method. It is shown that the procedure proposed reproduces with considerable accuracy geometry characteristics of values of the Fe(II) complexes with both mono‐ and polydentate ligands. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Ionization potentials within semiempirical antisymmetrized product of strictly localized geminals approach
Authors: Tokmachev A. M. , Tchougréeff A. L. , Misurkin I. A.
Published: August 2002

The APSLG‐MINDO/3 method is evolved to reproduce the vertical ionization potentials for organic molecules. Two different schemes—one allowing for adjustment of the local electronic structure to the hole in each configuration and another one with a fixed local electronic structure—are developed and implemented. These methods are applied to a series of normal hydrocarbons. The possibility of localization of a hole in the polyethylene cation is discussed. Vertical ionization potentials are also obtained for a set of organic molecules with heteroatoms. Their values together with degeneracy of ionized states are compared with the data of photoelectron spectroscopy. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Numerical solution of a two‐dimensional time‐independent Schrödinger equation by using symplectic schemes
Authors: Liu Xue‐Shen , Su Li‐Wei , Liu Xiao‐Yan , Ding Pei‐Zhu
Published: August 2002

Symplectic schemes are extended to the solution of a two‐dimensional time‐independent Schrödinger equation. The Schrödinger equation is first transformed into a Hamiltonian canonical equation and then the numerical method is developed to solve the numerical solution of the two‐dimensional time‐independent Schrödinger equation. This called the symplectic scheme–matrix eigenvalue method (SSMEM). This method is applied to calculations of the two‐dimensional harmonic oscillator and the two‐dimensional Henon–Heils potential. It is shown that the numerical results of the two‐dimensional harmonic oscillator by using the SSMEM tend to the exact ones monotonically with decreasing space step length and the numerical eigenvalues of the two‐dimensional Henon–Heils potential by using the SSMEM are lower than those by using the Gaussian basis set method. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 303–309, 2001
Model systems for rod‐like polyheteroarylethynylenes
Authors: Göller Andreas , Klemm E. , Egbe D. A. M.
Published: August 2002

B3LYP density functional theory (DFT) and MM3 molecular mechanics/dynamics are used to model the flexibility of the building blocks of poly(phenyleneethynylene)s, which are rod‐like segmented polymers usually assumed to be strongly rigid, with well‐defined, highly fluorescent fragments and beneficial material properties like electroluminescence and large nonlinear optical hyperpolarizabilities. Whereas the DFT‐calculated torsional barriers of the building block molecules 2,2′‐bipyridine and some tolane derivatives give insight into weak intramolecular effects in these molecules, the much less detailed MM3 barriers are nevertheless of sufficient quality to use MM3 for polymer modeling. From MM3 molecular dynamics gas phase and water box simulations at different temperatures, insight into the time‐dependent behavior of the model compounds was obtained as well as the conditions at which cis–trans isomerizations occur. It turns out that these formally rigid polymers are quite flexible and do not at all possess strictly coplanar aryl rings over time, significantly decreasing the effective conjugation length. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 86–98, 2001
BSSE‐free description of the formamide dimers
Authors: Bende A. , Vibók Á. , Halász G. J. , Suhai S.
Published: August 2002

The different configurations (linear, zig‐zag, and cyclic) of formamide dimers have been studied at the level of both Hartree–Fock (HF) and second order Møller–Plesset perturbation theory (MP2). The widely used a posteriori Boys–Bernardi “counterpoise” (CP) correction scheme has been compared with our a priori methods utilizing the “chemical Hamiltonian approach” (CHA). The appropriate interaction energies have been calculated in six different basis sets (6‐31G, 6‐31G**, DZV, DZP, TZV, and cc‐pVDZ). © 2001 John Wiley & Sons, Inc. Int J Quant Chem, 2001
Theoretical study of AlC3+
Authors: Redondo Pilar , Largo Antonio , García Flor , Barrientos Carmen
Published: August 2002

A theoretical study of the AlC3+species has been carried out. Predictions have been made for some of the molecular properties (geometries, dipole moments, and harmonic vibrational frequencies) which could help in their possible experimental detection. In addition, a topological analysis of the electron density and its associated Laplacian has also been carried out. The global ground state is predicted to be a linear species with1Σ electronic state, but a rhombic four‐membered ring (1A1) lies close in energy. It seems that both isomers could be accessible to experimental detection. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Ionization and protonation of MgC3: A theoretical study
Authors: Barrientos Carmen , Redondo Pilar , Largo Antonio
Published: August 2002

A theoretical study of the MgC3+ and MgC3H+ species has been carried out. Predictions for their geometries and vibrational frequencies have been made at both second‐order Møller–Plesset (MP2) and B3LYP levels, whereas electronic energies have been computed at G2 and coupled cluster single and double excitation model augmented with a noniterative triple excitation conection (CCSD(T)) levels. The predicted global minimum for MgC3+ is a rhombic structure (2A1 electronic state), whereas a T‐shaped structure and an open‐chain isomer lie about 10 and 12 kcal/mol, respectively, higher in energy. In the case of MgC3H+ the predicted global minimum is also a four‐membered ring obtained upon protonation of the most stable neutral isomer. Low ionization potentials and high proton affinities are generally obtained, especially for the most stable MgC3+ isomer. The estimated values at the CCSD(T) level for the predicted global minimum are 7.20 eV [ionization potential (IP)] and 256.5 kcal/mol [proton affinities (PA)]. Therefore, if present in the interstellar medium, MgC3 should be easily ionized and would react quite easily to give the protonated species. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Molecular structure of fulvic acids by electrospray with quadrupole time‐of‐flight mass spectrometry
Authors: Plancque Gabriel , Amekraz Badia , Moulin Valérie , Toulhoat Pierre , Moulin Christophe
Published: August 2002

Characterisation of the molecular structure of aquatic fulvic acids (FA) has been performed using a quadrupole time‐of‐flight (Q‐TOF) mass spectrometer equipped with an electrospray ionisation interface. Molecular masses centred around 450 Da and sinusoidal spectral distributions have been obtained for all fulvic acids. Tandem mass spectrometry (MS/MS) experiments showed losses of 18 Da (H2O) and 44 Da (CO2), and possible molecular structures were determined for the first time to our knowledge. A methodology is reported for evaluating the average elemental composition of FA from high‐resolution mass spectra by processing post‐acquisition data calculations using molecular size distributions and atomic compositions of ions. The results are found to be consistent with elemental analysis data. Copyright © 2001 John Wiley & Sons, Ltd.
Matrix‐ and surface‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of dibromocalix[4]crown ether
Authors: Kang Weekyung , Kim Junghwan , Paek Kyungsoo , Shin Kuan Soo
Published: August 2002

Laser desorption/ionization mass spectrometry (LDI‐MS) has been investigated for dibromocalix[4]crown ether, a compound known to undergo prompt dissociation in excited electronic states. As a result of direct absorption by the analyte, a considerable proportion of fragment ions were observed in the UV matrix‐assisted LDI mass spectrum. This would make it difficult to study host‐guest complexation by this crown ether using matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. However, the molecular ion peak is largely dominant without the debrominated ions in the LDI mass spectrum obtained using visible laser radiation with a graphite plate as a photon‐absorbing material. This mass spectrum shows good signal‐to‐noise ratio, with a high spot‐to‐spot reproducibility, reflecting homogeneous sample distribution on the graphite plate. This study suggests that use of a visible laser for LDI with a graphite plate could provide advantages for macromolecules with general transparency within the visible region. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of the disulfide bond pattern of the endogenous and recombinant angiogenesis inhibitor endostatin by mass spectrometry
Authors: John Harald , Forssmann Wolf‐Georg
Published: August 2002

Endostatin, a C‐terminal fragment of collagen XVIII, is a promising protein drug which is in development for cancer therapy due to its anti‐angiogenic activity. Although several endogenous molecular forms of human endostatin differing in their N‐terminal length and their post‐translational modifications (18.5–22 kDa) have been discovered, only one recombinant form of 20 kDa is used in clinical trials. This protein, recombinantly expressed inPichia pastoris, contains four cysteines forming two disulfide bonds (Cys1‐Cys4 and Cys2‐Cys3). In contrast, there are conflicting data about the disulfide pattern of endogenous material. This report presents the disulfide analyses of both the endogenous circulating endostatins isolated from human hemofiltrate and the recombinant protein. The determination of the disulfide pattern was performed by Edman degradation, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) and electrospray ionization ion trap mass spectrometry (ESI‐ITMS) performed in the off‐line nanospray mode. All native and recombinant endostatins exhibited a Cys1‐Cys4 (Cys162‐Cys302) and Cys2‐Cys3 (Cys264‐Cys294) linkage. For a clear discussion of fragmented disulfide‐bridged peptide chains obtained from MSnexperiments, a modified general nomenclature is proposed. Copyright © 2001 John Wiley & Sons, Ltd.
Unusual MSn fragmentation patterns of 2,4‐dinitrophenylhydrazine and its propanone derivative
Authors: Kölliker Stephan , Oehme Michael , Merz Leo
Published: August 2002

During the structural elucidation of carbonyl‐2,4‐dinitrophenylhydrazone derivatives in the low‐ng range by multiple mass spectrometry combined with high performance liquid chromatography (HPLC/MSn) some fragments were detected which were difficult to explain by ordinary fragmentation rules. Atmospheric pressure chemical ionization in the negative ion mode was applied. The ion formation was studied by labelling the parent compounds with D, 13C and 15N and recording the MS/MS, MS3 and MS4 spectra. This allowed an investigation of the detailed fragmentation of 2,4‐dinitrophenylhydrazine and its propanone derivative as well as the structures of the MS2 and MS3 product ions. A highly reactive product ion was found which undergoes unexpected reactions inside the ion trap of an HPLC/MSn system. In addition, reactions of MSn fragments with solvents or species generated in situ in the ion source and/or the ion trap were observed. It is demonstrated that unusual fragments in the MS/MS or MSn spectra of a compound may be formed by such reactions and that the eluent used for HPLC might have an influence on the observed fragmentation even if the mass spectrum itself is completely free from adducts. Copyright © 2001 John Wiley & Sons, Ltd.
Mass spectrometric analysis of cyclofenil and its metabolites in human urine
Authors: Myung Seung‐Woon , Min Hye‐Ki , Kim Dong‐Hyun , Kim Myungsoo , Cha SuJin , Yoo Eun‐Ah , Yim Yong‐Hyeon
Published: August 2002

Using gas chromatography/electron impact‐mass spectrometry (GC/EI‐MS) and high performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI‐MS/MS), the structures of cyclofenil metabolites in human urine have been assigned. The hydroxyl metabolites liberated from the glucuronide conjugates after acid hydrolysis were characterized as the trimethylsilyl (O‐TMS) derivatives using GC/MS. The conjugate glucuronide forms were detected without hydrolysis by HPLC/MS. Cyclofenil was not observed in urine. Tentative structures for the two metabolites are proposed. Copyright © 2002 John Wiley & Sons, Ltd.
The hyporheic zone: Linking groundwater and surface water—understanding the paradigm
Authors: Biksey Thomas M. , Gross Elisa D.
Published: August 2002

The hyporheic zone, the transition region between groundwater and surface water, represents an important
interface between terrestrial and aquatic ecosystems. When groundwater combines with surface water in this zone,
the characteristics of each are blended and new gradients are established, especially for contaminants. Therefore,
the hyporheic zone is important in considering the “big ecological picture” as the hydrologic continuum
connecting groundwater and surface water. The importance is reflected by the current focus of this zone in
ecological risk assessments conducted under the Resource Conservation and Recovery Act (RCRA),
Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), and Clean Water Act
(CWA) programs. A variety of tools can be used to measure, analyze, and predict the physical, chemical,
and biological processes that occur within the hyporheic zone. Directly measuring the flux of water across the
interface between groundwater and surface water determines whether surface water enters the streambed at
downwelling zones or groundwater discharges from the streambed in upwelling zones. In addition to direct
measurements of the flux of water, several states have developed models to characterize the interaction of
groundwater and surface water. The variability in physical and chemical characteristics between upwelling and
downwelling zones influences the local ecology within the zone. The study of the species within the hyporheic zone
includes ecological surveys and ecotoxicological investigations. The evolving study of the hyporheic zone will
necessitate an increase in basic research into hydraulic considerations, an identification of regional
representative sites with contaminated hyporheic zones, and a better understanding of the ecology of the species
within the zone. © 2001 John Wiley & Sons, Inc.
Linear time computation of feasible regions for robust compensators
Authors: Fadali M. Sami , LaForge Laurence E.
Published: August 2002

We introduce an application of computational geometry, including figures of merit standard in the analysis of algorithms, to the design of robust control systems. With respect to system transfer function magnitude, we show how to compute feasible regions for compensators whose plant transfer function is the ratio of uncertain interval polynomials. Our solution sweeps the Minkowski quotient set of the corresponding Kharitonov rectangles. Enumerating the winding numbers of Minkowski sum convolution curves, we obtain optimal, linear time algorithms that eliminate three factors from the execution inefficiency of traditional gridding approaches. We illustrate with examples pertinent to quantitative feedback theory (QFT). Copyright © 2001 John Wiley & Sons, Ltd.
Normal form representation of control systems
Authors: Cheng Daizhan , Martin Clyde F.
Published: August 2002

This paper is to investigate the normal form representation of control systems. First, as numerical tools we develop an algorithm for normal form expression and the matrix representation of the Lie derivative of a linear vector field over homogeneous vector fields. The concept of normal form is modified. Necessary and sufficient conditions for a linear transformation to maintain the Brunowsky canonical form are obtained. It is then shown that the shift term can always be linearized up to any degree. Based on this fact, linearization procedure is proposed and the related algorithms are presented. Least square linear approximations are proposed for non‐linearizable systems. Finally, the method is applied to the ball and beam example.The efforts are focused on the numerical and computer realization of linearization process. Copyright © 2002 John Wiley & Sons, Ltd.
A path following control for unicycle robots
Authors: Díaz del Río F. , Jiménez G. , Sevillano J. L. , Vicente S. , Civit Balcells A.
Published: August 2002

In this work we present a new path following control for unicycle robots that is applicable for almost all the possible desired paths and whose analysis is very straightforward. First we select the path following method that consists of two steps: choosing a “projection” that relates the actual posture to the desired path and imposing a “motion exigency” to ensure that the robot advances. A “projection” that considers all the error coordinates is selected and closed equations are obtained for it. The uniqueness projection is carefully analyzed and a necessary and sufficient condition is also presented. This condition shows that a slight bound on the curvature derivative of desired paths must be imposed to preserve uniqueness. It is remarkable that the selected path following is applicable for paths containing zero‐radius turns, a problem that has never been resolved as far as we know. In addition, an asymptotically stable control law is found using the closed form equation of the proposed path following and the second Lyapunov method. Finally, we show the behavior of the path following and the control law through several simulated and experimental results, using a computerized wheelchair built at our research facility. © 2001 John Wiley & Sons, Inc.
Perfect position/force tracking of robots with dynamical terminal sliding mode control
Authors: Parra‐Vega V. , Rodríguez‐Angeles A. , Hirzinger G.
Published: August 2002

According to a given performance criteria, perfect tracking is defined as the performance of zero tracking error in finite time. It is evident that robotic systems, in particular those that carry out compliant task, can benefit from this performance since perfect tracking of contact forces endows one or many constrained robot manipulators to interact dexterously with the environment. In this article, a dynamical terminal sliding mode controller that guarantees tracking in finite‐time of position and force errors is proposed. The controller renders a dynamic sliding mode for all time and since the equilibrium of the dynamic sliding surface is driven by terminal attractors in the position and force controlled subspaces, robust finite‐time convergence for both tracking errors arises. The controller is continuous; thus chattering is not an issue and the sliding mode condition as well the invariance property are explicitly verified. Surprisingly, the structure of the controller is similar with respect to the infinite‐time tracking case, i.e., the asymptotic stability case, and the advantage becomes more evident because terminal stability properties are obtained with the same Lyapunov function of the asymptotic stability case by using more elaborate error manifolds instead of a more complicated control structure. A simulation study shows the expected perfect tracking and a discussion is presented. © 2001 John Wiley & Sons, Inc.
Changes in riparian forests in the Kushiro Mire, Japan, associated with stream channelization
Authors: Nakamura Futoshi , Jitsu Mieko , Kameyama Satoshi , Mizugaki Shigeru
Published: August 2002

The Kushiro Mire, the largest mire in Japan, presently faces the serious problem of turbid water flooding. Shortening of stream channels associated with agricultural development is a major cause of streambed aggradation. This aggradation reduces the carrying capacity of the channel, resulting in sediment laden water spilling over the wetlands in a flood event. Sedimentation progresses with repeated inundation by turbid water, which significantly alters the edaphic conditions, and thereby the composition and structure of marsh forests. Aggradation of the geomorphic surfaces with sedimentation lowers the water level, and increases soil particle size and nutrient status. This situation was clearly displayed in an ordination of canonical correspondence analysis. Among the environmental variables, water level was related most strongly to the pattern of a forest community. Salix species dominated the flood areas, which were characterized by a low water level, coarse sediment, and high electrical conductivity. Alnus japonica, the most common tree species in the Kushiro Mire, favors soil conditions represented by high water table and organic content. A. japonica adapts to a higher water level by developing lenticels with hypertrophied and adventitious roots, multiple sprouting and regenerates vegetatively. Basal areas (BAs) of A. japonica, however, seem to be limited by high fluctuations in water levels, which are amplified by channelization. This raises serious concerns for the integrity of the Kushiro Mire. It is important to implement a conservation plan from a watershed perspective because most problems originate in upper basins. Creating riparian buffer strips, sediment‐filtering wetlands, and restoring the original meandering course may slow down sedimentation in the mire, and thus help to restore the natural hydrological regime. Copyright © 2002 John Wiley & Sons, Ltd.
On a multivariate contraction method for random recursive structures with applications to Quicksort
Authors: Neininger Ralph
Published: August 2002

The contraction method for recursive algorithms is extended to the multivariate analysis of vectors of parameters of recursive structures and algorithms. We prove a general multivariate limit law, which also leads to an approach to asymptotic covariances and correlations of the parameters. As an application, the asymptotic correlations and a bivariate limit law for the number of key comparisons and exchanges of median‐of‐(2t+1) Quicksort are given. Moreover, for the Quicksort programs analyzed by Sedgewick the exact order of the standard deviation and a limit law follow, considering all the parameters counted by Sedgewick. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 498–524, 2001
Infinite paths in randomly oriented lattices
Authors: Grimmett Geoffrey R.
Published: August 2002

The square lattice is used to generate an oriented graph in which a rightward or upward arrow is present on each edge with probability a, and a leftward or downward arrow with probability b. Independence between different edges of the square lattice is assumed, but nothing is assumed concerning the dependence between the two possible orientations at any given edge. A property of self‐duality is exploited to show that, when a+b=1, the process is, in a sense to be made precise, either critical or supercritical, but not subcritical. This observation enables progress with the percolation problem in which each horizontal edge is oriented rightward with probability p and otherwise leftward, and each vertical edge is oriented upward with probability p and otherwise downward. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 18, 257–266, 2001
The diameter of long‐range percolation clusters on finite cycles
Authors: Benjamini Itai , Berger Noam
Published: August 2002

Bounds for the diameter and expansion of the graphs created by long‐range percolation on the cycle ℤ/Nℤ are given. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 102–111, 2001
Design aspects of satellite–cellular hybrid wireless systems
Authors: ElBatt Tamer , Ephremides Anthony
Published: August 2002

In this paper we investigate various issues related to the design of satellite–cellular hybrid systems. First, we review the fundamental problems of channel partitioning and call admission/assignment. Second, we study the impact of different frequency reuse constraints, in both layers, on the optimum channel partitioning. Third, we investigate, analytically and via simulation, the effect of reducing the cell size. We emphasize the blocking‐forced termination probabilities trade‐off for pure cellular and satellite–cellular hybrid systems. Accordingly, an optimization problem with respect to the cell size is formulated. Finally, we search for the optimum dynamic call re‐assignment policy that improves the system capacity at the expense of the complexity associated with tearing down a connection in one system and setting‐up an alternative one in the other system. For a small hybrid system, we characterized the optimum re‐assignment policies that minimize the blocking probability, dropping probability, and a weighted cost function of these probabilities. Copyright © 2002 John Wiley & Sons, Ltd.
Families' engagement with young children's science and technology learning at home
Authors: Hall Robin L. , Schaverien Lynette
Published: August 2002

There is accumulating evidence of the worth of involving families in young children's learning in informal contexts. By exploring families' engagement with their children's science and technology learning at home over a 6‐month period, the present investigation sought to illuminate both the nature and the educational significance of what families do. Initially, in order to seed scientific and technological inquiry in homes, kindergarten and year‐one children investigated flashlights with family members at school. Each day, equipment was available to take home. Using established anthropological methods, one of the researchers investigated children's further inquiries beyond the classroom in diverse ways; for example, by visiting homes and conversing via telephone and facsimile. The findings showed that families engaged with children's inquiries at home in many ways—by providing resources, conversing, and investigating collaboratively with children. Moreover, when families pursued inquiries together and when children conducted their own sustained intellectual searches, children's ideas deepened. Such evidence of the educational significance of what families do suggests that early science and technology education might be made more effective if it were aligned with the ways people learn together outside formal institutions. © 2001 John Wiley & Sons, Inc. Sci Ed 85:454–481, 2001.
An efficient image mapping method for 3D surface textures
Authors: Matsushita Kenji , Kaneko Toyohisa
Published: August 2002

To generate 3D computer graphics models, we need to obtain their surface geometrical data as well as texture data. This task is usually quite laborious. When real objects are on hand, there are scanners to acquire these data directly. This paper is concerned with an efficient method to acquire texture data for an object whose geometrical data are already known. We set up 320 viewpoints around an object and select a minimal number of viewpoints to cover all of its surfaces. Photographs are taken from the viewpoints. For the surfaces not in the photographs, new photographs are usually taken from viewpoints closer to the object. Lastly, those photographs are mapped exactly onto the object's surface. This method has the advantage of not requiring exact setting of viewpoint positions, since the actual camera positions are found by moving known geometrical data virtually. We conducted experiments with three models whose geometrical data were acquired through CT. © 2001 Scripta Technica, Syst Comp Jpn, 32(4): 14–24, 2001
Effects of neuronal dynamics on memory storing in stimulus–response scheme model
Authors: Katada Naofumi , Nishimura Haruhiko
Published: August 2002

Previously, the authors introduced a stimulus–response scheme that supports plastic variation of synapse weights in chaotic neural networks, and analyzed how memory formation evolved under external stimulation. In this paper, the same analysis is applied to stochastic neural networks with different dynamics, and the obtained results are compared to those for chaotic networks to examine the influence exerted by dynamic parameters on the memorization process. In experiments, chaotic networks proved to be more efficient than stochastic networks. This is indicative of functionality of neural chaos in stimulus–response scheme that is close to natural learning, while further experiments are required to confirm the generality of this conclusion. © 2001 Scripta Technica, Syst Comp Jpn, 32(6): 29–35, 2001
A classification method to reduce the number of categories in ART1
Authors: Takaoka Tetsuya , Izumida Masanori , Murakami Kenji
Published: August 2002

The ART (Adaptive Resonance Theory) neural network was proposed by Grossberg and colleagues to classify by certain criterion (vigilance parameter) a data set distributed across feature space. With ART1, the selection of existing categories and generation of new categories is performed appropriately using two procedures called competition and resonance. Past learning can coexist with new learning without contradictions (that is, the so‐called plasticity–stability dilemma is avoided). However, ART classification results are influenced by the data presentation order, so that different numbers of categories and different classification results may be obtained for the same data set, which is basically unacceptable. As a solution to this problem, this study introduces two procedures, namely, asymptotic setting of the vigilance parameter and probabilistic restoration of prototypes. Asymptotic setting of the vigilance parameter is a procedure to reduce the number of generated categories to a minimum by varying the vigilance parameter gradually from its minimum to a preset target value; in the process, the classification results develop from rough to fine. Probabilistic restoration of prototypes handles changes in the order of data presentation by probabilistic variation of existing prototypes (representative values). By adding these two procedures, an ART modification may be designed with a reduced number of generated categories, while not being dependent on data presentation order. In this study, the two additional procedures were introduced into ART1, variety of ART for dealing with binary patterns, and the effectiveness of the proposed algorithm was verified against several data sets. Experiments proved that the proposed method provides order‐independent data classification with a minimum (or nearly minimum) number of categories. © 2001 Scripta Technica, Syst Comp Jpn, 32(11): 61–69, 2001
Contradictions between WTO and sustainable development? The case of environmental dumping
Authors: Lothe Solveig
Published: August 2002

This paper discusses how the WTO agreement deals with the environmental and competitiveness concerns linked to trade and environmental policies. As the use of traditional export subsidies and other protectionist trade policies are now strongly restricted in the WTO, many countries will try to find other ways to increase competitiveness. One way of doing this is to use lax environmental taxation or regulation as indirect subsidies (i.e. ‘environmental dumping’). If this is done, the reduced possibilities of using traditional protectionist trade policies could harm the environment, thus reducing the overall welfare gain from trade liberalization. Environmental countervailing tariffs have been suggested as a way of reducing incentives for environmental dumping. The WTO rules are examined in order to analyse the feasibility of the uses of environmental countervailing tariffs in the current and future framework of WTO, and the incentives and welfare consequences are analysed under different market scenarios. Copyright © 2001 John Wiley & Sons, Ltd and ERP Environment
Sustainable development: an evolutionary economic approach
Authors: van Griethuysen Pascal
Published: August 2002

In this paper, it is argued that the view of the economic sphere as a closed system cannot appropriately deal with the issue of sustainable development. Evolutionary economics is then presented as a fruitful alternative to apprehend the interactions between the economic, the human and the natural spheres. This emerging field offers both a firm theoretical basis (based upon recent developments in physics, biology, dynamic systems theory and the sciences of complexity) and practical, pragmatic answers to the implementation of a sustainable path of development. This is further illustrated with the presentation of the evolutionary logic of a multi‐level common regime. Such a regime could be an institutional counterpart of social and environmental dynamics. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment.
Group model building effectiveness: a review of assessment studies
Authors: Rouwette Etiënne A. J. A. , Vennix Jac A. M. , Mullekom Theo van
Published: August 2002

Over the last decades system dynamicists have experimented with approaches to achieve more involvement of their clients in the model building process. As a result the number of reports in the literature on the use of system dynamics as an organizational intervention tool has increased dramatically. From the literature we have identified 107 cases that provide details on the modeling process and the assessment of results. The cases show a wide variety in the way the interventions are reported and assessed. From a research point of view this is clearly an undesirable state of affairs. This article reports on a meta analysis of findings of these studies and tries to provide an overview of outcome studies on system dynamics interventions. It attempts to draw some preliminary conclusions on the effectiveness of system dynamics modeling interventions, to clarify differences in definitions of outcomes, and to provide guidelines for more standardized assessments and reports. Rather than remaining in the stage of single case descriptions, the latter will enable the accumulation of research results in the future, a prerequisite for institutional learning within the system dynamics community. Copyright © 2002 John Wiley & Sons, Ltd.
Imaging and measurement of local mechanical material properties by atomic force acoustic microscopy
Authors: Rabe U. , Amelio S. , Kopycinska M. , Hirsekorn S. , Kempf M. , Göken M. , Arnold W.
Published: August 2002

In atomic force acoustic microscopy (AFAM) the cantilever of an atomic force microscope is vibrated at ultrasonic frequencies while a sample surface is scanned with the sensor tip contacting the sample. As a consequence, the amplitude and phase of the cantilever vibration as well as the shift of the cantilever resonance frequencies contain information about local tip–sample contact stiffness and can be used as imaging quantities. An appropriate theoretical description of the transfer of ultrasound in an atomic force microscope enables the measurement of the local mechanical material parameters of the sample surface by evaluating experimental cantilever vibration spectra. In the experiments presented here, we examine the sensitivity of the technique using silicon single crystals. Furthermore, we show that the ferroelectric domains of lead zirconate–titanate ceramics can be imaged by AFAM and that local elastic constants of the sample surface can be determined quantitatively. The lateral resolution of the technique is given by the contact area formed by the sensor tip and the sample surface, which can have a diameter of <10 nm. Copyright © 2002 John Wiley & Sons, Ltd.
Extending the capabilities of scanning probe microscopy for microroughness analysis in surface engineering
Authors: Ferré‐Borrull Josep , Steinert Jörg , Duparré Angela
Published: August 2002

We present a method for extending the capabilities of scanning probe microscopy (SPM) methods in surface engineering by specific processing and interpretation of topographic data. The first part of this processing permits SPM measurements of different scan sizes to be combined with other microtopographical techniques. The result is a comprehensive description of the surface microstructure based on power spectral density functions. The second part consists of the extraction of a small set of characteristic parameters that objectively characterize the statistical properties of the surface and separate different roughness contributions. Copyright © 2002 John Wiley & Sons, Ltd.
Use of scanning force microscopy studies with combined friction, stiffness and thermal diffusivity contrasts for microscopic characterization of automotive brake pads
Authors: Munz M. , Schulz E. , Sturm H.
Published: August 2002

A scanning force microscopy (SFM) study encompassing a thermal and various mechanical contrasts was performed on a sample related to automotive brake pads. The sample consisted of polybutadiene (PBD) and the solid lubricant antimony sulphide (Sb2S3), both dispersed in a polymeric matrix of phenolic resin. Via this highly simplified composition, the assignment of contrasts to the ingredients was assured. The mechanical measurements, namely the stiffness measurements via force modulation microscopy (FMM) and the friction measurements via lateral force microscopy (LFM) and harmonically modulated lateral force microscopy (HM‐LFM), were carried out in one combined experiment (using the same silicon tip). Owing to the available stiffness data, the results of the lateral force measurements are discussed in terms of the size of the mechanical contact radius. Compared with LFM, HM‐LFM is less prone to topographic artefacts and shows enhanced contrasts. The additional phase image indicates deviations from perfect elastic behaviour. Consistently with the FMM measurement, the HM‐LFM phase image displays a distinct phase shift on PBD. For performing thermal measurements, a probe made up of Wollaston was employed. The resulting images are interpreted in terms of the thermal diffusivity and the thermal conductance of the tip– sample contact. Beyond the mechanical properties of the material under investigation, the influence of the bridging water layer also has to be taken into account. Copyright © 2002 John Wiley & Sons, Ltd.
Calibration of electron spectrometers operating in the high energy range
Authors: Kövér L.
Published: August 2002

In spite of the increasing use of electron spectroscopic methods at energies well above the region conventional in surface analysis, standard methods for the calibration of electron spectrometers in this high energy range are not available.

In the present work problems of energy, efficiency and resolution calibration of electron spectrometers operating in the high energy (1.5–10 keV) range are discussed and the possibilities of using photoexcited and backscattered electrons, as well as electrons emitted from radioactive samples for calibration, are reviewed. Recommended data available for energy calibration, namely x‐ray and Auger transition energies and deep core binding energies (including recent results of high‐resolution experiments), are presented and the methods proposed (with the necessary experimental conditions) for using these data for energy calibration purposes are discussed. Different methods (based on the use of photoexcited, backscattered electrons or radioactive samples) for determining the relative and absolute efficiency functions, as well as the energy resolution of electron spectrometers operating in the high energy range, are also reviewed and discussed. Copyright © 2002 John Wiley & Sons, Ltd.
High spatial resolution extended x‐ray emission fine structure (EXEFS) spectra of an electronic device measured by electron probe microanalysis (EPMA)
Authors: Kawai Jun , Takahashi Hideyuki
Published: August 2002

Silicon K x‐ray emission spectra of a model electronic device are measured using a commercial electron probe microanalyser equipped with a wavelength‐dispersive spectrometer. Extended x‐ray emission fine structure (EXEFS) is observed at the low‐energy side of the K x‐ray emission diagram lines. The EXEFS spectra are known to be similar to the XANES (x‐ray absorption near‐edge structure) spectra. The measured silicon K x‐ray EXEFS spectra are compared with Si, SiC, Si3N4 and SiO2 EXEFS spectra. The EXEFS spectra at two places on the electronic devices are different from each other; one is similar to the spectrum of SiO2 and the other is the sum of SiO2 and Si. These results correspond well to the multilayer structure of the measured points. The present results demonstrate that a high spatial resolution chemical‐state analysis is possible using the XANES‐like EXEFS spectra. Copyright © 2001 John Wiley & Sons, Ltd.
Output characteristics of stacked CMOS‐type active pixel sensor for charged particles
Authors: Nagashima Kazuhide , Kunihiro Takuya , Takayanagi Isao , Nakamura Junichi , Kosaka Koji , Yurimoto Hisayoshi
Published: August 2002

A stacked CMOS‐type active pixel sensor (SCAPS) for charged particles has been developed. The SCAPS is an integral‐type detector that has several advantages over conventional systems, including two‐dimensional detection, wide dynamic range, no insensitive time, direct detection of charged particles and a high degree of robustness. The output characteristics of the SCAPS for incident charged particles has been analysed both theoretically and experimentally. The relationships between the output voltage of the SCAPS and the number of incident charged particles were formulated by including corrections for the non‐ideal characteristics of transistors in a pixel. The fluctuation of output characteristics of the SCAPS was evaluated experimentally by irradiation of secondary 4.5 keV Si+ ions generated by SIMS. The function was used to determine the number of incident ions into each SCAPS pixel within twice the statistical error. The SCAPS is useful as a two‐dimensional detector for microanalysis, such as stigmatic SIMS. Copyright © 2001 John Wiley & Sons, Ltd.
Functional data analysis with application to periodically stimulated foetal heart rate data. I: Functional regression
Authors: Ratcliffe Sarah J. , Leader Leo R. , Heller Gillian Z.
Published: August 2002

Functional regression is used to model longitudinal data where the number of measurements on the functional covariate is much greater than the number of subjects in the study. Thus, functional regression can be thought of as singular longitudinal analysis. We have modified existing functional regression techniques to the case of a functional covariate with a repeated stimulus. We applied this modified functional regression to periodically stimulated foetal heart rates. The heart rate tracings were used as a predictor of the child's psychomotor development at approximately 18 months of age. In the past, this type of data has been analysed using the partially subjective concept of habituation. By using the entire heart rate tracings through functional regression, we have the advantage that habituation does not need to be defined and all available information is used to predict later child development. Copyright © 2002 John Wiley & Sons, Ltd.