bluuebunny/crossref_metadata_2025_split huggingface dataset:
meta and para substitution effects on the electronic state energies and ring‐expansion reactivities of phenylnitrenes
Authors: Johnson William T. G. , Sullivan Michael B. , Cramer Christopher J. 
Published: August 2002

AbstractThe electronic structures of the triplet ground states and first three excited singlet states for phenylnitrene, 14 meta‐, and 17 para‐substituted congeners have been characterized using density functional theory and multireference second‐order perturbation theory (CASPT2). Ring expansion pathways to form didehydroazepines have activation enthalpies of about 9 kcal⋅mol−1 and are fairly insensitive to substitution—in the case of the strongest para donor, MeNH–, this barrier increases to about 13 kcal⋅mol−1. The trends in state energies as a function of substitution are rationalized using a (2,2) configuration interaction theory and qualitative molecular orbital theory. Analysis of spin‐orbit coupling in the nitrenes using the same model in conjunction with explicit calculation of spin‐orbit coupling matrix elements rationalizes why electron donating substituents increase rates of intersystem crossing. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Theory and applications of the integrated molecular transform and the normalized molecular moment structure descriptors: QSAR and QSPR paradigms
Authors: Molnar Stephen P. , King James W. 
Published: August 2002

AbstractThe chemical and mathematical rationalé in the development of the numerically unitary integrated molecular transform (FTm), its analogous electronic (FTe) and charge (FTc) transforms, and the normalized molecular moment (Mn), and its analogous electronic (Me) and charge (Mc) moment as molecular structure descriptors are presented. The reported application and utilization of these indices for predictive capability correlations of structure with physicochemical, pharmacological, and thermodynamic properties are reviewed. The further use of these descriptors in considerations of chemical similarity is noted, as is their capability for searching compound databases whose contents include the noted calculated indices. Their potential for characterizing peptides, proteins, and oligomers as well as their possible function in mathematical models is discussed. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Experimentation with different thermodynamic cycles used for pKa calculations on carboxylic acids using complete basis set and Gaussian‐n models combined with CPCM continuum solvation methods
Authors: Liptak Matthew D. , Shields George C. 
Published: August 2002

AbstractComplete basis set and Gaussian‐n methods were combined with Barone and Cossi's implementation of the polarizable conductor model (CPCM) continuum solvation methods to calculate pKa values for six carboxylic acids. Four different thermodynamic cycles were considered in this work. An experimental value of −264.61 kcal/mol for the free energy of solvation of H+, ΔGs(H+), was combined with a value for Ggas(H+) of −6.28 kcal/mol, to calculate pKa values with cycle 1. The complete basis set gas‐phase methods used to calculate gas‐phase free energies are very accurate, with mean unsigned errors of 0.3 kcal/mol and standard deviations of 0.4 kcal/mol. The CPCM solvation calculations used to calculate condensed‐phase free energies are slightly less accurate than the gas‐phase models, and the best method has a mean unsigned error and standard deviation of 0.4 and 0.5 kcal/mol, respectively. Thermodynamic cycles that include an explicit water in the cycle are not accurate when the free energy of solvation of a water molecule is used, but appear to become accurate when the experimental free energy of vaporization of water is used. This apparent improvement is an artifact of the standard state used in the calculation. Geometry relaxation in solution does not improve the results when using these later cycles. The use of cycle 1 and the complete basis set models combined with the CPCM solvation methods yielded pKa values accurate to less than half a pKa unit. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Electrospray ionisation mass spectrometric study of degradation products of quercetin, quercetin‐3‐glucoside and quercetin‐3‐rhamnoglucoside, produced by in vitro fermentation with human faecal flora
Authors: Justesen Ulla , Arrigoni Eva 
Published: August 2002

AbstractEight phenolic compounds, obtained by in vitro fermentation of quercetin, quercetin‐3‐glucoside and quercetin‐3‐rhamnoglucoside were analysed by electrospray ionisation mass spectrometry (ESI‐MS). Low‐energy collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) was performed on the [M − H]− precursor ions to obtain specific fragmentation. Typical fragmentation of the phenolic acids was loss of 44 (CO2) and 18 (H2O) u. Production of m/z 108 by loss of neutral radicals, e.g. HCO2, CH3 or HCO, was also favoured. Structures of the compounds, numbered 1–8, were suggested based on the fragmentation patterns. Copyright © 2001 John Wiley & Sons, Ltd.
Direct analysis of pharmaceutical compounds in human plasma with chromatographic resolution using an alkyl‐bonded silica rod column
Authors: Plumb Robert , Dear Gordon , Mallett David , Ayrton John 
Published: August 2002

AbstractMonolithic columns have been successfully used with steep gradient and high flow rates for the direct analysis of a candidate pharmaceutical compound in human plasma. The monolithic columns showed excellent robustness with nearly 300 20‐µL injections of plasma (diluted 1:1 with water) being made onto one column without significant deterioration in performance. The system gave excellent sensitivity with a limit of quantification of 5 ng/mL being achieved. Unlike previous methods of direct analysis the monolithic columns showed excellent resolution even after nearly 300 plasma injections. The column performance was measured before and after the analysis of the plasma samples. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of drug concentrations in plasma by a highly automated, generic and flexible protein precipitation and liquid chromatography/tandem mass spectrometry method applicable to the drug discovery environment
Authors: O'Connor Desmond , Clarke Dawn E. , Morrison Denise , Watt Alan P. 
Published: August 2002

AbstractThis report presents a highly automated procedure for the determination of drug concentrations in plasma samples. The method is generic, in that it has been applied without adaptation to many different drug candidate molecules, but is also flexible, in that variations in the nature and number of samples to be analyzed can be readily accommodated. The method includes preparation of dilutions of analyte stock solutions, spiking these into control plasma to generate analytical standards, and preparation of samples suitable for analysis by high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) by precipitation of plasma proteins with acetonitrile, centrifugation, and dilution of the supernatants with HPLC buffer. All of these steps, apart from centrifugation, are performed without manual intervention on an automated liquid‐handling workstation using 96‐well plates. Analysis is by HPLC/MS/MS, using a generic HPLC gradient. Commercially available software was used for optimization of parameters for analysis by HPLC/MS/MS, integration of chromatographic peaks, and quantification of drug concentrations. The use of this methodology in our laboratory has greatly facilitated the analysis of small sample sets for a large number of analytes, a situation regularly encountered in an early drug discovery environment. Copyright © 2002 John Wiley & Sons, Ltd.
Molecular epidemiology of respiratory syncytial virus
Authors: Cane Patricia A. 
Published: August 2002

AbstractHuman respiratory syncytial virus (RSV) is the major cause of lower respiratory tract disease in infants. It is unusual in that it causes repeated infections throughout life. Despite considerable efforts there is as yet no satisfactory vaccine available. This paper reviews the molecular epidemiology of the RSV and describes the complex genotypic structure of RSV epidemics. The evolution of the virus is discussed, with particular reference to the antigenic and genetic variability of the attachment glycoprotein. Copyright © 2001 John Wiley & Sons, Ltd.
LPV controller design for the nonlinear RTAC system
Authors: Park PooGyeon , Choi Doo Jin 
Published: August 2002

AbstractThis paper proposes three kinds of state‐feedback controllers for the nonlinear rotational and translational actuator (RTAC) benchmark problem. Interpolating a nonlinear system into an LPV system associated with time‐varying and state‐dependent weighting functions allows one to apply various linear system theories and techniques for analysing and synthesizing nonlinear systems, and thus to generate LMI criteria to supply various stabilizers and guaranteed cost controllers. This approach is more flexible for this benchmark problem than existing approaches in the literature because the other controllers excessively depend on the structure of the nonlinear system. Simulation results show the performance of the resulting controllers. Copyright © 2001 John Wiley & Sons, Ltd.
Some nonlinear optimal control problems with closed‐form solutions
Authors: Margaliot Michael , Langholz Gideon 
Published: August 2002

AbstractOptimal controllers guarantee many desirable properties including stability and robustness of the closed‐loop system. Unfortunately, the design of optimal controllers is generally very difficult because it requires solving an associated Hamilton–Jacobi–Bellman equation. In this paper we develop a new approach that allows the formulation of some nonlinear optimal control problems whose solution can be stated explicitly as a state‐feedback controller. The approach is based on using Young's inequality to derive explicit conditions by which the solution of the associated Hamilton–Jacobi–Bellman equation is simplified. This allows us to formulate large families of nonlinear optimal control problems with closed‐form solutions. We demonstrate this by developing optimal controllers for a Lotka–Volterra system. Copyright © 2001 John Wiley & Sons, Ltd.
Missile autopilot design via a multi‐channel LFT/LPV control method
Authors: Pellanda Paulo C. , Apkarian Pierre , Tuan Hoang Duong 
Published: August 2002

AbstractIn this paper, the missile pitch‐axis autopilot design is revisited using a new and recently available linear parameter‐varying (LPV) control technique. The missile plant model is characterized by a linear fractional transformation (LFT) representation. The synthesis task is conducted by exploiting new capabilities of the LPV method: firstly, a set ofH2/H∞criteria defined channel‐wise is considered; secondly, different Lyapunov and scaling variables are used for each channel/specification which is known to reduce conserva tism; and finally, the controller gain‐scheduling function is constructed as affine matrix‐valued function in the polytopic co‐ordinates of the scheduled parameter. All these features are examined and evaluated in turn for the missile control problem. The method is shown to provide additional flexibility to tradeoff conflicting and demanding performance and robustness specifications for the missile while preserving the practical advantage of previous single‐objective LPV methods. Finally, the method is shown to perform very satisfactorily for the missile autopilot design over a wide range of operating conditions. Copyright © 2001 John Wiley & Sons, Ltd.
Interactive force control of an operator–mobile manipulator coordination system
Authors: Chung Jae H. 
Published: August 2002

AbstractIn this article, a new type of coordination control called interactive force control is developed for an operator–mobile manipulator coordination system (OMMCS) based on a base force/torque sensor. In the interactive force control scheme, a robust force control of the manipulator and impedance control of the mobile platform are integrated to achieve smooth interaction between the operator, the manipulator, and the mobile platform. In simulation, the developed methods are compared for control performance in tracking and force regulation. Simulation results show the promise of the developed control scheme, which utilizes robust force control based on a base force/torque sensor. © 2002 Wiley Periodicals, Inc.
Spherically actuated platform manipulator
Authors: Williams Robert L. , Poling Dana B. 
Published: August 2002

AbstractThis article presents the inverse and forward pose and rate kinematics solutions for a novel 6‐DOF platform manipulator, actuated by two base‐mounted spherical actuators. The moving platform is connected to the fixed base by two identical spherical‐prismatic‐universal serial chain legs. The S‐joint is active, and the remaining two joints in each chain are passive. An analytical solution is presented for the inverse pose problems, a semi‐analytical solution is presented for the rate problems, and the numerical Newton–Raphson technique is employed to solve the forward pose problem. Unfortunately, the passive joint variables cannot be ignored in the kinematics solutions as they can for the Gough–Stewart platform. Examples are presented and hardware has been built, using two Rosheim Omni‐Wrists on loan from NASA as the spherical actuators. © 2001 John Wiley & Sons, Inc.
A performance criterion for the depth estimation with application to robot visual servo control
Authors: Fang Chang‐Jia , Lin Shir‐Kuan 
Published: August 2002

AbstractThis article deals with the depth observability problem of a robot visual system with a moving camera. In the visual system, the unknown depth of a feature point is estimated from the input of the camera velocity and the output of the image of the feature point. Although it is well known that the linear velocity of the camera must satisfy some constraints for successful depth estimation, this proposes a criterion to measure the performance of the depth estimation, which is a heuristic extension from an estimation result of a linear system. This performance criterion depends on both the image position and the linear velocity of the camera. Some simulation and experiment examples demonstrate and verify the proposed performance criterion. Furthermore, this criterion is used to develop a new visual servo control scheme that has good performance in both the depth estimation and the visual control. This control scheme is also verified by a simulation example. © 2001 John Wiley & Sons, Inc.
Analytic determination of workspace and singularities in a parallel pointing system
Authors: Di Gregorio Raffaele 
Published: August 2002

AbstractThis paper studies a parallel pointing system, named U‐2PUS, used in biomechanic and aerospace
applications. In the literature, U‐2PUS position analysis has already been solved in closed form, whereas
simple and efficient tools to address workspace determination and singularity locations are still lacking. In this
paper, the analytic expression of the U‐2PUS workspace is derived, and a bidimensional representation of
the workspace is proposed. The U‐2PUS mobility analysis is addressed, and a singularity locus analytic
expression, explicitly containing the manipulator geometric parameters and the end‐effector orientation
parameters, is derived. Moreover, it is shown that the U‐2PUS singularity locus can be represented by
curves (singularity curves) on a Cartesian plane having the U‐2PUS generalized coordinates on the
coordinate axes. Finally, the presented singularity conditions are geometrically interpreted. © 2002 John
Wiley & Sons, Inc.
Identifying the natural flow regime and the relationship with riparian vegetation for two contrasting western Australian rivers
Authors: Pettit N.E. , Froend R.H. , Davies P.M. 
Published: August 2002

AbstractThe natural flow regime and the relationship between flows and riparian vegetation are described for sites on both the Blackwood River in south‐western Australia and the Ord River in north‐western Australia. Analysis of long‐term flow data showed the historic mean monthly river discharge for the Blackwood River is strongly seasonal and highly predictable with generally low variability each month. The Ord River showed a strong seasonality of flows with about 92% of the (total) yearly flow occurring between December and March. Flow variability was very high (e.g. coefficient of variation >100% for all months) but highly predictable, with this mostly attributed to low but constant dry‐season flows. Water depth, duration of flood events and the number of flood events per year show a significant correlation with aspects of the riparian vegetation within experimental vegetation plots. Results highlight the strong relationship between floristics, life form structure and population dynamics with stream hydrology. On the Blackwood River, species richness and cover of shrubs reduced with increased duration and frequency of flooding, while cover of exotic species and annual herbs increased with increased flooding. Germination of tree seedlings was not influenced by flood regime but size class of tree species increased with flooding frequency. On the Ord River, species richness was not influenced by flooding regime. However, cover of perennial grasses increased with flooding frequency whilst cover of shrubs decreased. There was no relationship between flooding and seedling establishment whilst tree size class decreased with increased flooding. The methods described here can be used to compare the response of different components of the riparian vegetation to different fluvial regimes (e.g. because of impoundment and abstraction). This technique can be expanded for the management of riparian zones and planning rehabilitation programmes. It may also be useful for improving the ecological knowledge base for setting environmental flows in regulated systems. Copyright © 2001 John Wiley & Sons, Ltd.
Stochastic optimization of LMS resource assignments
Authors: Jahn Axel 
Published: August 2002

AbstractThis paper presents stochastic optimization methods for frequency assignments in land mobile satellite systems. Genetic algorithms and simulated annealing can be used for channel assignment in satellite multibeam antennas. The principles of stochastic optimization is described, the performance of the assignment is evaluated as fitness or cost criteria based on the co‐channel interference. Several operators for selection, mutation and crossover are investigated. Finally, results show the applicability and power of the algorithms. The results are compared against regular reuse patterns for satellite antennas with equal beamwidth and equal cell area. Copyright © 2001 John Wiley & Sons, Ltd.
“Mapping to know”: The effects of representational guidance and reflective assessment on scientific inquiry
Authors: Toth Eva Erdosne , Suthers Daniel D. , Lesgold Alan M. 
Published: August 2002

AbstractThis study documents an instructional methodology to teach a fundamental reasoning skill during scientific inquiry: the evaluation of empirical evidence against multiple hypotheses. Using the “design experiment” approach, with iterative cycles we developed an instructional framework that lends itself to authentic scientific inquiry by providing a nontraditional approach to three aspects of learning: the activities students are engaged in during scientific inquiry, the tools students use while constructing knowledge, and the assessment of learning outcomes. The present article focuses on the contribution of two components of this instructional framework: the effect of technology‐based knowledge‐representation tools and the effect of reflective assessment on learning to act and think scientifically. The technological tools of the framework allowed students to represent their developing knowledge of natural phenomena with either graphical mapping or with word‐processed prose. The reflective assessment we used was a form of inquiry rubrics that provided clear expectations for optimal progress throughout the entire process of inquiry by indicating specific assessment criteria for the various components of scientific inquiry. The results indicated that in real‐life‐like classroom investigations designed to teach students how to evaluate data in relation to theories, the use of evidence mapping is superior to prose writing. Furthermore, this superior effect of evidence mapping was greatly enhanced by the use of reflective assessment throughout the inquiry process. Modes of representational guidance explain both the superior effect of evidence mapping as well as the discrepancy between the effects of explicit reflection on evidence mapping compared to prose writing. These results have fundamental implications for the development of cognitively‐based classroom learning environments and for the design of further research on learning. © 2002 Wiley Periodicals, Inc. Sci Ed 86:264–286, 2002; DOI 10.1002/sce.10004
Considering the nature of scientific problems when designing science curricula
Authors: Stewart James , Rudolph John L. 
Published: August 2002

AbstractA recurring theme of science education reform has been the creation of classroom opportunities that allow students to develop insights into the professional practice of scientists. The posing and solving of problems of a variety of types, a process central to scientific practice, provides a useful framework for structuring such opportunities for students. Most problems that students encounter can be characterized as model–data fit problems, in which solvers fit available data to an appropriate explanatory model. Although these problems are important, we argue that it is essential to expand the range of problems students encounter to include those that require solvers to confront the conceptual coherence of their explanatory models and to examine the relationship of those models to other scientific models, methodological norms, and common worldviews. In this article, we describe the nature and existence of both model–data fit and conceptual problems in science and then examine two curricular projects, one in genetics and one in evolutionary biology, that attempt to integrate these problems into classroom instruction. © 2001 John Wiley & Sons, Inc. Sci Ed 85:207–222, 2001.
Precise subpixel estimation on area‐based matching
Authors: Shimizu Masao , Okutomi Masatoshi 
Published: August 2002

AbstractArea‐based matching is a common procedure in various fields such as image‐based measurements, stereo image processing, and fluidics. Subpixel estimation using parabola fitting over three points with their similarity measures is also a common method to increase the resolution of matching. However, few investigations or studies concerning the characteristics of this estimation have been reported. In this paper, we have analyzed the subpixel estimation error by using an approximate image function and three kinds of similarity measures for matching. The results illustrate some inherently problematic phenomena such as so‐called “pixel‐locking.” In addition, we propose a new algorithm to greatly reduce subpixel estimation error. This method is independent of the similarity measure and quite simple to implement. The advantage of our novel method is confirmed through experiments using three different types of images. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(7): 1–10, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10098