bluuebunny/crossref_metadata_2025_split huggingface dataset:
JWKB method as an exact technique
Authors: Shen Hujun , Silverstone Harris J. 
Published: March 2004

AbstractThe JWKB method involves divergent asymptotic expansions in powers of ħ. Borel summability turns divergence into convergence, leading to exact solutions of the Schrödinger equation. The formulas that connect real solutions across linear turning points, where the terms of the expansion are singular, are complex but nonunidirectional. A series of basic problems constructed from linear potentials—for which the JWKB solutions are simple, in which the boundary conditions and physics differ, but for which the turning points are the same—is used to demonstrate the nondirectionality of the turning points and how “Borel sum approximants” lead to exact energy eigenvalues. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Bicyclopropylidene radical cation: A rehybridization ring opening to tetramethyleneethane
Authors: Norberg Daniel , Larsson Per‐Erik , Dong Xi‐Cheng , Salhi‐Benachenhou Nessima , Lunell Sten 
Published: March 2004

AbstractA computational study has been undertaken to elucidate the mechanism of the bicyclopropylidene radical cation (BCP•+) rearrangement into the tetramethyleneethane radical cation (TME•+). A stepwise mechanism is found for the first ring opening, with an activation energy of 7.3 kcal mol−1, while the second ring opening proceeds with no activation energy. Each ring opening is combined with a striking pyramidalization of one carbon atom in the central bond. In a natural bond orbital (NBO) analysis, the dominating reaction coordinate during the ring opening is found to be the olefinic carbon atom rehybridization, which also favors the continued bond breaking. Widely different ESR parameters are computed for the two sets of four protons in BCP•+, in excellent agreement with the observed spectrum, which are interpreted in the NBO analysis in terms of two hyperconjugative effects. Two minimum energy structures are located for TME•+, separated by a cusp on the internal rotation path of this cation, both of which show ESR parameters in good agreement with the observed spectrum for TME•+. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Semi‐classical formulation of time‐dependent discrete variable representation method
Authors: Puzari Panchanan , Adhikari Satrajit 
Published: March 2004

AbstractIn this article, we apply a novel time‐dependent discrete variable representation (TDDVR) method proposed by Barkakaty and Adhikari to investigate tunneling through an Eckart barrier. This semi‐classical method is theoretically rigorous and straightforward to implement. Among the TDDVR formulations, this report presents the first derivation of a rigorous form of quantum force (QF) for the present perspective. The validity of this semi‐classical approach is demanded based on the excellent agreement of the tunneling probability with the corresponding quantum results. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Liquid supports for ultraviolet atmospheric pressure matrix‐assisted laser desorption/ionization
Authors: Turney Kevin , Harrison W. W. 
Published: March 2004

AbstractAtmospheric pressure (AP) liquid matrices for ultraviolet (UV) matrix‐assisted laser desorption/ionization (MALDI) are presented. Doping a known organic chromophore, α‐cyano‐4‐hydroxycinnamic acid (CHCA), into liquid media yielded a homogenous sample system with simplified sample preparation, increased sample lifetime, and added utility for APMALDI ion sources. Compared with vacuum situations, AP matrices are not as limited by vapor pressure, so liquid matrix formulations can focus on desorption and ionization versus vacuum stability and source contamination. The parameters studied include chromophore concentration, liquid support variations, and quantitation capability. Chromophore concentration adjustments provided insight into the necessary absorbance for UV‐APMALDI and demonstrated the importance of laser penetration depth. Liquid support variations allowed adjustments of sample lifetime and analyte solvents. Extended sample lifetime is beneficial for instrument tuning and source optimization; however, increased liquid viscosity lowers signal intensity. The shot‐to‐shot reproducibility, as examined with individual ion packets, suggests that the liquid matrix can alleviate some inconsistencies seen with solid MALDI, suggesting a possibility for better quantitation. The measurements for laser penetration depth, solution viscosity, and solvent additives could add to the information on MALDI mechanisms. The liquid matrix offers advantages that complement current MALDI methods. Copyright © 2004 John Wiley & Sons, Ltd.
A sensitive method for the determination of the novel cholinesterase inhibitor ZT‐1 and its active metabolite huperzine A in rat blood using liquid chromatography/tandem mass spectrometry
Authors: Li Chuan , Du Feifei , Yu Chen , Xu Xing , Zheng Jiang , Xu Fang , Zhu Dayuan 
Published: March 2004

AbstractZT‐1 has been developed as a novel acetylcholinesterase inhibitor, but is rapidly degraded to huperzine A (Hup A) in water or aqueous organic solvents. A sensitive method has been developed for simultaneous determination of ZT‐1 and its active metabolite Hup A in blood, and was applied to the investigation of the pharmacokinetics of ZT‐1 in rats. The method involves immediate hydrogenation of ZT‐1 with sodium borohydride to the stable form rZT‐1 following blood sampling. The NaBH4‐treated blood sample is then submitted to liquid‐liquid extraction, and the resultant extract is analyzed by liquid chromatography with electrospray ionization and tandem mass spectrometry. Huperzine B is used as internal standard for the quantification. ZT‐1 was found to be rapidly absorbed in the intestinal tract, with a time to reach the peak blood concentration (Tpeak) of 5 min after an intragastric dose of ZT‐1 embedded in povidone to rats at 0.5 mg ZT‐1/kg. The mean maximum blood concentration (Cmax) and area under the blood level‐time curve (AUC0 → 8) of ZT‐1 were 1.57 ng/mL and 0.48 ng · h/mL, respectively. The Tpeak, Cmax, and AUC values of the metabolite Hup A were 0.22 h, 109.9 ng/mL, and 96.3 ng · h/mL, respectively. Following an intravenous dose of 0.1 mg ZT‐1/kg rat body weight, the blood concentration of ZT‐1 was higher than that of Hup A, and the AUC0 → 8 values were 26.2 ng · h/mL for ZT‐1 and 6.0 ng · h/mL for Hup A. The elimination half‐lives (T1/2) of ZT‐1 and Hup A were 0.68 and 1.47 h, respectively. The oral bioavailability (F) of intact ZT‐1 in rats treated with ZT‐1 embedded in povidone was very low, 0.37%. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of betamethasone, dexamethasone and related compounds by liquid chromatography/electrospray mass spectrometry
Authors: Arthur Kathryn E. , Wolff Jean‐Claude , Carrier Dan J. 
Published: March 2004

AbstractA reversed‐phase high‐performance liquid chromatography/electrospray ionisation mass spectrometry (HPLC/ESI‐MS) method has been developed to conclusively differentiate the epimers betamethasone and dexamethasone and various esterification products (betamethasone and dexamethasone 21‐acetate, betamethasone and dexamethasone 21‐phosphate, betamethasone 17‐valerate, betamethasone 21‐valerate and betamethasone 17,21‐dipropionate) in counterfeit drugs. Good separation with baseline resolution of all epimers or isomers was obtained on a Zorbax Eclipse XDB or Luna C8 column, using a step gradient with mobile phases of 0.05 M ammonium acetate and acetonitrile. Betamethasones can also be distinguished by the relative abundance of their m/z 279 ion in the positive electrospray tandem mass spectra. The LC/MS or LC/MS/MS method developed was successfully applied to the analysis of drug product samples, i.e. creams and tablets. Copyright © 2004 John Wiley & Sons, Ltd.
Using a non‐invasive stable isotope tracer to measure the absorption of water in humans
Authors: Hill Rebecca J. , Bluck Leslie J. C. , Davies Peter S. W. 
Published: March 2004

AbstractThe development of solutions that prevent dehydration or promote adequate re‐hydration play a vital role in preventing fatigue during exercise, however, the methods commonly used to assess the hydration ability of such solutions are invasive and often assess the components of absorption separately. This paper describes using a non‐invasive deuterium tracer technique that assesses gastric emptying and intestinal absorption simultaneously to evaluate the uptake of water during rest and exercise. The kinetics of absorption are further examined by mathematical modelling of the data generated. For the rest group, 0.05 g/kg of body weight of deuterium, contained in gelatine capsules, was ingested with ordinary tap water and saliva samples were collected every 5 min for one hour while the subject remained seated. The deuterium was administered as above for the exercise group but sample collection was during one hour of exercise on a treadmill at 55% of the subject's maximum heart rate. The enrichment data for each subject were mathematically modelled and the parameters obtained were compared across groups using an independent samples t‐test. Compared with the rest condition, the exercise group showed delayed absorption of water as indicated by significant differences for the modelling parameters t2, t½, maximum absorption rate and solution absorption amount at t1. Labelling with a deuterium tracer is a good measure of the relative rate ingested fluids are absorbed by the body. Mathematical modelling of the data generates rates of maximum absorption and allows calculation of the percentage of the solution that is absorbed at any given time during the testing period. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of triforine using high‐performance liquid chromatography with tandem mass spectrometry
Authors: Harrold Julie A. , Sykes Mark D. , Goodrum Martin , Fussell Richard J. 
Published: March 2004

AbstractA method for determination of triforine using high‐performance liquid chromatography with electrospray tandem mass spectrometry was developed. A simple ethyl acetate extraction with solvent exchange into water/methanol was used for sample preparation. The method was validated at 0.01 and 0.05 mg kg−1 levels in apple, tomato and tinned blackcurrants. Recoveries were in the range 56.6–99.8% and no matrix suppression or enhancement effects were observed. © Crown Copyright 2004. Reproduced with the permission of Her Majesty's Stationary Office. Published by John Wiley & Sons, Ltd.
Co‐ordinated control design of generator excitation and SVC for transient stability and voltage regulation enhancement of multi‐machine power systems
Authors: Cong L. , Wang Y. , Hill D. J. 
Published: March 2004

AbstractThis paper presents a co‐ordinated control scheme for generator excitation and a static var compensator (SVC) to achieve transient stability, adequate damping and voltage regulation enhancement of multimachine power systems. By using the feedback linearization technique, the nonlinearities of the generator and the SVC model are cancelled. With the help of robust control theory, the interconnection between controllers, the variation of system structure and the parameter uncertainties are taken into consideration in the controller design. Only local measurements are required. Simulation results obtained from a three‐machine, one‐SVC example system show that the proposed controllers can provide good stability, voltage control and damping over a wide range of operating conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Adaptive nonlinear output feedback for transient stabilization and voltage regulation of power generators with unknown parameters
Authors: Damm Gilney , Marino Riccardo , Lamnabhi‐Lagarrigue Françoise 
Published: March 2004

AbstractThis work presents a nonlinear adaptive output feedback excitation control, designed for a synchronous generator modelled by a standard third‐order model on the basis of the physically available measurements of relative angular speed, active and reactive electric power and terminal voltage. The power angle, which is a crucial variable for the excitation control, as well as mechanical power and the impedance of the transmission line connecting the generator to an infinity bus, are not assumed to be available for feedback. The feedback control achieves transient stabilization and voltage regulation when faults occur to the turbines or the transmission lines, such that parameters (mechanical power and line impedance) may permanently take any (unknown) value. The controller recovers by adaptation the unknown values and simultaneously generates trajectories to be followed by the states, that converge to the new equilibrium point. Copyright © 2004 John Wiley & Sons, Ltd.
Co‐ordinatedH∞control of excitation and governor of hydroturbo‐generator sets: a Hamiltonian approach
Authors: Mei Shengwei , Liu Feng , Chen Ying , Lu Qiang 
Published: March 2004

AbstractThis paper presents a co‐ordinatedH∞controller design of excitation and governor of hydroturbo‐generator sets, which is on the basis of the port‐controlled Hamiltonian (PCH) method. Firstly, the dissipative Hamiltonian realization is achieved via static state feedback, and sequentially the Hamiltonian controller is obtained based on the theory of PCH system with dissipation. Such control strategies fully consider the inherent nonlinearities and non‐minimum phase characteristic of the system dynamics, including the rigid water‐hammer phenomenon. Furthermore, the property of disturbance attenuation of this controller is revealed in the sense ofH∞. The selection of the disturbance attenuation level and the corresponding feedback gain is discussed as well. Then the effects of control input constraints are analysed, sequentially, applied to design the co‐ordinatedH∞saturating control of the considered system. Finally, digital simulations that performed on a one‐machine, infinite‐bus (OMIB) system have verified the effectiveness of the proposed co‐ordinated controllers. Copyright © 2004 John Wiley & Sons, Ltd.
Transient stability improvement through excitation control
Authors: Bazanella A. S. , Conceição C. L. 
Published: March 2004

AbstractIn this paper we present, discuss, extend and compare different design methods for excitation control aiming at improving transient and steady‐state stability. A benchmark with bothLgVand interconnection and damping assignment (IDA) controllers is studied. Furthermore, dynamic extensions for these controllers, that do not require the knowledge of the operating point, are presented. Copyright © 2004 John Wiley & Sons, Ltd.
Accounting for Poisson noise in the multivariate analysis of ToF‐SIMS spectrum images
Authors: Keenan Michael R. , Kotula Paul G. 
Published: March 2004

AbstractRecent years have seen the introduction of many surface characterization instruments and other spectral imaging systems that are capable of generating data in truly prodigious quantities. The challenge faced by the analyst, then, is to extract the essential chemical information from this overwhelming volume of spectral data. Multivariate statistical techniques such as principal component analysis (PCA) and other forms of factor analysis promise to be among the most important and powerful tools for accomplishing this task. In order to benefit fully from multivariate methods, the nature of the noise specific to each measurement technique must be taken into account. For spectroscopic techniques that rely upon counting particles (photons, electrons, etc.), the observed noise is typically dominated by ‘counting statistics’ and is Poisson in nature. This implies that the absolute uncertainty in any given data point is not constant, rather, it increases with the number of counts represented by that point. Performing PCA, for instance, directly on the raw data leads to less than satisfactory results in such cases. This paper will present a simple method for weighting the data to account for Poisson noise. Using a simple time‐of‐flight secondary ion mass spectrometry spectrum image as an example, it will be demonstrated that PCA, when applied to the weighted data, leads to results that are more interpretable, provide greater noise rejection and are more robust than standard PCA. The weighting presented here is also shown to be an optimal approach to scaling data as a pretreatment prior to multivariate statistical analysis. Published in 2004 by John Wiley & Sons, Ltd.
A more general method for ranking the enrichment of alloying elements in passivation films
Authors: Castle J. E. , Asami K. 
Published: March 2004

AbstractThe corrosion of alloys is often characterized by an enrichment of one or other of the alloying elements within the surface oxide or even within the underlying metallic phase. For some three decades the measurement of such surface enrichment has been one of the most important contributions made by XPS to corrosion science. X‐ray photoelectron spectroscopy permits the composition of the oxide film to be distinguished from that of the metallic surface underlying the oxide so that both can be determined independently. In the mid‐1970s these measurements were crucial in showing that the selective enrichment of chromium in the electrochemical passivation of stainless steel occurred by selective dissolution of iron, and not by selective oxidation of chromium. Measurements of this type are important also in active corrosion, where there is no stable oxide film, as in studies of dealloying phenomena.The literature now contains numerous cases, many published by one of us (K.A.) based on studies of novel alloys produced in the Institute for Materials Research at Sendai. Typically, measurements are made for a series of binary compositions AxBy ranging from A‐rich to B‐rich alloys, in media that reflect the intended use of the alloy. The results are normally produced in the form of plots of cation composition An+/(An+ + Bm+) against bulk composition A/(A + B) or, in the case of dealloying, as Asurface/(Asurface + Bsurface) against the bulk composition. Although graphical representation is useful in giving the full picture of the alloy's behaviour, it is not so useful in cataloguing or indexing performance.In this paper we suggest a means to give a rank or performance index as a single number that will characterize the behaviour of the alloy over a wide range of composition for a given medium or exposure condition. The rank number does not imply that any particular mechanism of enrichment is in operation; in various cases of corrosion it might occur by selective precipitation (FeOOH on steels, CuO on cupronickels), by selective dissolution (dezincification of brass) or by preferential incorporation of ions in a passivating oxide or oxyhydroxide (Cr3+ on stainless steels). Although the rank has no mechanistic implications, it is useful within a known class of mechanistic behaviour for indicating the magnitude of the effect and thus for enabling an XPS measurement to be indicative of wanted, or unwanted, behaviour. For example, the rank number could be useful in indicating, perhaps from a single alloy composition, whether a degree of passivation is likely to be achieved for that mix of metallic elements. Copyright © 2004 John Wiley & Sons, Ltd.
Surface analysis of Co–Cr–Mo alloy and Ti substrates silanized with trialkoxysilanes and silane mixtures
Authors: Matinlinna J. P. , Laajalehto K. , Laiho T. , Kangasniemi I. , Lassila L. V. J. , Vallittu P. K. 
Published: March 2004

AbstractTitanium and cobalt–chromium–molybdenum alloy are widely used inert and biocompatible materials in dentistry and biomedicine. Both materials are non‐degradable and widely relevant in prosthodontics and orthopaedics. The aim of this study was to study the reactions of allyltrimethoxysilane (ALS) and a mixture of allyltrimethoxysilane and 3‐methacryloxypropyltrimethoxysilane (MPS) on Ti and Co–Cr–Mo alloy surfaces. The formation of a uniform, smooth siloxane film, a covalently bonded three‐dimensional Si and O layer, is a prerequisite for the substrate to be bonded with a composite resin. Two silane mixtures of different concentrations were applied onto titanium and Co–Cr–Mo alloy. The silanes were allowed to react with the substrate surface at room temperature and for 1 h at 110 °C. The hypothesis was that a mixture of MPS and ALS could form a uniform, smooth siloxane film on the substrate surface, although ALS is a structurally different trialkoxysilane. Fourier transform infrared spectroscopy, XPS and atomic force microscopy characterization and analysis verified the formation of the siloxane layer on metal substrates, especially on titanium, with silane and silane mixture treatments. Copyright © 2004 John Wiley & Sons, Ltd.
Surface modification of glass and glass fibres by plasma surface treatment
Authors: Lim Kyung‐Bum , Lee Duck‐Chool 
Published: March 2004

AbstractIn this study, glass and glass fibres were treated to dry interfacial treatment by the use of plasma technology. It has been presented that the optimum parameters for the best wettability of the samples at the time of plasma generation were an oxygen atmosphere, 0.1 Torr system pressure, 100 W discharge power and 3 min discharge time. Also, the surface resistance rate and dielectric property were improved. Copyright © 2004 John Wiley & Sons, Ltd.
Using roles in Java
Authors: Schrefl Michael , Thalhammer Thomas 
Published: March 2004

AbstractUsing roles in object‐oriented design leads to a more natural representation of a given problem domain. Despite a lot of research into role–based systems, there is still a gap between conceptual representations of roles and the usage of roles in strongly typed object‐oriented programming languages such as C++ or Java. Since these languages associate classes and their instances exclusively and permanently, representing evolving objects that may take on different roles over time is difficult without special support: (i) entities must be reclassified any time they evolve and (ii) class hierarchies may grow exponentially if entities may take on several independent roles.This article shows how role hierarchies can be easily implemented in Java. It introduces the Java Role Package, which provides a set of classes to support handling of evolving objects without modifying the semantics of Java itself. Copyright © 2004 John Wiley & Sons, Ltd.
Sex differences in opioid analgesia: clinical and experimental findings
Authors: Fillingim Roger B. , Gear Robert W. 
Published: March 2004

AbstractSex differences in analgesic responses to opioids have received increasing attention in recent years. This article examines the literature on sex differences in opioid analgesia, including the results of studies from the authors' own laboratories. In general, nonhuman animal studies suggest more robust opioid analgesic responses in males relative to females; however, the human studies completed to date seem to indicate greater opioid analgesia among females. The most consistent evidence of sex differences in analgesia comes from studies of κ‐agonist‐antagonists administered to patients following oral surgery. These data indicate more robust analgesia in females, and dose‐response characteristics suggest that these agents possess both analgesic and antianalgesic properties, and the agonists may produce these effects in different proportions for women versus men. In contrast, the data from laboratory pain models in humans suggest greater analgesic effects in women in response μ‐opioid agonists but not κ‐agonist‐antagonists. Multiple mechanisms may explain sex differences in opioid analgesia, including gonadal hormonal effects, pharmacokinetics and pharmacodynamics, genetic influences, balance of analgesic/antianalgesic processes, and psychological factors. However, the disparity of results obtained from different pain models—animals versus humans and clinical pain versus experimental pain in humans—suggests that the models themselves are mechanistically different. Additional investigation is warranted in order to further explicate the nature of sex differences in opioid analgesia and to elucidate the underlying mechanisms.