bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐level ab initio predictions of CO2N2O structure
Authors: Valdés H. , Rayón V. M. , Sordo J. A. 
Published: August 2002

AbstractAb initio calculations using MPn, QCISD, QCISD(T), and CCSD(T) methodologies and cc‐pVDZ, aug‐cc‐pVDZ, and cc‐pVTZ correlation‐consistent basis sets were carried out to determine the most stable structure of the CO2N2O van der Waals system. Rovibrational absorption and microwave spectroscopic constants are consistent with an approximately slipped parallel structure, but the experimental data cannot determine the orientation of N2O in the dimer. MPn and QCI methods lead to contradictory predictions. The QCI most stable structure, with the oxygen atom of N2O nearly over the carbon atom of CO2, is consistent with the experimental data. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 78–85, 2001
Structural motifs in α‐pyridyl‐ and α‐furylcinnamic acid assemblies— A molecular modeling study
Authors: Pálinkó I. , Körtvélyesi T. 
Published: August 2002

AbstractThe aggregation properties of stereoisomeric 2‐(3′‐furyl)‐3‐phenylpropenoic acids (FU3E, FU3Z, α‐furylcinnamic acids) and 2‐(4′‐pyridyl)‐3‐phenylpropenoic acids (PY4E, PY4Z, α‐pyridylcinnamic acids) were studied by the PM3 semiempirical quantum chemical method. Calculations revealed that (aromatic)CHN(O) hydrogen bonds made possible the attachment of dimer units; thus, virtually infinite chains can be built out of FU3Z, PY4E, and PY4Z. The energy‐minimized structure had zig‐zag configuration. PY4Z dimers allowed the formation of ribbonlike network; however, the number of structural units could not be increased infinitely. One of the furyl derivatives (FU3E) could not be stabilized either in the ribbon or the chain form; however, (aromatic)CHπ or (aromatic)π(aromatic)π interactions contribute to the packing pattern of the two dimers. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 269–275, 2001
The one‐particle Green function—Revisited
Authors: Winkler Peter , Dai Song‐Tao 
Published: August 2002

AbstractBased on the newly developed multichannel propagator theory for nonelectronic projectiles by Cederbaum and Winkler, the theory of the elastic, one‐particle propagator for electron projectiles has been revisited and formulated in the new framework. In the inelastic propagator theory, the contributions of all possible scattering channels are formally included and, as a result, closed sets of equations can be developed for both the advanced and retarded parts of the inelastic propagator. Furthermore, although the association of exact optical potentials with inelastic propagators has been established for nonelectronic projectiles, the same has not yet been achieved for electronic projectiles. In an early landmark study, Bell and Squires have shown the existence of an exact optical potential associated with the elastic electron propagator. The present article studies the same problem as it presents itself as the restriction of the inelastic propagator theory to the elastic case. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
A novel arsenical in clam kidney identified by liquid chromatography/electrospray ionisation mass spectrometry
Authors: Francesconi Kevin A. , Edmonds John S. 
Published: August 2002

AbstractKidneys of clams of the genus Tridacna accumulate metabolic products from symbiotic unicellular algae that grow in the mantles of the clams. These metabolites include organoarsenic compounds that are biosynthesised by algae from arsenate in seawater. The arsenic compounds in aqueous extracts of the kidney of the giant clam T. derasa were investigated by liquid chromatography/electrospray ionisation mass spectrometry. About 50% of the water‐soluble arsenic was present as dimethylarsinoylribosides and dimethylarsinate which are common algal metabolites. The major compound in the kidney (50% of water‐soluble arsenic) was identified as a 5‐dimethylarsinoyl‐2,3,4‐trihydroxycarboxylic acid, a new natural product. Copyright © 2001 John Wiley & Sons, Ltd.
Characterization and sequence confirmation of unnatural amino acid containing peptide libraries using electrospray ionization mass spectrometry
Authors: Rozenski Jef , Chaltin Patrick , Aerschot Arthur Van , Herdewijn Piet 
Published: August 2002

AbstractThe content of 24 12‐membered heptapeptide libraries was investigated using capillary liquid chromatography coupled with an electrospray ionization quadrupole orthogonal acceleration time‐of‐flight mass spectrometer. Adjustment of the chromatographic parameters led to the separation of most of the components. Extraction of the [M + 2H]2+ ions allowed us to demonstrate the presence of all expected species in the library and to evaluate their relative abundance in the mixture. Rapid sequence confirmation was achieved by subtraction of product ion spectra, a way to eliminate common ions and to simplify the spectra for interpretation. This technique can also easily be applied to other libraries consisting of components with a common core. Copyright © 2002 John Wiley & Sons, Ltd.
Planning for the next pandemic of influenza
Authors: Gust Ian D. , Hampson Alan W. , Lavanchy Daniel 
Published: August 2002

AbstractWorldwide influenza pandemics have occurred at irregular and unpredictable intervals throughout history and it is confidently expected that they will continue to occur in the future. It is now recognised that these pandemics result when avian influenza A viruses succeed in adaption to and transmission between humans. The impact of pandemic influenza is substantial in terms of morbidity, mortality and economic cost and there is the potential for serious social disruption. Influenza vaccines remain the most effective defence against influenza but will be in short supply during a pandemic, as will the new specific anti‐influenza drugs, due to the lead‐time required for production and rapid spread of the virus. To minimise the impact of pandemics it is imperative to maximise the availability of both vaccines and antivirals and to ensure that they are used optimally. This requires planning at both the international and national levels. The World Health Organization has, therefore, developed a staged plan for responding to a pandemic threat which is based principally on its surveillance program. It has also prepared guidelines to assist national agencies in their planning. However, there may be further options for increasing our preparedness which should also be considered. Copyright © 2001 John Wiley & Sons, Ltd.
Prophylaxis for CMV should now replace pre‐emptive therapy in solid organ transplantation
Authors: Hart Gregory D. , Paya Carlos V. 
Published: August 2002

AbstractCytomegalovirus is a significant cause of morbidity and mortality in transplantation. Controversy exists concerning whether prophylactic or pre‐emptive therapy is the optimal strategy for preventing CMV disease. In addition, CMV impacts the transplanted graft, transplant recipient and transplant programme beyond just causing CMV disease; thus questioning whether ‘asymptomatic’ CMV replication should also be prevented. In this Forum article, prophylactic therapy is advocated as the preferred approach for preventing CMV disease. Prophylactic therapy has a large body of supportive controlled clinical studies demonstrating its efficacy and cost effectiveness. In addition, prophylactic therapy has the benefit of preventing other herpes viruses and other opportunistic superinfections by reducing the immunosuppressive effects of CMV. Moreover, a small but growing body of information suggests that prophylactic therapy may also have a beneficial effect on organ outcomes, including rejection. In contrast, pre‐emptive therapy is limited by its reliance on intensive surveillance, which presents logistical difficulties and requires perfect patient compliance. Ambiguity still exists concerning the best surveillance method and its effect on patient‐care costs. Each proposed diagnostic approach has limitations, which are affected by the prevalence of CMV in the population studied, the particular assay employed, and the frequency of surveillance. The suggested benefits of pre‐emptive therapy, such as decreased cost, fewer adverse medication effects and less antiviral resistance have not been adequately proven in head‐to‐head clinical studies. We therefore support the proposition that transplant patients at risk for any level of CMV replication will significantly benefit from effective antiviral prophylaxis. Copyright © 2001 John Wiley & Sons, Ltd.
Human cytomegalovirus terminase as a target for antiviral chemotherapy
Authors: Bogner Elke 
Published: August 2002

AbstractHerpesviral DNA packaging is a complex process involving binding and cleavage of DNA containing the specific DNA‐packaging motifs, pac1 and pac2, and packaging of the resulting unit‒length genomes into preformed procapsids. This process is believed to be mediated by two packaging proteins, the terminase subunits. In the case of human cytomegalovirus the terminase consists of the proteins pUL56 and pUL89. While pUL56 (i) mediates the specific binding to pac sequences on the concatamers, (ii) provides energy for the translocation of the DNA to the procapsids and (iii) associates itself with the capsid for enabling the entry of the DNA into the procapsid, pUL89 is mainly required to effect DNA cleavage. Based on the limited efficacy of the current drugs ganciclovir, cidofovir and foscarnet, new antiviral therapeutics appear to be in demand. Inhibitors targeting pUL56 and/or pUL89 may offer an attractive alternative since mammalian cell DNA replication does not involve cleavage of concatameric DNA. Drugs targeted to terminase‐like proteins should therefore be safe and highly selective. Copyright © 2002 John Wiley & Sons, Ltd.
Observer‐based adaptive robust control of a class of nonlinear systems with dynamic uncertainties
Authors: Yao Bin , Xu Li 
Published: August 2002

AbstractIn this paper, a discontinuous projection‐based adaptive robust control (ARC) scheme is constructed for a class of nonlinear systems in an extended semi‐strict feedback form by incorporating a nonlinear observer and a dynamic normalization signal. The form allows for parametric uncertainties, uncertain nonlinearities, and dynamic uncertainties. The unmeasured states associated with the dynamic uncertainties are assumed to enter the system equations in an affine fashion. A novel nonlinear observer is first constructed to estimate the unmeasured states for a less conservative design. Estimation errors of dynamic uncertainties, as well as other model uncertainties, are dealt with effectively via certain robust feedback control terms for a guaranteed robust performance. In contrast with existing conservative robust adaptive control schemes, the proposed ARC method makes full use of the available structural information on the unmeasured state dynamics and the prior knowledge on the bounds of parameter variations for high performance. The resulting ARC controller achieves a prescribed output tracking transient performance and final tracking accuracy in the sense that the upper bound on the absolute value of the output tracking error over entire time‐history is given and related to certain controller design parameters in aknownform. Furthermore, in the absence of uncertain nonlinearities, asymptotic output tracking is also achieved. Copyright © 2001 John Wiley & Sons, Ltd.
Oscillation elimination of tip regulation for a single‐link flexible manipulator
Authors: Cao Wen‐Jun , Xu Jian‐Xin 
Published: August 2002

AbstractMany existing variable structure control schemes for flexible manipulators use a conventional sliding surface, which is linear with respect to system states. It results in a reduced‐order sliding motion, i.e. the closed‐loop dynamics during ideal sliding has reduced number of eigenvalues to be assigned, and the fixed eigenvalue at the origin functions as integrator and may degrade system robustness. In this paper, an integral‐type sliding surface is proposed which obtains a full‐order sliding motion, such that all the eigenvalues of the closed‐loop dynamics can be assigned. The integral‐type sliding surface is derived from a reference model which does not have any finite zero but all negative real poles. In order to force the system to follow the reference model in the presence of the unstructured uncertainties, a variable structure controller is adopted. When in sliding mode, the system performs as the reference model. Hence there will be no vibration and the tip position regulation can be achieved when the system approaches steady‐state. Simulation results demonstrate the effectiveness of the proposed approach. Copyright © 2001 John Wiley & Sons, Ltd.
On relay feedback and chaotic systems
Authors: Sugiki Akihiko , Hatakeyama Shoshiro , Furuta Katsuhisa 
Published: August 2002

AbstractThe feedback connection of a linear system with a memoryless nonlinearity is recognized as a candidate for chaos‐generating structure. This paper proposes a chaotic nonlinear feedback system with a relay connected to a biproper linear system. The proposed chaotic system is analysed using chaos criteria proposed by Genesio and Tesi. This paper also shows an equivalence relation between the proposed system and the Brockett chaotic system through the linear input–output transformation. Copyright © 2001 John Wiley & Sons, Ltd.
Compositionality issues in discrete, continuous, and hybrid systems
Authors: van der Schaft A. J. , Schumacher J. M. 
Published: August 2002

AbstractModels of complex dynamical systems are often built by connecting submodels of smaller parts. The key to this method is the operation of ‘interconnection’ or ‘composition’ which serves to define the whole in terms of its parts. In the setting of smooth differential equations the composition operation has often been regarded as trivial, but a quite different attitude is found in the discrete domain where several definitions of composition have been proposed and different semantics have been developed. The non‐triviality of composition carries over from discrete systems to hybrid systems. The paper discusses the compositionality issue in the context of discrete, continuous, and hybrid systems, mainly on the basis of a number of examples. Copyright © 2001 John Wiley & Sons, Ltd.
Hybrid control of force transients for multi‐point injection engines
Authors: Balluchi Andrea , Benvenuti Luca , Di Benedetto Maria Domenica , Sangiovanni‐Vincentelli Alberto L. 
Published: August 2002

AbstractWe address the problem of delivering as quickly as possible a requested torque produced by a spark ignition engine equipped with a multi‐point port injection manifold and with electronic throttle. The optimal control problem, subject to the constraint that the air–fuel ratio stays within a pre‐assigned range around the stoichiometric ratio, is solved for a detailed, cycle‐accurate hybrid model with a hybrid control approach based on a two‐step process. In the first step, a continuous approximation of the hybrid problem is solved exactly. Then, the control law so obtained is adjusted to satisfy the constraints imposed by the hybrid model. The quality of the control law has been in part analytically demonstrated and in part validated with simulations. Copyright © 2001 John Wiley & Sons, Ltd.
Pointing control design for a high precision flight telescope using quantitative feedback theory
Authors: Bentley Anthony E. 
Published: August 2002

AbstractA pointing control system is developed and tested for a flying gimbaled telescope. The two‐axis pointing system is capable of sub‐microradian pointing stability and high accuracy in the presence of large host vehicle jitter. The telescope also has high agility — it is capable of a 50° retarget (in both axes simultaneously) in less than 2 s. To achieve the design specifications, high‐accuracy, high‐resolution, two‐speed resolvers were used, resulting in gimbal‐angle measurements stable to 1.5 µrad. In addition, on‐axis inertial angle displacement sensors were mounted on the telescope to provide host‐vehicle jitter cancellation. The inertial angle sensors are accurate to about 100 nrad, but do not measure low‐frequency displacements below 2 Hz. The gimbal command signal includes host‐vehicle attitude information, which is band‐limited. This provides jitter data below 20 Hz, but includes a variable latency between 15 and 25 ms. One of the most challenging aspects of this design was to combine the inertial‐angle‐sensor data with the less perfect information in the command signal to achieve maximum jitter reduction. The optimum blending of these two signals, along with the feedback compensation were designed using Quantitative Feedback Theory. Copyright © 2001 John Wiley & Sons, Ltd.
Experimental testing of a discrete‐time sliding mode controller for trajectory tracking of a wheeled mobile robot in the presence of skidding effects
Authors: Corradini M. Letizia , Leo T. , Orlando G. 
Published: August 2002

AbstractThis article addresses the trajectory tracking problem for a wheeled mobile base, considering the presence of disturbances that violate the nonholonomic constraint, and using an approximated discrete‐time model for the vehicle. The proposed solution is based on discrete‐time sliding mode control, in order to ensure that the controller is both robust and implementable. The asymptotic boundedness of the discrete‐time tracking errors is theoretically proved, and experimental results are reported, showing the effectiveness of the proposed control law. © 2002 Wiley Periodicals, Inc.
Globally asymptotically stable tracking control for a trailer system
Authors: Kim Doh‐Hyun , Oh Jun‐Ho 
Published: August 2002

AbstractThis article addresses a tracking controller design for a trailer system consisting of a steering tractor and a passive trailer linked with a rigid free joint and having nonholonomic constraints. We design the tracking controller using the Lyapunov direct method, for both forward and backward driving of the trailer system. Backward driving is unstable, and thus is more difficult than forward driving. In previous research, we proposed a globally asymptotically stable (GAS) tracking control for forward driving of a trailer system with nonholonomic constraints. In this article, we implement the GAS tracking controller for forward and backward driving, and perform experiments using visual feedback and remote control systems. The experimental results represent stable responses and demonstrate the effectiveness of our method. © 2002 Wiley Periodicals, Inc.
Autonomous selection and modification of camera configurations using visibility and manipulability measures
Authors: Chu Gil W. , Chung Myung J. 
Published: August 2002

AbstractIn this article, we present a camera control method in which the selection of an optimal camera position and the modification of camera configurations are accomplished according to changes in the surroundings. For the autonomous selection and modification of camera configurations during tasks, we consider the camera's visibility and the manipulator's manipulability. The visibility constraint guarantees that the whole of a target object can be “viewed” with no occlusions by the surroundings, and the manipulability constraint guarantees avoidance of the singular position of the manipulator and rapid modification of the camera position. By considering visibility and manipulability constraints simultaneously, we determine the optimal camera position and modify the camera configuration such that visual information for the target object can be obtained continuously during tasks. The results of simulations and experiments show that the active camera system with an eye‐in‐hand configuration can modify its configuration autonomously according to the motion of the surroundings by applying the proposed camera control method. © 2002 Wiley Periodicals, Inc.
Vision‐based terrain characterization and traversability assessment
Authors: Howard Ayanna , Seraji Homayoun 
Published: August 2002

AbstractThis article presents novel techniques for real‐time terrain characterization and assessment of terrain traversability for a field mobile robot using a vision system and artificial neural networks. The key terrain traversability characteristics are identified as roughness, slope, discontinuity, and hardness. These characteristics are extracted from imagery data obtained from cameras mounted on the robot and are represented in a fuzzy logic framework using perceptual, linguistic fuzzy sets. The approach adopted is highly robust and tolerant to imprecision and uncertainty inherent in sensing and perception of natural environments. The four traversability characteristics are combined to form a single Fuzzy Traversability Index, which quantifies the ease‐of‐traversal of the terrain by the mobile robot. Experimental results are presented to demonstrate the capability of the proposed approach for classification of different terrain segments based on their traversability. © 2001 John Wiley & Sons, Inc.
Responses of consumers and food resources to a high magnitude, unpredicted flood in the upper Mississippi River basin
Authors: Delong Michael D. , Thorp James H. , Greenwood Kim S. , Miller Michael C. 
Published: August 2002

AbstractThe Mississippi and Missouri Rivers experienced flooding in 1993 that fell outside the annual predictable flood period of spring and early summer. Flooding began in late June, peaked in late July (25 232 m3/s on the upper Mississippi and 21 240 m3/s on the Missouri) and remained at or near flood stage into October 1993. This study was performed to determine if disturbance by an unpredicted flood event would alter trophic dynamics of river–floodplain systems by creating shifts in the composition of organic matter available to consumers. The Ohio River, which did not flood during the same period, was examined for comparison. Stable isotopic ratios of carbon and nitrogen from samples collected in 1993 and 1994 were used to characterize potential food sources and determine linkages between food sources and invertebrate and fish consumers. Pairwise contrasts, performed separately for each river, indicated there were few interannual differences in δ13C and δ15N of organic matter sources and consumers. Between sample period (flood year versus normal water year) trends in both flooded rivers were similar to between‐year trends observed for the Ohio River. Trophic structure of the Mississippi and Ohio Rivers was similar in both years, with fine and ultra‐fine transported organic matter and dissolved organic matter representing the major sources of organic matter. Overlapping isotopic signatures in the Missouri River made tracking of sources through the consumers difficult, but similarities in δ13C and δ15N between years indicated trophic structure did not change in response to the flood. The results suggest that consumers continued to rely on sources of organic matter that would be used in the absence of the unpredicted 1993 flood. It is proposed that trophic structure did not change in response to flooding in the Mississippi and Missouri Rivers because both rivers exhibited the same trends observed in the Ohio River. Copyright © 2001 John Wiley & Sons, Ltd.