Distribution by Scientific Domains

Selected Abstracts

Maximum likelihood constrained deconvolution.

I: Algorithm, qualitative, quantitative enhancement in synthetic two-dimensional NMR spectra
Abstract The maximum likelihood method is a constrained iterative spectral deconvolution technique in which a spectral fitting model is determined by minimizing the variance of fit in the time domain in a nonlinear iterative manner. Application of this method to synthetic 2-dimensional (2-D) NMR spectra, which have heavily overlapped multiplets associated with low signal to noise ratios, yields contrast-enhanced spectra with simultaneous noise suppression and resolution improvement. This protocol greatly facilitates peak recognition and often partitions overlapping multiplets into individual components, leading to a more accurate interpretation of resonance frequencies, coupling constants, and multiplets than does the conventional apodization or Fourier transform method. These advantages are useful for constructing reliable 3-D molecular structures for complex molecular systems. © 2002 Wiley Periodicals, Inc. Concepts Magn Reson 14: 402,415, 2002 [source]

A North American multilaboratory study of CD4 counts using flow cytometric panleukogating (PLG): A NIAID-DAIDS Immunology Quality Assessment Program Study,,§¶

CYTOMETRY, Issue S1 2008
Thomas N. Denny
Abstract Background The global HIV/AIDS pandemic and guidelines for initiating anti-retroviral therapy (ART) and opportunistic infection prophylaxis demand affordable, reliable, and accurate CD4 testing. A simple innovative approach applicable to existing technology that has been successfully applied in resource-challenged settings, PanLeukogated CD4 (PLG), could offer solutions for cost saving and improved precision. Methods Day-old whole blood from 99 HIV+ donors was simultaneously studied in five North-American laboratories to compare the performance of their predicate methods with the dual-platform PLG method. The predicate technology included varying 4-color CD45/CD3/CD4/CD8 protocols on different flow cytometers. Each laboratory also assayed eight replicate specimens of day-old blood from 10 to 14 local donors. Bias and precision of predicate and PLG methods was studied between- and within-participating laboratories. Results Significantly (P < 0.0001) improved between-laboratory precision/coefficient of variation (CV%) was noted using the PLG method (overall median 9.3% vs. predicate median CV 13.1%). Within-laboratory precision was also significantly (P < 0.0001) better overall using PLG (median 4.6% vs. predicate median CV 6.2%) and in 3 of the 5 laboratories. PLG counts tended to be 11% smaller than predicate methods (P < 0.0001) for shipped (median of predicate,PLG = 31) and local specimens (median of predicate,PLG = 23), both overall and in 4 of 5 laboratories (median decreases of 4, 16, 20, and 21% in shipped specimens); the other laboratory had a median increase of 5%. Conclusion Laboratories using predicate CD4 methods similar to those in this study could improve their between-laboratory and their within-laboratory precision, and reduce costs, by switching to the PLG method after adequate training, if a change (usually, a decrease) in CD4 counts is acceptable to their health systems. © 2008 Clinical Cytometry Society [source]

Structural and biophysical simulation of angiogenesis and vascular remodeling ,

Ralf Gödde
Abstract The purpose of this report is to introduce a new computer model for the simulation of microvascular growth and remodeling into arteries and veins that imitates angiogenesis and blood flow in real vascular plexuses. A C++ computer program was developed based on geometric and biophysical initial and boundary conditions. Geometry was defined on a two-dimensional isometric grid by using defined sources and drains and elementary bifurcations that were able to proliferate or to regress under the influence of random and deterministic processes. Biophysics was defined by pressure, flow, and velocity distributions in the network by using the nodal-admittance-matrix-method, and accounting for hemodynamic peculiarities like Fahraeus-Lindqvist effect and exchange with extravascular tissue. The proposed model is the first to simulate interdigitation between the terminal branches of arterial and venous trees. This was achieved by inclusion of vessel regression and anastomosis in the capillary plexus and by remodeling in dependence from hemodynamics. The choice of regulatory properties influences the resulting vascular patterns. The model predicts interdigitating arteriovenous patterning if shear stress-dependent but not pressure-dependent remodeling was applied. By approximating the variability of natural vascular patterns, we hope to better understand homogeneity of transport, spatial distribution of hemodynamic properties and biomass allocation to the vascular wall or blood during development, or during evolution of circulatory systems. © 2001 Wiley-Liss, Inc. [source]

Classical conditioning in the rat fetus: Temporal characteristics and behavioral correlates of the conditioned response

William P. Smotherman
Abstract This study examined the temporal characteristics and behavioral correlates of the conditioned response (CR) following classical conditioning of the embryonic Day 20 (E20 rat fetus). The conditioning procedure involved pairing of an artificial nipple (the CS) with an infusion of milk (the US) to establish classical conditioning. The test for classical conditioning involved measurement of a stimulus-evoked facial wiping response in a classical conditioning test. Experiment 1 compared the effectiveness of one- and three-trial procedures to establish classical conditioning. Experiment 2, 3, and 4 described the time course for the CR following one- and three-trial conditioning procedures. Experiments 3b and 4b describe the behavioral responses to (a) presentation of the CS at the time of conditioning, (b) infusion of the milk US at the time of conditioning, and (c) reexposure to the CS before the test for classical conditioning. Experiments 5 and 6 exposed the fetus to manipulations that either increased or decreased stretching (a behavior found to be associated with the CR). The results are discussed in terms of the temporal characteristics and behavioral correlates of conditioned and unconditioned responses and their mediation by activity in endogenous mu and kappa opioid systems. © 2002 Wiley Periodicals, Inc. Dev Psychobiol 40: 116,130, 2002. DOI 10.1002/dev.10017 [source]

A new method for transient stability analysis

Naoto Yorino
Abstract This paper proposes a brand-new method for transient stability analysis in power systems. The proposed method directly computes the critical trajectory for a given contingency to obtain the critical condition of the studied system. Although the method may be useful for general nonlinear dynamic systems, it is applied to the problem of obtaining a controlling UEP, unstable equilibrium point, which provides inevitable information for the energy function methods to assess transient stability. Namely, the proposed method effectively yields a critical trajectory on PEBS together with the controlling UEP, thus improving the conventional BCU method. The effectiveness of the proposed method is demonstrated in 3-machine 9-bus and 6-machine 30-bus systems. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 26,33, 2007; Published online in Wiley InterScience ( DOI 10.1002/eej.20245 [source]

Tagging (Arene)ruthenium(II) Anticancer Complexes with Fluorescent Labels

Fabio Zobi
Abstract Fluorescent (arene)ruthenium(II) complexes have been prepared by tagging a small fluorogenic reporter onto the chelating ligand of complexes of the type [(,6 -arene)RuCl(Z)]+ (Z = chelating ligand). Complexes [(,6 - p -cym)RuCl(NNO)](Cl) (2), [(,6 - p -cym)RuCl(L3)](Cl) (3) and [(,6 - p -cym)RuCl(L4)](Cl) (4) {p -cym = p- cymene, NNO = 2-[(2-aminoethyl)amino]ethanol, L3 = 2-[(2-aminoethyl)amino]ethyl-2-(methylamino)benzoate and L4 = N -{2-[(2-aminoethyl)amino]ethyl}-2-(methylamino)benzamide} were obtained in good yield from the reaction of the Ru dimer [(,6 - p -cym)RuCl2]2 (1) and the corresponding ligand. The compounds have been fully characterized and their X-ray crystal structures are reported. Compounds 3 and 4 show a photoluminescence response centered at 435 nm with partial fluorescence quenching of the fluorogenic reporters L3 and L4 upon coordination to the metal center. Species 2,4 show good solubility both in water and organic solvents. In water, 2,4 readily hydrolyze to form the aqua complexes. These are stable at acidic pH forming 10,15,% of the corresponding hydroxido complexes in buffered solution (25 mM HEPES) as the pH is raised to a physiological value (pH = 7.44). Under these conditions, 4 (but not 2 or 3) undergoes a fast pH-dependent reversible intramolecular rearrangement. Experimental data and semiempirical calculations indicate that the major species arising from this transformation is a complex with a tridentate chelating ligand following deprotonation at the nitrogen atom of the amide group. Esterase-catalyzed hydrolysis of 3 liberates isatoic acid (MIAH) and generates 2 indicating that the complex is a substrate for the enzyme. Complexes similar to 3 may have potential for esterase-activated Ru-based prodrug delivery systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Assembly and Formation of Biomorphic Tin Dioxide by a Biomimetic Sol,Gel Approach Involving Glycoprotein

Qun Dong
Abstract Three diverse layers of eggshell membrane (ESM) were introduced in a biogenic sol,gel technique for the synthesis of hierarchical SnO2 nanomaterials with corresponding configurations. Typically, the biomorphic replication of the interwoven inner eggshell membrane was systematically investigated by controlling synthesis conditions such as pH value, dipping time, and calcination temperature. The as-prepared SnO2 tubes consisting of interconnected 5-nm nanocrystallite units were successfully interwoven into ESM-morphic films. Herein, the biomaterial ESM served both as the physical substrate and the functional macromolecule template to realize the precision replication, by the interactions between ESM macromolecules (containing carboxyl, hydroxy, amino groups, etc.) and Sn colloid ingredients. Moreover, some biomacromolecules also acted as the surfactant to yield small-scaled and well-distributed SnO2 nanocrystallites based on the strong bondage of short-chained amino acids within ESM glycoprotein with SnO2 nuclei. This technique can be attributed to a biomimetic sol,gel process and is widely applicable to the synthesis of other functional material systems. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Ruthenium Complexes Containing Chiral N-Donor Ligands as Catalysts in Acetophenone Hydrogen Transfer , New Amino Effect on Enantioselectivity

Montserrat Gómez
Abstract New p -cymene ruthenium species containing chiral amino alcohols (1,3), primary (4,7) and secondary (8, 9) amino-oxazolines, were tested as catalysts in the hydrogen transfer of acetophenone, using 2-propanol as the hydrogen source. A remarkable effect on the enantioselectivity, but also on the activity, was observed depending on the amino-type oxazoline, Ru/8 and Ru/9 being low active and nonselective catalytic systems, in contrast to their primary counterpart Ru/5. Complexes containing amino-oxazolines (10,12) were prepared and fully characterized, both in solution and in solid state. The X-ray structure was determined for (SRu,RC)- 10. The diastereomeric ratios observed for complexes 10 and 11 were determined by 1H NMR and confirmed by means of structural modeling (semi-empirical PM3(tm) level). DFT theoretical calculations for the transition states involved in the hydrogen transfer process proved the important differences in their relative populations, which could justify the enantioselectivity divergences observed between primary and secondary amino-oxazoline ruthenium systems. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Synthesis and Photophysical Studies of a Pyrenylindole and a Phenalenoindole Obtained from Dehydroamino Acid Derivatives , Application as Fluorescent Probes for Biological Systems

Goreti Pereira
Abstract Two pyrenyl-dehydroamino acid derivatives were cyclized by a metal-assisted C,N intramolecular cyclization developed in our research group, to give a pyrenylindole and a phenalenoindole. The pyrenylindole was inserted into a peptide by solid-phase coupling, with use of a 2-chlorotrityl chloride resin and a Fmoc strategy. The photophysical properties of the pyrenylindole and phenalenoindole in several solvents were studied and showed that these compounds can be used as fluorescence probes. The results obtained with the peptide labelled with the pyrenylindole moiety show potential for use of this compound as a fluorescence label avoiding the aggregation propensity of pyrene compounds. Photophysical studies of the pyrenylindole and of the phenalenoindole in lipid membranes were also carried out. Steady-state fluorescence anisotropy measurements revealed that both compounds adopt locations inside the lipid bilayers and are able to report the transition between the gel and liquid-crystalline phases. The results point to potential use of these compounds as fluorescent probes for biological systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

2,3-Di- n -undecylanthracene and 2,3-Di- n -decyloxyanthracene (DDOA) , on the Connecting Link between the Aromatic Substrate and the Aliphatic Chain in Self-Assembling Systems

Henning Hopf
Abstract In contrast to its bis(oxa) analog 1 (DDOA), the hydrocarbon 11 was not found to form organogels with linear alcohols, alkanes, toluene, acetonitrile and other solvents. Whereas the photoreactivity of 1 did not follow the usual behaviour of anthracene derivatives, compound 11, irradiated in cyclohexane, produced the two expected [4+4]cycloadducts 12 and 13 (anti and syn photodimers, respectively). These facts point to the role of the connecting link between the rigid core and the flexible chain for some self-assembled systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Input-to-state stability, numerical dynamics and sampled-data control

Lars Grüne
Abstract We investigate the relation between asymptotic stability for dynamical systems and families of approximations. Using suitably perturbed systems and the input-to-state stability property we develop a framework which yields necessary and sufficient conditions on the stability of the approximations ensuring stability of the approximated system. The results are formulated for numerical one step schemes for ordinary differential equations and for sampled-data systems. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Quantitative isolation of ,1AT mutant Z protein polymers from human and mouse livers and the effect of heat,

HEPATOLOGY, Issue 1 2005
Jae-Koo An
Alpha-1-antitrypsin (,1AT) deficiency in its most common form is caused by homozygosity for the ,1AT mutant Z gene. This gene encodes a mutant Z secretory protein, primarily synthesized in the liver, that assumes an abnormal conformation and accumulates within hepatocytes causing liver cell injury. Studies have shown that mutant ,1ATZ protein molecules form unique protein polymers. These Z protein polymers have been hypothesized to play a critical role in the pathophysiology of liver injury in this disease, although a lack of quantitative methods to isolate the polymers from whole liver has hampered further analysis. In this study, we demonstrate a quantitative ,1ATZ polymer isolation technique from whole liver and show that the hepatocellular periodic acid-Schiff,positive globular inclusions that are the histopathological hallmark of this disease are composed almost entirely of the polymerized ,1ATZ protein. Furthermore, we examine the previously proposed but untested hypothesis that induction of ,1ATZ polymerization by the heat of physiological fever is part of the mechanism of hepatic ,1ATZ protein accumulation. The results, however, show that fever-range temperature elevations have no detectable effect on steady-state levels of intrahepatic Z protein polymer in a model in vivo system. In conclusion, methods to separate insoluble protein aggregates from liver can be used for quantitative isolation of ,1ATZ protein polymers, and the effect of heat from physiological fever may be different in vivo compared with in vitro systems. (HEPATOLOGY 2005;41:160,167.) [source]

Using discrete event simulation to model excavator operator performance

Khaliah Hughes
Abstract The traditional design process of fluid power systems such as hydraulic excavators has placed much emphasis on technical performance rather than human components. This research aims to develop human-performance models to assess operator performance and human interaction during excavation processes. Task analysis, time studies, and statistical distributions were developed into task-network models and imbedded into four Micro Saint simulation models with regard to various expertise and control types. An empirical study was conducted using the simulation models. Results indicated that both expertise and control type had a significant impact on operator performance, resulting in both time and consistency differences at various points during excavation processes. Models also revealed implications of operator fatigue leading to stress for the operator. Recommendations suggest that designers consider the placement of controls and measures to reduce operator workload for better performance in future systems. © 2010 Wiley Periodicals, Inc. [source]

Design for usability on supply chain management systems implementation

Chao-Hsien Lin
Supply chain management (SCM) systems implementation has become a fashion due to advances in information technology and pressures of market competition. Unfortunately, successful implementation was rare. In this article, the concept of usability was extended in an explorative case study to crystallize design for usability (DFU) principles in a large-scale SCM systems implementation project at a leading semiconductor manufacturing company in Taiwan. Proposed was a holistic usability framework to guide the analysis of DFU as well as the compilation of an evidence database composed of design documentation, post hoc evaluation, semistructured interviews, and participant observation. This research revealed a set of usability needs and coping strategies found throughout a series of systems design and redesign processes at the case company. As a result, an emergent usability framework in the form of ICOM (Input, Control, Output, and Mechanism) dimensions was proposed to guide the implementation of SCM systems. © 2009 Wiley Periodicals, Inc. [source]

Measurement of trust over time in hybrid inspection systems

Reena Master
A study was conducted to measure the effects of human trust and to determine how it develops over time in a hybrid inspection system given different types of errors (i.e., false alarms and misses). The study also looked at which of the four dimensions of trust (competence, predictability, reliability, and faith) were the best predictors of overall trust. Results from the study showed that trust is sensitive to the type of errors made by a system. There was a significant change in overall trust between the stages for the conservative and risky systems, but no significant change in the neutral system. In regards to the best predictors of trust, faith appeared as one of the predictors in all three trial blocks for the conservative and risky systems. As time progressed, predictability emerged in the second and third trial blocks for the conservative system. Competence played an important role in the development of trust for the risky system, whereas reliability played an important role for the neutral system. These results suggest that subjective ratings of trust and the properties of the system can be used to predict the allocation of functions in hybrid inspection systems. © 2005 Wiley Periodicals, Inc. Hum Factors Man 15: 177,196, 2005. [source]

Evaluation of best system performance: Human, automated, and hybrid inspection systems

Xiaochun Jiang
Recently, 100% inspection with automated systems has seen more frequent application than traditional sampling inspection with human inspectors. Nevertheless, humans still outperform machines in most attribute inspection tasks. Because neither humans nor automation can achieve superior inspection system performance, hybrid inspection systems where humans work cooperatively with machines merit study. In response to this situation, this research was conducted to evaluate three of the following different inspection systems: (1) a human inspection system, (2) a computer search/human decision-making inspection system, and (3) a human/computer share search/decision-making inspection system. Results from this study showed that the human/computer share search/decision-making system achieve the best system performance, suggesting that both should be used in the inspection tasks rather than either alone. Furthermore, this study looked at the interaction between human inspectors and computers, specifically the effect of system response bias on inspection quality performance. These results revealed that the risky system was the best in terms of accuracy measures. Although this study demonstrated how recent advances in computer technology have modified previously prescribed notions about function allocation alternatives in a hybrid inspection environment, the adaptability of humans was again demonstrated, indicating that they will continue to play a vital role in future hybrid systems. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 137,152, 2003. [source]

Convergence in human resource systems: A comparison of locally owned and MNC subsidiaries in Taiwan

Shyh-Jer Chen
This article investigates issues of convergence in human resource systems in Taiwan, with reference to the similarities and differences between locally owned companies and subsidiaries of multinational corporations (MNCs). Traditionally, management in Taiwanese companies has been largely influenced by Confucian values and is quite distinct from approaches common to MNCs. However, globalization has engendered significant competitive pressures, coupled with cultural and institutional change within Taiwan. This article provides a theoretical framework for understanding such changes and provides empirical evidence indicating that Taiwanese companies are acting very much like MNCs with regard to the adoption of flexible, highperformance work systems. © 2005 Wiley Periodicals, Inc. [source]

Low-Noise Fully Differential Amplifiers Using JFET-CMOS Integration Technology for Smart Sensors

Hidekuni Takao Member
Abstract In this paper, CMOS-based low-noise amplifiers with JFET-CMOS technology for high-resolution sensor interface circuits are presented. A differential difference amplifier (DDA) configuration is employed to realize differential signal amplification with very high input impedance, which is required for the front-end circuit in many sensor applications. Low-noise JFET devices are used as input pair of the input differential stages or source-grounded output load devices, which are dominant in the total noise floor of DDA circuits. A fully differential amplifier circuit with pure CMOS DDA and three types of JFET-CMOS DDAs were fabricated and their noise performances were compared. The results show that the total noise floor of the JFET-CMOS amplifier was much lower compared to that of the pure CMOS configuration. The noise-reduction effect of JFET replacement depends on the circuit configuration. The noise reduction effect by JFET device was maximum of about , 18 dB at 2.5 Hz. JFET-CMOS technology is very effective in improving the signal-to-noise ratio (SNR) of a sensor interface circuit with CMOS-based sensing systems. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Assessing the hazard of metals and inorganic metal substances in aquatic and terrestrial systems. edited by William J. Adams and Peter M. Chapman

Glenn Suter SETAC Book Reviews Editor
No abstract is available for this article. [source]

Video compression for multicast environments using spatial scalability and simulcast coding

Wade K. Wan
Abstract A common problem with many video transmission applications is the wide range of available bandwidths between the server and different clients. These environments require efficient multicast video service, the capability to transmit and receive the same video sequence at different resolutions. Two approaches to achieve multicast service are scalable coding (dependent bitstream coding) and simulcast coding (independent bitstream coding). One would expect scalable coding to have higher coding efficiency because a scalable coded bitstream can exploit similar information in another bitstream. This reasoning would suggest that multicast implementations should only use scalable coding for maximum coding efficiency. However, this article shows results where simulcast coding has been found to outperform spatial scalability (one type of scalable coding). In this article, methods are described to select between simulcast coding and spatial scalability for multicast video transmission. These techniques can be used to determine the proper multicast coding approach for providing service to clients with different communication links. The methodology described can also be used to construct decision regions to guide more general scenarios or adaptively switch between the two coding approaches. A number of important results were obtained that may be directly applicable to commercial multicast systems. © 2004 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 331,340, 2003; Published online in Wiley InterScience ( DOI 10.1002/ima.10065 [source]

Empirical assessment of a collaborative filtering algorithm based on OWA operators

Miguel-Angel Sicilia
Classical collaborative filtering algorithms generate recommendations on the basis of ratings provided by users that express their subjective preference on concrete items. The correlation of ratings is used in such schemes as an implicit measure of common interest between users, that is used to predict ratings, so that these ratings determine recommendations. The common formulae used for the computation of predicted ratings use standard weighted averaging schemes as the fixed aggregation mechanism that determines the result of the prediction. Nonetheless, the surrounding context of these rating systems suggest that an approach considering a degree of group consensus in the aggregation process may better capture the essence of the "word,of,mouth" philosophy of such systems. This paper reports on the empirical evaluation of such an alternative approach in which OWA operators with different properties are tested against a dataset to search for the better empirical adjustment. The resulting algorithm can be considered as a generalization of the original Pearson formula based algorithm that allows for the fitting of the aggregation behavior to concrete databases of ratings. The results show that for the particular context studied, higher orness degrees reduce overall error measures, especially for high ratings, which are more relevant in recommendation settings. The adjustment procedure can be used as a general-purpose method for the empirical fit of the behavior of collaborative filtering systems. © 2008 Wiley Periodicals, Inc. [source]

Aspect graphs for three-dimensional object recognition machine vision systems

Tatiana Tambouratzis
The purpose of this research is to seek evidence for viewer-centered (especially aspect-graph-based) visual processing in the elementary task of object understanding. Two homologous, bilaterally symmetrical three-dimensional (3-D) objects have been employed that differ in that one is based on parts with flat surfaces and the other on parts with curved surfaces. The following procedure has been followed, separately for each object. In the training (saturated free inspection and manipulation) phase, a location (identical for both objects) of the object is marked with a red strip and the subjects' task is to memorize the object structure as well as the position of the strip. In the test phase, two-dimensional views of the object without the strip are presented and the subjects' task is to determine whether the previously marked location should be visible or invisible in the particular view. Findings have been found consistent with an aspect-graph-based 3-D object representation: (a) the reaction times and errors show characteristic dependencies on viewpoint; (b) a number of views (corresponding to certain aspects and aspect transitions of the aspect graph) consistently produce faster and more accurate recognition; (c) the differences in the aspect graphs of the two objects are reflected in differing patterns of reaction times and errors; furthermore; (d) the subjects impose a standard orientation on the objects, whereby a strong inversion effect is observed; and (e) performance varies in a similar way for both objects as a function of tilt. It is concluded that object understanding is viewpoint dependent, that is, based on a number of views. The characteristics of the views found to be most important for object understanding can be employed for creating efficient 3-D object recognition machine vision systems. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 47,72, 2005. [source]

Efficient probabilistic reasoning in BNs with mutual exclusion and context-specific independence

Carmel Domshlak
Prior work has shown that context-specific independence (CSI) in Bayes networks can be exploited to speed up belief updating. We examine how networks with variables exhibiting mutual exclusion (e.g., "selector variables"), as well as CSI, can be efficiently updated. In particular, directed-path singly connected and polytree networks that have an additional common selector variable can be updated in linear time (given null and general conjunctive evidence, respectively), where quadratic time would be needed without the mutual exclusion requirement. The above results have direct applications, as such network topologies can be used in predicting the ramifications of user selection in some multimedia data browsing systems. © 2004 Wiley Periodicals, Inc. Int J Int Syst 19: 703,725, 2004. [source]

A data warehouse/online analytic processing framework for web usage mining and business intelligence reporting

Xiaohua Hu
Web usage mining is the application of data mining techniques to discover usage patterns and behaviors from web data (clickstream, purchase information, customer information, etc.) in order to understand and serve e-commerce customers better and improve the online business. In this article, we present a general data warehouse/online analytic processing (OLAP) framework for web usage mining and business intelligence reporting. When we integrate the web data warehouse construction, data mining, and OLAP into the e-commerce system, this tight integration dramatically reduces the time and effort for web usage mining, business intelligence reporting, and mining deployment. Our data warehouse/OLAP framework consists of four phases: data capture, webhouse construction (clickstream marts), pattern discovery and cube construction, and pattern evaluation and deployment. We discuss data transformation operations for web usage mining and business reporting in clickstream, session, and customer levels; describe the problems and challenging issues in each phase in detail; provide plausible solutions to the issues; and demonstrate the framework with some examples from some real web sites. Our data warehouse/OLAP framework has been integrated into some commercial e-commerce systems. We believe this data warehouse/OLAP framework would be very useful for developing any real-world web usage mining and business intelligence reporting systems. © 2004 Wiley Periodicals, Inc. [source]

Exactly solvable effective mass Schrödinger equation with coulomb-like potential

C. Pacheco-García
Abstract Exactly solvable Schrödinger equation (SE) with a position-dependent mass distribution allowing Morse-like eigenvalues is presented. For this, the position-dependent mass Schrödinger equation is transformed into a standard SE, with constant mass, by means of the point canonical transformation scheme. In that method, the choice of potential for the position-dependent mass Schrödinger equation allows us to obtain the transformation that should be used to find the exactly solvable SE. As a useful application of the proposal, the equivalent of the Witten superpotential is chosen to be constant to find the position-dependent mass distribution and the exactly solvable potential V(m(x)) allowing Morse-type energy spectra. This V(m(x)) is shown to have a Coulomb potential structure and can be useful in the study of the electronic properties of materials in which the carrier effective mass depends on the position. Moreover, the worked example, the approach is general and can be applied in the search of new potentials suitable on the study of quantum chemical systems. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Theory of chemical bonds in metalloenzymes.


Abstract Reaction mechanisms of oxygen evolution in native and artificial photosynthesis II (PSII) systems have been investigated on the theoretical grounds, together with experimental results. First of all, our previous broken-symmetry (BS) molecular orbitals (MO) calculations are reviewed to elucidate the instability of the d,-p, bond in high-valent (HV) Mn(X)O systems and the d,-p,-d, bond in HV MnOMn systems. The triplet instability of these bonds entails strong or intermediate diradical characters: ,Mn(IV)O, and ,MnOMn,; the BS MO resulted from strong electron correlation, leading to the concept of electron localizations and local spins. The BS computations have furthermore revealed guiding principles for derivation of selection rules for radical reactions of local spins. As a continuation of these theoretical results, the BS MO interaction diagrams for oxygen-radical coupling reactions in the oxygen evolution complex (OEC) in the PSII have been depicted to reveal scope and applicability of local singlet diradical (LSD) and local triplet diradical (LTD) mechanisms that have been successfully utilized for theoretical understanding of oxygenation reactions mechanisms by p450 and methane monooxygenase (MMO). The manganese-oxide cluster models examined are London, Berlin, and Berkeley models of CaMn4O4 and related clusters Mn4O4 and Mn3Ca. The BS MO interaction diagrams have revealed the LSD and/or LTD mechanisms for generation of molecular oxygen in the total low-, intermediate and high-spin states of these clusters. The spin alignments are found directly corresponding to the spin-coupling mechanisms of oxygen-radical sites in these clusters. The BS UB3LYP calculations of the clusters have been performed to confirm the comprehensive guiding principles for oxygen evolution; charge and spin densities by BS UB3LYP are utilized for elucidation and confirmation of the LSD and LTD mechanisms. Applicability of the proposed selection rules are examined in comparison with a lot of accumulated experimental and theoretical results for oxygen evolution reactions in native and artificial PSII systems. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Adjusting magnetic moments of Sc13 and Y13 clusters by doping different X atom (X = Na, Mg, Al, Si, P)

Fu-Yang Tian
Abstract We have investigated the structural and magnetic properties of the doped XM12 and charged M13 (X = Na, Mg, Al, Si, P; M = Sc, Y) clusters using the density-functional theory with spin-polarized generalized gradient approximation. It was found that doped atoms can induce significant change of the magnetic moments of Sc13 and Y13 clusters. The total magnetic moments of the NaM12, MgM12, AlM12, SiM12, and PM12 clusters are regular 5, 6 (12), 7, 8, and 9 ,b, respectively (but 19 ,b for Sc13 and Y13, 12 ,b for Y, 18 ,b for Sc, Sc, and Y). The doped atom substituting the surface atom of the plausible icosahedral configuration is viewed as the ground-state structure of the XM12 (X = Na, P; M = Sc, Y) and MgSc12 clusters. While for XM12 (X = Al, Si; M = Sc, Y) and MgY12 clusters, the doped atom occupying the central position of the icosahedral configuration is viewed as the ground-state structure. The doping and the charging both enhance the stability of the Sc13 and Y13 clusters. These findings should have an important impact on the design of the adjustable magnetic moments systems. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

DFT study for the heterojunction effect in the precious metal clusters

Mitsutaka Okumura
Abstract In the case of the precious metal catalysts, the precious metal nanoparticles deposited on the several supports exhibit extremely high-catalytic activity for many catalytic reactions. The boundary region between the nanoparticles and the support is one of the active sites in these catalysts. Moreover, the core/shell-type bimetallic nanoparticles also show the high-catalytic activities for several catalytic reactions. In these systems, the electronic states of the surfaces in the clusters are modified by the heterojunction between the two different compositions. Therefore, we investigate the heterojunction effect in these model catalysts, such as precious metal core/shell clusters and Pd supported on single-wall carbon nanotube model cluster, using hybrid density functional theory. From the calculation results, we find that the charge transfer interactions and the variation of the ground spin states in the metal clusters are the characteristics induced by the heterojunction in these model systems. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]

Test and modification of the van der Waals' radii employed in the default PCM model

Wei-Hua Mu
Abstract High level ab initio calculations at the B3LYP/6-311++G(d,p) and MP2(full)/6-311++G(d,p) levels employing PCM/UA0 model with different van der Waals' radii for the systems that contain lithium atoms have been carried out, in order to see if the van der Waal's radius for lithium atom employed in the default PCM/UA0 model is proper or not. Comparative analysis indicated that the van der Waals' radius for alkali metals, especially for lithium atom in the default PCM/UA0 model within the Gaussian 03 package, is too small, which causes erroneous redundant imaginary frequencies (RIFs) in the characterization of Li-containing compounds from moderate to big size. A new set of van der Waals' atomic radii based on QTAIM, proposed by Bader, was suggested for a better choice in the characterization of compounds containing alkali metals, for which it can effectively avoid the erroneous RIFs for corresponding geometries of these Li-containing systems. © 2008 Wiley Periodicals, Inc. Int. J. Quantum Chem, 2008 [source]

Grid-based density functional calculations of many-electron systems

Amlan K. RoyArticle first published online: 10 DEC 200
Abstract Exploratory variational pseudopotential density functional calculations are performed for the electronic properties of many-electron systems in the 3D cartesian coordinate grid (CCG). The atom-centered localized gaussian basis set, electronic density, and the two-body potentials are set up in the 3D cubic box. The classical Hartree potential is calculated accurately and efficiently through a Fourier convolution technique. As a first step, simple local density functionals of homogeneous electron gas are used for the exchange-correlation potential, while Hay-Wadt-type effective core potentials are employed to eliminate the core electrons. No auxiliary basis set is invoked. Preliminary illustrative calculations on total energies, individual energy components, eigenvalues, potential energy curves, ionization energies, and atomization energies of a set of 12 molecules show excellent agreement with the corresponding reference values of atom-centered grid as well as the grid-free calculation. Results for three atoms are also given. Combination of CCG and the convolution procedure used for classical Coulomb potential can provide reasonably accurate and reliable results for many-electron systems. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]