bluuebunny/crossref_metadata_2025 huggingface dataset:
An exploration of supplier selection practices across the supply chain
Authors: Choi Thomas Y. , Hartley Janet L.
Published: April 2003

The US auto industry has undergone tremendous changes during the past decade. Companies have increased their level of out‐sourcing and are relying more heavily on their supply chain as a source of their competitive advantage. Thus, determining which suppliers to include in the supplier chain has become a key strategic consideration. However, previous studies of supplier selection have not considered a company's position in the supply chain. In this paper, we compare supplier‐selection practices based on a survey of companies at different levels in the auto industry. Our findings rebut the common thinking that indirect suppliers who are more involved in commodity purchasing emphasize initial price and de‐emphasize relational considerations. We learned that selecting suppliers based on the potential for a cooperative, long‐term relationship is just as important to direct and indirect suppliers as it is to the auto assemblers. We also learned that price is one of the least important selection items, regardless of position on the supply chain. Further, contrary to the existing understanding that quality and delivery are separate constructs, they formed a single construct in our study. To summarize the empirical results, no differences among the auto assemblers, direct suppliers, and indirect suppliers were found for the importance placed on consistency (quality and delivery), reliability, relationship, flexibility, price, and service. Statistically significant differences were found between the auto assemblers and indirect suppliers on the importance placed on technological capability and financial issues.
The relative importance of journals used in operations management research A citation analysis
Authors: Vokurka Robert J.
Published: April 2003

Journal rankings are important for a variety of reasons, most importantly as the basis of academic tenure and promotion decisions. A common approach in other fields is the citations methodology which is used in this study to determine the relative importance of various operations management (OM) journals. The citations analysis noted the frequency that all other journals are cited in Decision Sciences, Journal of Operations Management, and Management Science during the period 1992 to 1994. Rankings are provided based on total citations, citations per article, and citations per words published. The study shows that the journals with the most importance to OM research are Management Science, Decisions Sciences and Operations Research. Other journals important to OM research are the Harvard Business Review, Journal of Operations Management, and IIE Transactions.
A meta‐analysis model of manufacturing capabilities
Authors: White Gregory P.
Published: April 2003

Recent research in operations strategy has focused on showing the extent to which manufacturing's competence in developing and executing one or more competitive capabilities affects the organization's overall business performance. Several of those efforts have produced models, such as the ‘sand cone’, that suggest an ideal sequence in which manufacturing capabilities should be developed. However, efforts to empirically validate such sequential models, except for one recent study, have been inconclusive. This paper takes a different approach to examining the relationships among competitive capabilities. The existing cross‐sectional studies of manufacturing capabilities are integrated to synthesize a proposed model of: (1) the relationships among manufacturing capabilities, and (2) the relationships between those capabilities and business performance. The proposed model is synthesized using data from previous studies, other models and theoretical arguments. Meta‐analysis is used to identify aspects of the model that appear better supported by empirical research and those that require further study. The implications of this proposed model with regard to research, practice and future research in operations strategy are discussed.
A tutorial on implementing concurrent engineering in new product development programs
Authors: Swink Morgan L.
Published: April 2003

The ‘concurrent engineering’ approach has radically changed the ways that new products are developed in many firms. However, implementing concurrent engineering has not always proved easy. As the popularity of concurrent engineering has grown and its applications have become more diverse, the core concepts that define concurrent engineering have become more and more vague. In addition, managers have found that different project, company, and industry contexts often necessitate customized approaches to concurrent engineering. This tutorial clarifies the concepts and methods that are central to the concurrent engineering approach. In addition, it examines the need to tailor the elements of concurrent engineering to match specific program priorities and product characteristics. Finally, the tutorial suggests ways that managers can make early concurrent engineering attempts more successful.
The relationship between self-esteem and psychiatric disorders in adolescents
Authors: Guillon M.S. , Crocq Marc-Antoine , Bailey P.E.
Published: April 2003

Objective

To examine the relationship between self-esteem and psychiatric disorders in adolescents.

Methods

Seventy-six adolescents (mean age: 16.02 years; range: 12-20) treated in an inpatient unit and presenting with DSM-IV psychotic disorder, depressive disorder, anxious disorder, anorexia nervosa, personality disorder, or conduct disorder were compared with a control group of 119 adolescents drawn from a normal population. All the subjects were assessed with the French translation of the Coopersmith self-esteem inventory (SEI).

Results

Self-esteem was significantly higher in the control than in the clinical population (P= 0.0001). Female patients showed significantly lower SEI scores than male patients. Self-esteem increased significantly after 12 weeks in patients with a first psychotic episode who responded successfully to antipsychotic drug treatment. In the clinical group, a history of suicide attempts and sexual abuse was associated with significantly lower SEI scores. Lack of boy- or girlfriend, dropping out of school, and social withdrawal were also associated with lower self-esteem.

Conclusions

The presence of a psychiatric disorder in adolescents is associated with decreased self-esteem. This decrease in self-esteem varies according to the psychiatric disorder. Appropriate treatment can enhance self-esteem in adolescent patients.
Multidimensional Properties of the Access to Categories of Experience Scale1
Authors: Creed Peter A. , Machin M. Anthony
Published: April 2003

Summary: This paper tests the factor structure and construct validity of the Access to Categories of Experience scale (ACE; Evans, 1986 ), which has been widely used to measure the five latent benefits of employment proposed by Jahoda (1981) . The ACE and the General Health Questionnaire (GHQ; Goldberg, 1972 ) were administered to 425 unemployed individuals. This original sample was randomly split into two subsamples. Exploratory factor analyses conducted on the first subsample demonstrated four rather than the five separate factors for the ACE scale, which has been asserted by its development and its previous use. The scale was dominated by one major factor of Activity. Confirmatory factor analysis conducted on the second subsample demonstrated a better fit for the four factors rather than the five. Construct validity was established for the ACE scale. When the identified ACE factors were correlated with the GHQ, higher levels of access to the latent benefits was associated with lower levels of psychological distress, although this result was not identified for all factors. The implications of this finding for the latent deprivation model ( Jahoda, 1981 ) are discussed, and recommendations are made in relation to the use of the ACE scale in this area of research.
Fatty acids liberated from high-density lipoprotein phospholipids by endothelial-derived lipase are incorporated into lipids in HepG2 cells
Authors: STRAUSS Juliane G. , HAYN Marianne , ZECHNER Rudolt , LEVAK-FRANK Sanja , FRANK Sasa
Published: April 2003

We previously reported that endothelial-derived lipase (EDL) efficiently hydrolyses high-density-lipoprotein-derived phosphatidycholine (HDL-PC). In the present study, we assessed the ability of EDL to supply HepG2 cells with non-esterified fatty acids (NEFA) liberated from HDL-phospholipids. For this purpose, HepG2 cells infected with adenovirus encoding human EDL (EDL-Ad), or with control β-galactosidase-expressing adenovirus (LacZ-Ad), were incubated with 14C-HDL-PC. The analysis of the cellular lipids by TLC revealed that EDL overexpression led to an increase in the amount of cellular 14C-lipids, whereby the label was mainly incorporated into phospholipids and triacylglycerols (TAG). Cells expressing mutant enzymically inactive EDL (MUT-EDL-Ad) contained similar amounts of 14C-TAG but higher amounts of 14C-phosphatidylcholine (PC) compared with LacZ-Ad-infected cells. The co-expression of CD36 augmented the EDL-mediated accumulation of 14C-lipids in HEK-293 cells. The quadrupole MS analysis of the cellular lipids revealed an increased content of PC and TAG in EDL-expressing HepG2 cells compared with MUT-EDL-Ad-expressing and control cells. However, the MUT-EDL-Ad-expressing cells contained more PC than control cells. Additionally, EDL overexpression led to a 2-fold decrease in the amount of fatty acid synthase mRNA and, in turn, a slightly, but significantly, decreased rate of fatty acid (FA) synthesis in HepG2 cells. In the present study, we show for the first time that EDL efficiently supplies HepG2 cells with NEFA derived from HDL-PL, thus affecting cellular lipid composition and FA synthesis.
Upstream stimulatory factor (USF) and neurogenic differentiation/beta-cell E box transactivator 2 (NeuroD/BETA2) contribute to islet-specific glucose-6-phosphatase catalytic-subunit-related protein (IGRP) gene expression
Authors: MARTIN Cyrus C. , SVITEK Christina A. , OESER James K. , HENDERSON Eva , STEIN Roland , O'BRIEN Richard M.
Published: April 2003

Islet-specific glucose-6-phosphatase (G6Pase) catalytic-subunit-related protein (IGRP) is a homologue of the catalytic subunit of G6Pase, the enzyme that catalyses the final step of the gluconeogenic pathway. The analysis of IGRP-chloramphenicol acetyltransferase (CAT) fusion-gene expression through transient transfection of islet-derived βTC-3 cells revealed that multiple promoter regions, located between −306 and −97, are required for maximal IGRP-CAT fusion-gene expression. These regions correlated with trans-acting factor-binding sites in the IGRP promoter that were identified in βTC-3 cells in situ using the ligation-mediated PCR (LMPCR) footprinting technique. However, the LMPCR data also revealed additional trans-acting factor-binding sites located between −97 and +1 that overlap two E-box motifs, even though this region by itself conferred minimal fusion-gene expression. The data presented here show that these E-box motifs are important for IGRP promoter activity, but that their action is only manifest in the presence of distal promoter elements. Thus mutation of either E-box motif in the context of the −306 to +3 IGRP promoter region reduces fusion-gene expression. These two E-box motifs have distinct sequences and preferentially bind NeuroD/BETA2 neurogenic differentiation/β-cell E box transactivator 2 and upstream stimulatory factor (USF) in vitro, consistent with the binding of both factors to the IGRP promoter in situ, as determined using the chromatin-immunoprecipitation (ChIP) assay. Based on experiments using mutated IGRP promoter constructs, we propose a model to explain how the ubiquitously expressed USF could contribute to islet-specific IGRP gene expression.
Protein-protein interactions involved in the recognition of p27 by E3 ubiquitin ligase
Authors: XU Kui , BELUNIS Charles , CHU Wei , WEBER David , PODLASKI Frank , HUANG Kuo-Sen , REED Steven I. , VASSILEV Lyubomir T.
Published: April 2003

The p27Kip1 protein is a potent cyclin-dependent kinase inhibitor, the level of which is decreased in many common human cancers as a result of enhanced ubiquitin-dependent degradation. The multiprotein complex SCFSkp2 has been identified as the ubiquitin ligase that targets p27, but the functional interactions within this complex are not well understood. One component, the F-box protein Skp2, binds p27 when the latter is phosphorylated on Thr187, thus providing substrate specificity for the ligase. Recently, we and others have shown that the small cell cycle regulatory protein Cks1 plays a critical role in p27 ubiquitination by increasing the binding affinity of Skp2 for p27. Here we report the development of a homogeneous time-resolved fluorescence assay that allows the quantification of the molecular interactions between human recombinant Skp2, Cks1 and a p27-derived peptide phosphorylated on Thr187. Using this assay, we have determined the dissociation constant of the Skp2–Cks1 complex (Kd 140 ± 14 nM) and have shown that Skp2 binds phosphorylated p27 peptide with high affinity only in the presence of Cks1 (Kd 37 ± 2 nM). Cks1 does not bind directly to the p27 phosphopeptide or to Skp1, which confirms its suggested role as an allosteric effector of Skp2.
The aorta and heart differentially express RGS (regulators of G-protein signalling) proteins that selectively regulate sphingosine 1-phosphate, angiotensin II and endothelin-1 signalling
Authors: CHO Hyeseon , HARRISON Kathleen , SCHWARTZ Owen , KEHRL John H.
Published: April 2003

Normal cardiovascular development and physiology depend in part upon signalling through G-protein-coupled receptors (GPCRs), such as the angiotensin II type 1 (AT1) receptor, sphingosine 1-phosphate (S1P) receptors and endothelin-1 (ET-1) receptor. Since regulator of G-protein signalling (RGS) proteins function as GTPase-activating proteins for the Gα subunit of heterotrimeric G-proteins, these proteins undoubtedly have functional roles in the cardiovascular system. In the present paper, we show that human aorta and heart differentially express RGS1, RGS2, RGS3S (short-form), RGS3L (long-form), PDZ-RGS3 (PDZ domain-containing) and RGS4. The aorta prominently expresses mRNAs for all these RGS proteins except PDZ-RGS3. Various stimuli that are critical for both cardiovascular development and function regulate dynamically the mRNA levels of several of these RGS proteins in primary human aortic smooth muscle cells. Both RGS1 and RGS3 inhibit signalling through the S1P1 (formerly known as EDG-1), S1P2 (formerly known as EDG-5) and S1P3 (formerly known as EDG-3) receptors, whereas RGS2 and RGS4 selectively attenuate S1P2-and S1P3-receptor signalling respectively. All of the tested RGS proteins inhibit AT1-receptor signalling, whereas only RGS3 and, to a lesser extent, RGS4 inhibit ETA-receptor signalling. The conspicuous expression of RGS proteins in the cardiovascular system and their selective effects on relevant GPCR-signalling pathways provide additional evidence that they have functional roles in cardiovascular development and physiology.
Iron-sulphur cluster assembly in plants: distinct NFU proteins in mitochondria and plastids from Arabidopsis thaliana
Authors: LÉON Sébastien , TOURAINE Brigitte , RIBOT Cécile , BRIAT Jean-François , LOBÉRAUX Stéphane
Published: April 2003

Recent results are in favour of a role for NFU-like proteins in Fe–S cluster biogenesis. These polypeptides share a conserved CXXC motif in their NFU domain. In the present study, we have characterized Arabidopsis thalianaNFU1–5 genes. AtNFU proteins are separated into two classes. NFU4 and NFU5 are part of the mitochondrial type, presenting a structural organization similar to Saccharomyces cerevisiae Nfu1p. These proteins complement a Δisu1Δnfu1 yeast mutant and NFU4 mitochondrial localization was confirmed by green fluorescent protein fusion analysis. AtNFU1–3 represent a new class of NFU proteins, unique to plants. These polypeptides are made of two NFU domains, the second having lost its CXXC motif. AtNFU1–3 proteins are more related to Synechocystis PCC6803 NFU-like proteins and are localized to plastids when fused with the green fluorescent protein. NFU2 and/or NFU3 were detected in leaf chloroplasts by immunoblotting. NFU1 and NFU2 are functional NFU capable of restoring the growth of a Δisu1Δnfu1 yeast mutant, when addressed to yeast mitochondria. Furthermore, NFU2 recombinant protein is capable of binding a labile 2Fe–2S cluster in vitro. These results demonstrate the presence of distinct NFU proteins in Arabidopsis mitochondria and plastids. Such results suggest the existence of two different Fe–S assembly machineries in plant cells.
On certain integrals that appear in conformal field theory
Authors: Geronimo Jeffrey S. , Navelet Henri
Published: April 2003

We consider several types of integrals that arise in the context of quantum field theory that factor into a holomorphic and antiholomorphic piece. This gives rise to a conformal block representations for some of the integrals.
Low-temperature specific heat of frustrated ferrimagnets BaFe12−xInxO19 with x=3.0 and x=3.6
Authors: Anders A. G. , Efimova N. N. , Valiev V. B. , Kufterina S. R. , Gurevich A. M. , Krivchikov A. I. , Terechkov A. V. , Chagovets T. V.
Published: April 2003

Studies of the temperature dependence of the specific heat C in the temperature range 4.2–16 K and of the magnetization polytherms σH(T) in the ZFC and FC regimes for H=(1–25)×102 Oe in the temperature range 4.2 K<T⩽180 K are carried out for two dilute frustrated ferrimagnetic oxides BaFe12−xInxO19 (x=3.0 and 3.6), in which the transition to disordered states of the spin-glass type at T<90 K can be caused by destruction of a helicoidal structure. For the sample with x=3.6 it is found that C(T)∝T, while for x=3.0 a dependence C(T)∝T3/2 is found. Taken together with the results of a study of the magnetic properties, this behavior allows one to identify the low-temperature state in the sample with x=3.6 as a spin glass. For the sample with x=3.0, in which clearly expressed spin-glass properties are seen in combination with a temperature dependence C(T)∝T3/2, the low-temperature state requires further study.
High energy proton acceleration in interaction of short laser pulse with dense plasma target
Authors: Sentoku Y. , Cowan T. E. , Kemp A. , Ruhl H.
Published: April 2003

The generation of high energy protons from the interaction of a short laser pulse with a dense plasma, accompanied by a preformed low density plasma, has been studied by particle-in-cell simulations. The proton acceleration toward the laser direction in the preformed plasma is characterized by a time-dependent model and the peak proton energy is given. The effect of electron recirculation on the rear side sheath acceleration is discussed and it is found that the peak proton energy increases in inverse proportion to the target thickness. These results shed light on the peak proton energy dependence on laser intensity, laser pulse length, and target thickness. Finally the optimal parameters of the laser pulse for large ion peak energy and conversion efficiency are discussed.
High β, long pulse, bootstrap sustained scenarios on the National Spherical Torus Experiment (NSTX)
Authors: Gates D. A. ,   NSTX National Research Team
Published: April 2003

Long pulse, high β scenarios have been established on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. βt(≡2μ0〈P〉/Bt02)∼35% has been achieved during transient discharges. The machine improvements that lead to these results, including error field reduction and high temperature bakeout of plasma facing components are described. The highest βt plasmas have high triangularity (δ=0.8) and elongation (κ=2.0), at low aspect ratio A≡R/a=1.4. The strong shaping permits large values of normalized current, IN(≡Ip/(aBt0))≊6 while maintaining moderate values of q95=4. Long pulse discharges up to 1 s in duration have been achieved with substantial bootstrap current. The total noninductive current drive can be as high as 60%, comprised of 50% bootstrap current and ∼10% neutral beam current drive. The confinement enhancement factor H89P is in excess of 2.7. βN * H89P≳15 has been maintained for 8 * τE∼1.6 * τCR, where τCR is the relaxation time of the first radial moment of the toroidal current density. The ion temperature for these plasmas is significantly higher than that predicted by neoclassical theory.
Suppression of nonlinear frequency-sweeping of resonant interchange modes in a magnetic dipole with applied radio frequency fields
Authors: Maslovsky D. , Levitt B. , Mauel M. E.
Published: April 2003

Interchange instabilities excited by energetic electrons trapped by a magnetic dipole nonlinearly saturate and exhibit complex, coherent spectral characteristics and frequency sweeping [H. P. Warren and M. E. Mauel, Phys. Plasmas 2, 4185 (1995)]. When monochromatic radio frequency (rf) fields are applied in the range of 100–1000 MHz, the saturation behavior of the interchange instability changes dramatically. For applied fields of sufficient intensity and pulse-length, coherent interchange fluctuations are suppressed and frequency sweeping is eliminated. When rf fields are switched off, coherent frequency sweeping reappears. Since low frequency interchange instabilities preserve the electron’s first and second adiabatic invariants, these observations can be interpreted as resulting from nonlinear resonant wave–particle interactions described within a particle phase-space, (ψ,φ), comprised of the third adiabatic invariant and the azimuthal angle. Self-consistent numerical simulation is used to study (1) the nonlinear development of the instability, (2) the radial mode structure of the interchange instability, and (3) the suppression of frequency sweeping. When the applied rf heating is modeled as an “rf collisionality,” the simulation reproduces frequency sweeping suppression and suggests an explanation for the observations that is consistent with Berk and co-workers [H. L. Berk et al., Phys. Plasmas 6, 3102 (1999)].
Galaxies and the magnetization of intergalactic space
Authors: Kronberg Philipp P.
Published: April 2003

There is increasing evidence that widespread magnetic fields in the intergalactic medium (IGM) originate in galaxies. Up to now the field strengths have been easiest to estimate where the ambient intergalactic (i.g.) nonrelativistic gas density is highest, i.e., in galaxy clusters, the gravitational “sinks” of large scale matter flows. Intracluster gas densities reach 10−3–10−2 cm−3, and magnetic field strength estimates range from 1 to 40 μG. For much of the intracluster volume the plasma β∼1, a consequence of the intracluster magnetic field measurements, and x-ray-determined densities and temperatures of the thermal intracluster (ic) gas. While these ic gas densities represent an impressively good vacuum by terrestrial standards, they are still about 1000× more than in the general IGM. The logical next question is: Are there significant magnetic fields in the wider IGM beyond clusters? Recent, preliminary estimates in i.g. zones beyond, but not far from clusters are 10−6–10−7 G. Integrating this field strength over a typical intergalaxy separation volume gives an average magnetic energy density within the “walls and filaments” of intergalactic space of ∼10−15 B−6.5 ergs cm−3. Interestingly, for Big∼3×10−7 G, and plausible values of nig∼5×10−6 cm−3, and Tig∼108 K—the intergalactic plasma β may be within a factor 10 of unity, roughly comparable to β within the ∼103 times denser medium in galaxy clusters. It is now widely accepted that the only plausible energy source for these intergalactic fields is gravitational, e.g., not the aggregate thermonuclear energy from stars. Two sufficiently large gravitational energy reservoirs are (1) the kinetic energy from large scale intergalactic matter flows, and (2) the gravitational binding energy of supermassive black holes that have been found to be nearly ubiquitous in the nuclei of medium-to-large galaxies. This paper focuses mostly on (2), and also discusses why the largest radio sources are the best independent calibrators, and calorimeters of magnetic energy release into i.g. space from individual galaxy systems.
Unexpected axial asymmetry in radiated power from high-temperature dynamic-hohlraum x-ray sources
Authors: Sanford T. W. L. , Mock R. C. , Leeper R. J. , Peterson D. L. , Watt R. C. , Chrien R. E. , Idzorek G. C. , Oliver B. V. , Roderick N. F. , Haines M. G.
Published: April 2003

Radiation from the interior of a dynamic hohlraum within a wire-array Z pinch is used to generate high-power x-ray pulses in both the up and down axial directions through radiation exit holes (REHs) in the anode and cathode, respectively. Despite a concerted effort to ensure a symmetrical up-down configuration, the measured peak top radiated power remained about twice that of the bottom (with similar total radiated energies from each REH), as compared to current simulations that predict equal powers. This large asymmetry suggests the need for improved physics models and simulation capabilities.
Multireference perturbation theory with optimized partitioning. I. Theoretical and computational aspects
Authors: Witek Henryk A. , Nakano Haruyuki , Hirao Kimihiko
Published: April 2003

A multireference perturbation method is formulated, that uses an optimized partitioning. The zeroth-order energies are chosen in a way that guarantees vanishing the first neglected term in the perturbational ansatz for the wave function, Ψ(n)=0. This procedure yields a family of zeroth-order Hamiltonians that allows for systematic control of errors arising from truncating the perturbative expansion of the wave function. The second-order version of the proposed method, denoted as MROPT(2), is shown to be (almost) size-consistent. The slight extensivity violation is shown numerically. The total energies obtained with MROPT(2) are similar to these obtained using the multireference configuration interaction method with Davidson-type corrections. We discuss connections of the MROPT(2) method to related approaches, the optimized partitioning introduced by Szabados and Surján and the linearized multireference coupled-cluster method. The MROPT(2) method requires using state-optimized orbitals; we show on example of N2 that using Hartree–Fock orbitals for some excited states may lead to nonphysical results.
Dust-acoustic wave instability at the diffuse edge of radio frequency inductive low-pressure gas discharge plasma
Authors: Fortov V. E. , Usachev A. D. , Zobnin A. V. , Molotkov V. I. , Petrov O. F.
Published: April 2003

A spontaneous excitation of a grain density wave in a dusty cloud of monodisperse particles suspended at the diffuse edge of an rf inductive gas discharge has been discovered. The main physical parameters of this wave (phase velocity, wavelength, and growth rate) and of the background plasma (distributions of the electron density, electron temperature, and space potential) were measured. A theoretical model of the observable phenomenon based on the theory of dust acoustic waves in a collisional dusty plasma correlates well with the experimental data in a broad range of experimental conditions. The influence of a varying dust grain charge on the development of the observed dusty plasma instability has been analyzed. It is shown that the necessary condition for the instability excitation is the availability of a permanent electrical field (E0 ⩾3 V/cm) in the dusty cloud region.
Solving simple quaternionic differential equations
Authors: De Leo Stefano , Ducati Gisele C.
Published: April 2003

The renewed interest in investigating quaternionic quantum mechanics, in particular tunneling effects, and the recent results on quaternionic differential operators motivate the study of resolution methods for quaternionic differential equations. In this paper, by using the real matrix representation of left/right acting quaternionic operators, we prove existence and uniqueness for quaternionic initial value problems, discuss the reduction of order for quaternionic homogeneous differential equations and extend to the noncommutative case the method of variation of parameters. We also show that the standard Wronskian cannot uniquely be extended to the quaternionic case. Nevertheless, the absolute value of the complex Wronskian admits a noncommutative extension for quaternionic functions of one real variable. Linear dependence and independence of solutions of homogeneous (right) H-linear differential equations is then related to this new functional. Our discussion is, for simplicity, presented for quaternionic second order differential equations. This involves no loss of generality. Definitions and results can be readily extended to the n-order case.
Study of improved confinement modes with edge and/or internal transport barriers on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U)
Authors: Miura Y. ,   JT-60 Team
Published: April 2003

Two types of advanced tokamak scenarios, namely, high βp H-mode and reversed shear (RS) mode, are developed and studied extensively in Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [S. Ide and the JT-60 Team, Phys. Plasmas 7, 1927 (2000)]. These plasmas have both an internal transport barrier (ITB) and an edge transport barrier (ETB). The goal of the recent studies was therefore to get a deeper insight into the physics of ITB and ETB and to increase the discharge performance under a controlled manner based on the physics understanding. In the studies of ETB in an extended high triangularity operation with pellet injection from the high-field side, we have clarified the linkage between main parameters determining the pedestal structure. In the studies of type I edge localized modes (ELMs), simultaneous fast ELM measurements revealed four different phases in an ELM event. It was also established that the density collapse is poloidally asymmetric and is localized at the low-field side. In the studies of ITB, the response of the ion thermal diffusivity to the radial electric field (Er) shear and the effect of electron heating on ITB have been investigated. The importance of nonlocality and the effective Er shear are discussed. In the case of the RS plasma with a strongly reversed current profile, it has been found that there is no plasma current in the central region (called the “current hole”), and it is impossible to drive current in either the positive or negative direction by an electron cyclotron wave inside the current hole. Based on the new understanding of ETB and ITB, the control of the transport barriers is also discussed briefly.
Hamiltonian canonical formulation of Hall-magnetohydrodynamics: Toward an application to weak turbulence theory
Authors: Sahraoui F. , Belmont G. , Rezeau L.
Published: April 2003

The different levels of description of fluid media [e.g., magnetohydrodynamics (MHD), Hall-magnetohydrodynamics, bi-fluid,…] are commonly known under the form of Newtonian systems of equations. Nevertheless, this form proves to be ill-suited to derive a fully analytical weak turbulence theory of these media, due to the well-known complexity of the calculations implied. For such studies, therefore, a more appropriate mathematical frame needs to be found and this is shown to be the Hamiltonian formalism, even though it can often appear difficult to handle. The goal of this paper is to look for Hamiltonian formulations for the different levels of the fluid description of a plasma using the variational principle. Starting from the bi-fluid system, it is shown that such a formulation can be obtained by combining the Lagrangians already used for describing: (i) the motion of a charged particle in an electromagnetic field; (ii) the evolution of an electromagnetic field in presence of sources; (iii) the motion of a neutral fluid (Clebsch variables). The equivalence of the obtained description in terms of the generalized-Clebsch variables to the familiar Newtonian formulation is discussed. It is shown that each solution of the Hamiltonian system is also a solution for the Newtonian one, but that the converse is not true. The origin and the implication of this restriction are discussed. Reducing the Hamiltonian formulation obtained for the bi-fluid system to lower orders of the fluid approximations is then shown to be mandatory when one tries to obtain analytical results for linear waves and nonlinear wave–wave couplings. It is shown that this goal can be reached in two steps. The first one leads to a “reduced bi-fluid” system, which is identical to the bi-fluid one when the displacement current is neglected but the electron inertia is still working. The number of linear modes then goes down from six to three. The second step, leading to the Hall-MHD system, consists in neglecting the electron mass. It is demonstrated that the only four generalized Clebsch variables are sufficient to describe the full Hall-MHD dynamics. Some future applications of such a powerful formalism are outlined.
A relationship between semiclassical and centroid correlation functions
Authors: Shi Qiang , Geva Eitan
Published: April 2003

A general relationship is established between semiclassical and centroid-based methods for calculating real-time quantum-mechanical correlation functions. It is first shown that the linearized semiclassical initial-value-representation (LSC-IVR) approximation can be obtained via direct linearization of the forward-backward action in the exact path integral expression for the correlation function. A Kubo-transformed two-time correlation function, with the position operator as one of the two operators, is then cast in terms of a carefully crafted exact path integral expression. Linearization of the corresponding forward–backward action, supplemented by the assumption that the dynamics of the centroid is decoupled from that of the higher normal modes, is then shown to lead to the centroid correlation function.
Joint analysis of the attractive and repulsive regions of the Na2 a 3Σu+ state potential: A new empirical potential energy curve
Authors: Ivanov V. S. , Sovkov V. B. , Li Li
Published: April 2003

Disagreements between empirical and ab initio potential curves of the Na2 a 3Σu+ state are examined. These disagreements are explained mainly by the influence of spin-rotation-type interactions with the effective constant γ≅−5.6⋅10−3 cm−1. A new potential energy function of this state is determined from the joint analysis of the continuous 2 3Σg+→a 3Σu+ and the discrete 3 3Πg→ a3Σu+ experimental spectra. The new potential function is able to reproduce all the available spectroscopic data within experimental accuracy, and is closer to the modern high quality ab initio potentials than all the earlier reported empirical potential functions.
Structure of the protected dipeptide Ac-Val-Phe-OMe in the gas phase: Towards a β-sheet model system
Authors: Unterberg C. , Gerlach A. , Schrader T. , Gerhards M.
Published: April 2003

In this paper we report on the structure of the isolated dipeptide Ac–Val–Phe–OMe (Val=valine, Phe=phenylalanine) which is protected at the terminal positions by introducing an acetyl and a methyl group. Both resonant two-photon ionization (R2PI) and IR/R2PI spectroscopy are applied. This is the first application of IR/R2PI spectroscopy to a dipeptide. Both the region of the C–H and N–H stretching vibrations as well as the region of the C=O stretching vibrations are investigated. The chosen dipeptide exhibits only one prominent conformer in the gas phase containing a “linear” non-hydrogen-bonded structure which is an ideal candidate for a β-sheet model.
Local correlation in the virtual space in multireference singles and doubles configuration interaction
Authors: Walter Derek , Venkatnathan Arun , Carter Emily A.
Published: April 2003

We describe a multireference configuration interaction method that takes advantage of local correlation methods in both the internal (originally occupied) and external (originally unoccupied or virtual) orbital spaces. In the internal space, implementation of local correlation is trivial and involves neglecting configurations having simultaneous excitations out of widely separated orbitals. In the external space, the method involves restricting the space of allowed correlating orbitals to those localized near the hole orbitals. Of course, this necessitates the use of localized virtual orbitals which in turn requires one to sacrifice the orthogonality of the virtual space. This complicates the formalism substantially, and we discuss the necessary changes to the traditional expressions in detail. The scaling of the method with system size, basis set size, and the average number of allowed virtual orbitals is explored. An examination of systems having up to 8 heavy atoms reveals that the computational costs of the method scales somewhere between the third and fourth power of the size of the system. Furthermore, this reduced scaling method is capable of recovering greater than 97% of the correlation energy. Additionally, we demonstrate that the method can produce smooth potential energy surfaces and recover bond dissociation energies in organic molecules at a fraction of the cost (⩾tenfold less expensive) while retaining accuracy. We go on to use this new reduced scaling approach to predict bond energies in several large organic molecules for which no experimental data are available.
Testing the kinetic energy functional: Kinetic energy density as a density functional
Authors: Sim Eunji , Larkin Joe , Burke Kieron , Bock Charles W.
Published: April 2003

A new method for defining an energy density for the noninteracting kinetic energy of density functional theory is given. The resulting energy density is a density functional determined completely by the kinetic energy functional itself. Although this method is not constructive, it allows for a direct comparison between exact and approximate functionals pointwise in space. For simple systems, the new energy density is calculated exactly, and compared with traditional choices, on both formal and physical grounds. Finally, the energy densities of both the gradient expansion and the von Weizsäcker approximation are calculated, and compared with the exact quantity. The errors in the von Weizsäcker approximation are identified.
Transitions of turbulence in plasma density limits
Authors: Xu X. Q. , Nevins W. M. , Rognlien T. D. , Bulmer R. H. , Greenwald M. , Mahdavi A. , Pearlstein L. D. , Snyder P.
Published: April 2003

A series of BOUT [X. Q. Xu et al., Phys. Plasmas 7, 1951 (2000)] simulations is conducted to investigate the physical processes which limit the density in tokamak plasmas. Simulations of turbulence in tokamak boundary plasmas are presented which show that turbulent fluctuation levels and transport increase with collisionality. At high edge density, the perpendicular turbulent transport dominates the parallel classical transport, leading to substantially reduced contact with divertor plates and the destruction of the edge shear layer, and the region of high transport then extends inside the last closed flux surface. As the density increases these simulations show resistive X-point mode→resistive ballooning modes. The simulations also show that it is easier to reach the density limit as the density increases while holding pressure constant than holding temperature constant. A set of 2D transport simulations with increasingly large radial outboard transport, as indicated by BOUT for increasing density, shows that such transport can lead to an X-point multifaced asymmetric radiation from the edge when impurity radiation is included, which is a common symptom of density-limit related disruptions. BOUT further demonstrates that the local transport scaling with the current is similar to the global low-confinement-mode (L-mode) transport model (τE∝Ip) (by fixing q profiles). This current scaling appears on a plot of discharge current versus density as abruptly large radial transport once the Greenwald density is approached or exceeded. All of these results indicate that rapid edge cooling due to large radial transport is a key for the physics of the tokamak density limit.
Collision induced rotational energy transfer probed by time-resolved coherent anti-Stokes Raman scattering
Authors: Knopp G. , Radi P. , Tulej M. , Gerber T. , Beaud P.
Published: April 2003

We show that the technique of femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy provides a powerful tool for the investigation of collision-induced linewidths and the validation of rotational energy transfer (RET) models. The fs-CARS method is applied to the N2–N2 collision system, and a comparison between the commonly used exponential gap (ECS-E), power gap (ECS-P), frequency corrected (EFCS), and the recently proposed angular momentum and energy corrected (AECS) variants of the ECS model is presented. As result we show that the AECS scaling law requires only two free parameters, and is appropriate for the determination of RET rates from the measured fs-CARS signals. The AECS model is also applied to the more complex C2H2–C2H2 collision system. As vibrational energy transfer and dephasing is not negligible in this case, the model has to be modified by introducing a vibrational relaxation factor. With this modification the fs-CARS signals from acetylene can be described successfully.
Localization of compressional Alfvén eigenmodes in spherical tori
Authors: Smith H. , Fülöp T. , Lisak M. , Anderson D.
Published: April 2003

Edge-localized compressional Alfvén eigenmodes (CAE) may be responsible for the observed emission in the ion cyclotron frequency range in the National Spherical Torus experiments (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. These modes can be driven unstable by resonant interaction with a small population of energetic ions, having an anisotropic distribution in velocity space. In the present paper, the radial and poloidal structure of these eigenmodes is analyzed, by solving the eigenmode equation using a variational approach. The analysis shows that CAE are radially and poloidally localized near the plasma edge and have eigenfrequencies in the range corresponding to experimentally measured frequencies in NSTX.
The norm-1-property of a quantum observable
Authors: Heinonen Teiko , Lahti Pekka , Pellonpää Juha-Pekka , Pulmannova Sylvia , Ylinen Kari
Published: April 2003

A normalized positive operator measure X⟼E(X) has the norm-1-property if ‖E(X)‖=1 whenever E(X)≠O. This property reflects the fact that the measurement outcome probabilities for the values of such observables can be made arbitrarily close to one with suitable state preparations. Some general implications of the norm-1-property are investigated. As case studies, localization observables, phase observables, and phase space observables are considered.
Multiphoton fabrication of periodic structures by multibeam interference of femtosecond pulses
Authors: Kondo Toshiaki , Matsuo Shigeki , Juodkazis Saulius , Mizeikis Vygantas , Misawa Hiroaki
Published: April 2003

Femtosecond laser pulses are useful for laser microfabrication through multiphoton absorption. However, it is difficult to create interference of femtosecond pulses for the fabrication of periodic structures. In this letter, we report the fabrication of two-dimensional periodic structures by means of multibeam interference of femtosecond pulses. Scanning electron microscopy revealed a rod structure arranged into a square lattice. The possibility of controlling the period of the lattice, rod thickness, and rod shape were demonstrated.
GaN Schottky barrier photodetectors with a low-temperature GaN cap layer
Authors: Lee M. L. , Sheu J. K. , Lai W. C. , Chang S. J. , Su Y. K. , Chen M. G. , Kao C. J. , Chi G. C. , Tsai J. M.
Published: April 2003

By using organometallic vapor phase epitaxy, we have prepared i-GaN/low-temperature (LT) GaN/Ni/Au (sample A) and i-GaN/Ni/Au (sample B) Schottky barrier UV photodiodes (PDs). It was found that we could significantly reduce the leakage current and achieve a much larger photocurrent to dark current contrast ratio by introducing a LT GaN on top of the conventional nitride-based UV PDs. With incident light wavelength of 350 nm and a −1 V reverse bias, it was found that the measured responsivity was around 0.1 and 0.37 A/W for samples A and B, respectively. Furthermore, it was found that the operation speed of sample A is slower than that of sample B due to the highly resistive LT–GaN layer induced large RC time constant.
Security architectures for network clients
Authors: Skoularidou Victoria , Spinellis Diomidis
Published: April 2003

Enumerates and compares a number of security‐enabling architectures for network clients. These architectures, either proposed as methodologies or currently implemented in software and/or hardware, are capable of protecting the client’s software integrity and its environment. The most important methodologies include the reference monitor model, firewalls, and virtual machines. Software implementations are the Java Sandbox, and the code signing concept. Hardware that can be used includes smart cards, and the TCPA/Palladium security initiative. Describes their most important features and provide a review and comparative study based on a number of criteria. Believes that ongoing research can empower these mechanisms for protecting network clients in a more effective way.
Comparison of 13CαH and 15NH backbone dynamics in protein GB1
Authors: Idiyatullin Djaudat , Nesmelova Irina , Daragan Vladimir A. , Mayo Kevin H.
Published: April 2003

This study presents a site‐resolved experimental view of backbone CαH and NH internal motions in the 56‐residue immunoglobulin‐binding domain of streptococcal protein G, GB1. Using 13CαH and 15NH NMR relaxation data [T1, T2, and NOE] acquired at three resonance frequencies (1H frequencies of 500, 600, and 800 MHz), spectral density functions were calculated as F(ω) = 2ωJ(ω) to provide a model‐independent way to visualize and analyze internal motional correlation time distributions for backbone groups in GB1. Line broadening in F(ω) curves indicates the presence of nanosecond time scale internal motions (0.8 to 5 nsec) for all CαH and NH groups. Deconvolution of F(ω) curves effectively separates overall tumbling and internal motional correlation time distributions to yield more accurate order parameters than determined by using standard model free approaches. Compared to NH groups, CαH internal motions are more broadly distributed on the nanosecond time scale, and larger CαH order parameters are related to correlated bond rotations for CαH fluctuations. Motional parameters for NH groups are more structurally correlated, with NH order parameters, for example, being larger for residues in more structured regions of β‐sheet and helix and generally smaller for residues in the loop and turns. This is most likely related to the observation that NH order parameters are correlated to hydrogen bonding. This study contributes to the general understanding of protein dynamics and exemplifies an alternative and easier way to analyze NMR relaxation data.