bluuebunny/crossref_metadata_2025 huggingface dataset:
Activity‐dependent plasticity of inhibitory and excitatory amino acid transmitter systems in cultured rat cerebral cortex
Authors: Ramakers G.J.A. , van Galen H. , Feenstra M.G.P. , Corner M.A. , Boer G.J.
Published: April 2003

Chronic suppression of spontaneous bioelectric activity in cultures of dissociated fetal rat cerebral cortex increases neuronal cell death and results in electrophysiological changes which indicate an altered balance between excitatory and inhibitory neurotransmission in culture. To delineate whether alterations in neurotransmitter release could underlie this imbalance, we investigated the effects of chronic tetrodotoxin (TTX) treatment on the content and release of glutamate, aspartate and γ‐aminobutyric acid (GABA) in culture. Chronic TTX treatment decreased the content of all amino acids investigated. However, only GABA was decreased relative to the neuronal marker NSE (neuron‐specific enolase), indicating a disproportionate loss of GABA production following chronic silencing. Depolarization‐induced release of GABA, glutamate and aspartate increased about 10‐fold between 7 and 21 days in control cultures. Chronic TTX treatment significantly increased the depolarization‐induced release of glutamate and aspartate at 7 days in vitro relative to control levels. At all ages it caused a two‐fold increase in the ratio of evoked excitatory amino acid release to that of GABA. These observations suggest that chronic silencing of developing neocortex cell cultures increases the ratio of excitatory to inhibitory synaptic activity either by differential cell death or by reduced synaptic efficiency, on which a decrease in GABA neurotransmission appears to play a major role. Since similar mechanisms may be involved in activity‐dependent plasticity in vivo, these cultures provide a useful model to analyse this phenomenon at the cell biological and molecular level.
Early nutritional changes modify the kinetics and phosphorylation capacity of tryptophan‐5‐hydroxylase
Authors: Manjarrez G.G. , Chagoya G.G. , Hernández R. J.
Published: April 2003

Gestational malnutrition induces an acceleration of the serotonin biosynthetic pathway in the developing brain with an increase in brain L‐tryptophan (L‐Trp), tryptophan‐5‐hydroxylase (TrpOH) activity and serotonin content. In the present work we report results on the possible mechanism of TrpOH activation. Kinetic experiments were done with different L‐Trp concentrations in the rat brain at different ages. Also various phosphorylating conditions of the enzyme were tested in order to compare its activation in developmentally malnourished and normal brains. The results showed lower Km values and no changes in the Vmax in the malnourished as compared to controls. Interestingly, in the malnourished group, TrpOH showed an increased activity under the phosphorylating conditions employed. We propose that in the activation of brain TrpOH by developmental malnutrition, not only is an elevation of L‐Trp involved, but also a change in the enzyme itself reflected in a higher affinity for L‐Trp and in a greater response to phosphorylation. This allows us to propose the possibility that early chronic malnutrition induces structural changes in the enzymatic molecule.
Development of the gabaergic phenotype in murine spinal cord‐dorsal root ganglion cultures
Authors: Caserta Maria T. , Barker Jeffery L.
Published: April 2003

Murine spinal cord and dorsal root ganglion GABAergic neurons, derived from 12‐day‐old fetuses, were examined autoradiographically, biochemically and immunocytochemically in vitro to determine the timecourse of appearance and maturation of this phenotype and the extent and mode of its innervation of target neurons. Specific 3H‐GABA uptake into spinal cord neurons was the first property to develop and was present at the earliest time studied, one day in vitro. Immunocytochemical localization of glutamic acid decarboxylase (GAD) revealed positively stained neurons beginning at four days. At five days in vitro, electron microscopic immunocytochemistry revealed GAD‐immunoreactive (GAD‐IMR) boutons investing neuronal perikarya as well as neuronal processes. By one week in vitro, GAD‐IMR neurons constituted 27% of the total population and GAD‐IMR boutons could be seen contacting every cell with a neuronal morphology. The mode of investment of target neurons by GAD‐IMR boutons was not circumscribed to either soma or dendrites but usually involved the entire neuronal perimeter and did not change with time in culture. Three morphologically distinct types of GAD‐IMR neurons were evident: a small, bipolar type; a medium‐sized multipolar neuron which was the most common and a large, multipolar type, resembling a motoneuron. A small population (8%) of dorsal root ganglion neurons was found to contain GAD both biochemicaly and immunocytochemically but was never invested by GAD‐IMR boutons. GAD activity in vitro paralleled in vivo levels with maximal activity being reached at four weeks in vitro and 10 days postnatally in the intact mouse spinal cord. Murine spinal cord GABAergic neurons are a morphologically diverse and abundant neuronal population with extensive, precocious innervation of all other neuronal phenotypes in vitro suggesting that GABA has a widespread influence over other developing neuronal systems in the murine spinal cord.
Postnatal development of NMDA, AMPA and kainate receptors in individual layers of rat visual cortex and the effect of monocular deprivation
Authors: Kumar Ashok , Schliebs Reinhard , Bigl Volker
Published: April 2003

The postnatal development of the ligand binding to n‐methyl‐d‐aspartate (NMDA), alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA), and kainate receptor sites was studied in individual layers of rat visual cortex with [3H]MK‐801, [3H]CNQX and [3H]kainate, respectively. The studies were performed by quantitative receptor autoradiography in the different visual cortical layers from normally raised rats and from monocularly deprived animals.

In normally raised rats, in all visual cortical layers, [3H]MK‐801 and [3H]CNQX binding increased significantly from birth to around postnatal day 20, at which age already the adult values are reached. In contrast, the increase in [3H]kainate binding from day 1 to day 15 is followed by a significant decrease in binding sites up to day 25; at this age the adult binding level is nearly attained.

Monocular deprivation, by unilateral eyelid suture at the age of 11 days onwards, leads to a transient decrease in [3H]CNQX binding in all visual cortical layers, whereas [3H]kainate binding results to a permanent decrease in AMPA receptor sites in cortical layers II to VI in both sides of the cortex. In contrast, only long‐term monocular deprivation until the age of 90 days resulted in decreased [3H]MK‐801 binding levels as compared to age‐matched controls. The data suggest that the laminar development of glutamate receptor subtypes is differentially affected by visual experience during early brain maturation.
Zinc ions promote the interaction between heparin and heparin cofactor II
Authors: Eckert Ralf , Ragg Hermann
Published: April 2003

The effects of bivalent cations on heparin binding, structure, and thrombin inhibition rates of heparin cofactor II were examined. Zn2+ – and to a lesser extent Cu2+ and Ni2+ – enhanced the interaction between heparin cofactor II and heparin as demonstrated by heparin affinity chromatography and surface plasmon resonance experiments. Metal chelate chromatography and increased intrinsic protein fluorescence in the presence of Zn2+ indicated that heparin cofactor II has metal ion‐binding properties. The results are compatible with the hypothesis that Zn2+ induces a conformational change in heparin cofactor II that favors its interaction with heparin.
NF‐κB and AP‐1 regulate activation‐dependent CD137 (4‐1BB) expression in T cells
Authors: Kim Jae-Ouk , Kim Ho Won , Baek Kyoung-Min , Kang Chang-Yuil
Published: April 2003

4‐1BB(CD137) is a member of the tumor necrosis factor receptor superfamily and provides a costimulatory signal by interaction with 4‐1BB ligand expressed on antigen‐presenting cells. The expression of 4‐1BB is known to be activation‐dependent. Here, we investigated the transcriptional machinery required for T cell receptor (TCR) activation‐dependent induction of 4‐1BB expression in CD3‐CEM cells treated with phorbol myristate acetate and ionomycin. Using 5′‐deletion constructs of 4‐1BB promoter in luciferase reporter assays, we demonstrated that the transcriptional elements mediating 4‐1BB upregulation were located in the region between ∼0.9 and ∼1.1 kb from the translational start site. Characterization of these sites by electrophoretic mobility shift assay and site‐directed mutagenesis revealed that nuclear factor κB (NF‐κB) and activating protein‐1 (AP‐1) are involved. MEK and c‐Jun N‐terminal kinase‐1 activity was required for activation‐dependent 4‐1BB upregulation. Thus, NF‐κB and AP‐1 are involved in the TCR stimulation‐dependent transcriptional regulation of the 4‐1BB promoter.
Tricorn protease (TRI) interacting factor 1 from Thermoplasma acidophilum is a proline iminopeptidase
Authors: Tamura Tomohiro , Tamura Noriko , Lottspeich Friedrich , Baumeister Wolfgang
Published: April 2003

Tricorn protease (TRI), a high molecular mass complex from the archaeon T. acidophilum, forms the core of a modular proteolytic system; upon interacting with low molecular mass factors intrinsic activities are enhanced and novel activities are generated. Here we characterize the first factor, F1, which turns out to be homologous with several bacterial proline iminopeptidases (PIPs). Surprisingly, it cleaves not only typical PIP substrates such as H‐Pro‐AMC, but a wide spectrum of amino acid substrates and several peptide substrates without a proline at the N‐terminus. The pip gene encodes a 293 amino acid residue protein with a molecular mass of 33487 Da. By means of site‐directed mutagenesis we identified Ser105 and His271 as the active site nucleophile and proton donor, respectively. Experiments with inactive mutant PIPs indicate that the activities elicited by interacting with TRI are contributed by PIP.
Activation of the plant plasma membrane H+‐ATPase. Is there a direct interaction between lysophosphatidylcholine and the C‐terminal part of the enzyme?
Authors: Gomés Eric , Kees Venema , Francoise Simon-Plas , Marie-Louise Milat , Michael Gjedde Palmgren , Jean-Pierre Blein
Published: April 2003

The antagonistic effects of the fungal toxin beticolin1 and of l‐α‐lysophosphatidylcholine (lysoPC) were investigated on the plasma membrane H+‐ATPase of the plant Arabidopsis thaliana (isoform 2) expressed in yeast, using both wild‐type enzyme (AHA2) and C‐terminal truncated enzyme (aha2Δ92). Phosphohydrolytic activities of both enzymes were inhibited by beticolin‐1, with very similar 50% inhibitory concentrations, indicating that the toxin action does not involve the C‐terminal located autoinhibitory domain of the proton pump. Egg lysoPC, a compound that activates the H+‐ATPase by a mechanism involving the C‐terminal part of the protein, was found to be able to reverse the inhibition of AHA2 by beticolin‐1. The lack of effect of other detergents and the comparison of different carbon chain length lysoPCs show that the capacity to reverse the enzyme inhibition is clearly related to their ability to activate the pump. Long chain length lysoPC was also shown to reverse the inhibition of aha2A92 by beticolin‐1, which strongly suggests that lysoPC binds to the H+‐ATPase on site(s) not located on its autoinhibitory domain.
Factors affecting supplier quality performance
Authors: Forker L.B.
Published: April 2003

The interest among practitioners and researchers in quality management and other factors that may affect quality performance reflects the understanding that a firm's output (i.e., performance) can be only as good as the quality of its inputs. However, studies of the quality management‐quality performance relationship have led to mixed results regarding the existence of a positive correlation between the two. The results of a survey of 348 aerospace component manufacturers are examined here to provide new insights into factors that affect supplier quality performance. In this study, the inconsistent association between practice and performance is accounted for by considering the process view of quality management. Process management links quality management with process optimization to address both effectiveness and efficiency concerns. Performance is also affected by transaction‐specific investments (asset specificity) in the buyer/supplier relationship that lead to poorer component quality and higher transaction costs. Asset specificity and organizational efficiency at implementing Total Quality Management hold great promise for resolving the mixed practice‐performance findings in the quality management literature.
Assessing the impact of JIT using economic theory
Authors: Brox James A. , Fader Christina
Published: April 2003

This paper combines ideas that are well founded in the production and inventory management literature, with analytical approaches that have been long established in the economic theory literature, to reveal and explore production‐function characteristic differences between JIT producers and non‐JIT producers among electronic firms in Ontario, Canada. The methodology employed is the estimation of the CES‐TL total cost system. Our primary conclusion is that JIT firms are more cost‐efficient and appear to be distinct from the non‐JIT group. This conclusion is supported by: (1) the fact that, in most cases, the elasticities calculated from the two groups of firms are significantly different; (2) the fact that the cost elasticity with respect to output is lower for the JIT firms than for the non‐JIT firms, indicating that the former are better able to capture economies of scale and density; (3) the difference between the elasticities of factor productivity, with respect to output changes, shows the JIT firms as being more labor‐ and materials‐saving than the non‐JIT firms.
A review and classification of empirical research in operations management
Authors: Scudder Gary D. , Hill Craig A.
Published: April 2003

The progress in the use of empirical research methods has been a topic of interest in the Operations Management (OM) area for the last 15 years. It is considered desirable to accompany traditional OM research, which develops and tests theories using mathematics, modelling, and simulation, with research that makes use of empirical data. The use of empirical research helps support the understanding of OM practices within industry. This paper expands and updates previous literature review studies dealing with empirical research in OM. The journal publications reviewed for this paper were published in the years 1986 to 1995. This is a review of the articles published in thirteen journals that are traditional outlets for OM research. These articles are classified and the results of these classifications presented. There has been an increase in the amount of published articles that make use of empirical research methods in the OM area, both in number and as a percentage of the total number of articles published in these journals.
Dimensions of manufacturing strength in the furniture industry
Authors: Vickery Shawnee K. , Dröge Cornelia , Markland Robert E.
Published: April 2003

This paper explores dimensions of manufacturing competitive strength in the furniture industry. A theoretically relevant set of manufacturing competitive priorities is identified from the operations literature and factor analyzed to determine the core dimensions of manufacturing performance. Relationships between these core dimensions of manufacturing strength and overall business performance are examined. The results identify four dimensions of manufacturing strength in the furniture industry: innovation, delivery, flexibility, and value, with the latter encompassing the combined effects of quality and cost. The study supports innovation as a key order winner in the furniture industry.
Effects of diuretic treatment on cardiac and circulating RAS in chronic heart failure post‐myocardial infarction in rats
Authors: Seeland Ute , Kouchi Ichiro , Zolk Oliver , Jockenhövel Friedrich , Itter Gabi , Linz Wolfgang , Böhm Michael
Published: April 2003

Background:

Cardiac angiotensin converting enzyme (ACE) is activated by an increase in wall stress and is involved in remodeling processes. Heart failure is often treated with ACE inhibitors and diuretics although diuretic treatment could activate the renin–angiotensin system (RAS).

Aims:

To examine the effects of diuretic treatment on cardiac and circulating RAS in post‐infarction chronic heart failure.

Methods:

Myocardial infarction was produced by coronary artery ligation in spontaneously hypertensive rats. The rats were randomly assigned to receive either ramipril (1 mg/kg/day), furosemide (4 mg/kg/day), or combination therapy for 6 weeks, commencing 2 weeks after infarction.

Results:

All three treatment protocols equivalently attenuated reactive hypertrophy of the right ventricle and ventricular septum and improved left ventricular systolic function. Both cardiac ACE mRNA and activity were significantly increased in untreated rats. This increase was attenuated by both ramipril and furosemide and further depressed by the combination. The increase in activity was completely inhibited by either agent alone. Plasma renin activity was upregulated by ramipril or ramipril plus furosemide but not influenced by infarction or furosemide alone.

Conclusions:

Furosemide and ramipril significantly reduced cardiac ACE and remodeling. Diuretics work favorably and do not interfere with the effects of ACE inhibitors. Possibly, a reduction in wall stress due to decreased volume overload accounts for the effects of diuretics on cardiac ACE in the treatment of post‐infarction remodeling in hypertensive hearts. These data suggest a new mechanism for the frequently observed beneficial effect of diuretics in heart failure.
The Relationship of Compliance with Coping Strategies and Self-Esteem
Authors: Gudjonsson Gisli H. , Sigurdsson Jon Fridrik
Published: April 2003

Summary: The Gudjonsson Compliance Scale (GCS), the COPE Scale, and the Rosenberg Self-Esteem Scale were administered to 212 men and 212 women. Multiple regression of the test scores showed that low self-esteem and denial coping were the best predictors of compliance in both men and women. Significant sex differences emerged on all three scales, with women having lower self-esteem than men, being more compliant, and using different coping strategies when confronted with a stressful situation. The sex difference in compliance was mediated by differences in self-esteem between men and women.
The Assessment of Spatial Ability with a Single Computerized Test
Authors: Colom Roberto , Contreras Ma José , Shih Pei Chun , Santacreu José
Published: April 2003

Summary: Spatial cognitive ability has to do with how individuals deal with spatial information. Spatial ability is routinely assessed to predict performance in a variety of job positions, air traffic control being an example. Spatial tests are good predictors of performance in those occupations. One of the most valuable pieces of knowledge for psychological assessment in personnel selection is that concerning efficient ways to measure a given psychological trait, meaning that the measure shows high validity and low application costs. This article reports two studies showing the high efficiency of a new measure of spatial ability: SODT-R, a computer-administered test of dynamic spatial performance in which the person is required to simultaneously orient two moving points to a given destination that change from trial to trial. In the first study, 602 applicants for an air traffic control training course completed a battery of nine cognitive tests. In the second study, 105 university undergraduates completed a battery of 11 tests. Both batteries comprise tests of reasoning, visualization, spatial relations, and dynamic spatial performance. SODT-R emerges as a good measure of general spatial ability (Gv). This is especially true in the second study, where a broader sample of spatial tests is considered. A theoretical account based on the well-known high correlation between working memory capacity and cognitive abilities is discussed.
Epidermal-growth-factor receptor and metalloproteinases mediate thromboxane A2-dependent extracellular-signal-regulated kinase activation
Authors: GALLET Carole , BLAIE Stéphanie , LÉVY-TOLEDANO Sylviane , HABIB Aïda
Published: April 2003

The signalling pathways that link G-protein-coupled receptors to mitogen-activated protein kinases involve receptor and non-receptor tyrosine kinases and protein kinase C (PKC). We explored the pathways that are implicated in the thromboxane (TX) A2-dependent activation of extracellular-signal-regulated protein kinase (ERK) and the role of the two TX receptor (TP) isoforms, TPα and TPβ. ERK activation by IBOP, a TX analogue, was dependent on epidermal-growth-factor receptor (EGFR) in TPα- or TPβ-transfected cells and in human aortic smooth muscle cells (hASMCs), since AG1478, a selective inhibitor of tyrosine phosphorylation of the EGFR, strongly blocked ERK and EGFR phosphorylation. In addition, EGFR transactivation leading to ERK activation involved matrix metalloproteinases (MMPs), since BB2516, an inhibitor of MMP, decreased ERK and EGFR phosphorylation in TPα- or TPβ-transfected cells. Moreover, we showed that both isoforms activate ERK phosphorylation in an Src-kinase-dependent manner, whereas PKC was mainly implicated in ERK activation and EGFR phosphorylation by TPβ. In hASMCs, we showed that ERK activation depended on both pertussis-sensitive and -insensitive Gα-proteins. We demonstrated further that EGFRs, PKC, Src kinase and MMPs are involved in ERK activation by TX. The results of the present study highlight a role for MMPs and PKC in EGFR transactivation triggered by the TPs and demonstrate this mechanism for the first time in primary cells, i.e. hASMCs.
Detection of 3-hydroxykynurenine in a plant pathogenic fungus
Authors: WILSON T. J. Greer , THOMSEN Karl Kristian , PETERSEN Bent O. , DUUS Jens Ø. , OLIVER Richard P.
Published: April 2003

A redox-active compound has been purified from the barley powdery mildew fungus Blumeria (Erysiphe) graminis f. sp. hordei. A combination of spectrophotometry, MS and NMR has identified it as 3-hydroxykynurenine (3OHKyn). This compound, never previously detected in any fungus or pathogen, is best known for its role in vertebrate cataracts. It is found abundantly in developing and germinating spores and also in runner hyphae. Two roles for 3OHKyn are discussed: first, the presence of active oxygen species would enable 3OHKyn to cross-link the spore chemically with the plant. Secondly, it may be acting as an UV protectant and an antioxidant.
Wigner’s theorem in a class of Hilbert C*-modules
Authors: Bakić Damir , Guljaš Boris
Published: April 2003

Let H be a complex Hilbert space, dim H>1, and let A⊆B(H) be a C*-algebra such that the ideal K(H) of all compact operators on H is contained in 𝒜. Let X be a Hilbert C*-module over 𝒜. We prove that any function F:X→X which preserves the absolute value of the 𝒜-valued inner product on X is of the form F(x)=φ(x)Ux, x∈X, where φ is a phase function and U is an 𝒜-linear isometry. The result generalizes Wigner’s classical unitary-antiunitary theorem and its extension to Hilbert K(H)-modules.
Lie point symmetries and first integrals: The Kowalevski top
Authors: Marcelli M. , Nucci M. C.
Published: April 2003

We show how the Lie group analysis method can be used in order to obtain first integrals of any system of ordinary differential equations. The method of reduction/increase of order developed by Nucci [J. Math. Phys. 37, 1772–1775 (1996)] is essential. Noether’s theorem is neither necessary nor considered. The most striking example we present is the relationship between Lie group analysis and the famous first integral of the Kowalevski top.
Modular localization of massive particles with “any” spin in d=2+1
Authors: Mund Jens
Published: April 2003

We discuss a concept of particle localization which is motivated from quantum field theory, and has been proposed by Brunetti, Guido and Longo and by Schroer. It endows the single-particle Hilbert space with a family of real subspaces indexed by the space–time regions, with certain specific properties reflecting the principles of locality and covariance. We show by construction that such a localization structure exists also in the case of massive anyons in d=2+1, i.e., for particles with positive mass and with arbitrary spin s∈R. The construction is completely intrinsic to the corresponding ray representation of the (proper orthochronous) Poincaré group. Our result is of particular interest since there are no free fields for anyons, which would fix a localization structure in a straightforward way. We present explicit formulas for the real subspaces, expected to turn out useful for the construction of a quantum field theory for anyons. In accord with well-known results, only localization in string-like, instead of point-like or bounded, regions is achieved. We also prove a single-particle PCT theorem, exhibiting a PCT operator which acts geometrically correctly on the family of real subspaces.
Improved performance of direct-drive inertial confinement fusion target designs with adiabat shaping using an intensity picket
Authors: Goncharov V. N. , Knauer J. P. , McKenty P. W. , Radha P. B. , Sangster T. C. , Skupsky S. , Betti R. , McCrory R. L. , Meyerhofer D. D.
Published: April 2003

Hydrodynamic instabilities seeded by laser imprint and surface roughness limit the compression ratio and neutron yield in the direct-drive inertial confinement fusion target designs. New improved-performance designs use adiabat shaping to increase the entropy of only the outer portion of the shell, reducing the instability growth. The inner portion of the shell is kept on a lower entropy to maximize shell compressibility. The adiabat shaping is implemented using a high-intensity picket in front of the main-drive pulse. The picket launches a strong shock that decays as it propagates through the shell. This increases the ablation velocity and reduces the Rayleigh–Taylor growth rates. In addition, as shown earlier [T.J.B. Collins and S. Skupsky, Phys. Plasmas 9, 275 (2002)], the picket reduces the instability seed due to the laser imprint. To test the results of calculations, a series of the picket pulse implosions of CH capsules were performed on the OMEGA laser system [T.R. Boehly, D.L. Brown, R.S. Craxton et al., Opt. Commun. 133, 495 (1997)]. The experiments demonstrated a significant improvement in target yields for the pulses with the picket compared to the pulses without the picket. Results of the theory and experiments with adiabat shaping are being extended to future OMEGA and the National Ignition Facility’s [J.A. Paisner, J.D. Boyes, S.A. Kumpan, W.H. Lowdermilk, and M.S. Sorem, Laser Focus World 30, 75 (1994)] cryogenic target designs.
Perturbative analysis of dynamical localization
Authors: Barata J. C. A. , Cortez D. A.
Published: April 2003

In this paper we present a mathematical investigation of the phenomenon of dynamical localization in a class of quasi-periodically and periodically time-dependent two-level systems. Our results are based on a sort of “renormalization” procedure, which is developed here in a systematic way in order to adapt it to the case of dynamical localization. In the quasi-periodic case this procedure leads to a formal perturbative expansion free of secular terms. In the periodic case a convergent perturbative solution is obtained and, in particular, a convergent perturbative expansion for the secular frequency is presented. The case of ac–dc fields is discussed in some detail, leading to the conclusion that the phenomenon of dynamical localization is not exact in that situation.
Towards Euclidean theory of infrared singular quantum fields
Authors: Smirnov A. G.
Published: April 2003

A new generalized formulation of the spectral condition is proposed for quantum fields with highly singular infrared behavior whose vacuum correlation functions are well defined only under smearing with analytic test functions in momentum space. The Euclidean formulation of QFT developed by Osterwalder and Schrader is extended to theories with infrared singular indefinite metric. The corresponding generalization of the reconstruction theorem is obtained. The fulfilment of the generalized spectral condition is verified for quantum fields representable by infinite series in the Wick powers of indefinite metric free fields.
New formulations of monotonically convergent quantum control algorithms
Authors: Maday Yvon , Turinici Gabriel
Published: April 2003

Most of the numerical simulation in quantum (bilinear) control have used one of the monotonically convergent algorithms of Krotov (introduced by Tannor et al.) or of Zhu and Rabitz. However, until now no explicit relationship has been revealed between the two algorithms in order to understand their common properties. Within this framework, we propose in this paper a unified formulation that comprises both algorithms and that extends to a new class of monotonically convergent algorithms. Numerical results show that the newly derived algorithms behave as well as (and sometimes better than) the well-known algorithms cited above.
Nonlinear Thomson scattering: A tutorial
Authors: Lau Y. Y. , He Fei , Umstadter Donald P. , Kowalczyk Richard
Published: April 2003

Recent advances in table-top, ultrahigh intensity lasers have led to significant renewed interest in the classic problem of Thomson scattering. An important current application of these scattering processes is the generation of ultrashort-pulse-duration x rays. In this tutorial, the classical theory of nonlinear Thomson scattering of an electron in an intense laser field is presented. It is found that the orbit, and therefore its nonlinear scattering spectra, depends on the amplitude and on the phase at which the electron sees the laser electric field. Novel, simple asymptotic expansions are obtained for the spectrum of radiation that is backscattered from a laser by a counter-propagating (or co-propagating) electron. The solutions are presented in such a way that they explicitly show—at least in the single particle regime—the relative merit of using an intense laser and of an energetic electron beam in x-ray production. The close analogy with free electron laser/synchrotron source is indicated.
Inverse ion-cyclotron damping: Laboratory demonstration and space ramifications
Authors: Koepke M. E. , Teodorescu C. , Reynolds E. W. , Chaston C. C. , Carlson C. W. , McFadden J. P. , Ergun R. E.
Published: April 2003

The familiar and ubiquitous phenomenon of ion-cyclotron damping is shown to be invertible in a laboratory plasma resembling ionospheric plasma in terms of important dimensionless parameters. The ion-cyclotron waves that arise spontaneously appear at all harmonics of the ion-cyclotron frequency, well into the lower-hybrid range. The sign change of the usual ion-cyclotron damping is induced by shear in the magnetic-field-aligned (parallel) ion drift velocity. Full experimental characterization of the wave propagation and particle-velocity distributions are presented to document the case of inverse damping (i.e., growth) and the case in which the damping is significantly reduced. These results support the parallel-velocity-shear interpretation of the multiscale structure observed by the Fast Auroral Snapshot (FAST) satellite. FAST observations of simultaneous shear and multiharmonic ion-cyclotron waves in the upward-current and downward-current regions of the ionosphere (4000-km altitude) are presented and discussed in terms of a new, small-scale analysis of the mechanisms in the auroral region.
Anomalous diffusion: Fractional Fokker–Planck equation and its solutions
Authors: Lenzi E. K. , Mendes R. S. , Fa Kwok Sau , Malacarne L. C. , da Silva L. R.
Published: April 2003

We analyze a linear fractional Fokker–Planck equation for the case of an external force F(x)∝x|x|α−1 and diffusion coefficient D(x)∝|x|−θ (α,θ∈R). We also discuss the connection of the solutions found here with the Fox functions and the nonextensive statistics based on the Tsallis entropy.
Terahertz studies of carrier dynamics and dielectric response of n-type, freestanding epitaxial GaN
Authors: Zhang W. , Azad Abul K. , Grischkowsky D.
Published: April 2003

We report the characterization of the complex conductivity and dielectric function of GaN by terahertz time-domain spectroscopy. Transmission measurements are performed on an n-type, 180-μm-thick, freestanding GaN crystal. Frequency dependent electron dynamics, power absorption and optical dispersion are observed over the frequency range from 0.1 to 4.0 THz. The measured conductivity is well fit by Drude theory.
Cu depletion at the CuInSe2 surface
Authors: Liao Dongxiang , Rockett Angus
Published: April 2003

The chemical composition of the (112)B surface of epitaxial CuInSe2 thin films is investigated by angle resolved x-ray photoelectron spectroscopy. Results show that a severe Cu depletion exists in the top 1–2 atomic layers. No bulk second phase is found at the surface. The source of this depletion and its relation to the Cd doping at the CdS/CuInSe2 interface are discussed.
Heat Transfer In Turbulent Boundary Layers Subjected to Free-Stream Turbulence—Part II: Analysis and Correlation
Authors: Barrett Michael J. , Hollingsworth D. Keith
Published: April 2003

A new heat transfer correlation for turbulent boundary layers subjected to free-stream turbulence was developed. The new correlation estimates dimensionless heat transfer coefficients without the use of conventional boundary-layer thickness measures and the associated Reynolds numbers. Using only free-stream parameters (mean velocity, turbulence intensity and length scale), the new correlation collected many authors’ elevated-turbulence, flat-plate Stanton number data to within ±11%. The level of scatter around the new correlation compared well to previous correlations that require additional flow information as input parameters. For a common subset of data, scatter using earlier correlation methods ranged from 5–10%; scatter around the new correlation varied from 6–9% over the same data subset. A length-scale dependence was identified in a Stanton number previously defined using a near-wall streamwise velocity fluctuation, St′. A new near-wall Stanton number was introduced; this parameter was regarded as a constant in a two-region boundary layer model on which the new correlation is based.
CFD Optimization of Cooling Air Offtake Passages Within Rotor Cavities
Authors: Young Colin , Snowsill Guy D.
Published: April 2003

In modern gas turbine engines, up to 20% of the core airflow is bled off from various compressor stages to facilitate internal cooling, bearing chamber, and rim sealing, as well as axial load management. As this secondary airflow makes no direct contribution to engine thrust, there are strong economic incentives to reduce the quantity and quality of offtake air and maximize its effective use. Secondary airflows are commonly bled off via circular drillings in the compressor rotor, thereby augmenting their swirl velocity. This results in the creation of vortices within the rotor cavity and strong radial pressure gradients opposing inflow. In the present work the relative performance of a series of noncircular offtake passages has been assessed using CFD techniques. The results of this work demonstrate the degree of control that may be exercized over swirl uptake, which can be used to suppress the creation of vortices in rotor cavities.
Leading-Edge Film-Cooling Physics—Part III: Diffused Hole Effectiveness
Authors: York William D. , Leylek James H.
Published: April 2003

A proven computational methodology was applied to investigate film cooling from diffused holes on the simulated leading edge of a turbine airfoil. The short film-hole diffuser section was conical in shape with a shallow half-angle, and was joined to a plenum by a cylindrical metering section. The diffusion resulted in a film-hole breakout area of 2.5 times that of a cylindrical hole. In the present paper, predictions of adiabatic effectiveness for the cases with diffused holes are compared to results for standard cylindrical holes, and performance is analyzed in the context of extensive flowfield data. The leading edge surface was elliptic in shape to accurately model a turbine airfoil. The geometry consisted of one row of holes centered on the stagnation line, and two additional rows located 3.5 hole (metering section) diameters downstream on either side of the stagnation line. Film holes in the downstream rows were centered laterally between holes in the stagnation row. All holes were angled at 20 deg with the leading edge surface, and were turned 90 deg with respect to the streamwise direction (radial injection). The average blowing ratio was varied from 1.0 to 2.5, and the coolant-to-mainstream density ratio was equal to 1.8. The steady Reynolds-averaged Navier-Stokes equations were solved with a pressure-correction algorithm on an unstructured, multi-block grid containing 4.6 million finite-volumes. A realizable k-ε turbulence model was employed to close the equations. Convergence and grid-independence was verified using strict criteria. Based on the laterally averaged effectiveness over the leading edge, the diffused holes showed a marked advantage over standard holes through the range of blowing ratios. However, ingestion of hot crossflow and thermal diffusion into the second row of film holes was observed to cause significant, and potentially detrimental, heating of the film-hole walls.
Modification of the Atropisomeric N,N-Ligand 2,2'-Di(pyridin-2-yl)-1,1'-binaphthalene and Its Application to the Asymmetric Allylation of Benzaldehyde
Authors: Charmant Jonathan P. H. , Hunt Neil J. , Lloyd-Jones Guy C. , Nowak Thorsten
Published: April 2003

The atropisomeric compound 2,2'-di(pyridin-2-yl)-1,1'-binaphthalene (1) has been chlorinated, via its bis-N-oxide 2, at the 4 and 6 pyridine ring positions so as to generate the three isomeric species: 2,2'-bis(6-chloropyridin-2-yl)- (3a), 2-(4-chloropyridin-2-yl)-2'-(6-chloropyridin-2-yl)- (3b) and 2,2'-bis(4-chloropyridin-2-yl)-1,1'-binaphthalene (3c). The dichlorinated compounds underwent Ni-catalysed Kumada cross-coupling with MeMgI to give the methylated pyridine isomers: 2,2'-bis(6-methylpyridin-2-yl)- (4a), 2-(4-methylpyridin-2-yl)-2'-(6-methylpyridin-2-yl)- (4b) and 2,2'-bis(4-methylpyridin-2-yl)-1,1'-binaphthalene (4c). The enantiomerically pure forms of the six novel ligands (3a-3c and 4a-4c), prepared from enantiomerically pure 2,2'-di(pyridin-2-yl)-1,1'-binaphthalene (1), were tested in asymmetric catalysis, but proved to be no better and in most cases poorer than parent 1. The coordination of the ligands to Zn and Pd fragments has been explored and compared with the parent compound 1 so as to rationalise the negative effect of pyridine substitution on asymmetric induction in the zinc-catalysed allylation of benzaldehyde.
FAULT-TOLERANT RING EMBEDDING IN A HONEYCOMB TORUS WITH NODE FAILURES
Authors: MEGSON G. M. , LIU XIAOPING , YANG XIAOFAN
Published: April 2003

Honeycomb torus networks have been recognised as an attractive alternative to existing torus interconnection networks in parallel and distributed applications. In this paper we establish that there exists a hamiltonian cycle in a honeycomb torus with two adjacent faulty nodes and that with a single fault a ring embedding with one less node than the fault free torus can be found.
THE DUALIZED STANDARD MODEL AND ITS APPLICATIONS — AN INTERIM REPORT
Authors: CHAN HONG-MO , TSOU SHEUNG TSUN
Published: April 2003

Based on a non-Abelian generalization of electric–magnetic duality, the Dualized Standard Model (DSM) suggests a natural explanation for exactly three generations of fermions as the "dual colour" [Formula: see text] symmetry broken in a particular manner. The resulting scheme then offers on the one hand a fermion mass hierarchy and a perturbative method for calculating the mass and mixing parameters of the Standard Model fermions, and on the other hand testable predictions for new phenomena ranging from rare meson decays to ultra-high energy cosmic rays. Calculations to one-loop order gives, at the cost of adjusting only three real parameters, values for the following quantities all (except one) in very good agreement with experiment: the quark CKM matrix elements ‖Vrs‖, the lepton CKM matrix elements ‖Urs‖, and the second generation masses mc, ms, mμ. This means, in particular, that it gives near maximal mixing Uμ3 between νμ and ντ as observed by SuperKamiokande, Kamiokande and Soudan, while keeping small the corresponding quark angles Vcb, Vts. In addition, the scheme gives (i) rough order-of-magnitude estimates for the masses of the lowest generation, (ii) predictions for low energy FCNC effects such as KL→ eμ, and (iii) a possible explanation for the long-standing puzzle of air showers beyond the GZK cut-off. All these together, however, still represent but a portion of the possible physical consequences derivable from the DSM scheme, the majority of which are yet to be explored.
TRANSITIONS BETWEEN STATIONARY STATES OF THE ELECTRON–PHOTON FIELD SYSTEM: A NEW MECHANISM FOR INTERPRETING HIGH OPTICAL FIELD PHENOMENA
Authors: GAO J. , SHEN F. , EDEN J. G.
Published: April 2003

Optical transitions between stationary states of the electron–photon field system, known as quantum Volkov states, offer a new framework within which to interpret a rich variety of phenomena observed in intense optical fields. In this view, photons and electrons interact to form transient complexes which are capable of annihilating fundamental photons to produce more energetic radiation, or releasing photons back to the optical field. That is, they mediate the exchange of energy between the fundamental and secondary optical fields. The application of this new picture, which has no classical analog, to high harmonic generation is reviewed here. In previous publications [J. Gao, F. Shen, and J. G. Eden, Phys. Rev. Lett.81, 1833 (1998); J. Phys.B32, 4153 (1999); Phys. Rev.A61, 043812 (2000)], theoretical predictions of harmonic spectra and the polarization characteristics of individual harmonics have been compared with semiclassical calculations and experiment and several key results are summarized here. Specifically, an analytic expression for the harmonic generation transition matrix element has been derived that is valid for an arbitrary polarization of the fundamental optical field and is in agreement with the experimental data in the literature. Also, recent calculations of the spectral lineshapes of individual harmonics are presented here and compared with published measurements. QED theory predicts that the harmonic linewidth is essentially independent of the fundamental intensity when the ponderomotive potential is less than the atomic ionization potential but increases rapidly at higher intensities. The implications of these results for future experiments are also discussed.
AN ALGORITHM FOR STRONGLY CORRELATED NOISE
Authors: MANNELLA RICCARDO
Published: April 2003

An algorithm for the numerical integration of Langevin equations driven by green noise is proposed. The algorithm is local in time, hence it is particularly suitable for the integration when non equilibrium quantities (like, first exit times) are under investigation.
LOW FREQUENCY NOISE IN CMOS TRANSISTORS: AN EXPERIMENTAL AND COMPARATIVE STUDY ON DIFFERENT TECHNOLOGIES
Authors: FANTINI PAOLO , VENDRAME LORIS , RICCARDI DAMIANO
Published: April 2003

In this work, we experimentally investigate fundamental aspects of 1/f noise in silicon CMOS transistors, considering a broad group of technological families. We bring out some device down-scaling issues. A direct comparison between our experimental data and the noise dominant theories in MOS-FETs is dealt with.
Neural Correlates of the Left-Visual-Field Superiority in Face Perception Appear at Multiple Stages of Face Processing
Authors: Yovel Galit , Levy Jerre , Grabowecky Marcia , Paller Ken A.
Published: April 2003

Studies in healthy individuals and split-brain patients have shown that the representation of facial information from the left visual field (LVF) is better than the representation of facial information from the right visual field (RVF). To investigate the neurophysiological basis of this LVF superiority in face perception, we recorded event-related potentials (ERPs) to centrally presented face stimuli in which relevant facial information is present bilaterally (B faces) or only in the left (L faces) or the right (R faces) visual field. Behavioral findings showed best performance for B faces and, in line with the LVF superiority, better performance for L than R faces. Evoked potentials to B, L, and R faces at 100 to 150-msec poststimulus showed no evidence of asymmetric transfer of information between the hemispheres at early stages of visual processing, suggesting that this factor is not responsible for the LVF superiority. Neural correlates of the LVF superiority, however, were manifested in a shorter latency of the face-specific N170 component to L than R faces and in a larger amplitude to L than R faces at 220—280 and 400—600 msec over both hemispheres. These ERP amplitude differences between L and R faces covaried across subjects with the extent to which the face-specific N170 component was larger over the right than the left hemisphere. We conclude that the two hemispheres exchange information symmetrically at early stages of face processing and together generate a shared facial representation, which is better when facial information is directly presented to the right hemisphere (RH; L faces) than to the left hemisphere (LH; R faces) and best when both hemispheres receive facial information (B faces).
How well does the ECMWF Ensemble Prediction System predict blocking?
Authors: Pelly Joanna L. , Hoskins Brian J.
Published: April 2003

Forecasting atmospheric blocking is one of the main problems facing medium‐range weather forecasters in the extratropics. The European Centre for Medium‐Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS) provides an excellent basis for medium‐range forecasting as it provides a number of different possible realizations of the meteorological future. This ensemble of forecasts attempts to account for uncertainties in both the initial conditions and the model formulation.

Since 18 July 2000, routine output from the EPS has included the field of potential temperature on the potential vorticity (PV) D 2 PV units (PVU) surface, the dynamical tropopause. This has enabled the objective identification of blocking using an index based on the reversal of the meridional potential‐temperature gradient. A year of EPS probability forecasts of Euro‐Atlantic and Pacific blocking have been produced and are assessed in this paper, concentrating on the Euro‐Atlantic sector. Standard verification techniques such as Brier scores, Relative Operating Characteristic (ROC) curves and reliability diagrams are used.

It is shown that Euro‐Atlantic sector‐blocking forecasts are skilful relative to climatology out to 10 days, and are more skilful than the deterministic control forecast at all lead times. The EPS is also more skilful than a probabilistic version of this deterministic forecast, though the difference is smaller. In addition, it is shown that the onset of a sector‐blocking episode is less well predicted than its decay. As the lead time increases, the probability forecasts tend towards a model climatology with slightly less blocking than is seen in the real atmosphere. This small under‐forecasting bias in the blocking forecasts is possibly related to a westerly bias in the ECMWF model. Copyright © 2003 Royal Meteorological Society