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At least 289 records · Page 16Linked to original sources
PubMed2001

Interplay between Zeeman coupling and swap action in spin-based quantum computer models: error correction in inhomogeneous magnetic fields.

We consider theoretically the interplay between Zeeman coupling and exchange-induced swap action in spin-based quantum dot quantum computer models in the presence of inhomogeneous magnetic fields, which are invariably present in real systems. We estimate quantitatively swap errors caused by the inhomogeneous field, establishing that error correction would, in principle, be possible in the presence of nonuniform magnetic fields in realistic structures.

Journal Article↗
PubMed2002

Interplay of Rabi oscillations and quantum interference in semiconductor quantum dots.

We investigated the manifestation of Rabi oscillation in the coherent dynamics of excitons in self-assembled semiconductor quantum dots. The Rabi oscillation phenomenon was directly observed as a function of the input pulse area. Furthermore, by performing wave packet interferometry in the nonlinear excitation regime, we discover a new type of quantum interference phenomenon, resulting from the interplay between Rabi oscillation and quantum interference.

Journal Article↗
PubMed2003

X-ray studies of the structure and electronic behavior of alkanethiolate-capped gold nanoparticles: the interplay of size and surface effects.

We report a study of the structure and electronic properties of a series of thiol-capped Au nanoparticles (NP) of nominal sizes of 1.6, 2.4, and 4.0 nm. Transmission electron microscopy, x-ray powder diffraction, x-ray absorption fine structure, and x-ray photoemission spectroscopy have been used to investigate the size-dependent systematics of lattice contraction and charge redistribution of these NPs. It is found that the lattice contracts and the d charge at the Au atom site depletes relative to bulk Au as the size of the NP decreases. The implication of these observations is discussed in terms of the interplay of quantum-size and surface effect.

Journal Article↗
PubMed2003

Interplay of collective excitations in quantum-well intersubband resonances.

Intersubband resonances in a semiconductor quantum well (QW) display fascinating features involving various collective excitations such as Fermi-edge singularity (FES) and intersubband plasmon (ISP). Using a density matrix approach, we treated many-body effects such as depolarization, vertex correction, and self-energy consistently for a two-subband system. We found a systematic change in resonance spectra from FES- to ISP-dominated features, as QW width or electron density is varied. Such an interplay between FES and ISP significantly changes both line shape and peak position of the absorption spectrum. We found that a cancellation of FES and ISP undresses the resonant responses and recovers the single-particle features of absorption for semiconductors with a strong nonparabolicity such as InAs, leading to a dramatic broadening of the absorption spectrum.

Journal Article↗
PubMed2003

Temperature dependent fluorescence in disordered Frenkel chains: interplay of equilibration and local band-edge level structure.

We model the optical dynamics in linear Frenkel exciton systems governed by scattering on static disorder and lattice vibrations and calculate the temperature dependent fluorescence spectrum and lifetime. The fluorescence Stokes shift shows a nonmonotonic behavior with temperature, which derives from the interplay of the local band-edge level structure and thermal equilibration. The model yields excellent fits to experiments performed on linear dye aggregates.

Journal Article↗
PubMed2003

Interplay of Rayleigh and Peierls instabilities in metallic nanowires.

A quantum-mechanical stability analysis of metallic nanowires within the free-electron model is presented. The stability is determined by an interplay of electron-shell effects, the Rayleigh instability due to surface tension, and the Peierls instability. Although the latter effect limits the maximum length also for wires with "magic radii," it is found that nanowires in the micrometer range can be stable at room temperature.

Journal Article↗
PubMed2003

Interplay between disorder and quantum and thermal fluctuations in ferromagnetic alloys: the case of UCu2Si2-xGex.

We consider, theoretically and experimentally, the effects of structural disorder, quantum fluctuations, and thermal fluctuations in the magnetic and transport properties of certain ferromagnetic alloys. We study the particular case of UCu2Si2-xGex. The low temperature resistivity, rho(T,x), exhibits Fermi liquid behavior as a function of temperature T for all values of x, which can be interpreted as a result of the magnetic scattering of the conduction electrons from the localized U spins. The residual resistivity, rho(0,x), follows the behavior of a disordered binary alloy. The observed nonmonotonic dependence of the Curie temperature, T(c)(x), with x can be explained within a model of localized spins interacting with an electronic bath. Our results clearly show that the Curie temperature of certain alloys can be enhanced due to the interplay between quantum and thermal fluctuations with disorder.

Journal Article↗
PubMed2004

Interplay of intra-atomic and interatomic effects: an investigation of the 2p core level spectra of atomic Fe and molecular FeCl2.

The 2p photoabsorption and photoelectron spectra of atomic Fe and molecular FeCl2 were studied by photoion and photoelectron spectroscopy using monochromatized synchrotron radiation and atomic or molecular beam technique. The atomic spectra were analyzed with configuration interaction calculations yielding excellent agreement between experiment and theory. For the analysis of the molecular photoelectron spectrum which shows pronounced interatomic effects, a charge transfer model was used, introducing an additional 3d(7) configuration. The resulting good agreement between the experimental and theoretical spectrum and the remarkable similarity of the molecular with the corresponding spectrum in the solid phase opens a way to a better understanding of the interplay of the interatomic and intra-atomic interactions in the 2p core level spectra of the 3d metal compounds.

Journal Article↗
PubMed2005

Interplay of magnetic and superconducting proximity effects in ferromagnet-superconductor-ferromagnet trilayers.

We present theoretical results on the interplay of magnetic and superconducting orders in diffusive ferromagnet-superconductor-ferromagnet trilayers. The induced triplet superconducting correlations throughout the trilayer lead to an induced spin magnetization. We include self-consistency of the order parameter in the superconducting layer at arbitrary temperatures, arbitrary interface transparency, and any relative orientation of the exchange fields in the two ferromagnets. We propose to use the torque on the trilayer in an external magnetic field as a probe of the presence of triplet correlations in the superconducting phase.

Journal Article↗
PubMed2006

Interplay of spin and charge channels in zero-dimensional systems.

We study the interplay of charge and spin (zero-mode) channels in quantum dots. The latter affects the former in the form of a distinct signature on the differential conductance. We also obtain both longitudinal and transverse spin susceptibilities. All these observables, underlain by spin fluctuations, become accentuated as one approaches the Stoner instability. The nonperturbative effects of zero-mode interaction are described in terms of the propagation of gauge bosons associated with charge [U(1)] and spin [SU(2)] fluctuations in the dot, while transverse spin fluctuations are analyzed perturbatively.

Journal Article↗
PubMed2006

Interplay between diffusive and displacive phase transformations: time-temperature-transformation diagrams and microstructures.

Materials which can undergo extremely fast displacive transformations as well as very slow diffusive transformations are studied using a Ginzburg-Landau framework. This simple model captures the essential physics behind microstructure formation and time-temperature-transformation diagrams in alloys such as steels. It also predicts the formation of mixed microstructures by an interplay between diffusive and displacive mechanisms. The intrinsic volume changes associated with the transformations stabilize mixed microstructures such as martensite-retained austenite (responsible for the existence of a martensite finish temperature) and martensite-pearlite.

Journal Article↗
PubMed2006

Interplay between ferromagnetism and superconductivity in tunneling currents.

We study tunneling currents in a model consisting of two nonunitary ferromagnetic spin-triplet superconductors separated by a thin insulating layer. We find a novel interplay between ferromagnetism and superconductivity, manifested in the Josephson effect. This offers the possibility of tuning dissipationless currents of charge and spin in a well-defined manner by adjusting the magnetization direction on either side of the junction.

Journal Article↗
PubMed1989

Iron nutrition in childhood: the interplay of genes, development and environment.

The state of a child's iron nutrition depends on his genetic endowment, the stage of development he has reached and the environment in which he lives. Genetic disorders lead more commonly to iron overload than to deficiency. Generally interplay between genes and environment is apparently of little importance when considering iron deficiency; are we missing something? The greatest demands for iron are at the time of most rapid growth, i.e. during infancy and puberty, but during early infancy body stores can meet the demand without a need for dietary iron. Oxygen, diet and microbes are the important environmental factors related to iron nutrition. The relationship of oxygen toxicity to iron nutrition in the newborn has received only fleeting study, the availability of iron from many foods is unclear; the clinical significance of iron overload and deficiency in the evolution of an infection is also unclear despite a wealth of in vitro observation. I am not convinced that the bottle fed baby should receive iron in his diet during the first 4-6 months of life. Thereafter, while the concept of universal unselective supplementation causes some uneasiness there are considerable epidemiological arguments for fortification of food with iron.

Adolescent↗
PubMed2002

High-level fluoroquinolone resistance in Pseudomonas aeruginosa due to interplay of the MexAB-OprM efflux pump and the DNA gyrase mutation.

Fluoroquinolone resistance in Pseudomonas aeruginosa is mainly attributable to the constitutive expression of the xenobiotic efflux pump and mutation in DNA gyrase or topoisomerase IV. We constructed cells with a double-mutation in gyrA and mexR encoding DNA gyrase and repressor for the mexAB-oprM operon, respectively. The mutant showed 1,024 times higher fluoroquinolone resistance than cells lacking the MexAB-OprM. Cells with a single mutation in gyrA and producing a wild-type level of the MexAB-OprM efflux pump showed 128 times higher fluoroquinolone resistance than cells lacking the MexAB-OprM. In contrast, a single mutation in gyrA or mexR caused only 4 and 64 times higher resistance, respectively. These findings manifested the interplay between the MexAB-OprM efflux pump and the target mutation in fluoroquinolone resistance.

Anti-Infective Agents↗
PubMed2004

An interplay of alleviating mutations in the clinical phenotype of beta-thalassaemia intermedia.

Prediction of a beta-thalassaemia major phenotype from the beta-genotype is generally relatively straightforward. However, despite the ability to accurately define the beta-thalassaemia mutations, prediction of a beta-thalassaemia intermedia phenotype from the genotype sometimes remains problematic and this has important implications in genetic counselling and prenatal diagnosis. We report a 11-year-old Indian male child with a thalassaemia intermedia phenotype. beta-Globin gene analysis of the family showed that he was a compound heterozygote with the -88 (C-->T) beta+-mutation and the IVS1 nt 130 (G-->C) beta0-mutation. Both these mutations are rare among Indians. The propositus was also found to be heterozygous for the XmnI polymorphism and had a normal alpha-genotype. In this family interplay of two alleviating mutations (a milder promoter mutation along with a gene for raised HbF) might have synergistically compensated for lack of globin chains in the patient. Hence, the nature of the beta-genotype as well as the knowledge of the presence or absence of alleviating factors will help the clinician to decide whether early commencement of a regular transfusion regime is necessary.

Child↗
PubMed2004

The formation of the rodlet layer of streptomycetes is the result of the interplay between rodlins and chaplins.

Streptomycetes form hydrophobic aerial hyphae that eventually septate into hydrophobic spores. Both aerial hyphae and spores possess a typical surface layer called the rodlet layer. We present here evidence that rodlet formation is conserved in the streptomycetes. The formation of the rodlet layer is the result of the interplay between rodlins and chaplins. A strain of Streptomyces coelicolor in which the rodlin genes rdlA and/or rdlB were deleted no longer formed the rodlet layer. Instead, these surfaces were decorated with fine fibrils. Deletion of all eight chaplin genes (strain DeltachpABCDEFGH) resulted in the absence of the rodlet layer as well as the fibrils at surfaces of aerial hyphae and spores. Apart from coating these surfaces, chaplins are involved in the escape of hyphae into the air, as was shown by the strong reduction in the number of aerial hyphae in the DeltachpABCDEFGH strain. The decrease in the number of aerial hyphae correlated with a lower expression of the rdl genes in the colony. Yet, expression per aerial hypha was similar to that in the wild-type strain, indicating that expression of the rdl genes is initiated after the hypha has sensed that it has grown into the air.

Bacterial Proteins↗
PubMed2004

The target cell plasma membrane is a critical interface for Salmonella cell entry effector-host interplay.

Salmonella species trigger host membrane ruffling to force their internalization into non-phagocytic intestinal epithelial cells. This requires bacterial effector protein delivery into the target cell via a type III secretion system. Six translocated effectors manipulate cellular actin dynamics, but how their direct and indirect activities are spatially and temporally co-ordinated to promote productive cytoskeletal rearrangements remains essentially unexplored. To gain further insight into this process, we applied mechanical cell fractionation and immunofluorescence microscopy to systematically investigate the subcellular localization of epitope-tagged effectors in transiently transfected and Salmonella-infected cultured cells. Although five effectors contain no apparent membrane-targeting domains, all six localized exclusively in the target cell plasma membrane fraction and correspondingly were visualized at the cell periphery, from where they induced distinct effects on the actin cytoskeleton. Unexpectedly, no translocated effector pool was detectable in the cell cytosol. Using parallel in vitro assays, we demonstrate that the prenylated cellular GTPase Cdc42 is necessary and sufficient for membrane association of the Salmonella GTP exchange factor and GTPase-activating protein mimics SopE and SptP, which have no intrinsic lipid affinity. The data show that the host plasma membrane is a critical interface for effector-target interaction, and establish versatile systems to further dissect effector interplay.

Animals↗
PubMed2005

Functional interplay between the Bacillus subtilis DnaD and DnaB proteins essential for initiation and re-initiation of DNA replication.

Initiation and re-initiation of chromosomal DNA replication in bacteria rely on divergent multiprotein assemblies, which direct the functional delivery of the replicative helicase on single-stranded DNA (ssDNA) at specific sites. These two processes are triggered either at the single chromosomal origin oriC or at arrested forks by the conserved DnaA and PriA proteins respectively. In Bacillus subtilis, these two pathways further require the three essential proteins DnaB, DnaD and DnaI, restrictively encoded in Gram positive bacteria of low GC content. We have recently shown that DnaI and DnaB act as a pair of loaders of the DnaC replicative helicase. The role of DnaD appeared more enigmatic. It was previously shown to interact with DnaA and to display weak ssDNA binding activity. Here, we report that purified DnaD can interact physically with PriA and with DnaB. We show that the lethality of the temperature-sensitive dnaD23 mutant can be suppressed by different DnaB point mutants, which were found to be identical to the suppressors of priA null mutants. The DnaD23 protein displays lower ssDNA binding activity than DnaD. Conversely, the DnaB75 protein, the main dnaD23 suppressor, has gained affinity for ssDNA. Finally, we observed that this interplay between DnaD and DnaB is crucial for their concerted interaction with SSB-coated ssDNA, which is the expected substrate for the loading of the replicative helicase in vivo. Altogether, these results highlight the need for both DnaD and DnaB to interact individually and together with ssDNA during the early stages of initiation and re-initiation of chromosomal DNA replication. They also point at a main structural role of DnaD in the multiprotein assemblies built during these two essential processes.

Bacillus subtilis↗