bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of disease measures for assessing resistance in canola (Brassica napus) to blackleg (Leptosphaeria maculans)
Authors: Rempel Curtis B. , Hall Robert
Published: November 2007

Disease incidence, disease severity, areas under the disease incidence and disease severity progress curves, and maximum and minimum incidence and severity of disease were evaluated as measures of resistance in canola (Brassica napus) to blackleg caused by Leptosphaeria maculans. Seven genotypes of spring canola were tested in Ontario at three locations 60, 81, and 102 days after sowing in 1990 and at two locations 55, 70, 85, and 100 days after sowing in 1991. Disease incidence was expressed as the percentage of sampled plants with basal stem canker, and disease severity was assessed as the percentage discolouration of a cross section of the stem base. Based on ease of measurement, range of values, number of significant differences among genotypes, and constancy of rank of genotypes at different locations, measures of disease severity or disease incidence in mature plants proved to be most useful. No advantage was gained by using area under the disease incidence and disease severity progress curves, or maximum and minimum incidence and severity of disease at the last sampling time. It is recommended that resistance of canola stems to blackleg be evaluated from measures of disease severity or disease incidence in mature plants. Keywords: canola, blackleg, Leptosphaeria maculans, resistance measurements.
Variation in sex expression of Taxus brevifolia in western Oregon
Authors: DiFazio S. P. , Wilson M.V. , Vance N. C.
Published: November 2007

Sex expression of Taxus brevifolia Nutt. was studied at four sites in western Oregon. Of 115 trees examined, 17 were cosexual. All cosexual trees had predominantly male sex expression, suggesting that male sterility is much more constant than female sterility for T. brevifolia. Some implications of the observed patterns are discussed, along with suggestions for further research. Keywords: Taxus brevifolia, yew, sex expression, dioecy.
Relationships between lateral root order, arbuscular mycorrhiza development, and the physiological state of the symbiotic fungus in Platanus acerifolia
Authors: Tisserant B. , Gianinazzi S. , Gianinazzi-Pearson V.
Published: November 2007

The rapid development of an efficient root system resulting from arbuscular mycorrhiza formation is essential to the successful establishment of many plant species. We have analysed root system development and used histochemical staining to define relationships between lateral root order dynamics, arbuscular mycorrhiza development, and the physiological state of the symbiotic fungus Glomus fasciculatum (Thaxter sensu Gerdeman) Gerd & Trappe amend. Walker and Koske, in a woody plant species Platanus acerifolia Willd. Arbuscular mycorrhiza induced modifications in root system development in P. acerifolia, compared with nonmycorrhizal root systems. Third-order lateral roots dominated in arbuscular mycorrhizal plants, while second-order laterals were most numerous in nonmycorrhizal systems. Arbuscular mycorrhiza colonization was closely related to the appearance of different root orders; the most active mycelium (characterized by fungal succinate dehydrogenase and alkaline phosphatase activities) was mainly localized in newly formed lateral roots. Nine weeks after inoculation with G. fasciculatum the proportion of alkaline phosphatase-active mycelium strongly decreased in all root orders, and this was related to an increased phosphorus content of the host plant. The dynamics of development of the arbuscular mycorrhizal fungus and the possible regulation of its activity by the host plant are discussed. Keywords: arbuscular mycorrhiza, fungal enzyme, root system morphology, Platanus acerifolia, Glomus fasciculatum.
Seed dispersal capacity of six perennial grassland species measured in a wind tunnel at varying wind speed and height
Authors: Dorp D. van , Hoek W. P. M. van den , Daleboudt C.
Published: November 2007

The dispersal capacity of six perennial grassland species with different seed aerodynamic attributes was assessed in a wind tunnel. The selected species have difficulty in recolonizing restored ecosystems because of a poor dispersal of seeds. The variation in dispersal distances of seeds within and between species was assessed by releasing seeds at varying wind speeds and release heights, and expressed as 1st percentile, mode, and 99th percentile values. Dispersal distances of long-range dispersed seeds (99th percentile values) increased exponentially with wind speed. At wind speeds of 14 m/s, predicted maximum distances are 10–15 m for small and relatively heavy spherical seeds and 20–30 m for large and relatively light cylindrical or disk-like seeds. In the study area, wind gusts > 10 m/s at plant height occur at least annually, and plants of the selected species live up to several decades. This suggests a great potential for long-range dispersal during the lifetime of a plant. Plants may gain wider dispersal of seeds by increasing the release height (e.g., taller infructescences) and by requiring stronger winds to release seeds (e.g., dispersal in autumn and winter). Keywords: dispersal, wind tunnel, seeds, perennial, wind gust.
Phenotypic plasticity in relation to ploidy level and corm production in the perennial grass Arrhenatherum elatius
Authors: Petit Christophe , Thompson John D. , Bretagnolle François
Published: November 2007

Phenotypic plasticity may play a critical role in the response of natural populations to selective pressures in variable environments and may help explain differences in the ecological and geographical distribution of closely related taxa. In this study we quantify phenotypic plasticity in three subspecies of the European grass polyploid complex Arrhenatherum elatius, ssp. sardoum, elatius, and bulbosum, to test two hypotheses: (i) Does the widespread tetraploid ssp. elatius show greater phenotypic homeostasis in fitness related traits than its Mediterranean endemic related diploid ssp. Sardoum? (ii) Does the corm-forming tetraploid ssp. bulbosum (which is widespread throughout northwest Europe) differ from ssp. elatius (which does not have corms) in patterns of resource allocation across environments? Eight genotypes from each of two populations of each subspecies were cloned and grown in four replicated garden environments (a combination of two light and nutrient levels). Mean reaction norms for each subspecies showed no consistent variation between tetraploids and diploids in the plasticity of fitness-related traits over the range of the studied environments. Tetraploid genotypes showed consistently greater values than diploids across all environments, which may partly explain the more widespread distribution of tetraploids. The two tetraploids differed in patterns of resource allocation across environments, with ssp. bulbosum maintaining a relatively more constant vegetative to floral biomass ratio across three of the four environments. Keywords: phenotypic plasticity, ploidy levels, corm production, Arrhenatherum elatius.
Ultrastructure des parois de cerises Bigarreau Burlat de textures différentes au cours de la maturation
Authors: Batisse C. , Coulomb P. J. , Coulomb C. , Buret M.
Published: November 2007

The changes in texture of fruits during ripening are linked to cell wall degradation involving synthesis and degradation of polymers. An increase in pectin solubility leads to cell sliding and an elastic aspect of tissues. The biochemical cell wall process differs between soft and crisp fruits originating from a same cultivar but cultivated under different agroclimatic conditions. Although the proportions of cell wall material are similar, the composition and structure of the two cell walls are very different at maturity. A solubilization of the middle lamella and a restructuration of the primary cell walls arising from the cells separation is observed in crisp fruits. In contrast, the middle lamella of the soft fruits is better preserved and the primary cell walls are thin and show degradation bags delimited by residual membrane formations. In addition, the macroendocytosis process by endosome individualization is more important in soft fruits. In conclusion, the fruit texture depends on the extent of the links between cell wall polymers. Keywords: cherry, cell wall, texture, ultrastructural study.
Flavan accumulation in stems ofPlatanus×acerifoliaseedlings inoculated withCeratocystis fimbriataf.sp.platani, the canker stain disease agent
Authors: Modafar C. El , Clérivet A. , Macheix J. J.
Published: November 2007

Inoculation of Platanus × acerifolia stems with Ceratocystis fimbriata f.sp. platani, the canker stain disease agent, induced the accumulation of preexisting phenolic compounds such as flavan-3-ols and proanthocyanidins in the infected internode of the stem. These flavan compounds and their polymerized products were most quickly accumulated near the inoculation site, particularly in the medulla, vascular tissues, tyloses, and gels. Thus, these plane tree reactions were considered as defensive responses. Their involvement in the restriction of Ceratocystis fimbriata f.sp. platani development around the inoculation site, associated with other located responses previously described, was discussed. Keywords: Ceratocystis fimbriata, flavan-3-ols, Platanus × acerifolia, proanthocyanidins.
Role of temperature and light in the germination ecology of buried seeds of weedy species of disturbed forests. II.Erechtites hieracifolia
Authors: Baskin Carol C. , Baskin Jerry M.
Published: November 2007

At maturity in September, about half the seeds (achenes) of Erechtites hieracifolia (Asteraceae) collected in Kentucky were dormant (did not germinate at any test condition), whereas the others were conditionally dormant (germinated only at a narrow range of test conditions). Seeds sown on top of soil in an unheated greenhouse in September failed to germinate in autumn because temperatures were below those required for germination; however, they germinated at comparable temperatures the following spring. Seeds buried in soil in September 1987 and exposed to natural seasonal temperature changes were nondormant (germinated over full range of test conditions) by April 1988, but they entered conditional dormancy by October 1988. Each October through 1995, exhumed seeds exhibited conditional dormancy. Since 89% of the seeds were viable after 8 years of burial, it appears that although seeds of this species are wind dispersed, they also have the potential to form a long-lived seed bank. Thus, soil disturbance at any time from May to September could result in establishment of plants from seeds in the seed bank. Keywords: seed dormancy, Asteraceae, dormancy cycles, buried seeds, light.
MULTIPLICITY FLUCTUATIONS IN Au+Au COLLISIONS AT RHIC
Authors:   for the PHOBOS Collaboration, WOŹNIAK KRZYSZTOF
Published: November 2007

In the PHOBOS experiment, charged particles are measured in almost the full solid angle. This enables the study of fluctuations and correlations in the particle production over a very wide kinematic range. In this paper, we show results of a direct search for fluctuations identified by an unusual shape of the pseudorapidity distribution. In addition, we use analysis of correlations of the multiplicity in similar pseudorapidity bins, placed symmetrically in the forward and backward hemispheres, to test the hypothesis of production of particles in clusters.
PAIR MOMENTUM AND CENTRALITY DEPENDENCES OF 3-D HBT RADII OF CHARGED PIONS MEASURED BY RHIC-PHENIX
Authors:   for the PHENIX Collaboration (For the full list of PHENIX authors and acknowledgements, see Appendix ‘Collaborations’ of this volume.), ENOKIZONO AKITOMO
Published: November 2007

We report recent HBT measurements of charged pions in Au + Au and Cu + Cu collisions at [Formula: see text] by PHENIX at RHIC. The 3-D correlation functions are measured for several centrality and pair momentum regions and 3-D HBT radii are obtained by a traditional Gaussian fit function. By comparing the pion 3-D HBT radii with those measured in Au + Au collisions at [Formula: see text], we investigate systematic differences in the 3-D HBT radii as functions of centrality and pair momentum for different collision species and energies.
BOSE–EINSTEIN CORRELATIONS OF DIRECT PHOTONS IN Au+Au COLLISIONS AT $\sqrt{s_{NN}} = 200\, {\rm GeV}$
Authors:   for the PHENIX collaboration (For the full list of the PHENIX collaboration and acknowledgments, see Ref. 9.), PERESSOUNKO D.
Published: November 2007

The current status of the analysis of direct photon Bose-Einstein correlations in Au + Au collisions at [Formula: see text] done by the PHENIX collaboration is summarized. All possible sources of distortion of the two-photon correlation function are discussed and methods to control them in the PHENIX experiment are presented.
MESONIC CORRELATION FUNCTIONS AT FINITE TEMPERATURE AND DENSITY IN THE NAMBU–JONA–LASINIO MODEL WITH A POLYAKOV LOOP
Authors: HANSEN HUBERT
Published: November 2007

We investigate the properties of scalar and pseudo-scalar mesons at finite temperature and quark chemical potential in the framework of the Nambu–Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement. In the phase of broken chiral symmetry a narrower width for the σ meson is obtained with respect to the NJL case; on the other hand, the pion still behaves as a Goldstone boson.
FURTHER ANALYSIS OF EXCITATIONS OF QUARKS AT FINITE TEMPERATURE — MASS EFFECT AND POLE STRUCTURE
Authors: MITSUTANI KAZUYA , KITAZAWA MASAKIYO , KUNIHIRO TEIJI , NEMOTO YUKIO
Published: November 2007

We calculate the spectral function of the massive quark at finite temperature ( T ) using a Yukawa model and show that the peak in the negative energy region among the three-peaks found in a previous work for the massless quark is largely suppressed. To explore the underlying mechanism of this behavior, we also investigate the pole structure of the retarded Green function of the quark. We will show the result only for the massless quark. We find the residues of the poles corresponding the three-peaks are all comparable at T ∼ mb. We also show that the multi-peak structure of the quark spectra is well described in the pole approximation which indicates that the quasi-particle picture is valid in this T region.
SIMULATION OF THE TRANSITION BETWEEN MESON-SYSTEM AND QGP IN A TRANSPORT MODEL
Authors: TAN ZHIGUANG , BONASERA ALDO , YANG CHUBIN , ZHOU DAIMEI , TERRANOVA S.
Published: November 2007

Some thermodynamical properties of the interacting meson system and QGP at finite temperature are discussed. For a pure meson gas the Hagedorn limiting temperature is reproduced when the experimentally observed resonances are included. For QGP our results for different numbers of flavors Nf compare very well to the theoretical ones. A transport model based on the mean free path approach is used to simulate the evolution of the system. During the evolution we use the MIT bag model to perform the transition between meson gas and QGP.
ENERGY DEPENDENCE OF NUCLEAR SUPPRESSION IN THE FRAGMENTATION REGION
Authors: TYWONIUK KONRAD , ARSENE IONUT , BRAVINA LARISSA , ZABRODIN EVGENY , KAIDALOV ALEXEI
Published: November 2007

Energy dependence of nuclear shadowing and nuclear absorption is discussed in the framework of the Glauber–Gribov model and the AGK cutting rules. We calculate gluon shadowing using recent data on diffractive structure functions from HERA. Phenomenological implications for light particle production at SPS and RHIC are described and compared to charged particle production at mid- and forward rapidities. Comparison of the suppression at these energies leaves nevertheless little room for additional suppression phenomena.
ASYMMETRIC FERMI SUPERFLUID WITH TWO TYPES OF PAIRINGS
Authors: HUANG XUGUANG , HAO XUEWEN , ZHUANG PENGFEI
Published: November 2007

We investigate the phase diagram in the plane of temperature and chemical potential mismatch for an asymmetric fermion superfluid with double- and single-species pairings. There is no mixing of these two types of pairings at fixed chemical potential, but the introduction of the single species pairing cures the magnetic instability at low temperature.
NEUTRAL DENSE QUARK MATTER AT INTERMEDIATE TEMPERATURE
Authors: HE LIANYI , JIN MENG , ZHUANG PENGFEI
Published: November 2007

In two flavor neutral quark matter the uniform color superconducting state suffers the chromomagnetic instability at zero temperature. While this instability is extended to low temperature, it is fully cured above a turning temperature. There is a continuous phase transition from some non-uniform phase to the uniform 2SC/g2SC phase at the turning temperature. The introduction of the LOFF state removes the strange temperature behavior of the diquark condensate and significantly changes the phase diagram of neutral dense quark matter.
DISSIPATIVE HYDRODYNAMICS IN 2 + 1 DIMENSIONS
Authors: CHAUDHURI A. K.
Published: November 2007

In a first order theory of dissipative hydrodynamics, we have simulated hydrodynamic evolution of QGP fluid with dissipation due to shear viscosity only. Simulation confirms that compared to an ideal fluid, energy density or temperature of a viscous fluid evolve slowly. Transverse expansion is also more in viscous fluid. We also study the effect of viscosity on particle production. Particle production is enhanced, more at large pT. The elliptic flow on the otherhand decreases and shows a tendency to saturate at large pT.
JET-FLUID STRING FORMATION AND DECAY IN HIGH-ENERGY HEAVY-ION COLLISIONS
Authors: ISSE M. , HIRANO T. , MIZUKAWA R. , OHNISHI A. , YOSHINO K. , NARA Y.
Published: November 2007

We propose a new hadronization mechanism, jet-fluid string (JFS) formation and decay, to understand observables in intermediate to high-pT regions comprehensively. In the JFS model, hard partons produced in jet lose their energy in traversing the QGP fluid, which is described by fully three-dimensional hydrodynamic simulations. When a jet parton escapes from the QGP fluid, it picks up a partner parton from a fluid and forms a color singlet string, then it decays to hadrons. We find that high-pTv2 values in JFS are about two times larger than in the independent fragmentation model.
ELECTROMAGNETIC RADIATION FROM BROKEN SYMMETRIES IN RELATIVISTIC NUCLEAR COLLISIONS
Authors: QIN GUANG-YOU , GALE CHARLES , MAJUMDER ABHIJIT
Published: November 2007

A new channel of direct photon production from a quark gluon plasma (QGP) is explored in the framework of high-temperature QCD. This process appears at next-to-leading order, in the presence of a charge asymmetry in the excited matter. The photon production rate from this new mechanism is suppressed compared to the QCD annihilation and Compton scattering at low baryon density but assumes importance in baryon-rich matter.
INHOMOGENEOUS PAIRING CONDENSATES IN ASYMMETRIC NUCLEAR MATTER
Authors: JIN MENG , HE LIANYI , ZHUANG PENGFEI
Published: November 2007

We present a phase diagram for a fermion pairing system with density imbalance, including homogenous and inhomogeneous phases (LOFF and phase separation). The phase structure of neutron-proton condensate in isospin asymmetric nuclear matter is investigated as a realistic example.
SATURATION PHYSICS AND THE ELECTRON-ION COLLIDER
Authors: GONÇALVES V. P. , KUGERATSKI M. S. , NAVARRA F. S.
Published: November 2007

Using an extension of the Iancu-Itakura-Munier model to nuclear targets we look for saturation effects in electron-ion collisions. In previous publications we have made definite predictions. Here we try to compare our results with already existing experimental data on structure functions and on total and diffractive cross sections. Strictly speaking such a comparison is not well justified because the present data are not yet in the saturation domain. Nevertheless our results agree qualitatively with data and, in some cases, even quantitatively.
PION-NUCLEON SCATTERING WITHIN A GAUGED LINEAR SIGMA MODEL WITH PARITY-DOUBLED NUCLEONS
Authors: WILMS SUSANNA , GIACOSA FRANCESCO , RISCHKE DIRK H.
Published: November 2007

We compute pion-nucleon scattering at tree-level within a gauged linear sigma model which contains the nucleon and its chiral partner. Such an investigation in principle allows to make definite predictions as to whether the main contribution to the nucleon mass comes from the chiral condensate or from the mixing with its chiral partner. We find that there seems to be no set of model parameters that allows for a simultaneous description of all experimentally measured scattering lengths and range parameters. This indicates the need to improve the dynamical ingredients of the model.
THE CBM EXPERIMENT AT FAIR EXPLORING THE QCD PHASE DIAGRAM AT HIGH NET BARYON DENSITIES
Authors:   for the CBM Collaboration, HÖHNE CLAUDIA
Published: November 2007

The Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt will be a dedicated heavy-ion experiment exploring the QCD phase diagram in the region of moderate temperatures but very high baryon densities. The currently foreseen CBM detector setup, physics observables of interest, and first feasibility studies of their measurement will be presented.
PERFORMANCE OF FORWARD RESISTIVE PLATE CHAMBERS FOR MUON TRIGGERING AT CMS/LHC
Authors: HONG B. , AHN S. H. , ITO M. , KANG T. I. , KIM B. I. , KIM H. C. , KIM J. H. , LEE K. B. , LEE K. S. , LIM J. K. , MOOM D. H. , PARK S. , RYU M. S. , SIM K. S.
Published: November 2007

We present the production procedure and the quality assurance process of gas gaps for the forward resistive plate chambers of the CMS detector at LHC/CERN. We also present the results from an aging study performed by using a gamma ray source. No significant aging effect was observed because of intense gamma irradiation, equivalent to approximately 12 years of the CMS operation.
PROTON-PROTON PHYSICS WITH THE ALICE MUON SPECTROMETER AT THE LHC
Authors:   for the Alice Collaboration, BASTID N.
Published: November 2007

ALICE, the dedicated heavy ion experiment at the LHC, will also have an important impact on the proton-proton physics program. The physics analyses foreseen with the ALICE muon spectrometer are reviewed. A particular emphasis is placed on heavy flavor measurement.
SHORT LIVED RESONANCES IN ALICE
Authors: BADALÀ A. , BARBERA R. , BLANCO F. , PULVIRENTI A. , RIGGI F. , RE G. LO , PAPPALARDO G. S.
Published: November 2007

The ability of the ALICE detector to reconstruct the K*(892)0 resonance in p – p and Pb – Pb collisions at LHC energies has been investigated, by means of a detailed study of simulated events. PYTHIA events for p – p collisions and HIJING events for Pb – Pb collisions have been generated and fully reconstructed. The K*(892)0 was identified by its hadronic decay into Kπ through invariant mass analysis. The combinatorial background has been estimated using an event-mixing technique for p – p events and a like-sign technique for the Pb – Pb ones. The role of the particle identification of the decay product is also discussed.
QUARKONIA MEASUREMENTS WITH THE CENTRAL DETECTORS OF ALICE
Authors:   for the ALICE Collaboration, SOMMER WOLFGANG , BLUME CHRISTOPH , KRAMER FREDERICK , GROSSE-OETRINGHAUS JAN FIETE
Published: November 2007

A Large Ion Collider Experiment – ALICE will become operational with the startup of the Large Hadron Collider – LHC at the end of 2007. One focus of the physics program is the measurement of quarkonia in proton-proton and lead-lead collisions. Quarkonia states will be measured in two kinematic regions and channels: di-muonic decays will be measured in the forward region by the muon arm, the central part of the detector will measure di-electronic decays. The presented studies show the expected performance of the di-electron measurement in proton-proton and central lead-lead collisions.
NEW RESULTS AND PERSPECTIVES ON RAA MEASUREMENTS BELOW 20 GeV CM-ENERGY AT FIXED TARGET MACHINES
Authors:   for the NA49 Collaboration, LÁSZLÓ ANDRÁS , FODOR ZOLTÁN , VESZTERGOMBI GYÓRGY
Published: November 2007

Transverse momentum spectra of π± at midrapidity are measured at high pT in p + p and p + Pb collisions at 158 GeV/nucleon beam energy by the NA49 experiment. This study is complementary to our previous results on the same spectra from Pb + Pb collisions. The nuclear modification factors RA+A/p+p, Rp+A/p+p and RA+A/p+A as a function of pT are extracted and compared to RHIC measurements, thus providing insight into the energy dependence of nuclear modification. The modification factor RA+A/p+A proved to be consistent with our previous results on the central to peripheral modification factor RCP.

The limitation of our current pT range is discussed and planned future upgrades are outlined. Some aspects of the FAIR-CBM experiment are also presented as a natural future continuation of the measurements at very high pT.
HEAVY-ION PHYSICS WITH THE ATLAS DETECTOR AT THE LHC – A PROGRESS TOWARDS OPERATION
Authors:   for the ATLAS Collaboration, DOLEJSI J.
Published: November 2007

Building of ATLAS is progressing well towards recording first pp collisions at 0.9 TeV in 2007, pp at 14 TeV in 2008 and hopefully PbPb soon later. The complexity of the detector is illustrated and several observables interesting for heavy-ion physics are discussed.
ELECTRON STRUCTURE INVESTIGATIONS OF InGaP/GaAs(100) HETEROSTRUCTURES WITH InP QUANTUM DOTS
Authors: DOMASHEVSKAYA E. P. , TEREKHOV V. A. , KASHKAROV V. M. , YU. TURISHCHEV S. , MOLODTSOV S. L. , VYALIKH D. V. , ARSENTYEV I. N. , TARASOV I. S. , VINOKUROV D. A. , STANKEVICH A. L.
Published: November 2007

Ultrasoft X-ray emission spectra (USXES) and X-ray absorption near-edge structure (XANES) spectra with the use of synchrotron radiation in the range of P L2,3-edges were obtained for the first time for nanostructures with InP quantum dots grown on GaAs 〈100〉 substrates by vapor-phase epitaxy from metal–organic compounds. These spectra represent local partial density of states in the valence and conduction bands. The additional XANES peak is detected; its intensity depends on the number of monolayers forming quantum dots. Assumptions are made on the band-to-band origin of luminescence spectra in the studied nanostructures.
TRANSPORT PROPERTIES OF 2D ELECTRON GAS IN AN n-InGaAs/GaAs DQW IN A VICINITY OF LOW MAGNETIC-FIELD-INDUCED HALL INSULATOR–QUANTUM HALL LIQUID TRANSITION
Authors: ARAPOV YU. G. , GUDINA S. V. , HARUS G. I. , NEVEROV V. N. , SHELUSHININA N. G. , YAKUNIN M. V. , PODGORNYH S. M. , USKOVA E. A. , ZVONKOV B. N.
Published: November 2007

The resistivity (ρ) of low mobility dilute 2D electron gas in an n- InGaAs / GaAs double quantum well (DQW) exhibits the monotonic "insulating-like" temperature dependence (dρ/dT < 0) at T = 1.8–70 K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kBTτ/ħ > 0.1–3.5) for our samples, and the electron density is on an "insulating" side of the so-called B = 0 2D metal–insulator transition. We show that the observed features of localization and Landau quantization in a vicinity of the low magnetic-field-induced insulator–quantum Hall liquid transition is due to the σxy(T) anomalous T-dependence.
ELECTRO-OPTICAL EFFECT IN COMPOSITE PHOTONIC STRUCTURES BASED ON GROOVED SILICON AND LIQUID CRYSTAL
Authors: ASTROVA E. V. , PILYUGINA YU. A. , PEROVA T. S. , GRUDINKIN S. A.
Published: November 2007

One-dimensional periodic structures with deep vertical grooves were obtained by wet anisotropic etching of (110)-oriented silicon-on-insulator (SOI) structure. Grooves of various widths (4–16 μm) were filled with a nematic liquid crystal (LC) E7. Inter-digital configuration of silicon electrodes was used to apply a voltage which altered the refractive index of the liquid crystal. Reproducible Freedericksz effect with a threshold voltage from 2 to 3 V was registered visually in the polarized light of a microscope and studied by means of micro-Raman spectroscopy. The electro-optical effect in the structures can be used to tune the band gaps of 1D photonic crystals, the spectral response of microcavities and to steer light beams in high contrast planar waveguides and waveguide arrays.
2D ANOMALOUS MAGNETORESISTANCE IN THE PRESENCE OF SPIN–ORBIT SCATTERING
Authors: AVERKIEV NIKITA S. , ROMANOV KONSTANTIN S.
Published: November 2007

The model of weak localization in 2D semiconductor structures in the whole range of classically weak magnetic fields in the presence of the Elliot–Yafet spin relaxation has been developed. It was shown that the spin–orbit interaction influences the value of magnetoresistance in small magnetic fields (within diffusion approximation) and when diffusion approximation is no longer valid.
SPIN RELAXATION IN MAGNETIC FIELD FOR InP QUANTUM DOTS
Authors: YA. GERLOVIN I. , IGNATIEV I. V. , YU. VERBIN S. , PAL B. , MASUMOTO Y.
Published: November 2007

Effect of external magnetic field on the optical orientation of electron spins in negatively charged InP quantum dots is studied experimentally using the PL pump–probe method.
(GaIn)(NAsSb): MBE GROWTH, HETEROSTRUCTURE AND NANOPHOTONIC DEVICES
Authors: HARRIS JAMES S.
Published: November 2007

Dilute nitride GaInNAs and GaInNAsSb alloys grown on GaAs have quickly become excellent candidates for a variety of lower cost 1.2–1.6 μm lasers, optical amplifiers, and high power Raman pump lasers that will be required in the networks to provide high speed communications to the desktop. Because these quantum well active regions can be grown on GaAs , the distributed mirror technology for vertical cavity surface emitting lasers coupling into waveguides and fibers and photonic crystal structures can be readily combined with GaInNAsSb active regions to produce a variety of advanced photonic devices that will be crucial for advanced photonic integrated circuits. GaInNAs ( Sb ) provides several new challenges compared to earlier III–V alloys because of the limited solubility of N , phase segregation, nonradiative defects caused by the low growth temperature, and ion damage from the N plasma source. This paper describes progress in overcoming some of the material challenges and progress in realizing record setting edge emitting lasers, the first VCSELs operating at 1.5 μm based on GaInNAsSb and integrated photonic crystal and nanoaperture lasers.
ADATOM INCORPORATION AND STEP CROSSING AT THE EDGES OF 2D NANOISLANDS
Authors: FILIMONOV S. N. , YU. HERVIEU YU.
Published: November 2007

Adatom incorporation into the "faceted" steps bordering the 2D nanoislands is analyzed. The step permeability and incorporation coefficients are derived for some typical growth situations. It is shown that the step consisting of equivalent straight segments can be permeable even in the case of fast edge migration if there exist factors delaying creation of new kinks. The step consisting of alternating rough and straight segments may be permeable if there is no adatom transport between neighboring segments through the corner diffusion.
EFFECT OF NUCLEAR SPINS ON THE ELECTRON SPIN DYNAMICS IN NEGATIVELY CHARGED InP QUANTUM DOTS
Authors: IGNATIEV I. V. , YA. GERLOVIN I. , YU. VERBIN S. , MARUYAMA W. , PAL B. , MASUMOTO Y.
Published: November 2007

Kinetics of polarized photoluminescence of the negatively charged InP quantum dots in weak magnetic field is studied experimentally. Effect of both the nuclear spin fluctuations and the dynamical nuclear polarization on the electron spin orientation is observed.
COHERENCE AND SPIN RELAXATION OF INTERWELL EXCITONS IN GaAs/AlGaAs COUPLED QUANTUM WELLS
Authors: LARIONOV A. V. , TIMOFEEV V. B.
Published: November 2007

The kinetics of spin orientated interwell excitons gas has been investigated in GaAs / AlGaAs coupled quantum wells (n–i–n heterostructures). In these structures, the electrons and the holes are spatially separated between neighboring quantum wells by a narrow AlAs barrier. The time evolution and kinetics of photoluminescence spectra of interwell excitons have been measured under the pulse resonance excitation of intrawell 1sHH excitons using a pulsed tunable laser. The temporal formation of collective excitons phase and the temperature dependence of its spin relaxation rate have been studied. It was observed that spin relaxation rate of interwell excitons in the collective phase is strongly reduced. The observed effect is an evidence of the coherence of indirect excitons' collective phase at the temperatures below the critical one.
Decreased function of voltage-gated potassium channels contributes to augmented myogenic tone of uterine arteries in late pregnancy
Authors: Telezhkin Vsevolod , Goecks Tara , Bonev Adrian D. , Osol George , Gokina Natalia I.
Published: November 2007

Increased pressure-induced (myogenic) tone in small uteroplacental arteries from late pregnant (LP) rats has been previously observed. In this study, we hypothesized that this response may result from a diminished activity of vascular smooth muscle cell (SMC) voltage-gated delayed-rectifier K+(Kv) channels, leading to membrane depolarization, augmented Ca2+influx, and vasoconstriction (tone). Elevation of intraluminal pressure from 10 to 60 and 100 mmHg resulted in a marked, diltiazem-sensitive rise in SMC cytosolic Ca2+concentration ([Ca2+]i) associated with a vasoconstriction of uteroplacental arteries of LP rats. In contrast, these changes were significantly diminished in uterine arteries from nonpregnant (NP) rats. Gestational augmentation of pressure-induced Ca2+influx through L-type Ca2+channels was associated with an enhanced SMC depolarization, the appearance of electrical and [Ca2+]ioscillatory activities, and vasomotion. Exposure of vessels from NP animals to 4-aminopyridine, which inhibits the activity of Kvchannels, mimicked the effects of pregnancy by increasing pressure-induced depolarization, elevation of [Ca2+]i, and development of myogenic tone. Furthermore, currents through Kvchannels were significantly reduced in myocytes dissociated from arteries of LP rats compared with those of NP controls. Based on these results, we conclude that decreased Kvchannel activity contributes importantly to enhanced pressure-induced depolarization, Ca2+entry, and increase in myogenic tone present in uteroplacental arteries from LP rats.
Cellular redox state protects acetaldehyde-induced alteration in cardiomyocyte function by modifying Ca2+release from sarcoplasmic reticulum
Authors: Oba Toshiharu , Maeno Yoshitaka , Nagao Masataka , Sakuma Nagahiko , Murayama Takashi
Published: November 2007

Recent studies indicate that low concentrations of acetaldehyde may function as the primary factor in alcoholic cardiomyopathy by disrupting Ca2+handling or disturbing cardiac excitation-contraction coupling. By producing reactive oxygen species, acetaldehyde shifts the intracellular redox potential from a reduced state to an oxidized state. We examined whether the redox state modulates acetaldehyde-induced Ca2+handling by measuring Ca2+transient using a confocal imaging system and single ryanodine receptor type 2 (RyR2) channel activity using the planar lipid bilayer method. Ca2+transient was recorded in isolated rat ventricular myocytes with incorporated fluo 3. Intracellular reduced glutathione level was estimated using the monochlorobimane fluorometric method. Acetaldehyde at 1 and 10 μM increased Ca2+transient amplitude and its relative area in intact myocytes, but acetaldehyde at 100 μM decreased Ca2+transient area significantly. Acetaldehyde showed a minor effect on Ca2+transient in myocytes in which intracellular reduced glutathione content had been decreased against challenge of diethylmaleate to a level comparable to that induced by exposure to ∼50 μM acetaldehyde. Channel activity of the RyR2 with slightly reduced cytoplasmic redox potential from near resting state (−213 mV) or without redox fixation was augmented by all concentrations of acetaldehyde (1–100 μM) used here. However, acetaldehyde failed to activate the RyR2 channel, when the cytoplasmic redox potential was kept with a reduced (−230 mV) or markedly oxidized (−180 mV) state. This result was similar to effects of acetaldehyde on Ca2+transient in diethylmaleate-treated myocytes, probably being in oxidized redox potential. The present results suggest that acetaldehyde acts as an RyR2 activator to disturb cardiac muscle function, and redox potential protects the heart from acetaldehyde-induced alterations in myocytes.
Coronary effluent from a preconditioned heart activates the JAK-STAT pathway and induces cardioprotection in a donor heart
Authors: Huffman Lynn C. , Koch Sheryl E. , Butler Karyn L.
Published: November 2007

Preconditioning (PC) protects against ischemia-reperfusion (I/R) injury via the activation of the JAK-STAT pathway. We hypothesized that the mediators responsible for PC can be transferred to naive myocardium through the coronary effluent. Langendorff-perfused hearts from male Sprague-Dawley rats were randomized to paired donor/acceptor protocols with or without PC in the presence or absence of the JAK-2 inhibitor AG-490 ( n = 6 for each group). Warmed, oxygenated coronary effluent collected during the reperfusion phases of PC (3 cycles of 5 min ischemia and 5 min reperfusion) was administered to acceptor hearts. The hearts were then subjected to 30 min ischemia and 40 min reperfusion. The left ventricles were analyzed for phosphorylated (p)STAT-1, pSTAT-3, Bax, Bcl, Bcl-XL/Bcl-2-associated protein (BAD), and caspase-3 expression by Western blot. A separate group of hearts ( n = 6) was analyzed for STAT activation immediately after the transfer of the PC effluent (no I-R). Baseline cardiodynamics were not different among the groups. End-reperfusion maximal change in pressure over time (+dP/d tmax) was significantly ( P < 0.05) improved in acceptor PC (3,637 ± 199 mmHg/s) and donor PC (4,304 ± 347 mmHg/s) hearts over non-PC donor (2,020 ± 363 mmHg/s) and acceptor (2,624 ± 345 mmHg/s) hearts. Similar differences were seen for minimal change in pressure over time (−dP/d tmin). STAT-3 activation was significantly increased in donor and acceptor PC hearts compared with non-PC hearts. Conversely, pSTAT-1 and Bax expression was decreased in donor and acceptor PC hearts compared with non-PC hearts. No differences in Bcl, BAD, or caspase-3 expression were observed. Treatment with AG-490 attenuated the recovery of ±dP/d t in acceptor PC hearts and significantly reduced pSTAT-3 expression. The PC coronary effluent activates JAK-STAT signaling, limits apoptosis, and protects myocardial performance from I/R injury.
Mitochondria protection from hypoxia/reoxygenation injury with mitochondria heat shock protein 70 overexpression
Authors: Williamson Courtney L. , Dabkowski Erinne R. , Dillmann Wolfgang H. , Hollander John M.
Published: November 2007

The majority of mitochondrial proteins are encoded by nuclear genes and synthesized in the cytosol as preproteins containing a mitochondria import sequence. Preproteins traverse the outer mitochondrial membrane in an unfolded state and then translocate through the inner membrane into the matrix via import machinery that includes mitochondrial heat shock protein 70 (mtHSP70). Neonatal rat cardiac myocytes (NCM) infected with an adenoviral vector expressing mtHSP70 or an empty control (Adv−) for 48 h were submitted to 8 h of simulated ischemia (hypoxia) followed by 16 h of reperfusion (reoxygenation). Infection with mtHSP70 virus yielded an increase in mtHSP70 protein in NCM mitochondria compared with Adv−( P < 0.05). Cell viability after simulated ischemia/reperfusion (I/R) was decreased in both Adv−and mtHSP70 groups, relative to control ( P < 0.05), but mtHSP70-infected NCM had enhanced viability after I/R relative to Adv-infected NCM ( P < 0.05). Simulated I/R caused an increase in reactive oxygen species generation and lipid peroxidation in Adv-infected NCM ( P < 0.05, for both) that was not observed in mtHSP70-infected NCM. Mitochondrial complex III and IV activities were greater in mtHSP70-infected NCM after simulated I/R compared with Adv−( P < 0.05 for both). After simulated I/R, ATP content increased in mtHSP70-infected NCM, compared with Adv−( P < 0.05). Apoptotic markers were decreased in mtHSP70-infected NCM compared with Adv−after simulated I/R ( P < 0.05). These results indicate that overexpression of mtHSP70 protects the mitochondria against damage from simulated I/R that may be due to a decrease in reactive oxygen species leading to preservation of mitochondrial complex function activities and ATP formation.
Cholesterol depletion modulates basal L-type Ca2+current and abolishes its β-adrenergic enhancement in ventricular myocytes
Authors: Tsujikawa Hiroto , Song Yumei , Watanabe Makino , Masumiya Haruko , Gupte Sachin A. , Ochi Rikuo , Okada Takao
Published: November 2007

Cholesterol is a primary constituent of the plasmalemma, including the lipid rafts/caveolae, where various G protein-coupled receptors colocalize with signaling proteins and channels. By manipulating cholesterol in rabbit and rat ventricular myocytes using methyl-β-cyclodextrin (MβCD), we studied the role of cholesterol in the modulation of L-type Ca2+currents ( ICa,L). MβCD was mainly dialyzed from BAPTA-containing pipette solution during whole cell clamp. In rabbit myocytes dialyzed with 30 mM MβCD for 10 min, a positive shift in membrane potential at half-maximal activation ( V0.5) from −8 to −2 mV developed and was associated with an increase in current density at positive potentials (42% at +20 mV vs. time-matched controls). Isoproterenol (ISO) increased ICa,Lapproximately threefold and caused a negative shift in V0.5in control cells, but it did not increase ICa,Lin MβCD-treated myocytes, nor did it shift V0.5. The effect of MβCD (10 or 30 mM) was concentration dependent: 30 mM MβCD suppressed the ISO-induced increase in ICa,Lmore effectively than 10 mM MβCD. MβCD dialysis also abolished the increase in ICa,Lelicited by forskolin or dibutyryl cAMP, but not that elicited by (−)BAY K 8644. External application of MβCD-cholesterol complex to rat myocytes attenuated the MβCD-mediated inhibition of the ISO-induced increase of ICa,L. Biochemical analysis confirmed that the myocytes′ cholesterol content was diminished by MβCD and increased by MβCD-cholesterol complex. Cholesterol thus appears to contribute to the regulation of basal ICa,Land β-adrenergic cAMP/PKA-mediated increases in ICa,L. We suggest that cholesterol affects the structural coupling between L-type Ca2+channels and adjacent regulatory proteins.
Sex differences in the mechanism of Met5-enkephalin-induced cardioprotection: role of PI3K/Akt
Authors: Cao Zhiping , Liu Lijuan , Packwood William , Merkel Matthias , Hurn Patricia D. , Van Winkle Donna M.
Published: November 2007

Met5-enkephalin (ME)-induced cardioprotection occurs via epidermal growth factor receptor (EGFR) transactivation with the subsequent activation of phosphatidylinositol 3-kinase (PI3K). In the present study, we investigated whether there is a sex difference in ME-elicited PI3K signaling. Neonatal murine cardiomyocytes were isolated by collagenase digestion and subjected to 90 min hypoxia and 180 min reoxygenation at 37°C ( n = 5 to 7 replicates). PI3K/Akt signaling was interrogated using pharmacological inhibitors and small interfering RNA (siRNA). Cell death was assessed by propidium iodide. More than 300 cells were examined for each treatment. The data are presented as means ± SE. There was not a sex difference in the basal content of total Akt. ME (100 μM) elicited comparable protection in both sexes. Wortmannin and the nonselective Akt inhibitor IV completely abolished ME-induced protection in male cardiomyocytes but only attenuated protection in female cardiomyocytes. Isoform-selective knockdown of Akt in males with siRNAs against Akt1/2 completely abolished ME-induced cardioprotection, whereas the siRNAs against Akt3 only attenuated protection of ∼40%. In contrast, in females the siRNAs against Akt1/2 attenuated and against Akt3 eliminated ME-induced cardioprotection. There is not a sex difference in the degree of ME-induced protection, and there is a sex difference in the cardioprotective signaling pathways after the administration of ME; ME-induced cardioprotection in males primarily utilizes a PI3K/Akt1/2 pathway and in females primarily utilizes a PI3K/Akt3 pathway. The incomplete loss of protection in females following the blockade of PI3K suggests that additional factors may facilitate the maintenance or function of activated Akt.
Maintenance of intercellular coupling by the antiarrhythmic peptide rotigaptide suppresses arrhythmogenic discordant alternans
Authors: Kjølbye Anne Louise , Dikshteyn Maria , Eloff Benjamin C. , Deschênes Isabelle , Rosenbaum David S.
Published: November 2007

Discordant action potential alternans creates large gradients of refractoriness, which are thought to be the mechanisms linking T-wave alternans to cardiac arrhythmogenesis. Since intercellular coupling acts to maintain synchronization of repolarization between cells, we hypothesized that intercellular uncoupling, such as during ischemia, would initiate discordant alternans and that restoration of intercellular coupling by the gap junction opener rotigaptide may provide a novel approach for suppressing arrhythmogenic discordant alternans. Optical mapping was used to record action potentials from ventricular epicardium of Langendorff-perfused guinea pig hearts. Threshold for spatially synchronized (i.e., concordant) alternans and discordant alternans was determined by increasing heart rate step-wise during 1) baseline, 2) treatment with rotigaptide or vehicle, and 3) global low-flow ischemia + rotigaptide or vehicle. Ischemia reduced the threshold for concordant alternans in both groups from 362 ± 8 to 305 ± 9 beats/min ( P < 0.01) and for discordant alternans from 423 ± 6 to 381 ± 7 beats/min ( P < 0.01). Interestingly, rotigaptide also increased the threshold for discordant alternans relative to vehicle both before (438 ± 7 vs. 407 ± 8 beats/min, P < 0.05) and during (394 ± 7 vs. 364 ± 9 beats/min, P < 0.05) ischemia. Rotigaptide increased conduction velocity and prevented conduction slowing and dispersion of repolarization during ischemia. Confocal immunofluorescence revealed that total connexin43 quantity and cellular distribution were unchanged before or after low-flow ischemia, with and without rotigaptide. However, connexin43 dephosphorylation in response to low-flow ischemia was significantly prevented by rotigaptide (15.9 ± 7.0 vs. 0.3 ± 6.4%, P < 0.001). These data suggest that intercellular uncoupling plays an important role in the transition from concordant to discordant alternans. By suppressing discordant alternans, repolarization gradients, and connexinx43 dephosphorylation, rotigaptide may protect against ischemia-induced arrhythmias. Drugs that selectively open gap junctions offer a novel strategy for antiarrhythmic therapy.