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  • Springer  (15)
  • Springer Nature  (1)
  • 1995-1999  (16)
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  • 1
    Electronic Resource
    Electronic Resource
    Semiclassical States of Nonlinear Schrödinger Equations (1997)
    Springer
    Archive for rational mechanics and analysis 140 (1997), S. 285-300 
    Details
    ISSN: 1432-0673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract. The existence of semiclassical states to some nonlinear Schrödinger equations that concentrate near the critical points of the potential V is studied by means of a local approach, variational in nature. We also discuss stability and necessary conditions for concentration. The same method is used to find multiple homoclinic orbits to a class of second‐order Hamiltonian systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002050050067
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  • 2
    Electronic Resource
    Electronic Resource
    Polarization effects in nitride semiconductors and device structures (1999)
    Springer
    Materials research innovations 3 (1999), S. 97-106 
    Details
    ISSN: 1433-075X
    Keywords: Key words GaN ; Semiconductor nitrides ; Spontaneous polarization ; Strain ; Piezoelectric polarization ; AlGaN heterostructures ; AlGaN/GaN MODFETs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Wide bandgap nitride semiconductors have recently attracted a great level of attention owing to their direct bandgaps in the visible to ultraviolet regions of the spectrum as emitters and detectors. Moreover, this material system with its favorable hetero-junctions and transport properties began to produce very respectable power levels in microwave amplifiers. If and when the breakdown fields achieved experimentally approach the predicted values, this material system would also be very attractive for power switching devices. In addition to the premature breakdown, high concentration of defects, and inhomogeneities, a number of scientific challenges remain including a clear experimental investigation of polarization effects. In this paper, following a succinct review of the progress that has been made, spontaneous and piezoelectric polarization effects and their impact on sample device-like hetero-structures will be treated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190050132
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  • 3
    Electronic Resource
    Electronic Resource
    Exciton dynamics in ZnSe/ZnS x Se1−x superlattices (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1429-1433 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Localised single-particle electronic states (excluding impurities) ; Photoluminescence ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Time-resolved photoluminescence experiments in a wide carrier density range up to and beyond the threshold for stimulated emission in ZnSe/ZnS x Se1−x superlattices are presented. Different localisation mechanisms of free excitons are identified giving rise to different radiative recombination channels. At high carrier density localised energy states merge into miniband that allows for exciton-exciton interaction, such as screening of the free-exciton absorption and inelastic exciton-exciton scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457222
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental evidence of the exciton centre-of-mass quantization in Zn1−x Cd x Se/ZnSe multiple quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1473-1479 
    Details
    ISSN: 0392-6737
    Keywords: Surface and interface electron states ; Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report the evidence of exciton-polariton centre-of-mass quantization in II–VI quantum wells consisting of ternary alloy. Absorption and photoluminescence studies on Zn0.89Cd0.11Se/ZnSe quantum wells, covering the intermediate region between two- and three-dimensional exciton behaviour, exhibit distinct optical resonances in the high-energy tail of the free-exciton structure. We reproduce the well width dependence of the centre-of-mass states by modeling the optical response of the QWs with a thin-slab variational wave function, which takes into account non-adiabatic terms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457229
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetism as a probe for wave function localization in GaSb/AlGaSb quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1465-1471 
    Details
    ISSN: 0392-6737
    Keywords: Surface and interface electron states ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The localization of the wave function on the scale length of a single monolayer has been studied by magnetophotoluminescence in GaSb/AlGaSb quantum wells. The studied range of well width includes the direct-indirect transition involvingL-point conduction states and Γ-point valence states induced by quantum size effects. Separate carrier localization dominates at higher field values (B〉2T), whereas the excitonic effects are important only in the low field range. Variational calculations of the excitonic transverse extension provide a quantitative description of the experimental data. The dependence of the effective reduced mass on the well width has been obtained experimentally by magnetoluminescence that is highly sensitive to the modifications of the wave function, even on the scale of a single monolayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457228
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic-field effects in the luminescence of V-shaped quantum wires (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1681-1685 
    Details
    ISSN: 0392-6737
    Keywords: Surface and interface electron states ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Quantum wire heterostructures, such as V- and T-shaped wires, are very promising candidates for low-threshold lasing. A crucial issue is the excitonicvs. free-carrier nature of the radiative recombination. Here, we report on magnetophotoluminescence studies of GaAs and InGaAs V-shaped wires that allow to discriminate different regimes of radiative recombination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457263
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  • 7
    Electronic Resource
    Electronic Resource
    Optical transitions involving excitons in quantum wires (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1219-1228 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We present a comprehensive discussion of the excitonic properties of V-shaped GaAs and InGaAs quantum wires grown on patterned substrates. Systematic linear and non-linear spectroscopic studies have been performed in order to clarify the impact of lateral confinement on the exciton wave function, namely: enhanced exciton binding energy, localization in magnetic field, recombination from excited states and multiphoton absorption. The careful evaluation of the electron confinement energies, based on the actual quantum wire profile obtained by TEM micrographs, including the internal piezoelectric field induced by off-diagnoal terms of strain tensor, reproduces quite well the measured one-dimensional states. Finally, application of quantum wires in a p-i-n wave guide for bistable operation is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457193
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  • 8
    Electronic Resource
    Electronic Resource
    Allozymic and morphometric evidence for two stocks of the European anchovy Engraulis encrasicolus in Adriatic waters (1996)
    Springer
    Marine biology 126 (1996), S. 529-538 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Allozyme electrophoresis and morphometric analyses were used to investigate the stock structure of European anchovies (Engraulis encrasicolus L.) captured by Italian vessels in the Adriatic Sea. Twenty four putative enzyme loci were studied, all of which exhibited genotypic proportions in accordance with Hardy-Weinberg predictions. Two loci, IDHP-2 * (isocitrate dehydrogenase, 1.1.1.42) and G3PDH-2 * (glycerol-3-phosphate dehydrogenase, 1.1.1.8), showed significant allele-frequency differences among samples. IDHP-2 * 100 frequencies ranged between 0.35 and 0.88, with lower frequencies recorded in northern waters and areas close to the Italian coastline, while G3PDH-2 * 100 frequencies followed a similar, if less distinct, pattern. For both loci, the trends observed were spatially stable over a 2 yr sampling period. A putative stock-boundary was superimposed onto a map of IDHP-2 * 100 frequencies, and a bootstrapped dendrogram confirmed the genetic separation of the two putative stocks, one located around the north-western Adriatic and the other in the central-southern region. Canonical variate analysis (CVA) of morphometric data collected using a “truss network” indicated that the two putative stocks were morphologically distinct; 89.6 and 88.3% of north-western and central-southern anchovies, respectively, were correctly assigned by discriminant-function analysis. This variation may be related to the presence of two anchovy colour phenotypes, silver and blue, in the Adriatic Sea. Silver anchovies are characteristic of northern areas, while the larger blue fish are found mainly in the deeper southern waters. Current assessment models for the fishery are based on the concept of a consistent identity between consecutive catches at single ports, which our data reject. We discuss the possibility of partitioning fishing effort based on the proportions of the two stocks landed at individual ports.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354635
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  • 9
    Electronic Resource
    Electronic Resource
    Biphasic changes in relaxation following reperfusion after myocardial ischemia (1996)
    Springer
    Molecular and cellular biochemistry 160-161 (1996), S. 123-128 
    Details
    ISSN: 1573-4919
    Keywords: myocardial stunning ; diastolic stiffness ; myocardial relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The present study provides evidences of left ventricular diastolic alterations following reperfusion in a model of global ischemia. Isolated perfused rabbit and rat hearts, were subjected to ischemia for 15 and 20 min respectively, followed by 30 min of reperfusion. In rabbit heart at the end of the reperfusion period, isovolumic left ventricular developed pressure (LVDP) and +dP/dtmax stabilized at 55 ± 3% and 60 ± 2% of preischemic values respectively and, in rat heart LVDP = 61 ± 8% and +dP/dtmax = 57 ± 9% of preischemic values. Stunned heart was then obtained from both species. Left ventricular end diastolic pressure (LVEDP) values stabilized at the end of reperfusion period at values higher than preischemic conditions in both species (38.9 ± 4.4 mmHg and 30.3 ± 3.1 mmHg in rabbit and rat respectively). The time constant of relaxation (T) increased early in reperfusion in both species, but then decreased and stabilized at the end of reperfusion period at values lower than preischemic values. The ratio between both maximal velocities (+P/-P), also showed a transitory impairment in relaxation, followed by normalization and stabilization at values lower than preischemic values. This biphasic pattern in relaxation was detected in both species. The changes in relaxation were dissociated from the diastolic compliance and could be the result of a transitory calcium overload and/or sarcoplasmic reticulum dysfunction. The faster myocardial relaxation at the end of reperfusion period is consistent with the decreased myofilament sensitivity, which characterizes the stunned myocardium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240041
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  • 10
    Electronic Resource
    Electronic Resource
    Is stunning prevented by ischemic preconditioning? (1998)
    Springer
    Molecular and cellular biochemistry 186 (1998), S. 123-129 
    Details
    ISSN: 1573-4919
    Keywords: stunning ; ischemic preconditioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In a model of global ischemia in the isolated perfused rat heart, a 20-min ischemic period followed by 30 min of reperfusion induces a decrease in isovolumic developed pressure (LVDP) and +dP/dtmax to 61 ± 6% and 61 ± 7% of baseline, respectively. Left ventricular end-diastolic pressure (LVEDP) increases to 36 ± 4 mmHg at the end of the reperfusion period. No significant necrotic area as assessed by triphenyltetrazolium chloride (TTC) was detected at the end of the reperfusion period. By an immunohistochemical method using antiactin monoclonal antibodies 10.8 ± 1.9% of unstained cells were detected in the stunned hearts and 10.3 ± 1.2% in control hearts. Preceding the ischemic episode with a cycle of 5 min of ischemia followed by 10 min of reperfusion (ischemic preconditioning) protected contractile function. LVDP and +dP/dtmax now stabilized at 89 ± 5% and 94 ± 5% of baseline respectively. LVEDP was 20 ± 2 mmHg at the end of the reperfusion period. The protection of contractile dysfunction after 20 min of ischemia was achieved also by early reperfusion of low Ca2+-low pH perfusate. With this intervention LVDP stabilized at 87 ± 5% of baseline. LVEDP was 12 ± 2 mmHg at the end of the reperfusion period. A positive inotropic intervention induced by a modified postextrasystolic potentiation protocol at the end of the reperfusion period increases LVDP to levels higher than baseline in the stunned hearts. However, these values were less than those obtained in control hearts. Ischemic preconditioning significantly increased the maximal inotropic response. Therefore, ischemic preconditioning diminishes the contractile dysfunction of early stunning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006879616265
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