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  • 101
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1607-1612 
    ISSN: 0392-6737
    Keywords: Optical properties of thin films, surfaces, and thin layer structures (including superlattices, heterostructures, and intercalation compounds) ; Nonlocalized single-particle electronic states ; Collective effects ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary High magnetic and electric fields are used to investigate the excitonic properties of strain-balanced InGaAs coupled quantum wells, providing details of their band structure. The bands are strongly non-parabolic and the heavy in-plane hole mass deduced for a lattice-matched structure is shown to be reduced by either tensile or compressive strain. The different band-offsets on changing from InGaAs to AlInAs barriers modify the interwell coupling and result in the observation of Stark ladder transitions and conventional Stark effect behaviour, respectively.
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  • 102
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1699-1703 
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Localized single-particle electronic states (including impurities) ; III–V compounds and systems ; Photoluminescence ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have performed time-integrated and time-resolved photoluminescence experiments on high-quality stressor-induced InGaAs/GaAs quantum dots. The optical spectra of these dot structures exhibit large quantization effects together with remarkably low inhomogeneous broadenings of the respective excitonic transitions. Thus a detailed investigation of the relaxation and recombination dynamics within the distinct electronic dot states becomes feasible. We find that the initial relaxation of optically generated carriers down to the lowest dot states is very efficient. This fast thermalization is ascribed to Coulomb scattering between carriers confined in dot states and carriers located in the higher-energetic quantum well states.
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  • 103
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; III–V and II–VI inorganics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Photoluminescence excitation experiments have been performed with a non-intentionally doped GaInAs/AlGaInAs superlattice lattice-matched to an InP substrate. The superlattice is the intrinsic part of a p-i-n diode. We have observed the 1s and 2s heavy-hole exciton states and the Wannier-Stark ladder associated to the light-hole exciton. Three other lines in our spectrum are related to the Wannier-Stark ladder associated to the first excited state of the heavy hole. These transitions are weakly allowed from the built-in voltage existing in the superlattice. Calculations based on Airy functions quantitatively support our interpretation.
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  • 104
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1787-1790 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; II–VI compounds and other chalcogenides ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on the observation of the doubly resonant secondary emission involving 2s and 1s exciton states. The resonance conditions have been realized in CdTe/Cd1-xMnx Te quantum well structures by magnetic-field tuning of the 2s-1s energy spacing to the LO-phonon energy. Theoretical analysis shows the doubly resonant process to be indirect, with hot 1s excitons acting as intermediate states. It is concluded that the resonance width of 2.6 meV gives the 2s-exciton homogeneous linewidth governed by elastic scattering into the hot 1s exciton states.
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  • 105
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1797-1799 
    ISSN: 0392-6737
    Keywords: Excitions 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 demonstrate that a hybridization of Frenkel and Wannier-Mott excitons in parallel neighbouring organic and semiconductor quantum wires may occur due to the resonance dipole-dipole interaction between the wires. The hybridization might be especially efficient for excitons with small wave vectors along the wires when the transition dipole moments of excitons are oriented perpendicular to the wires. The hybrid wire excitons may possess both a large radius and a relatively large oscillator strength which could be important in non-linear optics.
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  • 106
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 803-810 
    ISSN: 0392-6737
    Keywords: Nonlinear optics ; Fluctuation phenomena, random processes, and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have investigated, experimentally and theoretically, the occurrence of stochastic resonance (SR) in a laser with saturable absorber: a non-linear optical system presenting optical bistability and self-pulsed regimes for the laser output intensity. In the optical-bistability regime we have obtained an excellent demonstration of SR by studying Fourier spectra and residence time distributions; operating just below the Hopf bifurcation that originates pulsed periodic regime we have obtained experimental evidence of the SR phenomenon. For operation close to the Hopf bifurcation, the theoretical analysis (performed through numerical simulations) has demonstrated that simultaneous presence of noise and periodic forcing generates excursions far from equilibrium; from the locking between these excursions and periodic forcing the SR phenomenon may arise.
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  • 107
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 819-825 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics information theory, cybernetics, and bionics) ; Fluctuation phenomena, random processes, and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The phenomenon of stochastic resonance is predicted in a monostable system displaying transient bimodality during the evolution. The signal-to-noise ratio as a function of the noise intensity calculated within the rate equation theory with many simplifying assumptions exhibits a promising peak. The numerical simulations are also reported.
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  • 108
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 827-834 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We consider the transmission of a periodic signal by noisy threshold devices. A general expression for the input-output characteristic is developed and applied to two particular threshold devices. It is shown that the amplitude of the signal output shows in the subthreshold regime a maximum as a function of the noise strength—the fingerprint of stochastic resonance.
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  • 109
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 835-846 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Fluctuation phenomena, random processes, and Brownian motion ; Probability theory, stochastic processes, and statistics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The Fitzhugh-Nagumo equations (FHN) provide a simple description of the dynamics of a large class of neurons. We characterize synchronization and stochastic resonance in this model using two complementary points of view: the signal-to-noise ratio (SNR), and the absolute as well as normalized peak heights of the interspike interval histograms (ISIHs). At low stimulus frequencies, multiple firings can occur during one period, while at high frequencies, the refractoriness precludes firing at every cycle. The behaviors of the SNR and ISIHs are thus investigated at low, medium and high frequencies to illustrate special synchronization properties of the FHN system. In particular, the behavior of the SNRvs. noise is found to be similar for forcing amplitudes just below and above that at which a 2:1 deterministic phase-locked firing solution becomes stable. Our results rely on an accurate method of estimation of the power spectrum of the point process formed by the firing times. A theoretical analysis for the shape of the simulated power spectra is also presented.
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  • 110
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 699-707 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The purpose of this study was to investigate the sex particularities in human cardiovascular responses to different external influences using the traditional physiological approach and non-traditional methods of dynamical systems theory. Measurements were taken in 21 healthy women and 15 men exposed to noise stress, passive coping, and in 35 women and 25 men exposed to double mental arithmetic stress, active coping. Results showed that, firstly, cardiovascular reactivity in men and women was determined by the type of stress. Thus, in a majority of humans heart rate did not change during noise but increased during mental stress, blood pressure decreased during noise but increased during mental stress. Secondly, results demonstrated the significant sex differences in the basal and stress cardiovascular activity. So, the women showing the greater basal and stress heart rate displayed the hypotensive responses to passive coping more often and the hypertensive responses to active coping less often than men. Thirdly, the changes in normalized entropy of the electrocardiogram signal, reflecting the changes in heart physiological variability, also depended on the sex of subjects and the nature of stress. During noise normalized entropy increased in a majority of women but decreased in a majority of men. Mental stress caused both decreases and increases in normalized entropy in men and women. But the increases in normalized entropy during stress and especially during recovery were greater in women than in men. Normalized entropy was demonstrated to be a more sensitive marker of sex and individual differences in cardiovascular responses to stress than heart rate and blood pressure. Results suggest that the lower blood pressure reactions and the greater increases in normalized entropy,i.e. in physiological heart variability, may partly result in higher cardiovascular stress resistance in women relative to men.
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  • 111
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 765-773 
    ISSN: 0392-6737
    Keywords: Muscle contraction, nerve conduction, synaptic transition memorization and other neurophysiological processes (excluding perception processes and speech) ; Biophysical instrumentation and techniques ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Two procedures aimed at a synthetic, quantitative characterization of the integrative activity in a small system of nerve cells are proposed, and applications to the buccal ganglion of the molluskAplysia are described. Both methods are based on cross-correlation evaluation. The first method processes intracellular signals simultaneously recorded from pairs of neurones, and reveals and measures the occurrence of shared synaptic input. The second method processes extracellular multiunit signals recorded by two cuff electrodes placed around one nerve, and evaluates the impulse traffic, subdivided according to direction and speed of propagation. The outcome of both methods may be used to represent the state of the system, and may provide a basis to further studies on its dynamics.
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  • 112
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1277-1284 
    ISSN: 0392-6737
    Keywords: II–IV semiconductors ; Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Steady-state and picosecond photoluminescence experiments on CdTe/CdZnTe and CdTe/CdMnTe asymmetric double quantum wells are presented. An external magnetic field is used to tune the coupling between the two QWs by allowing resonances to occur between excitonic states. Very efficient tunnelling is found when an exciton from the high-energy QW can transfer either with the emission of an LO phonon or via the resonance with the 2s state of the low-energy QW.
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  • 113
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1305-1313 
    ISSN: 0392-6737
    Keywords: Molecular and atomic beam epitaxy ; Localized single-particle electronic states (excluding impurities) ; Electron states in low-dimensional structures (including quantum wells, superlattices layer structures, and intercalation compounds) ; III–V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on the intrinsic radiative lifetime of excitons in InP quantum dots embedded in an In0.48Ga0.52 P matrix. This lifetime is about 400 ps as measured by time-resolved photoluminescence with resonant excitation of the ground states. It is independent of excitation density and temperature demonstrating the quantum dot nature of the InP islands and the strong localization of the excitons. Similar experiments on excitons localized by well width fluctuations in a GaAs quantum well reveal distinct differences: weakly localized excitons disappear with increasing density or temperature.
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  • 114
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1339-1342 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Fast initial decays of both the luminescence intensity and the circular luminescence polarization at high exciton densities, under resonant excitation, are reported for the first time. These fast decays are simultaneously initiated by the increase of the ellipticity of the photogenerating picosecond laser beam. The theory of the mechanism illustrates the driving role of the interexciton exchange interaction.
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  • 115
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1367-1370 
    ISSN: 0392-6737
    Keywords: 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 Our interest is centred on the very thin layers consisting of only one or a few monolayers of InAs. The optical transition energies, measured by photoluminescence spectroscopy, are compared with theoretical calculations obtained in envelope function approximation and through an empirical tight-binding method. This comparison yields values for the not well-known valence band offset at the InAs/InP interface, and the luminescence lines observed at different energies could be assigned to layers between one and 13 monolayers thick.
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  • 116
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1389-1393 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We calculated the energy and the wave function of the exciton for i) a V-shaped quantum wire, ii) a T-shaped quantum wire and iii) a quantum wire resulting from strain-induced lateral confinement. The full Luttinger and Bir-Pikus Hamiltonian are taken into account in the three calculations. We used different parameters inside the well and at the barrier. The basis states |3/2m〉 are defined with respect to [110], the direction of the wire in the three kinds of structures, instead of the usual [001] direction. The hole dispersion curve allows one to define an effective mass which is to be introduced in the variational calculation of the exciton binding energy. We show that the hole is confined in a wire only in case i).
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  • 117
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1413-1416 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary An opening (antidot) in two-dimensional (2D) electron gas placed in a strong perpendicular magnetic field makes it possible the formation of ring-shaped excitons stemming from the skipping-states of electrons and holes. The binding energy of the ground state of such excitons is logarithmically larger than that of the «bulk» 2D excitons. The possibility of tunnelling electron to hole (or vice versa) around the antidot results in a shift for each of the excitons levels that oscillates with the magnetic field.
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  • 118
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1359-1366 
    ISSN: 0392-6737
    Keywords: Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical mutation) ; Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Weak localization effects (e.g., quantized states) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The optical properties of multiple quantum wells in the transition from isolated wells to a superlattice are investigated theoretically and experimentally. For superlattices with a miniband width similar to the binding energy of the 2s exciton of the isolated quantum well we find an exciton state energetically between the 1s exciton state and the onset of the miniband absorption. We find this state to be an interwell exciton, with the electron confined to one well and the hole to the neighboring well. The interwell exciton resembles the first Wannier-Stark localized exciton of a biased superlattice. However, the localization in the present case is mediated by the Coulomb interaction of the electron and hole. The state has considerable oscillator strength and is observed experimentally in linear and nonlinear experiments.
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  • 119
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1395-1400 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Tunneling ; Other semiconductor-to-semiconductor contacts,p-n junctions, and heterojunctions ; Electroluminescence ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The electroluminescence of p-i-n GaAs double-barrier resonant tunnelling diodes has been investigated for various concentrations of free carriers (either holes or electrons) in the quantum well (QW). For these structures it is possible to change the relative electron or hole density quasi-continuously with applied bias-voltage. New low-temperature excitonic recombinations are identified in the electroluminescence spectra. Continuous variation of the carrier density in the quantum well from a hole-rich into an electron-rich environment leads to the observation of positively charged excitons (X 2 +), neutral excitons (X), negatively charged excitons (X −) and finally an unbound electron-hole recombination. An increased temperature causes the dissociation of the charged excitons in favour of the neutral heavy-hole free excitonX. In high magnetic fields the unbound electron-hole recombination is transferred into an excitonic recombination.
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  • 120
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1417-1422 
    ISSN: 0392-6737
    Keywords: Polaritons (including photon-phonon and photon-magnon interactions) ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The excitonic energies are computed in superlattices from the poles in the imaginary part of the susceptibility, using an appropriate Green's function expression for the coherent amplitude function of the electron-hole pair. Solving the Maxwell equations, the polariton states are obtained and the optical properties are computed. The procedure includes the effects of coherence between the carriers and the electromagnetic field, and it does not require any type of additional boundary conditions. Detailed calculations in GaAs/Ga1−x Al x As superlattices show polaritonic effects in the optical properties, in particular a peculiar fine-structure lineshape of then=1 andn=2 hh and lh excitons is obtained. A comparison with similar calculations in bulk GaAs clearly shows the roles of quantum confinement and of anisotropy in the superlattice.
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  • 121
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1441-1446 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; Optical properties of thin films, surfaces, and layer structures (superlattices, heterojunctions, and multilayers) ; II–VI compounds and other chalcogenides ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Experimental studies of high-resolution reflectivity and a temperature dependence of the photoluminescence for periodic MQWs of CdTe/CdZnTe with periods equal to a one-half and one-forth of the light wavelength are presented. Energies and radiative lifetimes of the polariton-like excitations in the relevant structures are computed, and linked to experimental observations.
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  • 122
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1465-1471 
    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.
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  • 123
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1505-1508 
    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) ; III-V and II-VI inorganics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A model for calculating exciton binding energies in quantum wells (QWs) is presented, which can be applied to situations in which one of the two band discontinuities is large, while the second one can be arbitrary (positive, negative, or zero). The model is applied to ZnSe/ZnSSe and InGaAs/GaAs QWs., The crossover between strong-and weak-confinement, regimes for excitons in narrow QWs is studied within a simplified model with two one-parameter, variational wave functions.
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  • 124
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1527-1530 
    ISSN: 0392-6737
    Keywords: Exchange and superexchange interactions ; Magnetic semiconductors ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Interaction of two magnetic polarons formed either by single carriers or by excitons is considered in bulk crystal, quantum well and quantum wire. It is shown that the magnetic bipolaron can be formed if the distance between two polarons is less than some critical value. This critical radius is the larger the lower the dimensionality of the system, the lower the temperature and the larger the single-polaron radius. The critical distance for the neutral-magnetic-bipolaron formation is much longer than for the charged bipolaron.
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  • 125
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1549-1553 
    ISSN: 0392-6737
    Keywords: Studies of specific magnetic materials ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The influence of the electron spin splitting on the stability of quasi-two-dimensional donor bound excitons (D 0 X) has been investigated in the Cd0.97Mn0.03Te/Cd0.7Mg0.3Te semi-magnetic semiconductor quantum well (QW) structure. TheD 0 X binding energy has been measured directly from emission spectra recorded at magnetic field parallel to the QW plane. Complexes have been shown to dissociate into a neutral donor and a free exciton with a spin flip of the electron at high magnetic fields when the electron spin splitting exceeds the binding energy.
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  • 126
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1561-1565 
    ISSN: 0392-6737
    Keywords: III–V semiconductors ; III–V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on a theoretical calculation of the optical anisotropies in (113)-grown corrugated GaAs/AlAs superlattices using a 6-bankk·p valence band Hamiltonian. By comparison of the calculation with the experimental polarization of the superlattice luminescence we can estimate the corrugation height to be at most 0.3 nm.
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  • 127
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1629-1633 
    ISSN: 0392-6737
    Keywords: III–V semiconductors ; Excitons and related phenomena (including electron-hole drops) ; III–V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on the biexciton formation of the pseudodirect exciton consisting of the AlAs-X z electron and the GaAs-Γ heavy hole in (GaAs) m /(AlAs) m type-II superlattices withm=10, 12, and 13 monolayers. The photoluminescence lineshape of the pseudodirect exciton exhibits a doublet feature having an energy separation of ∼3 meV at the excitation power of the order of mW/cm2 in all the samples, and the low-energy band grows superlinearly. The transient profiles of the doublet photoluminescence band early indicate the biexciton formation: the delay of the rise of the biexciton photoluminescence on the low-energy side and its shorter decay time in comparison with the exciton photoluminescence.
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  • 128
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1635-1639 
    ISSN: 0392-6737
    Keywords: II–VI compounds and other chalcogenides ; Nonlinear optics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report two-photon absorption photoluminescence excitation (TPA-PLE) measurements in ZnSe/ZnSSe strained-layer superlattices (SLS). Polarization-dependent selection rules are observed in TPA spectra depending on the direction of the exciting field with respect to the growth axis of the SLS. Experimental exciton transition energies have found to be in good agreement with theoretical predictions considering strain and confinement effects. Furthermore by means of comparative non-linear technique the TPA coefficient has been measured at different energies and compared with theoretical predictions including quasi-bidimensional excitonic effects. A satisfactory agreement has been shown for the overall spectral behaviour and in some cases also for the TPA coefficient values.
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  • 129
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1487-1492 
    ISSN: 0392-6737
    Keywords: III-V semiconductors ; Electron states in low-dimensional structures (including, quantum wells, superlattices, layer structures, and intercalation compounds) ; Excitons and related phenomena (including electron-hole drops) ; Brillouin and Rayleigh scattering ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A detailed study of the relative role played by localized and/or propagating intermediate excitonic states in, resonant Rayleigh scattering (RRS) is presented for a large set of GaAs quantum well (QW) and bulk structures. We show that the two kinds of states contribute to RRS through different mechanisms. We concluded that RRS occurs via localized states in QW heterostructures, very likely due to localization by the interface roughness, while bulk, crystals turn out to be better candidates for RRS via propagating states.
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  • 130
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    Keywords: Surface and interface electron states ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
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    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.
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  • 131
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1601-1605 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Low-temperature time-resolved luminescence experiments with picosecond resolution have been performed on excitons in a microcavity containing InGaAs quantum wells. The decay curves are very dependent on the energy difference between the cavity mode and the exciton. They agree qualitatively with a model which takes into account a reservoir at the exciton energy and two splitted radiant states.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1613-1617 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; 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 an analysis of the inter- and intrasubband relaxation dynamics of excitons due to Fröhlich coupling in an unbiased asymmetric double quantum well made from CdTe/CdMnTe. We consider the relaxation processes that take place in the time interval between the excitation of the lowest exciton localized in the narrow well and the recombination in the wide well, by means of Fermi's golden rule. As the excitation falls in the range of a Fano resonance, we have to employ an extended set of rate equations to incorporate the effect of the continuum of initially populated states. Thus, we obtain the transient luminescence, which can directly be compared with time-resolved luminescence experiments.
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  • 133
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1619-1623 
    ISSN: 0392-6737
    Keywords: Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have measured the optical properties of a series of strained In x Ga1−x As/GaAs (x=0.09) double-quantum-well structures with different barrier thicknesses grown on (111)B-orientated GaAs substrates. We observed an increase in the Stark shift due to the internal-strain-induced piezoelectric field as a function of increased barrier thickness. As the optical excitation density was increased the Stark shift was found to decrease due to photoscreening of the internal field by the spatially separated electron/hole populations. The extent of the photoscreening was found to be ultimately limited by occupancy of the second heavy-hole subband. Good agreement was found between the measured photoscreening of the piezoelectric field and self-consistent solutions of Schrödinger's and Poisson's equations.
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  • 134
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1663-1667 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We calculate scattering rates of QW excitons by acoustic phonons using realistic deformation potentials for electrons and holes in structures based on GaAs. We use these rates in order to reproduce the exciton dynamics in a time-resolved photoluminescence experiment. Rise time and decay time of the luminescence signal are studied as a function of temperature and QW size. The exciton distribution function reaches a stationaryshape after the luminescence passes through its maximum. This shape shows strong deviations from the thermalequilibrium distribution, at least for temperatures below 50 K. As a consequence, exciton radiative recombination is slower than the usually expected thermal average of the radiative rate. We discuss the dependence of this effect on the well width.
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  • 135
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    Keywords: Surface and interface electron states ; Conference proceedings
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    Topics: Physics
    Notes: Summary Photoluminescence (PL) and electroluminescence (EL) measurement of GaAs/AlGaAs quantum wires (QWR) located in the active region of a p-i-n junction are reported. The samples are fabricated by molecular-beam epitaxial growth on V-grooved substrates. Good control of the interface, defect density and doping profile have been achieved. Homogeneous current injection into the quantum wires is achieved with efficiencies comparable to current injection into a quantum well control sample. PL with and without an applied voltage across the junction was measured at 86 K and 300 K for different excitation densities. Peaks appearing with an applied voltage correspond to the active-region QWR transitions and are also observed on the EL spectra measured at 120 K and at 300 K. Clear evidence of 1D confinement is observed in both PL and EL spectra. They show a one-dimensional splitting of about 24 meV and a saturation of the ground state at high excitation density. The polarisation of the PL and EL is in good agreement with the expected anisotropy of the 1D matrix elements.
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  • 136
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1729-1733 
    ISSN: 0392-6737
    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; II–VI compounds and other chalcogenides ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Picosecond photoluminescence spectroscopy was used to investigate the recombination dynamics of excitons in deep etched CdZnSe/ZnSe quantum wires with lateral extensions down to 20 nm. In the low-temperature regime (T≤10 K), no significant reduction of the exciton lifetime was found down to a wire width of 20 nm, indicating a negligible influence of carrier loss at the wire sidewalls. At higher temperatures, the lifetime decreases for decreasing wire width,e.g., from 330 ps in the mesa structure to 21 ps in the 28 nm wide wires at room temperature. Simple model calculations indicate that this drop of the lifetime is due to diffusive carrier transport to the wire sidewalls and subsequent non-radiative surface recombination.
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  • 137
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1723-1728 
    ISSN: 0392-6737
    Keywords: Polarons and electron-phonon interactions ; 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 The self-trapping of a Frenkel exciton in quantum wells of various dimensionalities and thicknesses is theoretically studied. Using a (2J x +1)×(2J y +1)×(2J z +1) lattice-site model, we variationally calculate the relaxed exciton state for various strength of the coupling constantg of the short-range exciton-lattice interaction. In slab-type QWs (∞×∞×(2J z +1)), asg increases the stable state abruptly changes from the free stateF to the self-trapped stateS as in the exact three-dimension. In wire-type QWs (∞×(2J y +1)×(2J z +1)), wheng is small the stable state is a weakly localized state (large-radius polaron), which corresponds toF ing=0 limit, but the Stokes shift of the emission from thisF state is non-zero. Wheng becomes large this large-radius polaron state,F, characteristic of a one-dimensional system coexists with a small-radius polaron state,S, characteristic of a three-dimensional system.
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  • 138
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1753-1757 
    ISSN: 0392-6737
    Keywords: Brillouin and Rayleigh scattering ; Polaritons (including photon-phonon and photon-magnon interactions) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures and intercalation compounds) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Resonant Brillouin scattering in ultrathin MBE-grown epitaxial layers of ZnSe with thicknesses from 50 to 200 nm is esployed to investigate the properties of the 1s exciton-polariton states. The effective masses are found different from that in bulk ZnSe caused by the energetic decoupling of heavy- and light-hole states due to strain. In the 50 nm sample the momentum selection rule is relaxed, leading to broad Brillouin lines that show fine structure due to the phonon quantization in these layers, whereby dilatation and flexural phonon modes are involved in the scattering.
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  • 139
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1769-1774 
    ISSN: 0392-6737
    Keywords: Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical nutation) ; Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have studied experimentally the coherent exciton-photon dynamics in a single, a double, and a quintuple quantum well structure under resonant excitation. In pump and probe experiments we observe an initial fast decay of the exciton population. This initial decay depends on the number of quantum wells. The population decay is accompanied by a coherent light emission induced by the first-order polarization, the intensity of which increases quadratically with the quantum well number. Interference effects and electromagnetic coupling effects between polarizations located in distinct quantum wells probably play a crucial role in the superlinear coherent emission process.
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  • 140
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1791-1795 
    ISSN: 0392-6737
    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Exciton dynamics including thermalisation, radiative recombination and migration in growth-interrupted and hydrogen-passivated GaAs/AlAs single quantum wells have been investigated under non-resonant and resonant excitation.
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  • 141
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 661-683 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology and relevant aspects of thermodynamics, information theory, cybernetics and bionics) ; Fluctuation phenomena, random processes, and Brownian motion ; Probability theory, stochastic processes, and statistics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We outline the historical development of stochastic resonance (SR), a phenomenon in which the signal and/or the signal-to-noise ratio in a nonlinear system increase with increasing intensity of noise. We discuss basic theoretical ideas explaining and describing SR, and we review some revealing experimental data that place SR within the wider context of statistical physics. We emphasize the close relationship of SR to some effects that are well known in condensed-matter physics.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 775-783 
    ISSN: 0392-6737
    Keywords: Noise: its effects and control ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The double-well Duffing oscillator is investigated experimentally when a small noise is present in the system. It results that the noise influences the mean lifetime of the transient chaos showing some similarities with the phenomenon of the stochastic resonance. This behaviour is in agreement with a simple model based on the one-dimensional logistic map.
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  • 143
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 785-793 
    ISSN: 0392-6737
    Keywords: Chemical kinetics ; Fluctuation phenomena, random processes, and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Stochastic resonance in a bistable potential is characterized as a syncronization effect of the hopping mechanism induced by the external periodic bias. Most notably, syncronization is shown i) to attain a maximum with increasing the forcing frequency close to the relevant switching rate, thus revealing abona fide resonant process; ii) to occur even in the absence of symmetry breaking by the periodic forcing term.
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  • 144
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 863-871 
    ISSN: 0392-6737
    Keywords: Chaos ; Nonequilibrium thermodynamics, irreversible processes ; Statistical mechanics ; Probability theory, stochastic processes, and statistics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Locla and global statistical properties of a class of one-dimensional dissipative chaotic maps and a class of 2-dimensional conservative hyperbolic maps are investigated. This is achieved by considering the spectral properties of the Perron-Frobenius operator (the evolution operator for probability densities) acting on two different types of function space. In the first case, the function space is piecewise analytic, and includes functions having support over local regions of phase space. In the second case, the function space essentially consists of functions which are “globally» analytic,i.e. analytic over the given systems entire phase space. Each function space defines a space of measurable functions or observables, whose statistical moments and corresponding characteristic times can be exactly determined.
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  • 145
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 915-924 
    ISSN: 0392-6737
    Keywords: Chaos ; Classical mechanics of discrete systems: general mathematical aspects ; Fluctuation phenomena, random processes and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A new type of non-linear resonance is reported. It possesses an unusual counterintuitive feature, namely that: strong non-linear response to a weak periodic force can be obtained in the absence of exact resonance between frequency of the force and any eigenfrequency of the system. It is shown that the topology of phase trajectories differs substantially from the case of conventional non-linear resonance. The frequency of a driving force at which the transition between the conventional non-linear resonance and the zero-dispersion one takes place is found. Possible applications are discussed.
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  • 146
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 959-967 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Quantum statistical mechanics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We look for stochastic resonance in the very low temperature limit, where a quantum-mechanical treatment is needed. The canonical example of a dissipative double-well potential subject to periodic forcing is studied within the two-state approximation. The cases of both ohmic and superohmic dissipation are investigated in detail.
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  • 147
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 755-764 
    ISSN: 0392-6737
    Keywords: Chemical kinetics ; Fluctuation phenomena, random processes, and Brownian motion ; Probability theory, stochastic processes, and statistics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The response of an overdamped system to quasi-monochromatic (high-frequency narrow band) noise (QMN) has been investigated by means of analogue electronic experiments. Measurements of the stationary and prehistory probability distributions demonstrate that large occasional, fluctuations are markedly different in character from those that occur when the system is driven by white or exponentially correlated noise. In particular, we report the first experimental observation of a switching point, a critical value of the coordinatex that separates regions which, with an overwhelming probability, are accessed by the fluctuating system along topologically different paths. The results are discussed in terms of, and shown to be consistent with, an existing theoretical description of the QMN-driven system.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 847-854 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Fluctuation phenomena, random processes and Brownian motion ; Probability theory, stochastic processes, and statistics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We define and develop a novel process, related to stochastic resonance, in which a particle experiences three forces: a constant drift, a zero-mean white noise, and a time-periodic modulation. Upon reaching a threshold, the particle immediately returns to the starting point. The resulting process exhibits multiple maxima in the output power at the modulation frequency as a function of the white-noise variance, multimodal first-passage-time densities, and evidence of phase locking. Our model is an extension of the Gerstein-Mandelbrot model of neuron firing to the case of periodic stimuli, and therefore has applications in neural modeling.
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  • 149
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1295-1303 
    ISSN: 0392-6737
    Keywords: Polaritons (including photon-phonon and photon-magnon interactions) ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have investigated the dynamics of impulsively excited planar microcavities in the strongly couple regime. With resonant, coherent excitation, the emitted light shows vacuum-Rabi oscillations and a lifetime corresponding to twice the cavity lifetime. As the light intensity is increased, the exciton bleaching leads to reduced normal-mode splitting. The role of interface disorder on the dynamic splitting is discussed. Coherence transfer in exciton-exciton scattering is observed. Off-resonant excitation leads to long lifetimes limited by scattering into the radiatively coupled states of the exciton-cavity system.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1333-1337 
    ISSN: 0392-6737
    Keywords: Time resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The cooling of photoexcited hot carriers in 2D, 1D and 0D systems is studied experimentally. In comparison with a theoretical carrier relaxation model which holds for 2D and 1D systems, it is found that preferably recombination and a weaker electron-LO-phonon interaction dominates the carrier dynamics with decreasing dimensionality. Consequently, we conclude a less dominant role of hotphonon effects in 0D and 1D systems compared to 2D systems.
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  • 151
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    Keywords: Excitons and related phenomena (including electron-hole drops) ; II–VI semiconductors ; Wave propagation, transmission and absorption ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The spectra of transmission and reflection of synthetic opal which has 3-dimensional periodic structure were measured at different orientations of incident beam relative to the sample facets. It is shown that opal behaves as «semi-metallic» photonic band gap (PBG) material in the vicinity of photon energy 2.3 eV. The synthesis of CdS microcrystals embedded in the pores of opal was made for the first time in an attempt to form a system of quantum dots. Optical spectra (reflection and transmission, photoluminescence and Raman scattering) were studied. The results demonstrate good crystallinity of microcrystals embedded in opal matrix and exhibit well-pronounced quantum confinement effects in fundamental edge absorption spectra. The spectral overlap of the PBG of opal with electronic band gap of many of II–VI semiconductors seems to make opal/semiconductor system a promising media for experimental studies of such PBG-related effects as inhibition of spontaneous emission, microcavity polariton, etc.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1377-1382 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The influence of biexciton formation on the four-wave-mixing response of multiple quantum wells having a strong inhomogeneous broadening of the exciton transitions has been investigated. The experimental results are consistent with a model which distinguishes between crystal regions where the exciton energy is almost constant over the spatial extension of the biexciton state, and regions where the fluctuations of the exciton energy are comparable to or larger than the biexciton binding energy.
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  • 153
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    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Photoluminescence ; II–VI compounds and other chalcogenides ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on time-integrated and time-resolved optical experiments performed on a 26 Å thick Zn0.85Cd0.15Se/ZnSe quantum well, for temperatures in the 10–200 K range. Excitation spectroscoy allows an estimation of the relative valence band offset, which is found to be 10%. From the temperature variation of the decay time of the photoluminescence performed reasonantly on the e1h1 excitonic transition, we deduce that the main non-radiative mechanism is the heavy-hole thermal escape out of the well.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1459-1463 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Other luminescence and radiative recombination ; Structural modeling: serial-addition models, computer simulation ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have observed an anomaly in the low-temperature photoluminescence of dipole-oriented long-lived excitons in a coupled quantum well under an electrical bias. A discrepancy between the experiment and a Monte Carlo simulation for the exciton diffusion in the system suggests a boson correlation for a two-dimensional Bose system in a random potential with repulsive interaction between bosons.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1481-1486 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layers 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 report experimental results on photoluminescence and excitation of photoluminescence of GaAs/Ga0.7Al0.3As quantum wells (19, 38.5 and 77 Å) grown on nominal and vicinal GaAs substrates. In order to study the influence of the interface microscopic structure on the optical properties of the studied quantum wells, we perform luminescence experiments at low temperature by exciting selectively a small area of a few μm2. In this way the presence of isolated islands on the interface is evidenced by a fine structure in the photoluminescence and photoluminescence excitation spectra. The difference in localization length of excitons in samples with steps along the [110] and the [110] directions is emphasized.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1513-1517 
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on calculations of excitonic properties of weakly one-dimensional quantum wires where the exciton centre of mass is quantized by the harmonic potentials of electron and hole. The level scheme as well as the exciton scattering by alloy fluctuations and acoustical phonons are discussed.
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  • 157
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    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Magnetic semiconductors ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Precise-temperature-dependent measurements of energy of excitons confined in CdTe/CdMnTe quantum wells and superlattices were performed between 2 K and 100 K. We show that magnetic fluctuations lead to a variation of the valence band offset, in agreement with a model proposed previously for bulk materials.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1641-1650 
    ISSN: 0392-6737
    Keywords: III–V compounds and systems ; III–V semiconductors ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We investigated the optical properties of excitons in quasi-onedimensional semiconductor quantum structures by photoluminescence and photoluminescence excitation. High-quality GaAs/Al x Ga1−x As heterostructures were grown using low-pressure organometallic chemical vapour deposition (OMCVD) on non-planar substrates. The experimentally observed subband separations are in good agreement with a theoretical calculation of the quantum-confined eigenstates, which includes the mapping of the crescent-shaped wire obtained on TEM micrographs. Additionally, a temperature dependence study of excitonic spectra reveals the dominant role of potential and size fluctuations in localizing the excitons.
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  • 159
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1669-1673 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Quantum Hall effect (including fractional) ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Energy spectrum of an exciton and electron density distribution in it under the fractional quantum Hall regime are calculated within the framework of an anyon exciton model.
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  • 160
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1211-1218 
    ISSN: 0392-6737
    Keywords: Polaritons (including photon-phonon and photon-magnon interactions) ; Electrons states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; III–V and II–VI inorganics ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A description of polariton effects on excitons in multiple quantum wells (MQWs), superlattices (SLs), and semiconductor microvavities is presented. The non-local semi-classical theory in a transfer matrix formulation is adopted. The radiative width in MQWs atk=0 increases first with the number of wellsN, then goes to zero asN→∞, where stationary SL polaritons are recovered. The crossover from weak- to strong-coupling regimes for QW excitons in microcavities is described. The complex energies of the mixed exciton-radiation modes are shown to be measurable by time-resolved transmission experiments.
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  • 161
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1247-1254 
    ISSN: 0392-6737
    Keywords: Nonlinear optics ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We present wave-mixing techniques which are used to determine the tensor elements of the non-linear dielectric susceptibility, the dynamics of non-linear optical effects and the transport properties of a material. These techniques are applied to CdS nanocrystallites, prepared in a SiO2 matrix by a sol-gel method. They were prepared as thin films of variable density (up to 30% of volume). By the same experimental techniques, porous silicon is studied and the results are compared to those obtained from luminescence and time-of-flight measurements.
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  • 162
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1219-1228 
    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.
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  • 163
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1625-1628 
    ISSN: 0392-6737
    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; III–V compounds and systems ; III–V semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Low-temperature PL decay times, τPL, measured for a series of In x Ga1−x As/GaAs quantum wells (QWs) show an almost linear increase with increasing thickness (4≤L z ≤10 nm,x=0.15) and with increasing In composition (0.05≤x≤0.25,L z =8 nm). τPL also increases linearly with temperature up to 50K, as expected for free excitons and does not exhibit the interface effects seen for GaAs/AlGaAs QWs. Wells with different In compositions exhibit a similar temperature behaviour and there is a weak influence of strain on the decay time.
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  • 164
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1651-1656 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; III–V semiconductors ; Cooperative phenomena ; superradiance and superfluorescence ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We study excitons in double quantum wells (DQWs) embedded in a semiconductor microcavity (MC) by means of semi-classical theory, which yields analytic results in weak- and strong-coupling regimes. We show how to obtain subpicosecond radiative lifetime for the excitons. A model for disorder is investigated.
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  • 165
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1675-1680 
    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) ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We discuss the exciton centre-of-mass dispersion in a (Ga,Al)As-GaAs-AlAs-(Ga, Al)As quantum well taking into account the Γ-X coupling. The position of the Γ andX quantum well levels is monitored by applying an external electric field. Near the degeneracy, the coupling plays an important role mixing the Γ andX levels. As a consequence, the exciton in-plane mass presents a significant non-parabolicity as its values change from a Γ-reduced mass to aX-reduced mass.
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  • 166
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1229-1237 
    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) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We consider in this work the scattering of low-energy excitons in single quantum wells. In the first part we consider the elastic scattering by a static centre (charged impurity) and discuss the validity of the first Born approximation, which is expected to work well only for particles with large kinetic energy. The second part is devoted to the inelastic scatterings of individual excitons by a phonon reservoir. We discuss in particular the validity of the elastic approximation, which is well known to be very accurate for particles with large kinetic energy.
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  • 167
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1705-1712 
    ISSN: 0392-6737
    Keywords: Polaritons (including photon-phonon and photon-magnon interactions) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary By applying a transformation from fermion pair operators to boson operators which preserves the Fermi commutation rules for exciton operators, we introduce the correlation effects neglected in the crude boson approximation. We apply this method to describe saturation effects in cavity polaritons under resonant optical pumping. The reduction in Rabi splitting with increasing pump intensity and the non-linear behaviour of the input-output characteristics are described. Finally, by applying the linearized theory of fluctuations, we obtain an analytic expression for the normalized second-order correlation function for the transmitted light which exhibits photon antibunching even in the limit of weak pump power. The photon antibunching behaviour is inversely proportional to the number of states available for exciton formation.
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  • 168
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1239-1245 
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; III–V semiconductors ; Photoluminescence ; Metal-insulator transitions ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We implement optical spectroscopy to study charged excitons (trions) in modulation-doped GaAs/AlGaAs quantum wells. We observe for the first time several new trions: the positively charged exciton, the light-hole negatively charged exciton and the triplet state of the negatively charged exciton.
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  • 169
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1713-1716 
    ISSN: 0392-6737
    Keywords: Polaritons (including photon-phonon and photon-magnon interactions) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; III–V and II–VI inorganics ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A quantum-mechanical model for quantum well polaritons in semiconductor microcavities is presented. The real and imaginary parts of the polariton dispersion are obtained. They represent, respectively, the position and the linewidth of the luminescence peaks observed in typical experiments. The model includes the features of the distributed Bragg reflectors which constitute the cavity mirrors, and has the advantage of describing the weak-coupling as well as the strong-coupling regimes characteristic of this kind of systems. Furthermore, in the limit where no cavity is present, the well-known result for quantum well polaritons is recovered.
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  • 170
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1759-1762 
    ISSN: 0392-6737
    Keywords: Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical mutation) ; Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Optical properties of thin films, surfaces and thin layer structures (including superlattices, heterostructures, and intercalation compounds) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We study exciton ionization induced by an axial electric field in a strongly coupled GaAs/Al0.3 Ga0.7 As superlattice at low temperatures. The field-induced ionization times of the heavy-hole 1s exciton in the miniband field regime are determined from transient four-wave-mixing experiments and theoretical model calculations. They are found to lie between the field ionization times of excitons in bulk semiconductors, and in strongly confined quantum well systems.
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  • 171
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Electroopical effects ; Magnetooptical effects ; Photon interactions with atoms ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We describe the use of measurements of vacuum Rabi splitting to extract values for the exciton oscillator strengths in In0.13Ga0.87As-GaAs and GaAs-Al0.2Ga0.8As quantum wells. By varying both field and temperature we determine the changes in the oscillator strength in applied electric and magnetic fields. We show that these are in good agreement with the results of quantum well exciton calculations.
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  • 172
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 795-802 
    ISSN: 0392-6737
    Keywords: Circuit theory (including analysis and design of networks) ; Fluctuation phenomena, random processes, and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We describe the simplest system which shows stochastic resonance. A linear(ized) theory for white and (almost) arbitrarily coloured noise is presented. The presented new system has new, unique properties which originate from itsnon-dynamical character; for example, the strength and phase shift of periodic response of the system is independent of the frequency. Experiments have been carried out with the following noise processes: (physical) white noise, (physical) Lorentzian noise and (physical) 1/f noise. With a small extension of the system, its linear-response regime can be significantly increased. As the system is similar to some simple models of neurones, the new results might have not only physical but also biological importance.
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  • 173
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 811-817 
    ISSN: 0392-6737
    Keywords: Superconducting quantum interference devices (SQUIDs) (including magnetometers, electromagnetic radiation sources and detectors, and computer logic and memory devices) ; Stochastic processes ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We describe an experiment on a simple superconducting loop with a Josephson junction subject to a time-sinusoidal magnetic flux embedded in a noise background. The response is shown to display thestochastic-resonance effect, wherein the output signal-to-noise-ratio passes through a maximum at a critical value of the noise strength. Escape times probability density functions are also obtained experimentally
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  • 174
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 873-881 
    ISSN: 0392-6737
    Keywords: Junction breakdown and tunneling devices ; Probability theory, stochastic processes, and statistics ; Statistical mechanics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We study the signal-to-noise ratio, signal and noise output levels in a fast bistable electronic system: a tunnel diode. We observe stochastic resonance when the system is driven by a sum of a small periodic signal and noise. The phenomenon is investigated for values of the driving frequency as high as 10 kHz. This is the highest frequency value used in SR experiments until now. In the presence of «white noise», we observe a nonmonotonic behavior characterized by a sharp dip in the output noise level measured at 100Hz and 1 kHz. A similar behavior is predicated by recent theories. We also present preliminary experimental results of SR in the presence of an Ornstein-Uhlenbeck noise. For the set of investigated values of the correlation time of the noise, we still observe the characteristic dip in the output noise levels. The height of the dip is affected by the correlation time of the noise.
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  • 175
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 925-940 
    ISSN: 0392-6737
    Keywords: Optical bistability ; Fluctuation phenomena, random processes, and Brownian motion ; Probability theory, stochastic processes, and statistics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary In this paper, a comprehensive theory for the non-linear response of a periodically driven bistable system is presented. Analytic results for the full spectral response, including the signal-to-noise ratio (SNR), are obtained. In addition, the whole hierarchy of escape time distributions is calculated. Theoretical connection between these distributions and the SNR is made, enabling the SNR to be calculated from the knowledge of a single escape time distribution. The theoretical calculations are compared with the results of analogue simulation.
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  • 176
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 903-913 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodyamics, information theory, cybernetics, and bionics) ; Fluctuation phenomena, random processes, and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A neural-network model of the phenomenon of perceptual bistability in the presence of ambiguous figure is studied under the influence of a weak periodic perturbation. Computer simulations of the dynamical behaviour of the network show all the main characteristics of stochastic resonance. Preliminary results of a non-simulated experiment show a high degree of synchronization between the external modulation and the perceptual fluctuations.
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  • 177
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 969-976 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We study the impact of noise to the entrainment of underdamped nonlinear oscillators to resonant driving forces. We find that the power consumption is large at a certain noise level. In addition we find that power consumption drops significantly if the forcing function is off-resonant. We discuss possible applications for system identification.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 977-981 
    ISSN: 0392-6737
    Keywords: General, theoretical, and mathematical biophysics (including logic of biosystems, quantum biology, and relevant aspects of thermodynamics, information theory, cybernetics, and bionics) ; Fluctuation phenomena, random processes, and Brownian motion ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We discuss a recently discovered mechanism for stochastic resonance which involves only a single reference state with excitable dynamics and deterministic reinjection. While calculations based on an analogy with the shot effect capture the broadest features, detailed comparisons with specific dynamical systems suggest the need for certain refinements of the theory.
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  • 179
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 893-902 
    ISSN: 0392-6737
    Keywords: Muscle contraction, nerve conduction, synaptic transmission, memorization, and other neurophysiological processes (excluding perception processes and speech) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary In the retina of the turtle, prolonged illumination of the receptive field surrond can lead to the appearance of sustained oscillatory responses in horizontal cells. In most cells the oscillations consist of a main component of 40–50 Hz frequency modulated by slower waves. The experimental evidence suggests that these responses are due to the activation of the feeback circuit linking cone photoreceptors and horizontal cells in the vertebrate retina.
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 949-958 
    ISSN: 0392-6737
    Keywords: General theoretical and mathematical biophysics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Noise effects on phase lockings in a system consisting of a piecewise-linear van der Pol relaxation oscillator driven by a periodic input are studied. The problem of finding the period of the oscillator is reduced to the first-passage-time problem of the Ornstein-Uhlenbeck process with time-varying boundary. Using the probability density functions of the first-passage time, the operator which governs a transition of an input phase density after one cycle of the oscillator is defined. Phase lockings in a stochastic sense are investigated on the basis of the density evolution by the operator.
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  • 181
    ISSN: 1432-069X
    Keywords: Epidermal malignancies ; Immunohistochemistry ; Human skin (experimental model) ; Neoplastic cells ; SCID mouse ; Xenografts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using a full-thickness skin grafting technique, lesional skin from various human neoplastic and preneoplastic skin diseases was transplanted onto SCID (severe combined immunodeficiency) mice. Of 27 grafted lesions, 21 were successfully accepted by the mice and maintained in good condition. All these accepted grafts were finally excised 10–101 days after transplantation for histological examination. In most grafts, the characteristic histological configurations of each disease were well preserved. Immunohistochemical study using monoclonal antibodies to human blood group antigens ABH revealed that some elements of the grafts such as sweat glands were clearly positive, confirming that the tissue was from human skin. Neoplastic (atypical) cells were detected in 9 of 17 accepted grafts containing neoplastic cells from the beginning. The detection rates for neoplastic cells were very high (90%) in grafts from precursor lesions of squamous cell carcinomas such as Bowen's disease (5/5 specimens) and thermal keratosis (2/3). In contrast, no definite neoplastic cells were found in two grafts from extramammary Paget's disease and five grafts from the radial growth component of malignant melanoma. In most of the grafts from latter two diseases, characteristic histological configurations such as elongation of the rete ridges were maintained, suggesting that the neoplastic cells were selectively eliminated from the grafts. Split-thickness grafts of normal human skin were accepted and remained in a good condition for as long as 6 months. Engraftment of human lesional and non-lesional skin onto SCID mice therefore may well provide a useful in vivo experimental model of human skin diseases.
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  • 182
    ISSN: 1432-069X
    Keywords: Peptide T ; Histological score ; Immunohistochemistry ; CD1+ dendritic cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ten patients with plaque-type psoriasis were treated with 2 mg peptide T i.v. for 28 days. Six patients responded with a substantial clinical improvement. Sequential biopsies from skin lesions were taken before, during and after treatment. The histological score (defining the activity of the psoriasis), the epidermal thickness and the number of infiltrating dermal lymphocytes were all reduced in the six patients who responded to the treatment. An increase in the number of CD1+ dendritic cells was detected immunohistochemically in the epidermis of the responders. The nonresponders did not display any pronounced changes.
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    Archives of dermatological research 287 (1995), S. 146-151 
    ISSN: 1432-069X
    Keywords: Immunohistochemistry ; Melanoma prognosis ; Tumour suppressor gene p53
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It is currently widely accepted that the tumour suppressor gene p53 is critically involved in the proliferation and differentiation of tumour cells including melanoma cells. In the present study, we examined 60 cases of primary melanoma to compare the expression of p53 protein with conventional prognostic markers for melanoma such as clinical and histological parameters. No correlation was found between the p53 protein and clinical factors except for the presence of a metastatic node and development to clinical stage II. However, the expression of p53 protein was significantly associated with tumour thickness over 1.5 mm, levels IV and V of invasion, the presence of ulceration, and high mitotic rate for 5-year survival rate. Although many questions still remain to be answered, our results and those of others for various other malignant tumours, implicate p53 in malignant transformation of pigment cells. Indeed, it could be a new marker for an unfavourable prognosis of malignant melanoma, even though the gene mutation in this highly lethal tumour has yet to be established.
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  • 184
    ISSN: 1432-069X
    Keywords: Cathepsins B, H, L and D ; Melanocytic tumour ; Biochemistry ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We carried out biochemical and immunohistochemical analyses of cathepsins B, H, L and D in human melanocytic tumours using monospecific antibodies against rat cathepsins. In Western blot analysis, anti-rat cathepsin antibodies reacted with the cathepsins from normal human tissues and human malignant melanoma. However, the molecular profiles of the cathepsins from human melanoma were slightly different from those of the rat cathepsins, suggesting a distinct intracellular processing mechanism for cathepsins in human melanoma. Although cathepsins B, H, L and D were expressed in primary and metastatic melanomas and pigmented naevi immunohistochemically, the intensity of staining in metastatic melanomas was stronger than in primary melanomas and pigmented naevi. These findings suggest that anti-rat cathepsin antibodies may be useful in biochemical and/or immunohistochemical analysis of human melanocytic tumours.
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  • 185
    ISSN: 1432-069X
    Keywords: Cell differentiation ; Pulse labelling ; Cell kinetics ; 5-Bromo-2-deoxyuridine ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Calcitriol (1α,25-dihydroxyvitamin D3) and its analogues are antiproliferative agents which promote epidermal differentiation in vitro, possibly reflecting their modes of action in the treatment of psoriasis. We examined the effect of calcitriol on early and late terminal differentiation in mouse epidermis in vivo using an immunofluorescence assay to detect keratin K1 and filaggrin expression. Pulse labelling with the tymidine analogue 5-bromo-2-deoxyuridine (BrdUrd) was performed by intraperitoneal injection of mice immediately or 16 h after a single topical application of 0.72 nmol calcitriol. The BrdUrd labelling index (LI) and keratin K1 or filaggrin expression of postmitotic cell cohorts were scored by paired immunofluorescence staining for up to 72 h after BrdUrd labelling. Calcitriol induced cell proliferation as shown by a 100% increase in the BrdUrd LI 17 h after application. The onset of keratin K1 expression in the postmitotic period was, however, unchanged in both series after calcitriol treatment. Filaggrin expression appeared earlier after calcitriol treatment than in control epidermis, probably reflecting altered cell kinetics with increased epidermal turnover. The results suggest that calcitriol only influences the later stages of the keratinocyte differentiation programme, possibly secondarily to its hyperproliferative effect.
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  • 186
    ISSN: 1432-1173
    Keywords: Schlüsselwörter Multiple ekkrine Spiradenome ; Dermales Zylindrom ; Multiple Trichoepitheliome ; Immunhistochemie ; Key words Multiple eccrine spiradenomata ; Dermal cylindroma ; Multiple trichoepitheliomata ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A case of multiple eccrine spiradenomata is reported. One of the tumours was histopathologically associated with dermal cylindroma, and immunohistochemical studies showed that the cylindroma cells differentiate towards the secreting portion of the eccrine sweat gland. The relationship among multiple eccrine spiradenomata, dermal cylindroma and multiple trichoepitheliomata is discussed.
    Notes: Zusammenfassung Es wird über eine 46jährige Patientin mit multiplen ekkrinen Spiradenomen berichtet. Es zeigte sich hierbei histopathologisch die Assoziation mit einem dermalen Zylindrom. Immunhistochemisch zeigte das Zylindrom eine Differenzierung in Richtung auf den sezernierenden Teil der ekkrinen Schweißdrüsen. Der Zusammenhang zwischen multiplen ekkrinen Spiradenomen und dermalen Zylindromen sowie multiplen Trichoepitheliomen wird besprochen.
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    Experimental brain research 107 (1995), S. 9-16 
    ISSN: 1432-1106
    Keywords: Sympathetic preganglionic neurons ; Oxytocin ; Cholera toxin ; Immunohistochemistry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A combination of retrograde cell body labeling and immunohistochemistry was employed to elucidate how oxytocinergic fibers make contact with sympathetic preganglionic neurons (SPNs) in the rat spinal cord from T1 to T4. SPNs were labeled retrogradely using cholera toxin subunit B (CTb) or horseradish peroxidase-conjugated CTb. Oxytocin-immunoreactive (ir) fibers were found in the intermediate zone, including the sympathetic preganglionic subnuclei. In the central autonomie nucleus and the intercalated nucleus, brown-stained oxytocin-ir varicosities or terminals were frequently observed to stud black-stained dendrites of SPNs. Electron microscopical observations showed that oxytocin-ir terminals form synapses with dendrites or soma of the sympathetic preganglionic neurons. The terminals contained numerous small clear round vesicles and a few large, cored vesicles. These results clearly show that a large proportion of SPNs are innervated by oxytocin-containing fibers. The origin of these fibers is discussed, and it is concluded that they are probably descending fibers from the paraventricular nucleus of the hypothalamus.
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  • 188
    ISSN: 1432-1106
    Keywords: Platelet-derived growth factor ; Receptors ; Facial nerve ; Immunohistochemistry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the expression of platelet-derived growth factor (PDGF) and its receptors in rat facial nuclei following axotomy by in situ hybridization and immunohistochemistry. Facial nuclei were examined on days 3, 6, 12, 19 and 26 postoperatively (p.o.). Strong immunoreactivity for PDGF was found in facial neurons and surrounding astrocytes on the ipsilateral side of the brainstem already after 3 days p.o. and persisted at a high level until day 26 p.o. in rats with a facial nerve cut injury. After crushing of the facial nerve, a similar increase was seen in PDGF immunoreactivity which, however, decreased after day 19 p.o., when reinnervation had occurred. Reactive gliosis appeared on the operated side and was confirmed by an increase in intensity of GFAP staining. The kinetics of PDGF A-chain mRNA expression corresponded to the PDGF immunoreactivity, whereas the B-chain mRNA was present only in the neurons. The PDGF α-receptor immunoreactivity as well as the mRNA were detected in scattered glial cells. The density of the PDGF α-receptor mRNA expressing glial cells was higher on the injured side, but the intensity of the expression per cell did not change after axotomy. An increase in PDGF β-receptor immunoreactivity was seen in the ipsilateral facial nuclei after 3–6 days p.o., however, the increase in the mRNA could not be detected. The staining persisted until day 26 p.o., when transected facial neurons showed heavier staining than those that had been crushed. Furthermore, both mRNA and protein of the β-receptor were expressed in the blood vessels after 3–6 days p.o., increasing with time. These results imply a role for PDGF in the regeneration process following nerve injury.
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  • 189
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Knochen- und Knochenmarkbiopsien ; Histotechnologie ; Knochenmarkeisen ; Enzymhistochemie ; Immunhistochemie ; Key words Bone and marrow biopies ; Histotechnology ; Iron in bone marrow ; Enzyme histochemistry ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A survey is given of methods involving decalcification and paraffin embedding of iliac crest biopsy for osteological and haematological diagnostic procedures. In order to avoid shrinkage, loss of antigens, and fading of ferritin iron and enzymes, a fixative has been designed that is composed of an aqueous solution of calcium acetate (10–1 M), glutaraldehyde (0.5 %), and formaldehyde (1 %; CGF). CGF-fixated specimens are decalcified in an aqueous solution of 10 % di-sodium ethylene-diaminotetraacetate (EDTA) neutralized by tris[hydroxy]methyl-aminomethane and embedded in paraffin. Tissue prepared in this manner allows histochemical detection of naphthol AS-D chloroacetate esterase in the neutrophilic cell line and in tissue mast cells, tartrate-resistant acid phosphatase in hairy cells and certain other low malignant B-cell lymphomas, in Gaucher cells, and in osteoclasts, and a specific platelet esterase in megakaryocytes and leukaemic megakaryoblasts. A broad panel of antigens is well preserved. Beside haemosiderin, cytosolic ferritin can be detected by Perls' reaction in acute phase-stimulated macrophages. Emphasis is placed on the diagnostic impact of plasma cell siderosis and lysosomal sideroblastocytosis in haemochromatosis and in alcoholism respectively. A technique is presented to discriminate mineralized and non-mineralized bone even after decalcification.
    Notes: Zusammenfassung Beckenkammbioptische Untersuchungen erfordern eine problemorientierte histologische Bearbeitungstechnik. Alternativ stehen Verfahren der Kunststoffeinbettung unentkalkten Gewebes einer Paraffineinbettung nach Entkalkung gegenüber. Die Paraffineinbettung setzt die Fixierung in einer Lösung aus Kalziumazetat, Glutaraldehyd und Formaldehyd (KGF) sowie eine neutrale Chelatentkalkung voraus. Die KGF-Fixation vermeidet jegliche Hämolyse, bewirkt eine gute zelluläre Strukturerhaltung und garantiert den Nachweis von Ferritineisen in Markretikulumzellen. Die Unterscheidung von Ferritin- und Hämosiderineisen ist für die Differentialdiagnose von Anämien essentiell. Unter den extraphagozytären Eisenablagerungen verdienen lysosomale Siderosomen in Erythrozyten und Erythroblasten bei alkoholischer Dysmyelopoese sowie die Plasmazellsiderose bei Hämochromatose Beachtung. Eine breite Palette (immun)histochemischer Techniken wird tabellarisch dargestellt. Die Naphthol-AS-D-Chlorazetatesterase läßt sich in der neutrophilen granulozytopoetischen Zellreihe und Gewebsmastzellen darstellen und dient in einer speziellen Modifikation zur Darstellung mineralisierter Knochenstrukturen nach Entkalkung. Tartratresistente saure Phosphatase markiert Osteoklasten in unterschiedlichen Funktionszuständen, Gaucher-Zellen und bestimmte Lymphome. Als weiteres einbettungsresistentes Enzym wird erstmals die spezifische Plättchenesterase vorgestellt.
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  • 190
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    Der Pathologe 16 (1995), S. 106-119 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Maligne Lymphome ; Fokale reaktive lymphoide Hyperplasie ; Knochenmark ; Differentialdiagnose ; Histotopographie ; Fasergehalt ; Immunhistochemie ; Key words Malignant lymphomas ; Reactive lymphoid hyperplasia ; Bone marrow ; Differential diagnosis ; Histotopography ; Fiber content ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The purpose of this study was to provide criteria for the differentiation of reactive lymphoid hyperplasia (RLH) and focal involvement of the bone marrow by malignant lymphoma (ML). Using trephine bone-marrow biopsy specimens embedded in paraffin wax and unequivocally established samples with ML for comparison, all patients with questionable lymphoid or lymphohistiocytic marrow aggregates were re-examined, together with obviously reactive lesions. Following this procedure, a number of characteristics were found that differed in validity with regard to diagnosis. In addition to cytology, which is preferably assessed in Giemsa-stained specimens and evaluated by the Kiel classification, histotopography, fiber content, and immunohistochemical reactions are the most valuable tools for differential diagnosis. RLH is consistent with a central-perivascular localization, a distinctive border and the presence of germinal centers, no or only minimal reticulin fibrosis and a polyclonal reaction pattern with a mixed population of B- and T-lymphocytes, following staining with appropriate antibodies. In uncertain cases (i. e., extensive lymphoproliferations in HIV-myelopathy) the results of immunohistochemical staining are of definite importance for the diagnostic evaluation of these lesions.
    Notes: Zusammenfassung Die vorliegende Studie verfolgt das Ziel, Kriterien für die differentialdiagnostische Abgrenzung zwischen fokaler reaktiver lymphatischer Hyperplasie (RLH) und nodulären Infiltraten von malignen Lymphomen (ML) im Knochenmark festzulegen. Im Vergleich zu klinisch und histologisch gesicherten Fällen von ML und offensichtlich reaktiven Veränderungen wurden alle in ihrer diagnostischen Zuordnung fraglichen lymphoiden bzw. lymphohistiozytären Läsionen anhand von Beckenkammbiopsien nach Paraffineinbettung noch einmal untersucht. Als wesentliches Ergebnis konnte eine Reihe von diagnostischen Merkmalen herausgearbeitet werden, die allerdings von sehr unterschiedlicher Wertigkeit waren. Neben der Zytologie, welche besonders gut in nach Giemsa gefärbten Präparaten auswertbar ist und sich problemlos nach den entsprechenden Maßgaben der Kiel-Klassifikation zuordnen läßt, sind Histotopographie, Fasergehalt und Immunhistochemie von besonderer nosologischer Bedeutung. Für eine RLH sprechen eine zentral-perivaskuläre Lokalisation mit scharfer Abgrenzung sowie Keimzentren, keine oder allenfalls eine minimale Retikulinfibrose sowie schließlich nach Anwendung immunhistochemischer Verfahren ein polyklonales Reaktionsmuster mit einer Mischpopulation aus B- und T-Lymphozyten. Im Zweifelsfall (z. B. bei ausgedehnter Lymphoproliferation im Rahmen einer HIV-Myelopathie) ist alleine die Immunhistochemie in der Lage, diagnostisch wegweisende Anhaltspunkte zu geben.
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  • 191
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    Der Pathologe 16 (1995), S. 245-255 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter WHO-Klassifikation der Gehirntumoren ; Gradierung ; Immunhistochemie ; Proliferationsbestimmung ; Molekulargenetik ; Key words WHO classification of brain tumors ; Grading ; Immunohistochemistry ; Proliferation markers ; Molecular genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In recent years there has been considerable progress in brain tumor neuropathology. Several new diagnostic entities have been recognized, subclassification schemes have been modified, and new concepts on the histogenesis and cell biology of brain tumors have emerged. In 1993, a revised WHO classification of brain tumors was published by an international committee. This article summarizes the pertinent new aspects. As novel tumor entities, the central neurocytoma, the dysembryoplastic neuroepithelial tumor (DNT), desmoplastic infantile ganglioglioma (DIG) and pleomorphic xanthoastrocytoma (PXA) have been included. Several histopathological variants of meningiomas have been added of which only the papillary meningioma and the atypical meningioma are characterized by an increased rate of recurrence. Meningeal hemangiopericytomas and hemangioblastomas are classified as tumors of non-meningothelial origin. The glioblastoma multiforme, which had previously been listed as an embryonal tumor, is now recognized as an astrocytic glioma. Immunohistochemistry has greatly advanced the practical diagnosis and classification of brain tumors. There are specific markers for all normal and neoplastic cell types except for oligodendroglioma cells. The prognosis of and therapeutic approaches to brain tumors greatly depend on histopathological grading. The WHO proposes four tumor grades, i. e., I, II, III, and IV. As a rule, grades I and II tumors are viewed as benign or semi-benign neoplasms and grades III and IV tumors as malignant. There are attempts to use new biological parameters for the grading of brain tumors. Antibodies to proliferation-associated proteins reflect tumor growth. Molecular genetic approaches to tumor-associated genes and gene loci are particularly promising new tools for the future.
    Notes: Zusammenfassung Ein internationales Gremium hat 1993 eine revidierte Fassung der WHO-Klassifikation von Tumoren des Zentralnervensystems vorgelegt. Wesentliche Neuerungen sind die Einführung folgender Entitäten: Zentrales Neurozytom, dysembryoplastischer neuroepithelialer Tumor (DNT), desmoplastisches infantiles Gangliogliom (DIG) und pleomorphes Xanthoastrozytom. Bei den Meningeomen wurden eine Reihe von neuen histopathologischen Varianten aufgenommen. Das Glioblastom wird aufgrund seiner immunhistochemisch nachweisbaren GFAP-Expression nun den astrozytären Gliomen zugeordnet. Immunhistochemische Reaktionen haben wesentliche Fortschritte in der Diagnostik und Klassifikation von zentralnervösen Tumoren gebracht. In der Diagnostik zentralnervöser Tumoren spielt die histopathologische Gradierung eine besondere Rolle, da sie als Grundlage für die weitere Behandlung und prognostische Bewertung dient. Die WHO schlägt eine Gradierungsskala vor, welche die 4 Dignitätsgrade I, II, III und IV vorsieht. Als wesentliche histopathologische Parameter fließen Differenzierungsmerkmale der Tumorzellen, die Zelldichte, zelluläre und nukleäre Polymorphie, mitotische Aktivität, pathologische Endothelproliferate und Tumorgewebsnekrosen in die Bewertung ein. Bei der Gradierung zentralnervöser Tumoren wird in zunehmendem Maße versucht, neben histopathologischen Kriterien neue biologische Parameter einzusetzen.
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  • 192
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Mammakarzinom ; Hormonrezeptoren ; Immunhistologie ; Key words Breast cancer ; Hormone receptors ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary For evaluation of the hormone receptor status in breast cancer tissues two methods are mainly used: immunohistochemical detection by monoclonal antibodies on frozen sections (ER-ICA, PgR-ICA) and the biochemical radioligand-binding assay (DCC) of fresh tissue. Using new antibodies makes it possible to evaluate the estrogen and progesterone receptor status in formalin-fixed and paraffin-embedded tissue. In the present retrospective study, tissues from 223 primary breast carcinomas or breast carcinoma recurrences were reevaluated with the three methods mentioned above and the results were compared. We used antibody 1D5.26 reacting with the estrogen receptor and mPR1 specific for the progesterone receptor in paraffin-embedded tissue. The agreement of positive and negative cases between these two immunohistochemical procedures was 97.8 % for the estrogen receptor and 85.7 % for the progesterone receptor. Comparison of immunohistochemistry on paraffin-embedded tissue and biochemical evaluation showed an agreement of 74.7 % for the estrogen receptor and 68.7 % for the progesterone receptor. These results are comparable to the correspondence between ER-ICA and PgR-ICA and the DCC method. This study proves that the prognostically and therapeutically important hormone receptors can be reliably determined in formalin-fixed and paraffin-embedded tissues. These results are not only important for the evaluation of hormone receptors of a small breast carcinoma that is not found in the frozen section, but for the considerable difference in costs among the different methods.
    Notes: Zusammenfassung Zur routinemäßigen Bestimmung der Hormonrezeptoren am Mammakarzinomgewebe werden derzeit hauptsächlich 2 Verfahren verwendet: Die immunhistologische Detektion am Gefrierschnitt (ER-ICA und PgR-ICA) sowie die biochemische Rezeptoranalyse am Frischgewebe mit dem Radioliganden-Bindungs-Assay (DCC). Durch neue Antikörper ist jetzt die Rezeptorbestimmung an formalinfixiertem, in Paraffin eingebetteten Gewebe möglich. An 223 primären Mammakarzinomen und Mammakarzinomrezidiven wurden die Ergebnisse aller 3 Verfahren miteinander verglichen. Verwendet wurden die paraffingängigen Antikörper 1D5.26 gegen den Östrogenrezeptor (Fa. Immunotech, Hamburg) und mPR1 gegen den Progesteronrezeptor (Fa. Dianova, Hamburg). Die Übereinstimmung der positiven bzw. negativen Fälle in der Immunhistologie betrug 97,8 % für den Östrogen- und 85,7 % für den Progesteronrezeptor. Der Vergleich der Immunhistologie am Paraffinmaterial mit der Biochemie ergab eine Übereinstimmung für den Östrogenrezeptor von 74,7 % und für den Progesteronrezeptor von 68,7 %. Diese sind vergleichbar mit denen für ER-ICA und PgR-ICA gegenüber der Biochemie. Die Untersuchungen zeigen, daß die prognostisch und therapeutisch wichtigen Hormonrezeptoren auch an formalinfixiertem und in Paraffin eingebetteten Mammakarzinomgewebe immunhistologisch zuverlässig bestimmt werden können. Diese Ergebnisse sind zum einen wegen der Möglichkeit der Untersuchung eines nicht im Schnellschnitt gefundenen Karzinoms von großer Bedeutung, zum anderen bestehen deutliche Kostenunterschiede zwischen den verschiedenen Verfahren.
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  • 193
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Mammakarzinom ; uPA ; Immunhistochemie ; Prognose ; Key words Breast cancer ; uPA ; Immunohistochemistry ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary There is ample evidence that the protease urokinase plasminogen activator (uPA) plays a role in invasion and spread of tumours. Several publications suggest its biochemical measurement in tumour cytosols to be of prognostic significance in breast carcinomas. Our study set out to determine whether the immunohistochemical detection of uPA in formalin-fixed, paraffin-embedded primary breast cancer tissues is of prognostic relevance. We tested 269 surgical specimens of primary ductal infiltrating carcinoma immunohistochemically using a modified avidin-biotin method. Some 57 % of carcinoma specimens yielded specific positive staining in tumour cells. Detection of uPA correlated to tumour grade (P = 0.04), and to the detected level of the proliferation marker PCNA (P = 0.002), but not to patients' age or menopausal status, tumour size, nodal or steroid receptor status (P 〉 0.05). At median 68 months' follow-up, 34 % of patients had experienced tumour relapse and 28 % had died from cancer. Clinical course was correlated significantly to tumour size, tumour grade, nodal and steroid hormone receptor status (P 〈 0.05). Immunohistochemical detection of uPA, however, could not be demonstrated to be of any prognostic significance with regard to relapse-free or overall survival (P 〉 0.05) in the total study group or in the N0 (n = 120) and N + (n = 144) subgroups, regardless of whether univariate or multivariate analysis was applied.
    Notes: Zusammenfassung Die Protease Urokinase-Plasminogen-Aktivator (uPA) spielt bei der Invasion und Ausbreitung von Tumoren eine Rolle. Für die prognostische Bedeutung des biochemischen Nachweises von uPA in Mammakarzinomen gibt es umfangreiche Hinweise. Ziel unserer Studie war die Frage, inwieweit der immunhistochemische Nachweis von uPA am Paraffinschnitt Aussagen zur Prognose von Patientinnen mit primärem Mammakarzinom liefert. Wir untersuchten die Expression von uPA an 269 Geweben primärer Mammakarzinome (infiltrierende duktale Karzinome) immunhistochemisch mit einer modifizierten Avidin-Biotin-Methode. Eine positive Reaktion in Tumorzellen zeigten 57 % der Mammakarzinome. Der uPA-Nachweis korrelierte zum histologischen Grading (p = 0,04), sowie zum Proliferationsmarker PCNA (p = 0,002). Keine Beziehungen zeigte sich zum Alter oder Menopausenstatus der Patientinnen, zur Tumorgröße oder zum Lymphknoten- oder Steroidhormonrezeptorstatus (p 〉 0,05). Die mediane Nachbeobachtungszeit der Patientinnen beträgt derzeit 68 Monate. 34 % der Patientinnen erlitten ein Rezidiv und 28 % verstarben am Tumorleiden. Der klinische Verlauf korrelierte signifikant zu Tumorgröße, Lymphknotenbefall, Grading und Steroidhormonrezeptorstatus (p 〈 0,05). Demgegenüber zeigte der immunhistochemische Nachweis von uPA keine Korrelation zum rezidivfreien oder zum Gesamtüberleben (p 〉 0,05). Letzteres gilt sowohl für das Gesamtkollektiv, als auch für die Untergruppen der N0- (n = 120) und N +- (n = 144) Patienten. Ebensowenig erbrachte die Multivarianzanalyse für uPA eine signifikante Beziehung zur Prognose (p 〉 0,05).
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  • 194
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Knochenmarkhistologie ; Kunststoffeinbettung ; Methylmethacrylat ; Immunhistochemie ; Key words Bone marrow histology ; Plastic embedding ; Methyl-methacrylate ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A patented low-temperature polymerization method for methylmethacrylate (MMA) infiltrated bone marrow biopsies is described: it has been developed from our previous MMA technique and is a patented procedure. Differences from the previous method are (1) removal of stabilizer from the MMA monomer before its application, (2) the use of a different starter, (3) avoidance of O2 influence during polymerization by means of vacuum exchange with N2, and (4) polymerisation in a water bath to draw off residual heat. After this procedure, all immunohistochemical reactions are possible provided that the previous fixation is adequate. The effects of different fixatives are reviewed briefly without detailed analysis. Technically, this plastic embedding can be performed at least as rapidly as the classic paraffin embedding after decalcification. The advantages over the latter method are: (1) the cells can be better differentiated because semi-thin sections can be made; (2) the immunoreactions can also be performed on the basis of semi-thin sections, which means they can be interpreted more easily; (3) morphometric analyses yield more reliable results because of the constant thickness of sections; (4) osteological examination of bone trabeculae, especially the search for mineralisation deficiencies, is possible; (5) the plastic embedding procedure is less dependent on individual instabilities in the quality of performance of the staff members involved. Furthermore, it is worth mentioning that the costs for additional equipment necessary remain below DM 100,000 including an excellent microtome.
    Notes: Zusammenfassung Eine patentierte Methode zur Einbettung von Knochenmarkbiopsien durch Kaltpolymerisation von Methylmethacrylat (MMA) wird beschrieben, die als patentiertes Verfahren aus unserer bisherigen MMA-Technik entwickelt worden ist. Die Unterschiede zum bisherigen Verfahren sind die Destabilisierung des Monomers Methylmethacrylat, die Verwendung eines anderer Starters, der Ersatz von Raumluft durch Stickstoff vor der Polymerisation und die Polymerisation unter Restwärmeabführung im Wasserbad. Danach sind alle immunhistochemischen Reaktionen an Zellen und Geweben möglich, vorausgesetzt, daß in geeigneter Form fixiert worden ist. Auf die Unterschiede der Fixierungslösungen wird kurz eingegangen, ohne sie detailliert zu analysieren. Technisch läßt sich diese Kunststoffeinbettung mindestens ebenso schnell wie die Entkalkung und Paraffineinbettung durchführen. Die Vorteile gegenüber dem Entkalkungs-Paraffinierungs-Verfahren sind, daß• die Zellen besser zu differenzieren sind, weil Semidünnschnitte angefertigt werden können, • die Immunreaktionen ebenfalls am Semidünnschnittpräparat durchgeführt und die Reaktionsergebnisse deshalb leichter zugeordnet werden können, • morphometrische Analysen wegen der konstanten Schnittstärke zuverlässigere Werte ergeben und • osteologische Untersuchungen, insbesondere die Beurteilung von Mineralisationsstörungen, möglich sind. Ein fünfter Vorteil ist, daß das Kunststoffverfahren unempfindlicher gegenüber subjektiven Leistungsschwankungen der beteiligten Mitarbeiter ist. Die zusätzlich notwendigen Geräteinvestitionen liegen unter DM 100 000.–, worin ein optimales Mikrotom, z. B. Polycut, eingeschlossen ist.
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  • 195
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Thymom ; Hamartom ; Weichteilgewebe ; Immunhistochemie ; Key words Thymoma ; Hamartoma ; Soft tissue ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We report the case of an ectopic hamartomatous thymoma in a 56-year-old male patient. The lesion arose subcutaneously in the supraclavicular region. Histologically, the well-circumscribed but unencapsulated tumour was composed of uniform fusiform tumour cells. In addition, mature fatty tissue, scattered T-lymphocytes, and an epithelial and a myoepithelial tumour cell component were found. The epithelial differentiation of the spindle cell tumour component was confirmed immunohistochemically and by electron microscopy. Ectopic hamartomatous thymoma has to be distinguished from ectopic cervical thymoma, thymolipoma, ectopic salivary tissue, teratoma, peripheral nerve sheath tumours, malignant epithelial tumours with thymus-like differentiation, biphasic synovial sarcoma, and skin adnexal tumours.
    Notes: Zusammenfassung Vorgestellt wird der Fall eines ektopischen hamartomatösen Thymoms bei einem 56 jährigen männlichen Patienten. Der subkutan gelegene, gut umschriebene, jedoch nicht gekapselte Tumor war supraklavikulär lokalisiert und aus relativ uniformen, spindeligen Tumorzellen aufgebaut. Zusätzlich fanden sich reife Fettgewebsinseln, eingestreute T-Lymphozyten sowie eine epitheliale und eine myoepitheliale Tumorzellkomponente. Sowohl immunhistologisch als auch ultrastrukturell konnte die epitheliale Differenzierung der spindeligen Tumorzellen nachgewiesen werden. Differentialdiagnostisch muß das ektopische hamartomatöse Thymom gegenüber ektopischen zervikalen Thymomen, Thymolipomen, ektopischem Speicheldrüsengewebe, Teratomen, peripheren Nervenscheidentumoren, malignen epithelialen Tumoren mit einer thymusähnlichen Differenzierung, biphasischen Synovialsarkomen und Tumoren der Hautadnexe abgegrenzt werden.
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  • 196
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    Der Pathologe 16 (1995), S. 94-105 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Glykoprotein ; Kohlenhydratantigen ; Karzinom ; Adenom-Karzinom-Sequenz ; Immunhistochemie ; Key words Glycoprotein ; Carbohydrate antigen ; Carcinoma ; Adenoma-carcinoma sequence ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Mucins are heavily glycosylated glycoproteins which exhibit a variety of antigenic determinants consisting of carbohydrates and/or peptide sequences. The application of monoclonal antibodies and lectins in immunohistochemistry resulted in a considerable extension of knowledge regarding their topography during histogenesis. Additionally, typical alterations of antigenic profiles during neoplastic transformation of cells and tissues were described. A number of new results are in keeping with the assumption that mucin-associated antigens play an important role in tumor biology, for example metastasis, and as markers of prognosis. The purpose of the present paper is to give a review, including the authors' own results, of knowledge on the gastrointestinal mucin antigens in experimental and clinical pathology.
    Notes: Zusammenfassung Muzine sind stark glykosylierte Glykoproteine, die eine Vielzahl aus Kohlenhydraten und/oder Peptidsequenzen bestehender antigener Determinanten aufweisen. Die Verwendung von monoklonalen Antikörpern und Lektinen in der Immunhistochemie erbrachte umfangreiche Erkenntnisse über deren Topographie im Rahmen der Histogenese. Zudem konnten typische Veränderungen der Antigenprofile während der neoplastischen Transformation von Zellen und Geweben beschrieben werden. Eine Reihe neuerer Ergebnisse deutet ferner darauf hin, daß muzinassoziierte Antigene eine bedeutende Rolle in der Tumorbiologie, beispielsweise bei der Metastasierung und als Prognosemarker spielen. Die vorliegende Arbeit gibt unter Einschluß eigener Befunde eine Übersicht über die gastrointestinalen Muzinantigene in der experimentellen und klinischen Pathologie.
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  • 197
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    Experimental brain research 104 (1995), S. 177-190 
    ISSN: 1432-1106
    Keywords: Neuropeptides ; Basal ganglia ; Immunohistochemistry ; Haloperidol ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to further investigate the neurochemical anatomy of the primate nucleus accumbens (NAC), the distributions of the neuropeptides leucine-enkephalin (Leu-ENK), neurotensin (NT), and substance P (SP) and of haloperidol-induced c-fos expression were investigated in the macaque monkey using immunohistochemical methods. To define the boundaries of the NAC, dopamine (DA) and tyrosine hydroxylase (TH) immunohistochemistry was performed. In addition, to formulate the distinction between subdivisions of the nucleus accumbens, immunohistochemistry for calbindin-D28 (CBD) and SP was employed. In general, the medial part of NAC, which consisted of small to medium-sized cells, was low for CBD immunoreactivity and moderate to high for SP immunoreactivities, while the dorsolateral part, which was composed of small cells, showed the opposite pattern of immunostaining for CBD and SP. Many Leu-ENK-immunoreactive perikarya were observed in the dorsal NAC at its middle and caudal levels. There were moderate densities of Leu-ENK-positive fibers throughout the medial part of the NAC. At the dorsolateral margin of the NAC, Leu-ENK-positive fibers formed patches. Most NT-positive perikarya were found in the dorsolateral subdivision. SP-positive perikarya were scarce in the NAC. Dense distribution of NT-and SP-containing fibers or puncta were observed in the mediodorsal part (medial subdivision), where a dense field of DA-immunoreactive fibers was observed. The ventral part (ventral subdivision) contained moderate numbers of NT- and SP-immunoreactive fibers. Haloperidol-induced c-fos expression was very extensive in the medial half of NAC, particularly in the mediodorsal region, which overlapped with the DA- and peptide-rich region. The present study indicates that the NAC of the primate can be subdivided into at least three subterritories, the dorsolateral, medial and ventral subdivision, by neuropeptide histochemistry as well as by the response of its constituent neurons to haloperidol.
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  • 198
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 104 (1995), S. 207-217 
    ISSN: 1432-1106
    Keywords: Nitric oxide synthase ; Retina ; Immunohistochemistry ; Rat ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The distribution of neuronal nitric oxide synthase (NOS) immunoreactivity was examined in rat and rabbit retinas and was compared with the distribution of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reactivity and vasoactive intestinal peptide (VIP) immunoreactivity. An antibody raised against a C-terminal fragment of a cloned rat cerebellar NOS was used to localise NOS immunoreactivity. NOS immunoreactive cells were not detected in rat retinas at postnatal day 1 or 4, but were seen from postnatal day 7 onwards. NOS immunolabelling was seen in a small population of cells in the proximal inner nuclear layer. Most of the labelled cells had the position of amacrine cells and were seen to send processes into the inner plexiform layer. A few labelled cells were at times also seen in the ganglion cell layer, which are likely to correspond to displaced amacrine cells. The same NOS-labelling pattern was seen in rat and rabbit retinas. NADPH-diaphorase staining was observed in both species, in photoreceptor inner segments, in cells with the position of horizontal cells, in a subset of amacrine and displaced amacrine cells, in large cell bodies in the ganglion cell layer, in both plexiform layers, and in endothelium. Colocalisation of NOS immunoreactivity and NADPH-diaphorase staining was only observed among amacrine cells. However, not all NADPH-diaphorase-reactive amacrine cells were found to be NOS immunoreactive. VIP immunoreactivity was also localised in rat retinas in a subpopulation of amacrine cells, but no colocalisation of NOS and VIP immunoreactivity was observed. Our observations indicate that only amacrine cells contain the NOS form recognisable by the antibody used, and suggest that different isoforms of neuronal NOS may be present in retinal cells. Further, the onset of NOS expression in rat amacrine cells appears to occur independently of neuronal activity.
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  • 199
    ISSN: 1432-0711
    Keywords: Key words: p53 ; Breast cancer ; Immunohistochemistry ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract.  In a retrospective study, 204 formalin-fixed and paraffin-embedded biopsies of primary breast carcinomas were tested immunohistochemically for the expression of p53 protein (PAb 1801). 38% of the carcinomas were positive with respect to p53. The expression of p53 correlated significantly with the loss of tumor differentiation (P = 0.013), but not with menopausal status, patients' age, tumor size, axillary lymph node involvement or hormone receptor status. The influence of p53 expression on prognosis was evaluated in 197 patients (T1–4 N0–2 M0, median observation time 72 months). Detection of p53 protein was associated with a significantly longer disease-free survival in node-positive women (P = 0.03). However, p53 protein did not prove to be a prognostic factor in node-negative patients. The results demonstrate the prognostic value of p53 expression in breast cancer which appears to be limited to patients with node-positive tumors.
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  • 200
    Electronic Resource
    Electronic Resource
    Springer
    Archives of gynecology and obstetrics 258 (1995), S. 47-53 
    ISSN: 1432-0711
    Keywords: Key words: Malignant mixed Müllerian tumors (MMMT) ; Fallopian tube ; Homologous type ; Immunohistochemistry ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Four out of 42 cases of primary tubal malignancy diagnosed in our histopathological laboratory were malignant mixed Müllerian tumors (MMMT). All four patients were postmenopausal with a mean age of 66.5 years at diagnosis. A correct preoperative diagnosis was made only in one case. Tumor staging (FIGO) revealed stage IIa, IIIc and IV. One patient died of postoperative pulmonary embolism, a second patient of an unknown cause five month after surgery and a third patient died of disease after 11 months with secondary deposits in pelvic peritoneum, omentum and paraaortic lymph nodes. The fourth patient is still alive. One patient received chemotherapy alone, one by radiation and chemotherapy and two patients by radiation alone. Tumor spread at the time of diagnosis and the residual tumor volume were the most important prognostic factors. All tumors were histologically the homologous type of MMMT (carcinosarcomas). No heterologous elements were found. Metastatic tumors showed only sarcomatous elements.
    Type of Medium: Electronic Resource
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