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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 10 (1983), S. 129-142 
    ISSN: 1432-1017
    Keywords: Photoreceptor noise ; Phototransduction ; Tetrodotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Voltage noise analysis was performed on membrane potentials recorded from the photoreceptor cells of the honeybee drone. Voltage power spectra showed an increase in noise amplitude on passing from the dark to moderate light; with strong light noise fell to near the dark level. At intermediate light intensities the noise was reduced by application of tetrodotoxin. The probable effects on the power spectra of electrical coupling between cells are discussed. It is tentatively estimated that the unitary event in weak light is a conductance increase of 20 pS. The results are compared with previous results from photoreceptors of other species that appear to be specially adapted to weaker illuminations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 183-220 
    ISSN: 0392-6737
    Keywords: Quantum optics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Studiamo lo spettro di «schiacciamento» della luce trasmessa da un sistema atomico a due livelli in una cavità ottica pompata da una radiazione coerente come recentemente osservato da Kimble e collaboratori. La nostra analisi non introduce alcuna limitazione nei parametri di fuori-risonanza o negli ordini di grandezza relativi delle velocità di rilassamento dell'atomo e della cavità. Usando il formalismo «a modi vestiti», deriviamo espressioni analitiche esplicite dello spettro di «schiacciamento» e della funzione di correlazione al 2° ordine dell'intensità. Descriviamo la dipendenza dello spettro da vari parametri del sistema; questo studio fornisce indicazioni generali su come ottimizzare le condizioni di osservazione dello «schiacciamento» nella bistabilità ottica. Un'attenzione particolare è dedicata alle modifiche dello spettro duvote alla variazione dei parametri di fuori risonanza o del rapporto tra velocità di smorzamento dell'atomo e della cavità. In tutti i casi, le variazioni sono continue, con variazioni quantitative nel livello di «schiacciamento». Ciò indica l'esistenza di un'unica via per lo «schiacciamento» in questo sistema. La condizione di cavità cattiva è identificata come specialmente conveniente per ottenere una notevole quantità di «schiacciamento».
    Abstract: Резюме Мы исследуем спектр сжатия, который наблюдался Кимблом и сотрудниками, при прохождении света через систему двух-уровневых атомов в оптическом резонаторе, который управляется когерентным полем. Наш анализ не накладывает никаких ограничений на параметры расстройки или на относительный порядок величины атомной и резонаторной скоростей релаксации. Используя формализм «одетых» мод, мы выводим точные аналитические выражения для спектра сжатия и для функции корреляции интенсивности второго порядка. Мы описываем зависимость спектра от различных параметров системы. Наше исследование позволяет оптимизировать условия наблюдения сжатия в оптической бистабильности. Особое внимание уделяется изменениям спектра при вариации параметров расстройки или отношения интенсивностей резонаторного и атомного затуханий. Во всех случаях изменения являются непрерывными и плавными при количественных вариациях уровня сжатия. Этот результат указывает на существование единственного пути к сжатию в этой системе. Определяется направление особенно удобное для получения существенной величины сжатия.
    Notes: Summary We study the spectrum of squeezing in the light transmitted by a system of two-level atoms in an optical cavity driven by a coherent field, as recently observed by Kimble and collaborators. Our analysis does not introduce any restriction on the detuning parameters or on the relative order of magnitude of the atomic and cavity relaxation rates. Using the dressed-mode formalism, we derive explicit analytic expressions for the spectrum of squeezing and for the second-order intensity correlation function. We describe how the spectrum depends on the various parameters of the system; this study provides general indications on how to optimize the conditions to observe squeezing in optical bistability. A special attention is devoted to the changes of the spectrum under variation of the detuning parameters or of the ratio of cavity to atomic-damping rate. In all cases, the changes are continuous and smooth, with quantitative variations in the level of squeezing. This indicates the existence of a single avenue to squeezing in this system. The bad-cavity direction is identified as especially conventient to obtain a significant amount of squeezing.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Instruments and Methods 59 (1968), S. 136-140 
    ISSN: 0029-554X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Optics Communications 69 (1989), S. 414-418 
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Optics Communications 69 (1989), S. 419-424 
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 53 (1983), S. 63-69 
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A quantum Ising-like spin-1 model characterized by quadrupolar interaction, coupled to an external anisotropic field with both dipole and quadrupole momenta is analyzed. The general phase diagram (including temperature), as well as order parameter, specific heat, and susceptibility are evaluated in the mean-field approximation and exibit a rich structure with transitions of 2° and 1° order and tricritical points. ForT=0 the phase diagram is examined also by a recently formulated improved version of mean-field theory which has the usual mean-field theory as its zero-th order approximation.
    Type of Medium: Electronic Resource
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