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  • 1
    Electronic Resource
    Electronic Resource
    Thermal, pressure and wind fields at ground level in the area of the Italian base at Terra Nova Bay, Victoria Land, Antarctica, as observed by a network of automatic weather stations (1997)
    Springer
    Annales geophysicae 14 (1997), S. 1088-1094 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ground temperature, pressure and wind speed monthly averages in the area of the Italian Station at Terra Nova Bay, Antarctica, were analyzed for the period 1987–1991 by means of a network of nine AWS (automatic weather stations). Spatial configurations of temperature show a well-defined, relatively warm island in the area of Terra Nova Bay, between Drygalsky and Campbell ice tongues, throughout the year. A second warm island is present to the north along the coast, between Aviator and Mariner ice tongues, for most of the year. From February to March a rapid drop in temperature is observed at all stations. A strong thermal gradient develops during February, March, April and October, November, December, between the coastal region and inner highlands. The baric configuration follows the elevation of the area. Annual average pressure and temperature as functions of stations altitude show linear trends. Severe katabatic wind episodes are recorded at all stations, with wind speed exceeding 25 ms−1 and direction following the orographic features of the inner areas. Co-occurrences of these episodes were observed for stations located along stream lines of cold air drainage. The autocorrelation function of maximum wind speed time series shows wind persistence of 2–3 days and wind periodicity of about one week.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-1088-1
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  • 2
    Electronic Resource
    Electronic Resource
    First-order polarization-activated optical transitions in smecticC and planar nematic liquid crystals (1989)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 11 (1989), S. 385-392 
    Details
    ISSN: 0392-6737
    Keywords: Liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto È stato mostrato che, quando un fascio di luce laser interagisce con campioni di cristallo liquido smetticoC o nematico con allineamento planare, è possibile ottenere transizioni del primo ordine della polarizzazione della luce di uscita in funzione della polarizzazione della luce incidente. Queste transizioni danno luogo a cicli di isteresi e bistabilità ottica intrinseca, senza l'intervento di feed-back esterni né di campi statici di polarizzazione. È stato risolto esattamente, in condizioni stazionarie, un sistema di equazioni differenziali nonlineari che governa l'evoluzione del direttore molecolare e dello stato di polarizzazione della luce lungo il campione. I risultati ottenuti sono indipendenti dai valori delle costanti ottiche e meccaniche dei campioni di cristallo liquido. L'intensità della luce per cui si ottengono fenomeni di bistabilità ottica varia da 10 kW/cm2 a 1 MW/cm2 circa.
    Abstract: Резюме Показывается, что поляризация, активированная внутренней ортической биустойчивостью, может быть получена в жидких кристаллах типа смектика-C и типа плоского неиатика без резонатора с внешней обратной связью. Доказывается, что, в принципе, возникают переходы первого порядка, независимо от постоянных жидких кристаллов. Интенсивность света, необходимая для получения оптической биустойчивости, находится в области от 10 кВт/см2 до 1 МВт/м2.
    Notes: Summary It is shown that polarization-activated intrinsic optical bistability (OB) may be obtained in smecticC or planar nematic liquid crystals without external feed-back resonator. First-order transitions for twist are proved to occur, in principle, irrespective of the liquid-crystal material constants. The light intensity, needed to obtain OB, ranges from 10 kW/cm2 to 1 MW/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02450988
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  • 3
    Electronic Resource
    Electronic Resource
    Optical Freedericksz transitions in twisted planar nematics (1988)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 313-322 
    Details
    ISSN: 0392-6737
    Keywords: Orientational order of liquid crystals ; electric and magnetic field effects of order
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è studiata la propagazione di un fascio di luce polarizzata ellitticamente che incide normalmente su un campione di cristallo liquido nematico planare «twisted», cioè nel quale l'angolo α fra la direzione delle molecole nel piano di ingresso della luce e quella nel piano di uscita è≠O. È stato derivato un sistema non lineare di equazioni differenziali che governa l'evoluzione del direttore molecolare e dello stato di polarizzazione della luce. Questo sistema è stato risolto analiticamente nel limite di piccole variazioni intorno a soluzioni corrispondenti allo stato imperturbato. Si è dimostrato che transizioni di Freedericksz ottiche sono possibili solo se la luce incidente si trova in un particolare stato di polarizzazione. I risultati ottenuti sono peculiari dell'interazione ottica e non sono riconducibili al fenomeno della riorientazione molecolare indotta su campioni di questo tipo da campi statici, elettrici o magnetici.
    Abstract: Резюме Мы исследуем распространение эллипчески поляриэованного светового пучка, падаюшего номально на пленку эакрученного нематического жидкого кристалла. Выводится система нелинейных дифференциальиых уравнений для молекулярного директора и поляриэации светового пучка. Полуенная система решается аналитчески в пределе малЫх воэмущений относительно решений для стционарнЫх состояний, которЫе соответствуют не-переориентированному обраэцы. МЫ докаэЫваем, что оптические перехоые фредерикса воэможиы только для частично поляриэованного состояния падаюшего света. Исследуется пороповое поведение как функция интенсвности света и упла эакручивания между молекуляриыми директорами на стенках обраэца. Полученные реэультаты являются характерными для оптического вэаимодействия и не имеют аналога при молекулярной переориентации, индуцрованной в такой системе d.c. полями.
    Notes: Summary We study the propagation of an elliptically polarized light beam normally incident onto a twisted nematic liquid-crystal film. A set of nonlinear differential equations for the molecular director and the polarization of the light beam is derived; it is solved analytically in the limit of small perturbations around the steady-state solutions that represent the nonreoriented sample. We prove that optical Freedericksz transitions are possible only for a particular polarization state of the incident light. The threshold behaviour is studied as a function of the light intensity and of the twist angle between the molecular directors at the sample walls. The results are characteristic of the optical interaction and have no analogue in the molecular reorientation induced on such a system by d.c. fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02450121
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  • 4
    Electronic Resource
    Electronic Resource
    A new approach to global stability analysis of one-dimensional continuous dissipative systems (1990)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 31 (1990), S. 2105-2115 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: It is proved by a direct construction that symmetry-breaking instabilities in one-dimensional dissipative continuous systems can be studied in terms of a suitable function G whose minima correspond to stable steady states of the system, while other extremal points correspond to unstable states. The existence of such a function is proved for a large class of continuous dissipative physicochemical systems in one spatial dimension. The function G is exact, in the sense that it is obtained by taking into account all nonlinear terms in the evolution equations of the system. Since in some respect this function has properties similar to the Ginzburg–Landau function widely used in second-order phase transitions, it is called the nonlinear Ginzburg–Landau function (NLGLF) of the system. The NLGLF may be useful for studying the global stability under symmetry-breaking conditions as well as the character (first and second order) of the transitions between different steady states. The construction of the NLGLF usually requires simple numerical or analytical calculations. A specific example, taken from the physics of liquid crystals, has been worked out analytically in the present paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528663
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  • 5
    Electronic Resource
    Electronic Resource
    Polarization effects in the optical reorientation of freely suspended smectic-C liquid-crystal films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1269-1274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linearly polarized laser beam propagating in a freely suspended smectic-C liquid-crystal film can induce reorientation of the molecular director. A theoretical model is presented which, unlike previous works, takes into account the effects of the polarization changes of the light into the sample. Despite the nonlinearity of the problem, an analytical solution is found. The stability analysis of the trivial solutions has also been carried out. A physical interpretation of the results, some of which are unexpected on the basis of the old models, is given in terms of angular momentum conservation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348907
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  • 6
    Electronic Resource
    Electronic Resource
    Bond orbital models - II. Construction of zero-non-bonding-overlap hybrids and their use in approximate molecular computations
    Amsterdam : Elsevier
    Journal of Molecular Structure: THEOCHEM 105 (1983), S. 191-200 
    Details
    ISSN: 0166-1280
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0166-1280(83)80046-3
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  • 7
    Electronic Resource
    Electronic Resource
    A non-empirical and HAM/3 study of the geometry, conformational behaviour and electronic structure of isomeric vinylpyridines
    Amsterdam : Elsevier
    Journal of Molecular Structure: THEOCHEM 108 (1984), S. 35-43 
    Details
    ISSN: 0166-1280
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0166-1280(84)80097-4
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  • 8
    Electronic Resource
    Electronic Resource
    Model Hamiltonians in the study of chemisorption and catalysis
    Amsterdam : Elsevier
    Surface Science Letters 152-153 (1985), S. A142 
    Details
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-2584(85)90148-3
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic field induced light modulation in a slab waveguide-liquid crystal system
    Amsterdam : Elsevier
    Optics Communications 97 (1993), S. 173-177 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(93)90135-R
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  • 10
    Electronic Resource
    Electronic Resource
    Interferometric technique for the determination of thermal nonlinearities in semiconductor glasses
    Amsterdam : Elsevier
    Optics Communications 70 (1989), S. 502-508 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(89)90373-8
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