371 research outputs found
Novel pendant azobenzene/polymer systems for second harmonic generation and optical data storage
New poly(methyl methacrylate)s bearing push–pull azo-moieties, with the azo-dye content ranging from 31 wt% to 100 wt%, are synthesized by (co)polymerization of a methacrylamide-based azo-monomer. The high reactivity of the colored monomer allowed well-balanced structures to be achieved, characterized by a suitable thermal stability. The second harmonic generation efficiency of the poled samples is investigated by means of the SHG Maker fringes setup. Features that hinder the translation of the azo-moiety optical nonlinearity in the material at the macroscopic level are debated. The results underline the role of chromophore–chromophore and chromophore–polymer interactions on the alignment of the azo-moieties. The polarity of the polymer matrix is proven to influence the chromophore–chromophore interactions. Two-photon absorption is employed for gray scale encoding of second harmonic signals on poled thin films, thus pointing out the possibility to employ these new materials for optical data storage applications.
Are N=1 and N=2 supersymmetric quantum mechanics equivalent?
After recalling different formulations of the definition of supersymmetric
quantum mechanics given in the literature, we discuss the relationships between
them in order to provide an answer to the question raised in the title.Comment: 15 page
Scattering of slow-light gap solitons with charges in a two-level medium
The Maxwell-Bloch system describes a quantum two-level medium interacting
with a classical electromagnetic field by mediation of the the population
density. This population density variation is a purely quantum effect which is
actually at the very origin of nonlinearity. The resulting nonlinear coupling
possesses particularly interesting consequences at the resonance (when the
frequency of the excitation is close to the transition frequency of the
two-level medium) as e.g. slow-light gap solitons that result from the
nonlinear instability of the evanescent wave at the boundary. As nonlinearity
couples the different polarizations of the electromagnetic field, the
slow-light gap soliton is shown to experience effective scattering whith
charges in the medium, allowing it for instance to be trapped or reflected.
This scattering process is understood qualitatively as being governed by a
nonlinear Schroedinger model in an external potential related to the charges
(the electrostatic permanent background component of the field).Comment: RevTex, 14 pages with 5 figures, to appear in J. Phys. A: Math. Theo
A splitting line model for directional relations
Directional relations are fundamental to spatial data queries, analysis and reasoning. Consequently there has been a significant amount of effort to determine directional relations between two regions. However, many existing methods do not perform well when the regions are neighboring or intertwined. In this paper we introduce a new model for directional relations which is based on a splitting line separating the two regions in question. We identify essential quality criteria for directional relation models and translate them into measurable properties of a given splitting line. We present an efficient algorithm that computes an optimal splitting line for two regions and perform extensive experiments. Our results show that the splitting line model captures directional relations very well and that it clearly outperforms existing approaches on pairs of neighboring or intertwined regions
The Arabidopsis thaliana-Alternaria brassicicola pathosystem: A model interaction for investigating seed transmission of necrotrophic fungi
Seed transmission constitutes a major component of the parasitic cycle for several fungal pathogens. However, very little is known concerning fungal or plant genetic factors that impact seed transmission and mechanisms underlying this key biological trait have yet to be clarified. Such lack of available data could be probably explained by the absence of suitable model pathosystem to study plant-fungus interactions during the plant reproductive phase
Забезпечення сейсмічного захисту наземних об'єктів на кар'єрах, що видобувають вапняк та гіпс
The paper highlights the research undertaken at three limestone and gypsum quarries belonging to a large cement producer in Romania, in order to evaluate the seismic protection of civil and industrial objectives located near the exploitation perimeters. In this regard, the results obtained from the tests on the determination of seismic parameters are presented, in order to assess the seismic effect generated by the blasting works on civil and industrial objectives located in the vicinity of exploitation areas.У статті висвітлено дослідження, проведене на трьох кар’єрах вапняку та гіпсу, що належать великому виробнику цементу в Румунії, з метою оцінки сейсмічного захисту цивільних та промислових об’єктів, розташованих поблизу периметрів експлуатації. У зв'язку з цим представлені результати, отримані в результаті випробувань з визначення сейсмічних параметрів, з метою оцінки сейсмічного ефекту, що виникає підривними роботами на цивільні та промислові об'єкти, розташовані в районі експлуатаційних зон
Translation Representations and Scattering By Two Intervals
Studying unitary one-parameter groups in Hilbert space (U(t),H), we show that
a model for obstacle scattering can be built, up to unitary equivalence, with
the use of translation representations for L2-functions in the complement of
two finite and disjoint intervals.
The model encompasses a family of systems (U (t), H). For each, we obtain a
detailed spectral representation, and we compute the scattering operator, and
scattering matrix. We illustrate our results in the Lax-Phillips model where (U
(t), H) represents an acoustic wave equation in an exterior domain; and in
quantum tunneling for dynamics of quantum states
- …