Contribution a la connaissance de la flore de la peninsula tingitane (Maroc)

Dans le cadre du projet de création d’un espace naturel protégé (le futur Parc Naturel de Bouhachem) centré sur les Jbel Bouhachem et Jbel Sougna (péninsule tingitane, Maroc), une étude sur la flore et les habitats naturels de ce territoire a été menée en 2009 et 2010. Cet article présente les résultats des prospections et inventaires, qui concernent plus de 1000 taxons, dont plusieurs sont nouveaux régionalement: péninsule tingitane, Rif, Maroc, ou Afrique du nord. L’abondance locale et les habitats de chacun d’eux sont précisés. Enfin, une réflexion sur la notion de taux d’endémisme est posée.As part of the project for creating a natural protected area (the future Natural Park of Bouhachem) centered on the Jbel Bouhachem and Jbel Sougna (Tangier peninsula, Morocco), a study of the flora and natural habitats of this area was led in 2009 and 2010. This paper presents the results of these observations and inventories, which concern more than 1 000 taxa, among which some are new regionally: Tangier peninsula, Rif, Morocco, or North Africa. The local abundance and the habitats of each of them are specified. A reflection on the concept of endemism rate is exposed

The Influence Of The Available Scattering-vector Range On The Retrieval Of Particle-size Distributions From Small-angle Scattering Intensity Data

The determination of the particle-size distribution [D(r)J from small-angle scattering intensity data is discussed. The influence of the maximum available scattering vector hmax on D(r) retrieval is investigated with the help of numerical experiments with previously known solutions. The numerical corrector method provides a good answer even in cases where hmax is much smaller than those values necessary with other retrieval methods. © 1997 International Union of Crystallography all rights reserved.305 PART 2808810Fedorova, I.S., Schmidt, P.W., (1978) J. Appl. Cryst., 11, pp. 405-411Glatter, O., (1977) J. Appl. Cryst., 10, pp. 415-421Glatter, O., (1980) J. Appl Cryst., 13, pp. 7-11Glatter, O., Kratky, O., (1982) Small Angle X-ray Scattering, , New York: Academic PressGuinier, A., Fournet, A., (1955) Small Angle Scattering of X-rays, , New York: John WileyMulato, M., Chambouleyron, I., (1996) J. Appl. Cryst., 29, pp. 29-3

Exponential absorption edge and disorder in Column IV amorphous semiconductors

We discuss the likely origin of the exponential absorption tail, or Urbach edge, of fourfold coordinated amorphous (a-)semiconductors. The present analysis is based on a compilation of a considerable amount of experimental data originating from a great variety of sample, alloys, and authors and obtained with quite different spectroscopic techniques. An attempt is made to correlate the measured Urbach edge with the structural and optical properties of the samples, The present analysis indicates that the Urbach edge may not only reflect the shape of the joint density of states of the valence and conduction band tails, but may also have important contributions from short-range order potential fluctuations produced by charged defects or impurities. (C) 1998 American Institute of Physics. [S0021-8979(98)02921-1].8495184519

Average mass of seeds encountered by foraging dabbling ducks in Western Europe

Many dabbling ducks Anas spp. are largely granivorous, consuming a variety of seeds chiefly from aquatic plants. To assess the relative value and carrying capacity of wetlands for dabbling ducks, species-specific information about seed mass is needed, but it is still largely missing or scattered in the literature. By combining weights of seeds collected in the field with a literature review, we provide a reference table for seed mass of 200 western European plant taxa frequently encountered by foraging dabbling ducks. Seeds collected in the field were sampled in microhabitats and at depths at which ducks were observed to forage, and study sites represent wintering, staging as well as breeding areas within a flyway in western Europe. When combined with calorimetric data, the present reference table will aid managers and scientists in assessing the importance of seed food resources at different sites and during different parts of the annual cycle.</p

Optical diffraction gratings produced by laser interference structuring of amorphous germanium-nitrogen alloys

We use the interference of two pulsed laser beams (wavelength=355 nm) to produce an optical diffraction grating in amorphous germanium-nitrogen alloy (a-GeN). At the constructive maxima of the interference pattern, the absorption of light leads to crystallization. The crystallized region results of pure microcrystalline germanium (muc-Ge). An indication that Ge-N bonds have broken and nitrogen outdiffused of the film is obtained from infrared spectroscopy and confirmed by Raman spectra. A pattern of alternating a-GeN and muc-Ge lines with a period of about 4 mum acts as an optical diffraction grating due to the difference in optical properties between the two materials, and the three dimensional surface profile, caused by N-2 effusion, that is formed on the sample. (C) 2002 American Institute of Physics.81152731273

ESTIMATION OF INDIUM-TO-GERMANIUM AND GALLIUM-TO-GERMANIUM SPUTTERING YIELD RATIOS USING COSPUTTERING DEPOSITION

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Order parameter model for unstable multilane traffic flow

We discuss a phenomenological approach to the description of unstable vehicle motion on multilane highways that explains in a simple way the observed sequence of the phase transitions "free flow -> synchronized motion -> jam" as well as the hysteresis in the transition "free flow synchronized motion". We introduce a new variable called order parameter that accounts for possible correlations in the vehicle motion at different lanes. So, it is principally due to the "many-body" effects in the car interaction, which enables us to regard it as an additional independent state variable of traffic flow. Basing on the latest experimental data (cond-mat/9905216) we assume that these correlations are due to a small group of "fast" drivers. Taking into account the general properties of the driver behavior we write the governing equation for the order parameter. In this context we analyze the instability of homogeneous traffic flow manifesting itself in both of the mentioned above phase transitions where, in addition, the transition "synchronized motion -> jam" also exhibits a similar hysteresis. Besides, the jam is characterized by the vehicle flows at different lanes being independent of one another. We specify a certain simplified model in order to study the general features of the car cluster self-formation under the phase transition "free flow synchronized motion". In particular, we show that the main local parameters of the developed cluster are determined by the state characteristics of vehicle motion only.Comment: REVTeX 3.1, 10 pages with 10 PostScript figure

STUDY OF AMORPHOUS GERMANIUM-NITROGEN ALLOYS THROUGH X-RAY PHOTOELECTRON AND AUGER ELECTRON SPECTROSCOPIES

In this work, experimentally determined values of electron spectroscopic shifts induced by nitrogen in Ge core levels of substoichiometric amorphous germanium-nitrogen (a-GeN) alloys are discussed and presented. X-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XAES) are employed to study the behavior of the Ge 3d and LMM spectra, respectively, and combined the corresponding XPS and Auger core levels shifts to determine Δα′, the modified Auger parameter shift, which is exempt from problems inherent in the interpretation of XPS and XAES shifts. It is demonstrated how one can use Δα′ to reliably estimate ΔnGe, the change in Ge valence charge in the alloys, and how one can calibrate XPS shifts of Si and Ge based alloys in terms of approximate values of ΔnGe

Laser crystallization and structuring of amorphous germanium

The short-pulse laser crystallization and interference structuring of amorphous germanium films were investigated by time resolved reflection measurements and Raman spectroscopy, We demonstrate that submicrometer crystalline structures with very sharp lateral interfaces can be produced by laser interference crystallization of nonhydrogenated samples. In hydrogenated films, on the other hand, the film surface disrupts upon laser exposure leading to the formation of a free-standing crystalline membrane, The Raman spectra of laser crystallized germanium display effects of finite crystallite size and stress. (C) 1997 American Institute of Physics.70263570357