998 resultados para 448.9


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Part I: An approach to the total synthesis of the triterpene shionone is described, which proceeds through the tetracyclic ketone i. The shionone side chain has been attached to this key intermediate in 5 steps, affording the olefin 2 in 29% yield. A method for the stereo-specific introduction of the angular methyl group at C-5 of shionone has been developed on a model system. The attempted utilization of this method to convert olefin 2 into shionone is described.

Part II: A method has been developed for activating the C-9 and C-10 positions of estrogenic steroids for substitution. Estrone has been converted to 4β,5β-epoxy-10β-hydroxyestr-3-one; cleavage of this epoxyketone using an Eschenmoser procedure, and subsequent modification of the product afforded 4-seco-9-estren-3,5-dione 3-ethylene acetal. This versatile intermediate, suitable for substitution at the 9 and/or 10 position, was converted to androst-4-ene-3-one by known procedures.

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By now a great deal of work is known concerning the methods of determining the production of bacteria or similar questions; among these the problems of a common terminology is discussed. The article discusses formulae of production of bacterial populations over time.

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The rainfall regime and the karstic nature of the subsoil determines the alternation of a period of flow and a period of drought for a large number of Mediterranean streams. Amongst this type of stream it is possible to distinguish temporary streams, characterised by a period of flow for several months permitting the establishment of the principal groups of aquatic insects; and ephemeral streams whose very brief period of flow permits the establishment of a community reduced to a few species of Diptera. This paper aims to study the structure of the communities which colonise this particular type of stream and the ecology of the principal species which constitute these communities. Four French temporary streams were examined and temperature regimes, dissolved oxygen, calcium and magnesium measured. Samples of fauna were taken regularly and the biotic composition established. The analysis of similarities between the three permanent streams are discussed and compared with permanent streams.

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Dormancy has been observed in several species of Cyclops. Animals in dormancy are characterised by almost complete inactivity of the main appendages and sluggish intestinal peristalsis. In Cyclops vicinus dormancy can take place in copepod stages III (19%), IV (78%) and V (3%) but one and the same animal only in one developmental stage. The author gives his own results between frequency of dormancy and photoperiod (20 C, 1000 lux). He concludes that dormancy in C. vicinus can be influenced by day length and can be ended prematurely by short day length.

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This partial translation of a larger paper provides taxonomic descriptions of 5 fungal zoospores species: Olpidium vampyrellae, 0. pseudosporearum, 0. leptophrydis, Rhizophidium leptophrydis and Chytridium lateoperculatum.

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This short translation presents the conclusions only of a study of the proposed method of rearing cyprinid fry in cages and how this method can increase the amount of material produced of the stocked fry.

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As stated in the title, this is an introduction to all the reports contained in this technical document and related to the various workshops on Participatory Rural Appraisal (PRA) held in all the riparian countries around Lake Victoria within the LVFRP.

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The Laboratory of Lake Studies of the Academy of Sciences of the USSR in 1956 undertook this complicated study of Lake Ladoga. The plan of the laboratory made allowance for the detailed investigation of the phytoplankton of the lake during a series of years. In the present article are given the preliminary results of observations on the phytoplankton of the Yakimvarskii Bay from 1956 to 1957. Details are also given on the concentration of dissolved gases and biogenic substances of the bay.

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Based on electro-optic switch effect in crystal, a novel laser ranging method is proposed. CW-laser emitted by laser transmitter propagates forward to the measured target, after being reflected by the target, and then goes back to the transmitter. Close to the transmitter, a special mono-block LiNbO3 crystal is added into the round-trip light beams. High-voltage pulses with the sharp enough changes in rising edges are loaded on the crystal. Based on electro-optic effect, double refraction and internal double reflection effect in crystal, the crystal cuts off the round-trip light beams, and reflects a light pulse cut out by the crystal to a detector aside from the original beam path. The pulse width T is the period that laser propagates forward and back between the crystal and the target. The feasibility of the new idea is proved by our experiments and a brand-new way for the laser ranging is provided. (c) 2005 Elsevier GmbH. All rights reserved.

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The reaction 7Li(3He, p)9Be has been used to measure excitations and intrinsic widths of levels in 9Be below the 7Li + d threshold. Previously unreported levels have been found at excitations of (13.78 ± .03) MeV and (16.671 ± .008) MeV with widths of (590 ± 60) keV and (41 ± 4) keV respectively. Two overlapping levels have been found at (11.81 ± .02) MeV and (11.29 ± .03) MeV with widths of (400 ± 30) keV and (620 ± 70) keV respectively. Branching ratios from 9Be levels populated in this reaction to the ground and first excited states of 8Be have been measured by observing the associated protons in coincidence with the decay neutrons. Branching ratios were found to be:

Excitation in 9Be .... Branching Ratio.......... Final Nucleus.........

(MeV) .......................... (percent) .....................................

.. 2.43 ........................... 7.5 ± 1.5 .............. 8Be(g.s.)

.. 3.03 ........................... 87 ± 13......................................

.. 4.65 ........................... 13 ± 4.......................................

.. 6.76 .............................. ≤ 2 ......................................

.. 11.29 ...............................≤ 2 ......................................

.. 11.81 ...............................≤ 3 ......................................

.. 6.76 ........................... .41 ≤ B.R. ≤ .69 ....... 8Be(2+)

.. 11.29 ........................... 14 ± 4 .......................................

.. 11.81 ........................... 12 ± 4 .......................................

Corresponding reduced widths for neutron emission are calculated and a comparison of the results with the expectations of current nuclear models is made. In particular the measured branching ratio to 8Be(g.s.) from 9Be(2.43 MeV) corresponds to an f-wave reduced with θ2f = 2.1 x 10-2, in units of ħ2/mR2, with R = 4.35 fm. A comparison of this value with that predicted by a Nilsson model calculation, in which 9Be is taken to be a deformed nucleus, is discussed. The measured value for θ2f is found to be consistent with that expected on the basis of measured E2-transition rates between rotational levels in 9Be.

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This report presents five batches of data which have been despatched to the Joint Research Centre, Ispra. The data as been allocated to various ECDIN (Environmental Chemicals Data and Information Network) files. The data comprises environmental chemicals in the freshwater environment, taking in paricular consideration: aquatic toxicity, bioaccumulation, metabolism and elimination biodegradation.

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Cap. 1. Patrimonialización cultural y natural: un proceso, múltiples aproximaciones. Cap. 2. Comment un musée de ville peut-il être au service des citoyens? Un parcours et quelques pistes d’action. Jean-François Leclerc. Cap. 3. Los museos comunitarios de Kuna Yala y la memoria histórica. Anelio Merry López Cap. 4. Turismo y museos en la ciudad de Valencia. Javier Martí. Cap. 5. La Red de Museos Etnográficos de Asturias: proyecto y realidad. Juaco López Álvarez. Cap. 6. Culturas campesinas y conservación del patrimonio natur-rural. Jaime Izquierdo. Cap. 7. Faire et savoir faire un « territoire patrimonial » : Parc naturel régional du Haut-Jura (France). Olivier Givre. Cap. 8. Espacios naturales y especies salvajes. La construcción de la naturaleza como patrimonio en el Pallars Sobirà, Pirineo catalán. Oriol Beltran e Ismael Vaccaro. Cap. 9. L’histoire au cœur de la cité : l’exemple du laboratoire d’histoire et de patrimoine de Montréal. Joanne Burgess.