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  • 1
    ISSN: 0022-2852
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Time correlation functions from depolarized light scattering experiments at several temperatures were examined by biexponentials that simultaneously account for the unique axis molecular reorientations (on the picosecond time-scale) and collisional processes (on the subpicosecond time-scale). The first are found to be systematically slower than those obtained in previous studies. The important role played by dipolar interactions on the molecular organization in the liquid is confirmed. Comparison with dieletric relaxation times indicates that rotational diffusion provides only an approximate description of molecular reorientation in liquid acetonitrile. Application of the J-diffusion model shows that the exponential decay of the observed orientational correlation functions cannot be taken as evidence of rotational diffusion in liquid acetonitrile.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic processes in the liquid state can be examined from different points of view; the rapid development of highly sophisticated time-resolved experiments and very complex computer simulation techniques have certainly improved the accuracy of some laboratory results, but they are often not followed by an adequate attempt at interpretation. In any case, the extent of the subject and the enormous spread of experimental data do not help systematic analysis.This review attempts to contribute to a critical examination of a particular aspect of the dynamics of the liquid phase. Through a study of vibrational relaxation in isotropic molecular liquids it is possible to gain information about the molecular environment and the main intermolecular forces operative in this state of matter. It is therefore possible to formulate hypotheses about the force potentials and to describe the dynamic regime of the liquid system under consideration.At present, we may single out four groups of molecues that have been investigated by these methods:(1) diatomic and/or highly symmetric molecules (e.g. HCI, O2, CH4);(2) derivatives of hydrocarbons, especially methane (e.g. CH3NO2, CHCl3, CH2Cl2);(3) aromatic and cyclic aliphatic molecules (e.g. benzene and its derivatives, cyclohexane, pyridine);(4) hydrogen bonded (with OH and/or HCO groups).This paper concerns the comparison between vibrational motions that have similar normal coordinate descriptions; for this reason, we shall limit our considerations to the second and third groups in the above list. Hydrogen-bonded and highly symmetrical systems are excluded because they need specific considerations.The currently used basic nomenclature of this field will be illustrated, in addition to the physical meaning of the dynamic parameters usually obtained by steady-state (continuous Raman and infrared), time-resolved spectroscopy and computer simulation techniques; these different experimental data will be compared, when available. We shall also outline and discuss current theoretical models, and attempt to emphasize their potential and limitations.
    Additional Material: 7 Ill.
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  • 5
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trioxane-1,3-dioxolane copolymers of high molecular weights and good thermal stability are obtained with high yields by a crystallization-polymerization method. The feed consists of concentrated solutions of trioxane in cyclohexane in the presence of dissolved 1,3-dioxolane. The 1,3-dioxolane/trioxane molar ratio in the feed lies in the range 2 to 10%. The results are compared with those obtained from isothermal copolymerizations.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The well-known stochastic equation of Kubo–Anderson, widely adopted in the studies of time vibrational correlation functions, is put in a single-parametric form (defining a parameter α that describes the modulation regime of the dephasing) and Fourier transformed. It is shown how the corresponding analytical expression in the frequency domain can be compared with any experimental band shape, allowing the computation of the dynamical parameters. In particular, the more extensively addressed problems, in literature, in the field of vibrational relaxation studies, have been afforded and a contribution to their solution has been given; these are: the baseline positioning, the uncertainties of the dynamical variables involved in the stochastic model, and the frequency second moment computation. The algebraic development has been implemented in the KUBOFREQ© computer program; it has been applied in the fitting of two sets of experimental data: ν4 and ν5 mode of liquid CH3NO2 at various temperatures. The comparison of the dynamical variables computed with KUBOFREQ© and those previously obtained following the conventional time domain approach, shows a substantial agreement between the two methods: the former, however, gives more accurate values, because the baseline positioning and the second moment computation are based upon stringent criteria, allowing to correctly express the physical uncertainties of the variables. In the case of the ν5 mode, the uncertainty on α is about 5%, denoting that the Kubo–Anderson model is appropriate for the description of the vibrational relaxation of this mode; the uncertainties connected to the second moment are of the order of 10%–12%. The ν4 mode gives a band shape that still "wears'' the theoretical profile, but in a worse way with respect to the ν5 profile: the α uncertainty is, in fact, of the order of 10%, while the second moment uncertainties are around 30%–40%. Finally, the analytical equation in the frequency domain may be regarded as a new representation of any band profile, directly dependent only on one parameter. © 1996 American Institute of Physics.
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  • 7
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of nitromethane in the liquid phase is investigated by steady-state (Raman and Rayleigh) and time-resolved (optical Kerr effect) spectroscopic experiments performed at variable temperature. Both experiments show that the entire relaxation process is completed in a few picoseconds and that the dynamics can be described by assuming a biexponential function for the molecular response. The prominent dynamical feature at longer times appears to be that of a diffusionally reorienting symmetric top. The time dependence for orientational correlation at the shorter times observed in the coherent optical processes (Rayleigh and OKE) suggests that perturbative phenomena in the subpicosecond time scale (collisional and cage effects) are operative prior to the onset of the diffusional regime. Reorientational times from steady-state coherent and incoherent light scattering experiments enable us to exclude that pair-particle orientational correlation is effective. The same orientational activation energy was estimated from all the experiments. The reorientation times closely follow the η/T (η shear viscosity) linear dependence, conforming to the predictions of slip rather than stick Stokes–Einstein–Debye hydrodynamic theory. © 1995 American Institute of Physics.
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  • 8
    Publication Date: 2017-02-24
    Description: Drosophila suzukii (Matsumura), commonly known as Spotted Wing Drosophila (SWD), is a worldwide serious economic threat to the production of berries and stone fruits. The chemical control widely used against this pest is often not able to preventing yield losses because wild flora offers an abundance of fruits to D. suzukii where the pest is able to reproduce and from where it recolonizes neighbouring cultivated fields. Alternatively, within Integrated Pest Management protocols for D. suzukii, biological control could play a key role by reducing its populations particularly in non-cultivated habitats, thus increasing the effectiveness and reducing the side negative effects of other management strategies. Because of the scarcity and of the low efficiency of autochthonous parasitoids in the new invaded territories, in the last few years, a number of surveys started in the native area of D. suzukii to find parasitoid species to be evaluated in quarantine structures and eventually released in the field, following a classical biological control approach. This paper reports the results of these surveys carried out in South Korea and for the first time in China. Among the parasitoids collected, those belonging to the genus Asobara Foerster resulted dominant both by number and species diversity. By combining morphological characters and the mitochondrial COI gene as a molecular marker, we identified seven species of Asobara, of which two associated with D. suzukii, namely A. japonica and A leveri, and five new to science, namely Asobara brevicauda, A. elongata, A mesocauda, A unicolorata, A. triangulata. Our findings offer new opportunity to find effective parasitoids to be introduced in classical biological control programmes in the territories recently invaded by D. suzukii.
    Keywords: Drosophila suzukii ; Spotted Wing Drosophila ; South Korea ; China
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
    Format: application/pdf
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