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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6363-6374 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The hydrogen bonded heterodimer tetrahydrofuran(centered ellipsis)HCl has been investigated using molecular beam Fourier transform microwave spectroscopy in combination with ab initio calculations. The rotational spectrum, observed in the range 6–18 GHz, shows a complex pattern originated by the existence of small tunneling splittings in addition to the Cl-nuclear quadrupole coupling hyperfine structure. The vibrational energy difference between the members of the doublet, ΔE=3.550(25) MHz, has been determined from the analysis of the a-type Coriolis coupling interaction between them. Doublets of the same magnitude are also present in the spectra of the different HCl isotopomers analyzed. These tunneling splittings were not observed for the species C4D8O(centered ellipsis)H35Cl. The analysis of all the available data has allowed us to conclude that these splittings are due to pseudorotation within the tetrahydrofuran subunit. The spectroscopic constants have been interpreted in terms of a geometry in which tetrahydrofuran has a conformation close to the twisted ring-form with HCl lying on the plane bisector to the COC ring angle. The potential energy surface for the interaction between tetrahydrofuran and hydrogen chloride has been explored by using ab initio methodologies at the correlated level [MP2, MP4(SDTQ)] with Pople's 6-31G** and Dunning's aug-cc-pVDZ basis sets. One minimum and three transition structures were located and characterized at the MP2/6-31G** level. The geometry parameters and rotational constants of the minimum agree quite well with those determined from the spectroscopic data. The transition structures correspond to interconversions between equivalent conformations, the first one via an inversion motion and the remaining two via pseudorotation movements. One of these latter two is responsible for the splittings detected in the microwave spectroscopy study. The tetrahydrofuran(centered ellipsis)hydrogen chloride interaction can be seen as a combination of electrostatic and charge transfer contributions both consistent with the angular geometry exhibited by the complex. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9729-9734 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of 1-chloro-1-fluoroethane (CFC 151-a) has been studied in the frequency region 8–250 GHz using waveguide Fourier transform, Stark, and source modulation spectrometers. Accurate rotational, quartic, and sextic centrifugal distortion and quadrupole coupling constants have been obtained from a global fit for the ground, v17=1 (Cl–F skeletal bending mode), and v18=1 (CH3 torsional) vibrational states of the 35Cl isotopomer and for the ground state of the 37Cl isotopomer. The larger off-diagonal element of the χ tensor was also determined for the 35Cl isotopomer. Assignment of the v17=1 and v18=1 states was confirmed by the presence of small A–E internal rotation splittings in the v18=1 state, in agreement with ab initio calculations, but in contradiction with previous assignment of the microwave spectrum by Thomas et al. [J. Chem. Phys. 61, 5072 (1974)]. The barrier height for the internal rotation of the methyl group was determined to be 3814(11) cal/mol, and compared with the result of ab initio calculations made for 1-chloro-1-fluoroethane and other related chlorine or fluorine substituted ethanes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 36 (1995), S. 1123-1135 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: An extended Dyson and Holstein-Primakoff boson mapping is constructed for coordinate systems. Only functions which depend on even powers in the coordinates are considered. It is shown that the Holstein-Primakoff boson mapping for coordinate systems is different from the one using creation and annihilation operators, with some advantages in application. As an example the mapping is applied to the schematic model of constant gauge fields in Quantum-Chromo-Dynamics with SU(2) for color. Other possible applications related to field theory are briefly discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food processing and preservation 22 (1998), S. 0 
    ISSN: 1745-4549
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Acid hydrolysis of dried fodder's yeast Candida utilis was studied by a central composite design taking into account three independent variables: temperature (105–165C), processing time (30–70 min) and HCl concentration (7.5–17.5%). Response variables were: color, dry matter solubilization and amino nitrogen. Temperature was the most significant variable followed by acid concentration and processing time. Response surfaces were generated from fitted polynomials. Higher temperatures to prevent amino nitrogen degradation were not investigated. As different effects were found for color development and amino nitrogen, a combined function was tested which yields the behavior of all responses simultaneously. The best conditions were: 150C, 15% HCl and 40 min. After neutralization with 6N NaOH and centrifugation, the raw sauce was supplemented with 12% NaCl, 0.1% monosodium glutamate, 2% vinegar and 0.1% sodium benzoate and evaluated by sensory analysis for eight distinct attributes. Imitation sauce from yeast was at least as good as commercial hydrolyzed soybean sauce.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    JETP letters 69 (1999), S. 844-850 
    ISSN: 1090-6487
    Keywords: 31.15.Pf ; 33.15.−e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown by a variational method that the molecular ion H 3 ++ can exist for magnetic fields B〈 1011 G.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1090-6487
    Keywords: 99.10.+g ; 31.15.Pf ; 33.15.−e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1435-9456
    Keywords: Key words Spatial cognition ; Memory systems ; Fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is a considerable amount of evidence that mammals and birds can use different spatial learning strategies based on multiple learning and memory systems. Unfortunately, only a few studies have investigated spatial learning and memory mechanisms in other vertebrates. This study aimed to identify the strategies used by goldfish to solve two different spatial tasks in a series of three experiments. In experiment 1, two groups of goldfish (Carassius auratus) were trained either in a spatial constancy task (SC), in which visual cues signalled the goal indirectly, or in a directly cued task (DC) in which similar cues signalled the goal directly. Transfer tests were conducted to study the effects of discrete cue deletion on the performance in both tasks. In these transfer tests the performance of the animals trained in the DC task dropped to chance level when the cue that signalled the goal directly was removed. In contrast, the removal of any single cue did not disrupt SC performance. In experiment 2, fish trained in the SC or the DC task were trained with the goal reversed. Goldfish in the SC group needed fewer sessions to master the reversal task than DC animals. Finally, experiment 3 investigated the effects of a substantial modification of the geometrical features of the apparatus on the performance of animals trained in the SC or in the DC condition. The performance of DC goldfish was not affected, whereas the same change disrupted performance in the SC animals despite the presence of the visual cues. These results suggest that there are separate spatial learning and memory systems in fish. Whereas the DC animals used a typical guidance strategy, relying only on the cue that signalled the goal directly, SC fish relied on a strategy with the properties of an actual spatial mapping system. Thus, the comparative approach points to the generality of these learning strategies among vertebrates.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0142-2421
    Keywords: x-ray absorption spectroscopy ; total electron yield ; oxides ; EXAFS probing depth ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Calibration of the probing depth by x-ray absorption spectroscopy (XAS) in oxide materials is intended by measurement of the total electron yield (TEY) of electrons ejected by absorption of the radiation. Measurements have been carried out for three series of electrolytic metal oxide overlayers with different thickness. The experiments have been conducted at the Ti K, Ta LIII and Zr K edges. Analysis of the XAS spectra is carried out by factor analysis and conventional Fourier transformation and fitting analysis. The data showed that the information depth by XAS follows the order ZrO2〉TiO2〉Ta2O5 at the Ti K, Ta LIII and Zr K edges.As an alternative, the absorption spectra of the same samples were measured in the conversion electron yield (CEY) mode: i.e. by measuring the current of He+ ions produced by the ejected electrons in an atmosphere of He in contact with the sample. Here, the information depth is slightly different from that obtained by TEY. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 1016-1026 
    ISSN: 0142-2421
    Keywords: XPS analysis ; nanoparticles ; XAS ; EELS ; quantitative characterization of powders ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: For the present study we have considered powders made up of small particles (〈1 μm) coated with a uniform overlayer. Different models have been developed to predict the elemental compositions in this kind of sample by x-ray photoelectron spectroscopy (XPS) and absorption spectroscopies: electron energy-loss spectroscopy (EELS) and x-ray absorption spectroscopy (XAS). Isolated spherical or cubic particles, aggregated spherical particles and continuously layered models have been considered to take different possible textures of the samples into account. Theoretical curves have been compared to experimental data obtained for Al2O3/Al ultrafine powders made up of Al metal cores coated with an Al2O3 overlayer. The dependence of both photoelectron and absorption spectroscopy analysis on overlayer thickness and sample texture as a function of particle size is discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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