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  • 1
    Digitale Medien
    Digitale Medien
    The tetrahydrofuran(centered ellipsis)hydrogen chloride complex: Rotational spectrum and theoretical analysis (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6363-6374 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.479962
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  • 2
    Digitale Medien
    Digitale Medien
    Rotational spectrum, internal rotation barrier and ab initio calculations on 1-chloro-1-fluoroethane (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9729-9734 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.471734
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  • 3
    Digitale Medien
    Digitale Medien
    Bonding structure in amorphous carbon nitride: A spectroscopic and nuclear magnetic resonance study (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 675-681 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Since the prediction of Liu and Cohen [Science 245, 841 (1989)] of the potential extraordinary mechanical properties of crystalline β-C3N4, many authors have attempted its synthesis. However, in most cases, the obtained materials are amorphous phases with a complex bonding structure. Their characterization is complicated due to the absence of a reference compound, the lack of long-range order, and the poor knowledge about their bonding structure. In this article, we present 1H, 13C, and 15N solid-state nuclear magnetic resonance (NMR) measurements for the determination of the bonding types in amorphous CNx films. NMR measurements do not require long-range order and are able to clearly identify the signals from the sp2- and sp3-bonded phases. The analysis of the data obtained by other characterization techniques, such as infrared spectroscopy, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, and x-ray absorption near-edge spectroscopy on the same sample, based on the information acquired by NMR, enables the description of a structure model for the studied amorphous-CNx phase prepared by dc-magnetron sputtering and to revise the interpretation found in the literature. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1380998
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  • 4
    Digitale Medien
    Digitale Medien
    Boson mapping of symplectic algebras with Abelian subalgebra mapped as coordinates (1995)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 36 (1995), S. 1123-1135 
    Details
    ISSN: 1089-7658
    Quelle: AIP Digital Archive
    Thema: Mathematik , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.531109
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  • 5
    Digitale Medien
    Digitale Medien
    Visceral diphyllobothriosis in a cultured rainbow trout, Oncorhynchus mykiss (Walbaum), in Chile (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of fish diseases 25 (2002), S. 0 
    Details
    ISSN: 1365-2761
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2761.2002.00381.x
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  • 6
    Digitale Medien
    Digitale Medien
    Pseudorotation in tetrahydrofuran(centered ellipsis)HF heterodimer (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2760-2767 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Seven isotopomers of the hydrogen-bonded heterodimer tetrahydrofuran(centered ellipsis)HF have been investigated in the frequency range 6–18 GHz using molecular-beam Fourier transform microwave spectroscopy. The rotational spectra of C4H8O(centered ellipsis)HF and C4H8O(centered ellipsis)DF exhibit small tunneling splittings, which were not observed for C4D8O(centered ellipsis)HF and the four single 13C isotopomers. These observations analyzed in terms of symmetry considerations allow us to conclude that these splittings are due to pseudorotation within the tetrahydrofuran subunit of the complex and not to HF inversion. The spectroscopic parameters of the complex have been interpreted in terms of a geometry in which tetrahydrofuran has a conformation close to the twisted ring form, with HF lying on the plane bisector to the COC ring angle. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1305863
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  • 7
    Digitale Medien
    Digitale Medien
    PREPARATION OF AN IMITATION SOY SAUCE FROM HYDROLYZED DRIED YEAST CANDIDA UTILIS (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food processing and preservation 22 (1998), S. 0 
    Details
    ISSN: 1745-4549
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1745-4549.1998.tb00360.x
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  • 8
    Digitale Medien
    Digitale Medien
    Predicted existence of H 3 ++ molecular ions in strong magnetic fields (1999)
    Springer
    JETP letters 69 (1999), S. 844-850 
    Details
    ISSN: 1090-6487
    Schlagwort(e): 31.15.Pf ; 33.15.−e
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is shown by a variational method that the molecular ion H 3 ++ can exist for magnetic fields B〈 1011 G.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.568100
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  • 9
    Digitale Medien
    Digitale Medien
    Erratum: Predicted existence of H 3 ++ molecular ions in strong magnetic fields [JETP Lett. 69, No. 11, 844–850 (10 June 1999)] (1999)
    Springer
    JETP letters 70 (1999), S. 563-563 
    Details
    ISSN: 1090-6487
    Schlagwort(e): 99.10.+g ; 31.15.Pf ; 33.15.−e
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.568214
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  • 10
    Digitale Medien
    Digitale Medien
    Multiple spatial learning strategies in goldfish (Carassius auratus) (1999)
    Springer
    Animal cognition 2 (1999), S. 109-120 
    Details
    ISSN: 1435-9456
    Schlagwort(e): Key words Spatial cognition ; Memory systems ; Fish
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100710050031
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