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1985 (209)
81Author    E. E. Polymeropoulos, S. Löffler, J. BrickmannRequires cookie*
 Title    The Stability of Rare Gas Clusters by Ionization  
 Abstract    Computer simulations of the dissociation dynamics of argon and xenon neutral and singly charged clusters with 5 — 20 atoms were performed. It is shown that the stability of clusters with 'magic numbers' of atoms (« = 19 for argon, and n = 13,19 for xenon) as found in TOF mass spectra, is more enhanced by ionization than that of their neighbours, indicating the importance of the ionization for the cluster size distribution found in experiments. 
  Reference    Z. Naturforsch. 40a, 516—519 (1985); received February 4. 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0516 
 Volume    40 
82Author    K. Igarashi, Y. Iwadate, H. Ohno, J. MochinagaRequires cookie*
 Title    Molar Volume of Molten Binary CaCl 2 -NaCl, LaCl 3 -NaCl, and LaCl 3 -CaCl2 and Ternary LaCl 3 -CaCl 2 -NaCl Systems  
 Abstract    Molar volumes of molten CaCF-NaCl, LaCl 3 -NaCl, LaCl 3 -CaCl 2 and the quasi-binary systems LaCl 3 -/7NaCl • mCaCl 2 (mole ratio n:m= 1:3.2, 1:1, and 2.6:1) have been measured by the dilatometric method, and expressed as functions of both temperature and mole fraction by means of least squares regression. The molar volumes of molten LaCl 3 -NaCl and LaCl 3 -CaCl 2 showed positive and negative deviations, respectively, from additivity, while CaCl 2 -NaCl and the three quasi-binary systems satisfied approximately the additivity. The isotherm of molar volume for ternary LaCl 3 -CaCl 2 -NaCl system at 900 °C was represented according to the iso-therms of three binary and three quasi-binary systems. 
  Reference    Z. Naturforsch. 40a, 520—524 (1985); received February 5 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0520 
 Volume    40 
83Author    H. Görner, A. Fojtik, J. Wróblewski, L. J. CurrellRequires cookie*
 Title    Singlet Mechanism for Trans —* Cis Photoisomerization of Quaternary Salts of 4-Substituted 4 , -Azastilbenes (R = CN, H, CH 3 , and OCH 3 ) and their Quinolinium Analogues. VIII [1]  
 Abstract    , 1985 Dedicated to Professor Schulte-Frohlinde on the occasion of his 60th birthday The trans-»eis photoisomerization of a series of substituted stilbazolium salts (A t + X -, A t + : trans-l-alkyl-4-[4-R-styryl]-pyridinium and -quinolinium, R = CN. H, CH 3 and OCH 3 , X"=T and CIO4) was studied by laser flash photolysis and steady state irradiation measurements. The quantum yields of eis ^ trans photoisomerization (<£ c _ t and $ t _ c) and of fluorescence of the trans isomers (</> f) were determined in several solvents at room temperature and at low temperatures in mixtures of either 2-methyltetrahydrofuran-dichloromethane or ethanol-methanol (E-M). In polar solvents at room temperature <£ t _ c is substantial (S 0.3) and </ > f is small (10 _3 -10~ 2). Competition of fluorescence and an activated step in the trans-»eis pathway is indicated by the effects of temperature on (f) { and </> t _ c (activation energy: 2-3 kcal/mol). A transient, observed only at low temperatures (lifetime i T > 0.5 ms in E-M below -170°C), is assigned to the lowest triplet state with trans configuration. On the basis of the effects of temperature on (/> f , </> t _> c , r T , and the triplet yield and those of quenchers on </ > f and </> t _ c , involvement of the triplet state in the twisting process at room temperature is excluded. Therefore, a singlet mechanism is suggested for the trans-» • cis photoisomerization of the stilbazolium salts examined. Significant reduction of </> t _ c for iodides in solvents of moderate polarity, where ion pairs are present, is accounted for by photoinduced electron transfer in competition to trans -» • cis photoisomerization. 
  Reference    Z. Naturforsch. 40a, 525—537 (1985); received January 14 
  Published    1985 
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 Identifier    ZNA-1985-40a-0525 
 Volume    40 
84Author    Frank SpieweckRequires cookie*
 Title    Transitivity of "Gravitational Transformations"  
 Abstract    Taking into account a "theorem of the addition of gravitational potential differences", gravitational trans-formations turn out to be transitive. 
  Reference    Z. Naturforsch. 40a, 538 (1985); received March 30 1985 
  Published    1985 
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 TEI-XML for    default:Reihe_A/40/ZNA-1985-40a-0538_n.pdf 
 Identifier    ZNA-1985-40a-0538_n 
 Volume    40 
85Author    H. Daniel, F. J. Hartmann, B. PitesaRequires cookie*
 Title    57 Fe Isomer Shift Calibration Experiment  
 Abstract    The 4 s electron contact density was measured on 57 Fe atoms embedded in Au and in graphite. With the help of the isomer shifts measured on the same sources an estimate of the radial difference (A r 2) was obtained which is rather independent of assumptions: — (A r 2) < 9 x 10" 3 fm 2 at 80 per cent confidence. 
  Reference    Z. Naturforsch. 40a, 539—540 (1985); received March 30 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0539_n 
 Volume    40 
86Author    T. Sumiyoshi, W. Weber, W. SchnabelRequires cookie*
 Title    Thiophosphonyl Radicals Photolytic Generation and Reactivity Towards Olefinic Compounds  
 Abstract    Upon irradiation with UV light (A = 347 nm), 2,4,6-trimethylbenzoyldiphenylphosphine sulfide was found to be fragmented into free radicals by a-scission (0(a) = 0.3 ± 0.1): 
  Reference    Z. Naturforsch. 40a, 541—543 (1985); received March 18. 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0541 
 Volume    40 
87Author    B. Arcondo, G. Quintana, H. SirkinRequires cookie*
 Title    Glass Forming Ability of GeTeSn with Tin Concentration and Initial Conditions  
 Abstract    Solid samples of (Ge 15 Te 85)i_ x Sn v and (Sn^Ge^J^Te^ ternary alloys with different tin concentrations were obtained from the liquid state at different initial temperatures (7" 0) by the splat cooling technique. They were analized by X-ray diffraction and Mössbauer spectroscopy. The results were compared with results obtained in similar studies on slowly cooled and annealed samples. The previous observation that increasing tin concentration renders the formation of the amorphous phase more difficult, is confirmed. For a fixed x, and 7q < 800 °C, the higher Tq the easier the glassy phase is obtained. This behaviour reverses for T 0 > 800 °C. 
  Reference    Z. Naturforsch. 40a, 544—547 (1985); received February 16 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0544 
 Volume    40 
88Author    H. B. Sirkin, E. Arcondo, E. Duhalde, G. Nassif, QuintanaRequires cookie*
 Title    Mössbauer and X-Ray Studies on Splat Cooled SnGeCu Alloy  
 Abstract    Solid samples of (Sn Y Ge 1 _. T) 36 Cu 64 with different tin concentrations were produced by the Splat Cooling technique. The melted material was cooled down from different initial tem-peratures (T 0). These samples were analyzed by Mössbauer spectroscopy and X-ray diffraction. The results are compared with those obtained in similar measurements on the annealed samples and on the slowly cooled material. The fast quenched samples were all polycrystallines. The resultant phases are analized and a memory effect of the liquid state in the solid material is discussed. 
  Reference    Z. Naturforsch. 40a, 548—550 (1985); received March 16 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0548 
 Volume    40 
89Author    K. Schild, F. Frisius, P. Lamparter, S. SteebRequires cookie*
 Title    Evaluation of Partial Structure Factors in the Small £?-Region with Amorphous Ni 80 P 20 by Neutron Diffraction Using Isotopic Substitution  
 Abstract    Amorphous Ni 80 P20-alloys were produced under He-atmosphere by the melt spin technique. With three specimens produced from P with nat Ni, 62 Ni and °Ni elastic scattering expriments were performed using neutrons with /. = 5.4 A in the 0-region 6 • 10~ 3 A -1 = Q = 2.7 • 10"' A -1 . The measured intensities were corrected for absorption and background, desmeared, and normalized. The partial Bhatia Thornton structure factors 5 NN , See, and S»c were evaluated and allowed the following conclusions: The a-Ni 80 P 2 o-alloy contains regions with radii of about 6.5 A caused by concentration fluctuations. A method is presented which allows to determine the composition of the regions and the total content of regions within the specimen. In the small 0-region (6 • 10" 3 A -1 ^ Q ^ 4 • 10" 2 A -1) the run of the partial structure factors is proportional to Q~ 3 caused by concentration-and density-fluctuations. From the partial Fourier transforms follows a slight anisotropy concerning the chemical arrangement with correlation lengths elon-gated along the ribbon direction. 
  Reference    Z. Naturforsch. 40a, 551—558 (1985); received March 23 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0551 
 Volume    40 
90Author    A. Kawski, A. Kubicki, I. WeynaRequires cookie*
 Title    Temperature Dependence of Limiting Fluorescence Anisotropy of POPOP in Cellulose Acetate Film  
 Abstract    The effect of temperature (103 K < T < 303 K) upon the limiting fluorescence anisotropy /-0 of POPOP was investigated in a cellulose acetate film. A slow increase in /-0 was observed when reducing the temperature. Based on the Jabtonski theory, the frequency of the torsional vibrations of POPOP was determined to be co = 1.3 x 10 l2 s _1 . The depolarization due to these torsional vibrations was found to occur immediately following excitation during the thermal relaxation of the luminescent centre, thus somewhat lowering the value of the fundamental fluorescence anisotropy r { to the limiting r 0 value. 
  Reference    Z. Naturforsch. 40a, 559—561 (1985); received December 12 1984 
  Published    1985 
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 Identifier    ZNA-1985-40a-0559 
 Volume    40 
91Author    J. Peinke, B. A. Röhricht, J. Mühlbach, Ch Parisi, R. P. Nöldeke, Huebener, O. E. RösslerRequires cookie*
 Title    Hyperchaos in the Post-Breakdown Regime of p-Germanium  
 Abstract    p-Ge electrically driven into the post-breakdown regime at liquid-He temperatures produces voltage oscillations which can be attributed to the formation of a chaotic attractor. Under variation of an applied magnetic field, a change in this attractor takes place which apparently reflects an increase in attractor dimensionality. A sequence of phase plots is presented which is interpreted as a transition from ordinary chaos to hyperchaos. 
  Reference    Z. Naturforsch. 40a, 562—566 (1985); received February 28 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0562 
 Volume    40 
92Author    Tetsuo Asaji, Alarich WeissRequires cookie*
 Title    Pyroelectricity of Molecular Crystals: Benzene Derivatives  
 Abstract    The pyroelectric coefficient at constant stress was measured for meta-nitroaniline, meta-amino-phenol, and 2,3-dichlorophenol in the temperature range 90 S 7VK % melting point. A change in sign of the pyroelectric coefficient was observed in meta-nitroaniline and 2,3-dichlorophenol. At room temperature is 9 |aCm _2 K"' for meta-nitroaniline, 42 |iCm -2 K _l for meta-aminophenol, and 0.3 (iCm" 2 K _1 for 2,3-dichlorophenol (at 263 K for the latter one). By a classical harmonic oscillator model the contribution to the pyroelectric coefficient due to molecular dipole libra-tional motions was estimated to be fairly small for meta-nitroaniline. The temperature depen-dence of the coefficient of meta-nitroaniline is discussed on the basis of Boguslawski's theory. The importance of internal polar optical modes for the temperature dependence of the pyroelectric coefficient of molecular crystals is shown. 
  Reference    Z. Naturforsch. 40a, 567—574 (1985); received March 6 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0567 
 Volume    40 
93Author    J. Gripp, H. Dreizler, R. SchwarzRequires cookie*
 Title    Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum. The Methylbarrier of Ethylbromide  
 Abstract    For ethylbromide a determination of the parameters of internal rotation is given derived from the rotational spectrum of the torsional and vibrational ground state. The Br-hyperfine structure is reanalysed with higher precision. As high J transitions were measured a centrifugal distortion analysis was necessary. 
  Reference    Z. Naturforsch. 40a, 575—587 (1985); received March 13 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0575 
 Volume    40 
94Author    H. Utzel, M. StockhausenRequires cookie*
 Title    Dielectric Relaxation in Binary and Ternary Mixtures of Ethanol, Water, and Benzene or n-Hexane  
 Abstract    The complex permittivity of the partially miscible systems ethanol-water-benzene and ethanol-water-n-hexane has been measured in the frequency range from 20 MHz to 36 GHz at 20 °C. The results are described as superposition of Debye-terms, which are considered as physically significant and are ascribed to (i) higher, ill-defined, fluctuating self-and hetero-associates (main term), (ii) associates of lower order, relaxing by rotational tumbling, (iii) free molecules. The demultimerization by benzene appears to be more effective than by hexane. 
  Reference    Z. Naturforsch. 40a, 588—595 (1985); received April 4. 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0588 
 Volume    40 
95Author    -S Montjoie, W. Miiller-WarmuthRequires cookie*
 Title     
 Abstract    NMR spin-lattice relaxation rates \/T ] have been measured at 15 and 30 MHz and various temperatures in polycristalline sodium and potassium acetate. The results for CH 3 COONa are characteristic of methyl group tunnelling with a frequency which is very much larger than the NMR Larmor frequency. Derived values of the torsion energy (1.1 kJ/mol) and the ground state tunnel splitting (5.6 |aeV) agree with data obtained from inelastic neutron scattering by Clough et al. The shape of the hindering potential and the activation energy for classical reorientation (3.2 kJ/mol) have been determined. Since the relaxation rate of CH 3 COOK is a superposition of at least two mechanisms, in this case the results are less accurate and refer to one type of CH 3 rotor only: activation energy 5.4 kJ/mol, tunnel splitting 0.23 ueV. Comparison is made between tunnel splittings and classical activation energies for the acetates and various other materials: strong correlations are demonstrated and discussed. 
  Reference    Z. Naturforsch. 40a, 596—601 (1985); received April 12. 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0596 
 Volume    40 
96Author    S. Jurga, H. W. SpiessRequires cookie*
 Title    Interrelation between Molecular Motions and Phase Transitions in Monomethylammonium Perchlorate. A Study by DSC, Proton, and Deuteron NMR  
 Abstract    Differential scanning calorimetry, the temperature dependence of proton and deuteron line-shapes and spin-lattice relaxation times are reported for the isotopic species CH 3 NH 3 C10 4 , CD 3 NH 3 C104 and CH 3 ND 3 C104 of monomethylammonium Perchlorate. The data confirmed the existence of three different phase modifications in monomethylammonium Perchlorate and its selec-tively deuterated analogues. In addition they were used to identify the molecular motions occurring in the respective phases and to determine their activation parameters. In the low temperature phase III, stable below 320 K. the CH 3 and NH 3 groups reorient about their threefold symmetry axes C 3 with different frequencies. In the low-temperature range of this phase the deuteron quadrupole coupling constant indicates N-H ... O hydrogen bonds between the monomethylammonium and the Perchlorate ions. In the intermediate phase II, between 320 K and 451 K for CH 3 NH 3 C10 4 and CD 3 NH 3 C10 4 and 320 K and 437 K for CH 3 ND 3 C10 4 , the methylammonium ions reorient about an axis inclined at an angle of 18 degrees to the C 3 axis. The analysis of the entropy changes, associated with the III-II transitions indicates that the C10 4 ions have a large motional freedom in phase II, presumably because of breaking or weakening of N-H...Ö hydrogen bonds. In phase I the monomethylammonium ions undergo isotropic motion along with translational diffusion between different sites of the primitive cubic unit cell. 
  Reference    Z. Naturforsch. 40a, 602—610 (1985); received April 4. 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0602 
 Volume    40 
97Author    Ariel Fernández, Oktay SinanogluRequires cookie*
 Title    A Reactive System with Diffusive Transport Displaying Two Different Symmetry-Breaking Dissipative Structures  
 Abstract    An open reactive system is modelled by coupling the chemical kinetics to diffuse transport. This system operates far from the regime of linear irreversible thermodynamics. The kinetics correspond to a certain region in the parameter space of the Oregonator for which two symmetry-breakdowns occur: a) A periodic orbit contained in an unstable manifold of the phase space. This solution is invariant under time-translations generated by a period. b) A spatial stationary dissipative structure. This solution is invariant under a subgroup of the space symmetry group. The initial time periodicity of the system is followed by a spatial pattern. The restriction to the center manifold in the phase space allows to reduce an infinite-dimensional problem for the bifurcation of a semiflow to a finite dimensional system of ordinary differential equations. The ranges in the control concentrations for this dynamics is found in accord with the experimental values. We also demonstrate that if the vessel is stirred after the Turing pattern has emerged, the freezed wave is destroyed and the time-periodic behavior is achieved again. 
  Reference    Z. Naturforsch. 40a, 611—618 (1985); received October 15 1984 
  Published    1985 
  Keywords    Bifurcation under a symmetry group, Center Manifold Theorem, Dissipative structure 
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 Identifier    ZNA-1985-40a-0611 
 Volume    40 
98Author    Klaus Scheffler, Klaus Stolze, HartmutB. StegmannRequires cookie*
 Title    Konformationsuntersuchungen an Tetrahydroisochinolin-und Tetrahydronaphthalin-Semichinonen durch ESR-Spektroskopie  
 Abstract    Semiquinones of 6,7-dihydroxy-l,2,3,4-tetrahydroisoquinolines and -naphthalenes are inves-tigated by ESR-spectroscopy in the presence of diorganothalliumhydroxide. The ESR-spectra show a significant temperature dependence of the coupling constants of the /^-methylene protons due to ring inversion of the partially hydrogenated ring. Computer simulation of the spectra gave the rate constants and the activation parameters for this ring inversion process. The heterocyclic compounds show considerably lower rate constants due to implication of N-inversion. In comparison to analogous cyclohexene-semidione systems, our systems showed rate constants about 10 times higher than those of their monocyclic counterparts. 
  Reference    Z. Naturforsch. 40a, 619—626 (1985); eingegangen am 3. April 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0619 
 Volume    40 
99Author    NguyenX. Phuc, W. Otowski, J. Chruściel, H. Kresse, S. Urban, S. WróbelRequires cookie*
 Title    Megahertz Dielectric Relaxation in the Nematic Phases of 4,4 / -di-n-propyloxyazoxybenzene and 4,4'-di-n-pentyloxyazoxybenzene  
 Abstract    The dielectric properties of the third (3. OAOB) and fifth (5. OAOB) members of the PAA homologous series have been investigated in the frequency range from 0.1 to 12 MHz. Negative dielectric anisotropics have been obtained in the nematic phase of both substances. For the dielectric relaxation processes observed parallel to the nematic director, the relaxation times and activation energies have been estimated and discussed. 
  Reference    Z. Naturforsch. 40a, 627—631 (1985); received February 22 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0627 
 Volume    40 
100Author    S.Krishna Prasad, S. Pfeiffer, G. Heppke, R. ShashidharRequires cookie*
 Title    Effect of Pressure on Strongly Polar Liquid Crystals  
 Abstract    The effect of pressure on several mesogens which possess a strongly polar terminal group (CN or N0 2) is studied. In all cases the partially bilayer smectic A (A d) gets bounded while the nematic phase gets more stabilised at high pressures. In the case of reentrant nematogens, the maximum pressure of smectic stability is seen to be related to the temperature range of the nematic phase at 1 bar. 
  Reference    Z. Naturforsch. 40a, 632—635 (1985); received March 6. 1985 
  Published    1985 
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 Identifier    ZNA-1985-40a-0632 
 Volume    40 
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