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1994[X]
141Author    U. Lan In, U. H., YuM. Ladvishchenko1, K. K.Requires cookie*
 Title    Temperature Dependence of the Second Dielectric Virial Coefficients of Rare Gases  
 Abstract    Second dielectric virial coefficients BZ(T) of the rare gases Ne, Ar, Kr, and Xe are calculated in a broad range of temperature using accurate HFD-type interatomic interaction potentials and available information on the trace of the pair polarizability Aa. It is shown that the experimentally determined temperature-variation of BC(T) cannot be reproduced by existing theories. However, it is observed that the reduced dimensionless form of BC(T) follows a remarkably regular pattern, strongly resembling the sign-inverted temperature variation of the second density virial coefficient Be(T) with the same Boyle-temperature. 
  Reference    Z. Naturforsch. 49a, 890—894 (1994); received 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0890.pdf 
 Identifier    ZNA-1994-49a-0890 
 Volume    49 
142Author    Jacek ZaleskiRequires cookie*
 Title    Crystal Structure and Phase Transitions of [C(NH2)3]3Sb2C l9 * 0.9 H 20 A dam Pietraszko  
 Abstract    The room temperature structure of [C(NH2)3]3Sb2C l9 ■ 0.9 H 20 (GNCA) was solved. It crystal­ lizes in the monoclinic C2/c space group with a = 15.275, b = 8.794, c = 17.904 (in Ä), ß = 96.40°, V = 2390 Ä 3, Z = 4. Refinement of the atomic parameters by a least squares methods gave R = 0.042, wR = 0.039 for 1958 reflections with F>4ct(F). The structure consists of polyanionic (Sb2Cl|_)n layers built of deformed corner connected SbX^-octahedra. Two crystallographically inequivalent guanidinium cations are present, one situated between polyanionic layers, the other one together with a disordered water molecule inside cavities formed by polyanions. Temperature X-ray scattering experiments together with DSC studies were carried out above room temperature. Temperature dependence of the lattice parameters between 300 K and 380 K was determined and a phase transition of mixed order at 364 K was revealed. 
  Reference    Z. Naturforsch. 49a, 895—901 (1994); received June 7 1994 
  Published    1994 
  Keywords    Guanidinium, Chloroantimonate, Crystal structure, Phase transition, DSC 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0895.pdf 
 Identifier    ZNA-1994-49a-0895 
 Volume    49 
143Author    E. W. RichterRequires cookie*
 Title    Similarity Solutions of the Force-free Magnetic Field Equations  
 Abstract    Force-free magnetic fields are described as solutions of special nonlinear partial differential equations which are replaced frequently through linear equations. To record the diversity of the structures of these fields, a discussion of the nonlinear equations is necessary. For this purpose the method of similarity analysis is used. The Lie symmetry groups admitted by the nonlinear equations for force-free magnetic fields are presented. To record and classify the different types of group-invari-ant solutions, one-and two-dimensional optimal systems of subalgebras are listed. The reduced equations of the two-dimensional optimal system are systems of ordinary differential equations, and their solutions define similarity solutions which are force-free magnetic fields. Only in one case is it necessary to calculate similarity solutions numerically. The corresponding reduced equations are a nonautonomous dynamical system with the similarity variable in the place of time. 
  Reference    Z. Naturforsch. 49a, 902—912 (1994); received July 12 1994 
  Published    1994 
  Keywords    Magnetic fields, Nonlinear PDE, Plasma equilibrium, Similarity solutions 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0902.pdf 
 Identifier    ZNA-1994-49a-0902 
 Volume    49 
144Author    I. P., M. Hepp, R. Philipp, R. Schieder, G. WinnewisserRequires cookie*
 Title    Double Modulation Technique in Pulsed Jet Experiments with Tunable Diode Lasers  
 Abstract    A double modulation technique was used to achieve higher sensitivity in absorption measure­ ments with a pulsed supersonic jet. The wavelength of a lead-salt diode laser was modulated at a frequency of 10 kHz and detected at twice the frequency by a lock-in amplifier, reducing significantly the influence of the low frequency excess laser noise. The output of this lock-in amplifier was measured by a boxcar integrator, driven at 80 Hz, the frequency of the pulsed jet. In case the duration of the jet pulse is long enough, a second lock-in amplifier can also be used instead of the boxcar integrator. The optical path of the diode laser radiation through the jet was increased 16 times by using White type multireflection optics. The achieved value for the minimum detectable absorption of A r-C O complexes in the jet was 2 x 10-5 in relative absorption, limited by the excess noise of the diode laser. 
  Reference    Z. Naturforsch. 49a, 913—919 (1994); received July 27 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0913.pdf 
 Identifier    ZNA-1994-49a-0913 
 Volume    49 
145Author    R. Buchert, K. SchilcherRequires cookie*
 Title      
 Abstract    We use a resistor network model for electrical impedance reconstruction from boundary data. On the basis of a particular choice o f currents we construct a stable inversion algorithm. 
  Reference    Z. Naturforsch. 49a, 920 (1994); received April 15 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0920.pdf 
 Identifier    ZNA-1994-49a-0920 
 Volume    49 
146Author    R. C. Sharma, V. K. BhardwajRequires cookie*
 Title     
 Abstract    n d O l d r o y d i a n V i s c o e l a s t i c F l u i d s i n P o r o u s M e d i u m The Rayleigh-Taylor instability of viscous and viscoelastic (Oldroydian) fluids, separately, has been considered in porous medium. Two uniform fluids separated by a horizontal boundary and the case of exponentially varying density have been considered in both viscous and viscoelastic fluids. The effective interfacial tension succeeds in stabilizing perturbations of certain wave numbers (small wavelength perturbations) which were unstable in the absence of effective interfacial tension, for unstable configuration/stratification. 
  Reference    Z. Naturforsch. 49a, 927 (1994); received July 1993 
  Published    1994 
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 Identifier    ZNA-1994-49a-0927 
 Volume    49 
147Author    P. Bojarski1, A. K. Aw Ski1, B. Kukliń, K. I1, H. D. Iehl2Requires cookie*
 Title      
 Abstract    The reverse non-radiative excitation energy transfer (RNEET) in the system of rhodamine 6G (R6G, donor) and rhodamine B (RB, acceptor) is investigated. The presence of RNEET from the energy acceptors to the energy donors is dem onstrated using steady-state fluorescence and fluores­ cence anisotropy techniques. The spectra are deconvoluted and obtained results are analysed. 
  Reference    Z. Naturforsch. 49a, 931 (1994); received July 22 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0931.pdf 
 Identifier    ZNA-1994-49a-0931 
 Volume    49 
148Author    A. Kawski, G. PiszczekRequires cookie*
 Title     
 Abstract    h o t o s e l e c t i o n o f L u m i n e s c e n t M o l e c u l e s in A n i s o t r o p i c M e d i a i n t h e C a s e o f T w o -P h o t o n E x c i t a t i o n . P a r t I . T h e o r e t i c a l C o n s i d e r a t i o n s Photoselection of elongated luminescent m olecules oriented in a stretched polymer film is consid­ ered theoretically for the case of two-and three-photon excitation, having in mind the employment of this phenomenon for determining the angle between the absorption and emission transition moments. Two-photon photoselection provides information on electronic excited states which are not detectable by conventional one-photon spectroscopy due to selection principles. 
  Reference    Z. Naturforsch. 49a, 936 (1994); received August 6 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0936.pdf 
 Identifier    ZNA-1994-49a-0936 
 Volume    49 
149Author    B. A. Bilal, E. MüllerRequires cookie*
 Title     
 Abstract    f A q u e o u s S u l f u r i c A c i d o f D i f f e r e n t M o l a l i t i e s u p t o 4 7 3 K a n d 9 7 5 b a r The apparent formation constant and the dissociation degree of H SO 4 in aqueous H 2S 0 4 o f the m olalities 0.1, 0.5, and 1.0 m, as well as the real mean ionic coefficient have been calculated up to 473 K and 975 bar using the thermodynamic data reported by H olm es and Mesmer at saturation pressure and those given by the authors at higher pressure. 
  Reference    Z. Naturforsch. 49a, 939 (1994); received August 12 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0939.pdf 
 Identifier    ZNA-1994-49a-0939 
 Volume    49 
150Author    B. A. Bilal, E. M. ÜllerRequires cookie*
 Title     
 Abstract    o t e n t i a l o f t h e A q u e o u s A g -A g 2S 0 4 E l e c t r o d e in l m N a 2S 0 4 in C o n t a c t w ith 1 m H 2S 0 4 a t u p t o 4 7 3 K a n d 9 7 5 b a r The potential of the A g -A g 2S 0 4 electrode in 1 m N a 2S 0 4 solution in contact with 1 m H 2S 0 4 solution has been determined up to 473 K and 975 bar. The potential of the electrode in aqueous 1 m N a 2S 0 4 solution without accounting for any diffusion was calculated under the same p and T conditions taking the formation of N a S 0 4 into account. Small differencies (< 2%) have been found in comparison with the values given previously by the authors [1] assuming a complete dissociation o f N a 2S 0 4 . 
  Reference    Z. Naturforsch. 49a, 943 (1994); received August 12 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0943.pdf 
 Identifier    ZNA-1994-49a-0943 
 Volume    49 
151Author    M. Ehmet Birey, Huseyin Aktas, D. M. Ehmet ZenginRequires cookie*
 Title     
 Abstract    S R o f G a m m a I r r a d i a t i o n D a m a g e C e n t e r s in S i n g l e C r y s t a l s o f T h r i e t h a n o l a m i n e H y d r o c h l o r i d e We have observed two radicals in the ESR spectra of y-irradiated single crystals o f thriethanol­ amine hydrochloride: R -N H and H N = C -R . 
  Reference    Z. Naturforsch. 49a, 946—9 (1994); received August 9 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0946.pdf 
 Identifier    ZNA-1994-49a-0946 
 Volume    49 
152Author    S.V H, H. Ard, M. Stockhausen, J. Jad, P. Kędziora, A. G. Honeim, G. TurkyRequires cookie*
 Title    M ünster (Germany) Institute o f M olecular Physics, Polish Academy o f Sciences, 60-179 Poznan (Poland)  
 Abstract    The static and dynamic dielectric properties o f the title system are reported for a concentration series from about 8 mmol/1 up to 2.3 m ol/I at 2 0 °C. The apparent m om ent (4.2 D , extrapolated to infinite dilution) decreases with increasing concentration, the relaxation time increases proportional to viscosity, that is, somewhat steeper than usually observed. Com parison with other molecules suggests that these features are mainly due to the high dipole m om ent rather than being specifically related to the prolate shape o f the molecule. The broadening o f the spectrum toward the high frequency side, on the other hand, may be due to the molecular shape. 
  Reference    Z. Naturforsch. 49a, 949 (1994); received August 5 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0949.pdf 
 Identifier    ZNA-1994-49a-0949 
 Volume    49 
153Author    K.-P Zeyer, G. Dechert, W. H. Ohm, Ann, R. Blittersdorf, F. W. SchneiderRequires cookie*
 Title     
 Abstract    o u p l e d B i s t a b l e C h e m i c a l S y s t e m s -E x p e r i m e n t a l R e a l i z a t i o n o f B o o l e a n F u n c t i o n s U s i n g a S i m p l e F e e d f o r w a r d N e t We use the BZ-reaction and the M BO-reaction to implement the Boolean functions A N D , OR, N A N D , and N O R by the coupling of three chemical reactors. The experimental setup is analogous to a simple neural feedforward network with two reactors serving as the input layer and one reactor as the output layer. Coupling between the input and output reactors is carried out through the flow rate (BZ-and M BO-reaction) and through the electrical current by the use o f Pt working electrodes (BZ-reaction). The XOR-and X N O R functions may be realized with 5 reactors using com binations o f the A N D , N O R , N O R -and the A N D , NO R, Or-chemical gates, respectively. 
  Reference    Z. Naturforsch. 49a, 953 (1994); received M ay 28 1994 
  Published    1994 
  Keywords    Nonlinear systems, Flow-rate-coupling, functions 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0953.pdf 
 Identifier    ZNA-1994-49a-0953 
 Volume    49 
154Author    F. Burak, J. Tyrzyk, Z. PolackiRequires cookie*
 Title      
 Abstract    Time resolved em ission spectra and the luminescence decay of 2,5-diphenyloxasole in dioxane-water mixtures disclose an im portant influence o f water on the observed luminescence. We suppose that this is caused by structural changes of the solution connected with its water content. 
  Reference    Z. Naturforsch. 49a, 964 (1994); received July 16 1994 
  Published    1994 
  Keywords    Luminescence, Excimers, TRES, Em ission spectra, Solution structure 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0964.pdf 
 Identifier    ZNA-1994-49a-0964 
 Volume    49 
155Author    I. Bakó, G. Pálinká, K. HeinzingerRequires cookie*
 Title      
 Abstract    X-ray diffraction patterns o f m ethanol-water mixtures with mole fractions of m ethanol molecules o f 0.1, 0.25 and 0.9 have been measured. The experimental structure functions of mixtures are compared with those of pure solvents and with recent M olecular Dynam ics results. Difference structure functions similar to thermodynam ic excess functions are introduced for the analysis of methanol-water interactions. The com parison o f the total and the difference structure functions from experiments and sim ulations show s an overall good agreement. 
  Reference    Z. Naturforsch. 49a, 967—9 (1994); received August 18 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0967.pdf 
 Identifier    ZNA-1994-49a-0967 
 Volume    49 
156Author    TetsuoM. OrikawaRequires cookie*
 Title      
 Abstract    It is possible to regard two polygonal skeletons as the same in a special class o f carbocyclic and heterocyclic compounds, if the one is reducible to the other by means o f the contraction o f cyclic subskeletons, and if the numbers of conjugated patterns in them are equal to each other. In such polygonal skeletons, three forms of cyclic subskeletons are defined; the one is called "alternate", and the others, involving the one called "inclusive", have a path (b, b), where (b) is a conjugated vertex connecting with three vertices. Successive eliminations of the cyclic subskeletons enable to estimate the upper and lower bounds for the number o f conjugated patterns in a given polygonal skeleton. 
  Reference    Z. Naturforsch. 49a, 973—9 (1994); received July 25 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0973.pdf 
 Identifier    ZNA-1994-49a-0973 
 Volume    49 
157Author    M. Aria, PaolaM. Edda, Giorgio Piccaluga, Gabriella Pinna, M. Arco BettinelliRequires cookie*
 Title     
 Abstract    o o r d i n a t i o n o f E u 3 + I o n s i n a P h o s p h a t e G l a s s b y X -r a y D i f f r a c t i o Two vitreous samples, 0.9 Z n (P 0 3)2 • 0.1 E u (P 0 3)3 and pure zinc m etaphosphate, were examined by X-ray diffraction to determine the local environment o f the E u3+ ion. U sing a difference proce­ dure involving the radial functions of the two glasses, the results indicate that the rare-earth ion is surrounded on average by a polyhedron o f about 7.4 oxygens at 2.36 A and about 1.6 oxygens at 2.68 Ä. A possible different coordination of the zinc ion in the two samples, suggested by the experimental findings, is discussed. 
  Reference    Z. Naturforsch. 49a, 977 (1994); received July 25 1994 
  Published    1994 
  Keywords    X-ray diffraction, Structure o f glasses, Rare-earth ions phosphates 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0977.pdf 
 Identifier    ZNA-1994-49a-0977 
 Volume    49 
158Author    Nagt, Rajkumar RoychoudhuryRequires cookie*
 Title    Nivedita  
 Abstract    A set of exact eigen values and eigen functions for the two body Dirac problem described by the Hamiltonian H = (oil-a 2)p + ßi m i+ ß2rri2 + \ (ßi + ßi) Är­ are obtained using the properties of Supersymmetric Quantum Mechanics. 
  Reference    Z. Naturforsch. 49a, 983—986 (1994); received May 16 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0983.pdf 
 Identifier    ZNA-1994-49a-0983 
 Volume    49 
159Author    Yoshio Ogawaa, WasedaRequires cookie*
 Title    Hiroshi  
 Abstract    A new structure model of liquid silicon is tested by incorporating the local bond orientational order and the medium-range radial distribution. The shoulder observed on the high Q side of the principal peak in the structure factor of liquid silicon appears to be mainly caused by the atomic radial distribution in the range from 0.4 to 0.6 nm. On the other hand, a molecular dynamics simulation on liquid silicon shows that the angular distribution of neighboring atoms has tetrahedral-like features, similar to those in the ß-tin type crystal structure with c/a = 0.7. With these facts in mind, a new geometrical model of liquid silicon is proposed which simultaneously satisfies the experimental density, radial distribution, calculated bond orientational order, and typical liquid nature of random orientation in the long range. 
  Reference    Z. Naturforsch. 49a, 987—995 (1994); received August 24 1994 
  Published    1994 
  Keywords    Liquid silicon, Pair distribution function, Structure factor, Bond orientational order, Structure model 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0987.pdf 
 Identifier    ZNA-1994-49a-0987 
 Volume    49 
160Author    Bastian Bergerhoff, Gerhard SoffRequires cookie*
 Title      
 Abstract    The Dirac equation is solved for various types of scalar potentials. Energy eigenvalues and normalized bound-state wave functions are calculated analytically for a scalar 1 / r-potential as well as for a mixed scalar and Coulomb 1 / r-potential. Also continuum wave functions for positive and negative energies are derived. Similarly, we investigate the solutions of the Dirac equation for a scalar square-well potential. Relativistic wave functions for scalar Yukawa and exponential potentials are determined numerically. Finally, we also discuss solutions of the Dirac equation for scalar linear and quadratic potentials which are frequently used to simulate quark confinement. 
  Reference    Z. Naturforsch. 49a, 997—1012 (1994); received October 5 1994 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0997.pdf 
 Identifier    ZNA-1994-49a-0997 
 Volume    49 
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