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'N M R' in keywords
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1996 (1)
1994 (4)
1Author    N. F. Peirson, J.A S Smith, D. StephensonRequires cookie*
 Title    70 Quadrupole Dips in Ammonium Persulphate  
 Abstract    The magnetic field dependence of the *H spin-lattice relaxation time in ammonium persulphate shows pronounced minima near the JH magnetic resonance frequencies of 1,200 and 2,200 kHz. These are interpreted in terms of a m odel involving cross-relaxation between *H in the N H 4 ion and 170 in natural abundance in the S2O g_ ions, the latter having a much shorter spin-lattice relaxation time. A theoretical analysis of the shape of the minima is used to derive values for the 170 quadrupole parameters. This analysis results in best estimate values for the quadrupole coupling constant of 6.75 (± 0.05) M Hz and an asymmetry of 0.30 (± 0.02). Such values are indicative o f O -H hydrogen bonding and suggest the S2O g _ ion is not undergoing rapid reorientation at temperatures below 320 K. 
  Reference    Z. Naturforsch. 49a, 345 (1994); received August 16 1993 
  Published    1994 
  Keywords    N M R, N Q R, Field cycling, Oxygen-17 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0345.pdf 
 Identifier    ZNA-1994-49a-0345 
 Volume    49 
2Author    O. Wegener3, R. K. Üchler3, A. W. AtterichbRequires cookie*
 Title      
 Abstract    12STe nuclear spin relaxation (NSR) and electrical conductivity measurements were performed on ultrapure single-crystalline paratellurite (a -T e0 2) between about 50 K and the melting point (1007 K) at various oxygen partial pressures (1 b a r -10"4 bar). At elevated temperatures the NSR rate l / 7 \ and conductivity a are caused by the diffusive motion o f point defects. From the observed p02-dependence of 1/Ti and a a defect model is developed which is shown to be consistent with the experimental data. The m odel involves ionic oxygen interstitials (O"), doubly charged oxygen vacancies (Vo') and charge-com pensating electron holes (h'). The observed pressure dependence suggests that the N SR rate is induced by the m otion of \ q while the conductivity is due to the m obility o f h*. Evaluation o f the data leads to 3.3 eV for the incorporation enthalpy o f oxygen on interstitial sites and to 4.5 eV for the formation enthalpy of oxygen Frenkel pairs (O "-V q'). Further, the chemical diffusion coefficient Dc is found to be caused by the ambipolar diffusion o f OS' and h \ At 950 K we obtained from both the NSR and conductivity experiments D c = (1 ± 0.3) • 10" 5 cm 2/s. 
  Reference    Z. Naturforsch. 49a, 1151 (1994); received August 22 1994 
  Published    1994 
  Keywords    Oxides, Point defects, Diffusion, N M R, Conductivity 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-1151.pdf 
 Identifier    ZNA-1994-49a-1151 
 Volume    49 
3Author    Barbara Szafrańska, Zdzisław PająkRequires cookie*
 Title    Molecular Motion in Solid Tetraethyl-and Tetrabutylammonium Perchlorates  
 Abstract    The proton N M R second moment and spin-lattice relaxation time for polycrystalline tetraethyl-and tetrabutylammonium perchlorates have been measured over a wide range of temperatures. Solid-solid phase transitions related to the onset of cation tumbling were found for both compounds and confirmed by DSC. In the low temperature phases methyl-group reorientation was evidenced. For tetrabutylammonium cation a dynamic nonequivalence of one methyl group is found. The geared motion of the alkyl chains related with the onset of successive C H 2-group reorientations is suggested. 
  Reference    Z. Naturforsch. 49a, 465—468 (1994); received December 7 1993 
  Published    1994 
  Keywords    N M R, Molecular motions, Phase transitions 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0465.pdf 
 Identifier    ZNA-1994-49a-0465 
 Volume    49 
4Author    IouriE. Borissevitcha+, ChristianeP F Borgesa++, GalinaP. Borissevitcha+++, VictorE. Yushmanova+, SoniaR W Louroh, Marcel TabakaRequires cookie*
 Title    Binding and Location of Dipyridamole Derivatives in Micelles: the Role of Drug Molecular Structure and Charge  
 Abstract    Binding and localization of the vasodilator and antitumor drug coactivator dipyridamole (D IP) and of its three derivatives, RA14. RA47 and RA25 (D IP D), to cationic (cetyltrimeth-ylammonium chloride), anionic (sodium dodecylsulfate), zwitterionic (N-hexadecyl-N.N-di-methyl-3-ammonio-l-propanesulfonate). and neutral (r-octylphenoxypolyethoxyethanol) m i­ celles was studied using fluorescence, optical absorption and 'H N M R spectroscopy. The analysis of N M R . optical absorption and fluorescence data indicates that the depth of local­ ization of the drugs in the micelles from the surface decreased in the order D IP > RA 14 > RA47 > RA25. The binding constants for the neutral drug forms change in the same order in the range of 1400-3100 m _1 for D IP to 80-300 m _1 for RA25. This order is identical with the reported biological activity of D IP D . For the protonated drugs in zwitterionic or neutral micelles the binding constants are reduced by a factor of 20-75. 
  Reference    Z. Naturforsch. 51c, 578—590 (1996); received March 28/May 31 1996 
  Published    1996 
  Keywords    Dipyridamole and Derivatives, Micelle, Drug Location, Absorption, Fluorescence, N M R 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0578.pdf 
 Identifier    ZNC-1996-51c-0578 
 Volume    51 
5Author    G. Sulzer, B. Itterm, E. Diehl, B. Fischer, H.-P Frank, E. Jäger, W. Seelinger, H.-J Stockmann, H. AckermannRequires cookie*
 Title    Temperature Dependence of Impurity Induced EFG's in Extremely Diluted CuB  
 Abstract    The temperature dependence of impurity induced EFG 's around implanted 12B ions in Cu was measured for two lattice locations using the ß-N M R method. The induced EFG at the nearest neighbouring host atoms decreases with increasing temperature for the case of 12B stopped on interstitial sites, whereas the opposite temperature behaviour was found if 12B is situated in substi­ tutional sites. 
  Reference    Z. Naturforsch. 49a, 354 (1994); received July 23 1993 
  Published    1994 
  Keywords    N M R, ß radiation detected, Cross relaxation, Electric field gradient, Temperature dependence o f EFG, Impurity induced EFG 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0354.pdf 
 Identifier    ZNA-1994-49a-0354 
 Volume    49