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  • Analytical Chemistry and Spectroscopy  (18)
  • 25.70.Ef  (3)
  • Chiral pharmaceuticals  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Systematic studies of positron production in heavy-ion collisions near the Coulomb barrier (1992)
    Springer
    The European physical journal 342 (1992), S. 79-94 
    Details
    ISSN: 1434-601X
    Keywords: 14.60.Cd ; 25.70.Cd ; 25.70.Ef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results obtained from systematic studies of positron creation for a series of heavy-collision systems, with united chargeZ u =Z 1 +Z 2 ranging fromZ u =164 (Pb + Pb) toZ u =184 (U+U) at bombarding energies close to the Coulomb barrier, using the Orangeβ-spectrometer at GSI. For each collision system studied, the dominating continuous distributions due to quasiatomic and nuclear positron emission are determined accurately. This is essential in obtaining the characteristics of the still unexplained monoenergetic positron lines which appear in the energy range between 200 keV and 400 keV. Our results are compared with coupled-channels calculations for quasi-atomic positron creation. The latter describe quite well the global features of the measured spectra, but overestimate systematically their absolute values. From the comparison, a common normalization factor of about 0.75 can be established for the calculated spectra. In particular, the dependence onZ u of the measured emission probabilities was found to follow a power law (∝Z u 195±1), in fair agreement with the theoretical prediction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294492
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  • 2
    Electronic Resource
    Electronic Resource
    Investigations of correlated ρ+ e− emission in heavy-ion collisions near the Coulomb barrier (1993)
    Springer
    The European physical journal 346 (1993), S. 153-168 
    Details
    ISSN: 1434-601X
    Keywords: 14.60.Cd ; 25.70.Cd ; 25.70.Ef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results obtained from a series of ρ+ρ−-coincidence measurements in heavy-ion collisions using the double-Orangeβ-spectrometer at GSI. The collision systems U+U, U+Pb, and U+Ta were investigated at bombarding energies close to and slightly above (U+Ta) the Coulomb barrier. For all systems studied, very narrow (FWHM−20 keV) ρ+ρ− lines were observed in the sum-energy spectra, with kinetic energies ranging from ∼555 keV to ∼810 keV, superimposed on a continuous distribution mainly due to uncorrelated ρ+ρ− emission. Particularly in the U+Ta system, a pronounced sum-energy line appears at ∼634 keV, predominantly in deep-inelastic collisions. In some cases (e.g. U+Pb) the line characteristics is consistent with a two-body decay mode of an emitter which moves with the c.m. velocity of the colliding ions. However, other lines, and in particular the 634 keV line (U+Ta), exhibit a rather isotropical opening-angle distribution whereas their energy is unequally shared between positrons and electrons, thus being in clear disagreement with this scenario. In general, the data preclude an emission from the separated (moving) nuclei, and, in the latter cases, provide evidence that the e+e−-pair decay occurs in the vicinity of the Coulomb field of a third heavy (positively charged) partner having only a small transverse velocity (|v|⊥〈0.02c)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294631
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  • 3
    Electronic Resource
    Electronic Resource
    Positron lines from subcritical heavy ion-atom collisions (1987)
    Springer
    The European physical journal 328 (1987), S. 129-145 
    Details
    ISSN: 1434-601X
    Keywords: 14.60.Cd ; 25.70.Cd ; 25.70.Ef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Positron lines were observed in heavy ion-atom collisions at bombarding energies close to the Coulomb barrier in subcritical systems with the sum of the atomic numbers of the colliding nucleiZ u =Z 1+Z 2 being smaller thanZ u =172. Each collision system, studied,208Pb +208Pb(Zu=164),238U+181Ta(Zu=165), and238Au(Zu=171), exhibits the emission of two positron lines withZ u -independent c.m. energies of ∼ 258 keV and ∼ 340 keV, and with widths of about 30 keV, superimposed on continuous positron spectra from nuclear pair decay and pair emission induced by the time changing Coulomb field of the collision. The production cross section of thee +-lines rises with a high power ofZ u (ocZ u 22), which is comparable to theZ u 20-dependence for the collision induced positrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290655
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  • 4
    Electronic Resource
    Electronic Resource
    Negative ion FAB mass spectrometric analysis of non-charged key intermediates in oligonucleotide synthesis: Rapid identification of partially protected dinucleoside monophosphates (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 111-116 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dinucleoside monophosphates bearing usual protecting groups at the exocyclic amino functions of the heterocyclic bases, the 5′-hydroxy group, the phosphate moiety and the O-6-position of the guanine ring have been analysed by FAB mass specrometry in the negative ion mode. These non-charged key intermediates for oligodeoxynucleotide synthesis exhibit very simple spectra in the mass range of m/z 400-1500 using tetra-ethylene glycol as matrix. Most of the observed ions could easily be assigned. Apart from deprotonated molecular ions sequence specific ions arising from C-O-P bond cleavage and ions derived from loss of protecting groups were observed. The simplicity of spectra interpretation makes FAB mass spectrometry to a rapid and valuable tool for unambiguous identification of dimeric synthons for oligonucleotide synthesis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200140304
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  • 5
    Electronic Resource
    Electronic Resource
    Identification of volatile organic sulfur compounds in municipal sewage systems by GC/MS (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 415-416 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography/mass spectrometry ; Volatile sulfur compounds from waste water ; Adsorption of air samples on tenax GC ; Mechanism of corrosion of concrete ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240030808
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Gas chromatographic resolution of carbohydrate enantiomers. A new chiral phase for pentoses (1981)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 553-556 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Carbohydrate enantiomer separation ; New chiral stationary phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New chiral polymers have been prepared by conversion of cyano groups of polysiloxanes XE-60 and OV-225 into carboxylic groups and subsequent coupling to give the respective S-valine-R-α-phenyl-ethyl amide. In contrast to the corresponding stationary phases with S-α-phenylethyl amide groups, which have been used for the resoultion of trifluoroacetylated hexose derivatives, the new phase show high enantioselectivity for pentose and 6-deoxyhexose derivatives.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240041103
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  • 7
    Electronic Resource
    Electronic Resource
    GC/MS investigations of the constituents in a diethyl ether extract of an acidified roast coffee infusion (1978)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 69-71 
    Details
    ISSN: 0935-6304
    Keywords: Gas Chromatography Mass Spectrometry ; Capillary, glass/Varian, MAT 311A ; Separation and detection (El, Cl) of some roast coffee constituents ; Three new phenolic compounds found ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A roast coffee infusion (nicaragua arabica) was acidified (pH 1,5) with hydrochloric acid and extracted with diethyl ether in a perforator. After evaporation of the solvent the residue was treated with N-methyl-N-trimethylsilyl trifluoroacetamide and analyzed by glass capillary GC/MS. The main components were identified by their electron impact and isobutane chemical ionization mass spectra. 1,2,4-trihydroxy benzene, 1-ethyl-3, 4-dihydroxy benzene and 2,3-dihydroxy toluene were identified as new constituents of roast coffee with possible emetic properties.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240010114
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  • 8
    Electronic Resource
    Electronic Resource
    The use of glass capillary columns for the analysis of polar natural products (1979)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 378-384 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Glass capillaries for low volatile polar natural products analysis ; Application to N-TFA-dipeptide, TMS-ribose, TMS-manno-samin, peptide sequence analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two published procedures for glass capillary column production are applied to produce capillaries for chromatography of polar natural compounds. Soda lime glass capillaries, after leaching with aqueous HCL, are either treated with colloidal silicic acid or with barium carbonate and coated with either Silar 7CP or SE 52. A test mixture as well as polar carbohydrate and peptide mixtures are chromatographed on the different columns and their chromatographic properties are evaluated. Combined capillary gas chromatography-electron impact and chemical ionization mass spectrometry are used for identification of the peptide sequence.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240020622
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  • 9
    Electronic Resource
    Electronic Resource
    Separation of enantiomers by capillary gas chromatography with chiral stationary phases (1982)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 588-595 
    Details
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240051102
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  • 10
    Electronic Resource
    Electronic Resource
    Multidimensional capillary gas chromatography-enantiomeric separations of selected cuts using a chiral second column (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 404-410 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Multidimensional capillary columns ; Enantiomeric separations ; Intermediate trapping ; Mixed polarities ; Terpene alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240070711
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