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  • mesophases  (2)
  • Adolescents  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Cigarette withdrawal symptoms in adolescent smokers (1986)
    Springer
    Psychopharmacology 90 (1986), S. 533-536 
    Details
    ISSN: 1432-2072
    Keywords: Cigarette smoking ; Withdrawal ; Adolescents ; Cotinine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract One hundred and sixteen female adolescent smokers were asked about withdrawal symptoms experienced during past attempts to give up smoking for good. Sixty-three percent reported difficulties during abstinence of the kind experienced by adult smokers. Daily smokers were more likely to report withdrawal effects than non-daily smokers (74% versus 47%, P〈0.005). Reported experience of withdrawal symptoms was positively related to self-reports of cigarette consumption and depth of inhalation and nicotine intake as indexed by salivary cotinine concentrations. Reported occurrence of at least one withdrawal effect correlated positively with nicotine intake after controlling for behavioural variables. Our results indicate that teenage smokers are likely to suffer withdrawal symptoms when they try to give up. Behavioural factors and expectations based on observations of adults may have played a part in their experience of withdrawal, but it is also likely that pharmacological factors are implicated even at this early stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174074
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  • 2
    Electronic Resource
    Electronic Resource
    Some recent developments in polysilane chemistry (1992)
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 29-45 
    Details
    ISSN: 1572-8870
    Keywords: Polysilenes ; polysilanes ; liquid crystals ; mesophases ; birefringence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract (I) Ordered and disordered polysilane copolymers: Condensation of ClSiMe2Si(n-Hex)2SiMe2Cl with Na/K in toluene at 90°C produced a polymer with a strongly bimodal molecular weight distribution. The high-M w and low-M w portions were separated by fractional precipitation with 2-propanol, and the properties of the two fractions were investigated.29Si-NMR spectra show that the low-M w fraction is fully ordered but the high-M w fraction is randomized. (II) Liquid crystalline polysilanes: Condensation ofn-Bu(n-Hex)SiCl2 with Na in toluene led to a homopolymer which is a rubbery solid at 25°C. The polymer undergoes a second-order transition at −45°C and a first-order (melt) transition at −20°C. X-ray diffraction shows that the polymer has the same structure, a columnar hexagonal lattice, in all three phases; from −20 to 〉200°C, it exists in a columnar liquid crystalline mesophase. Similar hexagonal mesophases were observed at 25°C for the family of copolymers, (n-Hex2Si) n (Alk2Si) m , Alk =n-Pentyl,n-Bu,n-Pr, Et, Me.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696534
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Ethynylene-disilanylene copolymers (1991)
    Springer
    Journal of inorganic and organometallic polymers and materials 1 (1991), S. 545-565 
    Details
    ISSN: 1572-8870
    Keywords: Polysilanes ; sigma-pi conjugation ; mesophases ; polymer crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polymers of structure (SiR2SiR2-C ≡ C-SiR2′SiR2′-C ≡ C) n , in which ethynylene units alternate with disilylene units, have been prepared by two routes: (a) condensation of dichlorodisilanes with dilithium derivatives of 1,2-diethynyldisilanes and (b) ring-opening polymerization of strained cyclic disilanylene-acetylnes, (SiR2SiR2C ≡ C)2. The polymers display UV absorption near 240 nm indicative of σ − π conjugation between the Si2 and the C ≡ C moieties. Polymers with R=R′=n-Bu or R=n-Bu, R′=Ph, undergo solid-state transitions to form liquid crystalline mesophases resembling those observed for many poly(silylenes). Single crystals were obtained for the polymer with R=R′=CH3, by precipitation from dilute cyclohexane solution. The solid-state properties and structures of this family of polymers are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683516
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    Paper (German National Licenses)
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