Thermal cracking of n-hexadecane in the mild temperature (330−375 °C) range has been investigated in liquid and gas phases. The kinetic data of liquid-phase cracking are shown to be very similar to those of gas-phase cracking. However, the pattern and distribution of the products are greatly phase dependent. In liquid-phase cracking, there is an equimolar distribution of n-alkane and 1-alkene products in the C3−C13 range at low conversion; when the conversion is increased, more alkanes than alkenes are produced. To the contrary, more alkenes than alkanes are always determined in products from gas-phase cracking. Liquid-phase cracking gives a low selectivity of gas products and a high selectivity of addition compounds (C18−C30), whereas gas-phase cracking produces a large amount of gas products and no addition compounds. The phase dependence of products can be interpreted in terms of a low concentration of hexadecane, under which β-scission occurs more preferentially than in liquid phase. Reaction mechanisms are suggested based on the product analysis to account for cracking behaviors of liquid-phase and gas-phase cracking.

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Objective The purpose of this study was to compare the dentocraniofacial morphology of parents of children with cleft lip and/or palate (CUP) with that of parents of children without CUP and to use the results for genetic counseling. Participants Twenty-five fathers and 40 mothers of Japanese children with CL/P, who also had relatives with CL/P within three generations (experimental group), and 413 pairs of parents of children without CL/P (control) were used in this study. To test the accuracy of the discriminant function, 165 subjects were added to this study (test group). Materials and Methods Sixty-five dental casts were measured by digital sliding calipers, and 1056 frontal and 1056 lateral cephalograms were traced, digitized, and analyzed using analysis of variance (ANOVA) and discriminant analysis. Results Mesiodistal tooth diameters in parents of children with CL/P did not show any differences from those in parents of children without CL/P. The parents in the experimental group showed a distinct craniofacial morphology: wider interorbital width (IO-IO′), intercoronoid process distance (Cp-Cp′), and nasal cavity width (NC-NC′) and larger anterior cranial base length (S-N) and cranial base length (N-Ba). For genetic counseling, a discriminant function was obtained using four significant ratios on ANOVA. The percentage of correct classification using this function on the pooled experimental and control subjects was 67.9. Conclusion The parents in the experimental group showed a special craniofacial morphology, but the results suggest that the discriminant function might not be helpful in genetic counseling.

The parents in the experimental group showed a special craniofacial morphology, but the results suggest that the discriminant function might not be helpful in genetic counseling.