Converting non-Mesogenic to Mesogenic Stacking of Amino-s-Triazine-Based Dendrons with p-CN Phenyl Unit by Eliminating Peripheral Dipole.

Three new amino-s-triazine-based dendrons, 1a, 1b, and 1c, containing an aryl-CN moiety in the dendritic skeleton were prepared in 72-81% yields (1a: R1 = - N(n-C8H17)2, R2 = n-OC8H17, 1b: R1 = R2 = - N(n-C8H17)2, 1c: R1 = - N(n-C8H17)2, R2 = - N(n-C4H9)2). Dendrons 1a with N(n-C8H17)2 and n-OC8H17 peripheral substituents, surprisingly, did not show any mesogenic phase during the thermal process. However, non-mesogenic 1a can be converted to mesogenic 1b or 1c by eliminating the peripheral dipole arising from the alkoxy substituent; dendron 1b only comprising the same N(n-C8H17)2 peripheral groups showed a ~25 °C mesogenic range on heating and ~108 °C mesogenic range on cooling. In contrast, dendron 1c possessing different N(n-CmH2m+1)2 (m = 8 versus m = 4) peripheral units, having similar stacking as 1b, exhibited a columnar phase on thermal treatment, but its mesogenic range (~9 and ~66 °C on heating and cooling, respectively) was much narrower than that of 1b, attributed to 1c's less flexible alkyl chains in the peripheral part of dendron. Dendron 1a with the alkoxy substituent in the peripheral skeleton, creating additional dipole correspondingly, thus, leads to the dendritic molecules having a non-mesogenic stacking. Without the peripheral dipole for intermolecular side-by-side interaction, dendrons 1b and 1c exhibit a columnar phase on thermal treatment because of the vibration from the peripheral alkyl chain.

Clinical manifestations of parainfluenza infection in children.

Parainfluenza viruses are major pathogens causing respiratory illness, manifesting from mild upper respiratory tract infection to bronchiolitis and pneumonia. This retrospective study aimed at providing clinical and epidemiologic data addressing the parainfluenza virus infection in Taiwan. A total of 39 patients were enrolled in this study from March 1999 to December 2000. Infants and young children were the major susceptible population, with 87.2% of them younger than 3 years. No seasonal trend was noted for parainfluenza type 1 and type 2 infections. One clustering of parainfluenza virus type 3 infections occurred in late spring of 2000 based on collected results. Parainfluenza type 1 viral isolates accounted for all of the cases of croup. Most isolates of parainfluenza virus type 3 were associated with upper and/or lower respiratory tract infections. A substantial proportion of the patients had skin involvement; the identification of one case of possible parainfluenza virus-related erythema multiforme is particularly interesting, especially because the chances of a causal relation between viral infection and skin symptoms are formerly thought to be slight. The identification of parainfluenza virus in illnesses classically considered to be due to other viruses is intriguing and may have important implications in the management of childhood illness clinically.