The formation of ice mantles on interstellar grains revisited--the effect of exothermicity.

Modelling of grain surface chemistry generally deals with the simulation of rare events. Usually deterministic methods or statistical approaches such as the kinetic Monte Carlo technique are applied for these simulations. All assume that the surface processes are memoryless, the Markov chain assumption, and usually also that their rates are time independent. In this paper we investigate surface reactions for which these assumptions are not valid, and discuss what the effect is on the formation of water on interstellar grains. We will particularly focus on the formation of two OH radicals by the reaction H + HO2. Two reaction products are formed in this exothermic reaction and the resulting momentum gained causes them to move away from each other. What makes this reaction special is that the two products can undergo a follow-up reaction to form H2O2. Experimentally, OH has been observed, which means that the follow-up reaction does not proceed with 100% efficiency, even though the two OH radicals are formed in each other's vicinity in the same reaction. This can be explained by a combined effect of the directionality of the OH radical movement together with energy dissipation. Both effects are constrained by comparison with experiments, and the resulting parametrised mechanism is applied to simulations of the formation of water ice under interstellar conditions.

Sino-nasal bony and cartilaginous destruction associated with cocaine abuse, S. aureus and antineutrophil cytoplasmic antibodies.

Three male patients aged 29, 30 and 34 years and a 36-year-old female are reported with nasal septum perforation and a history of cocaine abuse. Two of the patients also had a perforation of the hard palate. In all four, antineutrophil cytoplasmic antibodies (ANCA) were found. One had a cytoplasmic immunofluorescence-staining pattern (c-ANCA), the other three showed a perinuclear staining pattern (p-ANCA). Furthermore, all patients were found to be nasal carriers of S. aureus. We hypothesise that tissue damage to the nasal and palatal area in patients using cocaine may partly be mediated by the presence of ANCA antibodies. Furthermore, we speculate that S. aureus facilitates the development of these ANCA antibodies.

[A painful swelling of the tongue]. / Een pijnlijke zwelling van de tong.

A 45-year-old patient had a progressive ulcer of the tongue. Routine examination, including a biopsy was not conclusive and could not entirely rule out a malignancy. The final diagnosis was made after generalised lesions developed, after which specific serological tests confirmed the diagnosis 'syphilis'. The patient was treated with benzathine benzylpenicillin and his complaints disappeared. In view of the increasing incidence of this disease remains an important consideration in case of ulcerative or other lesions in the oral cavity.

[A painful swelling of the tongue]. / Een pijnlijke zwelling van de tong.

A 45-year-old patient had a progressive ulcer of the tongue. Routine examination, including a biopsy was not conclusive and could not entirely rule out a malignancy. The final diagnosis was made after generalised lesions developed, after which specific serological tests confirmed the diagnosis 'syphilis'. The patient was treated with benzathinbenzylpenicillin and his complaints disappeared. In view of the increasing incidence of syphilis this disease remains an important consideration in case of ulcerative or other lesions in the oral cavity.

Biliary excretion of ciprofloxacin and piperacillin in the obstructed biliary tract.

Biliary excretion of ciprofloxacin and piperacillin was determined in cholestatic patients who had undergone endoscopic cholangiography. The median concentration of ciprofloxacin (n = 9) was 2.36 micrograms/ml (range, 0.29 to 19.8 micrograms/ml) in bile compared with 1.66 micrograms/ml (range, 0.73 to 2.69 micrograms/ml) in serum. The median concentration of piperacillin (n = 7) was < 5 micrograms/ml (range, < 5 to 26) in bile compared with 14.3 micrograms/ml (range, 5.3 to 80) in serum. Ciprofloxacin, but not piperacillin, can be actively excreted into bile in the presence of a biliary tract obstruction.

Long-term anorectal function after Duhamel operation for Hirschsprung's disease.

Long-term anorectal function was assessed in children operated on using Duhamel's technique for Hirschsprung's disease. The files of 75 patients (16 girls and 59 boys) operated on between 1977 and 1991 were reviewed. Questionnaires were analysed on 63 (12 girls and 51 boys) over 2 years of age. The median age at completing the questionnaire was 6.6 years. Forty-one of these 63 patients had aganglionosis of the rectosigmoid, 15 of a long colonic segment, and 7 of the total colon. Of 14 children age 4 or less, 6 had severe constipation, whereas 8 had regular spontaneous defaecation. Ten of the 49 over 4 years of age were continent without constipation, 22 had soiling and/or constipation, and 17 were incontinent, one of whom had a permanent colostomy. There was no correlation between age or sex and anorectal function. Anorectal function in children with long segment was not worse than in those with rectosigmoid aganglionosis, but only 1 of 7 with total colonic aganglionosis was continent. Because many adapt themselves to the handicap, symptoms are often underreported. A detailed questionnaire appears to be a reliable tool for elucidating the real situation. A systematic follow-up of patients with Hirschsprung's disease is proposed to anticipate the complications and to institute proper measures at an early stage.