Revisiting the bromination of 3ß-hydroxycholest-5-ene with CBr4/PPh3 and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior.

Cholesterol reacts under Appel conditions (CBr4/PPh3) to give 3,5-cholestadiene (elimination) and 3ß-bromocholest-5-ene (substitution with retention of configuration). Thus, the bromination of cholesterol deviates from the stereochemistry of the standard Appel mechanism due to participation of the Δ5 π-electrons. In contrast, the subsequent azidolysis (NaN3/DMF) of 3ß-bromocholest-5-ene proceeds predominantly by Walden inversion (SN2) affording 3α-azidocholest-5-ene. The structures of all relevant products were revealed by X-ray single crystal structure analyses, and the NMR data are in agreement to the reported ones. In light of these findings, we herein correct the previous stereochemical assignments reported by one of us in the Beilstein J. Org. Chem. 2015, 11, 1922-1932 and the Monatsh. Chem. 2018, 149, 505-517.

Perceived social support and discrimination and oral health behaviors in adolescents.

OBJECTIVES: The aims of this study were to examine the associations between perceived social support and oral health behaviors among adolescents and if this perception had a protective effect against the influence of perceived racial discrimination on oral health behaviors in this population. MATERIAL AND METHODS: Participants of this cross-sectional study were adolescents aged 12-18 years recruited from University dental clinic. They completed a questionnaire comprising three sections: demographics (14 items), oral health behaviors (6 items), and validated Personal Resource Questionnaire (25 items). Perceived discrimination was evaluated by a question asking if the adolescent had ever experienced discrimination based on their race. RESULTS: Of 252 participants, mean (SD) age of 14 (1.8) years, 60% were girls, 56% were self-identified as White, and 81% were born in Canada. Discrimination was reported by 21%. Frequency of toothbrushing and self-rated oral health were significantly associated with increased levels of perceived social support. Sugar consumption was significantly different for participants with and without perceived racial discrimination (p-value = 0.002). Perceived social support did not act as a buffer against perceived racial discrimination for sugar consumption (OR = 1.00; 95% CI: 0.98-1.01). CONCLUSIONS: Adolescents' perceived social support affected some aspects of their oral health but did not moderate the influence of perceived racial discrimination.

Young-onset Parkinson's disease: hospital utilization and medical comorbidity in a nationwide survey.

BACKGROUND/AIMS: 10% of Parkinson's disease (PD) patients have young-onset PD (YOPD). We compared YOPD patients to control patients in terms of hospital utilization and outcomes and medical comorbidities during hospitalization. METHODS: The Nationwide Inpatient Sample (NIS) provides yearly data on hospital admissions and discharges from approximately 1,000 hospitals. NIS data sets (1998-2003) were used to identify persons aged 18-40 years, including 714 PD patients and 2,007 randomly selected control patients (1:3 matching). RESULTS: Hospital length of stay (p < 0.001) and number of discharge diagnoses (p < 0.001) were higher in PD patients than controls. PD patients were more likely than controls to be discharged to a short-term hospital (odds ratio, OR, 2.23, 95% confidence interval, CI, 1.30-3.84, p = 0.004) or a skilled nursing facility (OR 4.14, 95% CI 3.06-5.61, p < 0.001); 20.4% required transfer to a short-term hospital or another facility. The most common discharge Diagnosis-Related Group code in PD patients was psychosis (23% of patients) whereas pneumonia and hip or pelvic fractures were not associated with PD. CONCLUSIONS: YOPD patients had greater healthcare utilization and hospital morbidity than controls. Upon discharge, 1 in 5 required transfer to a short-term hospital or another facility. Psychosis was the most common comorbidity whereas several comorbidities associated with older PD patients were not common.

Generation of atomistic models of periodic mesoporous silica by kinetic Monte Carlo simulation of the synthesis of the material.

We have developed a molecular simulation method for the generation of realistic atomic-level models for periodic mesoporous silicas. Using simplified interaction potentials and simplified representations of the templating micelles, the simulation follows the reaction path of the hydrothermal synthesis and calcination of the silica material in a kinetic Monte Carlo (kMC) simulation. The only input to the simulation is the geometry of the micelle and the number of silicic acid monomers at the beginning of the synthesis. We simulated the adsorption properties of the PMS models using Grand Canonical Monte Carlo simulation. With use of MCM-41 materials of different pore sizes as a prototype material, experimental and simulated adsorption isotherms for nitrogen, ethane, and carbon dioxide were compared, showing good agreement between simulation and experiment.

Packing of adsorbed molecules in microporous polymorphs aluminium methylphosphonates alpha and beta.

The adsorption of N2 and CO2 in the microporous aluminium methylphosphonate polymorphs alpha and beta is investigated by adsorption experiments in combination with Monte Carlo (MC) simulations. We find that close steric matching of N2 and polymorph alpha causes a packing transition not observed for the other pairs of adsorbate and adsorbent. This strong effect on adsorption behaviour of small differences in the adsorbent structure and adsorbent-adsorbate interactions suggests that microporous, hybrid inorganic organic materials of this type offer opportunities for highly selective adsorptive separations. The realism of the MC simulations is extraordinarily dependent upon the molecular size parameters used.