Bond breaking in vibrationally excited methane on transition metal catalysts

The role of vibrational excitation of a single mode in the scattering of methane is studied by wave packet simulations of oriented CH4 and CD4 molecules from a flat surface. All nine internal vibrations are included. In the translational energy range from 32 up to 128 kJ/mol we find that initial vibrational excitations enhance the transfer of translational energy towards vibrational energy and increase the accessibility of the entrance channel for dissociation. Our simulations predict that initial vibrational excitations of the asymmetrical stretch (nu_3) and especially the symmetrical stretch (nu_1) modes will give the highest enhancement of the dissociation probability of methane.Comment: 4 pages REVTeX, 2 figures (eps), to be published in Phys. Rev. B. (See also arXiv:physics.chem-ph/0003031). Journal version at http://publish.aps.org/abstract/PRB/v61/p1565

Bisphosphonate prescribing, persistence and cumulative exposure in Ontario, Canada

Summary: We studied new users of oral bisphosphonates and found that less than half persisted with therapy for 2 years, and interruptions in use were common. During a median observation period of 4.7 years, 10% of patients filled only a single prescription, 37% switched therapies and median cumulative exposure was 2.2 years. Introduction: We sought to describe bisphosphonate prescribing, persistence and cumulative exposure among seniors in Ontario, Canada. Methods: We used Ontario Drug Benefit pharmacy claims to identify residents aged $\geq$ 66 years who initiated oral bisphosphonate therapy between April 1996 and March 2009. The first date of bisphosphonate dispensing was considered the index date. Persistence with therapy was defined as continuous treatment with no interruption exceeding 60 days. We examined persistence with therapy and the number of extended gaps (>60 days) between prescriptions over time periods ranging from 1 to 9 years. We also identified the proportion of patients filling only a single prescription and switching to a different bisphosphonate, and calculated the median days of exposure irrespective of gaps in therapy. Results: A total of 451,113 eligible new bisphosphonate users were identified: mean age = 75.6 years (SD = 6.9), 84% female, and median follow-up length = 4.7 years. Persistence with therapy declined from 63% at 1 year to 46% at 2 years and 12% at 9 years. Among those with at least 5 years of follow-up (n = 213,029), 61% had one or more extended gaps in bisphosphonate therapy. Overall, 10% of patients filled only a single prescription, 37% switched to a different bisphosphonate and the median exposure was 2.2 years. Conclusion: Less than half of patients persisted with bisphosphonate therapy for 2 years and interruptions in therapy were common, with most patients experiencing two or more >60-day gaps in therapy. Interventions are needed to improve persistence with bisphosphonate therapy and reduce the frequency of gaps in treatment

Factors associated with initiation and completion of the quadrivalent human papillomavirus vaccine series in an ontario cohort of grade 8 girls

Abstract Background Although over a hundred million dollars have been invested in offering free quadrivalent human papillomavirus (HPV) vaccination to young girls in Ontario, there continues to be very little information about its usage. In order to successfully guide future HPV vaccine programming, it is important to monitor HPV vaccine use and determine factors associated with use in this population. Methods Linking administrative health and immunization databases, we conducted a population-based, retrospective cohort study of girls eligible for Ontario's Grade 8 HPV vaccination program in Kingston, Frontenac, Lennox, and Addington. We determined the proportion of girls who initiated (at least one dose) and completed (all three doses) the vaccination series overall and according to socio-demographics, vaccination history, health services utilization, medical history, and program year. Multivariable logistic regression was used to estimate the strength of association between individual factors and initiation and completion, adjusted for all other factors. Results We identified a cohort of 2519 girls, 56.6% of whom received at least one dose of the HPV vaccine. Among vaccinated girls, 85.3% received all three doses. Vaccination history was the strongest predictor of initiation in that girls who received the measles-mumps-rubella, meningococcal C, and hepatitis B vaccines were considerably more likely to also receive the HPV vaccine (odds ratio 4.89; 95% confidence interval 4.04-5.92). Nevertheless, HPV vaccine uptake was more than 20% lower than that of these other vaccines. In addition, while series initiation was not influenced by income, series completion was. In particular, girls of low income were the least likely to receive all three indicated doses of the HPV vaccine (odds ratio 0.45; 95% confidence interval 0.28-0.72). Conclusions The current low level of HPV vaccine acceptance in Kingston, Frontenac, Lennox, and Addington will likely have important implications in terms of the health benefits and cost-effectiveness of its publicly funded program. We identified important factors associated with series initiation and completion that should be considered in efforts to improve HPV vaccine use in this population

Gastrointestinal decontamination in the acutely poisoned patient

ObjectiveTo define the role of gastrointestinal (GI) decontamination of the poisoned patient.Data sourcesA computer-based PubMed/MEDLINE search of the literature on GI decontamination in the poisoned patient with cross referencing of sources.Study selection and data extractionClinical, animal and in vitro studies were reviewed for clinical relevance to GI decontamination of the poisoned patient.Data synthesisThe literature suggests that previously, widely used, aggressive approaches including the use of ipecac syrup, gastric lavage, and cathartics are now rarely recommended. Whole bowel irrigation is still often recommended for slow-release drugs, metals, and patients who "pack" or "stuff" foreign bodies filled with drugs of abuse, but with little quality data to support it. Activated charcoal (AC), single or multiple doses, was also a previous mainstay of GI decontamination, but the utility of AC is now recognized to be limited and more time dependent than previously practiced. These recommendations have resulted in several treatment guidelines that are mostly based on retrospective analysis, animal studies or small case series, and rarely based on randomized clinical trials.ConclusionsThe current literature supports limited use of GI decontamination of the poisoned patient

Oligodendrocytes: biology and pathology

Oligodendrocytes are the myelinating cells of the central nervous system (CNS). They are the end product of a cell lineage which has to undergo a complex and precisely timed program of proliferation, migration, differentiation, and myelination to finally produce the insulating sheath of axons. Due to this complex differentiation program, and due to their unique metabolism/physiology, oligodendrocytes count among the most vulnerable cells of the CNS. In this review, we first describe the different steps eventually culminating in the formation of mature oligodendrocytes and myelin sheaths, as they were revealed by studies in rodents. We will then show differences and similarities of human oligodendrocyte development. Finally, we will lay out the different pathways leading to oligodendrocyte and myelin loss in human CNS diseases, and we will reveal the different principles leading to the restoration of myelin sheaths or to a failure to do so