Molecular Modelling of Stimuli Responsive Gate Effects in Flexible Metal Organic Frameworks

Metal-Organic Frameworks (MOFs) are new remarkable nano-porous materials that exhibit exceptional thermal and chemical stabilities. They have a broad range\ud of applications ranging from, not limited to, gas storage/separation, molecular separations, sensor, catalysis, drug delivery and removal of toxic chemicals and detoxification of warfare agents. The properties of the materials are highly dependent on the nature of the atomic interactions and structural arrangement of the crystallise material. This thesis focused on the MOFs that respond to stimuli where the structure will undergo reversible transformation in which it can lead to remarkable sorption properties that enhance the material performance. The selected MOFs, ZIF-8 and Mg-MOF-74 were studied in this thesis. The materials were evaluated at atomistic and quantum levels. Here, we proposed a new theoretical concept regarding controlling molecular movements by implanting molecular machines in Mg-MOF-74. We designed the molecular machines to respond to external electric field and the machines are anchored within the onedimensional pore channel of Mg-MOF-74. The pore opening and closing was simultaneously controlled by the induced electric field; thus, the flow directions of methane can be controlled at molecular level. Moreover, this thesis moved onto the study regarding mechanical ‘gate’ opening movements in ZIF-8 which are stimulated by introduction of water molecules to the system. First, we examined with water models response in ZIF-8. Five types of different water models and six different ZIF-8 force fields were chosen and simulated with Grand Canonical Monte Carlo method. We found that the simulated adsorption isotherms are significant diverse in relation to water models. Afterward, we mimicked experimental water adsorption set up through the use of a graphene piston in molecular dynamics simulation. Here, we demonstrated through the use of water that we witnessed experimental ‘gate’ effect. However, we also found that current atomics force fields in literature were unable to replicate the adsorption isotherm at experimental conditions, resulting in the development and modifications for new force field that tune to water responses in ZIF-8

A systematic review of transitions between cigarette and smokeless tobacco product use in the United States

Abstract Background Smokeless tobacco use is becoming an increasingly important public health issue in the US and may influence cigarette smoking behavior. Systematic information on transitions between smokeless tobacco and cigarette use in the US is limited. Methods We conducted a systematic review of published literature on transitions between smokeless tobacco and cigarette use in the US. We searched PubMed, Web of Science and EbscoHost databases for all published articles from January 2000 to March 2014 that presented estimates of transitions in US youth and adult study populations over time between at least one of the following tobacco use states: exclusive cigarette smoking, exclusive smokeless tobacco use, dual use of both products, and use of neither product. We excluded non-English language studies, studies published before 2000, clinical trials, controlled cessation programs, and clinical studies or evaluations of smokeless tobacco cessation programs. Results The review identified six studies on US populations published since 2000 with longitudinal data on some or all of the transitions that users can undergo between smokeless tobacco and cigarette use. There was considerable heterogeneity across studies in design and tobacco use definitions. Despite these differences, the existing data indicate that switching behaviors from exclusive smoking to exclusive smokeless tobacco use are limited (adults: 0%-1.4%, adolescents: 0.8%-3.8%) but may be more common from exclusive smokeless tobacco use to exclusive smoking (adults: 0.9%-26.6%, adolescents: 16.6%-25.5%). Among adults, exclusive cigarette smoking was generally stable and consistent (79.7% to 87.6%) over follow-up across studies but less stable in adolescents (46.8%-78.7%). Exclusive smokeless tobacco use was less stable than exclusive cigarette smoking over time (adults: 59.4%-76.6%, adolescents: 26.2%-44.8%). Conclusion This review provides published estimates of the proportions of adults and adolescents transitioning between tobacco use categories from the most recently available studies on longitudinal transitions between smokeless tobacco and cigarettes in the US. These data can be used to track tobacco use behaviors and evaluate their effect on public health; however, the data for these studies were generally collected more than a decade ago. Additional research including nationally representative longitudinal estimates using consistent definitions and designs, would improve understanding of current tobacco transition behaviors.http://deepblue.lib.umich.edu/bitstream/2027.42/110803/1/12889_2015_Article_1594.pd

Head and Neck Cancer Online Support Groups: Disparities in Participation and Impact on Patients

OBJECTIVE: To characterize the users of the head and neck cancer (HNC) online support group (OSG) and describe the perceived benefits of membership. STUDY DESIGN: Cross-sectional. SETTING: Online. METHODS: An administered survey with questions asking about demographics, cancer history, treatment choices, and feelings about OSGs was posted on the 5 largest HNC OSGs on Facebook. RESULTS: A total of 97 participants completed the survey. Mean age was 57.8 years old (standard deviation = 10.7 years). Most participants were female (50.5%) and Caucasian (92.8%). This cohort was well educated with 65.5% holding at least a college degree. Annual income was high with 41.8% reporting annual income of $100,000 or greater. The most common treatment modality was radiation (88.7%). The most common surgery was neck dissection (46.4%). Most participants preferred OSGs (70.8%) over other support group types. OSGs were heavily utilized with our cohort reporting using the OSG at least several times a week (80.0%). The top reasons for joining the OSG were sharing one\u27s experience of HNC (76.3%) and gaining support from others with HNC (85.6%). OSGs were ranked as the #3 source of medical information for HNC behind otolaryngologists and oncologists. Membership in a HNC OSG had a minimal impact on decision-making. CONCLUSION: HNC OSGs appear to provide a beneficial community for HNC patients. Otolaryngologists should consider incorporating HNC OSG as a possible supplemental resource for their HNC patients