Towards Trigonal Prismatic Hexanuclear Copper Complexes For Catalytic Water Oxidation

Our planet is running out of energy resources and traditional renewables are not easily transported nor will be sufficient to cover the void left by fossil fuels. Therefore, a new energy storage system needs to be adopted. The medium with highest energy density that is readily available is hydrogen from water. However, to access hydrogen, water needs to be oxidized and water oxidation catalysts (WOCs) will be required for widespread adoption. In pursuit of WOCs, several hexauclear copper complexes were synthesized and characterized, including the isolation and characterization of a mixed-valent Cu6 (formally, CuII5CuIII) complex. Furthermore, early in the research, several novel coordination polymers (CPs) were serendipitously synthesized. This dissertation is divided into three major parts: (i) A series of trigonal prismatic Cu6-pyrazolato complexes (Cu6) form a unique arrangement of two O2- ions in a favorable position to form an O-O bond without much external influence. The Cu6 complexes undergo two reversible one-electron oxidations and a structurally characterized one-electron oxidized mixed-valent complex displays an O···O distance ~0.3 Å closer than the homovalent compound, which highlights the propensity of the system towards O-O bond formation. Spectroscopic findings and DFT calculations on the electronic structure of the mixed-valent Cu6-complex are reported. The results support the hypothesis that a variation of a Cu6 motif could function as a water oxidation catalyst. (ii) Three new coordination polymers containing trinuclear Cu(II)-4-formyl pyrazolato units connected by formyl group coordination were prepared and the crystal structures are reported: a 1D polymer formed by linking secondary building units (SBUs) and two 3D polymers with novel topologies consist of 14-nodal 3842,54-c and 3-nodal 3,3,4-c nets, respectively. (iii) Two new motifs of Cu6-pyrazolato complexes were prepared. One motif has two pyrazolato bridges between the trinuclear copper subunits with a µ4-Cl situated inside the open cage, and the other has the subunits bridged by a single pyrazolato ligand. Variable low-temperature NMR and magnetic studies were conducted. And for the first time, far-infrared spectroscopy studies were used to determine the characteristic absorptions of various coordination bonds in copper pyrazolate complexes

Osteoporosis-related fracture case definitions for population-based administrative data

<p>Abstract</p> <p>Background</p> <p>Population-based administrative data have been used to study osteoporosis-related fracture risk factors and outcomes, but there has been limited research about the validity of these data for ascertaining fracture cases. The objectives of this study were to: (a) compare fracture incidence estimates from administrative data with estimates from population-based clinically-validated data, and (b) test for differences in incidence estimates from multiple administrative data case definitions.</p> <p>Methods</p> <p>Thirty-five case definitions for incident fractures of the hip, wrist, humerus, and clinical vertebrae were constructed using diagnosis codes in hospital data and diagnosis and service codes in physician billing data from Manitoba, Canada. Clinically-validated fractures were identified from the Canadian Multicentre Osteoporosis Study (CaMos). Generalized linear models were used to test for differences in incidence estimates.</p> <p>Results</p> <p>For hip fracture, sex-specific differences were observed in the magnitude of under- and over-ascertainment of administrative data case definitions when compared with CaMos data. The length of the fracture-free period to ascertain incident cases had a variable effect on over-ascertainment across fracture sites, as did the use of imaging, fixation, or repair service codes. Case definitions based on hospital data resulted in under-ascertainment of incident clinical vertebral fractures. There were no significant differences in trend estimates for wrist, humerus, and clinical vertebral case definitions.</p> <p>Conclusions</p> <p>The validity of administrative data for estimating fracture incidence depends on the site and features of the case definition.</p

How many mailouts? Could attempts to increase the response rate in the Iraq war cohort study be counterproductive?

<p>Abstract</p> <p>Background</p> <p>Low response and reporting errors are major concerns for survey epidemiologists. However, while nonresponse is commonly investigated, the effects of misclassification are often ignored, possibly because they are hard to quantify. We investigate both sources of bias in a recent study of the effects of deployment to the 2003 Iraq war on the health of UK military personnel, and attempt to determine whether improving response rates by multiple mailouts was associated with increased misclassification error and hence increased bias in the results.</p> <p>Methods</p> <p>Data for 17,162 UK military personnel were used to determine factors related to response and inverse probability weights were used to assess nonresponse bias. The percentages of inconsistent and missing answers to health questions from the 10,234 responders were used as measures of misclassification in a simulation of the 'true' relative risks that would have been observed if misclassification had not been present. Simulated and observed relative risks of multiple physical symptoms and post-traumatic stress disorder (PTSD) were compared across response waves (number of contact attempts).</p> <p>Results</p> <p>Age, rank, gender, ethnic group, enlistment type (regular/reservist) and contact address (military or civilian), but not fitness, were significantly related to response. Weighting for nonresponse had little effect on the relative risks. Of the respondents, 88% had responded by wave 2. Missing answers (total 3%) increased significantly (p < 0.001) between waves 1 and 4 from 2.4% to 7.3%, and the percentage with discrepant answers (total 14%) increased from 12.8% to 16.3% (p = 0.007). However, the adjusted relative risks decreased only slightly from 1.24 to 1.22 for multiple physical symptoms and from 1.12 to 1.09 for PTSD, and showed a similar pattern to those simulated.</p> <p>Conclusion</p> <p>Bias due to nonresponse appears to be small in this study, and increasing the response rates had little effect on the results. Although misclassification is difficult to assess, the results suggest that bias due to reporting errors could be greater than bias caused by nonresponse. Resources might be better spent on improving and validating the data, rather than on increasing the response rate.</p

Fluid intake and incidence of renal cell carcinoma in UK women

Background:It has been suggested that the apparent protective effect of alcohol intake on renal cell carcinoma may be due to the diluting effect of carcinogens by a high total fluid intake. We assessed the association between intakes of total fluids and of specific beverages on the risk of renal cell carcinoma in a large prospective cohort of UK women.Methods:Information on beverage consumption was obtained from a questionnaire sent 3 years after recruitment into the Million Women Study. Cox proportional hazards models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for renal cell carcinoma associated with beverage consumption adjusted for age, region of residence, socioeconomic status, smoking, and body mass index.Results:After an average of 5.2 years of follow-up, 588 cases of renal cell carcinoma were identified among 779 369 women. While alcohol intake was associated with a reduced risk of renal cell carcinoma (RR for 2 vs 1 drink per day: 0.76; 95% CI: 0.61-0.96; P for trend0.02), there was no association with total fluid intake (RR for 12 vs 7 drinks per day: 1.15; 95% CI: 0.91-1.45; P for trend0.3) or with intakes of specific beverages.Conclusions:The apparent protective effect of alcohol on the risk of renal cell carcinoma is unlikely to be related to a high fluid intake. © 2011 Cancer Research UK All rights reserved