Electrochemical Studies of Transition Metal Hexahalometallates

This thesis determines the redox potentials of second and third row transition metal hexabromometallates using cyclic voltammetry methods in methylene chloride solution. The results are collated with the redox potentials of second and third row transition metal hexafluoro- and hexachlorometallates and the systematic trends exhibited by all the redox potentials are discussed. The contents of this thesis are divided as follows: In chapter one the nature of transition metal hexahalometallate bonding is discussed by drawing on ideas from ligand field theory and molecular orbital theory, both of which are described briefly. The contributions to the metal-halogen bond are described separately under a) purely electrostatic effects- which are treated using electronegativity differences, and b) covalency effects which are subdivided into sigma-covalency and pi-bonding. Lastly, chapter one includes a brief description of the vibrational and electronic spectra of transition metal hexahalometallates as these two methods were the principle means of identifying complexes. Chapter two begins with a conceptual description of charge transfer reactions at electrode surfaces and then approaches the same subject mathematically to derive the Butler-Volmer equation, the fundamental equation of electrode kinetics. The D. C. and A. C. cyclic voltammetry techniques are described and for a D. C. cyclic voltammogram, the current-potential profile is discussed and illustrated for reversible, quasi-reversible and irreversible electron transfer processes. The effects of coupled chemical reactions and adsorption of reactant and/or product on the electrode surface are also reviewed. Chapters three and four respectively describe the cyclic voltammetric investigations of the hexabromometallate complexes prepared in this work and the halogen/halide systems of chloride, bromide and iodide. The electrode potentials determined are compared with literature values wherever possible. Complex electrochemical activity at high oxidation potentials thwarted the detection of any of the possible [MBr6]0/1- redox couples. Adsorption of hexabroinometallate species onto the electrode at high oxidation potentials is put forward as a likely reason. Other problems which were encountered include the reaction of tungsten hexabromide with the supporting electrolyte and the propensity of trivalent hexabromometallate anions to dimerize when countered by the sterically large tetra-n-butylammonium cation. In chapter five, the electrode potentials of the transition metal hexabromometallate complexes determined in chapter three are collated with the electrode potentials of hexafluoro- and hexachlorometallate complexes already determined by previous workers. The systematic trends which emerged include 1. The electrode potentials of isovalent [MX6]z/z-1 redox couples increase regularly across a period except for a discontinuity at the d3/4 couple. 2. The discontinuity is more pronounced for second row than third row transition metal hexahalometallates. 3. [MX6]z complexes become more oxidizing with increasing oxidation state of the metal. 4. Third row transition metal hexahalometallate complexes are more reducing than their isoelectronic second row counterparts. By using simple thermodynamic arguments it is derived that the standard electrode potential of a redox couple is proportional to the free energy difference between the reduced and the oxidized species, which is in turn composed of two separate contributions: The entropy- which was associated with alterations to the solvation sphere which, it was concluded, have no influence on the systematic trends observed. The enthalpy- of which the principal contributions arise from 1. the ionization enthalpy of the metal. 2. the dn configuration of the metal. 3. the nature of the halide ligand. 4. the nature of the solvent. Chapter five concludes with a brief survey of some of the uses and applications of hexahalometallate redox potentials. Finally, chapter six details the synthesis and characterisation of the compounds studied in this thesis. Included is a description of the electrochemical cell and its manipulation, and the preparation of the solvent and supporting electrolyte

Accounting Expertise on the Compensation Committee and CEO Compensation

Executive compensation has long been a hot topic for regulators, investors and the business press, usually because of a misalignment of performance and CEO compensation. CEO compensation is an important topic because it can have a major impact on firms’ ability to attract and retain talented CEOs. The Dodd-Frank Act, passed in 2010, and resulting updated compensation committee rules have increased the scrutiny of compensation committees as they set and monitor executive pay. Additionally, Hoitash et al. (2012) and Manchiraju et al. (2016) call for firms to include directors with financial or accounting expertise on their compensation committees to improve performance measurement and executive compensation contracting. Using the presence of a certified public accountant (CPA) on the committee to proxy for accounting expertise, I investigate the association between accounting expertise on the compensation committee and several aspects of CEO compensation. I find that the percentage of firms with accounting expertise on the compensation committee has doubled over my sample period. I find evidence that accounting expertise on the compensation committee is associated with increased pay-for-performance sensitivity when performance is measured using stock returns. However, in areas where accounting expertise should be most beneficial, including pay sensitivity to accounting-based measures of performance, and compensation shielding from misclassified negative special items, I find no evidence of a significant impact. This study contributes to the literature on CEO compensation and the literature on corporate boards and is the first large sample study on the association between accounting expertise on the compensation committee and CEO compensation

The Effect of Fatigue on Shoulder Muscle Strength Ratios in Collegiate Water Polo Players

Introduction: A proposed mechanism of shoulder injuries is imbalances in the strength of the shoulder muscles, however, the effects of fatigue on these imbalances are unknown. The purpose of this study was to investigate the relationship of isokinetic-induced fatigue on the development of shoulder muscle imbalances using both the conventional and functional ratio

Relationship between Ground Reaction Force Characteristics and Bone Mineral Density of the Hip and Spine in Male Runners

International Journal of Exercise Science 15(1): 655-666, 2022. The purpose of this study was to determine the relationship between running ground reaction force (GRF) characteristics and hip and lumbar spine bone mineral density (BMD) values in male runners. Individuals who ran at least 48.3 km per week and were injury-free were recruited. Kistler force plates collected running vertical and anteroposterior GRF data. A Hologic Discovery W bone densitometer measured lumbar spine and five regional hip BMD values. Only runners who consistently used a rear foot strike pattern were included (n = 32). Pearson correlation coefficients were calculated between BMD values and various GRF values and step-wise multiple regression was run to predict BMD values from the various GRF values. The vertical impact force was significantly correlated with the lumbar spine and four of the five hip BMD values (r \u3e 0.374, p \u3c 0.035). Both the peak early loading rate (ELR) and average ELR were significantly correlated with the lumbar spine and Ward’s triangle BMD (r \u3e 0.430, p \u3c 0.014), while the average active loading rate was correlated only with the Ward’s triangle BMD (r = 0.438, p = 0.012). Multiple regression revealed the peak impact force was the predictor for every hip region BMD other than the trochanter and the average ELR as a predictor for the lumbar spine BMD. The peak braking force was negatively correlated with the Ward’s triangle BMD (r = - 0.414, p = 0.019). It appears that the large forces and loading rates associated with rear foot striking may be advantageous and predictive for BMD at the hip and spine

Clinical and angiographic characteristics and outcome of patients with rest-unstable angina occurring during regular aspirin use

AbstractToday many patients admitted with an acute coronary syndrome are already taking aspirin. Because they have symptoms despite antithrombotic therapy, these patients are presumed to be at higher risk for subsequent clinical events. In a pilot trial of antithrombotic therapy in patients with unstable angina at rest or non-Q wave infarction, 93 patients admitted within 48 h of pain were prospectively followed up for 12 weeks. On admission, 29 patients (31%) were already taking daily aspirin; 64 (68%) were receiving no antiplatelet agent. After enrollment all patients received antithrombotic therapy with either aspirin or heparin according to protocol regardless of prior aspirin use.The two groups (prior users versus nonusers of aspirin) were similar with regard to age, gender, coronary risk factors, prior antianginal medication, duration of symptomatic coronary disease, presentation with non-Q wave infarction and extent of electrocardiographic changes on admission. Quantitative analysis of coronary arteriograms (on a 0 to 10 scale) showed similar myocardium-in-jeopardy scores (JS). Follow-up events (recurrent ischemia [Isch], infarction [MI] and revascularization [Revasc]) were: Prior Aspirin UseIschMIRevascJSYes27%3%44%3.7%No33%5%51%3.9%Aspirin users experiencing rest angina are similar to other patients with ischemic rest pain. The “resistant to aspirin” group Joes not constitute a subgroup that is at higher risk for cardiac events or revascularization

Pre-Settlement Vegetation at Casey\u27s Paha State Preserve, Iowa

Paha are loess-capped ridges standing 10-30 m above the surrounding plain of the Iowan Surface. Although Iowa was almost entirely covered with prairie and wetlands just prior to Euro-American settlement, the paha are believed to have been forested based on soil types and on early vegetation maps. The objective of this study was to find evidence that paha were forested by measuring the δ13C value of humin, the fraction of soil organic matter that is insoluble in acid and base. Previous work has shown that humin retains the δ13C signature of vegetation on a 1000-year time scale, as opposed to the more mobile and soluble humic and fulvic acids that reflect the δ13C signature of more recent vegetation. Soil samples were obtained from Casey\u27s Paha State Preserve in Tama County from four locations at depths ranging from 5-85 cm. Carbonates were removed with 1.0 M HCl and humic and fulvic acids were removed by repeated application of 0.5 M NaOH. The δ13C values of the humin fraction (-22.031% to -24.358%) were within or slightly above the upper range of δ13C values for woody vegetation (-23% to -34%) and well below the range for prairie grasses (-9% to -17%). Although it has been suggested that prairie fires bypassed the paha or that perched water tables maintained the forest, we suggest that the paha forests resulted from activity by Native Americans

Genome sequence of the Bacteroides fragilis phage ATCC 51477-B1

The genome of a fecal pollution indicator phage, Bacteroides fragilis ATCC 51477-B1, was sequenced and consisted of 44,929 bases with a G+C content of 38.7%. Forty-six putative open reading frames were identified and genes were organized into functional clusters for host specificity, lysis, replication and regulation, and packaging and structural proteins