Graduation date: 1967

Vitreous humor is a fluid that is relatively well protected from postmortem degradation and contamination. Due to its postmortem stability, vitreous humor has high utility in forensic pathology. Vitreous humor biochemical constituents, especially potassium, have been widely used in the postmortem interval (PMI) estimations. The time dependant rise of vitreous potassium levels in the postmortem period has been considered to be helpful in PMI determinations. The relative stability of vitreous biochemistry is useful in assessing the antemortem metabolic status and in predicting the antemortem serum biochemistry of an individual. However, the validity of vitreous biochemistry in forensic applications has been questioned in light of the reported concentration differences of various biochemical constituents in the same pair of eyes at identical PMI. This study hypothesized that the concentration of vitreous biochemical constituents in the same pair of eyes change at the same rate and this change that occurs in a time dependent fashion may be utilized in accurately estimating the PMI. It was further hypothesized that postmortem vitreous humor biochemistry closely mimics antemortem serum biochemistry and may be a useful aid in establishing a postmortem diagnoses of hyperglycemia. To test these hypotheses, vitreous humor samples were collected from a total of 103 autopsies (Female, 35 and Male, 68; Mean Age ± SD, 60.6 ± 17.6) conducted at Royal University Hospital morgue between January 2003 to February 2005. In 61 of these subjects, the precise time of death was known. Right and left eye vitreous humor samples were collected separately through a scleral puncture at the lateral canthus. Most of the biochemical analyses were carried out immediately post-extraction. After centrifugation, the supernatant of the fluid were analyzed for sodium, potassium, chloride, calcium, magnesium, urea, creatinine, glucose and lactate on an LX-20 Analyzer (Beckman-Coulter). Osmolality was measured on an Osmometer model 3900 (Advanced Instruments Inc.). Vitreous humor hypoxanthine and xanthine were analyzed using a colorimetric method (Amplex® Red Xanthine/ Xanthine Oxidase Assay Kit, Molecular Probes Inc.). Vitreous humor lipid hydroperoxides were measured using the Ferrous Oxidation in Xylenol Orange assay version 2 (FOX 2). The data was statistically analyzed by paired t-test, linear regression analysis and Mann-Whitney test using Statistical Package for Social Sciences (SPSS) for Windows version 13.0. The results of this study indicated that there were no significant between-eye differences for all of the vitreous biochemical constituents that were studied. It was observed that there was a significant correlation between vitreous potassium (R, 0.731; P, <0.0001), hypoxanthine, (R, 0.450; P, <0.0001), xanthine (R, 0.590; P, <0.0001), lactate (R, 0.508; P, <0.0001), calcium (R, 0.33; P, <0.01) and PMI. The corresponding formulae derived from the linear regression equations to estimate PMI were for potassium (6.41 (K+) 46.25), hypoxanthine (0.32 (Hypoxanthine) 60.94), xanthine (0.14 (Xanthine) 50.08), lactate (5.21 (Lactate) 27.69) and calcium (200 (Ca2+) 380.4). On a comparison of the actual PMI and the estimated PMI calculated using the formulae derived from the linear regression correlationship, it was found that the lowest standard deviation and the highest correlationship was obtained for vitreous potassium. The mean paired actual and estimated PMI values were significantly correlated for potassium (P, <0.0001), hypoxanthine (P, <0.0001), xanthine (P, <0.0001), lactate (P, <0.0001) and calcium (P, <0.01). Only vitreous potassium along with lactate and xanthine were significantly correlated with PMI in the same linear regression model. It was found that there was a highly significant correlation between antemortem serum and postmortem vitreous urea (R, 0.967; P, < 0.0001) and antemortem serum and postmortem vitreous creatinine (R, 0.865; P, <0.0001) concentrations. There was a significant difference (P, <0.05) between the postmortem vitreous glucose levels in the diabetic subjects as compared to the non-diabetic subjects. Vitreous lactate and lipid hydroperoxide levels did not exhibit any significant differences in these two diagnostic subgroups. The results of the present study suggest that the previously reported between eye differences for various vitreous biochemical constituents in the same pair of eyes are insignificant so far as forensic applications are concerned. Vitreous potassium is a useful biochemical marker for PMI estimations. Vitreous hypoxanthine, xanthine, lactate and calcium are all significantly correlated with PMI and if used in conjunction with vitreous potassium may possibly enhance PMI estimations by narrowing the error margin. The knowledge of vitreous urea and creatinine levels are a useful index in predicting the antemortem metabolic and renal status of the deceased subject.

Vitreous humor is a fluid that is relatively well protected from postmortem degradation and contamination. Due to its postmortem stability, vitreous humor has high utility in forensic pathology. Vitreous humor biochemical constituents, especially potassium, have been widely used in the postmortem interval (PMI) estimations. The time dependant rise of vitreous potassium levels in the postmortem period has been considered to be helpful in PMI determinations. The relative stability of vitreous biochemistry is useful in assessing the antemortem metabolic status and in predicting the antemortem serum biochemistry of an individual. However, the validity of vitreous biochemistry in forensic applications has been questioned in light of the reported concentration differences of various biochemical constituents in the same pair of eyes at identical PMI. This study hypothesized that the concentration of vitreous biochemical constituents in the same pair of eyes change at the same rate and this change that occurs in a time dependent fashion may be utilized in accurately estimating the PMI. It was further hypothesized that postmortem vitreous humor biochemistry closely mimics antemortem serum biochemistry and may be a useful aid in establishing a postmortem diagnoses of hyperglycemia. To test these hypotheses, vitreous humor samples were collected from a total of 103 autopsies (Female, 35 and Male, 68; Mean Age ± SD, 60.6 ± 17.6) conducted at Royal University Hospital morgue between January 2003 to February 2005. In 61 of these subjects, the precise time of death was known. Right and left eye vitreous humor samples were collected separately through a scleral puncture at the lateral canthus. Most of the biochemical analyses were carried out immediately post-extraction. After centrifugation, the supernatant of the fluid were analyzed for sodium, potassium, chloride, calcium, magnesium, urea, creatinine, glucose and lactate on an LX-20 Analyzer (Beckman-Coulter). Osmolality was measured on an Osmometer model 3900 (Advanced Instruments Inc.). Vitreous humor hypoxanthine and xanthine were analyzed using a colorimetric method (Amplex® Red Xanthine/ Xanthine Oxidase Assay Kit, Molecular Probes Inc.). Vitreous humor lipid hydroperoxides were measured using the Ferrous Oxidation in Xylenol Orange assay version 2 (FOX 2). The data was statistically analyzed by paired t-test, linear regression analysis and Mann-Whitney test using Statistical Package for Social Sciences (SPSS) for Windows version 13.0. The results of this study indicated that there were no significant between-eye differences for all of the vitreous biochemical constituents that were studied. It was observed that there was a significant correlation between vitreous potassium (R, 0.731; P, <0.0001), hypoxanthine, (R, 0.450; P, <0.0001), xanthine (R, 0.590; P, <0.0001), lactate (R, 0.508; P, <0.0001), calcium (R, 0.33; P, <0.01) and PMI. The corresponding formulae derived from the linear regression equations to estimate PMI were for potassium (6.41 (K+) 46.25), hypoxanthine (0.32 (Hypoxanthine) 60.94), xanthine (0.14 (Xanthine) 50.08), lactate (5.21 (Lactate) 27.69) and calcium (200 (Ca2+) 380.4). On a comparison of the actual PMI and the estimated PMI calculated using the formulae derived from the linear regression correlationship, it was found that the lowest standard deviation and the highest correlationship was obtained for vitreous potassium. The mean paired actual and estimated PMI values were significantly correlated for potassium (P, <0.0001), hypoxanthine (P, <0.0001), xanthine (P, <0.0001), lactate (P, <0.0001) and calcium (P, <0.01). Only vitreous potassium along with lactate and xanthine were significantly correlated with PMI in the same linear regression model. It was found that there was a highly significant correlation between antemortem serum and postmortem vitreous urea (R, 0.967; P, < 0.0001) and antemortem serum and postmortem vitreous creatinine (R, 0.865; P, <0.0001) concentrations. There was a significant difference (P, <0.05) between the postmortem vitreous glucose levels in the diabetic subjects as compared to the non-diabetic subjects. Vitreous lactate and lipid hydroperoxide levels did not exhibit any significant differences in these two diagnostic subgroups. The results of the present study suggest that the previously reported between eye differences for various vitreous biochemical constituents in the same pair of eyes are insignificant so far as forensic applications are concerned. Vitreous potassium is a useful biochemical marker for PMI estimations. Vitreous hypoxanthine, xanthine, lactate and calcium are all significantly correlated with PMI and if used in conjunction with vitreous potassium may possibly enhance PMI estimations by narrowing the error margin. The knowledge of vitreous urea and creatinine levels are a useful index in predicting the antemortem metabolic and renal status of the deceased subject.

No description available.

Thesis--M. Phil., University of Hong Kong, 1985.

No description available.

The novel Vanadium Bromide (V/Br) redox flow cell employs a V (III)/V (II) couple in the negative half-cell and a Br/Br2 couple in the positive half-cell, with hydrobromic acid and hydrochloric acid as the supporting electrolyte. This study evaluated the chemical and electrochemical properties of the electrolytes and assessed experimental and commercial membranes for use in the V/Br flow cell. A number of techniques were employed to characterise the composition of the V/Br flow cell electrolytes. During charge, the conductivity of the positive half-cell electrolyte increased, whilst the density and viscosity increased. The reverse was observed for the negative half-cell. The UV-visible spectra of the electrolytes showed characteristic peak wavelengths of the vanadium oxidation states and provided and insight into the halogenated species forming during the operation of the V/Br flow cell. The electrochemical properties of the electrolytes were also examined using cyclic voltammetry. NMR studies examined the relationships between the 35CI and 79Br nuclei in the presence of halide and paramagnetic vanadium ions. It was established that the SOC and performance of the V/Br flow cell can be measured by changes in slllectral chemical shifts and line widths. Small-scale cycling experiments were conducted to evaluate the performance of ion exchange membranes in the V/Br redox flow cell. Of the membranes evaluated, a number were not suitable for use due to high membrane resistances or low chemical stability. The perfluorinated Nafion?? and Gore Select?? ion exchange membranes proved to be the most chemically inert and showed low resistances. The Gore Select?? membranes did however exhibit blistering during extended cycling. The chemical stability and cycling performance of the HiporeTM microporous separator showed promise for future studies to optimise the selectivity and ion exchange capacity of the membrane. Tests of membrane ion exchange capacity, diffusivity and conductivity mirrored the properties displayed in the cell cycling experiments. Results suggested that the structural characteristics of the membrane (including functionality and crosslinking) greatly influenced membrane properties and performance. Tests of long term stability showed a negative change in membrane properties. These changes did not however reflect measured changes during cell cycling experiments.

Typewritten copy / 1 v. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1958

Thesis (Ph. D.)--University of Adelaide, 1985. / Includes bibliographical references.

Thesis (M.Sc.) -- University of Adelaide, Department of Physical and Inorganic Chemistry, 1976.