Joseph M. A. Miller

Carbon aerogels for electrochemical applications

A major advantage of highly crosslinked, organic aerogels is the ability to transform many of these materials into electrically conductive carbon aerogels. Carbon aerogels have been formed as monoliths, microspheres, irregularly-shaped powders, and thin film composites. In all cases, the carbon aerogels retain their high surface area (400–800 m2/g) and ultrafine cell/pore size (<100 nm). Carbon aerogels are being examined as electrodes for double layer capacitors, pseudocapacitors, and capacitive deionization units. This paper examines the synthesis, structure–property relationships, and performance of carbon aerogel electrodes used in electrochemical applications.

Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set.

We present a compilation of endocranial volumes (ECV) for 176 non-human primate species based on individual data collected from 3813 museum specimens, at least 88% being wild-caught. In combination with body mass data from wild individuals, strong correlations between endocranial volume and body mass within taxonomic groups were found. Errors attributable to different techniques for measuring cranial capacity were negligible and unbiased. The overall slopes for regressions of log ECV on log body mass in primates are 0.773 for least-squares regression and 0.793 for reduced major axis regression. The least-squares slope is reduced to 0.565 when independent contrasts are substituted for species means (branch lengths from molecular studies). A common slope of 0.646 is obtained with logged species means when grade shifts between major groups are taken into account using ANCOVA. In addition to providing a comprehensive and reliable database for comparative analyses of primate brain size, we show that the scaling relationship between brain mass and ECV does not differ significantly from isometry in primates. We also demonstrate that ECV does not differ substantially between captive and wild samples of the same species. ECV may be a more reliable indicator of brain size than brain mass, because considerably larger samples can be collected to better represent the full range of intraspecific variation. We also provide support for the maternal energy hypothesis by showing that basal metabolic rate (BMR) and gestation period are both positively correlated with brain size in primates, after controlling for the influence of body mass and potential effects of phylogenetic relatedness.

Strategies for encapsulating biomolecules in sol–gel matrices

Abstract The encapsulation of biological molecules in sol–gel matrices has received considerable attention because of the prospect of creating novel materials which exhibit the characteristic chemical and biochemical functionalities of enzymes and other proteins. This paper explores the nature of the interactions between a sol–gel derived silica matrix and the electron transfer protein, cytochrome c. These interactions were found to be of central importance in determining the synthesis conditions for these materials, in creating the pores which confine the protein and in stabilizing the protein so that it retains its structure and chemical function.

Synthesis conditions for encapsulating cytochrome c and catalase in SiO2 sol-gel materials

Abstract The encapsulation of biological molecules in sol-gel materials has led to the development of a new class of chemical and biomedical sensors. The influence of sol-gel synthesis conditions on the stability, chemical function, and enzymatic reactivity for horse heart cytochrome c and bovine liver catalase encapsulated in silica sol-gel materials was studied. The effects of synthesis pH, alcohol/alkoxide ratio, and buffer type were examined using UV-V is absorption spectroscopy for cytochrome c -doped materials and gasometric analysis for assays of catalase in gels. In general, the behavior of the proteins encapsulated in silica gels mirrored their behavior in solution suggesting that the stability limiting factor for encapsulating these biological molecules is determined by the solution stability of the protein. In the case of catalase, the results indicate that the silica gel stabilizes the encapsulated enzyme to higher methanol concentrations.

Encapsulation of proteins in bulk and thin film sol-gel matrices

This paper considers the nature of the interactions between the sol-gel derived inorganic matrix and a specific biomolecule, cytochrome c. Optical absorption and impedance spectroscopies are used to characterize the influence of synthesis conditions on the protein’s stability and conformation within the silica matrix. In some instances, encapsulation within the sol-gel matrix provides stabilization. For example, protein denaturation is reversible and aggregation is prevented. Moreover, the drying process does not negatively affect the protein; it is possible to regenerate the aged gel state by rehydration. The flexibility of the sol-gel process enables high quality cytochrome c-doped SiO2 thin films to be prepared. These films possess the characteristic reactivity and chemical function of cytochrome c in solution.