A monoclonal antibody that blocks the activity of a neurite regeneration-promoting factor: studies on the binding site and its localization in vivo

Work from several laboratories has identified a proteoglycan complex secreted by a variety of non-neuronal cells that can promote neurite regeneration when applied to the surface of culture dishes. Using a novel immunization protocol, a monoclonal antibody (INO) was produced that blocks the activity of this outgrowth-promoting factor (Matthew, W. D., and P. H. Patterson, 1983, Cold Spring Harbor Symp. Quant. Biol. 48:625-631). We have used the antibody to analyze the components of the active site and to localize the complex in vivo. INO binding is lost when the complex is dissociated; if its components are selectively reassociated, INO binds only to a complex containing two different molecular weight species. These are likely to be laminin and heparan sulfate proteoglycan, respectively. On frozen sections of adult rat tissues, INO binding is present on the surfaces of glial cells of the peripheral, but not the central, nervous system. INO also binds to the basement membrane surrounding cardiac and skeletal muscle cells, and binding to the latter greatly increases after denervation. In the adrenal gland and kidney, INO selectively reacts with areas rich in basement membranes, staining a subset of structures that are immunoreactive for both laminin and heparan sulfate proteoglycan. In general, the outgrowth-blocking antibody binds to areas known to promote axonal regeneration and is absent from areas known to lack this ability. This suggests that this complex, which is active in culture, may be the physiological substrate supporting nerve regeneration in vivo

Emergence and Causal Powers

This thesis is concerned with the theory of ontological emergence; a theory that posits a new kind of entity – usually an emergent property – that occurs in complex systems and can explain some system-level behaviour. The theory holds that these emergent entities are dependent on, but novel with respect to, the components of those systems. Such entities have been invoked to explain behaviours as diverse as symmetry breaking in molecular physics to the possibility of personal agency. As a metaphysical theory it is useful wherever there is a lack of understanding about how system-level behaviour can occur based on what we know about the parts of that system. Besides its usefulness, the theory, if true, would profoundly impact our understanding of fundamental ontology. The first half of this thesis aims to do three things: first, identify a problem that emergence can explain; second, identify what emergence must do in order to solve that problem; third, identify a theory of emergence capable of doing it. The first and second of these aims will require us to outline issues in fundamental ontology and metaphysical methodology that are critical to any assessment of the possibility of emergence. They both also require making some commitments on these issues. Among such commitments will be a commitment to an ontology of properties as causal powers. I argue that emergence is a theory of macro-properties and that the primary problem it solves is the Problem of Reduction. I thereafter defend the theory of causal powers emergence against charges that it is incoherent and inconsonant with science and natural unity; these and other conflicts are shown to be unproblematic once the theory is properly explicated. In these respects, this thesis finds no fault with the coherence of emergence. The key claims in the second half of the thesis instead pertain to the necessity of emergence to solve the problem that I have identified. The argument is that even if causal novelty, holistic effects and top-down causation are apparent in a system, a properly developed causal powers ontology can account for them without positing new fundamental properties. I develop an option called non-reductive inherence based on a theory of powers admitting a plurality of compositional principles. The thesis ends by expounding this alternative to emergence and setting out some of the trade-offs between the positions

Correlation length and compressibility for polar fluids near their critical points

Ph.D.Donald C. O'She

Single-crystal metal oxides and supported metal nanoclusters as model catalyst sytems

We have investigated the morphology and electronic structure of two basic classes of systems: metal oxide surfaces that catalyze the formation of environmentally persistent free radicals (EPFRs) from aromatic precursors, and Au and Cu nanoparticles that may be suitable catalysts for the catalytic oxidation of CO or hydrogenation of CO2. First, we examine the adsorption behavior of phenol on rutile TiO2(110) and ultrathin films of alumina prepared on a NiAl(110) substrate. Electron paramagnetic resonance studies show that exposure of both γ-alumina and titania powder to phenol at 250°C results in the formation of persistent phenoxyl radicals. EELS studies of phenol dosed on single-crystal titania and alumina show that phenol adsorbed at elevated temperature demonstrates a significantly narrower HOMO-LUMO gap than molecular phenol in the gas phase or physisorbed molecular phenol. Ultraviolet photoelectron spectroscopy shows direct evidence of charge transfer from high-temperature adsorbed phenol to electronic states of TiO2(110) usually associated with the accumulation of charge at surface oxygen vacancies, providing direct evidence of a frequently-hypothesized radical formation mechanism. Second, we deposit and characterize Au nanoparticles on the self-assembled hexagonal boron nitride “nanomesh” prepared on a Rh(111) substrate. STM studies show that at all levels of coverage, Au clusters almost always remain confined to the nanomesh “pores” and are restricted in size to \u3c 3 nm diameter. XPS studies suggest that the resulting Au clusters are negatively charged, and for \u3c 1 ML Au coverage, the electronic properties of most of the clusters formed are dominated by final-state effects that arise from the reduced dimensionality of the smallest clusters (one or two Au layers). A similar morphology for Au deposited on ZnO(10-10) has been previously observed; however, we find that the Au-ZnO interaction instead results in positively charged clusters. Cu on ZnO(10-10) grows as three-dimensional clusters even at very small coverage and shows positive charging similar to Au. It is clear that catalytically relevant properties of supported metal nanoclusters are strongly influenced by interactions with the support, even if the cluster morphology is identical for particles on various different substrates