Working around the crisis in Libya

This is the first in a series of chair’s notes in Libyan Studies. We hope that future notes will address easier topics and more straightforward success, but for now we think it is important to communicate what we are doing given the difficult circumstances of Libya today. We trust that this report is useful, and we welcome any feedback

Losing energy in classical, relativistic and quantum mechanics.

A Zenonian supertask involving an infinite number of colliding balls is considered, under the restriction that the total mass of all the balls is finite. Classical mechanics leads to the conclusion that momentum, but not necessarily energy, must be conserved. Relativistic mechanics, on the other hand, implies that energy and momentum conservation are always violated. Quantum mechanics, however, seems to rule out the Zeno configuration as an inconsistent system

Does Quantum Electrodynamics Have an Arrow of Time?

Quantum electrodynamics is a time-symmetric theory that is part of the electroweak interaction, which is invariant under a generalized form of this symmetry, the PCT transformation. The thesis is defended that the arrow of time in electrodynamics is a consequence of the assumption of an initial state of high order, together with the quantum version of the equiprobability postulate

Knowledge-based diagnosis for aerospace systems

The need for automated diagnosis in aerospace systems and the approach of using knowledge-based systems are examined. Research issues in knowledge-based diagnosis which are important for aerospace applications are treated along with a review of recent relevant research developments in Artificial Intelligence. The design and operation of some existing knowledge-based diagnosis systems are described. The systems described and compared include the LES expert system for liquid oxygen loading at NASA Kennedy Space Center, the FAITH diagnosis system developed at the Jet Propulsion Laboratory, the PES procedural expert system developed at SRI International, the CSRL approach developed at Ohio State University, the StarPlan system developed by Ford Aerospace, the IDM integrated diagnostic model, and the DRAPhys diagnostic system developed at NASA Langley Research Center

Stabilization of DAPI in Base-Catalyzed Sol-Gels Using Surface Enhanced Raman Spectroscopy

Sol-gels can be used as substrates for sensory materials in solutions. A fluorescent dye that binds to DNA, 4’,6-diamidino-2-phenylindole (DAPI), could be used as a biosensor for a solution. Adsorption of DAPI onto silver nanoparticles causes rapid precipitation and loss of DAPI in solution. UV-vis and surface-enhanced Raman spectroscopy (SERS) were performed to observe a solution of silver nanoparticles and DAPI. Over time, spectra of the solution greatly diminished and could no longer be accurately observed. To facilitate the stabilization of DAPI in the solution, sol-gels were synthesized via base-catalyzed hydrolysis of tetramethyl orthosilicate while in the DAPI-silver solution. Sol-gels were successfully synthesized and DAPI precipitation was prevented as suggested by UV-vis and SERS

The preparation and properties of a glass-ceramic with an aligned microstructure

The work described in this thesis was performed on glass-ceramics in which a random arrangement of crystals is grown as a dispersed phase. The physical properties of this material are isotropic. The technique of hot extrusion has been used to produce a material with an aligned crystal microstructure in a Li₂O-SiO₂ glass-ceramic. The extruded material consists of a glass matrix and two crystalline phases; one of these phases is aligned morphologically and crystallographically parallel to the extrusion axis. The microstructure of this extruded material was analysed statistically in terms of the volume fraction of crystalline phases, the mean crystal- crystal spacing and the distribution function of the number of crystals N(Ɵ), making an angle Ɵ with a reference direction. Control specimens of the same composition heat-treated at the same temperature and for the same time as the extruded samples were also analysed statistically. The following physical properties were measured on the control and extruded specimens: (i) the coefficient of thermal expansion (ii) Young's modulus, rupture strength and microhardness (iii) Resistivity, dielectric constant and loss tangent. In the case of the extruded samples these measurements were made in directions parallel and perpendicular to the extrusion axis; the coefficient of thermal expansion, the mechanical properties and the resistivity were found to be anisotropic for these specimens