A topology for galois types in abstract elementary classes

We present a way of topologizing sets of Galois types over structures in abstract elementary classes with amalgamation. In the elementary case, the topologies thus produced refine the syntactic topologies familiar from first order logic. We exhibit a number of natural correspondences between the model‐theoretic properties of classes and their constituent models and the topological properties of the associated spaces. Tameness of Galois types, in particular, emerges as a topological separation principle. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Molecular quantum-dot cellular automata

Molecular electronics is commonly conceived as reproducing diode or transistor action at the molecular level. The quantum-dot cellular automata (QCA) approach offers an attractive alternative in which binary information is encoded in the configuration of charge among redox-active molecular sites. The Coulomb interaction between neighboring molecules provides device-device coupling. No current flow between molecules is required. We present an ab initio analysis of a simple molecular system which acts as a molecular QCA cell. The intrinsic bistability of the charge configuration results in dipole or quadrupole fields which couple strongly to the state of neighboring molecules. We show how logic gates can be implemented. We examine the role of the relaxation of nuclear coordinates in the molecular charge reconfiguration.     

Stochastic electron heating in a capacitive RF discharge withnon-Maxwellian and time-varying distributions

In capacitively coupled radio frequency discharges, the electrons gain and lose energy by reflection from oscillating, high voltage sheaths. When time-averaged, this results in stochastic heating, which at low pressure is responsible for most of the electron heating in these discharges. Previous derivations of stochastic heating rates have generally assumed that the electron distribution is a time-invariant, single-temperature Maxwellian, and that the sheath motion is slow compared to the average electron velocity, so that electrons gain or lose a small amount of energy in each sheath reflection. Here we solve for the stochastic heating rates in the opposite limit of fast sheath motion and consider the applicability of the slow and fast sheath equations in the intermediate region. We also consider the effect of a two-temperature Maxwellian distribution on particle balance and the effect of a time-varying temperature on the heating rates and densities     

Detonation interaction with a diffuse interface and subsequent chemical reaction

We have investigated the interaction of a detonation with an interface separating a combustible from an oxidizing mixture. The ethylene-oxygen combustible mixture had a fuel-rich composition to promote secondary combustion with the oxidizer in the turbulent mixing zone that resulted from the interaction. Diffuse interfaces were created by the formation of a gravity current using a sliding valve that initially separated the test gas and combustible mixture. Opening the valve allowed a gravity current to develop before the detonation was initiated. By varying the delay between opening the valve and initiating the detonation it was possible to achieve a wide range of interface conditions. The interface orientation and thickness with respect to the detonation wave have a profound effect on the outcome of the interaction. Diffuse interfaces result in curved detonation waves with a transmitted shock and following turbulent mixing zone. The impulse was measured to quantify the degree of secondary combustion, which accounted for 1–5% of the total impulse. A model was developed that estimated the volume expansion of a fluid element due to combustion in the turbulent mixing zone and predicted the resulting impulse increment.      

Porphyrins XXXV . Exciton coupling in μ-oxo Scandum dimers

The absorption and emission spectra at room temperature and at 77 K are reported for the monomers and μ-oxo dimers of (OEP)Sc(III) and (TPP)Sc(III). [Here (OEP) is octaethylporphin and (TPP) is tetraphenylporphin.] Exciton coupling effects are strongest in the B(Soret) band of [(OEP)Sc]₂O dimer: (i) The peak is blue shifted by 11 nm; (ii) the Soret band has a long red tail out to 480 mn; (iii) the fluorescence polarization shows a broad negativ band ≈ 440 nm. A vibronic exciton coupling model can roughly interpret the data if there is substantial and variable tilting of the ring planes. Exciton effects are weaker in the B(Soret) band of [(TPP)SC]₂O, presumably because there is less tilting. The effect of dimer formation on the Q band of [(OEP)Scl₂O is to red shift the band ≈ 420 cm^?1 and to nearly double the Q(0,0) halfwidth; there is no change in fluorescence yield with dimerization. Presumably for Q bands exciton coupling is weaker than inhomogeneous broadening. Both the phosphorescence yield and triplet lifetime at 77 K drop by $\text{case2}\text{3}$ in the dimer, showing faster radiationless decay.     

Pressurized membrane indicator system for fluorogenic-based fiber-optic chemical sensors

A new kind of fiber-optic-based chemical sensor for the detection of chemical species in solution is described. The sensor uses a fluorogenic indicator that is forced through an ultrafiltration membrane into the analyte solution. Complex formation between the indicator molecule and target ion occurs at the membrane/solution interface, where light from a bifurcated fiber-optic cable stimulates fluorescence. Fluorescence emission from the sample is transmitted back up the cable to a photodiode detector. Characterization of the sensor was performed using the response of the indicator, 8-hydroxyquinoline-5-sulfonic acid, to magnesium ion. The sensor responds linearly to increasing and decreasing concentration changes on time scales of 1 s. Chemical modification of the indicator solution to enhance sensitivity is demonstrated. The use of an internal standard to correct for variations in indicator flow-rate and pressure is discussed.