Advanced development of Pb-salt semiconductor lasers for the 8.0 to 15.0 micrometer spectral region

The technology was studied for producing Pb-salt diode lasers for the 8-51 micron spectral region suitable for use as local oscillators in a passive Laser Heterodyne Spectrometer (LHS). Consideration was given to long range NASA plans for the utilization of the passive LHS in a space shuttle environment. The general approach was to further develop the method of compositional interdiffusion (CID) recently reported, and used successfully at shorter wavelength. This technology was shown to provide an effective and reproducible method of producing a single-heterostructure (SH) diode of either the heterojunction or single-sided configuration. Performance specifications were exceeded in several devices, with single-ended CW power outputs as high as 0.88 milliwatts in a mode being achieved. The majority of the CID lasers fabricated had CW operating temperatures of over 60K; 30% of them operated CW above the boiling temperature of liquid nitrogen. CW operation above liquid nitrogen temperature was possible for wavelengths as long as 10.3 microns. Operation at 77K is significant with respect to space shuttle operations since its allows considerable simplification of cooling method

Measuring thermal conductivity in extreme conditions: sub-Kelvin temperatures and high (27 T) magnetic fields

We present a one-heater-two-thermometer set-up for measuring thermal conductivity and electric resistivity of a bulk sample at low temperatures down to 0.1 K and in magnetic fields up to 27 Tesla. The design overcomes the difficulties emerging in the context of large water-cooled resistive magnets.Comment: 4 pages including 4 figure

Continuous Time and Consistent Histories

We discuss the use of histories labelled by a continuous time in the approach to consistent-histories quantum theory in which propositions about the history of the system are represented by projection operators on a Hilbert space. This extends earlier work by two of us \cite{IL95} where we showed how a continuous time parameter leads to a history algebra that is isomorphic to the canonical algebra of a quantum field theory. We describe how the appropriate representation of the history algebra may be chosen by requiring the existence of projection operators that represent propositions about time average of the energy. We also show that the history description of quantum mechanics contains an operator corresponding to velocity that is quite distinct from the momentum operator. Finally, the discussion is extended to give a preliminary account of quantum field theory in this approach to the consistent histories formalism.Comment: Typeset in RevTe

Determination of stability constants using genetic algorithms

A genetic algorithm (GA)-simplex hybrid approach has been developed for the determination of stability constants using calorimetric and polarographic data obtained from literature sources. The GA determined both the most suitable equilibrium model for the systems studied and the values of the stability constants and the heats of formation for the calorimetric studies. As such, a variable length chromosome format was devised to represent the equilibrium models and stability constants (and heats of formation). The polarographic data were obtained from studies of cadmium chloride and lead with the crown ether dicyclohexyl-18-crown-6. The calorimetric data were obtained from a study of a two step addition reaction of Hg(CN)2 with thiourea. The stability constants obtained using the GA-simplex hybrid approach compare favourably with the values quoted in the literature

PACAP-induced ERK phosphorylation in VPAC1 and VPAC2-expressing HEK cells is mediated by receptor endocytosis and PKC signaling

Pituitary adenylate-cyclase activating polypeptide (PACAP) is highly conserved signaling molecule in eukaryotes known to regulate a myriad of metabolic processes within the brain as well as the body (Sherwood, Krueckl, & McRory, 2000; Vaudry et al., 2009). The mechanism of action underlying PACAP signaling is known to occur through the PAC1, VPAC1 and VPAC2 G protein-coupled receptors (GPCRs) to initiate signaling cascades that can phosphorylate extracellular signal-related kinase (ERK) proteins to influence many intracellular events including gene expression, long-term potentiation, or induce growth factors, all of which are a specific response to extracellular events (Chang, & Karin, 2001). In the current study, HEK cells expressing VPAC1 or VPAC2 receptors were exposed to PACAP27 (P27) to induce receptor activation and ERK phosphorylation (pERK). The VPAC expressing cells were treated with P27 for varying durations to assess the temporal changes in pERK; further, the cells were pre-treated with signaling pathway inhibitors to determine the predominant mechanisms of P27-mediated ERK phosphorylation. From previous work, it was hypothesized that PACAP-mediated ERK activation of VPAC-type receptors would be elicited via receptor endocytosis and the PKA pathway. Experiments were conducted in triplicate, and the pathway inhibitors included two receptor endocytosis blockers (Pitstop2 and Dynasore), a PKA inhibitor (KT5720), and a PKC inhibitor (Bim1). Relative expression of ERK1/2 and pERK proteins were visualized and compared by quantitative Western analyses. Unlike, PAC1 receptors, PACAP activation of VPAC receptors resulted in transient ERK activation. Contrary to expectations, the experimental results also showed that receptor endocytosis blocker Pitstop2 and PKC inhibitor Bim1 reduced ERK phosphorylation. These inhibitor results are similar to previous experiments conducted on HEK-expressing PAC1 receptors treated with the same pathway inhibitors (May, Buttolph, Girard, Clason, & Parsons, 2014), providing further sight into how PACAP-mediated mechanisms of ERK phosphorylation may be implicated physiological conditions