5,6-dihydropyridine: synthesis and characterization

5,6-dihydropyridine 1 is synthesized either by flash vacuum thermolysis of 1-azabicyclo[2.2.2] oct-2-ene 3 or by dehydrochlorination over solid bases of N-chloro-1,2,5,6-tetrahydropyridine 4 and characterized at low temperature by its ¹H and ¹³C nmr and ir spectra.     

The vibration-rotation spectrum of methinophosphide: The overtone bands 2ν1 and 2ν3, the summation bands ν1 + ν2 and ν2 + ν3, and the difference band ν1 - ν2

The vibration-rotation bands 2ν₁, 2ν₃, ν₁ + ν₂, ν₂ + ν₃, and ν₁ - ν₂ of H¹²CP were recorded and analyzed. These data were combined with previously reported results for this molecule to obtain an improved and extended set of vibrational and rotational constants. All x_ij and γ_ij were calculated except those that require data from a summation band involving ν₁ and ν₃.     

A Practical Optimisation Technique for a Queueing System

A scheduling problem in an outpatient clinic is considered. First the system is represented by means of a simple queueing model. The problem of minimising the patients' total queueing time is then formulated as a non-linear program and solved by applying the Kuhn-Tucker conditions. The results obtained enable the person who manages the appointment system to allocate appointment dates to patients who have different priorities.     

Development of an integrated optic oxygen sensor using a novel, generic platform

This paper describes the development of a generic platform for enhanced, integrated optic sensors based on fluorescence detection. The platform employs a novel optical configuration in order to achieve enhanced performance and has inherent multianalyte detection capability. The sensor element comprises a multimode ridge waveguide that has been patterned with an analyte-sensitive fluorescent spot, which is excited directly using a LED. The platform was applied to the detection of gaseous oxygen as a proof of principle. The sol-gel-derived sensor spots were doped with an oxygen-sensitive fluorescent dichlororuthenium dye complex and intensity-based calibration data were generated from the oxygen-dependent waveguide output. The sensor achieved a LOD of 0.62% and a resolution of less than 0.96% gaseous oxygen, which compares favourably with a similar, recently reported system. This device highlights the combination of inexpensive rapid prototyping techniques and a dedicated sensor enhancement strategy that together facilitate the production of an effective prototype sensor platform.     

The vibration-rotation spectrum of methinophosphide: l-Type doubling, l-type resonance and the ν2, 2ν2, and 3ν2 bands of H12CP; The ν1 and ν2 bands of H13CP

The vibration-rotation bands ν₂, 2ν₂, and several “hot” bands of H¹²CP have been recorded and assigned. The states with v₂ = 2, perturbed by l-type resonance and l-type doubling effects have been analyzed on the basis of the existing theory. The energy difference between the 02²0 and the 02⁰0 states was found to be 17.5095 (19) cm^?1. Because of insufficient data, the states with v₂ = 3 could not be corrected for l-type resonance interaction and therefore only an effective l-type doubling constant was obtained. The ν₁ and ν₂ bands of the H¹³CP isotopic molecule (present at natural concentration) were also identified and their spectroscopic constants obtained. The value of I_e for H¹²CP is found to be 25.18793 (26) amu Ų.     

Spaces of Tilings, Finite Telescopic Approximations and Gap-Labeling

The continuous Hull of a repetitive tiling T in ℝ^d with the Finite Pattern Condition (FPC) inherits a minimal ℝ^d-lamination structure with flat leaves and a transversal which is a Cantor set. This class of tiling includes the Penrose & the Amman Benkker ones in 2D, as well as the icosahedral tilings in 3D. We show that the continuous Hull, with its canonical ℝ^d-action, can be seen as the projective limit of a suitable sequence of branched, oriented and flat compact d-manifolds. As a consequence, the longitudinal cohomology and the K-theory of the corresponding C*-algebra are obtained as direct limits of cohomology and K-theory of ordinary manifolds. Moreover, the space of invariant finite positive measures can be identified with a cone in the d^th homology group canonically associated with the orientation of ℝ^d. At last, the gap labeling theorem holds: given an invariant ergodic probability measure μ on the Hull the corresponding Integrated Density of States (IDS) of any selfadjoint operators affiliated to takes on values on spectral gaps in the ℤ-module generated by the occurrence probabilities of finite patches in the tiling. Accepted in Revised Form: 7 May 2005     

Sorption thermodynamics of CO2, CH4, and their mixtures in the ITQ-1 zeolite as revealed by molecular simulations

The thermodynamic properties and siting of carbon dioxide and methane sorbed in the siliceous form of zeolite MCM-22, ITQ-1, were studied by means of grand canonical Monte Carlo simulation. ITQ-1 comprises two independent pore systems of different geometry. It was found to be CO(2)-selective toward CO(2)/CH(4) gas mixtures, its equilibrium selectivity being distinctly higher in its sinusoidal channel pore system than in the large cavity system over a wide range of pressures starting from the Henry law regime, at the three temperatures considered. A maximum in selectivity is observed at low temperature, high pressure, and methane-rich gas-phase composition.     

On the clarification of the IR stretching vibration assignment of adsorbed N2 on Rh0 and Rhdelta+ surface atoms of supported Rh crystallites

The low-temperature adsorption of N(2) on Rh/SiO(2) samples of various particle-size distributions was followed by FTIR. The addition of O(2) pulses on Rh(0) surfaces saturated with chemisorbed N(2) allowed us to reassign stretching frequencies attributed originally to N(2)-Rh(0) to N(2)-Rh(delta+). The formation of the latter oxidized Rh species is assumed to be induced by an electron withdrawal from adsorbed oxygen species on Rh surface centers neighboring those onto which N(2) species are chemisorbed. The present work, thus, enables us to delimit ranges of frequencies for which the adsorption of N(2) can be considered to occur on either Rh(0) or Rh(delta+) centers for nu(N2) lower or higher than 2243 cm(-1), respectively. The N(2)-FTIR experiments performed on the studied catalysts also suggest a lattice plane selectivity for N(2) adsorption on metallic Rh planes of different natures which, to our knowledge, has not been reported yet for Rh.