Synthesis,photooxidation and Z ⇌ E photoisomerization of benzalpyrrolinones

In contrast to oxodipyrromethenes and bilirubin, benzalpyrrolinones (H, P-OCH₃, p-Cl, p-N(CH₃)₂ and o-CH₃) and α-pyridalpyrrolinones appear not to undergo dye-sensitized photo-oxygenation. They do, however, undergo an unsensitized E ? Z photoisomerization reminiscent of stilbene photoisomerization, and the photostationary state varies with substituent. Intramolecular H-bonding is implicated in the α-pyridalpyrrolinone isomerization. In each case, the Z isomers are the therrnodynamically more stable ones, but the corresponding E isomers have been isolated and characterized following photoirradialion.     

Mutually exclusive and exhaustive quantum states

The identification of a set of mutually exclusive and exhaustive propositions concerning the states of quantum systems is a corner stone of the information-theoretic foundations of quantum statistics; but the set which is conventionally adopted is in fact incomplete, and is customarily deduced from numerous misconceptions of basic quantum mechanical principles. This paper exposes and corrects these common misstatements. It then identifies a new set of quantum state propositions which is truly exhaustive and mutually exclusive, and which is compatible with the foundations of quantum theory.Work supported by a grant from Research Corporation.     

Simultaneous Measurement,Phase-Space Distributions,and Quantum State Determination

Noting that a classical phase-space probability distribution w(q, p) may be calculated from moment expectation values {q^mpⁿ}, we inquire as to whether similar data in quantum mechanics would be adequate to determine the statistical operator ?. For the family of simultaneous (q, p) measurement schemes investigated, it turns out that such moments do not suffice to fix ?. Comparison of the empirical information that is adequate to determine ? with that required to find w(q, p) reveals that in a sense more data are needed for state determination in quantum statistics than are needed in the classical case.     

A model for the plane to plane variations in catalytic activity seen during nitric oxide decomposition on platinum

Previous work has shown that the reactivity of platinum for nitric oxide decomposition varies significantly with the geometry of the exposed surface of the platinum. Here, the available data are compared to the predictions of a model, which is based on conservation of orbital symmetry and a simplified picture of the band structure of the surface. The model predicts that the (100) face of platinum should be more active than either the (111) or the (110). The (410) should be more active still. These predictions agree with recent experiment. The model makes several other predictions which need to be tested experimentally. These results suggest that symmetry conservation methods, similar to the ones developed by Woodward and Hoffmann for organic reactions, could yield many valuable insights into the relative activity of various catalyst structures.     

The integral mean diffusivity for particle-gas mass transfer calculations under thermal plasma conditions

Plasma Chemistry and Plasma Processing - A new integral mean diffusivity is proposed for the calculation of the mass transfer rate around a small particle immersed in a thermal plasma gas....     

A shock-tube measurement of the SiO(E1Σ+ − X1Σ+) transition moment

The sum of the squares of the electronic transition moments, Σ|R_e|², for the E¹Σ⁺ ?X¹Σ⁺ band system of SiO has been determined from absorption measurements conducted in the reflected-shock region of a shock tube. The test gas was produced by shock-heating a mixture of SiCl₄, N₂O and Ar, and the spectra were recorded photographically in the 150–230 nm wavelength range. The values of the Σ|R_e|² were determined by comparing the measured absorption spectra with those produced by a line-be-line synthetic spectrum calculation. The value of the Σ|R_e|² so deduced at an r-centroid value of 3.0 Bohr was 0.86±0.10 atomic units.     

Release of N(2) from the carbon nanotubes via high-temperature annealing

Nitrogen (N)-doped carbon nanotubes (CNTs) were heated to 1000 degrees C under an ultrahigh vacuum. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) reveal three different N structures; graphitelike, pyridine-like, and molecular N(2). The vibrationally resolved XANES peaks of N(2) were first observed, suggesting the existence of molecular N(2) as intercalated and trapped forms. The annealing process can decrease the average N content from 6.3 at. % to 3.3 at. %, mainly by releasing molecular N(2). Electron energy-loss spectroscopy (EELS) confirms that the annealing releases molecular N(2) from the CNTs.     

Improved measurement of the form factors in the decay lambda+c-->lambda + nue

Using the CLEO detector at the Cornell Electron Storage Ring, we have studied the distribution of kinematic variables in the decay lambda(+)(c)lambda--> e(+)nu(e). By performing a four-dimensional maximum likelihood fit, we determine the form factor ratio, R= f(2)/f(1) = -0.31 +/- 0.05(stat) +/- 0.04(syst), the pole mass, M(pole) = [2.21 +/- 0.08(stat) +/- 0.14(syst)] GeV/c(2), and the decay asymmetry parameter of the lambda(+)(c), alpha (lambda(c)) = -0.86 +/-0.03(stat) +/- 0.02(syst), for q(2) = 0.67 (GeV/c(2))(2). We compare the angular distributions of the lambda(+)(c) and lambda(-)(c) and find no evidence for CP violation: A(lambda(c)) = (alpha(lambda(c)) + alpha (lambda(c)))/(alpha(lambda(c))-alpha(lambda(c))) = 0.00 +/- 0.03(stat) +/- 0.01(syst) +/- 0.02, where the third error is from the uncertainty in the world average of the CP-violating parameter, A(lambda), for ppi(-).     

Twist-grain-boundary structure in the B4 phase of a bent-core molecular system identified by second harmonic generation circular dichroism measurement

Second harmonic generation circular dichroism (SHG CD) measurements are performed on the B4 phase of a bent-core molecular system. Numerical analysis of SHG CD incorporating magnetic-dipole as well as electric-dipole interaction shows that the B4 phase is in a twist-grain-boundary structure with the helical axis along the bent direction of the molecules. The result is extremely important in the sense that achiral molecules are spontaneously optically resolved, i.e., deracemization, the chiral domains of which give rise to huge chiral nonlinear optical effect.     

Asymmetrically coupled directed percolation systems

We introduce a dynamical model of coupled directed percolation systems with two particle species. The two species A and B are coupled asymmetrically in that A particles branch B particles, whereas B particles prey on A particles. This model may describe epidemic spreading controlled by reactive immunization agents. We study nonequilibrium phase transitions with attention focused on the multicritical point where both species undergo the absorbing phase transition simultaneously. In one dimension, we find that the inhibitory coupling from B to A is irrelevant and the model belongs to the unidirectionally coupled directed percolation class. On the contrary, a mean-field analysis predicts that the inhibitory coupling is relevant and a new universality appears with a variable dynamic exponent. Numerical simulations on small-world networks confirm our predictions.