Delayed neutron emission probabilities of gallium,bromine, rubidium,indium, antimony,iodine, and cesium precursors

The delayed neutron emission probability(P _n) has been measured for^79-83Ga,^87-89Br,^92-96Rb^127-132In^134,135Sb^137-139I and^{141 -145}Cs, by means of sources produced at the OSIRIS isotope separator at Studsvik. The half-life determinations of^{127, 129, 132}In have been improved.     

Microwave and optical spectroscopy of carotenoid triplets in light-harvesting complex LHC II of spinach by absorbance-detected magnetic resonance

Absorbance-detected magnetic resonance (ADMR) of the light-harvesting complex LHC II of spinach revealed two triplet contributions, having differentD values, but equalE value (|E|=0.00379 cm^?1). The two triplets are assigned to two of the three carotenoids present in LHC II: lutein (|D|=0.03853 cm^?1) and neoxanthin (|D|=0.04003 cm^?1). The ADMR-detected Triplet-minus-Singlet (T—S) optical difference spectrum of the carotenoid (Car) triplet transition of LHC II showed, apart from bands in the Car absorption region, a contribution in the chlorophyll (Chl) absorption region due to a change in interaction between lutein and Chla at 670 nm, and neoxanthin and Chla at 670 and 677 nm. From Linear Dichroic (LD-)ADMR-detected LD-(T—S) spectra we have determined that the tripletz-axis (which corresponds roughly to the polyenal axis) of lutein and neoxanthin makes an angle of 47° and 38° with theQ _y transition moment of their adjacent Chla molecules, for the Chls absorbing at 670 and 677 nm, respectively. TheT _z triplet magnetic transition moment of lutein is parallel to the lutein singlet and triplet absorptions, whereas theT _x axis of neoxanthin makes an angle of about 20 degrees with the optical transition moments of the carotenoid molecule. The major Chla absorption bands of the optical absorption spectrum and the ADMR-detected T—S spectrum is best explained by assuming that all Chla is present in dimers. It is proposed that a free Chl dimer absorbs at 664 and 670 nm, whereas a Chl dimer bound to a carotenoid absorbs at 670 and 677 nm.     

A constructive theory for shock-free,isentropic flow

We construct by finite differences solutions of the Cauchy problem for the nonlinear wave equation in one space dimension. We make certain monotonicity assumptions about the initial data, and we show that the resulting solution is Lipschitz continuous for positive times. In addition, we prove the uniqueness of the solution in a certain class, and we characterize its large-time behavior in terms of the equilibrium state for a corresponding Riemann problem. Finally, we show how our results can be extended to more general 2 × 2 systems of hyperbolic conservation laws which are genuinely nonlinear.     

Levels and transition probabilities in 121Cd

The decay of isotope-separated ¹²¹Ag has been studied. A level scheme for ¹²¹Cd has been constructed. Information on lifetimes of excited states has been obtained by the method of delayed coincidences. Some low-lying energy levels of ¹²¹Cd show a considerable deviation from the systematics of similar levels in the lighter isotopes of Cd. This may be attributed to a different spatial symmetry of ¹²¹Cd.     

Analytical expressions for and geometrical meaning of the comparative indices of recording media

The indices for characterizing the performance of holographic recording media introduced recently by Tai and Yu can be related to the parameters of the optimal linear transfer function (OLTF). These parameters have been obtained in an analytical form by the author for the recording material with an exponential transfer curve and for the holographic setup using two plane waves and for the case of the fourier lensless hologram. The expressions for the indices in terms of the OLTF parameters are given and their geometrical meaning in relation to the OLTF is pointed out for the two holographic setups mentioned.     

Mechanism of white phosphorus activation by three-coordinate molybdenum(III) complexes: a thermochemical, kinetic, and quantum chemical investigation

White phosphorus (P(4)) reacts with three-coordinate molybdenum(III) trisamides or molybdaziridine hydride complexes to produce either bridging or terminal phosphide (P(3)(-)) species, depending upon the ancillary ligand steric demands. Thermochemical measurements have been made that place the MoP triple bond dissociation enthalpy at 92.2 kcal.mol(-)(1). Thermochemical measurements together with computational analysis rule out simple P-atom abstraction from P(4) as a step in the phosphorus activation mechanism. Kinetic measurements made by the stopped-flow method show that the reaction between the monomeric molybdenum complexes and P(4) is first-order both in metal complex and in P(4). Cyclo-P(3) complexes can be obtained when ancillary ligand steric demands are small, but kinetic measurements rule them out as monometallic intermediates in the P(4) activation mechanism. Also studied by calorimetric, kinetic, and in one case variable-temperature NMR methods is the process of mu-phosphide bridge formation. Post-rate-determining steps of the P(4) activation process were examined in a search for minima on the reaction's potential energy surface, leading to the proposal of two plausible, parallel, bimetallic reaction channels.     

Identification of special structure constraints in linear programs

In large LPs it may be that a major fraction of the constraints has a particularly simple form. Frequently this simple form may be exploited by either decomposition or implicit representation methods. In these cases, the effective size and computational difficulty are more closely related to the number of remaining nonspecial constraints than to the number of special constraints. A unified computational procedure is presented for mechanically identifying near maximal sets of special structure constraints for most of the kinds of special structures which have been identified thus far as being exploitable.     

THE ORIENTATION OF CHLOROPHYLL AND BACTERIOCHLOROPHYLL MOLECULES IN AN ORIENTED LECITHIN MULTILAYER

Abstract— Chlorophyll a and b and bacteriochlorophyll a have been incorporated in an oriented phospholipid multilayer. The orientation of the chlorophyll molecules in this layer has been measured by polarization spectroscopy. Formulas are given expressing the dichroic ratio R as a function of the angle of tilt θ between the molecule and the plane of the multilayer and the angle μ between this plane and the transition dipole moment measured in the plane of the molecule. The possibility of overlapping bands of mutually perpendicular polarization has been taken into account. Analysis of the experimental results gives the angles θ and μ as well as an estimate for the fraction of polarization of some bands along the dihydro axis in the plane of the chlorophyll molecule.