Linear programming solutions and distance functions under α-returns to scale

This note generalizes analytical relationships among activity variables of Dataenvelopment analysis models previously derived in a previous article by theauthors of this note. We relax the assumption of constant returns to scale byshowing that the key results hold under a weaker assumption of homogeneity. Weuse the notion of α-returns to scale to extend the analysis tostrictly increasing and decreasing returns, covering now the whole range ofreturns to scale for multi-output homogenous technologies.     

Raman Scattering from Liquid Crystals

Abstract

The use of Raman scattering technique as a tool for studying local order in complex liquid crystal systems is illustrated by three examples, namely the locally anisotropic liquid L-phase, lipid membranes, and PDLC's.     

Quark-hadron duality in neutron (3He) spin structure

We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_{1} of the neutron and 3He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c);{2}. Global duality is observed for the spin-structure function g_{1} down to at least Q;{2}=1.8 (GeV/c);{2} in both targets. We have also formed the photon-nucleon asymmetry A1 in the resonance region for 3He and found no strong Q2 dependence above 2.2 (GeV/c);{2}.     

Correlations between structure and far-infrared active modes in polythiophenes

We have investigated the experimental X-ray and far-infrared responses of three polythiophenes synthesized from a thiophene, alpha-bithiophene, and alpha-quaterthiophene monomer. The X-ray data show that the crystallinity of the different polythiophene samples depends on the synthesis conditions. An excellent correlation between the crystallinity of polythiophenes and their far-infrared signatures is demonstrated. In addition, the assignment of the far-infrared phonon modes in polythiophenes is given by using both an experimental filiation procedure and first-principles calculations. In particular, the ring libration inside the polymeric chain, directly involved in the electron-phonon coupling, is assigned.     

Probing molecular conformations in momentum space: the case of n-pentane

A comprehensive study, throughout the valence region, of the electronic structure and electron momentum density distributions of the four conformational isomers of n-pentane is presented. Theoretical (e,2e) valence ionization spectra at high electron impact energies (1200 eV+electron binding energy) and at azimuthal angles ranging from 0 degrees to 10 degrees in a noncoplanar symmetric kinematical setup are generated according to the results of large scale one-particle Green's function calculations of Dyson orbitals and related electron binding energies, using the third-order algebraic-diagrammatic construction [ADC(3)] scheme. The results of a focal point analysis (FPA) of relative conformer energies [A. Salam and M. S. Deleuze, J. Chem. Phys. 116, 1296 (2002)] and improved thermodynamical calculations accounting for hindered rotations are also employed in order to quantitatively evaluate the abundance of each conformer in the gas phase at room temperature and reliably predict the outcome of experiments on n-pentane employing high resolution electron momentum spectroscopy. Comparison with available photoelectron measurements confirms the suggestion that, due to entropy effects, the trans-gauche (tg) conformer strongly dominates the conformational mixture characterizing n-pentane at room temperature. Our simulations demonstrate therefore that experimental measurements of (e,2e) valence ionization spectra and electron momentum distributions would very consistently and straightforwardly image the topological changes and energy variations that molecular orbitals undergo due to torsion of the carbon backbone. The strongest fingerprints for the most stable conformer (tt) are found for the electron momentum distributions associated with ionization channels at the top of the inner-valence region, which sensitively image the development of methylenic hyperconjugation in all-staggered n-alkane chains.     

Kinetics and dynamic properties of equilibrium polymers

The statistical mechanics and scission-recombination mechanism of self-assembling linear micelles are investigated by Brownian dynamics using a newly proposed mesoscopic model representing the micelles as equilibrium polymer chains. A semidilute concentration regime, yet dynamically unentangled, is considered over a wide range of scission/recombination rates. We focus on the analysis of short and long time behaviors of the scission and recombination mechanisms. Our results show that at time scales larger than the life time of the average chain length, the kinetics is in agreement with the mean-field kinetic model proposed by Cates and Candau [J. Phys.: Condens. Matter 2, 6869 (1990)] provided the kinetic constants are estimated as effective ones. These values do take into account through a transmission coefficient that a fraction of scission/recombination events is correlated over a short time (diffusion controlled mechanism) and thus turn out to be ineffective reactive events by annihilation effects. By studying macroscopic relaxation phenomena such as the average micelle length evolution after a T jump, the monomer diffusion, and the zero shear stress relaxation function, we confirm that the effective kinetic constants found are indeed the relevant parameters when macroscopic relaxation is coupled to the kinetics of micelles.     

Enhanced all-optical tuning of leaky eigenmodes in photonic crystal waveguides

We demonstrate all-optical switching in an active two-dimensional photonic crystal waveguide, observing as large as 16 nm blueshifts of a leaky eigenmode at 839 nm and switching ratios of almost 70%. These results are larger than those previously observed in similar experiments performed on passive photonic crystal waveguides; the enhancement is due to resonant photogeneration of carriers by In(0.12)Al(0.2)Ga(0.68)As quantum wells in the core of the waveguide. The effective change in the refractive index of the structure is approximately10(-2), with a rise time of approximately1 ps and a decay time of approximately10 ps, potentially allowing high-speed switching and fast modulation rates.     

Utilisation of on-line acoustic irradiation as a means to counter-effect catalyst deactivation in heterogeneous catalysis

The effect of power ultrasound has been studied in the hydrogenation of 1-phenyl-1,2-propanedione (enantioselective hydrogenation) and linoleic acid (fat hardening). Furthermore the hydrogenation of d-xylose to xylitol and citral to citronellal and citronellol were studied under the influence of acoustic irradiation. We have investigated the effect of on-line acoustic irradiation of these heterogeneously catalysed liquid-gas-solid systems in which it was found to counter-effect catalyst deactivation, increase the reaction velocity and to enhance the selectivity of various heterogeneously catalysed reactions.