Partial-wave analysis of the (KKK) system in the reaction K−p→K−K−K+p at 10 and 16 GeV/c

The reaction K^?p→K^?K^?K⁺p is shown to have properties similar to those of the diffractive reaction K^?p→K^?π^?π⁺p. This is true, at least in first approximation, for (a) the energy dependence of the cross sections, (b) the shape of the three meson spectra and (c) the differential cross sections dσ/dt_pp which have the same slope for the same mass of the three-meson system. Furthermore, the partial-wave composition of the (KKK) system is similar to that of the (Kππ) system, both systems being produced mostly in unnatural spin-parity states by natural parity exchange. In the KKK system, the J^P = 1⁺ state with S-wave decay into Kø(1020) is dominant, (72 ± 11) % of all events with (KKK) masses below 2 GeV.     

Nonlinear wave-packet interferometry and molecular state reconstruction in a vibrating and rotating diatomic molecule

We formulate two-color nonlinear wave-packet interferometry (WPI) for application to a diatomic molecule in the gas phase and show that this form of heterodyne-detected multidimensional electronic spectroscopy will permit the reconstruction of photoinduced rovibrational wave packets from experimental data. Using two phase-locked pulse pairs, each resonant with a different electronic transition, nonlinear WPI detects the quadrilinear interference contributions to the population of an excited electronic state. Combining measurements taken with different phase-locking angles isolates various quadrilinear interference terms. One such term gives the complex overlap between a propagated one-pulse target wave packet and a variable three-pulse reference wave packet. The two-dimensional interferogram in the time domain specifies the complex-valued overlap of the given target state with a collection of variable reference states. An inversion procedure based on singular-value decomposition enables reconstruction of the target wave packet from the interferogram without prior detailed characterization of the nuclear Hamiltonian under which the target propagates. With numerically calculated nonlinear WPI signals subject to Gaussian noise, we demonstrate the reconstruction of a rovibrational wave packet launched from the A state and propagated in the E state of Li2.     

Molecular state reconstruction by nonlinear wave packet interferometry

We show that time- and phase-resolved two-color nonlinear wave packet interferometry can be used to reconstruct the probability amplitude of an optically prepared molecular wave packet without prior knowledge of the underlying potential surface. We analyze state reconstruction in pure- and mixed-state model systems excited by shaped laser pulses and propose nonlinear wave packet interferometry as a tool for identifying optimized wave packets in coherent control experiments.     

Finite-depth and intrinsic losses in vertically etched two-dimensional photonic crystals

We address the issue of out-of-plane losses in two-dimensional (2D) photonic crystals (PC) etched through a GaAs monomode waveguide clad with standard GaAlAs alloys. We correlate experimental transmission of PCs with two kinds of loss simulation results. The first kind is 2D and introduces an ad hoc imaginary index in the air holes to account for the losses [see (Benisty et al. Appl. Phys. Lett. 76, 532, 2000)]. The second kind is a novel exact three-dimensional calculation inspired by grating-Fourier analysis that provides quantitatively unprecedented agreement with experimental measurements taking into account hole depth as a limiting parameter. We conclude that, in revision to the conclusions of the above reference, the experimental losses are not the intrinsic ones, being larger by a factor of 5 to 10 due to insufficient hole depth. The transition occurs at a critical etch depth shown to be here around 700 nm. We thus predict, for holes deeper than 700 nm, much improved crystals with very low transmission losses and microresonators with ultra-high quality factors.     

An impact parameter description of single and double diffraction dissociation

An s-channel impact parameter model of inelastic diffraction dissociation is constructed which describes quantitatively the momentum transfer distributions of both pion and nucleon induced reactions. It is stressed that the impact parameter profile is peripheral and is approximately the same for all helicity amplitudes. From the fits to the data, the concept of a universal limiting strength (ULS) for each amplitude is deduced and its consequence for other diffractive processes, and the approximate TCHC hypothesis are discussed. Finally, detailed predictions are presented the momentum transfer distributions in the double diffraction process NN → (Nπ)(Nπ), and compared with a simple t-channel picture of diffraction dissociation.     

The role of new eudesmane-type sesquiterpenoid and known eudesmane derivatives from the red alga Laurencia obtusa as potential antifungal–antitumour agents

A new eudesmane sesquiterpenoid, eudesma-4(15),7-diene-5,11-diol (1) along with the known trinor-sesquiterene, teuhetenone (2), and a seco-eudesmane sesquiterpene, chabrolidione B (3), have been isolated from the Red Sea red alga Laurencia obtusa. The chemical structures were elucidated on the basis of extensive spectroscopic analysis. The antifungal and cytotoxic activities of the isolated metabolites were tested against several fungi, yeast and human mammary carcinoma cell line (MCF-7). Compounds 1 and 3 showed a much better activity [minimum inhibitory concentration (MIC): 2.9 μM] than that of amphotericin B (MIC: 4.6 μM). Interestingly, compound 2, the least active antifungal compound, retained the high anticancer activity against MCF-7 (22 μM) in comparison with cisplatin (59 μM), which was determined by employing lactate dehydrogenase assay. Compounds 1–3 are recorded here for the first time from algal flora. The chemotaxonomic importance of the isolated metabolites was discussed.     

Spectral Response of a Stochastic Oscillator under Impacts

An approximate analytical procedure is presented to estimate theresponse spectrum of an oscillator with elastic impacts under a Gaussian whitenoise excitation. The proposed approach is based on a perturbation analysis ofthe problem and on the use of the stochastic averaging principle. The basicidea is to replace the initial system by a more regular system obtained byapproximating the nonlinear restoring force by a Chebychev polynomial, and thento construct for this regular system two approximations: one for the flowand one for the stationary distribution of the response amplitude. Ananalytical approximation of the response spectrum can then be derived fromthese results. Predictions from this analytical approximation are compared with corresponding digital simulation estimates and with the ones obtained from theconventional equivalent linearization method.     

Combinatorial Library Based Engineering of Candida antarctica Lipase A for Enantioselective Transacylation of sec‐Alcohols in Organic Solvent

A method for determining lipase enantioselectivity in the transacylation of sec‐alcohols in organic solvent was developed. The method was applied to a model library of Candida antarctica lipase A (CalA) variants for improved enantioselectivity (E values) in the kinetic resolution of 1‐phenylethanol in isooctane. A focused combinatorial gene library simultaneously targeting seven positions in the enzyme active site was designed. Enzyme variants were immobilized on nickel‐coated 96‐well microtiter plates through a histidine tag (His₆‐tag), screened for transacylation of 1‐phenylethanol in isooctane, and analyzed by GC. The highest enantioselectivity was shown by the double mutant Y93L/L367I. This enzyme variant gave an E value of 100 (R), which is a dramatic improvement on the wild‐type CalA (E=3). This variant also showed high to excellent enantioselectivity for other secondary alcohols tested.