Bounded Entanglement Entropy in the Quantum Ising Model

Journal of Statistical Physics - A rigorous proof is presented of the boundedness of the entanglement entropy of a block of spins for the ground state of the one-dimensional quantum Ising model...     

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The inverse scattering transform: Tools for the nonlinear fourier analysis and filtering of ocean surface waves

Surface wave data from the Adriatic Sea are analysed in the light of new data analysis techniques which may be viewed as a nonlinear generalization of the ordinary Fourier transform. Nonlinear Fourier analysis as applied herein arises from the exact spectral solution to large classes of nonlinear wave equations which are integrable by the inverse scattering transform (IST). Numerical methods are discussed which allow for implementation of the approach as a tool for the time series analysis of oceanic wave data. The case for unidirectional propagation in shallow water, where integrable nonlinear wave motion is governed by the Korteweg-deVries (KdV) equation with periodic/quasi-periodic boundary conditions, is considered. Numerical procedures given herein can be used to compute a nonlinear Fourier representation for a given measured time series. The nonlinear oscillation modes (the IST ‘basis functions’) of KdV obey a linear superposition law, just as do the sine waves of a linear Fourier series. However, the KdV basis functions themselves are highly nonlinear, undergo nonlinear interactions with each other and are distinctly non-sinusoidal. Numerical IST is used to analyse Adriatic Sea data and the concept of nonlinear filtering is applied to improve understanding of the dominant nonlinear interactions in the measured wavetrains.     

The micro water/1,2-dichloroethane interface as a transducer for creatinine assay

Facilitated ammonium ion transfer reactions, using the crown ether dibenzo-18-crown-6, at a single microhole supported water/1,2-dichloroethane interface were used as the transducer to detect the biomolecule creatinine. The ammonium ion was produced during the enzymatic action of creatinine deiminase on creatinine. A prototype sensing device incorporating a Teflon gas permeable membrane, to exclude possible interferents, yielded a linear amperometric response to added creatinine from 20 M to 1 mM. This range is sufficient for that required for the determination of creatinine in serum.     

Cesium chromate,Cs2CrO4: heat capacity and thermodynamic properties from 5 to 350 K

The heat capacity of a sample of Cs₂CrO₄ was determined in the temperature range 5 to 350 K by aneroid adiabatic calorimetry. The heat capacity at constant pressure C_p^o(298.15 K), the entropy S^o(298.15 K), the enthalpy {H^o(298.15 K) - H^o(0)} and the function $\text{? {G}{}^{\mathrm{o}}\text{(298.15}\text{K}\text{) - H}{}^{\mathrm{o}}\text{(0)}}\text{298.15}\text{K}$ were found to be (146.06 ± 0.15) J K^?1 mol^?1, (228.59 ± 0.23) J K^?1 mol^?1, (30161 ± 30) J mol^?1, and (127.43 ± 0.13) J K^?1 mol^?1, respectively. The heat capacity C_p^o(298.15 K) and entropy S^o(298.15 K) and entropy S^o(298.15 K) of Rb₂CrO₄ are estimated to be (146.0 ± 1.0) J K^?1 mol^?1 and (217.6 ± 3.0) J K^?1 mol^?1, respectively.     

Low-divergence operation of a long-pulse excimer laser using a SBS phase-conjugate cavity

The use of an optical cavity containing a stimulated Brillouin scattering (SBS) phase-conjugate reflector to control the spatial and spectral output of a long pulse (>100 ns) X-ray preionized XeCl laser is reported. The divergence of the 3×4 cm² output beam has been improved by a factor of 20 to <150 rad. The temporal form of the output depends on the acoustic decay times of the liquid and gaseous SBS media used. Four-wave mixing via gain saturation has been observed within the discharge volume, leading to depolarisation of the output beam.     

Double diastereoselective [3,3]-sigmatropic aza-Claisen rearrangements

Asymmetric [3,3]-sigmatropic aza-Claisen rearrangement of the (Z)-N-allyl-N,O-silylketene aminal of (3S,4E,alphaR)-1-benzyloxy-3-(N-propionyl-N-alpha-methylbenzylamino)hex-4-ene furnishes (2S,3R,4E,alphaR)-N-alpha-methylbenzyl-2,3-dimethyl-7-benzyloxyhept-4-enamide in > 92% d.e.; rearrangement of the diastereomeric (3R,4E,alphaR)-(Z)-N,O-silylketene aminal proceeds with low diastereoselectivity.     

Conformational and receptor-binding properties of the insect neuropeptide proctolin and its analogues

Summary Proctolin (Arg-Tyr-Leu-Pro-Thr) was the first insect neuropeptide to be chemically characterised. It plays an essential role in insect neurophysiology and is involved in muscular contraction and neuromodulation. Elements of secondary structure in solution have been studied by comparing data obtained from NMR and molecular dynamics simulations. Different secondary structural requirements are associated with agonist and antagonist activities. A favoured conformation of proctolin has an inverse -turn, comprising an intramolecular hydrogen bond near the C-terminal end between Thr NH and Leu CO. Antagonists have a more compact structure resembling a paperclip loop, containing an intramolecular hydrogen bond between Tyr NH and Pro CO, possibly stabilised by a salt bridge between the N- and C-terminal groups. A cyclic analogue retains antagonist activity and resembles a -bulge loop, also comprising intramolecular hydrogen bonds between Tyr NH and Pro CO and Thr CO. These models may offer feasible starting points for designing novel compounds with proctolinergic activity.