Prediction of the crystal structure of a cyclic tetrapeptide

Prediction of the known crystal structure of cyclic-L-Ser(O-t-Bu)-β-Ala-Gly-L-β-Asp(OMe) has been attempted by establishing the low-energy conformations of the isolated molecule by conformational analysis, and then regarding each of these as a rigid molecule, by establishing the favorable crystal packing arrangements by molecular packing analysis. The theoretical model closest to the observed structure was one of the lowest-energy solutions and was recognized as essentially correct by reference to the x-ray data. The limitations of the model follow from the fact that the side chain conformations are somewhat affected by packing interactions.     

Partitioned state and parameter estimation for real-time flood forecasting

A new algorithm is developed for simultaneous state-parameter estimation in real-time flood-forecasting applications. Dubbed the partitioned state-parameter (PSP) algorithm, is it unusual in the way that the parameter filter is formulated explicitly in terms of the identifiable parameters in the transition and input coefficient matrices. By virtue of its parallel filter structure the algorithm is very fast, yet it has been designed so that essential error interactions between the forecasting and parameter filters are preserved. Furthermore, PSP is structured so that input coefficients are only updated when the corresponding inputs are actually applied. This feature is useful for systems subject to sporadic inputs. The algorithm is tested with real and synthesized daily rainfall-runoff data from the Hillsborough River in Florida. PSP is found to produce good forecasts and parameter estimates and is much faster than the extended Kalman filter.     

Approximation by discrete operators

A discrete, positive, weighted algebraic polynomial operator which is based on Gaussian quadrature is constructed. The operator is shown to satisfy the Jackson estimate and an optimal version is obtained.     

A proof of Hamblin's algorithm for translation of arithmetic expressions from infix to postfix form

We show that a particular algorithm for the translation of arithmetic expressions in infix form into postfix form is correct. The method used is ad hoc, in contrast to other work in this field, and it is hoped that this in itself is of interest.Work carried out at the University of Leeds, England.     

Correlation between the superconducting and normal state properties of amorphous molybdenum - silicon alloys

Measurements on amorphous Mo_1?xSi_x (0.27 ≤ × ≤ 0.77) show that with increasing x the superconducting transition temperature, T_c, decreases linearly with x for x ≤ x₀ ≡ 0.63 ± 0.05. The superconducting transition width and normal state resistivity increase rapidly with increasing x as x approaches x₀. For x > x₀, T_c drops below 1.5K. Transmission electron diffraction measurements (0.65 ≤ × ≤ 0.75) detect the presence of a second amorphous phase which resembles a-Si only for samples with x ? 0.75. The behavior near x₀ could be attributed to the onset of an electronic transition involving the conversion of metallically bonded Si to covalently bonded Si.     

Mode-locking dynamics of synchronously-pumped colour-centre lasers

A theoretical model has been developed for studying the steady-state pulse shaping dynamics of a synchronously-pumped colour-centre laser. A wide range of results is presented detailing effects on the mode-locking process of pump pulse power and width, laser bandwidth, cavity mismatch and, stochastic noise. From the results, we identify conditions which lead to the formation of single and multiple pulses. We show this can be understood on the basis of a simple scaling law between the principal laser parameters.     

Shape coexistence and intruder states: theZ=82 region

The phenomena associated with shape coexistence and intruder states are illustrated with examples from the Pt, Au, Hg, Tλ, Pb and Bi isotopes which lie far from beta stability midway between closed neutron shells 82 and 126. The type of spectroscopic measurements which have already been developed to investigate these structures as well as those types of measurements needed to extend and quantify the analysis, such as on-line nuclear orientation, are discussed.