Hydrodynamic stability of boundary layers with surface mass transfer

The linear stability of the flat plate boundary layer with surface blowing and suction is investigated by the application of numerical techniques. Complete neutral stability curves, critical Reynolds numbers and wave numbers, and other stability characteristics are determined for a wide range of surface mass transfer intensities. The critical Reynolds number, based on the displacement thickness, is found to vary from 59 to 32500 between the extreme limits of blowing and suction that are investigated. Comparisons are made between the present results and available linear stability information for boundary layers with surface mass transfer and with free-stream pressure gradients. The universal stability bound of Joseph is evaluated and compared with the corresponding numerically exact neutral stability curve.     

Baryon exchange effects in dual unitarisation

The effects of baryon exchanges in the renormalisation of Regge trajectories are studied in the dual unitarisation scheme. The main results are that: (i) the pomeron is boosted above α = 1, giving rising total cross sections beyond baryon-antibaryon thresholds, and (ii) the ω trajectory remains approximately at α = 0.5 but acquires a sizeable admixture of the exotic $\text{q}\text{q}\text{qq}$ state, which enhances its coupling to baryons. There are in addition a number of other interesting predictions.     

Strange baryoniums: Their spectrum,decay and production

Using a quark-gluon model we study exhaustively the states with $\text{qq}\text{q}\text{q}$, where at least one q is a strange quark. The spectrum is extremely rich, but a few trajectories are singled out by their distinctive decay pattern and production mechanism. States of unusual colour content, formed from a diquark in colour-6 and an antidiquark in $\text{6}\text{-}\text{colour}$, are weakly coupled to $\text{B}\text{B}$ or two-meson channels through decay. Instead they prefer to cascade by emitting a π or a K if possible. Narrow $\text{Λ}\text{N}$ states among these are expected to be seen in Kp interactions. States with S = 2 will occur with $\text{K}{}^{\mathrm{?}}\text{Λ}\text{p}\text{or K}{}^{\mathrm{+?}}\text{gL}\text{p}$ final states, but not for example $\text{π}\text{Λ}\text{Λ}$. Some of these can be produced diffractively, with cross sections in the region of 1 μb. Those that require quantum-number exchange for production are expected to have considerably lower cross sections. Some can occur as cascade decay products.     

Isolation, structure, and absolute stereochemistry of platensimycin, a broad spectrum antibiotic discovered using an antisense differential sensitivity strategy

Fatty acids are essential for survival of bacteria and are synthesized by a series of enzymes including the elongation enzymes, beta-ketoacyl acyl carrier protein synthase I/II (FabF/B). Inhibition of fatty acid synthesis is one of the new targets for the discovery and development of antibacterial agents. Platensimycin (1a) is a novel broad spectrum Gram-positive antibiotic produced by Streptomyces platensis. It was discovered by target-based whole-cell screening strategy using antisense differential sensitivity assay. It inhibits bacterial growth by selectively inhibiting condensing enzyme FabF of the fatty acid synthesis pathway and was isolated by a two-step process, a capture step followed by reversed-phase HPLC. The structure was elucidated by 2D NMR methods and confirmed by X-ray crystallographic analysis of a bromo derivative. It was determined that potential reactivity of the enone moiety does not play a key role in the biological activity of platensimycin. However, cyclohexenone ring conformation renders for the stronger binding interaction with the enzyme. The isolation, structure elucidation, derivatization, and biological activity of 6,7-dihydroplatensimycin are described.     

The rotating mass matrix,the strong CP problem and Higgs decay

We first show that the rotating mass matrix hypothesis suggested earlier, where the massive eigenvector of a rank-one mass matrix changes with renormalisation scale, is consistent with the latest experimental data on fermion mass hierarchy and mixing, including the CP violating KM phase. We obtain thereby a smooth trajectory for the massive eigenvector as a function of the scale. Using this trajectory we next study Higgs decay and find suppression of \(\varGamma(H\rightarrow c\bar{c})\) compared to the standard model predictions for a range of Higgs masses. We also give limits for flavour-violating decays, including a relatively large branching ratio for the τ ^? μ ⁺ mode.     

Magnetic ordering below 10K in the high-Tc superconductor YBa2(Cu0.985Fe0.015)3O7−σ

The high-temperature superconductor with the nominal composition YBa₂Cu₃O_7?σ has been doped with iron 93% enriched in⁵⁷Fe. When 1.5 at % Fe substitutes for Cu, the transition temperature is reduced by about 30° K with full ac shielding (X′=?1/4π) achieved by ≈40 K. At room temperature the Mössbauer spectrum consists of three overlapping doublets. Below 10 K, hyperfine-field splitting is observed; relaxation still takes place at T=1.8 K.     

Asymmetric synthesis of dihydroquinazolinones via directed ortho metalation and addition to tert-butanesulfinyl imines

An asymmetric route to dihydroquinazolinones via the addition of ortho metalated substrates to tert-butanesulfinyl imines is reported. The scope of the nucleophile and electrophile components and the absolute stereochemical outcome are presented.     

Advective flow and floc permeability

This work monitored advection flow through a floc by bubble tracking. Close examination of the motion of a swarm of hydrogen bubbles that passed over a free-falling floc allowed the extent of advection flow to be estimated at 53% for the original activated sludge floc, and 12% for the flocculated floc. The interior permeability of the sludge flocs was estimated from this information. The fluid force exerted on the falling floc was also considered.