A synthetic approach to the phorboxazoles – Synthesis of the C20–C32 central core

An enantiospecific synthesis of the C20–C32 central core of the phorboxazole scaffold, including the non-macrocyclic oxazole is detailed in 17 steps (longest linear sequence) from methacrolein in 7.8% overall yield. All of the stereocenters are communicated from a single Evans aldol reaction, and the final compound is suitably functionalized for further elaboration to the natural products.     

The delta-element reusable strain transducer

The paper describes a reusable biaxial-strain transducer consisting of a delta-shaped element in the form of a hollow equilateral traingle, with legs mounted perpendicular to its plane at the apices. The legs terminate in hard styli which are impressed into a test surface by axial forces acting on the legs. When the surface is strained, the displacements of the styli induce bending and torsional strains in the arms of the delta element. Strain gages mounted longitudinally on the arms detect the bending strains. It is shown that the strain in any arm is proportional to the strain in the test surface in the direction parallel to the arm. An instrument with a gage length of one inch is described and experimental results show that it has an accuracy of better than one percent.Paper was presented at the 1983 SESA Spring Meeting held in Cleveland, OH on May 15–19, 1983.     

Control of a coupled map lattice model for vortex shedding in the wake of a cylinder

The flow behind a vibrating flexible cable at low Reynolds numbers can exhibit complex wake structures such as lace-like patterns, vortex dislocations and frequency cells. These structures have been observed in experiments and numerical simulations, and are predicted by a previously developed low-order coupled map lattice (CML). The discrete (in time and space) CML models consist of a series of diffusively coupled circle map oscillators along the cable span. Motivated by a desire to modify the complex wake patterns behind flexible vibrating cables we have studied the addition of control terms into the highly efficient CML models and explored the resulting dynamics. Proportional, adaptive proportional and discontinuous non-linear (DNL) control methods were used to derive the control laws. The first method employed occasional proportional feedback. The adaptive method used spatio-temporal feedback control. The DNL method used a discontinuous feedback linearization procedure, and the controller was designed for the resulting linearized system using eigenvalue assignment. These techniques were applied to a modeled vortex dislocation structure in the wake of a vibrating cable in uniform freestream flow. Parallel shedding patterns were achieved for a range of forcing frequency-forcing amplitude combinations studied to validate the control theory. The adaptive proportional and DNL methods were found to be more effective than the proportional control method due to the incorporation of a spatially varying feedback gain across the cylinder span. The DNL method was found to be the most efficient controller of the low-order CML model. The required control level across the cable span was correlated to the 1/1 lock-on behavior of the temporal circle map.     

The development of information storage materials — How microscopy can help?

The response of giant magnetoresistance (GMR) devices depends critically on the film microstructure, with parameters such as layer thickness and interfacial abruptness being crucial. This paper presents results obtained using high resolution electron microscopy (HREM), chemical mapping and atom probe microanalysis. Local variations in the magnetic properties are induced by the microstructure and also when the films are patterned to form small elements. These lead to changes in the magnetization reversal mechanism. Some results of the studies of the magnetization reversal carried out using in situ in Lorentz transmission electron microscopy (LTEM) magnetizing experiments are also included.     

Synthesis of Migrastatin Analogues as Inhibitors of Tumour Cell Migration: Exploring Structural Change in and on the Macrocyclic Ring

Migrastatin and isomigrastatin analogues have been synthesised in order to contribute to structure–activity studies on tumour cell migration inhibitors. These include macrocycles varying in ring size, functionality and alkene stereochemistry, as well as glucuronides. The synthesis work included application of the Saegusa–Ito reaction for regio‐ and stereoselective unsaturated macroketone formation, diastereoselective Brown allylation to generate 9‐methylmigrastatin analogues and chelation‐induced anomerisation to vary glucuronide configuration. Compounds were tested in vitro against both breast and pancreatic cancer cell lines and inhibition of tumour cell migration was observed in both wound‐healing (scratch) and Boyden chamber assays. One unsaturated macroketone showed low affinity for a range of secondary drug targets, indicating it is at low risk of displaying adverse side effects.     

Reduced surface area chromatography for flow-through purification of viruses and virus like particles

A method for flow-through purification of viruses and virus like nano-particles using a combination of binding and size-exclusion chromatography was developed. This technique relies on minimizing the external surface area per unit volume available for virus binding by increasing the mean diameter of the beads used in the column. At the same time the impurity binding capacity of the column is maximized by utilizing beads with multiple functionalities of the optimum size. Purification of different types of viruses and virus-like-particles could be achieved using this technique. Flow-through purification of influenza virus using this technique yielded virus recoveries greater than 70-80% coupled with impurity removal greater than 80%. Finally an approach to optimize and facilitate process development using this technology is presented. Since the impurity binding occurs via a non-specific mechanism and virus recovery is achieved through reduced surface area, the technique is not limited to specific types of viruses and offers the potential as a universal purification tool.     

Derivations, isomorphisms, and second cohomology of generalized Witt algebras

Generalized Witt algebras, over a field of characteristic , were defined by Kawamoto about 12 years ago. Using different notations from Kawamoto's, we give an essentially equivalent definition of generalized Witt algebras over , where the ingredients are an abelian group , a vector space over , and a map which is linear in the first variable and additive in the second one. In this paper, the derivations of any generalized Witt algebra
, with the right kernel of being , are explicitly described; the isomorphisms between any two simple generalized Witt algebras are completely determined; and the second cohomology group for any simple generalized Witt algebra is computed. The derivations, the automorphisms and the second cohomology groups of some special generalized Witt algebras have been studied by several other authors as indicated in the references.