Matrix Near-rings over Centralizer Near-rings

For a finite group G and a subgroup A of Aut(G), let M_A(G) denote the centralizer near-ring determined by A and G. The group G is an M_A(G)-module. Using the action of M_A(G) on G, one has the n × n generalized matrix near-ring Mat_n(M_A(G);G). The correspondence between the ideals of M_A(G) and those of Mat_n(M_A(G);G) is investigated. It is shown that if every ideal of M_A(G) is an annihilator ideal, then there is a bijection between the ideals of M_A(G) and those of Mat_n(M_A(G);G).1991 Mathematics Subject Classification: 16Y30     

The convergent total synthesis and antibacterial profile of the natural product streptothricin F

A convergent, diversity-enabling total synthesis of the natural product streptothricin F has been achieved. Herein, we describe the potent antimicrobial activity of streptothricin F and highlight the importance of a total synthesis that allows for the installation of practical divergent steps for medicinal chemistry exploits. Key features of our synthesis include a Burgess reagent-mediated 1,2-anti-diamine installation, diastereoselective azidation of a lactam enolate, and a mercury(ii) chloride-mediated desulfurization-guanidination. The development of this chemistry enables the synthesis and structure–activity studies of streptothricin F analogs.

The second ever total synthesis of streptothricin F and the first achieved through a diversity-enabling convergent route. The synthesis is achieved in 35 total steps, with a longest linear sequence of 19 steps, and 0.40% overall yield.     

Study of locally dense and locally saturated basis sets in localized molecular orbital calculations of nuclear shielding: Ab initio LORG calculations for 13C and 17O in norbornenone

This study demonstrates the use of uneven atomic basis sets for ab initio calculations of NMR shielding in the localized orbital/local origin (LORG) approach with norbornenone as the test case. We distinguish between locally dense sets (extended basis on target atom only) and locally saturated sets (extended bases on target atom and atoms in its first bonding sphere), using 6-311G ** and 6-31G sets to describe the high and low level of function sets. It is shown that the use of these uneven sets can simulate high basis set level calculations of shieldings for ¹H and for all the ¹³C nuclei in this molecule and, hence, allows quite accurate ab initio calculations of shielding properties of these nuclei in large molecules using relatively modest computational facilities. The shielding of the double-bonded ¹⁷O nucleus is apparently sensitive to basis-set quality beyond the first bonding sphere. © 1996 John Wiley & Sons, Inc.     

The origins and diffusion of operational research in the UK

This paper analyses the origins and diffusion of operational research in the UK from the end of the Second World War to 1970. After acknowledging ORs military origins, the paper discusses the process of diffusion into the civilian sector. In this context, the critical role fulfilled by OR groups in the coal and iron and steel industries is highlighted, as well as the individual advocacy of key individuals such as Sir Charles Goodeve. The paper also comments on the development of OR in the UK corporate sector by presenting a number of representative case studies. It concludes with an examination of the factors which encouraged the diffusion of OR into civil government after 1965, contrasting this development with the muted response of Whitehall departments in the late 1940s.     

Observed 7-8 GHz Signal Attenuation During Rainfall

Records obtained on a microwave relay system south of Lake Michigan indicate that significant attenuation can occur during rainfall at frequencies as low as 7-8 GHz. Prolonged outages axe possible when a squall line moves along, rather than across, a relay system.     

Optical and crystallographic evidence for the choice of space group,nature of the crystal phase change and high birefringence in Ln(Apy)6I3

Reexamination of the structures and electronic spectra of Ln(antipyrene)₆I₃ crystals indicates that the series is isomorphous [space groupR3, (No. 146);Z=1] at room temperature despite spectral evidence of a centric ligand field for the Ln ions. High birefringence and phase changes at lower temperatures (<60 K for Ln=Pr) limit the possibilities for CD meaurement.     

Components of ideals in a commutative ring

Summary The notion of the S-component of an ideal is generalized, and the principal properties of the generalization are given. In memory of Guido Castelnuovo in the recurrence of the first centenary of his birth.