AC superconducting cables

The characteristics and economics of superconducting power transmission cables are discussed, and major research projects on these cables are described. At present Austria is the only European country continuing this research. The USSR has an active program and U.S. efforts are concentrated at the Brookhaven Laboratory which is constructing a 100 m-long 138 kV test facility. (LCL

Brookhaven program to develop a helium-cooled power transmission system

The particular system under design consists of flexible cables installed in a cryogenic enclosure at room temperature and cooled to the range 6 to 9$sup 0$K by supercritical helium, contraction of the cable is accommodated by proper choice of helix angles of the components of the cable. The superconductor is Nb$sub 3$Sn and at the present time the dielectric insulation is still the subject of intensive development. Two good choices appear to be forms of polyethylene and polycarbonate. Sample cables incorporating various dielectrics have been manufactured commercially in lengths of 1500 ft and tested in laboratory cryostats in shorter sections of about 70 ft. A test facility is under construction to evaluate cables and cryogenic components for this type of service, the first refrigerator uses a 350 H.P. screw compressor and three turbo- expander stages. It is hoped to achieve reliability of a very high order. The first three-phase tests will be conducted at 69 kV, although it appears that 230 to 345 kV is the most likely voltage range for future applications. (auth

Intermetallic superconductors---The state of development in 1991

The commercial fabrication of intermetallic superconductors has reached a high degree of maturity in the past thirty years. The only significant, commercial requirement for superconducting wire is the construction of magnetic resonance imaging (MRI) devices for medical diagnosis. In addition to this demand there are one-time projects such as high energy particle accelerators which often need considerable quantities of superconducting material over the few years of construction. R D projects also provide a fluctuating market for superconducting materials, in the past the projects have included power apparatus such as generators, motors, energy storage and transmission cables, and magnets for experimental fusion reactors. Superconducting magnetically levitated trains have undergone full scale trials in Japan and Germany. This is by no means a comprehensive list of all the possible applications. Virtually all the devices requiring a magnetic field to be produced by superconducting windings have used NbTi wire, but a few experimental Nb{sub 3}Sn high field magnets have been constructed. This report briefly discusses development of intermetallic superconductors

Pollution Liability: Rediscovery of Policy Language

Liability insurers have struggled for years to distinguish pollution incidents which they intend to cover from those they intend to exclude to the satisfaction of the courts. However, as the authors point out here, a number of recent cases indicate the courts' willingness to recognize the intent of policy language. In this exhaustive study, they examine how these cases have shed new light on the rule of ambiguity in policy language, on coverage for cleanup costs, on defense limitations, and on the pollution exclusion itself.Nous désirons présenter ici un travail publié par The John Liner Review, qui a bien voulu nous autoriser à le faire paraître avec la référence ci-dessous. Le but de cet article américain est de montrer la barrière entre les événements assurables et ceux qui sont inassurables, selon l’assurance de responsabilité civile des entreprises, tel que vu par les tribunaux. Étant donné la grande similitude du nouveau formulaire américain avec le nouveau formulaire canadien, force est de reconnaître l’intérêt de cette étude

From coprophagy to predation: a dung beetle that kills millipedes

The dung beetle subfamily Scarabaeinae is a cosmopolitan group of insects that feed primarily on dung. We describe the first case of an obligate predatory dung beetle and contrast its behaviour and morphology with those of its coprophagous sympatric congeners. Deltochilum valgum Burmeister killed and consumed millipedes in lowland rainforest in Peru. Ancestral ball-rolling behaviour shared by other canthonine species is abandoned, and the head, hind tibiae and pygidium of D. valgum are modified for novel functions during millipede predation. Millipedes were killed by disarticulation, often through decapitation, using the clypeus as a lever. Beetles killed millipedes much larger than themselves. In pitfall traps, D. valgum was attracted exclusively to millipedes, and preferred injured over uninjured millipedes. Morphological similarities placing D. valgum in the same subgenus with non-predatory dung-feeding species suggest a major and potentially rapid behavioural shift from coprophagy to predation. Ecological transitions enabling the exploitation of dramatically atypical niches, which may be more likely to occur when competition is intense, may help explain the evolution of novel ecological guilds and the diversification of exceptionally species-rich groups such as insects