After many years of fusion research, the conditions needed for a D–T fusion reactor have been approached on the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. For the first time the unique phenomena present in a D–T plasma are now being studied in a laboratory plasma. The first magnetic fusion experiments to study plasmas using nearly equal concentrations of deuterium and tritium have been carried out on TFTR. At present the maximum fusion power of 10.7 MW, using 39.5 MW of neutral-beam heating, in a supershot discharge and 6.7 MW in a high-βp discharge following a current rampdown. The fusion power density in a core of the plasma is ≊2.8 MW m−3, exceeding that expected in the International Thermonuclear Experimental Reactor (ITER) [Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 239] at 1500 MW total fusion power. The energy confinement time, τE, is observed to increase in D–T, relative to D plasmas, by 20% and the ni(0) Ti(0) τE product by 55%. The improvement in thermal confinement is caused primarily by a decrease in ion heat conductivity in both supershot and limiter-H-mode discharges. Extensive lithium pellet injection increased the confinement time to 0.27 s and enabled higher current operation in both supershot and high-βp discharges. Ion cyclotron range of frequencies (ICRF) heating of a D–T plasma, using the second harmonic of tritium, has been demonstrated. First measurements of the confined alpha particles have been performed and found to be in good agreement with TRANSP [Nucl. Fusion 34, 1247 (1994)] simulations. Initial measurements of the alpha ash profile have been compared with simulations using particle transport coefficients from He gas puffing experiments. The loss of alpha particles to a detector at the bottom of the vessel is well described by the first-orbit loss mechanism. No loss due to alpha-particle-driven instabilities has yet been observed. D–T experiments on TFTR will continue to explore the assumptions of the ITER design and to examine some of the physics issues associated with an advanced tokamak reactor.

Weyl semimetals are examples of a new class of topological states of matter which are gapless in the bulk with protected surface states. Their low energy sector is characterized by massless chiral fermions which are robust against translationally invariant perturbations. A variant of these systems have two non-degenerate bands touching along lines rather than points. A proposal to realize such a phase involves alternating layers of topological insulators and magnetic insulators, where the magnetization lies perpendicular to the symmetry axis of the heterostructure. The shape, size and the dispersion in the vicinity of the nodal lines varies with the strength of the magnetization, offering a new knob to control the properties of the system. In this paper we map out the evolution of the nodal lines and the dependence of the conductivity on magnetization and identify signatures of the low energy sector in quantum oscillation measurements.

Anaerobic chytridiomycete fungi are found in the gastrointestinal tracts of sheep, cattle and goats, as well as in many other domesticated ruminant and nonruminant herbivores and a wide variety of wild herbivorous mammals. They are principally found associated with the fibrous plant particles of digesta and as free swimming zoospores in the fluid phase. The presence of large fungal populations in animals consuming mature pasture or diets largely composed of hay or straw together with the production of highly active fibre degrading enzymes lead to' the belief that anaerobic fungi may have a significant role to play in the assimilation of fibrous feeds by ruminants. While many early studies focused on anaerobic fungi because of their unusual biology and metabolism, the large part of subsequent research has emphasized the biotechnological potential of their cellulases, xylanases and phenolic esterases. In recent years, the extent of the contribution of anaerobic fungi to the nutrition of ruminants has also been established through studies of fungal populations in the rumen and the dietary factors which influence them, as presented in this review. Further, we discuss the evidence supporting an important contribution of anaerobic fungal populations in the rumen to feed intake and digestion of poor quality feed by domesticated ruminants. In conclusion, the review explores some different methods for manipulating fungi in the rumen for increased feed intake and digestion.

Helical organisms with novel ultrastructural characteristics were isolated from the intestinal mucosa of rats and mice. These bacteria were characterized by the presence of 9 to 11 periplasmic fibers which appeared as concentric helical ridges on the surface of each cell. The cells were motile with a rapid corkscrewlike motion and had bipolar tufts of 10 to 14 sheathed flagella. The bacteria were microaerophilic, nutritionally fastidious, and physiologically similar to Helicobucter species and Wolinella succinogenes but could be differentiated from these organisms by their unique cellular ultrastructure. Using 16s rRNA sequencing, we found that strain STIT (T = type strain) was related to previously described Helicobucter species, "Flexispira rappini," and W . succinogenes. The closest relatives of strain STIT were Helicobacter mustelae and "F. rappini" (average similarity value, 96%). On the basis of phylogenetic data, strain STIT (= ATCC 49282T) represents a new species of the genus Helicobucter, for which we propose the name HeZicobucter muridarum.Bacteria with a variety of spiral morphologies are common inhabitants of the gastrointestinal tracts of both humans and animals (8-10, 20, 24-26, 30, 34, 39). Several of these spiral bacteria are helically coiled and possess bipolar tufts of flagella and concentric ridges that are due to periplasmic fibers that run the length of each cell. They have been seen in a variety of gastrointestinal preparations, including ceca (8) and ilea of rats (34), colons of mice (39), and gastric mucosa (26) and fundic glands of dogs and cats (20). Recently, organisms with a similar morphology have been implicated in ovine abortions (5, 21) and in intestinal diseases in animals and humans (1, 37).Much of the recent work on spiral bacteria has concentrated on Helicobacter pylori and other Campylobacter-like organisms because of the postulated association of these bacteria with human gastrointestinal disease (6,18,28,29). The taxonomy of this group of organisms is now being clarified. Recent phylogenetic work has resulted in the creation of the genus Helicobacter, and new species of this genus are rapidly being recognized (14, 17,32,33,36,40,43). Although three of the gastric helicobacters are very similar physiologically and show high degrees of similarity (96%) in their 16s rRNA sequences, these bacteria have very different morphologies (19,24,31). H. pylori is a relatively short organism with one or two turns in its spiral body, while Helicobacter musteleae is a short, slightly curved, rodshaped organism with an unusual flagellum configuration. In contrast, Helicobacter felis is 5 to 7 pm long and has a tightly spiralled body with five or six turns; it is entwined with a distinctive series of periplasmic fibers.The distinctive periplasmic fibers are not new to us because 10 years ago we observed similar structures on a bacterium isolated from a rat ileum (34). The same organism * Corresponding author.has been described previously in the elegant electron microscopic studies of Erland...