A high-density and high-confinement tokamak plasma regime for fusion energy.

The tokamak approach, utilizing a toroidal magnetic field configuration to confine a hot plasma, is one of the most promising designs for developing reactors that can exploit nuclear fusion to generate electrical energy1,2. To reach the goal of an economical reactor, most tokamak reactor designs3-10 simultaneously require reaching a plasma line-averaged density above an empirical limit-the so-called Greenwald density11-and attaining an energy confinement quality better than the standard high-confinement mode12,13. However, such an operating regime has never been verified in experiments. In addition, a long-standing challenge in the high-confinement mode has been the compatibility between a high-performance core and avoiding large, transient edge perturbations that can cause very high heat loads on the plasma-facing-components in tokamaks. Here we report the demonstration of stable tokamak plasmas with a line-averaged density approximately 20% above the Greenwald density and an energy confinement quality of approximately 50% better than the standard high-confinement mode, which was realized by taking advantage of the enhanced suppression of turbulent transport granted by high density-gradients in the high-poloidal-beta scenario14,15. Furthermore, our experimental results show an integration of very low edge transient perturbations with the high normalized density and confinement core. The operating regime we report supports some critical requirements in many fusion reactor designs all over the world and opens a potential avenue to an operating point for producing economically attractive fusion energy.

Integration of full divertor detachment with improved core confinement for tokamak fusion plasmas.

Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation of fusion reactors. Here, we demonstrate the excellent compatibility of actively controlled full divertor detachment with a high-performance (ßN ~ 3, H98 ~ 1.5) core plasma, using high-ßp (poloidal beta, ßp > 2) scenario characterized by a sustained core internal transport barrier (ITB) and a modest edge transport barrier (ETB) in DIII-D tokamak. The high-ßp high-confinement scenario facilitates divertor detachment which, in turn, promotes the development of an even stronger ITB at large radius with a weaker ETB. This self-organized synergy between ITB and ETB, leads to a net gain in energy confinement, in contrast to the net confinement loss caused by divertor detachment in standard H-modes. These results show the potential of integrating excellent core plasma performance with an efficient divertor solution, an essential step towards steady-state operation of reactor-grade plasmas.

Experimental Demonstration of the Collisionless Plasmoid Instability below the Ion Kinetic Scale during Magnetic Reconnection.

The spontaneous formation of magnetic islands is observed in driven, antiparallel magnetic reconnection on the Terrestrial Reconnection Experiment. We here provide direct experimental evidence that the plasmoid instability is active at the electron scale inside the ion diffusion region in a low collisional regime. The experiments show the island formation occurs at a smaller system size than predicted by extended magnetohydrodynamics or fully collisionless simulations. This more effective seeding of magnetic islands emphasizes their importance to reconnection in naturally occurring 3D plasmas.

An investigation of the in vivo stability of poly(ether urethaneurea) blood sacs.

In this paper we investigate the biostability of a series of Biolon blood sacs that were utilized in electric total artificial hearts for time periods of up to 19 weeks. A battery of experimental probes, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were used to characterize the bulk and surface properties of explanted and control blood sacs. Gel permeation chromatography (GPC) experiments showed that generally there was a dramatic increase in average molecular weight at longer implantation times. However, SEM and GPC observations suggest significant deterioration of the flex regions of right blood sacs after 17 weeks of service. XPS experiments indicated appreciable silicon and hydrocarbon concentrations on blood-contacting surfaces both before and after implantation, and we speculate as to their origin.

Rejection of rat skin xenografts by either murine CD4 or CD8 T cells.

Although xenografts can be rejected by humoral or cellular mechanisms, the relative contribution of each remains unknown for any given recipient-donor combination. Moreover, the cells involved in cell-mediated events, as well as the mechanisms by which these cells recognize xenoantigens, remain controversial. It would be advantageous to have a model in which either, as well as various parts of either, could be investigated in the absence of the other, as well as in the absence of events taking place during organ engraftment. In the present report, rejection of rat skin xenografts was monitored after adoptive transfer of unique populations of highly purified lymphoid cells to previously transplanted immunodeficient C.B17 Scid/Scid mice. Purified T cells and, unexpectedly, purified CD4+ T cells alone and purified CD8+ T cells alone rejected rat xenografts. Alternatives that may explain these findings are discussed.

[Acute intestinal occlusion caused by phytobezoar in Israel. Role of oranges and persimmons]. / L'occlusion intestinale aiguë par phytobézoards en Israël. Rôle de l'orange et du persimmon.

Forty-one patients were operated upon for acute intestinal obstruction secondary to the presence of phytobezoars, 34 of these patients (83%) having a history of previous gastric surgery for ulcer. The etiologic factor in 44% of cases was oranges and in 56% persimmons (Kakis). Treatment was by enterotomy in 27 patients (65,85%) and by "milking" in 14 (34,15%). Postoperative mortality was 2,44% (1 case). Recurrence was noted in three cases (7,3%) including one with an ileocutaneous fistula, treatment being by enterotomy in 2 cases and "milking" in the third patient. First intention intestinal resection was never required. Five patients required several admissions for subacute obstruction treated conservatively. These findings suggest that gastric surgery predisposes to intestinal obstruction by phytobezoar. Careful exploration of the digestive tube and particularly the stomach should avoid postoperative relapse, while prevention depends on a dietary regimen avoiding excessive intake of foods rich in cellulose, particularly oranges and persimmon fruit.

Physicians' private clinics in a Northern Thai town--patient-healer "collaboration" and the shape of biomedical practice.

Physicians' private clinics in small Northern Thai towns offer the patient the services of official biomedicine's most sophisticated clinical talent, and the physicians themselves an opportunity to significantly supplement their incomes. The clinic form, while familiar to Westerners and Japanese, has been adapted to the Northern Thai medical environment and Northern Thai notions of the therapeutic process. Because of sociocultural constraints and the pressure of the plural medical environment, physicians' private clinics result in a "collaboration" between patient and practitioner in which some prerogatives of each are compromised and others upheld to shape a clinical institution that satisfies the needs of each. This paper discusses three private clinics in a small Northern Thai town from the perspectives of the physicians and the patients, and then describes the "collaboration" that shapes practices within the clinics.

The practice of 'Dr' Paep: continuity and change in indigenous healing in northern Thailand.

Dr. Paep Plienphleng is an indigenous curer in a rural district in Chiang Mai Province, Northern Thailand, where he is numbered among the group of healers known as mqq mueang ('Northern doctors'). He specializes in curing saan or 'tumors' by combining several techniques: indigenous surgery, herbal curing and supernatural curing. Other aspects of Dr Paep's practice have been due to larger trends in indigenous healing that have affected him and other curers over past decades. This paper describes the practice of Dr Paep and some aspects of his healing, and examines the context of his practice by exploring other categories of indigenous healers found in this area of the North. It is concluded that Northern Thai healing is undergoing a transformation from a stress on general healing to an emphasis on the use of supernatural cures, more specialization among healers and efforts to adapt services to fit the plural system of care found in this rural Northern Thai environment. Thus, we find the skills of indigenous healers and the nature of indigenous Northern Thai medicine allow for creative adaptation to a changing medical environment.

Experimental observations consistent with a surface tension model of gliding motility of Myxococcus xanthus.

We have presented experimental evidence to support the model that gliding motility of Myxococcus xanthus is driven by surface tension. (i) Motility is inhibited by the addition of sufficient exogenous, nontoxic surfactants to swamp out the cells' own surfactant gradient. (ii) M. xanthus does not move polystyrene latex beads over its surface. (iii) Motility is prevented by elimination of an interfacial surface tension either by embedding the cells in soft agar or by placing them at an agar-aqueous interface. (iv) Wild-type cells excrete surfactant, whereas two nonmotile mutants excrete reduced amounts.

Method for measuring changes in surface tension on agar.

The surface tension of agar surfaces was determined by measuring the contact angles formed by drops of various hydrophobic liquids on the surface and then calculating the composite surface free energy function by solving a series of simultaneous equations derived from these data. This method was used to measure the change in the surface tension of agar produced by the addition of various concentrations of albumin. The resulting curve was typical of the effect of increasing concentrations of surfactants on surface tension. The method was compared with other methods of determining surface tension of solids, and it was concluded that the technique used here provided the most reliable results.

Northern Thai health care alternatives. Patient control and the structure of medical pluralism.

Two distinct features characterize village behavior in dealing with health care alternatives in Northern Thailand. First, the individual strives to preserve a secure social environment by controlling the course and choice of treatment during an illness crisis. Second, there are two spheres of health care discernible beyond any division based solely on type of medical technology, or urban-rural or modern-traditional dichotomies. One sphere, 'officially-sanctioned', is socially distant from the patient and totally dependent on the support, and under the aegis of central authority; the other sphere, 'locally-sanctioned', is socially close to the patient and dependent on the approval and support of only the local population. The nature of each sphere is dependent upon (1) the way in which practitioners are validated and sanctioned; (2) the internal organization of each practitioner group; and (3) the style of interaction between the practitioner and patient and his or her family. The variable success of patients in controlling the course of their treatment is demonstrated by the styles of interaction in the respective spheres. Attempts to manipulate the healer by influencing the context of healing, the amount and terms of payment for services rendered, and the type of therapy given are major parts of this control. The history of the local medical system suggests that patients in the research area became accustomed to these efforts to control quite early. Such attempts have been instrumental in shaping the present form of the medical system; therefore, a connection between those efforts to control the course of healing and the shape of the medical system is postulated and explored here.

Regression of malignant thymoma with metastases after treatment with adrenocortical steroids.

A patient with a malignant lymphoepithelial thymoma and pleural metastases is described. Incidental treatment with adrenocortical steroids after an allergic reaction resulted in a marked regression of the masses for a period of 18 months. A second course of treatment resulted in complete radiological regession of the tumors, and the patient has remained symptom free with normal chestX-rays for a further period of 18 months.

Spatio-temporal pattern discrimination in cats with insular-temporal lesions.

Previous studies have demonstrated that cats with bilateral insular-temporal lesions are impaired in their ability to perform temporal pattern discriminations of the general form A--B--A vs B--A--B. This deficit has been seen to occur when A and B are made up of two different auditory, visual, or vibrotractile stimuli. These data suggest that insular-temporal cortex is a multimodal area concerned with the perception of temporal sequences of stimuli. The present study extends these earlier observations by testing insular-temporal lesioned cats on a spatio-temporal pattern discrimination. A spatio-temporal pattern is defined as one in which the same stimulus is presented to the animal sequentially from different spatial locations. The data indicate that insular-temporal lesions disrupt a spatio-temporal pattern discrimination just as they do auditory, visual, or vibrotactile temporal pattern discriminations. Insular-temporal cortex appears to be critical for certain higher order perceptual abilities in the cat.