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.

First Evidence of Local E×B Drift in the Divertor Influencing the Structure and Stability of Confined Plasma near the Edge of Fusion Devices.

The structure of the edge plasma in a magnetic confinement system has a strong impact on the overall plasma performance. We uncover for the first time a magnetic-field-direction dependent density shelf, i.e., local flattening of the density radial profile near the magnetic separatrix, in high confinement plasmas with low edge collisionality in the DIII-D tokamak. The density shelf is correlated with a doubly peaked density profile near the divertor target plate, which tends to occur for operation with the ion B×∇B drift direction away from the X-point, as currently employed for DIII-D advanced tokamak scenarios. This double-peaked divertor plasma profile is connected via the E×B drifts, arising from a strong radial electric field induced by the radial electron temperature gradient near the divertor target. The drifts lead to the reversal of the poloidal flow above the divertor target, resulting in the formation of the density shelf. The edge density shelf can be further enhanced at higher heating power, preventing large, periodic bursts of the plasma, i.e., edge-localized modes, in the edge region, consistent with ideal magnetohydrodynamics calculations.

Formation of a High Pressure Staircase Pedestal with Suppressed Edge Localized Modes in the DIII-D Tokamak.

We observe the formation of a high-pressure staircase pedestal (≈16-20 kPa) in the DIII-D tokamak when large amplitude edge localized modes are suppressed using resonant magnetic perturbations. The staircase pedestal is characterized by a flattening of the density and temperature profiles in midpedestal creating a two-step staircase pedestal structure correlated with the appearance of midpedestal broadband fluctuations. The pedestal oscillates between the staircase and single-step structure every 40-60 ms, correlated with oscillations in the heat and particle flux to the divertor. Gyrokinetic analysis using the cgyro code shows that when the heat and particle flux to the divertor decreases, the pedestal broadens and the E×B shear at the midpedestal decreases, triggering a transport bifurcation from the kinetic ballooning mode (KBM) to trapped electron mode (TEM) limited transport that flattens the density and temperature profiles at midpedestal and results in the formation of the staircase pedestal. As the heat flux to the divertor increases, the pedestal narrows and the E×B shear at the midpedestal increases, triggering a back transition from TEM to KBM limited transport. The pedestal pressure increases during the staircase phase, indicating that enhanced midpedestal turbulence can be beneficial for confinement.

E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak.

A bifurcative step transition from low-density, high-temperature, attached divertor conditions to high-density, low-temperature, detached divertor conditions is experimentally observed in DIII-D tokamak plasmas as density is increased. The step transition is only observed in the high confinement mode and only when the B×∇B drift is directed towards the divertor. This work reports for the first time a theoretical explanation and numerical simulations that qualitatively reproduce this bifurcation and its dependence on the toroidal field direction. According to the model, the bifurcation is primarily driven by the interdependence of the E×B-drift fluxes, divertor electric potential structure, and divertor conditions. In the attached conditions, strong potential gradients in the low field side (LFS) divertor drive E×B-drift flux towards the high field side divertor, reinforcing low density, high temperature conditions in the LFS divertor leg. At the onset of detachment, reduction in the potential gradients in the LFS divertor leg reduce the E×B-drift flux as well, such that the divertor plasma evolves nonlinearly to high density, strongly detached conditions. Experimental estimates of the E×B-drift fluxes, based on divertor Thomson scattering measurements, and their dependence on the divertor conditions are qualitatively consistent with the numerical predictions. The implications for divertor power exhaust and detachment control in the next step fusion devices are discussed.

Pedestal bifurcation and resonant field penetration at the threshold of edge-localized mode suppression in the DIII-D Tokamak.

Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge-localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal that reduces the perpendicular electron flow there to near zero. These events occur simultaneously with an increase in the inner-wall magnetic response. These observations are consistent with strong resonant field penetration of n=2 fields at the onset of ELM suppression, based on extended MHD simulations using measured plasma profiles. Spontaneous transitions into (and out of) ELM suppression with a static applied n=2 field indicate competing mechanisms of screening and penetration of resonant fields near threshold conditions. Magnetic measurements reveal evidence for the unlocking and rotation of tearinglike structures as the plasma transitions out of ELM suppression.

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.

Management of acute and chronic iliofemoral venous outflow obstruction: a multidisciplinary team consensus.

The aim of this manuscript was to establish a consensus for the management of acute and chronic venous obstruction among specialists in the UK. Specialist physicians representing vascular surgery, interventional radiology and hematology were invited to 3 meetings to discuss management of acute and chronic iliofemoral obstruction. The meetings outlined controversial areas, included a topic-by-topic review; and on completion reached a consensus when greater than 80% agreement was reached on each topic. Physicians from 19 UK hospitals agreed on treatment protocols and highlighted areas that need development. Potential standard treatment algorithms were created. It was decided to establish a national registry of venous patients led by representatives from the treating multidisciplinary teams. Technical improvements have facilitated invasive treatment of patients with acute and chronic venous obstruction; however, the evidence guiding treatment is weak. Treatment should be conducted in centers with multi-disciplinary input; robust, coordinated data collection; and regular outcome analysis to ensure safe and effective treatment and a basis for future evolvement.

Outcomes of natural cycles versus programmed cycles for 1677 frozen-thawed embryo transfers.

The study compares outcomes for patients with frozen embryos who had frozen-thawed embryo transfer (FET) timed to their natural ovulation cycle versus cycles in which endometrial timing was programmed with oestrogen and progesterone. A total of 1205 patients undergoing 1677 FET cycles between 1 January 2000 and 31 December 2006 were analysed. Comparisons were made for patients undergoing modified natural versus programmed FET cycles, as well as between patients using their own eggs for frozen embryos versus those using donor-egg-derived embryos. Clinical pregnancy (gestational sac on 7 week ultrasound) rates (CPR), as well as miscarriage rates, were significantly higher in programmed FET cycles in patients using their own eggs (106/262, 40.5% per embryo transfer, P = 0.015) However, there was not a difference in delivered pregnancies between cycle types in own egg patients (natural cycle delivery rate 245/862, 28.4%; programmed cycle delivery rate 77/262, 29.4%). Furthermore, CPR were not different in natural (38/129, 29.5%) versus programmed cycles (144/424, 34.0%) for ovum donor recipients, nor were delivered pregnancy rates different in natural (33/129, 25.6%) versus programmed cycles (114/424, 26.9%) for ovum donor recipients. In conclusion, there is no significant difference in delivery rates for FET in natural (278/991, 28.1%) versus programmed (191/686, 27.8%) cycles using both own embryos and donor-egg-derived embryos.

Interactive educational diabetes/insulin tutorial at www.2aida.info.

The World Wide Web now hosts a multitude of diabetes educational materials in various formats. Of particular interest is the diabetes/insulin tutorial available at the AIDA Website (accessible directly at: www.2aida.info). The tutorial combines textual or "static" information with an interactive diabetes simulator-AIDA online-to provide an engaging and effective educational tool. AIDA online (accessible directly at: www.2aida.net) enables the simulation of plasma insulin and blood glucose levels from user-defined insulin injection and carbohydrate intake data. A haemoglobin A1c value is also computed, giving an indication of overall blood glucose control in the virtual patient with diabetes. The diabetes/insulin tutorial is currently composed of four sections: the first two cover in considerable depth insulin injection regimens and insulin dosage adjustment; the third section introduces the principles of carbohydrate counting and, specifically, matching insulin doses to carbohydrate intake; and the fourth section illustrates the relationship between blood glucose levels and renal excretion of glucose. The simulator runs alongside the tutorial, and allows various concepts described in the text to be explored freely by the user and simulated interactively. This introduces a novel way of learning how injected insulin and dietary carbohydrate interact in various insulin injection regimens. A fifth section- for which any offers of assistance would be gratefully received-is planned. This will consider the use of insulin pumps and rapidly acting and very long-acting insulin analogues. Further improvements that may strengthen the existing tutorial and/or use of the online simulator are discussed in this column.

Retrospective pilot feedback survey of 200 users of the AIDA Version 4 Educational Diabetes Program. 1--Quantitative Survey Data.

This column reports a detailed, questionnaire-based, post-release feedback survey of 200 users of the AIDA version 4 educational diabetes simulator. AIDA is a freeware computer program that permits the interactive simulation of plasma insulin and blood glucose profiles for educational, demonstration, self-learning, and research purposes. Since its Internet launch in 1996 over 700,000 visits have been logged to the AIDA Websites-including www.2aida.org-and over 200,000 program copies have been downloaded free-of-charge. The main goals of the current study were: (1) to establish what people have thought about the AIDA program, (2) to assess the utility of the software, and (3) to ascertain how much people have actually used it. An analysis was therefore undertaken of the first 200 feedback forms that were returned by AIDA users. The questionnaire-based survey methodology was found to be robust and reliable. Feedback forms were received from participants in 21 countries. One hundred six of 209 responses (50.7%) were received from people with diabetes, and 36 of 209 (17.2%) from relatives of patients, with lesser numbers from doctors, students, diabetes educators, nurses, pharmacists, and other end users. Please note some respondents fulfilled more than one end-user category, hence the denominator <200; for example, someone with diabetes who was also a doctor. This study has established the feasibility of using a simple feedback form to survey a substantial number of diabetes software users. In addition, it has yielded interesting data in terms of who are the main users of the AIDA program, and has also provided technical (computer) information that has aided the release of a freeware upgrade to the software. In general, users reported finding the program to be of educational value. The majority also felt it would be of interest to diabetes educators and people with diabetes. Most were clear about its limitations as a simulator-based learning tool. The implications of these findings will be discussed.

Diabetes and the World Wide Web.

The World Wide Web has become remarkably quickly an alternative source of information for patients and their relatives, as well as students and health-care professionals. A whole plethora of websites and Internet-based applications related to diabetes have appeared in recent years. In this column, selected issues surrounding the use of such websites are considered and the need for more evaluation of such diabetes sites, as well as the Internet medium itself, is highlighted.

Diabetes website review: www.2aida.org.

Previous Diabetes Information Technology & WebWatch columns have addressed the use of diabetes simulators, and, in particular, aspects of the AIDA software. AIDA is a freeware computer program, which simulates the interaction of carbohydrates and insulin administered in people with insulin-dependent (type 1) diabetes mellitus. The program is intended to be used as an educational support tool, and is available via the Internet without charge from www.2aida.org. In this article, the AIDA Website is described and reviewed in terms of both content and functionality. This popular non-commercial Internet site provides free access to a downloadable PC version of AIDA, as well as access to a Web-based version of the simulator that can be run online (accessible directly at: www.2aida.net). User feedback suggests that the Website and the AIDA software have been of significant interest and value to many patients, their relatives and carers, students, and a variety of health-care professionals and researchers. The interactive and dynamic nature of the simulations adds a real-life dimension to the Web-based educational material, and the software is complemented by a substantial amount of supporting information at the Website. The on-going collection of subjective feedback continues to provide anecdotal evidence of the utility of the software, and this will hopefully be corroborated by results from more formal and objective evaluations. The future potential of diabetes simulators, in both education and research, is becoming increasingly apparent, and the AIDA Website is evolving accordingly.

Website review: diabetes insight--www.diabetes-insight.info.

In previous Diabetes Information Technology & WebWatch columns some different diabetes Websites have been highlighted. In this issue we focus on one particular site and use this to illustrate how such Internet-based repositories of information can provide important and useful resources for people with diabetes and their carers. Diabetes is perhaps unique in the fact that much of the day-to-day responsibility for care rests with individuals themselves. Successful therapy demands considerable understanding of the condition by the person with diabetes, or his or her carer, and this can only be made possible with access to appropriate information. Provision of information via a Website is now recognised to be cost-effective and convenient, available 24 hours a day, 365 days a year-and access to the Internet by the general public has grown rapidly in recent years. The increasing way in which the Internet is being used to supply individuals with tools and information for their self-care is exemplified by the Diabetes Insight Website (at: www.diabetes-insight.info).

Biaxial flexure testing of calcium phosphate bioceramics for use in tissue engineering.

This study analyzes data from 206 CaP specimens (68 HA, 70 BCP, and 68 beta-TCP) fractured via biaxial flexure testing. Specimens were divided into four groups: (a) Group I, dry; (b) Group II, wet (day 0, immersion time approximately 5-10 s); (c) Group III, after immersion in media for 21 days (day 21); and (d) Group IV, after culturing osteoblasts (OBs) on the surface for 21 days (day 21 with cells). X-ray diffraction verified the presence of minor second phases in HA and beta-TCP while BCP was a biphasic mixture of HA and beta-TCP with minor phases present. The statistical significance (p < 0.05) of differences in the measured biaxial flexure fracture strength, S, between groups was assessed via one-way ANOVA with Tukey's test. Also, a two-parameter Weibull analysis assessed the mechanical reliability of each group. Osteoblasts increase the biaxial flexure fracture strength in a statistically significant way compared to both the HA discs in Groups II and III. Scanning electron microscope examination revealed grain boundary grooving on the sintered surfaces and with thermal expansion anisotropy, likely leads to the observed rapid strength decline upon exposure to media found in Groups II, III and IV.

Further user comments regarding usage of an interactive educational diabetes simulator (AIDA).

This "Diabetes Information Technology & WebWatch" column continues the diabetes simulation theme from previous issues and overviews various user experience with the AIDA v4 interactive educational freeware diabetes simulator. AIDA is a diabetes computer program that permits the interactive simulation of plasma insulin and blood glucose (BG) profiles for educational, demonstration, and self-learning purposes. It has been made freely available, without charge, via the Web as a noncommercial contribution to continuing diabetes education. Since its Internet launch in 1996, over 145,000 visits have been logged at the AIDA Website--www.2aida.org--and over 29,000 copies of the program have been downloaded, free of charge. While these statistics may appear impressive, they do not tell the personal story of how people have been making use of the software, and what they actually think about the program. In this respect, this column documents some of the independent user comments about AIDA sent in spontaneously via electronic mail (email) by patients with diabetes and their relatives, as well as by health-care professionals. Comments posted to diabetes newsgroups and diabetes email lists, as well as a selection of those which have been found at other, linked, diabetes Websites are also highlighted.

Research use of the AIDA www.2aida.org diabetes software simulation program: a review--part 2. Generating simulated blood glucose data for prototype validation.

The purpose of this review is to describe research applications of the AIDA diabetes software simulator. AIDA is a computer program that permits the interactive simulation of insulin and glucose profiles for teaching, demonstration, and self-learning purposes. Since March/April 1996 it has been made freely available on the Internet as a noncommercial contribution to continuing diabetes education. Up to May 2003 well over 320,000 visits have been logged at the main AIDA Website--www.2aida.org--and over 65,000 copies of the AIDA program have been downloaded free-of-charge. This review (the second of two parts) overviews research projects and ventures, undertaken for the most part by other research workers in the diabetes computing field, that have made use of the freeware AIDA program. As with Part 1 of the review (Diabetes Technol Ther 2003;5:425-438) relevant research work was identified in three main ways: (i) by personal (e-mail/written) communications from researchers, (ii) via the ISI Web of Science citation database to identify published articles which referred to AIDA-related papers, and (iii) via searches on the Internet. Also, in a number of cases research students who had sought advice about AIDA, and diabetes computing in general, provided copies of their research dissertations/theses upon the completion of their projects. Part 2 of this review highlights some more of the research projects that have made use of the AIDA diabetes simulation program to date. A wide variety of diabetes computing topics are addressed. These range from learning about parameter interactions using simulated blood glucose data, to considerations of dietary assessments, developing new diabetes models, and performance monitoring of closed-loop insulin delivery devices. Other topics include evaluation/validation research usage of such software, applying simulated blood glucose data for prototype training/validation, and other research uses of placing technical information on the Web. This review confirms an unexpected but useful benefit of distributing a medical program, like AIDA, for free via the Internet--demonstrating how it is possible to have a synergistic benefit with other researchers--facilitating their own research projects in related medical fields. A common theme that emerges from the research ventures that have been reviewed is the use of simulated blood glucose data from the AIDA software for preliminary computer lab-based testing of other decision support prototypes. Issues surrounding such use of simulated data for separate computer prototype testing are considered further.

British Diabetic Association review of the AIDA v4 diabetes software simulator program.

AIDA is a diabetes-computing program freely available from www.2aida.org on the Web. The software is intended to serve as an educational support tool, and can be used by anyone who has an interest in diabetes, whether they be patients, relatives, health-care professionals, or students. In 1996, during the beta-testing phase of the AIDA v4 project, the British Diabetic Association (BDA)-now called Diabetes UK-was approached and offered the AIDA software by the author, without charge, as a noncommercial contribution to continuing diabetes education. The BDA undertook their own independent assessment of the program, which involved distributing AIDA to a panel of potential end-users (health-care professionals and patients). Comments were solicited regarding the utility, clarity, and perceived safety of the software from users outside the BDA, as well as from various internal assessors. As a result of the feedback, a decision was taken by the BDA to offer AIDA to health-care professionals through the BDA's health-care professional brochure. One thousand copies of the software were produced on diskette, and 1,000 copies of the BDA's version of the program's user guide-printed as a small book-were made available for distribution by post. In this Diabetes Information Technology & WebWatch column an overview is given of the anonymous feedback provided to the BDA by some of the external evaluators. Looking back, nearly 8 years after the launch of AIDA, it is interesting to review some of the comments received and compare these with what has actually happened with the software. To date over 400,000 visits have been logged at the AIDA Web pages, and over 80,000 copies of the program have been downloaded free-of-charge. It is highlighted that this widespread downloading of, and interest in, the AIDA software seems to largely have been fuelled by the program's free availability on the Internet. The use of the World Wide Web to enhance the distribution of other medical (diabetes) programs is highlighted.

Usage of the www.2aida.org AIDA diabetes software Website: a pilot study.

AIDA is a diabetes-computing program freely available from www.2aida.org on the Web. The software is intended to serve as an educational support tool, and can be used by anyone who has an interest in diabetes, whether they be patients, relatives, health-care professionals, or students. In previous "Diabetes Information Technology & WebWatch" columns various indicators of usage of the AIDA program have been reviewed, and various comments from users of the software have been documented. One aspect of AIDA, though, that has been of considerable interest has been to investigate its Web-based distribution as a wider paradigm for more general medically related usage of the Internet. In this respect we have been keen to understand in general terms: (1) why people are turning to the Web for health-care/diabetes information; (2) more specifically, what sort of people are making use of the AIDA software; and (3) what benefits they feel might accrue from using the program. To answer these types of questions we have been conducting a series of audits/surveys via the AIDA Website, and via the software program itself, to learn as much as possible about who the AIDA end users really are. The rationale for this work is that, in this way, it should be possible to improve the program as well as tailor future versions of the software to the interests and needs of its users. However, a recurring observation is that data collection is easiest if it is as unobtrusive and innocuous as possible. One aspect of learning as much as possible about diabetes Website visitors and users may be to apply techniques that do not necessitate any visitor or user interaction. There are various programs that can monitor what pages visitors are viewing at a site. As these programs do not require visitors to do anything special, over time some interesting insights into Website usage may be obtained. For the current study we have reviewed anonymous logstats data, which are automatically collected at many Websites, to try and establish a baseline level of usage for the AIDA site. For the initial pilot study the analysis was performed from October 1, 2000 to November 1, 2001. The study has yielded an interesting insight into how the AIDA Website is being used. The results also confirm those of previous audits based on different self-reported methodologies, confirming, amongst other things, what countries people are visiting from and what operating systems/computers they are using. These analyses have been informative and useful. Given this, it is proposed to repeat the current pilot survey approach on a routine basis, in the future, as a way of monitoring on-going usage of the AIDA Website.

Information technology in clinical diabetes care--a look to the future.

In the last Diabetes Information Technology & WebWatch column (Diabetes Technol Ther 2004;6:422-429) various hurdles to the implementation of computerised decision-support tools in clinical diabetes care were highlighted. In this column a look is made to the future, considering ways in which information technology tools may be applied in diabetes clinics, and elsewhere, in years to come. Particular attention is focused on discussion of the ways in which existing technologies are likely to become better integrated--in the short to medium term--to provide benefits to people with diabetes, their relatives, and carers.