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Showing papers by "David W. Johnson published in 2000"


Journal ArticleDOI
TL;DR: The National Spherical Torus Experiment (NSTX) is being built at the Princeton Plasma Physics Laboratory to test the fusion physics principles for the spherical torus (ST) concept at the MA level as discussed by the authors.
Abstract: The National Spherical Torus Experiment (NSTX) is being built at the Princeton Plasma Physics Laboratory to test the fusion physics principles for the Spherical Torus (ST) concept at the MA level. The NSTX nominal plasma parameters are R {sub 0} = 85 cm, a = 67 cm, R/a greater than or equal to 1.26, B {sub T} = 3 kG, I {sub p} = 1 MA, q {sub 95} = 14, elongation {kappa} less than or equal to 2.2, triangularity {delta} less than or equal to 0.5, and plasma pulse length of up to 5 sec. The plasma heating/current drive (CD) tools are High Harmonic Fast Wave (HHFW) (6 MW, 5 sec), Neutral Beam Injection (NBI) (5 MW, 80 keV, 5 sec), and Coaxial Helicity Injection (CHI). Theoretical calculations predict that NSTX should provide exciting possibilities for exploring a number of important new physics regimes including very high plasma beta, naturally high plasma elongation, high bootstrap current fraction, absolute magnetic well, and high pressure driven sheared flow. In addition, the NSTX program plans to explore fully noninductive plasma start-up, as well as a dispersive scrape-off layer for heat and particle flux handling.

384 citations


01 Mar 2000
TL;DR: 3D computer simulations and experiments are employed to study random packings of compressible spherical grains under external confining stress, finding a continuous transition in which the stress vanishes as (straight phi-straight Phi(c))(beta), where straight phi is the (solid phase) volume density.
Abstract: 3D computer simulations and experiments are employed to study random packings of compressible spherical grains under external confining stress. In the rigid ball limit, we find a continuous transition in which the stress vanishes as (straight phi-straight phi(c))(beta), where straight phi is the (solid phase) volume density. The value of straight phi(c) depends on whether the grains interact via only normal forces (giving rise to random close packings) or by a combination of normal and friction generated transverse forces (producing random loose packings). In both cases, near the transition, the system's response is controlled by localized force chains.

285 citations


Journal ArticleDOI
TL;DR: Renal transplantation seems to confer a substantial survival advantage over dialysis in patients with end-stage renal failure who are rigorously screened and considered suitable for renal transplantation.
Abstract: Background. Patients over age 60 constitute half of all new patients accepted into the renal replacement therapy programs in Australia. However, the optimal treatment of their end-stage renal disease remains controversial. The aim of the present study was to compare survival for dialysis and renal transplantation in older patients who were rigorously screened and considered eligible for transplantation. Methods. The study cohort consisted of 174 consecutive patients over 60 who were accepted on to the Queensland cadaveric renal transplant waiting list between January 1, 1993 and December 31, 1997, Follow-up was terminated on October 1, 1998, Data were analyzed on an intention-to-transplant basis using a Cox regression model with time-varying explanatory variables. An alternative survival analysis was also performed, in which patients no longer considered suitable for transplantation were censored at the time of their removal from the waiting list. Results. There were 67 patients receiving a renal transplant, whereas the other 107 continued to undergo dialysis, These two groups were well matched at baseline with respect to age, gender, body mass index, renal disease etiology, comorbid illnesses, and dialysis duration and modality. The overall mortality rate was 0.096 per patient-year (0.131 for dialysis and 0.029 for transplant, P<0.001), Respective 1-, 3- and B-year survivals were 92%, 62%, and 27% for the dialysis group and 98%, 95%, and 90% (P<0.01) for the transplant group. Patients in the transplant group had an adjusted hazard ratio 0.16 times that of the dialysis group (95% confidence interval 0.06 - 0.42), If patients were censored at the time of their withdrawal from the transplant waiting list, the adjusted hazard ratio was 0.24 (95% confidence interval 0.09 - 0.69), Conclusions. Renal transplantation seems to confer a substantial survival advantage over dialysis in patients with end-stage renal failure who are rigorously screened and considered suitable for renal transplantation.

154 citations


Journal ArticleDOI
TL;DR: In this paper, the tin-filled skutterudites were synthesized under high pressure and temperature conditions; they cannot be synthesised under normal synthesis approaches; they exhibit n-type semiconducting behavior with relatively high Seebeck coefficients for compounds whose electronic properties have not been optimized.
Abstract: Thermal conductivity, resistivity, Seebeck coefficient, and structure measurements of CoSb3 with tin interstitially placed in the voids are reported. These tin-filled skutterudites were synthesized under high pressure and temperature conditions; they cannot be synthesized under “normal” synthesis approaches. The tin atoms exhibit very large atomic displacement parameters indicating a large “rattling” motion inside their atomic “cages.” The disorder induced by the Sn atoms is a very good phonon scattering mechanism. The thermal conductivity of these compounds is very low with a temperature dependence that is atypical of simple solids. The tin-filled compounds exhibit n-type semiconducting behavior with relatively high Seebeck coefficients for compounds whose electronic properties have not been optimized. The potential for thermoelectric applications is discussed.

149 citations


Journal ArticleDOI
TL;DR: The Educative Power of Intellectual Conflict: Constructive Controversy: The Educative power of intellectual conflict as discussed by the authors is a seminal work in the field of conflict resolution in higher education.
Abstract: (2000). Constructive Controversy: The Educative Power of Intellectual Conflict. Change: The Magazine of Higher Learning: Vol. 32, No. 1, pp. 28-37.

139 citations


Journal ArticleDOI
04 Feb 2000-Cell
TL;DR: The complete sequence of a heterochromatic island of Arabidopsis thaliana chromosome 4 provides an opportunity to study sequence determinants of chromosome condensation.

123 citations


Journal ArticleDOI
TL;DR: Obese patients should not be discouraged from receiving peritoneal dialysis purely on the basis of BMI, and maintaining a higher-than-average BMI to preserve “nutritional reserve” may help to reduce the mortality and morbidity rates associated with PD.
Abstract: ObjectiveTo determine the influence of an elevated body mass index (BMI) on cardiovascular outcomes and survival in peritoneal dialysis (PD) patients.DesignProspective, observational study of a pre...

123 citations



Journal Article
TL;DR: The optimal timing of parenthood appears to be upon completion of medical training, and women were less likely to recommend parenting, less satisfied with the time available for parenting and more likely to value flexibility within the college program to accommodate family needs.
Abstract: BACKGROUND: Studies of career and parenting satisfaction have focused separately on medical students, residents and practising physicians. The objective of this study was to compare satisfaction across a spectrum of stages of medical career. METHODS: A survey of incoming medical students, current medical students, residents and physician teachers at the University of Saskatchewan was conducted in the spring of 1997. Response rates were 77% (43/56), 81% (177/218), 65% (134/206) and 39% (215/554) respectively. Factors assessed in the stepwise regression analysis were the effect of sex, parenting and level of training on the likelihood of recommending parenting to medical students or residents, and on parenting dissatisfaction, job dissatisfaction, career dissatisfaction and the importance of flexibility within the college program to accommodate family obligations. RESULTS: More male than female physician teachers had partners (92% v. 81%, p < 0.01) and were parents (94% v. 72%, p < 0.01). Female physician teachers spent equal hours per week at work compared with their male counterparts (mean 52 and 58 hours respectively) and more than double the weekly time on family and household work (36 v. 14 hours, p < 0.01). Physician teachers were the most likely respondents to recommend parenting to residents and their peers. Residents were the most dissatisfied with their parenting time. At all career stages women were less likely than men to recommend parenting, were more dissatisfied with the amount of time spent as parents and were more likely to regard flexibility within the college program as beneficial. There were no sex-related differences in job dissatisfaction and career dissatisfaction. However, married women were more dissatisfied with their jobs than were married men. Job dissatisfaction was greatest among medical students, and career dissatisfaction was greatest among residents. INTERPRETATION: The optimal timing of parenthood appears to be upon completion of medical training. Women were less likely to recommend parenting, less satisfied with the time available for parenting and more likely to value flexibility within the college program to accommodate family needs. These differences did not translate into women experiencing more job or career dissatisfaction.

74 citations


Journal ArticleDOI
TL;DR: The authors examines the policy of the UK Labour Government between 1997 and 1999 in relation to the production and implementation of the National Numeracy Strategy, within the structure of context of influence, context of policy texts and context of practice.
Abstract: This article examines the policy of the UK Labour Government between 1997 and 1999 in relation to the production and implementation of the National Numeracy Strategy, within the structure of context of influence, context of policy texts and context of practice. It examines its roots in, and differences from, numeracy and mathematics policies of previous regimes. Some tensions between the philosophies of modernisation and traditionalism, which are represented among those responsible for the New Labour education policies and which are reflected in the National Numeracy Strategy are discussed. Finally, evidence from the context of practice demonstrates that despite the attempt at tight prescription and control, cyclical recontextualisation and multiple interpretations exist.

72 citations


Journal ArticleDOI
TL;DR: In this paper, the installation and performance of vibro stone columns supporting a strip foundation in a variable fill and the performance of a similar strip foundation on untreated ground were investigated, and the results from site investigation and laboratory testing were presented.
Abstract: Full-scale instrumented load tests have been carried out to study the installation and performance of vibro stone columns supporting a strip foundation in a variable fill and the performance of a similar strip foundation on untreated ground. The results from site investigation and laboratory testing are presented, and the vibro design principles—in particular the use of a modification to a standard formula that reflects the radial densification of soil around the stone column—are outlined. The treated foundation performance is compared with predicted behaviour; calculated settlements are in reasonable agreement with measured values, but stress measurements suggest that current design assumptions significantly overestimate the degree of stress concentration on the stone columns. The degree of radial densification of fill around the stone columns varied according to installation technique and soil type. The implications of the trial observations for existing design methods are considered.

Journal ArticleDOI
TL;DR: The network approach is a feasible field technique, and can identify core groups involved in the intense transmission of syphilis, and may be useful in attempts to eliminate syphilis.
Abstract: BACKGROUND: Social network methods have improved our understanding of sexually transmitted disease transmission dynamics, and may be of use in routine field operations for partner notification. GOAL: To augment traditional syphilis-control activities with social network methods in an Atlanta area with high syphilis morbidity. STUDY DESIGN: Disease investigators conducted interviews, used network diagrams to prioritize their work, and relied on network connections for finding hard-to-reach persons. RESULTS: A total of 396 contacts were elicited from 48 infected and 50 uninfected persons. The cumulative prevalence of syphilis was 12.6%, and 24 persons infected with HIV were identified. Network methods disclosed a large, interconnected group (276 persons) characterized by high network centrality and the substantial presence of small, interactive subgroups (microstructures). CONCLUSION: The network approach is a feasible field technique, and can identify core groups involved in the intense transmission of syphilis. The targeted, network-based approach may be useful in attempts to eliminate syphilis.

Journal ArticleDOI
TL;DR: Low HDL lipid levels exhibited complex inheritance, as 12 quantitative trait loci with significant or suggestive likelihood of observed data scores were identified and novel genes are likely to be important in the control of HDL metabolism.

Journal ArticleDOI
TL;DR: Significant differences between trained and untrained children occurred in their knowledge and retention of the conflict resolution procedure, willingness and ability to use the procedure in conflict situations, and conceptual understanding of friendship.
Abstract: The effectiveness of a conflict resolution training program was examined in an American midwestern suburban elementary school. Participants were 80 kindergartners randomly assigned to an experimental or control condition in morning or afternoon time blocks. Children in the experimental condition received 9 hr of conflict resolution training integrated into a curriculum unit on friendship taught daily for 4 consecutive weeks. Children in the control condition were taught the identical friendship unit for the same period of time without conflict resolution training. Teachers rotated equally across conditions. Significant differences between trained and untrained children occurred in their knowledge and retention of the conflict resolution procedure, willingness and ability to use the procedure in conflict situations, and conceptual understanding of friendship.

Journal ArticleDOI
TL;DR: The development of a new class of derivatives, the alkyldimethylaminoethyl ester iodides, for the analysis of fatty acids by electrospray ionization tandem mass spectrometry is described.
Abstract: The development of a new class of derivatives, the alkyldimethylaminoethyl ester iodides, for the analysis of fatty acids by electrospray ionization tandem mass spectrometry is described They are prepared by quaternization of dimethylaminoethyl esters with alkyl iodides The trimethylaminoethyl (choline) ester iodide affords between 8 and 12 times greater signal intensity than the corresponding dimethylaminoethyl ester used in the analysis of long to very long chain fatty acids in plasma samples It is a superior derivative for unsaturated and monohydroxylated long chain fatty acids but unsuitable for bile acids and dicarboxylic acids

Journal ArticleDOI
TL;DR: In this article, a political decision is reached through the following procedure: Citizens form advocacy groups and present the best case possible for the alternative course of action t.r.t.
Abstract: The purposes of political discourse include (a) clarifying citizens' understanding of the issue, (b) helping citizens reach their best reasoned judgment as to which course of action will solve a problem, (c) increasing citizen participation in the political process, and (d) socializing the next generation into the procedures and attitudes they need to be active citizens. A responsibility of psychology within a democratic society is to provide the theory, research, and normative procedures needed to make political discourse constructive. Constructive controversy provides a theory, validated by research, that has been operationalized into a normative procedure. Constructive controversy exists when one person's ideas, information, conclusions, theories, and opinions are incompatible with those of another, and the 2 seek to reach an agreement. A political decision is reached through the following procedure. Citizens form advocacy groups and present the best case possible for the alternative course of action t...

Journal ArticleDOI
TL;DR: Results are indicative of significant losses in the bryophyte cover of acidic grasslands at atmospheric input rates of 5 g N m−2 yr−1 or less, and suggest that these species may be particularly at risk from the high atmospheric nitrogen deposition rates that are becoming a feature of many upland areas.
Abstract: Regular applications of NH4NO3 (3.5–14 g N m−2 yr−l) and (NH4)2SO4 (14 g N m−2 yr−l) to areas of acidic grassland in the Derbyshire Peak District over a period of six years have resulted in marked changes in the abundance of the bryophyte species present on the site. A dose-related reduction in bryophyte cover, significant at all levels of nitrogen addition, was obtained after only one year of applications and this effect has been maintained over a further five years of treatment.(NH4)2SO4 additions at the same rate as the highest NH4NO3 input (14 g N m−2 yr−1) produced greater reductions in cover with losses of 80–95% compared with 45–55% for the 14 g NH4NO3 treatment. Soil pH measurements taken from cores collected in December 1994 showed a small reduction in the pH of the (NH4)2SO4 treated plots (4.03 compared with 4.41 for the controls), whereas the NH4NO3 treatments were unaffected.The mean stem density of the dominant bryophyte species Rhytidiadelphus squarrosus was significantly reduced at ...


Journal ArticleDOI
TL;DR: Blood spots collected from four peroxisomal patients between 2 and 10 days after birth and stored for up to 17 years, were shown to give between 33% and 233% higher C26:0/C22:0 ratios compared to age-matched controls.
Abstract: A rapid method with potential to screen for many of the peroxisomal disorders using 5 microl of plasma or a 3-mm blood spot (3.6 microl blood impregnated on filter paper) is described. Fatty acids are liberated from plasma or blood spots and converted to dimethylaminoethyl esters. Trideuterated fatty acids, added as internal standards, are used to quantify eicosanoic (C20:0), docosanoic (C22:0), tetracosanoic (C24:0) and hexacosanoic (C26:0) acids by electrospray tandem mass spectrometry. The C26:0/C22:0 and C24:0/C22:0 ratios are significantly greater in the plasma of patients with peroxisomal disorders compared to controls. The C20:0/C22:0 ratio is elevated in the plasma of peroxisomal patients who accumulate phytanic acid. Blood spots collected from four peroxisomal patients between 2 and 10 days after birth and stored for up to 17 years, were shown to give between 33% and 233% higher C26:0/C22:0 ratios compared to age-matched controls.

Journal ArticleDOI
TL;DR: D discrete mathematics and algorithmics, a strand within discrete mathematics, provides a natural ‘home’ for programming and supports the use of a programming language in mathematical contexts for which pupil designed algorithms can be used to explore concepts and relationships.
Abstract: The contribution of programming in the learning of school mathematics has been demonstrated in numerous project and research settings. However, it would appear that this activity has failed to permeate the system on any large and systemic scale. I suggest here that one reason for the current situation is that the exciting developments have not themselves been a required component embedded in a major curriculum theme. Further, the position that the programming environments themselves, e.g., Logo microworlds, would become the school mathematics curriculum has clearly failed to gain the support of the educational system. However, discrete mathematics and algorithmics, a strand within discrete mathematics, provides a natural ‘home’ for programming. This in turn supports the use of a programming language in mathematical contexts for which pupil designed algorithms can be used to explore concepts and relationships.



Journal ArticleDOI
01 Dec 2000-Nephron
TL;DR: ACE inhibition directly prevents CyA-induced interstitial fibrosis, but not proximal tubule cytotoxicity, independently of haemodynamic and systemic renin-angiotensin system effects.
Abstract: Background/Aims: Several recent studies have suggested that angiotensin-converting enzyme (ACE) inhibitors ameliorate chronic cyclosporin A (CyA) tubulo-interstitial disease by mech

Book ChapterDOI
01 Jan 2000
TL;DR: Based on social interdependence theory and the ideas of Lewin's Center for the Study of Group Dynamics, Morton Deutsch proposed in 1949 that how group members believe their goals are related very much impacts their dynamics and success as mentioned in this paper.
Abstract: Based on social interdependence theorizing and the ideas of Lewin’s Center for the Study of Group Dynamics, Morton Deutsch proposed in 1949 that how group members believe their goals are related very much impacts their dynamics and success. Hundreds of studies summarized in meta-analyses document that cooperative goals promote communication and exchange and, more recently, the open-minded discussion of opposing views, dynamics in turn that result in group productivity, individual learning, psychological health, and relationships. Recent research has used the theory to understand such organizational issues as power and to test the theory’s universalistic aspirations. Validated procedures are being used around the world to promote educational goals. Leaders and members can use cooperation knowledge to make their increasingly diverse and dispersed teams work.

Journal ArticleDOI
TL;DR: In this paper, the authors summarize the results of recent measurements of the high-constraint mode (H-mode) edge transport barrier in Alcator C-Mod and provide measurements of plasma parameters (electron density and temperature, and impurity density) in the pedestal region.
Abstract: In this paper we summarize the results of recent measurements of the high confinement mode (H-mode) edge transport barrier in Alcator C-Mod. A number of new, high-resolution edge diagnostics provide measurements of plasma parameters (electron density and temperature, and impurity density) in the pedestal region. Pedestal parameters are measured both at the top edge of the plasma and at the midplane. Very narrow (2-5 mm) electron density and temperature and impurity density pedestals are observed. The impurity pedestal is located inside the density and temperature pedestals in the midplane measurements, but coincides with the ne pedestal at the top edge. Correlation of both width and height of the pedestals at the midplane with global plasma parameters and core confinement characteristics is observed. At the same time there are no clear indications of scaling for the electron density and impurity pedestal widths measured at the top of the plasma.

Journal ArticleDOI
01 Aug 2000-Burns
TL;DR: A case of a childhood scald injury where immediate first aid consisted of the application of fountain pen ink, and continuing education is required to inform parents of the use of cold water in the immediate firstAid treatment of scalds.

Journal ArticleDOI
TL;DR: In this paper, an extensive set of {[TiSe2]l[NbSe2 ]m}n superlattices has been prepared through controlled annealing of elementally modulated reactants.
Abstract: An extensive set of {[TiSe2]l[NbSe2]m}n superlattices has been prepared through controlled annealing of elementally modulated reactants. Electrical conductances were measured from 1.5 K to room temperature. The room temperature conductances are linearly dependent on the number (m) of NbSe2 layers per repeat layer, and independent of the number (l) of semimetallic TiSe2 layers per repeat layer, suggesting that the electronic transport is dominated by the metallic NbSe2 layers. For small l, a positive temperature coefficient of resistance (TCR) is observed, indicative of normal metallic behavior. In general, increasing l reduces the TCR, and for smaller m, the TCR becomes negative at larger l. These samples exhibit a √T temperature dependence to the resistivity variation at low temperatures, characteristic of both weak localization and electron−electron interaction effects for three-dimensional electron flow in strongly disordered systems. Superconducting critical temperatures were also observed to depend s...

Journal ArticleDOI
TL;DR: The role of the mathematics coordinator has become increasingly demanding over the last 10 years as mentioned in this paper, and some coordinators find it problematic, the nature and causes of their difficulties, and the way in which they are growing in confidence and relishing new challenges they are encountering.
Abstract: The role of the mathematics coordinator has become increasingly demanding over the last 10 years. Implementing the National Numeracy Strategy (NNS) means that now all coordinators must come to terms with delivering In-Service Education for Teachers (INSET) sessions, monitoring the classroom teaching of their colleagues, sharing subject expertise, as well as coordinating their work with the local education authority (LEA) NNS consultants. This article reports on research which includes a focus on how some coordinators are coping with these demands – at the aspects of the role they find problematic, the nature and causes of their difficulties, and also at the way in which they are growing in confidence and relishing the new challenges they are encountering. Six characteristics of coordination and the whole school environment in which the coordinators work are identified as facilitating their role as agents of change – the coordinators' enthusiasm for the role; their vision of goals and ways of work...

Journal ArticleDOI
TL;DR: Repeated surveillance of peripheral blood from both recipients, using a novel application of the technique of nested polymerase chain reaction to amplify donor DNA, demonstrated no persistence of donor cells, supporting effective eradication of the donor malignancy.
Abstract: Background. In this report we describe a malignant lymphoma of donor origin inadvertently transplanted into two renal allograft recipients, despite standard comprehensive donor screening, The successful clearance of the tumor from both patients and a novel method of surveillance are detailed.

Journal ArticleDOI
TL;DR: Elevated plasma concentrations of Hcy are not efficiently reduced by PD, which is largely accounted for by a high degree of plasma protein binding and is significantly influenced by peritoneal membrane permeability.
Abstract: Objectives: To investigate the degree and the determinants of peritoneal homocysteine (Hcy) clearance and to compare measured Hey clearance with the Hey clearance predicted based on molecular weight (MW). Design: Cross-sectional observational analysis. Setting: Tertiary care institutional dialysis center. Patients: Sixty-five stable peritoneal dialysis (PD) patients. Outcome Measures: Fasting blood and 24-hour pooled dialysate effluents were collected for determination of peritoneal clearances of Hey (CpHcy), urea (CpUr), and creatinine (CpCr). The dialysate-to-plasma creatinine ratio at 4 hours (D/P Cr 4 h) and levels of red cell folate, B-12 ferritin, and C-reactive protein (CRP) were measured concurrently. Observed CpHcy was compared with predicted clearance, based an Hey plasma protein binding and the relative molecular weights of Hey, urea, and creatinine. Results: Plasma concentrations of Hey averaged 24.6 +/- 1.1 mu mol/L and were elevated above the upper limit of normal in 59 (91%) patients. The mean dialysate concentration of Hey was 2.9 +/- 0.3 mu mol/L, equating to a daily peritoneal elimination of 34.6 +/- 3.6 mu mol. Observed CpHcy was closely approximated by predicted CpHcy (8.7 +/- 0.6 L/week/1.73 m(2) vs 9.0 +/- 0.3 L/week/1.73 m(2) respectively, p = 0.55), Patients maintained on automated PD (n = 5) had a CpHcy similar to that of patients treated with continuous ambulatory peritoneal dialysis (8.9 +/- 1.0 L/week/1.73 m(2) vs 8.7 +/- 0.6 L/week/1.73 m(2), p = 0.92). The CpHcy was significantly correlated with C-reactive protein (CRP), D/P creatinine, CpUr, CpCr, and peritoneal protein loss, but not with plasma Hey, albumin, B-12, ferritin, age, dialysis duration, peritonitis episodes, or daily dialysate effluent volume. By multivariate analysis, the only variables that remained significant independent predictors of CpHcy were CRP and D/P Cr 4 h. High and high-average transporters had a higher CpHcy than low and low-average transporters (9.7 +/- 0.8 L/week/1.73 m(2) vs 7.0 +/- 0.7 L/week/1.73 m(2), p mol/L vs 23.4 +/- 1.6 mu mol/L, p = nonsignificant (NS)]. Conclusions: Elevated plasma concentrations of Hey are not efficiently reduced by PD. The relatively low peritoneal clearance of Hey is largely accounted for by a high degree of plasma protein binding and is significantly influenced by peritoneal membrane permeability.