David W. Johnson

Bio: David W. Johnson is an academic researcher from University of Queensland. The author has contributed to research in topics: Peritoneal dialysis & Kidney disease. The author has an hindex of 160, co-authored 2714 publications receiving 140778 citations. Previous affiliations of David W. Johnson include Minnesota Department of Transportation & Open University.

High-beta operation and magnetohydrodynamic activity on the TFTR tokamak

Abstract: Magnetohydrodynamic (MHD) activity within three zones (core, half‐radius, and edge) of TFTR [Plasma Physics and Controlled Nuclear Fusion Research 1986 (IAEA, Vienna, 1987), Vol. 1, p. 51] tokamak plasmas are discussed. Near the core of the plasma column, sawteeth are often observed. Two types of sawteeth are studied in detail; one with complete, and the other with incomplete, magnetic reconnection. Their characteristics are determined by the shape of the q profile. Near the half‐radius the m/n=3/2 and 2/1 resistive ballooning modes are found to correlate with a beta collapse. The pressure and the pressure gradient at the mode rational surface are found to play an important role in stability. MHD activity is also studied at the plasma edge during limiter H modes. The edge localized modes (ELM’s) are found to have a precursor mode with a frequency between 50–200 kHz and a mode number m/n=1/0. The mode does not show a ballooning structure. While these instabilities have been studied on many other machines, ...

Peritoneal small solute clearance is nonlinearly related to patient survival in the Australian and New Zealand peritoneal dialysis patient populations.

Abstract: BackgroundThe contribution of peritoneal small solute clearance per se to peritoneal dialysis (PD) patient outcomes remains uncertain. The aim of the present study was to determine whether baseline...

Anaphylactoid Reactions to Intravenous N-Acetylcysteine during Treatment for Acetaminophen Poisoning

Abstract: Anaphylactoid reactions to intravenous (IV) N-acetylcysteine (NAC) are well-recognized adverse events during treatment for acetaminophen (APAP) poisoning. Uncertainty exists regarding their incidence, severity, risk factors, and management. We sought to determine the incidence, risk factors, and treatment of anaphylactoid reactions to IV NAC in a large, national cohort of patients admitted to hospital for acetaminophen overdose. This retrospective medical record review included all patients initiated on the 21-h IV NAC protocol for acetaminophen poisoning in 34 Canadian hospitals between February 1980 and November 2005. The primary outcome was any anaphylactoid reaction, defined as cutaneous (urticaria, pruritus, angioedema) or systemic (hypotension, respiratory symptoms). We examined the incidence, severity and timing of these reactions, and their association with patient and overdose characteristics using multivariable analysis. An anaphylactoid reaction was documented in 528 (8.2%) of 6455 treatment courses, of which 398 (75.4%) were cutaneous. Five hundred four (95.4%) reactions occurred during the first 5 h. Of 403 patients administered any medication for these reactions, 371 (92%) received an antihistamine. Being female (adjusted OR 1.24 [95%CI 1.08, 1.42]) and having taken a single, acute overdose (1.24 [95%CI 1.10, 1.39]) were each associated with more severe reactions, whereas higher serum APAP concentrations were associated with fewer reactions (0.79 [95%CI 0.68, 0.92]). Anaphylactoid reactions to the 21-h IV NAC protocol were uncommon and involved primarily cutaneous symptoms. While the protective effects of higher APAP concentrations are of interest in understanding the pathophysiology, none of the associations identified are strong enough to substantially alter the threshold for NAC initiation.

Use of Superlattice Structure To Control Reaction Mechanism: Kinetics and Energetics of Nb5Se4 Formation

Abstract: This paper presents a study of the reaction of thin film niobium/selenium multilayers as a function of layer thickness. Diffraction and calorimetry data show a distinct difference in reactions between films with layer thicknesses above and below 60 A. The thicker films are shown to nucleate NbsSe4 heterogeneously at the niobium-selenium interfaces. Thinner films form kinetically stable amorphous reaction intermediates before crystallizing NbSSe4 homogeneously. The nucleation barrier was measured using a Kissinger analysis demonstrating the kinetic stability of the amorphous intermediate. An energy versus reaction progress diagram is presented that contrasts the two reaction mechanisms. ~~~~

Therapeutic monitoring of mycophenolate in transplantation: is it justified?

Abstract: Mycophenolate mofetil (MMF) is the preferred antimetabolite in solid organ transplantation. It is a prodrug that undergoes pre-systemic metabolism to mycophenolic acid (MPA), the active drug moiety. MMF is typically administered as a fixed dose without routine monitoring of MPA concentrations. However, a role for therapeutic drug monitoring (TDM) of MPA has been suggested based on the drug's narrow therapeutic window and considerable between-subject variability. Dose-normalized MPA area under the concentration-time curve (AUC) has been observed to vary >/=10-fold. Some of this variability may be accounted for by patient variability in renal and liver function, serum albumin and haemoglobin levels, body mass, concomitant medication exposure and genetic polymorphisms in enzymes responsible for drug metabolism and transport, but much is unexplained. Widespread adoption of MPA TDM has been limited by the impracticality of full 0 to 12 hour AUC measurement (AUC(0-12)), poor correlation between pre-dose MPA concentration and AUC(0-12), ongoing questions regarding the utility of free versus total MPA measurements and lack of evidence correlating MPA exposure with clinical outcomes. Two recent randomized studies evaluating the role of MPA TDM in renal transplant recipients have reported conflicting results. Promising areas of ongoing study include use of Bayesian forecasting to predict MPA dosage and measurement of inosine monophosphate dehydrogenase activity. This review provides an overview of the pharmacokinetics of MMF in solid organ transplantation, and discusses the benefits and limitations of MPA monitoring. Areas that require additional research are identified.

Initial sequencing and analysis of the human genome.

Abstract: The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The social identity theory of intergroup behavior

Abstract: This chapter presents an outline of a theory of intergroup conflict and some preliminary data relating to the theory. Much of the work on the social psychology of intergroup relations has focused on patterns of individual prejudices and discrimination and on the motivational sequences of interpersonal interaction. The intensity of explicit intergroup conflicts of interests is closely related in human cultures to the degree of opprobrium attached to the notion of "renegade" or "traitor." The basic and highly reliable finding is that the trivial, ad hoc intergroup categorization leads to in-group favoritism and discrimination against the out-group. Many orthodox definitions of "social groups" are unduly restrictive when applied to the context of intergroup relations. The equation of social competition and intergroup conflict rests on the assumptions concerning an "ideal type" of social stratification in which the salient dimensions of intergroup differentiation are those involving scarce resources.