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.

The relationship between motivation and achievement in interdependent situations

Abstract: This meta-analysis investigates the degree to which achievement is positively associated with motivation within situations characterized by positive, negative, and no interdependence. First, the relative effects of positive, negative, and no interdependence on motivation and achievement were determined. Then the amount of variance in achievement explained by motivation (and vice versa) was calculated. In all, 629 independent studies were included, representing 26 different countries. Results also showed that motivation accounted for 14% of the variance in achievement (and vice versa). When the lowest-quality studies were eliminated, the percentage of achievement explained by motivation increased to 24%. Positive interdependence resulted in greater motivation and achievement than did negative or no interdependence. Implications for theory and application are discussed.

Practice variations in the treatment of febrile infants among pediatric emergency physicians.

Abstract: OBJECTIVES The objectives of this study were to characterize variations in treatment decisions for young febrile infants in pediatric emergency departments across Canada and to document the extent of practice variations among pediatric emergency department practitioners. METHODS This was a prospective, concurrent, cohort study of consecutive infants up to 90 days of age who presented to 6 pediatric emergency departments in Canada with fever (rectal temperature of >or=38.0 degrees C). We recorded information in the emergency department and contacted the families by telephone to confirm the final disposition. RESULTS A total of 257 infants were recruited over 2 to 4 months. Patients were similar across centers in terms of gestational age and weight, chronologic age at arrival, weight, and gender. Temperatures measured at home and during triage and durations of fever also were similar among centers. In one center, significantly more children arrived with cough; in another center, fewer parents reported sick contacts at home. Rates of blood and urine testing were not significantly different across sites, but rates of lumbar puncture, respiratory virus testing, and chest radiography were different. A total of 55% of infants received antibiotics, and significant practice variations in the numbers and types of antibiotics used were documented. CONCLUSIONS Practices in the evaluation of young infants with fever in tertiary pediatric emergency departments varied substantially. Blood and urine tests were ordered in the majority of centers, but rates of cerebrospinal fluid testing and antibiotic treatment differed across centers.

Nebulized epinephrine for croup in children

Abstract: Background Croup is a common childhood illness characterized by barky cough, stridor, hoarseness and respiratory distress. Children with severe croup are at risk for intubation. Nebulized epinephrine may prevent intubation. Objectives To assess the efficacy (measured by croup scores, rate of intubation and health care utilization such as rate of hospitalization) and safety (frequency and severity of side effects) of nebulized epinephrine versus placebo in children with croup, evaluated in an emergency department (ED) or hospital setting. Search methods We searched CENTRAL 2013, Issue 6, MEDLINE (1966 to June week 3, 2013), EMBASE (1980 to July 2013), Web of Science (1974 to July 2013), CINAHL (1982 to July 2013) and Scopus (1996 to July 2013). Selection criteria Randomized controlled trials (RCTs) or quasi-RCTs of children with croup evaluated in an ED or admitted to hospital. Comparisons were: nebulized epinephrine versus placebo, racemic nebulized epinephrine versus L-epinephrine (an isomer) and nebulized epinephrine delivered by intermittent positive pressure breathing (IPPB) versus nebulized epinephrine without IPPB. Primary outcome was change in croup score post-treatment. Secondary outcomes were rate and duration of intubation and hospitalization, croup return visit, parental anxiety and side effects. Data collection and analysis Two authors independently identified potentially relevant studies by title and abstract (when available) and examined relevant studies using a priori inclusion criteria, followed by methodological quality assessment. One author extracted data while the second checked accuracy. We use the standard methodological procedures expected by the Cochrane Collaboration. Main results Eight studies (225 participants) were included. In general, children included in the studies were young (average age less than two years in the majority of included studies). Severity of croup was described as moderate to severe in all included studies. Six studies took place in the inpatient setting, one in the ED and one setting was not specified. Six of the eight studies were deemed to have a low risk of bias and the risk of bias was unclear in the remaining two studies. Nebulized epinephrine was associated with croup score improvement 30 minutes post-treatment (three RCTs, standardized mean difference (SMD) -0.94; 95% confidence interval (CI) -1.37 to -0.51; I2 statistic = 0%). This effect was not significant two and six hours post-treatment. Nebulized epinephrine was associated with significantly shorter hospital stay than placebo (one RCT, MD -32.0 hours; 95% CI -59.1 to -4.9). Comparing racemic and L-epinephrine, no difference in croup score was found after 30 minutes (SMD 0.33; 95% CI -0.42 to 1.08). After two hours, L-epinephrine showed significant reduction compared with racemic epinephrine (one RCT, SMD 0.87; 95% CI 0.09 to 1.65). There was no significant difference in croup score between administration of nebulized epinephrine via IPPB versus nebulization alone at 30 minutes (one RCT, SMD -0.14; 95% CI -1.24 to 0.95) or two hours (SMD -0.72; 95% CI -1.86 to 0.42). None of the studies sought or reported data on adverse effects. Authors' conclusions Nebulized epinephrine is associated with clinically and statistically significant transient reduction of symptoms of croup 30 minutes post-treatment. Evidence does not favor racemic epinephrine or L-epinephrine, or IPPB over simple nebulization. The authors note that data and analyses were limited by the small number of relevant studies and total number of participants and thus most outcomes contained data from very few or even single studies.

Liming and nitrogen fertilization affects phosphatase activities, microbial biomass and mycorrhizal colonisation in upland grassland

Abstract: We have studied the effects of factorial combinations of lime and N additions on soil microbial biomass, respiration rates and phosphatase activity of an upland grassland. We also used an Agrostis capillaris seedling bioassay to assess the effect of the treatments on the activity of arbuscular-mycorrhizal (AM) fungi and root surface phosphatase enzymes and the concentrations of N and P in the bioassay plant shoots. In the F and H horizons, soil microbial biomass carbon (Cmic) decreased in response to the liming, while addition of lime and N together reduced basal respiration rates. In the Ah horizon, Cmic was unaffected by the treatments but basal respiration rates decreased in the plots receiving nitrogen. Soil phosphatase activity decreased only in the Ah horizon in plots receiving lime, either in combination with N or alone. The mass of root fwt. colonized by AM fungi increased in response to the treatments in the order nitrogen

The Impact of Size of Cooperative Group on Achievement, Social Support, and Self-Esteem

Abstract: The effect of cooperative learning in pairs and groups of 4 and in individualistic learning were compared on achievement, social support, and self-esteem. Sixty-two Italian 7th-grade students with no previous experience with cooperative learning were assigned to conditions on a stratified random basis controlling for ability, gender, and self-esteem. Students participated in 1 instructional unit for 90 min for 6 instructional days during a period of about 6 weeks. The results indicate that cooperative learning in pairs and 4s promoted higher achievement and greater academic support from peers than did individualistic learning. Students working in pairs developed a higher level of social self-esteem than did students learning in the other conditions.

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.