Aesthetics and Power Considerations in Multiple Testing – A Contradiction?

In this paper we discuss aesthetical concepts and requirements for reasonable multiple test procedures. Aesthetical considerations lead to logical decision patterns which are conceivable and, if possible, simple to use and to communicate. Such considerations are sometimes contradictory to the ubiquitous requirement of maximizing power for a multiple test procedure. We illustrate the necessary trade-offs with several examples. We start by considering important logical properties and then discuss three different concepts of monotonicity. Afterwards we have a closer look at the recently proposed "fallback procedure" and show that it has some less appealing properties. Finally, we investigate the distribution of the numbers of significant results with respect to both expectation and variance.     

Group-specific quantification of methanotrophs in landfill gas-purged laboratory biofilters by tyramide signal amplification-fluorescence in situ hybridization

The aim of this study was to quantitatively analyse methanotrophs in two laboratory landfill biofilters at different biofilter depths and at temperatures which mimicked the boreal climatic conditions. Both biofilters were dominated by type I methanotrophs. The biofilter depth profiles showed that type I methanotrophs occurred in the upper layer, where relatively high O(2) and low CH(4) concentrations were present, whereas type II methanotrophs were mostly distributed in the zone with high CH(4) and low O(2) concentrations. The number of type I methanotrophic cells declined when the temperature was raised from 15 degrees C to 23 degrees C, but increased when lowered to 5 degrees C. A slight decrease in type II methanotrophs was also observed when the temperature was raised from 15 degrees C to 23 degrees C, whereas cell numbers remained constant when lowered to 5 degrees C. The results indicated that low temperature conditions favored both type I and type II methanotrophs in the biofilters.     

A modelling approach to explore some hypotheses of the failure of neuroprotective trials in ischemic stroke patients

Ischemic stroke is the third cause of death in industrialised countries, but no satisfactory treatment is currently available. The hundreds of neuroprotective drugs developed to block the ischemic cascade gave very promising results in animal models but the clinical trials performed with these drugs showed no beneficial effects in stroke patients. Many hypotheses were advanced to explain this discrepancy, among which the morphological and functional differences between human and rodent brains. This discrepancy could be partly due to the differences in white matter and glial cell proportions between human and rodent brains. In order to test this hypothesis, we built a mathematical model of the main early pathophysiological mechanisms of stroke in rodent and in human brains. This model is a two-scale model and relies on a set of ordinary differential equations. We built two versions of this model (for human and rodent brains) differing in their white matter and glial cell proportions. Then, we carried out in silico experiments with various neuroprotective drugs. The simulation results obtained with a sodium channel blocker show that the proportion of penumbra recovery is much higher in rodent than in human brain and the results are similar with some other neuroprotective drugs tested during phase III trials. This in silico investigation suggests that the proportions of glial cells and white matter have an influence on neuroprotective drug efficacy. It reinforces the hypothesis that histological and morphological differences between rodent and human brains can partly explain the failure of these agents in clinical trials.     

Relationship between decomposition of cellulose strips and chemical properties of humus layer in natural boreal forests

The relationships between the decomposition of cellulose strips buried completely within the humus layer (Of + Oh) for two 1-year periods and humus layer properties were studied at forested sites with minimal anthropogenic influence. The 18 study sites are clustered in four catchments located between 61° and 69° N in Finland. The stands were composed of varying proportions of Scots pine, Norway spruce and deciduous species. Of the 23 humus layer properties studied, significant correlations were found between decomposition and soil pH, effective cation exchange capacity, base saturation, C/N ratio, the concentrations of P, Mn, Pb, Zn and Cu. The relationships, however, were inconsistent except for heavy metal concentrations which were positive in all cases. Decomposition was more strongly and consistently correlated to tree stand characteristics (mean height and stem volume) than to the humus layer properties. Both the decomposition of cellulose strips and the concentrations of heavy metals were intercorrelated with climate and the stand characteristics. Partial correlation analysis revealed that the relationships between decomposition and humus layer heavy metal concentrations were more strongly affected by the tree stand characteristics than by climate. After the statistical elimination of the effects of stand characteristics, no significant positive correlations between decomposition and humus layer heavy metal concentrations remained and, in some cases for total and extractable Zn, the correlations became significant and negative. Results from litterfall chemistry (nutrients and heavy metals) also underlined that any specific effects of humus layer heavy metal concentrations on decomposition may be masked if the effects of stand characteristics are not accounted for. We conclude that the relationships between decomposition and soil chemical properties can not be elucidated without considering stand structure and composition of the forest stand.     

Pseudoxanthomonas bacteria that drive deposit formation of wood extractives can be flocculated by cationic polyelectrolytes

Runnability problems caused by suspended bacteria in water using industries, have, in contrast to biofilms, received little attention. We describe here that Pseudoxanthomonas taiwanensis, a wide-spread and abundant bacterium in paper machine water circuits, aggregated dispersions of wood extractives ("pitch") and resin acid, under conditions prevailing in machine water circuits (10⁹ cfu ml⁻¹, pH 8, 45°C). The aggregates were large enough (up to 50 μm) so that they could be expected to clog wires and felts and to reduce dewatering of the fiber web. The Pseudoxanthomonas bacteria were negatively charged over a pH range of 3.2–10. Cationic polyelectrolytes of the types used as retention aids or fixatives to flocculate "anionic trash" in paper machines were effective in flocculating the Pseudoxanthomonas bacteria. The polyelectrolyte most effective for this purpose was of high molecular weight (7–8 × 10⁶ g mol⁻¹) and low charge density (1 meq g⁻¹), whereas polyelectrolytes that effectively zeroed the electrophoretic mobility (i.e., neutralized the negative charge) of the bacterium were less effective in flocculating the bacteria. Based on the results, we concluded that the polyelectrolytes functioning by bridging mechanism, rather than by neutralization of the negative charge, may be useful as tools for reducing harmful deposits resulting from interaction of bacteria with wood extractives in warm water industry.     

Effect of molybdate ions on methanation of simulated and natural waste-waters

Summary Sulphate in concentrations of 500 and 1000 mg SO₄-S/l did not inhibit methanation of synthetic waste-water (acetate + methanol + glucose) by sludge from a digester treating neutral spent sulphite process effluents. The role of sulphate reducers in the conversion of those substrates was minor although sulphate-reducing bacteria were present with a viable count similar to that of methane-producing bacteria in the sludge. Neutral spent sulphite liquor was partially converted to methane (40% of chemical oxygen demand) under these conditions.Molybdate (20 mM) inhibited methanation of both synthetic waste-water and neutral spent sulphite liquor. Acetate accumulated in glucose plus molybdate media. Molybdate had a direct inhibitory effect on enriched acetoclastic methane-producing bacteria. Molybdate was bacteriocidic to sulphate-reducing bacteria and bacteriostatic to methane-producing bacteria.     

Global environmental change effects on plant community composition trajectories depend upon management legacies

The contemporary state of functional traits and species richness in plant communities depends on legacy effects of past disturbances. Whether temporal responses of community properties to current environmental changes are altered by such legacies is, however, unknown. We expect global environmental changes to interact with land‐use legacies given different community trajectories initiated by prior management, and subsequent responses to altered resources and conditions. We tested this expectation for species richness and functional traits using 1814 survey‐resurvey plot pairs of understorey communities from 40 European temperate forest datasets, syntheses of management transitions since the year 1800, and a trait database. We also examined how plant community indicators of resources and conditions changed in response to management legacies and environmental change. Community trajectories were clearly influenced by interactions between management legacies from over 200 years ago and environmental change. Importantly, higher rates of nitrogen deposition led to increased species richness and plant height in forests managed less intensively in 1800 (i.e., high forests), and to decreases in forests with a more intensive historical management in 1800 (i.e., coppiced forests). There was evidence that these declines in community variables in formerly coppiced forests were ameliorated by increased rates of temperature change between surveys. Responses were generally apparent regardless of sites’ contemporary management classifications, although sometimes the management transition itself, rather than historic or contemporary management types, better explained understorey responses. Main effects of environmental change were rare, although higher rates of precipitation change increased plant height, accompanied by increases in fertility indicator values. Analysis of indicator values suggested the importance of directly characterising resources and conditions to better understand legacy and environmental change effects. Accounting for legacies of past disturbance can reconcile contradictory literature results and appears crucial to anticipating future responses to global environmental change.     

The incidence and survival of acute de novo leukemias in Estonia and in a well-defined region of western Sweden during 1997–2001: A survey of patients aged ≥65 years

Background: In a recently published retrospective population-based study over three 5-year periods (1982–1996) we investigated the outcome for de novo acute leukemia (AL) patients aged ≥65 years at diagnosis in Estonia (a country that had been occupied by the Soviet Union over 5 decades) and in the so-called Western Swedish Health Care Region. The age-standardized yearly incidence rates regarding the total number of de novo AL was 5.3/100 000 inhabitant for Estonia and 8.0 for Sweden, this difference being statistically significant merely as regards acute myeloid leukemia (AML). The relative survival for the total cohort of de novo AL as well as for de novo AML was significantly longer (p < 0.001) for Swedish as compared to Estonian patients. Methods: In view of the miserable outcome for the Estonian patients we decided to prospectively compare the results for incidence and outcome of de novo AL between the two countries. Results: The present report covers the first 5-year period comprising 1997–2001 and deals only with patients aged ≥65 years at diagnosis. The age-adjusted annual incidence rates for de novo AML were lower in Estonia (6.4/100 000) than in Sweden (9.2/100 000) but not significantly so. The present results also show that the outcome for the Estonian AML patients had improved considerably over the study period; thus, at no time point, i.e., at 1, 3 and 5 years did relative survival between the two countries differ significantly. Conclusion: Yet, as compared to the Swedish cohort relative survival for the Estonian patients did still not reach an acceptable level.     

Gene deletions in X-linked muscular dystrophy

Of the approximately 170 families with X-linked muscular dystrophy of the Duchenne (DMD) and Becker (BMD) type in Finland, we have studied 90 unrelated patients for intragenic deletions by using the cDNA probes described by Koenig et al. Forty-five patients (50%) had molecular deletions of one or several of the 65 exon-containing HindIII fragments. In six deletion cases junction fragments of altered size were seen. Thirty-eight (84%) of the 45 deletions were detected using only two (1–2a and 8) of the six cDNA subclones. Using a wheelchair age of 12 years to distinguish between DMD and BMD, we found that the proportions of patients with deletions were similar. Deletions were equally common in familial and sporadic disease. BMD was more commonly caused by deletions in the 5' end of the gene than was DMD. In at least three instances deletions of similar type resulted in diseases of similar severity. Of 14 patients with mental retardation seven had deletions; six of these comprised exons contained in probe 8. We conclude that cDNA hybridization studies provide a powerful diagnostic tool in DMD and BMD and that they promise to produce better insights into molecular-clinical correlations.