Highly seasonal climate and reproductive phenology in the Mayombe forest: contribution of historical data from the Luki Reserve in the Democratic Republic of Congo

peer reviewedEn Afrique, la phénologie reproductive des arbres tropicaux, majoritairement annuelle, semble présenter une certaine régularité. Cette étude documente les variations intra- et interannuelles de la phénologie reproductive des arbres de la forêt du Mayombe à partir des données historiques de la Réserve de Luki (République démocratique du Congo). Le diamètre de reproduction des espèces exploitées pour le bois, encore largement méconnu, a été également examiné pour les espèces suffisamment représentées dans les données. Le suivi phénologique de 3 642 arbres appartenant à 158 espèces et 39 familles a été réalisé tous les 10 jours de 1948 à 1957. Les statistiques circulaires ont été utilisées pour tester le synchronisme de la phénologie entre arbres, à l’échelle de la communauté, pour la forêt dans son ensemble, et individuellement pour 87 espèces, dont 35 espèces bien représentées (n ≥ 20 arbres), 16 espèces commerciales et 36 autres espèces. Des régressions logistiques ont permis de déterminer le diamètre de fructification (minimum et régulier) de ces espèces. Pour la majorité des espèces, la floraison était régulière, annuelle et largement saisonnière (81,6 %, 71 espèces). Les pics étaient plus marqués pour la floraison que pour la fructification, plus étalée dans le temps, bien que significativement agrégée temporellement. La majorité des arbres et des espèces fleurissaient entre décembre et février, pendant la petite saison sèche, bien que des fleurs et des fruits étaient observables toute l’année à l’échelle de la communauté. Seules 13 espèces ont montré une relation significative entre le diamètre et la reproduction, parmi lesquelles sept espèces de canopée, cinq de sous-bois et une héliophile. Pour ces espèces, la moyenne du diamètre minimum de reproduction était de 17,3 cm

Outcome in patients perceived as receiving excessive care across different ethical climates: a prospective study in 68 intensive care units in Europe and the USA.

PURPOSE: Whether the quality of the ethical climate in the intensive care unit (ICU) improves the identification of patients receiving excessive care and affects patient outcomes is unknown. METHODS: In this prospective observational study, perceptions of excessive care (PECs) by clinicians working in 68 ICUs in Europe and the USA were collected daily during a 28-day period. The quality of the ethical climate in the ICUs was assessed via a validated questionnaire. We compared the combined endpoint (death, not at home or poor quality of life at 1 year) of patients with PECs and the time from PECs until written treatment-limitation decisions (TLDs) and death across the four climates defined via cluster analysis. RESULTS: Of the 4747 eligible clinicians, 2992 (63%) evaluated the ethical climate in their ICU. Of the 321 and 623 patients not admitted for monitoring only in ICUs with a good (n = 12, 18%) and poor (n = 24, 35%) climate, 36 (11%) and 74 (12%), respectively were identified with PECs by at least two clinicians. Of the 35 and 71 identified patients with an available combined endpoint, 100% (95% CI 90.0-1.00) and 85.9% (75.4-92.0) (P = 0.02) attained that endpoint. The risk of death (HR 1.88, 95% CI 1.20-2.92) or receiving a written TLD (HR 2.32, CI 1.11-4.85) in patients with PECs by at least two clinicians was higher in ICUs with a good climate than in those with a poor one. The differences between ICUs with an average climate, with (n = 12, 18%) or without (n = 20, 29%) nursing involvement at the end of life, and ICUs with a poor climate were less obvious but still in favour of the former. CONCLUSION: Enhancing the quality of the ethical climate in the ICU may improve both the identification of patients receiving excessive care and the decision-making process at the end of life

Variation in Onset of Leaf Unfolding and Wood Formation in a Central African Tropical Tree Species

A diversity of phenological strategies has been reported for tropical tree species. Defoliation and seasonal dormancy of cambial activity inform us on how trees cope with water stress during the dry season, or maximize the use of resources during the rainy season. Here, we study the matching between leaf phenology (unfolding and shedding) and cambial activity for Prioria balsamifera, a key timber species in the Democratic Republic of Congo. In particular, we (i) evaluated the seasonality of cambial activity and synchrony of phenology among trees in response to climate and (ii) identified the seasonality of leaf phenology and its relation with cambial phenology. The study was conducted in the Luki Man and Biosphere Reserve, located in the Mayombe forest at the southern margin of the Congo Basin. Historic defoliation data were collected every ten days using weekly crown observations whereas recent observations involved timelapse cameras. Cambial pinning was performed on ten trees during 20 months and radius dendrometers were installed on three trees during 13 months. Tree rings were measured on cores from 13 trees and growth synchrony was evaluated. We found that P. balsamifera defoliates annually with a peak observed at the end of the dry season and the beginning of the rainy season. The new leaves unfolded shortly after shedding of the old leaves. The peak defoliation dates varied across years from September 12 to November 14 and the fraction of number of trees that defoliated at a given time was found to be negatively correlated with annual rainfall and temperature; during the dry season, when precipitation and temperatures are the lowest. Wood formation (radial growth), was found to be highly seasonal, with cambial dormancy occurring during the dry season and growth starting at the beginning of the rainy season. Individual ringwidth series did not cross date well. The within species variability of leaf phenology and cambial rhythms provides indication about resistance of the population against climatic changes

Unraveling gene regulatory networks from time-resolved gene expression data -- a measures comparison study

Peer reviewedPublisher PD

Risk-adjusted cancer screening and prevention (RiskAP): complementing screening for early disease detection by a learning screening based on risk factors

Background: Risk-adjusted cancer screening and prevention is a promising and continuously emerging option for improving cancer prevention. It is driven by increasing knowledge of risk factors and the ability to determine them for individual risk prediction. However, there is a knowledge gap between evidence of increased risk and evidence of the effectiveness and efficiency of clinical preventive interventions based on increased risk. This gap is, in particular, aggravated by the extensive availability of genetic risk factor diagnostics, since the question of appropriate preventive measures immediately arises when an increased risk is identified. However, collecting proof of effective preventive measures, ideally by prospective randomized preventive studies, typically requires very long periods of time, while the knowledge about an increased risk immediately creates a high demand for action. Summary: Therefore, we propose a risk-adjusted prevention concept that is based on the best current evidence making needed and appropriate preventive measures available, and which is constantly evaluated through outcome evaluation, and continuously improved based on these results. We further discuss the structural and procedural requirements as well as legal and socioeconomical aspects relevant for the implementation of this concept.Genome Instability and Cance

Scientific merits and analytical challenges of tree-ring densitometry

R.W. was supported by NERC grant NE/K003097/1.X-ray microdensitometry on annually-resolved tree-ring samples has gained an exceptional position in last-millennium paleoclimatology through the maximum latewood density parameter (MXD), but also increasingly through other density parameters. For fifty years, X-ray based measurement techniques have been the de facto standard. However, studies report offsets in the mean levels for MXD measurements derived from different laboratories, indicating challenges of accuracy and precision. Moreover, reflected visible light-based techniques are becoming increasingly popular and wood anatomical techniques are emerging as a potentially powerful pathway to extract density information at the highest resolution. Here we review the current understanding and merits of wood density for tree-ring research, associated microdensitometric techniques, and analytical measurement challenges. The review is further complemented with a careful comparison of new measurements derived at 17 laboratories, using several different techniques. The new experiment allowed us to corroborate and refresh ?long-standing wisdom?, but also provide new insights. Key outcomes include; i) a demonstration of the need for mass/volume based re-calibration to accurately estimate average ring density; ii) a substantiation of systematic differences in MXD measurements that cautions for great care when combining density datasets for climate reconstructions; and iii) insights into the relevance of analytical measurement resolution in signals derived from tree-ring density data. Finally, we provide recommendations expected to facilitate future inter-comparability and interpretations for global change research.Publisher PDFPeer reviewe

Discretization Provides a Conceptually Simple Tool to Build Expression Networks

Biomarker identification, using network methods, depends on finding regular co-expression patterns; the overall connectivity is of greater importance than any single relationship. A second requirement is a simple algorithm for ranking patients on how relevant a gene-set is. For both of these requirements discretized data helps to first identify gene cliques, and then to stratify patients

Influence of Statistical Estimators of Mutual Information and Data Heterogeneity on the Inference of Gene Regulatory Networks

The inference of gene regulatory networks from gene expression data is a difficult problem because the performance of the inference algorithms depends on a multitude of different factors. In this paper we study two of these. First, we investigate the influence of discrete mutual information (MI) estimators on the global and local network inference performance of the C3NET algorithm. More precisely, we study different MI estimators (Empirical, Miller-Madow, Shrink and Schürmann-Grassberger) in combination with discretization methods (equal frequency, equal width and global equal width discretization). We observe the best global and local inference performance of C3NET for the Miller-Madow estimator with an equal width discretization. Second, our numerical analysis can be considered as a systems approach because we simulate gene expression data from an underlying gene regulatory network, instead of making a distributional assumption to sample thereof. We demonstrate that despite the popularity of the latter approach, which is the traditional way of studying MI estimators, this is in fact not supported by simulated and biological expression data because of their heterogeneity. Hence, our study provides guidance for an efficient design of a simulation study in the context of network inference, supporting a systems approach