Construction of Parsimonious Event Risk Scores by an Ensemble Method. An Illustration for Short-Term Predictions in Chronic Heart Failure Patients from the GISSI-HF Trial

Selecting which explanatory variables to include in a given score is a common difficulty, as a balance must be found between statistical fit and practical application. This article presents a methodology for constructing parsimonious event risk scores combining a stepwise selection of variables with ensemble scores obtained by aggregation of several scores, using several classifiers, bootstrap samples and various modalities of random selection of variables. Selection methods based on a probabilistic model can be used to achieve a stepwise selection for a given classifier such as logistic regression, but not directly for an ensemble classifier constructed by aggregation of several classifiers. Three selection methods are proposed in this framework, two involving a backward selection of the variables based on their coefficients in an ensemble score and the third involving a forward selection of the variables maximizing the AUC. The stepwise selection allows constructing a succession of scores, with the practitioner able to choose which score best fits his needs. These three methods are compared in an application to construct parsimonious short-term event risk scores in chronic HF patients, using as event the composite endpoint of death or hospitalization for worsening HF within 180 days of a visit. Focusing on the fastest method, four scores are constructed, yielding out-of-bag AUCs ranging from 0.81 (26 variables) to 0.76 (2 variables).

Construction and Update of an Online Ensemble Score Involving Linear Discriminant Analysis and Logistic Regression

The present aim is to update, upon arrival of new learning data, the parameters of a score constructed with an ensemble method involving linear discriminant analysis and logistic regression in an online setting, without the need to store all of the previously obtained data. Poisson bootstrap and stochastic approximation processes were used with online standardized data to avoid numerical explosions, the convergence of which has been established theoretically. This empirical convergence of online ensemble scores to a reference “batch” score was studied on five different datasets from which data streams were simulated, comparing six different processes to construct the online scores. For each score, 50 replications using a total of 10N observations (N being the size of the dataset) were performed to assess the convergence and the stability of the method, computing the mean and standard deviation of a convergence criterion. A complementary study using 100N observations was also performed. All tested processes on all datasets converged after N iterations, except for one process on one dataset. The best processes were averaged processes using online standardized data and a piecewise constant step-size.

Thermophysical and Mechanical Characterization of Poto-Poto Compressed Blocks for Use as Fill Material

This article is devoted to the thermophysical and mechanical study of an eco-material, poto-poto. The objective is to study the influence of the addition of bamboo fibers on the thermophysical properties of the material, while verifying that it complies with the mechanical standards in Cameroon. A double study is therefore carried out: a mechanical characterization whose objective is to determine the mechanical properties (compressive strength, flexural strength and Young’s modulus) and a thermophysical characterization whose objective is to determine the thermal conductivity. For the thermophysical characterization, the asymmetric hot plane experimental setup based on 1D quadrupole modelling was developed and simulated for the estimation of thermal effusivity E and volume heat capacity ρCp. The obtained experimental results show that the apparent thermal conductivity of the developed materials decreases with increasing fibers. Although the reference material (0% fibers) has a much higher conductivity than the ordinary sand block (1.15 Wm-1 K-1), the addition of fibers, already at 2%, contributes to decrease this conductivity (0.95 Wm-1 K-1). From the point of view of thermal insulation and energy savings, the thermal conductivity results obtained show that the use of these materials with a maximum fibercontent of 6% would be a better thermal insulator than sand block or compressed earth brick. The compressive strength obtained is such that Rc > 0.6 MPa. All the materials developed meet the design standards when used as infill.

高性能大规模分子动力学的前沿进展--近35年生物体系的分子动力学模拟研究回顾

对近35年来数值模拟方法,特别是经典分子动力学方法和相关的优先采样技术在生物体系研究中的应用作了回顾.由于生物体系研究对象的特点是体系空间尺度大且细胞机制时间跨度长,因此所涉及的结构生物学和生物物理学方面的研究构成了分子动力学模拟的最大挑战.从生物学的角度对分子动力学的基本理论、算法发展以及在生物体系中的应用进行综述,重点阐释在生理活动相关的时间尺度上生物体系的模拟是如何逐步发展的.另一方面,回顾了生物模拟体系在空间和时间尺度上得益于计算机硬件和算法的飞速发展而急速扩张的历程.最后,基于最近生物体系分子动力学模拟领域的尖端研究成果,对该领域未来发展的趋势进行了思考和展望.

Potentiation of NETs release is novel characteristic of TREM-1 activation and the pharmacological inhibition of TREM-1 could prevent from the deleterious consequences of NETs release in sepsis

During sepsis,neutrophil activation induces endothelial cell(EC)dysfunction partly through neutrophil extracellular trap(NET)release.The triggering receptor expressed on myeloid cell-1(TREM-1)is an orphan immune receptor that amplifies the inflammatory response mediated by Toll-like receptor-4(TLR4)engagement.Although the key role of TLR4 signaling in NETosis is known,the role of TREM-1 in this process has not yet been investigated.Here,we report that TREM-1 potentiates NET release by human and murine neutrophils and is a component of the NET structure.In contrast,pharmacologic inhibition or genetic ablation of TREM-1 decreased NETosis in vitro and during experimental septic shock in vivo.Moreover,isolated NETs were able to activate ECs and impair vascular reactivity,and these deleterious effects were dampened by TREM-1 inhibition.TREM-1 may,therefore,constitute a new therapeutic target to prevent NETosis and associated endothelial dysfunction.

sTREM-1 is a specific biomarker of TREM-1 pathway activation

TREM-1(triggering receptor expressed on myeloid cells-1)is a transmembrane receptor expressed by innate immune cells,including endothelial cells and platelets.TREM-1 is a crucial mediator of septic shock that acts by synergizing with Toll-like receptors(TLRs)to amplify the inflammatory responses to pathogens,thus promoting sepsis-induced immune dysregulation and organ dysfunction[1,2,3].

Compost Effect on Diuron Retention and Transport in Structured Vineyard Soils

Diuron is frequently detected in surface- and groundwater under the vineyards, where organic amendments are often used, in Burgundy of France. Undisturbed column experiments were conducted to study the influence of three composted organic amendments on diuron leaching through columns of two vineyard soils from Vosne-Roman′ee(VR, calcareous Cambisol) and Beaujolais(Bj, sandy Leptosol), France. Bromide(used as non-reactive tracer) and diuron breakthrough curves(BTCs) were analyzed using convectivedispersive equation(CDE), two-region(mobile-immobile, MIM) and two-site models. No influence of the composts was observed on the bromide recovery rates. The CDE model described well the bromide BTCs for all columns of the Bj soil and seven of the VR soil, suggesting a homogeneous water flow. However, for five VR soil columns, the MIM model fitted better, suggesting a partition of the water flow(15%–50% of matrix flow). The texture, the coarse material content and the tillage of the VR soil could explain this heterogeneity. However, for all columns, diuron leaching was greater through the Bj soil(46%–68%) than the VR soil(28%–39%). The compost addition resulted in a contrasting effect on diuron leaching: no difference or a decrease was observed for the VR soil, probably due to an increase of adsorption sites, whereas no difference or an increase was observed for the Bj soil possibly because of interactions and/or competition of diuron with the compost water-extractable organic matter which could facilitate its transport. All the diuron BTCs were best described using the two-site model, suggesting a large proportion of time-dependent sorption sites(30%–50%). The soil type and the nature of the amendments had contrasting influences on diuron transport. Composts with a high water-soluble fraction must be avoided in sandy soils to reduce the risk of groundwater contamination.

Taxonomy of Ochroconis, genus including opportunistic pathogens on humans and animals

The genus Ochroconis(Sympoventuriaceae,Venturiales)is revised and currently contains 13 species for which the phylogenetic position has been determined using multilocus sequencing.The older generic name Scolecobasidium is considered to be of doubtful identity because the type specimen is ambiguous.Within the Ochroconis lineage,phylogenetic distances of all markers analyzed are exceptionally large,both between and within species.A new genus Verruconis is proposed for the neurotropic opportunist Ochroconis gallopava.Species accepted within the lineages are keyed out on the basis of phenotypic characters.Main ecological traits within each species are discussed.Verruconis species are thermophilic and one of them is an important agent of infection in the brain,while Ochroconis is mesophilic,several species causing infections in cold-blooded animals.