University of Grenoble

About: University of Grenoble is a education organization based out in Saint-Martin-d'Hères, France. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 25658 authors who have published 45143 publications receiving 909760 citations.

New recommendations for testing indirect effects in mediational models: The need to report and test component paths.

Abstract: In light of current concerns with replicability and reporting false-positive effects in psychology, we examine Type I errors and power associated with 2 distinct approaches for the assessment of mediation, namely the component approach (testing individual parameter estimates in the model) and the index approach (testing a single mediational index). We conduct simulations that examine both approaches and show that the most commonly used tests under the index approach risk inflated Type I errors compared with the joint-significance test inspired by the component approach. We argue that the tendency to report only a single mediational index is worrisome for this reason and also because it is often accompanied by a failure to critically examine the individual causal paths underlying the mediational model. We recommend testing individual components of the indirect effect to argue for the presence of an indirect effect and then using other recommended procedures to calculate the size of that effect. Beyond simple mediation, we show that our conclusions also apply in cases of within-participant mediation and moderated mediation. We also provide a new R-package that allows for an easy implementation of our recommendations. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

LDpred2: better, faster, stronger.

Abstract: Motivation Polygenic scores have become a central tool in human genetics research. LDpred is a popular method for deriving polygenic scores based on summary statistics and a matrix of correlation between genetic variants. However, LDpred has limitations that may reduce its predictive performance. Results Here we present LDpred2, a new version of LDpred that addresses these issues. We also provide two new options in LDpred2: a "sparse" option that can learn effects that are exactly 0, and an "auto" option that directly learns the two LDpred parameters from data. We benchmark predictive performance of LDpred2 against the previous version on simulated and real data, demonstrating substantial improvements in robustness and predictive accuracy compared to LDpred1. We then show that LDpred2 also outperforms other polygenic score methods recently developed, with a mean AUC over the 8 real traits analyzed here of 65.1%, compared to 63.8% for lassosum, 62.9% for PRS-CS and 61.5% for SBayesR. Note that LDpred2 provides more accurate polygenic scores when run genome-wide, instead of per chromosome. Availability LDpred2 is implemented in R package bigsnpr. Supplementary information Supplementary data are available at Bioinformatics online.

The Formation and Evolution of the Continental Crust

Abstract: In the Archean, like now, the granitoids that constitute the core of the continental crust formed in subduction zones. Hydrous basaltic magmas from the mantle wedge rose to the base of the crust where they fractionally crystallised or remelted underplated rocks to yield more evolved granitic magmas. Alternative models to explain Archean granitoids, which call on melting in intraplate settings such as the bases of oceanic plateaus, are implausible because such settings lack the water that is essential to form voluminous granitic melt. From the end of the Archean to the late Proterozoic, the continental crust grew in a series of major pulses, each triggered by accelerated mantle convection. The arrival of large mantle plumes displaced material from the upper mantle, accelerating the rate of subduction and causing a pulse of crustal growth. The Hadean crust was mafic and it underwent internal partial melting to produce the granitic melts that crystallised the Jack Hills zircons. This crust was disrupted by the Late Heavy Bombardment and from then on, since about 3.9 Ga, plate tectonics has operated.

Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory

Abstract: The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from ντ charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of ντ at EeV energies. Assuming an Eν-2 differential energy spectrum the limit set at 90% C.L. is Eν2dNντ/dEν<1.3×10-7GeVcm-2s-1sr-1 in the energy range 2×1017eV

The role of quantum measurement in stochastic thermodynamics

Abstract: This article sets up a new formalism to investigate stochastic thermodynamics in the quantum regime, where stochasticity and irreversibility primarily come from quantum measurement. In the absence of any bath, we define a purely quantum component to heat exchange, that corresponds to energy fluctuations caused by quantum measurement. Energetic and entropic signatures of measurement-induced irreversibility are then explored for canonical experiments of quantum optics, and the energetic cost of counter-acting decoherence is studied on a simple state-stabilizing protocol. By placing quantum measurement in a central position, our formalism contributes to bridge a gap between experimental quantum optics and quantum thermodynamics, and opens new paths to characterize the energetic features of quantum processing. Measuring a quantum system is an ultimately random operation. It induces a genuinely quantum time arrow, increasing the system’s entropy. But because it perturbs its state, quantum measurement also provides energy to the quantum system. These energetic quantum fluctuations play the same role as thermal fluctuations in thermodynamics, while being of quantum nature. Building on such “Quantum Heat”, a group of scientists from france provided a thermodynamic analyzis of canonical experiments of quantum optics. They show that quantum heat is a major concept to evaluate the performances of a basic protocol to counteract the decoherence of a quantum bit. The findings pave the way towards a new generation of quantum engines, powered by quantum measurement. They bring new tools to investigate the energetic cost of quantum protocols performed at ultra-low temperature, in the presence of decoherence.