Collège de France

About: Collège de France is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Receptor. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

Popper, Karl R

Abstract: Born 1902; died 1994. Famous as a philosopher of science, Popper maintained that scientific truth is not manifest, but that indeed that scientific theories are conjectures open to refutation or falsification. Popper controversially denounced inductive reasoning—validity of a scientific theory from empirical observations to general regularities—insisting instead that scientific theories should be open to testing. As a theory passes more severe tests, it becomes more highly “corroborated”. He called this approach hypothetico-deductive. ‘Realism and the Aim of Science’ (1982) is his work most relevant to biostatistics, re-examining in detail problems of truth, corroboration, and probability. Keywords: conjecture; refutation; induction; inference; epistemology; probability; propensity; indeterminism

Solutions of the Two Dimensional Hubbard Model: Benchmarks and Results from a Wide Range of Numerical Algorithms

Abstract: Numerical results for ground state and excited state properties (energies, double occupancies, and Matsubara-axis self energies) of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an assessment of our ability to compute accurate results in the thermodynamic limit. Many methods are employed, including auxiliary field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed node approximation, unrestricted coupled cluster theory, and multi-reference projected Hartree-Fock. Comparison of results obtained by different methods allows for the identification of uncertainties and systematic errors. The importance of extrapolation to converged thermodynamic limit values is emphasized. Cases where agreement between different methods is obtained establish benchmark results that may be useful in the validation of new approaches and the improvement of existing methods.

Correlation Between Microstructure and Na Storage Behavior in Hard Carbon

Abstract: Hard carbons are considered among the most promising anode materials for Na-ion batteries. Understanding their structure is of great importance for optimizing their Na storage capabilities and therefore achieving high performance. Herein, carbon nanofibers (CNFs) are prepared by electrospinning and their microstructure, texture, and surface functionality are tailored through carbonization at various temperatures ranging from 650 to 2800 degrees C. Stepwise carbonization gradually removes the heteroatoms and increases the graphitization degree, enabling us to monitor the corresponding electrochemical performance for establishing a correlation between the CNFs characteristics and Na storage behavior. Outstandingly, it is found that for CNFs carbonized at above 2000 degrees C, a single voltage Na uptake plateau at similar or equal to 0.1 V with a capacity of similar or equal to 200 mAh g(-1). This specific performance may be nested in the higher degree of graphitization, lower active surface area, and different porous texture of the CNFs at such temperatures. It is demonstrated via the assembly of a CNF/Na2Fe2(SO4)(3) cell the benefit of such CNFs electrode for enhancing the energy density of full Na-ion cells. This finding sheds new insights in the quest for high performance carbon based anode materials.

Determination of the fine-structure constant with an accuracy of 81 parts per trillion

Abstract: The standard model of particle physics is remarkably successful because it is consistent with (almost) all experimental results. However, it fails to explain dark matter, dark energy and the imbalance between matter and antimatter in the Universe. Because discrepancies between standard-model predictions and experimental observations may provide evidence of new physics, an accurate evaluation of these predictions requires highly precise values of the fundamental physical constants. Among them, the fine-structure constant α is of particular importance because it sets the strength of the electromagnetic interaction between light and charged elementary particles, such as the electron and the muon. Here we use matter-wave interferometry to measure the recoil velocity of a rubidium atom that absorbs a photon, and determine the fine-structure constant α−1 = 137.035999206(11) with a relative accuracy of 81 parts per trillion. The accuracy of eleven digits in α leads to an electron g factor1,2—the most precise prediction of the standard model—that has a greatly reduced uncertainty. Our value of the fine-structure constant differs by more than 5 standard deviations from the best available result from caesium recoil measurements3. Our result modifies the constraints on possible candidate dark-matter particles proposed to explain the anomalous decays of excited states of 8Be nuclei4 and paves the way for testing the discrepancy observed in the magnetic moment anomaly of the muon5 in the electron sector6. The fine-structure constant is determined with an accuracy of 81 parts per trillion using matter-wave interferometry to measure the rubidium atom recoil velocity.