Crystal and magnetic structure of substituted lanthanum cobaltites

The crystal and magnetic structures of the lanthanum cobaltites La0.6Sr0.4CoO3, La0.6Sr0.4Co0.9Fe0.1O3 and La0.6Ba0.4Co0.9Fe0.1O3 have been studied by neutron powder diffraction at temperatures of 2, 300 and 900 K. All compounds undergo a phase transition from cubic to rhombohedral structure. Below the room temperature La0.6Sr0.4CoO3 becomes ferromagnetic while for the components with 10% Fe substituted for Co, we found an antiferromagnetic order

Impact of Many-Body Effects on Landau Levels in Graphene

We present magneto-Raman spectroscopy measurements on suspended graphene to investigate the charge carrier density-dependent electron-electron interaction in the presence of Landau levels. Utilizing gate-tunable magneto-phonon resonances, we extract the charge carrier density dependence of the Landau level transition energies and the associated effective Fermi velocity $v_\mathrm{F}$. In contrast to the logarithmic divergence of $v_\mathrm{F}$ at zero magnetic field, we find a piecewise linear scaling of $v_\mathrm{F}$ as a function of charge carrier density, due to a magnetic field-induced suppression of the long-range Coulomb interaction. We quantitatively confirm our experimental findings by performing tight-binding calculations on the level of the Hartree-Fock approximation, which also allow us to estimate an excitonic binding energy of $\approx$ 6 meV contained in the experimentally extracted Landau level transitions energies.Comment: 10 pages, 6 figure

Bootstrap approximation for the exchange-correlation kernel of time-dependent density functional theory

A new parameter-free approximation for the exchange-correlation kernel $f_{\rm xc}$ of time-dependent density functional theory is proposed. This kernel is expressed as an algorithm in which the exact Dyson equation for the response as well as a further approximate condition are solved together self-consistently leading to a simple parameter-free kernel. We apply this to the calculation of optical spectra for various small bandgap (Ge, Si, GaAs, AlN, TiO$_2$, SiC), large bandgap (C, LiF, Ar, Ne) and magnetic (NiO) insulators. The calculated spectra are in very good agreement with experiment for this diverse set of materials, highlighting the universal applicability of the new kernel.Comment: 4 figures 5 page

A Deep Generative Model for Interactive Data Annotation through Direct Manipulation in Latent Space

The impact of machine learning (ML) in many fields of application is constrained by lack of annotated data. Among existing tools for ML-assisted data annotation, one little explored tool type relies on an analogy between the coordinates of a graphical user interface and the latent space of a neural network for interaction through direct manipulation. In the present work, we 1) expand the paradigm by proposing two new analogies: time and force as reflecting iterations and gradients of network training; 2) propose a network model for learning a compact graphical representation of the data that takes into account both its internal structure and user provided annotations; and 3) investigate the impact of model hyperparameters on the learned graphical representations of the data, identifying candidate model variants for a future user study

Band structures of rare gas solids within the GW approximation

Band structures for solid rare gases (Ne, Ar) have been calculated using the GW approximation. All electron and pseudopotential ab initio calculations were performed using Gaussian orbital basis sets and the dependence of particle-hole gaps and electron affinities on basis set and treatment of core electrons is investigated. All electron GW calculations have a smaller particle-hole gap than pseudopotential GW calculations by up to 0.2 eV. Quasiparticle electron and hole excitation energies, valence band widths and electron affinities are generally in very good agreement with those derived from optical absorption and photoemission measurements.Comment: 7 pages 1 figur

Reforestation in a high-CO2 world - Higher mitigation potential than expected, lower adaptation potential than hoped for

We assess the potential and possible consequences for the global climate of a strong reforestation scenario for this century. We perform model experiments using the Max Planck Institute Earth System Model (MPI-ESM), forced by fossil-fuel CO2 emissions according to the high-emission scenario Representative Concentration Pathway (RCP) 8.5, but using land use transitions according to RCP4.5, which assumes strong reforestation. Thereby, we isolate the land use change effects of the RCPs from those of other anthropogenic forcings. We find that by 2100 atmospheric CO2 is reduced by 85 ppm in the reforestation model experiment compared to the reference RCP8.5 model experiment. This reduction is higher than previous estimates and is due to increased forest cover in combination with climate and CO2 feedbacks. We find that reforestation leads to global annual mean temperatures being lower by 0.27 K in 2100. We find large annual mean warming reductions in sparsely populated areas, whereas reductions in temperature extremes are also large in densely populated areas

Application of current in situ hybridization techniques for grape phylloxera (Daktulosphaira vitifoliae, Fitch) and grapevine (Vitis spp. L.)

In situ hybridization and in situ PCR directly localize specific DNA and RNA sequences in tissues. To exactly focus on the processes occurring on cell- or tissue level, in situ techniques can be efficiently employed. Recent advances in viticultural research in the fields of genomics, proteomics and metabolomics are likely to employ these techniques to link DNA- or mRNA sequence information to physiological traits and processes occurring in the grapevine. In this paper, we present a range of possibilities for in situ techniques that can be applied in grapevine research. Two examples covering in situ PCR of grapevine roots and in situ hybridization of grape phylloxera will be given for illustration. Moreover, key steps of the techniques are discussed, which may be helpful to researchers aiming to employ in situ hybridization or in situ PCR.

Enhanced rates of regional warming and ocean acidification after termination of large-scale ocean alkalinization

Termination effects of large‐scale Artificial Ocean Alkalinization (AOA) have received little attention because AOA was assumed to pose low environmental risk. With the Max‐Planck‐Institute Earth System Model, we use emission‐driven AOA simulations following the Representative Concentration Pathway 8.5 (RCP8.5). We find that after termination of AOA warming trends in regions of the Northern hemisphere become ∼50% higher than those in RCP8.5 with rates similar to those caused by termination of solar geoengineering over the following three decades after cessation (up to 0.15 K/year). Rates of ocean acidification after termination of AOA outpace those in RCP8.5. In warm shallow regions where vulnerable coral reefs are located, decreasing trends in surface pH double (0.01 units/year) and the drop in the carbonate saturation state (Ω) becomes up to one order of magnitude larger (0.2 units/year). Thus, termination of AOA poses higher risks to biological systems sensitive to fast‐paced environmental changes than previously thought. <br