Ab initio structure search and in situ 7Li NMR studies of discharge products in the Li-S battery system.

The high theoretical gravimetric capacity of the Li-S battery system makes it an attractive candidate for numerous energy storage applications. In practice, cell performance is plagued by low practical capacity and poor cycling. In an effort to explore the mechanism of the discharge with the goal of better understanding performance, we examine the Li-S phase diagram using computational techniques and complement this with an in situ (7)Li NMR study of the cell during discharge. Both the computational and experimental studies are consistent with the suggestion that the only solid product formed in the cell is Li2S, formed soon after cell discharge is initiated. In situ NMR spectroscopy also allows the direct observation of soluble Li(+)-species during cell discharge; species that are known to be highly detrimental to capacity retention. We suggest that during the first discharge plateau, S is reduced to soluble polysulfide species concurrently with the formation of a solid component (Li2S) which forms near the beginning of the first plateau, in the cell configuration studied here. The NMR data suggest that the second plateau is defined by the reduction of the residual soluble species to solid product (Li2S). A ternary diagram is presented to rationalize the phases observed with NMR during the discharge pathway and provide thermodynamic underpinnings for the shape of the discharge profile as a function of cell composition.Fellowship support to KAS from the ConvEne IGERT Program of the National Science Foundation (DGE 0801627) is gratefully acknowledged. AJM acknowledges the support from the Winton Programme for the Physics of Sus-tainability. PDM and DSW thank the UK-EPSRC for financial support. This research made use of the shared experimental facilities of the Materials Research Laboratory (MRL), sup-ported by the MRSEC Program of the NSF under Award No. DMR 1121053. The MRL is a member of the NSF-funded Mate-rials Research Facilities Network (www.mrfn.org). CPG and ML thank the U.S. DOE Office of Vehicle Technologies (Con-tract No. DE-AC02-05CH11231) and the EU ERC (via an Ad-vanced Fellowship to CPG) for funding.This is the final published version. It first appeared at http://pubs.acs.org/doi/abs/10.1021/ja508982p

Implications of Compressed Supersymmetry for Collider and Dark Matter Searches

Martin has proposed a scenario dubbed ``compressed supersymmetry'' (SUSY) where the MSSM is the effective field theory between energy scales M_{\rm weak} and M_{\rm GUT}, but with the GUT scale SU(3) gaugino mass M_3<< M_1 or M_2. As a result, squark and gluino masses are suppressed relative to slepton, chargino and neutralino masses, leading to a compressed sparticle mass spectrum, and where the dark matter relic density in the early universe may be dominantly governed by neutralino annihilation into ttbar pairs via exchange of a light top squark. We explore the dark matter and collider signals expected from compressed SUSY for two distinct model lines with differing assumptions about GUT scale gaugino mass parameters. For dark matter signals, the compressed squark spectrum leads to an enhancement in direct detection rates compared to models with unified gaugino masses. Meanwhile, neutralino halo annihilation rates to gamma rays and anti-matter are also enhanced relative to related scenarios with unified gaugino masses but, depending on the halo dark matter distribution, may yet be below the sensitivity of indirect searches underway. In the case of collider signals, we compare the rates for the potentially dominant decay modes of the stop_1 which may be expected to be produced in cascade decay chains at the LHC: \tst_1\to c\tz_1 and \tst_1\to bW\tz_1. We examine the extent to which multilepton signal rates are reduced when the two-body decay mode dominates. For the model lines that we examine here, the multi-lepton signals, though reduced, still remain observable at the LHC.Comment: 22 pages including 24 eps figure

Global Carbon Budget 2016

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere &ndash; the &ldquo;global carbon budget&rdquo; &ndash; is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2&nbsp;emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in&nbsp;SOCEAN&nbsp;is evaluated with data products based on surveys of ocean CO2&nbsp;measurements. The global residual terrestrial CO2&nbsp;sink (SLAND) &nbsp;is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as &plusmn;1&sigma;, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006&ndash;2015),&nbsp;EFF was 9.3 &plusmn; 0.5 GtC yr-1,&nbsp;ELUC 1.0 &plusmn; 0.5 GtC yr-1,&nbsp;GATM 4.5 &plusmn; 0.1 GtC yr-1,&nbsp;SOCEAN&nbsp;2.6 &plusmn; 0.5 GtC yr-1, and&nbsp;SLAND 3.1 &plusmn; 0.9 GtC yr-1. For year 2015 alone, the growth in&nbsp;EFF was approximately zero and emissions remained at 9.9 &plusmn; 0.5 GtC yr-1, showing a slowdown in growth of these emissions compared to the average growth of 1.8 % yr-1 that took place during 2006&ndash;2015. Also, for 2015,&nbsp;ELUC was 1.3 &plusmn; 0.5 GtC yr-1,&nbsp;GATM&nbsp;was 6.3 &plusmn; 0.2 GtC yr-1,&nbsp;SOCEAN&nbsp;was 3.0 &plusmn; 0.5 GtC yr-1, and&nbsp;SLAND was 1.9 &plusmn; 0.9 GtC yr-1.&nbsp;GATM&nbsp;was higher in 2015 compared to the past decade (2006&ndash;2015), reflecting a smaller&nbsp;SLAND for that year. The global atmospheric CO2&nbsp;concentration reached 399.4 &plusmn; 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in&nbsp;EFF with +0.2 % (range of &minus;1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of&nbsp;EFF in 2016, the growth rate in atmospheric CO2&nbsp;concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (SLAND) in response to El Ni&ntilde;o conditions of 2015&ndash;2016. From this projection of&nbsp;EFF and assumed constant&nbsp;ELUC for 2016, cumulative emissions of CO2&nbsp;will reach 565 &plusmn; 55 GtC (2075 &plusmn; 205 GtCO2) for 1870&ndash;2016, about 75 % from&nbsp;EFF and 25 % from&nbsp;ELUC . This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Qu&eacute;r&eacute; et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2016).</p