Capillary based Li-air batteries for <i>in situ</i> synchrotron X-ray powder diffraction studies

A novel design for in situ X-ray diffraction Li–O2 battery reveals the crystallographic details for the precipitation and decomposition of Li2O2 for the 1st and 2nd cycles of the battery.</p

All-solid-state lithium-sulfur battery based on a nanoconfined LiBH₄ electrolyte

In this work we characterize all-solid-state lithium-sulfur batteries based on nano-confined LiBH4in mesoporous silica as solid electrolytes. The nano-confined LiBH4has fast ionic lithium conductivity at room temperature, 0.1 mScm-1, negligible electronic conductivity and its cationic transport number (t+= 0.96), close to unity, demonstrates a purely cationic conductor. The electrolyte has an excellent stability against lithium metal. The behavior of the batteries is studied by cyclic voltammetry and repeated charge/discharge cycles in galvanostatic conditions. The batteries show very good performance, delivering high capacities versus sulfur mass, typically 1220 mAhg-1after 40 cycles at moderate temperature (55°C), 0.03 C rates and working voltage of 2 V. © The Author(s) 2016

CO2 Enhancement of Forest Productivity Constrained by Limited Nitrogen Availability

Stimulation of terrestrial productivity by rising CO~2~ concentration is projected to reduce the airborne fraction of anthropogenic CO~2~ emissions; coupled climate-carbon (C) cycle models, including those used in the IPCC Fourth Assessment Report (AR4), are sensitive to this negative feedback on atmospheric CO~2~^1^. The representation of the so-called CO~2~ fertilization effect in the 11 models used in AR4 and subsequent models^2,3^ was broadly consistent with experimental evidence from four free-air CO~2~ enrichment (FACE) experiments, which indicated that net primary productivity (NPP) of forests was increased by 23 +/- 2% in response to atmospheric CO~2~ enrichment to 550 ppm^4^. Substantial uncertainty remains, however, because of the expectation that feedbacks through the nitrogen (N) cycle will reduce the CO~2~ stimulation of NPP^5,6^; these feedbacks were not included in the AR4 models and heretofore have not been confirmed by experiments in forests^7^. Here, we provide new evidence from a FACE experiment in a deciduous Liquidambar styraciflua (sweetgum) forest stand in Tennessee, USA, that N limitation has significantly reduced the stimulation of NPP by elevated atmospheric CO~2~ concentration (eCO~2~). Isotopic evidence and N budget analysis support the premise that N availability in this forest ecosystem has been declining over time, and declining faster in eCO~2~. Model analyses and evidence from leaf- and stand-level observations provide mechanistic evidence that declining N availability constrained the tree response to eCO2. These results provide a strong rationale and process understanding for incorporating N limitation and N feedback effects in ecosystem and global models used in climate change assessments

C-type related order in the defective fluorites La2Ce2O7 and Nd2Ce2O7 studied by neutron scattering and ab initio MD simulations

This work presents a structural investigation of La2-xNdxCe2O7 (x = 0.0, 0.5, 1.0, 1.5, 2.0) using X-ray powder diffraction and total scattering neutron powder diffraction, analysed using Rietveld and the reverse Monte Carlo method (RMC). Ab initio molecular dynamics (MD) modelling is also performed for further investigations of the local order. The main intensities in the neutron diffraction data for the La2-xNdxCe2O7 series correspond to the fluorite structure. However, additional C-type superlattice peaks are visible for x > 0 and increase in intensity with increasing x. The Nd-containing compositions (x > 0) are best fitted with Rietveld analysis by using a combination of oxygen deficient fluorite and oxygen excess C-type structures. No indications of cation order are found in the RMC or Rietveld analysis, and the absence of cation order is supported by the MD modelling. We argue that the superlattice peaks originate from oxygen vacancy ordering and associated shift in the cation position away from the ideal fluorite site similar to that in the C-type structure, which is seen from the Rietveld refinements and the observed ordering in the MD modelling. The vacancies favour alignments in the , and especially the direction. Moreover, we find that such ordering might also be found to a small extent in La2Ce2O7, explaining the discernible modulated background between the fluorite peaks. The observed overlap of the main Bragg peaks between the fluorite and C-type phase supports the co-existence of vacancy ordered and more disordered domains. This is further supported by the observed similarity of the radial distribution functions as modelled with MD. The increase in long range oxygen vacancy order with increasing Nd-content in La2-xNdxCe2O7 corresponds well with the lower oxide ion conductivity in Nd2Ce2O7 compared to La2Ce2O7 reported earlier

Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging

CO2-enrichment experiments consistently show that rooting depth increases when trees are grown at elevated CO2 (eCO2), leading in some experiments to increased capture of available soil nitrogen (N) from deeper soil. However, the link between N uptake an

The Mississippian Section at Paddys Bluff, Crittenden County, Kentucky

Paddys Bluff (Figs. 1-3) is located on the south side of the Illinois Basin on the Cumberland River, 1.7 miles downstream from Dycusburg in Crittenden County, Ky., in Carter coordinate section 23-I-16 and ecoregion 71f of the Western Highland Rim of Kentucky (Woods and others, 2002). This bluff is on a right-descending bend 18 liver miles above its junction with the Ohio River at Smithland, Livingston County. The bluff (Figs. 4A, B) is locally famous as the location for a scene from the classic 1962 film, How the West Was Won,\u27 a winner of three Academy Awards, starling James Stewart, John Wayne, and others. We observed Paddys Bluff from the starboard Texas deck of the steamboat Della Queen one rainy morning in October 2005; the thick, persistent white bed midway in the bluff especially attracted our attention (Fig. 4). Paddys Bluff is the best natural exposure of Mississippian limestone between Barkley Dam and the Ohio River, a distance of 31 river miles. The bluff, some 1,700 feet long (Fig. 4), rises 160 feet above the Cumberland River and deflects it about 16° into a long westward reach, the river removing all talus at the base of the bluff. The bluff lies in a graben between two inferred faults st liking N40 to 45°E (Amos and Hayes, 1974). Readily seen in the limestones along the river at the base of the bluff is a prominent joint set parallel to these faults. This bluff is mapped on the Dycusburg geologic quadrangle map (Table 1) as the combined Salem and St. Louis Limestones (Amos and Hayes, 1974) and is capped by at least 15 feet of poorly exposed gravel of the Cretaceous Tuscaloosa Formation (Olive, 1980). Across the river less than 2 miles distant are scattered continental deposits of reddish brown Lafayette-type, sandy cobble-gravel (Olive, 1980), below which are outliers of the Cretaceous Tuscaloosa Formation; both cap hilltops of the same underlying Mississippian limestones. Why is Paddys Bluff of interest? There are at least six reasons to study it. First, can the Salem and St. Louis Limestones be individually identified at the bluff? If, in fact, they can be separated, the upper boundary of sequence S4 recognized in the Lake Cumberland area of south-central Kentucky by Khetani and Read (2002, Fig. 12) extends much farther west. Still another challenge is the enigmatic, massive, fine-grained, whitish-weathering carbonate mudstone bed, unit C of our section, high in the bluff. What does it represent? How widespread is it? Why do beds below rt have a strong petroliferous odor and not those above it? Why are some of the coral heads (Fig. 5) at Paddys Bluff overturned and others not? The last challenge is the bluff itself: Why is it there and how long has it been there

Measurement of the local Jahn-Teller distortion in LaMnO_3.006

The atomic pair distribution function (PDF) of stoichiometric LaMnO_3 has been measured. This has been fit with a structural model to extract the local Jahn-Teller distortion for an ideal Mn(3+)O_6 octahedron. These results are compared to Rietveld refinements of the same data which give the average structure. Since the local structure is being measured in the PDF there is no assumption of long-range orbital order and the real, local, Jahn-Teller distortion is measured directly. We find good agreement both with published crystallographic results and our own Rietveld refinements suggesting that in an accurately stoichiometric material there is long range orbital order as expected. The local Jahn-Teller distortion has 2 short, 2 medium and 2 long bonds.Comment: 5 pages, 3 postscript figures, minor change