22 research outputs found
In situ phase behaviour of a high capacity LiCoPO4 electrode during constant or pulsed charge of a lithium cell
The phase changes that occur during lithium extraction from LiCoPO4 in lithium half-cells were studied using synchrotron X-ray diffraction. The existence of two two-phase regions with an intermediate phase present was observed. Significant variations in the composition of the phases of nominal stoichiometry LiCoPO4, Li2/3CoPO4 and CoPO4 resulted in unit cell volume variations. On current pulsing, lattice parameter shifts and phase recovery were directly observed
Assessing molecular simulation for the analysis of lipid monolayer reflectometry
Using molecular simulation to aid in the analysis of neutron reflectometry
measurements is commonplace. However, reflectometry is a tool to probe
large-scale structures, and therefore the use of all-atom simulation may be
irrelevant. This work presents the first direct comparison between the
reflectometry profiles obtained from different all-atom and coarse-grained
molecular dynamics simulations. These are compared with a traditional model
layer structure analysis method to determine the minimum simulation resolution
required to accurately reproduce experimental data. We find that systematic
limits reduce the efficacy of the MARTINI potential model, while the Berger
united-atom and Slipids all-atom potential models agree similarly well with the
experimental data. The model layer structure gives the best agreement, however,
the higher resolution simulation-dependent methods produce an agreement that is
comparable. Finally, we use the atomistic simulation to advise on possible
improvements that may be offered to the model layer structures, creating a more
realistic monolayer model.Comment: Electronic Supplementary Information (ESI) available: All
analysis/plotting scripts and figure files, allowing for a fully
reproducible, and automated, analysis workflow for the work presented is
available at \url{https://github.com/arm61/sim_vs_trad} (DOI:
10.5281/zenodo.2600729) under a CC BY-SA 4.0 licens
Towards a neutron and X-ray reflectometry environment for the study of solid–liquid interfaces under shear
Funder: Infineum UK LtdAbstract: A novel neutron and X-ray reflectometry sample environment is presented for the study of surface-active molecules at solid–liquid interfaces under shear. Neutron reflectometry was successfully used to characterise the iron oxide–dodecane interface at a shear rate of 7.0×102s-1 using a combination of conventional reflectometry theory coupled with the summation of reflected intensities to describe reflectivity from thicker films. Additionally, the structure adopted by glycerol monooleate (GMO), an Organic Friction Modifier, when adsorbed at the iron oxide–dodecane interface at a shear rate of 7.0×102s-1 was studied. It was found that GMO forms a surface layer that appears unaltered by the effect of shear, where the thickness of the GMO layer was found to be 24.3-10.2+9.9 Å under direct shear at 7.0×102s-1 and 25.8-5.2+4.4 Å when not directly under shear. Finally, a model to analyse X-ray reflectometry data collected with the sample environment is also described and applied to data collected at 3.0×103s-1
Direct observation of active material concentration gradients and crystallinity breakdown in LiFePO4 electrodes during charge/discharge cycling of lithium batteries
The phase changes that occur during discharge of an electrode comprised of LiFePO4, carbon, and PTFE binder have been studied in lithium half cells by using X-ray diffraction measurements in reflection geometry. Differences in the state of charge between the front and the back of LiFePO4 electrodes have been visualized. By modifying the X-ray incident angle the depth of penetration of the X-ray beam into the electrode was altered, allowing for the examination of any concentration gradients that were present within the electrode. At high rates of discharge the electrode side facing the current collector underwent limited lithium insertion while the electrode as a whole underwent greater than 50% of discharge. This behavior is consistent with depletion at high rate of the lithium content of the electrolyte contained in the electrode pores. Increases in the diffraction peak widths indicated a breakdown of crystallinity within the active material during cycling even during the relatively short duration of these experiments, which can also be linked to cycling at high rate
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Covalent Binding Sites of Victorin in Oat Leaf Tissues Detected by Anti-Victorin Polyclonal Antibodies
Structure, Nanomechanical Properties, and Wettability of Organized Erucamide Layers on a Polypropylene Surface
Towards a neutron and X-ray reflectometry environment for the study of solid-liquid interfaces under shear
The parton distribution functions (PDFs) are a non-negotiable input to almost
all theory predictions at hadron colliders. In this talk, I introduce PDF
determination by global analysis and discuss selected topics concerning recent
relevant data from HERA and the Tevatron, before giving some prospects for the
LHC. The combination of H1 and ZEUS cross sections reduces uncertainties and
will be an important input to future global PDF analyses. The theoretical
description of the heavy-quark contribution to structure functions at HERA has
a significant influence on predictions at the LHC. New W and Z data from the
Tevatron Run II provide important PDF constraints, but there are currently
problems describing the latest data on the lepton charge asymmetry from W -> l
nu decays. The Tevatron Run II jet production data prefer a smaller high-x
gluon than the previous Run I data, which impacts on predictions for Higgs
cross sections at the Tevatron. It is now possible to consistently calculate a
combined "PDF+alpha_S" uncertainty on hadronic cross sections, which is around
2-3% for the W and Z total cross sections at the LHC, reflecting their
potential as a "standard candle" to measure machine luminosity. Parton
luminosity functions are useful quantities for studying properties of hadronic
cross sections. Precision measurements at the LHC will provide further
constraints on PDFs as data accumulates in the early running period.Comment: 6 pages. Invited talk at the XXth Hadron Collider Physics Symposium
(HCP 2009), Evian, France, 16-20 November 200
Influence of the lipid backbone on electrochemical phase behavior
Sphingolipids are an important class of lipids found in mammalian cell membranes with important structural and signaling roles. They differ from another major group of lipids, the glycerophospholipids, in the connection of their hydrocarbon chains to their headgroups. In this study, a combination of electrochemical and structural methods has been used to elucidate the effect of this difference on sphingolipid behavior in an applied electric field. N-Palmitoyl sphingomyelin forms bilayers of similar coverage and thickness to its close analogue di-palmitoyl phosphatidylcholine. Grazing incidence diffraction data show slightly closer packing and a smaller chain tilt angle from the surface normal. Electrochemical IR results at low charge density show that the difference in tilt angle is retained on deposition to form bilayers. The bilayers respond differently to increasing electric field strength: chain tilt angles increase for both molecules, but sphingomyelin chains remain tilted as field strength is further increased. This behavior is correlated with disruption of the hydrogen-bonding network of small groups of sphingomyelin molecules, which may have significance for the behavior of molecules in lipid rafts in the presence of strong fields induced by ion gradients or asymmetric distribution of charged lipids