The transcriptional landscape of αß T cell differentiation.

The differentiation of αßT cells from thymic precursors is a complex process essential for adaptive immunity. Here we exploited the breadth of expression data sets from the Immunological Genome Project to analyze how the differentiation of thymic precursors gives rise to mature T cell transcriptomes. We found that early T cell commitment was driven by unexpectedly gradual changes. In contrast, transit through the CD4(+)CD8(+) stage involved a global shutdown of housekeeping genes that is rare among cells of the immune system and correlated tightly with expression of the transcription factor c-Myc. Selection driven by major histocompatibility complex (MHC) molecules promoted a large-scale transcriptional reactivation. We identified distinct signatures that marked cells destined for positive selection versus apoptotic deletion. Differences in the expression of unexpectedly few genes accompanied commitment to the CD4(+) or CD8(+) lineage, a similarity that carried through to peripheral T cells and their activation, demonstrated by mass cytometry phosphoproteomics. The transcripts newly identified as encoding candidate mediators of key transitions help define the 'known unknowns' of thymocyte differentiation.

Identification of transcriptional regulators in the mouse immune system.

The differentiation of hematopoietic stem cells into cells of the immune system has been studied extensively in mammals, but the transcriptional circuitry that controls it is still only partially understood. Here, the Immunological Genome Project gene-expression profiles across mouse immune lineages allowed us to systematically analyze these circuits. To analyze this data set we developed Ontogenet, an algorithm for reconstructing lineage-specific regulation from gene-expression profiles across lineages. Using Ontogenet, we found differentiation stage-specific regulators of mouse hematopoiesis and identified many known hematopoietic regulators and 175 previously unknown candidate regulators, as well as their target genes and the cell types in which they act. Among the previously unknown regulators, we emphasize the role of ETV5 in the differentiation of γδ T cells. As the transcriptional programs of human and mouse cells are highly conserved, it is likely that many lessons learned from the mouse model apply to humans.

The interaction of ethylammonium tetrafluoroborate [EtNH3+][BF4-] ionic liquid on the Li(001) surface: towards understanding early SEI formation on Li metal.

The electrode cyclability of high energy density Li-metal batteries can be significantly improved with the use of ionic liquid (IL) based electrolytes, which can ameliorate device issues through the suppression of dendrite initiation and propagation. This enhancement is often attributed to the formation of a stable solid electrolyte interphase (SEI) layer between the electrode and the electrolyte. In this paper, we have modelled the adsorption of the IL ethylammonium tetrafluoroborate [EtNH3+][BF4-] on a Li(001) surface, using density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations to capture the initial stages of the SEI layer formation, and gain a greater insight into the stability of [EtNH3+][BF4-] on a lithium surface. Eleven unique minimum energy structures of the [EtNH3+][BF4-] pair adsorbed on the Li(001) surface were found, having binding energies between -1.80 eV to -1.58 eV. The interface between the electrolyte molecules and electrode surface were stabilized by the formation of Li-F bonds between the anion and Li surface leading to formation of Lix-BF4 clusters, where x = 2-4. This was accompanied by a transfer of charge from the lithium surface to the cation and anion. The thermal stability of the IL was investigated via AIMD simulations, and the IL was found not to spontaneously dissociate on the surface at room temperature or at an elevated temperature of 157 °C within the examined simulation time of 4.64 ps, with Lix-BF4 clusters forming early into the simulations (<1 ps). These findings provide useful information for future development of Li-metal batteries.

A Hybrid Anion for Ionic Liquid and Battery Electrolyte Applications: Half Triflamide, Half Carbonate.

The synthesis of a new imide type anion, methylcarbonate(trifluoromethylsulfonyl)imide (MCTFSI) is described and the physicochemical properties of its sodium and N-butyl-N-methyl pyrrolidinium salts as well as structural information obtained by X-ray diffraction studies of the sodium salt are discussed in terms of charge delocalisation, coordination chemistry and electrochemical behaviour with respect to the analogous imdides bis(trifluoromethanesulfonyl)imide (TFSI) and bis(fluorosulfonyl)imide (FSI). The insight obtained from studying the new anion informs and reemphasizes the concept of weakly coordinating anions and coordination chemistry in designing electrolyte salts.

Effect of Pseudomonas fluorescens on Buried Steel Pipeline Corrosion.

Buried steel infrastructure can be a source of iron ions for bacterial species, leading to microbiologically influenced corrosion (MIC). Localized corrosion of pipelines due to MIC is one of the key failure mechanisms of buried steel pipelines. In order to better understand the mechanisms of localized corrosion in soil, semisolid agar has been developed as an analogue for soil. Here, Pseudomonas fluorescens has been introduced to the system to understand how bacteria interact with steel. Through electrochemical testing including open circuit potentials, potentiodynamic scans, anodic potential holds, and electrochemical impedance spectroscopy it has been shown that P. fluorescens increases the rate of corrosion. Time for oxide and biofilms to develop was shown to not impact on the rate of corrosion but did alter the consistency of biofilm present and the viability of P. fluorescens following electrochemical testing. The proposed mechanism for increased corrosion rates of carbon steel involves the interactions of pyoverdine with the steel, preventing the formation of a cohesive passive layer, after initial cell attachment, followed by the formation of a metal concentration gradient on the steel surface.

The importance of transport property studies for battery electrolytes: revisiting the transport properties of lithium-N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide mixtures.

Transport properties are examined in some detail for samples of the low temperature molten salt N-propyl-N-methyl pyrrolidinium bis(fluorosulfonyl)imide [Pyr13][FSI] from two different commercial suppliers. A similar set of data is presented for two different concentrations of binary lithium-[Pyr13][FSI] salt mixtures from one supplier. A new and significantly different production process is used for the synthesis of Li[FSI] as well as the [Pyr13]+ salt used in the mixtures. Results for the viscosity, conductivity, and self-diffusion coefficients, together with the density and expansivity and apparent molar volume, are reported over the temperature range of (0 to 80) °C. The data for neat [Pyr13][FSI] are discussed in the context of velocity cross correlation (VCC or fij) and Laity resistance (rij) coefficients. Unusually, f+- ∼ f++ < f--. The three resistance coefficients are of similar magnitude indicating all three ion-ion interactions contribute to the transport properties, not just the cation-anion interaction. The composition dependence of the transport properties is compared to previously reported data for the same and related compounds: in contrast to high-temperature molten salt mixtures, this is an exponential dependence. The Nernst-Einstein parameter Δ, which contains information on the correlations of the ionic velocities and is determined by differences in the VCC for the various ion-ion combinations, was calculated for both the neat ionic liquid and its binary mixture. It increases with increasing lithium concentration. The new data set also allows some conclusions with regards to the lithium-[FSI]- coordination environment.

Physical properties of high Li-ion content N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide based ionic liquid electrolytes.

Electrolytes based on bis(fluorosulfonyl)imide (FSI) with a range of LiFSI salt concentrations were characterized using physical property measurements, as well as NMR, FT-IR and Raman spectroscopy. Different from the behavior at lower concentrations, the FSI electrolyte containing 1 : 1 salt to IL mole ratio showed less deviation from the KCl line in the Walden plot, suggesting greater ionic dissociation. Diffusion measurements show higher mobility of lithium ions compared to the other ions, which suggests that the partial conductivity of Li(+) is higher at this higher composition. Changes in the FT-IR and Raman peaks indicate that the cis-FSI conformation is preferred with increasing Li salt concentration.

Anatomy, histology, development and functions of Ossa cordis: A review.

This systematic review highlights the similarities and variations in Ossa cordis prevalence, histology and anatomical location between differing veterinary species and in humans. In addition, it also identifies associated factors such as aging and cardiovascular disease for each species in relation to functional roles and developmental mechanisms that these bone structures may play. The potential functions of Ossa cordis are presented, ranging from aiding cardiac contraction and conduction, providing cardiac structure, and protecting components of the heart, through to counteracting high mechanical stress. Furthermore, this review discusses the evidence and rationale behind the theories regarding the formation and development of Ossa cordis in different veterinary species and in people.

In situ NMR observation of the formation of metallic lithium microstructures in lithium batteries.

Lithium metal has the highest volumetric and gravimetric energy density of all negative-electrode materials when used as an electrode material in a lithium rechargeable battery. However, the formation of lithium dendrites and/or 'moss' on the metal electrode surface can lead to short circuits following several electrochemical charge-discharge cycles, particularly at high rates, rendering this class of batteries potentially unsafe and unusable owing to the risk of fire and explosion. Many recent investigations have focused on the development of methods to prevent moss/dendrite formation. In parallel, it is important to quantify Li-moss formation, to identify the conditions under which it forms. Although optical and electron microscopy can visually monitor the morphology of the lithium-electrode surface and hence the moss formation, such methods are not well suited for quantitative studies. Here we report the use of in situ NMR spectroscopy, to provide time-resolved, quantitative information about the nature of the metallic lithium deposited on lithium-metal electrodes.

Transport properties and phase behaviour in binary and ternary ionic liquid electrolyte systems of interest in lithium batteries.

A binary ionic liquid (IL) system based on a common cation, N-methyl-N-propylpyrrolidinium (C(3) mpyr(+)), and either bis(trifluoromethanesulfonyl)imide (NTf(2) (-)) or bis(fluorosulfonyl) imide (FSI(-) as the anion is explored over its entire composition range. Phase behavior, determined by DSC, shows the presence of a eutectic temperature at 247 K and composition around an anion ratio of 2:1 (FSI(-) :NTf(2)(-)) with the phase diagram for this system proposed (under the thermal conditions used). Importantly for electrochemical devices, the single phase melting transition at the eutectic is well below ambient temperatures (247 K). To investigate the effect of such anion mixing on the lithium ion speciation, conductivity and PFG-NMR diffusion measurements were performed in both the binary IL system as well as the Li-NTf(2) -containing ternary system. The addition of the lithium salt to the mixed IL system resulted in a decrease in conductivity, as is commonly observed in the single-component IL systems. For a fixed lithium salt composition, both conductivity and ion diffusion have linear behaviour as a function of the anion ratio, however, the rate of change of the diffusion coefficient seems greater in the presence of lithium. From the application point of view, the addition of the FSI(-) to the NTf(2)(-) IL results in a considerable increase in lithium ion diffusivity at room temperature and no evidence of additional complex ion behaviour.

Predicting properties of new ionic liquids: density functional theory and experimental studies of tetra-alkylammonium salts of (thio)carboxylate anions, RCO2⁻, RCOS⁻ and RCS2⁻.

Density functional theory calculations of alkyl-carboxylate anions and their sulfur substituted variants are presented here as an aid for the development of new ionic liquids. Electron transfer both within the anion, and between the anion and cation of an ion pair, are described using natural bond order analysis, using tetraethylammonium as a common cation. The overall stabilising effect of this electron transfer is quantified for the series of anions, and is found to correlate with clear trends in ion-pair binding energy. These and other electronic properties determine which compounds are synthesised, and experimental results validate the computational results. In combination with tetraethylammonium, a carboxylate with an unsaturated alkyl chain produces an ionic liquid at room temperature. However, computations suggest that sulfur substituted anions will produce a lower melting point and perhaps more fluid ionic liquid, but one which would be less stable against oxidation.

Lithium-Ion Battery Separators for Ionic-Liquid Electrolytes: A Review.

Ionic liquids (ILs) are widely studied as a safer alternative electrolyte for lithium-ion batteries. The properties of IL electrolytes compared to conventional electrolytes make them more thermally stable, but they also have poor wetting with commercial separators. In a lithium-ion battery, the electrolyte should completely wet out the separator and electrodes to reduce the cell internal resistance. Investigations of cell materials with IL electrolytes have shown that the wetting issues in IL-electrolyte cells are most likely due to poor separator compatibility, not electrode compatibility. A compatible separator must be developed before IL electrolytes can be used in commercial lithium-ion batteries. Herein, separators for IL electrolytes, including commercial and novel separators, are reviewed. Separators with different processing methods, polymers, additives, and different IL electrolytes are considered. Collated, the separator studies show a strong correlation between ionic conductivity and membrane porosity, even more than the electrolyte type. The challenge of a suitable separator for IL electrolytes is not solved yet. Herein, it is revealed that a separator for IL electrolytes will most likely require a combination of high thermal and mechanical stability polymer, ceramic additives, and an optimized manufacturing process.

Ordered Mesoporous Graphitic Carbon/Iron Carbide Composites with High Porosity as a Sulfur Host for Li-S Batteries.

The lithium-sulfur battery (LSB) is a promising candidate for future energy storage but faces technological challenges including the low electronic conductivity of sulfur and the solubility of intermediates during cycling. Additionally, current host materials often lack sufficient conductivity and porosity to raise the sulfur loading to over 80 wt %. Here, ordered mesoporous graphitic carbon/iron carbide nanocomposites were prepared via an evaporation-induced self-assembly process using soluble resol, prehydrolyzed tetraethyl orthosilicate (TEOS), and iron(III) chloride as the carbon, silica (SiO2), and iron precursors, respectively. Graphitization and SiO2 etching were conducted simultaneously via Teflon-assisted, solid-state decomposition at high temperature. A high surface area (∼3100 m2 g-1), large pore volume (∼3.3 cm3 g-1), and graphitized carbon frame were achieved, giving a high sulfur loading (85 wt %) while tolerating volumetric expansion during discharge. Electrochemical testing of a LSB containing the composite/sulfur cathode exhibited a superior reversible capacity exceeding 1300 mAh g-1 at a moderate current (C/10) and a low decay in capacity of 9% after 500 cycles at C/5. The interaction between mesoporous graphitic carbon and sulfur is proposed.

Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO4 and FePO4.

Experimental measurements used to validate previous electronic band structure calculations for olivine LiFePO4 and its delithiated phase, FePO4, have been re-investigated in this study. Experimental band gaps of LiFePO4 and FePO4 have been determined to be 6.34 eV and 3.2 eV by electron energy loss spectroscopy (EELS) and UV-Vis-NIR diffusion reflectance spectroscopy, respectively. X-ray photoemission (XPS) and Raman spectroscopy show that the surfaces of very carefully synthesized LiFePO4 display Li-depletion, which affects optical reflectance determinations. Based on these experimental measurements, functionals for density functional theory (DFT) calculations of the electronic properties have been revisited. Overall, electronic structures of LiFePO4 and FePO4 calculated using sX-LDA show the best self-consistent match to combined experimentally determined parameters. Furthermore, the open-circuit voltages of the LiFePO4 half-cell have been interpreted in terms of both Fermi levels and Gibbs free energies, which provides additional support for the electronic band structures determined by this research.

Purification or contamination? The effect of sorbents on ionic liquids.

Commonly used for purification, alumina and silica are found to contaminate ionic liquids with particles; these particles cannot be removed easily and can have a non-negligible impact on the electrochemical, spectroscopic and physical properties of an ionic liquid, including its nucleation and crystallisation kinetics.

Catching TFSI: A Computational-Experimental Approach to ß-Cyclodextrin-Based Host-Guest Systems as electrolytes for Li-Ion Batteries.

Cyclodextrins (CDs) are pyranoside-based macromolecules with a hydrophobic cavity to encapsulate small molecules. They are used as molecular vehicles, for instance in pharmaceutical drug delivery or as solubility enhancer of monomers for their polymerization in aqueous solution. In this context, it was discovered about 10 years ago that the bis(trifluoromethylsulonyl)imide (TFSI) anion forms host-guest complexes with ßCD in aqueous media. This sparked interest in using the TFSI anion in lithium-based battery electrolytes open for its encapsulation by ßCD as an attractive approach to increase the contribution of the cation to the total ion conductivity. By using semi-empirical quantum mechanical (SQM) methods and the conductor-like screening model for a real solvent (COSMO-RS), a randomly methylated ßCD (RMßCD) is here identified as a suitable host for TFSI when using organic solvents often used in battery technology. By combining molecular dynamics (MD) simulations with different NMR and FTIR experiments, the formation of the corresponding RMßCD-TFSI complex was investigated. Finally, the effects of the addition RMßCD to a set of electrolytes on the ion conductivity are measured and explained using three distinct scenarios.

A supramolecular nematic phase in sulfonated polyaramides.

A water-soluble polyaramide "sulfo-invert-PPTA" surprisingly, already at a molecular weight of 10,000 g mol(-1), exhibits a nematic liquid crystalline phase in water at very low polymer concentrations, around 1-2wt%, indicating that supramolecular assemblies of molecules are the building blocks of the nematic phase.

Transport properties of ionic liquid electrolytes with organic diluents.

Ionic liquids (ILs) form a novel class of electrolytes with unique properties that make them attractive candidates for electrochemical devices. In the present study a range of electrolytes were prepared based on the IL N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl) amide ([C(3)mpyr][NTf(2)]) and LiNTf(2) salt. The traditional organic solvent diluents vinylene carbonate (VC), ethylene carbonate (EC), tetrahydrofuran (THF) and toluene were used as additives at two concentrations, 10 and 20 mol%, leading to a ratio of about 0.6 and 1.3 diluent molecules to lithium ions, respectively. Most promisingly, the lithium ions see the greatest effect in the presence of all the diluents, except toluene, producing a lithium self-diffusion coefficient of almost a factor of 2.5 times greater for THF at 20 mol%. Raman spectroscopy subtly indicates that THF may be effectively breaking up a small portion of the lithium ion-anion interaction. While comparing the measured molar conductivity to that calculated from the self-diffusion coefficients of the constituents indicates that the diluents cause an increase in the overall ion clustering. This study importantly highlights that selective ion transport enhancement is achievable in these materials.