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Mixed-matrix membranes (MMMs) are based on polymeric membranes filled with inorganic particles as a means to improve their gas separation performance. In this study, MMMs were prepared from polysulfone (PSf) containing embedded nonporous fumed silica nanoparticles and the gas permeation properties of the resulting membranes were investigated. Physical properties such as film density, thermal degradation and glass transition temperature of PSf/silica MMMs were characterized. The distribution of the silica nanoparticles in PSf was observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Furthermore, the interface between the polymer and silica agglomerates was studied in relation with the gas transport properties. The gas permeabilities of hydrogen, helium, oxygen, nitrogen, methane, and carbon dioxide were measured as a function of silica volume fraction and diffusion and solubility coefficients were determined by the time-lag method. The effect of silica nanoparticles in PSf membranes on gas permeability is in contrast with predictions based on the Maxwell model. The O 2 permeability is approximately four times higher and CH 4 permeability is over five times greater than in a pure PSf membrane. However, the performance comprising permeability versus selectivity of PSf/silica MMMs for O 2 /N 2 and CO 2 /CH 4 follows a similar slope to that of the trade-off upper bound with increasing silica content. Crown

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Gas transport behavior of mixed-matrix membranes composed of silica nanoparticles in a polymer of intrinsic microporosity (PIM-1) Ahn, Juhyeon; Chung, Wook-Jin; Pinnau, Ingo; Song, Jingshe; Du, Naiying; Robertson, Gilles P.; Guiver, Michael D.This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Recently, high-free volume, glassy ladder-type polymers, referred to as polymers of intrinsic microporosity (PIM), have been developed and their reported gas transport performance exceeded the Robeson upper bound trade-off for O 2 /N 2 and CO 2 /CH 4 . The present work reports the gas transport behavior of PIM-1/silica nanocomposite membranes. The changes in free volume, as well as the presence and volume of the void cavities, were investigated by analyzing the density, thermal stability, and nano-structural morphology. The enhancement in gas permeability (e.g., He, H 2 ,O 2 ,N 2 , and CO 2 ) with increasing filler content shows that the trend is related to the true silica volume and void volume fraction. Crown

Spatial patterns of transcriptional activity in the chromosome of Escherichia coli

Analysis of the transcriptional activity in Escherichia coli K12 revealed an asymmetry in the distribution of transcriptional patterns along the bacterial chromosome and showed that spatial patterns of transcription could be modulated pharmacologically and genetically. Abstract Background: Although genes on the chromosome are organized in a fixed order, the spatial correlations in transcription have not been systematically evaluated. We used a combination of genomic and signal processing techniques to investigate the properties of transcription in the genome of Escherichia coli K12 as a function of the position of genes on the chromosome.

Suchy FJ. Histone H3K4 trimethylation by MLL3 as part of ASCOM complex is critical for NR activation of bile acid transporter genes and is downregulated in cholestasis. Am J Physiol Gastrointest Liver Physiol 300: G771-G781, 2011. First published February 17, 2010 doi:10.1152/ajpgi.00499.2010.-The nuclear receptor Farnesoid x receptor (FXR) is a critical regulator of multiple genes involved in bile acid homeostasis. The coactivators attracted to promoters of FXR target genes and epigenetic modifications that occur after ligand binding to FXR have not been completely defined, and it is unknown whether these processes are disrupted during cholestasis. Using a microarray, we identified decreased expression of mixed lineage leukemia 3 (MLL3), a histone H3 lysine 4 (H3K4) lysine methyl transferase at 1 and 3 days of post-common bile duct ligation (CBDL) in mice. Chromatin immunoprecipitation analysis (ChIP) analysis revealed that H3K4me3 of transporter promoters by MLL3 as part of activating signal cointegrator-2 -containing complex (ASCOM) is essential for activation of bile salt export pump (BSEP), multidrug resistance associated protein 2 (MRP2), and sodium taurocholate cotransporting polypeptide (NTCP) genes by FXR and glucocorticoid receptor (GR). Knockdown of nuclear receptor coactivator 6 (NCOA6) or MLL3/MLL4 mRNAs by small interfering RNA treatment led to a decrease in BSEP and NTCP mRNA levels in hepatoma cells. Human BSEP promoter transactivation by FXR/RXR was enhanced in a dose-dependent fashion by NCOA6 cDNA coexpression and decreased by AdsiNCOA6 infection in HepG2 cells. GST-pull down assays showed that domain 3 and 5 of NCOA6 (LXXLL motifs) interacted with FXR and that the interaction with domain 5 was enhanced by chenodeoxycholic acid. In vivo ChIP assays in HepG2 cells revealed ligand-dependent recruitment of ASCOM complex to FXR element in BSEP and GR element in NTCP promoters, respectively. ChIP analysis demonstrated significantly diminished recruitment of ASCOM complex components and H3K4me3 to Bsep and Mrp2 promoter FXR elements in mouse livers after CBDL. Taken together, these data show that the "H3K4me3" epigenetic mark is essential to activation of BSEP, NTCP, and MRP2 genes by nuclear receptors and is downregulated in cholestasis. hepatoma cells; microarray; epigenetics; gene regulation; activating signal cointegrator-2-containing complex; H3 lysine 4; nuclear receptors; mixed lineage leukemia 3 LIGAND-ACTIVATED NUCLEAR RECEPTORS (NRs), such as Farnesoid x receptor (FXR) and glucocorticoid receptor (GR), initiate transcription by binding to specific DNA regulatory elements in promoters of target genes and recruiting coactivator proteins to modify chromatin structure and induce assembly of the transcription complex containing RNA polymerase II (PolII) (2, 3, 6, 18). The primary coactivators including the p160 coactivators such as TIF2/GRIP-1/SRC-2 and related members of the p300 family bind directly to ligand-activated NRs and recruit an array of secondary coactivators such as p300/cAMP resp...

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In Li‐rich cation‐disordered rocksalt oxide cathodes (DRX), partial fluorine substitution in the oxygen anion sublattice can increase the capacity contribution from transition‐metal (TM) redox while reducing that from the less reversible oxygen redox. To date, limited fluorination substitution has been achieved by introducing LiF precursor during the solid‐state synthesis. To take full advantage of the fluorination effect, however, a higher F content is desired. In the present study, the successful use of a fluorinated polymeric precursor is reported to increase the F solubility in DRX and the incorporation of F content up to 10–12.5 at% into the rocksalt lattice of a model Li‐Mn‐Nb‐O (LMNO) system, largely exceeding the 7.5 at% limit achieved with LiF synthesis. Higher F content in the fluorinated‐DRX (F‐DRX) significantly improves electrochemical performance, with a reversible discharge capacity of ≈255 mAh g−1 achieved at 10 at% of F substitution. After 30 cycles, up to a 40% increase in capacity retention is achieved through the fluorination. The study demonstrates the feasibility of using a new and effective fluorination process to synthesize advanced DRX cathode materials.