203 research outputs found
Mixture including hydrogen and hydrocarbon having pressure-temperature stability
The invention relates to a method of storing hydrogen that employs a mixture of hydrogen and a hydrocarbon that can both be used as fuel. In one embodiment, the method involves maintaining a mixture including hydrogen and a hydrocarbon in the solid state at ambient pressure and a temperature in excess of about 10 K
Tetrahedrally coordinated carbonates in Earth's lower mantle
Carbonates are the main species that bring carbon deep into our planet
through subduction. They are an important rock-forming mineral group,
fundamentally distinct from silicates in Earth's crust in that carbon binds to
three oxygen atoms, while silicon is bonded to four oxygens. Here, we present
experimental evidence that under the sufficiently high pressures and high
temperatures existing in the lower mantle, ferromagnesian carbonates transform
to a phase with tetrahedrally coordinated carbons. Above 80 GPa, in situ
synchrotron infrared experiments show the unequivocal spectroscopic signature
of the high-pressure phase of (Mg,Fe)CO. Using ab-initio calculations, we
assign the new IR signature to C-O bands associated with tetrahedrally
coordinated carbon with asymmetric C-O bonds. Tetrahedrally coordinated
carbonates are expected to exhibit substantially different reactivity than low
pressure three-fold coordinated carbonates, as well as different chemical
properties in the liquid state. Hence this may have significant implications on
carbon reservoirs and fluxes and the global geodynamic carbon cycle
Families of superhard crystalline carbon allotropes induced via cold-compressed graphite and nanotubes
We report a general scheme to systematically construct two classes of
structural families of superhard sp3 carbon allotropes of cold compressed
graphite through the topological analysis of odd 5+7 or even 4+8 membered
carbon rings stemmed from the stacking of zigzag and armchair chains. Our
results show that the previously proposed M, bct-C4, W and Z allotropes belong
to our currently proposed families and that depending on the topological
arrangement of the native carbon rings numerous other members are found that
can help us understand the structural phase transformation of cold-compressed
graphite and carbon nanotubes (CNTs). In particular, we predict the existence
of two simple allotropes, R- and P-carbon, which match well the experimental
X-ray diffraction patterns of cold-compressed graphite and CNTs, respectively,
display a transparent wide-gap insulator ground state and possess a large
Vickers hardness comparable to diamond.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let
Differential effect of CLK SR Kinases on HIV-1 gene expression: potential novel targets for therapy
<p>Abstract</p> <p>Background</p> <p>RNA processing plays a critical role in the replication of HIV-1, regulated in part through the action of host SR proteins. To explore the impact of modulating SR protein activity on virus replication, the effect of increasing or inhibiting the activity of the Cdc2-like kinase (CLK) family of SR protein kinases on HIV-1 expression and RNA processing was examined.</p> <p>Results</p> <p>Despite their high homology, increasing individual CLK expression had distinct effects on HIV-1, CLK1 enhancing Gag production while CLK2 inhibited the virus. Parallel studies on the anti-HIV-1 activity of CLK inhibitors revealed a similar discrepant effect on HIV-1 expression. TG003, an inhibitor of CLK1, 2 and 4, had no effect on viral Gag synthesis while chlorhexidine, a CLK2, 3 and 4 inhibitor, blocked virus production. Chlorhexidine treatment altered viral RNA processing, decreasing levels of unspliced and single spliced viral RNAs, and reduced Rev accumulation. Subsequent experiments in the context of HIV-1 replication in PBMCs confirmed the capacity of chlorhexidine to suppress virus replication.</p> <p>Conclusions</p> <p>Together, these findings establish that HIV-1 RNA processing can be targeted to suppress virus replication as demonstrated by manipulating individual CLK function and identified chlorhexidine as a lead compound in the development of novel anti-viral therapies.</p
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