A silicon nanocrystal/polymer nanocomposite as a down-conversion layer in organic and hybrid solar cells.

Silicon nanocrystal (Si-nc) down-conversion is demonstrated to enhance organic and hybrid organic/inorganic bulk heterojunction solar cells based on PTB7:[70]PCBM bulk heterojunction devices. Surfactant free surface-engineered Si-ncs can be integrated into the device architecture to be optically active and provide a means of effective down-conversion of blue photons (high energy photons below ∼450 nm) into red photons (above ∼680 nm) leading to 24% enhancement of the photocurrent under concentrated sunlight. We also demonstrate that the down-conversion effect under 1-sun is enhanced in the case of hybrid solar cells where engineered Si-ncs are also included in the active layer.

Oncogenic Y641 mutations in EZH2 prevent Jak2/ß-TrCP-mediated degradation.

EZH2 (enhancer of zeste homolog 2) is a critical enzymatic subunit of the polycomb repressive complex 2 (PRC2), which trimethylates histone H3 (H3K27) to mediate gene repression. Somatic mutations, overexpression and hyperactivation of EZH2 have been implicated in the pathogenesis of several forms of cancer. In particular, recurrent gain-of-function mutations targeting EZH2 Y641 occur most frequently in follicular lymphoma and aggressive diffuse large B-cell lymphoma and are associated with H3K27me3 hyperactivation, which contributes to lymphoma pathogenesis. However, the post-translational mechanisms of EZH2 regulation are not completely understood. Here we show that EZH2 is a novel interactor and substrate of the SCF E3 ubiquitin ligase ß-TrCP (FBXW1). ß-TrCP ubiquitinates EZH2 and Jak2-mediated phosphorylation on Y641 directs ß-TrCP-mediated EZH2 degradation. RNA interference-mediated silencing of ß-TrCP or inhibition of Jak2 results in EZH2 stabilization with attendant increase in H3K27 trimethylation activity. Importantly, the EZH2(Y641) mutants recurrently implicated in lymphoma pathogenesis are unable to bind ß-TrCP. Further, endogenous EZH2(Y641) mutants in lymphoma cells exhibit increased EZH2 stability and H3K27me3 hyperactivity. Our studies demonstrate that ß-TrCP has an important role in controlling H3K27 trimethylation activity and lymphoma pathogenesis by targeting EZH2 for degradation.

First astronomical detection of the cumulene carbon chain molecule H2C6 in TMC-1.

The cumulene carbenes are important components of hydrocarbon chemistry in low-mass star-forming cores. Here we report the first astronomical detection of the long-chain cumulene carbene H2C6 in the interstellar cloud TMC-1, from observations of two of its rotational transitions: J(K,K') = 7(1,7) --> 6(1,6) at 18.8 GHz and 8(1,8) --> 7(1,7) at 21.5 GHz, using NASA's Deep Space Network 70 m antenna at Goldstone, California. In addition we also observed the shorter cumulene carbene H2C4 at the same position. The fractional abundance of H2C6 relative to H2 is about 4.7 x 10(-11) and that of H2C4 is about 4.1 x 10(-9). The abundance of H2C6 is in fairly good agreement with gas-phase chemical models for young molecular cloud cores, but the abundance of H2C4 is significantly larger than predicted.

The IRS 1 circumstellar disk, and the origin of the jet and CO outflow in B5.

We report the discovery of the inner edge of the high velocity CO outflow associated with the bipolar jet originating from IRS 1 in Barnard 5 and the first ever resolution of its circumstellar disk in the 2.6 mm dust continuum and C18O. From high spatial resolution observations made with the Owens Valley Millimeter Array we are able to locate the origin of the outflow to within approximately 500 AU on either side of IRS 1 and apparently at the edge of, or possibly within, its circumstellar disk. The orientation of the continuum disk is perpendicular to the highly collimated jet outflow recently seen in optical emission at much farther distances. The disk has been detected in C18O giving a disk mass approximately 0.16 M (solar). Our HCO+ and HCN maps indicate significant chemical differentiation in the circumstellar region on small scales with HCO+ tracing an extended disk of material. The 12CO interferometer maps of the outflow show two conelike features originating at IRS 1, the blue one fanning open to the northeast and the red one to the southwest. The vertices of the cones are on either side of the circumstellar disk and have a projected opening angle of about 90 degrees. The intrinsic opening angle is in the range of 60 degrees-90 degrees which leads to significant interaction between outflow and infall.

Evolutionary status of the pre-protostellar core L1498.

L1498 is a classic example of a dense cold pre-protostellar core. To study the evolutionary status, the structure, dynamics, and chemical properties of this core we have obtained high spatial and high spectral resolution observations of molecules tracing densities of 10(3)-10(5) cm-3. We observed CCS, NH3, C3H2, and HC7N with NASA's DSN 70 m antennas. We also present large-scale maps of C18O and 13CO observed with the AT&T 7 m antenna. For the high spatial resolution maps of selected regions within the core we used the VLA for CCS at 22 GHz, and the Owens Valley Radio Observatory (OVRO) MMA for CCS at 94 GHz and CS (2-1). The 22 GHz CCS emission marks a high-density [n(H2) > 10(4) cm -3] core, which is elongated with a major axis along the SE-NW direction. NH3 and C3H2 emissions are located inside the boundary of the CCS emission. C18O emission traces a lower density gas extending beyond the CCS boundary. Along the major axis of the dense core, CCS, NH3 and C3H2 emission show evidence of limb brightening. The observations are consistent with a chemically differentiated onion-shell structure for the L1498 core, with NH3 in the inner and CCS in the outer parts of the core. The high angular resolution (9"-12") spectral line maps obtained by combining NASA Goldstone 70 m and VLA data resolve the CCS 22 GHz emission in the southeast and northwest boundaries into arclike enhancements, supporting the picture that CCS emission originates in a shell outside the NH3 emitting region. Interferometric maps of CCS at 94 GHz and CS at 98 GHz show that their emitting regions contain several small-scale dense condensations. We suggest that the differences between the CCS, CS, C3H2, and NH3 emission are caused by a time-dependent effect as the core evolves slowly. We interpret the chemical and physical properties of L1498 in terms of a quasi-static (or slowly contracting) dense core in which the outer envelope is still growing. The growth rate of the core is determined by the density increase in the CCS shell resulting from the accretion of the outer low-density gas traced by C18O. We conclude that L1498 could become unstable to rapid collapse to form a protostar in less than 5 x 10(6) yr.