4,949 research outputs found

    Cell-type, Dose, and Mutation-type Specificity Dictate Mutant p53 Functions In Vivo

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    SummaryThe specific roles of mutant p53's dominant-negative (DN) or gain-of-function (GOF) properties in regulating acute response and long-term tumorigenesis is unclear. Using “knockin” mouse strains expressing varying R246S mutant levels, we show that the DN effect on transactivation is universally observed after acute p53 activation, whereas the effect on cellular outcome is cell-type specific. Reducing mutant p53 levels abrogated the DN effect. Mutant p53's DN effect protected against radiation-induced death but did not accentuate tumorigenesis. Furthermore, the R246S mutant did not promote tumorigenesis compared to p53−/− mice in various models, even when MDM2 is absent, unlike the R172H mutant. Together, these data demonstrate that mutant p53's DN property only affects acute responses, whereas GOF is not universal, being mutation-type specific

    High-Velocity Jets and Slowly Rotating Envelope in B335

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    We have performed detailed imaging and analyses of SMA observations in 230 GHz continuum, 12CO (2-1), 13CO (2-1), and C18O (2-1) emission toward B335, a Bok globule with an embedded Class 0 source (Lbol ~ 1.5 Lsun). We report the first discover of high-velocity 12CO jets with a size of ~ 900 AU x 1500 AU along the E-W direction in B335. The estimated mass-loss rate (~ 2.3 x 10^-7 Msun yr^-1) and the momentum flux (~ 3.7 x 10^-5 Msun yr^-1 km s^-1) of the 12CO jets in B335 are one order of magnitude lower than those of other 12CO jets in more luminous sources such as HH 211 (Lbol ~ 3.6 Lsun) and HH 212 (Lbol ~ 14 Lsun). The weaker jet activity in B335 could be due to the lower active accretion onto the central protostar. The C18O emission shows a compact (~ 1500 AU) condensation associated with the central protostar, and it likely traces the protostellar envelope around B335. The envelope exhibits a velocity gradient from the east (blueshifted) to west (redshifted) that can be interpreted as an infalling motion. The estimated central stellar mass, the mass infalling rate, and the accretion luminosity are 0.04 Msun, 6.9 x 10^-6 Msun yr^-1, and 2.1 Lsun, respectively. On the other hand, there is no clear velocity gradient perpendicular to the outflow axis in the C18O envelope, suggesting little envelope rotation on a hundred-AU scale. The upper limits of the rotational velocity and specific angular momentum were estimated to be 0.04 km s^-1 and 7.0 x 10^-5 km s^-1 pc at a radius of 370 AU, respectively. The specific angular momentum and the inferred Keplerian radius (~ 6 AU) in B335 are 1 - 2 orders of magnitude smaller than those in other more-evolved sources. Possible scenarios to explain the lower specific angular momentum in B335 are discussed.Comment: 35 pages, 11 figures, and ApJ accepted; http://stacks.iop.org/0004-637X/710/178

    Carbon-Dot-Sensitized, Nitrogen-Doped TiO2in Mesoporous Silica for Water Decontamination through Nonhydrophobic Enrichment-Degradation Mode

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    Mesoporous silica synthesized from the co-condensation of tetraethoxysilane and silylated carbon dot containing amide group has been adopted as the carrier for the in-situ growth of TiO2 through an impregnation-hydrothermal crystallization process. Benefitted from the initial complexing between the titania precursor and carbon dot, highly dispersed anatase TiO2 nanoparticles can be formed inside the mesoporous channel. The hybrid material possesses ordered hexagonal mesostructure with a p6mm symmetry, high specific surface area (446.27 m2g-1), large pore volume (0.57 cm3g-1), uniform pore size (5.11 nm) and a wide absorption band between 300-550 nm. TiO2 nanocrystals are anchored to carbon dot through bonds of Ti-O-N and Ti-O-C as revealed by X-ray photoelectron spectroscopy. Moreover, the nitrogen doping of TiO2 is also verified by the formation of Ti-N bond. This composite shows excellent adsorption capability to organic 2, 4-dichlorophenol and acid orange 7 with electron-deficient aromatic ring through the electron donor-acceptor interaction between carbon dot and organics instead of hydrophobic effect as analyzed by the contact angle analysis, which can be photocatalytically recycled through visible light irradiation after the adsorption. The narrowed bandgap by nitrogen doping and the photosensitization effect of carbon dot are revealed to be co-responsible for the visible-light activity of TiO2. The adsorption capacity does not suffer obvious loss after being recycled 3 times

    Compositionally Complex Perovskite Oxides as a New Class of Li-Ion Solid Electrolytes

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    Compositionally complex ceramics (CCCs), including high-entropy ceramics (HECs) as a subclass, offer new opportunities of materials discovery beyond the traditional methodology of searching new stoichiometric compounds. Herein, we establish new strategies of tailoring CCCs via a seamless combination of (1) non-equimolar compositional designs and (2) controlling microstructures and interfaces. Using oxide solid electrolytes for all-solid-state batteries as an exemplar, we validate these new strategies via discovering a new class of compositionally complex perovskite oxides (CCPOs) to show the possibility of improving ionic conductivities beyond the limit of conventional doping. As an example (amongst the 28 CCPOs examined), we demonstrate that the ionic conductivity can be improved by >60% in (Li0.375Sr0.4375)(Ta0.375Nb0.375Zr0.125Hf0.125)O3-{\delta}, in comparison with the state-of-art (Li0.375Sr0.4375)(Ta0.75Zr0.25)O3-{\delta} (LSTZ) baseline, via maintaining comparable electrochemical stability. Furthermore, the ionic conductivity can be improved by another >70% via grain boundary (GB) engineering, achieving >270% of the LSTZ baseline. This work suggests transformative new strategies for designing and tailoring HECs and CCCs, thereby opening a new window for discovering materials for energy storage and many other applications

    TMRT observations of 26 pulsars at 8.6 GHz

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    Integrated pulse profiles at 8.6~GHz obtained with the Shanghai Tian Ma Radio Telescope (TMRT) are presented for a sample of 26 pulsars. Mean flux densities and pulse width parameters of these pulsars are estimated. For eleven pulsars these are the first high-frequency observations and for a further four, our observations have a better signal-to-noise ratio than previous observations. For one (PSR J0742-2822) the 8.6~GHz profiles differs from previously observed profiles. A comparison of 19 profiles with those at other frequencies shows that in nine cases the separation between the outmost leading and trailing components decreases with frequency, roughly in agreement with radius-to-frequency mapping, whereas in the other ten the separation is nearly constant. Different spectral indices of profile components lead to the variation of integrated pulse profile shapes with frequency. In seven pulsars with multi-component profiles, the spectral indices of the central components are steeper than those of the outer components. For the 12 pulsars with multi-component profiles in the high-frequency sample, we estimate the core width using gaussian fitting and discuss the width-period relationship.Comment: 33 pages, 49 figures, 5 Tables; accepted by Ap