Surface soil (0–10
cm) samples from 53 sampling sites including rural and urban areas of Hong Kong were collected and analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs). Total PAH ...concentrations were in the range of 7.0–410
μg
kg
−1 (dry wt), with higher concentrations in urban soils than that in rural soils. The three predominant PAHs were Fluoranthene, Naphthalene and Pyrene in rural soils, while Fluoranthene, Naphthalene and Benzo(b + k)fluoranthene dominated the PAHs of urban soils. The values of PAHs isomer indicated that biomass burning might be the major origin of PAHs in rural soils, but vehicular emission around the heavy traffic roads might contribute to the soil PAHs in urban areas. A cluster analysis was performed and grouped the detectable PAHs under 4 clusters, which could be indicative of the PAHs with different origins and PAHs affected by soil organic carbon contents respectively.
Baseline information is provided on levels, distributions and possible sources of PAHs in Hong Kong soils.
Two-dimensional crystals with angstrom-scale pores are widely considered as candidates for a next generation of molecular separation technologies aiming to provide extreme, exponentially large ...selectivity combined with high flow rates. No such pores have been demonstrated experimentally. Here we study gas transport through individual graphene pores created by low intensity exposure to low kV electrons. Helium and hydrogen permeate easily through these pores whereas larger species such as xenon and methane are practically blocked. Permeating gases experience activation barriers that increase quadratically with molecules' kinetic diameter, and the effective diameter of the created pores is estimated as ∼2 angstroms, about one missing carbon ring. Our work reveals stringent conditions for achieving the long sought-after exponential selectivity using porous two-dimensional membranes and suggests limits on their possible performance.
Inactivation of the tumor suppressor p53 and/or overexpression of the oncogene MDM2 frequently occur in human cancers, and are associated with poor prognosis, advanced forms of the disease, and ...chemoresistance. MDM2, the major negative regulator of p53, induces p53 degradation and inactivates its tumor suppressing activity. In turn, p53 regulates MDM2 expression. This MDM2-p53 negative feedback loop has been widely studied and presents an attractive target for cancer therapy, with a few of the inhibitors of this interaction already having advanced into clinical trials. Additionally, there is an increasing interest in understanding MDM2's p53-independent activities in carcinogenesis and cancer progression, which may also have implications for cancer therapy. This review aims to highlight the various roles that the MDM2-p53 interaction plays in cancer, the p53 independent oncogenic activities of MDM2 and the various strategies that may be used to target MDM2 and the MDM2-p53 interaction. We will summarize the major preclinical and clinical evidences of MDM2 inhibitors for human cancer treatment and make suggestions to further improve efficacy and safety of this interesting class of cancer therapeutics.
Based on an e+e− collision data sample corresponding to an integrated luminosity of 567 pb−1 taken at the center-of-mass energy of s=4.6 GeV with the BESIII detector, we measure the absolute ...branching fraction of the inclusive decay Λc+→Λ+X to be B(Λc+→Λ+X)=(38.2−2.2+2.8±0.9)% using the double-tag method, where X refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain ACP≡B(Λc+→Λ+X)−B(Λ¯c−→Λ¯+X)/B(Λc+→Λ+X)+B(Λ¯c−→Λ¯+X)=(2.1−6.6+7.0±1.6)%, a statistically limited result with no evidence of CP violation.
Based on 10 billion J/psi events collected at the BESIII experiment, a search for CP violation in Lambda decay is performed in the difference between CP-odd decay parameters alpha_ for Lambda -> p ...pi(-) and alpha(+) for (Lambda) over bar -> (p) over bar pi(+) by using the process e(+)e(-) -> J/psi -> Lambda(Lambda) over bar. With a five-dimensional fit to the full angular distributions of the daughter baryon, the most precise values for the decay parameters arc determined to be a_ = 0.7519 +/- 0.0036 +/- 0.0024 and alpha(+) = -0.7559 +/- 0.0036 +/- 0.0030, respectively. The Lambda and (Lambda) over bar averaged value of the decay parameter is extracted to be a(avg) = 0.7542 +/- 0.0010 +/- 0.0024 with unprecedented accuracy. The CP asymmetry A(CP) = (alpha_ + alpha(+))/(a_-alpha(+)) is determined to be -0.0025 +/- 0.0046 +/- 0.0012, which is one of the most precise measurements in the baryon sector. The reported results for the decay parameter will play an important role in the studies of the polarizations and CP violations for the strange, charmed and beauty baryons.
Titanium matrix composites with the discontinuous reinforcement of graphene nanoplatelets (GNPs) were produced by powder metallurgy and subsequent hot-rolling. In the process of spark plasma ...sintering (SPS), the GNPs were well preserved at low temperature and high compressive pressure. Hot-rolling process was applied to improve the microstructure and properties of the GNPs-Ti matrix composites. The GNPs were uniformly distributed and arranged along with the rolling direction (RD). Also, the GNPs blocked slipping so that the matrix generated {101̅1} <101̅2̅> compressive twining to be compatible with deformation in the rolling process with the increase of GNPs content. Tensile strength test demonstrated an excellent ultimate tensile strength that was 54.2% higher than pure titanium with merely 0.1wt% GNPs addition. The strengthening mechanism of composites was discussed by three main strengthening factors combined with a modified load transfer model and it was thought that the composites were strengthen by grain refinement, load transfer from Ti matrix to GNPs and texture strengthening.
Using a data sample of ${e}^{+}{e}^{{-}}$ collisions corresponding to an integrated luminosity of $567\text{ }\text{ }{\mathrm{pb}}^{{-}1}$ collected at a center-of-mass energy of $\sqrt{s}=4.6\text{ ...}\text{ }\mathrm{GeV}$ with the BESIII detector, we measure the absolute branching fraction of the inclusive semileptonic ${\mathrm{{\Lambda}}}_{c}^{+}$ decay with a double-tag method. We obtain $\mathcal{B}({\mathrm{{\Lambda}}}_{c}^{+}{\rightarrow}X{e}^{+}{{\nu}}_{e})=(3.95\pm{}0.34\pm{}0.09)%$, where the first uncertainty is statistical and the second systematic. Using the known ${\mathrm{{\Lambda}}}_{c}^{+}$ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons (${D}^{0}$ and ${D}^{+}$), we obtain the ratio of the inclusive semileptonic decay widths $\mathrm{{\Gamma}}({\mathrm{{\Lambda}}}_{c}^{+}{\rightarrow}X{e}^{+}{{\nu}}_{e})/\overline{\mathrm{{\Gamma}}}(D{\rightarrow}X{e}^{+}{{\nu}}_{e})=1.26\pm{}0.12$.
Topological semimetals are characterized by symmetry-protected band crossings, which can be preserved in different dimensions in momentum space, forming zero-dimensional nodal points, one-dimensional ...nodal lines, or even two-dimensional nodal surfaces. Materials harboring nodal points and nodal lines have been experimentally verified, whereas experimental evidence of nodal surfaces is still lacking. Here, using angle-resolved photoemission spectroscopy (ARPES), we reveal the coexistence of Dirac nodal surfaces and nodal lines in the bulk electronic structures of ZrSiS. As compared with previous ARPES studies on ZrSiS, we obtained pure bulk states, which enable us to extract unambiguously intrinsic information of the bulk nodal surfaces and nodal lines. Our results show that the nodal lines are the only feature near the Fermi level and constitute the whole Fermi surfaces. We not only prove that the low-energy quasiparticles in ZrSiS are contributed entirely by Dirac fermions but also experimentally realize the nodal surface in topological semimetals.
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