Using 7.33~fb$^{-1}$ of $e^{+}e^{-}$ collision data collected by the BESIII
detector at center-of-mass energies in the range of $\sqrt{s}=4.128 -
4.226$~GeV, we search for the rare decays $D_{s}^+\to ...h^+(h^{0})e^{+}e^{-}$,
where $h$ represents a kaon or pion. By requiring the $e^{+}e^{-}$ invariant
mass to be consistent with a $\phi(1020)$, $0.98<M(e^{+}e^{-})<1.04$
~GeV/$c^2$, the decay $D_s^+\to\pi^+\phi,\phi\to e^{+}e^{-}$ is observed with a
statistical significance of 7.8$\sigma$, and evidence for the decay
$D_s^+\to\rho^+\phi,\phi\to e^{+}e^{-}$ is found for the first time with a
statistical significance of 4.4$\sigma$. The decay branching fractions are
measured to be $\mathcal{B}(D_s^+\to\pi^+\phi, \phi\to e^{+}e^{-}
)=(1.17^{+0.23}_{-0.21}\pm0.03)\times 10^{-5}$, and
$\mathcal{B}(D_s^+\to\rho^+\phi, \phi\to e^{+}e^{-} )=(2.44^{+0.67}_{-0.62}\pm
0.16)\times 10^{-5}$, where the first uncertainties are statistical and the
second systematic. No significant signal for the three four-body decays of
$D_{s}^{+}\to \pi^{+}\pi^{0}e^{+}e^{-},\ D_{s}^{+}\to K^{+}\pi^{0}e^{+}e^{-}$,
and $D_{s}^{+}\to K_{S}^{0}\pi^{+}e^{+}e^{-}$ is observed. For $D_{s}^{+}\to
\pi^{+}\pi^{0}e^{+}e^{-}$, the $\phi$ mass region is vetoed to minimize the
long-distance effects. The 90$\%$ confidence level upper limits set on the
branching fractions of these decays are in the range of $(7.0-8.1)\times
10^{-5}$.
By analyzing $e^+e^-$ annihilation data corresponding to an integrated
luminosity of 2.93 $\rm fb^{-1}$ collected at a center-of-mass energy of 3.773
GeV with the \text{BESIII} detector, the first ...observation of the semileptonic
decays $D^0\rightarrow K_S^0\pi^-\pi^0 e^+ \nu_e$ and $D^+\rightarrow
K_S^0\pi^+\pi^- e^+ \nu_e$ is reported. With a dominant hadronic contribution
from $K_1(1270)$, the branching fractions are measured to be
$\mathcal{B}(D^0\rightarrow {K}_1(1270)^-(\to
K^0_S\pi^-\pi^0)e^+\nu_e)=(1.69^{+0.53}_{-0.46}\pm0.15)\times10^{-4}$ and
$\mathcal{B}(D^+\to \bar{K}_1(1270)^0(\to
K^0_S\pi^+\pi^-)e^+\nu_e)=(1.47^{+0.45}_{-0.40}\pm0.20)\times10^{-4}$ with
statistical significance of 5.4$\sigma$ and 5.6$\sigma$, respectively. When
combined with measurements of the $K_1(1270)\to K^+\pi^-\pi$ decays, the
absolute branching fractions are determined to be $\mathcal{B}(D^0\to
K_1(1270)^-e^+\nu_e)=(1.05^{+0.33}_{-0.28}\pm0.12\pm0.12)\times10^{-3}$ and
$\mathcal{B}(D^+\to
\bar{K}_1(1270)^0e^+\nu_e)=(1.29^{+0.40}_{-0.35}\pm0.18\pm0.15)\times10^{-3}$.
The first and second uncertainties are statistical and systematic,
respectively, and the third uncertainties originate from the assumed branching
fractions of the $K_1(1270)\to K\pi\pi$ decays.
A new family of anhydrous sulfates, A{sup 2+}Mn{sub 5}(SO{sub 4}){sub 6} (A=Pb, Ba, Sr) is reported. The crystal structures of PbMn{sub 5}(SO{sub 4}){sub 6} and SrMn{sub 5}(SO{sub 4}){sub 6} are ...solved by powder X-ray and neutron diffraction. BaMn{sub 5}(SO{sub 4}){sub 6} is isostructural. PbMn{sub 5}(SO{sub 4}){sub 6} crystallizes with P3-bar symmetry and unit cell parameters of a=14.551(1) A and c=7.535(1) A. The structure has rich features, including dimers of face-sharing MnO{sub 6} octahedra, and two complementary triangular layers of Mn atoms. All compounds undergo a magnetic ordering transition at 10 K, below which, the magnetic susceptibility of the compounds varies systematically with the radius of the non-magnetic cation. Low temperature neutron diffraction shows that the complementary triangular layers result in a ferrimagnet with a net moment corresponding to one high spin Mn{sup 2+} per unit cell, correlating well with the magnetization data. The non-magnetic variant PbMg{sub 5}(SO{sub 4}){sub 6} is also reported. - Graphical abstract: A new family sulfates, A{sup 2+}Mn{sub 5}(SO{sub 4}){sub 6} (A=Pb, Ba, Sr) is reported. Structures are solved by powder neutron diffraction. PbMn{sub 5}(SO{sub 4}){sub 6} is trigonal with lattice parameters of a=14.551(1) A and c=7.535(1) A. The structure has dimers of face-sharing MnO{sub 6} octahedra, and two complementary triangular layers of Mn atoms that result in a ferrimagnet. All compounds magnetically order at 10 K. Low field susceptibility varies systematically with non-magnetic cation radius.
A combination of electrostatic interactions and covalent bonding is used to form films with low‐molecular‐weight chromophores by a layer‐by‐layer deposition process. Using a common, commercially ...available red dye, this deposition process results in noncentrosymmetric films (see scheme) that exhibit second‐harmonic generation (red→green), with χ(2) values as large as 11.3×10−9 esu, that is, six times that of quartz.
Using a sample of $448.1 \times 10^6$ $\psi(2S)$ events collected with the
BESIII detector, we perform a study of the decay $J/\psi\rightarrow K^+K^-$ via
$\psi(2S)\rightarrow \pi^+\pi^-J/\psi$.
The ...branching fraction of $J/\psi\rightarrow K^+K^-$ is determined to be
$\mathcal{B}_{K^+K^-}=(3.072\pm 0.023({\rm stat.})\pm 0.050({\rm syst.}))\times
10^{-4}$, which is consistent with previous measurements but with significantly
improved precision.
Hydroxyapatite (HAp) coatings were prepared using electrochemical deposition and post-hydrothermal synthesis. The composition and morphology of coatings at each processing step was studied through ...the application of scanning electron microscopy (SEM), X-ray diffraction (XRD) and infra-red spectroscopy (IR). The mechanism and kinetics of hydrothermal synthesis were considered in particular, and the influence of the temperature and time on the HAp formation rate was also investigated. The results show that the electrochemical deposition coatings are composed of CaHPO42H2O crystals which are converted into needle-like HAp crystals after post-hydrothermal treatment. The HAp content of the coatings increases with the treatment temperature and time. The synthesis rate also increases with the pH value of the water. The formation of HAp coatings is considered to be a combination of several reactions. An Arrhenius relationship was found between the HAp formation rate and the temperature, and an apparent activation energy of 94.4 KJ/mol was obtained by calculation.
A new optical fiber sensor for monitoring tetracycline has been described, based on the fluorescence quenching of 1,4-bis(5,5′-dimethylbenzoxazole-1′,3′-yl-2′)benzene incorporated into a thin ...plasticized polymer film by tetracycline extracted from aqueous phase into film phase. The sensor is fully reversible and highly reproducible. Furthermore, the sensor exhibits a linear response to tetracycline in the range 6.98×10
−7–8.73×10
−5 mol l
−1 with a detection limit of 1.06×10
−7 mol l
−1, and with the response time <30 s. The response is also selective to tetracycline, with some common pharmaceutical species, alkali and alkali-earth metal salts being highly discriminated, suggesting that the sensor can be used to monitor tetracycline in three pharmaceutical preparations. The recovery of tetracycline from commercial formulations is 95.3–98.3%.
A main obstacle to overcome during the treatment of tumors is drug resistance to chemotherapy; emerging studies indicate that a key factor contributing to this problem is the acidic tumor ...microenvironment. Here, we found that LASS2 expression was significantly lower in drug-resistant Michigan Cancer Foundation-7/adriamycin (MCF-7/ADR) human breast cancer cells than the drug-sensitive MCF-7 cells, and low expression of LASS2 was associated with poor prognosis in patients with breast cancer. Our results showed that the overexpression of LASS2 in MCF-7/ADR cells increased the chemosensitivity to multiple chemotherapeutic agents, including doxorubicin (Dox), whereas LASS2 knockdown in MCF-7 cells decreased the chemosensitivity. Cell-cycle analysis revealed a corresponding increase in apoptosis in the LASS2-overexpressing cells following Dox exposure, showing that the overexpression of LASS2 increased the susceptibility to Dox cytotoxicity. This effect was mediated by a significant increase in pHe (extracellular pH) and lysosomal pH, and more Dox entered the cells and stayed in the nuclei of cells. In nude mice, the combination of LASS2 overexpression and Dox significantly inhibited the growth of xenografts. Our findings suggest that LASS2 is involved in chemotherapeutic outcomes and low LASS2 expression may predict chemoresistance.
The zinc metalloenzyme protein farnesyltransferase (FTase) catalyzes the transfer of a 15-carbon farnesyl moiety from farnesyl diphosphate (FPP) to a cysteine residue near the C-terminus of a protein ...substrate. Several crystal structures of inactive FTase·FPP·peptide complexes indicate that K164α interacts with the α-phosphate and that H248β and Y300β form hydrogen bonds with the β-phosphate of FPP Strickland, C. L., et al. (1998) Biochemistry 37, 16601−16611. Mutations K164Aα, H248Aβ, and Y300Fβ were prepared and analyzed by single turnover kinetics and ligand binding studies. These mutations do not significantly affect the enzyme affinity for FPP but do decrease the farnesylation rate constant by 30-, 10-, and 500-fold, respectively. These mutations have little effect on the pH and magnesium dependence of the farnesylation rate constant, demonstrating that the side chains of K164α, Y300β, and H248β do not function either as general acid−base catalysts or as magnesium ligands. Mutation of H248β and Y300β, but not K164α, decreases the farnesylation rate constant using farnesyl monophosphate (FMP). These data suggest that, contrary to the conclusions derived from analysis of the static crystal structures, the transition state for farnesylation is stabilized by interactions between the α-phosphate of the isoprenoid substrate and the side chains of Y300β and H248β. These results suggest an active substrate conformation for FTase wherein the C1 carbon of the FPP substrate moves toward the zinc-bound thiolate of the protein substrate to react, resulting in a rearrangement of the diphosphate group relative to its ground state position in the binding pocket.
Femtosecond time-resolved studies using fluorescence depletion spectroscopy were performed on Rhodamine 700 in acetone solution and on Oxazine 750 in acetone and formamide solutions at different ...temperatures. The experimental curves that include both fast and slow processes have been fitted using a biexponential function. Time constants of the fast process, which corresponds to the intramolecular vibrational redistribution (IVR) of solute molecules, range from 300 to 420 fs and increase linearly as the temperature of the environment decreases. The difference of the average vibrational energy of solute molecules in the ground state at different temperatures is a possible reason that induces this IVR time-constant temperature dependence. However, the time constants of the slow process, which corresponds to the energy transfer from vibrational hot solute molecules to the surroundings occurred on a time scale of 1−50 ps, changed dramatically at lower temperature, nonlinearly increasing with the decrease of temperature. Because of the C−H···O hydrogen-bond between acetone molecules, it is more reasonable that acetone molecules start to be associated, which can influence the energy transfer between dye molecules and acetone molecules efficiently, even at temperatures far over the freezing point.
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