Search

A nickel-catalyzed intramolecular coupling of thioesters and olefins has been developed for the efficient synthesis of spirocycles, a privileged scaffold commonly found in natural products. This transformation is characterized by the simultaneous transfer of both acyl and thiol moieties to the alkene, with the suppression of decarbonylation and β-hydrogen elimination. Initial mechanistic investigations are consistent with an oxidative addition/olefin insertion/reductive elimination mechanism. The incorporated methylene sulfide substituent can undergo a variety of further reactions to increase molecular diversity and complexity. These results demonstrate that thioester derivatives can be used as powerful building blocks for the assembly of complex scaffolds.

`Are we alone?' The Search for Extra-Terrestrial Intelligence (SETI) aims to answer this profound question. Apart from examining environments in our solar system and detecting biosignatures in exoplanet atmospheres, SETI is another main approach to search for life beyond Earth by detecting technosignatures indicative of extra-terrestrial intelligence (ETI), such as engineering radio signals. Massive efforts have been made by SETI scientists using radio telescopes around the world. Though some candidate signals were detected, none of them has been confirmed as an ETI technosignature so far. Most targeted SETI observations performed in recent years use on-off strategy to distinguish signals transmitted from celestial bodies from radio frequency interference (RFI) generated near the ground. Here we report a SETI campaign employing another SETI observation strategy, multi-beam coincidence matching (MBCM), at the Five-hundred-meter Aperture Spherical radio Telescope (FAST) towards 33 currently discovered planetary systems, searching for narrow band drifting signals at a band of $1.05-1.45$ GHz. Our observations achieve an unprecedented sensitivity with a minimum Equivalent Isotropic Radiated Power (EIRP) of $1.5 \times 10^{9} ~\text{W}$. We process the data of two orthogonal polarization separately, aiming to discriminate instrumental RFI signals. A particular signal at 1140.604 MHz from the observation towards Kepler-438 passes our initial selection criteria. Although we have not yet determined the exact cause of this signal, its polarization characteristic suggests that it is most likely to be attributed to RFI. In spite of this, our work verifies that compared to single-beam on-off strategy, MBCM greatly improves both time efficiency and radio frequency interference (RFI) identification effectiveness of targeted SETI observations.

As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to detecting technosignatures such as engineered radio signals that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multi-beam coincidence matching (MBCM) at the Five-hundred-meter Aperture Spherical radio Telescope (FAST) towards 33 known exoplanet systems, searching for ETI narrow-band drifting signals across 1.05-1.45 GHz in two orthogonal linear polarization directions separately. A signal at 1140.604 MHz detected from the observation towards Kepler-438 originally peaked our interest because its features are roughly consistent with assumed ETI technosignatures. However, evidences such as its polarization characteristics are almost able to eliminate the possibility of an extraterrestrial origin. Our observations achieve an unprecedented sensitivity since the minimum equivalent isotropic radiated power (EIRP) we are able to detect reaches 1.48 x10^9 W., Comment: 17 pages, 12 figures, matches the published version

Herein, we demonstrate a coating-etching strategy to directly synthesize hollow Prussian blue (PB) nanocubes with well-dispersed Ag nanoparticles (denoted as Ag-HPB). The method is accomplished by introduction of PB precursors, K3Fe(CN)6 and Fe3+ into a reaction system containing AgNO3 and ascorbic acid, in which a series reactions contain formation of Ag nanoparticles, coating of PB on the nanoparticles, and diffusion of Ag into the PB frameworks occur. The strategy for preparation of the hollow structured Ag-HPB is intrinsically simple and does not require pre-preparation of any sacrificial templates or toxic etching agents. The obtained Ag-HPB nanocubes possess uniform size (69 nm), well-defined hollow structure, strong near-infrared photothermal conversion capacity, and excellent photoacoustic and magnetic resonance imaging abilities. Furthermore, an injectable photothermal implants are prepared for the first time by mixing the Ag-HPB nanocubes with clinically used biological glue, which significantly enhance photothermal anti-tumor efficacy, showing great potential for clinical tumor treatment.

We applied the Koch snowflake fractal antenna in planning calibration of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), hypothesizing second-order fractal primary reflectors can optimize the orientated sensitivity of the telescope. Meanwhile, on the grounds of NASA Science Working Group Report in 1984, we reexamine the strategy of Search for Extraterrestrial Intelligence (SETI). A mathematical analysis of the radar equation will be performed in the first section, aiming to make it convenient to design a receiver system that can detect activities of an extraterrestrial civilization, according to the observable region of the narrowband. Taking advantage of the inherent potential of FAST, we simulate the theoretical detection of a Kardashev Type I civilization by a snowflake-selected reflecting area., Comment: 7 pages,2 figures, Matching the published version with correct references

A method for Ni-catalyzed controlled decarbonylation of α-ketothioesters is described. Mono- and double-decarbonylations, which gave thioesters and thioethers, respectively, were selectively achieved by changing the ligand. A fundamental study of Ni-catalyzed decarbonylation of α-ketothioesters is presented.

In this work, we design mesoporous silica-coated Prussian blue nanocubes with PEGyltation to construct multifunctional PB@mSiO2-PEG nanocubes. The PB@mSiO2-PEG nanocubes have good biocompatibility, excellent photothermal transformation capacity, in vivo magnetic resonance and photoacoustic imaging ability. After loading antitumor drug doxorubicin (DOX) in the PB@mSiO2-PEG nanocubes, the constructured PB@mSiO2-PEG/DOX nanoplatforms show an excellent pH-responsive drug release character within 48 h, namely, an ultralow cumulative drug release amount of 3.1% at pH 7.4 and a high release amount of 46.6% at pH 5.0. Upon near-infrared laser irradiation, the PB@mSiO2-PEG/DOX nanoplatforms show an enhanced synergistic photothermal and chemical therapeutic efficacy for breast cancer than solo photothermal therapy or chemotherapy.

Terbium doped tantalum oxide (Tb-Ta2O5) particles were synthesized with a low hydrothermal method. The phase structure of Tb-Ta2O5 obtained was performed by X-ray diffraction (XRD). The result revealed that the terbium doped Ta2O5 belongs to orthorhombic crystal. The electrochemical property of methylene blue (MB) at Tb-Ta2O5 film electrode in 0.5 mol dm-3 KCl aqueous solution was investigated with cyclic voltgrammetry (CV). The CV result indicated that the electrochemical kinetics of MB was diffusion controlling at Tb-Ta2O5 film electrode. Tb dopping imporved the electrochemical property of Ta2O5 film electrode. Tb-Ta2O5 is used as a kind of electrode material which has some new potential applications.

Cerium doped tantalum oxide (Ce-Ta2O5) particles were synthesized with hydrothermal method. The electrochemical behaviour of Ce-Ta2O5 film electrode in 0.1 mol dm-3 KCl containing 10 mmol dm-3 K3Fe(CN)6 was investigated with cyclic voltgrammetry (CV). The CV results indicated that the electrochemical reaction on the Ce-Ta2O5 film electrode exhibited stable electrochemical property. In addition, the phase structure of Ce-Ta2O5 prepared was performed by X-ray diffraction (XRD). The result revealed that the cerium doped Ta2O5 belongs to orthorhombic crystal.

To evaluate the effects of different concentrations of platelet-rich plasma (PRP) on human dental pulp stem cells (hDPSC) proliferation and osteogenic differentiation activity so as to provide basis for future application of dental pulp stem cells and PRP in tissue engineering and bone repair therapy.hDPSC were isolated and cultivated in vitro. Flow cytometric analysis was carried out to test the expression of STRO-1.hDPSC were cultured in various concentrations of PRP (1%, 5%, 10%, 20%). At the 2nd and 6th day 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was tested. Osteogenic differentiation of hDPSC was assessed using alkaline phosphatase (ALP) staining and Alizarin Red staining at the 7th and 14th day.Flow cytometric analysis demonstrated that 14.82% of hDPSC were STRO-1 positive. One percent to 20% PRP showed significant effect of promoting hDPSC proliferation. One percent to 10% PRP showed significant effect of promoting hDPSC osteogenic differentiation.Certain concentrations of PRP can promote hDPSC proliferate and osteogenic differentiate, and this finding suggests future application of dental pulp stem cells and PRP in bone tissue engineering.

In the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model, the energy conditions provides model-independent bounds on the behavior of the distance modulus. However, this method can not provide us the detailed information about the violation between the energy conditions and the observation. In this paper, we present an extended analysis of the energy conditions based upon the entropy density of the universe. On the one hand, we find that these conditions imply that entropy density s depends on Hubble parameter H(z). On the other hand, we compare the theoretical entropy density from the conservation law of energy-momentum tensor with that from the energy conditions using the observational Hubble parameter. When we consider a FLRW universe, according to the theoretical prediction, OHD, thermodynamics and several independent cosmological probes, show that the dominant energy condition is fitter than other energy conditions., Comment: 6 pages,4 figures;published in Results in Physics