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Abstract Three new cholestane-type sterols bearing an unusual ∆ 22–24-oxo side chain, namely, dictyoptesterols A–C (1 – 3), were isolated from the brown alga Dictyopteris undulata Holmes, together with five known strutural analogues (4 – 8). Their structures were elucidated on the basis of by extensive spectroscopic analysis. The absolute configurations of the steroidal nuclei of the new compounds were proposed by a comparison of NMR data with those of related known compounds as well as biogenetic considerations. All of the isolates were evaluated in vitro for their potential to inhibit protein tyrosine phosphatase-1B (PTP1B) activity. The results showed that compounds 1 – 5 exhibited different levels of PTP1B inhibitory activities with IC 50 values ranging from 3.03 ± 0.76 to 15.01 ± 2.88 μM. In particular, compounds 3 and 4 showed promising inhibitory effects towards PTP1B with IC 50 values of 3.03 ± 0.76 and 3.72 ± 0.40 μM, respectively, when compared to the positive control oleanolic acid (IC 50 , 2.83 ± 0.39 μM). The chemotaxonomic significance of these isolated ∆ 22–24-oxo cholestanes has also been discussed. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

A novel fluorescent Fe3+ probe (L)based on 2-(2-hydroxyphenyl)benzothiazole has been synthesized and characterized. Both UV-vis and fluorescence spectroscopic studies demonstrated that L was highly sensitive and selective towards Fe3+ over other metal ions in acetonitrile. Upon binding with Fe3+, the emission band of L red-shifted from 370 nm to 420 nm and the fluorescence intensity was enhanced ∼103-fold. The lowest detection limit for L is 6.04 × 10−8 M and the dissociation constants Kd is 1.13 × 10−11 M, which were calculated from the fluorescence titration curves. The detailed UV-vis and fluorescent titrations studies suggested that the binding stoichiometry of the L–Fe3+ complex was 2 : 1, and the structure between L and the Fe3+ complex was confirmed by the 1H NMR titration. Then IR spectra provided further proof of the binding mode of the L–Fe3+ complex. [ABSTRACT FROM AUTHOR]

The origin of cosmic rays can be deciphered by accurately measuring the components and energy spectrum in the knee region. Study of Extensive air shower (EAS) relies on information provided by secondary high energy hadrons, which generate evaporation neutrons when they interact with matter in the environment. In the early 21st century, the electron–neutron detector (EN-detector) was developed at the Institute for Nuclear Research of the Russian Academy of Science (INR RAS). The PRImary Spectrum Measurement Array (PRISMA) project was introduced to enhance the array capabilities of cosmic ray composition separation and improve measurement accuracy. Within the framework of Chinese–Russian cooperation, at the Large High Altitude Air Shower Observatory (LHAASO) at Mt. Haizi (4400 m a.s.l.) in Daocheng, Sichuan province, China, a proposal was launched to establish the EN-Detector Array (ENDA) composed of 400 detectors in area of 10000 m to measure cosmic rays up to 300 PeV. In China, in 2018, a cluster, having 16 EN-detectors, was built at Tibet University (TU, 3700 m a.s.l.) in Lhasa, Tibet, to test specification of the array, and later it was moved to the Yangbajing (YBJ) Cosmic Ray Observatory (4300 m a.s.l.) in Tibet. Since 2019, another cluster so called ENDA-16 has started running at LHAASO, and here we give the first result of thermal neutron distribution. After gaining experience from these previous works, in April 2023, we successfully extended ENDA to ENDA-64 composed of 64 EN-detectors in area of 1000 m at LHAASO to measure cosmic rays from 400 TeV to 20 PeV. Here we describe installation and running status of ENDA-64 and present first results of thermal neutron distributions at different locations and hybrid detection of cosmic ray by using ENDA and LHAASO. [ABSTRACT FROM AUTHOR]

Prototype lanthanide metal–organic frameworks (LnMOFs), Ln(BTC) (Ln = Eu and Tb; BTC = benzene-1,3,5-tricarboxylate), have been considered as luminescent sensors for detecting toxic anions, while their neutral pore structures have limited the entrance and encapsulation of anions to produce highly anion-responsive photoluminescence (PL). To facilitate anions to enter the pore space of Ln(BTC), a one-pot synthesis method was proposed in which BTC was partially replaced with its structural analogue L·BF4 (H3L·BF4 = 2,4,6-tricarboxy-1-methylpyridinium tetrafluoroborate) which consists of an anion affinity site of cationic methylpyridinium. Compared to the original Ln(BTC), the co-doped cationic framework Eu0.05Tb0.95-BTC0.9L0.1 is highly sensitive for detecting different toxic anions by tuning the energy absorption of organic chromophores, the energy transfer efficiency to Ln3+ ions and the energy allocation between different Ln3+ ions in the PL spectra. We demonstrated that the Eu0.05Tb0.95-BTC0.9L0.1 PL sensor has the capability of decoding various toxic anions with a clearly differentiable and unique emission intensity ratio of 5D4→7F5 (Tb3+, 545 nm) to 5D0→7F2 (Eu3+, 618 nm) transitions (ITb/IEu). Compared to Ln(BTC), the co-doped Eu0.05Tb0.95-BTC0.9L0.1 presents self-calibrating, high distinguishable and stable PL signals for detecting toxic anions. [ABSTRACT FROM AUTHOR]

The new type of EAS array consisting of EN-detectors possesses the ability to discriminate the composition of cosmic rays. At the Yangbajing Cosmic Ray Observatory, the PRISMA-16-YBJ array has been running for three years. We installed 16 so-called "sand cubes" with one cubic meter size, and compared the data obtained by placing PRISMA-16-YBJ on and away from the sand cubes to study the influence of target material, which is a major environmental factor, on the performance of the array. [ABSTRACT FROM AUTHOR]

By accurate measurement of components and energy spectrum in the knee region, problem of origin of cosmic ray can be solved. In one extensive air shower (EAS), high energy hadrons, which constitute the EAS skeleton as G.T. Zatsepin called it, carry important information for multi-parameter correlation studies. The nuclear reaction between hadrons and matter in the surrounding environment produces a large number of evaporation neutrons, moderating to thermal neutrons. At the beginning of the 21th century, a new technology, electron–neutron detector (EN-detector) was designed at Institute for Nuclear Research of Russian Academy of Science (INR RAS), and the PRImary Spectrum Measurement Array (PRISMA) project was proposed to reinforce array capability of cosmic ray composition separation and then improve measurement accuracy of cosmic ray components and energy spectrum. Besides, EN-detectors can be used for continuous environmental thermal neutron flux monitoring and its variation study is needed not only for EAS experiment background estimation but also for geophysical applications (e.g., earthquakes, thunderstorms, radioactive aerosol control, etc.) and solar activity study (e.g., solar flares, Forbush effects, etc.). Under the Chinese–Russian cooperation, we put forward to build so called EN-Detector Array (ENDA) at high altitude in China. At YangBaJing Hybrid Array (YBJHA, 4300 m a.s.l.) and at Large High Altitude Air Shower Observatory (LHAASO, 4410 m a.s.l.), two clusters of ENDA were built individually and all have obtained coincident events with the local arrays. In the near future, we plan to extend ENDA to ENDA-64 with array area of 1000 m inside LHAASO to study the knee region of the light components (H and He). After it, ENDA will be extended up to 400 detectors with array area of 10 000 m to extend the energy range up to 300 PeV. [ABSTRACT FROM AUTHOR]

Theoretical investigations of the interactions between carbon monoxide (CO) and bromopentafluorobenzene (C6F5Br) have been carried out at both M06-2X/6-311++G(2d,2p) and M06-2X/aug-cc-pVTZ levels of theory. Because both C and O atom-ends of CO show negative electrostatic potential, they can favorably interact with the positive electrostatic potential generated by the σ-hole of Br and the π-hole of the aromatic ring of C6F5Br, yielding four different dimers and trimers. Their structures, spectroscopy and nature were systematically studied. The competition between the interactions involving the σ-hole of the Br atom and the π-hole of C6F5Br with the C and O atom-ends of CO was illustrated for the dimers and trimers, and meanwhile, the cooperativity between the two components of the trimers was elaborated. In addition, the experimental FT-IR and fluorescence spectra were measured for C6F5Br and the mixed C6F5Br and CO system without and with the solvent of hexane to gain information on the formation of molecular complexes between C6F5Br and CO. The results presented in this work are beneficial for the understanding of the competition and cooperativity of σ- and π-hole intermolecular interactions. [ABSTRACT FROM AUTHOR]