Search for: All records

An in‐depth study of donor‐acceptor (D/A) interactions between the high‐dipole acceptor C60F18 (A) and PAH donors — pyrene, perylene, and coronene — reveals a surprisingly strong PAH size influence on the D/A complex stoichiometry and  ordering  in co‐crystals, and on the surface of PAH monolayers deposited on Au(111). Crystallographic study shows the tendency of the D/A mixtures to form stacked layered structures, such as D/A/D/A  or  D/A/A/D/A/A , for larger PAHs, perylene and coronene, respectively, while the role of aromatic π–π interactions diminishes, in contrast to Pyrene/C60F18 system. Attempts to achieve similarly ordered D/A assemblies on surfaces, by sequential deposition or co‐evaporation of C60F18 and coronene on Au(111), are presented. Scanning tunneling microscopy (STM) shows that the flat lying configuration adopted by coronene, which forms a highly‐ordered close‐packed monolayer stabilized by the interaction between their π electrons and the high density of gold surface states, hinders the formation of ordered co‐crystals. The critical role played by electronic and steric effects in the co‐crystal formation are believed to be at the basis of such lack of viability. However, adsorbed single C60F18 molecules are revealed to be centered on top of one coronene molecule, facilitating charge transfer between D and A molecules. 

A new deep-blue emitting and highly fluorescent anthracene (ANTH) derivative containing perfluorobenzyl (Bn_F) groups, 9,10-ANTH(Bn_F)₂, was synthesized in a single step reaction of ANTH or ANTH(Br)₂with Bn_FI, using either a high-temperature Cu-/Na₂S₂O₃-promoted reaction or via a room-temperature photochemical reaction. Its structure was elucidated by NMR spectroscopy and single crystal X-ray diffractometry. The latter revealed no π–π interaction between neighboring ANTH cores. A combination of high photoluminescence quantum yield (PLQY) of 0.85 for 9,10-ANTH(Bn_F)₂, its significantly improved photostability compared to ANTH and 9,10-ANTH derivatives, and a simple synthetic access makes it an attractive material as a deep-blue OLED emitter and an efficient fluorescent probe. 

Abstract Melanoma and nonmelanoma skin cancers are among the most prevalent and most lethal forms of skin cancers. To identify new lead compounds with potential anticancer properties for further optimization, in vitro assays combined with in‐silico target fishing and docking have been used to identify and further map out the antiproliferative and potential mode of action of molecules from a small library of compounds previously prepared in our laboratory. From screening these compounds in vitro against A375, SK‐MEL‐28, A431, and SCC‐12 skin cancer cell lines, 35 displayed antiproliferative activities at the micromolar level, with the majority being primarily potent against the A431 and SCC‐12 squamous carcinoma cell lines. The most active compounds11(A431: IC₅₀ = 5.0 μM, SCC‐12: IC₅₀ = 2.9 μM, SKMEL‐28: IC₅₀ = 4.9 μM, A375: IC₅₀ = 6.7 μM) and13(A431: IC₅₀ = 5.0 μM, SCC‐12: IC₅₀ = 3.3 μM, SKMEL‐28: IC₅₀ = 13.8 μM, A375: IC₅₀ = 17.1 μM), significantly and dose‐dependently induced apoptosis of SCC‐12 and SK‐MEL‐28 cells, as evidenced by the suppression of Bcl‐2 and upregulation of Bax, cleaved caspase‐3, caspase‐9, and PARP protein expression levels. Both agents significantly reduced scratch wound healing, colony formation, and expression levels of deregulated cancer molecular targets including RSK/Akt/ERK1/2 and S6K1. In silico target prediction and docking studies using the SwissTargetPrediction web‐based tool suggested that CDK8, CLK4, nuclear receptor ROR, tyrosine protein‐kinase Fyn/LCK, ROCK1/2, and PARP, all of which are dysregulated in skin cancers, might be prospective targets for the two most active compounds. Further validation of these targets by western blot analyses, revealed that ROCK/Fyn and its associated Hedgehog (Hh) pathways were downregulated or modulated by the two lead compounds. In aggregate, these results provide a strong framework for further validation of the observed activities and the development of a more comprehensive structure–activity relationship through the preparation and biological evaluation of analogs. 

Abstract The relationship between extreme precipitation intensity and temperature has been comprehensively studied over different regions worldwide. However, the effect of temperature on the spatiotemporal organization of precipitation, which can have a significant impact on precipitation intensity, has not been adequately studied or understood. In this study, we propose a novel approach to quantifying the spatial and temporal concentration of precipitation at the event level and study how the concentration varies with temperature. The results based on rain gauge data from 843 stations in the Ganzhou county, a humid region in south China, show that rain events tend to be more concentrated both temporally and spatially at higher temperature, and this increase in concentration qualitatively holds for events of different precipitation amounts and durations. The effects of temperature on precipitation organization in space and in time differ at high temperatures. The temporal concentration increases with temperature up to a threshold (approximately 24°C) beyond which it plateaus, whereas the spatial concentration keeps rising with temperature. More concentrated precipitation, in addition to a projected increase of extreme precipitation, would intensify flooding in a warming world, causing more detrimental effects. 

Abstract Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy is ideally absorbed at constant stress. Conventionally, compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large monodomain devices. Here, we use direct-ink writing 3D printing to fabricate bulk (>cm 3 ) monodomain LCE devices and study their compressive soft-elasticity over 8 decades of strain rate. At quasi-static rates, the monodomain soft-elastic LCE dissipated 45% of strain energy while comparator materials dissipated less than 20%. At strain rates up to 3000 s −1 , our soft-elastic monodomain LCE consistently performed closest to an ideal-impact absorber. Drop testing reveals soft-elasticity as a likely mechanism for effectively reducing the severity of impacts – with soft elastic LCEs offering a Gadd Severity Index 40% lower than a comparable isotropic elastomer. Lastly, we demonstrate tailoring deformation and buckling behavior in monodomain LCEs via the printed director orientation. 

We present the measurement of ${\pi }^{+}$-argon inelastic cross sections using the ProtoDUNE single-phase liquid argon time projection chamber in the incident ${\pi }^{+}$kinetic energy range of 500–800 MeV in multiple exclusive channels (absorption, charge exchange, and the remaining inelastic interactions). The results of this analysis are important inputs to simulations of liquid argon neutrino experiments such as the Deep Underground Neutrino Experiment and the Short Baseline Neutrino program at Fermi National Accelerator Laboratory. They will be employed to improve the modeling of final state interactions within neutrino event generators used by these experiments, as well as the modeling of ${\pi }^{+}$-argon secondary interactions within the liquid argon. This is the first measurement of ${\pi }^{+}$-argon absorption at this kinetic energy range as well as the first ever measurement of ${\pi }^{+}$-argon charge exchange. 

A<sc>bstract</sc> A measurement of the angular structure of inclusive jets and those containing a prompt D⁰meson in proton-proton collisions at the LHC at a center-of-mass energy of 5.02 TeV is presented. The data corresponding to an integrated luminosity of 301 pb⁻¹were collected by the CMS experiment in 2017. Two jet grooming algorithms, late-k_Tand soft drop, are used to study the intrajet radiation pattern using iterative Cambridge-Aachen declustering. The splitting-angle distributions of jets with transverse momentum (p_T) of around 100 GeV, obtained with these two algorithms, show that there is a shift of the distribution for jets containing a prompt D⁰meson with respect to inclusive jets. The suppression of emissions at small angles observed in the late-k_Tgrooming approach is consistent with the dead-cone effect, whereas the similar suppression for splittings selected with the soft-drop algorithm appears to be induced by gluon splitting to charm quark-antiquark pairs at large angles. The measured distributions are corrected to the particle level and can be used to constrain model predictions for the substructure of high-p_Tcharm quark jets.