A series of supramolecular assemblies of types Ag8(L)4(PF6)8 and Ag4(L)2(PF6)4, obtained from the tetraphenylethylene (TPE) bridged tetrakis(1,2,4‐triazolium) salts H4‐L(PF6)4 and AgI ions, is ...described. The assembly type obtained dependends on the N‐wingtip substituents of H4‐L(PF6)4. Changes in the lengths of the N4‐wingtip substituents enables controlled formation of assemblies with either Ag4(L)2(PF6)4 or Ag8(L)4(PF6)8 stoichiometry. The molecular structures of selected Ag8(L)4(PF6)8 and Ag4(L)2(PF6)4 assemblies were determined by X‐ray diffraction analyses. While H4‐L(PF6)4 does not exhibit fluorescence in solution, their tetra‐NHC (NHC=N‐heterocyclic carbene) assemblies do upon NHC–metal coordination. Upon irradiation, all assemblies undergo a light‐induced, supramolecule‐to‐supramolecule structural transformation by an oxidative photocyclization involving phenyl groups of the TPE core, resulting in a significant change of the luminescence properties.
Silver links: Tetrakis(1,2,4‐triazolium) salts H4‐L(PF6)4, featuring different N4 substituents, react with Ag2O to give, depending on the length of the N4 alkyl substituent, tetranuclear metallo‐supramolecular assemblies of type Ag4(L)2(PF6)4 or octanuclear assemblies of type Ag8(L)4(PF6)8. Both types of assemblies, upon irradiation, undergo oxidative photocyclization of the central tetrakisarylethylene unit to yield the complexes with a 9,10‐phenyl‐substituted phenanthrene bridge.
GeTe is an interesting material presenting both spontaneous polarization (ferroelectrics) and outstanding electrical conductivity (ideal for thermoelectrics). Pristine GeTe exhibits classic 71° and ...109° submicron ferroelectric domains, and near unity thermoelectric figure of merit ZT at 773 K. In this work, it is demonstrated that Bi2Te3 alloying in GeTe lattice can introduce vast Ge vacancies which can further evolve into nanoscale van der Waals gaps upon proper heat treatment, and that these vacancy gaps can induce 180° nanoscale ferroelectric domain boundaries. These microstructures eventually become a hierarchical ferroelectric domain structure, with size varying from submicron to nanoscale and polarization from 71°, 109° to 180°. The establishment of hierarchical ferroelectric domain structure, together with the nanoscale Ge vacancy van der Waals gaps, has profound effects on the electrical and thermal transport properties, resulting in a striking peak thermoelectric ZT ≈ 2.4 at 773 K. These findings might provide an alternative conception for thermoelectric optimization via microstructure modulation.
Nanoscale‐charged domain walls and microdomains, together with Ge van der Waals gaps in Bi2Te3 alloyed GeTe, combine to make a complex hierarchical architecture which realizes an outstanding figure of merit ZT ≈ 2.4 at 773 K via simultaneous modulation of charge carriers and phonons.
•Stress-based failure criteria are implemented in NOSB-PD.•The effect of flaw length on the propagation of cracks is researched.•The effect of ligament angle on the coalescence of cracks is ...studied.•The effect of the confining stresses on the coalescence of flaws is investigated.
The maximum tensile stress criterion and the Mohr-Coulomb criterion are incorporated into the extended non-ordinary state-based peridynamics (NOSB-PD) to simulate the initiation, propagation and coalescence of the pre-existing flaws in rocks subjected to compressive loads. Wing cracks, oblique secondary cracks, quasi-coplanar secondary cracks and anti-wing cracks can be modeled and distinguished using the proposed numerical method. In the present study, a four-point beam in bending with two notches as a benchmark example is firstly conducted to verify the ability, accuracy and numerical convergence of the proposed numerical method. Then, the numerical samples of rock materials containing the one single pre-existing flaw with various lengths under uniaxial compression are modeled. Four significant factors, i.e. the axial stress versus axial strain curves, the peak strength, the ultimate failure mode and crack coalescence process, are obtained from the present numerical simulation. The effect of the flaw length on the propagation of cracks is investigated. Next, sandstone samples containing three pre-existing flaws with different ligament angles under uniaxial compression are also simulated. The effect of ligament angle on the propagation and coalescence of cracks is studied. Finally, rock-like samples containing two parallel pre-existing flaws subjected to biaxial compressive loads with confining stresses of 2.5, 5.0, 7.5 and 10.0MPa are simulated. The effect of the confining stresses on the initiation, propagation and coalescence of flaws is investigated. The present numerical results are in good agreement with the previous experimental ones.
Gas sensors for the detection of toxic or explosive gases both in outdoor and indoor air are of great interest for applications. A lot of effort has been devoted to develop the sensing properties in ...the area of metal–organic frameworks (MOFs) and semiconductor metal oxide based sensors. In our work, we report a semiconductor ZnO doped Uio-MOF heterostructure which can combine the advantage of both to improve the gas monitoring character. After post-synthesis of Eu 3+ , a novel fluorescent sensor based on the heterostructure has been fabricated for detection of volatile aldehyde gases (FA, AA and ACA) at room temperature. Here, MOFs with a high surface area act as gas pre-concentrators, and transfer their charge to ZnO. The ZnO nanoparticles act as reaction centers, and react much more intensively with aldehydes for the release of charge. Then Eu 3+ ions can convert the transferred charge from the reaction centers into fluorescence sensing signals. Due to this, the sensor shows excellent selectivity, sensitivity (LOD: 42 ppb for FA, 58 ppb for AA and 66 ppb for ACA) and reusability. In addition, due to the temperature-independent fluorescence response, easy preparation and low cost, the sensor can be conveniently applied for the practical detection of aldehyde gases in vehicles. The combined action of all kinds of analytes on the fluorescence character provides the possibility of early detection of the aldehydes and hence prevention of their emission. This original MOF encapsulation strategy applied to construct heterostructures paves the way for the assembly of new and complex materials for sensing or other applications.
Successful phase 3 trial outcomes have been reported for numerous vaccines that induce robust humoral and cellular immune responses against the SARS-CoV-2 spike protein.1–6 To gain rapid control of ...accelerating cases and maximise public health impact, the UK Government has adopted the strategy of delaying second vaccination to 12 weeks. 21 (29%) participants had evidence of previous SARS-CoV-2 infection: 16 with positive baseline serology, and five further with strong T-cell responses to non-spike antigens post-vaccination (>100 spot forming units SFU per 106 peripheral blood mononuclear cells PBMC). ...those with serological evidence of previous disease at baseline mount robust antibody and T-cell responses after a single dose of vaccine.
Studies of novel coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have reported varying estimates of epidemiological parameters, ...including serial interval distributions-i.e., the time between illness onset in successive cases in a transmission chain-and reproduction numbers. By compiling a line-list database of transmission pairs in mainland China, we show that mean serial intervals of COVID-19 shortened substantially from 7.8 to 2.6 days within a month (9 January to 13 February 2020). This change was driven by enhanced nonpharmaceutical interventions, particularly case isolation. We also show that using real-time estimation of serial intervals allowing for variation over time provides more accurate estimates of reproduction numbers than using conventionally fixed serial interval distributions. These findings could improve our ability to assess transmission dynamics, forecast future incidence, and estimate the impact of control measures.
Herein, we report a nickel-catalyzed allylic defluorinative alkylation of trifluoromethyl alkenes through reductive decarboxylation of redox-active esters. The present reaction enables the ...preparation of functionalized
-difluoroalkenes with the formation of sterically hindered C(sp
)-C(sp
) bonds under very mild reaction conditions, while tolerating many sensitive functional groups and requiring minimal substrate protection. Therefore, this method provides an efficient and convenient approach for late-stage modification of biologically interesting molecules.
Fractals are fascinating, not only for their aesthetic appeal but also for allowing the investigation of physical properties in non-integer dimensions. In these unconventional systems, many intrinsic ...features might come into play, including the fractal dimension and the fractal geometry. Despite abundant theoretical studies, experiments in fractal networks remain elusive. Here we experimentally investigate quantum transport in fractal networks by performing continuous-time quantum walks in fractal photonic lattices. We unveil the transport properties through the photon evolution patterns, the mean square displacement and the Pólya number. Contrarily to classical fractals, we observe anomalous transport governed solely by the fractal dimension. In addition, the critical point at which there is a transition from normal to anomalous transport depends on the fractal geometry. Our experiment allows the verification of physical laws in a quantitative manner and reveals the transport dynamics in great detail, thus opening a path to the understanding of more complex quantum phenomena governed by fractality.Quantum transport in fractal networks is experimentally investigated by performing continuous-time quantum walks in fractal photonic lattices. Contrarily to classical fractals, anomalous transport governed solely by the fractal dimension is observed.
An efficient cascade reaction of tryptamine‐derived isocyanides with C,N‐cyclic azomethine imines is described. The polycyclic pyrrolo2,3‐cquinoline derivatives, which benefited from rearrangement ...process driven by hydrogen bonding, could be directly assembled in moderate to good yields (40–87 %) under metal‐free and mild conditions. This transformation involved four new heterocyclic rings formations and uniquely, ring opening of indole as well as ring expansion of C,N‐cyclic azomethine imine. Both experimental and DFT studies provided guidance on the in‐depth insight into the reaction pathways and hydrogen bonding was identified to lower the free energy barrier in transition states. This work constitutes a rare example of tryptamine‐derived isocyanide‐based cascade reactions, and potentially could be a powerful synthetic strategy for accessing polycyclic analogues involved in natural products.
Natural‐product‐like polycyclic pyrrolo2,3‐cquinoline derivatives have been easily constructed in one‐step process from easily available starting materials. This reaction involves two ring enlargements and four heterocyclic ring formations via cascade rearrangement process. DFT studies reveal the crucial hydrogen‐bonding interaction in the detailed mechanistic investigation.
Pancreatic ductal adenocarcinoma (PDAC) is a highly fatal malignancy with extremely poor prognosis. Gemcitabine resistance is a major challenge in the treatment of PDAC. Here, we showed that ...LINC00460 was associated with the response to gemcitabine both in PDAC patients and PDAC‐PDX. After knocking down LINC00460 in PDAC tumor cells, results of RNA sequencing followed by gene ontology analysis indicated that LINC00460 influenced the activity of growth factors and modified the extracellular matrix. FISH showed that LINC00460 is mostly located in the cytoplasm. Results of RNA pull‐down, LC–MS/MS, RIP, and immunoblotting confirmed that LINC00460 could directly bind to PDAP1. Furthermore, we demonstrated that LINC00460 mediated the cellular communication of PDAC tumor cells and CAFs by PDAP1/PDGFA/PDGFR signaling pathway and regulated the gemcitabine‐resistance function of CAFs, which could be reversed by treatment with a PDGFR inhibitor (crenolanib). PDAC‐PDX tumors with lower expression of LINC00460 showed a better response to gemcitabine plus crenolanib treatment. Our finding supported the application of LINC00460 in precision medicine that uses gemcitabine plus crenolanib to treat PDAC with low expression of LINC00460.
LINC00460 regulates the gemcitabine chemotherapy‐resistance function of CAFs via the PDAP1/PDGFA/PDGFR pathway, which could be attenuated by treatment with a PDGFR inhibitor (crenolanib).PDAC with low expressed LINC00460 is an indicator to apply treatment therapy of gemcitabine combine with crenolanib.
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