Abstract Luminescent covalent organic frameworks (COFs) find promising applications in chemical sensing, photocatalysis, and optoelectronic devices, however, the majority of COFs are non or weakly emissive owing to the aggregation‐caused quenching (ACQ) or the molecular thermal motion‐based energy dissipation. Here, we report a previously unperceived approach to improve luminescence performance of COFs by introducing isotope effect, which is achieved through substitution of hydrogen from high‐frequency oscillators X‐H (X=O, N, C) by heavier isotope deuterium. Combining the “bottom‐up” and in situ deuteration methods generates the first deuterated COF, which exhibits an impressively 19‐fold enhancement in quantum yield over that of the non‐deuterated counterpart. These results are interpreted by theoretical calculations as the consequence of slower C/N‐D and OD⋅⋅⋅O vibrations that impede the nonradiative deactivation process. The proposed strategy is proved applicable to many other types of emissive COFs.
Taking Xiaolinghe River Basin,located in the western part of Liaoning Province,as an example,selecting the rainfall and runoff data of Gangwakou Hydrological Station from 1963 to 2011, applying variation coefficient,extreme ratio,anomaly percentage,the cumulative filter,rank correlation test etc,. Various statistic methods,yearly variation characteristics for rainfall and runoff are analyzed,in which annual precipitation change is more intense,the abundant water period is short; runoff also has intense interannual variability,high water period is short and low water period lasts long,and rainfall and runoff indicate a reducing trend on the whole.
Objective To investigate the clinical efficacy of guided interscalene brachial plexus block anesthesia of the nerve stimulator.Methods 60 cases of patients with intermusculargroove brachial plexus block during January 2012 to January 2013 in Funan Hospital of Traditional Chiese Medicine were divided into experimental group and control group with 30 cases in each group,the experimental group with nerve stimulator assisted positioning,the control group traditional paresthesia we compared anesthesia results between two groups of patients. Results The onset time of anesthesia and anesthesia operation time in expenimental group were shorter than those in the control group In experimental group anesthesia success rate was 93. 3%,compared with a success rate of 71. 1% in control group. The anesthesia effect of experimental group was better than that of the control group,the incidence rate of complications of patients in the experimental group was lower than that in control patients,with statistically significant difference( P 0. 05). Conclusions Interscalene brachial plexus block guided by nerve stimulator is operational and accurate with good anesthesia effect and less complications,which is worthy of clinical application.
A light controlled switchable host–guest system based on a non-photoresponsive H-bonded macrocycle and pyridinium salts was developed using a photoacid.
An ultrastable zirconium phosphonate framework (SZ-7) exhibits superior Sr 2+ ion-exchange properties in 1 M NaOH solution with high adsorption capacity (183 mg g −1 ) and in-depth removal performance ( K d = 3.9 × 10 5 mL g −1 ).
Casting velocity affects greatly the slab liquid-core position.A typical fluctuation process of casting velocity is used as an example to quantitatively analyze the variation of slab liquid-core when the casting velocity fluctuates greatly.Some conclusions about the degree and velocity of liquid-core fluctuation are made respectively.These conclusions are applied into the dynamic soft reduction model of practical continuous casting process.The application results show the validity of the quantitative analysis and the corresponding results.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A light-responsive system constructed from hydrogen-bonded azo-macrocycles demonstrates precisely controlled propensity in molecular encapsulation and release process. A significant decrease in the size of the cavity is observed in the course of the E→Z photoisomerization based on the results from DFT calculations and traveling wave ion mobility mass spectrometry. These macrocyclic hosts exhibit a rare 2:1 host-guest stoichiometry and guest-dependent slow or fast exchange on the NMR timescale. With the slow host-guest exchange and switchable shape change of the cavity, quantitative release and capture of bipyridinium guests is achieved with the maximum release of 68 %. This work underscores the importance of slow host-guest exchange on realizing accurate release of organic cations in a stepwise manner under light irradiation. The light-responsive system established here could advance further design of novel photoresponsive molecular switches and mechanically interlocked molecules.
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