The first highly atroposelective construction of N−N axially chiral indole scaffolds was established via a new strategy of de novo ring formation. This strategy makes use of the organocatalytic ...asymmetric Paal–Knorr reaction of well‐designed N‐aminoindoles with 1,4‐diketones, thus affording N‐pyrrolylindoles in high yields and with excellent atroposelectivities (up to 98 % yield, 96 % ee). In addition, this strategy is applicable for the atroposelective synthesis of N−N axially chiral bispyrroles (up to 98 % yield, 97 % ee). More importantly, such N−N axially chiral heterocycles can be converted into chiral organocatalysts with applications in asymmetric catalysis, and some molecules display potent anticancer activity. This work not only provides a new strategy for the atroposelective synthesis of N−N axially chiral molecules but also offers new members of the N−N atropisomer family with promising applications in synthetic and medicinal chemistry.
The first highly atroposelective construction of N−N axially chiral indole scaffolds was established via a new strategy of de novo ring formation, which is also applicable for the synthesis of N−N axially chiral bispyrroles. Such N−N axially chiral heterocycles can be converted into chiral organocatalysts. They may also display potent anticancer activity, thus offering new members of the N−N atropisomer family with promising applications in synthetic and medicinal chemistry.
A new class of axially chiral styrene‐based thiourea tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements, and multiple ...activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo‐, diastereo‐, and enantioselective (2+4) cyclization of 2‐benzothiazolimines with homophthalic anhydrides in good yields (up to 96 %) with excellent stereoselectivities (all >95:5 dr, up to 98 % ee). More importantly, theoretical calculations elucidated the important role of an axially chiral styrene moiety in controlling both the reactivity and enantioselectivity. This work not only represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, but also gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.
A new class of axially chiral styrene‐based organocatalysts has been rationally designed. They enable the chemo‐, diastereo‐ and enantioselective (2+4) cyclization of 2‐benzothiazolimines. This work represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, and it gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.
This study establishes the first organocatalytic enantioselective synthesis of axially chiral N,N′‐bisindoles via chiral phosphoric acid‐catalyzed formal (3+2) cycloadditions of indole‐based ...enaminones as novel platform molecules with 2,3‐diketoesters, where de novo indole‐ring formation is involved. Using this new strategy, various axially chiral N,N′‐bisindoles were synthesized in good yields and with excellent enantioselectivities (up to 87 % yield and 96 % ee). More importantly, this class of axially chiral N,N′‐bisindoles exhibited some degree of cytotoxicity toward cancer cells and was derived into axially chiral phosphine ligands with high catalytic activity. This study provides a new strategy for enantioselective synthesis of axially chiral N,N′‐bisindoles using asymmetric organocatalysis and is the first to realize the applications of such scaffolds in medicinal chemistry and asymmetric catalysis.
An organocatalytic enantioselective synthesis of axially chiral N,N′‐bisindoles has been established via chiral phosphoric acid‐catalyzed formal (3+2) cycloaddition of indole‐based enaminones with 2,3‐diketoesters. This study provides a new strategy for the highly selective synthesis of axially chiral N,N′‐bisindoles and shows the successful application of such skeletons in medicinal and synthetic chemistry.
This letter presents a novel reconfigurable dual- band bandpass filter (DBBPF) with independently controlled passbands and constant absolute bandwidths (ABW). The design procedures follow the ...traditional synthesis approach of filters. Moreover, in order to meet the requirement of constant ABW, theoretical analysis and calculation are carried out to determine proper parameters of coupling regions. Finally, the proposed DBBPF exhibits 21.8% fractional tuning range of the first passband from 0.98 to 1.22 GHz and 17.9% of the second passband from 1.63 to 1.95 GHz, and 3-dB ABWs are 76 <inline-formula> <tex-math notation="LaTeX">\pm</tex-math></inline-formula> 4 MHz and 100 <inline-formula> <tex-math notation="LaTeX">\pm</tex-math></inline-formula> 4 MHz, respectively.
In this letter, a wideband fully tunable bandpass filter with three adjustable transmission poles is proposed. The fundamental structure consists of two half-wave length (λ/2) resonators with ...center-tapped open and shorted stubs. Due to the same odd-mode resonant frequency, these two dual-mode resonators can form a wideband bandpass filter with three poles. Further, the fully tunable filter is designed by utilizing varactors to control three transmission poles flexibly. As a demonstrator, the prototypical filter with six varactors is implemented to validate the design concept. The filter reports 60.5% fractional bandwidth (FBW) at 2.48 GHz. In this state, the filter also achieves 138% FBW tuning and 20.8% center frequency tuning. Meanwhile, two transmission zeros (TZs) located at both sides of the passband are introduced by the center-tapped stubs to enhance the selectivity.
Aims
To understand the status quo of self‐directed learning ability, self‐efficacy and academic burnout of junior nursing college students, since the closed management mode was implemented during ...COVID‐19 pandemic disease.
Design
Cross‐sectional study.
Methods
Participants came from 3,051 junior nursing college students of a college in Zhengzhou City, Henan Province, China. Data were collected by online questionnaire and analysed by SPSS25.0 (a statistical package for social science) and AMOS24.0 software.
Results
High self‐directed learning ability and self‐efficacy were related to low levels of academic burnout (p < .01). In addition, the analysis of mediation effect indicated that the influence of self‐directed learning ability on academic burnout was not mediated by self‐efficacy.
A novel multi-mode resonator is presented to design compact tunable balanced bandpass filters (BPFs). From the theoretical analysis, the common-mode (CM) resonant frequencies are different from that ...of the differential-mode (DM) response, so the CM suppression can be achieved without adding any extra lumped elements. For the DM response, the modal frequencies of odd and even modes can be adjusted simultaneously by varying the varactors. This helps to design the DM response with tunable passband center frequency. Moreover, the even-mode resonant frequency can be tuned independently, leading to controllable passband bandwidth of the DM. To verify the design method, a compact tunable balanced BPF is developed, fabricated and measured. Good agreement can be attained between the measurement and simulation.
•Statistical analysis during saturated nucleate boiling of ethane were studied.•This paper has a certain guiding significance on the selection of sample size.•Sequential analysis and random sampling ...were conducted to investigate the sensitivity of bubble sample size.•Statistical analysis was employed to research the data distribution characteristics under different heat fluxes and pressures.
This study aims to investigate the sensitivity of bubble sample size during the saturated nucleate boiling of ethane. Experiments were conducted on a horizontal flat surface, under pressures of 0.15, 0.2, and 0.3 MPa with heat fluxes varying from 14.27 kW m−2 to 81.22 kW m−2. Mathematical tools like statistical analysis were used for the standardized study on boiling. Sequential analysis and random sampling were conducted to investigate the sensitivity of bubble sample size. The trend in which parameters changed with sample size was observed. The relative deviation (ε) was within ±10%, ±5%, and ±2% for sample sizes of 40, 95, and 215, respectively. The analytical results could provide reference to establish uniform standards in the boiling field. In addition, common statistical analysis was performed to examine the data distribution characteristics of bubble departure diameters. The Gauss function was evaluated as the best fitted probability distribution function. Data distribution changed with heat flux and pressure. The experimental results have a direct and substantial contribution to the boiling area.
Retrieved the literature on randomized controlled trials (RCT) of acupuncture and moxibustion from 2011 to 2020 in the Web of Science (WOS) database, and explored research hotspots and frontiers in ...the field of acupuncture and moxibustion by visually analyze to countries, institutions, authors, keywords, cited literature, etc. using CiteSpace V5.6.R2. A total of 1147 articles were included. China has the largest number of publications, and the top 3 publications are Beijing University of Chinese Medicine, Capital Medical University and Kyung Hee University. The hot research interventions in acupuncture and moxibustion include acupuncture, electroacupuncture, and bee acupuncture. The hot research topics include nerve regeneration, spasms, nausea, pain, obesity, cancer, etc. The research frontiers include acupuncture analgesia, diversification of acupuncture and its clinical effects, brain effects of acupuncture and acupuncture clinical mechanisms. It is believed that the cooperation between countries and insti
Background
Neck pain caused by cervical spondylosis (CS) is a chronic pain condition, with an increasingly high incidence in the general population. Electroacupuncture is a common analgesic modality ...that has been widely applied in neck pain treatment. However, current electroacupuncture instruments used in the clinic have low intelligence levels and obscure parameter standards. We here designed this study for assessing the effect and safety of a new, intelligent electroacupuncture instrument, the CX-DZ-II, in treating neck pain.
Methods
The present study is a prospective, two-center, randomized, controlled, open-label, non-inferiority trial for CX-DZ-II on treating neck pain caused by CS. Totally 160 eligible patients will be included in this trial and randomly assigned to an experimental group and a control group in a 1:1 ratio. A semi-standard acupoint selection strategy will be employed. In the experimental group, selected acupoints will be stimulated by CX-DZ-II. Electroacupuncture treatment will be accomplished by a pre-existing electroacupuncture instrument in the control group. The duration of treatment will be 2 weeks. The primary outcome is the change of Visual Analog Scale (VAS) score after one course of treatment. The secondary outcomes include the VAS scores after each treatment, the responder rate, drug-usage rate of non-steroidal antipyretic analgesics, the rate of adverse events occurrence, and the performance of instrument.
Discussion
This study will evaluate the effect and safety of the CX-DZ-II intelligent electroacupuncture therapeutic instrument in comparison with a pre-existing non-intelligent instrument in the treatment of neck pain caused by CS. The results will hopefully demonstrate a more optimal electroacupuncture instrument for the treatment of neck pain. (Trial registration No. gov NCT03005301).
