Abstract
The N−N atropisomer, as an important and intriguing chiral system, was widely present in natural products, pharmaceutical lead compounds, and advanced material skeletons. The anisotropic ...structural characteristics caused by its special axial rotation have always been one of the challenges that chemists strive to overcome. Herein, we report an efficient method for the enantioselective synthesis of N−N axially chiral frameworks via a cobalt-catalyzed atroposelective C-H activation/annulation process. The reaction proceeds under mild conditions by using Co(OAc)
2
·4H
2
O as the catalyst with a chiral salicyl-oxazoline (Salox) ligand and O
2
as an oxidant, affording a variety of N−N axially chiral products with high yields and enantioselectivities. This protocol provides an efficient approach for the facile construction of N−N atropisomers and further expands the range of of N−N axially chiral derivatives. Additionally, under the conditions of electrocatalysis, the desired N−N axially chiral products were also successfully achieved with good to excellent efficiencies and enantioselectivities.
Ideal transmitting and receiving (Tx/Rx) array response is always desirable in multiple-input multiple-output (MIMO) radar. In practice, nevertheless, Tx/Rx arrays may be susceptible to unknown ...gain-phase errors (GPE) and yield seriously decreased positioning accuracy. This paper focuses on the direction-of-departure (DOD) and direction-of-arrival (DOA) problem in bistatic MIMO radar with unknown gain-phase errors (GPE). A novel parallel factor (PARAFAC) estimator is proposed. The factor matrices containing DOD and DOA are firstly obtained via PARAFAC decomposition. One DOD-DOA pair estimation is then accomplished from the spectrum searching. Thereafter, the remainder DOD and DOA are achieved by the least squares technique with the previous estimated angle pair. The proposed estimator is analyzed in detail. It only requires one instrumental Tx/Rx sensor, and it outperforms the state-of-the-art algorithms. Numerical simulations verify the theoretical advantages.
A novel adsorbent based on cellulose (CGD) was prepared via modifying with glycidyl methacrylate (GMA) and diethylenetriamine pentaacetic acid (DTPA), characterized by scanning electron microscopy ...(SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential thermogravimetry (DTA/TGA). Malachite green (MG) and basic fuchsine (BF) were used to resemble cationic dyes in wastewaters. The influences of several parameters (contact time, pH, temperature, initial concentration) were evaluated to determine the best adsorption conditions. Langmuir adsorption isotherm items explained MG adsorption well, while BF was fitted well with the Freundlich model. The maximum adsorption capacities were greater than some other reports, 1155.76 mg·g–1 for a BF internal concentration of 2000 mg·L–1 and 458.72 mg·g–1 for MG in theory. Kinetics and thermodynamics were adopted to explain in-depth information associated with the adsorption process. The adsorption processes of dyes were both feasible spontaneous and well-described by the pseudosecond-order model. The dynamic adsorption/desorption experiments, with saturated sodium bicarbonate solution as the eluent, show that the adsorbent could be reused for five cycles or four cycles, keeping the adsorption rate above 85 % and 90 % for BF and MG, respectively.
Highly crystalline polyaniline (PANI) was strongly anchored on a multiwalled carbon nanotube (MWNT) surface, slowly grown from a controlled isothermal crystallization method utilizing π–π ...interactions. The crystalline PANI particles are approximately 10–38 nm thick, and the space between them varies from near 0 to 55 nm as reaction conditions vary. The highly crystalline nanohybrid (CNH) showed electrochemical performance enhancement compared with that of neat MWNTs, PANI, and the reference hybrid synthesized from chemical polymerization. The specific capacitance (SC) of CNHs was 726 F g–1 coupled with an excellent rate capability. Moreover, the strong combination between PANI and MWNTs as well as the crystalline structure in PANI improved the bulk conductivity, the interfacial charge transportation, and the cycling stability of the CNHs. The SC value of the CNHs remained almost unchanged upon 1000 charge–discharge cycles, followed by just a slight decline of 2.6% after 10 000 cycle tests. X-ray diffraction data shows the SC decline mainly resulted from the structural variation of crystalline PANI. Furthermore, the resulting CNHs showed significant electrocatalytic behavior toward H2O2 and exhibited a low detection limit of 4.4 μM due to the enhanced electron transportation between MWNTs and PANI. The reported method opens a gateway to design high-performance MWNT/PANI hybrids for use in electrochemical sensors, fuel cells, and energy-storage related devices.
Basis mismatch challenges the conventional direction‐of‐arrival estimation constrained by sparse representation, especially in the case of massive antennas limited to a single snapshot. In this ...letter, we develop a real‐valued gridless direction‐of‐arrival estimation method to improve angular precision in the aforementioned circumstances. A new data model is first established through real‐valued transformation and then estimate the large low‐rank matrix with nuclear norm minimization. A fast iterative algorithm is designed to recover the underlying matrix faithfully and efficiently by the alternating direction method of multipliers. Numerical examples validate the performance improvement of the proposed method in the massive uniform linear array. This work also shows the potential to apply in measured data of the millimeter‐wave multiple‐input multiple‐output system.
In this paper, a type of effective electronic counter-countermeasures (ECCM) technique for suppressing the high-power deception jamming using an orthogonal frequency division multiplexing (OFDM) ...radar is proposed. Concerning the velocity deception jamming, the initial phases of the pulses transmitted in a coherent processing interval (CPI) are designed to minimize the jamming power within a specific range, forming a notch around the jamming in the Doppler spectrum. For the purpose of suppressing the range deception jamming and the joint range-velocity deception jamming, the phase codes of the subcarriers belonging to the OFDM pulses are optimized to minimize the jamming power, distributing some specific bands in the range and the range-velocity domain, respectively. According to Parseval's theorem, the phase encoding, acting as the coding manner of the OFDM subcarriers can ensure that the energy of each OFDM symbol stays the same. It is worth noticing that the phase codes of the OFDM subcarriers can influence the peak-to-average power ratio (PAPR). Thus, an optimization problem is formulated to optimize the phase codes of the subcarriers under the constraint of global PAPR, which can regulate the PAPRs of multiple OFDM symbols at the same time. The proposed problem is non-convex; therefore, it is a huge challenge to tackle. Then we present a method named by the phase-only alternating direction method multipliers (POADMM) to solve the aforementioned optimization problem. Some necessary simulation results are provided to demonstrate the effectiveness of the proposed radar signaling strategy.
In this paper, we first present multiple numerical simulations of the anti-symmetric matrix in the stability criteria for fractional order systems (FOSs). Subsequently, this paper is devoted to the ...study of the admissibility criteria for descriptor fractional order systems (DFOSs) whose order belongs to (0, 2). The admissibility criteria are provided for DFOSs without eigenvalues on the boundary axes. In addition, a unified admissibility criterion for DFOSs involving the minimal linear matrix inequality (LMI) variable is provided. The results of this paper are all based on LMIs. Finally, numerical examples were provided to validate the accuracy and effectiveness of the conclusions.
GEA-1, a proprietary stream cipher, was initially designed and used to protect against eavesdropping general packet radio service (GPRS) between the phone and the base station. Now, a variety of ...current mobile phones still support this standard cipher. In this paper, a structural weakness of the GEA-1 stream cipher that has not been found in previous works is discovered and analyzed. That is the probability that two different inputs of GEA-1 generate the identical keystream can be up to 2−7.30, which is quite high compared with an ideal stream cipher that generates random sequences. Based on this newfound weakness, a new practical distinguishing attack on GEA-1 is proposed, which shows that the keystreams generated by GEA-1 are far from random and can be easily distinguished with a practical time cost. After then, a new practical key recovery attack on GEA-1 is presented. It has a time complexity of 221.02 GEA-1 encryptions and requires only seven related keys, which is much less than the existing related key attack on GEA-1. The experimental results show that GEA-1 can be broken within about 41.75 s on a common PC in the related key setting. These cryptanalytic results show that GEA-1 cannot provide enough security and should be immediately prohibited to be supported in the massive GPRS devices.
As the world’s fourth most deadly cancer, colorectal cancer (CRC) still needed the novel therapeutic drugs and target urgently. Although cyclin-dependent kinase 12 (CDK12) has been shown to be ...implicated in the malignancy of several types of cancer, its functional role and mechanism in CRC remain largely unknown. Here, we found that suppression of CDK12 inhibited tumor growth in CRC by inducing apoptosis. And CDK12 inhibition triggered autophagy by upregulating autophagy related gene 7 (ATG7) expression. Inhibition of autophagy by ATG7 knockdown and chloroquine (CQ) further decreased cell viability induced by CDK12 inhibition. Further mechanism exploration showed that CDK12 interacted with protein kinase B (AKT) regulated autophagy via AKT/forkhead box O3 (AKT/FOXO3) pathway. FOXO3 transcriptionally upregulated ATG7 expression and autophagy when CDK12 inhibition in CRC. Level of CDK12 and p-FOXO3/FOXO3 ratio were correlated with survival in CRC patients. Moreover, CDK12 inhibition improved the efficacy of anti-programmed cell death 1(PD-1) therapy in CRC murine models by enhancing CD8 + T cells infiltration. Thus, our study founded that CDK12 inhibition upregulates ATG7 triggering autophagy via AKT/FOXO3 pathway and enhances anti-PD-1 efficacy in CRC. We revealed the roles of CDK12/FOXO3/ATG7 in regulating CRC progression, suggesting potential biomarkers and therapeutic target for CRC.
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•Suppression of CDK12 inhibited tumor growth in CRC by inducing apoptosis.•CDK12 inhibition upregulating ATG7 expression triggered autophagy by AKT/FOXO3 pathway.•CDK12 interacted with AKT and FOXO3 transcriptionally upregulated ATG7 expression and autophagy when CDK12 inhibition in CRC.•CDK12 inhibition improved the efficacy of anti-PD-1 therapy in CRC murine models by enhancing CD8 + T cells infiltration.
The efficacy of anti-PD-1 therapy is primarily hindered by the limited T-cell immune response rate and immune evasion capacity of tumor cells. Autophagy-related protein 7 (ATG7) plays an important ...role in autophagy and it has been linked to cancer. However, the role of ATG7 in the effect of immune checkpoint blockade (ICB) treatment on high microsatellite instability (MSI-H)/mismatch repair deficiency (dMMR) CRC is still poorly understood.
In this study, patients from the cancer genome altas (TCGA) COAD/READ cohorts were used to investigate the biological mechanism driving ATG7 development. Several assays were conducted including the colony formation, cell viability, qRT-PCR, western blot, immunofluorescence, flow cytometry, ELISA, immunohistochemistry staining and in vivo tumorigenicity tests.
We found that ATG7 plays a crucial role in MSI-H CRC. Its knockdown decreased tumor growth and caused an infiltration of CD8
T effector cells in vivo. ATG7 inhibition restored surface major histocompatibility complex I (MHC-I) levels, causing improved antigen presentation and anti-tumor T cell response by activating reactive oxygen species (ROS)/NF-κB pathway. Meanwhile, ATG7 inhibition also suppressed cholesterol accumulation and augmentation of anti-tumor immune responses. Combining ATG7 inhibition and statins improved the therapeutic benefit of anti-PD-1 in MSI-H CRC. Importantly, CRC patients with high expression of both ATG7 and recombinant 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) experienced worse prognosis compared to those with low ATG7 and HMGCR expression.
Inhibition of ATG7 leads to upregulation of MHC-I expression, augments immune response and suppresses cholesterol accumulation. These findings demonstrate that ATG7 inhibition has therapeutic potential and application of statins can increase the sensitivity to immune checkpoint inhibitors.
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