Direct difunctionalization of simple alkenes, the incorporation of two functional groups onto a carbon–carbon double bond, is of particular interest to the chemical community owing to its important ...applications in organic synthesis. Mechanistically, two types of reactions – metal‐catalyzed nucleophilic difunctionalization and radical difunctionalization – dominate this research field. Radical difunctionalization is more appealing from a synthetic perspective than metal‐catalyzed nucleophilic difunctionalization because it allows the conversion of simple alkenes into complex molecules in a rapid and convenient manner. Furthermore, radical difunctionalization allows addition to simple alkenes by various carbon‐centered radicals and even heteroatom‐centered radicals. This review gives an overview of intermolecular and intramolecular radical difunctionalization of simple alkenes, with an emphasis on the reaction patterns and mechanisms, as well as potential applications in synthetic chemistry.
Radical difunctionalization of simple alkenes, incorporating two functional groups onto a carbon–carbon double bond, is a fascinating methodology for increasing molecular complexity. This has been a rapidly developing area, especially in the last three years. This microreview collects recent advances and provides synthetic methods, catalytic systems, and reaction mechanisms.
Solar energy‐driven conversion of CO2 into fuels with H2O as a sacrificial agent is a challenging research field in photosynthesis. Herein, a series of crystalline porphyrin‐tetrathiafulvalene ...covalent organic frameworks (COFs) are synthesized and used as photocatalysts for reducing CO2 with H2O, in the absence of additional photosensitizer, sacrificial agents, and noble metal co‐catalysts. The effective photogenerated electrons transfer from tetrathiafulvalene to porphyrin by covalent bonding, resulting in the separated electrons and holes, respectively, for CO2 reduction and H2O oxidation. By adjusting the band structures of TTCOFs, TTCOF‐Zn achieved the highest photocatalytic CO production of 12.33 μmol with circa 100 % selectivity, along with H2O oxidation to O2. Furthermore, DFT calculations combined with a crystal structure model confirmed the structure–function relationship. Our work provides a new sight for designing more efficient artificial crystalline photocatalysts.
COF catalysts: A series of crystalline covalent organic frameworks (COFs) was designed and applied for CO2 photoreduction coupled with H2O photooxidation, in the absence of photosensitizers and sacrificial agents. This approach gives a more straightforward and clear understanding of the structure–function relationship of artificial photosynthesis.
Follicular helper T (Tfh) cells are specialized in helping B lymphocytes, which play a central role in autoimmune diseases that have a major B cell component, such as in rheumatoid arthritis (RA). ...Follicular regulatory T (Tfr) cells control the over-activation of Tfh and B cells in germinal centers. Dysregulation of Tfh cells and Tfr cells has been reported to be involved in the pathogenesis of some autoimmune diseases. However, the balance of Tfh and Tfr cells, and their roles in the development and progression of RA are still not clear.
In this study, we enrolled 44 patients with RA (20 patients with active RA and 24 patients with inactive RA) and 20 healthy controls, and analyzed the frequencies of circulating Tfh and Tfr cells, expression of programmed death-1 (PD-1), inducible co-stimulator (ICOS), intracellular IL-21, and pSTAT3 in Tfh cells, and serum levels of IL-6. The correlation among these parameters and that of Tfh or Tfr cells with disease activity were also analyzed.
Patients with RA (especially active RA) had higher frequencies of Tfh cells, but lower percentages of Tfr cells, thereby resulting in elevated ratios of Tfh/Tfr. Expression levels of PD-1 and IL-21 in Tfh cells were higher in patients with RA than in healthy subjects, while no difference in ICOS expression was observed between patients and controls. Both pSTAT3 expression and serum IL-6 levels increased in patients with RA, and positive correlation between them was observed. Additionally, pSTAT3 expression was positively correlated with Tfh cell frequency. The Disease Activity Score in 28 joints based on C-reactive protein (DAS28-CRP) was negatively correlated with Tfr cell frequency, but was positively correlated with both Tfh/Tfr ratio and PD-1 expression.
Results demonstrated that enhanced IL-6/pSTAT3 signaling may contribute to promotion of Tfh cells, consequently skewing the ratio of Tfh to Tfr cells, which may be crucial for disease progression in RA.
Clustered binary data with a large number of covariates have become increasingly common in many scientific disciplines. This paper develops an asymptotic theory for generalized estimating equations ...(GEE) analysis of clustered binary data when the number of covariates grows to infinity with the number of clusters. In this "large n, diverging p" framework, we provide appropriate regularity conditions and establish the existence, consistency and asymptotic normality of the GEE estimator. Furthermore, we prove that the sandwich variance formula remains valid. Even when the working correlation matrix is misspecified, the use of the sandwich variance formula leads to an asymptotically valid confidence interval and Wald test for an estimable linear combination of the unknown parameters. The accuracy of the asymptotic approximation is examined via numerical simulations. We also discuss the "diverging p" asymptotic theory for general GEE. The results in this paper extend the recent elegant work of Xie and Yang Ann. Statist. 31 (2003) 310-347 and Balan and Schiopu-Kratina Ann. Statist. 32 (2005) 522-541 in the "fixed p" setting.
Macroautophagy/autophagy plays an important role against pathogen infection in mammals and plants. However, little has been known about the role of autophagy in the interactions of insect vectors ...with the plant viruses, which they transmit. Begomoviruses are a group of single-stranded DNA viruses and are exclusively transmitted by the whitefly Bemisia tabaci in a circulative manner. In this study, we found that the infection of a begomovirus, tomato yellow leaf curl virus (TYLCV) could activate the autophagy pathway in the Middle East Asia Minor 1 (MEAM1) species of the B. tabaci complex as evidenced by the formation of autophagosomes and ATG8-II. Interestingly, the activation of autophagy led to the subsequent degradation of TYLCV coat protein (CP) and genomic DNA. While feeding the whitefly with 2 autophagy inhibitors (3-methyladenine and bafilomycin A
1
) and silencing the expression of Atg3 and Atg9 increased the viral load; autophagy activation via feeding of rapamycin notably decreased the amount of viral CP and DNA in the whitefly. Furthermore, we found that activation of whitefly autophagy could inhibit the efficiency of virus transmission; whereas inhibiting autophagy facilitated virus transmission. Taken together, these results indicate that TYLCV infection can activate the whitefly autophagy pathway, which leads to the subsequent degradation of virus. Furthermore, our report proves that an insect vector uses autophagy as an intrinsic antiviral program to repress the infection of a circulative-transmitted plant virus. Our data also demonstrate that TYLCV may replicate and trigger complex interactions with the insect vector.
The increasingly wide application of Cloud Computing enables the consolidation of tens of thousands of applications in shared infrastructures. Thus, meeting the QoS requirements of so many diverse ...applications in such shared resource environments has become a real challenge, especially since the characteristics and workload of applications differ widely and may change over time. This paper presents an experimental system that can exploit a variety of online QoS aware adaptive task allocation schemes, and three such schemes are designed and compared. These are a measurement driven algorithm that uses reinforcement learning, secondly a "sensible" allocation algorithm that assigns tasks to sub-systems that are observed to provide a lower response time, and then an algorithm that splits the task arrival stream into sub-streams at rates computed from the hosts' processing capabilities. All of these schemes are compared via measurements among themselves and with a simple round-robin scheduler, on two experimental test-beds with homogenous and heterogenous hosts having different processing capacities.
At present, the development speed of international economic and cultural integration is accelerating. As one of the world’s common languages, English is of great significance in university teaching. ...As the foundation of English education, linguistics plays an irreplaceable role in the study of the nature, law and application of language. Studying linguistics can enable students to better understand and use English. Therefore, guided by the basic principles of English linguistics, discussing the countermeasures of English teaching plays a very important role in improving college students’ comprehensive ability of English listening, speaking, reading and writing and their ability to carry out cross-cultural communication in universities. This study will take English linguistics theory as the research object, and from the construction of reasonable teaching task, create reasonable teaching environment, build team linguistics learning model three aspects put forward the English linguistics theory in college English teaching strategy, for the development of college English teaching to provide certain guidance.
Recent studies have demonstrated a marked decrease in peripheral lymphocyte levels in patients with coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 ...(SARS‐CoV‐2). Few studies have focused on the changes of NK, T‐ and B‐cell subsets, inflammatory cytokines and virus‐specific antibodies in patients with moderate COVID‐19. A total of 11 RT‐PCR‐confirmed convalescent patients with COVID‐19 and 11 patients with non‐SARS‐CoV‐2 pneumonia (control patients) were enrolled in this study. NK, CD8+ T, CD4+ T, Tfh‐like and B‐cell subsets were analysed using flow cytometry. Cytokines and SARS‐CoV‐2‐specific antibodies were analysed using an electrochemiluminescence immunoassay. NK cell counts were significantly higher in patients with COVID‐19 than in control patients (P = 0.017). Effector memory CD8+ T‐cell counts significantly increased in patients with COVID‐19 during a convalescent period of 1 week (P = 0.041). TIM‐3+ Tfh‐like cell and CD226+ Tfh‐like cell counts significantly increased (P = 0.027) and decreased (P = 0.022), respectively, during the same period. Moreover, ICOS+ Tfh‐like cell counts tended to decrease (P = 0.074). No abnormal increase in cytokine levels was observed. The high expression of NK cells is important in innate immune response against SARS‐CoV‐2. The increase in effector memory CD8+ T‐cell counts, the up‐regulation of inhibitory molecules and the down‐regulation of active molecules on CD4+ T cells and Tfh‐like cells in patients with COVID‐19 would benefit the maintenance of balanced cellular and humoural immune responses, may prevent the development of severe cases and contribute to the recovery of patients with COVID‐19.
A method for designing broadband dual-polarization thin aperture with a small focal length to diameter ratio (F/D) is proposed for low-profile transmitarray antenna (TA). The aperture is composed of ...two types of narrowband subwavelength unit cells, namely the wire-loop Huygens' unit cell and the stacked I-shaped cross unit cell. The two types of unit cells collaborate to achieve complete 360° phase coverage and uphold a high transmittance (> −1.3 dB). Both unit cells possess the capability to manipulate dual polarization electromagnetic (EM) waves, exhibit strong angular stability, and have a period of <inline-formula> <tex-math notation="LaTeX">0.165\lambda _{0} </tex-math></inline-formula> (where <inline-formula> <tex-math notation="LaTeX">\lambda _{0} </tex-math></inline-formula> is the free space wavelength at 9 GHz). Furthermore, the subwavelength period of the unit cells enhances the sampling frequency of the aperture, thereby effectively mitigating aperture distortion caused by unit cell failure resulting from frequency variations. Hence, despite the narrowband nature of the unit cells, the aperture enables broadband performance. The proposed aperture design method offers a more efficient solution for broadband small F/D compared to the conventional TA design method, with reduced design complexity, thinner aperture thickness, and simplified unit cell structure. Finally, the proposed methodology is utilized to design the aperture of a TA prototype with an F/D of 0.32, which is equipped with a broadband magneto-electric (ME) dipole feed. The measured results demonstrate that the 2.5-dB gain bandwidth (BW) of the TA prototype is 17.02%.
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