Many cyclobutane natural products have intriguing biological properties that arise from their fascinating chemical structures. Cyclobutane natural products feature a cyclobutane scaffold as the core ...or as a part of the spirocyclic or fused cyclic core. However, the highly functionalized nature and the inherent stereochemistry of these cyclobutane natural products, which are associated with their biological activities, pose tremendous challenges to their preparation. In this perspective, we present contemporary advancements in synthetic methods and/or strategies en route to the bioactive cyclobutane natural products. We begin by describing the representative bioactive cyclobutane natural products and then focus on illustrative examples of their syntheses reported from 2018 to 2021. These advances will enable efficient syntheses of cyclobutanes of structural and biological importance.
This perspective highlights the synthesis of bioactive cyclobutane natural products reported from 2018 to 2021. Contemporary advancements in synthetic methodology accomplished the advanced cyclobutane intermediates en route to natural products.▪
The morphing wing has a significant positive effect on the aerodynamic performance of the aircraft. This paper describes a leading-edge of variable camber wing with concentrated flexibility based on ...the geared five-bar mechanism. The driving points of morphing skin formed by the glass fibre composite sheet were optimized to make the skin deformation smooth. A geared five-bar kinematic mechanism rigidly connected to the skin was proposed to drive the leading-edge deformation. Besides, a new kind of concentrated flexure hinge was designed using the pseudo-rigid-body method and applied to the joint between the rigid mechanism and the skin. Finally, the leading-edge prototypes with traditional hinges and flexure hinges were produced, respectively. The feasibility of the concentrated flexibility leading-edge was verified through the comparative experiments of ground deformation. Simultaneously, aerodynamic analysis was carried out to compare the concentrated flexure leading-edge wing with the original airfoil.
Vocabulary mastery is critical to English as Foreign Language students. Mobile technologies enable students to learn vocabulary without space and time limitations. However, existing mobile-assisted ...vocabulary learning research often employed teacher-directed activities that increased instructors' workload, undermined student motivation or targeted individual cognitive outcomes only. In this study, a Contribution-oriented Self-Directed Mobile Learning Ecology (CSDMLE) model is proposed for developing student-directed and motivational vocabulary learning activities in groups. Through a mixed-method design, we administered a survey and a vocabulary test to 55 freshmen students in a Chinese university, and conducted follow-up interviews. We found that students in the CSDMLE group outperformed those not in the group in the post-test vocabulary test, but there was no statistically significant difference between the two groups' delayed vocabulary test or L2 motivation. However, the treatment group displayed a highly favorable attitude toward the learning approach and a strong intention to use it continuously. The findings have implications for technology-supported vocabulary learning activities.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A specific 3-dimensional intrachromosomal architecture of core stem cell factor genes is required to reprogram a somatic cell into pluripotency. As little is known about the epigenetic readers that ...orchestrate this architectural remodeling, we used a novel chromatin RNA in situ reverse transcription sequencing (CRIST-seq) approach to profile long noncoding RNAs (lncRNAs) in the Oct4 promoter.
We identify Platr10 as an Oct4 - Sox2 binding lncRNA that is activated in somatic cell reprogramming. Platr10 is essential for the maintenance of pluripotency, and lack of this lncRNA causes stem cells to exit from pluripotency. In fibroblasts, ectopically expressed Platr10 functions in trans to activate core stem cell factor genes and enhance pluripotent reprogramming. Using RNA reverse transcription-associated trap sequencing (RAT-seq), we show that Platr10 interacts with multiple pluripotency-associated genes, including Oct4, Sox2, Klf4, and c-Myc, which have been extensively used to reprogram somatic cells. Mechanistically, we demonstrate that Platr10 helps orchestrate intrachromosomal promoter-enhancer looping and recruits TET1, the enzyme that actively induces DNA demethylation for the initiation of pluripotency. We further show that Platr10 contains an Oct4 binding element that interacts with the Oct4 promoter and a TET1-binding element that recruits TET1. Mutation of either of these two elements abolishes Platr10 activity.
These data suggest that Platr10 functions as a novel chromatin RNA molecule to control pluripotency in trans by modulating chromatin architecture and regulating DNA methylation in the core stem cell factor network.
A dental Implant is a prosthetic device made of alloplastic materials implanted into the bone to provide retention and support for a dental prosthesis. Sirtuin1 (SIRT1) molecule, a nicotinamide ...adenine dinucleotide (NAD)-dependent histone deacetylase, regulates a variety of physiological and pathological processes, including oxidative stress, metabolism, cell proliferation, cell differentiation, inflammatory, and apoptosis. We explored whether the expression of SIRT1 correlates in patients receiving implants with peri-implant mucositis (PIM) and peri-implantitis (PI) in comparison to patients with healthy peri-implant area (PIH).
A number of 198 patients with dentition defects were enrolled in the study after their implants were functional for at least 6 months. All 198 subjects were divided into 3 groups: 1) control patients with PIH healthy implants; 2) patients with PIM mucositis; and 3) patients with PI implantitis. To distinguish these three groups, peri-implant crevicular fluid (PICF) was collected by inserting a sterile paper strip into the gap around the implant and the levels of SIRT1 and cytokines were measured by the enzyme linked immunosorbent assay (ELISA). Demographic and clinical data included age, sex, Body Mass Index (BMI), probing depth (PD), plaque index (PLI), bleeding on probing (BOP), oral health impact profile (OHIP-14), history of periodontitis and the use time of implants.
The PD, PLI, OHIP-14 evaluation scores in patients with periodontitis of PIM mucositis and PI implantitis were all significantly higher than in patients with PIH healthy implants. Overall, the SIRT1 levels in PICF of the PIM and PI patients were significantly lower than of the PIH patients. In comparison with PIM patients, SIRT1 levels of the PI patients were remarkably lower than the PIH patients. Pearson's analysis showed that SIRT1 levels were negatively correlated with levels of interleukin (IL)-6, C-reactive protein (CRP) and IL-1β in patients with PIM and PI. We suggest that SIRT1 levels could serve as a potential diagnostic biomarker of PI or PIM. The PICF levels of SIRT1, CRP, IL-6, IL-1β and the history of periodontitis were the risk factors for patients with peri-implant inflammatory process.
The measurement of SIRT1 expression in PICF may serve as a biomarker for the ongoing inflammatory process in patients with dental implants. The low SIRT1 levels correlated with PI implantitis and PIM mucositis as well as the elevated levels of pro-inflammatory cytokines (CRP, IL-6 and IL-1β).
•Basic characteristics of all patients.•Comparisons of SIRTI and inflammatory factors among PIH, PIM and PI patients.•Correlation between PICF SIRT1 level and PIM or PI patients' clinical outcome.•Diagnostic value of SIRT1 for PIM or PI.
Display omitted
•Various factors lead to tumor immune escape.•Polysaccharides can regulate the immune function of the body as a natural immune regulators.•Polysaccharides alter the gut microbiota, ...modulating the anti-tumor effect of anti-PD-1/PD-L1.•Polysaccharides induce ferroptosis in cancer cells through the xCT/GPX4 pathway.•Polysaccharides inhibit tumor immune escape.
A disorder of the immune system is the fundamental cause of cancer. The body can defend against external threats only when the immune system is robust. Polysaccharides are natural immune regulators that can regulate the immune function of the body at multiple levels and targets. Recent studies have shown that polysaccharides can inhibit tumor growth by stimulating the immune system, thereby promoting immune cell proliferation, increasing cytokine secretion, and regulating the immune functions of the body as a whole. However, there are few reports on the potential mechanism by which polysaccharides inhibit tumor immune escape. Therefore, this article reviews the immune anti-tumor effect of polysaccharides, the mechanism by which they inhibit tumor immune escape, and their signaling pathways, in order to provide a theoretical basis for the development of anti-tumor drugs and malignant tumor treatment.
This paper takes the high-frequency vibration characteristics of a bionic robot fish as the research object. Through research on the vibration characteristics of a bionic fish, we quantified the role ...of voltage and beat frequency in high-speed and stable swimming. We proposed a new type of electromagnetic drive. The tail is made of 0° silica gel to simulate the elastic characteristics of fish muscles. We completed a series of experimental studies on the vibration characteristics of biomimetic robotic fish. Through the single-joint fishtail underwater experiment, the influence of vibration characteristics on parameters during swimming was discussed. In terms of control, the central mode generator control method (CPG) control model is adopted, and a replacement layer is designed in combination with particle swarm optimization (PSO). By changing the elastic modulus of the fishtail, the fishtail resonates with the vibrator, and the swimming efficiency of the bionic fish is improved. Finally, through the prototype experiment, it is found that the bionic robot fish can achieve high-speed swimming through high-frequency vibration.
As an important part of the medical health monitoring field, heart rate (HR) monitoring has become an important application field of sensing technology in recent years. Due to the flexibility, ...chemical inertness, and anti-electromagnetic interference, optical fiber sensor (OFS) is widely concerned and studied in the field of HR monitoring. This paper summarizes the development of recent fiber-optic HR monitoring technology, introduces the sensing principles and applications of OFS for HR monitoring, which can be divided into intensity-based, interference-based, and FBG-based. For intensity modulation, bending and polishing methods are discussed. The main types of interference-based OFS are summarized and for FBG, packaging technology and materials are mainly introduced. Finally, the discussion and conclusions are summarized.
The aim of this study was to compare the phenolic compound profiles and antioxidant capacities of eight varieties of longan (
Dimocarpus longan
Lour.) planted in the middle and upper Yangtze River ...area. The total polyphenols content (TPC) and total flavonoids content (TFC) of dried longan pulp ranged from 1.07 ± 0.05 to 1.22 ± 0.05 mg gallic acid equivalents/g and 0.25 ± 0.07 to 0.87 ± 0.14 mg rutin equivalents/g. UHPLC-QqQ-MS/MS analysis revealed 12 individual polyphenol compounds in longan. The Fuwan8, Dongliang and FD97 varieties showed the strongest DPPH scavenging activity (IC
50
of 1.03 g/mL). The highest ABTS
+
scavenging activity was found in the Dongliang. In the enzyme assays, the Fuwan8 and Dongliang varieties demonstrated maximum α-amylase and α-glucosidase inhibition activities, with values of 97.56 and 88.58%, respectively. The principal component analysis indicated that the Rongyu8 and Songfengben cultivars have nearly analogous polyphenol compounds.
PDF
