Abstract
Low electrical conductivity caused by low degree of
π
-conjugation and structural disorders induces critical limitations in electronic applications of covalent organic frameworks (COFs). ...Here we focus on improving the electrical properties of COFs by synthesis of highly conjugated and crystalline COF (hcc-COF). Addition of a small amount of water and acetic acid induces the efficient reversible dynamic imine condensation reaction that is required to obtain uniform and crystalline products. Also, simulated sunlight irradiation facilitates the reversible imine condensation reaction, and achieves formation of hcc-COF with high-yield within short reaction time. The obtained hcc-COF has an extended
π
-conjugated structure along the lateral direction and an inclined stacking structure. The intrinsic electron transport properties along the in-plane direction are evaluated using a hcc-COF film grown on a water surface from a polarity-controlled precursor solution. To the best of our knowledge, our hcc-COF film shows the highest reported electrical conductivity for highly conjugated organic porous polymers.
Resveratrol is a natural polyphenolic stilbene derivative found in a variety of edible fruits, including nuts, berries, and grape skin. Although resveratrol has been suggested to improve ...thermogenesis in the brown adipose tissues of obese animals, there have been no reports on the anti-adipogenic and anti-inflammatory effects of resveratrol in the white adipose tissues of obese animals. The primary aim of this study was to investigate whether resveratrol attenuates high-fat diet (HFD)-induced adipogenesis and inflammation in the epididymal fat tissues of mice and to explore the underlying mechanisms involved in this attenuation. In comparison with HFD-fed mice, mice fed with a 0.4% resveratrol-supplemented diet (RSD) showed significantly lower body weight gain (−48%), visceral fat-pad weights (−58%), and plasma levels of triglyceride, FFA, total cholesterol, glucose, tumor necrosis factor (TNF) α, and monocyte chemoattractant protein-1 (MCP1). Resveratrol significantly reversed the HFD-induced up-regulation of galanin-mediated signaling molecules (GalR1/2, PKCδ, Cyc-D, E2F1, and p-ERK) and key adipogenic genes (PPARγ2, C/EBPα, SREBP-1c, FAS, LPL, aP2, and leptin) in the epididymal adipose tissues of mice. Furthermore, resveratrol significantly attenuated the HFD-induced up-regulation of pro-inflammatory cytokines (TNFα, IFNα, IFNβ, and IL-6) and their upstream signaling molecules (TLR2/4, MyD88, Tirap, TRIF, TRAF6, IRF5, p-IRF3, and NF-κB) in the adipose tissues of mice. The results of this study suggest that resveratrol inhibits visceral adipogenesis by suppressing the galanin-mediated adipogenesis signaling cascade. It may also attenuate cytokine production in the adipose tissue by repressing the TLR2- and TLR4-mediated pro-inflammatory signaling cascades in HFD-fed mice.
In the Republic of Korea (ROK), social distancing and public behavior changes mitigated COVID-19 spread. However, a second wave of the epidemic is expected in the fall if neither vaccine nor ...antiviral drugs become available. This study investigated the impact of non-pharmaceutical measures on short- and long-term outbreak dynamics.
A mathematical model based on Susceptible-Exposed-Infectious-Recovered model is developed considering isolated and behavior-changed groups. Using the least-squares fitting method, transmission and behavior change rates were estimated using cases reported from February 16 to April 20, 2020.
The estimated transmission rate of COVID-19 was 4·6180 and behavior change rate was 2·6044. The model predicted the number of new cases to continuously decrease, with less than one case expected after May 6, 2020. Concurrently, a 25% reduction in behavioral changes during the outbreak would increase the case count by 60,000, resulting in 4,000 cases at maximum, exceeding the medical system's capacity. As behavioral restrictions are eased, local transmission will likely increase, with forecasted second wave peak in October 2020.
Social distancing and public behavior changes have curbed the spread of COVID-19 in the ROK. Mathematical modeling demonstrates the importance of these measures in reducing and delaying outbreaks. Nevertheless, non-pharmaceutical interventions cannot eliminate the disease. In the future, vaccines and antiviral treatments combined with social distancing and public behavior changes will be paramount to ending COVID-19 epidemic.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that alters cortical excitability in a polarity specific manner and has been shown to influence learning ...and memory. tDCS may have both on-line and after-effects on learning and memory, and the latter are thought to be based upon tDCS-induced alterations in neurochemistry and synaptic function. We used ultra-high-field (7 T) magnetic resonance spectroscopy (MRS), together with a robotic force adaptation and de-adaptation task, to investigate whether tDCS-induced alterations in GABA and Glutamate within motor cortex predict motor learning and memory. Note that adaptation to a robot-induced force field has long been considered to be a form of model-based learning that is closely associated with the computation and 'supervised' learning of internal 'forward' models within the cerebellum. Importantly, previous studies have shown that on-line tDCS to the cerebellum, but not to motor cortex, enhances model-based motor learning. Here we demonstrate that anodal tDCS delivered to the hand area of the left primary motor cortex induces a significant reduction in GABA concentration. This effect was specific to GABA, localised to the left motor cortex, and was polarity specific insofar as it was not observed following either cathodal or sham stimulation. Importantly, we show that the magnitude of tDCS-induced alterations in GABA concentration within motor cortex predicts individual differences in both motor learning and motor memory on the robotic force adaptation and de-adaptation task.
The direct conversion of methane to methanol would enable better utilization of abundant natural gas resources. In the presence of stoichiometric PtIV oxidants, PtII ions are capable of catalyzing ...this reaction in aqueous solutions at modest temperatures. Practical implementation of this chemistry requires a viable strategy for replacing or regenerating the expensive PtIV oxidant. Herein, we establish an electrochemical strategy for continuous regeneration of the PtIV oxidant to furnish overall electrochemical methane oxidation. We show that Cl-adsorbed Pt electrodes catalyze facile oxidation of PtII to PtIV at low overpotential without concomitant methanol oxidation. Exploiting this facile electrochemistry, we maintain the PtII/IV ratio during PtII-catalyzed methane oxidation via in situ monitoring of the solution potential coupled with dynamic modulation of the electric current. This approach leads to sustained methane oxidation catalysis with 70% selectivity for methanol.
An atomically thin two-dimensional (2D) covalent organic framework (COF) was successfully synthesized via the photon-assisted imine condensation reaction within 1 h from the highly uniform and ...homogeneous precursor solution layer floating on the water surface. The polarity optimization of the precursor solution was the key step for the successful formation of the high-quality 2D COF because only the precursor solution consisting of polarity-controlled solvents allows ideal floating on the water surface. The polarity-controlled solution not only prohibits the agglomeration of the organic precursors on the water surface but also facilitates the wafer scale and layer number-controllable synthesis of the 2D COF. The resulting 2D COF has a uniform porous structure and highly oriented layered structure along the out-of-plane direction as observed by microscopy analysis and X-ray diffraction, respectively. In addition, we successfully fabricated field effect transistor type polyimine-based COF (pi-COF) electronic devices to demonstrate the prompt electrical responses to photo-exposure and water vapor exposure, suggesting the potential applications of the pi-COF in electrical photodetector or moisture-detector devices.
Covalent organic frameworks (COFs), newly emerging crystalline and porous materials, have been widely studied in many fields because of their unique periodic porous structures, high surface area, and ...strong interlayer π–π interaction when they are formed into a layered structure. Among the various types of COFs, highly oriented COF thin films with a layered structure have received great attention as one of the most promising organic-based two-dimensional (2D) materials due to their modifiability, flexibility, and multifunctional properties. In this mini-review, we aim to provide information on recent advances in highly oriented 2D COF thin film, which have one molecular thickness level to tens of nanometers. We first discuss the preparation of high-quality 2D COF thin films in terms of interfacial synthesis and exfoliation methods, which are representative methods for bottom-up and top-down approaches, respectively. Also, we summarize the applications of 2D COF thin film focusing on semiconducting devices, membranes, and highly sensitive and selective sensors.
Near‐trace concentrations (0.02 vol%) of crumpled graphene nanosheets suspended within a polystyrene matrix drastically inhibit the permeation of oxygen molecules through the resulting ...polymer‐graphene nanocomposite. This decrease in permeability is a direct result of the low solubility of oxygen within the nanocomposite, which is considerably densified by the graphene.
Abstract
Argonaute is the primary mediator of metazoan miRNA targeting (MT). Among the currently identified >1,500 human RNA-binding proteins (RBPs), there are only a handful of RBPs known to enhance ...MT and several others reported to suppress MT, leaving the global impact of RBPs on MT elusive. In this study, we have systematically analyzed transcriptome-wide binding sites for 150 human RBPs and evaluated the quantitative effect of individual RBPs on MT efficacy. In contrast to previous studies, we show that most RBPs significantly affect MT and that all of those MT-regulating RBPs function as MT enhancers rather than suppressors, by making the local secondary structure of the target site accessible to Argonaute. Our findings illuminate the unappreciated regulatory impact of human RBPs on MT, and as these RBPs may play key roles in the gene regulatory network governed by metazoan miRNAs, MT should be understood in the context of co-regulating RBPs.
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