Single-atom catalysts have recently attracted considerable attention because of their highly efficient metal utilization and unique properties. Finding a green, facile method to synthesize them is ...key to their widespread commercialization. Here we show that single-atom catalysts (including iron, cobalt, nickel and copper) can be prepared via a top-down abrasion method, in which the bulk metal is directly atomized onto different supports, such as carbon frameworks, oxides and nitrides. The level of metal loading can be easily tuned by changing the abrasion rate. No synthetic chemicals, solvents or even water were used in the process and no by-products or waste were generated. The underlying reaction mechanism involves the mechanochemical force in situ generating defects on the supports, then trapping and stably sequestering atomized metals.
Recently, studies of 2D organic layered materials with unique electronic properties have generated considerable interest in the research community. However, the development of organic materials with ...functional electrical transport properties is still needed. Here, a 2D fused aromatic network (FAN) structure with a C5N basal plane stoichiometry is designed and synthesized, and thin films are cast from C5N solution onto silicon dioxide substrates. Then field‐effect transistors are fabricated using C5N thin flakes as the active layer in a bottom‐gate top‐contact configuration to characterize their electrical properties. The C5N thin flakes, isolated by polydimethylsiloxane stamping, exhibit ambipolar charge transport and extraordinarily high electron (996 cm2 V−1 s−1) and hole (501 cm2 V−1 s−1) mobilities, surpassing the performance of most pristine organic materials without doping. These results demonstrate their vast potential for applications in thin‐film optoelectronic devices.
A crystalline fused aromatic network with a basal plane stoichiometry of C5N exhibits exceptionally high carrier mobility. The thin flakes of C5N, obtained by poly(dimethylsiloxane) stamping, show ambipolar charge transport and remarkably high electron and hole mobilities, demonstrating their huge potential for applications in thin‐film electronics.
This paper presents transformer-based self-starting boost converter architecture with low-power maximum power point tracking (MPPT) control for low-voltage thermoelectric generator applications. The ...minimum working voltage of the proposed boost converter is 40 mV with oscillation through a positive feedback loop formed by a native MOS and transformer. The oscillation autonomously starts up by thermal noise and V OUT is charged up to 1.2 V by the oscillation so that the control block can operate. After that, the transformer for start-up is reused as an inductor, and the normal boost converter mode is enabled for better energy transfer efficiency. An improved MPPT sensing method is also proposed to simplify the circuit. The prototype chip is implemented in a 0.13-μm CMOS process. It operates with an input voltage range of 40 mV to 300 mV and provides a maximum output power of 2.7 mW with a maximum efficiency of 61% at an output voltage of 2 V.
Butyrate is a bacterial metabolite of dietary fiber in the colon that has been used to treat inflammatory disease. However, the effect of oral supplementation with butyrate on colitis has not been ...fully explored. We evaluated the effects of and mechanisms underlying oral supplementation with butyrate on experimental murine colitis. In an in vitro study, we found that LPS induced the secretion of cytokines (i.e., IL-8 in COLO 205; TNF-α, IL-6, IL-12, and IL-10 in RAW 264.7; and TNF-α, IL-6 and IL-12 in peritoneal macrophages obtained from IL-10-deficient IL-10−/− mice). Butyrate (100μM and 500μM) inhibited pro-inflammatory cytokine production (i.e., IL-8 in COLO205 and TNF-α, IL-6 and IL-12 in macrophages) but promoted anti-inflammatory cytokine (i.e., IL-10) production in RAW264.7 cells. Butyrate attenuated both the LPS-induced degradation/phosphorylation of IκBα and DNA binding of NF-κB and enhanced histone H3 acetylation. To confirm that butyrate played a protective role in colitis, an acute colitis model was induced using dextran sulfate sodium (DSS) and a chronic colitis model was induced in IL-10−/− mice. The administration of oral butyrate (100mg/kg) significantly improved histological scores in both colitis models, including the IL-10−/− mice. In immunohistochemical staining, IκBα phosphorylation was attenuated, and histone H3 acetylation was reversed in the treated colons of both colitis models. Our results indicate that oral supplementation with butyrate attenuates experimental murine colitis by blocking NF-κB signaling and reverses histone acetylation. These anti-colitic effects of butyrate were IL-10-independent. Butyrate may therefore be a therapeutic agent for colitis.
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•Butyrate inhibits the production of TNF-α, IL-6 and IL-12 in macrophages.•Butyrate inhibits NF-κB signaling and histone deacetylation in IEC and macrophages.•Oral supplementation with butyrate suppressed colitis, even in IL-10−/− mice.•Butyrate attenuated IκBα phosphorylation and histone H3 deacetylation in the colon.•The anti-inflammatory effect of butyrate is IL-10 independent.
HfZrO x (HZO) materials exhibiting ferroelectricity in ultra-thin layers can be deposited in various ways. Specifically, in sputtered HZO layers, only weak ferroelectric switching with gradual ...transition and small remnant polarization (Pr) is demonstrated using conventional rapid thermal annealing at high temperatures of at least 750°C. Here we show that rapidly transited ferroelectric switching with a larger 2 Pr of 24μ C/cm 2 is achieved by introducing a high pressure annealing (HPA) at even lower temperature of 550 °C. Our findings reveal that the HPA enhances the crystallinity of grains in the HZO, thereby enlarging the Pr and strengthening breakdown conditions. Through short pulse techniques, how interface and bulk region in the HZO are involved in the switching depending on the HPA is also investigated.
Herein, a soft and flexible polymer composite sensor with a surface structure is manufactured that is sensitive to a wide range of mechanical stimuli, including small actions and large motions. A ...polymer sensor performing with a piezoresistive mechanism is proposed by synthesizing a new conductive polymer composite to fabricate a microline structure by itself, named Ag-reduced poly(ethylene glycol) diacrylate (PEGDA) composite directional bending sensor (ACBS). A simple but effective process of forming nanoparticles (NPs) and surface structures is a notable characteristic. High sensitivity to a small stimulus was achieved by forming Ag NPs within PEGDA, particularly concentrating on the surface and applying the microline structure. With the structural characteristics of a line structure, the ACBS achieved anisotropic sensitivity to bulk motion along the arranged line direction. The excellent sensitivity of this polymer sensor was experimentally demonstrated via water droplets, blowing, and breathing. Combining the advantages of a simple synthetic and simple fabrication process along with the fabrication ability of the microsurface structure with the material itself and the conductive Ag/PEGDA integrated layer, this ACBS is outstanding as a soft and flexible polymer composite sensor and has potential application in physical devices such as wearable devices and biosensors.
Clustering of high‐aspect‐ratio micropillars is a common phenomenon in nature, and has been utilized to build complex and large‐scale microarchitectures. To induce the clustering, the micropillars ...should be prepared to be metastable, so that they cluster under perturbation, such as the drying of water. Consequently, once micropillars cluster, they cannot de‐cluster spontaneously. This article shows that the micropillars of thermo‐responsive hydrogels can cluster and de‐cluster spontaneously and reversibly by changing the temperature. This behavior is called clustering transition. When the temperature is low, the micropillars swell and become soft. When the temperature is high, the micropillars de‐swell and become stiff. This phase transition alters the lowest energy state of the system, resulting in a reversible clustering transition. To demonstrate, high‐aspect‐ratio micropillars of poly(N‐isopropylacrylamide‐co‐acrylamide) hydrogels are fabricated through a soft‐molding technique. The micropillars show the clustering transition, and the behavior is studied using a thermodynamic model. By controlling the temperature, the micropillars grip and release microparticles on‐demand.
An array of micropillars made of thermo‐responsive hydrogels spontaneously cluster and de‐cluster depending on the temperature. Such a clustering transition is reversible as each state is energetically stable. The clustering transition is understood by using a thermodynamic model.
Background
Former cigarette smokers are at risk of developing ulcerative colitis (UC). However, the impact of smoking behavior on the occurrence of UC according to the amount smoked remains elusive. ...We aimed to determine the relationship between smoking behavior and the risk of UC development.
Methods
We conducted a retrospective population-based cohort study using the National Health Insurance Service database in South Korea. From January 2009 to December 2012, 23,235,771 individuals over 18 years of age who underwent a national health examination were enrolled and followed until 2016. All study participants were divided into the following 3 groups: nonsmokers, former smokers, and current smokers. The primary endpoint was newly developed UC.
Results
Compared with nonsmokers, the risk of UC development was significantly higher in former smokers adjusted hazard ratio (aHR) 1.83; 95% confidence interval (CI) 1.73–1.95 but significantly lower in current smokers (aHR 0.92; 95% CI 0.87–0.98). Among current smokers, individuals who stopped smoking after the baseline evaluation had a significantly higher risk of UC development than those who continued to smoke (aHR 2.42; 95% CI 2.10–2.80). The risk of UC development among former smokers was significantly associated with smoking amount and duration. Among current smokers, however, the risk of UC development was not correlated with the cumulative lifetime smoking exposure. The preventive effect of current smoking on UC development was observed only in men (aHR 0.90; 95% CI 0.84–0.96).
Conclusions
Compared with nonsmokers, former smokers have a significantly higher risk of UC development that may be proportional to the cumulative smoking exposure.
Whether eradication of Helicobacter pylori reduces the incidence of metachronous gastric cancer (MGC) is still debatable. We aimed to evaluate the long-term effect of H pylori eradication on the ...development of MGC after endoscopic gastric tumor resection.
We undertook an open-label, prospective, randomized controlled trial at a tertiary hospital in Seoul, Korea. Participants were recruited during April 2005 to February 2011 and followed until December 2016. We assigned 898 patients with H pylori infection treated with endoscopic resection (ER) for gastric dysplasia or early gastric cancer to receive (n =442) or not receive (n =456) eradication therapy using a random-number chart. Eradication group patients received oral omeprazole 20 mg, amoxicillin 1 g, and clarithromycin 500 mg twice daily for a week, whereas control group patients received no H pylori treatment. The primary outcome was the incidence of MGC (intention-to-treat analysis).
The 877 patients who attended ≥1 follow-up examination (eradication group, 437; control group, 440) were analyzed. Median follow-up was 71.6 months (interquartile range, 42.1-90.0). MGC developed in 18 (4.1%) eradication and 36 (8.2%) control group patients (log-rank test, P = .01). In our yearly analysis, the effect of eradication showed a significant difference in 5 years after allocation (log-rank test, P = .02). The adjusted hazard ratio for the control group was 2.02 (95% CI, 1.14-3.56; P = .02), compared with the eradication group.
H pylori eradication significantly reduces the incidence of MGC after ER of gastric tumors and should be considered for H pylori–positive gastric tumor patients treated with ER. (Clinical trial registration number: NCT01510730.)
A crossbar array architecture employing resistive switching memory (RRAM) as a synaptic element accelerates vector-matrix multiplication in a parallel fashion, enabling energy-efficient pattern ...recognition. To implement the function of the synapse in the RRAM, multilevel resistance states are required. More importantly, a large on/off ratio of the RRAM should be preferentially obtained to ensure a reasonable margin between each state taking into account the inevitable variability caused by the inherent switching mechanism. The on/off ratio is basically adjusted in two ways by modulating measurement conditions such as compliance current or voltage pulses modulation. The latter technique is not only more suitable for practical systems, but also can achieve multiple states in low current range. However, at the expense of applying a high negative voltage aimed at enlarging the on/off ratio, a breakdown of the RRAM occurs unexpectedly. This stuck-at-short fault of the RRAM adversely affects the recognition process based on reading and judging each column current changed by the multiplication of the input voltage and resistance of the RRAM in the array, degrading the accuracy. To address this challenge, we introduce a boost-factor adjustment technique as a fault-tolerant scheme based on simple circuitry that eliminates the additional process to identify specific locations of the failed RRAMs in the array. Spectre circuit simulation is performed to verify the effect of the scheme on Modified National Institute of Standards and Technology dataset using convolutional neural networks in non-ideal crossbar arrays, where experimentally observed imperfective RRAMs are configured. Our results show that the recognition accuracy can be maintained similar to the ideal case because the interruption of the failure is suppressed by the scheme.
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