Precise control of the motion of micromachines is the key to achieving their functions for practical applications. The main challenge is that a given micromachine can typically exhibit only one ...motion mode, i.e., translation or rotation, while having multiple modes of motion resulting from a simple actuation is still rare. Here we designed and synthesized photochemically powered zinc oxide/gold (ZnO/Au) rods that exhibit multiple motion modes. Under homogeneous UV irradiation, these ZnO/Au rods undergo a transition from ballistic motion to persistent rotational motion upon increasing the fuel concentration or the light intensity. In addition, the rods can switch modes from a circular motion to a helical motion and then a straight-line motion by tuning the angle of incident light. We envision that such attractive colloidal micromachines with controllable motions hold considerable promise for diverse practical applications.
An efficient and eco-friendly protocol for synthesizing difluoromethylated oxindoles through a visible-light-induced one-pot tandem reaction of N-arylacrylamides, difluoroacetic acid and PhI(OAc)2 ...was developed. This reaction proceeded in the absence of any additive, base, metal-catalyst and external photosensitizer, using cheap CHF2CO2H as a difluoromethylation reagent and bulk biomass-derived 2-MeTHF as a solvent.
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An efficient and eco-friendly protocol for synthesizing difluoromethylated oxindoles through a visible-light induced one-pot tandem reaction of N-arylacrylamides, difluoroacetic acid and PhI(OAc)2 was developed. This reaction proceeded in the absence of any additive, base, metal-catalyst and external photosensitizer, using cheap and easily available CHF2CO2H as the difluoromethylation reagent and bulk biomass-derived 2-MeTHF as the sole solvent. 26 Examples of N-arylacrylamide substrates were investigated, and all of them successfully underwent difluoromethylation to deliver the target products in good to excellent yields.
•The ice shapes on the moveable conductor surface display more ice accumulation on the upper half of the upwind face.•Joule heat affects the energy balance at water film- ice interface and decreases ...ice growth rate.•The onset wind speed at which the conductor vibration starts is lower on the iced conductor than that of on the non-ice conductor.
There have been theoretical and experimental reports of glaze icing process which limited to fixed overhead power lines or cables, but very few are related to conductor motions, not to mention its effects on the conductor's aerodynamic characteristics. Thus, a preliminary study is conducted to demonstrate glaze icing process on a moveable overhead conductor and to discuss the effects of the conductor motions on water films, ice shapes and its corresponding aerodynamic characteristics. Based on lubrication theory, an analytical glaze accretion model on upwind side of the overhead conductor is established by considering water film thickness, ice thickness, conductor motions and joule heats. Wind pressures and frictions, and aerodynamic coefficients are computed with computational fluid dynamics(CFD) method. Comparison between the fixed conductors and the moveable conductors on water films and the ice shapes are carried out, and the effects of upper rivulets on aerodynamic vibrations of the iced conductors are discussed accordingly. The results shown that the conductor motion has obviously effect on the water films and upper rivulet positions, and further affected ice shapes. Moreover, in the glaze icing process, the conductor motion presented a kind of wind velocity and amplitude-restricted vibrations. It turns out proposed models can capture main features of glaze icing on the moveable overhead conductor and shed light on more actual glaze icing analysis.
Plant DNA methylation that occurs at CG, CHG, and CHH sites (H = A, C, or T) is a hallmark of the repression of repetitive sequences and transposable elements (TEs). The rice (Oryza sativa) genome ...contains about 40% repetitive sequence and TEs and displays specific patterns of genome-wide DNA methylation. The mechanism responsible for the specific methylation patterns is unclear. Here, we analyzed the function of OsDDM1 (Deficient in DNA Methylation 1) and OsDRM2 (Deficient in DNA Methylation 1) in genome-wide DNA methylation, TE repression, small RNA accumulation, and gene expression. We show that OsDDM1 is essential for high levels of methylation at CHG and, to a lesser extent, CG sites in heterochromatic regions and also is required for CHH methylation that mainly locates in the genic regions of the genome. In addition to a large member of TEs, loss of OsDDM1 leads to hypomethylation and up-regulation of many protein-coding genes, producing very severe growth phenotypes at the initial generation. Importantly, we show that OsDRM2 mutation results in a nearly complete loss of CHH methylation and derepression of mainly small TE-associated genes and that OsDDM1 is involved in facilitating OsDRM2-mediated CHH methylation. Thus, the function of OsDDM1 and OsDRM2 defines distinct DNA methylation pathways in the bulk of DNA methylation of the genome, which is possibly related to the dispersed heterochromatin across chromosomes in rice and suggests that DNA methylation mechanisms may vary among different plant species.
Landslides are a common natural hazard that causes casualties and unprecedented economic losses every year, especially in vulnerable developing countries. Considering the high cost of in-situ ...monitoring equipment and the sparse coverage of monitoring points, the Sentinel-1 images and Interferometric Synthetic Aperture Radar (InSAR) technique were used to conduct landslide monitoring and analysis. The Muyubao landslide in the Three Gorges Reservoir area in China was taken as a case study. A total of 37 images from March 2016 to September 2017 were collected, and the displacement time series were extracted using the Stanford Method for Persistent Scatterer (StaMPS) small baselines subset method. The comparison to global positioning system monitoring results indicated that the InSAR processing of the Muyubao landslide was accurate and reliable. Combined with the field investigation, the deformation evolution and its response to triggering factors were analyzed. During this monitoring period, the creeping process of the Muyubao landslide showed obvious spatiotemporal deformation differences. The changes in the reservoir water level were the trigger of the Muyubao landslide, and its deformation mainly occurred during the fluctuation period and high-water level period of the reservoir.
Abstract
The electrochemical CO
2
reduction reaction (CO
2
RR) represents a very promising future strategy for synthesizing carbon-containing chemicals in a more sustainable way. In spite of great ...progress in electrocatalyst design over the last decade, the critical role of wettability-controlled interfacial structures for CO
2
RR remains largely unexplored. Here, we systematically modify the structure of gas-liquid-solid interfaces over a typical Au/C gas diffusion electrode through wettability modification to reveal its contribution to interfacial CO
2
transportation and electroreduction. Based on confocal laser scanning microscopy measurements, the Cassie-Wenzel coexistence state is demonstrated to be the ideal three phase structure for continuous CO
2
supply from gas phase to Au active sites at high current densities. The pivotal role of interfacial structure for the stabilization of the interfacial CO
2
concentration during CO
2
RR is quantitatively analysed through a newly-developed in-situ fluorescence electrochemical spectroscopic method, pinpointing the necessary CO
2
mass transfer conditions for CO
2
RR operation at high current densities.
Mountain asymmetry is defined by the ratio of the lengths of two river systems across a drainage divide and is determined by the normalized location of the drainage divide. Understanding how ...asymmetric uplift influences the drainage divide, and therefore mountain asymmetry, is one of the preconditions for extracting tectonic information from topography. However, there is no consensus on this fundamental problem. Here we combined analytical solutions and numerical landscape evolution modeling to examine the impact of two key parameters (uplift gradient, and ratio of uplift rates at two edges) on mountain asymmetry. We followed the convention by assuming uniform gradient of uplift rate and erosion coefficient across the drainage divide. Our analytical approach and numerical simulations show that mountain asymmetry is not always controlled by the uplift gradient as previously suggested; instead, it is governed by the ratio of uplift rates at two edges across the divide. We quantified the relationship between the normalized divide location and the ratio of uplift rates. We applied the new formula to two natural examples to reconstruct the tectonics from the locations of the drainage divides. Moreover, we compared the influences of vertical and horizontal movements on the mountain asymmetry in different situations. The result suggests that in mountain belt with weak tectonic activity or high erosion coefficient, the mountain asymmetry is mainly controlled by the ratio of uplift rates.
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•Mountain asymmetry is controlled by the ratio of uplift rates at two edges.•A quantitative solution for the relationship between D1/M and U1/U2.•Numerical simulations corroborate the relationship between D1/M and U1/U2.•We applied the new relationship to the Wula Shan and the Zhongtiao Shan horsts.
Increasing attention is being paid to hydrothermal carbonization (HTC) of waste biomass, due to energy shortages, environmental crises and developing customer demands. However, most research has been ...dedicated to the production of bio-oil, with few studies focusing on the application of hydrothermal carbon (hydrochar), a solid residue from HTC of biomass. In this study, a novel porous carbon (PC) was prepared from hydrochar, via pyrolysis at different temperatures (300–700°C), the characteristics of PC as well as tetracycline (TC) adsorption behavior were investigated. The hydrochar and PC samples showed a remarkable range of surface properties, as characterized by Boehm titration, the Fourier transform infrared spectra and nuclear magnetic resonance spectra. The changes in characteristics suggested that the PC samples produced at high activation temperature (500–700°C) were well carbonized and exhibited a high surface area (>270m2/g). Linear relationships were obtained between Freundlich adsorptive capacity (KF) and elemental atomic ratios, surface area and pore volume. The high adsorption capacity of PC samples can be attributed to its low polarity and high aromaticity, surface area and pore volume. The molecular variations among the hydrochar and PC samples translated into differences in their ability to adsorb TC.
Micromotors are an emerging class of micromachines that could find potential applications in biomedicine, environmental remediation, and microscale self-assembly. Understanding their propulsion ...mechanisms holds the key to their future development. This is especially true for a popular category of micromotors that are driven by asymmetric surface photochemical reactions. Many of these micromotors release ionic species and are propelled via a mechanism termed “ionic self-diffusiophoresis”. However, exactly how it operates remains vague. To address this fundamental yet important issue, we have developed a dielectric-AgCl Janus micromotor that clearly moves away from the AgCl side when exposed to UV or strong visible light. Taking advantage of numerical simulations and acoustic levitation techniques, we have provided tentative explanations for its speed decay over time as well as its directionality. In addition, photoactive AgCl micromotors demonstrate interesting gravitactic behaviors that hint at three-dimensional transport or sensing applications. The current work presents a well-controlled and easily fabricated model system to understand chemically powered micromotors, highlighting the usefulness of acoustic levitation for studying active matter free from the effect of boundaries.
The World Health Organization has declared SARS-CoV-2 virus outbreak a worldwide pandemic. However, there is very limited understanding on the immune responses, especially adaptive immune responses ...to SARS-CoV-2 infection. Here, we collected blood from COVID-19 patients who have recently become virus-free, and therefore were discharged, and detected SARS-CoV-2-specific humoral and cellular immunity in eight newly discharged patients. Follow-up analysis on another cohort of six patients 2 weeks post discharge also revealed high titers of immunoglobulin G (IgG) antibodies. In all 14 patients tested, 13 displayed serum-neutralizing activities in a pseudotype entry assay. Notably, there was a strong correlation between neutralization antibody titers and the numbers of virus-specific T cells. Our work provides a basis for further analysis of protective immunity to SARS-CoV-2, and understanding the pathogenesis of COVID-19, especially in the severe cases. It also has implications in developing an effective vaccine to SARS-CoV-2 infection.
•SARS-CoV-2-specific antibodies are detected in COVID-19 convalescent subjects•Most COVID-19 convalescent individuals have detectable neutralizing antibodies•Cellular immune responses to SARS-CoV-2 are found in COVID-19 convalescent subjects•Neutralization antibody titers correlate with the numbers of virus-specific T cells.
In blood samples from COVID-19 convalescent subjects, Ni et al. have detected SARS-CoV-2-specific humoral and cellular immunity. Most subjects display serum neutralizing activities, which correlate with the numbers of virus-specific T cells.
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