Search

The Ti/Cr clusters, from dimers to pentamers, on a single-layer h-BN are investigated using first-principles calculations. The relatively weak interaction with the h-BN monolayer makes it possible to build versatile and interesting 3D nanostructures.

Nanozymes with high catalytic stability and sustainability have emerged as powerful competitors to natural enzymes for diverse biocatalytic applications. However, constructing a nanozyme with high specificity is one of their biggest challenges. Herein, we develop a facile solid migration strategy to access a flower-like single copper site nanozyme (Cu SSN) via direct transformation of copper foam activated by 2-methylimidazole. With highly clustered CuN

The ice water path (IWP) is an important cloud parameter in atmospheric radiation, and there are still great difficulties in its retrieval. Artificial neural networks have become a popular method in atmospheric remote sensing in recent years. This study presents a global IWP retrieval based on deep neural networks using the measurements from the Microwave Humidity Sounder (MWHS) aboard the FengYun-3B (FY-3B) satellite. Since FY-3B/MWHS has quasi-polarization channels at 150 GHz, the effect of the polarimetric radiance difference (PD) was also studied. A retrieval database was established using collocations between MWHS and CloudSat 2C-ICE (CloudSat and CALIPSO Ice Cloud Property Product). Then, two types of networks were trained for cloud scene filtering and IWP retrieval. For the cloud filtering network, the microwave channels show a capacity with a false alarm ratio (FAR) of 0.31 and a probability of detection (POD) of 0.61. For the IWP retrieval network, different combination inputs of auxiliaries and channels were compared. The results show that the five MWHS channels combined with scan angle, latitude, and the ocean/land mask of inputs of auxiliary variables perform best. Applying the cloud filtering network and IWP retrieval network, the final root mean squared error (RMSE) is 916.76 g m−2, the mean absolute percentage error (MAPE) is 92 %, and the correlation coefficient (CC) is 0.65. Then, a tropical cyclone case measured simultaneously by MWHS and CloudSat was chosen to test the performance of the networks, and the result shows a good correlation (0.73) with 2C-ICE. Finally, the global annual mean IWP of MWHS is very close to that of 2C-ICE, and the 150 GHz channels give a significant improvement in the midlatitudes compared to using only 183 GHz channels.

A controlled chemical reaction on a specific bond in a single molecule is an inevitable step toward atomic engineering and fabrication. Here, we explored the debromination of a single 9,10-dibromoanthracene (DBA) molecule on a surface as stimulated by the voltage pulse through the tip of a scanning tunneling microscope (STM). A voltage threshold of about 2.2 V is obtained, and the nature of single-electron process is revealed. The spatially resolved debromination yield is obtained as a function of the pulse magnitude, which presents strong asymmetry for the two C-Br bonds. The optimal stimulation parameters including the pulse magnitude and the tip locations are suggested. The distinct dynamics in dissociation of the two bonds are illustrated by their energy diagrams and recoil paths, as derived by the first-principles density functional theory (DFT) calculation. The influence of the local electric field due to the STM tip on the dissociation of the C-Br bond has also been discussed. The study presents detailed practice for the controlled debromination in a single DBA molecule, which may lead to automated atomic engineering and fabrication of artificial nanostructures in the future.

In this paper, we focus on the vehicle-to-vehicle dynamic channel in tactical communication environments, which shows time-varying and nonstationary characteristics due to the fast mobility, directional antennas, and harsh terrain. These situations present great challenges for the channel state information (CSI) acquisition. To obtain an accurate CSI and reduce pilot overhead, we propose a CSI predictor based on the long short-term memory (LSTM) network. As an improved recurrent neural network (RNN), LSTM units have an excellent learning result on both long- and short-term inputs by adding the gating mechanism. Using the outdated sampling CSI sequence as input data of LSTM units enables the predictor to extract complex data characteristics and capture the temporal law of the nonstationary channel. Simulation results are demonstrated to verify that the LSTM-based predictor has better performance than conventional algorithms in IEEE 802.11p standard. Additionally, the key factors that affect the performance of the proposed predictor are further analyzed.

The hydrological exchange process between Poyang Lake (PYL), the largest freshwater lake in China, and the Yangtze River leads to drastic changes in water area (WA) and water level (WL), as well as apparent fluctuations in lake nutrients, algal organisms, and trophic level index. This study investigated the current status of the PYL water environment and the influence of hydrological changes on the nutrient status of the floodplain of the lake. Based on monthly measured data from six hydrological stations from 2016 to 2019, it was hypothesized that WA and WL were the key regulators of the spatial and temporal distribution patterns of lake water quality and algal growth, including water temperature, water clarity (Secchi depth [SD]), and nutrient levels. The results revealed that (1) the spatial and temporal distribution characteristics of major nutrients in PYL were influenced by dynamic changes in hydrological characteristics (SD, total nitrogen [TN], and total phosphorus [TP]); (2) the eutrophication level in PYL has been in a steady state in recent years, while the central area has been more prone to the risk of eutrophication (e.g., the peak eutrophication index during Period 1 [January to April] in the water near the Duchang station reached 70); and (3) there were significant correlations among environmental variables, nutrients, and algal organisms, with different spatial and temporal distribution characteristics (p 0.05), while the changes in WA and WL considerably influenced the water environment in the PYL.

Embryonic tissues undergoing shape change draw mechanical input from extraembryonic substrates. In avian eggs, the early blastoderm disk is under the tension of the vitelline membrane (VM). Here we report that the chicken VM characteristically downregulates tension and stiffness to facilitate stage-specific embryo morphogenesis. Experimental relaxation of the VM early in development impairs blastoderm expansion, while maintaining VM tension in later stages resists the convergence of the posterior body causing stalled elongation, failure of neural tube closure, and axis rupture. Biochemical and structural analysis shows that VM weakening is associated with the reduction of outer-layer glycoprotein fibers, which is caused by an increasing albumen pH due to CO2 release from the egg. Our results identify a previously unrecognized potential cause of body axis defects through mis-regulation of extraembryonic tissue tension.

The evaluation of the habitat quality dynamics is important to conservation management and sustainable development. Forecasting future habitat quality changes depends on reliable projections of future land uses that align with government’s future land-use planning. Additionally, the spatial heterogeneity problem cannot be dismissed in spatial modelling and the uneven distribution of urban development should be considered in the land use simulation and prediction. To address these issues, we established a bidirectional framework: from the top-down side, we impose land use and land cover (LULC) quantity constraints considering the goals of government land use planning; from the bottom-up side, we adopt zoning methods to consider the spatial heterogeneity of land use transition rules for improving the accuracy of land use prediction. We applied this approach to project habitat quality of Beijing in 2035 under different development scenarios. Firstly, we constructed multiple future scenarios (natural development, ND; economic development, ED; ecological protection, EP; livable city, LC) and computed the quantities of various land uses under those scenarios. Secondly, we addressed the spatial heterogeneity issue by adopting the zoning methods to improve the land use simulation accuracy of the PLUS model. Finally, based on the predicted LULC data, we analyzed the future habitat quality patterns in Beijing under different scenarios using InVEST model. We found that the zoning method can improve the simulation accuracy of LULC. Furthermore, significant spatial differences can be found in the habitat quality under different land use scenarios, which represent various government land use strategies. Among the four scenarios, the LC scenario is the most conducive one due to its ability to achieve a good balance between economic and ecological benefits. This study provides evidence for justifying the feasibility of Beijing’s development plan to become a livable city.

Heavy neutrinos are usually introduced to accommodate tiny neutrino masses via seesaw mechanism, or to alleviate the cosmology problem, and there may exist charged Higgs which couple to the leptons with different flavors. These two features can appear in the Twin Higgs models. What interests us is that such new particles and interactions may lead to new contributions to the lepton flavor violating processes [Formula: see text] and [Formula: see text]. We find that current experimental data can constrain the parameter spaces and certain lepton flavor violating processes can possibly be tested by the next generation experiments.

As of now, direct measurements of middle and upper atmospheric wind are still scarce, and the observation method is limited, especially for the upper stratosphere and lower mesosphere. A new method to derive line-of-sight wind from 30 to more than 120 km is proposed using a high-resolution Terahertz (THz) radiometer, which can fill the measurement gap between lidar and interferometer. Simulations from 0.1 THz to 5 THz for evaluating the feasibility of the spaceborne THz limb sounder are performed in this study. The results show that high-precision wind (better than 5 m s−1) can be obtained from 40 to 70 km by covering a cluster of strong O3 lines. By choosing strong O2 or H2O lines, the high-quality measurement can be extended to 105 km. The O atom (OI) lines can provide wind signals in the higher atmosphere. In addition, performance of different instrument parameters include resolution, bandwidth and measurement noise are analyzed and four different band combinations are suggested at last.

The curse of dimensionality has long been one of the biggest challenges in solving large-scale simulation ranking and selection (R&S) problems. As the number of systems grows, existing approaches to R&S relying on the Bonferroni correction become increasingly conservative, rendering them overachieving in error control and consuming more computational resources than necessary. In “Bonferroni-Free and Indifference-Zone-Flexible Sequential Elimination Procedures for Ranking and Selection,” Wang, Wan, and Chen develop Bonferroni-free and indifference-zone-optional ranking and selection procedures to deliver the prescribed probabilistic guarantee without overshooting. Their approach is to conduct always valid and fully sequential hypothesis tests that enable continuous monitoring of each candidate system and control the probability of correct selection. In addition, the indifference-zone parameter becomes dispensable in their procedures; however, when provided appropriately, it could improve the procedures’ computational and statistical efficiency.

Boosted dark matter is a promising method for probing light dark matter, with a well-developed computational framework for spin-independent scattering already existing. The spin-dependent case, on the other hand, lacks a coherent treatment. We therefore give the first comprehensive derivation of the spin-dependent scattering cross section for boosted dark matter, finding that certain effects can lead to enhanced experimental sensitivity compared to the conventional contact interaction. For example, when the transfer momentum is sufficiently large, the time component of the dark matter current contributes significantly to the proton structure factor. Also, even without a light mediator, we find a residual momentum dependence in the quark-nucleon matching operation that can contribute similarly. We promote this endeavor by deriving direct limits on sub-GeV spin-dependent scattering of boosted dark matter from terrestrial data. We find that the exclusion limits from the boosted structure factor differ by as much as six orders of magnitude from those calculated using nonrelativistic structure factors.

Supplemental Figure 1. KDM6B and KDM6A expression profiles in breast cancer subtypes. Supplemental Figure 2. KDM6A over-expression is not associated with poor clinical outcome. Supplemental Figure 3.KDM6B knockdown does not result in cell death in SKBR3, MDA-MB-415, BT20 and SUM159 cells. Supplemental Figure 4.IGFBP5 is a prognostic factor that predicts poor prognosis in luminal breast cancer patients. Supplemental Figure5.IGFBP5 regulated by KDM6B and its effect on cell survival.

Despite showing promise against PIK3CA-mutant breast cancers in preclinical studies, PI3K/AKT pathway inhibitors demonstrate limited clinical efficacy as monotherapy. Here, we found that histone H3K27me3 demethylase KDM6B-targeted IGFBP5 expression provides a protective mechanism for PI3K/AKT inhibitor-induced apoptosis in breast cancer cells. We found that overexpression of KDM6B and IGFBP5 in luminal breast cancer are positively associated with poorer disease outcomes. Mechanistically, KDM6B promotes IGFBP5 expression by antagonizing EZH2-mediated repression, and pharmacologic inhibition of KDM6B augments apoptotic response to PI3K/AKT inhibitor treatment. Moreover, the IGFBP5 expression is upregulated upon acquired resistance to the PI3K inhibitor GDC-0941, which is associated with an epigenetic switch from H3K27me3 to H3K27Ac at the IGFBP5 gene promoter. Intriguingly, GDC-0941–resistant breast cancer cells remained sensitive to KDM6B or IGFBP5 inhibition, indicating the dependency on the KDM6B–IGFBP5 axis to confer the survival advantage in GDC-0941–resistant cells. Our study reveals an epigenetic mechanism associated with resistance to targeted therapy and demonstrates that therapeutic targeting of KDM6B-mediated IGFBP5 expression may provide a useful approach to mitigate both intrinsic and acquired resistance to the PI3K inhibitor in breast cancer. Mol Cancer Ther; 17(9); 1973–83. ©2018 AACR.

In recent years, arginine deiminase (ADI, EC 3.5.3.6) has attracted much attention as a biocatalyst that produces the functional amino acid l-citrulline from l-arginine and also as an anticancer enzyme. Here, we identified and characterized a putative ADI from the thermophilic bacterium Halothermothrix orenii. The H. orenii ADI (H-ADI) protein was expressed in Escherichia coli BL21(DE3) with a specific activity of 91.8 U/mg protein at 55°C and pH 6.5. The enzyme remained at 74% relative activity after incubation at 45°C for 180 min, only 25% at 50°C. The melting temperature was 56°C. H-ADI is not a metal-requiring enzyme; Ni