Diverse forms of unwanted signal variations in mass spectrometry-based metabolomics data adversely affect the accuracies of metabolic profiling. A variety of normalization methods have been developed ...for addressing this problem. However, their performances vary greatly and depend heavily on the nature of the studied data. Moreover, given the complexity of the actual data, it is not feasible to assess the performance of methods by single criterion. We therefore developed NOREVA to enable performance evaluation of various normalization methods from multiple perspectives. NOREVA integrated five well-established criteria (each with a distinct underlying theory) to ensure more comprehensive evaluation than any single criterion. It provided the most complete set of the available normalization methods, with unique features of removing overall unwanted variations based on quality control metabolites and allowing quality control samples based correction sequentially followed by data normalization. The originality of NOREVA and the reliability of its algorithms were extensively validated by case studies on five benchmark datasets. In sum, NOREVA is distinguished for its capability of identifying the well performed normalization method by taking multiple criteria into consideration and can be an indispensable complement to other available tools. NOREVA can be freely accessed at http://server.idrb.cqu.edu.cn/noreva/.
In this paper, a theoretical and experimental analysis of polarimetric synthetic aperture radar (SAR) architectures is undertaken for sea oil slick observation purposes. Reference is made to the ...conventional full-polarimetric (FP) SAR that is here contrasted with new-generation polarimetric SAR architectures, known as compact-polarimetric (CP) SAR. Two CP modes are considered, i.e., the hybrid-polarity and π/4 modes, whose measurements are emulated from actual L- and C-band FP SAR data. Polarimetric sea surface scattering is predicted according to an extended version of the Bragg scattering model (X-Bragg) in order to point out the differences exhibited between FP and CP SAR architectures and among CP SAR modes. Theoretical predictions are then contrasted with experiments undertaken on actual polarimetric SAR data collected over well-known oil slicks and weak-damping surfactants. Results confirm model prediction, showing that differences mainly apply when polarimetric features are estimated over slick-free sea surface using different SAR architectures, with the π/4 mode behaving closer to FP SAR. Although CP SAR architectures measure only a subset of the FP information content, they represent an interesting operational alternative for both detecting oil slicks and discriminating them from weak-damping surfactants.
The study of the high-temperature superconductive property in compressed hydrogen (H)-rich hydrides has been motivated by hydrides, which become superconducting at low pressure due to chemical ...precompression. In the present study, we report the first-principles structure searches for stable vanadium(V) hydrides over a pressure scope 0–200 GPa, where stable unexpected stoichiometries of H-rich V hydrides (e.g., VH3, VH5, and VH8) emerge. These dense H-rich V hydrides are metallic with a strong ionic feature, and the coordination number of metal V gradually increases with H content. In particular, C2/m-VH8, which consists of infinite zigzag chains of sole H2 molecules, has the highest coordination number of 16. From our electron–phonon calculations, one can see that P63/mmm-VH5 and C2/m-VH8 are superconductors with estimated superconducting temperatures (T c) of 18.5 and 71.4 K at 200 GPa, respectively. Our simulations not only uncovered the crystal structures of V hydrides, but also established the high-temperature superconductive nature of them.
We report the first example of 2D covalent organic framework nanosheets (Redox‐COF1) for the selective reduction and in situ loading of valence‐variable, redox‐sensitive and long‐lived radionuclides ...(abbreviated as VRL nuclides). Compared with sorbents based on chemical adsorption and physical adsorption, the redox adsorption mechanism of Redox‐COF1 can effectively reduce the impact of functional group protonation under the usual high‐acidity conditions in chemisorption, and raise the adsorption efficiency from the monotonous capture by pores in physisorption. The adsorption selectivity for UO22+ reaches up to unprecedented ca. 97 % at pH 3, more than for any analogous adsorbing material.
In U go: High‐performance novel sorbing materials with prospective applications in selective separation of target long‐lived radionuclides are prepared. Using the layered covalent organic framework (COF) material, the adsorption selectivity for UO22+ reaches up to unprecedented 97 % at pH 3, which is more than for any analogous adsorbing material.
Training schemes for full duplex two-way relays are investigated. We propose a novel one-block training scheme with a maximum likelihood estimator to estimate the channels between the nodes as well ...as the residual self-interference (RSI) channel simultaneously. A quasi-Newton algorithm is used to solve the estimator. As a baseline, a multi-block training scheme is also considered. The Cramer-Rao bounds of the one-block and multi-block training schemes are derived. By using the Szegö's theorem about Toeplitz matrices, we analyze how the channel parameters and transmit powers affect the Fisher information. We show analytically that exploiting the structure arising from the RSI channel increases its Fisher information. Numerical results show the benefits of estimating the RSI channel.
The preparation of subnanoporous covalent-organic-framework (COF) membranes with high performance for ion/molecule sieving still remains a great challenge. In addition to the difficulties in ...fabricating large-area COF membranes, the main reason is that the pore size of 2D COFs is much larger than that of most gas molecules and/or ions. It is urgently required to further narrow their pore sizes to meet different separation demands. Herein, we report a simple and scalable way to grow large-area, pliable, free-standing COF membranes via a one-step route at organic-organic interface. The pore sizes of the membranes can be adjusted from >1 nm to sub-nm scale by changing the stacking mode of COF layers from AA to AB stacking. The obtained AB stacking COF membrane composed of highly-ordered nanoflakes is demonstrated to have narrow aperture (∼0.6 nm), uniform pore distribution and shows good potential in organic solvent nanofiltration, water treatment and gas separation.
Circumstantial evidence for the sources of uranium in ore deposits may be drawn from the study of deposit geochemistry and mineralogy. However, direct evidence supporting uranium leaching from source ...rocks has rarely been found. This study investigates the source of uranium in the Baiyanghe deposit in the Xiemisitai Mountains, northwest China. The main uranium ore bodies occur as fracture-fillings along contact zones between the Yangzhuang granite porphyry and the Devonian volcanic rocks. Zircon, thorite, columbite-(Mn), and bastnasite are the dominant accessory minerals that host uranium in the granite porphyry. In situ columbite-(Mn) LA-ICP-MS U-Pb dating yields a weighted mean 206Pb/238U age of 310±4 Ma, suggesting that the Yangzhuang granite porphyry was emplaced during the Late Carboniferous. Backscattered electron (BSE) images reveal that various degrees of alteration of these same accessory minerals may be observed in the granite porphyry, and the altered domains of these minerals have lower BSE intensities compared to the unaltered domains. Results indicate that the altered domains of zircon grains have lower concentrations of Zr, Si, and U, and higher concentrations of Y, Fe, Ca, and P relative to the unaltered domains, and the altered domains of columbite-(Mn) grains are enriched in Ti and Fe and are depleted in Nb, Ta, Mn, U, and Zr. The altered domains of thorite grains have higher concentrations of Zr, Fe, Ca, Nb, and P, and lower Th and U compared to those of the relict domains. The petrochemical data indicate that the granite porphyry experienced losses in U, Be, F, Ba, Sr, Pb, Zr, Mo, Nb, Ta, and Hf during alteration. These results suggest that the past-magmatic hydrothermal fluids might be responsible for the mobilization of uranium form minerals in the granite porphyry. It is concluded that U-bearing accessory minerals in the granite porphyry were the primary source of uranium, and that post-magmatic hydrothermal processes caused remobilization and significant localized enrichment of the uranium to form high-grade ores as fracture-fillings along its contacts.
A hybrid backscattering model is built to provide a consistent description for C-band VH- and VV-polarized normalized radar cross sections (NRCSs). Ocean surface coand cross-polarized NRCS are both ...treated as a sum of Bragg and non-Bragg scattering components. To better understand the synthetic aperture radar (SAR) observed NRCS signals under high-wind conditions, five C-band RADARSAT-2 dual-polarization SAR hurricane images and the collocated wind vectors measured by the airborne stepped-frequency microwave radiometer (SFMR) are collected. Based on the match-up data, we add a non-Bragg term in the composite Bragg theory to explain the discrepancy between the measurements in the cross-polarization channel and the existing theory results. The non-Bragg scattering to Bragg scattering ratio (Br) is found to be a constant. We build the hybrid backscattering model with Br and establish a relationship between the cross-polarization NRCS and the radar incidence angle under different wind conditions. The NRCS dependence on incidence angle is simulated by the hybrid backscattering model. Finally, a C-band Cross-Polarization Coupled-Parameters Ocean (C-3PO) model is developed to retrieve hurricane winds using VH-polarized ScanSAR by including the radar incidence angle. The collocated SAR and SFMR data sets are separated into two parts: data set-A, for hybrid backscattering model derivation and C-3PO model coefficients tuning, and data set-B, for hurricane wind validation. C-3PO model validation results show that the model is suitable for ocean surface wind mapping from RADARSAT-2 cross-polarization ScanSAR images. The retrieval has a rootmean-square error less than 3 m/s for wind speed up to 40 m/s.
Two cases of mode-2 internal solitary waves (ISWs) induced by an anticyclonic eddy (AE) were clearly present in two synthetic aperture radar images acquired in the South China Sea (SCS) in April ...2001. Similar ISWs were repeatedly observed in the same area one month later in May, but in that case, the ISW patterns indicated that they were regular mode-1 ISWs. To confirm that those ISWs in April are of mode-2 type, we analyze the in situ and other remote sensing data and propose two possible mode-2 ISW generation processes: 1) an eddy-induced change of the water stratification, which results in favorable hydrographic conditions for internal wave generation, and 2) the resonance between mode-1 internal tides and AE excites mode-2 internal tides, and the mode-2 internal tides disintegrate into mode-2 ISWs. The sea level anomaly and sea surface temperature data in April 2001 show that an AE existed in this area in April. Argo profile data within AEs from 1990 to 2014 in the SCS are used to show how an AE affects the vertical water properties and creates favorable conditions for mode-2 ISWs, and these conditions did exist in the study area in April 2001. The observed mode-2 ISW cases provide the first evidence of the existence of eddy-induced mode-2 ISWs in the SCS.
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