Searching for the signature of the violation of chiral charge conservation in solids has inspired a growing passion for the magneto-transport in topological semimetals. One of the open questions is ...how the conductivity depends on magnetic fields in a semimetal phase when the Fermi energy crosses the Weyl nodes. Here, we study both the longitudinal and transverse magnetoconductivity of a topological Weyl semimetal near the Weyl nodes with the help of a two-node model that includes all the topological semimetal properties. In the semimetal phase, the Fermi energy crosses only the 0th Landau bands in magnetic fields. For a finite potential range of impurities, it is found that both the longitudinal and transverse magnetoconductivity are positive and linear at the Weyl nodes, leading to an anisotropic and negative magnetoresistivity. The longitudinal magnetoconductivity depends on the potential range of impurities. The longitudinal conductivity remains finite at zero field, even though the density of states vanishes at the Weyl nodes. This work establishes a relation between the linear magnetoconductivity and the intrinsic topological Weyl semimetal phase.
In this study high‐valent Cu(III) trifluoromethyl compounds in combination with DMSO is shown to be an efficient and mild oxidizing system for the conversion of alcohols to ketones (aldehydes as ...well). Trifluoromethoxylated sulfonium species is proposed to be initially formed that engages in crucial steps of alkoxy replacement at sulfonium center and deprotonative collapse of the resulting alkoxysulfonium intermediate in the presence of a base. This reaction is highly selective without over‐oxidation, and can tolerate a broad range of functional groups owing to mild oxidizing ability of the Cu(III)‐CF3/DMSO system and the inert N2 conditions. This method can be applied to the synthesis and functionalization of commercial drug compounds. This study illustrates an unusual reactivity property of high‐valent Cu(III) trifluoromethyl compounds beyond the conventional CF3 group transfer reactivity, and opens up new opportunities for developing novel reactions of Cu(III)‐CF3 compounds. The combined use of high‐valent Cu(III)‐CF3 compound and DMSO is anticipated to find more applications to develop other novel and useful oxidation reactions.
When high‐valent Cu(III)‐CF3 compounds meet DMSO, a unique platform is set up to manipulate sulfonium chemistry. A case study of oxidation of alcohols to ketones is shown herein. Crucial trifluoromethoxysulfonium is initially generated, and reacts with alcohols to give new alkoxysulfonium species via ligand exchange. Subsequent base‐promoted E2 elimination gives ketones with the release of Me2S.
• Soybean (Glycine max) production is severely affected in unfavorable environments. Identification of the regulatory factors conferring stress tolerance would facilitate soybean breeding.
• In this ...study, through coexpression network analysis of salt-tolerant wild soybeans, together with molecular and genetic approaches, we revealed a previously unidentified function of a class B heat shock factor, HSFB2b, in soybean salt stress response.
• We showed that HSFB2b improves salt tolerance through the promotion of flavonoid accumulation by activating one subset of flavonoid biosynthesis-related genes and by inhibiting the repressor gene GmNAC2 to release another subset of genes in the flavonoid biosynthesis pathway. Moreover, four promoter haplotypes of HSFB2b were identified from wild and cultivated soybeans. Promoter haplotype II from salt-tolerant wild soybean Y20, with high promoter activity under salt stress, is probably selected for during domestication. Another promoter haplotype, III, from salt-tolerant wild soybean Y55, had the highest promoter activity under salt stress, had a low distribution frequency and may be subjected to the next wave of selection.
• Together, our results revealed the mechanism of HSFB2b in soybean salt stress tolerance. Its promoter variations were identified, and the haplotype with high activity may be adopted for breeding better soybean cultivars that are adapted to stress conditions.
Rebleeding is a serious complication of aneurysmal subarachnoid hemorrhaging. To date, there are conflicting data regarding the factors contributing to rebleeding and their significance.
A systematic ...review of PubMed and Embase databases was conducted for studies pertaining to aneurysmal subarachnoid hemorrhage (aSAH) and rebleeding in order to assess the associated risk factors. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated from fourteen studies comprised of a total of 5693 patients that met the inclusion criteria.
Higher rebleeding rates were observed < 6 h after the initial aSAH (OR = 3.22, 95% CI = 1.46-7.12), and were associated with high systolic blood pressure (OR = 1.93, 95% CI = 1.31-2.83), poor Hunt-Hess grade (III-IV) (OR = 3.43, 95% CI = 2.33-5.05), intracerebral or intraventricular hematomas (OR = 1.65, 95% CI = 1.33-2.05), posterior circulation aneurysms (OR = 2.15, 95% CI = 1.32-3.49), and aneurysms >10 mm in size (OR = 1.70, 95% CI = 1.35-2.14).
Aneurysmal rebleeding occurs more frequently within the first 6 hours after the initial aSAH. Risk factors associated with rebleeding include high systolic pressure, the presence of an intracerebral or intraventricular hematoma, poor Hunt-Hess grade (III-IV), aneurysms in the posterior circulation, and an aneurysm >10 mm in size.
The article reviews comprehensively the emergence and development of China’s national legislative system for cultural heritage, with a particular focus on built heritage. It covers the period from ...the late Qing Dynasty to the present. The antiquity preservation legislation and policies from the late Qing Dynasty to the early Republic of China (ROC) era signify the initial emergence of the state-led legislative system for cultural heritage protection and management. The Interim Regulations on the Conservation and Management of Cultural Heritage, passed in 1960, represent the state’s first targeted effort to protect significant historic monuments and sites. The 1982 Cultural Heritage Protection Law (CHPL) established the mechanism for the conservation of Protected Cultural Heritage Sites (PCHS), while the 2008 Regulation on the Conservation of Famous Historic and Cultural Cities, Towns and Villages (RCFHCCTV) defined the principles for the conservation and management of historic cities. China’s current jurisdiction for the conservation of cultural heritage is underpinned by legislation such as the CHPL, the Intangible Cultural Heritage Law (ICHL), and the RCFHCCTV. This article analyses the characteristics of the current state legislative system for built heritage conservation and the challenges and constraints regarding urban conservation. It concludes with strategic guidance for improving the legislation for China’s built heritage conservation in the present era of rapid economic development and urban regeneration.
A selective intermolecular amino‐trifluoromethylation of alkenes is developed to produce a range of biologically active β‐trifluoromethyl amines. This method exploits a crucial high‐valent ...Cu(III)−CF3 complex as a combined source of CF3 radical and Cu(II) oxidant through homolytic Cu(III)−CF3 bond cleavage. This unique mode of CF3 radical generation is distinct from current dominant methods that rely largely on photoredox catalysis or the use of sacrificing radical initiator. This represents a significant advantage in that it greatly simplifies the reaction conditions, brings about operational convenience, and is beneficial to suppress various side reactions under otherwise more complicated conditions. A tertiary alkyl radical generated from addition of CF3 radical to alkenes is proposed to react with amines to enable C−N formation with the assistance of in‐situ Cu(II) oxidant. This reaction shows good chemo‐ and regio‐selectivity, suppressing a number of potential side reactions. The free manipulation of readily available Cu(III)−CF3 compound and feedstock compounds of alkenes and anilines greatly broadens the reaction scope. The good chemo‐ and regioselectivity, and operational convenience make this reaction attractive from the synthetic viewpoint. The reactivity of high‐valent Cu(III)−CF3 compounds disclosed in this study may be exploited to develop other interesting reactions, and to enrich the currently underdeveloped Cu(III) chemistry.
Abstract
The search for extraterrestrial intelligence (SETI) commensal surveys aim to scan the sky to find possible technosignatures from an extraterrestrial intelligence (ETI). The mitigation of ...radio frequency interference (RFI) is an important step, especially for the most sensitive Five-hundred-meter Aperture Spherical radio Telescope (FAST), which can detect more weak RFI. In this paper, we propose several new techniques for RFI mitigation and use our procedure to search for ETI signals from the archival data of FAST’s first SETI commensal survey. We detect the persistent narrowband RFI by setting a threshold of the signals’ sky separation and detect the drifting RFI (and potentially other types of RFI) using the Hough transform. We also use the clustering algorithms to remove more RFI and select candidates. The results of our procedure are compared to the earlier work on the same FAST data. We find that our methods, though relatively simpler in computation, remove more RFI (99.9912% compared to 99.9063% in the earlier work) but preserve the simulated ETI signals, except for those (5.1%) severely affected by the RFI. We also report more interesting candidate signals, about a dozen of which are new candidates that were not previously reported. In addition, we find that the proposed Hough transform method, with suitable parameters, also has the potential to remove the broadband RFI. We conclude that our methods can effectively remove the vast majority of the RFI while preserving and finding the candidate signals that we are interested in.
Vertical deformation can be revealed by various techniques such as precise leveling, satellite imagery, and extensometry. Despite considerable effort, recording detailed subsurface deformation using ...traditional extensometers remains challenging when attempting to detect localized deformation. Here we introduce distributed fiber optic sensing based on Brillouin scattering as a geophysical exploration method for imaging distributed profiles of vertical deformation. By examining fiber optic cable‐soil interaction we found a threshold in confining pressure to achieve a strong cable‐soil coupling, thus validating data collected from a borehole‐embedded fiber optic cable deployed in Shengze, southern Yangtze Delta, China. Clear‐cut strain profiles acquired from November 2014 to December 2016 allowed us to pinpoint where compaction or rebound was actively occurring and examine strain responses at various locations along the entire cable length. We suggest that distributed fiber optic sensing can complement with extensometry and remote sensing techniques for improved monitoring of vertical deformation.
Plain Language Summary
Recording detailed subsurface deformation using traditional methods (e.g., extensometers) is sometimes difficult due to limited measuring points. This dilemma may be overcome by using the emerging distributed fiber optic sensing technology, which transforms common telecommunication fiber optic cables into sensors capable of making distributed strain measurements. We report the use of this technology for monitoring distributions of vertical deformation resulting from groundwater ion in Shengze, southern Yangtze Delta, China. An evaluation of the performance of a borehole‐embedded fiber optic cable helps us to validate the in situ strain data. The advantage of using this technology for vertical deformation sensing is the ability to locate any strata undergoing compaction or rebound and look at strain responses at any depth of interest. Moreover, recording subsurface changes in this fashion may also be useful in other geophysical and engineering applications that require refined monitoring of the media.
Key Points
Distributed fiber optic sensing with Brillouin scattering provides a clear subsurface strain profile using a single fiber optic cable
We find a threshold in confining pressure to achieve a strong fiber optic cable‐soil coupling
Distributed fiber optic sensing can complement with existing techniques for improved monitoring of vertical deformation
This paper presents a method to unwrap phase pixel by pixel by solely using geometric constraints of the structured light system without requiring additional image acquisition or another camera. ...Specifically, an artificial absolute phase map, Φmin, at a given virtual depth plane z = zmin, is created from geometric constraints of the calibrated structured light system; the wrapped phase is pixel-by-pixel unwrapped by referring to Φmin. Since Φmin is defined in the projector space, the unwrapped phase obtained from this method is absolute for each pixel. Experimental results demonstrate the success of this proposed novel absolute phase unwrapping method.
A general and selective method is developed that allows direct vinylic C−H bond trifluoromethylation of 1,1‐diarylalkenes by a high‐valent copper(III) trifluoromethyl complex, producing biologically ...active trifluoromethylated alkenes (as well as trifluoromethylated carbocyclic compounds). This fundamental reactivity of Cu(III)−CF3 compounds has thus far been unknown. The presence of a tertiary amine is crucial to this reaction, acting as both a weak base and a single electron transfer (SET) promoter to the vinylic hydrogen. This method starts from bulk olefins under cost‐effective conditions (without the need for external noble metal photocatalyst or stoichiometric amounts of oxidant), and thus is valuable for practical and sustainable applications.
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