This cutting-edge research work presents a comprehensive and in-depth theoretical investigation into the mechanism of Au(i)-catalyzed annulations between ynamides and 1,2-benzisoxazoles, as well as ...the chemoselectivity of the reactions in the presence of different ligands (L = JohnPhos, IPr) and the factors influencing the Z/E-configuration of the resulting 6-membered cyclic products. State-of-the-art density functional theory calculations reveal that (i) the reaction mechanism involves three distinct processes: process 1 corresponds to the transformation of a gold-π-alkyne precursor into a gold–carbene intermediate; process 2 involves the conversion of gold–carbene intermediates into 6-membered/7-membered cyclic intermediates; process 3 involves the conversion of 6-membered/7-membered cyclic intermediates to furnish 6-membered/7-membered cyclic products, respectively. (ii) The distinct chemoselectivity exhibited by the two ligands, JohnPhos and IPr, has been thoroughly explored through distortion/interaction analysis. The distortion energy is responsible for ligand-controlled chemoselectivity. (iii) The Z/E-configuration of 6-membered cyclic products is determined by the N-attack step of 1,2-benzisoxazole on the gold-π-alkyne. These theoretical findings hold significant implications for synthetic chemists, providing valuable insights into the design of novel catalytic systems and the prediction of reaction pathways and selectivity patterns in related organic transformations involving ynamides and isoxazoles.
An efficient and site-selective aromatic C–H λ3-iodanation reaction is achieved using benziodoxole triflate (BXT) as an electrophile under room temperature conditions. The reaction tolerates a ...variety of electron-rich arenes and heteroarenes to afford the corresponding arylbenziodoxoles in moderate to good yields. The reaction can also be performed mechanochemically by grinding a mixture of solid arenes and BXT under solvent-free conditions. The arylbenziodoxoles can be used for various C–C and C–heteroatom bond formations, and are also amenable to further modification by electrophilic halogenation. DFT calculations suggested that the present reaction proceeds via a concerted λ3-iodanation–deprotonation transition state, where the triflate anion acts as an internal base.
Ectopic spleen (ES) is a rare condition. It is difficult to diagnose with conventional imaging modalities. In this case series, we presented the imaging features of three misdiagnosed ES cases in our ...hospital and previously reported cases to compare the consistency of enhancement patterns among different imaging modalities with varied phases. Finally, 22 cases were reviewed. We determined that variable arterial phase enhancement and persistent enhancement throughout the portal and delayed phases are present in contrast-enhanced ultrasound (CEUS) imaging of the ES and found the arterial phase of CEUS had the highest consistency compared with computerized tomography (CT) and magnetic resonance imaging (MRI).
Novel adsorbent, diethylenetriamine-grafted
Spirodela polyrhiza
(DSP), was synthesized via modifying natural
S. polyrhiza
(SP) with diethylenetriamine by cross-linking with epichlorohydrin and ...applied to adsorb Ni
2+
and Pb
2+
from water. The effecting parameters on adsorption of Ni
2+
and Pb
2+
such as adsorbent dosage, pH, contact time, temperature, and initial concentration were studied through equilibrium experiments. The adsorption of Ni
2+
and Pb
2+
followed the pseudo-second-order model and the Langmuir isotherm adsorption model. The study discusses thermodynamic parameters, including changes in Gibbs free energy, entropy, and enthalpy, for the adsorption of Ni
2+
and Pb
2+
on DSP, and revealed that the adsorption process was spontaneous and exothermic under natural conditions. The maximum Ni
2+
and Pb
2+
adsorption capacities of DSP were 33.02 and 36.50 mg/g, respectively. The newly prepared materials were characterized through scanning electron microscopy (SEM), mapping analysis, and zeta potential analysis. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that functional groups (-OH and N-H) were involved in Ni
2+
and Pb
2+
adsorption. Notably, DSP can be easily regenerated and reused for multiple cycles. Therefore, DSP is a promising adsorbent for effective Ni
2+
and Pb
2+
removal.
Considering the diversity of soil contents, quality and usability, a systematic scientific study on the elemental and chemical composition (major and minor nutrients elements, trace elements, heavy ...metals, etc.) of soil is very important. Rapid and accurate detection and prevention of soil contamination (mainly in pollutants of heavy metals) is deemed to be a concerned and serious central issue in modern agriculture and agricultural sustainable development. In order to study the chemical composition of soil, laser induced breakdown spectroscopy (LIBS) has been applied recently. LIBS technology, a kind of atomic emission spectroscopy, is regarded as a future “Superstar” in the field of chemical analysis and green analytical techniques. In this work, the research achievements and trends of soil elements detection based on LIBS technology were reviewed. The structural composition and operating principle of LIBS system was briefly introduced. The paper offered a review of LIBS applications, including detection and analysis of major element, minor nutrient element and heavy metal element. Simultaneously, LIBS applications to analysis of the soil related materials, plants-related issues (nutrients, pesticide residues, and plants disease) were briefly summarized. The research tendency and developing prospects of LIBS in agriculture were presented at last.
•Structural composition and operating principle of LIBS was introduced.•Applications of major, micro, heavy metal, and soil related materials were stated.•Research tendency and developing prospects of LIBS in soil detection are summarized.
A new design adhesive mixed with flame retardant was developed by an optimized and modified dedicated flame retardant and selected at a suitable proportion between the adhesive and flame retardant as ...well as the coating amount of the adhesive. The new design adhesive was applied to ecological board production, and the flame-retardant properties of products were examined. The dipping and peeling properties, surface bonding strength, and formaldehyde emission reached the national standard GB/T 34722-2017, the flame retardancy meets the requirements of GB/T 8626-2017, GB/T 20284-2006, GB/T20285-2006, and it also reaches the B1-C level (the nonflammable level in the flame retardant level). This study not only has theoretical guidance but also has strong practical value to provide a basis and data support for the research and development of flame-retardant ecological boards.
We address all round development of the standard cell library including simulation, layout, and testing. We present a new circuit analysis scheme based on Monte-Carlo simulations and process corners. ...Using a phase modulation decoder as an example circuit, we identify weak spots in the design that was originally optimized for parameter margins. To support static timing analysis for very high complexity circuits, we describe the timing characterization of library cells as a function of its load, and demonstrate digital timing verification with timing back-annotation using Verilog hardware descriptive language. For the layout of library cells, we present architecture for the dual RSFQ/ERSFQ standard cell library for the MIT-LL, 10 kA/cm 2 , SFQ4EE and SFQ5EE processes. Testing and characterizing hundreds of library cells, including unique cells and their layout variations, is a challenge. For efficient characterization of the digital cells, we have developed an NDRO cell-based multiplexing scheme that lets us characterize hundreds of cells on a single chip. For better model-to-hardware correlation, we have implemented a differential delay measurement scheme using ring oscillators that facilitates timing characterization of the synchronous and asynchronous cells. We also report design and measurement of statistical variations for the critical current of decision-making pair of junctions.
Abstract
The pollution of heavy metals in irrigation water was related to the management-control of the risk of heavy metals in farmland and the safe production of crops. There were various sources ...of irrigation water in the suburb farmlands of Xijiang River. We investigated the sources and distribution characteristics of heavy metals in the irrigation water sources on a riverside and inside-dyke farmland of Xijiang River. According to sample test results, it was found that nearly 100% of heavy metals that we were concerned about were detected in the irrigation water sources in the study. The box plot showed that the average content of other elements ranged from 1.65 to 43.75 μg·L−1, and the average level of cadmium was 0.02 μg·L−1 in the studied area. According to quantitative evaluation index and analysis of distribution characteristics, most heavy metals were at relatively low concentration in the irrigation water sources, while mercury content was far greater than other elements, followed by arsenic. Arsenic and mercury had become increasingly prominent problems in local irrigation water sources. River quality was more likely to be affected by river water and agricultural activities, while groundwater quality was more likely to be affected by natural causes. According to single/comprehensive water-quality evaluations, the comprehensive water quality evaluation ranged from level I to level III, but the single-factor index evaluations of mercury in most water samples and arsenic in two groundwater samples were of ‘Inferior’ level. Attention should be paid to the monitoring of mercury and arsenic (in the groundwater) in the studied area. The disposal methods of farmland water inflow and drainage should be increased if necessary, and reducing the influence of human activities on the natural weathering and leaching of heavy metals was an effective measure to avoid risk of agricultural production.
A three-component photoredox 1,2-alkylamination of styrenes involving functionalization of C(sp3)–H bonds in alkyl halides instead of functionalization of C-halogen bonds is disclosed. A variety of ...commercialized C(sp3)–H alkanes, including dichloromethane, acetonitrile, and acetone, used as alkyl radical precursors and solvents, were compatible with this methodology. The mechanistic study shows that alkyl radicals are generated by hydrogen atom transfer (HAT) between aryl radicals and alkyl halides.
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