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排序方式: 共有741条查询结果,搜索用时 31 毫秒
41.
Adrián Serrano Mora Sean T. McBeath Clément A. Cid Michael R. Hoffmann Nigel J.D. Graham 《Current Opinion in Electrochemistry》2022
While diamond electrodes have been commonly used to generate ?OH to treat a variety of persistent water and wastewater micropollutants, mass transfer limitations and the non-selective, short-lived nature of the ?OH restrict the degradation to the solution at, or near, the electrode surface. However, diamond electrodes can generate oxidizing species that facilitate micropollutant degradation in the bulk water solution. These include persulfate, sulfate radicals, peroxodiphosphate, ferrate, permanganate, reactive chlorine species, hydrogen peroxide, and ozone, which have been reported during electrochemical treatment of water with diamond electrodes. Although still restricted to specialized applications, recent studies, summarized in this review, have proven the electrogeneration of these additional oxidant species to be effective. They have shown the adaptability and potential of diamond electrode-based water treatment to mitigate the presence of micropollutants in water. 相似文献
42.
Surendra V. Singh Jayaram Vishakantaiah Jaya K. Meka Vijayan Sivaprahasam Vijayanand Chandrasekaran Rebecca Thombre Vijay Thiruvenkatam Ambresh Mallya Balabhadrapatruni N. Rajasekhar Mariyappan Muruganantham Akshay Datey Hugh Hill Anil Bhardwaj Gopalan Jagadeesh Kalidevapura P. J. Reddy Nigel J. Mason Bhalamurugan Sivaraman 《Molecules (Basel, Switzerland)》2020,25(23)
The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures. Such structures are formed on timescales of about 2 ms due to impact induced shock heating and subsequent cooling. This discovery suggests that the building blocks of life could have self-assembled not just on Earth but on other planetary bodies as a result of impact events. Our study also provides further experimental evidence for the ‘threads’ observed in meteorites being due to assemblages of (bio)molecules arising from impact-induced shocks. 相似文献
43.
We report a simple approach to the production of carbon fiber‐based amperometric microbiosensors for selective detection of hydrogen peroxide (H2O2), which was achieved by electrometallization of carbon fiber microelectrodes (CFMs) by electrodeposition of Pt nanoparticles. The Pt‐carbon hybrid sensing interface provided a sensitivity of 7711±587 μA ? mM?1 ? cm?2, a detection limit of 0.53±0.16 μM (S/N=3), a linear range of 0.8 μM–8.6 mM, and a response time of <2 sec. The morphologies of the Pt nanoparticle‐modified CFMs were characterized by scanning electron microscopy. To achieve selectivity, permseletive layers, polyphenylenediamine (PPD) and Nafion, were deposited resulting in exclusion of the anionic and cationic interferents, ascorbic acid and dopamine, respectively, at their physiologically relevant concentrations. The resultant sensors displayed a sensitivity to hydrogen peroxide of 1381±72 μA ? mM?1 ? cm?2, and a detection limit of 0.86±0.19 μM (S/N=3). This simple and rapid metallization method converts carbon fiber microelectrodes, which are readily accessible, to microscale Pt electrodes in 2 min, providing a platform for oxidase‐based amperometric biosensors with improved spatial resolution over more commonly used platinum electrode array microprobes. 相似文献
44.
Reductions in leaf growth are a commonly observed response to ultraviolet radiation, but the underlying mechanisms remain poorly defined. This study examined the response of leaves exposed to a UV environment across a range of organizational scales, including leaf expansion rate, epidermal cell size and number, biomechanical properties, leaf–water relations and activity of cell-wall peroxidases. Two experimental approaches were used; Lettuce ( Lactuca sativa L.) plants were propagated under (a) supplementary UV-B (9 kJ m−2 day−1 ) in controlled environment (CE) conditions, and (b) field conditions, where plants were placed under three horticultural films with differing UV transmissions. In both experiments, UV-B caused the greatest reductions in leaf expansion and final leaf size, with some reductions attributable to UV-A wavelengths. In supplementary UV-B conditions, adaxial cell size was reduced, while in field plants, both cell size and cell number were lower in an increased UV environment, as was the case with abaxial cells in CE plants. Although leaf turgor and leaf extensibility were not affected by UV wavelengths, breaking strain of leaf tissue was decreased under supplementary UV-B. Cell-wall peroxidase activity was increased in both supplementary UV conditions and in the field, where only a zero UV environment showed no upregulation of cell-wall peroxidase. 相似文献
45.
Blagovest Bahnev Mark D. Bowden Agnieszka Stypczyńska Sylwia Ptasińska Nigel J. Mason Nicholas St.J. Braithwaite 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(6):1-5
The coupled-channel optical method (CCOM) is implemented in this work to study the scattering of electron on rubidium atom at 20 eV. In order to provide a realistic calculation, the continuum effect of the scattering system is accounted by incorporate an ab initio optical potential into the CCOM calculation. The differential cross sections (DCS), as well as the reduced Stokes parameters of 5p excitation are reported and compared to the available experimental and theoretical data. 相似文献
46.
47.
Nonactin is a macrotetrolide antibiotic produced by Streptomyces griseus subsp. griseus ETH A7796 that has shown activity against the P170-glycoprotein efflux pump associated with multiple drug resistant cancer cells. Nonactin is a polyketide, albeit a highly atypical one. The structure is composed of two units of each of the enantiomers of nonactic acid, arranged in a macrocycle, so that the molecule has S4 symmetry and is achiral. The monomer units, (+)- and (-)-nonactic acid, are derived from acetate, succinate, and propionate, although the exact details of the assembly process are quite unclear. We have used feeding experiments with a series of multiple stable isotope labeled precursors to elucidate the details of the first committed step of nonactic acid biosynthesis. We have found that the (13)C label from 3-ketoadipate is incorporated specifically into both nonactic acid and its homologue, homononactic acid. The data conclusively show that the first committed step of nonactin biosynthesis is the coupling of a succinate derivative with either acetate or malonate. The differentiation into either nonactate or homononactate occurs after the initial condensation; the homologues are not derived from use of a different "starter unit" by the nonactate polyketide synthase. The first step of nonactin biosynthesis involves achiral intermediates; differentiation between the known enantiocomplementary biosynthesis pathways to form each enantiomer of the precursor monomer units likely occurs after the initial condensation reaction. 相似文献
48.
Ice structuring proteins - a new name for antifreeze proteins 总被引:1,自引:0,他引:1
Antifreeze proteins (AFPs) have been reported in the academic literature for many years, and are increasingly arousing interest in the technical and popular media, particularly because of their potential applications. However, the term "antifreeze" does not always accurately describe their natural function, or their application in frozen systems, where they do not prevent freezing, but control the size, shape and aggregation of ice crystals. We survey the properties and applications of AFPs and propose a more generally applicable name based on the fact that all AFPs bind to ice and consequently influence crystal growth and interactions: "Ice Structuring Proteins". 相似文献
49.
David M. Rackham Sarah E. Morgan W. R. Nigel Williamson 《Magnetic resonance in chemistry : MRC》1980,14(6):515-516
The 13C NMR spectra of four pairs of 1,3,4-thiadiazole/thiadiazoline isomers have been recorded using broad band and off-resonance proton decoupling techniques and in the coupled mode. Differences in the chemical shifts of the heterocyclic ring and the carbonyl carbons allow identification of the isomer present. Their IR and UV spectra are in agreement with literature reports for azole/azoline analogues. 相似文献
50.
Direct photolysis of 1? or 2-diazonaphthalenone and 2-diazonaphthalenone -5-sulfonyl chloride at 77K yields the respective indeno- ketenes which were identified by ultra-violet and infra-red spectroscopy. 相似文献