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91.
K. Hardt Y. K. Agarwal C. Günther M. Guttormsen R. Kroth J. Recht F. A. Beck T. Byrski J. C. Merdinger A. Nourredine D. C. Radford J. P. Vivien C. Bourgeois 《Zeitschrift für Physik A Hadrons and Nuclei》1983,312(3):251-256
High-Spin states in188Hg have been investigated using the168Er(24Mg,4n) reaction. The rotation aligned vi 13 2/2 band, which intersects the weakly oblate ground state band atI≈10, is observed up toI π =20+ with an isomeric 12+ level with T1/2=134(15)ns. The coexisting strongly deformed band, built on the 825 keV 0+ level, is observed up to the 14+ state. The systematics of the vi 13 2/2 rotation aligned bands is discussed. 相似文献
92.
C. Radford 《General Relativity and Gravitation》1979,11(5):329-332
It is shown that only for spins 1 and 2 (electronmagnetism and gravitation) does the generic integer spin, source-free, zero-rest-mass field generate an irreducible representation of the proper orthochronous Lorentz group,L+. The conclusion is then drawn that as these higher-spin fields can in no sense be considered as elementary we have strong mathematical (and physical) grounds for their (apparent) nonexistence in nature. 相似文献
93.
ZDM – Mathematics Education - This article is a commentary on the mathematical working space (MWS) approach and draws on the articles contained in this ZDM issue. The article is divided into... 相似文献
94.
Madine J Jack E Stockley PG Radford SE Serpell LC Middleton DA 《Journal of the American Chemical Society》2008,130(45):14990-15001
Many unrelated proteins and peptides can assemble into amyloid or amyloid-like nanostructures, all of which share the cross-beta motif of repeat arrays of beta-strands hydrogen-bonded along the fibril axis. Yet, paradoxically, structurally polymorphic fibrils may derive from the same initial polypeptide sequence. Here, solid-state nuclear magnetic resonance (SSNMR) analysis of amyloid-like fibrils of the peptide hIAPP 20-29, corresponding to the region S (20)NNFGAILSS (29) of the human islet amyloid polypeptide amylin, reveals that the peptide assembles into two amyloid-like forms, (1) and (2), which have distinct structures at the molecular level. Rotational resonance SSNMR measurements of (13)C dipolar couplings between backbone F23 and I26 of hIAPP 20-29 fibrils are consistent with form (1) having parallel beta-strands and form (2) having antiparallel strands within the beta-sheet layers of the protofilament units. Seeding hIAPP 20-29 with structurally homogeneous fibrils from a 30-residue amylin fragment (hIAPP 8-37) produces morphologically homogeneous fibrils with similar NMR properties to form (1). A model for the architecture of the seeded fibrils is presented, based on the analysis of X-ray fiber diffraction data, combined with an extensive range of SSNMR constraints including chemical shifts, torsional angles, and interatomic distances. The model features a cross-beta spine comprising two beta-sheets with an interface defined by residues F23, A25, and L27, which form a hydrophobic zipper. We suggest that the energies of formation for fibril form containing antiparallel and parallel beta-strands are similar when both configurations can be stabilized by a core of hydrophobic contacts, which has implications for the relationship between amino acid sequence and amyloid polymorphism in general. 相似文献
95.
The present article has reported the effects of several nanofiller’s aspect ratio, length and interfacial strength on Mode-I fracture toughness (KIC) of geopolymer as the matrix of continuous fibre reinforced composites. These nanofillers have been chosen based on the variations in the surface chemistry and nature of interfacial bonding with geopolymer, which include Carbon, Alumina and Silicon carbide. Geopolymer matrix was subjected to the addition of single volume fraction, 2% of each type of nanofiller with two aspect ratios, designated as nanoparticles and nanofibers. Notched beam flexure tests (SEVNB) of neat and each nanofiller reinforced samples suggest that, while baseline KIC of neat geopolymer improved with heat treatment, nanofibers with high interfacial bond strength showed maximum capability in further improving KIC. Among those nanofibers, 2 vol% Silicon Carbide Whisker (SCW) showed the largest improvement in KIC of geopolymer, which is ~164%. After heat treatment at 650 °C, SCW reinforcement was also found to be effective, with only ~28% lower than the reinforcing performance at 250 °C, while the performance of Alumina Nanofiber reinforced geopolymer notably reduced. SEM and EDS analysis suggested that the inhomogeneity in neat geopolymer and length of nanofibers control the reinforcing capability as well as crack propagation resistance of geopolymer. For instance, minimum length of nanofillers to toughen this geopolymer at 250 °C was required as ~2 μm. The results further suggested that the sample failure occurred due to the dominance of tensile failure of nanofibers over the interfacial separation. 相似文献
96.
Nowadays, aerodynamic computational modeling is carried out on a daily basis in an industrial setting. This is done with the aim of predicting the performance and flow characteristics of new components. However, limited resources in terms of time and hardware force the engineer to employ relatively coarse computational grids, thus achieving results with variable degree of inaccuracy. In this article, a novel combination of feature and adjoint‐based mesh adaptation methods is investigated and applied to typical three‐dimensional turbomachinery cases, such as compressor and fan blades. The proposed process starts by employing feature‐based mesh movement to improve the global flow solution and then adjoint refinement to tune the mesh for each quantity of interest. Comparison of this process with one utilizing only the adjoint refinement procedure shows significant benefits in terms of accuracy of the performance quantity. 相似文献
97.
Andrew J. Maneffa Dr. Adrian B. Harrison Dr. Stewart J. Radford Dr. A. Steve Whitehouse Prof. James H. Clark Dr. Avtar S. Matharu 《ChemistryOpen》2020,9(5):559-567
Deep eutectic solvents (DES) are one of the most promising green technologies to emerge in recent years given their combination of environmentally friendly credentials and useful functionalities. Considering the continued search for new DES – especially those that exemplify the aforementioned characteristics, we report the preparation of DES based on natural analogues of l -ascorbic acid for the first time. The onset of eutectic melting occurred at temperatures far below the melting point of the individual components and resulted in the generation of glass forming fluids with glass transition temperatures, viscosities and flow behavior that are comparable to similar systems. This work expands the current array of DES that can be produced using naturally occurring components, which given their potential to be bio-derived, interesting physicochemical properties (e. g. propensity to supercool and vitrify) and apparent antibacterial nature, may provide utility within a range of applications. 相似文献
98.
Andrei Loas Robert J. Radford Alexandria Deliz Liang Stephen J. Lippard 《Chemical science》2015,6(7):4131-4140
We describe a modular, synthetically facile solid-phase approach aimed at separating the fluorescent reporter and binding unit of small-molecule metal-based sensors. The first representatives contain a lysine backbone functionalized with a tetramethylrhodamine fluorophore, and they operate by modulating the oxidation state of a copper ion ligated to an [N4] (cyclam) or an [N2O] (quinoline-phenolate) moiety. We demonstrate the selectivity of their Cu(ii) complexes for sensing nitroxyl (HNO) and thiols (RSH), respectively, and investigate the mechanism responsible for the observed reactivity in each case. The two lysine conjugates are cell permeable in the active, Cu(ii)-bound forms and retain their analyte selectivity intracellularly, even in the presence of interfering species such as nitric oxide, nitrosothiols, and hydrogen sulfide. Moreover, we apply the new probes to discriminate between distinct levels of intracellular HNO and RSH generated upon stimulation of live HeLa cells with ascorbate and hydrogen sulfide, respectively. The successful implementation of the lysine-based sensors to gain insight into biosynthetic pathways validates the method as a versatile tool for producing libraries of analogues with minimal synthetic effort. 相似文献
99.
David E. Radford 《代数通讯》2013,41(1):241-291
Abstract In the present paper we consider a correspondence weaker than Galois connection and prove that this produces Kurosh–Amitsur radicals in a very general setting including all universal classes of Ω-groups. As a framework we introduce a simple combinatorial structure which uses mappings between complete lattices. 相似文献
100.
The selective reduction of the distal olefin of many types of terpenoid-based natural products has been commonly approached using gaseous HCl in CH2Cl2. We herein present evidence that this method is inefficient and produces many side products, whose formation, in our hands, was difficult to avoid (over several reaction runs). A more efficient procedure for geranyl acetate using 1 equiv. of TiCl4 in CH2Cl2 at −78°C is reported. 相似文献