72,552 research outputs found
Clean to dirty limit and<i>T</i><sub>c</sub>suppression in NdFeAsO<sub>0.7</sub>F<sub>0.3</sub>studied by<i>H</i><sub>c2</sub>analysis
No full textIn this work, we investigate the temperature dependence of the upper critical field, dH c2/dT, in an increasingly disordered NdFeAsO0.7F0.3 (NdFeAs(O,F)) single crystal that has been progressively irradiated up to a 5.25 ×1016 cm- 2 total particle dose. For the H||ab-plane, dH c2/dT does not vary remarkably with irradiation, while for the H||c-axis it increases sharply after the first irradiation of 3.60 ×1015 cm-2 and then more gradually with further irradiation doses. Focusing on the H||c-axis, we develop a phenomenological analysis of the H c2 slope which allows us to inspect the crossover from the clean to the dirty regime. From the H c2 slope normalized to the critical temperature and to its clean limit value, we extract the ratio of the coherence length ξ BCS to the mean free path and we find that when T c is reduced by a factor of four from its pristine value, ξ BCS/ becomes as large as ∼7 and reaches values of ∼1.8 nm, indicating that NdFeAs(O,F) is well into the dirty regime. Our analysis of the H c2 slope also allows us to compare the pair-breaking effectiveness of scattering in different superconductors, showing similarity between unconventional NdFeAs(O,F) and moderate-T c phonon-mediated devices, such as MgB2 and A15 compounds, but much a stronger difference with YBa2Cu3O7-δ. This work thus shows that dH c2/dT is a reliable parameter, providing an alternative to residual resistivity, for investigating the pair-breaking mechanism induced by impurity scattering in superconductors
Fig. 2. – Primulina dongguanica F. Wen, Y. G. Wei & R. Q. Luo. A in Primulina dongguanica F. Wen, Y. G. Wei & R. Q. Luo (Gesneriaceae), a new species from South China
No full textFig. 2. – Primulina dongguanica F. Wen, Y. G. Wei & R. Q. Luo. A. Natural hillside habitat; B. Natural habitat; C. Plant in natural habitat; D. Plant with cymes and flowers in cultivation; E. Frontal view of cyme and flowers; F. Anatomical dissections of the cyme, showing bracts, pistil and opened corolla; G. Lateral view of flower, calyx and pistil; H. daxial and abaxial views of calyx lobes. [D-H: Fang Wen 100803, IBK] [Photos: A-C: Fang Wen; D-E: Shi-Liang Mo; F-H: Wen-Hong Lin]Published as part of Wen, Fang & Wei, Yi-Gang, 2014, Primulina dongguanica F. Wen, Y. G. Wei & R. Q. Luo (Gesneriaceae), a new species from South China, pp. 9-19 in Candollea 69 (1) on page 12, DOI: 10.15553/c2014v691a2, http://zenodo.org/record/576184
Letter from C. H. Gensler, Havasupai Agency to Carl Hayden
No full textLetter from C. H. Gensler expressing concern on behalf of the Havasupai Tribe regarding the proposed park boundaries
Citations of the author H C Rajpoot
No full textThe list of the articles, research papers, theses, and book chapters globally citing the author H. C. Rajpoot</p
Letter from Carl Hayden to C. H. Gensler
No full textLetter from Carl Hayden to C. H. Gensler informing him of the proposed Grand Canyon National Park bill
meta-C−H Functionalization and Sustainable Electro- /Photoelectrocatalytic C−H/Si−H/Ge−H Activation
No full textC−H activation provides a crucial new tool for the construction of C−C bonds in organic chemical synthesis, especially for agrochemistry, the pharmaceutical industry, and materials science, using a large number of existing metals on Earth. This dissertation overcomes the major challenge of selective functionalization of inert C-H bonds, which is related to the ubiquity of C-H bonds in organic compounds, and introduces several innovative synthesis methods. These methods use low-cost ruthenium and photocatalysis to achieve sustainable and selective C-H transformations. In the first project, we developed ruthenium-catalyzed meta-C-H secondary alkylation and benzylation using Katritzky pyridine salts that are easy to prepare. Ruthenium catalysis is characterized by good chemical selectivity and wide functional group tolerance. The second part describes the multicomponent transformation of glycosyl bromides catalyzed by ruthenium. General C-alkyl glycosides with high meta- and anomeric selectivity have been prepared. Our ruthenium-catalyzed multicomponent reaction has extremely mild reaction conditions and a broad substrate scope, which makes it possible to use in the synthesis of C-alkyl glycosides. In the third project, we developed the first palladium-catalyzed electro-C-H dearomatic spiro-annulation of 1-aryl-2-naphthalene enantioselective [3+2] cyclization catalyzed by chiral rhodium. Electrocatalysis provides a simple method for the formation of structurally distinct helical ring compounds. In the fourth project, we developed a highly efficient iron-catalyzed photoelectrochemical silane functionalization to selectively obtain silyl oxoindole with excellent chemo- and regio-selectivity. The photochemical reaction of iron (III) complexes was first used for hydro germane activation. In the fifth project, we report the photoelectrochemical borylation of C(sp3)-H bonds by combining LMCT and HAT processes, enabling the feedstock chemical transformation into value-added compounds.2024-06-2
Letter from C. H. Gensler, Havasupai Agency to Carl Hayden
No full textLetter from C. H. Gensler to Carl Hayden asking for a meeting in regards to the Havasupai pasture land in light of the national park bill
Deaminative meta -C–H alkylation by ruthenium( ii ) catalysis
No full textPrecise structural modifications of amino acids are of importance to tune biological properties or modify therapeutical capabilities relevant to drug discovery.Precise structural modifications of amino acids are of importance to tune biological properties or modify therapeutical capabilities relevant to drug discovery. Herein, we report a ruthenium-catalyzed meta -C–H deaminative alkylation with easily accessible amino acid-derived Katritzky pyridinium salts. Likewise, remote C–H benzylations were accomplished with high levels of chemoselectivity and remarkable functional group tolerance. The meta -C–H activation approach combined with our deaminative strategy represents a rare example of selectively converting C(sp 3 )–N bonds into C(sp 3 )–C(sp 2 ) bonds
Multi-Layer Epidemic Dynamics Simulation (MEDSIM) for spatial transmission of acute respiratory diseases
No full textSilver-Mediated Direct sp(3) C-H Bond Functionalization
No full textDirect sp(3) C-H bond functionalization is an efficient, straightforward, and powerful method to construct new C-X (X = C, N, F, S) bonds from nonfunctionalized aliphatic motif of organic molecules, which has been used in late-stage modification of complex molecules. In this chapter, the recent developments of silver-mediated direct sp(3) C-H functionalizations are reviewed, categorized by C-C bond formation (C-H insertion), C-N bond formation (intramolecular and intermolecular amination/amidation), C-F bond formation, and C-S bond formation.SCI(E)[email protected]
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