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排序方式: 共有216条查询结果,搜索用时 15 毫秒
1.
The steel ASTM A213 P22 is used for superheater outlet header in power plants. During duty cycles lasting over tens of years the temperature is of the order of 545°C and the pressure 125 atm. The microscopic changes in these steels are hard to analyze under working conditions, but they are believed to be responsible for the appearance of creeps in such devices. Investigation of the microscopic modifications will help to predict future failures due to creeps, increasing the reliability and saving a lot of money.We report the investigation of such changes in ASTM A213 P22 steel in use for 30 years as a Superheater header at Haifa power station. The analysis has been carried out using Mössbauer Spectroscopy, X-ray diffraction and optical microscopy. As a result it seems that the morphology and phase change of the carbide phases M3C/M7C3 and M23C6 are the most prominent changes leading to the material failures. 相似文献
2.
Ettore Carletti 《Annali dell'Universita di Ferrara》1983,29(1):37-44
Riassunto Scopo di questo lavoro è dare una formula asintotica per il numero degli zeri di ReF
K(λ+it) e di ImF
K(λ+it), dove
eζ
K(8) è la funzione zeta di Dedekind associata al campo numericoK, con 0<t<T e λ numero reale fissato tale che 1−1/n<λ<1 doven è il grado diK.
Summary The aim of this paper is to give an asymptotic formula for the number of zeros of ReF K(λ+it) and ImF K(λ+it), where andζ K(8) is the Dedekind zeta function for a number fieldK, with 0<t<T and λ fixed real number such that 1−1/n<λ<1, wheren is the degree ofK.相似文献
3.
Benzyl 5,6-dihydroxyindole-2-carboxylate 3 and the free acid 4 were synthesized by oxidative cyclization of dopa benzyl ester with ceric ammonium nitrate and subsequent removal of the benzyl group by hydrogenation. 相似文献
4.
In this paper we consider discrete-time positive switched systems, switching among autonomous subsystems, characterized either by monomial matrices or by circulant matrices. Necessary and sufficient conditions are provided guaranteeing either (global uniform) asymptotic stability or stabilizability (i.e. the possibility of driving to zero the state trajectory corresponding to any initial state by resorting to some switching sequence). Such conditions lead to simple algorithms that allow to easily detect, under suitable conditions, whether a given positive switched system is not stabilizable. 相似文献
5.
Stefano Federico Tuhina Khan Nicola Relitti Giulia Chemi Margherita Brindisi Simone Brogi Ettore Novellino Daniela M. Zisterer Giuseppe Campiani Sandra Gemma Stefania Butini 《Tetrahedron letters》2018,59(51):4466-4470
We developed a Jocic-type protocol for the construction of the pyrrolonaphthoxazepine (PNOX) core. After an initial investigation based on the isolation of a trichloromethyl carbinol derivative, we shifted our attention towards a multicomponent single-step protocol. Screening of a variety of bases and solvents led to the identification of the optimum conditions for the preparation of the key α-aryloxy carboxylic acids to undergo intramolecular cyclization. The novel chemical route significantly improved overall yields for the preparation of PNOX-based compounds and was successfully extended to the preparation of 1,4-benzoxazinone-based templates. 相似文献
6.
Bolognese A Correale G Manfra M Lavecchia A Novellino E Barone V 《Organic & biomolecular chemistry》2004,2(19):2809-2813
Microwave irradiation of a mixture of benzylidene-anilines and mercaptoacetic acid in benzene gives 1,3-thiazolidin-4-ones in very high yield (65-90%), whereas the same reaction performed through using the conventional method, at reflux temperature, requires a much longer time and gives a much lower yield (25-69%). This difference seems to be due to some intermediates and by-products formed during the conventional reaction. On the basis of 1H NMR studies, two different mechanisms, acting in benzene and in DMF, respectively, have been hypothesized for the thiazolidin-4-one system formation. 相似文献
7.
A novel application of an electrochemical biosensor is here employed as analytical method for the detection and presumptive identification of antimicrobial drug residues in milk. The measurement was based on carbon dioxide production rate in relation to inhibition of microbial grow (Escherichia coli ATCC 11303). In this pilot study quinolone and tetracycline residues have been taken into consideration because use of these last in livestock production has been identified as area of particular concern. The experimental approach and analytical method developed appear adequate for the purpose, and compared to older screening methods as, for example, the microbial inhibition assays and immunoassays, offers the advantages of (i) very short analysis time (about 120 min); (ii) smaller sample amount (approximately 0.5 mL); (iii) no sample treatment (iv) good precision; and (v) the possibility of following, in a continuous manner, the inhibition process. Moreover, sensitivity of electrochemical biosensor system is resulted very high considering that for all quinolones and tetracyclines investigated it has been possible detect a residue concentration below or equal to 25 μg L−1. Under this point of view, it must be considered that the maximum residue limits fixed by UE for quinolones and tetracyclines in milk are, at present, all higher of this concentration. 相似文献
8.
An expedient and highly stereocontrolled route to (R)-α-methyltryptophan and its orthogonally protected analogs has been developed via a four-step conversion from L-alanine in good overall yields. The stereochemistry of the products is confirmed by X-ray diffraction analysis, NMR spectroscopy and optical rotations. 相似文献
9.
Stable Peptides Instead of Stapled Peptides: Highly Potent αvβ6‐Selective Integrin Ligands 下载免费PDF全文
Dr. Oleg V. Maltsev Dr. Udaya Kiran Marelli Tobias G. Kapp Dr. Francesco Saverio Di Leva Dr. Salvatore Di Maro Dr. Markus Nieberler Prof. Dr. Ute Reuning Prof. Dr. Markus Schwaiger Prof. Dr. Ettore Novellino Prof. Dr. Luciana Marinelli Prof. Dr. Horst Kessler 《Angewandte Chemie (International ed. in English)》2016,55(4):1535-1539
The αvβ6 integrin binds the RGD‐containing peptide of the foot and mouth disease virus with high selectivity. In this study, the long binding helix of this ligand was downsized to an enzymatically stable cyclic peptide endowed with sub‐nanomolar binding affinity toward the αvβ6 receptor and remarkable selectivity against other integrins. Computational studies were performed to disclose the molecular bases underlying the high binding affinity and receptor subtype selectivity of this peptide. Finally, the utility of the ligand for use in biomedical studies was also demonstrated here. 相似文献
10.
Dr. Chiara Platella Dr. Ettore Napolitano Dr. Claudia Riccardi Prof. Domenica Musumeci Prof. Daniela Montesarchio 《ChemistryOpen》2022,11(5):e202200090
DNA G-quadruplexes (G4s) are key structures for the development of targeted anticancer therapies. In this context, ligands selectively interacting with G4s can represent valuable anticancer drugs. Aiming at speeding up the identification of G4-targeting synthetic or natural compounds, we developed an affinity chromatography-based assay, named G-quadruplex on Oligo Affinity Support (G4-OAS), by synthesizing G4-forming sequences on commercially available polystyrene OAS. Then, due to unspecific binding of several hydrophobic ligands on nude OAS, we moved to Controlled Pore Glass (CPG). We thus conceived an ad hoc functionalized, universal support on which both the on-support elongation and deprotection of the G4-forming oligonucleotides can be performed, along with the successive affinity chromatography-based assay, renamed as G-quadruplex on Controlled Pore Glass (G4-CPG) assay. Here we describe these assays and their applications to the screening of several libraries of chemically different putative G4 ligands. Finally, ongoing studies and outlook of our G4-CPG assay are reported. 相似文献