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901.
Duy‐Khiet Ho Xabier Murgia Chiara De Rossi Rebekka Christmann Antonio G. Hüfner de Mello Martins Marcus Koch Anastasia Andreas Jennifer Herrmann Rolf Müller Martin Empting Rolf W. Hartmann Didier Desmaele Brigitta Loretz Patrick Couvreur Claus‐Michael Lehr 《Angewandte Chemie (International ed. in English)》2020,59(26):10201-10201
902.
Jacques H. Poupaert Sandro Duarte Evelina Colacino Patrick Depreux Christopher R. McCurdy Didier L. Lambert 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):1959-1973
The Willgerodt-Kindlerreaction was applied to a series of aromatic aldehydes and ketones. The reactions were performed in a dipolar aprotic solvent (mainly DMF) in the presence of a base catalyst (4-methylmorpholine) and utilized microwave (mw) irradiation. The pulsed mw technique rather than the continuous irradiation was preferred because it limited side reactions and hydrogen sulfide production. While not always superior to the thermal activation of the reaction, the procedure involving repetitive short pulses of microwave irradiation was found to be faster and result in consistently cleaner products. The technique can be easily applied in a fast parallel synthesis process. 相似文献
903.
Lucas Pizzuti Paula L.G. Martins Bruna A. Ribeiro Frank H. Quina Ernani Pinto Alex F.C. Flores Dalila Venzke Claudio M.P. Pereira 《Ultrasonics sonochemistry》2010,17(1):34-37
An ultrasound-assisted preparation of a series of novel 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides that proceeds via the efficient reaction of chalcones with aminoguanidine hydrochloride under clean conditions is described. 相似文献
904.
905.
Ornella Abollino Maurizio Aceto Sandro Buoso Carmela La Gioia Corrado Sarzanini Edoardo Mentasti 《International journal of environmental analytical chemistry》2013,93(6-7):471-492
The composition of seawater in the Ross Sea (Antarctica) was investigated. The distribution of heavy metals (Cd, Cu, Fe, Mn, Ni), minor and trace (B, Ba, Li, Sr, Si) and major (Na, K, Ca, Mg) elements in coastal and offshore sites was determined. The samples were collected during the XIII Campaign of the Italian “National Programme of Research in Antarctica”, PNRA, at different depths and different stages of the Antarctic summer. In the subsequent campaign the concentrations in the water top micro-layer, and just below it, were compared. Results are also given for the data treatment by pattern recognition. 相似文献
906.
Ana M. Mouad Mariana P. Martins Hosana M. Debonsi Ana L. L. de Oliveira Rafael de Felicio Nair S. Yokoya Mutue T. Fujii Claúdia B. A. de Menezes Fabiana Fantinatti‐Garboggini André L. M. Porto 《Helvetica chimica acta》2011,94(8):1506-1514
The biocatalytic reduction of acetophenone derivatives was exploited by using algal biomass from Bostrychia radicans and B. tenella producing exclusively (S)‐2‐phenylethanols with high enantiomeric excess (>99% ee). Bacterial populations associated with algal biomass were identified as the Bacillus genus. This report deals with the first investigations involving the use of marine bacteria associated with B. radicans and B. tenella marine algae for the biocatalytic reduction of acetophenone derivatives. 相似文献
907.
908.
The 1H and 13C NMR chemical shift assignments of a series of (E) - and (Z)-N,N-Dialkylacetamides [CH3C(O)NR1R2, with R1/R2=Me/Et (1), Me/n-Bu (2), Et/n-Bu (3), Et/t-Bu (4), Me/Hydrcxyethyl (5)., Et/Hydroxyethyl (6), Et/Acetylhydroxyethyl (7)] are reported. The 1H chemical shifts for the N-substituents of the amides 1–7 recorded in benzene-d6 and in chloroform-d1 are in agreement with the Hatton and Richards (ASIS) and Paulsen-Todt models, respectively. The 13C chemical shifts for the N-substituents of compounds 1–3 were compared with data of the corresponding symmetrical amides, and the results can be explained by the reciprocal steric compression effect of one N-substituent on the other. The validity of this explanation is confirmed by 13C spin-lattice relaxation time (T1) measurements. 相似文献
909.
Marco Martins Afonso 《Physica D: Nonlinear Phenomena》2010,239(14):1241-1250
In order to model pressure and viscous terms in the equation for the Lagrangian dynamics of the velocity gradient tensor in turbulent flows, Chevillard & Meneveau [L. Chevillard, C. Meneveau, Lagrangian dynamics and geometric structure of turbulence, Phys. Rev. Lett. 97 (174501) (2006) 1-4] introduced the Recent Fluid Deformation closure. Using matrix exponentials, the closure allows us to overcome the unphysical finite-time blow-up of the well-known Restricted Euler model. However, it also requires the specification of a decorrelation timescale of the velocity gradient along the Lagrangian evolution, and when the latter is chosen too short (or, equivalently, the Reynolds number is too high), the model leads to unphysical statistics. In the present paper, we explore the limitations of this closure by means of numerical experiments and analytical considerations. We also study the possible effects of using time-correlated stochastic forcing instead of the previously employed white-noise forcing. Numerical experiments show that reducing the correlation timescale specified in the closure and in the forcing does not lead to a commensurate reduction of the autocorrelation timescale of the predicted evolution of the velocity gradient tensor. This observed inconsistency could explain the unrealistic predictions at increasing Reynolds numbers. We perform a series expansion of the matrix exponentials in powers of the decorrelation timescale, and we compare the full original model with a linearized version. The latter is not able to extend the limits of applicability of the former but allows the model to be cast in terms of a damping term whose sign gives additional information about the stability of the model as a function of the second invariant of the velocity gradient tensor. 相似文献
910.
J.A.C. Martins M.D.P. Monteiro Marques 《Journal of Mathematical Analysis and Applications》2008,343(2):1007-1021
This paper discusses the stability of quasi-static paths for a continuous elastic-plastic system with hardening in a one-dimensional (bar) domain. Mathematical formulations, as well as existence and uniqueness results for dynamic and quasi-static problems involving elastic-plastic systems with linear kinematic hardening are recalled in the paper. The concept of stability of quasi-static paths used here is essentially a continuity property of the system dynamic solutions relatively to the quasi-static ones, when (as in Lyapunov stability) the size of initial perturbations is decreased and the rate of application of the forces (which plays the role of the small parameter in singular perturbation problems) is also decreased to 0. The stability of the quasi-static paths of these elastic-plastic systems is the main result proved in the paper. 相似文献