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591.
This contribution reports the results obtained in the definition of a catalytic method for the nucleophilic ring opening of epoxides by activated methylenes promoted by a polymer-supported base. The attention has been focused on the use of polymer supported bases and the best results have been obtained by using 4-(dimethylamino)pyridine (PS-DMAP) and 2-tert-butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine both on polystyrene (PS-BEMP). Solvent-free conditions has been essential for reaching a sufficient reactivity to realize this process, in fact when a reaction medium is used, the processes are almost unfeasible. 相似文献
592.
It is shown how information contained in the pairwise correlations (in general, partial) between atoms of a gas can be used
to completely convert heat taken from a thermostat into mechanical work in a process of relaxation of the system to its thermal
equilibrium state. Both classical correlations and quantum correlations (entanglement) are considered. The amount of heat
converted into work is proportional to the entropy defect of the initial state of the system. For fully correlated particles,
in the case of entanglement the amount of work obtained per particle is twice as large as in the case of classical correlations.
However, in the case of entanglement, the amount of work does not depend on the degree of correlation, in contrast to the
case of classical correlations. The results explicitly demonstrate the equivalence relation between information and work for
the case of two-particle correlations. 相似文献
593.
594.
Recently the Navier-Stokes equations have been derived from the duality with the black branes in 5AdS. The zero modes of black branes are reinterpreted as dynamical degrees of freedom of a conformal fluid on the boundary of 5AdS. Here, we derive the corrections to the Navier-Stokes equations due to fermionic zero modes of the black branes. We study only the contributions due to bilinears in the fermionic zero modes in the first order of the parameter expansion. The need of a superextension of the fluid dynamics is a consequence of the full AdS/CFT correspondence and yet to be investigated. 相似文献
595.
Tommaso Benincasa Angelo Favini Costică Moroşanu 《Journal of Optimization Theory and Applications》2011,148(1):31-45
In this paper we prove the convergence of an iterative scheme of fractional steps type for a non-homogeneous Cauchy-Neumann
boundary optimal control problem governed by non-linear phase-field system, when the boundary control is dependent both on
time and spatial variables. Moreover, necessary optimality conditions are established for the approximating process. The advantage
of such approach leads to a numerical algorithm in order to approximate the original optimal control problem. 相似文献
596.
597.
Ravagnan L Mazza T Bongiorno G Devetta M Amati M Milani P Piseri P Coreno M Lenardi C Evangelista F Rudolf P 《Chemical communications (Cambridge, England)》2011,47(10):2952-2954
The presence and stability of sp hybridized atoms in free carbon nanoparticles was investigated by NEXAFS spectroscopy. The experiments show that a predominant fraction of carbon atoms is found in linear sp-chains and that conversion into sp(2) structures proceeds already at low temperature and in the gas phase. 相似文献
598.
Franck Bassani Priyanka Periwal Bassem Salem Nicolas Chevalier Denis Mariolle Guillaume Audoit Pascal Gentile Thierry Baron 《固体物理学:研究快报》2014,8(4):312-316
Silicon nanowires (SiNWs) with axial doping junctions were synthesized via the Au‐catalyzed vapor–liquid–solid growth method with the use of HCl. In this work, dopant profiling from three axially doped SiNWs with p–i, p–n and n–i–p junctions were investigated using both scanning electron microscopy (SEM) and scanning capacitance microscopy (SCM). It turns out that observed doping contrasts in SEM are also affected by the surface roughness and sample charging. In contrast, SCM allows us to delineate with sub‐10 nm resolution the electrical junctions and provides a relative value of the doping concentration in each segment of the NW. SCM clearly evidences the expected doping regions within these SiNWs thanks to the addition of HCl during the growth that strongly prevents shell overgrowth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
599.
Rosalia Zianni Giuliana Bianco Filomena Lelario Ilario Losito Francesco Palmisano Tommaso R.I. Cataldi 《Journal of mass spectrometry : JMS》2013,48(2):205-215
A full characterization of sulfoquinovosyldiacylglycerols (SQDGs) in the lipid extract of spinach leaves has been achieved using liquid chromatography/electrospray ionization‐linear quadrupole ion trap mass spectrometry (MS). Low‐energy collision‐induced dissociation tandem MS (MS/MS) of the deprotonated species [M ? H]? was exploited for a detailed study of sulfolipid fragmentation. Losses of neutral fatty acids from the acyl side chains (i.e. [M ? H ? RCOOH]?) were found to prevail over ketene losses ([M ? H ? R'CHCO]?) or carboxylates of long‐chain fatty acids ([RCOO]?), as expected for gas‐phase acidity of SQDG ions. A new concerted mechanism for RCOOH elimination, based on a charge‐remote fragmentation, is proposed. The preferential loss of a fatty acids molecule from the sn‐1 position (i.e. [M ? H ? R1COOH]?) of the glycerol backbone, most likely due to kinetic control of the gas‐phase fragmentation process, was exploited for the regiochemical assignment of the investigated sulfolipids. As a result, 24 SQDGs were detected and identified in the lipid extract of spinach leaves, their number and variety being unprecedented in the field of plant sulfolipids. Moreover, the prevailing presence of a palmitic acyl chain (16:0) on the glycerol sn‐2 position of spinach SQDGs suggests a prokaryotic or chloroplastic path as the main route for their biosynthesis. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
600.
Ballistreri FP Gentile S Pappalardo A Tomaselli GA Pradhan S Di Bari L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(1):322-328
M40 is a four-fold symmetry macrocyclic ligand endowed with axial and central chiral elements, all of R configuration. It promptly binds late lanthanides (Yb(III) and Lu(III) ) yielding a negative helicity, as witnessed by NIR-electronic circular dichroism. In the course of a few hours, a new conformation of the complex takes over, which has opposite helicity and allows for a dynamic free-bound equilibrium. Upon slow solvent evaporation, the original conformation is retrieved and the whole dynamic process can be started again, as in a sandclock, allowing one to envisage applications as a time-marker chiral switch. 相似文献