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51.
Luzian Porwol Daniel J. Kowalski Alon Henson De‐Liang Long Nicola L. Bell Leroy Cronin 《Angewandte Chemie (International ed. in English)》2020,59(28):11256-11261
We present a chemical discovery robot for the efficient and reliable discovery of supramolecular architectures through the exploration of a huge reaction space exceeding ten billion combinations. The system was designed to search for areas of reactivity found through autonomous selection of the reagent types, amounts, and reaction conditions aiming for combinations that are reactive. The process consists of two parts where reagents are mixed together, choosing from one type of aldehyde, one amine and one azide (from a possible family of two amines, two aldehydes and four azides) with different volumes, ratios, reaction times, and temperatures, whereby the reagents are passed through a copper coil reactor. Next, either cobalt or iron is added, again from a large number of possible quantities. The reactivity was determined by evaluating differences in pH, UV‐Vis, and mass spectra before and after the search was started. The algorithm was focused on the exploration of interesting regions, as defined by the outputs from the sensors, and this led to the discovery of a range of 1‐benzyl‐(1,2,3‐triazol‐4‐yl)‐N‐alkyl‐(2‐pyridinemethanimine) ligands and new complexes: [Fe(L1)2](ClO4)2 ( 1 ); [Fe(L2)2](ClO4)2 ( 2 ); [Co2(L3)2](ClO4)4 ( 3 ); [Fe2(L3)2](ClO4)4 ( 4 ), which were crystallised and their structure confirmed by single‐crystal X‐ray diffraction determination, as well as a range of new supramolecular clusters discovered in solution using high‐resolution mass spectrometry. 相似文献
52.
Step bunching to step-meandering transition induced by electromigration on Si(1 1 1) vicinal surface
The step configuration of a vicinal Si surface is studied under electromigration and a gradient of temperature. An abrupt transition (ΔT = 4 °C) from step-meandering to step bunching is found at 1225 °C for a step-down direct-current direction. This transition starts by random fluctuations which then extend on the whole surface. The transition is studied in the framework of a linear stability analysis of the usual Burton-Cabrera-Frank model by comparing the amplification factors of step-meandering and step bunching instabilities. Both compete at a given temperature, but since the amplification factors behave differently with temperature, bunching abruptly supersedes meandering above a critical temperature. 相似文献
53.
Mohammad Alaghemandi Joachim Schulte Frédéric Leroy Florian Müller‐plathe Michael C. Böhm 《Journal of computational chemistry》2011,32(1):121-133
The thermal conductivity (λ) of carbon nanotubes (CNTs) with chirality indices (5,0), (10,0), (5,5), and (10,10) has been studied by reverse nonequilibrium molecular dynamics (RNEMD) simulations as a function of different bond length alternation patterns (Δri). The Δri dependence of the bond force constant (krx) in the molecular dynamics force field has been modeled with the help of an electronic band structure approach. These calculations show that the Δri dependence of krx in tubes with not too small a diameter can be mapped by a simple linear bond length–bond order correlation. A bond length alternation with an overall reduction in the length of the nanotube causes an enhancement of λ, whereas an alternation scheme leading to an elongation of the tube is coupled to a decrease of the thermal conductivity. This effect is more pronounced in carbon nanotubes with larger diameters. The formation of a polyene‐like structure in the direction of the longitudinal axis has a negligible influence on λ. A comparative analysis of the RNEMD and crystal orbital results indicates that Δri‐dependent modifications of λ and the electrical conductivity are uncorrelated. This behavior is in‐line with a heat transfer that is not carried by electrons. Modifications of λ as a function of the bond alternation in the (10,10) nanotube are explained with the help of power spectra, which provide access to the density of vibrational states. We have suggested longitudinal low‐energy modes in the spectra that might be responsible for the Δri dependence of λ. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
54.
C. Leroy T. Cardinal M. Treguer-Delapierre C. Boissière C. Sanchez F. Pellé 《Journal of luminescence》2009,129(12):1641-1645
In this paper, a series of europium-activated titania mesoporous and dense thin films were prepared by sol-gel process. Structural characterizations show that high europium ion loadings can be incorporated into titanium dioxide walls without destroying the mesoporous arrangement. However, high europium content locks the titanium dioxide crystallization process. Upon 10% europium ions loading, mesoporous thin films are mainly amorphous, whereas dense ones are still partially crystallized. Eu3+ ion luminescence has been investigated by exciting through the semiconductor host lattice. Emission features reveal that europium ions adopt similar environments (nanocrystalline and glassy-like ones) in both dense and mesoporous thin films. Fluctuations of europium emission under continuous UV excitation have been observed. One observes that the effect strongly depends on the thin films’ crystalline character which is strongly related with the texturation and existence at the mesoscopic length scale. 相似文献
55.
56.
A novel methodology based upon the allylmetalation step followed by an Intramolecular Sakurai Cyclization (IMSC) provides an efficient access to a variety of tetrahydropyran derivatives. This new strategy nicely complements our initial protocol that embodied a tandem ene reaction/IMSC sequence. Both mono- and dihydroxy-tetrahydropyrans could be easily assembled with complete stereocontrol at the various chiral centers. 相似文献
57.
58.
N. Amos M. M. Block G. J. Bobbink M. Botje J. Debaisieux D. Favart C. Leroy F. Linde P. Lipnik J. -P. Matheys D. H. Miller K. Potter C. Vander Velde-Wilquet S. Zucchelli 《Physics letters. [Part B]》1983,120(4-6)
Proton-antiproton and proton-proton elastic scattering have been measured in the four-momentum transfer range 0.001|t|0.06 GeV2 for center-of-mass energy 52.8 GeV at the CERN Intersecting Storage Rings (ISR). Using the known pp total cross section, a simultaneous fit to the p
and pp differential cross sections yields the p
total cross section; in addition, we obtain the ratio of the real-to-imaginary part of the forward nuclear-scattering amplitude and the nuclear-slope parameter for both p
and pp. Our results show conclusively that the p
total cross section is rising at ISR energies and lend support to conventional theories in which the difference between the p
and pp total cross section vanishes at very high energy. 相似文献
59.
Oswald Leroy 《Proceedings Mathematical Sciences》1971,73(5):232-239
In the problem of the diffraction of light by two parallel supersonic waves, consisting of a fundamental tone and itsn-th harmonic, the solution of the system of difference-differential equations for the amplitudes has been reduced to the integration of a partial differential equation. The expressions for the amplitudes of the diffracted light waves are obtained as the coefficients of the Laurent expansion of the solution of this partial differential equation. The latter has been integrated for two approximations:
- Forρ = 0, the results of Murty’s elementary theory are reestablished.
- Forρ ≤ 1, a power series inρ, the terms of which are calculated as far as the third one, leads to a new expression for the intensities of the diffracted light waves, verifying the general symmetry properties obtained by Mertens.
60.