排序方式: 共有27条查询结果,搜索用时 15 毫秒
1.
Amable Liñán Daniel Moreno-Boza Immaculada Iglesias Forman A. Williams 《Combustion Theory and Modelling》2016,20(6):1010-1028
Frank-Kamenetskii's analysis of thermal explosions is revisited, using also a single-reaction model with an Arrhenius rate having a large activation energy, to describe the transient combustion of initially cold gaseous mixtures enclosed in a spherical vessel with a constant wall temperature. The analysis shows two modes of combustion. There is a flameless slowly reacting mode for low wall temperatures or small vessel sizes, when the temperature rise resulting from the heat released by the reaction is kept small by the heat-conduction losses to the wall, so as not to change significantly the order of magnitude of the reaction rate. In the other mode, the slow reaction rates occur only in an initial ignition stage, which ends abruptly when very large reaction rates cause a temperature runaway, or thermal explosion, at a well-defined ignition time and location, thereby triggering a flame that propagates across the vessel to consume the reactant rapidly. Explosion limits are defined, in agreement with Frank-Kamenetskii's analysis, by the limiting conditions for existence of the slowly reacting mode of combustion. In this mode, a quasi-steady temperature distribution is established after a transient reaction stage with small reactant consumption. Most of the reactant is burnt, with nearly uniform mass fraction, in a subsequent long stage during which the temperature follows a quasi-steady balance between the rates of heat conduction to the wall and of chemical heat release. The changes in the explosion limits caused by the enhanced heat-transfer rates associated with buoyant motion are described in an accompanying paper. 相似文献
2.
Steven van Zutphen Vicente J. Margarit Guilhem Mora Pascal Le Floch 《Tetrahedron letters》2007,48(16):2857-2859
Nucleophilic substitution of a phospholide anion onto protected 3-iodoalanine leads to the formation of an amino acid with an appended phosphole in excellent yield. Manipulation of the protecting groups, leads to building blocks suitable for the synthesis of phosphole-containing polypeptides. 相似文献
3.
4.
Heterotrimetallic complexes with a Pt---Hg---Pt arrangement are formed by reaction of zerovalent platinum complexes with [(PPh3)2RPt---HgR]; X-ray diffraction has established the structure of [(PPh3)2(2,4,6-C6H2Cl3)Pt]2Hg. 相似文献
5.
Digital simulation treatments supposing constant current flowing suddenly imposed across the internal electrode for two rotating systems, the ring-disk and the double ring, are compared. Results are given for a double ring system. 相似文献
6.
7.
Andrs Cordn‐Franco Alejandro Fernndez‐Margarit F. Flix Lara‐Martín 《Mathematical Logic Quarterly》2005,51(3):313-328
By a theorem of R. Kaye, J. Paris and C. Dimitracopoulos, the class of the Πn+1‐sentences true in the standard model is the only (up to deductive equivalence) consistent Πn+1‐theory which extends the scheme of induction for parameter free Πn+1‐formulas. Motivated by this result, we present a systematic study of extensions of bounded quantifier complexity of fragments of first‐order Peano Arithmetic. Here, we improve that result and show that this property describes a general phenomenon valid for parameter free schemes. As a consequence, we obtain results on the quantifier complexity, (non)finite axiomatizability and relative strength of schemes for Δn+1‐formulas. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Dr. Davide Oldrini Dr. Linda del Bino Dr. Ana Arda Dr. Filippo Carboni Pedro Henriques Dr. Francesca Angiolini Jon I. Quintana Dr. Ilaria Calloni Dr. Maria R. Romano Dr. Francesco Berti Prof. Jesus Jimenez-Barbero Dr. Immaculada Margarit Dr. Roberto Adamo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(31):7018-7025
Identification of glycan functional epitopes is of paramount importance for rational design of glycoconjugate vaccines. We recently mapped the structural epitope of the capsular polysaccharide from type III Group B Streptococcus (GBSIII), a major cause of invasive disease in newborns, by using a dimer fragment (composed of two pentasaccharide repeating units) obtained by depolymerization complexed with a protective mAb. Although reported data had suggested a highly complex epitope contained in a helical structure composed of more than four repeating units, we showed that such dimer conjugated to a carrier protein with a proper glycosylation degree elicited functional antibodies comparably to the full-length conjugated polysaccharide. Here, starting from the X-ray crystallographic structure of the polysaccharide fragment–mAb complex, we synthesized a hexasaccharide comprising exclusively the relevant positions involved in binding. Combining competitive surface plasmon resonance and saturation transfer difference NMR spectroscopy as well as in-silico modeling, we demonstrated that this synthetic glycan was recognized by the mAb similarly to the dimer. The hexasaccharide conjugated to CRM197, a mutant of diphtheria toxin, elicited a robust functional immune response that was not inferior to the polysaccharide conjugate, indicating that it may suffice as a vaccine antigen. This is the first evidence of an X-ray crystallography-guided design of a synthetic carbohydrate-based conjugate vaccine. 相似文献
9.
Zambrano S Allaria E Brugioni S Leyva I Meucci R Sanjuán MA Arecchi FT 《Chaos (Woodbury, N.Y.)》2006,16(1):013111
A well-known method to suppress chaos in a periodically forced chaotic system is to add a harmonic perturbation. The phase control of chaos scheme uses the phase difference between a small added harmonic perturbation and the main driving to suppress chaos, leading the system to different periodic orbits. Using the Duffing oscillator as a paradigm, we present here an in-depth study of this technique. A thorough numerical exploration has been made focused in the important role played by the phase, from which new interesting patterns in parameter space have appeared. On the other hand, our novel experimental implementation of phase control in an electronic circuit confirms both the well-known features of this method and the new ones detected numerically. All this may help in future implementations of phase control of chaos, which is globally confirmed here to be robust and easy to implement experimentally. 相似文献
10.
Direct Synthesis of Nano‐Ferrierite along the 10‐Ring‐Channel Direction Boosts Their Catalytic Behavior
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vicente J. Margarit M. Rocío Díaz‐Rey Dr. M. Teresa Navarro Dr. Cristina Martínez Prof. Avelino Corma 《Angewandte Chemie (International ed. in English)》2018,57(13):3459-3463
Ferrierite zeolites with nanosized crystals and external surface areas higher than 250 m2 g?1 have been prepared at relatively low synthesis temperature (120 °C) by means of the collaborative effect of two organic structure directing agents (OSDA). In this way, hierarchical porosity is achieved without the use of post‐synthesis treatments that usually involve leaching of T atoms and solid loss. Adjusting the synthesis conditions it is possible to decrease the crystallite size in the directions of the 8‐ and 10‐ring channels, [010] and [001] respectively, reducing their average pore length to 10–30 nm and increasing the number of pores accessible. The small crystal size of the nano‐ferrierites results in an improved accessibility of reactants to the catalytic active centers and enhanced product diffusion, leading to higher conversion and selectivity with lower deactivation rates for the oligomerization of 1‐pentene into longer‐chain olefins. 相似文献