排序方式: 共有19条查询结果,搜索用时 15 毫秒
1.
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
2.
Joo Leong Tham Margarit M.A. Pregardier B. Hull C.D. Magoon R. Carr F. 《Solid-State Circuits, IEEE Journal of》1999,34(3):286-291
A 2.7-V 900-MHz/1.9-GHz dual-band transceiver IC consisting of receive, transmit, and local oscillator (LO) sections is presented. The transmit section achieves an unwanted sideband suppression of -43 dBc, LO leakage of -59 dBc, and third-order spurious rejection of -70 dBc. The transmit output noise level is -165 dBc/Hz at a 20-MHz offset from the carrier. The on-chip very high-frequency oscillator has a phase-noise level of -106 dBc/Hz at 100-kHz offset when operating at 800 MHz. The receive section has 36 dB of gain with 36 dB of gain range in 12-dB steps. The transceiver IC has been fabricated using a 25-GHz ft silicon bipolar process and is designed to operate over a supply-voltage range of 2.7-5.0 V 相似文献
3.
Margarit M.A. Joo Leong Tham Meyer R.G. Deen M.J. 《Solid-State Circuits, IEEE Journal of》1999,34(6):761-771
Voltage controlled oscillators (VCOs) used in portable wireless communications applications, such as cellular telephony, are required to achieve low phase-noise levels while consuming minimal power. This paper presents the design challenges of a VCO with automatic amplitude control, which operates in the 300 MHz to 1.2 GHz frequency range using different external resonators. The VCO phase noise level is -106 dBc/Hz at 100-KHz offset from an 800-MHz carrier, and it consumes 1.6 mA from a 2.7-V power supply. An extensive phase-noise analysis is employed for this VCO design in order to identify the most important noise sources in the circuit and to find the optimum tradeoff between noise performance and power consumption 相似文献
4.
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
5.
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
6.
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
7.
Direct Synthesis of Nano‐Ferrierite along the 10‐Ring‐Channel Direction Boosts Their Catalytic Behavior
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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
8.
Andrs Cordn‐Franco Alejandro Fernndez‐Margarit F. Flix Lara‐Martín 《Mathematical Logic Quarterly》2006,52(1):51-70
A well known theorem proved (independently) by J. Paris and H. Friedman states that B Σn +1 (the fragment of Arithmetic given by the collection scheme restricted to Σn +1‐formulas) is a Πn +2‐conservative extension of I Σn (the fragment given by the induction scheme restricted to Σn ‐formulas). In this paper, as a continuation of our previous work on collection schemes for Δn +1(T )‐formulas (see [4]), we study a general version of this theorem and characterize theories T such that T + B Σn +1 is a Πn +2‐conservative extension of T . We prove that this conservativeness property is equivalent to a model‐theoretic property relating Πn ‐envelopes and Πn ‐indicators for T . The analysis of Σn +1‐collection we develop here is also applied to Σn +1‐induction using Parsons' conservativeness theorem instead of Friedman‐Paris' theorem. As a corollary, our work provides new model‐theoretic proofs of two theorems of R. Kaye, J. Paris and C. Dimitracopoulos (see [8]): B Σn +1 and I Σn +1 are Σn +3‐conservative extensions of their parameter free versions, B Σ–n +1 and I Σ–n +1. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
The mechanism of nitrogen atom transfer from four-coordinate tris(carbene)borate iron(IV) nitrido complexes to phosphines and phosphites has been investigated. In the absence of limiting steric effects, the rate of nitrogen atom transfer to phosphines increases with decreasing phosphine σ-basicity. This trend has been quantified by a Hammett study with para-substituted triarylphosphines, and is contrary to the expectations of an electrophilic nitrido ligand. On the basis of electronic structure calculations, a dual-nature transition state for nitrogen atom transfer is proposed, in which a key interaction involves the transfer of electron density from the nitrido highest occupied molecular orbital (HOMO) to the phosphine lowest unoccupied molecular orbital (LUMO). Compared to analogous atom transfer reactions from a 5d metal, these results show how the electronic plasticity of a 3d metal results in rapid atom transfer from pseudotetrahedral late metal complexes. 相似文献
10.