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651.
652.
Bueno-Alejo CJ D'Alfonso C Pacioni NL González-Béjar M Grenier M Lanzalunga O Alarcon EI Scaiano JC 《Langmuir : the ACS journal of surfaces and colloids》2012,28(21):8183-8189
We report a novel nanosecond laser ablation synthesis for spherical gold nanoparticles as small as 4 nm in only 5 s (532 nm, 0.66 J/cm(2)), where the desired protecting agent can be selected in a protocol that avoids repeated sample irradiation and undesired exposure of the capping agent during ablation. This method takes advantage of the recently developed synthesis of clean unprotected polymorph and polydisperse gold nanostructures using H(2)O(2) as a reducing agent. The laser drop technique provides a unique tool for delivering controlled laser doses to small drops that undergo assisted fall into a solution or suspension of the desired capping agent, yielding monodisperse custom-derivatized composite materials using a simple technique. 相似文献
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654.
Gilat David Meilijson Isaac Sacerdote Laura 《Journal of Theoretical Probability》2022,35(3):1952-1955
Journal of Theoretical Probability - For an $${text {L}}_2$$ -bounded martingale starting at 0 and having final variance $$sigma ^2$$ , the expected local time at $$a in text {R}$$ is at most... 相似文献
655.
Felipe Castro-Medina Lisbeth Rodríguez-Mazahua Asdrúbal Lpez-Chau Jair Cervantes Giner Alor-Hernndez Isaac Machorro-Cano 《Entropy (Basel, Switzerland)》2020,22(12)
Fragmentation is a design technique widely used in multimedia databases, because it produces substantial benefits in reducing response times, causing lower execution costs in each operation performed. Multimedia databases include data whose main characteristic is their large size, therefore, database administrators face a challenge of great importance, since they must contemplate the different qualities of non-trivial data. These databases over time undergo changes in their access patterns. Different fragmentation techniques presented in related studies show adequate workflows, however, some do not contemplate changes in access patterns. This paper aims to provide an in-depth review of the literature related to dynamic fragmentation of multimedia databases, to identify the main challenges, technologies employed, types of fragmentation used, and characteristics of the cost model. This review provides valuable information for database administrators by showing essential characteristics to perform proper fragmentation and to improve the performance of fragmentation schemes. The reduction of costs in fragmentation methods is one of the most desired main properties. To fulfill this objective, the works include cost models, covering different qualities. In this analysis, a set of characteristics used in the cost models of each work is presented to facilitate the creation of a new cost model including the most used qualities. In addition, different data sets or reference points used in the testing stage of each work analyzed are presented. 相似文献
656.
Dr. Isaac G. Sonsona Dr. Juan V. Alegre-Requena Dr. Eugenia Marqués-López Prof. Dr. M. Concepción Gimeno Prof. Dr. Raquel P. Herrera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5469-5478
The first asymmetric catalyzed aza-Henry reaction of hydrazones is presented. In this process, quinine was used as the catalyst to synthesize different alkyl substituted β-nitrohydrazides with ee up to 77 %. This ee was improved up to 94 % by a further recrystallization and the opposite enantiomer can be obtained by using quinidine as the catalyst, opening exciting possibilities in fields in which the control of chirality is vital, such as the pharmaceutical industry. Additionally, experimental and ab initio studies were performed to understand the reaction mechanism. The experimental results revealed an unexpected secondary kinetic isotope effect (KIE) that is explained by the calculated reaction pathway, which shows that the protonation of the initial hydrazone and the C−C bond forming reaction occur during a concerted process. This concerted mechanism makes the catalysis conceptually different to traditional base-promoted Henry and aza-Henry reactions. 相似文献
657.
Isaac Premkumar I. J. Prabhu A. Vijayan V. Godwin Antony A. Venkatesh R. 《Journal of Thermal Analysis and Calorimetry》2020,142(4):1457-1467
Journal of Thermal Analysis and Calorimetry - Shallow reentrant piston (SRP) and deep cylindrical piston (DCP) geometries were designed by modifying the compression ratio of an engine with baseline... 相似文献
658.
Experimental Mechanics - Impulsive blast loading studies typically require facilities with sub-millisecond decay time simulation capability. Using a conventional shock tube for such studies,... 相似文献
659.
Pyrroloiminoquinone alkaloids represent a structurally intriguing class of natural products that display an array of useful biological properties. Here, we present a versatile and scalable platform for the synthesis of this diverse family – and in particular the antitumor discorhabdins – built upon sequential selective C–H functionalization of tryptamine. The utility of this strategy is showcased through short formal syntheses of damirones A–C, makaluvamines D and I, and discorhadbin E. Additionally, we describe efforts to develop the first catalytic asymmetric entry to the discorhabdin subclass. 相似文献
660.
Meccanica - Present work investigates the biaxial buckling of three-phase, angle-ply laminates reinforced with graphene platelets and carbon or glass fibres. The analysis is based on Classical... 相似文献