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151.
Denayer JF Ocakoglu RA Thybaut J Marin G Jacobs P Martens J Baron GV 《The journal of physical chemistry. B》2006,110(17):8551-8558
Low-coverage adsorption properties (Henry constants, adsorption enthalpy, and entropy) of linear and branched alkanes (C3-C8) on zeolite MCM-22 were determined using the chromatographic technique at temperatures between 420 and 540 K. It was found that adsorption enthalpy and entropy of linear alkanes vary in a nonmonotonic way with carbon number. The adsorption behavior of alkanes was rationalized on the basis of the pore geometry. Short molecules prefer to reside in the pockets of the MCM-22 supercage, where they maximize energetic interaction with the zeolite. Longer molecules reside in the larger central part of the supercage. For carbon numbers up to six, singly branched alkanes are selectively adsorbed over their linear counterparts. This preference originates from the entropic advantage of singly branched molecules inside MCM-22 supercages, where these species have high rotational freedom because of their small length. 相似文献
152.
In this paper, we analyze a discrete-time preemptive resume priority queue. We consider two classes of customers which have to be served, where customers of one class have preemptive resume priority over customers of the other. Both classes contain customers with generally distributed service times. We show that the use of probability generating functions is beneficial for analyzing the system contents and customer delays of both classes. It is shown (theoretically as well as by some practical procedures) how moments and approximate tail probabilities of system contents and customer delays are calculated. The influence of the priority scheduling discipline and the service time distributions on the performance measures is shown by some numerical examples. 相似文献
153.
Due to the short loading times and high deformation rates inherent to impact experiments, measurement of the occurring deformations is not straightforward. Presented in this paper is a technique to obtain the displacements and deformations of a specimen subjected to a uni-axial impact load. During the experiment the deformation of a line grating attached to the specimen is captured using a streak camera. From the recorded deforming grating the specimen displacements are automatically derived using an advanced numerical algorithm, based on the interference between the specimen grating and a virtual reference grating. Numerical interference is considered because it allows that the pitch of the reference grating is adapted to the changing amplitude of the deformation. Indeed, at each moment of the deformation process the pitch of the reference grating is chosen such that the highest possible accuracy and sensitivity is guaranteed. Because of this, large changes in deformation amplitude are allowed, and the technique is applicable to a wide range of materials. Eventual imperfections of the specimen grating and temperature effects are taken into account. Specimen displacements are extracted automatically by means of a phase-shifting technique.
The non-contact measurement technique yields high resolution, quantitative information on the specimen deformation, along the entire length of the specimen and during the full duration of the experiment. Interaction by the operator is excluded. Results are presented of a high strain rate tensile test on a steel sheet specimen showing local deformations up to about 170%. 相似文献
154.
Prof. Emil Roduner Dr. Christopher Jensen Prof. Joris van Slageren Dr. Rainer A. Rakoczy Dr. Oliver Larlus Prof. Michael Hunger 《Angewandte Chemie (International ed. in English)》2014,53(17):4318-4321
We are used to being able to predict diamagnetic susceptibilities χD to a good approximation in atomic increments since there is normally little dependence on the chemical environment. Surprisingly, we find from SQUID magnetization measurements that the χD per Pt atom of zeolite‐supported Pt13 nanoclusters exceeds that of Pt2+ ions by a factor of 37–50. The observation verifies an earlier theoretical prediction. The phenomenon can be understood nearly quantitatively on the basis of a simple expression for diamagnetic susceptibility and the superatom nature of the 13‐atom near‐spherical cluster. The two main contributions come from ring currents in the delocalized hydride shell and from cluster molecular orbitals hosting the Pt 5d and Pt 6s electrons. 相似文献
155.
Patrick M. Becker Dr. Christoph Förster Dr. Luca M. Carrella Pit Boden David Hunger Prof. Joris van Slageren Prof. Markus Gerhards Prof. Eva Rentschler Prof. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(32):7199-7204
The chromium(III) complex [CrIII(ddpd)2]3+ (molecular ruby; ddpd=N,N′-dimethyl-N,N′-dipyridine-2-yl-pyridine-2,6-diamine) is reduced to the genuine chromium(II) complex [CrII(ddpd)2]2+ with d4 electron configuration. This reduced molecular ruby represents one of the very few chromium(II) complexes showing spin crossover (SCO). The reversible SCO is gradual with T1/2 around room temperature. The low-spin and high-spin chromium(II) isomers exhibit distinct spectroscopic and structural properties (UV/Vis/NIR, IR, EPR spectroscopies, single-crystal XRD). Excitation of [CrII(ddpd)2]2+ with UV light at 20 and 290 K generates electronically excited states with microsecond lifetimes. This initial study on the unique reduced molecular ruby paves the way for thermally and photochemically switchable magnetic systems based on chromium complexes complementing the well-established iron(II) SCO systems. 相似文献
156.
Joris Huguenin Sidi Ould Saad Hamady Patrice Bourson 《Journal of Raman spectroscopy : JRS》2015,46(11):1062-1066
Gallic acid (GA) is involved in many biochemical processes and reactions and is of great importance in environment thanks to its antioxidant and pro‐oxidant properties. We present in this paper a comprehensive study of GA deprotonation by means of Raman spectroscopy. In the Raman spectra, we identified the characteristic bands that were sensitive to the five pH‐dependent GA forms. From these results, we extracted the GA pKa values that are consistent with the reference values. These results permit the monitoring of GA forms for applications. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
157.
Maarten A. C. Broeren Jeffrey G. Linhardt Hinke Malda Bas F. M. de Waal Ron M. Versteegen Joris T. Meijer Dennis W. P. M. Lwik Jan C. M. van Hest Marcel H. P. van Genderen E. W. Meijer 《Journal of polymer science. Part A, Polymer chemistry》2005,43(24):6431-6437
Water‐soluble guest–host complexes are prepared in a two‐step process. For this a new, polydisperse ethylene glycol containing guest molecule is synthesized that is soluble in both chloroform and water. This guest is able to bind to urea–adamantyl‐modified poly(propylene imine) dendrimers in chloroform in a noncovalent manner. When the chloroform is slowly evaporated and D2O is added, the hydrophobic dendrimer is solubilized in water. This is not possible when the hydrophobic dendrimer is directly added to the hydrophilic guests in water. When the unmodified poly(ethylene glycol) starting material is used, no solubilization occurs, and this indicates that the urea–acetic acid head group is necessary to solubilize the dendrimer. Approximately 26 guests are required for solubilization of the dendrimer. A lower number of guests results in aggregation and precipitation of the dendrimer. A monodisperse guest molecule has been used in NMR studies to show that the guest molecule binds with its acidic head group to the periphery of the dendrimer. This methodology opens the way to functional dendrimer aggregates in aqueous media. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6431–6437, 2005 相似文献
158.
Mehdi Dastani Joris Hulstijn Leendert van der Torre 《European Journal of Operational Research》2005,160(3):762-784
There are many conceptualizations and formalizations of decision making. In this paper we compare classical decision theory with qualitative decision theory, knowledge-based systems and belief–desire–intention models developed in artificial intelligence and agent theory. They all contain representations of information and motivation. Examples of informational attitudes are probability distributions, qualitative abstractions of probabilities, knowledge, and beliefs. Examples of motivational attitudes are utility functions, qualitative abstractions of utilities, goals, and desires. Each of them encodes a set of alternatives to be chosen from. This ranges from a small predetermined set, a set of decision variables, through logical formulas, to branches of a tree representing events through time. Moreover, they have a way of formulating how a decision is made. Classical and qualitative decision theory focus on the optimal decisions represented by a decision rule. Knowledge-based systems and belief–desire–intention models focus on an alternative conceptualization to formalize decision making, inspired by cognitive notions like belief, desire, goal and intention. Relations among these concepts express an agent type, which constrains the deliberation process. We also consider the relation between decision processes and intentions, and the relation between game theory and norms and commitments. 相似文献
159.
Previous published methods for the analysis of ETU and PTU are time-consuming and furthermore use dichloromethane (DCM) for extraction or clean-up. This study details the development and validation of a rapid method that combines a simple extraction step with UHPLC-ESI(+)-MS/MS. This is the first application of UHPLC-MS/MS to analyse these compounds. Besides that, we replaced DCM with a more environmental-friendly solvent. The analytical performance was evaluated with the analysis of spiked celery samples at 50 μg kg(-1) (LOQ) and 300 μg kg(-1). The recoveries were between 65% and 90% for ETU and between 71% and 127% for PTU with RSDs in repeatability and reproducibility conditions below 10% for ETU. This method is rapid (a chromatographic run time of 2 min) and can easily be performed (no laborious clean-up). The presented method is environmental friendly with significant reduction in solvent consumption. 相似文献
160.