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71.
Yousof?Mardoukhi Esa?R?s?nenEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(6):144
Semiconductor quantum dots are among the leading candidates for next-generation nanoscale devices due to their tunable size, shape, and low energy consumption. Here we apply quantum optimal control theory to coherently manipulate the single-electron charge distribution in quantum-dot lattices of various sizes. In particular, we show that to control the charge distribution it is sufficient to optimize the gate voltage acting on a single quantum dot in the lattice. We generally find yields around 99% in the picosecond time scale when using realistic models for the quantum-dot lattices on a real-space grid. We analyze and discuss both the limitations of the model regarding the gate parameters as well as the potential of the scheme for applications as quantum-dot cellular automata. 相似文献
72.
73.
The influence of the ligand structure on activation of hafnocene polymerization catalysts: A theoretical study 总被引:1,自引:0,他引:1
Virve A. Karttunen Anniina Turunen John R. Severn Esa Kokko 《Journal of organometallic chemistry》2008,693(1):155-163
The influence of ligand structure of hafnocenes on activation of the polymerization catalysts has been studied by quantum chemical methods. Altogether 54 hafnocenes were included in the analysis, supplemented by four zirconocenes for comparison. The trends in structural and electronic parameters relevant in the catalyst activation step were studied for the dichloride, dimethyl and cationic monomethyl forms of the catalysts. The effects of ligand modifications were analyzed as functions of the metal, ancillary cyclopentadienyl-based ligand, ligand substituent and the ligand bridge, making comparisons to experimental data. Generally, large aromatic ligands together with electron donating ligand substituents stabilize the catalytically active species, thus facilitating the catalyst activation process. The obtained trends are expected to aid in the development of new high-performance polymerization catalysts. 相似文献
74.
Anne Silset Geir Rune Flåten Herman Helness Esa Melin Gisle Øye Johan Sjöblom 《Journal of Dispersion Science and Technology》2013,34(3):392-408
A matrix of 30 crude oils have been analyzed to investigate if there is any correlation between the physiochemical properties of the crude oils and the quality of the produced water. As an approach to study produced water quality, oil. and brine water (3.5 wt%) have been mixed together, and transmission profiles from the separation process have been investigated by means of Turbiscan LAb. The Turbiscan LAb enables the study of stability of colloidal dispersions without any dilution or modification of the sample. The oil-in-water emulsions (30:70) were made by mixing oil and water at low speed to be sure that they separate within a short period of time. Drop size distributions were investigated for all crude oil emulsions by using a Coulter Counter (COULTER Multisizer II). The correlations between transmission profiles and crude oil characteristics were made by using principal component analysis (PCA), a method that helps visualize the most important information contained in a data set and find combinations of variables that describe major trends. A Vortoil K-liner hydrocyclone connected to a mixing rig has been used to separate oil and water in larger scale experiments. The objective with these experiments was to compare the results with separation experiments done at bench scale. Six crude oils have been investigated at the separation rig, and both droplet size distribution and dispersed oil concentration have been performed. The main conclusions from this work are that Turbiscan LAb is a suitable technique to study the separation of oil-in-water with good reproducibility. The results from the multivariate data analysis show that the crude oils group according to if they are light or heavy and according to if they get high or low transmission. From the larger scale experiments it has been shown that the droplet sizes, oil/water density differential, and viscosity have a significant impact on separation efficiency. 相似文献
75.
Esa Saukkonen Katja Lyytikäinen Pavel Geydt Kaj Backfolk 《Cellulose (London, England)》2014,21(5):3677-3690
In this study, the effect of enzyme treatment on refined, never-dried bleached birch kraft pulp was investigated, using an endo-1,4-β-xylanase, that is substantially free from cellulase activity. The xylanase treatment of refined never-dried pulp revealed a rapid initial hydrolysis rate with a time-dependent saturation level in the amount of hydrolyzed pulp carbohydrates. Surprisingly short xylanase treatment times were found to have an impact on the fiber surface structure and on the physicochemical properties of kraft pulp fibers. Xylanase treatment led to mild microscopic differences in the ultrastructure of a never-dried fiber, whereas local topographical differences were distinguishable with atomic force microscopy. Results from the analysis of dissolved carbohydrates and the interfacial properties of the xylanase-treated never-dried fibers thus confirm a selective removal of xylan from the fiber surfaces. The zeta-potential charge and dewatering properties of the pulp slurry, fiber morphology, and strength properties of the paper were affected, which is a concomitant of xylanase treatment. However, the papermaking properties of the fibers were mainly preserved with simultaneous improvement in the dewatering rate of the pulp. Thus, optimized xylanase treatment of refined bleached kraft pulp provides a fiber for papermaking or fiber modification purposes with a selectively modified chemical composition of the fiber surface layer. 相似文献
76.
Dr. Sarina Sarina Prof. Dr. Huai‐Yong Zhu Qi Xiao Prof. Esa Jaatinen Prof. Jianfeng Jia Yiming Huang Prof. Zhanfeng Zheng Prof. Haishun Wu 《Angewandte Chemie (International ed. in English)》2014,53(11):2935-2940
Supported nanoparticles (NPs) of nonplasmonic transition metals (Pd, Pt, Rh, and Ir) are widely used as thermally activated catalysts for the synthesis of important organic compounds, but little is known about their photocatalytic capabilities. We discovered that irradiation with light can significantly enhance the intrinsic catalytic performance of these metal NPs at ambient temperatures for several types of reactions. These metal NPs strongly absorb the light mainly through interband electronic transitions. The excited electrons interact with the reactant molecules on the particles to accelerate these reactions. The rate of the catalyzed reaction depends on the concentration and energy of the excited electrons, which can be increased by increasing the light intensity or by reducing the irradiation wavelength. The metal NPs can also effectively couple thermal and light energy sources to more efficiently drive chemical transformations. 相似文献
77.
Esa T. T. Kumpulainen Ari M. P. Koskinen Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10901-10911
The influence of catalyst components in the copper–TEMPO (2,2,6,6‐tetramethylpiperidine N‐oxide) catalysed aerobic oxidation of alcohols was investigated. The type and amount of base greatly influences reactivity. The bipyridyl ligand concentration had no major influence on catalysis, but excessive amounts led to a decrease in activity for longer reaction times. The kinetic dependency for TEMPO was found to be 1.15, and for copper 2.25, which is an indication of a binuclear catalytic system. Optimised conditions with various allylic and aliphatic alcohols give good to excellent rapid oxidations. 相似文献
78.
Faulhuber and Steinerberger conjectured that the logarithmic derivative of has the property that is strictly decreasing and strictly convex. In this small note, we prove this conjecture. 相似文献
79.
Esa ?J?rvenp??Email author Maarit?J?rvenp?? Mika?Leikas 《Communications in Mathematical Physics》2005,254(3):695-717
We show that, unlike in the 2-dimensional case [LL], the Hausdorff dimension of a measure invariant under the geodesic flow is not necessarily preserved under the projection from the unit tangent bundle onto the base manifold if the base manifold is at least 3-dimensional. In the 2-dimensional case we reprove the preservation theorem due to Ledrappier and Lindenstrauss [LL] using the general projection formalism of Peres and Schlag [PS]. The novelty of our proof is that it illustrates the reason behind the failure of the preservation in the higher dimensional case. Finally, we show that the projected measure has fractional derivatives of order for all <(–2)/2 provided that the invariant measure has finite -energy for some >2 and the base manifold has dimension 2.MJ and ML acknowledge the support of the Academy of Finland, project #48557.Acknowledgement. We thank the referee for valuable comments clarifying the exposition. 相似文献
80.
Dev?Chandra Esa?R?Korpi Celia?P?Miralles Angel?L?De Blas Gregg?E?HomanicsEmail author 《BMC neuroscience》2005,6(1):30