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排序方式: 共有5974条查询结果,搜索用时 15 毫秒
891.
Alberto Ghirri Andrea Candini Marco Evangelisti Gian Carlo Gazzadi Florence Volatron Benoit Fleury Laure Catala Christophe David Talal Mallah Marco Affronte 《Small (Weinheim an der Bergstrasse, Germany)》2008,4(12):2240-2246
Prussian blue CsNiCr nanoparticles are used to decorate selected portions of a Si substrate. For successful grafting to take place, the Si surface needs first to be chemically functionalized. Low‐dose focused ion beam patterning on uniformly functionalized surfaces selects those portions that will not participate in the grafting process. Step‐by‐step control is assured by atomic force and high‐resolution scanning electron microscopy, revealing a submonolayer distribution of the grafted nanoparticles. By novel scanning Hall‐probe microscopy, an in‐depth investigation of the magnetic response of the nanoparticles to varying temperature and applied magnetic field is provided. The magnetic images acquired suggest that low‐temperature canted ferromagnetism is found in the grafted nanoparticles, similar to what is observed in the equivalent bulk material. 相似文献
892.
Rita Tse Yubin Xiao Giovanni Pau Serge Fdida Marco Roccetti Gustavo Marfia 《Mobile Networks and Applications》2016,21(4):688-707
Transportation policy and planning strategies, as well as Intelligent Transportation Systems (ITS), can all play important roles in decreasing pollution levels and their negative effects. Interestingly, limited effort has been devoted to exploring the potential of social network analysis in such context. Social networks provide direct feedback from people and, hence, potentially valuable information. A post telling how a person feels about pollution at a given time at a given location, could be useful to policy-makers, planners or environmentally-aware ITS designers. This work verifies the feasibility of sensing air pollution from social networks and of integrating such information with real sensors feeds, unveiling how people advertise such phenomenon, acting themselves as smart objects, and how online posts relate to true pollution levels. This work explores a new dimension in pollution sensing for the benefit of environmental and transportation research in future smart cities, confronting over 1,500,000 posts and pollution readings obtained from governmental on-the-field sensors over a one-year span. 相似文献
893.
Polymeric membrane ion-selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ion-exchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy, and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface-localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity. 相似文献
894.
Gonen R Marco R German U Katorza E Alfassi ZB Haquin G Tshuva A Pelled O 《Radiation protection dosimetry》2007,125(1-4):460-464
The Organic Bound Tritium (OBT) amount in the body may induce changes in the evaluation of the internal exposure to tritium, due to its different retention time relative to HTO. OBT measurements for urine are not performed routinely, mainly because of the lengthy work needed in preparation of the samples, when using the standard oxygen combustion method. A simpler and more rapid method based on liquid scintillation counting (LSC) was employed, and an evaluation was performed to check its suitability for urine samples. The principle of the proposed method is based on subtracting the LSC counts of the water phase sample (HTO) from the total activity of the urine sample (OBT+HTO). A good correlation was found between the results obtained when applying the proposed direct method and the Gold standard method. The minimum detectable activity when using this method was determined. 相似文献
895.
Using first-principles calculations in the framework of density functional theory, we investigated the electronic and transport properties of metal(II)-phthalocyanine (M(II)Pc) systems, both in a single-molecule configuration and in a model device geometry. In particular, using copper(II)-Pc and manganese(II)-Pc as prototypical examples, we studied how electronic correlations on the central metal ion influence the analysis of the electronic structure of the system and we demonstrated that the choice of the exchange-correlation functional, also beyond the standard local or gradient corrected level, is of crucial importance for a correct interpretation of the data. Finally, our electronic transport simulations have shown that M(II)Pc-based devices can act selectively as molecular conductors, as in the case of copper, or as spin valves, as in the case of manganese, demonstrating once more the great potential of these systems for molecular nanoelectronics applications. 相似文献
896.
Entrepreneurship and the process of firms' entry, survival and growth 总被引:12,自引:0,他引:12
897.
Kasrayan A Bocola M Sandström AG Lavén G Bäckvall JE 《Chembiochem : a European journal of chemical biology》2007,8(12):1409-1415
A number of model structures of the CalA suggested by comparative modeling were tested by site-directed mutagenesis. Enzyme variants were created where amino acids predicted to play key roles for the lipase activity in the different models were replaced by an inert amino acid (alanine). The results from activity measurements of the overproduced and purified mutant enzymes indicate a structure where the active site consists of amino acid residues Ser184, His366, and Asp334 and in which there is no lid. This model can be used for future targeted modifications of the enzyme to obtain new substrate acceptance, better thermostability, and higher enantioselectivity. 相似文献
898.
Galimberti M 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(2):304-310
When a fast moving transparent sample (with a speed close to c) is probed with a laser pulse, some artifacts can occur from data analysis. These artifacts are connected to the transit time of the probe through the sample and can mask the presence of a steep gradient of refractive index in the sample. We study this problem in the case of interferometry. In fact, the problem can affect the femtosecond interferometry of the media under ultrafast ionization by a propagating laser pulse. Two algorithms are introduced: the first based on the phase difference and the second based on visibility. Both algorithms allow for the reconstruction, under suitable assumptions, of an approximated refractive index profile from the distorted fringes. 相似文献
899.
The calibration of conceptual models for the design of urban drainage networks is an important and well-known problem in hydraulic engineering. In this paper the problem is analysed and the use of black-box identification methods is proposed and applied to experimental data. Both linear (ARX and state space) and nonlinear (polynomial and neural NARX) models are considered and their performance in the simulation and prediction of the network flow from rainfall measurements is evaluated. 相似文献
900.
Paolo Arena Luigi Fortuna Marco Branciforte 《The Journal of VLSI Signal Processing》1999,23(2-3):267-280
In this paper a reaction-diffusion CNN is implemented to generate and adaptively control locomotion in a biologically inspired walking robot. In particular a dedicated CNN development system has been realised to make the mechatronic device able to select, based on sensory stimuli, the most suitable locomotion type according to the environment. The first example of analog implementation of the biological paradigm of the Central Pattern Generator is therefore presented. 相似文献