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21.
Sajib Saha Yakov Nesterets Rajib Rana Murat Tahtali Frank de Hoog Timur Gureyev 《International journal of imaging systems and technology》2017,27(4):333-344
Localizing the sources of electrical activity in the brain from electroencephalographic (EEG) data is an important tool for noninvasive study of brain dynamics. Generally, the source localization process involves a high‐dimensional inverse problem that has an infinite number of solutions and thus requires additional constraints to be considered to have a unique solution. In this article, we propose a novel method for EEG source localization. The proposed method is based on dividing the cerebral cortex of the brain into a finite number of “functional zones” which correspond to unitary functional areas in the brain. To specify the sparsity profile of human brain activity more concisely, the proposed approach considers grouping of the electrical current dipoles inside each of the functional zones. In this article, we investigate the use of Brodmann's areas as the functional zones while sparse Bayesian learning is used to perform sparse approximation. Numerical experiments are conducted on a realistic head model obtained from segmentation of MRI images of the head and includes four major compartments namely scalp, skull, cerebrospinal fluid (CSF), and brain with relative conductivity values. Three different electrode setups are tested in the numerical experiments. The results demonstrate that the proposed approach is quite promising in solving the EEG source localization problem. In a noiseless environment with 71 electrodes, the proposed method was found to accurately locate up to 6 simultaneously active sources with accuracy >70%. 相似文献
22.
The single-pellet moment techniques previously developed for the evaluation of effective diffusion coefficient and effective thermal conductivity of a porous solid are combined and a procedure is proposed for the simultaneous evaluation of these constants from a single set of pulse response experiments. It is shown that both temperature and concentration response curves can be measured from a single pulse of oxygen injected into hydrogen carrier gas flowing past a catalyst pellet. It is shown that the zeroth moment of the concentration response peaks are sufficient for finding the effective diffusivity while both zeroth and first order moments are required for thermal conductivity. Experiments conducted at 110°C with a boehmite pellet of porosity 0.57 gave a thermal conductivity value of 3.6 x 10-4 cal/cm °K s and an effective diffusivity (for H2O) of 0.054 cm2/s. The adsorption equilibrium constant of H2O was determined as ρpK = 24.5 from the first moment data. If sorption resistance to diffusion through the pellet is included in the diffusion coefficient, an apparent value of 0.0011 cm2/s would be obtained for Deff. This result indicates the importance of separation of diffusion and sorption parameters in the analysis. 相似文献
23.
Cleiser Thiago P. da Silva Ashlee J. Howarth Martino Rimoldi Timur Islamoglu Andrelson W. Rinaldi Joseph T. Hupp 《Israel journal of chemistry》2018,58(9-10):1164-1170
Here we report a new highly microporous zirconium phosphonate material synthesized under solvothemal conditions. The specific Brunauer-Emmett-Teller (BET) surface area of the “unconventional metal−organic framework” (UMOF) is measured to be ∼900 m2/g, after following an appropriate activation protocol. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows that the material bears a free −OH functionality on the phosphonate linker that may interact with CO2. CO2 adsorption isotherms were collected and a measured heat of adsorption of 31 kJ/mol was obtained. In addition, adsorption isotherms of CO2, N2, and CH4 at 298 K combined with Ideal Adsorbed Solution Theory (IAST) show that the material can be expected to display high selectivities for uptake of CO2 versus N2 or CH4. 相似文献
24.
Nanoplasmonic sensing is typically based on quantification of changes in optical extinction or scattering spectra. Here we explore the possibility of facile self-referenced hydrogen sensing based on angle-resolved spectroscopy. We found that heterodimers built from closely spaced gold and palladium nanodisks exhibit pronounced directional scattering, that is, for particular wavelengths, much more light is scattered toward the Au than toward the Pd particle in a dimer. The effect is due to optical phase shifts associated with the material asymmetry and therefore highly sensitive to changes in the permittivity of Pd induced by hydrogen loading. In a wider perspective, the results suggest that directional scattering from bimetallic antennas, and material asymmetry in general, may offer many new routes toward novel nanophotonic sensing schemes. 相似文献
25.
26.
Daria Artemova Polina Vishnyakova Elena Khashchenko Andrey Elchaninov Gennady Sukhikh Timur Fatkhudinov 《International journal of molecular sciences》2021,22(10)
Endometriosis and cancer have much in common, notably their burgeoning of cells in hypoxic milieus, their invasiveness, and their capacity to trigger remodeling, vascularization, and innervation of other tissues. An important role in these processes is played by permissive microenvironments inhabited by a variety of stromal and immune cells, including macrophages. Remarkable phenotypical plasticity of macrophages makes them a promising therapeutic target; some key issues are the range of macrophage phenotypes characteristic of a particular pathology and the possible manners of its modulation. In both endometriosis and cancer, macrophages guard the lesions from immune surveillance while promoting pathological cell growth, invasion, and metastasis. This review article focuses on a comparative analysis of macrophage behaviors in endometriosis and cancer. We also highlight recent reports on the experimental modulation of macrophage phenotypes in preclinical models of endometriosis and cancer. 相似文献
27.
A general criterion is developed for testing the relative importance of intraparticle and external, concentration and temperature gradients on the observed rates, for reactions catalyzed by porous solids. The criterion is applicable to any multiple reaction system and to reactions conforming to any rate law. The applicability of such criteria is extended to reaction systems with highly nonlinear temperature and concentration dependence, by taking into-account the higher order terms in the Taylor expansion of the rate expressions in the derivation. 相似文献
28.
Variations in pore structure cause significant changes in diffusion resistance and adsorption characteristics during the reaction of SO2 with activated soda. Breakthrough and moment analysis of the SO2-activated soda ash reaction showed that the effective diffusion coefficient of SO2 in the solid product (mostly Na2SO3) was about three times smaller than its value in the original activated soda. About 30% of the diffusion flux of SO2 in the solid product was found to be due to surface diffusion. The adsorption equilibrium constant of SO2 on the solid product was found to be about half the value of the adsorption equilibrium constant on activated soda. It was also determined that SO2 was irreversibly adsorbed on the solid product Na2SO3 at 200°C and 3.7 atm. The gaseous product CO2 was not adsorbed on the solid product while it was slightly adsorbed on activated soda. 相似文献
29.
Edwina L. Rissland David B. Skalak M. Timur Friedman 《Artificial Intelligence and Law》1997,5(1-2):1-74
In this article we evaluate the BankXX program from several perspectives. BankXX is a case-based legal argument program that retrieves cases and other legal knowledge pertinent to a legal argument through a combination of heuristic search and knowledge-based indexing. The program is described in detail in a companion article in Artificial Intelligence and Law 4: 1--71, 1996. Three perspectives are used to evaluate BankXX:(1) classical information retrieval measures of precision and recall applied against a hand-coded baseline; (2) knowledge-representation and case-based reasoning, where the baseline is provided by the functionality of a well-known case-based argument program, HYPO (Ashley, 1990); and (3) search, in which the performance of BankXX run with various parameter settings, for instance, resource limits, is compared. In this article we report on an extensive series of experiments performed to evaluate the program. We also describe two additional experiments concerning(1) the program's search behavior; and (2) the use of a modified form of precision and recall based on case similarity. Finally we offer some general conclusions that might be drawn from these particular experiments. 相似文献
30.
Use of input power information for load sharing in parallel connected boost converters 总被引:1,自引:1,他引:0
A. D. Erdogan Mehmet Timur Aydemir 《Electrical Engineering (Archiv fur Elektrotechnik)》2009,91(4-5):229-250
Parallel operation of several small rated converters may be preferred for various reasons instead of using a single, high power converter. Sharing of the load among the converters is a serious problem of parallel operation. There are basically two kinds of algorithms for sharing: systems using communication and systems using droop characteristics without communication. This paper investigates these concepts, and then proposes modifications for each method. Basic suggestion is the use of input power as the control parameter, a technique which is especially useful for the converters designed for renewable energy systems. Another modification is to utilize an offset voltage in the droop method while determining the set values. This technique has been shown to improve the voltage regulation. Simulation and experimental results are provided to verify the concepts. 相似文献