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931.
Jiadi Sun Ying Gan Tao Liang Shuqi Zhou Xinyi Wang Hao Wan Ping Wang 《Current Opinion in Electrochemistry》2019
Heavy-metal pollution has attracted intensive attention from the public because of the severe threats of heavy metals to the ecosystem and human health. Ultralow concentration of heavy metals in aquatic environment leads to the urgent needs of sensitive approaches for heavy-metal detection. Electrochemical DNA biosensors present outstanding superiority in convenience, selectivity, and sensitivity compared with conventional methods. To achieve the ultralow detection limit, efforts have been made to implement signal enhancement strategies to develop electrochemical DNA biosensors with enhanced sensing performance. This review focuses on the recent progress in signal enhancement strategies applied to electrochemical DNA biosensors for heavy-metal-ion detection including nicking enzyme–assisted amplification, the utilization of core–shell nanoparticles, and nanocomposites modification. 相似文献
932.
本文通过在PET薄膜上的叉指电极间沉积Pd纳米团簇制备了柔性应变传感器件.传感器通过测量纳米团簇薄膜的电导随PET薄膜形变的变化而产生对应变的响应,不仅具有高的仪表因子,而且具有宽的量程.实验发现,由于密排纳米团簇阵列的电子输运具有渗流特征,造成应变传感器的响应特性与纳米团簇的覆盖率紧密相关.通过控制纳米团簇的沉积过程,制备了由覆盖率接近有效渗流阈值的纳米团簇点阵构成的应变传感器.从最低应变探测限到0.3%应变之间,传感器件具有线性响应且仪表因子高达55.在更高的应变时,仪表因子进一步达到200.纳米团簇薄膜甚至还可以对达到8%应变的巨大形变产生响应,对应的应变因子达到惊人的3500. 相似文献
933.
Diffusion is a ubiquitous physical phenomenon where thermodynamic nonequilibrium effects(TNEs) are outstanding issues. In this work, we employ the discrete Boltzmann method to investigate the TNEs in the dynamic process of binary diffusion. The main features of the distribution function in velocity space are recovered and discussed.It is found that, with the decreasing gradients of macroscopic quantities(such as density, concentration, velocity, etc.),both the local and global TNEs decrease with the time but increase with the relaxation time in a power law, respectively. 相似文献
934.
As a typical multiphase fluid flow process, drainage in porous media is of fundamental interest both in nature and in industrial applications. During drainage processes in unsaturated soils and porous media in general, saturated regions, or clusters, in which a liquid phase fully occupies the pore space between solid grains, affect the relative permeability and effective stress of the system. Here, we experimentally study drainage processes in unsaturated granular media as a model porous system. The distribution of saturated clusters is analysed by optical imaging under different drainage conditions, with pore-scale information from Voronoi and Delaunay tessellation used to characterise the topology of saturated cluster distributions. By employing statistical analyses, we describe the observed spatial and temporal evolution of multiphase flow and fluid entrapment in granular media. Results indicate that the distributions of both the crystallised cell size and pore size are positively correlated to the spatial and temporal distribution of saturated cluster sizes. The saturated cluster size is found to follow a lognormal distribution, in which the generalised Bond number (\( Bo^{*} \)) correlates negatively to the scale parameter (μ) and positively to the shape parameter (σ). With further consideration of the total surface energy obtained based on liquid–air interfaces, we were able to include additional grain-scale information in the constitutive modelling of unsaturated soils using both the degree of saturation and generalised Bond number. These findings can be used to connect pore-scale behaviour with overall hydro-mechanical characteristics in granular systems. 相似文献
935.
We present a two-photon three-dimensional multiparty quantum secret sharing scheme. The secret messages are encoded by performing local operations. This is different from those quantum secret sharing protocols that all sharers must make a state measurement. The merit of our protocol is the high capacity. 相似文献
936.
Symmetric positive definite (SPD) data have become a hot topic in machine learning. Instead of a linear Euclidean space, SPD data generally lie on a nonlinear Riemannian manifold. To get over the problems caused by the high data dimensionality, dimensionality reduction (DR) is a key subject for SPD data, where bilinear transformation plays a vital role. Because linear operations are not supported in nonlinear spaces such as Riemannian manifolds, directly performing Euclidean DR methods on SPD matrices is inadequate and difficult in complex models and optimization. An SPD data DR method based on Riemannian manifold tangent spaces and global isometry (RMTSISOM-SPDDR) is proposed in this research. The main contributions are listed: (1) Any Riemannian manifold tangent space is a Hilbert space isomorphic to a Euclidean space. Particularly for SPD manifolds, tangent spaces consist of symmetric matrices, which can greatly preserve the form and attributes of original SPD data. For this reason, RMTSISOM-SPDDR transfers the bilinear transformation from manifolds to tangent spaces. (2) By log transformation, original SPD data are mapped to the tangent space at the identity matrix under the affine invariant Riemannian metric (AIRM). In this way, the geodesic distance between original data and the identity matrix is equal to the Euclidean distance between corresponding tangent vector and the origin. (3) The bilinear transformation is further determined by the isometric criterion guaranteeing the geodesic distance on high-dimensional SPD manifold as close as possible to the Euclidean distance in the tangent space of low-dimensional SPD manifold. Then, we use it for the DR of original SPD data. Experiments on five commonly used datasets show that RMTSISOM-SPDDR is superior to five advanced SPD data DR algorithms. 相似文献
937.
V.?V.?Ustinov Yu.?P.?Sukhorukov M.?A.?Milyaev A.?B.?Granovski? A.?N.?Yurasov E.?A.?Gan’shina A.?V.?Telegin 《Journal of Experimental and Theoretical Physics》2009,108(2):260-266
The magnetotransmission and magnetoreflection spectra of a seven-layer Cr(28 Å)/Fe(36 Å)/Cr(13 Å)/Fe(18 Å)/Cr(13 Å)/Fe(36 Å)/Cr(28 Å) film, their temperature and field dependences measured at various directions of a magnetic field with respect to the film plane, and the correlations between these effects are studied. The experimental results are compared with the data on the magnetization and transverse Kerr effect. The magnetotransmittance and magnetoreflectance are calculated for this film in terms of the magnetorefractive effect theory. Apart from the film layer thickness, the effective relaxation time, the plasma frequency, and the spin asymmetry parameter are shown to strongly affect both the magnitudes and spectral dependences of the magnetotransmittance and magnetoreflectance. Although the calculation results qualitatively describe the signs and the spectral and field dependences of the magnetotransmittance and magnetoreflectance, they do not agree quantitatively with the experimental results, in particular, near the visible region. The causes of the quantitative discrepancies are discussed. 相似文献
938.
T.?V.?Murzina A.?V.?Shebarshin I.?A.?Kolmychek E.?A.?Gan’shina O.?A.?Aktsipetrov A.?I.?Stognij N.?N.?Novitski? A.?Stashkevich 《Journal of Experimental and Theoretical Physics》2009,109(1):107-116
The structural and magnetic properties of a cobalt nanolayer placed between a silicon substrate and a protective gold layer are studied. At a cobalt layer mass thickness of 1–2 nm, a nanoisland structure is shown to form. This thickness range is characterized by a local maximum of the magnetooptical Kerr effect and enhanced nonlinear optical and magnetic nonlinear optical responses at the second-harmonic frequency. This enhancement can be caused by the excitation of local surface plasmons and an increase in the local fields at the probing-radiation and second-harmonic frequencies in metallic nanoislands. The surface-sensitive nonlinear magnetooptical Kerr effect at the second-harmonic frequency is maximal at a cobalt layer thickness of about 2 nm, which corresponds to the characteristic scale of magnetization formation in the near-surface layer in cobalt. 相似文献
939.
Ji-Sen Jiang Zhi-Feng Gan Yong Yang Bing Du Min Qian Ping Zhang 《Journal of nanoparticle research》2009,11(6):1321-1330
Preparation and characterization in vitro and in vivo of a novel magnetic fluid based on starch-coated magnetite nanoparticles
functionalized with homing peptide is reported in this paper. Precursory magnetic fluids stabilized with starch were prepared,
in a polymeric starch matrix, by controlled chemical coprecipitation of magnetite phase from aqueous solutions. The average
hydrodynamic diameter of starch-coated iron oxide nanoparticles (SIONs) was 46 nm. As a homing peptide, A54 is the most effective
peptide specific to the human hepatocellular carcinoma cell line BEL-7402. Final magnetic fluids were obtained through chemical
coupling of homing peptide labeled with 5-carboxyl-fluorescein (FAM-A54) and SIONs. Magnetic measurements showed the saturation
magnetization value of SIONs amounted to 45 emu/g and the FAM-A54-coupled SIONs showed a good magnetic response in magnetic
field. The results of experiments in vitro and in vivo showed that SIONs were endowed with specific affinity to corresponding
tumor cells after coupling with FAM-A54 and the FAM-A54-coupled SIONs could be accumulated in the tumor tissue with more efficiency
than individual magnetic targeting or biomolecular targeting. This novel magnetic fluid with dual function has great potential
applications in diagnostics and therapeutics of human tumor such as drug targeting, magnetic hyperthermia, and magnetic resonance
imaging. 相似文献
940.
Banach空间的型与独立Banach空间值随机变量序列的不等式 总被引:3,自引:0,他引:3
本文建立了独立B值随机变量序列部分和的极大值函数S*与p方根函数S(p,X)的分布函数不等式与矩不等式,讨论了这些不等式的成立与Banach空间的p型与q余型的关系,同时给出了与Hilbert空间同构的Banach空间的特征。 相似文献