An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS),
is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling
of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation.
After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS
has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid–base
reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension.
Figure We have systematically investigated the analytical potential of Raman spectroscopy of samples in acoustically levitated drops. 相似文献
Sort the bigs from the smalls : Reverse‐selective membranes, through which bigger molecules selectively permeate, are attractive for developing chemical processes. A new adsorption‐based reverse‐selective membrane that utilizes a Na cation occluded in a zeolitic framework is presented. The membrane developed enables the selective permeation and separation of bigger polar molecules, such as methanol and water, from hydrogen above 473 K.
We report systematic, high-precision measurements of the low-T (down to 70 mK) thermal conductivity kappa of YBa2Cu3O(y), La(2-x)Sr(x)CuO4, and Bi2Sr2CaCu2O(8+delta). Careful examinations of the Zn- and hole-doping dependences of the residual thermal conductivity kappa0/T, as well as the in-plane anisotropy of kappa0/T in Bi2Sr2CaCu2O(8+delta), indicate a breakdown of the universal thermal conductivity, a notable theoretical prediction for d-wave superconductors. Our results point to an important role of electronic inhomogeneities, which are not considered in the standard perturbation theory for thermal conductivity, in the underdoped to optimally doped regime. 相似文献
Our goal is to achieve the precise quantitative imaging of tissue elasticity in clinical settings. In the present study, we measured basic ultrasonic characteristics of atherosclerosis by two-dimensional (2D) intravascular tissue velocity imaging. Radio-frequency (RF) signal from a clinically used IVUS apparatus was digitized at 500 MSa/s and stored in a workstation. First, the correlation coefficient between two consecutive frames was calculated in the rotational direction and the rotational disuniformity was corrected to obtain the maximum correlation coefficient. Then, the polar coordinate images were converted into rectangular coordinate images and the images were divided into 64 by 64 square shaped regions of interest (ROIs). The correlation and displacement of the ROIs between the consecutive two frames were calculated by template matching method. Two-dimensional tissue velocity was defined as the vectors of displacement of ROI with 0.7 and more correlation. IVUS studies were performed in directional coronary atherectomy (DCA) procedures. The specimens excised by DCA were stained with Elastica-Masson's trichrome staining and CD68 immunochemical staining. Eleven cases (including two no re-flow cases and one perforation case) were intraoperatively observed by IVUS and the specimens obtained by DCA were observed by optical microscopy. The specimen from homogeneous 2D strain was collagen dominant fibrosis and the specimen from a lesion with complex vectors contained CD68 positive cells and degenerated collagen fibers, which indicated the plaque was vulnerable. 相似文献
Chemically disordered face-centered cubic FePt nanoparticles (NPs) were synthesized via pyrolysis of iron(III)ethoxide and platinum(II)acetylacetonate. The surface ligands of these NPs were then exchanged from oleic acid to 2-aminoethanethiol (AET). The AET-capped FePt NPs were found to be well dispersed in water when pH<8, and the zeta potential was more than +30 mV when pH?7. 相似文献
We study a nondegenerate jump process on Euclidean space determined by SDE. We show the existence of the smooth density of its transition probability and its short time asymptotics as . Assumptions required for these facts are relaxed considerably from past works by Picard and Ishikawa–Kunita. We show these facts using Malliavin calculus on Poisson space. Our calculus is simpler and more efficient than previous works. 相似文献
We investigated the relationship between the average and local crystal structures and the ferroelectric properties of Bi2SiO5, Bi4Si3O12, or Bi2O3 added Sr1−xBi2+xTa2O9 (x=0, 0.2) produced by a solid-state reaction. By measuring the P-E hysteresis, we found that Sr1−xBi2+xTa2O9 (x=0, 0.2) has higher Pr and Ec than SrBi2Ta2O9 (SBT). Pr increased and Ec decreased by adding Bi2SiO5, Bi4Si3O12, or Bi2O3 to Sr1−xBi2+xTa2O9. The average crystal structures were determined by the Rietveld method. On the other hand, the local structure is important, because the ferroelectric property is related to the distortion, and ferroelectric complex oxides have domains. We also investigated the local crystal structure using atomic pair distribution function (PDF) analysis. Based on the results, the bond angle variance, σ2, of each TaO6 octahedron increased by substituting Si for the Ta site. The tilting angle, αa,αb, of each TaO6 octahedron increased relative to that of the average structure, and the symmetry of the TaO6 octahedron in the local structure deteriorated in comparison to that of the average structure. This distortion and symmetry of TaO6 contributes to the remanent polarization. 相似文献
The elimination reaction of acrylonitrile from 2′-O-cyanoethylated nucleosides by Bu4NF was studied computationally. The transition structures for the reaction of 3-methoxypropionitrile with Me4NF were located at the MP2, B3LYP, and B3LYP-SCRF(Dipole) levels with 6-31 + G* basis set. The α-hydrogen of the cyano group was removed via a proton transfer from the α-carbon to the oxygen with a syn-periplanar arrangement rather than the deprotonation reaction with F?. In the presence of an excess amount of Me4NF, the activation energy decreased by the coordination of Me4N+ to the cyano group. The reaction of 3-methoxypropionitrile with Bu4NF and 2′-O-cyanoethylated uridine with Me4NF also occurred via a proton transfer mechanism with lower activation energies. The reactivity tendency corresponds to the amount of the negative charge on the oxygen atom and part of the reason for the faster elimination with F? rather than with DBU concerns entropy. The experimental results are well explained by these calculations. 相似文献