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921.
A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4 pmol kg−1 for 250 mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2 pmol kg−1 at <200 m) to deep water (29.2 pmol kg−1 from 3500 m to the bottom). 相似文献
922.
We used an asymmetric layered system functioning as a plasmon waveguide coupler to couple surface plasmon modes with gap plasmon
modes. The planar system was analyzed by the transfer matrix method to design the optical dimensions of the system. We simulated
the effective mode indexes and H-field distribution of the coupled modes, for different gap widths and refractive indexes. For the calculated modes the propagation
lengths were calculated. Furthermore, a sample structure was fabricated and odd gap plasmon modes were excited with a coupling
prism in an attenuated-total-reflection (ATR) configuration. The mode index measurement showed good agreement with the simulation
data. 相似文献
923.
Lévêque JM Fujita M Bosson A Sohmiya H Pétrier C Komatsu N Kimura T 《Ultrasonics sonochemistry》2011,18(3):753-756
The Molybdate-catalyzed bromination of various aromatic compounds in the presence of KBr/H(2)O(2) in an aqueous/chloroform biphasic system occurred under ultrasonic irradiation, whereas the reaction did not take place under conventional mechanical stirring (1400 rpm). The sonochemical activation was found to be of secondary effect, attributed to lowering pH by sonolysis of CHCl(3)-H(2)O solvents mixture. 相似文献
924.
Abstract
Visualization of volume data is difficult to realize and control because the most common output device is a two-dimensional (2D) display and the most common input device is a mouse, which only allows 2D operation. For example, volume rendering projects the data structure onto a 2D image plane, but this type of view-dependent method gives rise to occlusion. In addition, 2D mouse operation does not allow direct selection of three-dimensional (3D) regions or coordinates. In this article, we propose a method that expands the octree structure of volume data onto a 2D plane. The proposed method uses the self-similarity of the fractal diagram and achieves multi-scale visualization of volume data in two dimensions. With this method, we can browse the entire domain of volume data without occlusion. For greater effectiveness, we combined the proposed method and existing 3D-based methods. Since each cell has a one-to-one correspondence with squares in the Sierpinski carpet, we can assign arbitrary 3D regions or positions by selecting the corresponding squares. This provides direct access to 3D regions and coordinates by 2D mouse operation. We propose some functions for interactive visualization and discuss how to exploit the advantages and lessen the disadvantages of the proposed method. 相似文献925.
Yeon-Su Park Yukihiro Okamoto Noritada Kaji Manabu Tokeshi Yoshinobu Baba 《Journal of nanoparticle research》2011,13(11):5781-5798
We synthesized, in aqueous solution at room temperature, small water-soluble CdSe quantum dots (QDs) with strong photoluminescence
(PL) and then correlated the PL with their adsorption layer structure. For synthesizing the QDs, their initial synthesis condition
was controlled to form small Cd-containing species capable of passivating dangling bonds on the CdSe core surface. Each CdSe
QD (d ~ 2.5 nm) consisted of a CdSe core (d ~ 2.1 nm), a cysteine (cys)-ligand shell, and an adsorption layer composed of Cd–cys complexes (mainly CdL(-H)−, cys ≡ H2L), cys (as L2−), Cd(OH)2, and CdO
x
(x ≥ 1). Our CdSe QDs showed strong blue band-edge PL as well as strong green surface trap PL. Their PL quantum yield (QY) of
~18% was unexpectedly high, considering their extremely small core size and their absence of any wide-bandgap inorganic shell.
We attributed the QY to their adsorption layer species. The small weakly charged Cd–cys complex and the small neutral cadmium
oxides in the adsorption layer could relatively readily diffuse into the unprotected surface sites on the core. These wide-bandgap
species coalesced selectively on the unprotected surface sites with minimal spatial disturbance to the preexisting surface
Cd-ligand coordination, and passivated them effectively. These decreased nonradiative recombination of the excitons significantly
and thus led to the unexpectedly high QYs. 相似文献
926.
Water is a very poor glass former, but its link to the thermodynamic and kinetic anomalies remains elusive. We experimentally reveal that the glass-forming ability and fragility of a water-salt mixture are closely related to its equilibrium phase diagram. We propose that frustration between local and global orderings controls both the glass-forming ability and the fragility. Relying on the same role of salt and pressure, which commonly break tetrahedral order, we apply this idea to pure water under pressure. This scenario not only explains unusual behavior of water-type liquids such as water, Si, and Ge but also provides a mechanism for a link between the equilibrium phase diagram, glass-forming ability, and fragility for various materials including oxides, chalcogenides, and metallic glasses. 相似文献
927.
Hayashi Y Pirozhkov AS Kando M Fukuda Y Faenov A Kawase K Pikuz T Nakamura T Kiriyama H Okada H Bulanov SV 《Optics letters》2011,36(9):1614-1616
The interaction between a 25 TW laser and Xe clusters at a peak intensity of 1 × 101? W/cm2 has been investigated. Xe K-shell x rays, whose energies are approximately 30 keV, were clearly observed with a hard x-ray CCD at 3.4 MPa. Moreover, we studied the yield of the Xe K-shell x rays by changing the pulse duration of the laser at a constant laser energy and found that the pulse duration of 40 fs is better than that of 300 fs for generating Xe K-shell x rays. 相似文献
928.
We report that a spectrum can be retrieved with a planar waveguide spatial heterodyne spectrometer (SHS) incorporating an active phase-shift scheme, where the phase shifts are distributed around π/2. This was confirmed experimentally with an SHS that had 32 interleaved Mach-Zehnder interferometers and whose free spectral range was 625 GHz. The phase shifts ranged from 0.71 to 2.2 rad against the target of π/2 rad. 相似文献
929.
Itaru OikawaMariko Ando Yasuto NodaKoji Amezawa Hajime KiyonoTadashi Shimizu Masataka TanshoHideki Maekawa 《Solid State Ionics》2011,192(1):83-87
Local structure around Sc in BaZr1 − xScxO3 − δ protonic conductor has been investigated by 45Sc MAS-NMR. The MAS-NMR spectra were consisted of several peaks, which can be assigned to Sc in different coordination environment. Compositional dependence of the spectrum was observed. The coordination environment of Sc is determined from the peak deconvolution, and the oxygen vacancy concentration and the protonic defect concentration around Sc were obtained. The present investigation suggests that oxygen vacancies preferentially located around Sc and the concentration of oxygen vacancies in the vicinity of Sc increases with increasing the Sc content. Protonic defects were found to be preferentially located around Sc at lower Sc content. 相似文献
930.
Rh-catalyzed direct carboxylation of unactivated aryl C-H bond under atmospheric pressure of carbon dioxide was realized via chelation-assisted C-H activation for the first time. Variously substituted and functionalized 2-arylpyridines and 1-arylpyrazoles underwent the carboxylation in the presence of the rhodium catalyst and a stoichiometric methylating reagent, AlMe(2)(OMe), to give carboxylated products in good yields. The catalysis is proposed to consist of methylrhodium(I) species as the key intermediate, which undergoes C-H activation to afford rhodium(III), followed by reductive elimination of methane to give nucleophilic arylrhodium(I). This approach demonstrates promising application of C-H bond activation strategy in the field of carbon dioxide fixation. 相似文献