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81.
K. Oda Y. Kikawada T. Oi T. Honda 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(2):475-478
A total of 19 elements in the samples of atmospheric deposition collected in Kawasaki, Japan, were determined by neutron activation
analysis, ICPAES and flame photometry. The amounts of soil dust depositions were larger in springs and those of Sb and Zn
depositions were larger in summers than in the other seasons. The values of the enrichment factors were higher for Sb and
Zn than for the other elements determined throughout the sampling period. A factor analysis showed that the two elements were
characterized as industrial components. Rubber products like tires that contain noncombustibles and rubber accelerators were
a possible origin of high concentrations of Sb and Zn in the present samples. 相似文献
82.
Wu G Mikhailovsky A Khant HA Fu C Chiu W Zasadzinski JA 《Journal of the American Chemical Society》2008,130(26):8175-8177
An elusive goal for systemic drug delivery is to provide both spatial and temporal control of drug release. Liposomes have been evaluated as drug delivery vehicles for decades, but their clinical significance has been limited by slow release or poor availability of the encapsulated drug. Here we show that near-complete liposome release can be initiated within seconds by irradiating hollow gold nanoshells (HGNs) with a near-infrared (NIR) pulsed laser. Our findings reveal that different coupling methods such as having the HGNs tethered to, encapsulated within, or suspended freely outside the liposomes, all triggered liposome release but with different levels of efficiency. For the underlying content release mechanism, our experiments suggest that the microbubble formation and collapse due to the rapid temperature increase of the HGN is responsible for liposome disruption, as evidenced by the formation of solid gold particles after the NIR irradiation and the coincidence of a laser power threshold for both triggered release and pressure fluctuations in the solution associated with cavitation. These effects are similar to those induced by ultrasound and our approach is conceptually analogous to the use of optically triggered nano-"sonicators" deep inside the body for drug delivery. We expect HGNs can be coupled with any nanocarriers to promote spatially and temporally controlled drug release. In addition, the capability of external HGNs to permeabilize lipid membranes can facilitate the cellular uptake of macromolecules including proteins and DNA and allow for promising applications in gene therapy. 相似文献
83.
84.
Ab initio calculations (MP2/6-311+G**//B3LYP/6-31G*) were employed to investigate the mechanism of metal chloride-promoted Mukaiyama aldol reaction between trihydrosilyl enol ether and formaldehyde. The metal chlorides considered include TiCl4, BCl3, AlCl3, and GaCl3. In contrast to the concerted pathway of the uncatalyzed aldol reaction, the Lewis acid-promoted reactions favor a stepwise mechanism. Three possible stepwise pathways were located. The lowest energy pathway corresponds to a simultaneous C-C bond formation and a chlorine atom shift in the first (rate-determining) step. This process is calculated to have a low activation barrier of 12 kJ mol-1 for the TiCl4-promoted reaction. The alternative [2+2] cycloaddition and direct carbon-carbon bond formation pathways are energetically competitive. BCl3, AlCl3, and GaCl3 are predicted to be efficient catalysts for the silicon-directed aldol reaction as they strongly activate the formaldehyde electrophile. Formation of a stable pretransition state intermolecular pi-pi complex between enol silane and the activated formaldehyde (CH2=O...MCln) is a key driving force for the facile metal chloride-promoted reactions. 相似文献
85.
86.
Significantly higher in energy (24 kJ mol−1) than the triplet ground state (3Σg−) is the 1Δg state of ethenedithione (S=C=C=S), in agreement with Hund's rule. This result was obtained from high-level ab initio calculations. Thus, ethenedithione cannot, as had been proposed, be considered as the first example for the violation of Hund's rule in an equilibrium structure. 相似文献
87.
88.
89.
Takao Oi Kaishu Seki Yoshikazu Kikawada 《Isotopes in environmental and health studies》2019,55(2):199-210
18O/16O isotope effects were observed at the cathode of a polymer electrolyte membrane fuel cell at 25 and 35°C. Results of experiments in which the 18O/16O isotope ratios of the oxygen gases supplied to and exhausted from the cell were measured revealed that the lighter isotope 16O reacted more preferentially to form water molecules at the cathode than the heavier one, 18O. The value of the oxygen isotope separation factor, S1, defined as the ratio of the 18O/16O isotope ratios of the oxygen gases supplied to and exhausted from the cell, ranged from 1.0030 to 1.0139, and tended to decrease with decreasing rate of oxygen utilisation (θ) and with increasing flow rate of the feed oxygen gas (DF). The value of another separation factor, S2, defined as the ratio of the 18O/16O isotope ratios of the exhausted oxygen gas and oxygen having reacted to form water molecules at the cathode, ranged from 1.0049 to 1.0304. The S2 value was much less affected by the change in θ and DF than the S1 value with the majority of the S2 value being in the range of 1.0240–1.0304. 相似文献
90.
A focused as opposed to collimated light beam is typically used as probe in order to achieve a smaller as well as more intense light interrogation area in spectroscopic ellipsometry of thin films. In this work, we performed geometric ray analysis at the illumination and recording ends of such a system. The numerical results revealed substantial changes in (i) average optical path length and (ii) optical path length differences, which varied according to wavelength despite the film thickness remaining uniform. These results were able to consistently explain the anomalies found when different focus probe beam sizes were used in experimental spectroscopic ellipsometry measurements. 相似文献