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The effect of dodecanethiolate-protected metallic nanoclusters of gold (Au:SC12, 1), silver (Ag:SC12), palladium (Pd:SC12), and platinum (Pt:SC12) on the catalytic activity of Mn(TPP)Cl (TPP = tetraphenylporphinato) was investigated in styrene oxidation with iodosylbenzene. Among the four metal clusters, only Au:SC12 led to appreciable acceleration of the catalytic reaction. The major role of the Au cluster was to regenerate the active catalytic path involving Mn(III) and Mn(V) from the deactivated Mn(IV) species. The binary 1/Mn(TPP)Cl catalyst system showed an absorption spectrum characteristic of Mn(III)-porphyrin after reaction, whereas a catalytically ineffective Mn(IV) species was observed as the sole porphyrin species in the absence of the Au cluster or in the presence of Pd, Ag, and Pt clusters. Accordingly, the slow oxidation reaction with Mn(TPP)Cl was accelerated by the addition of Au:SC12, and complete conversion of Mn(IV) into Mn(III) was observed in the absorption spectrum. 1H NMR inspection of the reaction of Au:SC12 and iodosylbenzene revealed that the surface dodecyl groups were partially oxidized into dodecanal and eliminated from the cluster surface, thereby producing unprotected gold sites on the surface. A reactivation mechanism involving the reaction of the Mn-porphyrin and the oxidant activated on the gold surface is proposed. 相似文献
104.
K. Konishi H. Kokame K. Hirata 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(4):715-722
The jam phenomenon in traffic flow wastes not only considerable traffic-transportation time but also great amounts of fuel
due to many accelerate-decelerate actions. From traffic-economic and traffic-pollution viewpoints, the suppression of traffic
jam is an important issue we have to solve. The present paper shows that -norm, which has been used in the field of control theory, can reveal the traffic jam phenomenon in an optimal velocity traffic
model under an open boundary condition. Furthermore, we suppress the traffic jam in the model by the decentralized delayed-feedback
control method. Some numerical simulations are shown to verify our theoretical results.
Received 27 October 1999 相似文献
105.
We demonstrate a new tool called optical spectrogram scope for visualization of a spectrogram or a scalogram of optical ultrafast phenomena. The optical spectrogram scope is constructed on the basis of the time-to-two-dimensional-space conversion technique capable of converting a set of time-varying frequency distributions into two-dimensional spatial ones. 相似文献
106.
T. Sekine M. Konishi H. Kudo K. Tagami S. Uchida 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(3):483-487
A95mTc tracer with an excellent quality was prepared by a simple sublimation method after α-bombardment of niobium metal. Technetium-95m
produced by the93Nb(α,2n)95mTc reaction was separated from the niobium targets in a quartz tube by heating at 1100°C in an oxygen gas flow. Technetium-95m
sublimed as an oxide was deposited on the inner wall of the quartz tube outside an electric furnace, and then collected as
a pertechnetate solution by washing with water. The ICP-MS analysis of the95mTc solution revealed its excellent quality, compared to a95mTc solution prepared from the same targets through a wet chemical separation method and a commercial95mTc solution. With this tracer, the precision of ICP-MS analysis of99Tc in environmental samples are highly improved. 相似文献
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109.
Kazuyuki Minami Toshiyuki Ishida Yasuki Asada Seiji Shirakawa Masanao Kobayashi Shoichi Suzuki Tomimasa Konishi Hidenori Mimura 《X射线光谱测定》2019,48(6):691-695
We investigate a miniaturized X-ray source using an ultraviolet (UV) laser and a pyroelectric crystal and discuss potential applications in medicine. The UV laser is the fourth harmonic of a Nd:YAG laser with a wavelength of 266 nm, repetition rate of 10 Hz, and pulse energy of 40 mJ. The pyroelectric crystal is a LiNbO3 cylinder of diameter 10 mm and length 6 mm. The prototype X-ray source we fabricated is an aluminum parallelepiped of dimensions 3 × 3 × 5 cm. The X-ray count rate of the X-ray source is maximized at approximately 1,400 cps for UV laser irradiation of approximately 5 min. After 30 min of irradiation by the UV laser, the temperature of the pyroelectric crystal rose from 295 K to 312 K. The principles of X-ray generation ensure that X-ray sources using UV lasers and pyroelectric crystals offer ample opportunity for miniaturization. We believe the X-ray source developed in this work is suitable for medical applications, although further study is needed to address points such as increasing the X-ray count rate and adjusting the temperature of the pyroelectric crystal. 相似文献
110.
The correlation between protonic conduction and the amount of radiation-induced defects in gamma-ray-irradiated perfluorosulfonic acid (PFSA) polymers (Aciplex-SF-1004®) has been investigated using a direct-current resistance method, transmission spectroscopy for the ultraviolet (UV) and visible (Vis) wavelength ranges and Fourier transform infrared (FTIR) spectroscopy with the attenuated total refraction (ATR) technique. The proton conductivity of the polymers, which are irradiated with a dose of up to 532 kGy under vacuum at room temperature and subsequently exposure to air, is enhanced by approximately three orders of magnitude as compared to that of the unirradiated polymer. The UV–Vis spectra of the irradiated polymers reveal the presence of fluorocarbon radicals, which increase with the irradiation dose. It is also observed in the UV–Vis and FTIR spectra that peroxy free radicals, unsaturated species (COF), and a carboxyl group (COOH) containing a carbon-oxygen double bond are formed by reactions of the fluorocarbon radicals with oxygen or water vapor in air. In addition, an increase in the hydrogen concentration is observed in the near-surface regions of the irradiated polymers by using an elastic recoil detection (ERD) technique. The production of charge carriers such as protons and oxonium ions (H3O+) by the interaction of water vapor with the activating-radiation-induced defects leads to the enhancement of the proton conductivity. 相似文献