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991.
A highly sensitive photodetection system with a detection limit of 1 photon/s was developed. This system uses a commercially available 200-microm-diameter silicon avalanche photodiode (APD) and an in-house-developed ultralow-noise readout circuit, which are both cooled to 77 K. When the APD operates at a low gain of approximately 10, it has a high-linearity response to the number of incident photons and a low excess noise factor. The APD also has a high quantum efficiency and a dark current of less than 1 e/s at 77 K. This photodetection system will shorten measurement time and permit higher spatial and wavelength resolution for near-field scanning optical microscopes. 相似文献
992.
Mibe T Chang WC Nakano T Ahn DS Ahn JK Akimune H Asano Y Daté S Ejiri H Fujimura H Fujiwara M Hicks K Hotta T Imai K Ishikawa T Iwata T Kawai H Kim ZY Kino K Kohri H Kumagai N Makino S Matsuda T Matsumura T Matsuoka N Miwa K Miyabe M Miyachi Y Morita M Muramatsu N Niiyama M Nomachi M Ohashi Y Ooba T Ohkuma H Oshuev DS Rangacharyulu C Sakaguchi A Sasaki T Shagin PM Shiino Y Shimizu H Sugaya Y Sumihama M Titov AI Toi Y Toyokawa H Wakai A Wang CW Wang SC Yonehara K Yorita T Yoshimura M Yosoi M 《Physical review letters》2005,95(18):182001
Photoproduction of a phi meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections at t = -|t|min do not increase smoothly as Egamma increases but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that phi mesons are photoproduced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes. 相似文献
993.
994.
Cytotoxic major saponin from tomato fruits 总被引:1,自引:0,他引:1
A major novel steroidal alkaloid glycoside, possessing cytotoxic activity has been isolated from the fruits of Lycopersicon esculentum. 相似文献
995.
996.
An improved hybrid method is proposed for analyzing sound scattering by a periodic structure. Part of the scattered field formulated with the mode expansion method is combined with other components of the field formulated with the boundary integration method in one period of the structure. Structures treated by this method can have arbitrary periodic forms made of locally reactive boundaries and porous materials. The oblique incident absorption coefficient of the structure is obtained simply from the reflection factor calculated for each elemental wave of the scattered field. The accuracy of the method is demonstrated by the agreement between calculated and measured values of the normal absorption coefficient of some test structures. 相似文献
997.
Fujiwara N Môri N Uwatoko Y Matsumoto T Motoyama N Uchida S 《Physical review letters》2003,90(13):137001
Pressure-induced superconductivity in a spin-ladder cuprate Sr2Ca12Cu24O41 has not been studied on a microscopic level thus far although the superconductivity was already discovered in 1996. We have improved the high-pressure technique using a large high-quality crystal, and succeeded in studying the superconductivity using 63Cu nuclear magnetic resonance. We found that the anomalous metallic state reflecting the spin-ladder structure is realized and the superconductivity possesses an s-wave-like character in the meaning that a finite gap exists in the quasiparticle excitation: At a pressure of 3.5 GPa, we observed two excitation modes in the normal state from the relaxation rate T-11. One gives rise to an activation-type component in T-11, and the other T-linear component linking directly with the superconductivity. This gapless mode likely arises from free motion of holon-spinon bound states appearing by hole doping, and the pairing of them likely causes the superconductivity. 相似文献
998.
Synchronization of chaotic oscillations was observed in mutually injected vertical-cavity surface-emitting lasers (VCSELs) in a low-frequency fluctuation regime. In the experiments, only one of the two polarization modes (x mode) showed synchronized oscillations, and the other polarization components (y mode) were synchronized as a result of the effect of anticorrelated oscillations that is a characteristic feature of VCSELs. 相似文献
999.
1000.
S. Baba K. Hata S. Ichikawa T. Sekine Y. Nagame A. Yokoyama M. Shoji T. Saito N. Takahashi H. Baba I. Fujiwara 《Zeitschrift für Physik A Hadrons and Nuclei》1988,331(1):53-62
Evaporation-residue excitation functions for16O and12C+197Au reactions were measured by means of the activation technique. The competition between evaporation and fission of the compound nuclei was studied by comparing the observed evaporation-residue data with the published fission excitation functions. A newly devised analysis was applied in order to deduce a fission barrier height at a specified angular momentum and determine the relevant fissioning nucleus as well. We found the fission barriers to be 8.2 MeV for the211Fr nucleus at 16? and 8.2 MeV for the207At nucleus at 27?. 相似文献