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71.
Daisuke Uemura Katsuhiro Ueda Yoshimasa Hirata Hideo Naoki Takashi Iwashita 《Tetrahedron letters》1981,22(29):2781-2784
The full structure of palytoxin, a potent coelenterate toxin, is reported. 相似文献
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A first-passage problem for a cumulative process is investigated. The cumulative process is assumed to be generated by a Poisson process, and the amplitude generated by an event is assumed to decay exponentially. An integral equation for the probability density of the first-passage time until the total amplitude exceeds a pre-specified threshold level is derived. The Laplace transform of the probability density of the first-passage time is obtained explicity when each amplitude generated by an event is distributed exponentially. The mean first-passage times are given in a closed form and plotted versus the threshold level. 相似文献
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Takashi Takeo Tomohiko Kanie Katsuhiro Satoh Shigeyuki Aoyama Haruhiko Itoh Hajime Hattori 《Optical Review》1995,2(5):366-370
In lightwave community antena television (CATV) systems as well as other optical fiber communication networks, a transmitted optical signal is known to be degraded by an intensity noise produced within the fiber due to the interference between the signal and doubly reflected light. We report on the improvements to the signal degradation due to the double Rayleigh backscattering by inserting optical isolators in the trunk lines of the systems. A carrier-to-noise ratio (CNR) has been calculated as a function of the number and the insertion loss of the isolators. The calculated results indicate that there is an optimum number of isolators, and if the insertion loss is less than 0.3 dB, the CNR degradation can be restored by more than 60%. To test the calculated results, we conducted experiments for the specific case of employing one isolator, and obtained good agreements between the two. 相似文献
79.
Shintaro Ichikawa Utaroh MotosugiTomoaki Ichikawa Katsuhiro SanoHiroyuki Morisaka Tsutomu Araki 《Magnetic resonance imaging》2013
Purpose
To investigate the relationship between estimated glomerular filtration rate (eGFR) and parameters calculated using intravoxel incoherent motion (IVIM) imaging of the kidneys.Materials and Methods
We studied 365 patients, divided into 4 groups based on eGFR levels (mL/min/1.73 m2): group 1, eGFR ≥ 80(n = 80); group 2, eGFR 60–80 (n = 156); group 3, eGFR 30–60 (n = 114); and group 4 ,eGFR < 30 (n = 15). IVIM imaging was used to acquire diffusion-weighted images at 12 b values. The diffusion coefficient of pure molecular diffusion (D), the diffusion coefficient of microcirculation or perfusion (D*), and perfusion fraction (f) were compared among the groups using group 1 as control.Results
In the renal cortex, D* values were significantly lower in groups 2, 3, and 4 than in group 1. The D value of renal cortex was significantly low in only group 3. In the renal medulla, the D* and D values were significantly lower only in groups 2 and 3, respectively.Conclusion
As renal dysfunction progresses, renal perfusion might be reduced earlier and affected more than molecular diffusion in the renal cortex. These changes are effectively detected by IVIM MR imaging. 相似文献80.
We control the number of critical points of a height function arising from the Nash isometric embedding of a compact Riemanniann-manifoldM. The Ln/2 curvature norm ∥R∥ and a similar scalar ∥R∥ are introduced and their integralR(M) andR(M) overM. We prove thatR(M) is bounded below by a constant depending only onn and the Betti numbers ofM. Thus a new sphere theorem is proved by eliminating allith Betti numbers fori = 1, .…n −1. The emphasis is that our sphere theorem imposes no restriction on the range of curvature.
Research partially supported by Grant-in-Aid for General Scientific Research, grant no. 07454018. 相似文献