Hepatic sinusoid, the smallest vessel in the liver, plays important roles in hepatic microcirculation. Although the structure of the hepatic sinusoids affects diverse functions of the liver, little is known about morphological alterations in the sinusoids under pathological conditions. In this study, we show that the structure of hepatic sinusoids can be identified three-dimensionally in normal and carbon tetrachloride-injured mouse liver, using the absorption mode of synchrotron radiation micro-computed tomography. We observed that the hepatic sinusoidal structure on tomographic slice images was similar to that on histological images of normal and acutely injured mice. Moreover, centrilobular necrosis and structural alterations of the sinusoids in the necrotic region were detectable on tomographic slice and volume-rendered images of the acutely injured mice. Furthermore, quantitative analyses on 3D volume-rendered images of the injured sinusoid revealed decrease in the volume of the sinusoid and connectivity of the sinusoidal network. Our results suggest that the use of synchrotron radiation micro-computed tomography may improve our understanding of the pathogenesis of hepatic diseases by detecting the hepatic sinusoids and their alterations in three-dimensional structures of the damaged liver.

Direct evidence of the fast beam-ion instability (FBII) was obtained in the Pohang Light Source by measuring the bunch-by-bunch parameters from the snapshots of the beam image. With the direct observation, we confirmed the FBII signals and clarified uncertainties of the blowup factors quantitatively: bunch size blowup of ϳ2s y and the oscillation amplitude of ϳ0.75s y . Suppression of the FBII was also demonstrated in the presence of the multiple gases or an extra clearing gap in the bunch train. [S0031-9007(98)07688-1] PACS numbers: 29.27.Bd, 41.75.Ht As the bunch current and the number of bunches become very large in future low emittance accelerators, a new kind of beam instability, so-called the fast beamion instability (FBII) [1,2], has become an important subject of the beam physics. The FBII is distinguished as a transient beam instability excited by the beamgenerated ions accumulated in a single passage of the bunch train, while the conventional ion trapping [3,4] is excited by the trapped ions accumulated in the periodic beam potential over multiple passages of the beam. One of the characteristic signals of the FBII is a coherent beam-ion oscillation with increasing amplitude along the bunch train. According to the linear theory [1,2], the initial amplitude of oscillation y͑t, z͒ grows quasiexponentially as y͑t, z͒ ϳ exp͓͑z͞l͒ p t͞t ͔ with the phase factor v i z͞c 2 v b t, where z is the position within a bunch train, l is the length of the bunch train, t is the characteristic growth time of the FBII, and v i , v b are the ion and betatron frequencies, respectively. As the amplitude increases, however, the nonlinearity becomes important. Computer simulation studies [1,2,[5][6][7] have shown that the amplitude of oscillation saturates at about s y of the bunch size due to the nonlinearity of the beam-ion interaction. This fully developed FBII will cause harmful effects on the performance of the planned colliding beam facilities like the KEKB [7], PEP-II [8], and the future linear colliders. A more serious problem would be that the growth time of the FBII is too fast to be damped effectively by the existing active feedback systems, nor can it be cured by including a clearing gap long enough to overfocus the ions out of the beam path.There have been experimental studies to confirm the FBII in ALS [9], TRISTAN AR [10], PEP-II [11], and PLS [12]. The first observation of the FBII was made in the ALS with the injection of helium gas into the storage ring to raise the growth rate. Both the transverse and longitudinal beam feedback systems were used to suppress the coupled bunch instabilities, and a chargecoupled-device (CCD) camera was used to observe the FBII by measuring the projected beam size of the whole bunch train. When the 80 nTorr He was injected, the projected vertical beam size blew up by a factor of 2 to 3. The growth time of the FBII was also estimated by measuring the onset of the FBII as a function of the length of the bunch train. On the other hand, a single pass beam position monitor (SBPM) w...

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We developed an off-axis-illuminated zone-plate-based hard x-ray Zernike phase-contrast microscope beamline at Pohang Light Source. Owing to condenser optics-free and off-axis illumination, a large field of view was achieved. The pinhole-type Zernike phase plate affords high-contrast images of a cell with minimal artifacts such as the shade-off and halo effects. The setup, including the optics and the alignment, is simple and easy, and allows faster and easier imaging of large bio-samples.

The coherency of the synchrotron radiation at Pohang Accelerator Laboratory has been investigated using Young's interferometer. The electron beam size can be measured precisely using the interferometer. An interferogram using 650 nm light at the diagnostics beamline at Pohang Light Source (PLS) has been measured to determine the electron beam distribution and the spatial coherence length. Interferograms obtained by numerical study are compared with experimental results in order to understand the measured data. From this comparison, the electron beam at PLS is revealed to be a Gaussian distribution with a standard deviation of 210 microm. The spatial coherency length of 650 nm light at PLS is measured to be 0.57 cm, and that of 0.1 nm light at PLS is predicted to be 0.88 microm by the same numerical study.