M. Kato

Measurement Of Radiocarbon Content In Leaves From Some Japanese Sites

We have measured radiocarbon contents in leaves collected from 15 sites in Japan, including mountain areas and big city areas for last three years. Comparing the radiocarbon contents in various areas, high 14 C concentrations (80-100‰ as δ 14 C) are seen for the leaves from the mountain and country sites. On the contrary, low concentrations (5-40‰) were observed for the leaves from city region, especially near the road with heavy traffic. These results indicate that the atmosphere of the mountain and country sites in Japan is still clean but the CO 2 gas coming from fossil non-radioactive carbon significantly pollutes the atmosphere of the city sites. The value of δ 14 C for the mountain areas implies that 14 C produced by nuclear bomb test in 1960s still remains. The decrease of δ 14 C at heavy traffic sites in Tokyo is consistent with the increase of CO 2 concentration in the atmosphere assuming that almost all CO 2 gas in this region originates from the fossil fuel.

Effects of Acute Portal Hypertension by Portal Venous Stenosis on Systemic Hemodynamics in Dogs

Effects of acute portal hypertension on systemic hemodynamics after hepatectomy were evaluated by portal venous stenosis (PVS) model in dogs. In protocol 1, portal hypertension of about twice portal venous pressure (PVP) decreased cardiac output (CO) and left atrial pressure (LAP) by 24.5% (p less than 0.01) and 1.0 mm Hg (p less than 0.01), respectively. In protocol 2, stepwise PVS demonstrated that CO change (%) and LAP change (mm Hg) were inversely proportional to PVP change (r = -0.937 and -0.883, respectively). The ratio of CO change to LAP change with stepwise PVS was comparable to that obtained by repeated hemorrhage in protocol 3. The present study shows that low CO with portal hypertension is caused by a reduction of venous return to the heart.

Inelastic energy loss of low energy proton colliding with cryogenic crystals of Ar, Kr and Xe

For a collision energy of 500 eV, the energy spectra of protons scattered from thick cryogenic crystals of Ar, Kr and Xe have been measured, and analyzed by using a simple statistical model. The conduction band width has been estimated as 3.2, 2.4 and 1.7 eV, for Ar, Kr and Xe, respectively. A large probability of electronic excitation was observed, and it has been estimated as 0.4, 0.8 and 0.9 for Ar, Kr and Xe, respectively. In the previous study [Surf. Sci. 513 (2002) 71], a large neutralization probability could be interpreted in terms of delocalization of the hole, which was transferred from the proton to the valence band. Similarly, the enhancement of electronic excitation probability can be interpreted in terms of the dissipation of excited electron through the conduction band. Moreover, a potential usefulness of ion energy loss spectroscopy for the electronic band structural analysis has been confirmed.

Changes in Hepatic Hemodynamics and Oxygen Consumption after Partial Hepatic Congestion in Dogs

The effects of 66% hepatic congestion (group 2, n = 6) on liver blood flow and hepatic oxygen metabolism were investigated in anesthetized dogs using an ultrasonic transit time flowmeter. The results were compared with those for control dogs (group 1, n = 6) and for 60% hepatectomized dogs (group 3, n = 6) wherein almost the same amount of hepatic parenchyma was removed as was congested in group 2. Portal blood flow (PVF) in group 2 and group 3 decreased similarly to 60 and 63% of the baseline values, respectively (p less than 0.05). Cardiac output (CO) in group 2 and group 3 also decreased significantly in proportion to the decrease in PVF. Among the dogs in group 2, hepatic arterial blood flow (HAF) was fairly well maintained at 86% of the baseline value, despite the decrease of cardiac output, whereas the HAF in group 3 decreased to 49% of the baseline value at 1 h after hepatectomy. The calculated hepatic arterial resistance (HAR) in group 3 increased significantly due to the 60% loss of the hepatic arterial vascular bed. The HAR in group 2, by contrast, became lower than that in group 1, suggesting a compensatory decrease of HAR for the obstructed portal flow to the congested area. These results were well consistent with our angiographic findings (n = 3) that the portal flow to the congested segments was completely obstructed and the congested segments received only an arterial blood supply. The centrilobular hepatocytes of the congested segments showed marked vacuolar degeneration and the total hepatic oxygen consumption in group 2 was reduced (p less than 0.05). However, the decrease in oxygen consumption in group 2 was not so severe as in group 3 (p less than 0.05). These data suggest that some parts of the preserved congested segments were still viable and had the capacity of aerobic metabolism even 4 h after the ligation of the drainage vein of those segments. In this study, the importance of the hepatic arterial flow to the congested segment has been demonstrated. When the congested hepatic segment is to be preserved intraoperatively, care must be taken to maintain the hepatic arterial blood flow during the perioperative period.

Angular straggling associated with fluctuations in charge state of the projectile in grazing ion-surface scattering

Abstract We have studied the angular straggling of a few keV ions scattered off metal surfaces at grazing scattering condition. The angular straggling of scattered particles is large when the charge state of the particle fluctuates significantly in the surface region. The important physical parameters responsible for the angular straggling are the particle induced density of states and the rate of change of the energy of the atomic level with distance from the surface. An implication for the mechanism underlying skipping motion is discussed.

THE SPECTRUM LINE WIDTH OBSERVED IN ELECTRON EMISSION FROM THE AUTODETACHMENT OF THE HE-* (1S2S2; 2S) FORMED IN COLLISIONS OF THE HE+ PROJECTILES WITH LOW WORKFUNCTION METALLIC SURFACES

Abstract The broadening effect on the line-spectrum width of autodetachment electrons from He −∗ (1s2s 2 ; 2 S) at low workfunction metallic surfaces is studied. There are at least three broadening mechanisms: (1) lifetime broadening of the He −∗ state because of the He −∗ -to-He ∗ decay, (2) image-like shift of the resonance energy position of He −∗ state, and (3) the dynamical effect associated with the motion of the He atom. Based on Borisov et al. (Surf. Sci. 284 (1993) 337 and 325 (1995) 323), it is found that the relative importance of the three mechanisms is (1) > (3) ≥ (2) for the case of energetic He + -surface scattering experiments.

Changes in liver blood flow after hepatectomy in conscious dogs

Hepatic circulation after hepatectomy was investigated in conscious dogs under fasting and feeding conditions. After a 40% hepatectomy, both the hepatic arterial and portal blood flow were measured simultaneously using ultrasonic transit time flowmeters. During fasting, the total hepatic blood flow (i.e., the sum of arterial and portal blood flow) changed in a biphasic pattern after hepatectomy. The first peak (517.9±42.7 ml/min; 130.1% of preoperative flow) was seen on the 1st postoperative day (POD) and the second peak (444.8±25.6 ml/min; 112.7% of preoperative flow) occurred on the 7th POD. The portal flow demonstrated the same biphasic changes as the total hepatic flow, although the hepatic arterial flow showed only the first peak. A heart rate analysis suggested that the first peak was probably due to hyperdynamic circulatory conditions, as has been previously reported. In addition, the existence of the second peak was established by the present study. The postprandial hepatic blood flow decreased during the first 2 weeks postoperatively, but exceeded the presurgical levels on PODs 21 and 28.

Theory of proton neutralization based on the Kleber–Zwiegel model of screening electron pickup

Abstract The Kleber–Zwiegel (KZ) model for proton neutralization, in which some electron is picked up from the screening electron cloud around the proton, has been reformulated in terms of quantum field theory of solids. Using the reformulated KZ model, the cases of an Al (high electron density case) and a Cs (low electron density) metal are investigated within the Thomas–Fermi approximation for the screening effects. For high electron density metals, the resonant neutralization is a predominant process and it can be regarded as an electron pickup process from the screening electron cloud in the surface region. In contrast, for low electron density metals, it appears that the Auger neutralization, which is disregarded in the KZ model, cannot be neglected.