The structural characteristics of a pentane-insoluble asphaltene isolated from the vacuum residue of an Arabian crude mixture have been investigated by pyrolysis gas chromatography/ mass spectrometry (py/GC/MS), 1 H/ 13 C NMR, gel permeation chromatography (GPC), and matrixassisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry. Assignments of NMR signals of the asphaltene have been discussed briefly on the basis of the information from the literature and compared with those of an aliphatic fraction isolated from the ruthenium ion catalyzed oxidation products of the asphaltene. The comparison data indicated that aliphatic substitution 〉C 1 on aromatics are little; however, most of the chain methylene groups are located within a polymeric-saturated fraction of the asphaltene. The average size of aromatic fused ring systems has been determined to be 4-5 for the sample. Pyrolysis tests implied that the asphaltene sample is constructed with relatively large polycyclic units connected by relatively strong bonds. Our results also support a view that asphaltene is the mixture of complex polydispersed molecules with large variation of molecular sizes.

Because of a lack of information about the rates of growth of aortic aneurysms, such rates in thoracic and abdominal aortic aneurysms were determined. One hundred seventy-one patients with atherosclerotic aortic aneurysm managed nonoperatively were followed up for more than 6 months with sequential computed tomography (CT). There were 211 aneurysms (thoracic aortic, 82; abdominal aortic, 129). The growth rates of thoracic and abdominal aortic aneurysms were 0.42 and 0.28 cm/y, respectively. Aneurysms at the aortic arch (n = 34) grew at a faster average rate (0.56 cm/y) than aneurysms arising at other levels, even when the rate was corrected for the initial diameter. It is recommended that thoracic aortic aneurysms, especially aortic arch aneurysms, be followed frequently with CT examination of size.

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Nasotracheal intubation under CTSC guidance increases the success rate of airway instrumentation, and also reduces the incidence and severity of epistaxis.

We experienced seven cases of hepatocellular carcinoma (HCC) with extrahepatic primary malignant neoplasms (PMNs), which accounted for 7.5% of 93 HCC cases in our department during a 5.5-year investigation period. No common characteristics of the seven patients with extrahepatic PMNs in terms of age, sex, computed tomographic (CT) features of hepatocellular carcinoma, or presence of liver cirrhosis were evident. One of the seven cases had triple PMNs. Extrahepatic PMNs were found in various organs: stomach, colon, kidney, lung, larynx, and esophagus. Attention to extrahepatic organs should be undertaken in the management of HCC. Two patients in hepatic coma died 4 and 6 months after the diagnosis of HCC due to the advanced HCC, and accompanying extrahepatic malignancies were not the primary cause of death.

Surface planarization of strain-relaxed SiGe buffer layers by chemical mechanical polishing ͑CMP͒, particularly the influence of a post-CMP cleaning process which is indispensable after CMP, on the surface morphology of SiGe buffer layers was investigated. It was found that the cleaning tended to enhance the surface roughness due to the etching effect that increased with increasing cleaning temperature. The etching effect was suppressed by optimizing cleaning reagents, and the ultrasmooth surfaces of SiGe buffer layers with Ge contents of 30 to 70% were obtained, irrespective to growth methods. The root mean square roughness reached 0.4 to 0.6 nm, which was the lowest value that was ever obtained.It is now well recognized that heterostructures of strained-Si or strained-Ge on strain-relaxed Si 1Ϫx Ge x buffer layers have many advantages over the conventional Si field-effect-transistor ͑FET͒ structure, because carrier mobility of strained-channel devices is drastically enhanced due to the strain effects. Strained Si-channel metal oxide semiconductor FETs 1-3 and strained Ge-channel modulationdoped FETs 4-6 with high channel mobility have been demonstrated so far. High quality SiGe strain-relaxed buffer layers ͑SiGe virtual substrates͒ are, however, required for realization of these high performance devices. This is because the relaxed SiGe layers tend to have threading dislocations and rough surfaces which cause strong carrier scattering and mobility lowering in the strain channels. To reduce the threading dislocation density and the surface roughness, various growth methods such as the compositionally graded buffer method 7,8 and the low temperature buffer method 9-11 have been studied. However, it is very difficult to obtain relaxed SiGe buffer layers with an ultrasmooth surface whose flatness is comparable to that of a Si substrate, that is, less than 1 nm as the root mean square ͑rms͒ surface roughness. Even the graded buffer method, which is thought to be very useful and to become a popular method to lower the threading dislocation density (ϳ10 5 cm Ϫ2 ͒, is not able to suppress the roughening of the surface to less than 10 nm. It is, therefore, more appropriate to fabricate the high quality buffer layer by combining a certain growth technique providing low threading dislocation density and surface polishing after growth.As for surface polishing, chemical mechanical polishing ͑CMP͒ technique has been introduced even in the SiGe alloy system. There are several reports on successful planarization of SiGe buffer layers with Ge contents of less than 30%. 12-16 On the other hand, the CMP of SiGe buffers with higher Ge composition which are necessary for strained-Ge channel devices and optical devices has been reported only by Currie et al. 17 However, their aim was to suppress nucleation of additional threading dislocation during growth. Due to the difference of the chemical properties between Si and Ge ͑SiGe͒, it is not clear whether the same CMP method as for Si can be applied to SiGe with high Ge contents or no...

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