Cultured aortic smooth muscle cells (SMC) of diabetic rats and rabbits, which overexpress platelet-derived growth factor (PDGF) beta-receptor compared with controls, have a unique phenotype. In this study we report on the PDGF beta-receptor overexpression in aortas of diabetic animals and the increased intimal thickening of carotid arteries in diabetic rabbits after balloon catheter injury compared with that in controls. In diabetic aortas with no treatments of balloon catheter injury, intimal thickening was not observed in spite of the overexpression of PDGF beta-receptor, indicating that the growth property of medial SMC in diabetic aortas was changed before the intimal thickening could take place. PDGF is known to be the main contributor to the intimal thickening induced by balloon catheter injury, which is one of several forms of arterial injuries. Intimal thickening after balloon catheter injury in diabetic rabbits increased compared with that in controls. These results imply that PDGF beta-receptor overexpression of SMC in medial layers plays an important role in intimal thickening in the formation of advanced diabetic macroangiopathy.

No abstract

The mechanism determining heterointerface cross-sections is studied for GaAs ridge quantum wires (QWRs) grown by selective molecular beam epitaxy (MBE). Arrays of < 1 10>-and < 1 1 2>-orientated QWRs were grown on (001) and (111)B GaAs patterned substrates, respectively. A detailed investigation of cross-sections of wires has shown that the boundary planes appear on both sides of QWRs, keeping a constant angle, with respect to the flat top of the substrate pattern, and they determine the lateral wire width. Their evolution mechanism has turned out to be a kinetic process, reflecting differences in migration and atom incorporation rates on different facets. Simple formulas for have been derived, and they have shown excellent agreements with experiment. This has led to precise kinetic control of the wire width by growth conditions. PACS codes: 81.07.Vb, 81.16.Dn Keywords: selective growth, molecular beam epitaxy (MBE), patterned substrate, growth mechanism, GaAs *Corresponding author. Fax: +81-11-716-6004, e-mail: taketomo@rciqe.hokudai.ac.jp IntroductionSelective molecular beam epitaxy (MBE) / metal organic vapour phase epitaxy (MOVPE) of III-V semiconductor heterointerfaces on pre-patterned substrates is one of the most promising techniques for the formation of position-and size-controlled arrays of quantum wires (QWRs) and quantum dots (QDs) [1][2][3][4]. Recently, we have reported that < 1 10>-oriented QWRs can be successfully formed on (001) patterned substrates by a selective MBE growth for both and GaAs-based materials [6,7]. However, growth on non-planar substrates is complicated due to the simultaneous involvement of various high-index facets and related kinetic processes. Actually, the cross-sectional features of grown QWRs were quite different in various orientations of patterned substrates. For precise control of the feature size, proper understanding of the underlying growth mechanism for various crystal orientations is inevitable.The purpose of this paper is to clarify the mechanism which determines heterointerface cross-sections of GaAs ridge QWRs grown by selective MBE process. From a new understanding of the growth mechanism, precise control of the wire width has been realized for both < 1 10>-and < 1 1 2>-oriented wires grown on (001) and (111)B patterned substrates, respectively.

No abstract

In view of applications to hexagonal binary decision diagram (BDD) quantum circuits, the growth of hexagonal GaAs nanowire networks was attempted by selective molecular beam epitaxy (MBE) on (111)B prepatterned substrates. The basic feasibility of <112>-oriented straight nanowires was first investigated. GaAs nanowires were selectively formed on the top (111)B plane of AlGaAs mesa structures with high uniformity. The lateral width of the wires was determined by two facet boundary planes separating the growth regions on the top and the side facets of the mesa structures. The angle of the boundary planes remained constant during growth, resulting in the wire width being precisely controlled by the thickness of the AlGaAs barrier layer. Then, GaAs/AlGaAs hexagonal nanowire networks were grown on the patterned substrates consisting of three equivalent <112>-oriented wires for a (111)B plane. The results of detailed structural and optical studies showed that highly uniform and smoothly connected hexagonal nanowire networks having threefold symmetry were successfully fabricated by the present selective MBE growth technique.