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Thin films of SrAl2O4:Eu,Dy were successfully deposited on polyethylene substrates at room temperature by pulsed ion-beam evaporation. From X-ray diffraction analysis results, the thin films were found to consist of a crystallized SrAl2O4:Eu,Dy phase. In the measurements of the photoluminescence properties of the thin films, broad peaks at 520 nm, which were characteristic of SrAl2O4:Eu,Dy phosphor, were observed. From the observation by scanning electron microscopy, the thin films were prepared on polyethylene substrates. From various observations, crystallized SrAl2O4:Eu,Dy phosphor thin films on polyethylene substrates were successfully obtained by IBE without damaging the substrates. These results suggest the possibility of IBE to deposit crystallized oxide thin films on various low-melting point substrates.

Heme oxygenase (HO-1) plays an important role in cellular protection against various stresses. The induction of HO-1 is an effective strategy for reactive oxygen species-related diseases, inflammatory diseases, as well as suppressing carcinogenesis. On the other hand, the high expression of HO-1 is now well known in many tumors. In this study, we investigated the dynamics of HO-1 expression in the host and the tumor. In the mouse sarcoma S180 solid tumor model and the rat hepatoma AH136B ascitic tumor model, HO-1 expression in the tumor, as indicated by the end product of HO-1 activation, i.e., carbon monoxide, gradually increased along with tumor growth. Over-expression of HO-1 expression in mouse colon cancer C26 tumor cells significantly promoted tumor growth as well as lung metastasis, whereas opposite results were found when the HO-1 expression was reduced in the cells. On the other hand, upregulating HO-1 levels in the host by using an HO-1 inducer protected the progression of the xenograft tumor in mice, whereas lowering HO-1 expression in the host with an HO-1 inhibitor showed accelerated tumor growth and lung metastasis after subcutaneous tumor xenograft inoculation. These findings strongly suggest that the balance of HO-1 levels in the host and the tumor cells is essential for the occurrence, progression, and prognosis of cancer. Maintenance of appropriately high HO-1 levels in the host is favorable for cancer prevention, whereas suppression of HO-1 in the tumor cells may thus become a therapeutic strategy for cancer.

Continuous wave operation at 400nm was reported in GalnN/AIGaN multiple quantum well structure laser diode. '' The shortest wavelength of the GalnN quantum well structure laser diode was 367.5nm at room temperature under pulsed operation.*' However GaN, AIN and related semiconductors are expected as a wide-band gap semiconductor for UV emitting d e v i c e~.~'~'In this paper, it is discussed that possible application of W I N ternary and (BAIGA)N quaternary to UVlight emitting devices and the quality of epitaxial layer grown by low pressure metal-organic chemical vapor deposition(LP-MOCVD). Fig.1 shows schematic diagram of LP-MOCVD with two flow channels for epitaxial growth of high quality AIN , (AIGa)N or related semiconductors. maximum flow rat e as high as 400 m/ s. Typical growth temperature and growth pressure were around 11 00-1 200 C and 76 Torr, respectively.Fig. 2 shows calculated band gap of (BAlGa) N quat ernary completely lattice matched to (0001)surfaced 6H-Sic substrate. The shortest band gap wavelength becomes 201 nm of (B0.02A10.98)N which is an indirect band gap semiconductor. Then the (BAIGa)N quaternary becomes a direct band gap semiconductor from (B0.05A10.95)N t o (BO.17@0.83)N, where corresponding band gap wavelength becomes 203 nm to 320 nm of UV region, respectively.Fig.3 shows photoluminescence spectrum obtained at room temperature from theGaN(2-3 m thick) grown onthe6H-Sicsubstrate by changing (V/III)-ratio from 300 t o 1200 without buffer layer. Peak wavelength and FWHM of the PL spectra were364.2 nm and around 40 meV at room temperature. Calculated strain included in the GaN layer grown on the Sic becomes -0.04 %. The strain affects to the PLemission characteristics as shown in Fig. 4. Thin GaN layers (0.1 m thick) were grown on BN or (BAI)N bottom layer which was also 372 0-7803-3895-2/97/$10.00 0 1 997 IEEE