We present Spitzer IRS spectroscopy of CO2 ice toward 19 young stellar objects (YSOs) with luminosity lower than 1L⊙ . Pure CO2 ice forms only at elevated temperatures, T > 20 K, and thus at higher luminosities. Current internal luminosities of YSOs with L < 1L⊙ do not provide such conditions out to radii of typical envelopes. Significant amounts of pure CO2 ice would signify a higher past luminosity. We analyze 15.2 μm CO2 ice bending mode absorption lines in comparison to the laboratory data. We decompose pure CO2 ice from 12 out of 19 young low luminosity sources. The presence of the pure CO2 ice component indicates high dust temperature and hence high luminosity in the past. The sum of all the ice components (total CO2 ice amount) can be explained by a long period of low luminosity stage between episodic accretion bursts as predicted in an episodic accretion scenario. Chemical modeling shows that the episodic accretion scenario explains the observed total CO2 ice amount best.

The study of this experiment is focused on labor saving of healthy rice seedling production using PSF (polypropylene spunbonded fabrics) as thermal protection material. Several factors such as different compositions of nursery soil and PSF materials were tested to produce healthy rice seedlings. The inner thermal protection material in PE film (polyethylene film) showed 0.9-1.7~circC higher than that of PSF 40-100 ~textrmgm-2 . The light transmittance-ratio also showed similar trends. It is considered that the appropriate PSF material density was 40 gm~textrmgm-2 in accordance with economic values and healthy rice seedlings. Plant height and dry weight according to various nursery soil showed the rang-es of 8.5-14.2cm and 5.5-10.0mg, respectively. In composition of nursery soil, artificial soil combined with paddy soil was effective in producing healthy seedling for rice seedling production. The total sugar content also showed the difference between PSF 40, 60 ~textrmgm-2 PE film (0.43-0.52mg FW ~textrmg-1 ) and PSF 80, 100 ~textrmgm-2 (0.28-0.35mg FW ~textrmg-1 ) and it showed the same tendency among varieties as well as various nursery soil. These results demonstrate that PSF 40 ~textrmgm-2 economically affordable, and can be recommended as thermal protection material for producing good healthy rice seedling.