Cosmic Star Formation Activity at z=2.2 Probed by H-alpha Emission Line Galaxies

We present a pilot narrow-band survey of H-alpha emitters at z=2.2 in the Great Observatories Origins Deep Survey North (GOODS-N) field with MOIRCS instrument on the Subaru telescope. The survey reached a 3 sigma limiting magnitude of 23.6 (NB209) which corresponds to a 3 sigma limiting line flux of 2.5 x 10^-17 erg s^-1 cm^-2 over a 56 arcmnin^2 contiguous area (excluding a shallower area). From this survey, we have identified 11 H-alpha emitters and one AGN at z=2.2 on the basis of narrow-band excesses and photometric redshifts. We obtained spectra for seven new objects among them, including one AGN, and an emission line above 3 sigma is detected from all of them. We have estimated star formation rates (SFR) and stellar masses (M_star) for individual galaxies. The average SFR and M_star is 27.8M_solar yr^-1 and 4.0 x 10^10M_solar, respectivly. Their specific star formation rates are inversely correlated with their stellar masses. Fitting to a Schechter function yields the H-alpha luminosity function with log L = 42.82, log phi = -2.78 and alpha = -1.37. The average star formation rate density in the survey volume is estimated to be 0.31M_solar yr^-1Mpc^-3 according to the Kennicutt relation between H-alpha luminosity and star formation rate. We compare our H-alpha emitters at z=2.2 in GOODS-N with narrow-band line emitters in other field and clusters to see their time evolution and environmental dependence. We find that the star formation activity is reduced rapidly from z=2.5 to z=0.8 in the cluster environment, while it is only moderately changed in the field environment. This result suggests that the timescale of galaxy formation is different among different environments, and the star forming activities in high density regions eventually overtake those in lower density regions as a consequence of "galaxy formation bias" at high redshifts.Comment: Accepted for publication in PASJ Subaru Special Issue, 11 pages, 10 figure

Integrable discretizations of the SIR model

Structure-preserving discretizations of the SIR model are presented by focusing on the hodograph transformation and the conditions for integrability for their discrete SIR models are given. For those integrable discrete SIR models, we derive their exact solutions as well as conserved quantities. If we choose the parameter appropriately for one of our proposed discrete SIR models, it conserves the conserved quantities of the SIR model. We also investigate an ultradiscretizable discrete SIR model.Comment: 31 pages, 8 figure

Experimental Model of Asthma by Toluene Diisocyanate (TDI)

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。Attention has been paid to respiratory hypersensitivity in workers who are exposed to toluene diisocyanate (TDI) in their workshops. An experimental model of asthma in guinea pigs by TDI has been developed. A 10% TDI solution dissolved in ethyl acetate was painted on the nasal cavities of guinea pigs with a thin cotton applicator once daily for five consecutive days. Three weeks later, the animals were challenged with a 5% TDI solution. Exertional breathing accompanied by the prolongation of expiratory phase was observed among the test animals. The number of the animals suffering from the attacks increased by the repetitive provocations. Although some of the guinea pigs suffered from anaphylaxis by the provocation procedures, the attacks including the anaphylactic shocks hardly brought about deaths in the animals. It was found that passive transfer of the symtom was possible in our experimental system. Both eosinophilic infiltration in the lung and eosinophilia in the peripheral bood were found among the test animals. This experimental model was developed by the appliaction of a simple chemical alone to the respiratory tract of guinea pigs. A significance of the model is discussed with the review of the literatures concerned

Bacillus subtilis cell factory converting phytic acid into scyllo-inositol, a therapeutic agent for Alzheimer\u27s disease

Phytic acid, known as myo-inositol (MI) hexakisphosphate, is the principal storage form of phosphorus in many plant tissues, especially bran and seeds. Phytases comprise a group of phosphatases that can trim inorganic phosphates from phytic acid. B. subtilis laboratory standard strain 168 and its derivatives exhibit no phytase activity, whereas a natto starter secretes significant phytase actively. The natto phytase gene was cloned into strain RIK1285, a protease-defective derivative of 168, to construct a random library of its N-terminal fusions with 173 different signal peptides identified in the 168 genome. The library was screened to assess the efficiency of phytase secretion based on clear zones around colonies on plates, which appeared when phytic acid was hydrolyzed. The pbp signal peptide enhanced the secretion of the natto phytase most efficiently, i.e., twice that of the original signal peptide. The secreted phytase can be one of the enzymatic tools to liberate MI from phytic acid contained in agricultural wastes including rice bran. As described above, MI is the most abundant inositol stereoisomer in nature and thus supplied cheap. On the other hand, scyllo-Inositol (SI) is one of the inositol stereoisomers, rare in the nature, and expected as a promising disease-modifying therapeutic agent for Alzheimer\u27s disease. B. subtilis 168 has the ability to metabolize inositol stereoisomers, including MI and SI. Previously, we reported a B. subtilis cell factory with modified inositol metabolism that converts MI into SI in the culture medium. The strain was constructed by deleting all genes related to inositol metabolism and overexpressing key enzymes, IolG and IolW. By using this strain, 10 g/l of MI initially included in the medium was completely converted into SI within 48 h of cultivation in a rich medium containing 2% (w/v) Bacto soytone. When the initial concentration of MI was increased to 50 g/l, conversion was limited to 15.1 g/l of SI. Therefore, overexpression systems of IolT and PntAB, the main transporter of MI in B. subtilis and the membrane-integral nicotinamide nucleotide transhydrogenase in Escherichia coli respectively, were additionally introduced into the B. subtilis cell factory, but the conversion efficiency hardly improved. We systematically determined the amount of Bacto soytone necessary for ultimate conversion, which was 4% (w/v). As a result, the conversion of SI reached to 27.6 g/l within 48 h of cultivation. The B. subtilis cell factory was improved to yield a SI production rate of 27.6 g/l/48 h by simultaneous overexpression of IolT and PntAB, and by addition of 4% (w/v) Bacto soytone in the conversion medium. The concentration of SI was increased even in the stationary phase perhaps due to nutrients in the Bacto soytone that contribute to the conversion process. Thus, MI conversion to SI may be further optimized via identification and control of these unknown nutrients. References: Tsuji, S., Tanaka, K., Takenaka, S., and Yoshida, K. (2015) Enhanced secretion of natto phytase by Bacillus subtilis. Biosci Biotechnol Biochem.. 79(11):1906-1914. Tanaka, K., Takanaka, S., and Yoshida, K. (2014) A second-generation Bacillus cell factory for rare inositol production. Bioengineered. 5(5):331-334. Tanaka, K., Tajima, S., Takenaka, S., and Yoshida, K. (2013) An improved Bacillus subtilis cell factory for producing scyllo-inositol, a promising therapeutic agent for Alzheimer\u27s disease. Microb Cell Fact. 12:124. Yamaoka, M., Osawa, S., Morinaga, T., Takenaka, S., and Yoshida, K. (2011) A cell factory of Bacillus subtilis engineered for the simple bioconversion of myo-inositol to scyllo-inositol, a potential therapeutic agent for Alzheimer\u27s disease. Microb Cell Fact. 10:69

Design and Performance Tests of a Low Power DC Arcjet Thruster

This paper describes a quasi-one-dimensional flow model which can be used for the design of an arcjet thruster. Owing to the simplicity of the model, the performance characteristics of the thruster can be calculated easily for finding an optimum configuration suitable for various missions. In order to verify adequacy of the model, a thruster was fabricated and its performance characteristics were measured. The experimental results were compared with the calculation predicted with the model. Both are in satisfactory agreement, and it is concluded that this flow model is a useful tool for the design of the arcjet thruster