Japan Aerospace Exploration Agency

About: Japan Aerospace Exploration Agency is a facility organization based out in Tokyo, Japan. It is known for research contribution in the topics: Galaxy & Telescope. The organization has 4327 authors who have published 12054 publications receiving 208330 citations.

Search for antihelium with the BESS-Polar spectrometer.

Abstract: In two long-duration balloon flights over Antarctica, the BESS-Polar collaboration has searched for antihelium in the cosmic radiation with higher sensitivity than any reported investigation. BESSPolar I flew in 2004, observing for 8.5 days. BESS-Polar II flew in 2007-2008, observing for 24.5 days. No antihelium candidate was found in BESS-Polar I data among 8.4 x 10(exp 6) [Z] = 2 nuclei from 1.0 to 20 GV or in BESS-Polar II data among 4.0 x 10(exp 7) [Z] = 2 nuclei from 1.0 to 14 GV. Assuming antihelium to have the same spectral shape as helium, a 95% confidence upper limit of 6.9 x 10(exp -8) was determined by combining all the BESS data, including the two BESS-Polar flights. With no assumed antihelium spectrum and a weighted average of the lowest antihelium efficiencies from 1.6 to 14 GV, an upper limit of 1.0 x 10(exp -7) was determined for the combined BESS-Polar data. These are the most stringent limits obtained to date.

Four-year bacterial monitoring in the International Space Station—Japanese Experiment Module “Kibo” with culture-independent approach

Abstract: Studies on the relationships between humans and microbes in space habitation environments are critical for success in long-duration space missions, to reduce potential hazards to the crew and the spacecraft infrastructure. We performed microbial monitoring in the Japanese Experiment Module "Kibo", a part of the International Space Station, for 4 years after its completion, and analyzed samples with modern molecular microbiological techniques. Sampling was performed in September 2009, February 2011, and October 2012. The surface of the incubator, inside the door of the incubator, an air intake, air diffuser, and handrail were selected as sampling sites. Sampling was performed using the optimized swabbing method. Abundance and phylogenetic affiliation of bacteria on the interior surfaces of Kibo were determined by quantitative PCR and pyrosequencing, respectively. Bacteria in the phyla Proteobacteria (γ-subclass) and Firmicutes were frequently detected on the interior surfaces in Kibo. Families Staphylococcaceae and Enterobacteriaceae were dominant. Most bacteria detected belonged to the human microbiota; thus, we suggest that bacterial cells are transferred to the surfaces in Kibo from the astronauts. Environmental bacteria such as Legionella spp. were also detected. From the data on bacterial abundance and phylogenetic affiliation, Kibo has been microbiologically well maintained; however, the microbial community structure in Kibo may change with prolonged stay of astronauts. Continuous monitoring is required to obtain information on changes in the microbial community structure in Kibo.

Can we measure the accretion efficiency of active galactic nuclei

Abstract: The accretion efficiency for individual black holes is very difficult to determine accurately. There are many factors that can influence each step of the calculation, such as the dust and host galaxy contribution to the observed luminosity, the black hole mass and more importantly the uncertainties on the bolometric luminosity measurement. Ideally, we would measure the active galactic nuclei (AGNs) emission at every wavelength, remove the host galaxy and dust, reconstruct the AGN spectral energy distribution and integrate them to determine the intrinsic emission and the accretion rate. In reality, this is not possible due to observational limitations and our own galaxy line-of-sight obscuration. We have then to infer the bolometric luminosity from spectral measurements made in discontinuous wavebands and at different epochs. In this paper, we tackle this issue by exploring different methods to determine the bolometric luminosity. We first explore the trend of accretion efficiency with black hole mass (e ∝ M∼0.5) found in recent work by Davis & Laor and discuss why this is most likely an artefact of the parameter space covered by their Palomar–Green quasar sample. We then target small samples of AGNs at different redshifts, luminosities and black hole masses to investigate the possible methods to calculate the accretion efficiency. For these sources we are able to determine the mass accretion rate and, with some assumptions, the accretion efficiency distributions. Even though we select the sources for which we are able to determine the parameters more accurately, there are still factors affecting the measurements that are hard to constrain. We suggest methods to overcome these problems based on contemporaneous multiwavelength data measurements and specifically targeted observations for AGNs in different black hole mass ranges.

Front shock behavior of stable curved detonation waves in rectangular-cross-section curved channels

Abstract: The propagation of curved detonation waves of gaseous explosives stabilized in rectangular-cross-section curved channels is investigated. Three types of stoichiometric test gases, C 2 H 4 + 3O 2 , 2H 2 + O 2 , and 2C 2 H 2 + 5O 2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel ( r i ) to the normal detonation cell width ( λ ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around r i / λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity ( D n )−curvature ( κ ) relations are evaluated. The D n nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity ( D CJ ) is a function of the κ nondimensionalized by λ . The D n / D CJ − λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the D n / D CJ − λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same r i / λ , regardless of the curved channel and test gas.

Microgravity elicits reproducible alterations in cytoskeletal and metabolic gene and protein expression in space-flown Caenorhabditis elegans.

Abstract: Although muscle atrophy is a serious problem during spaceflight, little is known about the sequence of molecular events leading to atrophy in response to microgravity. We carried out a spaceflight experiment using Caenorhabditis elegans onboard the Japanese Experiment Module of the International Space Station. Worms were synchronously cultured in liquid media with bacterial food for 4 days under microgravity or on a 1-G centrifuge. Worms were visually observed for health and movement and then frozen. Upon return, we analyzed global gene and protein expression using DNA microarrays and mass spectrometry. Body length and fat accumulation were also analyzed. We found that in worms grown from the L1 larval stage to adulthood under microgravity, both gene and protein expression levels for muscular thick filaments, cytoskeletal elements, and mitochondrial metabolic enzymes decreased relative to parallel cultures on the 1-G centrifuge (95% confidence interval (P⩽0.05)). In addition, altered movement and decreased body length and fat accumulation were observed in the microgravity-cultured worms relative to the 1-G cultured worms. These results suggest protein expression changes that may account for the progressive muscular atrophy observed in astronauts.