Spore-forming halophilic bacteria isolated from Arctic terrains: Implications for long-range transportation of microorganisms     

Kise Yukimura  Ryosuke Nakai  Shiro Kohshima  Jun Uetake  Hiroshi Kanda  Takeshi Naganuma 《Polar Science》2009,3(3):163-169

Organisms living in the Arctic terrains such as Greenland have to deal with low temperature conditions. The mechanisms by which bacteria resist to low temperature are largely unknown; however, a well-known survival strategy of the microorganisms inhabiting the Arctic is spore forming. Moreover, halophilic bacteria are often resistant to various stresses. We have attempted isolation of spore-forming halophilic bacteria from Arctic terrains. We isolated 10 strains of spore-forming halophilic bacteria from the samples collected from a glacial moraine in Qaanaaq, Greenland in July 2007. Identification based on 16S rRNA gene sequence similarities showed that the isolates were closely related to the Oceanobacillus, Ornithinibacillus, Virgibacillus, Gracilibacillus, and Bacillus genera. In addition, the 16S rRNA sequences of some isolates were extremely similar to those of strains from the desert sand in China (100% identity, near full length), the source of the so-called “yellow dust.” Previous research indicated that yellow dust had been transported to Greenland by the wind. Our research implies the long-range transportation of these microorganisms to locations such as the Arctic.  相似文献   

Automatic substepping integration of the subloading tij model with stress path dependent hardening     

Márcio M. Farias  Dorival M. Pedroso  Teruo Nakai 《Computers and Geotechnics》2009

This paper discusses the numerical integration of the subloading tij model. This is an elastoplastic model with stress path dependent hardening, which can predict the behaviour of normally consolidated clays or loose sands, as well as of over-consolidated clays or dense sands, with a small number of material parameters. Three features distinguish the subloading tij model from the conventional ones: (a) the use of a modified stress space given by tensor t_ij; (b) the split of the plastic strain increments in two components leading to a stress path dependent hardening; and (c) the use of two yield surfaces (subloading yield surface and normal yield surface). This last feature is based on the concept of sub-yielding stress states and adds an extra internal strain-like hardening variable, related to the relative density state, which demands its own evolution law. The three characteristics above greatly improve the prediction capabilities of the model, with respect to those of the well-known Cam clay model, at the cost of only two additional parameters. Nonetheless, the numerical integration of the constitutive equations of subloading tij model is a bit challenging, mainly due to the stress path dependent hardening. In order to integrate the equations of subloading tij model in the same way as for any conventional model, the authors reformulated its equations in a simpler and direct manner. Here, these equations are integrated using multi-step explicit schemes, such as modified-Euler and Runge–Kutta–Dormand–Price, with automatic error control. Simple forward-Euler scheme is also used for the sake of comparison. The results show that the modified-Euler scheme is more accurate as well as faster than the other schemes analysed over a wide range of error tolerance. Besides, the automatic feature of these schemes is a great convenience for the users of numerical codes.  相似文献   

Secular perturbations of asteroids in secular resonance     

Hiroshi Nakai  Hiroshi Kinoshita 《Celestial Mechanics and Dynamical Astronomy》1985,36(4):391-407

When the precessional rate of the orbital plane of an asteroid is nearly equal to that of Jupiter, the orbital inclination of the asteroid changes quite largely due to this near equality of their precessional rates, which is called a secular resonance. In the vicinity of the exact resonance the difference of their longitudes of nodes librates with quite a long period of order of 1×10⁶ yr. In this paper we treat this secular resonance by a method of semianalytical secular perturbations with use of numerical averaging for both non-resonant and resonant asteroids and show that the results by the semi-analytical treatment agrees qualitatively with those obtained by direct numerical integrations of asteroid's orbits.  相似文献   

Motions of the perihelions of Neptune and Pluto     

Hiroshi Kinoshita  Hiroshi Nakai 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):203-217

Five outer planets are numerically integrated over five million years in the Newtonian frame. The argument of Pluto's perihelion librates about 90 degrees with an amplitude of about 23 degrees. The period of the libration depends on the mass of Pluto: 4.0×10⁶ years forM _pluto=2.78×10^–6 M _sun and 3.8×10⁶ years forM _pluto=7.69×10^–9 M _sun, which is the newly determined mass. The motion of Neptune's perihelion is more sensitive to the mass of Pluto. ForM _pluto=7.69×10^–9 M _sun, the perihelion of Neptune does circulate counter-clockwise and forM _pluto=2.78×10^–6 M _sun, it does not circulate and the Neptune's eccentricity does not have a minimum. With the initial conditions which do not lie in the resonance region between Neptune and Pluto, a close approach between them takes place frequently and the orbit of Pluto becomes unstable and irregular.  相似文献   

Morphological and evolutional features of Ellerman bombs     

H. Kurokawa  I. Kawaguchi  Y. Funakoshi  Y. Nakai 《Solar physics》1982,79(1):77-84

Morphological and evolutional features of Ellerman bombs were studied with H filtergrams of two active regions very close to the solar limb. We quantitatively determined the elongated or spike-like shape of the bomb. The mean apparent length of 174 bombs is 1.1 arc sec, while 80% of 204 bombs have a diameter of less than 0.6 arc sec. The mean lifetime of 77 bombs is about 12 min at H - 1.2 Å. The first maximum brightness of a typical bomb is attained, on average in about 2 min. Bombs grow longer in the first brightening phase and their mean upward velocity explains the blue asymmetry of H emission profiles of moustaches.  相似文献   

A trachyte–syenite core within a basaltic nest: filtering of primitive injections by a multi-stage magma plumbing system (Oki-Dōzen,south-west Japan)     

Marco Brenna  Setsuya Nakada  Daisuke Miura  Kiyoshi Toshida  Hisatoshi Ito  Natsumi Hokanishi  Shun’ichi Nakai 《Contributions to Mineralogy and Petrology》2015,169(2):1-21

  相似文献   

Seasonal variations in coastal debris on Awaji Island, Japan   总被引：1，自引：1，他引：0  

Shimizu T  Nakai J  Nakajima K  Kozai N  Takahashi G  Matsumoto M  Kikui J 《Marine pollution bulletin》2008,57(1-5):182-186

The subject of our study was Awaji Island, an island located in the west of Japan that is surrounded by sea and that has serious problems relating to coastal debris. We conducted a long-term investigation focusing on three beaches and evaluated the results. The study was designed to develop an understanding of the actual situation, to inform local citizens, and raise their concerns about the problem of debris with a view to taking action against it. We obtained the following results: the amount, type, and ratio of debris changed according to weather and ocean conditions; debris also differs according to geographical conditions; social and economic activities of the surrounding area influence the type of debris encountered. Following this study, we have continued our investigation, and are continuing to gather data. At the same time, it is important to spread our ideas and enlighten people so as to encourage them not to dump debris. We hope that these actions manage to raise the level of consciousness among local citizens and to expand their anti-debris activities.  相似文献   

Zircon U–Pb sensitive high mass-resolution ion microprobe dating of granitoids in the Ryoke metamorphic belt, Kinki District, Southwest Japan     

Teruo Watanabe  Trevor Ireland  Yoshiaki Tainosho and  Yutaka Nakai 《Island Arc》2000,9(1):55-63

Abstract Zircon U–Pb sensitive high mass-resolution ion microprobe dating was carried out on three types of granitic rock (gneissose biotite granodiorite, biotite granite and two-mica granite) from the Cretaceous Ryoke belt of the Kinki district, Southwest Japan. The results give the ages of granitic magmatism in the Shigi-san area of between 87 and 78 Ma and suggest extensive melting of the Cretaceous Ryoke granitic crust to form the two-mica granite, probably at ca 80 Ma. Discrimination into older and younger granites based on development of gneissosity does not appear to represent the sequence of magma generation, although there is some scope in the interpretation of the zircon U–Pb data that would allow all three granites to form at 83 Ma. Compilation of chemical Th-U-total Pb isochron dating method ages, whole rock Rb–Sr isotope ages and U–Pb isotope ages indicates that most Ryoke plutonism occurred from ca 70 Ma to ca 100 Ma. Younger (85 Ma–70 Ma) plutonism with the formation of two-mica granite occurred only in the eastern sector of the Ryoke belt, including the Kinki District.  相似文献   

Osumilite and a spinel + quartz association in garnet–sillimanite gneiss from Rundvågshetta,Lützow-Holm Complex,East Antarctica     

Toshisuke Kawasaki  Nobuhiko Nakano  Yasuhito Osanai 《Gondwana Research》2011,19(2):430-445

This is the first report of osumilite occurring as fine isolated inclusions within garnet porphyroblasts, as observed in garnet–sillimanite gneiss from Rundvågshetta, Lützow-Holm Complex, East Antarctica. The osumilite is characterized by high Si content (10.60 and 10.95 atoms based on 30 oxygens per formula unit), low Al content (2.99 and 3.82), a high content of M site-occupying cations (2.51 and 3.03), and high X_Mg values (about 0.81). We also report a spinel + quartz association found as inclusions within garnet porphyroblasts. Spinel grains, which are in direct contact with quartz and are spatially associated with sillimanite, show extremely high Zn contents (X_Zn^Spl = 0.33 ? 0.46) and high X_Mg values (0.45–0.54). The garnet is rimmed by sillimanite, K-feldspar, plagioclase, and quartz. Biotite and cordierite are found only as inclusions within garnet porphyroblasts, where biotite coexists with spinel–quartz or with rutile. Porphyroblastic garnet contains rutile needles and has low X_Mg values (about 0.36). The sillimanite contains a high Fe content (about 1.2 wt.% Fe₂O₃).The occurrence of osumilite and spinel + quartz indicates a clockwise pressure–temperature path of ultrahigh-temperature metamorphism, involving the following events: (1) the Rundvågshetta granulites suffered prograde metamorphism within the kyanite and sapphirine + quartz fields; (2) subsequent retrograde metamorphism, involving near-isothermal decompression, occurred in the orthopyroxene + sillimanite + quartz field; (3) the granulites passed through the garnet + cordierite + sillimanite + quartz field during decreasing temperature; (4) the granulites entered the osumilite stability field at around 8 kbar and 950 °C; and (5) the granulites retain a final record of retrograde metamorphism within the biotite + sillimanite + K-feldspar and quartz field at 6.1 kbar and about 830 °C.  相似文献   

La β-decay constant estimated from geochronological studies     

A. Masuda  H. Shimizu  S. Nakai  A. Makishima  S. Lahti 《Earth and Planetary Science Letters》1988,89(3-4)

LaCe ages are reported for two sets of Finnish pegmatites, Lövböle and Mustikkamäki, and for an Amiˆtsoq gneiss, Greenland. When λ_β¹³⁸La value (2.29 × 10⁻¹² yr⁻¹) obtained by radioactivity measurement [1] is used for the chronological calculation, the LaCe ages (2129, 2325, 3271 Myr) evaluated for these rocks are 18–35% older than the SmNd ages for the same samples. To make the LaCe age fit to the SmNd age for the same sample, a new value of (2.77 ± 0.21) × 10⁻¹² yr⁻¹ is evaluated for λ_β¹³⁸La. In this calculation, the LaCe and SmNd ages reported for a Bushveld gabbro [2] have been also taken into account together with those for the Lövböle pegmatite and the Mustikkamäki pegmatite, while the Amiˆtsoq gneiss (GGU110999) has been omitted because of the complicated thermal history of this sample.  相似文献