The impact of a supernova explosion in a very massive binary

We consider the effect of a supernova (SN) explosion in a very massive binary that is expected to form in a portion of Population III stars with the mass higher than  100 M_⊙  . In a Population III binary system, a more massive star can result in the formation of a black hole (BH) and a surrounding accretion disc. Such BH accretion could be a significant source of the cosmic reionization in the early Universe. However, a less massive companion star evolves belatedly and eventually undergoes a SN explosion, so that the accretion disc around a BH might be blown off in a lifetime of companion star. In this paper, we explore the dynamical impact of a SN explosion on an accretion disc around a massive BH, and elucidate whether the BH accretion disc is totally demolished or not. For the purpose, we perform three-dimensional hydrodynamic simulations of a very massive binary system, where we assume a BH of  10³ M_⊙  that results from a direct collapse of a very massive star and a companion star of  100 M_⊙  that undergoes a SN explosion. We calculate the remaining mass of a BH accretion disc as a function of time. As a result, it is found that a significant portion of gas disc can survive through three-dimensional geometrical effects even after the SN explosion of a companion star. Even if the SN explosion energy is higher by two orders of magnitude than the binding energy of gas disc, about a half of disc can be left over. The results imply that the Population III BH accretion disc can be a long-lived luminous source, and therefore could be an important ionizing source in the early Universe.     

The Triassic conodonts of the NW Malayan Kodiang Limestone revisited: Taxonomy and paleogeographic significance

The revision of the Middle and early Late Triassic conodonts in the Nogami (1968) collection from the NW Malaya Kodiang Limestone Formation provides clues to the multi-element reconstruction of Triassic Gondolellacea. Septi- to octomembrate multi-elements characterize the families Gondolellidae and Gladigondolellidae nov. fam. The distribution of cratognathodiform and ozarkodiniform P2 elements supports the hypothesis of sexual dimorphism in Gladigondolella rather than that of two genera. Pseudofurnishius murcianus confers a Southern Tethyan low latitude character to the Kodiang Limestone, a part of the Cimmerian string of terranes that in Triassic times formed a diagonal partition between the gradually closing Paleo-Tethys and the accordingly widening Neo-Tethys. Our findings suggest that such a realm stretched from the Southern Alps (Dinarids) in the West to Malaya (Shan Thai Terrane) in the East. Only the Eastern edge collided with Eurasia in the Late Triassic, forming the platform of Sundaland. Consequently, the Paleo-Tethys closure remained limited to SE Asia, while a substantial Paleo-Tethys still existed in Western direction, ending up in the Pindos and Vardar oceans. The Jurassic Neo-Tethys ocean extended south of the consolidated SE Asia block and Cimmerian string of terranes.     

Seasonal and spatial variations in the partial pressure of carbon dioxide in a eutrophic brackish lake,Lake Hamana,Japan

The dissolved inorganic carbon and total alkalinity in the surface brackish waters of Lake Hamana were investigated monthly from October 2017 to September 2019 at 14 stations. The partial pressure of carbon dioxide (pCO₂) in the surface water ranged from 29 to 1476 μatm and was undersaturated for atmospheric CO₂ during the observation periods, although most coastal waters were net source areas because of the large amount of terrestrial organic and inorganic carbon input. Since there was a strong negative correlation between pCO₂ and the dissolved oxygen, seasonal and temporal variations in pCO₂ were mainly derived from phytoplankton activity. The high phytoplankton activity induced by the effluents from sewage treatment plants, which was low in carbon and high in nitrogen. Therefore, in urbanized coastal waters with sewage treatment plants, such as the coastal waters of Japan, there is a possibility of shifting from weaker carbon dioxide source areas to sink areas. However, pCO₂ was oversaturated at the polluted river mouth, especially after high precipitation events due to the large carbon supply.

     

Cosmogenic nuclides in the Brenham pallasite

Abstract— Cosmic‐ray‐produced (cosmogenic) nuclides were studied in fragments of the Brenham pallasite, a large stony iron meteorite. The contents of light noble gases (He, Ne, and Ar) and long‐lived radionuclides (¹⁰Be, ²⁶Al, ³⁶Cl, and ⁵³Mn), produced by nuclear reactions with cosmic rays, were measured in the separated metal and olivine phases from numerous samples representing a wide range of shielding conditions in the meteoroid. The distribution of cosmogenic nuclide concentrations in the metal follows patterns similar to that observed in large iron meteorites. Shielding effects were estimated from the relative proportions of low‐ and high‐energy reaction products. The production rates varied, from surface to interior, by a factor of more than several hundred. The ³⁶Cl‐³⁶Ar cosmic‐ray exposure age of Brenham is 156 ± 8 Myr. This determination is based on a multiple nuclide approach that utilizes cosmogenic nuclide pairs. This approach not only yields a “shielding independent” exposure age but also demonstrates that the production of cosmogenic nuclides occurred in a single stage. The depth profiles of ¹⁰Be in the stone phase and ⁵³Mn in the metal phase are shown superimposed on corresponding profiles from the Apollo 15 long drill core. Surprisingly low abundances of lithophile elements, such as K, U, and Th, provided a unique opportunity to examine the production systematics of those nuclides whose inventories typically have significant contributions from non‐cosmogenic sources, particularly radiogenic contributions. The U and Th contents of the olivine samples are extremely low, allowing detection of cosmogenic ⁴He production from oxygen, magnesium, silicon, and iron.     

大气492 GHz亚毫米波不透明度的测量

使用移动式亚毫米波望远镜(POST)在位于青藏高原海拔3200米的紫金山天文台德令哈射电天文观测站址测量地球大气492GHz频率处天顶方向的不透明度(τ0)的结果．在1999—2000年冬季和2000—2001年冬季的两个观测季节内累计共进行了约870个小时的测量，取得了25842组τ0的有效数据．对数据的统计表明，观测季节内τ0值主要分布在1．5—3．0之间．观测时段内大气不透明度τ0≤1．0的时间比例约占3％．在给出实测资料的基础上，将所测量的亚毫米波不透明度与国际现有亚毫米波台址的不透明度进行了初步比较．     

Better cars or older cars?: Assessing CO2 emission reduction potential of passenger vehicle replacement programs

The primary motivation for the vehicle replacement schemes that were implemented in many countries was to encourage the purchase of new cars. The basic assumption of these schemes was that these acquisitions would benefit both the economy and the environment as older and less fuel-efficient cars were scrapped and replaced with more fuel-efficient models. In this article, we present a new environmental impact assessment method for assessing the effectiveness of scrappage schemes for reducing CO₂ emissions taking into account the rebound effect, driving behavior for older versus new cars and entire lifecycle emissions for during the manufacturing processes of new cars. The assessment of the Japanese scrappage scheme shows that CO₂ emissions would only decrease if users of the scheme retained their new gasoline passenger vehicles for at least 4.7 years. When vehicle replacements were restricted to hybrid cars, the reduction in CO₂ achieved by the scheme would be 6–8.5 times higher than the emissions resulting from a scheme involving standard, gasoline passenger vehicles. Cost–benefit analysis, based on the emission reduction potential, showed that the scheme was very costly. Sensitivity analysis showed that the Japanese government failed to determine the optimum, or target, car age for scrapping old cars in the scheme. Specifically, scrapping cars aged 13 years and over did not maximize the environmental benefits of the scheme. Consequently, modifying this policy to include a reduction in new car subsidies, focused funding for fuel-efficient cars, and modifying the target car age, would increase environmental benefits.     

西南日本秋吉带石炭系高山(Ko-yama)灰岩群的褶皱构造

The study area is located in Kawakami-cho, Okayama Prefecture, which is occupied by Lower Carboniferous to Middle Permian Ko-yama Limestone Group (Yokoyama et al., 1979), Permian Yoshii Group (Sano et al., 1987) and Triassic Nariwa Group (Tera-oka, 1959). The Nariwa Group unconformably covers the Paleozoic successions (Otoh, 1985). These succes-sions belong to the Akiyoshi Belt. The Ko-yama Limestone Group is composed mainly of massive limestone, with basic volcanic rocks, acidic tuff and chert. The group was dated by foraminifer and fusu-linid as Lower Carboniferous to Middle Permian (Yo-koyama et al., 1979).     

西南日本秋吉带石炭系高山(Ko-yama)灰岩群的石炭纪(Visean – Moscovian)牙形石序列

The Carboniferous conodont faunal succession of the lower part of Ko-yama Limestone Group was studied. The confirmed upper Visean–lower Moscovian lithostratigraphy of the group is characterized by the clastic carbonates with common association of the basaltic pyroclastics and some intercalation of spicular chert beds. The faunal succession of Gnathodus semiglaber (upper Visean), Gnathodus praebilineatus – Lochriea multinodosa (upper Visean), Lochriea ziegleri – Gnathodus girtyi girtyi s.l. (lower Serpukhovian), Neoganthodus symmetricus – Idiognathodus primulus (middle – upper Bashkirian), and Idiognathoides convexus – Gondolella clarki (lower Moscovian) faunas, appears in concordance with the lithostratigraphic order. The faunas are correlative with those from the conodont zones of the Hina, Atetsu, Akiyoshi and Omi limestone groups in the Akiyoshi Belt. The Visean/Serpukhovian boundary of the section was recognized by the FAD of Lochriea ziegleri.     

Chemical overprinting of magmatism by weathering: A practical method for evaluating the degree of chemical weathering of granitoids

Quantitative determination of the degree of chemical weathering of rocks is a fundamental task in environmental and engineering geology, and many weathering indices based on whole-rock chemistry have been proposed. However, most classical indices are of limited application to granitoids in a wide area, because these lithotypes generally exhibit wide chemical variation arising from their petrogenesis. The chemical evolution produced during rock weathering, therefore, overprints pre-existing magmatic chemical variation. This problem can cause many classical weathering indices to yield misleading results. This study proposes a method that compensates for the influence of petrogenesis on calculation of the weathering index. The method is based on a bivariate plot of the magmatic chemical variation (MCV) in granitoids, and the degree of chemical weathering (DCW). The MCV axis must be based on an element that reflects magmatic processes and is also relatively immobile during rock weathering. In this study TiO₂ contents are utilized for the MCV. The DCW axis is fundamentally defined by the ratios of more-mobile to less-mobile elements during weathering, and hence many classical indices can be applied. The improved value of the degree of chemical weathering (DCW_i) for a weathered rock is derived by:

DCWi=s×(MCVCV-MCV₁)+DCW₁${\text{DCW}}_{\text{i}}=\text{s}\times ({\text{MCV}}_{\text{CV}}-{\text{MCV}}_1)+{\text{DCW}}_1$

where MCV₁ is the measured composition (e.g. TiO₂ content) of the weathered rock. DCW₁ denotes the ratios of more-mobile to less-mobile elements of the weathered rock. The “s” parameter is the slope of the least square linear regression for fresh granitoids in the MCV–DCW relationship. MCV_CV is a correction factor which is given by the average point on the MCV axis (e.g. average TiO₂) of the fresh rocks. This method is useful for evaluating the degree of weathering of various granitoids, and enhances the practical application of many weathering indices.