近年のアタカマ大型ミリ波サブミリ波干渉計(ALMA望遠鏡)やハワイ・マウナケアの大型光学赤外望遠鏡(すばる望遠鏡)など大型望遠鏡を用いた原始惑星系円盤観測の進歩により惑星形成領域にギャップ構造をもつ円盤が多数発見されている.このような円盤ギャップ構造の形成を説明する有力なメカニズムとして,惑星と円盤との重力相互作用が挙げられる.本稿では,観測されたギャップが惑星によって形成されたとすると,その構造からギャップを形成した惑星にどのような制限をつけることができるのかについて紹介する.また,ALMAの長基線観測キャンペーンで得られたデータを元にHL Tau円盤のギャップの構造から惑星質量を見積もった結果も併せて紹介したい.

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Chechnya is important in terms of issues related to the nature of the state and minorities in the Russian Federation. When considering the Chechen problem, one notices that it has a dual structure. First, as a minority in Russia, the Chechen people have been affected by changes in the Russian state. Most extant research on this issue has examined the Chechen problem by focusing on the Chechens’ relationship with the Russian state.

However, there is also another aspect—the form and nature of the “state” sought by the Chechen people has had an impact on both themselves and the Russian side. Existing research has mainly studied the kinds of tensions that “the state” sought by the Chechen people has caused in Russia. Thus, the effects of this “state” on the Chechens themselves have not been adequately studied.

This article seeks to consider the Chechen problem by focusing on the nature of the “state” sought by the Chechen people. In particular, it seeks to clarify the kind of influence exerted by the changes in the nature of the “state” advocated by a minority group on that minority group itself. Further, it also considers the current situation and problems in the Chechen Republic.

To achieve these aims, this article undertakes two tasks. First, it considers whether the form of the Chechen “state” governed by Ramzan Kadyrov is adequately accepted by its residents. In Chechnya, there have been terrorist activities and revolts by independence-seeking and radical Islamic groups, who do not recognize the legitimacy of the Kadyrov regime. This article analyzes the GTD (Global Terrorism Database) to assess whether the incidents of terror and rebellion have decreased over time to the present.

The second task is to consider issues related to the nature of the “state” under the incumbent Kadyrov regime. Terrorism and rebellion are reactions against the government that can be easily observed externally, but there are also cases where these are subdued through strict crackdowns by the government. However, issues that concern the form and legitimacy of the state are often raised during the process of moving toward a stable statehood. Based on a fieldwork conducted in August 2018 and by considering the relationship between the Chechen general public and the “state,” particularly from the dual perspectives of history and public opinion, this article reveals the current problems relevant to the Chechen “state.”

In conclusion, the number of terrorist activities in Chechnya as well as in North Caucasus has declined, and the Chechen republic is stable at present. Under the Kadyrov regime, it is difficult to research modern Chechen history because of the loss of research materials due to war and political issues preventing objective research. Therefore, especially the history and experience under the Chechen separatist “state” (1991–2000) are beginning to be forgotten in the current Chechen society. The Kadyrov regime emphasizes the legitimacy of its own “state” by comparing it with the Chechen separatist “state,” which it has labeled as a symbol of chaos, destruction, and destabilization. However, there are differences between the government and the people in Chechnya since the Kadyrov regime ignores the general public. Consequently, this would lead people to doubt the legitimacy of Kadyrov’s “state.”

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The Maskhadov regime relied on Islam to resolve feuds among major leaders in Chechnya after the first Chechen war ended in 1996. Taking advantage of the situation, the Wahhabi expanded their influence in the republic. The Wahhabi were comprised mainly of Arabic political Islamists, who had fought against the Soviets in Afghanistan and come to Chechnya to participate in the first Chechen war.
In the summer of 1998, Osama Bin Laden, a new sponsor of the Wahhabi in Chechnya, began to establish a close relationship with anti-Maskhadov leaders (field commanders) attracting them by his abundant funds and his idea of establishing a unified Islamic republic in the north Caucasus. Encouraged by Bin Laden, Chechen armed forces attempted to invade the Russian republic of Dagestan in August 1999.
As Moscow lost no time in launching a counter attack, another Chechen war commenced. The Chechen conflict posed a threat to Russia in that it might not have only undermined Russia's territorial integrity, but could have also become a pretext for western countries, including the United States, to meddle in Russia's domestic affairs. Russia tried in vain to persuade Washington that Chechen separatists were disguised international terrorists and that Russia suffered from the same terrorism as the U.S. had during 1998 with American embassy attacks in Africa. The United States continued to attach importance to the human-rights aspects of the Chechen issue. President Vladimir Putin, taking office in 2000, was not able to make the U.S. change its attitude toward the Chechen problem as his predecessor, Boris Yeltsin, had likewise found impossible.
In Russia, moreover, some forces, especially the military elite, were opposed to cooperation with the United States. They alleged that none other than the U.S. had played a role in stirring up the situation in the north Caucasus. Thus, there would be no cooperation between the two countries for an anti-terrorist struggle.
The situation abruptly changed after the terrorist attacks on September 11, 2001. U.S.-Russian relations as concerned terrorism seemed to take a 180 degree turnabout. Close analysis of the relationship, however, would show that Russia gave way more in the U.S. direction than vice versa. President Putin allowed Central Asian countries to accept U.S. military presence two weeks after the terrorist attacks, with the Republic of Georgia to follow suit during the spring of 2002 in defiance of the resistance of the political and military elite in Russia. He expected to ease their frustrations by successfully suppressing Chechen armed forces as a result of promoting cooperation between Russia and the United States. He also expected that Washington would admit Russia's war in Chechnya to be a war on terrorism. Such expectations, however, were not met.
The political forces in Russia, therefore, having assumed a negative attitude toward cooperation with the U.S., grew more frustrated. President Putin was forced to take steps to soothe their feelings. When he implied that he was ready to dispatch Russian troops to the Pankisskoye Gorge in the Republic of Georgia to eradicate Chechen fighters during September 2002, he intended to assuage the political and military elite which had not welcomed the U.S. military presence in Georgia from its inception.

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The author report the evacuation order for Chernobyl victims in the radioactive contamination area due to the Chernobyl nuclear power station accident. Seven years have passed since nuclear power station explosion at Chernobyl. In the last few years, several articles have been devoted to the studies of Thyroid cancer and Leukemia at Gomel district in Belarus, one of the most seriously contaminated area. On the other hand, surprisingly few studies have so far been made at evacuation order for Chernobyl victims. This subject deserves more than a passing notice. It is because I believe that importance of evacuation order cannot be overemphasized. We must do all we can to prevent the Chernobyl nuclear accident from spreading.

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Cr exhibited much better corrosion resistance to H₂SO₄ and HCl than those of Fe-Cr alloys and Ti at low temperature and low concentration. Because a wide passive potential range with a low passive current was observed for Cr in H₂SO₄ and HCl solutions. However Cr was severely corroded in high temperature or concentrated conditions. The corrosion resistance of Cr was improved by adding noble metals such as Pd and Ru.
The corrosion behavior of Cr-Pd and Cr-Ru alloys in H₂SO₄ solutions was investigated by measurement of the polarization curves, the change in corrosion potential with time and the average corrosion rate. And then, surface filmes of Cr-based alloys immersed in H₂SO₄ have been studied by means of AES and ESCA.
The corrosion resistance of Cr-based alloys in H₂SO₄ was improved by adding noble metals such as Pd and Ru. The addition of Pd and Ru to Cr increased the cathodic current, and decreased the anodic dissolution current in the active state. Accordingly the corrosion potential of the alloys shifted to the noble direction and the alloys were easily passivated. And the addition of Ru is more effective than that of Pd at a high temperature up to 400 K.
The composition of the surface films formed on Cr-Ru and Cr-Pd immersed in H₂SO₄ were Cr oxide such as Cr₂O₃. Ru and Pd were concentrated in these films. SO₂⁻⁴ existed in the surface oxide films. Pd in the surface oxide films exist in the form of Pd⁰, and Ru in the form of Ru²⁺. The effect of the Pd addition on the corrosion behaviour of Cr is caused mainly by cathodic depolarization, while the effect of the Ru addition is caused by cathodic depolarization and improvement of the passive films on Cr.

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Tantalum (Ta) has excellent corrosion resistance, but is rather expensive. Therefore, Ta has been used for critical components in chemical plants operating in highly corrosive environments. However, one typical degradation phenomenon of Ta is hydrogen absorption embrittlement. The object of this paper is to present the case study of a failure analysis on a Ta sheath tube of a thermometer used in a sulfuric-acid-containing environment. In the analysis, the nondestructive evaluation (NDE) method for estimation of hydrogen concentration and the changes in mechanical properties of Ta with hydrogen absorption was examined. Furthermore, with the aim of life extension of the components of interest, a hydrogen desorption procedure to recover the mechanical properties of the samples was also examined. Based on NDE of hydrogen concentration of Ta and hydrogen desorption heat treatment on service-exposed materials, life estimation and management procedures of components in chemical plants are proposed.

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This study was intended to elucidate the behavior of minute creep strain in ferritic stainless steel SUS430 specimens which were subjected to various states of hydrogen evolution environment. Creep tests were carried out under various hydrogen evolution potentials and the results were compared and examined.
The results obtained are summarized as follows.
(1) From the comparison of creep curves obtained under various setting potentials with those in atmosphere, the creep strain was found to become smaller with lowering setting potential and the increase of hardness in the surface vicinity layer was observed. The creep curves obtained under different setting potentials were aligned in the order of atmosphere, -1.0V, -1.5V and -2.0V(vs. S.C.E.).
(2) The anomalous phenomenon in which minute creep strain increases with a wave motion appeared after testing for 10⁴sec. in all setting potentials. When the applied load exceeded 160kgf of the yield point, this anomaly appeared in large numbers and the value of wave motion became 0.4% or more in the minute creep strain. The minute creep strain increased by repeating this behavior. Therefore, even if the applied load is a yield point load at which the specimens don't fracture immediately, it may lead to fracture in a short period.

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The corrosion behavior of metal is closely related to its polarization behavior in a corrosive solution. The polarization behavior is said to be useful for understanding pitting corrosion or stress corrosion cracking and hydrogen embrittlement in particular. In this study, in order to elucidate the relation between the catholic potential and mechanical properties, the slow strain rate tension tests were carried out under various cathodic potentials.
The main results obtained are summarized as follows.
(1) Under tensile stress, the pitting initiation potentials of SUS 430 and SUS 304 shifted towards the less-noble side but SUS 316 did not show such a shift. The hydrogen overpotential of the testing materials shifted towards the noble side with increasing applied stress in the elastic region. Consequently, the hydrogen evolution reaction in 3%NaCl solution was promoted by the presence of stress.
(2) In the case of SUS 430, the degradation of mechanical properties (reduction in size and time to fracture, etc.) became more pronounced with increasing setting cathodic potential, but in the case of molybdenum-bearing SUS 316, the degradation of mechanical properties was less than the other materials. The above phenomenon can be also understood from the observation results obtained by S.E.M.. Such a correlation between the mechanical properties and electrochemical properties became more pronounced at slower strain rates.

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