Reversing cooling flows with AGN jets: shock waves, rarefaction waves, and trailing outflows

The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains highly debated. Using an idealized simulation of a cool-core cluster, we study the development of central cooling catastrophe and how a subsequent powerful AGN jet event averts cooling flows, with a focus on complex gasdynamical processes involved. We find that the jet drives a bow shock, which reverses cooling inflows and overheats inner cool core regions. The shocked gas moves outward in a rarefaction wave, which rarefies the dense core and adiabatically transports a significant fraction of heated energy to outer regions. As the rarefaction wave propagates away, inflows resume in the cluster core, but a trailing outflow is uplifted by the AGN bubble, preventing gas accumulation and catastrophic cooling in central regions. Inflows and trailing outflows constitute meridional circulations in the cluster core. At later times, trailing outflows fall back to the cluster centre, triggering central cooling catastrophe and potentially a new generation of AGN feedback. We thus envisage a picture of cool cluster cores going through cycles of cooling-induced contraction and AGN-induced expansion. This picture naturally predicts an anti-correlation between the gas fraction (or X-ray luminosity) of cool cores and the central gas entropy, which may be tested by X-ray observations.Comment: Slightly revised version, accepted for publication in MNRAS. 14 pages, 10 figure

Numerical investigation of airborne contaminant transport under different vortex structures in the aircraft cabin.

Airborne contaminants such as pathogens, odors and CO2 released from an individual passenger could spread via air flow in an aircraft cabin and make other passengers unhealthy and uncomfortable. In this study, we introduced the airflow vortex structure to analyze how airflow patterns affected contaminant transport in an aircraft cabin. Experimental data regarding airflow patterns were used to validate a computational fluid dynamics (CFD) model. Using the validated CFD model, we investigated the effects of the airflow vortex structure on contaminant transmission based on quantitative analysis. It was found that the contaminant source located in a vorticity-dominated region was more likely to be "locked" in the vortex, resulting in higher 62% higher average concentration and 14% longer residual time than that when the source was on a deformation dominated location. The contaminant concentrations also differed between the front and rear parts of the cabin because of different airflow structures. Contaminant released close to the heated manikin face was likely to be transported backward according to its distribution mean position. Based on these results, the air flow patterns inside aircraft cabins can potentially be improved to better control the spread of airborne contaminant

How Belief in a Just World Benefits Mental Health: The Effects of Optimism and Gratitude

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Past research suggests that individuals’ belief in a just world (BJW) is closely connected with their mental health. To clarify the underlying mechanism, the current study proposes that BJW encourages optimism and gratitude which then mediates the relation- ship between BJW and mental health as indicated by subjective well-being (SWB) and depression. A sample of 1,200 undergraduates yields results indicating that (a) BJW influences optimism, gratitude, SWB, and depression after controlling for gender, age, income, and personality; (b) optimism and gratitude mediate BJW effects by increasing SWB and decreasing depression. The issues of BJW’s adaptive functions are discussed

Criminal Networks: Who is the Key Player?

We analyze delinquent networks of adolescents in the United States. We develop a theoretical model showing who the key player is, i.e. the criminal who once removed generates the highest possible reduction in aggregate crime level. We also show that key players are not necessary the most active criminals in a network. We then test our model using data on criminal behaviors of adolescents in the United States (AddHealth data). Compared to other criminals, key players are more likely to be a male, have less educated parents, are less attached to religion and feel socially more excluded. They also feel that adults care less about them, are less attached to their school and have more troubles getting along with the teachers. We also find that, even though some criminals are not very active in criminal activities, they can be key players because they have a crucial position in the network in terms of betweenness centrality.Crime; bonacich centrality; betweenness centrality; network characteristics; crime policies

The Process of Learning Japanese Kanji (Chinese character) Words in Chinese-Native Learners of the Japanese Language : Effects of Orthographical and Phonological Similarities between the Chinese and the Japanese Languages

本研究では，中国語を母語とする日本語学習者における中国語と日本語の漢字単語の学習過程を検討した。具体的には，漢字単語の処理過程を検討することによって，学習者の学習過程を推測した。中国語と日本語間の漢字の形態・音韻類似性を操作し，母語と第二言語の両方を操作した2つの実験を行った。実験1では，2（呈示言語：母語，第二言語）×2（形態類似性：高，低）の2要因計画，実験2では，2（呈示言語：母語，第二言語）×2（音韻類似性：高，低）の2要因計画，がそれぞれ用いられた。実験の結果，以下の2点が明らかとなった。 (1)習熟度に関係なく形態類似性の高い単語は母語と第二言語で同様な処理過程をもつこと， (2)習熟度の低い学習者では母語の音韻表象がより活性化することによって単語の処理に影響を及ぼしやすく，習熟度の高い学習者では第二言語の音韻表象がより活性化することによって単語の処理に影響を及ぼしやすいこと，の2点である。中国語を母語とする学習者においては，単語の中日2言語間の形態情報を容易に識別することができるが，2言語間の音韻情報を瞬時に弁別することが容易ではないことが示された。学習者が中国語漢字の形態・音韻知識を用いて日本語の漢字単語を学習する過程をもつことが明らかとなった。日本語漢字単語を中国語の発音で読むという学習過程に十分に注意することの重要性が窺える。The current study examined the process of learning Chinese character words in Chinese and Japanese of Chinese-native learners of the Japanese language. We estimated the learner’s learning process by examining the process of Chinese character words. We conducted 2 experiments while manipulating the degrees of orthographical and phonological similarities. Experiment 1 used a two by two factorial design with presentation language (first language, and second language) and orthographical similarity (high and low), and Experiment 2 used a two by two factorial design with presentation language (First and second language) and phonological similarity (high and low). These experiments suggested the following: (1)Words with high orthographical similarity have similar processing both in the first and the second language regardless of the learner’s proficiency levels of the Japanese language, (2)learners with low proficiency had more active phonological representations of the native language that affected the processing of words, while learners with high proficiency had more active phonological representations of the second language that affected the processing of words. In learners of the Japanese language whose native language is Chinese, discrimination between the orthographical information of the Chinese and the Japanese languages was easy, while instant discrimination between the phonological information of the two languages was more difficult. The study elucidated that Chinese native speakers utilize both orthographical and phonological representations in their native Chinese language in learning Japanese kanji characters. The results indicate the importance of being keenly aware of the learning process where learners read Japanese kanji words using Chinese phonology.本論文は，Theory and Research for Developing Learning Systems, Vol.1 所収の英語論文 “The Process of Learning Japanese Kanji (Chinese character) Words in Chinese-Native Learners of the Japanese Language” の日本語訳論文である

The Process of Learning Japanese Kanji (Chinese character) Words in Chinese-Native Learners of the Japanese Language : Effects of Orthographical and Phonological Similarities between the Chinese and the Japanese Languages

The current study examined the process of learning Chinese character words in Chinese and Japanese of Chinese-native learners of the Japanese language. We estimated the learner’s learning process by examining the process of Chinese character words. We conducted 2 experiments while manipulating the degrees of orthographical and phonological similarities. Experiment 1 used a two by two factorial design with presentation language (first language, and second language) and orthographical similarity (high and low) , and Experiment 2 used a two by two factorial design with presentation language (First and second language) and phonological similarity (high and low). These experiments suggested the following; (1) Words with high orthographical similarity have similar processing both in the first and the second language regardless of the learner’s proficiency levels of the Japanese language, (2) learners with low proficiency had more active phonological representations of the native language that affected the processing of words, while learners with high proficiency had more active phonological representations of the second language that affected the processing of words. In learners of the Japanese language whose native language is Chinese, discrimination between the orthographical information of the Chinese and the Japanese languages was easy, while instant discrimination between the phonological information of the two languages was more difficult. The study elucidated that Chinese native speakers utilize both orthographical and phonological representations in their native Chinese language in learning Japanese kanji characters. The results indicate the importance of being keenly aware of the learning process where learners read Japanese kanji words using Chinese phonology

Deconfinement Phase Transition Heating and Thermal Evolution of Neutron Stars

The deconfinement phase transition will lead to the release of latent heat during spins down of neutron stars if the transition is the first-order one.We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. The results show that neutron stars may be heated to higher temperature.This feature could be particularly interesting for high temperature of low-magnetic field millisecond pulsar at late stage.Comment: 4 pages, to be published by American Institute of Physics, ed. D.Lai, X.D.Li and Y.F.Yuan, as the Proceedings of the conference Astrophysics of Compact Object