Kyushu University

About: Kyushu University is a education organization based out in Fukuoka, Japan. It is known for research contribution in the topics: Population & Catalysis. The organization has 68284 authors who have published 135190 publications receiving 3055928 citations. The organization is also known as: Kyūshū Daigaku.

Primary structures of beta- and delta-subunit precursors of Torpedo californica acetylcholine receptor deduced from cDNA sequences.

Abstract: The nicotinic acetylcholine receptor (AChR) from fish electric organ and mammalian skeletal muscle is the best characterized neurotransmitter receptor (reviewed in refs 1–3). The AChR from the electroplax of the ray Torpedo californica consists of five subunits present in a molar stoichiometry of α2βγδ (refs 4–6); the apparent molecular weights of the α-, β-, γ- and δ-subunits are 40,000 (40K), 50K, 60K and 65K, respectively7–11. Knowledge of the primary structures of these constituent polypeptides would facilitate the understanding of the molecular mechanism underlying the function of the neurotransmitter receptor. Recently, we have cloned cDNA for the α-subunit precursor of the T. californica AChR and have deduced the primary structure of this polypeptide from the nucleotide sequence of the cloned cDNA12. Here we report the cloning and nucleotide analysis of cDNAs for the AChR β- and δ-subunit precursors. The primary structures of the two polypeptides deduced from the cDNA sequences reveal conspicuous amino acid sequence homology among these and the α-subunits. The three subunits contain several highly conserved regions which may be essential for the receptor function or inter-summit interaction.

A Theory of Adaptive Pattern Classifiers

Abstract: This paper describes error-correction adjustment procedures for determining the weight vector of linear pattern classifiers under general pattern distribution. It is mainly aimed at clarifying theoretically the performance of adaptive pattern classifiers. In the case where the loss depends on the distance between a pattern vector and a decision boundary and where the average risk function is unimodal, it is proved that, by the procedures proposed here, the weight vector converges to the optimal one even under nonseparable pattern distributions. The speed and the accuracy of convergence are analyzed, and it is shown that there is an important tradeoff between speed and accuracy of convergence. Dynamical behaviors, when the probability distributions of patterns are changing, are also shown. The theory is generalized and made applicable to the case with general discriminant functions, including piecewise-linear discriminant functions.

Factors influencing the mechanism of superlong fatigue failure in steels

Abstract: When the fatigue life N f of a specimen of 10 mm in thickness is longer than 10 8 cycles, the average fatigue crack growth rate is much less than the lattice spacing (∼0.1 A or 0.01 nm) that is 10 -11 to 10 -12 m/cycle. In the early stage of the fatigue process, the crack growth rate should be much less than the average growth rate, and accordingly we cannot assume that crack growth occurs cycle by cycle. In this paper, possible mechanisms for extremely high cycle fatigue are discussed. Of some possible mechanisms, a special focus was put on a newly found particular fatigue fracture morphology in the vicinity of the fracture origin (non-metallic inclusions) of a heat-treated alloy steel, SCM435, which was tested to N ≥ 10 8 . The particular morphology observed by SEM and AFM was presumed to be influenced by the hydrogen around inclusions. The predictions of the fatigue limit by the √area parameter model are ∼ 10% unconservative for a fatigue life of N f = ∼10 8 , though it successfully predicts the conventional fatigue limit defined for N = 10 7 . Thus, the fatigue failure for N ≥ 10 8 is presumed to be caused by a mechanism which induces breaking or releasing of the fatigue crack closure phenomenon in small cracks. In the vicinity of a non-metallic inclusion at the fracture origin, a dark area was always observed inside the fish-eye mark for those specimens with a long fatigue life. Specimens with a short fatigue life of N f = ∼10 5 do not have such a dark area in the fish-eye mark. SEM and AFM observations revealed that the dark area has a rough surface quite different from the usual fatigue fracture surface in a martensite lath structure. Considering the high sensitivity of high-strength steels to a hydrogen environment and the high hydrogen content around inclusions, it may be concluded that the extremely high cycle fatigue failure of high-strength steels from non-metallic inclusions is caused by environmental effects, e.g. hydrogen embrittlement coupled with fatigue.

PINK1 autophosphorylation upon membrane potential dissipation is essential for Parkin recruitment to damaged mitochondria.

Abstract: Dysfunction of PINK1, a mitochondrial Ser/Thr kinase, causes familial Parkinson's disease (PD). Recent studies have revealed that PINK1 is rapidly degraded in healthy mitochondria but accumulates on the membrane potential (ΔΨm)-deficient mitochondria, where it recruits another familial PD gene product, Parkin, to ubiquitylate the damaged mitochondria. Despite extensive study, the mechanism underlying the homeostatic control of PINK1 remains unknown. Here we report that PINK1 is autophosphorylated following a decrease in ΔΨm and that most disease-relevant mutations hinder this event. Mass spectrometric and mutational analyses demonstrate that PINK1 autophosphorylation occurs at Ser228 and Ser402, residues that are structurally clustered together. Importantly, Ala mutation of these sites abolishes autophosphorylation of PINK1 and inhibits Parkin recruitment onto depolarized mitochondria, whereas Asp (phosphorylation-mimic) mutation promotes mitochondrial localization of Parkin even though autophosphorylation was still compromised. We propose that autophosphorylation of Ser228 and Ser402 in PINK1 is essential for efficient mitochondrial localization of Parkin.

The quiescent intracluster medium in the core of the Perseus cluster

Abstract: The Hitomi collaboration reports X-ray observations of the core of the Perseus cluster of galaxies the brightest X-ray-emitting cluster in the sky. Such clusters typically consist of tens to thousands of galaxies bound together by gravity and are studied as models of both small-scale cosmology and large-scale astrophysical processes. The data reveal a remarkably quiescent atmosphere, where gas velocities are quite low, with a line-of-sight velocity dispersion of about 164 kilometres per second at a distance of 3060 kiloparsecs from the central nucleus.