2006 Fragmentation of Comet 73P/Schwassmann-Wachmann 3B Observed with Subaru/Suprime-Cam

We analyzed the Subaru/Suprime-Cam images of 73P/Schwassmann-Wachmann 3B and detected no fewer than 154 mini-comets. We applied synchrone-syndyne analysis, modified for rocket effect analysis, to the mini-fragment spatial distribution. We found that most of these mini-comets were ejected from fragment B by an outburst occurring around 1 April 2006. The ratio of the rocket force to solar gravity was 7 to 23 times larger than that exerted on fragment B. No significant color variation was found. We examined the surface brightness profiles of all detected fragments and estimated the sizes of 154 fragments. We found that the radius of these mini-fragments was in the 5- to 108-m range (equivalent size of Tunguska impactor). The power-law index of the differential size distribution was q = -3.34 +/- 0.05. Based on this size distribution, we found that about 1-10% of the mass of fragment B was lost in the April 2006 outbursts. Modeling the cometary fragment dynamics revealed that it is likely that mini-fragments smaller than ~10-20 m could be depleted in water ice and become inactive, implying that decameter-sized comet fragments could survive against melting and remain as near-Earth objects. We attempted to detect the dust trail, which was clearly found in infrared wavelengths by Spitzer. No brightness enhancement brighter than 30.0 mag arcsec^-2 (3sigma) was detected in the orbit of fragment B.Comment: Total pages: 46 Figures: 12 Tables: 1 To appear ICARU

Symmetric equilibrium of multi-agent reinforcement learning in repeated prisoner's dilemma

We investigate the repeated prisoner's dilemma game where both players alternately use reinforcement learning to obtain their optimal memory-one strategies. We theoretically solve the simultaneous Bellman optimality equations of reinforcement learning. We find that the Win-stay Lose-shift strategy, the Grim strategy, and the strategy which always defects can form symmetric equilibrium of the mutual reinforcement learning process amongst all deterministic memory-one strategies.Comment: 29 pages, 6 figure

Applications of a novel biodetection system to saliva using protein fingerprints with data processing

A fundamental method has been developed focusing on a facile and rapid examination of periodontal disease. Periodontal disease is an oral disease thought to affect 80% of adults, and early detection with treatment is desirable for the improvement of the quality of life. Unfortunately conventional methods are not consistent as the disease is caused by a number of bacteria and detection relies on the skills of the dentist. Thus an objective detection system is required. We have performed an experiment on saliva using a novel biodetection system, designated PepTenChip®. A disease model for saliva was prepared using a specimen from a healthy subject and a mixture of hemoglobin (f-Hb) and lactate dehydrogenase (LDH), which is used as a periodontal disease marker protein with healthy saliva. PepTenChip® is a peptide microarray in which fluorescent labelled structured peptides are immobilized on a novel amorphous carbon substrate. Since the peptides used as capture molecules are fluorescently labelled, labeling of analytes is not necessary. The fluorescence intensity change before and after application of analytes are detected rather than the ON/OFF detection common to conventional microarrays using a set of antigen-antibody. The fluorescence intensity value changes according to the concentration of captured protein allowing the generation of protein fingerprint (PFP) and dendrograms. The present method does not rely on a "one to one" interaction, unlike conventional biodetection, and advantages can be envisaged in the case of an undefined or unknown cause of disease. The statistical analyses, such as multivariate analyses, allow classification of the type of proteins added in saliva as mimetics of disease. PepTenChip® system is useful and convenient for examination of periodontal disease in health care

Biological responses according to the shape and size of carbon nanotubes in BEAS-2B and MESO-1 cells

This study aimed to investigate the influence of the shape and size of multi-walled carbon nanotubes (MWCNTs) and cup-stacked carbon nanotubes (CSCNTs) on biological responses in vitro. Three types of MWCNTs - VGCF (R)-X, VGCF (R)-S, and VGCF (R) (vapor grown carbon fibers; with diameters of 15, 80, and 150 nm, respectively) - and three CSCNTs of different lengths (CS-L, 20-80 mu m; CS-S, 0.5-20 mu m; and CS-M, of intermediate length) were tested. Human bronchial epithelial (BEAS-2B) and malignant pleural mesothelioma cells were exposed to the CNTs (1-50 mu g/mL), and cell viability, permeability, uptake, total reactive oxygen species/superoxide production, and intracellular acidity were measured. CSCNTs were less toxic than MWCNTs in both cell types over a 24-hour exposure period. The cytotoxicity of endocytosed MWCNTs varied according to cell type/size, while that of CSCNTs depended on tube length irrespective of cell type. CNT diameter and length influenced cell aggregation and injury extent. Intracellular acidity increased independently of lysosomal activity along with the number of vacuoles in BEAS-2B cells exposed for 24 hours to either CNT (concentration, 10 mu g/mL). However, total reactive oxygen species/superoxide generation did not contribute to cytotoxicity. The results demonstrate that CSCNTs could be suitable for biological applications and that CNT shape and size can have differential effects depending on cell type, which can be exploited in the development of highly specialized, biocompatible CNTs.ArticleINTERNATIONAL JOURNAL OF NANOMEDICINE. 9:1979-1990 (2014)journal articl

Toxicoproteomic evaluation of carbon nanomaterials in vitro

Carbon nanotubes (CNTs) have already been successfully implemented in various fields, and they are anticipated to have innovative applications in medical science. However, CNTs have asbestos-like properties, such as their nanoscale size and high aspect ratio (> 100). Moreover, CNTs may persist in the body for a long time. These properties are thought to cause malignant mesothelioma and lung cancer. However, based on conventional toxicity assessment systems, the carcinogenicity of asbestos and CNTs is unclear. The reason for late countermeasures against asbestos is that reliable, long-term safety assessments have not yet been developed by toxicologists. Therefore, a new type of long-term safety assessment, different from the existing methods, is needed for carbon nanomaterials. Recently, we applied a proteomic approach to the safety assessment of carbon nanomaterials. In this review, we discuss the basic concept of our approach, the results, the problems, and the possibility of a long-term safety assessment for carbon nanomaterials using the toxicoproteomic approach.ArticleJournal of Proteomics. 74(12):2703-2712 (2011)journal articl