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Dark red debris from three short-period comets: 2P/Encke, 22P/Kopff, and 65P/Gunn
Ishiguro, Masateru,Sarugaku, Yuki,Ueno, Munetaka,Miura, Naoya,Usui, Fumihiko,Chun, Moo-Young,Kwon, Suk Minn Elsevier 2007 Icarus Vol.189 No.1
<P><B>Abstract</B></P><P>We present observations of the extended dust structures near the orbits of three short-period comets: 2P/Encke, 22P/Kopff, and 65P/Gunn. The dust trails were originally discovered by the Infrared Astronomical Satellite (IRAS). Our observations were made using wide-field optical CCD cameras on the University of Hawaii 2.24-m telescope, the Canada–France–Hawaii 3.6-m telescope, and the Kiso 1.05-m Schmidt telescope. We compared the observed images with models and found that the extended structures seen around 2P/Encke and 22P/Kopff before perihelion passage were most likely “dust trails,” whereas images taken after perihelion passage show a high contamination by recently released particles (i.e., particles in Neck-Line structures are visible). We could not confirm the existence of a dust trail from 65P/Gunn within the field of view of the camera used. The effective sizes of the particles responsible for the scattered light were estimated at 1–100 mm (2P/Encke), 1–10 mm (22P/Kopff), and 100 μm–1 mm (65P/Gunn), respectively, which is consistent with previous studies of dust trails made with infrared space telescopes and optical telescopes. We evaluated the mass loss rates of these comets, averaged over their orbits, as reaching 48±20 kg<SUP>s−1</SUP> (2P/Encke), 17±3 kg<SUP>s−1</SUP> (22P/Kopff), and 27±9 kg<SUP>s−1</SUP> (65P/Gunn). These values are consistent with previous work. Therefore, the total amount of material ejected from these three comets is <SUP>102</SUP> kg<SUP>s−1</SUP>, which would contribute a considerable fraction of the <SUP>104</SUP> kg<SUP>s−1</SUP> lost within 1 AU that needs to be replaced if the zodiacal cloud is to be maintained in a steady state. We also found that the particles in the dust structures are significantly redder than the Sun and the zodiacal light, and might be redder than the average short-period comet nuclei. Specifically, the reflectivity gradients of 2P/Encke, 22P/Kopff, and 65P/Gunn are 13±7 (% <SUP>103</SUP> <SUP>Å−1</SUP>), 20±5 (% <SUP>103</SUP> <SUP>Å−1</SUP>), and 15±4 (% <SUP>103</SUP> <SUP>Å−1</SUP>), respectively. We examined the change in color with distance from the nucleus. No clear correlation was detected for 2P/Encke or 22P/Kopff to an accuracy of 3–11%, while the 65P/Gunn tail did show color variation, becoming redder with increasing distance from the nucleus. This dark red material, consisting of particles of sand–cobble size, has marginally escaped from the nuclei and will evolve into finer-grained interplanetary dust particles after subsequent collisions.</P>
INFRARED AND OPTICAL IMAGINGS OF THE COMET 2P/ENCKE DUST CLOUD IN THE 2003 RETURN
Sarugaku, Yuki,Ishiguro, Masateru,Ueno, Munetaka,Usui, Fumihiko,Reach, William T. IOP Publishing 2015 The Astrophysical journal Vol.804 No.2
<P>We report contemporaneous imaging observations of the short-period comet 2P/Encke in infrared and optical wavelengths during the 2003 return. Both images show the same unique morphology consisting of a spiky dust cloud near the nucleus and a dust trail extending along the orbit. We conducted a dynamical simulation of dust particles to characterize the morphology and found that dust particles were ejected intensively for a short duration (less than or similar to 10 days) a few days after perihelion passage. The maximum particle size is at least on the order of 1 cm in radius following a differential power-law size distribution with an index of -3.2 to -3.6. The total mass ejected in the 2003 return is at least 1.5 x 10(9) -1.2 x 10(10) kg, which corresponds to 0.003%-0.03% of the nucleus mass. We derived the albedo of the dust cloud as 0.01-0.04 at a solar phase angle of 26 degrees. 2, which is consistent with or possibly greater than that of the nucleus. We suppose that impulsive activity such as an outburst is a key to understanding the peculiar appearance of 2P/Encke.</P>
Usuda, Katsuo,Sagawa, Motoyasu,Motono, Nozomu,Ueno, Masakatsu,Tanaka, Makoto,Machida, Yuichiro,Maeda, Sumiko,Matoba, Munetaka,Kuginuki, Yasuaki,Taniguchi, Mitsuru,Tonami, Hisao,Ueda, Yoshimichi,Sakuma Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.11
Background: Diffusion-weighted imaging (DWI) makes it possible to detect malignant tumors based on the diffusion of water molecules. However, it is uncertain whether DWI has advantages over FDG-PET for distinguishing malignant from benign pulmonary nodules and masses. Materials and Methods: One hundred-forty-three lung cancers, 17 metastatic lung tumors, and 29 benign pulmonary nodules and masses were assessed in this study. DWI and FDG-PET were performed. Results: The apparent diffusion coefficient (ADC) value ($1.27{\pm}0.35{\times}10^{-3}mm^2/sec$) of malignant pulmonary nodules and masses was significantly lower than that ($1.66{\pm}0.58{\times}10^{-3}mm^2/sec$) of benign pulmonary nodules and masses. The maximum standardized uptake value (SUVmax: $7.47{\pm}6.10$) of malignant pulmonary nodules and masses were also significantly higher than that ($3.89{\pm}4.04$) of benign nodules and masses. By using optimal cutoff values for ADC ($1.44{\times}10^{-3}mm^2/sec$) and for SUVmax (3.43), which were determined with receiver operating characteristics curves (ROC curves), the sensitivity (80.0%) of DWI was significantly higher than that (70.0%) of FDG-PET. The specificity (65.5%) of DWI was equal to that (65.5%) of FDG-PET. The accuracy (77.8%) of DWI was not significantly higher than that (69.3%) of FDG-PET for pulmonary nodules and masses. As the percentage of bronchioloalveolar carcinoma (BAC) component in adenocarcinoma increased, the sensitivity of FDG-PET decreased. DWI could not help in the diagnosis of mucinous adenocarcinomas as malignant, and FDG-PET could help in the correct diagnosis of 5 out of 6 mucinous adenocarcinomas as malignant. Conclusions: DWI has higher potential than PET in assessing pulmonary nodules and masses. Both diagnostic approaches have their specific strengths and weaknesses which are determined by the underlying pathology of pulmonary nodules and masses.
Usuda, Katsuo,Maeda, Sumiko,Motono, Nozomu,Ueno, Masakatsu,Tanaka, Makoto,Machida, Yuichiro,Matoba, Munetaka,Watanabe, Naoto,Tonami, Hisao,Ueda, Yoshimichi,Sagawa, Motoyasu Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.15
Background: It is sometimes difficult to assess patients who have multiple hilar and mediastinal lymph nodes (MHMLN) with FDG accumulation in PET-CT. Since it is uncertain whether diffusion-weighted magnetic resonance imaging (DWI) is useful in the assessment of such patients, its diagnostic performance was assessed. Materials and Methods: Twenty-three patients who had three or more stations of hilar and mediastinal lymph nodes with SUVmax of 3 or more in PET-CT were included in this study. Results: For diagnosis of disease, there were 20 malignancies (lung cancers 17, malignant lymphomas 2 and metastatic lung tumor 1), and 3 benign cases (sarcoidosis 2 and benign disease 1). For diagnosis of lymph nodes, there were 7 malignancies (metastasis of lung cancer 7 and malignant lymphoma 1) and 16 benign lymphadenopathies (pneumoconiosis/silicosis 7, sarcoidosis 4, benign disease 4, and atypical lymphocyte infiltration 1). The ADC value ($1.57{\pm}0.29{\times}10^{-3}mm^2/sec$) of malignant MHMLN was significantly lower than that ($1.99{\pm}0.24{\times}10^{-3}mm^2/sec$) of benign MHMLN (P=0.0437). However, the SUVmax was not significantly higher ($10.0{\pm}7.34$ as compared to $6.38{\pm}4.31$) (P=0.15). The sensitivity (86%) by PET-CT was not significantly higher than that (71%) by DWI for malignant MHMLN (P=1.0). The specificity (100%) by DWI was significantly higher than that (31%) for benign MHMLN (P=0.0098). Furthermore, the accuracy (91%) with DWI was significantly higher than that (48%) with PET-CT for MHMLN (P=0.0129). Conclusions: Evaluation by DWI for patients with MHMLN with FDG accumulation is useful for distinguishing benign from malignant conditions.
Usuda, Katsuo,Sagawa, Motoyasu,Motono, Nozomu,Ueno, Masakatsu,Tanaka, Makoto,Machida, Yuichiro,Matoba, Munetaka,Taniguchi, Mitsuru,Tonami, Hisao,Ueda, Yoshimichi,Sakuma, Tsutomu Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.2
Background: The epidermal growth factor receptor (EGFR) mutation status of lung cancer is important because it means that EGFR-tyrosine kinase inhibitor treatment is indicated. The purpose of this prospective study is to determine whether EGFR mutation status could be identified with reference to preoperative factors. Materials and Methods: One hundred-forty eight patients with lung cancer (111 adenocarcinomas, 25 squamous cell carcinomas and 12 other cell types) were enrolled in this study. The EGFR mutation status of each lung cancer was analyzed postoperatively. Results: There were 58 patients with mutant EGFR lung cancers (mutant LC) and 90 patients with wild-type EGFR lung cancers (wild-type LC). There were significant differences in gender, smoking status, maximum tumor diameter in chest CT, type of tumor shadow, clinical stage between mutant LC and wild-type LC. EGFR mutations were detected only in adenocarcinomas. Maximum standardized uptake value (SUVmax:$3.66{\pm}4.53$) in positron emission tomography-computed tomography of mutant LC was significantly lower than that ($8.26{\pm}6.11$) of wild-type LC (p<0.0001). Concerning type of tumor shadow, the percentage of mutant LC was 85.7% (6/7) in lung cancers with pure ground glass opacity (GGO), 65.3%(32/49) in lung cancers with mixed GGO and 21.7%(20/92) in lung cancers with solid shadow (p<0.0001). For the results of discriminant analysis, type of tumor shadow (p=0.00036) was most significantly associated with mutant EGFR. Tumor histology (p=0.0028), smoking status (p=0.0051) and maximum diameter of tumor shadow in chest CT (p=0.047) were also significantly associated with mutant EGFR. The accuracy for evaluating EGFR mutation status by discriminant analysis was 77.0% (114/148). Conclusions: Mutant EGFR is significantly associated with lung cancer with pure or mixed GGO, adenocarcinoma, never-smoker, smaller tumor diameter in chest CT. Preoperatively, EGFR mutation status can be identified correctly in about 77 % of lung cancers.