Three Small Planets Transiting a Hyades Star

We present the discovery of three small planets transiting K2-136 (LP 358 348, EPIC 247589423), a late K dwarf in the Hyades. The planets have orbital periods of $7.9757 \pm 0.0011$, $17.30681^{+0.00034}_{-0.00036}$, and $25.5715^{+0.0038}_{-0.0040}$ days, and radii of $1.05 \pm 0.16$, $3.14 \pm 0.36$, and $1.55^{+0.24}_{-0.21}$ $R_\oplus$, respectively. With an age of 600-800 Myr, these planets are some of the smallest and youngest transiting planets known. Due to the relatively bright (J=9.1) host star, the planets are compelling targets for future characterization via radial velocity mass measurements and transmission spectroscopy. As the first known star with multiple transiting planets in a cluster, the system should be helpful for testing theories of planet formation and migration.Comment: Accepted to The Astronomical Journa

Tilt Angle and Theoretical Target Strength of the Japanese Sandeel, Ammodytes personatus Captured on the Northern Coast of Hokkaido, Japan.

The tilt angle, i.e., the angle from horizontal made by the fish body as its head dives down or up, affects the readings on fish echo soundings. We measured the tilt angle of Japanese sandeels (Ammodytes personatus Girard) in a water tank, and calculated the acoustic target strength (TS) using a theoretical scattering model. This study examined the TS of sandeels from the northern coast of Hokkaido, which have a larger body size than those in other regions in Japan. TS values for sandeels, a swimbladderless fish, were estimated using a distorted-wave Born approximation (DWBA) model at two frequencies: 38 and 120 kHz. The mean tilt angle was 20.4?? (S.D. = 18.5??), which differed slightly from that of the lesser sandeel, Ammodytes marinus. The regression equations of the average TS values were TS38kHz = 8.2 log10SL ??? 74.2 and TS120kHz = 20.9 log10SL ??? 92.6, respectively. At 120 kHz, the slope was close to 20, suggesting that the acoustic backscattering strength was proportional to the square of the body length. This value was smaller at 38 kHz, suggesting that the acoustic backscattering strength was stable to differences in body length. We obtained a small discrepancy for both frequencies (??TS = TS120kHz???TS38kHz) were TS120kHz < TS38kHz. Discrepancies of ???1.3 dB for the maximum TS, and ???1.8 dB for averaged TS were found in 72 fish samples, which would be useful for identifying sandeel schools in practical analysis using TS differences

First detection of two superoutbursts during rebrightening phase of a WZ Sge-type Dwarf Nova : TCP J21040470+4631129

We report on photometric and spectroscopic observations and analysis of the 2019 superoutburst of TCP J21040470+4631129. This object showed a 9 mag superoutburst with early superhumps and ordinary superhumps, which are the features of WZ Sge-type dwarf novae. Five rebrightenings were observed after the main superoutburst. The spectra during the post-superoutburst stage showed Balmer, He I, and possible sodium doublet features. The mass ratio is derived as 0.0880(9) from the period of the superhump. During the third and fifth rebrightenings, growing superhumps and superoutbursts were observed, which have never been detected during a rebrightening phase among WZ Sge-type dwarf novae with multiple rebrightenings. To induce a superoutburst during the brightening phase, the accretion disk needs to have expanded beyond the 3 : 1 resonance radius of the system again after the main superoutburst. These peculiar phenomena can be explained by the enhanced viscosity and large radius of the accretion disk suggested by the higher luminosity and the presence of late-stage superhumps during the post-superoutburst stage, plus by more mass supply from the cool mass reservoir and/or from the secondary because of the enhanced mass transfer than those of other WZ Sge-type dwarf novae.peer-reviewe

First Detection of Two Superoutbursts during Rebrightening Phase of a WZ Sge-type Dwarf Nova: TCP J21040470+4631129

We report photometric and spectroscopic observations and analysis of the 2019 superoutburst of TCP J21040470+4631129. This object showed a 9-mag superoutburst with early superhumps and ordinary superhumps, which are the features of WZ Sge-type dwarf novae. Five rebrightenings were observed after the main superoutburst. The spectra during the post-superoutburst stage showed the Balmer, He I and possible sodium doublet features. The mass ratio is derived as 0.0880(9) from the period of the superhump. During the third and fifth rebrightenings, growing superhumps and superoutbursts were observed, which have never been detected during a rebrightening phase among WZ Sge-type dwarf novae with multiple rebrightenings. To induce a superoutburst during the brightening phase, the accretion disk was needed to expand beyond the 3:1 resonance radius of the system again after the main superoutburst. These peculiar phenomena can be explained by the enhanced viscosity and large radius of the disk suggested by the higher luminosity and the presence of late-stage superhumps during the post-superoutburst stage, plus by more mass supply from the cool mass reservoir and/or from the secondary because of the enhanced mass transfer than those of other WZ Sge-type dwarf novae.Comment: 13 pages, 10 figures, accepted for publication in PAS

Radioprotection of eye lens using protective material in neuro cone-beam computed tomography: Estimation of dose reduction rate and image quality.

In cerebral angiography, for diagnosis and interventional neuroradiology, cone-beam computed tomography (CBCT) scan is frequently performed for evaluating brain parenchyma, cerebral hemorrhage, and cerebral infarction. However, the patient\u27s eye lens is more frequently exposed to excessive doses in these scans than in the previous angiography and interventional neuroradiology (INR) procedures. Hence, radioprotection for the lenses is needed. This study selects the most suitable eye lens protection material for CBCT from among nine materials by evaluating the dose reduction rate and image quality

Experimental Study on Evaporation Characteristics of Light Cycle Oil Droplet under Various Ambient Conditions

The authors conducted droplet evaporation experiments of light cycle oil (LCO) at various ambient temperatures and pressures. Five kinds of LCO and three kinds of arranged fuels were used. We investigated the evaporation characteristics of LCO and the relationships between the evaporation characteristics and the cetane index. In addition to that, a surrogate fuel composed of four chemical species, which can simulate the droplet evaporation characteristics of LCO, was suggested. Experimental results show that the differences in droplet lifetime between fuel species become larger with decreasing ambient temperature. This is because the low volatile component made the evaporation rate outstandingly slow at a low ambient temperature. It was found that the relationship between droplet lifetime and the late-stage distillation temperature becomes stronger at low ambient temperature and high ambient pressure. By an analysis employing the properties of chemical species in LCO surrogate fuel, it is clarified that the mass evaporation rate becomes smaller than the internal diffusion, which is the condition similar to that in the distillation test. Finally, the relationship between the droplet lifetime and the cetane index was investigated. It can be concluded that the droplet lifetime is independent of the cetane index under all conditions tested in this study. The experimental data obtained by this research can be utilized for the validation of multicomponent fuel droplet evaporation models in the future

Morphological Patterns of the Anterior Median Fissure in the Cervical Spinal Cord Evaluated by Computed Tomography After Myelography

Objective Computed tomography following myelography (CTM) revealed an unusual flow of contrast dye into the anterior median fissure (AMF) in a patient with cervical spondylotic myelopathy. Since then, several AMF configurations have been observed on CTM. Therefore, we evaluated morphological patterns of the AMF on CTM and investigated the significance and mechanisms of contrast dye flow into the AMF. Methods Morphological patterns of the AMF on CTM were examined in 79 patients. Group A (24 patients) underwent surgery because of symptomatic cervical myelopathy. Group B (43 patients) had no clinical symptoms but showed spinal cord compression on CTM. Group C (12 patients), who showed neither clinical symptoms nor cord changes, underwent CTM for lumbar lesion evaluation. AMF patterns were classified into 4 types according to their configurations on CTM (reversed T, Y, V, and O types). Results In group B, the reversed T type and Y type appeared significantly more often near the compressed portion (p<0.001). A similar tendency was seen in group A. The V and O types were most frequently observed in group C (p<0.001). Conclusion On CTM, contrast dye tends to flow into the AMF of the cervical cord when the spinal cord is compressed. We speculate that there may be 3 possible mechanisms for this phenomenon: deformation of the epipial layer of the AMF due to cervical cord compression, AMF dilatation due to atrophy of the anterior funiculus or anterior horn, and temporary AMF dilatation when it becomes an alternative route for cerebrospinal fluid circulation

Fundamental Study on the Evaluation of the Vascular Lumen after Carotid Artery Stenting Using 3D-rotational Angiography with Diluted Contrast Medium

Objective: Due to the recent increase in the availability of cone-beam CT (CBCT), delineation of blood vessels and intracranial stents using CBCT has been well-reported, but reports using 3D-rotational angiography (3D-RA) have been few. We evaluated delineation of carotid artery stents using 3D-RA with diluted contrast medium.Methods: We prepared simulated blood vessel phantoms covered by carotid artery stents different in material and shape. The phantoms were encapsulated with different concentration of contrast medium, and scanned using 3D-RA. The appropriate concentration of contrast medium was evaluated.Results: The appropriate concentrations of diluted contrast medium were 50–17% for the Carotid Wall Stent (Boston Scientific, Natick, MA, USA) and 20%–10% for PRECISE (Johnson & Johnson, Miami, FL, USA) and PROTÉGÉ (Covidien, Irvine, CA, USA).Conclusion: The appropriate concentration of contrast medium varied with carotid artery stent. By selecting an appropriate degree of dilution, the stent shape, plaque, intimal thickening, and vascular lumen in the stent can be visualized. Therefore, it is possible to evaluate vascular lumen after carotid artery stenting