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Japanese Hayabusa2 spacecraft has successfully carried out an impact experiment using a small carry-on impactor (SCI) on an asteroid (162173) Ryugu. We examine the size distribution of particles inside and outside an artificial impact crater (the SCI crater) based on the images taken by the optical navigation camera onboard the Hayabusa2 spacecraft. The circumferential variation in particle size distribution inside the SCI crater is recognized and we interpret that major circumferential variation is caused by the large boulders inside the SCI crater that existed prior to the impact. The size distribution inside the SCI crater also shows that the subsurface layer beneath the SCI impact site had a large number of particles with a characteristic size of – 9 cm, which is consistent with the previous evaluations. On the other hand, the size distribution outside the SCI crater exhibits the radial variation, implying that the deposition of ejecta from the SCI crater is involved. The slope of the size distribution outside the crater at small sizes differs from the slope of the size distribution on the surface of Ryugu by approximately 1 or slightly less. This is consistent with the claim that some particles are buried in fine particles of the subsurface origin included in ejecta from the SCI crater. Thus, the particle size distributions inside and outside the SCI crater reveal that the subsurface layer beneath the SCI impact site is rich in fine particles with – 9 cm in size while the particles on the surface have a size distribution of a power-law form with shallower slopes at small sizes due to the deposition of fine ejecta from the subsurface layer. Finally, we discuss a process responsible for this difference in particle size distribution between the surface and the subsurface layers. The occurrence of segregation in the gravitational flow of particles on the surface of Ryugu is plausible. [ABSTRACT FROM AUTHOR]

Experiments on crater formation in the strength regime were conducted using projectiles of various shapes with an aspect ratio of ~ 1, including both solid and hollow interiors. The surface diameter, inner (pit) diameter, and depth of the craters on basalt and porous gypsum targets were measured. Using the bulk density of the projectile, the surface diameter and depth for basalt and the pit diameter and depth for porous gypsum were scaled using the pi-scaling law for crater formation in the strength regime. The numerical code iSALE was used to simulate the impact of projectiles of various shapes and interior structure with similar bulk densities. Results show that the distributions of the maximum (peak) pressure experienced and particle velocity in the targets were similar regardless of projectile shape and interior structure, implying that the dimensions of the final craters were almost identical. This is consistent with the experimental results. Thus, we conclude that the size of the craters formed by the impact of projectiles with different shape and interior structure can be scaled using a conventional scaling law in the strength regime, using bulk density as projectile density. [ABSTRACT FROM AUTHOR]

We performed cratering experiments on targets composed of glass beads with a power‐law size distribution that simulated the surface of rubble‐pile asteroids, and we improved the previously studied reduction factor on the crater size scaling relationship including the armoring effect using the momentum transfer efficiency. Cratering experiments were conducted using light gas guns at Kobe University and ISAS/JAXA to control the impact velocity, vi ${v}_{\mathrm{i}}$, from 50 to 4,400 m s−1. Two kinds of mixed targets were prepared by mixing glass beads with diameters of 0.1, 1, 3, and 10 mm—one with the smallest diameter beads, and one without. The size ratio of the target bead to the projectile (diameter of 1–3 mm), ϕ $\phi $, changed from 0.03 to 10. The crater size scaling relationships for the mixed targets were found to depend on the first contacted bead size. Notably, first contact with a 10 mm‐sized bead reduced the crater radius by 35% in maximum. The reduction factor due to this armoring effect on the crater size scaling relationship is written as follows: f(ϕ)=1+8.99×10−3vi0.630.34ϕ−0.19 $f(\phi)={\left[1+\left(8.99\times {10}^{-3}\right){v}_{\mathrm{i}}^{0.63}\right]}^{0.34}{\phi }^{-0.19}$; it decreased with the increase of the size ratio of the target bead to the projectile, while it increased with the increase of the impact velocity and approached unity. Our improved crater size scaling relationship that includes the reduction factor could be used to reconstruct the crater size frequency distribution on rubble‐pile asteroids such as Ryugu, and it may lead to a revision of the crater chronology of asteroids. Plain Language Summary: A rubble‐pile asteroid, 162173 Ryugu, was explored by Hayabusa2, and the crater size frequency distribution on the surface was examined. Ryugu's surface age can be estimated from this size distribution using the impact crater chronology, but the size of the asteroids forming the craters is necessary for this estimate. The crater size scaling law is used to estimate the impactor size, but this law was established using homogeneous grains such as granular sand, so it might not be applicable for rubble‐pile asteroids covered with boulders of various sizes. Moreover, because it is well known that cratering efficiency is significantly reduced by an armoring effect when a smaller asteroid collides with a larger boulder, a scaling law that includes the armoring effect is required. In this study, we performed cratering experiments on the surface of simulated rubble‐pile asteroids and examined the armoring effect on the crater size. Based on the results, we improved the previously studied armoring effect and introduced the momentum transfer efficiency, β $\beta $, into the effect, instead of a restitution coefficient, which was assumed to be zero. Using this improved scaling relationship, a more accurate chronology can be established for the asteroid craters. Key Points: We performed cratering experiments on glass bead targets with a power‐law bead size distribution at 50–4,400 m s−1The size of craters formed in the mixed bead target was speculated to be changed with the size of the first contacted beadThe armoring effect is less efficient for granular targets with a size distribution, compared with equal‐sized granular targets [ABSTRACT FROM AUTHOR]

Here we report the results of the first ever contemporaneous multi-wavelength observation campaign on the BL Lac object PKS 2155−304 involving Swift, NuSTAR, Fermi-LAT, and H.E.S.S. The use of these instruments allows us to cover a broad energy range, which is important for disentangling the different radiative mechanisms. The source, observed from June 2013 to October 2013, was found in a low flux state with respect to previous observations but exhibited highly significant flux variability in the X-rays. The high-energy end of the synchrotron spectrum can be traced up to 40 keV without significant contamination by high-energy emission. A one-zone synchrotron self-Compton model was used to reproduce the broadband flux of the source for all the observations presented here but failed for previous observations made in April 2013. A lepto-hadronic solution was then explored to explain these earlier observational results. [ABSTRACT FROM AUTHOR]

The nearby radio galaxy Centaurus A belongs to a class of active galaxies that are luminous at radio wavelengths. Most show collimated relativistic outflows known as jets, which extend over hundreds of thousands of parsecs for the most powerful sources. Accretion of matter onto the central supermassive black hole is believed to fuel these jets and power their emission1. Synchrotron radiation from relativistic electrons causes the radio emission, and it has been suggested that the X-ray emission from Centaurus A also originates in electron synchrotron processes2–4. Another possible explanation is inverse Compton scattering with cosmic microwave background (CMB) soft photons5–7. Synchrotron radiation needs ultrarelativistic electrons (about 50 teraelectronvolts) and, given their short cooling times, requires some continuous re-acceleration mechanism8. Inverse Compton scattering, on the other hand, does not require very energetic electrons, but the jets must stay highly relativistic on large scales (exceeding 1 megaparsec). Some recent evidence disfavours inverse Compton-CMB models9–12, although other work seems to be compatible with them13,14. In principle, the detection of extended γ-ray emission, which directly probes the presence of ultrarelativistic electrons, could distinguish between these options. At gigaelectronvolt energies there is also an unusual spectral hardening15,16 in Centaurus A that has not yet been explained. Here we report observations of Centaurus A at teraelectronvolt energies that resolve its large-scale jet. We interpret the data as evidence for the acceleration of ultrarelativistic electrons in the jet, and favour the synchrotron explanation for the X-rays. Given that this jet is not exceptional in terms of power, length or speed, it is possible that ultrarelativistic electrons are commonplace in the large-scale jets of radio-loud active galaxies. Observations of the radio galaxy Centaurus A at teraelectronvolt energies resolve its large-scale jet and favour electron synchrotron processes as the source of its X-ray emission. [ABSTRACT FROM AUTHOR]

We report on the detection of very high energy (VHE; E > 100 GeV) γ-ray emission from the BL Lac objects KUV 00311−1938 and PKS 1440−389 with the High Energy Stereoscopic System (H.E.S.S.). H.E.S.S. observations were accompanied or preceded by multiwavelength observations with Fermi /LAT, XRT and UVOT onboard the Swift satellite, and ATOM. Based on an extrapolation of the Fermi /LAT spectrum towards the VHE γ-ray regime, we deduce a 95 per cent confidence level upper limit on the unknown redshift of KUV 00311−1938 of |$z$| < 0.98 and of PKS 1440−389 of |$z$| < 0.53. When combined with previous spectroscopy results, the redshift of KUV 00311−1938 is constrained to 0.51 ≤ |$z$| < 0.98 and of PKS 1440−389 to 0.14 ⪅ |$z$| < 0.53. [ABSTRACT FROM AUTHOR]

Plate shaped Fe-Al alloy crystals were successfully grown using the -PD method. The orientation and grain size could be controlled by using the well oriented Fe0.95Al0.05 seed crystal. The as-grown Fe0.82Al0.18 and Fe0.80Al0.20 showed the magnetostriction 3=2 = 121 and 149 ppm, respectively, which is comparable to the values for single crystal samples grown by the Bridgman-Stockbarger method. Distributions of Fe and Al were homogenous along the growth direction within standard deviations of 0.35% and 1.3%, respectively. A prototype vibration energy harvester was demonstrated using the grown Fe-Al alloys. [ABSTRACT FROM AUTHOR]

Aims. Colliding wind binary systems have long been suspected to be high-energy (HE; 100MeV< E < 100 GeV) -ray emitters. ŋ Car is the most prominent member of this object class and is confirmed to emit phase-locked HE rays from hundreds of MeV to ~100 GeV energies. This work aims to search for and characterise the very-high-energy (VHE; E >100 GeV) -ray emission from ŋ Car around the last periastron passage in 2014 with the ground-based High Energy Stereoscopic System (H.E.S.S.). Methods. The region around ŋ Car was observed with H.E.S.S. between orbital phase p = 0.78-1.~10, with a closer sampling at p ≈ 0.95 and p ≈ 1.10 (assuming a period of 2023 days). Optimised hardware settings as well as adjustments to the data reduction, reconstruction, and signal selection were needed to suppress and take into account the strong, extended, and inhomogeneous night sky background (NSB) in the ŋ Car field of view. Tailored run-wise Monte-Carlo simulations (RWS) were required to accurately treat the additional noise from NSB photons in the instrument response functions. Results. H.E.S.S. detected VHE -ray emission from the direction of ŋ Car shortly before and after the minimum in the X-ray lightcurve close to periastron. Using the point spread function provided by RWS, the reconstructed signal is point-like and the spectrum is best described by a power law. The overall flux and spectral index in VHE rays agree within statistical and systematic errors before and after periastron. The -ray spectrum extends up to at least ~400 GeV. This implies a maximum magnetic field in a leptonic scenario in the emission region of 0.5 Gauss. No indication for phase-locked flux variations is detected in the H.E.S.S. data. [ABSTRACT FROM AUTHOR]

PKS 1830–211 is a known macrolensed quasar located at a redshift of z  = 2.5. Its high-energy gamma-ray emission has been detected with the Fermi- Large Area Telescope (LAT) instrument and evidence for lensing was obtained by several authors from its high-energy data. Observations of PKS 1830–211 were taken with the High Energy Stereoscopic System (H.E.S.S.) array of Imaging Atmospheric Cherenkov Telescopes in 2014 August, following a flare alert by the Fermi- LAT Collaboration. The H.E.S.S observations were aimed at detecting a gamma-ray flare delayed by 20–27 d from the alert flare, as expected from observations at other wavelengths. More than 12 h of good-quality data were taken with an analysis threshold of ∼67 GeV. The significance of a potential signal is computed as a function of the date and the average significance over the whole period. Data are compared to simultaneous observations by Fermi- LAT. No photon excess or significant signal is detected. An upper limit on PKS 1830–211 flux above 67 GeV is computed and compared to the extrapolation of the Fermi- LAT flare spectrum. [ABSTRACT FROM AUTHOR]

The flat spectrum radio quasar 3C 279 is known to exhibit pronounced variability in the high-energy (100 MeV <  E <  100 GeV) γ-ray band, which is continuously monitored with Fermi-LAT. During two periods of high activity in April 2014 and June 2015 target-of-opportunity observations were undertaken with the High Energy Stereoscopic System (H.E.S.S.) in the very-high-energy (VHE, E >  100 GeV) γ-ray domain. While the observation in 2014 provides an upper limit, the observation in 2015 results in a signal with 8.7σ significance above an energy threshold of 66 GeV. No VHE variability was detected during the 2015 observations. The VHE photon spectrum is soft and described by a power-law index of 4.2 ± 0.3. The H.E.S.S. data along with a detailed and contemporaneous multiwavelength data set provide constraints on the physical parameters of the emission region. The minimum distance of the emission region from the central black hole was estimated using two plausible geometries of the broad-line region and three potential intrinsic spectra. The emission region is confidently placed at r ≳ 1.7 × 1017 cm from the black hole, that is beyond the assumed distance of the broad-line region. Time-dependent leptonic and lepto-hadronic one-zone models were used to describe the evolution of the 2015 flare. Neither model can fully reproduce the observations, despite testing various parameter sets. Furthermore, the H.E.S.S. data were used to derive constraints on Lorentz invariance violation given the large redshift of 3C 279. [ABSTRACT FROM AUTHOR]

Context. Pulsar wind nebulae (PWNe) represent the most prominent population of Galactic very-high-energy gamma-ray sources and are thought to be an efficient source of leptonic cosmic rays. Vela X is a nearby middle-aged PWN, which shows bright X-ray and TeV gamma-ray emission towards an elongated structure called the cocoon. Aims. Since TeV emission is likely inverse-Compton emission of electrons, predominantly from interactions with the cosmic microwave background, while X-ray emission is synchrotron radiation of the same electrons, we aim to derive the properties of the relativistic particles and of magnetic fields with minimal modelling. Methods. We used data from the Suzaku XIS to derive the spectra from three compact regions in Vela X covering distances from 0.3 to 4 pc from the pulsar along the cocoon. We obtained gamma-ray spectra of the same regions from H.E.S.S. observations and fitted a radiative model to the multi-wavelength spectra. Results. The TeV electron spectra and magnetic field strengths are consistent within the uncertainties for the three regions, with energy densities of the order 10−12 erg cm−3. The data indicate the presence of a cutoff in the electron spectrum at energies of ~ 100 TeV and a magnetic field strength of ~6 μG. Constraints on the presence of turbulent magnetic fields are weak. Conclusions. The pressure of TeV electrons and magnetic fields in the cocoon is dynamically negligible, requiring the presence of another dominant pressure component to balance the pulsar wind at the termination shock. Sub-TeV electrons cannot completely account for the missing pressure, which may be provided either by relativistic ions or from mixing of the ejecta with the pulsar wind. The electron spectra are consistent with expectations from transport scenarios dominated either by advection via the reverse shock or by diffusion, but for the latter the role of radiative losses near the termination shock needs to be further investigated in the light of the measured cutoff energies. Constraints on turbulent magnetic fields and the shape of the electron cutoff can be improved by spectral measurements in the energy range ≳ 10 keV. [ABSTRACT FROM AUTHOR]

Young core-collapse supernovae with dense-wind progenitors may be able to accelerate cosmic-ray hadrons beyond the knee of the cosmic-ray spectrum, and this may result in measurable gamma-ray emission. We searched for gamma-ray emission from ten supernovae observed with the High Energy Stereoscopic System (H.E.S.S.) within a year of the supernova event. Nine supernovae were observed serendipitously in the H.E.S.S. data collected between December 2003 and December 2014, with exposure times ranging from 1.4 to 53 h. In addition we observed SN 2016adj as a target of opportunity in February 2016 for 13 h. No significant gamma-ray emission has been detected for any of the objects, and upper limits on the >1 TeV gamma-ray flux of the order of ~10−13 cm−2s−1 are established, corresponding to upper limits on the luminosities in the range ~2 × 1039 to ~1 × 1042 erg s−1. These values are used to place model-dependent constraints on the mass-loss rates of the progenitor stars, implying upper limits between ~2 × 10−5 and ~2 × 10−3M⊙ yr−1 under reasonable assumptions on the particle acceleration parameters. [ABSTRACT FROM AUTHOR]

A hotspot at a position compatible with the BL Lac object 1ES 2322−409 was serendipitously detected with H.E.S.S. during observations performed in 2004 and 2006 on the blazar PKS 2316−423. Additional data on 1ES 2322−409 were taken in 2011 and 2012, leading to a total live-time of 22.3 h. Point-like very-high-energy (VHE; |$E\gt 100\, \mathrm{GeV}$|⁠) γ-ray emission is detected from a source centred on the 1ES 2322−409 position, with an excess of 116.7 events at a significance of 6.0σ. The average VHE γ-ray spectrum is well described with a power law with a photon index Γ = 3.40 ± 0.66stat ± 0.20sys and an integral flux |$\Phi (E\gt 200\, \mathrm{GeV}) = (3.11\pm 0.71_{\rm stat}\pm 0.62_{\rm sys})\times 10^{-12} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$|⁠, which corresponds to 1.1 |${{\ \rm per\ cent}}$| of the Crab nebula flux above |$200\, \mathrm{GeV}$|⁠. Multiwavelength data obtained with Fermi LAT, Swift XRT and UVOT, RXTE PCA, ATOM, and additional data from WISE, GROND, and Catalina are also used to characterize the broad-band non-thermal emission of 1ES 2322−409. The multiwavelength behaviour indicates day-scale variability. Swift UVOT and XRT data show strong variability at longer scales. A spectral energy distribution (SED) is built from contemporaneous observations obtained around a high state identified in Swift data. A modelling of the SED is performed with a stationary homogeneous one-zone synchrotron-self-Compton leptonic model. The redshift of the source being unknown, two plausible values were tested for the modelling. A systematic scan of the model parameters space is performed, resulting in a well-constrained combination of values providing a good description of the broad-band behaviour of 1ES 2322−409. [ABSTRACT FROM AUTHOR]

Centaurus A (Cen A) is the nearest radio galaxy discovered as a very-high-energy (VHE; 100 GeV–100 TeV) γ-ray source by the High Energy Stereoscopic System (H.E.S.S.). It is a faint VHE γ-ray emitter, though its VHE flux exceeds both the extrapolation from early Fermi-LAT observations as well as expectations from a (misaligned) single-zone synchrotron-self Compton (SSC) description. The latter satisfactorily reproduces the emission from Cen A at lower energies up to a few GeV. New observations with H.E.S.S., comparable in exposure time to those previously reported, were performed and eight years of Fermi-LAT data were accumulated to clarify the spectral characteristics of the γ-ray emission from the core of Cen A. The results allow us for the first time to achieve the goal of constructing a representative, contemporaneous γ-ray core spectrum of Cen A over almost five orders of magnitude in energy. Advanced analysis methods, including the template fitting method, allow detection in the VHE range of the core with a statistical significance of 12σ on the basis of 213 hours of total exposure time. The spectrum in the energy range of 250 GeV–6 TeV is compatible with a power-law function with a photon index Γ = 2.52 ± 0.13stat ± 0.20sys. An updated Fermi-LAT analysis provides evidence for spectral hardening by ΔΓ ≃ 0.4 ± 0.1 at γ-ray energies above 2.8+1.0−0.6 2.8 − 0.6 + 1.0 $2.8\substack{+1.0 \\-0.6}$ GeV at a level of 4.0σ. The fact that the spectrum hardens at GeV energies and extends into the VHE regime disfavour a single-zone SSC interpretation for the overall spectral energy distribution (SED) of the core and is suggestive of a new γ-ray emitting component connecting the high-energy emission above the break energy to the one observed at VHE energies. The absence of significant variability at both GeV and TeV energies does not yet allow disentanglement of the physical nature of this component, though a jet-related origin is possible and a simple two-zone SED model fit is provided to this end. [ABSTRACT FROM AUTHOR]

Context. NGC 253 is one of only two starburst galaxies found to emit γ-rays from hundreds of MeV to multi-TeV energies. Accurate measurements of the very-high-energy (VHE; E > 100 GeV) and high-energy (HE; E > 60 MeV) spectra are crucial to study the underlying particle accelerators, probe the dominant emission mechanism(s) and to study cosmic-ray interaction and transport. Aims. The measurement of the VHE γ-ray emission of NGC 253 published in 2012 by H.E.S.S. was limited by large systematic uncertainties. Here, the most up to date measurement of the γ-ray spectrum of NGC 253 is investigated in both HE and VHE γ-rays. Assuming a hadronic origin of the γ-ray emission, the measurement uncertainties are propagated into the interpretation of the accelerated particle population. Methods. The data of H.E.S.S. observations are reanalysed using an updated calibration and analysis chain. The improved Fermi–LAT analysis employs more than 8 yr of data processed using pass 8. The cosmic-ray particle population is evaluated from the combined HE–VHE γ-ray spectrum using NAIMA in the optically thin case. Results. The VHE γ-ray energy spectrum is best fit by a power-law distribution with a flux normalisation of (1.34 ± 0.14stat ± 0.27sys) × 10−13 cm−2 s−1 TeV1 at 1 TeV – about 40% above, but compatible with the value obtained in Abramowski et al. (2012). The spectral index Γ = 2.39 ± 0.14stat ± 0.25sys is slightly softer than but consistent with the previous measurement within systematic errors. In the Fermi energy range an integral flux of F(E > 60 MeV) = (1.56 ± 0.28stat ± 0.15sys) × 10−8 cm−2 s−1 is obtained. At energies above ∼3 GeV the HE spectrum is consistent with a power-law ranging into the VHE part of the spectrum measured by H.E.S.S. with an overall spectral index Γ = 2.22 ± 0.06stat. Conclusions. Two scenarios for the starburst nucleus are tested, in which the gas in the starburst nucleus acts as either a thin or a thick target for hadronic cosmic rays accelerated by the individual sources in the nucleus. In these two models, the level to which NGC 253 acts as a calorimeter is estimated to a range of fcal = 0.1 to 1 while accounting for the measurement uncertainties. The presented spectrum is likely to remain the most accurate measurements until the Cherenkov Telescope Array (CTA) has collected a substantial set of data towards NGC 253. [ABSTRACT FROM AUTHOR]

Abstract: Objective: We determined the prevalence of dental caries in 3‐year‐old Japanese children in a cross‐sectional study and analysed its associations with birthweight, gestational age and birthweight for gestational age among the study subjects. Methods: Study subjects were 6327 children. Their parents or guardians completed our study questionnaire with information on birth conditions and oral examinations taken from their Maternal and Child Health Handbooks, as documented by medical personnel at the hospital, clinic or public health centre. Children with one or more primary teeth that had either decayed or been filled were categorized as having caries. Results: The prevalence of dental caries was 14.7%. We found a significant association between high birthweight (≥4000 g) and a higher prevalence of caries, compared with normal birthweight (2500‐3999 g). Low birthweight (<2500 g) was not associated with dental caries prevalence. In addition, no measurable associations between gestational age or birthweight for gestational age and caries prevalence were observed. Conclusions: Our findings indicate that high birthweight might increase the likelihood of dental caries in children. [ABSTRACT FROM AUTHOR]

The Small Carry-on Impactor (SCI) equipped on Hayabusa2 was developed to produce an artificial impact crater on the primitive Near-Earth Asteroid (NEA) 162173 Ryugu (Ryugu) in order to explore the asteroid subsurface material unaffected by space weathering and thermal alteration by solar radiation. An exposed fresh surface by the impactor and/or the ejecta deposit excavated from the crater will be observed by remote sensing instruments, and a subsurface fresh sample of the asteroid will be collected there. The SCI impact experiment will be observed by a Deployable CAMera 3-D (DCAM3-D) at a distance of ∼1 km from the impact point, and the time evolution of the ejecta curtain will be observed by this camera to confirm the impact point on the asteroid surface. As a result of the observation of the ejecta curtain by DCAM3-D and the crater morphology by onboard cameras, the subsurface structure and the physical properties of the constituting materials will be derived from crater scaling laws. Moreover, the SCI experiment on Ryugu gives us a precious opportunity to clarify effects of microgravity on the cratering process and to validate numerical simulations and models of the cratering process. [ABSTRACT FROM AUTHOR]

Hayabusa2 is a sample return mission of JAXA launched on 3 December 2014. Hayabusa2 is the successor of Hayabusa, which returned samples from the asteroid Itokawa to the Earth. Although the design of Hayabusa2 follows that of Hayabusa, the former is equipped with some new components. The small carry-on impactor (SCI) is one of those components. The SCI is a compact kinetic impactor designed to remove the asteroid surface regolith locally and create an artificial crater. One of the most important scientific objectives of Hayabusa2 is to investigate the chemical and physical properties of the internal materials and structures of the target body, asteroid Ryugu. Hayabusa2 will attempt to observe the resultant crater with some scientific instruments and to get samples from around the crater. High kinetic energy is required to create a meaningful crater, however, the impact system design needs to fit within strict constraints. Complicated functions, such as a guidance and control system, are not permitted. A special type of shaped charge is used for the acceleration of the impactor of the SCI in order to make system simpler. Using this explosion technique makes it possible to accelerate the impactor very quickly and to hit the asteroid without a guidance system. However, the impact operation will be complicated because the explosive is very powerful and it scatters high-speed debris at the detonation. This paper describes an overview of the SCI system, the results of the development testing and an outline of the impact experiment of the Hayabusa2 mission. [ABSTRACT FROM AUTHOR]

Deployable Camera 3-D (DCAM3-D) is a small high-resolution camera equipped on Deployable Camera 3 (DCAM3), one of the Hayabusa2 instruments. Hayabusa2 will explore asteroid 162137 Ryugu (1999 JU) and conduct an impact experiment using a liner shooting device called Small Carry-on Impactor (SCI). DCAM3 will be detached from the Hayabusa2 spacecraft and observe the impact experiment. The purposes of the observation are to know the impact conditions, to estimate the surface structure of asteroid Ryugu, and to understand the physics of impact phenomena on low-gravity bodies. DCAM3-D requires high imaging performance because it has to image and detect multiple targets of different scale and radiance, i.e., the faint SCI before the shot from 1-km distance, the bright ejecta generated by the impact, and the asteroid. In this paper we report the evaluation of the performance of the CMOS imaging sensor and the optical system of DCAM3-D. We also describe the calibration of DCAM3-D. We confirmed that the imaging performance of DCAM3-D satisfies the required values to achieve the purposes of the observation. [ABSTRACT FROM AUTHOR]

The thermal conductivity of powdered media is characteristically very low in vacuum, and is effectively dependent on many parameters of their constituent particles and packing structure. Understanding of the heat transfer mechanism within powder layers in vacuum and theoretical modeling of their thermal conductivity are of great importance for several scientific and engineering problems. In this paper, we report the results of systematic thermal conductivity measurements of powdered media of varied particle size, porosity, and temperature under vacuum using glass beads as a model material. Based on the obtained experimental data, we investigated the heat transfer mechanism in powdered media in detail, and constructed a new theoretical thermal conductivity model for the vacuum condition. This model enables an absolute thermal conductivity to be calculated for a powder with the input of a set of powder parameters including particle size, porosity, temperature, and compressional stress or gravity, and vice versa. Our model is expected to be a competent tool for several scientific and engineering fields of study related to powders, such as the thermal infrared observation of air-less planetary bodies, thermal evolution of planetesimals, and performance of thermal insulators and heat storage powders. [ABSTRACT FROM AUTHOR]

The present case-control study examined the relationship between IL5 RA SNPs and eczema in young adult Japanese women. Cases and control subjects were selected from pregnant women who participated in the baseline survey of the Kyushu Okinawa Maternal and Child Health Study, which is an ongoing prebirth cohort study. Cases comprised 188 women with eczema in the previous 12 months as defined according to the criteria of the International Study of Asthma and Allergies in Childhood ( ISAAC), regardless of the presence of a doctor's diagnosis of atopic eczema. Control subjects comprised 1130 women without eczema as defined according to the ISAAC criteria who also had not been diagnosed with atopic eczema by a doctor. Compared with the AA genotype of IL5 RA SNP rs17881144, the AT genotype, but not the TT genotype, was significantly associated with a decreased risk of eczema. The ATTAGA haplotype and the GTAGCA haplotype of rs17882210, rs3804797, rs334809, rs9831572, rs6771148 and rs17881144 were significantly associated with an increased risk of eczema. In contrast, the GCTGCA haplotype was significantly related to a decreased risk of eczema. Multiplicative interactions between IL5 RA SNPs rs334809 and rs17881144 and smoking with respect to eczema were marginally significant ( P = 0.07 and 0.07, respectively). This is the first study to show significant associations between IL5 RA SNP rs17881144, the ATTAGA haplotype, the GTAGCA haplotype, and the GCTGCA haplotype and eczema. Smoking may modify the relationships between SNPs rs334809 and rs17881144 and eczema. [ABSTRACT FROM AUTHOR]

Objective To examine the relationship between the intake of dairy products and calcium and the prevalence of depressive symptoms during pregnancy. Design Cross-sectional study. Setting Kyushu Okinawa Maternal and Child Health Study (KOMCHS). Sample A cohort of 1745 pregnant Japanese women. Methods Dietary intake during the preceding month was assessed using a self-administered diet history questionnaire. Scores of 16 or higher on the Center for Epidemiologic Studies Depression Scale denoted depressive symptoms. Adjustment was made for age, gestation, region of residence, number of children, family structure, history of depression, family history of depression, smoking, secondhand smoke exposure at home and at work, job type, household income, education, and body mass index. In our analyses regarding dairy products in general, adjustment was also made for fish intake; in our analysis regarding calcium, adjustment was also made for the intake of saturated fatty acids, eicosapentaenoic acid plus docosahexaenoic acid, and vitamin D. Main outcome measures Depressive symptoms during pregnancy. Results Higher intake levels of yogurt and calcium were independently related to a lower prevalence of depressive symptoms during pregnancy: the adjusted odds ratios between extreme quartiles were 0.69 (95% CI 0.48-0.99, P for trend = 0.03) and 0.59 (95% CI 0.40-0.88, P for trend = 0.006), respectively. No relationships were observed between the intake of all dairy products, milk, or cheese and depressive symptoms during pregnancy. Conclusions The current results suggest that a higher intake of yogurt and calcium may be associated with a lower prevalence of depressive symptoms during pregnancy. [ABSTRACT FROM AUTHOR]

Introduction: The small carry-on impactor (SCI) experiment performed by the Hayabusa2 mission on asteroid Ryugu does not only provide important insights to the properties and collisional evolution of the small body populations, but also represents an ideal test case to validate impact cratering models. The results of this experiment suggest that the surface cohesion on Ryugu must be small (⪅ 1 Pa) and that the impact might have taken place in the gravitydominated regime [1]. This low-strength, low-gravity cratering environment has not yet been explored before the SCI experiment and it is not clear if traditional impact models and crater scaling laws are applicable. Another important question is how much the target inhomogeneities (i.e., boulders located close to the impact point) affect the cratering process and the impact outcome, such as the crater size and morphology. Modeling approach: Here we use the Bern SPH impact code [2-4] to study the sensitivity of the SCI impact outcome to target cohesion and target inhomogeneities (i.e., boulders). Bern SPH is a shock physics code that includes material models suitable to simulate the behaviour of geological materials, various equations of state and a porosity compaction model (P - a). To model the entire crater formation, here we apply a recently developed numerical approach that allows for faster calculation times and for direct shock-physics code calculations of the entire process [5, 6]. We first performed a series of impact simulations on homogeneous targets to study the effects of material strength on the crater size. We systematically varied the initial cohesion (Y0 = 0-0.5 Pa) and the coefficient of internal friction (f = 0.4-1.0). Results from impacts into homogeneous targets: We find that the resulting crater is sensitive to our choice of cohesion and coefficient of internal friction, and that there is no unique solution. The same crater size can be produced by impacting targets with a combination of mechanical properties (e.g., friction coefficient and cohesion). To match the observed size of the SCI crater, a cohesionless (Y0 = 0 Pa) target requires a high friction coefficient (f > 0.8). On the other hand, a cohesion of ~ 0.2 Pa with a small friction coefficient (f = 0.4) also produces the required crater size. Results from impacts into targets with boulders: For a subset of target material properties, boulders with varying sizes are distributed within the target. The sizes and positions of the boulders are representative of the ones present on Ryugu close to the SCI impact point. Our simulations reproduce well the overall outcome of the SCI impact, including the displacement of the boulders. The presence of the large block leads to an asymmetric crater, similar to the observed one. We find that the presence of the boulders within the target affects the resulting crater size by less than 5%. Crater scaling laws and consequences for asteroid surface ages: By calibrating the general form of the impact cratering scaling [e.g. 7, 8] to our simulation results, we can determine the fitting constants. Our results suggest that for a fixed f = 0.55, a cohesion of Y0 = 0.05 Pa is required to match the SCI crater size, and that the SCI impact took place at the transition between the strength and gravity regime, where cohesive and gravitational forces determine the impact outcome concurrently. The cratering scaling-laws derived from our results predict very large cratering efficiencies (Dcrat/Dproj ~ 100), suggesting that surfaces of small asteroids must be very young, consistent with the analysis of the recently observed Ryugu and Bennu [e.g. 9-11]. However, our results also show that the presence of a small amount of cohesion (< 1 Pa) can strongly affect the cratering efficiency. Consequently, the influence of cohesion may be responsible for the varying ages of different geological surface units on Ryugu and more generally leads to a "crater reduction effect" for small-scale impacts on low-strength asteroid surfaces, contributing to the depletion of small craters in the observed crater distributions on small asteroids [12, 13]. Acknowledgements: This work has received funding from the EU's Horizon 2020 programme under grant agreement No. 870377 (NEO-MAPP). Y.Z. and P.M. acknowledge funding from the french space agency CNES. [ABSTRACT FROM AUTHOR]

Three previous genetic association studies conducted in Korea and China investigated the relationship between IL3 single nucleotide polymorphism ( SNP) rs40401 and asthma, but their results were inconsistent. We examined this relationship and the possibility of an interaction between IL3 SNP rs40401 and smoking in young adult Japanese women. Included were 89 women who met the criteria of the European Community Respiratory Health Survey ( ECRHS) for asthma. Control subjects were 700 women without asthma according to the ECRHS criteria who had not been diagnosed with asthma and/or allergic rhinitis by a doctor and/or who had not met the criteria of the International Study of Asthma and Allergies in Childhood for rhinoconjunctivitis. A significant positive association was found between SNP rs40401 and the risk of asthma, with the TT genotype as the reference under the additive model: the adjusted odds ratio was 1.39 (95% CI: 1.004-1.93). The positive association was not statistically significant in any other genetic model. Compared with subjects with the TT or TC genotype of SNP rs40401 who had never smoked, those with the CC genotype who had ever smoked had a significantly increased risk of asthma: the adjusted OR was 2.67 (95% CI: 1.23-5.79); the additive interaction, but not the multiplicative interaction, was significant. This study suggests that IL3 SNP rs40401 is significantly associated with the risk of asthma in young adult Japanese women and reveals that the combination of ever smoking and having the CC genotype of IL3 SNP rs40401 is significantly positively associated with asthma. [ABSTRACT FROM AUTHOR]

The Hayabusa2 mission reveals the nature of a carbonaceous asteroid through a combination of remote-sensing observations, in situ surface measurements by rovers and a lander, an active impact experiment, and analyses of samples returned to Earth. [ABSTRACT FROM AUTHOR]