Profiling ascidian promoters as the primordial type of vertebrate promoter

<p>Abstract</p> <p>Background</p> <p>CpG islands are observed in mammals and other vertebrates, generally escape DNA methylation, and tend to occur in the promoters of widely expressed genes. Another class of promoter has lower G+C and CpG contents, and is thought to be involved in the spatiotemporal regulation of gene expression. Non-vertebrate deuterostomes are reported to have a single class of promoter with high-frequency CpG dinucleotides, suggesting that this is the original type of promoter. However, the limited annotation of these genes has impeded the large-scale analysis of their promoters.</p> <p>Results</p> <p>To determine the origins of the two classes of vertebrate promoters, we chose <it>Ciona intestinalis</it>, an invertebrate that is evolutionarily close to the vertebrates, and identified its transcription start sites genome-wide using a next-generation sequencer. We indeed observed a high CpG content around the transcription start sites, but their levels in the promoters and background sequences differed much less than in mammals. The CpG-rich stretches were also fairly restricted, so they appeared more similar to mammalian CpG-poor promoters.</p> <p>Conclusions</p> <p>From these data, we infer that CpG islands are not sufficiently ancient to be found in invertebrates. They probably appeared early in vertebrate evolution via some active mechanism and have since been maintained as part of vertebrate promoters.</p

Development of a Compact Wide-Field Telescope to be Mounted on VERTECS

In recent years, CubeSat projects have initiated plans to conduct astronomical observations by deploying mission payloads. CubeSats present a promising solution for swiftly addressing critical challenges in astrophysics with flexibility. Within Cubeats, where both the bus system and mission payload occupy about half of the volume, there is a necessity to miniaturize mission equipment. The critical factor in astronomical observations, light-gathering ability, is determined not only by the aperture size but, more importantly for diffuse emission, by the optical throughput, i.e., the product of the aperture area and the observing solid angle. Consequently, even with a compact optical system, specializing in wide-field observations enables achieving light-gathering ability equivalent to that of a large-diameter telescope. Therefore, we propose equipping CubeSats with small, wide-field telescopes specialized for observing essential quantities in understanding the cosmic history of star formation, such as extragalactic background Light (EBL), and foreground components like zodiacal light and diffuse galactic light. Radiation from first-generation celestial bodies, which is challenging to detect due to their darkness in the distant universe, is included in the EBL in the visible to near-infrared wavelengths. Hence, wide-field survey observations in the visible and near-infrared play a crucial role in unraveling when, where, and how the first-generation stars were born in the early universe. However, current technology has not enabled the development of CubeSats with mechanisms capable of cooling infrared detectors to temperatures below a few tens of Kelvin. Therefore, we have designed an optical system focusing on the visible EBL. In the astronomical W6U CubeSat mission VERTECS (Visible Extragalactic background RadiaTion Exploration by CubeSat), we are developing a 3U mission payload, comprised of 1U-sized lens optics, camera modules, and baffles each. The lens optical system achieves a high throughput ( \u3e 10-6 m2 sr) by covering the entire field of view with 6 degrees by 6 degrees and each pixel with a field of view of 11 arcseconds by 11 arcseconds. The camera module uses a CMOS sensor with high quantum efficiency in visible light, featuring sufficiently low dark current noise (approximately 0.01 electrons per second at 269 K) and readout noise (approximately 2.6 electrons at 24 dB analog gain), compared to the photocurrent generated by the EBL and foreground photon noise. The baffle is designed to attenuate stray light from the Sun and Earth to negligible levels compared to the EBL signal. Additionally, a set of color filters divides the wavelength range of 400 to 800 nm into four bands. In our observation strategy, we capture 60-second exposure images by shifting the field of view by 3 degrees and perform photometry on the stacked images in the four bands. VERTECS project was selected in JAXA-Small Satellite Rush Program in 2022 and is currently advancing in satellite development, with a scheduled launch in FY2025. Thus far, a significant portion of the mission payload design meets the required specifications, and progress is underway towards the fabrication of the engineering model. In this presentation, we will report on the progress of our optical telescope development, our strategy for visible EBL observations, and our future plans

Heliocentric Distance Dependence of Zodiacal Light Observed by Hayabusa2#

Zodiacal light (ZL) is sunlight scattered by interplanetary dust particles (IDPs) at optical wavelengths. The spatial distribution of IDPs in the Solar System may hold an important key to understanding the evolution of the Solar System and material transportation within it. The number density of IDPs can be expressed as $n(r) \sim r^{-\alpha}$, and the exponent $\alpha \sim 1.3$ was obtained by previous observations from interplanetary space by Helios 1/2 and Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of $\alpha$ based on ZL observations from interplanetary space outside Earth's orbit have been performed since then. Here, we introduce initial results for the radial profile of the ZL at optical wavelengths observed over the range 0.76-1.06 au by ONC-T aboard the Hayabusa2# mission in 2021-2022. The ZL brightness we obtained is well reproduced by a model brightness, although there is a small excess of the observed ZL brightness over the model brightness at around 0.9 au. The radial power-law index we obtained is $\alpha = 1.30 \pm 0.08$, which is consistent with previous results based on ZL observations. The dominant source of uncertainty arises from the uncertainty in estimating the diffuse Galactic light (DGL).Comment: 22 pages, 19 figures, 4 tables, accepted for publication by Earth, Planets and Spac

Polarization Spectrum of Near-Infrared Zodiacal Light Observed with CIBER

We report the first measurement of the zodiacal light (ZL) polarization spectrum in the near-infrared between 0.8 and 1.8 μm. Using the low-resolution spectrometer on board the Cosmic Infrared Background Experiment, calibrated for absolute spectrophotometry and spectropolarimetry, we acquire long-slit polarization spectral images of the total diffuse sky brightness toward five fields. To extract the ZL spectrum, we subtract the contribution of other diffuse radiation, such as the diffuse galactic light, the integrated starlight, and the extragalactic background light. The measured ZL polarization spectrum shows little wavelength dependence in the near-infrared, and the degree of polarization clearly varies as a function of the ecliptic coordinates and solar elongation. Among the observed fields, the North Ecliptic Pole shows the maximum degree of polarization of ∼20%, which is consistent with an earlier observation from the Diffuse Infrared Background Experiment on board on the Cosmic Background Explorer. The measured degree of polarization and its solar elongation dependence are reproduced by an empirical scattering model in the visible band and also by a Mie scattering model for large absorptive particles, while a Rayleigh scattering model is ruled out. All of our results suggest that the interplanetary dust is dominated by large particles

Development of data storage system and GSE for cosmic infrared background experiment 2 (CIBER-2)

Cosmic Infrared Background ExpeRiment-2 (CIBER-2) is an international project to make a rocket-borne measurement of the Cosmic Infrared Background (CIB) using three HAWAII-2RG image sensors. Since the rocket telemetry is unable to downlink all the image data in real time, we adopt an onboard data storage board for each sensor electronics. In this presentation, the development of the data storage board and the Ground Station Electronics (GSE) system for CIBER2 are described. We have fabricated, integrated, and tested all systems and confirmed that all work as expected, and are ready for flight

Pre-flight optical test and calibration for the Cosmic Infrared Background ExpeRiment 2 (CIBER-2)

The total integrated emission from galaxies, known as the Extragalactic Background Light (EBL), is an important observable for understanding the history of star formation over the history of the universe. Spatial fluctuations in the infrared EBL as measured by the Cosmic Infrared Background ExpeRiment (CIBER), Spitzer and AKARI exceed the predicted signal from galaxy clustering alone. The CIBER-2 project seeks to extend CIBER observa- tions of the EBL throughout the near infrared into the optical, through measurements above Earth's atmosphere during a suborbital sounding rocket flight. The experiment has a LN2-cooled 28.5 cm Cassegrain telescope along with three optical paths and dichroic beamsplitters, which are used to obtain three wide-field images in six broad spectral bands between 0.5-2.0 μm. The three focal planes also contain linear variable filters (LVFs) which simultaneously take spectra with resolution R=20 across the same range. CIBER-2 is scheduled to y multiple times on a Black Brant IX sounding rocket from White Sands Missile Range in the New Mexico desert. For the first flight, scheduled for early 2021, we have completed a variety of pre-flight optical tests, which we use to make focus adjustments, spectral response measurements, and absolute photometric calibrations. In this paper, we describe the methods behind these tests and present their results for pre-flight performance evaluation. In particular, we present measurements of the PSF for each broad spectral band, along with absolute calibration factors for each band and the LVF. Through monochromator scans, we also measure the spectral responsivity of each LVF as a function of position

VERTECS: 6U CubeSat Mission to Study Star-Formation History by Observation of Visible Extragalactic Background Light

We describe an astronomical 6U CubeSat mission VERTECS (Visible Extragalactic background RadiaTion Exploration by CubeSat). The scientific purpose of VERTECS is to reveal star-formation history of the universe by observation of the extragalactic background light (EBL) in visible wavelengths. Earlier observations by sounding rockets and infrared astronomical satellites have shown that the near-infrared EBL is several times brighter than the integrated light of known galaxies. As candidates for the excess light, first-generation stars in the early universe or low-redshift intra-halo light have been proposed, but it has not been concluded. Since these objects are expected to show different emission spectra in visible wavelengths, precise visible observation is important to reveal the origin of excess light. Since detection sensitivity of the EBL is determined by the product of telescope aperture and field of view, a small wide-field telescope system enables the EBL observation with high sensitivity. In VERTECS mission, we develop a 6U CubeSat equipped with a 3U size telescope optimized for observation of visible EBL. The telescope is composed of lens optics and a CMOS sensor of 3k times 3k array format, which is designed to observe the sky in four photometric bands in 400-800nm. The satellite bus is composed of on-board computer (OBC), electric power system (EPS), communication (COM), attitude determination and control system (ACDS), and thermal structure. Design of OBC and EPS is based on heritage of CubeSats developed at Kyushu Institute of Technology, but deployable solar array wings is added to EPS to supply sufficient power to the VERTECS subsystems. In COM system, S-band is used for command uplink and X-band is used for high-speed downlink of large-size images captured by the telescope. Since the EBL measurement need discrimination of the background light from discrete foreground stars, VERTECS requires 10 arcseconds pointing stability (1 sigma) over 1 minute exposure. In 2022, VERTECS was selected for JAXA-Small Satellite Rush Program (JAXA-SMASH Program), a new program that encourages universities, private companies and JAXA to collaborate to realize small satellite missions utilizing commercial small launch opportunities, and to diversify transportation services in Japan. We have been working on functionality and interface teast using Bread Board Model (BBM), and enviroonmental tests by using the satellite structure thermal model. Launch of the satellite is planned in FY2025. We aim at developing the satellite and obtaining scientific results much more quickly than recent large astronomical-satellite missions

Near-infrared Polarization Charateristics of the Zodiacal Light Observed with DIRBE/COBE

We report near-infrared polarization of the zodiacal light (ZL) measured from space by the Diffuse Infrared Background Experiment (DIRBE) on board the Cosmic Background Explorer in photometric bands centered at 1.25, 2.2, and 3.5 μ m. To constrain the physical properties of interplanetary dust, we use DIRBE Weekly Sky Maps to investigate the solar elongation ( ϵ ), ecliptic latitude ( β ), and wavelength ( λ ) dependence of ZL polarization. We find that the polarization of the ZL varies as a function of ϵ and β , consistent with observed polarization at λ = 550 nm. While the polarization dependence on wavelength at ( ϵ , β ) = (90°, 0°) is modest (increasing from 17.7% ± 0.2% at 1.25% μ m to 21.0% ± 0.3% at 3.5 μ m), the variation is more pronounced at the north ecliptic pole (23.1% ± 1.6%, 35.1% ± 2.0%, and 39.3% ± 2.1% at 1.25, 2.2, and 3.5 μ m, respectively). The variation in ZL polarization with wavelength is not explained by either Rayleigh scattering or absorptive particles larger than 10 μ m