This paper presents a simple method to distinguish infrasonic signals from wind noise using a cross‐correlation function of signals from a microphone and a collocated seismometer. The method makes ...use of a particular feature of the cross‐correlation function of vertical ground motion generated by infrasound, and the infrasound itself. Contribution of wind noise to the correlation function is effectively suppressed by separating the microphone and the seismometer by several meters because the correlation length of wind noise is much shorter than wavelengths of infrasound. The method is applied to data from two recent eruptions of Asama and Shinmoe‐dake volcanoes, Japan, and demonstrates that the method effectively detects not only the main eruptions, but also minor activity generating weak infrasound hardly visible in the wave traces. In addition, the correlation function gives more information about volcanic activity than infrasound alone, because it reflects both features of incident infrasonic and seismic waves. Therefore, a graphical presentation of temporal variation in the cross‐correlation function enables one to see qualitative changes of eruptive activity at a glance. This method is particularly useful when available sensors are limited, and will extend the utility of a single microphone and seismometer in monitoring volcanic activity.
Key Points
A new method to detect infrasound using a single microphone and a seismometer
Infrasonic and eruptive activities of two recent eruptions of volcanoes in Japan
The method extends possibilities of infrasonic monitoring at active volcanoes
XL-Calibur is a hard X-ray (15-80 keV) polarimetry mission operating from a stabilised balloon-borne platform in the stratosphere. It builds on heritage from the X-Calibur mission, which observed the ...accreting neutron star GX 301 - 2 from Antarctica, between December 29th 2018 and January 1st 2019. The XL-Calibur design incorporates an X-ray mirror, which focusses X-rays onto a polarimeter comprising a beryllium rod surrounded by Cadmium Zinc Telluride (CZT) detectors. The polarimeter is housed in an anticoincidence shield to mitigate background from particles present in the stratosphere. The mirror and polarimeter-shield assembly are mounted at opposite ends of a 12 m long lightweight truss, which is pointed with arcsecond precision by WASP – the Wallops Arc Second Pointer. The XL-Calibur mission will achieve a substantially improved sensitivity over X-Calibur by using a larger effective area X-ray mirror, reducing background through thinner CZT detectors, and improved anticoincidence shielding. When observing a 1 Crab source for tdaydays, the Minimum Detectable Polarisation (at 99% confidence level) is ∼2%·tday−1/2. The energy resolution at 40 keV is ∼5.9 keV. The aim of this paper is to describe the design and performance of the XL-Caliburmission, as well as the foreseen science programme.
The design and performance of the XL-Calibur anticoincidence shield Iyer, N.K.; Kiss, M.; Pearce, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2023, Letnik:
1048
Journal Article
Recenzirano
Odprti dostop
The XL-Calibur balloon-borne hard X-ray polarimetry mission comprises a Compton-scattering polarimeter placed at the focal point of an X-ray mirror. The polarimeter is housed within a BGO ...anticoincidence shield, which is needed to mitigate the considerable background radiation present at the observation altitude of ∼40 km. This paper details the design, construction and testing of the anticoincidence shield, as well as the performance measured during the week-long maiden flight from Esrange Space Centre to the Canadian Northwest Territories in July 2022. The in-flight performance of the shield followed design expectations, with a veto threshold <100 keV and a measured background rate of ∼0.5 Hz (20–40 keV). This is compatible with the scientific goals of the mission, where %-level minimum detectable polarisation is sought for a Hz-level source rate.
The dynamics of explosive eruptions, such as Plinian, sub‐Plinian, Vulcanian, and Strombolian ones, is one of the most fascinating subjects in volcano physics. During the early period of volcanic ...activity at the Shinmoe‐dake Volcano in 2011, various kinds of activities, such as sub‐Plinian eruptions, a magma effusion, and Vulcanian eruptions, occurred sequentially. A different kind of tilt motion accompanied each activity. Here we clarify the characteristics of the tilt motions and their time sequences, presenting a new explanation of the triggering mechanism of a Vulcanian eruption. The sub‐Plinian and the Vulcanian eruptions at the Shinmoe‐dake Volcano were preceded by inflations at shallow depths near the summit. The inflation‐deflation cycles were also recorded during the magma‐effusive stage, with a typical period of 1 h, synchronized with volcanic tremors or long‐period events. Almost all Vulcanian eruptions were preceded by trapezoidal inflations, whose durations systematically lengthened as time progressed, and were followed by various time sequences of tilt motions, which became increasingly more complicated throughout the frequent Vulcanian eruptions. We have found clear linearity with a constant gradient of 0.45 between the logarithm of the preceding duration versus elapsed time for each substage. These observations can be consistently explained based on the assumption that a Vulcanian eruption is induced by a catastrophic rupture of the strongest closed, solid magma frame due to magma degassing overpressure, and the degassing from magma declines exponentially with time.
Key Points
A catastrophic rupture of strongest magma frame induces a Vulcanian eruption
A relationship between duration of a preceding inflation and elapsed time
Almost all Vulcanian eruptions are preceded by trapezoidal inflations
The effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling. This paper presents the first ...long‐term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source (Sakurajima Volcano, Japan). The data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media. Moreover, waveforms also change significantly in both time and space. Numerical simulations were performed using a two‐dimensional finite difference time domain (2‐D FDTD) method. Effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction. The simulation successfully reproduced the variations of amplitudes and waveforms. Results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers. Our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible. To evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data, atmospheric data with a time resolution higher than is currently available are required. If the data are available, the present results suggest that the propagation effects could be evaluated using 2‐D FDTD modeling at realistic calculation times.
Key Points
A long‐term data set spatial‐temporal infrasound propagation is presented
Numerical modeling with atmosphere and topography explains the observation
The propagation effects are non‐negligible and can be evaluated by our model
Burkholderia
sp. strain SJ98 (DSM 23195) was previously isolated and characterized for degradation and co-metabolic transformation of a number nitroaromatic compounds. In the present study, we ...evaluated its metabolic activity on chlorinated nitroaromatic compounds (CNACs). Results obtained during this study revealed that strain SJ98 can degrade 2-chloro-4-nitrophenol (2C4NP) and utilize it as sole source of carbon, nitrogen, and energy under aerobic conditions. The cells of strain SJ98 removed 2C4NP from the growth medium with sequential release of nearly stoichiometric amounts of chloride and nitrite in culture supernatant. Under aerobic degradation conditions, 2C4NP was transformed into the first intermediate that was identified as
p
-nitrophenol by high-performance liquid chromatography, LCMS-TOF, and GC-MS analyses. This transformation clearly establishes that the degradation of 2C4NP by strain SJ98 is initiated by “reductive dehalogenation”; an initiation mechanism that has not been previously reported for microbial degradation of CNAC under aerobic conditions.
We estimated the temporal changes of phase velocity of Rayleigh waves extracted from cross correlations of S‐coda waves recorded at 12 stations around Mt. Asama, Japan. First, we extracted a Rayleigh ...wave by taking cross correlations of S‐coda waves for 315 regional earthquakes between October 2005 and February 2009. The dispersion curve of the Rayleigh wave was measured and compared with the one extracted from 18 days of ambient seismic noise. We found that both dispersion curves are consistent with each other, demonstrating the dominance of the fundamental Rayleigh waves. We then divided the entire time period into sub‐periods, each of which consists of 80 earthquakes, to measure the temporal changes at frequencies between 0.3 and 0.6 Hz. The result shows the reduction of phase velocity by 1.5 % and the subsequent recovery before the eruption of Mt. Asama in 2008.
Wound healing and skin regeneration Takeo, Makoto; Lee, Wendy; Ito, Mayumi
Cold Spring Harbor perspectives in medicine,
01/2015, Letnik:
5, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The skin is a complex organ consisting of the epidermis, dermis, and skin appendages, including the hair follicle and sebaceous gland. Wound healing in adult mammals results in scar formation without ...any skin appendages. Studies have reported remarkable examples of scarless healing in fetal skin and appendage regeneration in adult skin following the infliction of large wounds. The models used in these studies have offered a new platform for investigations of the cellular and molecular mechanisms underlying wound healing and skin regeneration in mammals. In this article, we will focus on the contribution of skin appendages to wound healing and, conversely, skin appendage regeneration following injuries.
Mount Fuji has ejected a huge amount of basaltic products during the last 100,000 years. Even though the region around Mount Fuji is tectonically active, the seismicity below Mount Fuji is low, ...resulting in little knowledge about the seismic structure there. To gain more insight into the magma‐plumbing system, we obtain the seismic structure beneath Mount Fuji by the receiver function (RF) technique. RFs at seismic stations around Mount Fuji show positive phases at ~3 and ~6 s, representing the conversion of P to S waves at a positive velocity boundary in the Philippine Sea plate. Cross sections of RF amplitudes reveal two distinct velocity boundaries around Mount Fuji, at depths of 40–50 km and 20–30 km, which we interpret to be the boundary between the crust‐mantle transition layer and the uppermost mantle of the Izu‐Bonin arc and the velocity discontinuity just below the region where low‐frequency earthquakes (LFEs) of Mount Fuji have occurred, respectively. The velocity boundary at about 50 km depth shows a clear gap just beneath Mount Fuji. We suggest that this gap represents a weaker velocity contrast zone through which the magma of Mount Fuji ascends from the Pacific plate. A thorough grid search reveals that a low‐velocity zone at depths of ~13–26 km explains all the characteristics of RFs around Mount Fuji, leading us to interpret the high‐velocity boundary just below the LFE region as the lower boundary of Mount Fuji's magma chamber.
Key Points
We investigated the structure below Mount Fuji from a receiver function analysis
A gap of the velocity boundary below Mount Fuji is a weaker velocity contrast
A boundary at 25 km deep represents the bottom boundary of the magma chamber
The results of aeromagnetic observations at Izu-Oshima, Japan using an unmanned autonomous helicopter are reported. A practical observation system was assembled, adopting a bird-type magnetometer ...installation, and dense observations of the northern half of the caldera area including the central cone were made from a very low altitude. In the detailed magnetization intensity mapping deduced from the collected data, low magnetization intensity at the vent and three rows of high magnetization intensity on the caldera floor were found. The former is interpreted as the presence of high-temperature materials, such as magma or hot rock, or vacant space in the conduit. The latter is considered to be due to solidified dykes. Low magnetization intensity suggesting a magma body (or subsidiary magma chamber) was not detected below the caldera floor. The observation results confirmed that aeromagnetic observation using an unmanned autonomous helicopter had sufficient performance for volcanic observations, and could also be utilized as a low-altitude platform for other sensors.
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