Volcanic eruptions are caused by the release of pressure that has
accumulated due to hot volcanic fluids at depth. Here, we show that the
extent of the regions affected by pressurized fluids can be ...imaged
through the measurement of their response to transient stress
perturbations. We used records of seismic noise from the Japanese Hi-net
seismic network to measure the crustal seismic velocity changes below
volcanic regions caused by the 2011 moment magnitude (Mw) 9.0
Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity
reductions as related to the mechanical weakening of the pressurized
crust by the dynamic stress associated with the seismic waves. We
suggest, therefore, that mapping seismic velocity susceptibility to
dynamic stress perturbations can be used for the imaging and
characterization of volcanic systems.
The crystal structure and photoluminescence properties of undoped and Ce3+-doped CaAlSiN3 as well as the application of white-light LEDs are reported. CaAlSiN3 and CaAlSiN3:Ce3+ have been ...synthesized, starting from Ca3N2, AlN, Si3N4, and CeN or CeO2 with and without Li3N, by a solid state reaction at 1700 °C for 4 h under high purity nitrogen atmosphere. Instead of an ideal CaAlSiN3, a more appropriate formula is proposed to be CaAl1−4δ/3Si1+δN3 (δ ≈ 0.3−0.4) with an Al/Si ratio of about 1:2 on the basis of the bond valence sum calculations, in which Al/Si is disorderly occupied on the 8b site within Cmc21 space group. Ce3+ can be incorporated into the host lattice of CaAlSiN3, and the estimated maximum solubility of Ce3+ is about x = 0.02 (e.g., 2.0 mol % with respect to Ca) of Ca1−2x Ce x Li x AlSiN3. CaAlSiN3:Ce3+ can be efficiently excited by blue light (450−480 nm) and yields yellow-orange emission with a broadband peaking in the range of 570−603 nm, originating from the 5d1 → 4f1 transition of Ce3+. With an increase of Ce concentration, the emission band of Ce3+ shifts to longer wavelengths due to the increased Stokes shift corresponding to structural relaxation and energy transfer of Ce3+. Upon excitation in blue light range (450−480 nm), the absorption and external quantum efficiency are about 70% and 56%, respectively, for both Ca1−2x CexLixAlSiN3 and Ca1−x CexAlSiN3−2x/3O3x/2 at x = 0.01. In addition, Ca1−2x Ce x Li x AlSiN3 and Ca1−x Ce x AlSiN3−2x/3O3x/2 show high thermal stability in air with the quenching temperature above 300 °C for x = 0.01. Using single CaAlSiN3:Ce3+ as the wavelength conversion phosphor combined with a blue InGaN LED-chip (450 nm), warm white-light LEDs can be generated, yielding the luminous efficacy of about 50 lm/W at color temperature 3722 K and the color rendering index (Ra) of 70, which demonstrates that CaAlSiN3:Ce3+ is a highly promising yellow-orange phosphor for use in white-light LEDs.
Secondary scintillation light (S2 signal) has been used in two-phase detectors for searching direct dark matter because of its useful characteristics. In general, electrons extracted from the liquid ...phase of two-phase detectors produce excimers in the gaseous phase that emit a vacuum ultraviolet (VUV) S2 signal. However, recent research suggests that the S2 signal in argon has another luminescence mechanism called “neutral bremsstrahlung”. In this study, detailed measurements of neutral-bremsstrahlung-induced-S2-signal and VUV S2 signal in argon are reported.
Secondary scintillation light (S2 signal) has been used for direct dark matter search in two-phase detectors because of its appealing characters. In general, electrons extracted from the liquid phase ...of two-phase detectors produce excimers in the gaseous phase that emit a VUV (vacuum ultraviolet) S2 signal. However, recent research suggests that the S2 signal in argon has another luminescence mechanism called "neutral bremsstrahlung". In this work, detailed measurements of neutral-bremsstrahlung-induced -S2 -signal (and also VUV S2 signal) in argon are reported.
The Editors-in-Chief have retracted this article 1. Serious concerns have been raised about the data presented 2, and after careful consideration and additional investigation the Editors-in-Chief no ...longer have confidence in this article.
The Editors-in-Chief have retracted this article 1. Serious concerns have been raised about the data presented 2, and after careful consideration and additional investigation the Editors-in-Chief no ...longer have confidence in this article. All authors were contacted and did not respond to correspondence about this retraction.
It has been demonstrated that the liquid argon scintillation detector is an excellent particle detector for use in various physics experiments, particularly those seeking evidence of WIMPs dark ...matter. The detector observes primary scintillation signal (S1) and/or secondary electroluminescence signal (S2). It is crucial that the properties of the detector are understood comprehensively so that such projects reduce systematic uncertainty and improve sensitivity. This work covers the recent measurements, taken using the liquid argon test facility at Waseda University, of the liquid argon scintillation and ionization responses for nuclear and electronic recoils. Additionally, a basic study of the gaseous argon luminescence signal, which involves the S2 signal, is presented herein. The luminescence process of the S2 signal, based on this measurement, is then discussed along with a suggested new mechanism called neutral Bremsstrahlung.
In previous studies, human dental pulp stem cells (hDPSCs) were mainly isolated from adults. In this present study, we characterized hDPSCs isolated from an earlier developmental stage to evaluate ...the potential usage of these cells for tissue-regenerative therapy. hDPSCs isolated at the crown-completed stage showed a higher proliferation rate than those isolated at a later stage. When the cells from either group were cultured in medium promoting differentiation toward cells of the osteo/odontoblastic lineage, both became alkaline-phosphatase-positive, produced calcified matrix, and were also capable of forming dentin-like matrix on scaffolds in vivo. However, during long-term passage, these cells underwent a change in morphology and lost their differentiation ability. The results of a DNA array experiment showed that the expression of several genes, such as WNT16, was markedly changed with an increasing number of passages, which might have caused the loss of their characteristics as hDPSCs.
Defined sets of transcriptional factors can reprogram human somatic cells to induced pluripotent stem (iPS) cells. However, many types of human cells are not easily accessible to minimally invasive ...procedures. Here we evaluated dental pulp cells (DPCs) as an optimal source of iPS cells, since they are easily obtained from extracted teeth and can be expanded under simple culture conditions. From all 6 DPC lines tested with the conventional 3 or 4 reprogramming factors, iPS cells were effectively established from 5 DPC lines. Furthermore, determination of the HLA types of 107 DPC lines revealed 2 lines homozygous for all 3 HLA loci and showed that if an iPS bank is established from these initial pools, the bank will cover approximately 20% of the Japanese population with a perfect match. Analysis of these data demonstrates the promising potential of DPC collections as a source of iPS cell banks for use in regenerative medicine.
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