Misfit accommodation in a single interface atomic layer at a highly lattice-mismatched InN/GaN

Heterostructures of covalent semiconductors provide an invaluable platform for synthesizing the distinct properties of materials, leading to unprecedented functions in electronic and optoelectronic devices. The main challenge has been to forge high-quality interfaces of the heterostructures that guarantee the designed properties. To date, high-quality interfaces can be attained in heterostructures with a lattice mismatch of less than a few percent. For highly lattice-mismatched interfaces, such as InN/GaN (0001) (11.1% mismatch), interfacial structures remain unknown. Here, we investigate the atomic structure of the InN/GaN interface using atomic resolution transmission electron microscopy and large-scale density-functional calculations. Our findings show that an interface structure without any misfit dislocations are formed, where the InN single monolayer at the interface accommodates the entire misfit. We argue that the mechanism underlying the formation of this interface monolayer is the flexibility of the group III ? nitrogen bond network.journal articl

Valence/spin states of iron in peridotite glass to megabar pressure implications for dense ferric-iron-rich silicate melt at the bottom of the mantle

We have conducted electrical conductivity and energy-domain synchrotron Mossbauer spectroscopic measurements of peridotite glass as an analogue of silicate melts at the bottom of the mantle. The changes in the Mossbauer parameters and the change in the trend of the electrical conductivity profile have been observed at around 80 GPa, suggesting that the structural change of the glass from akimotoite-like to postperovskite-like structures. We also observed the changes in the Mossbauer parameters above 120 GPa, which might be due to the change in near-neighbor coordination number to iron. On the other hand, we did not observe the trend change in the electrical conductivity. This means that the effect of the coordination number change on the electrical conductivity is small. The pressure conditions of these changes in structure and coordination number are much lower than the lowermost mantle pressure, that is, the melt would become compact at the bottom of the mantle.journal articl

Determination of Pu isotopes in urine samples by a pseudo-isotope dilution method using non-isotopic tracer 237Np

Plutonium (Pu) isotopes are extremely hazardous radioactive materials. Rapid analysis of Pu in urine from contaminated persons is important for radiobiological verification and exposure dose assessment. Since Pu is classified as a nuclear fuel nuclide, the use of 242Pu tracer for isotope dilution (ID) quantification is commonly controlled and regulated, which can affect timely exposure dose assessment. In this study, a pseudo-isotope dilution (PID) method using a non-isotopic tracer (NIT) 237Np was developed. The method accuracy was validated using both spiked samples and urine standard reference materials. Uncertainties throughout the experiment, instrument analysis, and activity calculation were characterized by Monte Carlo simulation (MCS). The results showed that the activity concentrations of 239Pu, 240Pu, and 237Np quantified by PID were consistent with those measured by the ID method. For spiked samples with theoretical 239Pu concentrations of 0.028 pg/mL and 0.014 pg/mL, the coefficients of variation (CVs) derived by the PID method were 0.043 and 0.074, respectively, which were comparable to those quantified by the ID method with CVs of 0.042 and 0.045. From the parameter sensitivity analysis, the ICP-MS signal intensities of 237Np and 240Pu isotopes after standard addition and the 237Np signal intensity before the standard addition were identified as the key factors affecting the quantification of 239Pu, 240Pu and 237Np, respectively. Due to its considerable accuracy, precision and extensive application conditions, the PID method is judged to be a promising tool for radiological assessment of contaminated persons in an internal exposure situation and for providing decision-making information in emergency medical treatments.journal articl

Ion acceleration with an intense short-pulse laser and large-area suspended graphene in an extremely thin target regime

Graphene is an atomic thin 2D material, known as the strongest material with such a thin regime. Free- standing, large-area suspended graphene (LSG) has been developed for a target of laser-driven ion acceleration. The LSG has shown remarkable durability against laser prepulse, producing MeV protons and carbons by direct irradiation with an intense laser without a plasma mirror, yet no optimization has been concerned. Here we investigate the optimization of the laser-driven ion acceleration with LSG, paying special attention to the target conditions. We irradiate nanometer-thick LSG with an intense laser, where the incident angle and the target thickness are controlled. The maximum proton energy increases with increasing the number of LSG layers, where 25 ± 0.3 MeV protons at maximum are consistently observed with Thomson parabola spectrometer and diamond-based detectors. For comparison purposes, we perform ideal numerical simulations using particle-in-cell (PIC) code without consideration of the prepulse. In the PIC simulation, the protons are successively accelerated by the electric field associated with laser radiation pressure and the surface sheath field, yet the maximum proton energies are overestimated. The maximum proton energies from the experiment asymptotically approach the ideal PIC expectations, indicating that the thinner LSG is more affected by the prepulse. We expect higher proton energy with the optimized LSG conditions and a plasma mirror.journal articl

FRET analysis of unwrapping of nucleosomal DNA containing the sequence characteristic to the +1 nucleosome

Sequence-dependent mechanical properties of DNA could play essential roles in nuclear processes by affecting histone-DNA interactions. Previously, we found that the DNA entry site of the first nucleosomes from the transcription start site (+?1 nucleosome) in budding yeast enriches AA/TT steps, but not the exit site, and the biased presence of AA/TT in the entry site was associated with the transcription levels of yeast genes. Because AA/TT is a rigid dinucleotide step, we considered that AA/TT causes DNA unwrapping. However, our previous MNase-seq experiments with reconstituted nucleosomes left some doubt regarding this interpretation, owing to its high exonuclease activity. Furthermore, MNase cleavage did not provide direct evidence of its structural state. In this study, Forster resonance energy transfer (FRET) measurements were used to investigate salt-induced conformational changes in nucleosomal DNA containing AA/TT repeats at the entry site. We observed that the AA/TT region wrapped around the histone core was as likely as other DNA sequences at physiological salt concentrations. However, it unwrapped at a lower salt concentration, indicating weaker electrostatic interactions with the histone core. Ethidium-induced nucleosome disruption assay showed that the intercalator had greater access to DNA with AA/TT at the entry site. Taken together, these results suggest that AA/TT at the entry sites induces DNA unwrapping from the histone core on the promoter side, which may promote transcriptional activation in response to the approach of transcription-related proteins.journal articl

Lifespan data of B6C3F1 mouse age dependence experiment (gamma rays and carbon ions)

Lifespan data of B6C3F1 mice of both sexes irradiated at various ages with gamma rays and 13-keV/μm carbon ions. See the original paper below for details. Kakinuma S, Shang Y, Amasaki Y, Hirano-Sakairi S, Sawai T, et al. (2025) Influence of age and sex on the relative biological effectiveness of 13-keV/μm carbon ions for lifespan shortening of B6C3F1 Mice. PLOS ONE 20(9): e0332270. https://doi.org/10.1371/journal.pone.0332270journal articl

A neuroimaging dataset during sequential color qualia similarity judgments with and without reports

最近の神経科学の研究は意識についての理解を進展させているが、意識の特定の質的側面である「クオリア」と特定の脳領域やネットワークとの関連は依然として明確ではない。従来の方法では参加者からの言葉による説明に依存しており、これが神経画像研究での課題となっている。これに対処するため、私たちのグループはクオリアの徹底的な構造的および関係的比較に依存する新しい「クオリア構造」パラダイムを導入した。この研究では、35人の参加者から、各試行で9つの色クオリアのうち2つについての関係的類似性判断を捉えた初めてのfMRIデータセットを提示する。このデータセットは、報告の有無の影響を評価するために、試行の半分に「無報告」条件も含まれている。また、スキャナー外で行われた色差別能力評価を各参加者に対して実施した。私たちのデータは色クオリアに関連する脳機能についての貴重な洞察を提供し、意識の神経基盤の理解を深めることに寄与する。journal articl

Saturable absorption in highly excited laser-irradiated silicon and its suppression at the surface

Nonlinear electronic excitation in laser-irradiated silicon at finite electron temperatures is numerically investigated by first-principles calculations based on the time-dependent density functional theory. In bulk silicon at finite temperatures under near-infrared laser irradiation, we found that the absorbed energy is saturated when using a certain laser intensity even with a few-cycle pulse. Although one-photon processes of conduction-to-conduction and valence-to-valence transitions are dominant at such a laser intensity, the Pauli blocking inhibits further one-photon transition. With higher intensities, multi-photon excitation across the bandgap overwhelms the one-photon excitation and the saturable absorption disappears. At the surface of finite-temperature silicon, the Pauli blocking is suppressed by the symmetry breaking and the absorbed energy is relatively enhanced from the energy of the saturable absorption in the bulk region.journal articl

Excitation of the isoscalar giant monopole resonance using 6Li inelastic scattering

The incompressibility of infinite nuclear matter (K_{infty}) is a parameter in the description of the nuclear equation of state that governs the energy cost associated with density oscillations near the saturation density. The most direct proxy for studying this property of infinite nuclear matter is to probe the isoscalar giant monopole resonance (ISGMR) in finite nuclei. This work explores the use of 6Li as a probe to study the ISGMR in several stable nuclei: 58Ni, 90Zr, 116Sn, and 208Pb, as complementary to using inelastic scattering of \alpha-particles, which has been used to great effect over the last several decades. Elastic and inelastic scattering data for these targets were collected with 343-MeV 6Li beams. In all nuclei studied in this work, the ISGMR strength distributions extracted from multipole decomposition analyses of the inelastic scattering spectra agree very well with the previously measured ISGMR responses from \alpha-particle scattering, establishing the feasibility of employing 6Li inelastic scattering in the investigation of the ISGMR.journal articl

Implication of E3 ligase RAD18 in UV-induced mutagenesis in human induced pluripotent stem cells ant neuronal progenitor cells

Pluripotent stem cells (PSCs) have the potential to differentiate to any of the other organs. The genome DNA integrity of PSCs is maintained by a high level of transcription for a number of genes involved in DNA repair, cell cycle, and apoptosis. However, it remains unclear how high the frequency of genetic mutation is and how these DNA repair factors function in PSCs. In this study, we employed Sup F assay for the measurement of mutation frequency after UV-C irradiation in induced pluripotent stem cells (iPSCs) as PSC models and neural progenitor cells (NPCs) were derived from iPSCs as differentiated cells. iPSCs and NPCs exhibited a lower mutation frequency compared with the original skin fibroblasts. In RNA-seq analysis, iPSCs and NPCs showed a high expression of RAD18, which is involved in trans-lesion synthesis (TLS) for the emergency tolerance system during the replication process of DNA. Although RAD18 is involved in both error free and error prone TLS in somatic cells, it still remains unknown the function of RAD18 in PSCs. In this study we depleted of the RAD18 by siRNA knockdown resulted in decreased frequency of mutation in iPSCs and NPCs. Our results will provide information on the genome maintenance machinery in PSCs.journal articl