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We present a new realization of the time-domain double-slit experiment with photoelectrons, demonstrating that spontaneous radiation from a bunch of relativistic electrons can be used to control the quantum interference of single-particles. The double-slit arrangement is realized by a pair of light wave packets with attosecond-controlled spacing, which is naturally included in the spontaneous radiation from two undulators in series. Photoelectrons emitted from helium atoms are observed in the energy-domain under the condition of detecting them one by one, and the stochastic buildup of the quantum interference pattern on a detector plane is recorded.

RNA silencing (RNAi) induced by virus-derived double-stranded RNA (dsRNA), which is in a sense regarded as a pathogen-associated molecular pattern (PAMP) of viruses, is a general plant defense mechanism. To counteract this defense, plant viruses express RNA silencing suppressors (RSSs), many of which bind to dsRNA and attenuate RNAi. We showed that the tobacco calmodulin-like protein, rgs-CaM, counterattacked viral RSSs by binding to their dsRNA-binding domains and sequestering them from inhibiting RNAi. Autophagy-like protein degradation seemed to operate to degrade RSSs with the sacrifice of rgs-CaM. These RSSs could thus be regarded as secondary viral PAMPs. This study uncovered a unique defense system in which an rgs-CaM–mediated countermeasure against viral RSSs enhanced host antiviral RNAi in tobacco.

Synchrotron radiation, emitted by relativistic electrons traveling in a magnetic field, has poor temporal coherence. However, recent research has proved that time-domain interferometry experiments, which were thought to be enabled by only lasers of excellent temporal coherence, can be implemented with synchrotron radiation using a tandem undulator. The radiation generated by the tandem undulator comprises pairs of light wave packets, and the longitudinal coherence within a light wave packet pair is used to achieve time-domain interferometry. The time delay between two light wave packets, formed by a chicane for the electron trajectory, can be adjusted in the femtosecond range by a standard synchrotron technology. In this study, we show that frequency-domain spectra of the tandem undulator radiation exhibit fringe structures from which the time delay between a light wave packet pair can be determined with accuracy on the order of attoseconds. The feasibility and limitations of the frequency-domain interferometric determination of the time delay are examined.

Abstract This paper introduces a new approach to measure the muon magnetic moment anomaly $a_{\\mu} = (g-2)/2$ and the muon electric dipole moment (EDM) $d_{\\mu}$ at the J-PARC muon facility. The goal of our experiment is to measure $a_{\\mu}$ and $d_{\\mu}$ using an independent method with a factor of 10 lower muon momentum, and a factor of 20 smaller diameter storage-ring solenoid compared with previous and ongoing muon $g-2$ experiments with unprecedented quality of the storage magnetic field. Additional significant differences from the present experimental method include a factor of 1000 smaller transverse emittance of the muon beam (reaccelerated thermal muon beam), its efficient vertical injection into the solenoid, and tracking each decay positron from muon decay to obtain its momentum vector. The precision goal for $a_{\\mu}$ is a statistical uncertainty of 450 parts per billion (ppb), similar to the present experimental uncertainty, and a systematic uncertainty less than 70 ppb. The goal for EDM is a sensitivity of $1.5\\times 10^{-21}~e\\cdot\\mbox{cm}$.

A small-momentum-width muon beam, so-called ultra-slow muon beam, can be generated by laser ionization of muonium. To realize efficient ultra-slow muon generation, the Lyman-alpha and below 360 nm coherent light are required to resonantly excite the muonium from the ground state to 2 p and sequentially ionizes excited muonium to the unbound state. At the J-PARC MLF Ultra-Slow Muon beamline, we have successfully generated Lyman-alpha coherent light exceeding 10 μJ using an all-solid-state laser and high-efficiency vacuum ultraviolet light generation technologies. In this paper, we will describe the intense Lyman-alpha light source.

In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning the laser to the lowest resonant transition, the system becomes multiply excited, and more efficient, indirect ionization pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of the species de-excites to its ground state, transferring its energy to ionize another excited species. Here we show that on tuning to a higher resonant transition, a previously unknown type of interatomic Coulombic decay, intra-Rydberg ICD occurs. In it, de-excitation of an atom to a close-lying Rydberg state leads to electron emission from another neighbouring Rydberg atom. Moreover, systems multiply excited to higher Rydberg states will decay by a cascade of such processes, producing even more ions. The intra-Rydberg ICD and cascades are expected to be ubiquitous in weakly-bound systems exposed to high-intensity resonant radiation. Interatomic Coulombic decay (ICD) is a relaxation of an atom in a weakly bound environment by the transfer of excess energy to ionize the neighbouring atom. Here the authors observe intra-Rydberg ICD in neon clusters, which is a decay that involves the ionization of Rydberg atoms in the cluster.

Imogolite is a naturally occurring hydrated aluminum-silicate polymer that consists of a tubular structural unit having an external diameter of 2.3-2.7 nm and an inner diameter of ca. 1 nm. The tube length is from about 400 nm to several micrometers. The tube walls are composed of curved gibbsite-like sheets with SiOH groups on the inside and AlOH groups on the outside, having a composition (HO)3Al2O3SiOH-H. Imogolite is common in the clay fraction of soils derived from glassy volcanic ashes or pumice beds, and it has also been found in many podzols. In the present work, the authors attempt to improve a synthetic method and to characterize an aluminosilicate mineral forming such hollow tubular structures for the purpose of gas storage.

Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at ~5 keV. Our experiment was carried out at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with the molecular dynamics tool XMDYN. We found that in this unprecedented wavelength regime nanoplasma formation is a highly indirect process. In the argon clusters investigated, nanoplasma is mainly formed through secondary electron cascading initiated by slow Auger electrons. Energy is distributed within the sample entirely through Auger processes and secondary electron cascading following photoabsorption, as in the hard x-ray regime there is no direct energy transfer from the field to the plasma. This plasma formation mechanism is specific to the hard-x-ray regime and may, thus, also be important for XFEL-based molecular imaging studies. In xenon clusters, photo- and Auger electrons contribute more significantly to the nanoplasma formation. Good agreement between experiment and simulations validates our modelling approach. This has wide-ranging implications for our ability to quantitatively predict the behavior of complex molecular systems irradiated by high-intensity hard x-rays.

The bioavailability of macroalgal dissolved organic matter (DOM) was examined by decomposition experiments using released DOM fromEcklonia cavaKjellman (Phaeophyceae) living in Oura Bay, Shimoda, Izu Peninsula, Japan. The samples used for the decomposition experiments were obtained by enclosing the plants in bags. Based on the reduction rates of the concentrations of dissolved organic carbon (DOC), the turnover times of the macroalgal DOC were calculated to be between 24 and 172 d, with monthly-seasonal timescales. These values were mostly higher than those of phytoplanktonic DOC in previous studies (<1 mo). The relatively longer turnover time probably reflects the bio-refractory property of the macroalgal DOM. In most of the experiments (except for June), fucans and humic-like material were the major constituents of the released DOM. The fucans appeared to be partly decomposed during the experiments, but the compositional changes in the neutral carbohydrates in these seasons were less definite than those in June. The fluorescent intensity of the humic-like material did not decrease with time, suggesting a refractory character. Macroalgae are likely important DOM producers in Oura Bay, because the daily DOM production ofE. cavaaccounts for 1.5 to 34% of DOM stock in Oura Bay per day. The concentration and the distribution of DOC inside and outside the bay strongly suggests that the released DOM was extensively exported out of the bay. These facts indicate that the macroalgal DOM contributes to marine DOM pools in a wider area including the adjacent coastal region.