Evolution of the spin Hall effect in Pt nanowires: Size and temperature effects

We have studied the evolution of the Spin Hall Effect in the regime where the material size responsible for the spin accumulation is either smaller or larger than the spin diffusion length. Lateral spin valve structures with Pt insertions were successfully used to measure the spin absorption efficiency as well as the spin accumulation in Pt induced through the spin Hall effect. Under a constant applied current the results show a decrease of the spin accumulation signal is more pronounced as the Pt thickness exceeds the spin diffusion length. This implies that the spin accumulation originates from bulk scattering inside the Pt wire and the spin diffusion length limits the SHE. We have also analyzed the temperature variation of the spin hall conductivity to identify the dominant scattering mechanism.Comment: 4 pages, 4 figure

Dynamics of coupled vortices in a pair of ferromagnetic disks

We here experimentally demonstrate that coupled gyration modes can be resonantly excited primarily by the ac current in a pair of ferromagnetic disks with varied separating distance. The sole gyrotropic mode clearly splits into a higher and a lower frequency modes for different configurations of polarities via dipolar interaction. These experimental results indicate that the magnetostatically coupled pair of vortices behaves similar to a diatomic molecule with bonding and anti-bonding states. These findings lead to the possible extension of designing the magnonic band structure in a chain or an array of vortices.Comment: 4 pages, 4 figures, accepte

Domain Nucleation and Annihilation in Uniformly Magnetized State under Current Pulses in Narrow Ferromagnetic Wires

We investigate the current-driven magnetization dynamics in narrow Permalloy wires by means of Lorentz microscopy and electron holography. Current pulses are found to transform the magnetic structure in the uniformly magnetized state below the Curie temperature. A variety of magnetic states including reversed magnetic domains are randomly obtained in low probability. The dynamics of vortices found in most of observed magnetic states seems to play a key role in triggering the magnetization reversal.Comment: 11 pages, 3 figures, 1 video, to appear in Japanese Journal of Applied Physics (Express Letter

Search for sub-eV scalar and pseudoscalar resonances via four-wave mixing with a laser collider

The quasi-parallel photon-photon scattering by combining two-color laser fields is an approach to produce resonant states of low-mass fields in laboratory. In this system resonances can be probed via the four-wave mixing process in the vacuum. A search for scalar and pseudoscalar fields was performed by combining 9.3 $\mu$J/0.9 ps Ti-Sapphire laser and 100 $\mu$J/9 ns Nd:YAG laser. No significant signal of four-wave mixing was observed. We provide the upper limits on the coupling-mass relation for scalar and pseudoscalar fields, respectively, at a 95\% confidence level in the mass region below 0.15~eV.Comment: Accepted by Prog. Theor. Exp. Phy

Reforestation following harvesting of conifer plantations in Japan: Current issues from silvicultural and ecological perspectives

Following the Second World War, the number of Cupressaceae plantations in Japan increased, in accordance with government policy for the restoration of timber resources and conservation of soil and water. Currently, these even-aged plantations occupy approximately 44% of the forested area and 24% of the national land area of Japan. Although many of these plantations have become available as timber resources, there are several silviculture-related problems associated with reforestation following clear-cutting of these plantations. The abundant annual precipitation in Japan allows for dominance by competitive vegetation, which makes natural regeneration difficult and increases the cost of silvicultural operations during and after the planting of seedlings. Because the number of seedling producers has decreased, there has been little incentive to keep seedling production techniques up to date. Additionally, damage to planted seedlings by the overabundant sika deer (Cervus nippon) population has increased dramatically in the last dozen years or so. To determine how to overcome these difficulties, various studies are underway in Japan. For example, seedling studies have examined the relationship between seedling size and competitive ability with other species in reforested areas, and have led to the development of lower-cost systems to produce customized Cupressaceae seedlings, as well as measures to minimize transplanting damage to seedlings. Previous studies have shown that no-weeding operations might lower the risk of sika deer browsing seedlings, although this silvicultural countermeasure may potentially reduce seedling growth. Studies have also examined the types of physical protection against sika deer browsing that are most efficient. We must combine these findings into a unified silvicultural system for successful restoration via lower-cost plantations

Potential Biases of the Transmission Risks of COVID-19 estimated by Contact Tracing Surveys in Japan

Introduction: Contact tracing surveys are being conducted to identify and isolate close contacts of an identified patient to reduce the spread of coronavirus disease (COVID-19). However, the estimates of risk indexes based on information obtained from the surveys and normally used in practice can have biases comparing with true magnitude of risks of infection and spread.Method: We evaluated whether the estimates of the risk indexes obtained from information of the active epidemiological surveillance, contact tracing surveys in Japan, are suitable for quantitative assessment of the risk factors of COVID-19, using pseudo data via a simulation study. We discussed two types of risks considered in the issue of infectious disease, the probability of infection and that of spreading, and the estimates of these risks.Results and Discussion: A naive method to estimate the risks of infection and spreading of COVID-19 is to calculate the ratio of infected patients to close contacts and the ratio of patients who infected others to all the confirmed patients, respectively. However, these estimates could possibly have significant biases and result in being ineffective for both the exploration and the quantitative assessment of the risk factors in the following ordinary cases: a person contacts closely with many confirmed patients, or a confirmed patient contact closely with many people. Then, some steps are needed to reduce such possible biases for the estimation the risks of both the infection and spreading of COVID-19

Impact of eggplant consumption on urine cotinine examination results

Background and Objective: A urinary cotinine test is performed to assess the smoking status. Cotinine is a nicotinic metabolite. However, foodstuffs from the plant family Solanaceae, such as eggplant, contain trace amounts of nicotine, which may have affected the cotinine test results. This study investigated the impact of eggplant consumption on urine cotinine concentration tests. Methods: Six young women who were healthy and non-smokers consumed meals devoid of Solanaceous ingredients for three days before consuming 300 grams of eggplant. After eating eggplants, the participants did not consume Solanaceous food throughout the study. During the study, participants’ urine cotinine concentrations were sampled periodically using a urine nicotine and cotinine test kit. Results: Four participants’ urine tested positive for cotinine, whereas that of two participants tested negative. The time when a positive result was recorded after consuming eggplants varied among the individuals. Participants’ urine cotinine concentrations differed as well. Conclusions: Urine cotinine concentrations may increase after consuming Solanaceous foods, even in non-smokers. When assessing the smoking status, the influence of Solanaceous foods should be considered when measuring urine cotinine levels

Expression of the immunoreactive buckwheat major allergenic storage protein in Lactococcus lactis

Proteins from buckwheat (Fagopyrum esculentum) are strong allergens that can cause serious symptoms, including anaphylaxis, in patients with hypersensitivity. In this study, we successfully developed a modified lactic acid bacterial vector (pNSH) and a recombinant strain of Lactococcus lactis NZ9000 (NZ9000) that produced a major allergenic storage protein of buckwheat, Fagag1 (61.2 kDa, GenBank accession number AF152003), with or without a green fluorescent protein (GFP) tag. GFP fluorescence allows for rapid, simple, and accurate measurement of target protein expression by microscopy or fluorimetry. We describe a convenient method for production of rGFP-Fagag1 fusion and rFagag1 proteins with a good yield in an advantageous probiotic host. We found that in vitro treatment of splenocytes isolated from buckwheat crude protein-immunized mice with rFagag1 increased the expression of allergic inflammation cytokines such as IL-4, IL-13, and IL-17 F. Because it was less antigenic, rGFP-Fagag1 protein from NZ9000 might be of limited use; however, rFagag1 from NZ9000 evoked a robust response as measured by induction of IL-4 and IL-17 F expression levels. The observed allergic activity is indicative of a Th2 cell-mediated immune response and is similar to the effects induced by exposure to buckwheat crude protein. Our results suggest that expression of rFagag1 in NZ9000 may facilitate in vivo applications of this system aimed at improving the specificity of immunological responses to buckwheat allergens.ArticleAPPLIED MICROBIOLOGY AND BIOTECHNOLOGY. 97(8):3603-3611 (2013)journal articl