Study of Radiation Induced Electrical Degradation of Alumina in a Dynamic Pumping Condition in a Fission Reactor

The electrical conductivity of two ceramic insulators, alumina, and silicon nitride was measured in a fission reactor, JMTR under a dynamic vacuum condition. The instrumented irradiation rig was dynamically evacuated during fission reactor operation. The uppermost vacuum level attained was better than 10^ Torr. In this experiment, we attempted to reveal effects of the gaseous environment on the measurement of electrical conductivity under ionizing irradiation. The results showed that the gaseous environment has a most hazardous effect in a certain gas pressure range. In the second experiment, an electrical resistivity of polycrystal α-alumina was measured at about 680K in a dynamic pumping condition. In a good vacuum, we observed smaller RIC(radiation induced conductivity) than our previous results. We observed RIED(radiation induced electrical degradation)-like behavior. The results suggested that RIED would take off faster at a higher ionizing dose rate. In the meantime, the take-off occurred at about the same displacement damage of about 0.03-0.05dpa in the range of fast neutron flux of 3.4-15.1x10^n/cm^2s

Extension of the Coherence Time by Generating MW Dressed States in a Single NV Centre in Diamond

Nitrogen-vacancy (NV) centres in diamond hold promise in quantum sensing applications. A major interest in them is an enhancement of their sensitivity by the extension of the coherence time ($T_2$). In this report, we experimentally generated more than four dressed states in a single NV centre in diamond based on Autler-Townes splitting (ATS). We also observed the extension of the coherence time to $T_2 \sim$ 1.5 ms which is more than two orders of magnitude longer than that of the undressed states. As an example of a quantum application using these results we propose a protocol of quantum sensing, which shows more than an order of magnitude enhancement in the sensitivity.Comment: 8 pages, 9 figure

Natural Variation in the Flag Leaf Morphology of Rice Due to a Mutation of the NARROW LEAF 1 Gene in Oryza sativa L.

We investigated the natural variations in the flag leaf morphology of rice. We conducted a principal component analysis based on nine flag leaf morphology traits using 103 accessions from the National Institute of Agrobiological Sciences Core Collection. The first component explained 39% of total variance, and the variable with highest loading was the width of the flag leaf (WFL). A genome-wide association analysis of 102 diverse Japanese accessions revealed that marker RM6992 on chromosome 4 was highly associated with WFL. In analyses of progenies derived from a cross between Takanari and Akenohoshi, the most significant quantitative trait locus (QTL) for WFL was in a 10.3-kb region containing the NARROW LEAF 1 (NAL1) gene, located 0.4 Mb downstream of RM6992. Analyses of chromosomal segment substitution lines indicated that a mutation (G1509A single-nucleotide mutation, causing an R233H amino acid substitution in NAL1) was present at the QTL. This explained 13 and 20% of total variability in WFL and the distance between small vascular bundles, respectively. The mutation apparently occurred during rice domestication and spread into japonica, tropical japonica, and indica subgroups. Notably, one accession, Phulba, had a NAL1 allele encoding only the N-terminal, or one-fourth, of the wild-type peptide. Given that the Phulba allele and the histidine-type allele showed essentially the same phenotype, the histidine-type allele was regarded as malfunctional. The phenotypes of transgenic plants varied depending on the ratio of histidine-type alleles to arginine-type alleles, raising the possibility that H(233)-type products function differently from and compete with R(233)-type products

Fe-K line probing of material around the AGN central engine with Suzaku

We systematically analyzed the high-quality Suzaku data of 88 Seyfert galaxies. We obtained a clear relation between the absorption column density and the equivalent width of the 6.4 keV line above 10$^{23}$ cm$^{-2}$, suggesting a wide-ranging column density of $10^{23-24.5}$ cm$^{-2}$ with a similar solid and a Fe abundance of 0.7--1.3 solar for Seyfert 2 galaxies. The EW of the 6.4 keV line for Seyfert 1 galaxies are typically 40--120 eV, suggesting the existence of Compton-thick matter like the torus with a column density of $>10^{23}$ cm$^{-2}$ and a solid angle of $(0.15-0.4)*4pi$, and no difference of neutral matter is visible between Seyfert 1 and 2 galaxies. An absorber with a lower column density of $10^{21-23}$ cm$^{-2}$ for Compton-thin Seyfert 2 galaxies is suggested to be not a torus but an interstellar medium. These constraints can be understood by the fact that the 6.4 keV line intensity ratio against the 10--50 keV flux is almost identical within a range of 2--3 in many Seyfert galaxies. Interestingly, objects exist with a low EW, 10--30 eV, of the 6.4 keV line, suggesting that those torus subtends only a small solid angle of $<0.2*4pi$. Ionized Fe-K$\alpha$ emission or absorption lines are detected from several percents of AGNs. Considering the ionization state and equivalent width, emitters and absorbers of ionized Fe-K lines can be explained by the same origin, and highly ionized matter is located at the broad line region. The rapid increase in EW of the ionized Fe-K emission lines at $N_{H}>10^{23}$ cm$^{-2}$ is found, like that of the cold material. It is found that these features seem to change for brighter objects with more than several $10^{44}$ erg/s such that the Fe-K line features become weak. We discuss this feature, together with the torus structure.Comment: 32 pages, 20 figures, ApJ accepte

Symptomatic Developmental Venous Anomaly with an Increased β2-microglobulin Level in Cerebrospinal Fluid: A Case Report

Background: Gadolinium-enhanced magnetic resonance imaging (MRI) can be used to observe the progression of cerebral infarction, which sometimes mimics malignant brain tumors. While the β2-microglobulin (β2MG) level in blood plasma or cerebrospinal fluid (CSF) is useful for the diagnosis of malignant tumors or degenerative diseases, these results may create confusion regarding a definitive diagnosis, because it is not a specific marker. We present a rare case of symptomatic developmental venous anomaly (DVA), accompanied by transient, irregular, enhanced cerebral lesions and elevated β2MG in the CSF. Case Description: A 56-year-old woman developed dysarthria and underwent MRI, which revealed a right frontal hyperintense area around a previous lesion on diffusion-weighted imaging (DWI). She was treated based on the tentative diagnosis of an ischemic cerebrovascular event, and symptoms subsided in 3 days. MRI on day 7 revealed an enlargement of the hyperintense area on DWI. Post-gadolinium MRI showed multiple, enhanced patchy areas in the right frontal lobe and an abnormally large vein connected to dilated medullary venules, indicating DVA. Magnetic resonance angiography showed no stenosis or arterial occlusion. The β2MG level in the CSF was elevated at 2,061 μg/l, and a differential diagnosis from malignant tumor was required. However, MRI on day 23 revealed total disappearance of the enhanced lesions and a decrease in the high intensity area on DWI. Considering the clinical course, the DVA was symptomatic because of the perfusion disturbance. Conclusion: Careful evaluation is necessary when considering the associated pathologies and potential complications of DVA if detected near a gadolinium-enhanced lesion