Hokkaido, Japan
Hokkaido, Japan

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Sato M.,Hokkaido UniversitySapporo | Tojo Y.,Hokkaido UniversitySapporo | Matsuo T.,Hokkaido UniversitySapporo | Matsuto T.,Hokkaido UniversitySapporo
Sustainable Environment Research | Year: 2011

Long-term safety is essential for sustainable landfills, which should be operated and managed without environmental pollution caused by the release of hazardous compounds. However, knowledge of the long-term fate of compounds such as polycyclic aromatic hydrocarbons (PAHs) remains insufficient. This study determined the concentrations of 18 PAHs in bottom ash samples obtained from municipal solid waste incinerators in Japan and calculated their fate in a landfill using a simple model that accounted for the biodegradation of PAHs and their distribution in three phases. Naphthalene, phenanthrene, and fluoranthene were major compounds identified in all samples, in concentrations ranging from 10 to 1000 µg kg-1. The concentrations of other PAHs were lower than 100 µg kg-1. Although the total concentrations of the 18 PAHs varied by up to three orders of magnitude, the concentrations were not high relative to those of other environmental media. In particular, the PAH concentrations were similar to those of soil and sediment reported in previous studies. The simple calculation procedure applied in this study showed that the fate of PAHs was dominated by the presence of organic carbon in the modelled landfill. PAHs of high molecular weight remained long term because of their affinity for organic carbon. However, when conditions favouring biodegradation were achieved, the PAH concentrations diminished on a shorter timescale. © 2010, Chinese Institute of Environmental Engineering. All rights reserved.

Matsumura S.,Hokkaido UniversitySapporo | Yamazaki K.,Hokkaido UniversitySapporo | Yamazaki K.,Japan National Institute of Polar Research | Sato T.,Hokkaido UniversitySapporo
Journal of the Meteorological Society of Japan | Year: 2015

We investigate the formation mechanism of the summer Okhotsk High (OH) in terms of the land-atmosphere coupling in Siberia. A reanalysis data indicates that the formation mechanism of the OH clearly differs between early and late summer because it changes from a nearly barotropic to a baroclinic structure with seasonal changes. Then, we assess the influence of springtime snow cover on the formation of the late summer OH with the baroclinicity using a regional climate model. The model performs well in reproducing the land-atmosphere coupling in eastern Siberia and the OH in August 2008, when abnormal weather prevails in Japan, in conjunction with the intensively developed OH. The August OH develops with a distinct baroclinic structure owing to increased surface heating, which is related to land-atmosphere coupling in response to reduced spring snow cover in eastern Siberia. The land-atmosphere coupling can help to reinforce and maintain the baroclinic structure through surface heating, forming strong surface anticyclone to the southeast over the Sea of Okhotsk. Our results suggest that the late summer OH is a regional climate system that involves coupling among the atmosphere, the cool ocean, and the warm land surface. © 2015, Meteorological Society of Japan.

Oya T.,Hokkaido UniversitySapporo | Nomura T.,Hokkaido UniversitySapporo | Tsubota M.,Hokkaido University | Okinaka N.,Hokkaido University | Akiyama T.,Hokkaido University
Applied Thermal Engineering | Year: 2013

We developed new phase change composites (PCC) using erythritol as a phase change material (PCM) and graphite and nickel particles as highly thermal conductive fillers. Their effective thermal conductivities became two orders of magnitude larger than that of the original PCM. The PCC was prepared by using a conventional dispersion technique and its effective thermal conductivity was measured by the laser flash method at room temperature. We interpreted the results based on percolation theory, for which the effects of the graphite structure and the volumetric ratio on the effective thermal conductivity were examined. The results showed that the effective thermal conductivity increased gradually with increasing filler content and aspect ratio of filler. Of significance, they increased remarkably when we used 20 vol% spherical graphite. Moreover, among the three samples that we prepared, the greatest thermal conductivity, 4.72 W(m K)-1, was recorded for the PCC with 15 vol% expanded graphite content. This was 6.4 times higher than the thermal conductivity of pure erythritol. © 2012 Elsevier Ltd.

PubMed | Hokkaido UniversitySapporo and Hokkaido University
Type: | Journal: Frontiers in microbiology | Year: 2017

Human influenza pandemics have historically been caused by reassortant influenza A viruses using genes from human and avian viruses. This genetic reassortment between human and avian viruses has been known to occur in swine during viral circulation, as swine are capable of circulating both avian and human viruses. Therefore, avian-to-swine transmission of viruses plays an important role in the emergence of new pandemic strains. The amino acids at several positions on PB2, PB1, and PA are known to determine the host range of influenza A viruses. In this paper, we track viral transmission between avian and swine to investigate the evolution on polymerase genes associated with their hosts. We traced viral transmissions between avian and swine hosts by using nucleotide sequences of avian viruses and swine viruses registered in the NCBI GenBank. Using BLAST and the reciprocal best hits technique, we found 32, 33, and 30 pairs of avian and swine nucleotide sequences that may be associated with avian-to-swine transmissions for PB2, PB1, and PA genes, respectively. Then, we examined the amino acid substitutions involved in these sporadic transmissions. On average, avian-to-swine transmission pairs had 5.47, 3.73, and 5.13 amino acid substitutions on PB2, PB1, and PA, respectively. However, amino acid substitutions were distributed over the positions, and few positions showed common substitutions in the multiple transmission events. Statistical tests on the number of repeated amino acid substitutions suggested that no specific positions on PB2 and PA may be required for avian viruses to infect swine. We also found that avian viruses that transmitted to swine tend to process I478V substitutions on PB2 before interspecies transmission events. Furthermore, most mutations occurred after the interspecies transmissions, possibly due to selective viral adaptation to swine.

PubMed | Hokkaido UniversitySapporo and Hokkaido University
Type: | Journal: Frontiers in cell and developmental biology | Year: 2016

Boron (B) is a metalloid that is essential for plant growth but is toxic when present in excess. Arabidopsis BOR1 is a borate exporter, facilitating B translocation from root to shoot under limited-B conditions. BOR1 shows stele side polar localization in the plasma membrane of various root cells, presumably to support B translocation toward the stele. BOR1 is degraded under high-B supply through vacuolar sorting via ubiquitination at the K590 residue to prevent the accumulation of B to a toxic level in shoots. A previous study showed that overexpression of BOR1 under control of the cauliflower mosaic virus 35S RNA promoter improved the growth of Arabidopsis under limited-B conditions without affecting the growth under sufficient-to-excess-B conditions. In this study, we unexpectedly found that ubiquitous expression of a stabilized BOR1 variant improved tolerance to excess-B in Arabidopsis. We established transgenic plants expressing BOR1-GFP fused with hygromycin phosphotransferase (HPT) and BOR1(K590A)-GFP-HPT under control of the ubiquitin 10 promoter. BOR1-GFP-HPT and BOR1(K590A)-GFP-HPT were expressed in various cell types in leaves and roots and showed weak polar localization in root tip cells. BOR1-GFP-HPT, but not BOR1(K590A)-GFP-HPT, was degraded through an endocytic pathway under high-B conditions. Transgenic plants with the stabilized variant BOR1(K590A)-GFP-HPT showed improved root and shoot growth under excess-B conditions. The concentration of B was greater in the shoots of plants with BOR1(K590A)-GFP-HPT or BOR1-GFP-HPT than in those of untransformed wild-type plants. These results suggest that BOR1(K590A)-GFP-HPT confers tolerance to excess-B by excluding B from the cytosol of shoot cells. Results from this study indicate the potential for engineering the trafficking properties of a transporter to produce plants that are tolerant to mineral stress.

PubMed | Hokkaido UniversitySapporo and Hokkaido University
Type: | Journal: Frontiers in neuroscience | Year: 2016

To ensure survival, animals must update the internal representations of their environment in a trial-and-error fashion. Psychological studies of associative learning and neurophysiological analyses of dopaminergic neurons have suggested that this updating process involves the temporal-difference (TD) method in the basal ganglia network. However, the way in which the component variables of the TD method are implemented at the neuronal level is unclear. To investigate the underlying neural mechanisms, we trained domestic chicks to associate color cues with food rewards. We recorded neuronal activities from the medial striatum or tegmentum in a freely behaving condition and examined how reward omission changed neuronal firing. To compare neuronal activities with the signals assumed in the TD method, we simulated the behavioral task in the form of a finite sequence composed of discrete steps of time. The three signals assumed in the simulated task were the prediction signal, the target signal for updating, and the TD-error signal. In both the medial striatum and tegmentum, the majority of recorded neurons were categorized into three types according to their fitness for three models, though these neurons tended to form a continuum spectrum without distinct differences in the firing rate. Specifically, two types of striatal neurons successfully mimicked the target signal and the prediction signal. A linear summation of these two types of striatum neurons was a good fit for the activity of one type of tegmental neurons mimicking the TD-error signal. The present study thus demonstrates that the striatum and tegmentum can convey the signals critically required for the TD method. Based on the theoretical and neurophysiological studies, together with tract-tracing data, we propose a novel model to explain how the convergence of signals represented in the striatum could lead to the computation of TD error in tegmental dopaminergic neurons.

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