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Although variation among habitats in the ratio of gametophytes to sporophytes has been reported in various gigartinacean species, factors controlling the phase ratio remain poorly understood. Over 18 months, we examined the phase ratio of Chondrus ocellatus at three sites: a sheltered intertidal site, Hiruga A; an exposed intertidal site, Hiruga B; and a subtidal site, Shikimi. The mean proportion of gametophytes at Hiruga A (73.1%) was significantly higher than that at Shikimi (51.2%) and Hiruga B (44.7%). Due to a significantly higher water retention ability of the gametophytes, it was expected that the gametophytes would exhibit higher desiccation tolerance. After dehydration treatments, however, neither the photosynthetic rate of vegetative blades nor the survival rate of spores was significantly different between the phases. Measurements of blade strength indicated that the sporophytic blades were less stiff and more flexible, and a culture experiment revealed that the sporophytic germlings showed a significantly higher growth rate. Flexible blades and fast-growing germlings are considered advantageous for colonizing wave-swept intertidal habitats, so these properties may have caused the different fluctuation pattern of phase ratio among the sites. The present data demonstrate that biomechanical and physiological differences between the two phases of C. ocellatus make one phase advantageous in certain environmental conditions, and that these differences likely cause an unequal ratio of isomorphic phases.

Characterizing low-energy neutrons ( et al. (2020), this article newly presents and analyzes the data measured at the low operating voltage of 0.4 V. The dependence of SEU cross section on the neutron energy is similar between the operating voltages of 0.4 and 1.0 V, including onset energy of around 6 MeV. The existence of MCUs at 4.1-MeV neutrons was also confirmed at both the operating voltages. Based on the measurement, we approximate the dependence of SEU and MCU cross sections as Weibull functions of the neutron energy. The terrestrial SER of SEUs and MCUs was calculated by folding the Weibull function and the flux spectrum. The calculated result indicates that the SER originating from the low-energy neutrons is less than 6% in the terrestrial environment at New York and Tokyo City. We confirm that disregarding the flux of neutrons below 10 MeV in the acceleration factor calculation at accelerated neutron tests, which follows the current standard defined in JESD89, could give a reasonable SER estimation accuracy for both SEUs and MCUs. On the other hand, for covering the beams having an extremely high proportion of low-energy neutrons, considering the flux of neutrons above 6 MeV would be an option for better SER estimation.

Induced radioactivity is critical in a variety of fields including maintenance and decommissioning of accelerators and reactors, nuclear waste management, and radionuclide production for medical and industrial applications. Serving this purpose, DCHAIN-PHITS is the time-dependent radionuclide production, buildup, burnup, and decay code which is coupled to and distributed with the PHITS general purpose Monte Carlo particle transport code. While the core of the DCHAIN code was first written over forty years ago, the DCHAIN-PHITS incarnation of the code represents its most substantial update in nearly twenty years. This work provides an overview of the function of DCHAIN-PHITS and the new additions to the code. These additions include updated decay and cross section nuclear data libraries, statistical uncertainty propagation, support for tetrahedral and three-dimensional grid mesh geometries, reaction tracking capabilities, and general performance improvements.

Muon-induced single event upset (SEU) is predicted to increase with technology scaling. Although previous works investigated the dependencies of muon-induced SEU cross sections on energy, voltage, and technology, the angle of incidence of terrestrial muons is not always perpendicular to the chip surface. Consequently, the impact of the angle of incidence of muons on SEUs should be evaluated. This study conducts negative muon irradiation tests on bulk and fully depleted silicon on insulator static random access memories at two angles of incidence: 0° (vertical) and 45° (tilted). The tilted incidence drifts the muon energy peak to a higher energy as expected. However, the SEU characteristics in the bulk device between the vertical and tilted incidences, including the voltage dependences of the SEU cross sections and multiple cells upset patterns, are similar despite the unexpected impact on the SEU cross section at an operating voltage of 0.4 V.

Maintaining a certain number of spawning grounds for endangered fish is particularly important in rivers and streams where the environment changes drastically through floods and exploitations. Ryukyu-ayu Plecoglossus altivelis ryukyuensis is an endangered annual fish inhabiting the few streams and rivers flowing through the Amami-Oshima Island, southern Japan, and spawns in the lower reaches at sites with the specific riverbed conditions. In the island, resident volunteers along with researchers modify riverbed manually to provide conditions suitable for the natural spawning of the fish every year. This study investigated the effects of these activities on the riverbed conditions and consequently on the spawning by Ryukyu-ayu in two rivers. Our results showed that riverbed hardness and the amount of silt significantly decreased in the modified areas, but not in the adjacent unmodified areas. In one of the two rivers, the modification suppressed the settlement of net-spinning caddisfly larvae Stenopsyche schmidi that promote consolidation of the riverbed. The riverbed conditions in the modified areas were similar to those in the sites where P. a. ryukyuensis indeed spawned. These results suggest that manual modification is efficient in improving riverbed conditions for the spawning of Ryukyu-ayu. However, the eggs of the fish were not found at the modified areas in both rivers. It will be necessary to develop effective and practical ways of selecting sites for modification without obstructing the natural spawning in this fish.

The impact of the irradiation side on the cross sections of single-event upsets (SEUs) induced by neutrons was investigated by performing neutron irradiation measurements and simulations. A test board equipped with 65-nm bulk 6-T CMOS static random access memories was irradiated by quasi-monoenergetic neutrons, and the number of SEUs was counted. The number of SEUs obtained by the board-side irradiation was approximately 20% to 30% smaller than that obtained by irradiation on the plastic package side. We also investigated the impact of irradiation side on the soft error rates (SERs) obtained with by the terrestrial neutron energy spectrum via a Monte Carlo simulation. The SER obtained from the plastic package side irradiation was approximately twice that obtained for the board side irradiation, indicating that SERs can be reduced by equipping the device with the package side facing downward. Additionally, based on the simulation, the atomic composition of the material placed in front of the memory chip has a considerable influence on the SER because production yields and angular distributions of secondary H and He ions (the main causes of SEUs) depend on the composition. In particular, the existence of hydrides, such as plastic, considerably increases the SER because of the higher production yields of secondary H ions that are generated via elastic scattering of neutrons with hydrogen atoms.

Multiple-cell upset (MCU) in static random access memory (SRAM) is a major concern in radiation effects on very large scale integration (VLSI) since it can spoil error correcting codes (ECCs). Neutron-induced MCUs have been characterized for terrestrial environment. On the other hand, negative muon-induced MCUs, which are caused by secondary ions generated through muon capture process, were recently reported. Neutron- and negative muon-induced MCUs are both caused by secondary ions, and hence, they are expected to have some similarity. In this paper, we compare negative muon- and neutron-induced MCUs in 65-nm bulk SRAMs at the irradiation experiments using spallation and quasi-monoenergetic neutrons and monoenergetic negative muons. The measurement results show that the dependencies of MCU event cross section on operating voltage are almost identical. The high operating voltage makes both negative muon- and neutron-induced MCU cross sections larger due to parasitic bipolar action. Consequently, large-bit MCUs are observed under the irradiation using both neutrons and muons. On the other hand, at 0.4 V, neutrons induce larger-bit MCUs (> 12 bits) whereas negative muons cause up to 11-bit MCUs. Upsets of 3 or larger bits along word line (WL) are observed at spallation neutron beams. To explain the similarity of MCUs induced by neutrons and negative muons, the Monte Carlo simulation is conducted to investigate the deposited charge. The distributions of deposited charge obtained by the simulation are consistent with the above-mentioned experimental observations.

Negative and positive muon-induced single-event upset (SEU) rates were estimated for 65-nm bulk and ultrathin body and thin buried oxide silicon-on-insulator (UTBB-SOI) static random access memories (SRAMs). The SEU cross sections for muon incidence on the two SRAMs were experimentally characterized and compared. The experimental results showed that the negative muon SEU cross sections for the bulk SRAM are significantly larger than those for the UTBB-SOI. Estimation of muon SEU rates at ground level was performed using the experimental results and the Monte Carlo simulation with the Particle and Heavy Ion Transport code System (PHITS). The estimated muon SEU rates were compared with the measured neutron SEU rates. The contribution of muons was found to be considerably smaller than that of neutrons. Attenuation effect of muons and neutrons in a five-story building was also investigated by particle transport simulation with PHITS. The muon SEU rate on the first floor was estimated to be at most 10% of the neutron SEU rate on the same floor.

Although variation among habitats in the ratio of gametophytes to sporophytes has been reported in various gigartinacean species, factors controlling the phase ratio remain poorly understood. Over 18 months, we examined the phase ratio of Chondrus ocellatus at three sites: a sheltered intertidal site, Hiruga A; an exposed intertidal site, Hiruga B; and a subtidal site, Shikimi. The mean proportion of gametophytes at Hiruga A (73.1%) was significantly higher than that at Shikimi (51.2%) and Hiruga B (44.7%). Due to a significantly higher water retention ability of the gametophytes, it was expected that the gametophytes would exhibit higher desiccation tolerance. After dehydration treatments, however, neither the photosynthetic rate of vegetative blades nor the survival rate of spores was significantly different between the phases. Measurements of blade strength indicated that the sporophytic blades were less stiff and more flexible, and a culture experiment revealed that the sporophytic germlings showed a significantly higher growth rate. Flexible blades and fast-growing germlings are considered advantageous for colonizing wave-swept intertidal habitats, so these properties may have caused the different fluctuation pattern of phase ratio among the sites. The present data demonstrate that biomechanical and physiological differences between the two phases of C. ocellatus make one phase advantageous in certain environmental conditions, and that these differences likely cause an unequal ratio of isomorphic phases.

The impacts of hydrided and non-hydrided materials near transistors on neutron-induced single event upsets (SEUs) were investigated by simulating monoenergetic neutron irradiations on 65-nm technology bulk static random access memories. The onset energy of the SEUs induced by H ions depends on the shielding capability, i.e., the material and thickness, of components placed in front of transistors when those components do not contain hydrogen atoms. The shielding capability also influences the initial slope observed in the energy-dependence of SEU cross sections. Taking into account the non-hydrided component attached to memory cells used in the simulation, all experimental data measured at each neutron facility were reproduced well using SEU cross sections obtained by simulation. We also find that the effect of components near transistors on neutron-induced soft error rates is not negligible even for irradiation by white neutrons.

We have performed an irradiation test of low-energy positive and negative muons on 65-nm ultra-thin body and thin buried oxide silicon-on-insulator static random access memories. The single event upset (SEU) cross sections were measured systematically as a function of incident muon momentum and operating supply voltage. The experimental results show that the negative muon SEUs occur at about three times higher rate than the positive muon ones at the supply voltage of 0.5 V when the incident muons stop near the sensitive volume (SV). A Monte-Carlo simulation with the particle and heavy ion transport code system (PHITS) was carried out using a simple SV model. The simulation based on the PHITS using the SV model is found to reproduce generally well the momentum dependence of the measured SEU cross sections for both positive and negative muons. From the simulation, the charged particles and secondary ions having significant influence on SEUs are specified and the differences between negative and positive muons are discussed.

Irradiation experiments of positive and negative muon were conducted for 65-nm bulk CMOS static random-access memory. The experimental results reveal that parasitic bipolar action (PBA) contributes to negative muon-induced upsets. We observe an increase in single event upset (SEU) cross section at higher operation voltage under negative muon irradiation while positive muon shows an opposite decreasing tendency. Also, the proportion of multiple-cell upset (MCU) events to all the negative muon-induced upset events is up to 66, and more than a 20-bit MCU is observed. Furthermore, Monte Carlo simulation of particle and heavy ion transport code system (PHITS) is performed for explaining the difference in SEU between positive and negative muons. We also discuss the charge threshold that triggers PBA-induced MCU using measurement and simulation results with different momentum muons. The estimated threshold is much larger than the charge that the positive muons can deposit, which well explains that no PBA-induced MCUs are observed under positive muon irradiation.

We have upgraded many features of the Particle and Heavy Ion Transport code System (PHITS) and released the new version as PHITS3.02. The accuracy and the applicable energy ranges of the code were ...

We performed a benchmark study for 58 cases (22 cases reported in this paper and 36 cases reported in online as supplementary materials of this paper) using the recent version (version 2.88) of the Particle and Heavy-Ion Transport code System (PHITS) in the following fields: (1) particle production cross-sections for nuclear reactions from 20 MeV to 1 GeV, (2) thick-target neutron yields and neutron shielding, (3) depth–dose distribution in water using 12C beam, and (4) electron and photon transportation over a wide-energy range from keV to GeV. Overall agreements were found to be sufficiently satisfactory; however, several discrepancies are observed, particularly in particle productions with energies below 100 MeV, neutron production for 7Li(p,n)7Be, and photonuclear reactions. To overcome these inaccuracies and to further improve the code, it will be necessary to incorporate a high-energy version of the evaluated nuclear data library JENDL-4.0/HE and the photonuclear data file JENDL-PD in the PHITS package.

In this paper, we compare the negative and positive muon-induced SEU event cross sections of 28-nm and 65-nm planar bulk CMOS SRAMs. Our measurement results show a 3.6 X increase in muon-induced SEU event cross section from 65-nm to 28-nm technology, and negative muon-induced SEU event cross section is 3.3 X larger compared to positive muons at 28-nm technology. This result is consistent with the previous works reporting muon-induced SEU event cross section increases with technology scaling. The measured result also suggests the contribution of direct ionization to the total SEU event cross section is 54.1% at 28-nm node with operating voltage of 0.6 V while it is 1.8% at 65-nm node with 0.9 V.

We have constructed models for muon interactions (i.e., bremsstrahlung, electron–positron pair production, muon photonuclear interaction, and negative muon capture reaction) and implemented these models in the particle and heavy ion transport code system (PHITS). The PHITS2.86 agrees well with experimental data for the vertical intensities of cosmic-ray muons in water and standard rock. The calculated results for neutron production by muon photonuclear interaction and negative muon capture reaction are in good agreement with measured data, except in the case of lead target. PHITS2.86 can also reproduce the cross-section of radionuclide production by muons passing through a concrete wall very well. These results indicate the applicability of PHITS2.86 to the shielding design of muon facilities in which estimations of attenuation length and induced radioactivity are important.

A neutron irradiation test of static random access memories (SRAMs) was performed using a spallation neutron source at Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). The probability of neutron-induced single-event upsets (SEUs) was measured for 65-nm bulk and silicon on thin buried oxide (SOTB) SRAMs under neutron irradiation at the BL10 experimental facility. The measured SEU data were compared with the previous data of the same SRAMs which were measured at other irradiation facilities having different neutron spectra. The differences in the operating voltage dependence of the measured SEU probabilities are discussed with particular attention to the impact of irradiation side on SEUs. The particle and heavy ion transport code system (PHITS) simulation based on the simple sensitive volume model qualitatively reproduced the operating voltage dependence seen in the measured ratio of SEUs for the Bulk SRAM between the resin side and board side irradiations under different neutron fields.

Secondary cosmic-ray neutron-induced soft errors in an n-type metal-oxide-semiconductor field-effect transistor are analyzed based on the multiple sensitive volume (MSV) model using Particle and He...

Ayu Plecoglossus altivelis, a herbivorous fish, is an important fishery resource and key component of the foodweb in many Japanese streams. Radionuclide contamination of this species is likely transferred to higher trophic levels, include humans, in the food chain. After the Fukushima accident in March 2011, ayu were exposed to highly contaminated silt while feeding on algae attached to the riverbed stones. To understand the route by which herbivorous fish are exposed to radionuclides, the activity concentrations of sum of (134)Cs and (137)Cs (radiocesium) were analyzed in riverbed samples (algae and silt) and in the internal organs and the muscle of ayu in five river systems in the Fukushima Prefecture between summer 2011 and autumn 2013. Although there was a positive correlation between the radiocesium activity concentrations in the muscle and the internal organs of ayu, the median activity concentration in the muscle was much lower than those in the internal organs. The activity concentrations of radiocesium in the riverbed samples and the internal organs and the muscle of ayu were correlated with contamination levels in soil samples taken from the watershed upstream of the sample sites. The results of the generalized linear mixed models suggest that the activity concentrations in both the internal organs and the muscle of ayu declined over time. Additionally, the activity concentrations in the internal organs were correlated with those in the riverbed samples that were collected around the same time as the ayu. The activity concentrations in the muscle were correlated with ayu body size. Our results suggest that ayu ingest (134)Cs and (137)Cs while grazing silt and algae from the riverbed, and a part of the (134)Cs and (137)Cs is assimilated into the muscle of the fish.

With the aim of providing critical nuclear data of primary knock-on atoms (PKAs) created from proton-induced spallation reactions, a new detection system was designed and dedicated to the PKA measurement that requires lower measurement threshold energies and superior mass resolution than the conventional experimental setups. Such requirements can be fulfilled by employing the TOF-E and dE-E methods, and this new PKA detection system, which consists of two fast timing detectors and one dE-E gas ionization detector. The design of the detectors and the experimental setup, along with the estimated system performed are briefly described in this paper.

The Particle and Heavy Ion Transport code System, PHITS, has been developed under the collaboration of several research institutes in Japan and Europe. This system can simulate the transport of most particles with energy levels up to 1 TeV (per nucleon for ion) using different nuclear reaction models and data libraries. More than 2,500 registered researchers and technicians have used this system for various applications such as accelerator design, radiation shielding and protection, medical physics, and space- and geo-sciences. This paper summarizes the physics models and functions recently implemented in PHITS, between versions 2.52 and 2.88, especially those related to source generation useful for simulating brachytherapy and internal exposures of radioisotopes.

Neutron-induced single event upsets (SEUs) in a 25-nm NMOSFET are analyzed using PHYSERD simulation. We confirm that the secondary H and He ions dominate SEUs above the threshold energies of (n,p) and ( n, α) reactions although the production cross sections for H and He ions are smaller than the elastic scattering cross sections below 20 MeV. The SEUs induced by secondary H and He ions are influenced strongly by the size of the interaction volume considered in the simulation because the ranges of H and He ions are much longer than those of elastic recoils.

Terrestrial neutron-induced soft error rate (SER) analyses in the 25-nm design rule MOSFET are performed by means of multiscale Monte Carlo simulation with different nuclear reaction models used in PHITS code. It is clarified that a choice of nuclear reaction models has a great effect on the SER prediction. Even if the calculated production cross sections for secondary ions are the same among different reaction models, the difference in double-differential cross sections results in essential impact on the calculated SERs. Through validation of the nuclear reaction models used in PHITS code, it is concluded that the combined use of the e-mode with JENDL-4.0 below 20 MeV and the MQMD plus GEM above 20 MeV is the most suitable for the soft error simulation.

Summary We examined the relationship between the δ13C and taxonomic composition of benthic algae collected from a riffle (fast current habitat) of a non-shaded mountain stream, which is a tributary of the Kiso River, Japan. The benthic algal δ13C ranged from −20.6 to −14.2‰ and tended to be 13C-depleted with increasing relative abundance of upright filamentous cyanobacteria and 13C-enriched with increasing relative abundance of prostrate filamentous cyanobacteria. Using isotopic mass balance equations, the relative abundance of the dominant taxa, upright and prostrate filamentous cyanobacteria, small diatoms and others, explained 74% of δ13C variability. This study shows a case where the difference in taxonomic composition is a possible source of the isotopic variability of benthic algae, which is a mixture of taxa with distinct isotopic signatures.

The Fukushima nuclear accident led to deposition of radionuclides into the freshwater fishery ground of ayu Plecoglossus altivelis. For the purpose of more comprehensive understanding of the radioactive contamination, cesium-137 (137Cs) was analyzed in running water, muddy sediment, attached algae, and ayu using samples from three river systems with different levels of contamination within Fukushima Prefecture in summer and autumn 2011. The amount of 137Cs contained in water as well as in sediment declined over an interval of two months, although the concentration in sediment samples was up to 10,000-fold higher than that in water samples. The changes in 137Cs concentration of algae showed different courses among the three river systems, the concentration being greater in autumn in the river systems with high and moderate radioactive contamination. 137Cs detected within a single stock of ayu appeared to be excreted rather rapidly with a calculated half-life of approximately 39 days, while the concentration ratio ranged from 103 to 104 l/kg, attaining higher levels than previously reported. These findings indicate that the most important pathway of 137Cs into ayu is via intake of algae as food but that the retention time of 137Cs inside ayu is relatively short.

Transports of secondary cosmic-ray neutrons and muons in a building and a stacked server are simulated by Particle and Heavy Ion Transport code System (PHITS) with considering distributions of energy and zenith-angle of secondary cosmic-rays by PHITS based analytical radiation model in the atmosphere (PARMA) model. The calculated neutron fluxes are in surprisingly good agreement with measured data. Soft errors in an n-type metal-oxide-semiconductor field-effect transistor caused by secondary cosmic-ray neutron and muon in the open air and on the first floor of the building are analyzed based on the multiple sensitive volume (MSV) model using PHITS. It is found that the secondary cosmic-ray neutron-induced SER decrease by shielding effect of the building while that caused by secondary cosmic-ray muons is not affected.

We report the results of a multicenter phase 1 dose-escalation study of the selective Bruton tyrosine kinase (BTK) inhibitor ONO/GS-4059 in 90 patients with relapsed/refractory B-cell malignancies. There were 9 dose-escalation cohorts ranging from 20 mg to 600 mg once daily with twice-daily regimens of 240 mg and 300 mg. Twenty-four of 25 evaluable chronic lymphocytic leukemia (CLL) patients (96%) responded to ONO/GS-4059, with a median treatment duration of 80 weeks; 21 CLL patients remain on treatment. Lymph node responses were rapid and associated with a concurrent lymphocytosis. Eleven of 12 evaluable patients with mantle cell lymphoma (92%) responded (median treatment duration, 40 weeks). Eleven of 31 non-germinal center B-cell diffuse large B-cell lymphoma patients (35%) responded but median treatment duration was 12 weeks due to development of progressive disease. ONO/GS-4059 was very well tolerated with 75% of adverse events (AEs) being Common Toxicity Criteria for Adverse Events version 4.0 grade 1 or grade 2. Grade 3/4 AEs were mainly hematologic and recovered spontaneously during therapy. One CLL patient experienced a grade 3 treatment-related bleeding event (spontaneous muscle hematoma) but no clinically significant diarrhea, cardiac dysrhythmias, or arthralgia were observed. No maximal tolerated dose (MTD) was reached in the CLL cohort. In the non-Hodgkin lymphoma cohort, 4 patients developed a dose-limiting toxicity, yielding an MTD of 480 mg once daily. ONO/GS-4059 has significant activity in relapsed/refractory B-cell malignancies without major drug-related toxicity. The selectivity of ONO/GS-4059 should confer advantages in combination therapies. This trial was registered at www.clinicaltrials.gov as #NCT01659255.

We have proposed a multi-scale Monte Carlo simulation method of neutron induced soft errors by linking a particle transport code PHITS and a 3-D TCAD simulator HyENEXSS. An interface tool between PHITS and HyENEXSS is developed to generate the mesh structure optimized for an event where multiple secondary ions extending to arbitrary directions are generated simultaneously by neutron incidence on device. Using the interface tool, we have made it possible to perform the Monte Carlo calculation of soft error rates (SERs) based on event-by-event device simulation. The PHITS-HyENEXSS code system has been successfully applied to SER analyses for 65 nm, 45 nm, and 32 nm technology MOSFETs.

– Social and foraging modes in fish often vary between individuals with different body sizes and between populations under different ecological conditions. We studied social and foraging behaviour of algae-grazing fish Plecoglossus altivelis ryukyuensis (Ryukyu-ayu) inhabiting Japanese subtropical island streams. Ryukyu-ayu exhibited four behavioural modes: territorial, schooling, solitary and floating. Their body sizes differed among these modes. Territorial fish predominantly foraged on benthic algae, whereas schooling and solitary individuals frequently consumed drifting materials as well. Schooling fish were smaller than territorial fish, but, unlike some other algae-grazing fish species, did not use schooling to gain access to food within territories. Territorial fish attacked smaller conspecifics but exhibited lateral display towards larger fish and schooling fish while occasionally attacking grazing gobies. Larger fish maintained larger feeding territories and occupied territories for longer periods than smaller fish did. This suggests that, in Ryukyu-ayu, intra- and interspecific food competitions and relative body size can influence diverse behavioural modes and duration of territory occupation. We also found that Ryukyu-ayu foraged more often and had larger feeding territories than ayu P. a. altivelis inhabiting temperate streams. We conclude that foraging strategies of Ryukyu-ayu may have adapted to subtropical island streams, where algal productivity is much lower than that in temperate regions.

Rice-fish culture, which means the simultaneous culture of rice and fish, is one of the best options to increase food production from limited land and is practiced in many countries in the world. Although many researchers and farmers believe that the rice yield is increased by fish farming in paddy fields, this hypothesis has never been fully tested. Here, we report ecological processes leading to higher rice yields in the rice-fish culture using crucian carp (Carassius complex), which have adapted to the paddy field ecosystem in Japan. We compare the rice-fish and rice-only plots in the experimental paddy field for biota, water quality, and rice yield. Coverage of duckweed and densities of zooplankton and benthic invertebrates in the rice-fish plots were lower than those in the rice-only plots, indicating that fish utilized them as food. NO3–N concentration in the rice-fish plots was higher than that in the rice-only plots, indicating that the increase in NO3–N concentration results from excretion of unutilized food nutrients by the fish. Consequently, rice yield in the rice-fish plots was 20% higher than that in the rice-only plots. The fertilizing effect of the fish excrement probably increased rice yield.

Ecological characteristics of Japanese dace Tribolodon hakonensis were investigated in three small streams in Niigata Prefecture from 2001 to 2005 with special reference to the effect of Ayu Plecoglossus altivelis altivelis on the dace. Japanese dace were distributed in short sections below dams near the mouth of the streams flowing into the Sea of Japan. In this section, Ayu were numerically dominant from June to August, and the growth rate of dace in this period was negatively correlated with the density of Ayu. The population density of dace was high in October, but some adults stayed in the streams in June and August. When data for the five years were combined, the density of dace was negatively correlated with that of Ayu in two of the three streams. The increase in density of dace in October is considered to be due to the migration of dace from the sea. Eight dace were confirmed to migrate to different streams via the sea. Therefore, the life history of Japanese dace in the study region contained considerable individual variation.

1. Animals exploiting different resources may nevertheless interact if one species indirectly alters the abundance and distribution of the food of the other. To analyse this indirect effect, we conducted experiments in artificial pools and in the field to investigate the influence of the algivorous fish Plecoglossus altivelis altivelis (known as the ayu) on two species of insectivorous benthic fish, Pseudogobio esocinus esocinus and the goby Gymnogobius petschiliensis. 2. In the pool experiments, algal biomass was not correlated with the number of ayu, but the percentage of blue-green bacteria rose as the number increased. The number of aquatic macroinvertebrates on the upper surface of ceramic tiles placed in the pool bed decreased as the number of ayu increased. 3. Although ayu and the benthic species did not interact directly, the reduction in invertebrate abundance on the upper surface of tiles in the pool reduced the growth rate of the benthic insectivores. 4. In field experiments, the introduction of ayu into habitats with P. esocinus esocinus or G. petschiliensis reduced the growth rate of these benthic fish. In the field experiment that was carried out over 5 years in the G. petschiliensis habitat, the population density of the goby decreased when ayu were stocked. 5. The ayu is a strong interactor or bioengineer in streams, affecting not only benthic algae but also aquatic invertebrates and fishes. We conclude that to predict the outcome of interspecific interactions amongst fishes in streams with high algal production, possible indirect effects must be considered alongside better known direct effects.

Summary 1. In an experimental flume, we examined the effects of a biomass reduction and alteration of taxonomic composition, because of grazing by the fish Plecoglossus altivelis, on the net biomass accumulation of periphyton. 2. Grazed and ungrazed assemblages with different biomass and taxonomic composition were first prepared in fish enclosures and exclosures, respectively. These assemblages were then set out in the flume and incubated for 2 days under grazing-free conditions to examine (i) the relationship between biomass and biomass accumulation rate and (ii) the effect of taxonomic composition on the relationship between these two. 3. The grazed and ungrazed assemblages were dominated by upright filamentous cyanobacteria and diatoms, respectively. The rate of biomass accumulation decreased with increasing periphyton biomass in both the grazed and ungrazed assemblages, and was lower in the grazed than the ungrazed assemblages at any biomass level. 4. The results showed that the reduction in biomass and the alteration of taxonomic composition due to fish grazing have opposite effects on biomass-specific productivity. Biomass accumulation rate increased in response to biomass reduction, although a shift in dominance from diatoms to upright filamentous cyanobacteria decreased the overall productivity of the periphyton.

The great cormorant (Phalacrocorax carbo hanedae) is one of the largest piscivorous water birds in Japan. It is in the phase of recovery from a long-term decline in the numbers, with its population drastically increasing throughout Japan. This potentially impacts cormorant’s predation conflicts with inland fisheries. Recent cormorant migrants often appear to inhabit more urbanized areas although the species once preferred habitats remote from human activities. This novel dwelling preference remains unexplained. The present study aimed to understand the processes promoting their expansion, especially focusing on those that help acquire foraging success in urban habitats. Measurements on primary production in aquatic ecosystem did not detect superiority of urban habitats over rural ones. This indicates that exploitation of a habitat by cormorants is less explicable by the potential food richness. Our field survey revealed that more urbanized habitats provided more frequent contacts with pedestrians who were indifferent to wildlife, potentially allowing cormorants’ habituation to humans. The degree of tolerance to human-associated disturbances in cormorants was measured using flight-initiation distance (FID) defined as a distance at which an individual animal moves away from an approaching human. Urban cormorants showed shorter FID than those in the rural habitats suggesting that reduced threshold of risk-avoidance against approaching humans could be implicated in the increase in foraging opportunities. Our results suggest that recent urban environments are selectively advantageous for cormorants as new habitats.

We investigate the soft error rate (SER) deviations at sea level between calculation with JEDEC spectrum and measurements at acceleration test facilities. The ratio of SER calculated with the test facility's spectrum to that with the JEDEC spectrum is provided as a function of critical charge. This ration is used for estimation of the SER at sea level from the SER measured at test facilities. Single event upset (SEU) cross-sections necessary in derivation of the SER ratio are given by a multi-scale (particle transport and 3D TCAD) Monte Carlo simulation. Finally, the SER ratio is verified through acceleration tests in three facilities.

Ayu, Plecoglossus altivelis, is a herbivorous fish that is an important fishery resource and a key component of the food web in many Japanese streams. After the Fukushima Daiichi Nuclear Power Plant (FNPP) accident in March 2011, ayu were exposed to highly contaminated silt while feeding on benthic microalgae attached to riverbed stones. To understand the effects of radioactive contamination on ayu, radiocesium (134Cs + 137Cs) concentrations were analyzed in riverbed samples (microalgae and silt) and in the internal organs and muscle of ayu in five river systems in the Fukushima Prefecture between summer 2011 and autumn 2013. The concentrations of radiocesium in both the internal organs and the muscles of ayu declined over time. The radiocesium concentrations in the muscle were correlated with, but much lower than, those in the internal organs. The concentrations in the internal organs were correlated with those in the riverbed samples. The concentrations in the muscle were further correlated with ayu body size. Our results suggest that ayu ingest radiocesium while consuming silt and microalgae from the riverbed, and that a small proportion (about 15 %) is assimilated into the muscle of the fish.

Densities of two sympatric amphidromous grazing fishes, Plecoglossus altivelis and Sicyopterus japonicus, and gross primary production of benthic algae were investigated at the second, third and fourth-order sites located, respectively, 7.0, 6.7 and 3.6 km from the mouth of the Choshi River, Japan. Gross primary production estimated by multiplying gross photosynthetic rates by hours of insolation on the streambed increased downstream with decreasing canopy cover by valley walls and trees standing along the river. Density of P. altivelis was greatest at the fourth-order site with the higher primary production, while the distribution pattern of S. japonicus differed between adult (> ca. 7 cm in total length) and young individuals. Density of adult of S. japonicus was greater at the third-order site, although the young were more abundant at the fourth-order site. Aggressive acts against conspecifics and different species were observed only by adults of S. japonicus and most frequently observed at the third-order site. The upstream shift in the distribution of the adults of S. japonicus would mitigate interference competition with P. altivelis and contribute to their coexistence in the river.

SUMMARY Grazing effects of ayu, Plecoglossus altivelis Temminck et Schegel, on the benthic algal assemblages were investigated in the Chikuma River, Japan. Comparison of the algal composition on boulders with and without intensively grazed patches indicated that fish grazing decreased the abundance of diatoms and prostrate filamentous cyanobacteria and caused upright filamentous cyanobacteria to predominate. Differential consumption by ayu was estimated by comparing the relative abundance of algae in the stomach contents of ayu and that in the algal assemblages within the grazed patches. The results showed that ayu consumed the prostrate filamentous cyanobacteria proportionally to their abundance, whereas they ingested diatoms and the upright filamentous cyanobacteria in a larger and lower quantity, respectively, than that expected from their abundance. Differential consumption would involve the change in the algal composition toward the predominance of upright filamentous cyanobacteria under fish grazing conditions.

The local density of the grazing goby (Sicyopterus japonicus) and benthic algal production were investigated in a 720 m reach of the Sate River in the northern part of Okinawa Island, Japan. The reach was spatially heterogenous in riparian shade and was divided into three segments (open-canopy, shaded and patchy segment) based on vegetation cover. In the reach, the goby was more abundant in the open-canopy segment and open-canopy patches than in the adjacent shaded segment and shaded patches. Between the open-canopy and shaded segments there was no significant difference in the algal biomass; however, the algal growth rate was greater in the open-canopy segment than in the shaded segment. These results indicate that the spatial heterogeneity in riparian shade controls the habitat use of the goby, with open-canopy areas with high algal renewal rates being preferred.