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Hokkaido University Collection of Scholarly and Academic Papers (135.521 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

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Mostrando recursos 1 - 20 de 370

  1. Estimation of Evolutionary Rates of Mitochondrial DNA in Two Japanese Wood Mouse Species Based on Calibrations with Quaternary Environmental Changes

    Hanazaki, Kaori; Tomozawa, Morihiko; Suzuki, Yutaro; Kinoshita, Gohta; Yamamoto, Masanobu; Irino, Tomohisa; Suzuki, Hitoshi
    Reliable estimates of evolutionary rates of mitochondrial DNA might allow us to build realistic evolutionary scenarios covering broad time scales based on phylogenetic inferences. In the present study, we sought to obtain estimates of evolutionary rates in murine rodents using calibrations against historical biogeographic events. We first assumed that land-bridge-like structures that appeared intermittently at glacial maxima with 100,000-year intervals shaped the divergence patterns of cytochrome b (Cytb) sequences (1140 bp) of the larger Japanese wood mouse Apodemus speciosus. The comparison of sequences from peripheral remote islands that are separated from one another by deep straits allowed us to estimate...

  2. A multistate dynamic site occupancy model for spatially aggregated sessile communities

    Fukaya, Keiichi; Royle, J. Andrew; Okuda, Takehiro; Nakaoka, Masahiro; Noda, Takashi
    1. Estimation of transition probabilities of sessile communities seems easy in principle but may still be difficult in practice because resampling error (i.e. a failure to resample exactly the same location at fixed points) may cause significant estimation bias. Previous studies have developed novel analytical methods to correct for this estimation bias. However, they did not consider the local structure of community composition induced by the aggregated distribution of organisms that is typically observed in sessile assemblages and is very likely to affect observations. 2. We developed a multistate dynamic site occupancy model to estimate transition probabilities that accounts for...

  3. Spatio-temporal assessment and trend analysis of surface water salinity in the coastal region of Bangladesh

    Shammi, Mashura; Rahman, Md. Mostafizur; Islam, Md. Atikul; Bodrud-Doza, Md.; Zahid, Anwar; Akter, Yeasmin; Quaiyum, Samia; Kurasaki, Masaaki
    The study was designed to collect water samples over two seasons-wet-monsoon season (n = 96) (March-April) and dry-monsoon season (n = 44) (September October)-to understand the seasonal variation in anion and cation hydrochemistry of the coastal rivers and estuaries contributing in the spatial trend in salinity. Hydrochemical examination of wet-monsoon season primarily revealed Ca-MgHCO3 type (66%) and followed by Na-Cl type (17.70%) water. In the dry-monsoon season, the scenario reversed with primary water being Na-Cl type (52.27%) followed by Ca-Mg-HCO3 type (31.81%). Analysis of Cl/Br molar ratio vs. Cl (mg/L) depicted sampling area affected by seawater intrusion (SWI). Spatial analysis...

  4. Improved automatic estimation of winds at the cloud top of Venus using superposition of cross-correlation surfaces

    Ikegawa, Shinichi; Horinouchi, Takeshi
    Accurate wind observation is a key to study atmospheric dynamics. A new automated cloud tracking method for the dayside of Venus is proposed and evaluated by using the ultraviolet images obtained by the Venus Monitoring Camera onboard the Venus Express orbiter. It uses multiple images obtained successively over a few hours. Cross-correlations are computed from the pair combinations of the images and are superposed to identify cloud advection. It is shown that the superposition improves the accuracy of velocity estimation and significantly reduces false pattern matches that cause large errors. Two methods to evaluate the accuracy of each of the...

  5. Basin-scale distribution of prokaryotic phylotypes in the epipelagic layer of the Central South Pacific Ocean during austral summer

    Tada, Yuya; Shiozaki, Takuhei; Ogawa, Hiroshi; Suzuki, Koji
    In the present study, we used catalyzed reporter deposition-fluorescence in situ hybridization to quantify the abundance of five bacterial (Alphaproteobacteria, SAR11, Gammaproteobacteria, SAR86, and Bacteroidetes) and two archaeal (Crenarchaeota and Euryarchaeota) phylotypes in the epipelagic layer (0-200 m) of the Central South Pacific Ocean along 170A degrees W from 0A degrees to 40A degrees S. We found that the distribution patterns of these phylotypes differed from each other. All phylotypes except Gammaproteobacteria were particularly abundant at the surface water of the equatorial region, whereas Gammaproteobacteria was relatively abundant in the area from the southern part of the South Pacific Ocean....

  6. Cytotoxic effects of cadmium and zinc co-exposure in PC12 cells and the underlying mechanism

    Rahman, Md. Mostafizur; Ukiana, Junki; Uson-Lopez, Rachael; Sikder, Md. Tajuddin; Saito, Takeshi; Kurasaki, Masaaki
    Cadmium (Cd2+) is a well studied inducer of cellular necrosis and apoptosis. Zinc (Zn2+) is known to inhibit apoptosis induced by toxicants including Cd2+ both in vitro and in vivo. The mechanism of Zn2+-mediated protection from Cd2+-induced cytotoxicity is not established. In this study, we aimed to understand the effects of Zn2+ on Cd2+-induced cytotoxicity and apoptosis using PC12 cells. Cell viability and DNA fragmentation assays in PC12 cells exposed to Cd2+ and/or Zn2+ revealed that Cd2+ (5 and 10 μmol/L) alone induced significant cell death, and co-exposure to Zn2+ (5, 10, and 100 μmol/L) for 48 h had a...

  7. Investigation of Chromium Removal Efficacy from Tannery Effluent by Synthesized Chitosan from Crab Shell

    Hossain, Kaniz Fatima Binte; Sikder, Md. Tajuddin; Rahman, Md. Mostafizur; Uddin, Md. Khabir; Kurasaki, Masaaki
    The efficiency of chromium removal from tannery effluents using prepared crab shell chitosan was studied. Adsorption of Cr by chitosan was investigated at various contact times, pH values, adsorbent dosages, and temperatures. The amount of Cr adsorbed under different conditions was evaluated using atomic adsorption spectroscopy (AAS). Subsequently, the changes in the physicochemical parameters were also examined. It was found that the total dissolved solids (TDS), electrical conductivity (EC), and turbidity of the tannery effluent decreased significantly after treatment with crab shell chitosan. No significant changes were found after different soaking times; in most cases, the best adsorption was achieved...

  8. Climate reconstruction based on GDGT-based proxies in a paleosol sequence in Japan: Postdepositional effect on the estimation of air temperature

    Yamamoto, Yasuto; Ajioka, Taku; Yamamoto, Masanobu
    We investigated branched and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) in surface soils and a paleosol sequence to understand the effects of environmental and postdepositional factors on branched GDGT composition in different soil types and to reconstruct the past changes in the mean annual air temperature (MAAT) in southwestern Japan during the last 15 ka. The estimated MAAT was overestimated by 6 degrees C and 2 degrees C when the global and regional soil calibrations were applied, respectively. Additionally, the estimated MAAT increased downward by a maximum of 4 degrees C in the upper 30 cm of the soil sequence....

  9. Potential of Micranthemum umbrosum for phytofiltration of organic arsenic species from oxic water environment

    Islam, Md Shariful; Sikder, M. Tajuddin; Kurasaki, Masaaki
    Arsenic (As) is a toxic and carcinogenic metalloid that causes various hazards to human health. Phytofiltration is a more eco-friendly and green approach than chemoremediation, or other traditional technologies, for removing As from aquatic environments. Recently, Micranthemum umbrosum was shown as a promising candidate for phytofiltration of inorganic As species. This work examines the potential application of M. umbrosum to phytofiltration of organic As species, such as monomethylarsonic acid (MMAA, CH5AsO3) and dimethylarsinic acid (DMAA, C2H7AsO2), from oxic water environments. M. umbrosum plants were grown in two test concentrations of MMAA and DMAA, or a control, in a hydroponic experiment....

  10. Distribution and Sources of Dissolved Black Carbonin Surface Waters of the Chukchi Sea, Bering Sea, and the North Pacific Ocean

    Nakane, Motohiro; Ajioka, Taku; Yamashita, Youhei
    Pyrogenic carbon, also called black carbon (BC), is an important component in the global carbon cycle. BC produced by biomass burning or fossil fuel combustion is transported to oceans by the atmosphere or rivers. However, environmental dynamics (i.e., major sources and sinks) of BC in marine environments have not been well-documented. In this study, dissolved BC (DBC) collected from surface waters of the Chukchi Sea, the Bering Sea, and the subarctic and subtropical North Pacific were analyzed using the benzene polycarboxylic acid (BPCA) method. The DBC concentration and the ratio of B5CA and B6CA to all BPCAs (an index of...

  11. The function of appendage patterning genes in mandible development of the sexually dimorphic stag beetle

    Gotoh, Hiroki; Zinna, Robert A.; Ishikawa, Yuki; Miyakawa, Hitoshi; Ishikawa, Asano; Sugime, Yasuhiro; Emlen, Douglas J.; Lavine, Laura C.; Miura, Toru
    One of the defining features of the evolutionary success of insects is the morphological diversification of their appendages, especially mouthparts. Although most insects share a common mouthpart ground plan, there is remarkable diversity in the relative size and shapes of these appendages among different insect lineages. One of the most prominent examples of mouthpart modification can be found in the enlargement of mandibles in stag beetles (Coleoptera, Insecta). In order to understand the proximate mechanisms of mouthpart modification, we investigated the function of appendage-patterning genes in mandibular enlargement during extreme growth of the sexually dimorphic mandibles of the stag beetle...

  12. Foraging responses of bumble bees to rewardless floral patches: importance of within-plant variance in nectar presentation

    Nakamura, Shoko; Kudo, Gaku
    Spatiotemporal variation in nectar distribution is a key factor affecting pollinator movements between flowers and plants within a population. Pollinators having systematic searching ability can flexibly respond to the reward condition of floral patches, and they tend to revisit rewarding patches. However, foraging behaviour may be influenced by the nectar distribution within populations. To evaluate the effects of unrewarding experiences and plant distribution, we compared bumble bee foraging behaviours between naturally rewarding and artificially rewardless (by nectary removal) patches in two aconite populations with different plant densities. Visitation frequency to the patches, number of successive flower visits within inflorescences, and...

  13. A framework for quantifying the relationship between intensity and severity of impact of disturbance across types of events and species

    Iwasaki, Aiko; Noda, Takashi
    Understanding the impacts of natural disturbances on wildlife populations is a central task for ecologists; in general, the severity of impact of a disturbance (e.g., the resulting degree of population decline) is likely to depend primarily on the disturbance intensity (i.e., strength of forcing), type of disturbance, and species vulnerability. However, differences among disturbance events in the physical units of forcing and interspecific differences in the temporal variability of population size under normal (non-disturbance) conditions hinder comprehensive analysis of disturbance severity. Here, we propose new measures of disturbance intensity and severity, both represented by the return periods. We use a...

  14. Environmental factors determining the distribution of highland plants at low-altitude algific talus sites

    Wakui, Akimi; Sueyoshi, Masanao; Shimokawabe, Ayuma; Kudo, Gaku; Morimoto, Junko; Nakamura, Futoshi
    Algific talus is a micro-scale habitat type where highland plants (subalpine and alpine species) are found, disjunct from their typical range, in lowland forests. On algific talus, cold airflows from the interstices between talus fragments create a local microclimate colder than surrounding forests. Despite of the widely-known occurrence of unique vegetation on algific talus, critical environmental factors determining the distribution of highland species in this habitat type are unclear. In order to reveal the environmental factors enabling highland species to inhabit algific talus, we investigated the vegetation and environments of 26 algific talus sites and four reference (non-algific talus) sites...

  15. Can preferred atmospheric circulation patterns over the North-Atlantic-Eurasian region be associated with arctic sea ice loss?

    Crasemann, Berit; Handorf, Doerthe; Jaiser, Ralf; Dethloff, Klaus; Nakamura, Tetsu; Ukita, Jinro; Yamazaki, Koji
    In the framework of atmospheric circulation regimes, we study whether the recent Arctic sea ice loss and Arctic Amplification are associated with changes in the frequency of occurrence of preferred atmospheric circulation patterns during the extended winter season from December to March. To determine regimes we applied a cluster analysis to sea-level pressure fields from reanalysis data and output from an atmospheric general circulation model. The specific set up of the two analyzed model simulations for low and high ice conditions allows for attributing differences between the simulations to the prescribed sea ice changes only. The reanalysis data revealed two...

  16. Total synthesis and biological activity of dolastatin 16

    Casalme, Loida O.; Yamauchi, Arisa; Sato, Akinori; Petitbois, Julie G.; Nogata, Yasuyuki; Yoshimura, Erina; Okino, Tatsufumi; Umezawa, Taiki; Matsuda, Fuyuhiko
    The total synthesis of dolastatin 16, a macrocyclic depsipeptide first isolated from the sea hare Dolabella auricularia as a potential antineoplastic metabolite by Pettit et al., was achieved in a convergent manner. Dolastatin 16 was reported by Tan to exhibit strong antifouling activity, and thus shows promise for inhibiting the attachment of marine benthic organisms such as Amphibalanus amphitrite to ships and submerged artificial structures. Therefore, dolastatin 16 is a potential compound for a new, environmentally friendly antifouling material to replace banned tributyltin-based antifouling paints. The synthesis of dolastatin 16 involved the use of prolinol to prevent formation of a...

  17. Total synthesis and biological activity of dolastatin 16

    Casalme, Loida O.; Yamauchi, Arisa; Sato, Akinori; Petitbois, Julie G.; Nogata, Yasuyuki; Yoshimura, Erina; Okino, Tatsufumi; Umezawa, Taiki; Matsuda, Fuyuhiko
    The total synthesis of dolastatin 16, a macrocyclic depsipeptide first isolated from the sea hare Dolabella auricularia as a potential antineoplastic metabolite by Pettit et al., was achieved in a convergent manner. Dolastatin 16 was reported by Tan to exhibit strong antifouling activity, and thus shows promise for inhibiting the attachment of marine benthic organisms such as Amphibalanus amphitrite to ships and submerged artificial structures. Therefore, dolastatin 16 is a potential compound for a new, environmentally friendly antifouling material to replace banned tributyltin-based antifouling paints. The synthesis of dolastatin 16 involved the use of prolinol to prevent formation of a...

  18. Removal of Pollutants from Water by Using Single-Walled Carbon Nanotubes (SWCNTs) and Multi-walled Carbon Nanotubes (MWCNTs)

    Rahman, Md Mostafizur; Sime, Sanjida Akter; Hossain, M. Anwar; Shammi, Mashura; Uddin, Md. Khabir; Sikder, Md. Tajuddin; Kurasaki, Masaaki
    Water crisis is one of the supreme challenges worldwide as clean water is the ultimate need for human civilization and all other life on earth. In the present study, continuous adsorption experiments were carried out in an adsorption column to survey the efficiency of the carbon nanotubes (CNTs) for removal of pollutants from water/wastewater in terms of physicochemical parameters, such as electrical conductivity, total dissolved solids (TDS), pH, chemical oxygen demand (COD) and total organic carbon (TOC), by using both single-walled carbon nanotubes and multi-walled carbon nanotubes. Sample solutions were allowed to flow in down-flow mode through the fixed-bed of...

  19. Interannual and spatial variability of solar radiation energy potential in Kenya using Meteosat satellite

    Kariuki, Boniface Wainaina; Sato, Tomonori
    Kenya is faced with a rising demand in electricity resulting from a rapidly growing economy and an increasing population. Being a tropical country, lying astride the equator, solar energy is one of the readily available renewable energy resource options to meet this need. Unfortunately, there is still very low adoption of solar systems in the country which could be majorly attributed to lack of adequate solar resource assessment. Besides, past studies" on this area in Kenya only focused on the available amount of solar resource leaving out the issue of variability. To bridge this gap, the temporal and spatial variability...

  20. Temporal change in the distribution and composition of native, introduced, and hybrid charrs in northern Japan

    Fukui, Sho; May-McNally, Shannan L.; Katahira, Hirotaka; Kitano, Satoshi; Koizumi, Itsuro
    Introductions of non-native species have caused various negative impacts on native species and their ecosystems. Hybridization is particularly prevalent among closely related species, and can result in displacement, hybrid swarms, or the disruption of a locally adapted gene complex. Although hybridization between native and non-native species is widespread, long-term monitoring is generally lacking. In this study, we compared the distribution and composition of native white-spotted charr (Salvelinus leucomaenis), introduced brook trout (Salvelinus fontinalis), and their hybrids in the upper Sorachi River, Hokkaido, Japan in 2003 and 2013, especially focusing on (1) if genetic introgression or hybrid swarm has occurred and...

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