Hokkaido University of Science

Sapporo, Japan
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Wakimoto T.,Hokkaido University of Science
Chemical Record | Year: 2017

Considering the dynamic features of natural products, our access toward exploring the entire diversity of natural products has been quite limited. It is challenging to assess the diversity of natural products by using conventional analytical methods, even with tandem chromatographic techniques, such as LC-MS and GC-MS. This viewpoint is supported by the sequencing analyses of microbial genomes, which have unveiled the potential of secondary metabolite production far exceeding the number of isolated molecules. Recent advancements in metabolomics, in concert with genomics analyses, have further extended the natural product diversity, prompting growing awareness of the existence of reactive or short-lived natural molecules. This personal account introduces some examples of the discoveries of hitherto elusive natural products, due to physico-chemical or biological reasons, and highlights the significance of the dark matter of natural products. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Maruyama T.,Hokkaido University of Science
AIP Conference Proceedings | Year: 2017

This paper proposes novel design method of dual-band reflectarray using genetic algorithm (GA). Ordinary, each elements of reflectarray are designed to have desired reflection phase. However, when we adopt same polarization in dual frequencies, the element configuration designed to satisfy desired reflection phase in one frequency influences the characteristics in other frequency. Therefore, it is difficult to achieve dual-band reflectarray. To address the issues, we adopt two layer patches for element to increase flexibility of design and optimize the patches configuration using GA. As a result, we achieve novel reflectarray that reflect wave towards the direction of theta equal to 27 deg. and phi equal to 0 deg. in dual frequency simultaneously when incidence wave is coming from the direction of theta equal to 0 deg. and phi equal to 0 deg. in dual frequency. © 2017 Author(s).

Iijima M.,Hokkaido University of Science
Journal of Anatomy | Year: 2017

Although the establishment of trophic ecomorphology in living crocodylians can contribute to estimating feeding habits of extinct large aquatic reptiles, assessment of ecomorphological traits other than the snout shape has scarcely been conducted in crocodylians. Here, I tested the validity of the proposed trophic ecomorphological traits in crocodylians by examining the correlation between those traits and the snout shape (an established trophic ecomorphology), using 10 non-alligatoroid crocodylian species with a wide range of snout shape. I then compared the ontogenetic scaling of trophic ecomorphology to discuss its adaptive and taxonomic significance. The results demonstrated that degree of heterodonty, tooth spacing, size of supratemporal fenestra (STF), ventral extension of pterygoid flange and length of lower jaw symphysis are significantly correlated with snout shape by both non-phylogenetic and phylogenetic regression analyses. Gavialis gangeticus falls outside of 95% prediction intervals for the relationships of some traits and the snout shape, suggesting that piscivorous specialization involves the deviation from the typical transformation axis of skull characters. The comparative snout shape ontogeny revealed a universal trend of snout widening through growth in the sampled crocodylians, implying the existence of a shared size-dependent biomechanical constraint in non-alligatoroid crocodylians. Growth patterns of other traits indicated that G. gangeticus shows atypical trends for degree of heterodonty, size of STF, and symphysis length, whereas the same trends are shared for tooth spacing and ventral extension of pterygoid flange among non-alligatoroid crocodylians. These suggest that some characters are ontogenetically labile in response to prey preference shifts through growth, but other characters are in keeping with the conserved biomechanics among non-alligatoroid crocodylians. Some important taxonomic characters such as the occlusal pattern are likely correlated with ontogeny and trophic ecomorphology rather than are constrained by phylogenetic relationships, and careful reassessment of such characters might be necessary for better reconstructing the morphological phylogeny of crocodylians. © 2017 Anatomical Society.

Sato K.,Hokkaido University of Science
Development Growth and Differentiation | Year: 2017

During early embryonic development, epithelial cells form a monolayer sheet and migrate in a definite direction. This phenomenon, called epithelial cell migration, is an important topic in developmental biology. A characteristic feature of this process is attachment to adjacent cells during migration, which is necessary for maintaining the integrity of the sheet. However, it is unclear how these cohesive cells migrate without breaking their attachments. A mechanism for this phenomenon was recently proposed, in which direction-dependent contraction forces acting on cell boundaries induce unidirectional epithelial migration. In this review, we examine this proposed mechanism from various aspects and provide theoretical background for the collective migration of epithelial cells. This information may be helpful for investigators to realize the basic principles underlying collective epithelial migration and devise new mechanisms for it. © 2017 Japanese Society of Developmental Biologists.

Nagamatsu M.,Hokkaido University of Science
SAE Technical Papers | Year: 2017

The almost current sound localization methods do not have enough resolution in low frequency sound localization. To overcome this disadvantage, I am now developing the new sound localization method, Double Nearfield Acoustic Holography (DNAH) method. This method is a converted method of conventional Nearfield Acoustic Holography (NAH) method. In this proposing method, the resolution of low frequency sound localization is improved by using sound propagation information on doubled measurement planes. To prove the performance of proposing method, the basic experiments with variable conditions are conducted. In these experiments, the small speakers are used as sound sources. In this paper, to discuss the ability to apply to actual industry, the effect of measurement distance from the sound source is explained. Some experimental results with changing measurement distance are shown in this paper. The experiments are conducted for a 100Hz or 40Hz sound source, and measurement distance of NAH and DNAH method are changed from 0.1m to 1.0m. In all experiments, the experimental results of proposing DNAH method show higher resolution than the results of conventional NAH method. However, with the distance larger than 0.6m, the reconstructed images by DNAH method do not show the enough resolution to localize the sound sources of mechanical products. In the images by DNAH method with the distance shorter than 0.5m, the sound source can be detected. As a result, in the low frequency sound localization, the proposing DNAH method shows the better results than conventional NAH method, even if the measurement distance is not contacting distance. Copyright © 2017 SAE International.

Ogawa N.,Hokkaido University of Science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

Particle diffusion in a two-dimensional curved surface embedded in R3 is considered. In addition to the usual diffusion flow, we find a flow with an explicit curvature dependence. Diffusion equation is obtained in ε (thickness of surface) expansion. As an example, the surface of elliptic cylinder is considered, and curvature-dependent diffusion coefficient is calculated. © 2010 The American Physical Society.

Nihashi S.,Hokkaido University of Science | Ohshima K.I.,Hokkaido University
Journal of Climate | Year: 2015

Sinking of dense water from Antarctic coastal polynyas produces Antarctic Bottom Water (AABW), which is the densest water in the global overturning circulation and is a key player in climate change as a significant sink for heat and carbon dioxide. Very recent studies have suggested that landfast sea ice (fast ice) plays an important role in the formation and variability of the polynyas and possibly AABW. However, they have been limited to regional and case investigations only. This study provides the first coincident circumpolar mapping of Antarctic coastal polynyas and fast ice. The map reveals that most of the polynyas are formed on the western side of fast ice, indicating an important role of fast ice in the polynya formation. Winds diverging from a boundary comprising both coastline and fast ice are the primary determinant of polynya formation. The blocking effect of fast ice on westward sea ice advection by the coastal current would be another key factor. These effects on the variability in sea ice production for 13 major polynyas are evaluated quantitatively. Furthermore, it is demonstrated that a drastic change in fast ice extent, which is particularly vulnerable to climate change, causes dramatic changes in the polynyas and possibly AABW formation that can potentially contribute to further climate change. These results suggest that fast ice and precise polynya processes should be addressed by next-generation models to produce more accurate climate projections. This study provides the boundary and validation data of fast ice and sea ice production for such models. © 2015 American Meteorological Society.

Ichikawa S.,Hokkaido University of Science
Chemical Record | Year: 2016

It is important to pursue function-oriented synthesis (FOS), a strategy for the design of less structurally complex targets with comparable or superior activity that can be made in a practical manner, because compared to synthetic drugs, many biologically relevant natural products possess large and complex chemical structures that may restrict chemical modifications in a structure–activity relationship study. In this account, we describe recent efforts to simplify complex nucleoside natural products including caprazamycins. Considering the structure–activity relationship study with several truncated analogues, three types of simplified derivatives, namely, oxazolidine, isoxazolidine, and lactam-fused isoxazolidine-containing uridine derivatives, were designed and efficiently synthesized. These simplified derivatives have exhibited promising antibacterial activities. A significant feature of our studies is the rational and drastic simplification of the molecular architecture of caprazamycins. This study provides a novel strategy for the development of a new type of antibacterial agent effective against drug-resistant bacteria. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chiba K.,Hokkaido University of Science
2013 IEEE Congress on Evolutionary Computation, CEC 2013 | Year: 2013

Design Informatics has three points of view. First point is the efficient exploration in design space using evolutionary computation. Second point is the structurization and visualization of design space using data mining. Third point is the application to practical problems. In the present study, the influence of the seven pure and hybrid optimizers for design information has been investigated in order to explain the selection manner of optimizer for data mining. A single-stage hybrid rocket design problem is picked up as the present design object. As a result, mining result depends on not the number of generation (convergence) but the optimizers (diversity). Consequently, the optimizer with diversity performance should be selected in order to obtain global design information in the design space. Therefore, the diversity performance has also been explained for the seven optimization methods by using three standard mathematical test problems with/without noise. The result indicates that the hybrid method between the differential evolution and the genetic algorithm is beneficial performance for efficient exploration in the design space under the condition for large-scale design problems within 10 2 order evolution at most. Moreover, the comparison among eight crossovers indicates that the principal component analysis blended crossover is good selection on the hybrid method between the differential evolution and the genetic algorithm. © 2013 IEEE.

Ogawa N.,Hokkaido University of Science
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The diffusion of particles in confining walls forming a tube is discussed. Such a transport phenomenon is observed in biological cells and porous media. We consider the case in which the tube is winding with curvature and torsion, and the thickness of the tube is sufficiently small compared with its curvature radius. We discuss how geometrical quantities appear in a quasi-one-dimensional diffusion equation. © 2013 Elsevier B.V.

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