Research

High performance of microprocessors and semiconductor integrated circuits, which are the brains of smartphones and PCs, have been achieved by reducing the size of field-effect transistors (FETs), which are the basic elements, and installing approximately 2 to 3 billion of them. While higher performance is being achieved, the rapid increase in power consumption of these FETs is becoming a serious problem. This is because there is a physical limit (60 mV/digit) on the switching performance (sub-threshold factor) of FETs. To realize drastic energy saving in the future, it is necessary to develop a new switch element that can break through the physical limit on FETs and their practical application. With this research, we have proposed and realized an unprecedented low-power-consumption tunnel FET.

Research

Membrane fouling (decrease in membrane permeability) is mainly caused by polysaccharides and proteins produced by microorganisms. However, it is still unclear which polysaccharides and proteins play an important role in that mechanism, and efficient methods to control membrane fouling has yet to be developed. In this study, we accumulated fouling polysaccharides, purified them by lectin affinity chromatography, and then conducted partial hydrolysis and MALDI-TOF/MS analysis. By comparing the peaks detected by MALDI-TOF/MS analysis with the database, we have enabled estimation of the structure of the polysaccharide and the microorganism from which it originated. We have also succeeded in separating proteins by two-dimensional electrophoresis after purifying the membrane fouling material, enabling the reading of the amino acid sequences of the cut-out spots. It is also possible to estimate the structure and origin of the protein by comparing it with the database.

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Research

arch is to improve the quality of education by improving the learning experience using the internet (e-learning) and promoting open education. To effectively implement e-learning, it is essential to develop teaching materials and implement evaluation methods based on instructional design theory. We also conduct research to enhance learning effects through blended learning, which is the effective combining of e-learning with face-to-face education like flip teaching. In addition, through “open education” activities such as OCW (Open Courseware) and MOOC (Massive Open Online Course), which provide learning opportunities beyond educational institutions such as schools and universities, lecture videos and educational activities themselves are made available to the public, and education is provided while involving diverse learners and experts. Thus, we are also conducting research to continuously improve the teaching materials and education itself.

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We are proposing a system (e.g., planning, modeling and evaluation based on experiments and field studies) that can contribute to both the environment and regional development (economy) by linking energy recovered from biomass (e.g., food waste, sewage sludge, livestock manure, forest residues, and rice straw) through combustion and methane fermentation with local energy consumers (e.g., public facilities, nursing and welfare facilities, agricultural facilities such as greenhouses and food factories). Furthermore, by obtaining cooperation from private companies, we are conducting research on creation of community through biomass utilization in collaboration with the endowed laboratory of biomass community planning (Visiting Professor Toru Furuichi, Specially Appointed Assistant Professor Satoru Ochiai, https://smcs.eng.hokudai.ac.jp/bio-com-p.html).

Research

When ultrasonic waves are emitted from inside a liquid to the surface, the liquid is atomized. The atomized liquid becomes small droplets with a diameter of several micrometers. This liquid atomization technology can produce uniform fine droplets in an energy saving manner and is still widely used in our daily life. Although the mechanism of liquid atomization is still not completely understood, based on our previous research, it has become clear that microbubbles in the vicinity of the liquid surface promote atomization. In this study, we focus on the number of microbubbles in a liquid and aim to control the amount of liquid atomization by ultrasound. By adjusting the number of microbubbles appropriately, we aim to atomize liquids that could not be atomized by ultrasound and to further increase the amount of liquid atomization.

Research

As shown in Fig. 1, optical vortices have a helical phase distribution and a donut-shaped intensity distribution in the beam cross-section. These properties can be used to realize microscopes demonstrating performance that far exceeds the spatial resolution of conventional optical microscopes and nanometer-order microfabrication. In our laboratory, we are conducting research and development to enable further new applications by combining this kind of light with ultrashort optical pulses, which are extremely short in duration (10-12 to -15 seconds). We have succeeded in generating ultrashort optical vortex pulses that can computer-control the helical phase and has a peak power of several tens of GW. We have also succeeded in developing a completely new method for instantaneous measurement of the helical phase (Fig. 2). We are now applying these originally developed fundamental technologies to material processing and communication technologies.

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Silver iodide and ice-nucleating bacteria promote heterogeneous nucleation of water, which in turn promotes freezing of water. Although several compounds that have inhibitory effects on such ice-nucleating activity have been reported, the polyphenol used in this study is a relatively small molecule that can reduce the freezing temperature of aqueous solutions by several degrees by suppressing the activity of coexisting ice-nucleating substances at concentrations as low as several mM. They are also effective to maintain supercooling, even when physical stimuli such as vibration are applied. These polyphenols are also found in various plants, and we are studying conditions for their industrial use. For example, the preservation of plant and animal cells and food in subzero temperatures and the prevention of frost damage to crops are interesting topics. Since the freezing-inhibition effect is affected by various factors, we are examining application possibilities, including the combination use of existing freezing inhibitors, and are trying to elucidate the mechanism of inhibiting ice nucleation activity.

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This system translates strings of numbers input by degenerated keywords into a Japanese sentence with mixed Chinese characters and Japanese phonetic characters. Through degenerated keyword input, one line in the Japanese syllabary is matched with one number to allow fast and easy input. This system provides words by using inductive learning to compare the strings of numbers and the proofread translation results. Therefore, even if the dictionary is empty, the system can generate a dictionary adapted to the target field. However, input of a sequence of numbers from degenerated vowel information may cause ambiguity. To solve this problem, this system uses information on adjacent characters, top-level words and position presumption information. The use of top-level words and position presumption processing increases the number of words acquired, and the adjacent character information enables the conversion that takes connections between words into account.

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We are proposing spin devices that exceed the current mainstream CMOS devices in terms of performance and power, and are analyzing their performance using condensed matter theory. The main objective of this research is to create power-saving devices that provide superior performance to CMOS devices. To calculate the performance of novel spin devices, quantum field theory and relativity are used to calculate the spin conductivity and other properties. Currently, we are studying topological insulators and skyrmions. Topological insulators are bulk insulators, but spontaneous spin currents flow only on their surfaces. If successfully applied to devices, topological insulators make it possible to fabricate ultra-low power devices because the topological insulator itself is non-dissipative. Skyrmions are also a peculiar vortex generated in magnetic materials, and are expected to play the role of a switch by driving a current.

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Cellulose synthesized by bacteria and called bacterial cellulose (BC) has unique properties such as high water retention, high strength, biodegradability, and biocompatibility. In recent years, nano-sized cellulose materials (nanofibrillated cellulose (NFC)) has also been attracting attention. In general, NFC is prepared top-down from pulp by physical and chemical treatments, and the resulting NFC is highly dispersed in water. In contrast, by optimizing the culture conditions of cellulose-synthesizing bacteria, it is possible to prepare nanofibrillated BC (NFBC: Fibnano?) from low-molecular biomass in a bottom-up manner. In collaboration with a company in Hokkaido, we have succeeded in the mass production of NFBC (Fibnano?) from molasses, a byproduct of sugar production.

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EUV plasmas and soft X-ray plasmas can easily achieve high light intensity and are used for semiconductor lithography and material diagnostics. On the other hand, for optimization (wavelength selectivity and high efficiency), control of the electronic state (electron density and electron temperature) of the plasma is necessary, but measurement of the electronic state has not been achieved yet with conventional techniques, and the electronic state had been unknown. The feature of this technology is that it enables detailed measurement of electron density and temperature in EUV plasmas by laser scattering measurement (Thomson scattering method) using a unique spectroscopic system. This makes it possible to develop light sources based on an understanding of the electronic state, which is the root of the mechanism by which plasma emits light.

Research

In our original definition of “intestinal environment,” three elements, namely, food materials and ingredients, intestinal bacteria acting as parasites, and host Paneth cells α-defensin, determine the “intestinal environment,” and their crosstalk affects health maintenance and disease. This definition has prompted a paradigm shift in food functionality. The purpose of this study is to clarify the involvement of α-defensins in health maintenance, disease development and pathogenesis. This will help us establish a novel functional evaluation system of food and international criteria to evaluate the intestinal environment. By combining a tissue culture system with an α-defensin quantification system, we will lay the foundation for systematic analysis of the relationship between various intestinal functions and food functions of which the mechanisms are still unknown. This will be the first to elucidate immunostimulation and the control of aging substances by digested food materials and ingredients and drugs. We aim to obtain new scientific indicators to create high added value for food.

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The transport properties of porous materials such as concrete does not only depend on the porosity, but also on the spatial distribution of each phase. Therefore, the transport properties of HCP, which is a main component of concrete, was predicted. Figure 1 shows a cross section of HCP observed using a backscattered electron image, showing the distribution of each phase. We extracted each phase, calculated the autocorrelation function, and based on the results, distributed each phase in three-dimensional space to construct the three-dimensional spatial image model shown in Fig. 2. Figure 3 shows a comparison of the results of the diffusion coefficient calculated by the finite difference method and the measured values. The estimated and measured values agreed well with each other, even for different samples, indicating that the diffusion coefficients of hardened cement can be predicted using this model.

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In all-solid-state lithium secondary batteries that use a lithium-ion conductive solid electrolyte, the construction of a good electrode-electrolyte interface is very important to realize high energy-density batteries. We have conducted this research to construct a good electrode-electrolyte interface by preparing sulfide solid electrolytes from the liquid phase. We prepared a homogeneous solution of Li2S-P2S5-based solid electrolytes by dissolving them in N-methylformamide (NMF), and successfully redepositing Li2S-P2S5-based solid electrolytes by removing NMF from the solution. This solution was mixed with LiCoO2, a cathode material, and solid electrolyte was coated on LiCoO2 by removing NMF. Using this solution, we produced an electrode composite. Then, using the obtained electrode composite and sulfide inorganic solid electrolyte, we successfully produced all-solid-state lithium batteries and confirmed the stable operation of the batteries.

Research

China is continuing its economic growth. Economic ties with Hong Kong, Taiwan, and neighboring countries and regions are being strengthened, and the Greater China region is being formed, making the region a growth engine for the global economy. However, Japan-China relations also involve issues such as historical awareness and territorial sovereignty. Some people are concerned that expanding China will disrupt the existing order. So, how should Japanese regions try to build relations with China while taking the above risk factors into account? The Center for East Asian Media Studies at Hokkaido University has been analyzing media trends in East Asia. Based on this foundation, how should we distribute information to the Greater China region, and how can we build good relations with the people of East Asia for the future? We will consider how to do this by taking advantage of the characteristics of organizations that are the sources of the information.

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Plasmas generated in liquid are of great interest in the fields of nanotechnology, environmental engineering and medical engineering, but the need for high voltage to generate the plasma can be an obstacle. Meanwhile, in the field of ultrasonic engineering, it is known that the interior of a bubble becomes plasma at the same time as the collapse of acoustic cavitation. Using a very simple method of inserting a perforated metal plate into a liquid where ultrasonic waves are applied, we have succeeded in localizing and efficiently generating acoustic cavitation, which is difficult to fix in position. This has been valued as a unique method of generating plasma in liquid without using high voltage. Currently, we are working to clarify the mechanism of this method and to prepare guidelines for the design of a large-scale device. In the future, we hope to develop various new plasma application technologies.

Research

While the resolution of conventional optical lithography is determined by the wavelength, this lithographic technology is determined by the processing resolution of the metal nanostructure of the photomask. By irradiating the metal nanostructure of the photomask with infrared light, this technology can transfer patterns with the resolution of a single nanometer. This technology is unique since the shape of the mask pattern can be transferred as such by simply irradiating it with infrared light, high aspect ratio processing is expected because light propagation is used instead of near-field light, and it is possible to not only produce line and space patterns but also triangle, nano-gap, chain, and other shapes. It is expected to apply this technology to photonic crystals, plasmonic solar cells, and the technology for moth-eye structure formation on the surface of optical elements, which requires the transfer of nano-patterns over a relatively large area.

Research

We are studying new structured optical fibers to overcome the limitation of existing optical fibers, optical fiber application technologies to ensure safety and security, ultra-compact optical circuits to support opticalization, and optical simulators to support the design of optical fibers and optical circuits.

Research

Thanks to the development of molecular targeted therapies, antiangiogenic agents are now widely used. However, there are problems such as the lack of companion diagnostics to predict therapeutic effects and side effects due to injury to normal blood vessels.
We have successfully isolated and cultured human tumor vascular endothelial cells and have identified specific markers that they express. Tumor vascular endothelial cells expressing these markers are valuable materials for cell-based screening of novel drugs and compounds, and help us identify new therapeutic targets and drugs that cannot be discovered by studies using conventional tumor cell lines or clinical tumor tissue fragments. Markers expressed by these tumor vascular endothelial cells can also be used as companion diagnostics. This will contribute to the realization of personalized treatment by selecting the target cases as well as the timing and duration of administration with angiogenesis inhibitors.