Tag: Japan

Precise metal nanoclusters (NCs) are ideal for developing practical catalysts for chemical reactions. However, their catalytic activity is reduced either due to protective molecules called “ligands” surrounding them or aggregation resulting from ligand removal. In a new study, scientists from Japan elucidate the ligand removal mechanism for gold NCs and irradiate them with UV light to prevent aggregation, creating a high-functioning photocatalyst.

“When the ligands are removed without special treatment, the metal NCs easily aggregate on the support and lose their size-specific properties. It is essential understand the mechanism of ligand calcination to create highly functional heterogeneous catalysts under appropriate conditions,” says Prof. Yuichi Negishi of Tokyo University of Science, Japan, who researches on the synthesis of
nanoclusters.

In a new study published in Angewandte Chemie, Prof. Negishi led a team of researchers, including Assistant Professor Tokuhisa Kawawaki, Mr Yuki Kataoka, Ms Momoko Hirata, and Mr Yuki Akinaga, to dig deep into the mechanism of the ligand removal process in NCs. For their experiments, the researchers synthesized gold NCs protected by two ligands, 2-phenylethanethiolate and mercaptobenzoic acid and then supported them on a photocatalytic metal oxide.

Next, the team heated the prepared material at different temperatures ranging from 195°C to 500°C. After every step, they analyzed the products using techniques such as infrared spectroscopy, x-ray photoelectron spectroscopy, and transmission electron microscopy to identify the changes in their chemical composition.

After the ligands were completely released, the team embedded the gold NCs within a thin film of chromium oxide by irradiating the sample with UV light in order to prevent aggregation of the NCs. This process generated a photocatalyst with useful properties like high water-splitting activity and stability.

These findings guide the design for metal NC-based catalysts in the future, with applications in hydrogen generation for hydrogen fuel cells. “With our research, we hope to build a clean, sustainable, society, one brick at a time,” concludes Prof. Negishi.

Wearable technology seems all poised to take over next-generation electronics, yet most wireless communication techniques are not up to the task. To tackle this issue, scientists from the Tokyo University of Science, Japan, delved deep into human-body communications (HBC), in which human tissue is used as the transmission medium for electromagnetic signals. Their findings pave the way to more efficient and safer head-worn devices, such as binaural hearing aids and earphones.

To explore the full potential of HBC, researchers from Japan, including Dr. Dairoku Muramatsu from Tokyo University of Science and Professor Ken Sasaki from The University of Tokyo focused on using HBC for a yet unexplored use: binaural hearing aids.

Such hearing aid devices come in pairs—one for each ear—and greatly improve intelligibility and sound localization for the wearer by communicating with each other to adapt to the sound field. Because these hearing aids are in direct contact with the skin, they made for a perfect candidate application for HBC.

In a recent study, which was published in the journal Electronics, the researchers investigated, through detailed numerical simulations, how electric fields emitted from an electrode in one ear distribute themselves in the human head and reach a receiving electrode on the opposite ear, and whether it could be leveraged in a digital communication system. In fact, the researchers had previously conducted an experimental study on HBC with real human subjects, the results of which were also published in Electronics.

Using human-body models of different degrees of complexity, the researchers first determined the best representation to ensure accurate results in their simulations and then once this was settled, they proceeded to explore the effects of various system parameters and characteristics.

Dr. Muramatsu SAYS, “We calculated the input impedance characteristics of the transceiver electrodes, the transmission characteristics between transceivers, and the electric field distributions in and around the head. In this way, we clarified the transmission mechanisms of the proposed HBC system.”

Finally, with these results, they determined the best electrode structure out of the ones they tested. They also calculated the levels of electromagnetic exposure caused by their system and found that it would be completely safe for humans, according to modern safety standards.

Overall, this study showcases the potential of HBC and extends the applicability of this promising technology. After all, hearing aids are but one of all modern head-worn wireless devices. For example, HBC could be implemented in wireless earphones to enable them to communicate with each other using far less power.

Moreover, because the radio waves used in HBC attenuate quickly outside of the body, HBC-based devices on separate people could operate at similar frequencies in the same space without causing noise or interference.

“With our results, we have made great progress towards reliable, low-power communication systems that are not limited to hearing aids but also applicable to other head-mounted wearable devices. Not just this, accessories such as earrings and piercings could also be used to create new communication systems,” concludes Dr. Muramatsu.

Assistant Professor Yuji Ogihara from the Tokyo University of Science analyzed approximately 8,000 names of infants born between 2004 and 2018 obtained from the database of a life insurance company. He first chose four recent common names for boys and girls each (Boys: “大翔,” “陽翔,” “翔,” “颯,” Girls: “結愛,” “陽菜,” “愛,” “杏”) on the basis of popularity rankings for each year.

He then comprehensively surveyed all their readings and calculated the ratio and number of ways to read each name. These results were published on June 21, 2021 in the international journal Humanities and Social Sciences Communications.

Assistant Professor Ogihara discovered that there are at least 18 ways to read “大翔” (Figure 2), and at least 14 ways to read “結愛” (Figure 3). Even single-character names like “颯,” and “杏,” had seven and five readings, respectively. The readings each differed greatly in pronunciation, length, and meaning. Assistant Professor Ogihara showed that the
other names have many readings, too.

He further found that parents were not only using the common readings of each character, but also using readings that do not exist for a character or using a character for its meaning and imagery. For example, “大翔” was also read as “Tsubasa”(meaning “wing”). Neither “大” nor “翔” formally have “Tsubasa” as a reading. “翔” is read as “Tsubasa” because it has the meanings “flap” and “fly,” and a reading associated with the imagery of the character is observed. The character “大” is given, but not pronounced, and the meaning “to flap broadly” is obtained. Hence, the character is only added for its imagery or meaning.

Assistant Professor Ogihara also saw a pattern of abbreviating common readings. For example, “大翔” was read as “Taishi.” “大” has the reading “tai,” and “翔” has the reading “shou.” “Shou” was abbreviated to “shi” and combined with “tai.” He also found instances where the meanings of characters are read in foreign languages. Take “結愛 Yura,” for example. While “結” comes from the common reading “yu(u),” “愛” is generally not read as “ra,” but because “愛” means “love” (rabu) in English, it is possible to omit the “bu” and use it as “ra.”

In this study, Assistant Professor Ogihara systematically analyzed actual name data and empirically investigated the difficulty of correctly reading Japanese names. The investigation of these difficulties contributes to deepening our understanding of naming practices and the characteristics of names, not only in Japan but in the Sinosphere, which includes East and Southeast Asia.

A vital piece of gas engines, combustors—the chambers in which the combustion powering the engine occurs—have the problem of breaking down due to fatal high-frequency oscillations during the combustion process. Now, through advanced time-series analyses based on complex systems, researchers from Tokyo University of Science and Japan Aerospace Exploration Agency have found what causes them, opening up novel paths to solving the problem.

In a breakthrough, published in Physics of Fluids, a team including Prof. Hiroshi Gotoda, Ms. Satomi Shima, and Mr. Kosuke Nakamura from Tokyo University of Science (TUS), in collaboration with Dr. Shingo Matsuyama and Dr. Yuya Ohmichi from the Japan Aerospace Exploration Agency (JAXA), have used advanced time-series analyses based on complex systems to find out.

Explaining their work, Prof. Gotoda says, “Our main purpose was to reveal the physical mechanism behind the formation and sustenance of high-frequency combustion oscillations in a cylindrical combustor using sophisticated analytical methods inspired by symbolic dynamics and complex networks.” These findings have also been covered by the American Society of Physics in their news section, and by the Institute of Physics on their news platform Physics World.

The combustor the scientists picked to simulate is one of model rocket engines. They were able to pinpoint the moment of transition from the stable combustion state to combustion oscillations and visualize it. They found that significant periodic flow velocity fluctuations in fuel injector affect the ignition process, resulting in changes to the heat release rate. The heat release rate fluctuations synchronize with the pressure fluctuations inside the combustor, and the whole cycle continues in a series of feedback loops that sustain combustion oscillations.

Additionally, by considering a spatial network of pressure and heat release rate fluctuations, the researchers found that clusters of acoustic power sources periodically form and collapse in the shear layer of the combustor near the injection pipe’s rim, further helping drive the combustion oscillations.

These findings provide reasonable answers for why combustion oscillations occur, albeit specific to liquid rocket engines. Prof. Gotoda explains, “Combustion oscillations can cause fatal damage to combustors in rocket engines, aero engines, and gas turbines for power generation. Therefore, understanding the formation mechanism of combustion oscillations is an important research subject. Our results will greatly contribute to our understanding of the mechanism of combustion oscillations generated in liquid rocket engines.”

Indeed, these findings are significant and can be expected to open doors to novel routes of
exploration to prevent combustion oscillations in critical engines.

Two-dimensional “nanosheets” made of bonds between metal atoms and organic molecules are attractive candidates for photoelectric conversion, but get corroded easily. In a new study, scientists from Japan and Taiwan present a new nanosheet design using iron and benzene hexathiol that exhibits record stability to air exposure for 60 days, signalling the commercial optoelectronic applications of these 2D materials in the future.

Converting light to electricity effectively has been one of the persistent goals of scientists in the field of optoelectronics. While improving the conversion efficiency is a challenge, several other requirements also need to be met. For instance, the material must conduct electricity well, have a short response time to changes in input (light intensity), and, most importantly, be stable under long-term exposure.

Lately, scientists have been fascinated with “coordination nanosheets” (CONASHs), that
are organic-inorganic hybrid nanomaterials in which organic molecules are bonded to metal atoms in a 2D network. The interest in CONASHs stems mainly from their ability to absorb light at multiple wavelength ranges and convert them into electrons with greater efficiency than other types of nanosheets. This feat was observed in a CONASH comprising a zinc atom bonded with a porphyrin-dipyrrin molecule. Unfortunately, the CONASH quickly became corroded due to the low stability of organic molecules in liquid electrolytes (a medium commonly used for current conduction).

“The durability issue needs to be solved to realize the practical applications of CONASH-based photoelectric conversion systems,” says Professor Hiroshi Nishihara from Tokyo University of Science (TUS), Japan, who conducts research on CONASH and has been trying to solve the CONASH stability problem.

Now, in a recent study published in Advanced Science as a result of a collaborative research between National Institute for Materials Science (NIMS), Japan and TUS, Prof. Nishihara and his colleagues, Dr. Hiroaki Maeda and Dr. Naoya Fukui from TUS, Dr. Ying-Chiao Wang and Dr. Kazuhito Tsukagoshi from NIMS, Mr. Chun-Hao Chiang and Prof. Chun-Wei Chen from National Taiwan University, Taiwan, and Dr. Chi-Ming Chang and Prof. Wen-Bin Jian from National Chiao-Tung University, Taiwan, have designed a CONASH comprising an iron (Fe) ion bonded to a benzene hexathiol (BHT) molecule that has demonstrated the highest stability under air exposure reported so far. The new FeBHT CONASH-based photodetector can retain over 94% of its photocurrent after 60 days of exposure! Moreover, the device requires no external power source.

What made such a feat possible? Put simply, the scientists made some smart choices. Firstly, they went for an all-solid architecture by replacing the liquid electrolyte with a solid-state layer of Spiro-OMeTAD, a material known to be an efficient transporter of “holes” (vacancies left behind by electrons). Secondly, they synthesized the FeBHT network from a reaction between iron ammonium sulfate and BHT, which accomplished two things: one, the reaction was slow enough to keep the sulfur group protected from being oxidized, and two, it helped the resultant FeBHT network become resilient to oxidation, as the scientists confirmed using density functional theory calculations.

In addition, the FeBHT CONASH favoured high electrical conductivity, showed an enhanced
photoresponse with a conversion efficiency of 6% (the highest efficiency previously reported was 2%), and a response time < 40 milliseconds for UV light illumination.

With these results, the scientists are thrilled about the prospects of CONASH in commercialized optoelectronic applications. “The high performance of the CONASH-based photodetectors coupled with the fact that they are self-powered can pave the way for their practical applications such as in light-receiving sensors that can be used for mobile applications and recording the light exposure history of objects,” says Prof. Nishihara excitedly.

Scientists at Tokyo University of Science, Japan, engineered a long polymer with copper-containing side units that create regions with locally high copper density, boosting the antibacterial activity of hydrogen peroxide and paving the way to a new drug design concept.

Scientists are exploring a novel approach to boost the in vivo antibacterial activity of hydrogen peroxide (H₂O₂), a commonly used disinfectant. In a recent study published in Macromolecular Rapid Communications, a team led by Assistant Professor Shigehito Osawa and Professor Hidenori Otsuka reported their success in enhancing H₂O₂ activity using
carefully tailored copper-containing polymers.

To understand their approach, it helps to know how H2O2 acts against bacteria in the first place, and the role that copper plays. H2O2 can be decomposed into a hydroxyl radical (•OH) and a hydroxide anion (OH−), the former of which is highly toxic to bacteria as it readily destroys certain biomolecules. Copper in its first oxidation state, Cu(I), can catalyze the splitting of H2O2 into a hydroxyl radical and a hydroxide anion, turning into Cu(II) in the process through oxidation (Figure 1). Curiously, H2O2 can also catalyze the reduction of Cu(II) to Cu(I), but only if this reaction is somehow facilitated. One way to achieve this is to have Cu(II)-containing complexes get close enough together.

However, when using Cu(II)-containing complexes dissolved in a solution, the only way for them to come close together is by accidentally bumping into each other, which requires an excessively high concentration of copper.

The team found a workaround to this issue by drawing inspiration from cellular chemistry, as Dr. Osawa explains: “In living organisms, copper forms complexes with proteins to efficiently catalyze redox reactions. For example, tyrosinase has two copper complex sites in close proximity to each other, which facilitates the formation of reaction intermediates between oxygen species and copper complexes. We thought we could leverage this type of mechanism in artificially produced polymers with copper complexes, even if dispersed in a solution.”

With this idea, the researchers developed a long polymer chain with dipicolylamine (DPA) as copper-containing complexes. These DPA–copper complexes were attached to the long polymer backbone as “pendant groups.” When these polymers are dispersed in a solution, the Cu(II) atoms in the pendant groups are kept in close proximity and locally high densities, vastly increasing the chances that two of them will be close enough to be reduced to Cu(I) by H2O2. Through various experiments, the scientists demonstrated that the use of these tailored polymers resulted in higher catalytic activity for the splitting of H2O2 resulting in more OH• even for lower concentrations of copper. Further tests using Escherichia coli cultures showed that these polymers greatly enhanced the antibacterial potential of H2O2.

While the results of this study open up a new design avenue for antimicrobial drugs, there may also be useful applications in the food industry as well. “Because copper is an essential
nutrient for living organisms, the antibacterial agent developed in this study holds promise as an efficient food preservative, which could contribute to increasing the variety of foods that can be preserved over long shelf times,” highlights Dr Osawa.

In the fight against COVID-19, scientists have been scanning their arsenals of previously used drugs in hopes of finding any that can be used to treat the disease. One of the contenders under scrutiny, an anti-malarial drug called mefloquine shows great promise, according to a new breakthrough study by a team of Japanese scientists, perhaps giving us a better fighting chance.

In a breakthrough study, a team of scientists—comprising Dr. Koichi Watashi, Kaho Shionoya, Masako Yamasaki, Dr. Hirofumi Ohashi, Dr. Shin Aoki, Dr. Kouji Kuramochi, and Dr. Tomohiro Tanaka from Tokyo University of Science (along with scientists from the National Institute of Infectious Diseases, Kyushu University, The University of Tokyo, Kyoto University, Japanese Foundation for Cancer Research, and Science Groove Inc.)—have identified an anti-malarial drug, mefloquine (which is incidentally a derivative of hydrochloroquine), that is effective against SARS-CoV-2. Their findings are published
in Frontiers in Microbiology.

Detailing their modus operandi, lead scientist in the team Dr. Watashi says, “To identify drugs with higher antiviral potency than existing antivirals, we first screened approved
anti-parasitic/anti-protozoal drugs. We found that mefloquine had the highest anti-SARS-CoV-2 activity among the tested compounds. Upon testing it against other quinoline derivatives, such as hydrochloroquine, in a cell line mimicking the cell-based environments of human lung cells, we found it to be better.”

The team further explored mefloquine’s mechanism of action. Dr. Watashi explains the process, “In our cell assays, mefloquine readily reduced the viral RNA levels when applied at the viral entry phase but showed no activity during virus-cell attachment. This shows that mefloquine is effective on SARS-COV-2 entry into cells after attachment on cell
surface.”

Thus, to bolster mefloquine’s anti-viral activity, the scientists looked into the possibility of combining it with a drug that inhibits the replication step of SARS-CoV-2: Nelfinavir. Interestingly, they observed that the two drugs acted in “synergy” and the drug combination showed greater anti-viral activity than either showed alone, without being toxic to the cells in the cell lines themselves.

The scientists also mathematically modelled the effectiveness of mefloquine to predict its potential real-world impact if applied to treat COVID-19. What they predicted was that mefloquine could reduce the overall viral load in affected patients to under 7% and shorten the ‘time-till-virus-elimination’ by 6.1 days.

This study must of course be succeeded by clinical trials, but the world can hope that mefloquine becomes a drug used to effectively treat patients with COVID-19.