Toxicity and Molecular Identification of Green Toadfish Lagocephalus lunaris Collected from Kyushu Coast, Japan

Green toadfish Lagocephalus lunaris inhabits tropical and subtropical seas and contains high tetrodotoxin (TTX) levels in the muscle as well as liver and gonad. In 2008 to 2009, food poisoning due to ingesting L. lunais occurred in Western Japan. Five specimens of green toadfish caught in Kyushu coast, Japan, were analyzed for toxicity, toxins, and species identification. All five specimens were toxic by bioassay. Comparing the maximum toxicity in tissues, ovary contained the most toxin (1810 mouse unit [MU]/g), followed by liver (341 MU/g), muscle (135 MU/g), skin (79 MU/g), and intestine (72 MU/g). Liquid chromatography/mass spectrometry analysis revealed that TTX was the major toxin. Nucleotide sequence analysis of the 16S rRNA gene fragment of muscle mitochondrial DNA indicated that partial sequences of PCR products of four specimens were identical with that of L. lunaris. The sequence of one specimen was indistinguishable from that of the brown-backed toadfish Lagocephalus wheeleri, a nontoxic species

Expression of the CCCH-tandem zinc finger protein gene OsTZF5 under a stress-inducible promoter mitigates the effect of drought stress on rice grain yield under field conditions

Increasing drought resistance without sacrificing grain yield remains an ongoing challenge in crop improvement. In this study, we report that Oryza sativa CCCH‐tandem zinc finger protein 5 (OsTZF5) can confer drought resistance and increase grain yield in transgenic rice plants. Expression of OsTZF5 was induced by abscisic acid, dehydration and cold stress. Upon stress, OsTZF5‐GFP localized to the cytoplasm and cytoplasmic foci. Transgenic rice plants overexpressing OsTZF5 under the constitutive maize ubiquitin promoter exhibited improved survival under drought but also growth retardation. By introducing OsTZF5 behind the stress‐responsive OsNAC6 promoter in two commercial upland cultivars, Curinga and NERICA4, we obtained transgenic plants that showed no growth retardation. Moreover, these plants exhibited significantly increased grain yield compared to non‐transgenic cultivars in different confined field drought environments. Physiological analysis indicated that OsTZF5 promoted both drought tolerance and drought avoidance. Collectively, our results provide strong evidence that OsTZF5 is a useful biotechnological tool to minimize yield losses in rice grown under drought conditions

Self-evolving photonic crystals for ultrafast photonics

高速自己変化可能なフォトニック結晶による高ピーク出力・短パルス光の発生 --超スマート社会を支える高精度光センシングやレーザー微細加工応用に向けて--. 京都大学プレスリリース. 2023-01-27.Ultrafast dynamics in nanophotonic materials is attracting increasing attention from the perspective of exploring new physics in fundamental science and expanding functionalities in various photonic devices. In general, such dynamics is induced by external stimuli such as optical pumping or voltage application, which becomes more difficult as the optical power to be controlled becomes larger owing to the increase in the energy required for the external control. Here, we demonstrate a concept of the self-evolving photonic crystal, where the spatial profile of the photonic band is dynamically changed through carrier-photon interactions only by injecting continuous uniform current. Based on this concept, we experimentally demonstrate short-pulse generation with a high peak power of 80 W and a pulse width of <30 ps in a 1-mm-diameter GaAs-based photonic crystal. Our findings on self-evolving carrier-photon dynamics will greatly expand the potential of nanophotonic materials and will open up various scientific and industrial applications

Impact of MaaS Applications: Exploring Platform Business and Towards De-maturity

本稿の目的は、近年注目を集めるMaaS（Mobility as a Service）について考察し、その実現や本格普及が産業や企業にどのような影響を与えるのか、その役割について明らかにすることである。これまでMaaSの役割やメリットは、環境問題や地域課題の解決といったマクロ面か個人の利便性向上といったミクロ面に終始してきた。本稿では、その普及の中心となる企業への影響として①オープン化、②業態転換、③脱成熟化という3領域で変化を促進させる役割を新たに明らかにした。departmental bulletin pape

High-brightness scalable continuous-wave single-mode photonic-crystal laser

フォトニック結晶レーザーの高輝度単一モード連続動作の実現 --スマート製造を始めとする各種分野のゲームチェンジに向けて--. 京都大学プレスリリース. 2023-06-15.Realizing large-scale single-mode, high-power, high-beam-quality semiconductor lasers, which rival (or even replace) bulky gas and solid-state lasers, is one of the ultimate goals of photonics and laser physics. Conventional high-power semiconductor lasers, however, inevitably suffer from poor beam quality owing to the onset of many-mode oscillation, and, moreover, the oscillation is destabilized by disruptive thermal effects under continuous-wave (CW) operation. Here, we surmount these challenges by developing large-scale photonic-crystal surface-emitting lasers with controlled Hermitian and non-Hermitian couplings inside the photonic crystal and a pre-installed spatial distribution of the lattice constant, which maintains these couplings even under CW conditions. A CW output power exceeding 50 W with purely single-mode oscillation and an exceptionally narrow beam divergence of 0.05° has been achieved for photonic-crystal surface-emitting lasers with a large resonant diameter of 3 mm, corresponding to over 10, 000 wavelengths in the material. The brightness, a figure of merit encapsulating both output power and beam quality, reaches 1 GW cm⁻² sr⁻¹, which rivals those of existing bulky lasers. Our work is an important milestone toward the advent of single-mode 1-kW-class semiconductor lasers, which are expected to replace conventional, bulkier lasers in the near future

Photonic-crystal lasers with high-quality narrow-divergence symmetric beams and their application to LiDAR

Light detection and ranging (LiDAR) is a key technology for smart mobility of robots, agricultural and construction machines, and autonomous vehicles. However, current LiDAR systems often rely on semiconductor lasers with low-quality, large-divergence, and asymmetric beams, requiring high-precision integration of complicated lens systems to reshape the beam. Also, due to the broad linewidth and the large temperature dependence of their lasing spectrum, a bandpass filter with broad bandwidth must be used in front of the detector, so the detected signal is affected by noise from background light such as sunlight. These critical issues limit the performance, compactness, affordability, and reliability of the LiDAR systems. Photonic-crystal surface-emitting lasers (PCSELs) have attracted much attention as novel semiconductor lasers that can solve the issues of conventional semiconductor lasers owing to their capability of high-quality, very-narrow-divergence, and symmetric beam operation supported by broad-area band-edge resonance in their two-dimensional photonic crystal. In this paper, we show the progress and the state of the art of broad-area coherent PCSELs and their application to a time-of-flight (ToF) LiDAR system. We first review the progress of PCSELs made so far. Next, we show recent progress based on PCSELs with a double-lattice structure that enables higher-power and narrower-divergence operation while keeping a symmetric beam shape. By optimizing the double-lattice photonic crystal and the reflective properties of a backside distributed Bragg reflector (DBR), we achieve a high peak power of 10 W while maintaining a nearly diffraction-limited beam divergence of ∼0.1° (FWHM) from a 500 µm diameter resonator. Using this PCSEL, we construct a LiDAR system that uses no external lens system in its light source and demonstrate highly spatially resolved ToF sensing (measurement range of ∼20 m), which is appropriate for autonomous robots and factory automation

Wide-bandgap GaN-based watt-class photonic-crystal lasers

青色GaN系フォトニック結晶レーザーの高出力・高ビーム品質動作に成功 --次世代の高品位レーザー加工、高輝度照明、水中LiDAR等の実現に向けて--. 京都大学プレスリリース. 2022-11-04.Short-wavelength (blue-violet-to-green) lasers with high power and high beam quality are required for various applications including the machining of difficult-to-process materials and high-brightness illuminations and displays. Promising light sources for such applications are wide-bandgap GaN-based photonic-crystal surface-emitting lasers (PCSELs), which are based on two-dimensional resonance in the photonic crystal. Developments of these devices have lagged behind those of longer-wavelength GaAs-based PCSELs, because device designs for achieving robust two-dimensional resonance and a nanofabrication process that avoids introducing disorders have remained elusive for wide-bandgap GaN-based materials. Here, we address these issues and successfully realize GaN-based PCSELs with high, watt-class (>1 W) output power and a circular, single-lobed beam with a very narrow (~0.2°) divergence angle at blue wavelengths. In addition, we demonstrate continuous-wave operation with a high output power (~320 mW) and a high beam quality (M²~1). Our results will enable the use of GaN-based PCSELs in the above-mentioned applications

Proposal and Demonstration of Free-Space Optical Communication Using Photonic Crystal Surface-Emitting Lasers

We propose and demonstrate free-space optical (FSO) communication using photonic crystal surface-emitting lasers (PCSELs). Unlike other types of conventional semiconductor lasers, such as edge-emitting lasers (EELs) and vertical-cavity surface-emitting lasers (VCSELs), PCSELs achieve much larger area single-mode coherent lasing, and this unique feature enables high-power (>watt) and lens-free operations at the same time. To date, these advantages have been recognized to be game changing, especially in light detection and ranging (LiDAR) and laser processing applications. In this work, we show that FSO communication can also benefit from these advantages of PCSELs; more specifically, conventional transmitters that include low-power semiconductor lasers, optical lenses, and fiber-based amplifiers could be replaced with a single PCSEL. Since fiber amplifiers usually consist of bulky components and have low conversion efficiencies, PCSELs can offer more space- and power-saving solutions. Moreover, the narrow beam divergence angles directly obtained from large-area single-mode PCSELs can also eliminate the need for lens systems on the transmitter side. To experimentally verify these potential advantages, we performed FSO transmission experiments based on PCSELs and successfully transmitted 480-MHz and 864-MHz orthogonal frequency division multiplexed (OFDM) signals over 1.1 m using a 500-μm PCSEL in a lens-free transmitter configuration. We believe that PCSELs open new possibilities and choices in FSO communication

Feature Integration in the Mapping of Multi-Attribute Visual Stimuli to Responses

In the human visual system, different attributes of an object, such as shape and color, are separately processed in different modules and then integrated to elicit a specific response. In this process, different attributes are thought to be temporarily “bound” together by focusing attention on the object; however, how such binding contributes to stimulus-response mapping remains unclear. Here we report that learning and performance of stimulus-response tasks was more difficult when three attributes of the stimulus determined the correct response than when two attributes did. We also found that spatially separated presentations of attributes considerably complicated the task, although they did not markedly affect target detection. These results are consistent with a paired-attribute model in which bound feature pairs, rather than object representations, are associated with responses by learning. This suggests that attention does not bind three or more attributes into a unitary object representation, and long-term learning is required for their integration

Changes in Pediatric Patient Trends in Eating and Swallowing Disorders: A Comparison between the First and Fifth Year after Establishment of the Special Needs Dental Center

A Special Needs Dental Center （hereafter referred to as the Center） was established at Showa University Dental Hospital in April 2012 to treat patients who need special care. In cooperation with the Division of Dentistry for Persons with Disabilities, the Division of Hygiene and Oral Health is mainly engaged in the treatment of patients with eating and swallowing disorders. It has been five years since the establishment of the Center. The present study was aimed to establish an effective medical support method through a comparative study of changes in patient trends. A total of 65 patients who visited the Center from April 2017 to March 2018 were examined and their statistics were compared with those of 60 previously reported patients who initially visited the Center for medical examination in 2012. In 2012, many visits occurred during the nursing period; however, in 2017, the number of patients who visited after the weaning period increased. Other noted trends were increased diversity in primary disease, more patient referrals, fewer patients with severe swallowing dysfunction, and more patients with oral dysfunction. The necessity of eating and swallowing practice is thought to increase when lifestyle and oral environment change. The treatment of eating and swallowing disorders is important in the dental profession. Due to the introduction of insurance coverage in Japan in 2018 for developmental insufficiency of oral function, more pediatric patients with eating and swallowing disorders will likely be treated in the future