We performed a detailed error analysis in domain-specific neural machine translation (NMT) for the English and Japanese language pair with fine-grained manual annotation. Despite its importance for advancing NMT technologies, research on the performance of domain-specific NMT and non-European languages has been limited. In this study, we designed an error typology based on the error types that were typically generated by NMT systems and might cause significant impact in technical translations: “Addition,” “Omission,” “Mistranslation,” “Grammar,” and “Terminology.” The error annotation was targeted to the medical domain and was performed by experienced professional translators specialized in medicine under careful quality control. The annotation detected 4,912 errors on 2,480 sentences, and the frequency and distribution of errors were analyzed. We found that the major errors in NMT were “Mistranslation” and “Terminology” rather than “Addition” and “Omission,” which have been reported as typical problems of NMT. Interestingly, more errors occurred in documents for professionals compared with those for the general public. The results of our annotation work will be published as a parallel corpus with error labels, which are expected to contribute to developing better NMT models, automatic evaluation metrics, and quality estimation models.

We propose an on-chip micromanipulation method based on mode switching of vibration-induced asymmetric flow. The asymmetric flow can be induced around rotationally asymmetric structures on a microfluidic chip by applying a circular vibration to the chip. Thus, the flow pattern can be switched by changing directions of applied vibrations as clockwise or counter-clockwise. In this study, we applied the switching of flow patterns (e. g., trap mode and transport mode, or trap mode and alignment mode) to change the manipulation modes of microobjects. Furthermore, we demonstrated the proposed method for two applications, local cell concentration and single particle loading. These demonstrations show that the proposed manipulation method can realize versatile on-chip micromanipulations and will contribute to high-throughput and high-reliability cell analysis or diagnosis.

We present a novel cell manipulation method based on vibration-induced flow in open-chip environment. By applying circular vibration to a chip having micropillar patterns on its surface, local whirling flow is induced around the micropillars. Therefore, by patterning micropillar array on a chip and applying the circular vibration to the chip, we can achieve cell transportation along the array in an open chip environment. We theoretically analyzed this phenomenon with a single micropillar, and experimentally evaluated behaviours of manipulated microbeads with two micropillars. We confirm there are different manipulation modes according to the pitch of micropillars. We designed the micropillar array for an oocyte transportation based on these evaluations. We succeeded in the transportation of oocytes with up to 35.6 μm/s and confirmed that the velocity can be changed by changing the frequency and amplitude of the applied vibration.

Cell manipulations and cell surgeries are key techniques in biotechnology today. Micro/nanorobots integrated on a microfluidic chip (on-chip robot) are a promising technology for cell manipulations and cell surgeries because of their operator skill independency and robustness for external environments. These features enable high-throughput cell manipulations and cell surgeries on a microfluidic chip. However, it is difficult to apply previous on-chip robots for small cells of order ≈ 10 \bm μ m because the manipulation or surgery probes of those robots are a few micrometers in size. This size has been restricted by their fabrication, employing a standard mask lithography process. We fabricated on-chip robots of nanometer size by femtosecond laser exposure (nanorobots). The processing resolutions were 270 nm (linewidth) and 600 nm (thickness). Furthermore, our fabrication technique enabled the nanorobot to have a hybrid structure integrating functional nanomaterials (hybrid nanorobot). By integrating the various functional nanomaterials on the nanorobot, we can create a new function for the nanorobot. In this study, we fabricated a hybrid nanorobot with carbon nanotubes (CNTs) of high photothermal efficiency. We demonstrated a single-cell puncture with this nanorobot by irradiating the CNTs with an infrared laser and generating heat at that point. Additionally, we demonstrated an optical manipulation of the nanorobot that makes it possible to perform a cell puncture with high spatial flexibility and high positioning accuracy.

An earthworm moves by peristaltic crawling, which propagates extension and contraction waves along the anteroposterior direction from the anterior to posterior part, by varying the thickness and length of its segments. This locomotion mechanism is in contact with a large area on the ground when the robot moves. Furthermore, the amount of space required is less than that for other locomotion mechanisms. Therefore, this mechanism is suitable for not only rescue robots but also exploration robots in the ground and automatic endoscopic robots. In this study, we developed a peristaltic robot with a flexible feature actuated by servomotors. We proposed different turning patterns. In addition, we confirmed that the robot could move not only on a plane surface but also in a tube. The experiments revealed good performance.