Temperature-responsive culture surfaces for insect cell sheets to fabricate a bioactuator

ABSTRACT

For the first time, we have fabricated insect-derived cell sheets by using temperature-responsive culture surfaces having a phase-transition temperature below 25°C. We prepared the temperature-responsive cell culture surfaces (tissue culture polystyrene, TCPS) by grafting a copolymeric gel consisting of hydrophobic N-tert-butylacrylamide (tBAAm) and N-isopropylacrylamide (IPAAm) units. First, to characterize the hydrophilic and hydrophobic properties of the copolymeric gel-grafted surfaces, static water contact angles of each surface were measured at various temperatures. By increasing the amount of tBAAm in the grafted copolymeric gel, the transition temperature of the gel was shifted to lower temperatures. At 25°C, the grafted copolymeric gel was dehydrated, and the insect-derived cells (AeAl2 cells) adhered on all the copolymeric gel-grafted surfaces. At 20°C, AeAl2 cells cannot adhere on the P(IPAAm-1.62tBAAm)-TCPS surface (the initial molar ratio of IPAAm and tBAAm (tBAAm?=?1.62 mol%)) better than on other surfaces (TCPS and tBAAm?=?4.88, 8.17 mol%). These two findings implied that the lower critical solution temperature of the copolymeric gel-grafted-TCPS existed from 20°C to 25°C. The laminin-coated P(IPAAm-1.62tBAAm)-TCPS surface showed temperature-dependent cell attachment and detachment properties, while AeAl2 cells were not detached from the extracellular matrix uncoated P(IPAAm-1.62tBAAm)-TCPS surface. AeAl2 cells and insect muscle cells were harvested as the respective sheets.     

Ground object recognition and segmentation from aerial image‐based 3D point cloud

Several attempts have been made to grasp three‐dimensional (3D) ground shape from a 3D point cloud generated by aerial vehicles, which help fast situation recognition. However, identifying such objects on the ground from a 3D point cloud, which consists of 3D coordinates and color information, is not straightforward due to the gap between the low‐level point information (coordinates and colors) and high‐level context information (objects). In this paper, we propose a ground object recognition and segmentation method from a geo‐referenced point cloud. Basically, we rely on some existing tools to generate such a point cloud from aerial images, and our method tries to give semantics to each set of clustered points. In our method, firstly, such points that correspond to the ground surface are removed using the elevation data from the Geographical Survey Institute. Next, we apply an interpoint distance‐based clustering and color‐based clustering. Then, such clusters that share some regions are merged to correctly identify a cluster that corresponds to a single object. We have evaluated our method in several experiments in real fields. We have confirmed that our method can remove the ground surface within 20 cm error and can recognize most of the objects.     

Selective High‐Frequency Mechanical Actuation Driven by the VO2 Electronic Instability

Relaxation oscillators consist of periodic variations of a physical quantity triggered by a static excitation. They are a typical consequence of nonlinear dynamics and can be observed in a variety of systems. VO₂ is a correlated oxide with a solid‐state phase transition above room temperature, where both electrical resistance and lattice parameters undergo a drastic change in a narrow temperature range. This strong nonlinear response allows to realize spontaneous electrical oscillations in the megahertz range under a DC voltage bias. These electrical oscillations are employed to set into mechanical resonance a microstructure without the need of any active electronics, with small power consumption and with the possibility to selectively excite specific flexural modes by tuning the value of the DC electrical bias in a range of few hundreds of millivolts. This actuation method is robust and flexible and can be implemented in a variety of autonomous DC‐powered devices.     

Synthesis of Sintered Diamond with High Electrical Resistivity and Hardness

Diamond and diamond-ultrafine Co powder mixtures were sintered at 7.7 GPa and 1800° to 2000°C. A well-sintered body with a fine-grained homogeneous microstructure, high hardness, and high electrical resistivity was produced when a diamond-5 vol% Co powder mixture was used as the starting material.     

Transmission Characteristics of Hybrid Modes in Corrugated Waveguides Above the Bragg Frequency

We studied the transmission characteristics of hybrid modes in a corrugated circular waveguide above the Bragg frequency to develop a broad-band transmission line for millimeter waves. Millimeter waves at 294 GHz were transmitted into a straight waveguide. From observed power profiles in waveguide cross-sections, a high attenuation rate of 0.13 dB/m was obtained. To match a theoretical attenuation constant with the experimental one, we introduced an ad hoc coefficient of conventional surface reactance in the waveguide wall. This was necessary because the wall began to look like the surface with a decreasing anisotropic reactance owing to the frequency above the Bragg frequency. Using nonlinear optimization for mode content analysis, the observed power profiles in the waveguide cross-section were matched with theoretical profiles. There was good agreement between the calculated and observed centers of power profiles and attenuation rate along the waveguide. The theoretical analysis showed that the magnetic field at the waveguide wall increases and the substantial attenuation takes place. Above the Bragg frequency coupling to backwards propagating modes is a point of consideration. A combination of the backwards propagating EH_1,26 and the forward propagating HE₁₁ modes satisfied the Bragg condition at 294.7 GHz which was the nearest frequency of operating frequency. A strong attenuation of the incoming HE₁₁ mode by Bragg resonance was not expected due to large difference of 0.7 GHz. It becomes clear that the observed high transmission loss outside of the Bragg resonance can be explained by a decrease in anisotropic surface reactance at the wall.     

Electrical switching of the vortex core in a magnetic disk

A magnetic vortex is a curling magnetic structure realized in a ferromagnetic disk, which is a promising candidate for a memory cell for future non-volatile data-storage devices. Thus, an understanding of the stability and dynamical behaviour of the magnetic vortex is a major requirement for developing magnetic data-storage technology. Since the publication of experimental proof for the existence of a nanometre-scale core with out-of-plane magnetization in a magnetic vortex, the dynamics of vortices have been investigated intensively. However, a way to electrically control the core magnetization, which is a key for constructing a vortex-core memory, has been lacking. Here, we demonstrate the electrical switching of the core magnetization by using the current-driven resonant dynamics of the vortex; the core switching is triggered by a strong dynamic field that is produced locally by a rotational core motion at a high speed of several hundred metres per second. Efficient switching of the vortex core without magnetic-field application is achieved owing to resonance. This opens up the potentiality of a simple magnetic disk as a building block for spintronic devices such as a memory cell where the bit data is stored as the direction of the nanometre-scale core magnetization.     

Studies on steady‐state stability of looped power systems and stabilization by SMES

With the increasing number of dispersed power sources interconnected to the power supply system, power systems can take a form similar to that of a longitudinal system. Also, they can become looped, with both ends of the longitudinal system connected to each other. In the present paper, the steady‐state stability of longitudinal power systems and looped power systems is analyzed by means of the mode analysis method via eigenvalue and eigenvector calculation, and power system stabilization by SMES (Superconducting Magnetic Energy Storage) for looped systems is examined relative to that for longitudinal systems. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 48–54, 2000     

Performance analysis of shaft generator systems

A shaft generator system supplies electrical power required in a ship by using a part of the power produced by the main engine. Since the speed of the main engine can vary over a wide range, an externally commutated thyristor inverter, which has high reliability, is generally used to produce ac power with constant voltage and frequency. In this paper, a set of system equations, by which the total harmonic distortion of the output voltage, for example, can be estimated, is derived first. The effects of leading angle of the inverter and the reactance of ac reactor located in the output side of the inverter on the system performances and the operation limit of the system are then clarified. Moreover, a way of taking the system losses into account is proposed to obtain precise calculation results. Finally, the apparent power for the synchronous condenser to provide reactive power in the system is discussed. © 2000 Scripta Technica, Electr Eng Jpn, 131(3): 70–79, 2000     

Cell distributions in and sound absorption characteristics of flexible polyurethane foams

In this article, the two-dimensional distributions of cells from the cross section of some flexible polyurethane foams were cleared, and the three-dimensional distributions of cells based on Saltykov's theory were estimated further. As a result, it was found that a mean of the two-dimensional distributions of cells was a good linear relation with a mean of the three-dimensional distributions of cells, and it was confirmed that cell structure of the foams which should have been analyzed in the three-dimensional distributions was evaluated by analysis of the two-dimensional distributions fully. It was also found that not only cell number but also cell distribution was necessary in the evaluation of flexible polyurethane foams, and cell diameter was closely related to the sound absorption coefficient in polyester-based flexible polyurethane foams. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1395–1402, 1997     

CRISPR Screen Contributes to Novel Target Discovery in Prostate Cancer

Prostate cancer (PCa) is one of the common malignancies in male adults. Recent advances in omics technology, especially in next-generation sequencing, have increased the opportunity to identify genes that correlate with cancer diseases, including PCa. In addition, a genetic screen based on CRISPR/Cas9 technology has elucidated the mechanisms of cancer progression and drug resistance, which in turn has enabled the discovery of new targets as potential genes for new therapeutic targets. In the era of precision medicine, such knowledge is crucial for clinicians in their decision-making regarding patient treatment. In this review, we focus on how CRISPR screen for PCa performed to date has contributed to the identification of biologically critical and clinically relevant target genes.