Lithium Phenolate Complexes with a Pyridine‐Containing Polymer for Solution‐Processable Electron Injection Layers in PLEDs

A series of (vinylphenyl)pyridine‐based polymer binders, PVPh2Py, PVPh3Py, and PVPh4Py, are designed and synthesized and it is found that mixtures of Liq and the polymers exhibit superior electron injection characteristics as ultrathin (1.6 nm) electron injection layer (EIL) films. They are comparable to those of EILs composed only of Liq. The addition of the polymers does not deteriorate the performance of Liq EILs. Additionally, when the EIL thickness is increased from 1.6 nm to 16 nm, the driving voltages increase and the external quantum efficiencies decrease. The increase in the voltage and decrease in the EQE are suppressed in the device with mixed EILs compared to those observed for the device composed of 100 wt% Liq. Furthermore, the position of the nitrogen in the pyridine ring is considered to influence the electron transport properties of the EILs. The mixing PVPh4Py with Liq improves the driving voltage of the fabricated devices, even with a thick mixed EIL. This reduced dependence of the performance of EILs on their thickness will be advantageous for the coating of large areas using solution processes.     

Real-Time Amplitude and Phase Imaging of Optically Opaque Objects by Combining Full-Field Off-Axis Terahertz Digital Holography with Angular Spectrum Reconstruction

Terahertz digital holography (THz-DH) has the potential to be used for non-destructive inspection of visibly opaque soft materials due to its good immunity to optical scattering and absorption. Although previous research on full-field off-axis THz-DH has usually been performed using Fresnel diffraction reconstruction, its minimum reconstruction distance occasionally prevents a sample from being placed near a THz imager to increase the signal-to-noise ratio in the hologram. In this article, we apply the angular spectrum method (ASM) for wavefront reconstruction in full-filed off-axis THz-DH because ASM is more accurate at short reconstruction distances. We demonstrate real-time phase imaging of a visibly opaque plastic sample with a phase resolution power of λ/49 at a frame rate of 3.5 Hz in addition to real-time amplitude imaging. We also perform digital focusing of the amplitude image for the same object with a depth selectivity of 447 μm. Furthermore, 3D imaging of visibly opaque silicon objects was achieved with a depth precision of 1.7 μm. The demonstrated results indicate the high potential of the proposed method for in-line or in-process non-destructive inspection of soft materials.     

Feasibility study on cellular network analysis with patterned cell culture microdevice

In order to realize cellular network analysis on a chip-based system, our group has been developing a patterned cell culture microdevice with pillars in an array for tapping cells into space surrounded by the pillars. The pillar structures has advantages to trap both adhesive and non-adhesive cells and to precisely control positions of cells and distances between cells for understanding effects of various cell patterns on functions of a cellular network such as cell proliferation, differentiation, and network formation. In this paper, HeLa cell cultivation with the patterned cell culture microdevice having a pillar array fabricated by dry film of thick negative photoresist SU-8 on a glass substrate was executed as a feasibility study on a cellular network analysis. The results revealed that the device performance was found to be enough to culture HeLa cells for more than 48 h. In addition, relative extensibility of blocks of multiple cells compared with single cells tapped on the device was observed. Thus, the patterned cell culture microdevice proposed here could be applicable to analysis of cellular functions.     

The Direct Spectroscopy of Positronium Hyperfine Structure Using a Sub-THz Gyrotron

Positronium is an ideal system for research on Quantum Electrodynamics (QED), especially in a bound state. A discrepancy of 3.9 standard deviations has been found between the measured hyperfine structure (Ps-HFS) and the QED predictions. This may be due to the contribution of unknown new physics or common systematic effects in previous measurements, in all of which the Zeeman effect was used. We propose a new method to directly measure the Ps-HFS using a high power gyrotron. We compare two resonators which have been developed to supply sufficient power to drive the direct transition, a Fabry-Pérot resonator and a ring resonator with a diffraction grating. We plan to perform first direct measurement of Ps-HFS within the next six months.     

Direct Measurement of Positronium HyperFine Structure: ～ A New Horizon of Precision Spectroscopy Using Gyrotrons ～

Positronium is an ideal system for research on QED, especially in a bound state. A discrepancy (3.9σ) is found recently between measured HFS values and the QED prediction (including up-to O(α ³ log α ^− 1), where α is the fine-structure constant.). It might be due to a contribution of unknown new physics or common systematic problems in all the previous measurements. A new method to measure HFS directly is performed using a high power gyrotron. The transition from ortho-positronium to para-positronium has been observed with 5 σ CL, which is the first observation of M1 transition in (sub)Terahertz region. New technologies of high power gyrotrons are developed for precision spectroscopy.     

Degradation of organophosphorus pesticides in aqueous extracts of young green barley leaves (Hordeum vulgare L)

The degradation of the organophosphorus pesticides malathion, chlorpyrifos, guthion, diazinon, methidathion and parathion in an aqueous extract of young green barley leaves (Hordeum vulgare L) was monitored by gas chromatography. Aqueous solutions of various amounts of freeze‐dried young barley leaves containing 5.75 mg l⁻¹ of malathion were incubated at 37 °C and pH 7.4 over prolonged time periods. Over 95% of the malathion degraded in 4 h in a 3% (30 g l⁻¹) solution of young green barley leaves. When the barley solution was autoclaved at 120 °C for 25 min prior to the addition of malathion, no degradation of malathion was observed. When 10 mg l⁻¹ each of the above six pesticides was incubated in a 15% (150 g l⁻¹) solution of young green barley leaves for 3 h at 37 °C and pH 7.4, malathion and chlorpyrifos degraded 100%, whereas parathion (75%), diazinon (54%), guthion (41%) and methidathion (23%) showed lesser degrees of degradation. © 1999 Society of Chemical Industry     

Spectroscopic and Photoluminescent Properties of Indium Zinc Oxide (IZO) and IZO/Ag/IZO Sandwiched Film

We report the ellipsometric and photoluminescence (PL) properties of Indium zinc oxide (IZO) films, which were grown by radio frequency sputtering under Ar and O₂ atmospheres. IZO films grown under an O₂ atmosphere (IZO (O₂)) showed enhanced PL properties when compared to the films grown under an Ar atmosphere (IZO (Ar)), particularly with respect to the band-edge emission. The enhancement of band-edge emission can be attributed to the reduction in the non-emissive defect states related to oxygen vacancies, which were repaired by sputtering under O₂ atmosphere, whereas the PL enhancement in green region is probably due to the formation of the different types of defects under the excess oxygen environment. This was also supported by the results of time-resolved PL measurements, where the band-edge emission of IZO (Ar) showed rapid decay with a 50 ps lifetime, which indicates the dominance of the relaxation pathway to underlying defect states. In contrast, the PL decay profiles of IZO (O₂) for band-edge and emissive defect states showed moderate decay with time-constants of 2.3 ns and 5.7 ns, respectively. The exciton relaxation dynamics were sensitive to the presence and its kinds of defect states, which were controlled by the growth conditions.     

Oxygen doped Ge crystals Czochralski-grown from the B2O3-fully-covered melt

Local vibrations of oxygen in Ge crystals grown from a melt fully covered by B₂O₃ were evaluated by Fourier-transform infrared spectroscopy. Ge single crystals containing oxygen were grown by the Czochralski method under various growth conditions. Oxygen concentrations in the crystals were determined to be in the range between 8.5 × 10¹⁵ and 5.5 × 10¹⁷ cm⁻³ from the infrared absorption at 855 cm⁻¹ originating in local vibration of Ge-O_i-Ge quasi-molecules. Absorption peaks relating to GeO_x, SiO_x and Si-O_i-Si were not detected in the as-grown crystals. The calibration coefficient for determining oxygen concentration in Ge crystals from the absorption peak intensity at 1264 cm⁻¹ was estimated to be 1.15 × 10¹⁹ cm⁻².     

Modelling and prediction of phyto- and zooplankton dynamics in Lake Kasumigaura by artificial neural networks

An artificial neural network model was developed for Lake Kasumigaura to predict timing and magnitudes for chlorophyll a, five species of blue-green algae and three zooplankton groups. The model was trained by 8 years of limnological time series and validated by two independent years. The validation showed the potential of neural networks as predictive tools for highly non-linear phenomena such as blue-green algal blooms in freshwater lakes.     

Energy‐Dissipative Matrices Enable Synergistic Toughening in Fiber Reinforced Soft Composites

Tough hydrogels have shown strong potential as structural biomaterials. These hydrogels alone, however, possess limited mechanical properties (such as low modulus) when compared to some load‐bearing tissues, e.g., ligaments and tendons. Developing both strong and tough soft materials is still a challenge. To overcome this obstacle, a new material design strategy has been recently introduced by combining tough hydrogels with woven fiber fabric to create fiber reinforced soft composites (FRSCs). The new FRSCs exhibit extremely high toughness and tensile properties, far superior to those of the neat components, indicating a synergistic effect. Here, focus is on understanding the role of energy dissipation of the soft matrix in the synergistic toughening of FRSCs. By selecting a range of soft matrix materials, from tough hydrogels to weak hydrogels and even a commercially available elastomer, the toughness of the matrix is determined to play a critical role in achieving extremely tough FRSCs. This work provides a good guide toward the universal design of soft composites with extraordinary fracture resistance capacity.