Low confinement loss hybrid-guiding tellurite photonic bandgap fiber

A hybrid-guiding tellurite (TZNLP) photonic bandgap fiber (PBGF) with low confinement loss is presented in this paper. A detailed comparison between the hybrid-guiding tellurite PBGF in which the high-index rods (TLWMN) replace one row of air holes in the radial direction and the all-solid tellurite PBGF has been accomplished. Low confinement loss windows can be achieved in this novel fiber due to the collaborated action of two guiding mechanisms–total internal reflection and antiresonant reflection.     

Novel concept for the aggregation structure of fatty acid monolayers on the water surface and direct observation of molecular arrangements in their monolayers

The aggregation structure of fatty acid monolayers on water subphases of different pH’s was investigated by means of transmission electron microscopy. Fatty acid monolayers exhibited the phase transition from an amorphous state to a crystalline one by surface compression in the case of a highly dissociated state of hydrophilic groups, whereas they did not show the phase transition in the case of a slightly dissociated state. The aggregation structure of monolayers on the water surface was systematically classified into “the crystalline monolayer”, “the amorphous monolayer” and “the compressing crystallized monolayer” with respect to thermal and chemical (intermolecular repulsive) factors. Molecular-resolution images of fatty acid molecules in the monolayers on mica substrate were successfully observed with an atomic force microscope (AFM) for the first time. The AFM image of a lignoceric acid monolayer prepared at a surface pressure of 5mNm⁻¹ showed a two-dimensional periodic structure with locally disordered molecular arrangements. Also, the nondestructive AFM image observation was successful for a stearic acid monolayer which was prepared by a multistep creep method, indicating that a high mechanical stability of the monolayer is inevitably required for the nondestructive AFM observation.     

A digital driving method using pulse-density modulation with a random dither matrix for higher motion image quality

We propose a new digital driving technique using pulse-density modulation (PDM) with a random dither matrix for evenness of luminance uniformity and higher motion image quality. As a digital driving technique, pulse-width modulation (PWM) is conventionally used for active-matrix organic light-emitting diode (AMOLED) displays in order to improve luminance uniformity. However, in PWM driving, it is difficult to realize high-frame-rate driving for improving motion image quality. On the other hand, it is considered that PDM driving method is effective to obtain high motion image quality because of non-frame-refreshing property. In the present paper, we proposed a PDM driving technique using a random dither matrix and evaluated the relationship between the display image quality and the driving frequency in the proposed method through simulations. As a result, it is confirmed that good image quality can be obtained by using a blue-noise mask as a random dither matrix at a practical driving frequency. Moreover, we demonstrated the proposed technique using an actual AMOLED panel.     

Intracerebroventricular Treatment with 2-Hydroxypropyl-β-Cyclodextrin Decreased Cerebellar and Hepatic Glycoprotein Nonmetastatic Melanoma Protein B (GPNMB) Expression in Niemann–Pick Disease Type C Model Mice

Niemann–Pick disease type C (NPC) is a recessive hereditary disease caused by mutation of the NPC1 or NPC2 gene. It is characterized by abnormality of cellular cholesterol trafficking with severe neuronal and hepatic injury. In this study, we investigated the potential of glycoprotein nonmetastatic melanoma protein B (GPNMB) to act as a biomarker reflecting the therapeutic effect of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in an NPC mouse model. We measured serum, brain, and liver expression levels of GPNMB, and evaluated their therapeutic effects on NPC manifestations in the brain and liver after the intracerebroventricular administration of HP-β-CD in Npc1 gene-deficient (Npc1^−/−) mice. Intracerebroventricular HP-β-CD inhibited cerebellar Purkinje cell damage in Npc1^−/− mice and significantly reduced serum and cerebellar GPNMB levels. Interestingly, we also observed that the intracerebral administration significantly reduced hepatic GPNMB expression and elevated serum ALT in Npc1^−/− mice. Repeated doses of intracerebroventricular HP-β-CD (30 mg/kg, started at 4 weeks of age and repeated every 2 weeks) drastically extended the lifespan of Npc1^−/− mice compared with saline treatment. In summary, our results suggest that GPNMB level in serum is a potential biomarker for evaluating the attenuation of NPC pathophysiology by intracerebroventricular HP-β-CD treatment.     

Motion blur reduction with triangular waveform emission and optimized enhance filter

Degradation of moving image quality by motion blur on hold‐type displays is a well‐known issue. In order to reduce motion blur, a number of driving methods, such as a higher frame rate and a shorter temporal aperture, have been proposed. Methods to reduce motion blur by means of signal processing as a precompensation method have also been proposed. In these methods, however, hold emission that emits light at a constant intensity during a frame is used. Since the spatial frequency response of the hold emission in a moving picture has a null point, the effectiveness of precompensation methods is limited to the lower‐spatial frequency domain. A triangular waveform emission has been investigated, and it has a higher spatial frequency response than hold emission. In the present paper, we calculated an optimized enhancement filter for the triangular waveform emission as a precompensation method and demonstrated its effectiveness for reducing motion blur by using the triangular waveform emission and the optimized enhancement filter. As a result, the optimized enhancement filter reduced motion blur and suppressed distortion that emerged when using a conventional enhancement filter.     

Monolayer Transition Metal Dichalcogenides as Light Sources

Reducing the dimensions of materials is one of the key approaches to discovering novel optical phenomena. The recent emergence of 2D transition metal dichalcogenides (TMDCs) has provided a promising platform for exploring new optoelectronic device applications, with their tunable electronic properties, structural controllability, and unique spin valley–coupled systems. This progress report provides an overview of recent advances in TMDC‐based light‐emitting devices discussed from several aspects in terms of device concepts, material designs, device fabrication, and their diverse functionalities. First, the advantages of TMDCs used in light‐emitting devices and their possible functionalities are presented. Second, conventional approaches for fabricating TMDC light‐emitting devices are emphasized, followed by introducing a newly established, versatile method for generating light emission in TMDCs. Third, current growing technologies for heterostructure fabrication, in which distinct TMDCs are vertically stacked or laterally stitched, are explained as a possible means for designing high‐performance light‐emitting devices. Finally, utilizing the topological features of TMDCs, the challenges for controlling circularly polarized light emission and its device applications are discussed from both theoretical and experimental points of view.     

Self‐Aligned and Scalable Growth of Monolayer WSe2–MoS2 Lateral Heterojunctions

2D layered heterostructures have attracted intensive interests due to their unique optical, transport, and interfacial properties. The laterally stitched heterojunction based on dissimilar 2D transition metal dichalcogenides forms an intrinsic p–n junction without the necessity of applying an external voltage. However, no scalable processes are reported to construct the devices with such lateral heterostructures. Here, a scalable strategy, two‐step and location‐selective chemical vapor deposition, is reported to synthesize self‐aligned WSe₂–MoS₂ monolayer lateral heterojunction arrays and demonstrates their light‐emitting devices. The proposed fabrication process enables the growth of high‐quality interfaces and the first successful observation of electroluminescence at the WSe₂–MoS₂ lateral heterojunction. The electroluminescence study has confirmed the type‐I alignment at the interface rather than commonly believed type‐II alignment. This self‐aligned growth process paves the way for constructing various 2D lateral heterostructures in a scalable manner, practically important for integrated 2D circuit applications.     

A study on a driving method of OLED displays for better motion image quality with adaptive temporal aperture control

Degradation of motion image quality by motion blur on hold‐type displays, such as liquid‐crystal displays and organic light‐emitting diode displays, is a well‐known issue. To improve motion image quality, a driving method with a shorter temporal aperture has been proposed. However, a shorter temporal aperture requires higher instantaneous luminance on displays. Higher instantaneous luminance accelerates the lifetime degradation of organic light‐emitting diode. Therefore, we have been developing a driving method with adaptive temporal aperture control for a longer lifetime and better motion image quality. However, two image quality degradations were perceived when this driving method was applied. One of these degradations was caused at the boundary between the different temporal apertures. The other degradation was caused by switching the temporal aperture between frames. Hence, we have also proposed transition area and period insertion methods to suppress these degradations. In this paper, we discuss the mechanism of these degradations and confirm the effectiveness of our proposed methods by subjective evaluations. In the results, the degradations were suppressed by inserting 80 lines of transition area and by inserting 50 frames of transition period.     

Film pressure distributions in point contacts predicted by thermal EHL analyses

In general, lubricated rolling/sliding contact fatigue problems have been investigated by assuming Hertzian contact pressure distributions. In this paper, thermal EHL analyses in consideration of the variations in oil properties in all directions within the film have been carried out under conditions of circular and elliptical contacts. It has been found that the actual film pressure distributions differ markedly from the Hertzian pressure distribution depending on the thermal conductivities of both contacting surfaces, slide–roll ratios and viscosity–pressure coefficients.