Strong and Tough Nacre-Inspired Graphene Oxide Composite with Hierarchically Similar Structure.

We report a graphene oxide (GO)-based composite, featuring GO/cross-linking agent (CA) nanoparticles, inspired by a nacre-like hierarchical structure present in nature. The as-prepared GO/CA composite was powdered to nanoscale particles and then mixed with pure GO to be GO/CA/GO (GCG) composite forming hierarchical GO/CA nanoasperities on the GO surface. The strength and toughness of the nacre-inspired GCG composite films were simultaneously improved by adjusting the nanoparticle concentration and hierarchical level of the GO-based films. Compared to pristine GO films and GO/CA composites, which exhibit a low level of hierarchy in their structures, the tensile strength and toughness of the GCG composites with higher hierarchy were enhanced 3.1 and 1.6 times and 47.6 and 10.9 times, respectively. Furthermore, a plausible mechanism of increasing mechanical properties based on nanoscale asperities and homogeneous interactions between GO and CA has been discussed.

Asymmetric Dichroic Colors in Stretchable Film with Embedded Au/Ag Alloy Nanoparticles.

We present a new type of stretchable dichroic film in which Au and Ag alloy nanoparticles (NPs) are dispersed in polydimethylsiloxane (PDMS). The alloy NPs are synthesized with different atomic compositions and sizes to modulate their plasmonic resonance frequencies and absorption and scattering cross sections. The PDMS dichroic film in which 100 nm alloy NPs with a Au/Ag ratio of 7:3 are dispersed shows exotic optical properties under tensile strain. When 40% tensile strain is applied, the film exhibits a strain-sensitive transmission and strain-insensitive reflection behavior in which the transmittance is increased up to 2.6 times, whereas the reflectance remains unchanged. Moreover, we demonstrate a stretchable anticounterfeiting film and a flexible dichroic sculpture fabricated with the PDMS composite. This work demonstrates a new type of plasmonic application that has great potential in various applications, such as special-purpose optical films, security patterns, and smart windows.

Wearable Triboelectric Strain-Insensitive Pressure Sensors Based on Hierarchical Superposition Patterns.

Recently, wearable triboelectric sensors capable of self-powering, which can be widely used in artificial skin and robotics, have received much attention. Herein, we develop a stretchable triboelectric pressure sensor with a new pattern by superimposing two patterns using both polystyrene beads and UV-ozone treatment. This patterned structure works more sensitively to pressure than a general planar and one-kind patterned structure. The sensor is constructed by sandwiching styrene butadiene rubber (SBR) and poly(dimethylsiloxane) (PDMS). It demonstrates a high sensitivity of 0.078 kPa-1 (0-20 kPa), a low detection limit (1.2 kPa), and pressure sensitivity maintained under 40% strain. The detection behavior of the strain-insensitive triboelectric sensor against pressure is very consistent with the simulation based on the theory. In applications, we successfully detect various human motions, not only small motions such as bending fingers but also large motions such as standing up and raising arms.

Prevalence and risk factors of bowel symptoms in Korean patients with ulcerative colitis in endoscopic remission: a retrospective study.

BACKGROUND: Many patients with ulcerative colitis (UC) in clinical remission frequently complain of bowel symptoms such as increased stool frequency (SF) and rectal bleeding (RB). However, studies on these patient-reported outcomes in patients with inactive UC are limited, especially in Korea. Therefore, we investigated the prevalence and risk factors of bowel symptoms in Korean patients with inactive UC. METHODS: We investigated the prevalence of bowel symptoms in patients with endoscopically quiescent UC between June 1989 and December 2016 using a well-characterized referral center-based cohort. The Mayo clinic score (MCS) was used to evaluate bowel symptoms at the most recent visit near the date of endoscopy. Clinical characteristics of the patients were compared based on the presence or absence of bowel symptoms. RESULTS: Overall, 741 patients with endoscopically quiescent UC were identified, of whom 222 (30%) and 48 (6.5%) had an SF and RB subscore of ≥ 1, respectively. Patients with bowel symptoms (SF + RB ≥ 1; n = 244 [32.9%]) had higher rates of left-sided colitis (E2) or extensive colitis (E3) than patients without bowel symptoms (SF + RB = 0; n = 497 [67.1%]; P = 0.002). Multivariate analysis revealed that female sex (odds ratio [OR]: 1.568; 95% confidence interval [CI]: 1.023-2.402; P = 0.039) and E2 or E3 (OR 1.411; 95% CI 1.020-1.951; P = 0.038) were the significant risk factors for increased SF. CONCLUSIONS: This study revealed that one-third of patients with endoscopically quiescent UC reported increased SF. Female sex and disease extent may be associated with bowel symptoms.

Angle-Insensitive Transmission and Reflection of Nanopatterned Dielectric Multilayer Films for Colorful Solar Cells.

Aesthetically appealing photovoltaic (PV) panels with colorful layers are used in numerous applications involving color matching with the surroundings. To develop a colored film for a PV system, appropriate optical properties such as high transparency and low angle sensitivity are necessary because the colored layers can reduce the efficiency of the PV system by causing variations in the transmittance and angle of incidence. Herein, we propose a facile fabrication method for bioinspired three-dimensional (3D) photonic crystal (PC) films that exhibit broad angle-insensitive transmission and reflection, for application in colorful PV. This structure, patterned on a sequentially stacked 11-layer film of SiO2 and TiO2, is fabricated via nanoimprint lithography and a one-step dry-etching process, without using a metal mask. The changes in transmission and reflection are observed via ultraviolet-visible spectroscopy and from the reflected images obtained under various angles. The transmittance dips of the 3D PC film shift by less than 10 nm in wavelength, for angles from 0 to 45°, indicating low angle dependency. In addition, the change in the observed color, with respect to the viewing position, is less in the fabricated film. Once the 3D PC film was added to a commercial PV cell, it exhibited a higher efficiency (approximately 6% upper) when compared to a cell with a one-dimensional PC film, during the duration of the experiment, from 0 to 30°. Thus, the proposed method demonstrates excellent potential for developing structural color films for achieving aesthetically appealing PV cells.

Comparison of surgical outcomes of slanted procedure for exotropia with convergence insufficiency according to their response to preoperative monocular occlusion.

The aim of this prospective study was to compare surgical outcomes of slanted bilateral lateral rectus (LR) recession for intermittent exotropia (IXT) with convergence insufficiency (CI) according to their response to preoperative monocular occlusion. This prospective study included 55 children who underwent slanted bilateral LR recession for IXT with CI. Patients were divided into two groups according to their response to preoperative monocular occlusion for 2 hours. The True CI group was defined as having near-distance differences of ≥10 PD before and after occlusion; the Masked CI group as having near-distance differences of <10 PD and ≥10 PD prior to and after occlusion. Slanted procedure reduced distance and near exodeviations from 32.1 PD and 43.0 PD to 3.5 PD and 4.4 PD, and collapsed near-distance differences from 10.9 PD to 1.0 PD at 3 years postoperatively. Cumulative probabilities of surgical success were 76%, and the mean recurrence was 50 months at 3 years postoperatively; the True CI and Masked CI groups showed cumulative success rates of 89% and 55%, respectively (p = 0.0052). Patients in the True CI group demonstrated surgical outcomes superior to those demonstrated by patients in the Masked CI group after slanted bilateral LR recession.

A Robust Balance-Control Framework for the Terrain-Blind Bipedal Walking of a Humanoid Robot on Unknown and Uneven Terrain.

Research on a terrain-blind walking control that can walk stably on unknown and uneven terrain is an important research field for humanoid robots to achieve human-level walking abilities, and it is still a field that needs much improvement. This paper describes the design, implementation, and experimental results of a robust balance-control framework for the stable walking of a humanoid robot on unknown and uneven terrain. For robust balance-control against disturbances caused by uneven terrain, we propose a framework that combines a capture-point controller that modifies the control reference, and a balance controller that follows its control references in a cascading structure. The capture-point controller adjusts a zero-moment point reference to stabilize the perturbed capture-point from the disturbance, and the adjusted zero-moment point reference is utilized as a control reference for the balance controller, comprised of zero-moment point, leg length, and foot orientation controllers. By adjusting the zero-moment point reference according to the disturbance, our zero-moment point controller guarantees robust zero-moment point control performance in uneven terrain, unlike previous zero-moment point controllers. In addition, for fast posture stabilization in uneven terrain, we applied a proportional-derivative admittance controller to the leg length and foot orientation controllers to rapidly adapt these parts of the robot to uneven terrain without vibration. Furthermore, to activate position or force control depending on the gait phase of a robot, we applied gain scheduling to the leg length and foot orientation controllers, which simplifies their implementation. The effectiveness of the proposed control framework was verified by stable walking performance on various uneven terrains, such as slopes, stone fields, and lawns.

Iridescent and Glossy Effect on Polymer Surface Using Micro-/Nanohierarchical Structure: Artificial Queen of the Night Tulip Petals.

Many petals in nature have a hierarchical structure that imparts various optical properties. Among these, the petals of the Queen of the Night tulip exhibit an iridescent and glossy color due to the diffraction and scattering of light. Herein, we report a bioinspired micro-/nanohierarchical structure that mimics Queen of the Night tulip petal surfaces. Using a method that combined soft lithography and UV-ozone treatment, we fabricated nanoscale line patterns with a linewidth of 600 nm on microwrinkles of 15 µm width and 3 µm height. Using optical microscopy in the dark-field mode and monochromatic light diffraction measurements, we found that these hierarchical structures on a poly(dimethylsiloxane) (PDMS) substrate synergistically improved the scattering and diffraction effects, unlike the pristine, nano-, and microstructures. In addition, using a dye-colored PDMS material, we fabricated artificial Queen of the Night petals with iridescent and glossy effects. They show great potential for a range of applications, such as coloring, smart displays, dynamic gratings, and light-control devices.

Nacre-Mimetic Graphene Oxide/Cross-Linking Agent Composite Films with Superior Mechanical Properties.

We report a graphene oxide/cross-linking agent (GO/CA) composite inspired by the nacre structure. Based on the "brick-and-mortar" concept of nacre, graphene oxide and a cross-linking agent are covalently conjugated in the form of nacre. The mechanical characteristics of the nacre-mimetic GO/CA composite film can be controlled by adjusting the preparation method, degree of cross-linking, and cross-linking times. As a result, the cross-linking strategy can drastically enhance the tensile strength [142.9 ± 6.4 MPa (∼2.3-fold)], modulus [4.7 ± 0.36 GPa (∼15.7-fold)], and hardness [917.4 ± 85.7 MPa (∼9.0-fold)], which are superior to those of pristine materials. The cross-linking agent-based chemical bonding method for mechanically improved integration is mainly attributed to the formation of strong cross-linked networks between the GO-based 2D interfaces and CA. The facile fabrication process provides many opportunities to design advanced, robust, and integrated nacre-like GO/CA composites, which can be applied to future aerospace utilizations, electronic protectors, robotic elements, and permeable membranes.

Robots for the PyeongChang 2018 Winter Olympic Games.

Robotic and athletic achievements shared the stage at the PyeongChang 2018 Winter Olympic Games.

Historical difference between traditional Korean medicine and traditional Chinese medicine.

BACKGROUND: Although traditional Korean medicine (TKM) has been influenced by traditional Chinese medicine (TCM), it has developed distinctive features. Around the tenth century, Chinese medical books were introduced to Korea. In those days, Koreans started movement to develop its own medical system. METHODS: We reviewed Korean and Chinese medical literatures, and analysed the characteristics between two medical systems. RESULTS: In the early 17th century, Dongeuibogam was published by Dr Joon Hur. He provided a turning point to establish Korean medical system independent from TCM. TKM emphasizes specific characteristics of the individual who suffered from the disease, rather than single symptom. The concept was elaborated by Dr Jae Ma Lee who published Dongeuisusaebowon in the early 20th century. CONCLUSION: Through historical development, TKM has established the unique characteristic and modality as the whole-person-centered medicine.