Polarization- and Electrode-Optimized Polyvinylidene Fluoride Films for Harsh Environmental Piezoelectric Nanogenerator Applications.

While piezoelectric nanogenerators have demonstrated the effective conversion of tiny mechanical vibrations to electricity, their performances are rarely examined under harsh environmental conditions. Here, a multilayered polyvinylidene fluoride (PVDF) film-based piezoelectric nanogenerator (ML-PENG) is demonstrated to generate considerable and stable power outputs even at extremely low temperatures and pressures, and under strong UV. Up-/down-polarized PVDF films are alternately stacked, and Ag electrodes are intercalated between the two adjacent films. At -266 °C and 10-5  Torr, the ML-PENG generates an open-circuit voltage of 1.1 V, a short-circuit current density of 8 nA cm-2 , and a power density of 4.4 nW cm-2 . The piezoelectric outputs are quite stable against prolonged illumination of UV, large temperature- and pressure-variations, and excessive mechanical vibrations. The piezoelectric power density is greatly enhanced above the freezing and glass transition temperatures of PVDF and recorded to be 10, 105, and 282 nW cm-2 at -73, 0, and 77 °C, respectively. The ML-PENG generates sufficient power to operate five light-emitting diodes by harvesting biomechanical energy under simulated Martian conditions. This work suggests that polarization- and electrode-optimized ML-PENG can serve as a reliable and economic power source in harsh and inaccessible environments like polar areas of Earth and extraterrestrial Mars.

Large-Scale Assembly of Peptide-Based Hierarchical Nanostructures and Their Antiferroelectric Properties.

An effective strategy is developed to create peptide-based hierarchical nanostructures through the meniscus-driven self-assembly in a large area and fabricate antiferroelectric devices based on these nanostructures for the first time. The diphenylalanine hierarchical nanostructures (FF-HNs) are self-assembled by vertically pulling a substrate from a diphenylalanine (FF) solution dissolved in a miscible solvent under precisely controlled conditions. Owing to the unique structural properties of FF nanostructures, including high crystallinity and α-helix structures, FF-HNs possess a net electrical dipole moment, which can be switched in an external electric field. The mass production of antiferroelectric devices based on FF-HNs can be successfully achieved by means of this biomimetic assembly technique. The devices show an evident antiferroelectric to ferroelectric transition under dark conditions, while the ferroelectricity is found to be tunable by light. Notably, it is discovered that the modulation of antiferroelectric behaviors of FF-HNs under glutaraldehyde exposure is due to the FF molecules that are transformed into cyclophenylalanine by glutaraldehyde. This work provides a stepping stone toward the mass production of self-assembled hierarchical nanostructures based on biomolecules as well as the mass fabrication of electronic devices based on biomolecular nanostructures for practical applications.

Nelumbo nucifera Seed Extract Promotes Sleep in Drosophila melanogaster.

The sleep-promoting effects of the water extract of Nelumbo nucifera seeds (NNE) were investigated in an invertebrate model. The effects of NNE on the subjective nighttime activity, sleep episodes, and sleep time were determined using Drosophila melanogaster and locomotor activity monitoring systems in basal and caffeine-induced arousal conditions. The movements of fruit flies were analyzed using the Noldus EthoVision-XT system, and the levels of neuromodulators were analyzed using HPLC. Expression of neuromodulator receptors was analyzed using real-time PCR. NNE was shown to contain neurotransmission-related components; γ-aminobutyric acid (GABA) (2.33±0.22 mg/g), tryptophan (2.00±0.06 mg/g), quinidine (0.55±0.33 mg/g), and neferine (0.16±0.01 mg/g). The total activity of flies during nighttime was decreased by 52% with 1.0% NNE treatment. In the individual and collective conditions, the subjective nighttime activities (45/38%) and sleep bouts (20/14%) of flies was significantly decreased with NNE treatment, while total sleep times (10/27%) were significantly increased. This sleep-promoting effect is more pronounced in caffeine-treated conditions; the nighttime activity of flies was reduced by 53%, but total sleep time was increased by 60%. Our video-tracking analysis showed a significant decrease of the moving distance and velocity of flies by NNE. This NNE-mediated sleep-promoting effect was associated with up-regulation of GABAA/GABAB and serotonin receptors. The NNE-mediated increase of GABA content was identified in flies. These results demonstrate that NNE effectively promotes sleep in flies by regulating the GABAergic/serotonergic neuromodulators, and could be an alternative agent for sleep promotion.

Effects of deer bone extract on the expression of pro-inflammatory cytokine and cartilage-related genes in monosodium iodoacetate-induced osteoarthritic rats.

Deer bone extract has the potential to relieve the discomfort or the articular cartilaginous damage associated with osteoarthritic (OA) and may be useful as a natural supplement for OA treatment without serious side effects. We analyzed the expression of pro-inflammatory cytokine and cartilage-related genes in monosodium iodoacetate-induced OA rats. Increases in the levels of serum pro-inflammatory cytokines, such as interleukin-1ß, interleukin-6, and tumor necrosis factor-α were significantly inhibited by the administration of deer bone extract (p<0.05). Decreases in the expression of collagen type II (COL2) and tissue inhibitors of metalloproteinases (TIMPs) mRNAs in the cartilage were significantly inhibited by deer bone extract treatment (p<0.05). The deer bone extract significantly suppressed the expression of matrix metalloproteinases (MMPs) mRNAs in the cartilage. The deer bone extract induced the up-regulation of COL2 and TIMP mRNAs and the down-regulation of MMP mRNAs by suppressing the expression of pro-inflammatory cytokine mRNAs.

Hidden Direct Bandgap of Bi2O2Se by Se Vacancy and Enhanced Direct Bandgap of Bismuth Oxide Overlayer.

The Bi2O2Se surfaces are well-known to possess 50% Se vacancies, yet they have shown no in-gap states within the indirect bandgap (∼0.8 eV). We have found that the hidden in-gap states arising from the Se vacancies in a 2 × 1 pattern induce a reduced direct bandgap (∼0.5 eV). Such a reduced direct bandgap is responsible for the high electron mobility of Bi2O2Se. Moreover, the Bi oxide overlayers of the Bi thin films, formed through air exposure and annealing, unexpectedly exhibit a large direct bandgap (∼2.1 eV). The simplified fabrication of Bi oxide overlayers provides promise for improving Bi2O2Se electronic devices and enhancing photocatalytic activity.

Freestanding Oxide Membranes for Epitaxial Ferroelectric Heterojunctions.

Since facile routes to fabricate freestanding oxide membranes were previously established, tremendous efforts have been made to further improve their crystallinity, and fascinating physical properties have been also reported in heterointegrated freestanding membranes. Here, we demonstrate our synthetic recipe to manufacture highly crystalline perovskite SrRuO3 freestanding membranes using new infinite-layer perovskite SrCuO2 sacrificial layers. To accomplish this, SrRuO3/SrCuO2 bilayer thin films are epitaxially grown on SrTiO3 (001) substrates, and the topmost SrRuO3 layer is chemically exfoliated by etching the SrCuO2 template layer. The as-exfoliated SrRuO3 membranes are mechanically transferred to various nonoxide substrates for the subsequent BaTiO3 film growth. Finally, freestanding heteroepitaxial junctions of ferroelectric BaTiO3 and metallic SrRuO3 are realized, exhibiting robust ferroelectricity. Intriguingly, the enhancement of piezoelectric responses is identified in freestanding BaTiO3/SrRuO3 heterojunctions with mixed ferroelectric domain states. Our approaches will offer more opportunities to develop heteroepitaxial freestanding oxide membranes with high crystallinity and enhanced functionality.

Ultrahigh dielectric permittivity in oxide ceramics by hydrogenation.

Boosting dielectric permittivity representing electrical polarizability of dielectric materials has been considered a keystone for achieving scientific breakthroughs as well as technological advances in various multifunctional devices. Here, we demonstrate sizable enhancements of low-frequency dielectric responses in oxygen-deficient oxide ceramics through specific treatments under humid environments. Ultrahigh dielectric permittivity (~5.2 × 106 at 1 Hz) is achieved by hydrogenation, when Ni-substituted BaTiO3 ceramics are exposed to high humidity. Intriguingly, thermal annealing can restore the dielectric on-state (exhibiting huge polarizability in the treated ceramics) to the initial dielectric off-state (displaying low polarizability of ~103 in the pristine ceramics after sintering). The conversion between these two dielectric states via the ambient environment-mediated treatments and the successive application of external stimuli allows us to realize reversible control of dielectric relaxation characteristics in oxide ceramics. Conceptually, our findings are of practical interest for applications to highly efficient dielectric-based humidity sensors.

Acoustic Anomalies and the Critical Slowing-Down Behavior of MAPbCl3 Single Crystals Studied by Brillouin Light Scattering.

Inelastic light scattering spectra of organic-inorganic halide perovskite MAPbCl3 single crystals were investigated by using Brillouin spectroscopy. Sound velocities and acoustic absorption coefficients of longitudinal and transverse acoustic modes propagating along the cubic [100] direction were determined in a wide temperature range. The sound velocities exhibited softening upon cooling in the cubic phase, which was accompanied by the increasing acoustic damping. The obtained relaxation time showed a critical slowing-down behavior, revealing the order-disorder nature of the phase transition, which is consistent with the growth of strong central peaks upon cooling toward the phase transition point. The temperature dependences of the two elastic constants C11 and C44 were obtained in the cubic phase for the first time. The comparison of C11 and C44 with those of other halide perovskites showed that C11 of MAPbCl3 is larger and C44 is slightly smaller compared to the values of MAPbBr3 and MAPbI3. It suggests that MAPbCl3 has a more compact structure (smaller lattice constant) along with stronger binding forces, causing larger C11 and bulk modulus in this compound, and that the shear rigidity is exceedingly small similar to other halide perovskites. The reported elastic constants in this study may serve as a testbed for theoretical and calculational approaches for MAPbCl3.

Healing Ion-Implanted Semiconductors by Hybrid Microwave Annealing: Activation of Nitrogen-Implanted TiO2.

In order to recover the damaged structure of a nitrogen-implanted TiO2 (N-I-TiO2) photoanode, hybrid microwave annealing (HMA) is proposed as an alternative postannealing process instead of conventional thermal annealing (CTA). Compared to CTA, HMA provides distinctive advantages: (i) facile transformation of the interstitial N-N states into substitutional N-Ti states, (ii) better preservation of the ion-implanted nitrogen in TiO2, and (iii) effective alleviation of lattice strain and reconstruction of the broken bonds. As a result, the HMA-activated photoanode improves the photocurrent density by a factor of ∼3.2 from 0.29 to 0.93 mA cm-2 at 1.23 VRHE and the incident photon-to-current conversion efficiency (IPCE) from ∼2.9% to ∼10.5% at 430 nm relative to those of the as-prepared N-I-TiO2 photoanode in photoelectrochemical water oxidation, which are much better than those of the CTA-activated photoanode (0.58 mA cm-2 at 1.23 VRHE and IPCE of 5.7% at 430 nm), especially in the visible light region (≥420 nm).

Reversibly Controlled Ternary Polar States and Ferroelectric Bias Promoted by Boosting Square-Tensile-Strain.

Interaction between dipoles often emerges intriguing physical phenomena, such as exchange bias in the magnetic heterostructures and magnetoelectric effect in multiferroics, which lead to advances in multifunctional heterostructures. However, the defect-dipole tends to be considered the undesired to deteriorate the electronic functionality. Here, deterministic switching between the ferroelectric and the pinched states by exploiting a new substrate of cubic perovskite, BaZrO3 is reported, which boosts the square-tensile-strain to BaTiO3 and promotes four-variants in-plane spontaneous polarization with oxygen vacancy creation. First-principles calculations propose a complex of an oxygen vacancy and two Ti3+ ions coins a charge-neutral defect-dipole. Cooperative control of the defect-dipole and the spontaneous polarization reveals ternary in-plane polar states characterized by biased/pinched hysteresis loops. Furthermore, it is experimentally demonstrated that three electrically controlled polar-ordering states lead to switchable and nonvolatile dielectric states for application of nondestructive electro-dielectric memory. This discovery opens a new route to develop functional materials via manipulating defect-dipoles and offers a novel platform to advance heteroepitaxy beyond the prevalent perovskite substrates.

Hole doping effect of MoS2 via electron capture of He+ ion irradiation.

Beyond the general purpose of noble gas ion sputtering, which is to achieve functional defect engineering of two-dimensional (2D) materials, we herein report another positive effect of low-energy (100 eV) He+ ion irradiation: converting n-type MoS2 to p-type by electron capture through the migration of the topmost S atoms. The electron capture ability via He+ ion irradiation is valid for supported bilayer MoS2; however, it is limited at supported monolayer MoS2 because the charges on the underlying substrates transfer into the monolayer under the current condition for He+ ion irradiation. Our technique provides a stable and universal method for converting n-type 2D transition metal dichalcogenides (TMDs) into p-type semiconductors in a controlled fashion using low-energy He+ ion irradiation.

Synthesis and electrochemical studies of nano-scale carbon-coated LiFePO4 electrodes for Li-ion batteries.

Regardless of high capacity and stability during lithium extraction, LiFePO4 materials have difficulty in the applications for high electrical density because of low electrical conductivities. In order to optimize this problem, we synthesized carbon coated LiFePO4 by adding humic acid using solid state reaction method. We characterized the synthesized compounds via the crystallinity, the valence states of Fe ions, and their shapes. We found the carbon coating using X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). We also found that the iron ion is substituted from 3+ to 2+ through XPS measurement. We showed that the carbon coating increased the electrochemical behavior by measuring the charge-discharge characteristics.

Efficacy of Polygonatum sibiricum on Mild Insomnia: A Randomized Placebo-Controlled Trial.

Polygonatum sibiricum (PS) rhizome, which contains glyceryl-1-monolinoleate as its primary active component, has been shown to improve insomnia in animal models. Based on these findings, we aimed to investigate the safety and efficacy of PS rhizome extract in improving sleep quality in individuals with mild insomnia. Eighty individuals with mild insomnia were enrolled in a four-week, randomized, double-blind, placebo-controlled trial of PS rhizome extract (500 mg/day, n = 40, PS group) or placebo (n = 40, placebo group). The primary outcome measure was change in total score on the Athens Insomnia Scale (AIS) to indicate sleep quality. The secondary outcome measures included change in actigraphy data and perfusion levels in the brain regions within the default mode network (DMN), which is known to play a key role in insomnia. The PS group showed greater improvement in the total AIS score with a significant increase in total sleep time, relative to the placebo group. In addition, significant group-by-visit interactions were observed in the perfusion level of the medial prefrontal cortex within the DMN. Findings of the current study provide first evidence that PS rhizome extract could be an effective natural ingredient for improving sleep in mild insomnia using a human model.

A Micro-Level Data-Calibrated Agent-Based Model: The Synergy between Microsimulation and Agent-Based Modeling.

Artificial life (ALife) examines systems related to natural life, its processes, and its evolution, using simulations with computer models, robotics, and biochemistry. In this article, we focus on the computer modeling, or "soft," aspects of ALife and prepare a framework for scientists and modelers to be able to support such experiments. The framework is designed and built to be a parallel as well as distributed agent-based modeling environment, and does not require end users to have expertise in parallel or distributed computing. Furthermore, we use this framework to implement a hybrid model using microsimulation and agent-based modeling techniques to generate an artificial society. We leverage this artificial society to simulate and analyze population dynamics using Korean population census data. The agents in this model derive their decisional behaviors from real data (microsimulation feature) and interact among themselves (agent-based modeling feature) to proceed in the simulation. The behaviors, interactions, and social scenarios of the agents are varied to perform an analysis of population dynamics. We also estimate the future cost of pension policies based on the future population structure of the artificial society. The proposed framework and model demonstrates how ALife techniques can be used by researchers in relation to social issues and policies.

Deer Bone Extract Supplementation for Mild-to-Moderate Knee Osteoarthritis Symptoms: A Randomized, Double-Blind, Placebo-Controlled Trial.

In this randomized, double-blind, placebo-controlled study, we evaluated the efficacy of deer bone extract (DBE) in participants with knee osteoarthritis (OA). We enrolled 50 participants aged 50-70 years, having knee OA with a Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score ≥5.0. The participants were assigned to the placebo or DBE group (550 mg/day) for 12 weeks. The outcome measures were as follows: pain score on the visual analog scale (VAS); WOMAC score; and blood and urine biomarkers. In the DBE group, VAS scores, WOMAC total scores, and WOMAC subscores (for pain, stiffness, and physical function) improved significantly compared with the baseline values. However, there was no significant difference in outcomes between the DBE and placebo groups. The present findings suggest that DBE may mildly reduce joint pain and stiffness and improve joint function in patients with painful knee OA.

Purification and identification of adipogenesis inhibitory peptide from black soybean protein hydrolysate.

Adipogenesis inhibitory peptide was isolated and identified from black soybean (Rhynchosia volubilis Lour.) hydrolysate. An adipogenesis inhibitor was purified using consecutive methods including: ultrafiltration (MWCO; 3 and 10kDa), gel filtration chromatography (Superdex Peptide 10/300 GL column), and reverse-phase high-performance liquid chromatography (microBondapak C(18) column). Also, the adipogenesis inhibition effect of the purified peptide was measured by observation of droplet of 3T3-L1 adipocyte by Oil Red O staining in the highest active fraction in each step. The peptide was shown to inhibit the differentiation of the 3T3-L1 pre-adipocyte, which was confirmed by morphological study. The adipogenesis inhibitory peptide was purified 71.43-fold from black soybean hydrolysate throughout a five-step purification procedure. The adipogenesis inhibitor was identified to be a tripeptide, Ile-Gln-Asn, having an IC(50) value of 0.014 mg protein/ml. Furthermore, the synthetic tripeptide (Ile-Gln-Asn) exhibited the similar adipogenesis effects to the purified peptide. Thus, these results showed the potential anti-obesity effect of the purified peptide through control of adiposity.

Expression of antihypertensive peptide, His-His-Leu, as tandem repeats in Escherichia coli.

His-His-Leu (HHL), a tripeptide derived from a Korean soybean paste, is an angiotensin-I-converting enzyme (ACE) inhibitor. We report here a method of producing this tripeptide efficiently by expressing tandem multimers of the codons encoding the peptide in E. coli and purifying the HHL after hydrolysis of the peptide multiners. The HHL gene, tandemly multimerized to a 40-mer, was ligated with ubiquitin as a fusion gene (UH40). UH40 was inserted into vector pET29b; the UH40 fusion protein was then produced in E. coli BL21. The recombinant UH40 protein was purified by cation-exchange chromatography with a yield of 17.3 mg/l and analyzed by matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry and protein N-terminal sequencing. Leucine aminopeptidase was used to cleave a 405-Da HHL monomer from the UH40 fusion protein and the peptide was purified using reverse-phase high-performance liquid chromatography (HPLC) on a C18 HPLC column, with a final yield of 6.2 mg/l. The resulting peptide was confirmed to be HHL with the aid of MALDI-TOF mass spectrometry, glutamine-TOF mass spectrometry, N-terminal sequencing, and measurement of ACE inhibiting activity. These results suggest that our production method is useful for obtaining a large quantity of recombinant HHL for functional antihypertensive peptide studies.

Changes in Drosophila melanogaster Sleep-Wake Behavior Due to Lotus (Nelumbo nucifera) Seed and Hwang Jeong (Polygonatum sibiricum) Extracts.

We evaluated the sleep enhancement activity of the medicinal herbs valerian (Valeriana officinalis), jujube (Ziziphus jujube), lotus seed (Nelumbo nucifera), Gastrodia elata, Polygonatum sibiricum, and baekbokryung (Poria cocos), which can relieve insomnia in a Drosophila model. Locomotor activity was measured in the Drosophila model to evaluate the sleep activity of Korean medicinal herbs traditionally used as sleep aids. The group treated with lotus seed extract showed less nocturnal activity. Treatment with 10 or 20 mg/mL of P. sibiricum significantly reduced nocturnal activity compared to the control group (P<0.05). The activity and sleep bouts of fruit flies were significantly decreased by a high-dose treatment (10 mg/mL) of lotus or P. sibiricum extracts at night. Caffeine-treated Drosophila showed increased nocturnal activity and decreased total sleep time (P<0.05). Flies receiving the 10 mg-doses of lotus seed or P. sibiricum extract showed significantly different nocturnal locomotor activity and total sleep time compared to caffeine-treated Drosophila. Lotus seed and P. sibiricum extracts are attractive and valuable sleep-potentiating nutraceuticals.

The immune-enhancing activity of Cervus nippon mantchuricus extract (NGE) in RAW264.7 macrophage cells and immunosuppressed mice.

Chemotherapeutics are often used to inhibit the proliferation of cancer cells. However, they can also harm healthy cells and cause side effects such as immunosuppression. Especially traditional oriental medicines long used in Asia, may be beneficial candidates for the alleviation of immune diseases. Cervus nippon mantchuricus extract (NGE) is currently sold in the market as coffee and health drinks. However, NGE was not widely investigated and efficacy remain unclear and essentially nothing is known about their potential immune-regulatory properties. As a result, NGE induced the differentiation of RAW264.7 macrophage cells. NGE-stimulated RAW264.7 macrophage cells elevated cytokines levels and NO production. NGE-stimulated RAW264.7 macrophage cells activated MAPKs and NF-κB signaling pathways. NGE encouraged the immuno-enhancing effects in immunosuppressed short-term treated with NGE mice model. NGE or Red ginseng encouraged the immuno-enhancing effects in immunosuppressed long-term treated with NGE mice model. Our data clearly show that NGE contains immune-enhancing activity and can be used to treat immunodeficiency.

Robust nanogenerators based on graft copolymers via control of dielectrics for remarkable output power enhancement.

A robust nanogenerator based on poly(tert-butyl acrylate) (PtBA)-grafted polyvinylidene difluoride (PVDF) copolymers via dielectric constant control through an atom-transfer radical polymerization technique, which can markedly increase the output power, is demonstrated. The copolymer is mainly composed of α phases with enhanced dipole moments due to the π-bonding and polar characteristics of the ester functional groups in the PtBA, resulting in the increase of dielectric constant values by approximately twice, supported by Kelvin probe force microscopy measurements. This increase in the dielectric constant significantly increased the density of the charges that can be accumulated on the copolymer during physical contact. The nanogenerator generates output signals of 105 V and 25 µA/cm2, a 20-fold enhancement in output power, compared to pristine PVDF-based nanogenerator after tuning the surface potential using a poling method. The markedly enhanced output performance is quite stable and reliable in harsh mechanical environments due to the high flexibility of the films. On the basis of these results, a much faster charging characteristic is demonstrated in this study.