Emergence of two distinct phase transitions in monolayer CoSe2 on graphene.

Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures.

Prediction of Soluble-Solid Content in Citrus Fruit Using Visible-Near-Infrared Hyperspectral Imaging Based on Effective-Wavelength Selection Algorithm.

Citrus fruits were sorted based on external qualities, such as size, weight, and color, and internal qualities, such as soluble solid content (SSC), acidity, and firmness. Visible and near-infrared (VNIR) hyperspectral imaging techniques were used as rapid and nondestructive techniques for determining the internal quality of fruits. The applicability of the VNIR hyperspectral imaging technique for predicting the SSC in citrus fruits was evaluated in this study. A VNIR hyperspectral imaging system with a wavelength range of 400-1000 nm and 100 W light source was used to acquire hyperspectral images from citrus fruits in two orientations (i.e., stem and calyx ends). The SSC prediction model was developed using partial least-squares regression (PLSR). Spectrum preprocessing, effective wavelength selection through competitive adaptive reweighted sampling (CARS), and outlier detection were used to improve the model performance. The performance of each model was evaluated using the coefficient of determination (R2) and root mean square error (RMSE). In the present study, the PLSR model was developed using only a citrus cultivar. The SSC prediction CARS-PLSR model with outliers removed exhibited R2 and RMSE values of approximatively 0.75 and 0.56 °Brix, respectively. The results of this study are expected to be useful in similar fields such as agricultural and food post-harvest management, as well as in the development of an online system for determining the SSC of citrus fruits.

Performance Improvement of Partial Least Squares Regression Soluble Solid Content Prediction Model Based on Adjusting Distance between Light Source and Spectral Sensor according to Apple Size.

Apples are widely cultivated in the Republic of Korea and are preferred by consumers for their sweetness. Soluble solid content (SSC) is measured non-destructively using near-infrared (NIR) spectroscopy; however, the SSC measurement error increases with the change in apple size since the distance between the light source and the near-infrared sensor is fixed. In this study, spectral characteristics caused by the differences in apple size were investigated. An optimal SSC prediction model applying partial least squares regression (PLSR) to three measurement conditions based on apple size was developed. The three optimal measurement conditions under which the Vis/NIR spectrum is less affected by six apple size levels (Levels I-VI) were selected. The distance from the apple center to the light source and that to the sensor were 125 and 75 mm (Distance 1), 123 and 75 mm (Distance 2), and 135 and 80 mm (Distance 3). The PLSR model applying multiplicative scatter correction pretreatment under Distance 3 measurement conditions showed the best performance for Level IV-sized apples (Rpre2 = 0.91, RMSEP = 0.508 °Brix). This study shows the possibility of improving the SSC prediction performance of apples by adjusting the distance between the light source and the NIR sensor according to fruit size.

Performance Comparison of Tungsten-Halogen Light and Phosphor-Converted NIR LED in Soluble Solid Content Estimation of Apple.

A Tungsten-Halogen (TH) lamp is the most popular light source in NIR spectroscopy and hyperspectral imaging, which requires a warm-up to reach very high temperatures of up to 250 °C and take a long time for radiation stabilization. Consequently, it has a large enough volume to enable heat dissipation to prevent the thermal runaway of the electric circuit and turn out its power efficiency very low. These are major barriers for miniaturizing spectral systems and hyperspectral imaging devices. However, TH lamps can be replaced by pc-NIR LEDs in order to avoid high temperature and large volume. We compared the spectral emission of the available commercial pc-NIR LEDs under the same condition. As a replacement for the TH lamp, the VIS + NIR LED module was developed to combine a warm-white LED and pc-NIR LEDs. In order to feature out the availability of the VIS + NIR LED module against the TH lamp, they were used as the light source for evaluating the Soluble Solid Content (SSC) of an apple through VIS-NIR spectroscopy. The results show a remarkable feasibility in the performance of the partial least square (PLS) model using the VIS + NIR LED module; during PLS calibration, the correlation coefficient (R) values are 0.664 and 0.701, and the Mean Square Error (MSE) values are 0.681 and 0.602 for the TH lamp and VIS + NIR LED module, respectively. In VIS-NIR spectroscopy, this study indicates that the TH lamp could be replaceable with a warm-white LED and pc-NIR LEDs.

Highly Dispersed Pt Clusters on F-Doped Tin(IV) Oxide Aerogel Matrix: An Ultra-Robust Hybrid Catalyst for Enhanced Hydrogen Evolution.

Dispersing the minuscule mass loading without hampering the high catalytic activity and long-term stability of a noble metal catalyst results in its ultimate efficacy for the electrochemical hydrogen evolution reaction (HER). Despite being the most efficient HER catalyst, the use of Pt is curtailed due to its scarcity and tendency to leach out in the harsh electrochemical reaction environment. In this study, we combined F-doped tin(IV) oxide (F-SnO2) aerogel with Pt catalyst to prevent metallic corrosion and to achieve abundant Pt active sites (approximately 5 nm clusters) with large specific surface area (321 cm2·g-1). With nanoscopic Pt loading inside the SnO2 aerogel matrix, the as-synthesized hybrid F-SnO2@Pt possesses a large specific surface area and high porosity and, thus, exhibits efficient experimental and intrinsic HER activity (a low overpotential of 42 mV at 10 mA·cm-2 in 0.5 M sulfuric acid), a 22-times larger turnover frequency (11.2 H2·s-1) than that of Pt/C at 50 mV, and excellent robustness over 10,000 cyclic voltammetry cycles. The existing metal support interaction and strong intermolecular forces between Pt and F-SnO2 account for the catalytic superiority and persistence against corrosion of F-SnO2@Pt compared to commercially used Pt/C. Density functional theory analysis suggests that hybridization between the Pt and F-SnO2 orbitals enhances intermediate hydrogen atom (H*) adsorption at their interface, which improves the reaction kinetics.

Emergent Topological Hall Effect from Exchange Coupling in Ferromagnetic Cr2Te3/Noncoplanar Antiferromagnetic Cr2Se3 Bilayers.

The topological Hall effect has been observed in magnetic materials of complex spin structures or bilayers of trivial magnets and strong spin-orbit-coupled systems. In view of current attention on dissipationless topological electronics, the occurrence of the topological Hall effect in new systems or by an unexpected mechanism is fascinating. Here, we report a robust topological Hall effect generated in bilayers of a ferromagnet and a noncoplanar antiferromagnet, from the interfacial Dzyaloshinskii-Moriya interaction due to the exchange coupling of magnetic layers. Molecular beam epitaxy has been utilized to fabricate heterostructures of a ferromagnetic metal Cr2Te3 and a noncoplanar antiferromagnet Cr2Se3. A significant topological Hall effect at low temperature implies the development of nontrivial spin chirality, and density functional theory calculations explain the correlation of the Dzyaloshinskii-Moriya interaction increase and inversion symmetry breaking at the interface. The presence of noncoplanar ordering in the antiferromagnet plays a pivotal role in producing the topological Hall effect. Our results suggest that the exchange coupling in ferromagnet/noncoplanar antiferromagnet bilayers could be an alternative mechanism toward topologically protected magnetic structures.

Coherent control of interlayer vibrations in Bi2Se3 van der Waals thin-films.

Interlayer vibrations with discrete quantized modes in two-dimensional (2D) materials can be excited by ultrafast light due to the inherent low dimensionality and van der Waals force as a restoring force. Controlling such interlayer vibrations in layered materials, which are closely related to fundamental nanomechanical interactions and thermal transport, in spatial- and time-domain provides an in-depth understanding of condensed matters and potential applications for advanced phononic and photonics devices. The manipulation of interlayer vibrational modes has been implemented in a spatial domain through material design to develop novel optoelectronic and phononic devices with various 2D materials, but such control in a time domain is still lacking. We present an all-optical method for controlling the interlayer vibrations in a highly precise manner with Bi2Se3 as a promising optoelectronic and thermoelasticity material in layered structures using a coherently controlled pump and probe scheme. The observed thickness-dependent fast interlayer breathing modes and substrate-induced slow interfacial modes can be exactly explained by a modified linear chain model including coupling effect with substrate. In addition, the results of coherent control experiments also agree with the simulation results based on the interference of interlayer vibrations. This investigation is universally applicable for diverse 2D materials and provides insight into the interlayer vibration-related dynamics and novel device implementation based on an ultrafast timescale interlayer-spacing modulation scheme.

Engineering MoSe2/WS2 Hybrids to Replace the Scarce Platinum Electrode for Hydrogen Evolution Reactions and Dye-Sensitized Solar Cells.

In recent times, two-dimensional transition-metal dichalcogenides (TMDs) have become extremely attractive and proficient electrodes for dye-sensitized solar cells (DSSCs) and water electrolysis hydrogen evolution as alternatives to the scarce metal platinum (Pt). The active TMD molybdenum selenide (MoSe2) and tungsten disulfide (WS2) are inspiring systems owing to their abundance of active sulfur and selenium sites, but their outputs are lacking due to their inactive basal planes and ineffective transport behavior. In this work, van der Waals interrelated MoSe2/WS2 hybrid structures were constructed on conducting glass substrates by chemicophysical methodologies. For the first time, the constructed MoSe2/WS2 structures were effectively used as a counter electrode for DSSCs and an active electrode for hydrogen evolution to replace the nonabundant Pt. The assembled DSSCs using the designed MoSe2/WS2 heterostructure counter electrode provided a superior power-conversion efficiency of 9.92% and a photocurrent density of 23.10 mA·cm-2, unmatchable by most of the TMD-based structures. The MoSe2/WS2 heterostructure displayed excellent electrocatalytic hydrogen evolution behavior with a 75 mV overpotential to drive a 10 mA·cm-2 current density, a 60 mV·dec-1 Tafel slope, and an over 20 h durable process in an acidic medium. The results demonstrated the advantages of the MoSe2/WS2 hybrid development for generating interfacial transport and active facet distribution and enriching the electrocatalytic activity for DSSCs and the water-splitting hydrogen evolution process.

Skyrmion Phase in MnSi Thin Films Grown on Sapphire by a Conventional Sputtering.

Topologically protected chiral skyrmions are an intriguing spin texture that has attracted much attention because of fundamental research and future spintronic applications. MnSi with a non-centrosymmetric structure is a well-known material hosting a skyrmion phase. To date, the preparation of MnSi crystals has been investigated by using special instruments with an ultrahigh vacuum chamber. Here, we introduce a facile way to grow MnSi films on a sapphire substrate using a relatively low vacuum environment of conventional magnetron sputtering. Although the as-grown MnSi films have a polycrystalline nature, a stable skyrmion phase in a broad range of temperatures and magnetic fields is observed via magnetotransport properties including phenomenological scaling analysis of the Hall resistivity contribution. Our findings provide not only a general way to prepare the materials possessing skyrmion phases but also insight into further research to stimulate more degrees of freedom in our inquisitiveness.

The atlas of RNase H antisense oligonucleotide distribution and activity in the CNS of rodents and non-human primates following central administration.

Antisense oligonucleotides (ASOs) have emerged as a new class of drugs to treat a wide range of diseases, including neurological indications. Spinraza, an ASO that modulates splicing of SMN2 RNA, has shown profound disease modifying effects in Spinal Muscular Atrophy (SMA) patients, energizing efforts to develop ASOs for other neurological diseases. While SMA specifically affects spinal motor neurons, other neurological diseases affect different central nervous system (CNS) regions, neuronal and non-neuronal cells. Therefore, it is important to characterize ASO distribution and activity in all major CNS structures and cell types to have a better understanding of which neurological diseases are amenable to ASO therapy. Here we present for the first time the atlas of ASO distribution and activity in the CNS of mice, rats, and non-human primates (NHP), species commonly used in preclinical therapeutic development. Following central administration of an ASO to rodents, we observe widespread distribution and target RNA reduction throughout the CNS in neurons, oligodendrocytes, astrocytes and microglia. This is also the case in NHP, despite a larger CNS volume and more complex neuroarchitecture. Our results demonstrate that ASO drugs are well suited for treating a wide range of neurological diseases for which no effective treatments are available.

One-Pot Synthesis of W2C/WS2 Hybrid Nanostructures for Improved Hydrogen Evolution Reactions and Supercapacitors.

Tungsten sulfide (WS2) and tungsten carbide (W2C) are materialized as the auspicious candidates for various electrochemical applications, owing to their plentiful active edge sites and better conductivity. In this work, the integration of W2C and WS2 was performed by using a simple chemical reaction to form W2C/WS2 hybrid as a proficient electrode for hydrogen evolution and supercapacitors. For the first time, a W2C/WS2 hybrid was engaged as a supercapacitor electrode and explored an incredible specific capacitance of ~1018 F g-1 at 1 A g-1 with the outstanding robustness. Furthermore, the constructed symmetric supercapacitor using W2C/WS2 possessed an energy density of 45.5 Wh kg-1 at 0.5 kW kg-1 power density. For hydrogen evolution, the W2C/WS2 hybrid produced the low overpotentials of 133 and 105 mV at 10 mA cm-2 with the small Tafel slopes of 70 and 84 mV dec-1 in acidic and alkaline media, respectively, proving their outstanding interfaced electrocatalytic characteristics. The engineered W2C/WS2-based electrode offered the high-performance for electrochemical energy applications.

Visualizing Orbital Content of Electronic Bands in Anisotropic 2D Semiconducting ReSe2.

Many properties of layered materials change as they are thinned from their bulk forms down to single layers, with examples including indirect-to-direct band gap transition in 2H semiconducting transition metal dichalcogenides as well as thickness-dependent changes in the valence band structure in post-transition-metal monochalcogenides and black phosphorus. Here, we use angle-resolved photoemission spectroscopy to study the electronic band structure of monolayer ReSe2, a semiconductor with a distorted 1T structure and in-plane anisotropy. By changing the polarization of incoming photons, we demonstrate that for ReSe2, in contrast to the 2H materials, the out-of-plane transition metal dz2 and chalcogen pz orbitals do not contribute significantly to the top of the valence band, which explains the reported weak changes in the electronic structure of this compound as a function of layer number. We estimate a band gap of 1.7 eV in pristine ReSe2 using scanning tunneling spectroscopy and explore the implications on the gap following surface doping with potassium. A lower bound of 1.4 eV is estimated for the gap in the fully doped case, suggesting that doping-dependent many-body effects significantly affect the electronic properties of ReSe2. Our results, supported by density functional theory calculations, provide insight into the mechanisms behind polarization-dependent optical properties of rhenium dichalcogenides and highlight their place among two-dimensional crystals.

Facile electrodeposition of V-doped CoP on vertical graphene for efficient alkaline water electrolysis.

In this work, we demonstrate a highly enhanced electrocatalytic activity of vanadium-doped CoP (V-CoP), directly grafted on a vertical graphene/carbon cloth electrode (VG/CC) by a facile electrochemical deposition method. Impressively, V-CoP/VG/CC exhibited a superior catalytic activity toward the hydrogen evolution reaction (HER) in alkaline solution. Compared to CoP/VG/CC, V-doping decreased the overpotential for HER at 10 mA cm-2 by more than half to 40 mV. The new catalyst even outperformed Pt/C beyond 150 mA cm-2. The overpotential for OER at 50 mA cm-2 was merely 314 mV, more than 100 mV lower than that of IrO2. Moreover, our novel catalyst worked as an excellent bifunctional catalyst with a low cell voltage of 1.69 V to achieve a current density of 50 mA cm-2. Detailed characterizations revealed that the V-doping in CoP resulted in improved electrical conductivity and increased active sites. Our findings highlight the significant advantage of V doping on the catalytic activities of CoP, already boosted by VG. Furthermore, concurrent doping with the electrodeposition of catalyst offers a new approach for practical water electrolysis.

Synthesis of Mo2C and W2C Nanoparticle Electrocatalysts for the Efficient Hydrogen Evolution Reaction in Alkali and Acid Electrolytes.

The synthesis of low cost, high efficacy, and durable hydrogen evolution electrocatalysts from the non-noble metal group is a major challenge. Herein, we establish a simple and inexpensive chemical reduction method for producing molybdenum carbide (Mo2C) and tungsten carbide (W2C) nanoparticles that are efficient electrocatalysts in alkali and acid electrolytes for hydrogen evolution reactions (HER). Mo2C exhibits outstanding electrocatalytic behavior with an overpotential of -134 mV in acid medium and of -116 mV in alkaline medium, while W2C nanoparticles require an overpotential of -173 mV in acidic medium and -130 mV in alkaline medium to attain a current density of 10 mA cm-2. The observed results prove the capability of high- and low-pH active electrocatalysts of Mo2C and W2C nanoparticles to be efficient systems for hydrogen production through HER water electrolysis.

Novel polymorphic phase of two-dimensional VSe2: the 1T' structure and its lattice dynamics.

Polymorphisms allowing multiple structural phases are among the most fascinating properties of transition metal dichalcogenides (TMDs). Herein, the polymorphic 1T' phase and its lattice dynamics for bilayer VSe2 grown on epitaxial bilayer graphene are investigated via low temperature scanning tunneling microscopy (STM). The 1T' structure, mostly observed in group-6 TMDs, is unexpected in VSe2, which is a group-5 TMD. Emergence of the 1T' structure in bilayer VSe2 suggests the important roles of interface and layer configurations, providing new possibilities regarding the polymorphism of TMDs. Detailed topographical analysis elucidates the microscopic nature of the 1T' structure, confirming that Se-like and V-like surfaces can be resolved depending on the polarity of the sample bias. In addition, bilayer VSe2 can transit from a static state of the 1T' phase to a dynamic state consisting of lattice vibrations, triggered by tunneling current from the STM tip. Topography also shows hysteretic behavior during the static-dynamic transition, which is attributed to latent energy existing between the two states. The observed lattice dynamics involve vibrational motion of the Se atoms and the middle V atoms. Our observations will provide important information to establish in-depth understanding of the microscopic nature of 1T' structures and the polymorphism of two-dimensional TMDs.

Fabrication of Robust Hydrogen Evolution Reaction Electrocatalyst Using Ag2Se by Vacuum Evaporation.

Much research has been done on reliable and low-cost electrocatalysts for hydrogen generation by water splitting. In this study, we synthesized thin films of silver selenide (Ag2Se) using a simple thermal evaporation route and demonstrated their electrocatalytic hydrogen evolution reaction (HER) activity. The Ag2Se catalysts show improved electrochemical surface area and good HER electrocatalytic behavior (367 mV overpotential @ 10 mA·cm-2, exchange current density: ~1.02 × 10-3 mA·cm-2, and Tafel slope: 53 mV·dec-1) in an acidic medium). The reliability was checked in 0.5 M sulfuric acid over 20 h. Our first-principles calculations show the optimal energy of hydrogen adsorption, which is consistent with experimental results. The works could be further extended for finding a new catalyst by associating the selenide, sulfide or telluride-based materials without complex catalyst synthesis procedures.

Prospective Evaluation of Atrophic Acne Scars on the Face With Needle-Free High-Pressure Pneumatic Injection: Quantitative Volumetric Scar Improvement.

BACKGROUND: Atrophic acne facial scars still pose a treatment challenge. Needle-free high-pressure pneumatic injection has recently been introduced; however, few studies exist regarding its effectiveness. OBJECTIVE: To evaluate the efficacy and safety of pneumatic injection for treating atrophic acne scars using a 3-dimensional optical profiling system. METHODS AND MATERIALS: A pneumatic injection device with a 0.2-mm nozzle diameter, 50% pressure power, and 85-µL injection volume was used. The degree of depression was examined and analyzed using a 3-dimensional optical profiling system and clinical photographs. The patients also evaluated any side effects. Each subject underwent a single treatment session and was followed up after 1 and 2 months. RESULTS: A total of 13 atrophic acne scars from 10 Korean men and women aged 20 to 29 (mean age 25.8 ± 2.4) years were studied. The mean scar volume values were 0.964, 0.741, and 0.566 mm, respectively, at baseline, 1 month, and 2 months after the injection. Scar volumes after 2 months were significantly different compared with baseline volumes. However, there was no significant difference between the baseline and 1-month volumes. CONCLUSION: Treatment with pneumatic injection is safe and effective in reducing atrophic acne facial scars; it results in quantitative improvement in scar volumes.

Needle-free pneumatic injection device; histologic assessment using a rat model and parameter comparison in predicting collagen synthesis degree.

BACKGROUND: Needle-free pneumatic injections have been recently introduced to the field of dermatology to inject such substances as hyaluronic acid. However, data on the influence of various pneumatic injection parameters on collagen synthesis are lacking. OBJECTIVE: Compare the effect of diameter, pressure, and volume of a pneumatic injection jet on collagen synthesis and fluid dispersion pattern using a rat model. Investigate if the total work force of the injection jet is useful in predicting the degree of collagen synthesis. MATERIALS AND METHODS: We injected fluid with 1 mg/ml of hyaluronic concentration to adult rats. Different injection pressures and volumes were tested using devices with nozzles of different diameters. Collagen synthesis areas were then measured, and statistical analyses were performed. RESULTS: The area of collagen fibers increased for up to two months. The injection pressure and volume did not correlate with the degree of collagen synthesis. The nozzle diameter showed a significant after two and four weeks of injection. The total work force correlated with collagen synthesis 2, 4, and 8 weeks post-injection. (P = 0.043, 0.027, and 0.000, respectively). CONCLUSION: Collagen formation is more prominent 2 months post-hyaluronic acid injection than after 1 month when using a needle-free pneumatic injection device. The total work force, which is affected by both the nozzle diameter and injection pressure, can be helpful in predicting the degree of collagen synthesis. Lasers Surg. Med. 51:278-285, 2019. © 2019 Wiley Periodicals, Inc.

Successfully Treated Severe Acne Using Selective Electrothermolysis in a Patient with Nephrotic Syndrome.

Acne is very common in adolescents and young adults. Although there are various conventional treatment modalities, some patients are prone to side effects and need alternative options. A 22-year-old male patient who were treated with high dose systemic steroid for his nephrotic syndrome, encountered severe acne on his face and neck. Since the patient's medical condition was unable to administer systemic agent, he was treated with the selective electrothermolysis device. The sebaceous gland targeting treatment by selective electrothermolysis with microneedle radiofrequency device, had minimal adverse effect and the skin lesions improved dramatically. The patient was satisfied and did not want further treatment.

The role of Pax6 in brain development and its impact on pathogenesis of autism spectrum disorder.

Pax6 transcription factor is a key player in several aspects of brain development and function. Autism spectrum disorder (ASD) is a neurodevelopmental disorder in which several loci and/or genes have been suggested as causative candidate factors. Based on data obtained from meta-analyses of the transcriptome and ChIP analyses, we hypothesized that the neurodevelopmental gene PAX6 regulates and/or binds to a large number of genes (including many ASD-related ones) that modulate the fate of neural stem/progenitor cells and functions of neuronal cells, subsequently affecting animal behavior. Network analyses of PAX6/ASD-related molecules revealed significant clusters of molecular interactions involving regulation of cell-cell adhesion, ion transport, and transcriptional regulation. We discuss a novel function of Pax6 as a chromatin modulator that alters the chromatin status of ASD genes, thereby inducing diverse phenotypes of ASD and related neurodevelopmental diseases.