The rate of detection of thyroid nodules and carcinomas has increased with the widespread use of ultrasonography (US), which is the mainstay for the detection and risk stratification of thyroid ...nodules as well as for providing guidance for their biopsy and nonsurgical treatment. The Korean Society of Thyroid Radiology (KSThR) published their first recommendations for the US-based diagnosis and management of thyroid nodules in 2011. These recommendations have been used as the standard guidelines for the past several years in Korea. Lately, the application of US has been further emphasized for the personalized management of patients with thyroid nodules. The Task Force on Thyroid Nodules of the KSThR has revised the recommendations for the ultrasound diagnosis and imaging-based management of thyroid nodules. The review and recommendations in this report have been based on a comprehensive analysis of the current literature and the consensus of experts.
We report the synthesis of centimeter-scale, uniform 1T′- and 2H-MoTe2 thin films via the tellurization of Mo thin films. 1T′-MoTe2 was initially grown and converted gradually to 2H-MoTe2 over a ...prolonged growth time under a Te atmosphere. Maintaining excessive Te was essential for obtaining the stable stoichiometric 2H-MoTe2 phase. Further annealing under a lower partial pressure of Te at the same temperature, followed by a rapid quenching, led to the reverse phase transition from 2H-MoTe2 to 1T′-MoTe2. The orientation of the 2H-MoTe2 film was determined by the tellurization rate. Slow tellurization was the key for obtaining a highly oriented 2H-MoTe2 film over the entire area, while fast tellurization led to a 2H-MoTe2 film with a randomly oriented c-axis.
3D in vitro model systems such as spheroids and organoids provide an opportunity to extend the physiological understanding using recapitulated tissues that mimic physiological characteristics of in ...vivo microenvironments. Unlike 2D systems, 3D in vitro systems can bridge the gap between inadequate 2D cultures and the in vivo environments, providing novel insights on complex physiological mechanisms at various scales of organization, ranging from the cellular, tissue‐, to organ‐levels. To satisfy the ever‐increasing need for highly complex and sophisticated systems, many 3D in vitro models with advanced microengineering techniques have been developed to answer diverse physiological questions. This review summarizes recent advances in engineered microsystems for the development of 3D in vitro model systems. The relationship between the underlying physics behind the microengineering techniques, and their ability to recapitulate distinct 3D cellular structures and functions of diverse types of tissues and organs are highlighted and discussed in detail. A number of 3D in vitro models and their engineering principles are also introduced. Finally, current limitations are summarized, and perspectives for future directions in guiding the development of 3D in vitro model systems using microengineering techniques are provided.
3D in vitro models including spheroids and organoids provide an opportunity to extend the physiological understanding of in vivo microenvironments. In this review, engineered microsystems are categorized into four types: microwell‐, centrifugation‐, liquid drop‐, and microchannel‐based culture systems. The five mechanical principles that can uniquely influence the formation of 3D cellular structures are also recapitulated.
Although the exceptional theoretical specific capacity (1672 mAh g−1) of elemental sulfur makes lithium–sulfur (Li–S) batteries attractive for upcoming rechargeable battery applications (e.g., ...electrical vehicles, drones, unmanned aerial vehicles, etc.), insufficient cycle lives of Li–S cells leave a substantial gap before their wide penetration into commercial markets. Among the key features that affect the cyclability, the shuttling process involving polysulfides (PS) dissolution is most fatal. In an effort to suppress this chronic PS shuttling, herein, a separator coated with poled BaTiO3 or BTO particles is introduced. Permanent dipoles that are formed in the BTO particles upon the application of an electric field can effectively reject PS from passing through the separator via electrostatic repulsion, resulting in significantly improved cyclability, even when a simple mixture of elemental sulfur and conductive carbon is used as a sulfur cathode. The coating of BTO particles also considerably suppresses thermal shrinkage of the poly(ethylene) separator at high temperatures and thus enhances the safety of the cell adopting the given separator. The incorporation of poled particles can be universally applied to a wide range of rechargeable batteries (i.e., metal‐air batteries) that suffer from cross‐contamination of charged species between both electrodes.
Poling for polysulfide rejection: The fatal shuttling process in lithium–sulfur batteries is effectively suppressed by “poled” BaTiO3 or BTO particles coated on a poly(ethylene) separator. The permanent dipoles of poled BTO particles repel polysulfides via electrostatic repulsion. The coating of BTO particles also provides a resistance against thermal shrinkage of the polyethylene separator at high temperature, thus enhancing the safety of the given cell.
Incidental thyroid nodules are commonly detected on ultrasonography (US). This has contributed to the rapidly rising incidence of low-risk papillary thyroid carcinoma over the last 20 years. The ...appropriate diagnosis and management of these patients is based on the risk factors related to the patients as well as the thyroid nodules. The Korean Society of Thyroid Radiology (KSThR) published consensus recommendations for US-based management of thyroid nodules in 2011 and revised them in 2016. These guidelines have been used as the standard guidelines in Korea. However, recent advances in the diagnosis and management of thyroid nodules have necessitated the revision of the original recommendations. The task force of the KSThR has revised the Korean Thyroid Imaging Reporting and Data System and recommendations for US lexicon, biopsy criteria, US criteria of extrathyroidal extension, optimal thyroid computed tomography protocol, and US follow-up of thyroid nodules before and after biopsy. The biopsy criteria were revised to reduce unnecessary biopsies for benign nodules while maintaining an appropriate sensitivity for the detection of malignant tumors in small (1-2 cm) thyroid nodules. The goal of these recommendations is to provide the optimal scientific evidence and expert opinion consensus regarding US-based diagnosis and management of thyroid nodules.
Solid‐state conversion of single crystals from polycrystalline materials has the advantages of cost‐effectiveness, chemical homogeneity, and versatility over the conventional melt growth and solution ...growth methods, particularly for systems with high melting points, incongruent melting, high reactivity (volatility), and phase transformations at high temperature. Nevertheless, for commercial production, this technique has only been successful in a few limited systems, in particular ferroelectric systems. This is mostly because of the difficulty in controlling the microstructure, particularly suppressing grain growth in the polycrystal during its conversion. This article describes the principle and the current status of the solid‐state conversion of single crystals. We first introduce the recently developed principle of microstructural evolution to explain the basis of the microstructure control in polycrystals for solid‐state conversion. We then report recent technical developments in fabricating single crystals by the solid‐state single crystal growth (SSCG) method and their physical properties. The SSCG method is expected to be studied and utilized more widely in fabricating single crystals with complex compositions as a strong alternative to the melt growth and solution growth methods.
2D transition metal dichalcogenides (TMDCs) with intense and tunable photoluminescence (PL) have opened up new opportunities for optoelectronic and photonic applications such as light‐emitting ...diodes, photodetectors, and single‐photon emitters. Among the standard characterization tools for 2D materials, Raman spectroscopy stands out as a fast and non‐destructive technique capable of probing material's crystallinity and perturbations such as doping and strain. However, a comprehensive understanding of the correlation between photoluminescence and Raman spectra in monolayer MoS2 remains elusive due to its highly nonlinear nature. Here, the connections between PL signatures and Raman modes are systematically explored, providing comprehensive insights into the physical mechanisms correlating PL and Raman features. This study's analysis further disentangles the strain and doping contributions from the Raman spectra through machine‐learning models. First, a dense convolutional network (DenseNet) to predict PL maps by spatial Raman maps is deployed. Moreover, a gradient boosted trees model (XGBoost) with Shapley additive explanation (SHAP) to bridge the impact of individual Raman features in PL features is applied. Last, a support vector machine (SVM) to project PL features on Raman frequencies is adopted. This work may serve as a methodology for applying machine learning to characterizations of 2D materials.
A collection of machine‐learning techniques is utilized to effectively discover the hidden pattern between Raman‐ and PL‐spectra of molybdenum disulfide (MoS2), which provide insights into the physical mechanisms connecting PL and Raman features. This study's analysis further disentangles the strain and doping contributions from the Raman spectra through machine‐learning models.
We report the synthesis of centimeter-scale monolayer WS2 on gold foil by chemical vapor deposition. The limited tungsten and sulfur solubility in gold foil allows monolayer WS2 film growth on gold ...surface. To ensure the coverage uniformity of monolayer WS2 film, the tungsten source-coated substrate was placed in parallel with Au foil under hydrogen sulfide atmosphere. The high growth temperature near 935 °C helps to increase a domain size up to 420 μm. Gold foil is reused for the repeatable growth after bubbling transfer. The WS2-based field effect transistor reveals an electron mobility of 20 cm2 V–1 s–1 with high on–off ratio of ∼108 at room temperature, which is the highest reported value from previous reports of CVD-grown WS2 samples. The on–off ratio of integrated multiple FETs on the large area WS2 film on SiO2 (300 nm)/Si substrate shows within the same order, implying reasonable uniformity of WS2 FET device characteristics over a large area of 3 × 1.5 cm2.
2D layered materials with sensitive surfaces are promising materials for use in chemical sensing devices, owing to their extremely large surface‐to‐volume ratios. However, most chemical sensors based ...on 2D materials are used in the form of laterally defined active channels, in which the active area is limited to the actual device dimensions. Therefore, a novel approach for fabricating self‐formed active‐channel devices is proposed based on 2D semiconductor materials with very large surface areas, and their potential gas sensing ability is examined. First, the vertical growth phenomenon of SnS2 nanocrystals is investigated with large surface area via metal‐assisted growth using prepatterned metal electrodes, and then self‐formed active‐channel devices are suggested without additional pattering through the selective synthesis of SnS2 nanosheets on prepatterned metal electrodes. The self‐formed active‐channel device exhibits extremely high response values (>2000% at 10 ppm) for NO2 along with excellent NO2 selectivity. Moreover, the NO2 gas response of the gas sensing device with vertically self‐formed SnS2 nanosheets is more than two orders of magnitude higher than that of a similar exfoliated SnS2‐based device. These results indicate that the facile device fabrication method would be applicable to various systems in which surface area plays an important role.
A novel approach for fabricating self‐formed active‐channel devices based on 2D semiconductor materials with very large surface areas is proposed and their potential gas sensing ability is examined. The device exhibits extremely high response values and this novel fabrication method is expected to find use in various applications where surface area plays an important role in function.
We study the magnetic field evolution of an isolated spiral galaxy, using isolated Milky Way-mass galaxy formation simulations and a novel prescription for magnetohydrodynamic (MHD) supernova ...feedback. Our main result is that a galactic dynamo can be seeded and driven by supernova explosions, resulting in magnetic fields whose strength and morphology are consistent with observations. In our model, supernovae supply thermal energy and a low-level magnetic field along with their ejecta. The thermal expansion drives turbulence, which serves a dual role by efficiently mixing the magnetic field into the interstellar medium and amplifying it by means of a turbulent dynamo. The computational prescription for MHD supernova feedback has been implemented within the publicly available ENZO code and is fully described in this paper. This improves upon ENZO's existing modules for hydrodynamic feedback from stars and active galaxies. We find that the field attains microgauss levels over gigayear timescales throughout the disk. The field also develops a large-scale structure, which appears to be correlated with the disk's spiral arm density structure. We find that seeding of the galactic dynamo by supernova ejecta predicts a persistent correlation between gas metallicity and magnetic field strength. We also generate all-sky maps of the Faraday rotation measure from the simulation-predicted magnetic field, and we present a direct comparison with observations.
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