Oriented lateral growth of two-dimensional materials on c-plane sapphire.

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) represent the ultimate thickness for scaling down channel materials. They provide a tantalizing solution to push the limit of semiconductor technology nodes in the sub-1 nm range. One key challenge with 2D semiconducting TMD channel materials is to achieve large-scale batch growth on insulating substrates of single crystals with spatial homogeneity and compelling electrical properties. Recent studies have claimed the epitaxy growth of wafer-scale, single-crystal 2D TMDs on a c-plane sapphire substrate with deliberately engineered off-cut angles. It has been postulated that exposed step edges break the energy degeneracy of nucleation and thus drive the seamless stitching of mono-oriented flakes. Here we show that a more dominant factor should be considered: in particular, the interaction of 2D TMD grains with the exposed oxygen-aluminium atomic plane establishes an energy-minimized 2D TMD-sapphire configuration. Reconstructing the surfaces of c-plane sapphire substrates to only a single type of atomic plane (plane symmetry) already guarantees the single-crystal epitaxy of monolayer TMDs without the aid of step edges. Electrical results evidence the structural uniformity of the monolayers. Our findings elucidate a long-standing question that curbs the wafer-scale batch epitaxy of 2D TMD single crystals-an important step towards using 2D materials for future electronics. Experiments extended to perovskite materials also support the argument that the interaction with sapphire atomic surfaces is more dominant than step-edge docking.

Learning to read Chinese: the roles of phonological awareness, paired-associate learning, and phonetic radical awareness.

This study aimed to determine how Chinese children adapt to Chinese orthography-phonology correspondence by acquiring phonetic radical awareness (PRA). This study used two important Chinese encoding approaches (rote and orthographic approaches) as the developmental trajectory, in which the present study hypothesized that phonological awareness (PA) exerts not only a direct influence on PRA but also an indirect influence through paired- associate learning (PAL). We also explored whether the association between PA and PAL is affected by the complexity of visual stimuli embedded in PAL. This study recruited 70 s-grade students to participate in various tests, which assessed (a) PA (measured by onset and rhyme awareness), (b) PRA (measured by regularity and consistency of phonetic radicals), (c) PAL (measured by learning performance on strokes; pattern-object and strokes pattern-syllable mapping), and (d) Chinese character recognition ability. Path analyses indicated that (1) character size had a significant positive correlation with PRA but not with PAL, (2) PAL fully mediated the association between PA and PRA, and (3) compared with PAL with a low stroke count, PA had a stronger relationship with PAL with a high stroke count. The results of this study were consistent with previous studies and suggest that PRA is the most important literacy skill for children in the middle of their learning-to-read stage. The results also augment existing literature by revealing that PRA acquisition is increased by PAL supported by PA, rather than by PA alone. Moreover, when the visual complexity of PAL increases, the support of PA to PAL would increase to make up for the working memory shortage.

Graphdiyne-Based Nanofilms for Compliant On-Skin Sensing.

Thin-film electronics pliably laminated onto the epidermis for noninvasive, specific, and multifunctional sensing are ideal wearable systems for health monitoring and information technologies. However, it remains a critical challenge to fabricate ultrathin and compliant skin-like sensors with high imperceptibility and sensitivities. Here we report a design of conductive hydrogen-substituted graphdiyne (HsGDY) nanofilms with conjugated porous structure and inherent softness for on-skin sensors that allow minimization of stress and discomfort with wear. Dominated by the subtle deformation-induced changes in the interdomain tunneling conductance, the engineered HsGDY sensors show continuous and accurate results. Real-time noninvasive spatial mapping of dynamic/static strains in both tensile/compressive directions monitors various body motions with high sensitivity (GF ∼22.6, under 2% strain), fast response (∼60 ms), and long-term durability (∼5000 cycles). Moreover, such devices can dynamically distinguish between the temperature difference and frequency of air inhaled and exhaled through the nostril, revealing a quantitative assessment of the movement/health of the human body. The proof-of-concept strategy provides an alternative route for the design of next-generation wearable organic bioelectronics with multiple electronic functionalities.

Fast water transport and molecular sieving through ultrathin ordered conjugated-polymer-framework membranes.

The development of membranes that block solutes while allowing rapid water transport is of great importance. The microstructure of the membrane needs to be rationally designed at the molecular level to achieve precise molecular sieving and high water flux simultaneously. We report the design and fabrication of ultrathin, ordered conjugated-polymer-framework (CPF) films with thicknesses down to 1 nm via chemical vapour deposition and their performance as separation membranes. Our CPF membranes inherently have regular rhombic sub-nanometre (10.3 × 3.7 Å) channels, unlike membranes made of carbon nanotubes or graphene, whose separation performance depends on the alignment or stacking of materials. The optimized membrane exhibited a high water/NaCl selectivity of ∼6,900 and water permeance of ∼112 mol m-2 h-1 bar-1, and salt rejection >99.5% in high-salinity mixed-ion separations driven by osmotic pressure. Molecular dynamics simulations revealed that water molecules quickly and collectively pass through the membrane by forming a continuous three-dimensional network within the hydrophobic channels. The advent of ordered CPF provides a route towards developing carbon-based membranes for precise molecular separation.

Development and validation of a Chinese pseudo-character/non-character producing system.

This study developed and validated a Chinese pseudo-character/non-character producing system (CPN system) that can assist researchers in creating experimental materials using Chinese characters. Based on a large-scale dataset of 6097 characters, the CPN system provides researchers with precise Chinese orthographic information (structures and positions, radical frequency, number of strokes, number of radical-sharing neighbors, and position-based regularity) to create three types of experimental stimuli: pseudo-characters, semi non-characters, and whole non-characters. Featuring the position-based regularity of 446 radicals, the CPN system helps researchers to manipulate, or to control for, orthographic characteristics of radicals to study Chinese lexical processing. In two empirical validations for stimuli created by the system, Chinese-as-second-language learners (n = 79) and first-language users (n = 41), respectively, participated in a Chinese orthographic choice task in which participants compared two artificial characters and chose the one that more closely resembled a real Chinese character. Both validations demonstrate that highly proficient Chinese readers are better able to identify pseudo-characters, suggesting that the radical's position-based information impacts Chinese character identification to different extents. With the empirical support for the created stimuli, the system further affords researchers auto-generated outcomes with downloadable images and Excel sheets for creating customized stimuli, making material selection easy, efficient, and effective. This CPN system is the first large-scale, data-driven tool free for researchers who are interested in studies of written Chinese. CPN should benefit the field of Chinese orthographic processing, Chinese instruction, and cross-linguistic comparisons, providing a useful tool for studying Chinese lexical processing.

Wafer-scale single-crystal hexagonal boron nitride monolayers on Cu (111).

Ultrathin two-dimensional (2D) semiconducting layered materials offer great potential for extending Moore's law of the number of transistors in an integrated circuit1. One key challenge with 2D semiconductors is to avoid the formation of charge scattering and trap sites from adjacent dielectrics. An insulating van der Waals layer of hexagonal boron nitride (hBN) provides an excellent interface dielectric, efficiently reducing charge scattering2,3. Recent studies have shown the growth of single-crystal hBN films on molten gold surfaces4 or bulk copper foils5. However, the use of molten gold is not favoured by industry, owing to its high cost, cross-contamination and potential issues of process control and scalability. Copper foils might be suitable for roll-to-roll processes, but are unlikely to be compatible with advanced microelectronic fabrication on wafers. Thus, a reliable way of growing single-crystal hBN films directly on wafers would contribute to the broad adoption of 2D layered materials in industry. Previous attempts to grow hBN monolayers on Cu (111) metals have failed to achieve mono-orientation, resulting in unwanted grain boundaries when the layers merge into films6,7. Growing single-crystal hBN on such high-symmetry surface planes as Cu (111)5,8 is widely believed to be impossible, even in theory. Nonetheless, here we report the successful epitaxial growth of single-crystal hBN monolayers on a Cu (111) thin film across a two-inch c-plane sapphire wafer. This surprising result is corroborated by our first-principles calculations, suggesting that the epitaxial growth is enhanced by lateral docking of hBN to Cu (111) steps, ensuring the mono-orientation of hBN monolayers. The obtained single-crystal hBN, incorporated as an interface layer between molybdenum disulfide and hafnium dioxide in a bottom-gate configuration, enhanced the electrical performance of transistors. This reliable approach to producing wafer-scale single-crystal hBN paves the way to future 2D electronics.

Creativity in children with ADHD: Effects of medication and comparisons with normal peers.

This study is to identify the performance of children with and without ADHD in open-ended and closed-ended creativity assessments, and investigate the moderating effect of medicated and unmedicated Children. The study subjects included third to sixth graders: 43 children with ADHD and 43 typically developing children. The participants with ADHD were those who were identified by local Committees of Identification, Placement and Consultation for Children with Special Needs or those who were diagnosed by medical institutions. Children with ADHD were further divided into medicated (22 participants) and unmedicated groups (21 participants) based on their current medication treatment. This study employed the New Tests of Creative Thinking to gauge the participants' open-ended creativity, while Remote Associates Test and the Insight Test were used to assess the participants' closed-ended creativity. Although previous evidence for creativity in children with ADHD have been mixed, this study includes medication as moderation variable and suggests that the performance of unmedicated children with ADHD in the open-ended creativity assessments was better than medicated children with ADHD and typically developing children. The study results can further explore the creativity characteristics of children with ADHD.

Metal-Guided Selective Growth of 2D Materials: Demonstration of a Bottom-Up CMOS Inverter.

2D transition metal dichalcogenide (TMD) layered materials are promising for future electronic and optoelectronic applications. The realization of large-area electronics and circuits strongly relies on wafer-scale, selective growth of quality 2D TMDs. Here, a scalable method, namely, metal-guided selective growth (MGSG), is reported. The success of control over the transition-metal-precursor vapor pressure, the first concurrent growth of two dissimilar monolayer TMDs, is demonstrated in conjunction with lateral or vertical TMD heterojunctions at precisely desired locations over the entire wafer in a single chemical vapor deposition (VCD) process. Owing to the location selectivity, MGSG allows the growth of p- and n-type TMDs with spatial homogeneity and uniform electrical performance for circuit applications. As a demonstration, the first bottom-up complementary metal-oxide-semiconductor inverter based on p-type WSe2 and n-type MoSe2 is achieved, which exhibits a high and reproducible voltage gain of 23 with little dependence on position.

Multilayer Graphene-WSe2 Heterostructures for WSe2 Transistors.

Two-dimensional (2D) materials are drawing growing attention for next-generation electronics and optoelectronics owing to its atomic thickness and unique physical properties. One of the challenges posed by 2D materials is the large source/drain (S/D) series resistance due to their thinness, which may be resolved by thickening the source and drain regions. Recently explored lateral graphene-MoS21-3 and graphene-WS21,4 heterostructures shed light on resolving the mentioned issues owing to their superior ohmic contact behaviors. However, recently reported field-effect transistors (FETs) based on graphene-TMD heterostructures have only shown n-type characteristics. The lack of p-type transistor limits their applications in complementary metal-oxide semiconductor electronics. In this work, we demonstrate p-type FETs based on graphene-WSe2 lateral heterojunctions grown with the scalable CVD technique. Few-layer WSe2 is overlapped with the multilayer graphene (MLG) at MLG-WSe2 junctions such that the contact resistance is reduced. Importantly, the few-layer WSe2 only forms at the junction region while the channel is still maintained as a WSe2 monolayer for transistor operation. Furthermore, by imposing doping to graphene S/D, 2 orders of magnitude enhancement in Ion/Ioff ratio to ∼108 and the unipolar p-type characteristics are obtained regardless of the work function of the metal in ambient air condition. The MLG is proposed to serve as a 2D version of emerging raised source/drain approach in electronics.

Band Alignment at GaN/Single-Layer WSe2 Interface.

We study the band discontinuity at the GaN/single-layer (SL) WSe2 heterointerface. The GaN thin layer is epitaxially grown by molecular beam epitaxy on chemically vapor deposited SL-WSe2/c-sapphire. We confirm that the WSe2 was formed as an SL from structural and optical analyses using atomic force microscopy, scanning transmission electron microscopy, micro-Raman, absorbance, and microphotoluminescence spectra. The determination of band offset parameters at the GaN/SL-WSe2 heterojunction is obtained by high-resolution X-ray photoelectron spectroscopy, electron affinities, and the electronic bandgap values of SL-WSe2 and GaN. The valence band and conduction band offset values are determined to be 2.25 ± 0.15 and 0.80 ± 0.15 eV, respectively, with type II band alignment. The band alignment parameters determined here provide a route toward the integration of group III nitride semiconducting materials with transition metal dichalcogenides (TMDs) for designing and modeling of their heterojunction-based electronic and optoelectronic devices.

Microwave-Assisted Synthesis of Highly Dispersed PtCu Nanoparticles on Three-Dimensional Nitrogen-Doped Graphene Networks with Remarkably Enhanced Methanol Electrooxidation.

A well-dispersed PtCu alloy nanoparticles (NPs) on three-dimensional nitrogen-doped graphene (PtCu/3D N-G) electrocatalyst has been successfully synthesized by a conventional hydrothermal method combined with a high-efficiency microwave-assisted polyol process. The morphology, composition, and structures are well-characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy. Cyclic voltammograms illustrate that the as-prepared PtCu/3D N-G electrocatalyst possesses the larger electrochemical active surface area, lower onset potential, higher current density, and better tolerance to CO poisoning than PtCu NPs on reduced graphene oxide and XC-72 carbon black in acid solution. In addition, long-time chronoamperometry reveals that the PtCu/3D N-G catalyst exhibits excellent stability even longer than 60 min toward acid methanol electrooxidation. The remarkably enhanced performance is related to the combined effects of uniformly interconnected three-dimensional porous graphene networks, nitrogen doping, modified Pt alloy NPs, and strong binding force between Pt alloy NPs and 3D N-G structures.

High-Sulfur-Vacancy Amorphous Molybdenum Sulfide as a High Current Electrocatalyst in Hydrogen Evolution.

The remote hydrogen plasma is able to create abundant S-vacancies on amorphous molybdenum sulfide (a-MoSx ) as active sites for hydrogen evolution. The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.

Enhanced electrocatalytic activity of MoS(x) on TCNQ-treated electrode for hydrogen evolution reaction.

Molybdenum sulfide has recently attracted much attention because of its low cost and excellent catalytical effects in the application of hydrogen evolution reaction (HER). To improve the HER efficiency, many researchers have extensively explored various avenues such as material modification, forming hybrid structures or modifying geometric morphology. In this work, we reported a significant enhancement in the electrocatalytic activity of the MoSx via growing on Tetracyanoquinodimethane (TCNQ) treated carbon cloth, where the MoSx was synthesized by thermolysis from the ammonium tetrathiomolybdate ((NH4)2MoS4) precursor at 170 °C. The pyridinic N- and graphitic N-like species on the surface of carbon cloth arising from the TCNQ treatment facilitate the formation of Mo(5+) and S2(2-) species in the MoSx, especially with S2(2-) serving as an active site for HER. In addition, the smaller particle size of the MoSx grown on TCNQ-treated carbon cloth reveals a high ratio of edge sites relative to basal plane sites, indicating the richer effective reaction sites and superior electrocatalytic characteristics. Hence, we reported a high hydrogen evolution rate for MoSx on TCNQ-treated carbon cloth of 6408 mL g(-1) cm(-2) h(-1) (286 mmol g(-1) cm(-2) h(-1)) at an overpotential of V = 0.2 V. This study provides the fundamental concepts useful in the design and preparation of transition metal dichalcogenide catalysts, beneficial in the development in clean energy.

Ductus venosus Doppler velocimetry in normal pregnancies from 11 to 13 + 6 weeks' gestation - a Taiwanese study.

BACKGROUND: To investigate flow in the ductus venosus at 11-13 + 6 weeks of gestation in women with normal pregnancies in the Taiwanese population. METHODS: Two hundred and fifty-two normal singleton pregnancies with gestational ages ranging from 11 to 13 + 6 weeks were examined in this study. The pulsatility index for veins (PIV), resistance index (RI), peak velocity during ventricular systole (S-wave), and peak velocity during ventricular diastole (D-wave) were recorded from the ductus venosus. RESULTS: We analyzed 252 participants who all fulfilled the inclusion and exclusion criteria of our study. The mean maternal age was 31 (range 19-45 years), with a corresponding gestational age of 12 + 4 weeks (range 11-13 + 6). No significant change was found in the vascular indices as gestational age increased for the S-wave (S-wave = 1.4214 (GA) + 17.448, r = 0.09, P = 0.154), PIV (PIV = -0.0358 (GA) + 1.4143, r = -0.05, P = 0.378) and RI (RI = -0.035 (GA) + 1.1478, r = -0.064, P = 0.468). In contrast, the D-wave behaved differently from the other variables. There was a significant increase (r = 0.155, P = 0.013) in the D-wave with gestational age (D-wave = 1.4896 (GA) - 7.1547). CONCLUSION: D-wave velocity in the ductus venosus increased with gestational age. S-wave peak velocity showed an increasing trend and PIV showed a decreasing trend with gestational age, but they did not reach statistical significance.

Acute respiratory distress syndrome following scrub typhus: a case report.

PURPOSE: To discuss a case of scrub typhus complicated with acute respiratory distress syndrome (ARDS) in a 67-year-old female. An overview of the prevalence and pathogenesis of the disorder, clinical diagnosis, and treatment are presented. DATA SOURCES: Case report, diagnostic evidence, and scientific literature. CONCLUSIONS: If not properly treated, scrub typhus can cause serious complications, such as ARDS and septicemia. When left untreated, the mortality rate for scrub typhus will be increased. When there is a cause to believe that scrub typhus is present, doxycycline treatment leads to rapid symptom improvement. IMPLICATIONS FOR PRACTICE: People might not be aware of the possibility of scrub typhus because it had been a more common disease in the past. Nurse practitioners (NPs) should take a detail history and be aware of common clinical manifestations to promote the early recognition and appropriate treatment of scrub typhus, which would prevent severe complications and reduce mortality. A resurgence of the disease could occur at any time among military troops serving in endemic regions.

Prognostic nomogram for overall survival in stage IIB-IVA cervical cancer patients treated with concurrent chemoradiotherapy.

OBJECTIVE: On the basis of outcome data from concurrent chemoradiotherapy (CCRT) for locally advanced cervical squamous cell carcinoma, the authors developed a nomogram for predicting survival outcome. STUDY DESIGN: Two hundred fifty-one eligible patients with International Federation of Gynecology and Obstetrics stage IIB-IVA squamous cell carcinoma of the uterine cervix who underwent CCRT were included for the construction of the nomogram. Predictor variables included age, serum squamous cell carcinoma antigen, tumor size, parametrium invasion, hydronephrosis, bladder/rectum invasion, and lymph node metastases. Internal validation of the nomogram was performed. RESULTS: A nomogram for predicting the 5 year overall survival for these patients was constructed on the basis of a Cox regression model from 7 parameters. The concordance index was 0.69. CONCLUSION: This nomogram is a predictive tool, upon external validation, that can be used to counsel patients in predicting outcomes. The discriminatory ability of the nomogram indicates that this population should not be considered homogeneous with respect to risk of death.