A library of atomically thin metal chalcogenides.

Investigations of two-dimensional transition-metal chalcogenides (TMCs) have recently revealed interesting physical phenomena, including the quantum spin Hall effect1,2, valley polarization3,4 and two-dimensional superconductivity 5 , suggesting potential applications for functional devices6-10. However, of the numerous compounds available, only a handful, such as Mo- and W-based TMCs, have been synthesized, typically via sulfurization11-15, selenization16,17 and tellurization 18 of metals and metal compounds. Many TMCs are difficult to produce because of the high melting points of their metal and metal oxide precursors. Molten-salt-assisted methods have been used to produce ceramic powders at relatively low temperature 19 and this approach 20 was recently employed to facilitate the growth of monolayer WS2 and WSe2. Here we demonstrate that molten-salt-assisted chemical vapour deposition can be broadly applied for the synthesis of a wide variety of two-dimensional (atomically thin) TMCs. We synthesized 47 compounds, including 32 binary compounds (based on the transition metals Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re, Pt, Pd and Fe), 13 alloys (including 11 ternary, one quaternary and one quinary), and two heterostructured compounds. We elaborate how the salt decreases the melting point of the reactants and facilitates the formation of intermediate products, increasing the overall reaction rate. Most of the synthesized materials in our library are useful, as supported by evidence of superconductivity in our monolayer NbSe2 and MoTe2 samples21,22 and of high mobilities in MoS2 and ReS2. Although the quality of some of the materials still requires development, our work opens up opportunities for studying the properties and potential application of a wide variety of two-dimensional TMCs.

UWB Frequency-Selective Surface Absorber Based on Graphene Featuring Wide-Angle Stability.

In this paper, an ultra-wideband and polarization-insensitive frequency-selective surface absorber is presented with oblique incident stable behavior. Different from conventional absorbers, the absorption behavior is much less deteriorated with the increase in the incidence angle. Two hybrid resonators, which are realized by symmetrical graphene patterns, are employed to obtain the desired broadband and polarization-insensitive absorption performance. The optimal impedance-matching behavior is designed at the oblique incidence of electromagnetic waves, and an equivalent circuit model is used to analyze and facilitate the mechanism of the proposed absorber. The results indicate that the absorber can maintain a stable absorption performance with a fractional bandwidth (FWB) of 136.4% up to 40°. With these performances, the proposed UWB absorber could be more competitive in aerospace applications.

Laparoscopic Pelvic Exenteration with Bladder Sparing for Men with Locally Advanced Rectal Cancer (with Video).

OBJECTIVE: The aim of this article was to introduce a fascial space priority approach for laparoscopic pelvic exenteration (PE) with bladder-sparing for men with locally advanced rectal cancer. METHODS: We present a video of bladder-sparing laparoscopic PE with fascial space priority approach in a 70-year old man. The systematic de-arterialization of the prostate on the basis of complete separation of the avascular lateral pelvic spaces is introduced in detail. RESULTS: The operation time was 360 min and the estimated intraoperative blood loss was 50 mL. The postoperative course was uneventful and the patient was discharged on postoperative day 14. Histopathological examination showed all margins to be tumor-free. CONCLUSIONS: Bladder-sparing laparoscopic PE using a fascial space priority approach is a feasible and safe procedure that can be performed in well-selected patients following neoadjuvant chemoradiotherapy. Extensive multivisceral resection is possible without a permanent stoma.

Fascial space priority approach for laparoscopic total pelvic exenteration in patients with locally advanced rectal cancer.

BACKGROUND: Total pelvic exenteration (TPE) with intent to achieve a pathological R0 resection is now considered as the only chance of a long-term survival for locally advanced rectal cancer (LARC) invading into adjacent organs. Lately, laparoscopic total pelvic exenteration (LTPE) is performed and achieved in several specialized centers and showed a promising application prospect. Although this is universally realized by surgeons, there are only few specialized centers to perform this complex surgery, due to concerns about the high morbidity and mortality. The techniques associated need to be disclosed and facilitated. OBJECTIVE: The aim of this article is to introduce a fascial space priority approach for laparoscopic TPE step by step (with video). METHODS: We describe here a fascial space priority approach for LTPE in highly selected patients with locally advanced rectal cancer. The main principle of this approach is that all of the pelvic organs are considered as a whole, the non-vascular spaces surrounding it are separated in the first place, the vascular pedicle and nerve pedicle of pelvic organs can be isolated and then transected precisely. Meanwhile, the associated key landmarks of this approach are disclosed (see the video). RESULTS: The ureterohypogastric nerve fascia (UHGNF) and the vesicohypogastric fascia (VHGF) are two vital embryological planes on the lateral compartment of pelvis. The spaces on either side of them together with the retrorectal space, the space of Retzius, are all non-vascular spaces, and dissection of these spaces in LTPE surgery can be achieved simply and practicably. The ureter, the umbilical artery, the arcus tendinous fasciae pelvis (ATFP), piriformis and the puboprostatic ligament (PPL) are all important landmarks during surgery. Step-by-step illustration with precise anatomical landmarks in the present video may lead to less intraoperative blood loss and complications. CONCLUSIONS: LTPE with fascial space priority approach might be a standard surgical procedure for total pelvic exenteration with clear anatomy and reduced blood loss.

Chemical Vapor Deposition of Superconducting FeTe1-xSex Nanosheets.

FeTe1-xSex, a promising layered material used to realize Majorana zero modes, has attracted enormous attention in recent years. Pulsed laser deposition (PLD) and molecular-beam epitaxy (MBE) are the routine growth methods used to prepare FeTe1-xSex thin films. However, both methods require high-vacuum conditions and polished crystalline substrates, which hinder the exploration of the topological superconductivity and related nanodevices of this material. Here we demonstrate the growth of the ultrathin FeTe1-xSex superconductor by a facile, atmospheric pressure chemical vapor deposition (CVD) method. The composition and thickness of the two-dimensional (2D) FeTe1-xSex nanosheets are well controlled by tuning the experimental conditions. The as-prepared FeTe0.8Se0.2 nanosheet exhibits an onset superconducting transition temperature of 12.4 K, proving its high quality. Our work offers an effective strategy for preparing the ultrathin FeTe1-xSex superconductor, which could become a promising platform for further study of the unconventional superconductivity in the FeTe1-xSex system.

Two-step CVD synthesis of NiTe2-MoS2vertical junctions with improved MoS2transistors performance.

The primary challenge for widespread applications of two-dimensional electronics is to achieve satisfactory electrical contacts due to the difficulties in inevitable physical damages and selectively doping during traditional metal integration process. The two-dimensional (2D) metal-semiconductor junctions have attracted captivated attention for potential applications in future atomically thin electronics as perfect candidates for achieving reliable electrical contacts. Here we demonstrate the van der Waals epitaxial growth of 2D NiTe2-MoS2 metal-semiconductor vertical junctions which the upper NiTe2 selectively nucleate at the edge of underlying MoS2. Optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning transmission electron microscope (STEM) studies confirm that NiTe2-MoS2 metal-semiconductor vertical junctions are successfully synthesized. Electrical properties of the NiTe2-contacted MoS2 field-effect transistors (FETs) show higher field-effect mobilities (µFE) than those with deposited Cr/Au contacts. This study demonstrates an effective pathway to improved MoS2 transistors performance with metal-semiconductor junctions.

Two-step chemical vapor deposition synthesis of NiTe2-MoS2 vertical junctions with improved MoS2 transistor performance.

The primary challenge for the widespread application of two-dimensional (2D) electronics is to achieve satisfactory electrical contacts because, during the traditional metal integration process, difficulties arise due to inevitable physical damage and selective doping. Two-dimensional metal-semiconductor junctions have attracted attention for the potential application to achieve reliable electrical contacts in future atomically thin electronics. Here we demonstrate the van der Waals epitaxial growth of 2D NiTe2-MoS2 metal-semiconductor vertical junctions where the upper NiTe2 selectively nucleates at the edge of the underlying MoS2. Optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning transmission electron microscope (STEM) studies confirmed that NiTe2-MoS2 metal-semiconductor vertical junctions had been successfully synthesized. The electrical properties of the NiTe2-contacted MoS2 field-effect transistors (FETs) showed higher field-effect mobilities (µ FE) than those with deposited Cr/Au contacts. This study demonstrates an effective pathway to improved MoS2 transistor performance with metal-semiconductor junctions.

Controlled Growth of 3R Phase Tantalum Diselenide and Its Enhanced Superconductivity.

Transition metal dichalcogenides (TMDs) have become a playground for exploring rich physical phenomena like superconductivity and charge-density-waves (CDW). Here, we report the synthesis of the atom-thin TaSe2 with a rare 3R phase and enhanced superconductivity. The 3R phase is achieved by an ambient pressure chemical vapor deposition (CVD) strategy and confirmed by the high-resolution aberration-corrected STEM. Low-temperature transport data reveal an enhanced superconducting transition temperature (Tc) of 1.6 K in the 3R-TaSe2, which undoubtedly breaks the traditional perception of TaSe2 crystal as a material with Tc close to 0 K. This work demonstrates the strength of ambient pressure CVD in the exploration of crystal polymorphism, highlights a decisive role of layer stacking order in the superconducting transition, and provides fresh insights on manipulating crystal structures to gain access to enhanced Tc.

Air Stable Organic-Inorganic Perovskite Nanocrystals@Polymer Nanofibers and Waveguide Lasing.

Organic-inorganic hybrid perovskites have been considered as promising gain materials for lasing. Despite previous reports of lasing from nanocrystals, thin films and single crystals, the stability of perovskite lasers has been a challenge for its practical applications. Herein, a scalable strategy to prepare ultrastable perovskite@polymer hybrid fibers by employing a facile emulsion electrospinning approach is demonstrated. During the electrospinning process, polymethyl methacrylate (PMMA) first solidifies into an outer shell layer. Meanwhile, emulsion drops containing poly(vinylidene fluoride) (PVDF) and perovskite precursor are pushed inward and evolve into perovskite nanocrystals covered by PVDF. The PMMA with smooth surface benefits the light transport and the water-resistant PVDF blocks the moisture. The methylammonium lead bromide perovskite-embedded fibers can emit intensive light after storage in humid ambient environment (relative humidity >60%) or even in water. Amplified spontaneous emissions from the fibers network and waveguide lasing from chopped single fiber is demonstrated.

Self-gating in semiconductor electrocatalysis.

The semiconductor-electrolyte interface dominates the behaviours of semiconductor electrocatalysis, which has been modelled as a Schottky-analogue junction according to classical electron transfer theories. However, this model cannot be used to explain the extremely high carrier accumulations in ultrathin semiconductor catalysis observed in our work. Inspired by the recently developed ion-controlled electronics, we revisit the semiconductor-electrolyte interface and unravel a universal self-gating phenomenon through microcell-based in situ electronic/electrochemical measurements to clarify the electronic-conduction modulation of semiconductors during the electrocatalytic reaction. We then demonstrate that the type of semiconductor catalyst strongly correlates with their electrocatalysis; that is, n-type semiconductor catalysts favour cathodic reactions such as the hydrogen evolution reaction, p-type ones prefer anodic reactions such as the oxygen evolution reaction and bipolar ones tend to perform both anodic and cathodic reactions. Our study provides new insight into the electronic origin of the semiconductor-electrolyte interface during electrocatalysis, paving the way for designing high-performance semiconductor catalysts.

Metastasis to lateral lymph nodes with no mesenteric lymph node involvement in low rectal cancer: a retrospective case series.

PURPOSE: The aim of this study is to examine the pattern of lymph node metastasis (lateral vs. mesenteric lymph nodes) in low rectal cancer. METHODS: This retrospective analysis included all patients undergoing laparoscopic total mesorectal excision plus lateral lymph node dissection for advanced low rectal cancer (up to 8 cm from the anal verge) during a period from July 1, 2017, to August 31, 2019, at the Department of Colorectal Surgery, Tianjin Union Medical Center. The decision to conduct lateral lymph node dissection was based on positive findings in preoperative imaging assessments. RESULTS: A total of 42 patients were included in data analysis. Surgery was successfully completed as planned, without conversion to open surgery in any case. A minimum of 10 mesenteric lymph nodes and 1 lateral lymph node on each side were dissected in all patients. Pathologic examination of resected specimens showed no metastasis to either mesenteric or lateral lymph nodes in 7 (16.7%) case, metastasis to both mesenteric and lateral lymph nodes in 26 (61.9%) cases, metastasis to mesenteric but not lateral lymph nodes in 4 (9.5%) cases, and metastasis to lateral but not mesenteric lymph nodes in 5 (11.9%) cases (n = 2 in the obturator region; n = 3 in the iliac artery region). CONCLUSION: A clinically significant proportion of low rectal cancer patients have metastasis to lateral lymph nodes without involvement of mesenteric lymph nodes. More carefully planned prospective studies are needed to verify this preliminary finding.

Black Phosphorus Nanosheets: Synthesis, Characterization and Applications.

Black phosphorus (BP) is an emerging two-dimensional (2D) material with a natural bandgap, which has unique anisotropy and extraordinary physical properties. Due to its puckered structure, BP exhibits strong in-plane anisotropy unlike other layered materials. The bandgap tunability of BP enables a wide range of ultrafast electronics and high frequency optoelectronic applications ranging from telecommunications to thermal imaging covering the nearly entire electromagnetic spectrum, whereas no other 2D material has this functionality. Here, recent advances in the synthesis, fabrication, anisotropic physical properties, and BP-based devices including field effect transistors (FETs) and photodetectors, are discussed. Recent passivation approaches to address the degradation of BP, which is one of the main challenges to bring this material into real world applications, are also introduced. Finally, a comment is made on the recent developments in other emerging applications, future outlook and challenges ahead in BP research.

Controlled Synthesis of High-Quality Monolayered α-In2Se3 via Physical Vapor Deposition.

In this work, we have demonstrated the synthesis of high-quality monolayered α-In2Se3 using physical vapor deposition method under atmospheric pressure. The quality of the In2Se3 atomic layers has been confirmed by complementary characterization technologies such as Raman/photoluminescence spectroscopies and atomic force microscope. The atomically resolved images have been obtained by the annular dark-field scanning transmission electron microscope. The field-effect transistors have been fabricated using the atomically layered In2Se3 and exhibit p-type semiconducting behaviors with the mobility up to 2.5 cm(2)/ Vs. The In2Se3 layers also show a good photoresponsivity of 340A/W, as well as 6 ms response time for the rise and 12 ms for the fall. These results make In2Se3 atomic layers a promising candidate for the optoelectronic and photosensitive device applications.

Band engineering for novel two-dimensional atomic layers.

The discovery of graphene has sparked much interest in science and lead to the development of an ample variety of novel two-dimensional (2D) materials. With increasing research interest in the field of 2D materials in recent years, the researchers have shifted their focus from the synthesis to the modification of 2D materials, emphasizing their electronic structures. In this review, the possibilities of altering the band structures are discussed via three different approches: (1) alloying 2D materials, so called ternary 2D materials, such as hexagonal carbonized boron nitrides (h-BCN) and transition metal dichalcogenides (TMDs) ternary materials; (2) stacking 2D materials vertically, which results in 2D heterostructures named van der Waals (vdW) solids (using hexagonal boron nitrides (h-BN)/graphene and TMDs stacking as examples), and growing lateral TMDs heterostructrues; (3) controlling the thickness of 2D materials, that is, the number of layers. The electronic properties of some 2D materials are very sensitive to the thickness, such as in TMDs and black phosphorus (BP). The variations of band structures and the resulting physical properties are systematically discussed.

Chemical Vapor Deposition of High-Quality and Atomically Layered ReS2.

Recently, anisotropic 2D materials, such as black phosphorus and rhenium disulfides (ReS2 ), have attracted a lot attention because of their unique applications on electronics and optoelectronics. In this work, the direct growth of high-quality ReS2 atomic layers and nanoribbons has been demonstrated by using chemical vapor deposition (CVD) method. A possible growth mechanism is proposed according to the controlled experiments. The CVD ReS2-based filed-effect transistors (FETs) show n-type semiconducting behavior with a current on/off ratio of ≈10(6) and a charge carrier mobility of ≈9.3 cm(2) Vs(-1). These results suggested that the quality of CVD grown ReS2 is comparable to mechanically exfoliated ReS2, which is also further supported by atomic force microscopy imaging, high-resolution transmission electron microscopy imaging and thickness-dependent Raman spectra. The study here indicates that CVD grown ReS2 may pave the way for the large-scale fabrication of ReS2-based high-performance optoelectronic devices, such as anisotropic FETs and polarization detection.

High-resolution mapping of age- and gender-specific risk of Clonorchis sinensis infection risk in Guangdong, China: a geostatistical modeling study.

BACKGROUND: The latest national survey on the distribution of human parasites in China demonstrated that Guangdong was among the endemic provinces with the highest Clonorchis sinensis infection rates. High-resolution, age- and gender-specific risk maps of the temporal and spatial distributions are essential for the targeted control work. METHODS: Disease data on the prevalence of C. sinensis infection from 1990 onwards, either age- and gender-specific or aggregated across age and gender, were collected through systematic review and four large-scale surveys in Guangdong Province. Environmental and socioeconomic variables were obtained from open-access databases and employed as potential predictors. A Bayesian geostatistical model was developed to estimate the C. sinensis infection risk at high spatial resolution. RESULTS: The final dataset included 606 surveys at 463 unique locations for C. sinensis infection. Our findings suggested that following an initial increase and stabilization, the overall population-adjusted prevalence had declined to 2.2% (95% Bayesian credible interval: 1.7-3.0%) in the period of 2015 onwards. From 2015 onwards, moderate and high infection risks were found in the northern regions (e.g. Heyuan and Shaoguan cities) and the southern Pearl River Delta (e.g. Foshan, Zhongshan, Zhuhai and Jiangmen cities), respectively. Age- and gender-specific risk maps revealed that males had a higher infection risk than females, and the infection risk was higher in adults compared to children. CONCLUSIONS: Our high-resolution risk maps of C. sinensis infection in Guangdong Province identified the spatial, temporal, age and gender heterogeneities, which can provide useful information assisting tailored control strategies.

A NiMOF integrated with conductive materials for efficient bifunctional electrocatalysis of urea oxidation and oxygen evolution reactions.

The development of urea oxidation reaction (UOR) and oxygen evolution reaction (OER) bifunctional electrocatalysts has dual significance in promoting hydrogen energy production and urea-rich wastewater treatment. Herein, a carboxylated multi-walled carbon nanotube (MWCNT-COOH)-ferrocene carboxylic acid (Fc-COOH) modulated NiMOF hybrid material (MWCNT-NiMOF(Fc)) has been synthesized for dual electrocatalysis of the UOR and OER. The material characterization results indicated that MWCNT-COOH and Fc-COOH were integrated into the framework structure of the NiMOF. The direct interaction between the NiMOF and MWCNT/Fc facilitated electron transfer in the hybrid material and led to lattice strain, which improved the charge transfer kinetics, promoted the exposure of more unsaturated Ni sites, and increased the electrochemically active surface area. These factors together enhanced the electrocatalytic activity of MWCNT-NiMOF(Fc) towards the UOR and OER. Using a glassy carbon electrode as the substrate, MWCNT-NiMOF(Fc) exhibited low potential requirements, low Tafel slopes, and high stability. In overall urea and water splitting electrolysis cells, the excellent UOR and OER dual functional catalytic ability and enormous practical application potential of the MWCNT-NiMOF(Fc) modified foam nickel electrode were further demonstrated. On the basis of the above research, the influence of a KOH environment on urea electrolysis was further studied, and the urea electrolysis products were analyzed, promoting a more comprehensive understanding of the catalytic performance of MWCNT-NiMOF(Fc) for urea oxidation. This study provides a new approach for developing high-performance NiMOF-based electrocatalysts for challenging bifunctional UOR/OER applications, and has potential application value in hydrogen production from urea-containing wastewater electrolysis.

A radiomics model based on T2WI and clinical indexes for prediction of lateral lymph node metastasis in rectal cancer.

OBJECTIVE: The aim of this study was to explore the clinical value of a radiomics prediction model based on T2-weighted imaging (T2WI) and clinical indexes in predicting lateral lymph node (LLN) metastasis in rectal cancer patients. METHODS: This was a retrospective analysis of 106 rectal cancer patients who had undergone LLN dissection. The clinical risk factors for LLN metastasis were selected by multivariable logistic regression analysis of the clinical indicators of the patients. The LLN radiomics features were extracted from the pelvic T2WI of the patients. The least absolute shrinkage and selection operator algorithm and backward stepwise regression method were adopted for feature selection. Three LLN metastasis prediction models were established through logistic regression analysis based on the clinical risk factors and radiomics features. Model performance was assessed in terms of discriminability and decision curve analysis in the training, verification and test sets. RESULTS: The model based on the combined T2WI radiomics features and clinical risk factors demonstrated the highest accuracy, surpassing the models based solely on either T2WI radiomics features or clinical risk factors. Specifically, the model achieved an AUC value of 0.836 in the test set. Decision curve analysis revealed that this model had the greatest clinical utility for the vast majority of the threshold probability range from 0.4 to 1.0. CONCLUSION: Combining T2WI radiomics features with clinical risk factors holds promise for the noninvasive assessment of the biological characteristics of the LLNs in rectal cancer, potentially aiding in therapeutic decision-making and optimizing patient outcomes.

Carbon nanotube photoelectronic and photovoltaic devices and their applications in infrared detection.

Semiconducting carbon nanotubes (CNTs) are direct bandgap materials with outstanding electronic and optoelectronic properties and have been investigated for various electronic and optoelectronic device applications, such as light-emitting diodes, photodetectors and photovoltaic cells. Here, a brief review of the various types of CNT diodes is presented, with a focus on one particular type of CNT diodes fabricated via a doping-free process. Their application for constructing high-performance optoelectronic and photovoltaic devices is also discussed, as well as the newly discovered photovoltage multiplication effect in CNTs and its application in improving the efficiency of CNT-based infrared detector.