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We describe a high-performance molecular iodine optical frequency reference that is referenced to the R(56)32-0: a1 hyperfine transition of molecular iodine based on modulation transfer spectroscopy. We design an unsaturated iodine vapor cell with a gas pressure equivalent to the saturation pressure at −17 °C. Using this cell, we developed a compact, frequency-stabilized laser. The iodine cell operates at room temperature and is not actively temperature stabilized. We demonstrate a laser with fractional frequency instability of 1.4 × 10−14 at 1 s and 1.7 × 10−15 at 104 s. To our knowledge, the level of frequency instability at 104 s is comparable to the previously reported best results for an iodine stabilized laser. These results suggest that using an unsaturated iodine vapor cell is a valid approach for the development of long-term, stable iodine-based optical references. [ABSTRACT FROM AUTHOR]

The assessment of suitability is the cornerstone for the development of ecotourism in nature reserves. This paper adopts the Delphi method to invite 30 experts to score and screen a series of indicators and then calculates the weight of each indicator through the hierarchical analysis method (AHP) to establish a comprehensive evaluation index system for the suitability of ecotourism development. The AHP method includes four constraints layers (tourism resources, socio-economic environment, ecological conditions, and tourism market), in addition to eleven element layers and thirty-eight indicators. It establishes overarching criteria for evaluating ecotourism suitability. Our research focuses on Dinghushan, Xilin Gol Grassland, Hongze Lake Wetland, and Jiuzhai valley, and the results are as follows: (1) Ecotourism suitability evaluation level is divided into five levels, level I (0 ≤ S < 30) ecotourism development suitability is the lowest, meaning an area is extremely unsuitable for ecotourism development. Level V (90 ≤ S < 100) has a very high ecotourism value, meaning an area is highly suitable for ecotourism development. (2) Jiuzhai valley scored the highest ecotourism suitability evaluation score of 87.63, and Xilingol Grassland scored the lowest score of 81.27. However, the composite scores of all the nature reserves were above 80, placing them at Suitability Level IV, and thereby indicating a high suitability for ecotourism development. (3) Divergences in ecotourism suitability emerge among various nature reserve types, with grassland and meadow reserves exhibiting lower suitability levels. Addressing this, a robust management and monitoring system is imperative, alongside intensified efforts in ecological restoration, vegetation protection, community engagement, education, awareness, and increased policy support and tourism capital investment. (4) The results of the expert questionnaire showed that the maximum weight of the indicators affecting the evaluation of the suitability of ecotourism was the satisfaction of tourists (0.120), and the minimum weight was the accommodation facilities (0.002), which illustrated the important role of tourists in the ecotourism development carried out in the nature reserve. (5) Through empirical analysis of numerous cases, the study validates the practicality and effectiveness of the index system and provides scientific guidelines for the suitability of existing nature reserves for further ecotourism development. This contributes to the research theory on the suitability evaluation of ecotourism development and serves as a valuable reference for the future ecotourism development of diverse nature reserves. [ABSTRACT FROM AUTHOR]

Many space based gravity missions require frequency stabilized lasers with stringent requirements. Toward those requirements, we develop a compact frequency-stabilized laser which is referenced to the R(56)32−0: a1 transition of molecular iodine based on the modulation transfer spectroscopy technique. The stability of the laser is limited by the beam pointing noise, the electronic servo noise, and the residual amplitude modulation (RAM) noise. To improve the beam pointing stability, the system is constructed by gluing most components of the optical system on an ultra-low expansion glass base. We use a pre-amplifier to suppress the electronic servo noise, and use a wedged electro-optic phase modulator to suppress the RAM noise. The fractional frequency instability of the system is evaluated to be 3.3 × 10−15 at 2 s and 4 s averaging time, and is lower than 6 × 10−15 at averaging times from 1 s to 10 000 s. To our knowledge, this is the best short-term (1–4 s) instability reported so far for an iodine stabilized laser. The stability fully meets the requirements of next generation gravity mission and laser interferometer space antenna mission. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to develop and validate a virtual biopsy model to predict microsatellite instability (MSI) status in preoperative gastric cancer (GC) patients based on clinical information and the radiomics of deep learning algorithms. Methods: A total of 223 GC patients with MSI status detected by postoperative immunohistochemical staining (IHC) were retrospectively recruited and randomly assigned to the training (n = 167) and testing (n = 56) sets in a 3:1 ratio. In the training set, 982 high-throughput radiomic features were extracted from preoperative abdominal dynamic contrast-enhanced CT (CECT) and screened. According to the deep learning multilayer perceptron (MLP), 15 optimal features were optimized to establish the radiomic feature score (Rad-score), and LASSO regression was used to screen out clinically independent predictors. Based on logistic regression, the Rad-score and clinically independent predictors were integrated to build the clinical radiomics model and visualized as a nomogram and independently verified in the testing set. The performance and clinical applicability of hybrid model in identifying MSI status were evaluated by the area under the receiver operating characteristic (AUC) curve, calibration curve, and decision curve (DCA). Results: The AUCs of the clinical image model in training set and testing set were 0.883 [95% CI: 0.822–0.945] and 0.802 [95% CI: 0.666–0.937], respectively. This hybrid model showed good consistency in the calibration curve and clinical applicability in the DCA curve, respectively. Conclusions: Using preoperative imaging and clinical information, we developed a deep-learning-based radiomics model for the non-invasive evaluation of MSI in GC patients. This model maybe can potentially support clinical treatment decision making for GC patients. Key points: MSI is an important biomarker for immunotherapy in gastric cancer. Quantitative radiomics features were closely related to MSI in gastric cancer. Combining clinical and radiomics features with deep learning could evaluate MSI noninvasively. [ABSTRACT FROM AUTHOR]

Net ecosystem productivity ( NEP) represents the carbon sequestration capacity of a regional ecosystem. Based on the Google Earth Engine ( GEE) platform, this study analyzed the temporal and spatial variations in the NEP of the Three - River Headwaters Region ( TRHR) from 2001 to 2020 based on the Moderate Resolution Imaging Spectrometer ( MODIS) and meteorological data and revealed their relationships with climate factors. The results are as follows; 1 The TRHR had an important carbon sink function, with carbon sink areas accounting for 99. 89% ; The carbon source areas in the TRHR were primarily distributed in the northwest, accounting for only 0. 11%. The NEP of the TRHR decreased gradually from the southeast to the northwest and differed significantly among different ecological areas; 2 The NEP of the TRHR showed an upward trend overaU in the past 20 years, with an annual increasing rate of 1. 13 gC/(m ² • a), indicating huge carbon sequestration potential; 3 The area of zones whose NEP showed an upward trend accounted for 95. 05% of the total area. Ecological engineering construction significantly improved the NEP of vegetation. As a result, the carbon sink function gradually increased and was highly stable; 4 The TRHR had an annual average NEP of 120. 93 gC/( m ² • a), and the NEP was positively correlated with the annual precipitation but negatively correlated with average annual temperature and annual solar radiation. The warm, humid climate and the ecological engineering construction contributed to the carbon sink function of vegetation in the TRHR. This is of great significance for improving the carbon sink value of the terrestrial ecosystem and achieving the peak carbon dioxide emissions and carbon neutrality of China. [ABSTRACT FROM AUTHOR]

Carbonyl iron powder–polymer coating is one of the effective microwave absorption systems, which can be widely used as medium temperature structural materials in the aerospace industry. However, the significant mismatch of the coefficient of thermal expansion (CTE) between coatings and the titanium alloy substrates will cause serious cracking and peeling problems in practical applications. Thus, we designed to introduce Y2Mo3O12 (YMO) with negative CET into the carbonyl iron powder–boron-modified phenolic (BP) resin coating to reduce the CET of coating. The result showed that the CTE of the coatings is significantly decreased by the addition of Y2Mo3O12. The YMO/CIP/BP coating of 8 wt% YMO - 67 wt% CIP - 25 wt% BP shows a CTE of 21.1 × 10–6 ℃−1, which is 68% smaller than that of CIP/BP coating. The minimum RL (maximum of microwave absorption) of 8 wt% YMO - 67 wt% CIP - 25 wt% BP is – 12.3 dB at the thickness of 1.4 mm, which makes it an excellent candidate for the microwave absorptions applied on the titanium alloy surfaces. [ABSTRACT FROM AUTHOR]

The unique features of solution‐processed quantum dots (QDs) including emission tunability in the visible range, high‐quality saturated color and outstanding intrinsic stability in environment are highly desired in various application fields. Especially, quantum dot light‐emitting diodes (QLEDs) are promising light sources for applications in displays. However, the imbalance injection of holes and electrons have always been a challenging issue of QLED. In this study, the modified ligands which is synthesized by ourselves are incorporated into QDs through solution ligand exchange. The highest occupied molecular orbital (HOMO) of QDs is upshifted from ‐5.65eV to ‐5.35eV, leading to the decrement of the energy gap between the HOMO of QDs and the HOMO of hole transport layer. Through the successful ligands exchange, improvement by factors of 7.5 is achieved in maximum external quantum efficiency (EQE) compared with QLED with OA ligands. [ABSTRACT FROM AUTHOR]

Heat‐resistant energetic material (HREM) has shown its broad applications in petroleum and natural gas exploration, aerospace vehicle as well as solid rocket formulations. Benzopyridotetraazapentalene (BPTAP) (d: 1.84 g cm−3, D: 7670 m s−1, IS: 9 J, Td: 366 °C) is a heat‐resistant energetic material, which is more dense and energetic than those of commercial HREM hexanitrosilbene (HNS) (d: 1.74 g cm−3, D: 7612 m s−1, IS: 5 J, Td: 318 °C). However, low solubility in most of commonly‐used solvents has restricted its applications in detonators as nano‐energetic materials. Meanwhile, recognition on this fused organic backbone is still limited. Herein, we report a chlorine‐inclusion strategy and facile approaches to yield three new derivatives of BPTAP. It is notable that compound 6‐a exhibits its high density (1.92 g cm−3), superior thermal stability (Td: 334 °C), high detonation performance (D: 8084 m s−1), comparable sensitivity (IS: 3 J) to that of HNS, surpassing those of commercially‐used highly‐sensitive primary energetic material lead azide (LA). It is interesting that the chlorine‐inclusion in different position of fused benzopyridotetraazapentalene framework has greatly affected their physical properties such as crystal structure, thermal stability and sensitivity. This investigation offers a unique perspective for deeply exploring the relationship between structure and performance of energetic materials. [ABSTRACT FROM AUTHOR]

The analysis method based on high performance liquid chromatography (HPLC) is an important tool for the quality control of energetic materials. 1,1'-Diamino-4,4',5,5'-tetranitro-2,2'-biimidazole (DATNBI) as a new low-sensitivity and high-energy explosive, has many potential applications in both civil and military areas. However, the method based on HPLC is not known for the analysis of DATNBI. In this study, a HPLC method has been developed and validated for DATNBI. After the optimization of chromatographic conditions, a reversed-phase HPLC method has been established by using phenyl-hexyl column (4.6 × 150 mm, 3.5 µm) with the detection wavelength of 230 nm. The retention time of DATNBI is 10.37 min with the resolution of all peaks over 2.10. Meanwhile, the method has been also validated and displayed good accuracy, precision, stability and robustness for the analysis of DATNBI. The linear range of DATNBI analysis is 1.0–200 µg·mL−1 with the detection limit of 0.05 µg·mL−1. Further, this method had been applied to the analysis of real DATNBI. The purity of DATNBI was increased from 90.06 to 98.85% after the recrystallization for two times. This study indicates that the HPLC method is fast, efficient, sensitive and accurate for the analysis of DATNBI, and thus it can be used for the quality control of DATNBI. [ABSTRACT FROM AUTHOR]

Genotyping of the epidermal growth factor receptor (EGFR) mutation status is of great importance in the screening of appropriate patients with advanced non-small cell lung carcinoma (NSCLC) to receive superior tyrosine kinase inhibitor (TKIs) therapy. Yet conventional assays are generally costly with a relatively long turnaround time for obtaining results, which can lead to a bottleneck for immediately starting TKI therapy in late-staged patients. In this study, we propose an on-site electrochemical platform for sensitive simultaneous genotyping of the two major EGFR mutations (19del and L858R) through plasma ctDNA based on tetrahedral DNA nanostructure decorated screen-printed electrodes (SPE). Linear-after-the-exponential (LATE)-PCR combined with the amplification refractory mutation system (ARMS) was adopted to produce abundant biotin-labeled single-stranded DNA with high amplification efficiency and specificity. Disposable SPE decorated with self-assembled tetrahedral nanostructured DNA probes that showed ordered orientation and good target accessibility enabled the highly efficient hybridization of the specific amplicons through a sandwich-type and quantitatively translated the interfacial hybridization event into electrochemical signals via enzymatic amplification. Taking advantage of the ARMS-based LATE-PCR and the tetrahedral nanostructure-decorated SPE platform, we achieved the accurate detection of around 30 pg DNA of 19del or L858R, or as low as 0.1% of them in the presence of wild-type DNA. Moreover, the EGFR mutation profiles of 13 NSCLC patients we enlisted were accurately genotyped by our electrochemical platform, the results of which were in good agreement with those of commercial genetic detection methods. [ABSTRACT FROM AUTHOR]

In this study, by selecting the carrier injection and transport materials and optimizing the thickness of each functional layer in the device, we have solved the problem of unbalanced carrier injection in quantum dot light‐emitting diodes (QLED). The current efficiencies of red, green and blue spin‐coating QLED devices reach 30 cd/A, 70 cd/A, and 8 cd/A, respectively. By continuous optimization of the ink‐jet printing and film‐forming process, the suitable volume of printed ink drops and drying process conditions are obtained, and completed the fabrication of 55‐inch UHD AMQLED display. [ABSTRACT FROM AUTHOR]

The simultaneous incorporation of N-oxide and nitramine is a significant approach for improving the oxygen balance, density and detonation performance of energetic materials. Herein, an intramolecular hydrogen-bond block was stabilized in novel s-triazine energetic materials. Meanwhile, as the first instance of successful N-oxidation in the s-triazine backbone, the as-synthesized energetic compounds exhibited multipurpose applications. Compound 4 showed detonation performance comparable to that of FOX-12 but more insensitive and thermally stable (IS ＞ 80 J, Td: 275 °C). Compound 5 presented excellent physical and detonation properties similar to RDX, including high densities (up to 1.86 g cm−3), high energetic performances (calculated detonation velocity: 8762 m s−1) and low mechanical sensitivities (IS = 40 J) superior to those of RDX, demonstrating promise as a novel insensitive highly energetic material. [ABSTRACT FROM AUTHOR]

Dicarbohydrazide bis[3-(5-nitroimino-1,2,4-triazole)] (DCBNT) was firstly synthesized by ion exchange and salt formation reaction. A combination of single-crystal X-ray diffraction (SXRD), FTIR, 1H NMR, 13C NMR, and elemental analysis was utilized to analyze the structure and composition of DCBNT. DCBNT exhibits a high detonation velocity of 9234.87 m s−1 and a detonation pressure of 31.73 GPa as calculated by EXPLO5 v6.02 program. In addition, the sensitivities (impact sensitivity ＞40 J, H50 = 90 cm, and friction sensitivity = 216 N) and thermal stability (＞230 °C) of DCBNT were investigated. Moreover, we measured the solubility of DCBNT in 12 common solvents by a polythermal method system which demonstrates its poor solubility in common organic solvents and water. These excellent physicochemical properties make DCBNT an environmentally friendly, low-sensitivity and high-energy explosive. [ABSTRACT FROM AUTHOR]

Abstract: Synthesizing energetic metal–organic frameworks at ambient temperature and pressure has been always a challenge in the research area of energetic materials. In this work, through in situ controllable synthesis, energetic metal–organic framework gem‐dinitromethyl‐substituted dipotassium 4,5‐bis(dinitromethyl)‐1,2,3‐triazole with a “cage‐like” crystal packing was obtained and characterized. Most importantly, for the first time, we found that it could be successfully afforded with a catalytic effect of trifluoroacetic acid. This new compound exhibited its high density (2.04 g cm−3) at ambient temperature, superior detonation velocity (8715 m s−1) to that of lead azide (5877 m s−1) and comparable to that of RDX (8748 m s−1). Its detonation products are mainly N2 (48.1 %), suggesting it is also a green energetic material. The above‐mentioned performance indicates its potential applications in detonator devices as lead‐free primary explosive. [ABSTRACT FROM AUTHOR]

Modifying the properties of energetic materials is important not only for gaining insight into the relationship between structures and properties but also for multiple applications. A new family of energetic compounds, polynitroimidazoles featuring trinitromethyl, nitromethyl and methyl acetate moieties at the nitrogen position of heterocyclic rings were synthesized. The high‐energy oxidizers 2‐nitro and 4‐nitro‐1‐(trinitromethyl)‐1H‐imidazoles were obtained by nitration of 1‐acetonylpolynitroimidazoles in fuming HNO3 and concentrated H2SO4. 4,5‐Dinitro‐1‐(nitromethyl)‐1H‐imidazole and 4,5‐dinitro‐1‐(acetate methyl)‐1H‐imidazole were afforded by using 68 % HNO3 and concentrated H2SO4 through controllable synthesis. All the intermediates and the target compounds were confirmed by X‐ray diffraction. It is noteworthy that one of the N‐trinitromethyl nitroimidazole derivatives showed high density (ρ: 1.88 g cm−3), attractive positive oxygen balance (Ω: +18.3 %) and good detonation performance (D: 9003 m s−1) exceeding those of ADN, while N‐nitromethyl derivative behaved higher thermal stability and lower sensitivity in contrast to those of NG. N‐acetate methyl derivative gave an interesting melt‐castable property (Tm.p.: 86 oC, Td: 224 oC), acceptable detonation performance as well as low sensitivity towards impact and friction (IS>40 J, FS>360 N), making it a competitive replacement for DNAN. These chemical and physical properties indicate that these novel materials show promising energetic performance towards future applications. [ABSTRACT FROM AUTHOR]

Reliable cell tracking is essential to understand the fate of stem cells following implantation, and thus promote the clinical application of stem cell therapy. Dual or multiple modal imaging modalities mediated by different types of multifunctional contrast agent are generally needed for efficient cell tracking. Here, we created a new contrast agent—PLGA/iron oxide microparticles (PLGA/IO MPs) and characterized the morphology, structure and function of enhancing both photoacoustic (PA) and magnetic resonance imaging (MRI). Both PA and MRI signal increased with increased Fe concentration of PLGA/IO MPs. Fluorescent staining, Prussian blue staining and transmission electron microscope (TEM) certified that PLGA/IO MPs were successfully encapsulated in the labeled TSCs. The established PLGA/IO MPs demonstrated superior ability of dual-modal PA/MRI tracking of TSCs without cytotoxicity at relatively lower Fe concentrations (50, 100 and 200 μg/mL). The optimal Fe concentration of PLGA/IO MPs was determined to be 100 μg/mL, thus laying a foundation for the further study of dual-modal PA/MRI tracking of TSCs in vivo and promoting the repair of injured tendon. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this retrospective study is to evaluate the diagnostic value of contrast enhanced sonography plus gastric distention sonography, the Double Contrast-enhanced Ultrasound (DCUS) in gastric lesions. Methods: 107 cases with pathology confirmed gastric lesions were retrospectively reviewed, DCUS and oral contrast agent ultrasound (US) were performed in all cases prior to operation. Perfusion parameters including arrival time (AT), peak intensity (PI), time to peak (TTP), and area under the curve (AUC) of the lesion and surrounding normal tissue were analyzed. A reader blinded to pathology results were asked to rate and compare each case with surgical or resection biopsy pathology results. Results: From the 107 gastric lesions, 75 were malignant gastric lesions (33 gastric cancers,42 gastrointestinal stromal tumors (GISTs)) and 32 were benign gastric lesions (11 inflammatory masses and 21 polypoid adenomas). Compared with US, DCUS achieved higher value in sensitivity (90.6% vs. 70.6%), specificity (75% vs. 62.5%), positive predictive value (89.5% vs. 81.5%), negative predictive value (77.4% vs. 47.6%), and overall accuracy (85.9% vs. 68.2%). When US was tested against DCUS, the increase in correct diagnoses value was significant (P = .01). Furthermore, gastric cancer had faster AT, higher PI and AUC than normal tissue (P<0.05); GIST and Inflammatory mass had higher PI than normal tissue (P<0.05); gastric cancer and GIST had faster AT than polypoid adenoma (P<0.05), Inflammatory mass showed higher PI than other 3 lesions and gastric cancer had higher PI than polypoid adenoma and GIST (P<0.05); gastric cancer and inflammatory mass had larger AUC than polypoid adenoma and GIST (P<0.05). Conclusion DCUS improved diagnostic performance compared with US. The combination of different CEUS enhancement characteristics with quantitative perfusion parameters may provide a promising tool to help differentiate gastric cancer and GIST from benign lesions. [ABSTRACT FROM AUTHOR]

A metal-free oxyboration reaction, in which no acidic proton is involved and no intermediates bearing B−O σ-bond were observed, was recently reported by the Blum group. Since it showed potential as a general strategy to synthesize heterocyclic boronic esters, understanding the mechanistic details is very important. Two possible pathways of this oxyboration reaction were examined. Moreover, three key processes were highlighted in the pathway, including borylative cyclization, chloride shift, and demethylation. According to the calculations, the early demethylation (which leads to a formal O−B bond) was found to be slightly exergonic, but to have an inaccessible barrier, whereas demethylation after the cyclization step was feasible. The rate-determining step (RDS) was identified as the intramolecular cyclization for the oxyboration. Further theoretical investigation on the model reaction, in which an indole boronic ester is the product, revealed some interesting differences of reactivity between oxygen and nitrogen. Based on our calculation results, the N−C bond, which is usually treated as inert, can be cleaved in this case. Moreover, the there is a strong tendency for the RDS to shift from cyclization (as observed in the former oxyboration) to demethylation. Experiments were also conducted to confirm the calculations. [ABSTRACT FROM AUTHOR]