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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]

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]

Generalized zero-shot learning aims to classify samples of seen and unseen classes by providing only the labels of seen classes. Most GZSL methods directly associate seen classes' visual features with semantic information or leverage semantic information to synthesize samples of unseen classes to transfer the knowledge of seen classes to unseen classes. However, existing generative methods simply employ visual features extracted from the per-trained CNN backbone, which overlooks that the visual features of similar categories have significant similarities and lack enough discriminating information, leading to poor classification performance when generalizing the knowledge of seen classes to unseen classes. To mitigate this issue, we present a Visual-Semantic Consistency Matching Network (VSCM) for generalized zero-shot learning. Our proposed method employs a conditional VAE to generate the visual features of unseen classes and utilizes a visual-semantic consistency matching network that aligns visual space with semantic space to obtain visual-semantic consistency features. Specifically, we propose a semantic chunking network that teams up with semantic attention and a semantic encoder to guide the visual-semantic consistency matching network to get synthetic semantic information aligned with factual semantic information. The semantic relation network guarantees the consistency between the factual semantic information and the block features, while the semantic independence network measures the independence of the blocks. Finally, we concatenate visual features and synthetic semantic information as visual-semantic consistency features to improve the separability between categories. Extensive experiments on five GZSL benchmark datasets demonstrate the significant generalization performance of our proposed method over the state-of-the-art methods. Our codes have been available at: https://github.com/zzq158/VSCM-GZSL. [ABSTRACT FROM AUTHOR]

[Display omitted] • An UHPLC-Q-Orbitrap HRMS method was developed for the analysis of DATNBI and its raw material. • Evolution of impurities during the synthesis route of DATNBI was revealed. • The origin of impurities in DATNBI was deduced. 1,1′-diamino-4,4′,5,5′-tetranitro-2,2′-biimidazole (DATNBI) is an attractive insensitive highly energetic explosive. Even though DATNBI can be easily produced through deprotonation and ammoniation of 4,4′,5,5′-tetranitro-2,2′-biimidazole (TNBI), the type and source of impurities in DATNBI are still unclear. In present study, ultrahigh performance liquid chromatography coupled to a quadrupole-orbitrap mass spectrometry (UHPLC-Q-Orbitrap MS) was employed to analyze the chemical structures and origin of the impurities in DATNBI. A chromatographic method has been developed to separate the impurities of DATNBI and its raw material TNBI. The chemical structures of all impurities were tentatively identified by the analysis of retention time, UV–vis spectrum, elemental composition and MS/MS fragmentation patterns. In DATNBI, four impurities have been detected, including TNBI, mono-ammoniated TNBI, a dimer of DATNBI and the mono-ammoniated product of an impurity in TNBI. Interestingly, all compounds in the DATNBI sample produced fragment ions identical to the fragment ions of TNBI or its impurity, indicating TNBI and its impurity are the source of the impurities in DATNBI. This study gives an insight in the origin of impurities in DATNBI and provide the basis for quality improvement in future work. [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]

High-accuracy positioning and identification of vehicle parts are crucial for status detection, fault diagnosis, and the development of intelligent damage detection systems. However, detecting left–right and front-rear categories in vehicle parts remains challenging due to numerous categories and feature similarity. To address this, we propose the scene understanding vehicle part detection network (SU-VPDN). It comprises three subnetworks: vehicle orientation scene classification (VOSC), vehicle part instance segmentation (VPIS), and scene understanding (SU). VOSC performs preliminary classification of vehicle orientation scenes, while VPIS detects vehicle parts. SU fine-tunes VOSC results using the part logic correction module, fuses VOSC and VPIS results using the part replacement module, and obtains accurate VPIS results through confidence regulation and hierarchical filtering. SU-VPDN integrates results from multiple subnetworks, transforming the challenge of detecting similar objects into orientation scene detection for precise recognition. We evaluate the proposed method on a dataset containing 59 types of vehicle parts and compare it with advanced segmentation detection models. Experimental results demonstrate that SU-VPDN outperforms other models, achieving a 12.2% and 12.3% improvement in mean average precision (mAP) for box and mask, respectively, compared to the baseline model. Moreover, qualitative and quantitative experiments show that SU-VPDN significantly enhances the detection performance of objects with similar features. Overall, our proposed SU-VPDN offers a promising solution for detecting left–right and front-rear categories in vehicle parts. It surpasses existing models and can enable insurance companies to replace damaged parts and improve claims efficiency efficiently. [ABSTRACT FROM AUTHOR]

In this paper, the carbonyl iron powder/boron-modified phenolic resin (CIP/B-modified PR) composite coatings were designed and prepared by hot-pressing process. The density, microstructure, mechanical strength and microwave absorption properties of the coatings were investigated by Archimede’s method, scanning electron microscopy, universal mechanical testing machine and vector network analyzer, respectively. Results has demonstrated that the CIP/B-modified PR coatings with 75 wt% CIP give an ultra-strong adhesion strength above 12 MPa and a minimum reflection loss (RL) of −19.8 dB at 9.4 GHz with a thickness of 1.4 mm. In addition, the effective absorption band (RL < −10 dB) of 75 wt% CIP/B-modified PR coating measured at room temperature is fully covered in the X-band when the absorption thickness is only 1.2 mm. Moreover, the CIP/B-modified PR composite coatings can maintain a relatively stable microwave absorption capability in the X-band with a long-term life at high temperature (250 ℃ for 100 h). Therefore, CIP/B-modified PR coatings with an exceptional absorbing performance could be used in the field of high-temperature microwave absorption materials. [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]

The thermal expansion is one of the important reasons for the stress increase in polymer bonded explosive (PBX) and the damage of the long-term storage structure of explosives. Herein, the thermal expansion characteristics and crystal damage behavior under thermal stimulation of three crystal forms (β, α and γ) of 4,4′,5,5′-tetranitro-1H,1′H- [2,2′-biimidazole]-1,1′-diamine (DATNBI) were analyzed. The results show that DATNBI has obvious anisotropic thermal expansion, in which β- and α-DATNBI are first-order thermal expansion, and γ-DATNBI is second-order thermal expansion. The thermal expansion of DATNBI is reversible, but the crystal damage caused by thermal expansion is irreversible. Combined with Rietveld Refinement of powder X-ray diffraction (XRD) patterns, the volumetric expansion coefficients are 17.98 × 10−5 °C−1 (β-DATNBI), 23.28 × 10−5 °C−1 (α-DATNBI) and 14.39 × 10−5 °C−1 (γ-DATNBI), respectively. The relationship between crystal packing and thermal expansion characteristics of DATNBI at different temperatures was studied. It is demonstrated that the thermal expansion can probe certain intermolecular interactions resulting in anisotropic expansion behavior. Usually, the thermal expansion of most crystals (β-DATNBI) is positive, but slip or dislocation may cause a smaller negative expansion of a certain axis of the crystal cell (α-DATNBI). However, the unique cross-cross grid crystal packing (γ-DATNBI) will make a certain axis of the cell appear obvious negative expansion, which may lead to the overall decrease in the volumetric expansion coefficient of the crystal. [ABSTRACT FROM AUTHOR]

We have synthesized a series of new β-iminoenolates and their corresponding difluoroboron complexes without any traditional gelation moieties, and some of them were able to gelatinize organic solvents. It was found that the presence of halogen atoms as substituents had a significant effect on gelation ability. In particular, bromo-containing compounds 4 A and 4 B exhibited excellent gelation abilities compared with other halogen-substituted gelators. By analyses of the single-crystal structure, the PXRD pattern of the xerogel, and electronic spectral changes during gelation, we deemed that π-π, C−H⋅⋅⋅F, and C−H⋅⋅⋅Br interactions were the driving forces for the gelation of 4 B. Interestingly, ( Z)-1-(4-bromophenyl)-2-(3-methylpyrazin-2-yl)ethen-1-ol ( 8 A), prepared in this work, is the lowest-molecular-weight organogelator to have been reported. It should be noted that although β-iminoenolates 3 A- 5 A are nonemissive in solution, they emit strong yellow light in organogels, which suggests aggregation-induced emissive activity, whereas the difluoroboron complexes 3 B- 5 B show strong fluorescence in solutions, organogels, and xerogel-based films. Moreover, we found that the emission of 4 B in a nanofiber-based film could be quenched significantly upon exposure to gaseous trifluoroacetic acid and that the decay time and detection limit were 0.5 s and 0.17 ppm, respectively. Thus, through this work we have provided a new strategy for the design of nontraditional π gelators by introducing halogen atoms into π-conjugated systems with moderate polarities. [ABSTRACT FROM AUTHOR]

[Display omitted] • DAAF and its impurities were separated by ultra-performance liquid chromatography. • MS spectrum of the impurities were determined by high resolution mass spectrometry. • Chemical structure of the impurities in DAAF was analyzed by UHPLC-DAD-MS/MS. • The source of the impurities in DAAF was proposed in this study. Recently, 3,3-diamino-4,4-azoxyfurazan (DAAF) as one of most promising energetic furazan compounds has been widely studied because of its excellent explosive performances. Nowadays, the Oxone oxidation method is regarded as a main pathway to synthesize DAAF. However, several unknown impurities are yielded when the Oxone method is used to prepare DAAF. The identification of DAAF's impurities is beneficial to optimize synthetic route of DAAF and then improve its purity. In this study, chemical structures of DAAF and its main impurities were analyzed by developing an unknown analysis workflow based on ultrahigh-performance liquid chromatography-tandem diode array detector -tandem high resolution mass spectrometry (UHPLC-DAD-HRMS). They were fully separated by UHPLC after the optimization of chromatographic conditions. HRMS based on a Q-Orbitrap system was performed to elucidate chemical structure of the impurities by determining exact mass of the impurities and their MS/MS fragments. Besides DAAF, eight unknown impurities were detected under negative ion mode ([M-H]-) of HRMS with a heated electrospray ionization. Comprehensive analysis of UHPLC-DAD-HRMS provided more information including the retention time, UV–Vis spectrum, elementary composition and MS/MS fragments, and then possible structures of the impurities were proposed in this work. Further, the ion at m / z 211.0328, impurity I and impurity V were confirmed to be DAAF, DAF and DAAzF, respectively, through 1H NMR and 13C NMR after synthesizing their reference materials. In addition, the source of these impurities during the synthesis of DAAF has been analyzed. The impurities were originated from the precursor, the intermediate and byproduct of preparing DAAF through the hydrazine, the isomerism and the nitrosation. [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]

• Four novel HEPMs are prepared via the facile method. • HEPMs can be ignited without any additives under the combustion tests. • HEPMs have been first proposed for metal-free catalytic performance of AP. Energetic polymeric materials play vital roles in energetic materials fields to improve the comprehensive performances of rocket propellants and PBXs. Herein, four N-di/trinitrobenzene based heat-resistance energetic polymeric materials were synthesized via two facile approaches and fully characterized using FTIR, NMR, SEM and XRD. The combustion properties of energetic polymers were tested and recorded on a high-speed camera, physicochemical and energetic properties were also investigated. The results show that as-synthesized energetic polymers not only exhibit excellent thermal stabilities (the highest exothermic decomposition temperature of 336.7 °C) superior to those of GAP, poly(GLYN), triaminoguanidine-glyoxal polymer (TAGP) and graphene oxide (GO), but also produce great detonation and compatibility performance. In addition, the energetic polymer samples can be directly ignited without any additives. Worth noting that, we reported the thermal decomposition catalysis of AP by non-metallic energetic polymers as the first example, suggesting they can be potentially developed into metal-free catalysts replacing heavy metal-based energetic coordination polymers (ECPs) or energetic metal-organic frameworks (EMOFs). In summary, as-prepared energetic polymeric materials represent great application potential in solid rocket propellants and PBXs due to their promising catalytic effect, excellent chemical and physical performances. [ABSTRACT FROM AUTHOR]

The aim of the prospective study described here was to compare the tolerability, safety and diagnostic value of contrast-enhanced ultrasound-guided transoral core needle biopsy (CEUS-CNB) with that of conventional US-guided transoral CNB (US-CNB) and standard incisional biopsy in patients with oral masses. Between June 2017 and November 2019, consecutive patients with oral masses referred for biopsy were randomly assigned to undergo incisional biopsy, US-CNB or CEUS-CNB. Procedure time, intra‑operative blood loss volume, diagnostic performance and pain level before and after the procedure assessed by visual analogue score (VAS) were recorded and compared among the three procedures. Finally, 238 patients with pathology confirmation were analyzed: 80 patients underwent incisional biopsy, 78 patients US-CNB and 80 patients CEUS-CNB. In this study, no significant difference was found in biopsy time between CEUS-CNB, US-CNB and incisional biopsy (75 ± 11 s vs. 73.6 ± 12 s vs. 77 ± 13 s, p = 0.24). CEUS-CNB achieved the highest sensitivity (CEUS-CNB: 100%, US-CNB: 88.5%, incisional biopsy: 84.3%), negative predictive value (CEUS-CNB: 100%, US-CNB: 81.3%, incisional biopsy: 78.4%) and accuracy (CEUS-CNB: 100%, US-CNB: 92.3%, incisional biopsy: 90%). The VAS score for incision biopsy was higher (p = 0.01) and the amount of bleeding was larger (p < 0.001), yet there was no significant difference between CEUS-CNB and US-CNB. Our results indicate CEUS-guided transoral CNB is an efficient, safe and well-tolerated procedure, with biopsy time comparable to and diagnostic performance better than those of conventional US-guided transoral CNB and incisional biopsy. [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]

Purpose: To investigate the clinical value of real-time three-dimensional contrast-enhanced ultrasound (3D-CEUS) in the detection of sentinel lymph nodes (SLNs) and drainage lymphatics in breast cancer patients.Method: The prospective study was performed in women with pathology-confirmed T1/2 breast cancer between June 2016 and December 2017 who underwent sentinel lymph node biopsy and 3D-CEUS. The number, size, location, enhancement pattern of SLNs, and the lymphatic drainage patterns were reviewed. The routes, location of SLNs, and lymph channels (LCs) on the surface were marked. All patients underwent blue dye-guided sentinel lymph node biopsy (SLNB) finally.Results: According to the postoperative pathology findings and the blue dye staining of the lymphatic drainage routes, there are six patterns of lymphatic drainage routes and the coincidence rate of the 3D-CEUS was 97.4%; the sensitivity, specificity, positive predictive value, negative predictive value, the LN detection rate, and the correct diagnosis rate of the 3D-CEUS were 75%, 93.0%, 81.8%, 89.9%, 95.3%, and 87.7%, respectively.Conclusion: 3D-CEUS is a new feasible and useful approach to detect the SLNs and LCs. 3D-CEUS can accurately localize the LCs and SLNs and estimate the presence of metastatic lymph nodes.Key Points: • The three-dimensional contrast-enhanced ultrasound can detect the sentinel lymph nodes. • The three-dimensional contrast-enhanced ultrasound can show the stereo direction of sentinel lymph nodes and lymph drainage routes. • The three-dimensional contrast-enhanced ultrasound can accurately localize the LCs and SLNs and estimate the presence of metastatic lymph nodes. [ABSTRACT FROM AUTHOR]

We aimed to evaluate the value of sentinel lymph node contrast-enhanced ultrasound (SLN-CEUS) and surface tracing for the biopsy of intra-operative sentinel lymph nodes (SLNs). Between June 2015 and December 2017, a total of 453 patients with early invasive breast cancer were recruited. Patients received an intradermal injection of microbubble contrast agent around the areola on the day before surgery. The locations and sizes of lymphatic channels (LCs) and SLNs were marked on the body surface using gentian violet. Then, injection of double blue dye was performed half an hour before surgery. We compared the pathway of LCs and the location of SLNs obtained from SLN-CEUS and blue dye during surgery. Among the 453 patients, the mean numbers of LCs and SLNs detected by SLN-CEUS were 1.42 and 1.72, respectively, and the coincidence rate was 98.2% compared with blue dye during surgery. The median distance from the SLN to skin measured by pre-operative CEUS and blue dye was 1.95 ± 0.69 and 2.03 ± 0.87 cm (p = 0.35). There were three SLN enhancement in our research, including homogeneous enhancement, inhomogeneous enhancement and no enhancement, with the sensitivity, specificity, positive predictive value and negative predictive value of SLN-CEUS for the diagnosis of SLNs being 96.82%, 91.91%, 87.54% and 98.01%, respectively. SLN-CEUS with skin marking can identify the pathway of LCs and the location of the SLN before surgery, measure the distance from the SLN to skin and determine if the SLN is metastatic. SLN-CEUS can be used as an effective complement to the blue dye method. [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]

A novel core@self-shell hierarchical structure with excellent performance was constructed using an eco-friendly and effective strategy of autologous surface molecular reconfiguration. [Display omitted] • A novel hierarchical nano energetic material shows excellent performance. • This original strategy is effective and easy-to-scale. • Eco-friendly and no-additives preparation process. • Proposing the "solvate micro-dissolution shell" formation mechanism. Core-shell structured explosives (CSEs) are becoming increasingly prominent in the energetic materials, however, some fatal defects of CSEs including inadequate two-phase adhesion, insufficient shell coverage and thickness, and poor chemical stability seriously impact the security and dependability of weapon systems. Herein, we present a novel core-shell material in the field of organic crystals, the core@self-shell structure, constructed by an original strategy of autologous surface molecular reconfiguration. The solvate dioxane (DIOX) of 4,4′,5,5′-tetranitro-1 H ,1′ H -[2,2′-biimidazole]-1,1′-diamine (DATNBI) that screening based on computational prediction has the propensity to form a unique nanostructure after drying. According to this finding, we successfully designed the core@self-shell structure with a hierarchical nano-surface and proposed the "solvate micro-dissolution shell" formation mechanism. The core@self-shell energetic nanomaterials significantly improve impact sensitivity (22.5 J, raw material: 12 J) without greatly decreasing energy density through the eco-friendly and effective method, presenting great potential for industrial applications due to its excellent performance and simple construction process. [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]

[Display omitted] • Proposing an approach for high-performance solid DATNBI via rapid phase transition. • Obtaining a series of α-DATNBI with various morphologies by in-situ rapid preparation. • Proving a three-phase transition mechanism between solution, solvate, and target form. Using energetic materials (EMs) products with impure solid forms in practical application scenarios will lead to a series of serious consequences in terms of safety, mechanics, storage, detonation, and reliability properties. A novel approach to obtain the scarce and superior performance solid form of EMs was developed by the strategy of rapid in-situ solvate-mediated phase transformation, which is a promising and convenient method because of avoiding additional desolvating under specific external conditions and greatly reducing the risks in the production of EMs. In this strategy, the low sensitivity and highly energetic material 4,4′,5,5′-tetranitro-1 H ,1′ H -[2,2′-biimidazole]-1,1′-diamine (DATNBI) was used as a model substance and its α-DATNBI that is hard to gain but with better performance was successfully prepared. Furthermore, a mechanism of this solvate-mediated method was studied by exploring the types of solute clusters and intermolecular interaction of DATNBI in the microscopic view. These molecular assembly modes were determined in solid and solvents employing X-ray diffraction and in-situ micro-Raman technique, as well as attenuated total reflectance-Fourier transform infrared spectra combined with density functional theory calculation, respectively. It is found that solute molecules tend to exist as solvated monomers resulting in the prior precipitation of solvate in saturated solution of tetrahydrofuran (THF). From the perspective of crystal structure and transformation energy, the solvates consisting of DATNBI and THF can easily transform to the scarce α form of DATNBI. This study proposes a new practical strategy for a specific solid form mediated by solvates-mediated phase transformation, which is particularly beneficial for the preparation of high-purity solid forms of EMs with better energy and safety properties but also helps us to understand the key role of solvates in the polymorph formation.. [ABSTRACT FROM AUTHOR]

New difluoroboron β-diketonate complexes functionalized with tert -butyl carbazole and carbazole ( TCBM and CBM ) have been synthesized, and they give strong emission in solid states with the fluorescence quantum yields of 0.63 and 0.99, respectively. Reversible mechanofluorochromic behaviors of TCBM and CBM are realized upon the treatment of grinding/fuming with CH 2 Cl 2 . Interestingly, the emitting colors of the annealed samples gained from the ground powders of TCBM depend on the heating temperature, and change from orange to yellow, yellowish green, and green with increasing temperature. The X-ray diffraction patterns illustrate that the transformation processes from crystalline structure to partial destroyed crystalline structure, till to amorphous state lead to the multi-color solid-state luminescence during thermofluorochromism. We deduced that tert -butyl can lead to the incompact packing of luminophores, which is more sensitive to external stimuli, so that multi-color solid-state luminescence can be afforded during mechanofluorochromic and thermofluorochromic processes. [ABSTRACT FROM AUTHOR]

An L-phenylalanine derivative ( C12PhBPCP) consisting of a strong emission fluorophore with benzoxazole and cyano groups is designed and synthesized to realize dual responses to volatile acid and organic amine vapors. The photophysical properties and self-assembly of the said derivative in the gel phase are also studied. C12PhBPCP can gelate organic solvents and self-assemble into 1 D nanofibers in the gels. UV/Vis absorption spectral results show H-aggregate formation during gelation, which indicates strong exciton coupling between fluorophores. Both wet gel and xerogel emit strong green fluorescence because the cyano group suppresses fluorescence quenching in the self-assemblies. Moreover, the xerogel film with strong green fluorescence can be used as a dual chemosensor for quantitative detection of volatile acid and organic amine vapors with fast response times and low detection limits owing to its large surface area and amplified fluorescence quenching. The detection limits are 796 ppt and 25 ppb for gaseous aniline and trifluoroacetic acid (TFA), respectively. [ABSTRACT FROM AUTHOR]

Nanofibers based on phenanthroimidazole derivatives PCC, PDC, and PSC were fabricated by organogelation processes, and their fluorescence sensory properties towards acid were investigated. It was found that the emission of PCC in the nanofiber-based film could be quenched significantly upon exposure to gaseous TFA due to the formation of protonated PCC, in which ICT (intramolecular charge transfer) would occur. On the other hand, TFA vapor led to the emitting colors of PDC and PSC in the nanofiber-based films to turn to yellow and green from sky blue and blue, respectively. Additionally, we found that the decay times of PCC were 0.1 s and 1.9 s in probing the saturated vapor of TFA in nanofiber-based film and in spin-coated film, respectively. The results suggested that the high surface-to-volume ratio and large interspace in the nanofiber-based networks favored the enhanced adsorption, accumulation, and diffusion of gaseous molecules, resulting in such a high performance. [ABSTRACT FROM AUTHOR]

4-(Carbazol-9-yl)benzaldehyde could emit yellow RTP, which could last for 3 s because of efficient intersystem crossing. Moreover, multicolor luminescent switches could be realized by simply applying a mechanical force stimulus. [ABSTRACT FROM AUTHOR]

New triphenylvinyl substituted carbazole derivatives TPEICE , TPEC and TPECBr have been synthesized. They could self-assemble into nanofibers via organogelation processes in some organic solvents. Notably, the obtained xerogel-based films could emit strong fluorescence although the three compounds were non-emissive in solutions, indicating AIE in gel phases. The emission of TPEICE and TPEC in xerogel-based films could be quenched significantly upon exposed to gaseous DNT and TNT, while TPECBr could not sense nitro compounds on account of its poor electron donating ability. We also found that reversibility of the fluorescence response of TPEC was better than TPEICE because the photo-induced electron transfer would happen during the recognition of nitroaromatics for TPEICE and TPEC , except for the formation of charge–transfer complex between TPEICE and nitro compounds. Therefore, the different fluorescence response behaviors of TPEICE , TPEC and TPECBr towards nitroaromatics were resulted from their different electron donating abilities. [ABSTRACT FROM AUTHOR]

New branched benzothiadiazole-cored conjugated oligomers with terminal carbazoles 1 and 2 have been synthesized. It was found that no obvious shifts of the maximal absorption bands for 1 and 2 were detected in the films compared with those in solutions, indicating weak π-π stacking occurred in the solid states on account of site isolation effect of the branched architectures. Hence, the synthesized oligomers could emit strong red light in the films. Notably, the emission of the films based on 1 and 2 could be quenched obviously upon exposed to gaseous TNT and DNT. The fluorescence quenching efficiency of the oligomer 2 -based film reached 91% when exposed to the saturated vapor of DNT for 3 min at 55 °C. The linear Stern–Volmer plot and the decrease of the fluorescence lifetime of 2 induced by DNT suggested the fluorescence sensing mechanism was due to the photo-induced electron transfer. [ABSTRACT FROM AUTHOR]

Two L-phenylalanine derivatives with 5,8-bis(2-(carbazol-3-yl)vinyl)quinoxaline ( PCQ) and 5,8-bis[2-(carbazol-3-yl)]-2,3-dimethylquinoxaline ( DCQ) as fluorophores were synthesized, and their photophysical properties were measured and compared. The two compounds were found to gelate some organic solvents and self-assemble into 1D nanofibers in gels. The wet gel of PCQ emitted a weak orange fluorescence, but the DCQ gel had a strong green one. This result can be due to the presence of two methyl groups and the nonplanar conformation of fluorophore in DCQ. The gel film of DCQ also showed significantly stronger fluorescence than that of PCQ. Thus, the wet gel and xerogel film of DCQ were selected to study their sensing properties to acids. The yellow wet gel of DCQ transformed into a brown sol upon the addition of 0.2 equiv trifluoroacetic acid (TFA), accompanied by emission quenching. The xerogel film of DCQ rapidly responded to volatile acids, such as TFA, HCl, and HOAc. The fluorescence of the xerogel film was gradually quenched with increased concentration of volatile acid vapors. The fibrous film exhibited low detection limits for volatile acid. The detection limits of the thin films for TFA, HCl, and HOAc reached 43, 122, and 950 ppb, respectively. [ABSTRACT FROM AUTHOR]

A benzoxazole derivative called BVDA was synthesized. BVDA exhibited an AIE effect although there was H-aggregated dimer in the crystal. According to the spectral results and crystal structure, the presence of excimer and the restriction of intramolecular rotation are responsible for the AIE phenomenon. Moreover, BVDA could respond to proton in solution and to volatile acid vapours in film. BVDA exhibited three colours because its binding sites to proton have different basicities. These binding sites can then be protonated in turn. These results indicate that AIE fluorophores with H-aggregated dimer is possible. Furthermore, these fluorophores can exhibit stimuli-responsive characteristics through the introduction of functional moieties. [ABSTRACT FROM AUTHOR]

Novel nitrogen-rich hybrid via pyrazol-traizole and its ionic salts were designed and developed as thermally stable and insensitive next-generation green energetic materials. • Novel pyrazol-triazole nitrogen rich hybrids are prepared via facile methods. • Their physical performance and crystal packing with various characterizations are performed. • These new materials have high densities, low mechanical sensitivity, and excellent thermal stability. • This study provides a new concept of constructing nitrogen-rich compounds for green energetic materials. The barrier in the development of energetic material is the material design and performance improvement based on it. Currently, creative design and preparation of novel nitrogen-rich compounds are significant for new generation of green energetic materials. At the present work, organic heterocyclic hybrid pyrazol-triazole was constructed, synthesized and applied as building blocks in the development of versatile thermally stable high-energy materials. All derivatives were fully characterized by vibrational infrared spectroscopy (IR), multinuclear NMR (1H, 13C) spectroscopy, elemental analysis, differential scanning calorimetry (DSC), impact and friction-sensitivity test. Additionally, the structures of 4 – 8 and 10 – 13 were further confirmed by single-crystal X-ray diffraction and their crystal packing characteristics were thoroughly analyzed. Compound 2 not only enchanced physical properties of its ionic derivatives obviously, but also showed good detonation performance (D: 9075 m s−1) exceeding that of RDX, excellent insensitivity (IS > 80 J, FS > 360 N) comparable to that of TATB and superior thermal stability (331 °C) to that of HNS. Its ionic salts (compounds 4 – 14) also exhibit reasonable properties, such as good experimental densities (1.75–2.10 g cm−3), high thermal stability (174289 °C), good safety properties, excellent detionation performance (D v: 7745–8952 m s−1, P : 23.830.6 GPa), suggesting this new pyrazol-triazole hybrid is beneficial for improving their physical performance. This work is helpful for accelerating the discovery of insensitive, thermostable and high-energy green energetic materials. [ABSTRACT FROM AUTHOR]

• A series of aldehyde-functionalized dithienylethenes have been designed and synthesized. • They displays good photochromism with excellent fatigue resistance. • They can be utilized as versatile building blocks for NIR photochromic materials. A series of aldehyde-functionalized dithienylethenes 1b , 1c , 2b and 2c with extended π-conjugated systems have been synthesized by Wittig reaction. Their structures are confirmed by 1H NMR, 13C NMR and HRMS (ESI). As expected, investigation on their photochromic properties indicates that dithienylethenes 1b, 1c, 2b and 2c have good photochromic behaviors with excellent fatigue resistance upon irradiation with UV or visible light. The DFT calculations further validate the differences in their photochromic properties in solution. Furthermore, they can be utilized as versatile building blocks to construct novel near-infrared photochromic materials. [ABSTRACT FROM AUTHOR]