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Sub-Nyquist synthetic aperture radar (SAR) based on pseudo-random time–space modulation has been proposed to increase the swath width while preserving the azimuthal resolution. Due to the sub-Nyquist sampling, the scene can be recovered by an optimization-based algorithm. However, these methods suffer from some issues, e.g., manually tuning difficulty and the pre-definition of optimization parameters, and a low signal–noise ratio (SNR) resistance. To address these issues, a reweighted optimization algorithm, named pseudo-ℒ0-norm optimization algorithm, is proposed for the sub-Nyquist SAR system in this paper. A modified regularization model is first built by applying the scene prior information to nearly acquire the number of nonzero elements based on Bayesian estimation, and then this model is solved by the Cauchy–Newton method. Additionally, an error correction method combined with our proposed pseudo-ℒ0-norm optimization algorithm is also present to eliminate defocusing in the motion-induced model. Finally, experiments with simulated signals and strip-map TerraSAR-X images are carried out to demonstrate the effectiveness and superiority of our proposed algorithm. [ABSTRACT FROM AUTHOR]

A novel compressive sensing (CS) synthetic-aperture radar (SAR) called AgileSAR has been proposed to increase swath width for sparse scenes while preserving azimuthal resolution. AgileSAR overcomes the limitation of the Nyquist sampling theorem so that it has a small amount of data and low system complexity. However, traditional CS optimization-based algorithms suffer from manual tuning and pre-definition of optimization parameters, and they generally involve high time and computational complexity for AgileSAR imaging. To address these issues, a pseudo- L 0 -norm fast iterative shrinkage algorithm network (pseudo- L 0 -norm FISTA-net) is proposed for AgileSAR imaging via the deep unfolding network in this paper. Firstly, a pseudo- L 0 -norm regularization model is built by taking an approximately fair penalization rule based on Bayesian estimation. Then, we unfold the operation process of FISTA into a data-driven deep network to solve the pseudo- L 0 -norm regularization model. The network's parameters are automatically learned, and the learned network significantly increases imaging speed, so that it can improve the accuracy and efficiency of AgileSAR imaging. In addition, the nonlinearly sparsifying transform can learn more target details than the traditional sparsifying transform. Finally, the simulated and data experiments demonstrate the superiority and efficiency of the pseudo- L 0 -norm FISTA-net for AgileSAR imaging. [ABSTRACT FROM AUTHOR]

Background: Cancer is a serious public health problem worldwide, and difficulty in early diagnosis has been the chief obstacle to improve the prognosis of patients. Recently, microRNAs (miRNAs) were widely studied to be potential biomarkers for cancer detection. miR-16 is a prevalent but sophisticated one. In the current study, we aimed to assess the diagnostic value of serum miR-16 for cancer detection.Methods: A total of 1458 cancer patients, containing ten types of cancers, and 1457 non-cancer controls were recruited in this study. qRT-PCR was used for the amplification of miRNAs. In addition, a meta-analysis of reported studies was performed to confirm our findings systematically.Results: Consequently, miR-16 was down-regulated in ESCC, GCA and GNCA patients compared with NCs (all P < 0.001), while up-regulated in PDAC patients (P = 0.001), LAC, LSCC and EEC patients (all P < 0.001). But no significant differences were observed in CRC, EOC and TC patients when compared to NCs (P = 0.747, 0.235 and 0.268, respectively). The areas under the receiver operating characteristic (ROC) curve of miR-16 in GCA, ESCC, LAC, LSCC, GNCA, PDAC and EEC were 0.881, 0.780, 0.757, 0.693, 0.602, 0.614 and 0.681, respectively. Results of meta-analysis showed that miR-16 achieved an overall pooled sensitivity of 0.72, specificity of 0.79, and AUC of 0.85, suggesting that miR-16 was a promising biomarker in cancer detection.Conclusions: We provided a comprehensive view of the diagnostic value of serum miR-16 in cancer diagnosis, and confirmed that circulating miR-16 could play an important role in cancer detection. [ABSTRACT FROM AUTHOR]

To satisfy the growing demand for military and civil applications, it is necessary to develop high-efficiency microwave-absorbing materials. Herein, a pyrolysis process was developed to construct FeO x /Fe/C composites using filter papers saturated with ferric nitrate solution as the precursor. The three-dimensional textures of filter paper are well maintained during the pyrolysis process. Ferric nitrate is decomposed to Fe 2 O 3 and subsequently reduced to Fe 3 O 4 and Fe nanoparticles embedded in the carbon matrix via carbothermal reduction. Various gases produced during the pyrolysis process create foam and generate additional nanoscale pores in the carbon matrix. The chemical composition and structure of composites can be tailored by controlling the pyrolysis conditions. The microwave absorption properties of FeO x /Fe/C composites are closely related to the chemical composition and structure. The optimized product shows excellent microwave absorption properties: The strongest reflection loss (RL) is −37 dB at ∼12 GHz; the effective absorption bandwidth (RL < −10 dB) is 6.5 GHz with a thickness of 2.0 mm. The superior absorption properties of the optimized product can be ascribed to the synergies of multiple chemical components, hierarchically porous structures and abundant interfaces. This study also suggests a large-scale synthesis strategy for high-yield carbon-coated magnetic nanoparticles for high-performance microwave absorption materials. Image 1 • A pyrolysis process was developed to construct porous FeO x /Fe/C composites. • Magnetic nanoparticles are embedded in the porous carbon matrix. • The chemical composition and structure can be tailored by controlling the pyrolysis. • The microwave absorption properties are closely related to the composition and structure. • The effective absorption bandwidth of the optimized sample is 6.5 GHz with a thickness of 2.0 mm. [ABSTRACT FROM AUTHOR]

With the consumption of nonrenewable energy, environmental and energy issues require prompt solutions. With cellulose acetate being the main component, cigarette butts have become one of the most common items of household garbage due to nondegradability, which poses an important challenge in dealing with a series of problems caused by the discarded cigarette butts. Based on this problem, this work prepares nitrogen-doped cigarette butt-derived carbon (N-CBDC) through continuous carbonization, activation and a subsequent hydrothermal method and applies it to supercapacitor electrode materials. N-CBDC has high specific surface area (1633.37 m2 g−1), a hierarchical porous structure, oxygen-rich functional groups, and high contents of nitrogen doping. The results demonstrate that such nitrogen-doped cigarette butt-derived carbon applied has excellent specific capacitance (330.1 F g−1 at 0.5 A g−1), good rate performance (45.75% from 0.5 to 10 A g−1) and high cycling stability (93.48% after 10,000 cycles). This strategy, along with thoroughly disposing of cigarette butt wastes and avoiding cigarette butt pollution to the environment, is also expected to be used to develop various carbon-derived materials for supercapacitors to tackle the problem of nonrenewable energy consumption. • Nitrogen doped cigarette butt derived carbon (N-CBDC) was successfully prepared and applied to supercapacitors. • The characteristics of N-CBDC and its influence on the specific capacitance are described. • N-CBDC has good specific capacitance and excellent cycle stability. [ABSTRACT FROM AUTHOR]

Sub-Nyquist sampling technology can ease the conflict between high resolution and wide swath in a synthetic aperture radar (SAR) system. However, the existing sub-Nyquist SAR imposes a constraint on the type of the observed scene and can only reconstruct the scene with small sparsity (i.e., number of significant coefficients). The information channel model of microwave imaging radar based on information theory, in which scene, echo, and the mapping relation between the two correspond to information source, sink, and channel, is built, and noisy-channel coding theorem explains the reason for the aforementioned under this model. To allow the wider application of sub-Nyquist SAR, this paper proposes sub-Nyquist SAR based on pseudo-random space-time modulation. This modulation is the spatial and temporal phase modulation to the traditional SAR raw data and can increase the mutual information of information source and sink so that the scenes with large sparsity can be reconstructed. Simulations of scenes with different sparsity, e.g., an ocean with several ships and urban scenes, were run to verify the validity of our proposed method, and the results show that the scenes with large sparsity can be successfully reconstructed. [ABSTRACT FROM AUTHOR]

The polymer ultra‐low‐density proppants are critical to the development of slick‐water fracture technology, but which were prone to obvious deformation under high pressure in the fractures. To increase the stiffness of the styrene‐divinylbenzene copolymer (SDB) and obtain desired ultra‐low‐density (ULD) proppants, carbon dots (CDs) were introduced in‐situ considering their characteristics as the zero‐dimensional carbon nanomaterial. Taking the compressive strength and axial deflection, and so forth into consideration, the synthesis conditions of CDs modified SDB microspheres (CDs‐SDBs) were optimized. Taking the graphite modified SDBs (MG‐SDBs) as a reference, the density of CDs‐SDBs did keep almost constant at about 1.1800 ~ 1.1899 g·cm−3 with the increase of CDs amount. The CDs‐SDBs not only possess high‐peak pressure (41.5 N) but also minute axial deflection (0.090 mm). The advantages of CDs‐SDBs over MG‐SDBs become even more pronounced under higher pressure, which can withstand closure pressure of 80 MPa with a small crush ratio of 4.47%. CDs‐SDBs exhibit significant photoluminescence performances with maximum excitation and emission wavelengths of 634 nm and 554 nm. Highlights: CDs‐SDBs as ULD proppants with high strength and anti‐deformation were developed.Advantages of CDs‐SDBs become more pronounced under high‐closure pressure.With increasing of CDs amount, apparent density of CDs‐SDBs keep almost constant.Axial deflection of CDs‐SDBs is only 0.09 mm under 41.5 N.The crush ratio is only 4.47% under 80 MPa closure pressure. [ABSTRACT FROM AUTHOR]

Background: With the rise of high-calorie diets and the aging of populations, the incidence of diabetes was increased dramatically in the world and the number of people with diabetes was predicted to rise to 600 million by 2045. Numerous studies have confirmed that several organ systems, including the skeletal system, are seriously affected by diabetes. In that study, the bone regeneration and the biomechanics of the newly regenerated bone were investigated in diabetic rats, which may provide a supplement for previous studies. Methods: A total of 40 SD rats were randomly divided into the type 2 diabetes mellitus (T2DM) group (n = 20) and the control group (n = 20). Beyond that high fat diet and streptozotocin (STZ) were jointly used in the T2DM group, there were no differences between the two groups in terms of treatment conditions. Distraction osteogenesis was used in all animals for the next experimental observation. The evaluation criterion of the regenerated bone was based on radioscopy (once a week), micro-computed tomography (CT), general morphology, biomechanics (including ultimate load, modulus of elasticity, energy to failure, and stiffness), histomorphometry (including von Kossa, Masson trichrome, Goldner trichrome, and safranin O staining), and immunohistochemistry. Results: All rats in the T2DM group with fasting glucose levels (FGL, > 16.7 mmol/L) were allowed to complete the following experiments. The results showed that rats with T2DM have a higher body weight (549.01 g ± 31.34 g) than rats in the control group (488.60 g ± 33.60 g) at the end of observation. Additionally, compared to the control group, slower bone regeneration in the distracted segments was observed in the T2DM group according to radiography, micro-CT, general morphology, and histomorphometry. Furthermore, a biomechanical test showed that there was a worse ultimate load (31.01 ± 3.39%), modulus of elasticity (34.44 ± 5.06%), energy to failure (27.42 ± 5.87%), and stiffness (34.55 ± 7.66%) than the control group (45.85 ± 7.61%, 54.38 ± 9.33%, 59.41 ± 10.96%, and 54.07 ± 9.30%, respectively). Furthermore, the decreased expressions of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) were presented in T2DM group by immunohistochemistry. Conclusion: The present study demonstrated that diabetes mellitus impairs bone regeneration and biomechanics in newly regenerated bone, a phenomenon that might be related to oxidative stress and poor angiogenesis brought on by the disease. [ABSTRACT FROM AUTHOR]

The purpose of this paper lies in the preparation and utilization of phenolic resin hollow microspheres to enhance the induced carbonization performance of polymer materials and endow higher fire safety. PHM (phenolic resin hollow microspheres), CPHM (carbonized phenolic resin hollow microspheres), and CAPHM (carbonized phosphorylated phenolic resin hollow microspheres) were used as fillers in thermoplastic polyurethane elastomer. With the incorporation of 4 wt.% CPHM, as compared to pure TPU, the peak heat release rate (pHRR), total smoke release (TSR), and the peak CO release rates are decreased by 64.4%, 37.9%, and 86.2%, respectively. Simultaneous enhancement in flame retardancy, smoke suppression, and toxicity reduction is attributed to the formation of a compact residual layer in the polymer matrix, which significantly retards the dispersion of combustible gas, smoke particles, and toxic gas from the underlying substrate. Such outstanding characteristics make carbon microspheres a promising candidate for high fire safety polymers. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride/polyaniline doped with phosphoric acid (g-C 3 N 4 /PANI@PA) hybrids was prepared by polymerising aniline monomer on the surface of g-C 3 N 4 nanosheets, which used an in-situ chemical oxidative polymerisation method. Intumescent fire retardant (IFR) epoxy coatings with g-C 3 N 4 /PANI@PA were prepared, and fire resistance and waterproofing performance of coatings were investigated. The energy dispersive X-ray spectrometry image showed phosphorus element dispersing evenly on the fracture surface of epoxy composite with 0.25 wt% g-C 3 N 4 /PANI@PA (EP-0.25CP@PA), which indicated that g-C 3 N 4 /PANI@PA dispersed in coating evenly. The results of the cone calorimeter test (CCT) showed that the values of peak heat release rate (pHRR), total smoke release (TSR), total carbon monoxide production (TCOP) of pure epoxy resin (EP-0) were 1389.0 kW/m2, 22.6 m2 and 3.6 g, respectively. In addition, the related data of intumescent fire retardant coating (EP-IFR) were 374.8 kW/m2, 12.9 m2, and 2.1 g, respectively. When 0.25 wt% g-C 3 N 4 /PANI@PA was introduced into EP-IFR to get EP-IFR-0.25CP@PA sample, the pHRR, TSR, and TCOP values were reduced to 347.3 kW/m2, 7.9 m2, 1.5 g, which were reduced by 75.0%, 65.0%, and 60.0% compared with EP-0, respectively. Furthermore, g-C 3 N 4 /PANI@PA could also improve the hydrophobicity of IFR epoxy coatings. The water contact angle increased from 50.0° (EP-IFR) to 84.8° (EP-IFR-0.25CP@PA). It was confirmed that g-C 3 N 4 /PANI@PA could improve the fire protection, smoke suppression performance, and waterproof performance of IFR epoxy coating. All of those provide a certain theoretical support for applying g-C 3 N 4 /PANI@PA in intumescent fire retardant coatings. • G-C 3 N 4 /PANI@PA were prepared as flame retardant for IFR epoxy coating. • g-C 3 N 4 /PANI@PA can improve the fire protection, smoke and toxic gas suppression performance of IFR epoxy coating. • g-C 3 N 4 /PANI@PA can promote the cross-linking and carbonization of IFR epoxy coating. [ABSTRACT FROM AUTHOR]

In recent years, bio-based flame retardants have attracted extensive interest on account of their environmental-friendly character compared with traditional flame retardants. It is reported that oyster shell powder (OSP), composed of 95% calcium carbonate and 5 % organic matter, displays excellent flame retardant potential. In this paper, a novel bio-based flame retardant named functionalized oyster shell powder (FOSP) was prepared by mechanochemistry strategy based on OSP and ammonium polyphosphate (APP) and applied to enhance the fire safety of epoxy resin (EP) composites. The results showed that FOSP emerged with notable effects in improving the fire safety performance for EP composites. Compared with pure EP, the peak value of smoke production rate (pSPR) and peak value of heat release rate (pHRR) reduced by 69.4 % and 78.2 %, respectively. In addition, the char yields of EP composites were higher than EP. Conspicuously, the total CO production for EP composites with the addition of FOSP decreased by 44.9 % compared with EP composites with the addition of APP. Therefore, OSP, a typical marine solid waste, will become a promising candidate for high fire safety polymers. • FOSP as a novel flame retardant was synthesized via mechanochemical treatment of oyster waste. • FOSP can effectively improve the fire safety of epoxy composites. • FOSP can catalyze the formation of char residue layers and noncombustible gases during the combustion process. [ABSTRACT FROM AUTHOR]

• KH-560 acts as a bridge to connect boron nitride and ionic liquid, thus obtaining ionic liquid modified boron nitride nanosheets (BNO@IL). • Ionic liquid significantly enhances the interface interaction between boron nitride and epoxy resin. • After adding 2 wt% of BNO@IL nanosheets, the fire safety performance of epoxy resin composites is significantly enhanced compared with pure EP. Hexagonal boron nitride (h-BN) is more challenging to exfoliate into fewer layers than graphene due to the ionic bond between B and N atoms (lip-lip interaction) from adjacent layers. In this paper, boron nitride was exfoliated and hydroxylated by thermal oxidation in air. Hydroxylated boron nitride nanosheets (BNO) were modified by ionic liquids and added to epoxy resin to prepare epoxy matrix nanocomposites (EP/BNO@IL). The SEM results of EP/BNO@IL nanocomposites suggested that the introduction of ionic liquids enhanced the interfacial interaction between boron nitride nanosheets and epoxy resin (EP). Thermogravimetric (TG) results showed that introducing 2 wt% BNO@IL nanosheets improved the thermal stability of EP. In addition, cone calorimeter test (CCT) results showed that BNO@IL nanosheets enormously improved the fire safety performance of the epoxy resin. The peak heat release rate, total heat release, peak smoke release rate, and total smoke release of epoxy resin nanocomposites with 2 wt% BNO@IL nanosheets decreased significantly. In this work, the realization of ionic liquid modified boron nitride nanosheets (BNO@IL) provides new possibilities for improving the fire safety performance of EP. [ABSTRACT FROM AUTHOR]

• Phytic acid doped polyaniline-coupled g-C 3 N 4 (CP@PA) was synthesized as flame retardant for epoxy resin (EP). • CP@PA can improve the flame retardant efficiency and waterproof property of EP composites based on APP. • CP@PA could promote EP/APP to form a highly cross-linked network and char residue layer. In this study, polyaniline-coupled graphitic carbon nitride (g-C 3 N 4) doped with phytic acid (CP@PA) hybrids are prepared by an in-situ chemical oxidative method. The CP@PA and APP (Ammonium Polyphosphate) are added into epoxy resin (EP) for EP composites. The characteristic test results show that CP@PA can react with epoxy resin (EP) to promote the curing of EP. And CP@PA disperses in EP uniformly. The cone calorimetry test (CCT) results show that the pHRR, THR, and TSP of EP-8A4CP@PA (the EP sample with 8.0 wt% APP and 4.0 wt% CP@PA) reduce 85%, 76.8%, and 78.9%, respectively than EP-0 (pure EP), which are lower than any other samples. The results of the back temperature test show that EP-8A4CP@PA has better thermal insulation and flame-retardant properties than EP-12APP (the EP sample with 12.0 wt% APP). Moreover, CP@PA promotes the waterproof properties of EP with APP composites by synergizing with APP to form a labyrinth effect. After a comprehensive analysis, the fire protection mechanisms of EP-8A4CP@PA are proposed as follows. CP@PA promote EP charring and make more aromatic structure remain in the char. And CP@PA has a synergistic effect with APP to promote EP to form porous intumescent char layer with a higher graphitic degree, which protects the composites from the flame. As a result, the combination of CP@PA and APP in EP achieved a lower addition of flame retardant and better waterproof and fire safety performance, which provides a specific experimental and theoretical basis for the further application of CP@PA in epoxy resin. [ABSTRACT FROM AUTHOR]

Digital storage and transmission are common processes in modern synthetic aperture radar systems; thus, analog-to-digital converters are indispensable. Such processes can lead to two types of error: quantization (or granular) error and saturation (or clipping) error, which cause sampling noise, and radiometric and harmonic distortions in final images. Traditionally, reasonable choices of the gain and the number of quantization bits by the analog-to-digital converter based on the echo distribution can effectively reduce these errors. However, establishing the gain control repository of a synthetic aperture radar mission is a long process. In addition, if the dynamic range of the backscattering coefficient is extremely large or if unexpected strong targets appear in a scene, then harmonics occur in the echo, which turns the variable gain amplifier into chaos based on statistic and, inevitably, results in saturation in the raw data. Once raw data saturation occurs, the SAR system can conventionally adjust only the analog-to-digital converter in the next observation, thus reducing timeliness. Power loss compensation based on a statistical model and saturation (clipping) factor on a large-scale could compensate for the energy loss in images; however, detail interference, such as harmonic distortion, cannot be effectively suppressed, which will lead to false targets in the focused data. To address this particular problem, a novel anti-saturation method for large dynamic range scenes is proposed in this paper. The log-normal distribution is used in this article to describe dynamic range scenes with strong isolated targets, which mainly cause receiver saturation. Using the statistical distribution of complex scenes as a priori information, a maximum a posteriori estimation algorithm is proposed to simultaneously compensate for the saturated values in the raw data and retain the non-saturated values. Thus, the details of the weak background are well preserved, and the isolated strong targets with sparsity are reconstructed perfectly. With Monte Carlo simulation, the proposed method can improve the radiometric accuracy by 5 to 10 dB and effectively suppress the energy of false targets. Based on TerraSAR-X, ALOS-2, and Radarsat-1 synthetic aperture radar data, the effectiveness and robustness of the proposed method are also verified by simulations. [ABSTRACT FROM AUTHOR]