[en] The objective of this paper was to evaluate the influence of initial flaws in the beam-column connections on the seismic performance of steel frame structures. The finite element models were constructed with different initial flaw lengths by ABAQUS. The initial flaw length was 0, 8, and 16 mm, respectively. The dynamic elastic-plastic time history analysis and the pushover analysis were conducted to obtain the probabilistic characteristics of seismic demand and seismic capacity. Seismic demands are quantified in terms of the maximum drift angle (RDA) and the displacement ductility ratio $\left({\mathrm{\mu <!--\; ??\; -->}}_d\right)$. Moreover, the peak ground acceleration (PGA) was used for the pushover analysis. Formulas considering the influence of initial flaws on failure probability of a structure were derived for each length using different design basic acceleration of ground motion. The fragility curves were further constructed based on the data of seismic demand and capacity. The results show that the fragility of steel frame structures is similar across different seismic demand parameters. In addition, the analyses of fragility curves obviously indicate that the seismic fragility of steel frame structures increases as flaw length increases. Finally, the fragility of steel frame structures with initial flaws is consistent using different design basic acceleration of ground motion.

[en] Objective: To learn the endocardial strain patterns of the left ventricles on the short-axis views in normal youth volunteers using feature tracking techniques on cine cardiac MR imaging, and to build up the reference ranges of strain peak and time to peak (TTP) for endocardial strain analysis. Methods: Twenty-nine normal youth volunteers aged from 24-34 years old were enrolled in the study in march 2015. The Cine MR imaging were acquired using balance FFE sequence with 24 phases for each cardiac cycle. The standard short-axis imaging planes were basal, mid-cavity and apical levels and divided into 16 segments. The peaks and TTPs of myocardial displacement and its velocity, radial and circumferential strain and strain rate and its velocity in each segment were calculated using feature tracking techniques. The data with normal distribution were analyzed by ANOVA and Student-Newman-Keuls (SNK) method, and Kruskal-Wallis and Wilcoxon rank sum test were used for the data without normal distribution. Results: The peaks and TTPs of radial strain and strain rate differed in 16-segmental levels and basal, middle and apical plane levels and had no concordant reference ranges. The circumferential strain and strain rate were homogeneous at basal and middle plane levels [(-27.09 ± 9.51)%, (1.94 ± 0.98)/s, respectively]. Their TTPs were homogenous [0.38 (0.08) RR, 0.54 (0.08) RR, respectively], and there were no significant differences in planar-segments or inter-segment level. Except for middle level, the peaks of radial displacement and velocity differed in basal and apical levels and had no concordant reference ranges. But radial velocity TTPs were homogeneous in all 16 segments [0.21 (0.04) RR]. Except for the radial strain rate, TTPs showed no significant difference between basal level and middle level. The measurements at apical level revealed high variance. No regular pattern could be found on individual peak and TTP curves of velocity and strain rate. Conclusion: The peaks and TTPs of radial strain are different in segmental and planar levels without a concordant reference range. The peaks and TFPs of circumferential strain and the radial velocity rTTPs are homogeneous in middle and apical plane level and have homogeneous reference range. (authors)

[en] Antioxidants are healthy substances that are beneficial to the human body and exist mainly in natural and synthetic forms. Among many kinds of antioxidants, the natural antioxidants have great applications in many fields such as food chemistry, medical care, and clinical application. In recent years, many efforts have been made for the determination of natural antioxidants. Nano-electrochemical sensors combining electrochemistry and nanotechnology have been widely used in the determination of natural antioxidants due to their unique advantages. Therefore, a large number of nanomaterials such as metal oxide, carbon materials, and conducting polymer have attracted much attention in the field of electrochemical sensors due to their good catalytic effect and stable performance. This review mainly introduces the construction of electrochemical sensors based on different nanomaterials, such as metallic nanomaterials, metal oxide nanomaterials, carbon nanomaterials, metal–organic frameworks, polymer nanomaterials, and other nanocomposites, and their application to the detection of natural antioxidants, including ascorbic acid, phenolic acids, flavonoid, tryptophan, citric acid, and other natural antioxidants. In the end, the limitations of the existing nano-sensing technology, the latest development trend, and the application prospect for various natural antioxidant substances are summarized and analyzed. We expect that this review will be helpful to researchers engaged in electrochemical sensors. Graphical abstract

[en] High-temperature self-lubricating materials based on H13 steel are prepared by the powder metallurgy method. The sintering process, phase addition and high-temperature testing of the material are studied so that the mechanical and wear performance of the composites can be optimized. The results show that the optimum sintering process is 2 h at a temperature of 1250 °C. When the contents of Cr₂C₃ and CaF₂ are 10%, the mechanical and sintering properties of the composites are acceptable. The relative density reaches 80.2% and the bending strength reaches 720.2 MPa. Moreover, CaF₂ effectively reduces the friction coefficient and wear rate of the material. The friction coefficient decreases to a minimum of 0.24, but the wear rate increases to a maximum of 7.26 × 10⁻⁵ mm²/min at a load of 1065 g. Cr₂C₃ helps to alleviate the oxidation of the composites, and the precipitation of CaF₂ causes network cracks to reduce the thermal fatigue performance.

[en] Based on the service environment and requirements of hot working die,we proposed a H13-Cr₂C₃-CaF₂ self-lubricating material formula system and powder metallurgy process parameters, and prepared the high temperature composite materials. The phase composition and distribution of H13-Cr₂C₃-CaF₂ samples were analyzed by energy dispersive spectrometer. The friction coefficient, wear rate, wear morphology and spectrum of samples with different contents of CaF₂ were tested and compared by ball-on-disc high temperature tribometer under the conditions of test temperature 600 °C, disk rotation speed 200 r/min and friction for 15 min,and the mechanism of high temperature friction and wear was described. It will support the green manufacturing and sustainable development of forging industry. (paper)

[en] Objective: To compare the efficacies of MRI, X-ray mammography (XMG) and Ultrasound (US) in detecting and diagnosing breast ductal carcinoma in situ (DCIS). Methods: Two hundred and forty one consecutive patients with pathology-confirmed DCIS were retrospectively recruited from January 2011 to December 2017 in PLA General Hospital. The imaging examination modalities included MRI and/or XMG and/or US. The breast imaging reporting and data system (BI-RADS) categorizations by MRI, XMG and US were compared and their sensitivities of detecting DCIS were calculated. The causes of underestimation on MRI were interpreted with the information of XMG and US. Chi-square test was used to compare the differences. Results: The diagnostic sensitivity of XMG, US and MRI was 65.9% (29/44), 71.6% (101/141) and 91.2% (145/159), respectively, with statistical significant differences (X² = 24.034, P < 0.001). Breast density and lesion type would influence the sensitivity of XMG. And the sensitivity of US was decreased because of non-mass lesion. Of the 14 cases under-evaluated as BI-RADS category 1 to 3 on MRI, 5 were corrected by XMG and/or US to BI-RADS category 4. The cause of underestimation on MRI was the coexistence of DCIS with adenoma or other benign lesion. Conclusion: The retrospective comparison of MRI, XMG and US in this study showed that MRI had significant higher sensitivity in detecting breast DCIS, while the false negative rates of XMG and US were un-negligible. (authors)

[en] Thermal-crosstalk induced thermomigration failure in un-powered microbumps has been found in 2.5D integrated circuit (IC) circuit. In 2.5D IC, a Si interposer was used between a polymer substrate and a device chip which has transistors. The interposer has no transistors. If transistors are added to the interposer chip, it becomes 3D IC. In our test structure, there are two Si chips placed horizontally on a Si interposer. The vertical connections between the interposer and the Si chips are through microbumps. We powered one daisy chain of the microbumps under one Si chip; however, the un-powered microbumps in the neighboring chip are failed with big holes in the solder layer. We find that Joule heating from the powered microbumps is transferred horizontally to the bottom of the neighboring un-powered microbumps, and creates a large temperature gradient, in the order of 1000 °C/cm, through the un-powered microbumps in the neighboring chip, so the latter failed by thermomigration. In addition, we used synchrotron radiation tomography to compare three sets of microbumps in the test structure: microbumps under electromigration, microbumps under thermomigration, and microbumps under a constant temperature thermal annealing. The results show that the microbumps under thermomigration have the largest damage. Furthermore, simulation of temperature distribution in the test structure supports the finding of thermomigration.

[en] Highlights: • This work investigates the electronic and thermal transport properties of LaCuOSe under high pressure. • The physical inner mechanism of the influence from high pressure to the layered LaCuOSe has been investigated. • The reason why high pressure leads to high phonon vibrational frequency and large lattice thermal conductivity is studied. • Our results have important implications in leading us to investigate the application of LaCuOSe under high pressure. -- Abstract: In this study, first-principles calculations combined with semi-classical Boltzmann transport theory are carried out to study the thermal and electrical transport properties of LaCuOSe under high pressure. The results show that the Seebeck coefficient of LaCuOSe decreases significantly as the pressure rises, because of significant changes in crystal and electronic structures. Meanwhile, the electrical conductivity is also declined by high pressure. Additionally, the external pressure leads to decreased lattice parameters, high phonon vibrational frequency and enhanced heat transport. Therefore, the lattice thermal conductivity of LaCuOSe at 900 K increases with increasing pressure. As a result, the optimal figure of merit of LaCuOSe at 900 K is reduced from 0.99 (3.34) to 0.06 (0.35) along the a-axis (c-axis) as the pressure changes from 0 to 10 GPa. These results suggest that high hydrostatic pressure has negative effects on the thermoelectric properties of the layered LaCuOSe.

[en] We prospectively evaluated the efficacy and safety of microwave ablation (MWA) combined with ethanol injection (EI) in solitary nodular retrosternal goiters (RSGs). From November 2018 to November 2020, 72 patients diagnosed with solitary nodular RSG were treated by ultrasound-guided MWA with EI. Patients were followed up at 1, 3, 6, and 12 months and every 6-12 months thereafter by ultrasound and contrast-enhanced ultrasound (CEUS). The nodule volume, volume reduction ratio (VRR), neck circumference, symptom score, and cosmetic grading score were recorded to evaluate the treatment efficacy. All patients successfully underwent treatment. The mean initial nodule volume was 71.25 mL ± 61.61 mL, which decreased significantly to 7.47 mL ± 9.19 mL at a mean follow-up time of 23.89 months ± 7.66 months (range 15-39 months) with a mean VRR of 90.99% ± 7.52%. The neck circumference, symptom score, and cosmetic grading score significantly decreased from 36.94 cm ± 3.04 cm to 35.06 cm ± 2.84 cm, from 3.78 ± 1.19 to 0.36 ± 0.63, and from 3.42 ± 0.76 to 1.13 ± 0.37, at the 12 months after treatment, respectively (all 7 p < 0.001). Of all the nodules, eight (11.1%) received a second ablation. No major complications occurred. Ultrasound-guided MWA combined with EI is an effective and safe treatment for solitary nodular RSG and may be a potential alternative to surgery in selected patients, especially for those who are ineligible or unwilling to receive surgical treatment. MWA combined with EI is an effective and safe approach for the treatment of solitary nodular RSG. This treatment should be conducted by experienced physicians. It provides a potential alternative to surgery for solitary nodular RSG in patients who are ineligible or unwilling to receive surgical treatment.

[en] Memristors are an important component of the next-generation artificial neural network, high computing systems, etc. In the past, two-dimensional materials based memristors have achieved a high performance and low power consumption, though one at the cost of the other. Furthermore, their performance can not be modulated frequently once their structures are fixed, which remains the bottleneck in the development. Herein, a series of forming free memristors are fabricated with the same Cu/Fe₃GeTe₂ oxide/Fe₃GeTe₂/Al structure, yet the On/Off ratio and set voltage is modulated continuously by varying the oxidation time during fabrication. With an optimal oxidation time, a large On/Off ratio (1.58 × 10³) and low set voltage (0.74 V) is achieved in a single device. The formation and rapture of Al conductive filaments are found to be responsible for the memristors, and the filaments density and the cross-section area increase with the increase of current compliance, which achieves a higher On/Off ratio. The memristor can imitate basic biological synaptic functions using voltage pulses, demonstrating the potential for low-power consuming neuromorphic computing applications. (paper)