Search

Axial compression tests and corresponding finite element analysis were conducted on the basis of material property tests. It was shown that the failure mode of long column with a low width-thickness ratio is global instability, while the failure mode of short column with a high width-thickness ratio is that small bending deformation appeared firstly at the center of the column, then the deformation developed with the gradually increasing load and caused local buckling in the end. The results of finite element analysis can fit well with the test results, which means the feasibility and accuracy can be achieved by using this residual stress model into finite element analysis to simulate the axial compression behavior of cold-formed thick-walled steel members. Then, the finite element model was used based on the collected 26 groups of material properties of different tubes with representative size and thickness to get the axial bearing capacity data of members, and design reliability analysis of cold-formed thick-walled steel members under axial compression was conducted. Finally, the resistance partial factor and the design strength for Q235 and Q345 cold-formed thick-walled steel were proposed for the reference in current revising of related design codes. [ABSTRACT FROM AUTHOR]

In order to investigate the cold-forming effect on the yield strength of cold-formed thick-walled steel sections over 6. 0 mm thick, four cold-formed steel rectangular hollow sections with representative size and thickness were selected to investigate the material properties of different parts of the sections. Meanwhile, existing data of material property tests and short column tests were collected. The modifying formula for yield strength considering cold-forming effect based on different codes in the world were summarized, and the calculation results from those formulas were compared with the test results. It is shown that cold-forming has a strong influence on the yield strength of cold-formed thick-walled steel sections, and it depends greatly on the width to thickness ratio of each plate of the sections. The calculation results of Chinese code, AISI ( American Iron and Steel Institute) standard, Australian/New Zealand standard and the formula proposed by Zhu Aizhu are in conservatively agreement with the test results, while that of Eurocode is a little larger. The suitability of the improved method from Chinese Code was theoretically proved, and it can get a little safer results with a lower coefficient of variation, which means appropriate to be used in practice. [ABSTRACT FROM AUTHOR]

Built-up section members have been widely used in cold-formed thin-walled steel structures, but nowadays design methods for load-carrying capacity provided in related specifications in China are rather rough. The existing axial compression tests on lipped channel section members and built-up box section members, which are composed of lipped channel section members by self-drilling screws, are briefly introduced. The structural behaviors differences of built-up members and individual members were studied through existing experimental data, numerical analysis and theoretical studies. Then, the effects of installation errors and fastener spacing on built-up members' ultimate capacity were studied. Finally, a design method for built-up members with box and I sections under axial compression was proposed based on the above analysis. It can be concluded from this research that built-up box section member's global and distortional buckling strength and built-up I section member's global buckling strength are higher than corresponding single section member' s strength, and the existing test results can verify the reasonability of the proposed design method. [ABSTRACT FROM AUTHOR]

Based on comparison of stability coefficient between distortional buckling and local buckling, the critical condition without distortional buckling or distortional buckling occurring after local buckling for cold-formed thin-walled steel members with lipped channel section was put forward. At the same time, the critical condition for controlling distortional buckling by corresponding calculation length of members was presented. Furthermore, a countermeasure to avoid distortional buckling of cold-formed thin-walled steel members with lipped channel section by setting batten sheets between two lips was presented. A series of tests were carried out to show its validity, and the stiffness requirement of the batten sheets was proposed. The results show that, calculation of distortional bucking load-carrying capacity of cold-formed thin-walled steel members with lipped channel section can be avoided if the distortional buckling occurs after the local buckling or the distortional buckling does not occur by controlling the section sizes of members; distortional buckling doesn't occur when the calculated length is less than half of half-wave length of distortional buckling; the suggested countermeasure by setting batten sheets between two lips is valid to prevent the rotation of flanges, which leads to an evident increase of the elastic distortional buckling strength, and the load-carrying capacity of axial compression members as well; with different spacing of batten sheets, the corresponding increase of load-carrying capacities is obviously different. Generally, the spacing is smaller, increase of load-carrying capacity is higher. The example show that the batten sheets with a certain spacing and stiffness can increase the distortional buckling strength or avoid the occur of distortional buckling. [ABSTRACT FROM AUTHOR]

The seismic behavior of framing shear wall, which is the main lateral force-resistance assembly of cold-formed thin-walled steel framing system, is closely associated with the behavior of screw connections between steel studs and sheathing boards. A series of tests on behavior of screw connections between the cold-formed steel studs and structural oriented strand boards (OSBs), under monotonic and cyclic shear loading, were carried out. The main objectives of the tests were to investigate the effects of loading rate, sheathing orientation, end distance of screws and thickness of steel studs. It is shown that, the shear behavior of screw connections is little affected by both the tested loading rate and sheathing orientation; both the strength and deformation increase with the end distance increasing in the tested range; the peak load increases by about 10% with stud thickness increasing from 0. 8 mm to 1.0 mm, while the deformation does not exhibit a clear tendency. Finally, based on the tests results, a restoring force model of screw connections between cold-formed steel studs and structural OSB was obtained by the combination of modified exponential 'Foschi' skeleton curve and pivot hysteretic rule, which will support the numerical study on seismic behavior of framing shear walls, and even integral buildings. [ABSTRACT FROM AUTHOR]

A nonlinear dynamic analysis study on seismic behavior of a two-story cold-formed thin-walled steel framing building full-scale test model was carried out by the way of from components to integral structure. Restoring force behaviors of all framing shear walls of the shaking table test building were obtained based on the refined numerical framing shear wall model and restoring force model of tapping screw connections. Then, a dynamic numerical model of low-rise cold-formed thin-walled steel framing building was established based on the simplified shear wall model with nonlinear bracing and assumption of rigid diaphragm, and nonlinear dynamic analysis was carried out. The results of FEA agree well with the tests. Also, values range of damping ratio was proposed based on the parametric analysis of damping ratio and the comparison of FEA and shaking table tests. Finally, the application of linear dynamic analysis is investigated, and suggestions are offered. [ABSTRACT FROM AUTHOR]

Referring to Australian specifications and the actual requirements in China, a complete method of determining the design values of specimen capacity based on test data, rather than calculation from existing design formula, was presented. A modification factor was obtained which could determine the characteristic values of specimen capacity directly from the minimum testing result through probability analysis. The modification factor can ensure that the characteristic values have a certain level of survival probability. The resistance partial factors were calculated through design reliability analysis to determine the design values from characteristic values of specimen capacity. It is proven that by adopting the recommended resistance partial factors, the actual reliability index of structural members are no less than the target reliability index under all possible loading cases. Some experimental data were collected, and the design values of specimen strength calculated from design formula provided in the design code were compared with that determined directly from test results using the proposed method. It is found that the proposed method can rationally evaluate the design values of specimen strength. Finally, the preconditions and applicable situation of the proposed method were discussed, which might provide reference for further research and applications of the proposed method. [ABSTRACT FROM AUTHOR]

Based on static and dynamic experimental investigations on light-gauge composite framing walls, the suitable skeleton curve model, as well as the hysteretic curve model of the composite walls for seismic analysis was discussed and suggested at first in this paper. Then, seismic analysis methods for light-gauge composite framing building system were discussed in comparison with shaking table test of a full-scale model of high-strength cold-formed thin-walled steel framing building with yield strength over 550 MPa, including the equivalent base shear method, the response spectrum method and the elastic time-history analysis method for frequently occurred earthquake action design, and the nonlinear pushover method and the elasto-plastic time-history analysis method for rare earthquake action design. Meanwhile, the results based on different seismic analysis methods were compared and verified by the shaking table test data of the full-scale model. Finally, considering the basic requirements in current seismic design codes in China, some suggestions on seismic design methods for low-rise cold-formed thin-walled steel framing buildings were given. [ABSTRACT FROM AUTHOR]

As one of the main characteristics of neoplasia, metabolic reprogramming provides nutrition and energy to enhance cell proliferation and maintain environment homeostasis. Glycolysis is one of the most important components of cancer metabolism and the Warburg effect contributes to the competitive advantages of cancer cells in the threatened microenvironment. Studies show strong links between N 6 -methyladenosine (m 6 A) modification and metabolic recombination of cancer cells. As the most abundant modification in eukaryotic RNA, m 6 A methylation plays important roles in regulating RNA processing, including splicing, stability, transportation, translation and degradation. The aberration of m 6 A modification can be observed in a variety of diseases such as diabetes, neurological diseases and cancers. This review describes the mechanisms of m 6 A on cancer glycolysis and their applications in cancer therapy and prognosis evaluation, aiming to emphasize the importance of targeting m 6 A in modulating cancer metabolism., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: Previous studies have demonstrated the ubiquitin-proteasome inhibitor bortezomib (BTZ) can effectively alleviate hypoxia-induced pulmonary hypertension (HPH) by suppressing the intracellular calcium homeostasis in pulmonary arterial smooth muscle cells (PASMCs). Further evaluation showed that the antiproliferation roles of BTZ are mainly mediated by inhibition of the intracellular calcium homeostasis. Caveolin-1 belongs to one of the key regulators of the intracellular calcium homeostasis in PASMCs, which can regulate the store-operated calcium entry (SOCE). However, the effects of BTZ on Caveolin-1 remain unclear., Methods: Primarily cultured human PASMCs were used as the cell model. CCK-8 assay was performed to assess the PASMCs proliferation. Western blotting and real-time qPCR were used to detect the mRNA and protein expressions. Fura-2-based fluorescence imaging experiments were used to determine the intracellular calcium concentration ([Ca 2+ ] i ). The protein synthesis inhibitor cycloheximide (CHX) was utilized to determine the protein degradation process., Results: Firstly, in cultured human PASMCs, treatment of BTZ for 24 or 60 hours significantly downregulates Caveolin-1 at both mRNA and protein levels. Secondly, in the presence CHX, BTZ treatment also leads to downregulated protein expression and fastened protein degradation of Caveolin-1, indicating that BTZ can promote the Caveolin-1 protein degradation, other than the BTZ on Caveolin-1 mRNA transcription. Then, BTZ significantly attenuates the hypoxia-elevated baseline [Ca 2+ ] i , SOCE, and cell proliferation., Conclusion: We firstly observed that the ubiquitin-proteasome inhibitor BTZ can inhibit the Caveolin-1 expression at both mRNA transcription and protein degradation processes, providing new mechanistic basis of BTZ on PASMC proliferation., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2021 Chao Wang et al.)

Laser speckle contrast imaging (LSCI) is a high-resolution full-field optical technique for measuring blood flow, which has been widely used in clinical and biomedical research. However, most of the current LSCI instruments are bulky, limiting their application settings. In this work, we proposed a prototype system of portable laser speckle imager. Different from the desktop laser speckle systems that utilize personal computer (PC), our system was designed with embedded GPU system (Jetson TX2, NVIDIA, USA) and a LCD touch screen (16.5 × 12.4 cm in size, 380 g in weight). In-vivo experiments showed that the portable GPU-based system had comparable performance with our laboratory LSCI system. Such a portable LSCI imager could be potentially used in a situation that requires for easy operation and installation, such as intraoperative monitoring or bedside diagnosis.

Brain plasticity after amputation is related to the short-term unmasking of latent synapses as well as the long-term reorganization due to the sprouting new synaptic connections. The cortical functional reorganization has been reported along the intact somatosensory pathway after unilateral deafferentation. Cerebral blood flow (CBF) change serves as an important biomarker of the functional reorganization of brain. Using laser speckle contrast imaging (LSCI) technology, we performed a longitudinal study to unveil the cortical functional reorganization after forelimb amputation in rodent model, particularly along the intact somatosensory pathway. Our results showed that the CBF response to electrical stimulation of the intact forepaw increased significantly at 9 hours after amputation in acute stage. While in chronic stage (>14 days), the CBF response showed a pattern similar to the control group. The results showed the dynamic brain functional response along the intact somatosensory pathway at different stages after amputation and indicated that cortical functional reorganization occurred within the acute stage. Our work provided additional insights in understanding the inter-hemispheric functional changes from acute to chronic stages of amputation.