Soft optical metamaterials

Chen Yixin,Ai Bin,Wong Zi Jing 나노기술연구협의회 2020 Nano Convergence Vol.7 No.18

Optical metamaterials consist of artificially engineered structures exhibiting unprecedented optical properties beyond natural materials. Optical metamaterials offer many novel functionalities, such as super-resolution imaging, negative refraction and invisibility cloaking. However, most optical metamaterials are comprised of rigid materials that lack tunability and flexibility, which hinder their practical applications. This limitation can be overcome by integrating soft matters within the metamaterials or designing responsive metamaterial structures. In addition, soft metamaterials can be reconfigured via optical, electrical, thermal and mechanical stimuli, thus enabling new optical properties and functionalities. This paper reviews different types of soft and reconfigurable optical metamaterials and their fabrication methods, highlighting their exotic properties. Future directions to employ soft optical metamaterials in nextgeneration metamaterial devices are identified.

Inhibition of Ferroptosis by Mesenchymal Stem Cell-Derived Exosomes in Acute Spinal Cord Injury: Role of Nrf2/GCH1/BH4 Axis

Yixin Chen,Bingfa Li,Jing Quan,Zhe Li,Yan Li,Yinbo Tang 대한척추신경외과학회 2024 Neurospine Vol.21 No.2

Objective: The therapeutic benefits of exosomes obtained from mesenchymal stem cells (MSCs) in acute spinal cord injury (SCI) have been demonstrated in recent years, but the precise mechanisms remain unknown. In this study, the efficacy and mechanisms of MSCderived exosomes (MSC-Exo) in acute SCI were investigated. Methods: By utilizing a BV2 ferroptosis cellular model and an SCI rat model, we investigated the effects of MSC-Exo on iron death related indicators and NF-E2 related factor 2 (Nrf2)/ GTP cyclolase I (GCH1)/5,6,7,8-tetrahydrobiopterin (BH4) signaling axis, as well as their therapeutic effects on SCI rats. Results: The results revealed that MSC-Exo effectively inhibited the production of ferrous iron, lipid peroxidation products malonaldehyde and reactive oxygen species, and ferroptosis-promoting factor prostaglandin-endoperoxide synthase 2. Concurrently, they upregulated ferroptosis suppressors FTH-1 (ferritin heavy chain 1), SLC7A11 (solute carrier family 7 member 11), FSP1 (ferroptosis suppressor protein 1), and GPX4 (glutathione peroxidase 4), contributing to enhanced neurological recovery in SCI rats. Further analysis showed the Nrf2/GTP/BH4 signaling pathway’s critical role in suppressing ferroptosis. Additionally, MSC-Exo was found to inhibit lipopolysaccharide-induced ferroptosis in BV2 cells and SCI rats by activating the Nrf2/GCH1/BH4 axis. Conclusion: In summary, the study demonstrates that MSC-Exo mitigates microglial cell ferroptosis via the Nrf2/GCH1/BH4 axis, showing potential for preserving and restoring neurological function post-SCI.

Hemicastration induced spermatogenesis-related DNA methylation and gene expression changes in mice testis

Yixin Wang,Long Jin,Jideng Ma,Li Chen,Yuhua Fu,Keren Long,Silu Hu,Yang Song,Dazhi Shang,Qianzi Tang,Xun Wang,Xuewei Li,Mingzhou Li 아세아·태평양축산학회 2018 Animal Bioscience Vol.31 No.2

Objective: Hemicastration is a unilateral orchiectomy to remove an injured testis, which can induce hormonal changes and compensatory hypertrophy of the remaining testis, and may influence spermatogenesis. However, the underlying molecular mechanisms are poorly understood. Here, we investigated the impact of hemicastration on remaining testicular function. Methods: Prepubertal mice (age 24 days) were hemicastrated, and their growth was monitored until they reached physical maturity (age 72 days). Subsequently, we determined testis DNA methylation patterns using reduced representation bisulfite sequencing of normal and hemicastrated mice. Moreover, we profiled the testicular gene expression patterns by RNA sequencing (RNA-seq) to examine whether methylation changes affected gene expression in hemicastrated mice. Results: Hemicastration did not significantly affect growth or testosterone (p>0.05) compared with control. The genome-wide DNA methylation pattern of remaining testis suggested that substantial genes harbored differentially methylated regions (1,139) in gene bodies, which were enriched in process of protein binding and cell adhesion. Moreover, RNA-seq results indicated that 46 differentially expressed genes (DEGs) involved in meiotic cell cycle, synaptonemal complex assembly and spermatogenesis were upregulated in the hemicastration group, while 197 DEGs were downregulated, which were related to arachidonic acid metabolism. Integrative analysis revealed that proteasome 26S subunit ATPase 3 interacting protein gene, which encodes a protein crucial for homologous recombination in spermatocytes, exhibited promoter hypomethylation and higher expression level in hemicastrated mice. Conclusion: Global profiling of DNA methylation and gene expression demonstrated that hemicastration-induced compensatory response maintained normal growth and testicular morphological structure in mice.

Walking load model for single footfall trace in three dimensions based on gait experiment

Yixin Peng,Jun Chen,Guo Ding 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.5

This paper investigates the load model for single footfall trace of human walking. A large amount of single person walking load tests were conducted using the three-dimensional gait analysis system. Based on the experimental data, Fourier series functions were adopted to model single footfall trace in three directions, i.e. along walking direction, direction perpendicular to the walking path and vertical direction. Function parameters such as trace duration time, number of Fourier series orders, dynamic load factors (DLFs) and phase angles were determined from the experimental records. Stochastic models were then suggested by treating walking rates, duration time and DLFs as independent random variables, whose probability density functions were obtained from experimental data. Simulation procedures using the stochastic models are presented with examples. The simulated single footfall traces are similar to the experimental records.

On methods for extending a single footfall trace into a continuous force curve for floor vibration serviceability analysis

Chen, Jun,Peng, Yixin,Ye, Ting Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.2

An experimentally measured single footfall trace (SFT) from a walking subject needs to be extended into a continuous force curve, which can then be used as load for floor vibration serviceability assessment, or on which further analysis like discrete Fourier transform can be conducted. This paper investigates the accuracy, applicability and parametrical sensitivity of four extension methods, Methods I to IV, which extends the SFT into a continuous time history by the walking step rate, stride time, double support proportion and the double support time, respectively. Performance of the four methods was assessed by comparing their results with the experimentally obtained reference footfall traces in the time and frequency domain, and by comparing the vibrational response of a concrete slab subjected to the extended traces to that of reference traces. The effect of the extension parameter on each method was also explored through parametrical analysis. This study finds that, in general, Method I and II perform better than Method III and IV, and all of the four methods are sensitive to their extension parameter. When reliable information of walking rate or gait period is available in the test, Methods I or II is a better choice. Otherwise, Method III, with the suggested extension parameter of double support time proportion, is recommended.

On methods for extending a single footfall trace into a continuous force curve for floor vibration serviceability analysis

Jun Chen,Yixin Peng,Ting Ye 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.2

An experimentally measured single footfall trace (SFT) from a walking subject needs to be extended into a continuous force curve, which can then be used as load for floor vibration serviceability assessment, or on which further analysis like discrete Fourier transform can be conducted. This paper investigates the accuracy, applicability and parametrical sensitivity of four extension methods, Methods I to IV, which extends the SFT into a continuous time history by the walking step rate, stride time, double support proportion and the double support time, respectively. Performance of the four methods was assessed by comparing their results with the experimentally obtained reference footfall traces in the time and frequency domain, and by comparing the vibrational response of a concrete slab subjected to the extended traces to that of reference traces. The effect of the extension parameter on each method was also explored through parametrical analysis. This study finds that, in general, Method I and II perform better than Method III and IV, and all of the four methods are sensitive to their extension parameter. When reliable information of walking rate or gait period is available in the test, Methods I or II is a better choice. Otherwise, Method III, with the suggested extension parameter of double support time proportion, is recommended.

Alfalfa Regrowth Potential and Root Carbohydrates in Response to Fall Dormancy

Xiaoyan Lu,Shuren Ji,Chen Hou,Zhizhuo Geng,Yixin Shen 한국초지조사료학회 2016 한국초지조사료학회 학술대회논문집 Vol.2016 No.08

Spatial–Temporal Clustering and Optimization of Aircraft Descent and Approach Trajectories

Zhao Yang,Rong Tang,Yixin Chen,Bing Wang 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.6

This study presents a procedure for the spatial–temporal clustering and optimization of aircraft descent and approach trajectories. First, the spatial–temporal similarity between two trajectories is defined. Clustering analysis are conducted to identify the prevailing trajectories. The clustering centers obtained based on spatial–temporal distance are compared with those obtained based on the traditional Euclidean distance. Second, a multi-objective optimization model is established to minimize fuel consumption, aircraft emission and noise impact considering flight constraints. The Pareto solution that has the highest similarity with the prevailing trajectories is selected as the final optimized trajectory. The performance indicators of the optimized trajectory are compared with the average values of historic trajectories. It is found that travel time, fuel consumption and noise impact for the optimized trajectory are reduced by 5.34%, 0.96% and 11.86%, respectively. The percentages are 0.96%, 1.32%, 9.18%, 3.54% and 4.00% for CO2, SOx, NOx, CO and HC, respectively. Also, the performance indicators for the two clustering centers based on spatial–temporal distance are generally closer to average performance of original trajectories, as well as those of the optimized trajectories, as compared with the two clustering centers based on Euclidean distance. The spatial–temporal clustering methods may help to discover the valuable information that lies in those indicators associated with features reflected in time dimension.

Microbial diversity in the rumen, reticulum, omasum, and abomasum of yak on a rapid fattening regime in an agro-pastoral transition zone

Dan Xue,Huai Chen,Xiaolin Luo,Jiuqiang Guan,Yixin He,Xinquan Zhao 한국미생물학회 2018 The journal of microbiology Vol.56 No.10

The ruminant digestive system harbors a complex gut microbiome, which is poorly understood in the case of the four stomach compartments of yak. High-throughput sequencing and quantitative PCR were used to analyse microbial communities in the rumen, reticulum, omasum, and abomasum of six domesticated yak. The diversity of prokaryotes was higher in reticulum and omasum than in rumen and abomasum. Bacteroidetes predominated in the four stomach compartments, with abundance gradually decreasing in the trend rumen > reticulum > omasum > abomasum. Microorganism composition was different among the four compartments, all of which contained high levels of bacteria, methanogens, protozoa and anaerobic fungi. Some prokaryotic genera were associated with volatile fatty acids and pH. This study provides the first insights into the microorganism composition of four stomach compartments in yak, and may provide a foundation for future studies in this area.

Characteristics of Ground Surface Settlement of Double-Line Adjacent Metro Construction in Sandy Cobble Stratum: A Case Study of Beijing Airport Line

Xianjie Hao,Zhuowen Sun,Yixin Zhao,Yiqiang Kang,Qian Zhang,Jinguo Cheng,Yingnan Wei,Zeyu Chen 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.11

As a long-term urban transportation infrastructure, the stability of metro construction is very important. With the continuous expansion of urban metro network, metro adjacent construction is more and more frequently encountered. In this paper, taking the double-line adjacent construction problems encountered during excavation of Beijing New Airport Line metro in sandy cobble stratum as an example, the surface settlement caused by excavation of single-line metro and double-line adjacent metro is studied by computed tomography scan, electron microscope scanning, laboratory mechanical tests, orthogonal inversion and numerical simulation and other methods. The results show that 1) the sandy cobble particle size and sandy cobble distribution of Beijing sandy cobble samples are relatively dispersed, and the sandy cobble particle size is from 3 to 20 cm, of which the largest proportion is the sandy cobble particle size from 5 to 8 cm. 2) The internal friction angle of Beijing sandy cobble samples with different moisture content is from 27° to 40°, which is much larger than that of other soil samples. Even at the post-peak stage, the shear stress of some sandy cobble samples does not gradually tend to be gentle, but continuously increases or has secondary peaks. 3) For the excavation of double-line adjacent metro, the maximum settlement difference and the impact range of excavation are proposed as indicators to investigate the degree of interaction of the adjacent metro. 4) The results of numerical orthogonal analysis show that the width of surface settlement zone increases significantly with the increase of tunnel diameter and spacing when excavating adjacent metro in sandy cobble stratum, but the rate of increase with tunnel diameter (from 6 m to 14 m) almost reaches 2 times of the rate of increase with the spacing (from 3 m to 15 m). 5) The maximum settlement value of sandy cobble stratum increases with the increase of tunnel diameter and decreases with the increase of spacing. The orthogonal linear analysis shows that the influence of tunnel diameter on the maximum settlement value is much greater than the spacing. The maximum settlement increases with the increase of tunnel diameter, which is about 3.6 times of that with the decrease of spacing.