Peridynamic modeling of nonlinear surface acoustic waves propagating in orthotropic materials.

Due to the elastic nonlinearity of the material, high-amplitude surface acoustic waves undergo nonlinear evolution during propagation and may lead to material failure. To enable the acoustical quantification of material nonlinearity and strength, a comprehensive understanding of this nonlinear evolution is necessary. This paper presents a novel ordinary state-based nonlinear peridynamic model for the analysis of the nonlinear propagation of surface acoustic waves and brittle fracture in anisotropic elastic media. The relationship between seven peridynamic constants and second- and third-order elastic constants is established. The capability of the developed peridynamic model has been demonstrated by predicting surface strain profiles of surface acoustic waves after propagating in the silicon (111) plane and the 〈112¯ã€‰ direction. On this basis, the nonlinear wave-induced spatially localized dynamic fracture is also studied. The numerical results reproduce the main features of nonlinear surface acoustic waves and fracture observed in experiments.

Correlation of MLH1 and MSH2 levels with clinicopathologic characteristics in colorectal cancer.

OBJECTIVE: To determine the correlation of MLH1 and MSH2 expressions with clinicopathologic characteristics in colorectal cancer (CC). METHODS: Clinical data, CC tissue, and paracancerous tissue from 88 patients treated in Baoji City People's Hospital from February 2015 to February 2017 were analyzed retrospectively. The relative expression levels of MLH1 and MSH2 in the tissues were measured with qRT-PCR, and the relationship of MLH1 and MSH2 with the pathological data of patients was analyzed. The value of MLH1 and MSH2 in the diagnosis of clinical stage, lymph node metastasis, and degree of differentiation in CC patients was analyzed by receiver operating curve (ROC). Cox regression analysis was applied to identify factors affecting prognosis. RESULTS: The relative expression levels of MLH1 and MSH2 in CC tissue were lower than those in paracancerous tissue (P < 0.001). Tumor node metastasis stage (III + IV), poor differentiation, and lymph node metastasis were significantly increased in patients with low MLH1 and MSH2 expressions (P < 0.05). The levels of MLH1 and MSH2 in CC tissue of patients at stage I with moderately- or well-differentiated non-metastatic disease were higher than those in patients at stage II-IV with poor differentiation and lymph node metastasis, showing a good predictive ability. The 5-year survival rate of patients with low MLH1 and MSH2 expressions was lower as compared to its counterpart (P < 0.01). CONCLUSION: The low expressions of MSH2 and MLH1 in CC tissue have a correlation with pathological characteristics and survival, so they can be used as auxiliary references for the prognosis in CC patients.

Comparison of transcriptome profiles of mesenchymal stem cells derived from umbilical cord and bone marrow of giant panda (Ailuropoda melanoleuca).

Mesenchymal stem cells (MSCs) have pluripotent differentiation ability and play an important role in human clinical cell therapy. While, the research on MSCs in endangered wild animals is extremely rare. In our previous studies, the bone marrow mesenchymal stem cells (bmMSCs) and umbilical cord mesenchymal stem cells (ucMSCs) of giant panda (Ailuropoda melanoleuca) were successfully isolated. We aimed to characterize the differences in gene expression profiles between these two types of MSCs using RNA sequencing (RNA-Seq) and to determine which potential pathways are involved in functional regulation. In total, 1079 significantly differentially expressed genes (DEGs) were identified, of which 478 genes were upregulated and 601 genes were downregulated. The significantly enriched Gene Ontology (GO) terms mainly contained cell adhesion, biological adhesion, intracellular signal transduction, molecular function regulator, Ras protein signal transduction, small GTPase mediated signal transduction, and regulation of Rho protein signal transduction. The most enrichment pathways of DEGs enriched in Kyoto Encyclopedia of Genes Genomes (KEGG) were PI3K-AKT signaling pathway, Rap1 signaling pathway, MAPK signaling pathway, Hippo signaling pathway, Wnt signaling pathway, cGMP-PKG signaling pathway and Signaling pathways regulating pluripotency of stem cells. In addition, quantitative real time polymerase chain reaction (qRT-PCR) showed that the AKT3, CDK2, MAPK3, mTOR, PI3K and PTK2 genes associated with PI3K-AKT pathway were highly expressed (P < 0.01), and Caspase-3 was low expressed (P < 0.05) in ucMSCs group when compared with bmMSCs. After treatment with the PI3K inhibitor LY294002, genes AKT3, CDK2, MAPK3, mTOR, and PTK2 were significantly decreased in ucMSCs (P < 0.01), and Caspase-3 was significantly up regulated (P < 0.001). In conclusion, we for the first time compared and analyzed the transcriptome profiles of giant panda ucMSCs and bmMSCs, and found the PI3K-AKT pathway was highly activated and might be a key signaling pathway in the ucMSCs regulation. This study will be beneficial for the research on MSCs proliferation regulation and differentiation of giant pandas in the future, and lay the foundation for MSCs application and clinical therapy for endangered wild animals.

Inversion of surface damage and residual stress in ground silicon wafers by laser surface acoustic wave technology.

The paper presents a study of surface acoustic waves propagation in a damage layer with finite thickness and residual stress on an orthotropic semi-infinite medium to reveal the application of laser ultrasound in the surface inspection of ground silicon wafers. Biot's theory of small deformations influenced by initial stress forms the basis for this study. Considering the case that the displacement and boundary forces are continuous at the interface and the forces vanish on the free surface, the required dispersion relation is obtained. We consider a sample of (100) silicon wafer by grinding with fine abrasive grains, which has a machined face with a micrometer-level thickness of surface damage and residual stress. In order to discuss the impact of propagation directions, degree of surface damage, residual compressive stress on the velocity characteristics of surface waves, the numerical computation of the dispersion equations is performed. It has been found that surface damage has a significant effect on the dispersion curve, while the residual compressive stress can only cause a small decrease Δc in the surface wave velocity. The velocity decrease Δc becomes obvious at high frequencies. For a fixed residual compressive stress and frequency, Δc hardly changes with the degree of surface damage and propagation directions. Based on the above characteristics, we study the inverse problem on detecting both surface damage and residual stress simultaneously by SAW velocities and give a corresponding iterative algorithm. This study may provide theoretical guidance for non-destructive testing of residual stress.

Time-frequency analysis of laser-excited surface acoustic waves based on synchrosqueezing transform.

Laser-excited surface acoustic wave (LSAW) techniques can realize the measurement of surface properties through dispersion curve inversion. In addition to the conventional phase spectrum method, time-frequency analysis can also be used as a calculation tool for the dispersion curve. An accurate time-frequency analysis method is important in precisely inverting the surface properties. In this paper, synchrosqueezing transform (SST) is applied to the analysis of LSAW. By comparing the processing results of the constructed LSAW signal, SST shows higher time-frequency resolution and robustness than other common time-frequency analysis algorithms. Finite element model is used to simulate the propagation of LSAW in the film/substrate structure. And SST is used to calculate the dispersion curve of SAW information extracted during the simulation. A fast algorithm is introduced, where the film thickness is initially estimated by calculating the midrange. Through inversion, the resulting film thickness error is only 1.20% from the theoretical value. Therefore, SST is an effective tool for analyzing LSAW and calculating its dispersion curve.

Analysis of velocity calculation methods of laser-induced surface acoustic wave.

The key to measuring residual stress by surface acoustic wave method is the accurate measurement of velocity. In this paper, the velocity of laser-induced broadband surface acoustic wave is studied, and three velocity calculation methods of surface acoustic wave, time domain method, phase method and wavelet method are compared. The calculation error of the time domain method under the condition of dispersion is analyzed. A recursive method for calculating phase difference is proposed to improve the efficiency of phase method. The simulated surface acoustic waves are used to compare the phase method and wavelet method under the conditions of attenuation and dispersion. Compared with the wavelet method, the phase method cannot distinguish the time when the frequency band appears, and the velocity calculation of adjacent frequency points is related, while the wavelet method is independent of each other. The wavelet method can improve the calculation accuracy of the velocity curve by interpolating the original data. After interpolation, the trend of curve is more obvious, and the fitting error is greatly reduced.

Integrated Analysis of mRNA and miRNA Expression Profiles in the Ovary of Oryctolagus cuniculus in Response to Gonadotrophic Stimulation.

Molecular mechanisms responsible for gonadotrophic control of ovarian follicle development and ovulation have not been fully delineated. In this study, prepubertal female rabbits were subjected to a combined PMSG/hCG treatment for the induction of follicle maturation and ovulation. Ovaries of 6 does at different time points during gonadotrophic stimulation were collected for histomorphological examination and genome-wide analysis of miRNA and mRNA transcriptomes, and the plasma were separated for detecting melatonin (MT), prostaglandin E2 (PGE2), estradiol (E2), and progesterone (P4) levels. The results suggested that PMSG promoted the development of the reproductive tract by decreasing plasma levels of E2 and slightly increasing those of MT and PGE2 and that hCG induced ovulation and corpus luteum formation by significantly increasing MT, PGE2, and P4 levels. At the transcriptomic level, a total of 1,122 differentially expressed genes (DEGs) and 12 DE miRNAs were identified using three-group comparisons. Meanwhile, pairwise comparisons revealed that 279 and 103 genes as well as 36 and 20 miRNAs were up- and down-regulated during PMSG-stimulated follicle development while 11 and 5 genes as well as 33 and 16 miRNAs were up- and down-regulated during hCG-induced luteinization. KEGG enrichment analysis of the DEGs derived from both three-group- and two-group comparisons as well as the predicted target genes of DE miRNAs highlighted the crucial roles of pathways involving tissue remodeling, energy metabolism, and regulation of cellular functions in mediating gonadotrophin-induced follicle maturation. Specifically, 3 genes including the matrix metallopeptidase 13 (MMP13), protein phosphatase 1 regulatory subunit 3C (PPP1R3C), and solute carrier family 2 member 12 (SLC2A12), together with 2 miRNAs including the miR-205-1 and miR-34c, were predicted to be the promising downstream targets of both PMSG and hCG. Significantly, the miRNA-mRNA interaction pairs containing top 10 up- and down-regulated mRNAs/miRNAs upon PMSG/hCG stimulation were established, and so were those involved in the PI3K-Akt, ECM-receptor interaction, and focal adhesion pathways during PMSG-induced follicle maturation. Finally, qRT-PCR analysis confirmed the results from RNA-Seq and Small RNA-Seq. Our work may contribute to a better understanding of the regulatory mechanisms of gonadotrophins on ovarian follicle development and ovulation.

An Innovative Fingerprint Location Algorithm for Indoor Positioning Based on Array Pseudolite.

Since the signals of the global navigation satellite system (GNSS) are blocked by buildings, accurate positioning cannot be achieved in an indoor environment. Pseudolite can simulate similar outdoor satellite signals and can be used as a stable and reliable positioning signal source in indoor environments. Therefore, it has been proposed as a good substitute and has become a research hotspot in the field of indoor positioning. There are still some problems in the pseudolite positioning field, such as: Integer ambiguity of carrier phase, initial position determination, and low signal coverage. To avoid the limitation of these factors, an indoor positioning system based on fingerprint database matching of homologous array pseudolite is proposed in this paper, which can achieve higher positioning accuracy. The realization of this positioning system mainly includes the offline phase and the online phase. In the offline phase, the carrier phase data in the indoor environment is first collected, and a fingerprint database is established. Then a variational auto-encoding (VAE) network with location information is used to learn the probability distribution characteristics of the carrier phase difference of pseudolite in the latent space to realize feature clustering. Finally, the deep neural network is constructed by using the hidden features learned to further study the mapping relationship between different carrier phases of pseudolite and different indoor locations. In the online phase, the trained model and real-time carrier phases of pseudolite are used to predict the location of the positioning terminal. In this paper, by a large number of experiments, the performance of the pseudolite positioning system is evaluated under dynamic and static conditions. The effectiveness of the algorithm is evaluated by the comparison experiments, the experimental results show that the average positioning accuracy of the positioning system in a real indoor scene is 0.39 m, and the 95% positioning error is less than 0.85 m, which outperforms the traditional fingerprint positioning algorithms.

miR-148a-3p promotes rabbit preadipocyte differentiation by targeting PTEN.

Although emerging data support crucial roles for microRNAs (miRNAs) during adipogenesis, the detailed mechanisms remain largely unknown. In this study, it was shown that in rabbits, levels of miR-148a-3p not only increased in white adipose tissue during early stages of growth but also during in vitro cultured preadipocyte differentiation. Furthermore, overexpression of miR-148a-3p significantly upregulated the mRNA levels of PPARγ, C/EBPα, and FABP4, as well as the protein levels of PPARγ, as indicated by qPCR and western blotting analyses. Overexpression of miR-148a-3p also promoted intracellular triglyceride accumulation. In contrast, downregulation of miR-148a-3p inhibited the differentiation of rabbit preadipocytes. Next, based on target gene prediction and a luciferase reporter assay, we further demonstrated that miR-148a-3p directly targeted one of the 3' untranslated regions of PTEN. Finally, it was observed inhibition of PTEN by siRNA promoted rabbit preadipocyte differentiation. Taken together, our results suggested that miR-148a-3p could be involved in regulating rabbit preadipocyte differentiation through inhibiting expression of PTEN, which further highlighted the importance of miRNAs during adipogenesis.