Variable selection in nonparametric additive models

We consider a nonparametric additive model of a conditional mean function in which the number of variables and additive components may be larger than the sample size but the number of nonzero additive components is "small" relative to the sample size. The statistical problem is to determine which additive components are nonzero. The additive components are approximated by truncated series expansions with B-spline bases. With this approximation, the problem of component selection becomes that of selecting the groups of coefficients in the expansion. We apply the adaptive group Lasso to select nonzero components, using the group Lasso to obtain an initial estimator and reduce the dimension of the problem. We give conditions under which the group Lasso selects a model whose number of components is comparable with the underlying model, and the adaptive group Lasso selects the nonzero components correctly with probability approaching one as the sample size increases and achieves the optimal rate of convergence. The results of Monte Carlo experiments show that the adaptive group Lasso procedure works well with samples of moderate size. A data example is used to illustrate the application of the proposed method.Comment: Published in at http://dx.doi.org/10.1214/09-AOS781 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Exosomal miR-152-5p and miR-3681-5p function as potential biomarkers for ST-segment elevation myocardial infarction

Background: The strain parameters of Real-Time Three-Dimensional Spot Tracking Echocardiography (RT3D-STE) are GLS, GAS, GRS, and GCS, while each index can significantly diagnose Acute Myocardial Infarction (AMI) patients, but none of them can distinguish between NSTEMI and STEMI. MicroRNAs (miRNAs) play essential roles in Acute Myocardial Infarction (AMI), but little is known about the value of exosome miRNA combined with Real-Time Three-Dimensional Spot Tracking Echocardiography (RT3D-STE) between ST-segment Elevation Myocardial Infarction (STEMI) and Non-ST-segment Elevation Myocardial Infarction (NSTEMI). Aim: To estimate the exosomal miRNAs related to strain parameters of RT3D-STE as biomarkers for early detection of STEMI and NSTEMI. Methods: The present study collected plasma samples from thirty-four (34) patients with AMI (including STEMI and NSTEMI) and employed high-throughput sequence technology and real-time quantitative polymerase chain reaction (RT-qPCR) to identify the differentially expressed miRNAs. The Pearson correlation coefficient is used to measure the strength of a linear association between differentially expressed miRNAs and strain parameters of RT3D-STE. Results: Twenty-eight (28) differentially expressed exosomal miRNAs were universally identified between STEMI, NSTEM, and normal groups. Among them, there are 10 miRNAs (miR-152-5p, miR-3681-5p, miR-193a-5p, miR-193b-5p miR-345-5p, miR-125a-5p, miR-365a-3p, miR-4520-2-3p, hsa-miR-193b-3p and hsa-miR-5579-5p) with a Pearson correlation greater than 0.6 with RT3D-STE strain parameters. Especially, miR-152-5p and miR-3681-5p showed the most significant correlation with RT3D-STE strain parameters. Target genes of these 10 miRNAs are analyzed for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment, and they were found to be mainly involved in the cellular metabolism processes and HIF-1 signaling pathway. RT-qPCR verified the significant differential expression of miR-152-5p and miR-3681-5p between STEMI and NSTEM groups. Conclusion: RT3D-STE and exosome miRNAs can be used as a hierarchical diagnostic system in AMI. If the RT3D-STE is abnormal, the exosome miRNAs can be detected again to obtain more detailed and accurate diagnostic results between STEMI and NSTEM groups. Exosomal miR-152-5p and miR-3681-5p may serve as potential biomarkers for ST-segment elevation myocardial infarction

MicroRNA Let-7f Inhibits Tumor Invasion and Metastasis by Targeting MYH9 in Human Gastric Cancer

BACKGROUND: MicroRNAs (miRNAs) are important regulators that play key roles in tumorigenesis and tumor progression. A previous report has shown that let-7 family members can act as tumor suppressors in many cancers. Through miRNA array, we found that let-7f was downregulated in the highly metastatic potential gastric cancer cell lines GC9811-P and SGC7901-M, when compared with their parental cell lines, GC9811 and SGC7901-NM; however, the mechanism was not clear. In this study, we investigate whether let-7f acts as a tumor suppressor to inhibit invasion and metastasis in gastric cancers. METHODOLOGY/PRINCIPAL: Real-time PCR showed decreased levels of let-7f expression in metastatic gastric cancer tissues and cell lines that are potentially highly metastatic. Cell invasion and migration were significantly impaired in GC9811-P and SGC7901-M cell lines after transfection with let-7f-mimics. Nude mice with xenograft models of gastric cancer confirmed that let-7f could inhibit gastric cancer metastasis in vivo after transfection by the lentivirus pGCsil-GFP- let-7f. Luciferase reporter assays demonstrated that let-7f directly binds to the 3'UTR of MYH9, which codes for myosin IIA, and real-time PCR and Western blotting further indicated that let-7f downregulated the expression of myosin IIA at the mRNA and protein levels. CONCLUSIONS/SIGNIFICANCE: Our study demonstrated that overexpression of let-7f in gastric cancer could inhibit invasion and migration of gastric cancer cells through directly targeting the tumor metastasis-associated gene MYH9. These data suggest that let-7f may be a novel therapeutic candidate for gastric cancer, given its ability to reduce cell invasion and metastasis

SAR Image Coastline Detection Based on Regional Distance Regularized Geometric Active Contour Models

Synthetic aperture radar (SAR) satellite remote sensing images can greatly increase the frequency of the coastline coverage all over the country. However, due to the influence of the random sea surface roughness caused by waves, it's a challenge to distinguish the coastline and sea boundary. To solve this problem, this paper proposes regional distance regularized geometric active contour models (RDRGAC), in which the distance regularized term is introduced to avoid periodically initializing the degraded function with a signed distance function, accelerating the speed of convergence. Besides, it establishes the nonlinear regression relationship between the regional term parameters and equivalent number of looks (ENL) in SAR images, leading to the adaptive setting of RDRGAC model with different SAR images, which could improve the accuracy of coastline automatic detection in return. In the experiments, SAR images in Beidaihe and Dalian Jinzhou Bay respectively are adopted to detect the coastline, verifying the effective of the proposed method

Characteristics and determinants of sexual behavior among adolescents of migrant workers in Shangai (China)

Abstract Background China is facing a critical challenge of rapid and widespread human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) increase. Rural-to-urban migration plays a crucial role in shifting the HIV/sexual transmitted infection (STI) epidemic. The purpose of this study was to assess the prevalence of sexual behaviors and the correlates among the early adolescents of migrant workers in China. Methods A cross-sectional study was conducted in 10 junior high schools from April to June of 2008. A total of 2821 adolescents aged 14.06 ± 0.93 years (8.9% of migrant workers vs. 91.1% of general residents) participated in the survey. A self-administrated questionnaire was used to collect information on knowledge, attitude, and behaviors associated with increased risk for HIV/STI. Results The percentage of adolescents who ever had sexual intercourse or had sexual intercourse in last three months was 7.2% and 4.3% in adolescents of migrant workers, respectively; in contrast, 4.5% and 1.8% in their peers of general residents, respectively. 47.3% adolescents of migrant workers and 34.3% of those adolescents of general residents reported no condom use in sexual intercourse during last three months. Multivariate logistic regression analyses found that migration was a independent risk factor for sexual intercourse in last three months in our sampled adolescents (odds ratio [OR] = 1.23, 95% confidence interval [CI]: 1.01–1.72). In adolescents of migrant workers, factors such as lower family income (OR: 2.22, CI: 1.09–3.05 for low level; OR:1.25, CI: 1.04–1.59 for medium level), younger age at first sexual intercourse (OR: 1.24, CI: 1.09–1.57), lower knowledge on HIV/AIDS (OR: 0.93, CI: 0.90–0.97), and fewer communication on HIV/AIDS related issues (OR: 0.79, CI: 0.90–0.97) were related to sexual intercourse in last three months. Conclusion Based on these results, we advocated that heightened concerns targeting the adolescents of migrant workers be particularly necessary, given their higher level of sexual experience, lower socioeconomic status, restricted reproductive health information, and vulnerability to HIV/STI.</p

Does the issuance of green bonds nudge environmental responsibility engagements? Evidence from the Chinese green bond market

Abstract Policymakers and managers have increasingly adopted green bonds as a direct financing tool to address environmental degradation and climate change in emerging economies; however, the increasing green washing sentiments in the green bond market raise questions on whether green bonds can nudge polluting businesses to achieve green transformation. Therefore, this study joins the controversial debate by investigating the impact of green bond issuance on corporate environmental responsibilities and the potential impact mechanisms and economic consequences. Using the data of Chinese listed enterprises from 2011 to 2020 and the staggered issuance of green bonds as plausibly exogenous shocks, we determine that the enterprises in the experimental group that issued green bonds increased their environmental performance compared to their counterparts. Furthermore, this positive link is maintains after a series of robustness tests. Moreover, we identify that green bond issuance plausibly enhances environmental responsibility engagements through two governance channels, namely, internal management and external supervision. This beneficial effect appears more pronounced for subsamples of firms in low-polluting industries, without environmental subsidies and with higher managerial abilities. Furthermore, economic consequences indicate that the issuance of green bonds primarily motivates speculative shareholder benefits, as evidenced by short-term increases in stock yields but with limited impact on the short-run financial performance. Overall, these findings offer new evidence supporting that green financing tools could play a helpful hand toward environmental sustainability