Three-Dimensional Microwave Imaging for Concealed Weapon Detection Using Range Stacking Technique

Three-dimensional (3D) microwave imaging has been proven to be well suited for concealed weapon detection application. For the 3D image reconstruction under two-dimensional (2D) planar aperture condition, most of current imaging algorithms focus on decomposing the 3D free space Green function by exploiting the stationary phase and, consequently, the accuracy of the final imagery is obtained at a sacrifice of computational complexity due to the need of interpolation. In this paper, from an alternative viewpoint, we propose a novel interpolation-free imaging algorithm based on wavefront reconstruction theory. The algorithm is an extension of the 2D range stacking algorithm (RSA) with the advantages of low computational cost and high precision. The algorithm uses different reference signal spectrums at different range bins and then forms the target functions at desired range bin by a concise coherent summation. Several practical issues such as the propagation loss compensation, wavefront reconstruction, and aliasing mitigating are also considered. The sampling criterion and the achievable resolutions for the proposed algorithm are also derived. Finally, the proposed method is validated through extensive computer simulations and real-field experiments. The results show that accurate 3D image can be generated at a very high speed by utilizing the proposed algorithm

Investigation of Wavenumber Domain Imaging Algorithm for Ground-Based Arc Array SAR

Ground-based synthetic aperture radar (GB-SAR) has become an important technique for remote sensing deformation monitoring. However, most of the existing GB-SAR systems realize synthetic aperture by exploiting two closely spaced horn antennas to move along a linear rail. In order to obtain higher data acquisition efficiency and a wider view angle, we introduce arc antenna array technology into the GB-SAR system, which realizes a novel kind of system: ground-based arc array SAR (GB-AA-SAR). In this paper, we analyze arc observation geometry and derive analytic expressions of sampling criteria. Then, we propose a novel wavenumber domain imaging algorithm for GB-AA-SAR, which can achieve high image reconstruction precision through numerical solutions in the wavenumber domain. The proposed algorithm can be applied in wide azimuth view angle scenarios, and the problem of azimuth mismatch caused by distance approximation in arc geometric efficient omega-k imaging can be solved successfully. Finally, we analyze the two-dimensional (2D) spatial resolution of GB-AA-SAR, and verify the effectiveness of the proposed algorithm through numerical simulation experiments

Investigation of Azimuth Multichannel Reconstruction for Moving Targets in High Resolution Wide Swath SAR

The azimuth multichannel imaging scheme with the large receive antenna divided into multiple sub-apertures usually leads to azimuth non-uniform sampling, and echoes from all azimuth channels should be reconstructed based on the signal model before conventional SAR imaging. Unfortunately, the multichannel signal model of a moving target is different from that of a fixed target. This paper analyzes the multichannel signal model of the moving target and the effect of the target velocity on azimuth multichannel reconstruction. Based on the multichannel signal mode of the moving target, a new multichannel signal reconstruction algorithm is proposed. Furthermore, the slant range velocity is estimated by computing signal energy distribution. Simulation results on point targets validate the proposed approach

Time- and Space-Varying Atmospheric Phase Correction in Discontinuous Ground-Based Synthetic Aperture Radar Deformation Monitoring

Ground-based synthetic aperture radar (GB-SAR) uses active microwave remote-sensing observation mode to achieve two-dimensional deformation measurement and deformation trend extraction, which shows great prospects in the field of deformation monitoring. However, in the process of GB-SAR deformation monitoring, the disturbances caused by atmospheric effect cannot be neglected, and the atmospheric phases will seriously affect the precision of deformation monitoring. In discontinuous GB-SAR deformation monitoring mode, the atmospheric phases are particularly affected by changes of time and space, so the traditional models of atmospheric phase correction are no longer applicable. In this paper, the interferometric phase signal model considering atmospheric phase is first established. Then, the time- and space-varying characteristics of the atmospheric phase are analyzed, and a novel time- and space-varying atmospheric phase correction algorithm, based on coherent scatterers analysis, is proposed. Finally, slope deformation monitoring experiments are carried out to verify the validity and robustness of the proposed algorithm

Lower Fiber Consumption in Women with Polycystic Ovary Syndrome: A Meta-Analysis of Observational Studies

Polycystic ovary syndrome is a common endocrine disorder associated with metabolic abnormalities and gut microbiota dysbiosis. The deficiency of dietary fiber, a crucial nutrient in the daily diet, is also associated with a wide range of metabolic and reproductive abnormalities, as well as an altered gut microbial ecosystem. This study is a meta-analysis to summarize the available evidence on the dietary fiber intake level in PCOS patients. Databases of PubMed, Embase, Cochrane Library, Web of Science, and ClinicalTrials.gov were searched for observational studies, and 13 studies were finally included. The pooled standardized mean difference (SMD) with the 95% confidence interval (CI) of daily dietary fiber intake and total energy intake were calculated using the random-effects model. The pooled result (12 studies) on absolute dietary fiber intake showed that while there was no significant difference in the total energy intake [−0.17 (−0.44, 0.09), p = 0.208], the dietary fiber intake was significantly lower in PCOS women than those of controls [−0.32 (−0.50, −0.14), p < 0.001]. However, significant heterogeneity was detected across the studies (I2 = 65.6%, p = 0.001). Meta-regression suggested that geographic region and dietary assessment method may confer borderline significance of influence on the heterogeneity. The pooled result (two studies) on dietary fiber intake which adjusted for total energy intake, however, showed no significant difference [−2.11 (−4.77, 0.56), p = 0.122]. In subgroup analyses based on absolute dietary fiber intake, a lower dietary fiber intake in PCOS was observed in studies conducted in Asia, adopted food diary or records or food recall as the dietary assessment method, had a case–control study design, or used Rotterdam criteria for PCOS diagnosis. The difference in SMD was still significant in the adult subgroup or in studies matched or unmatched for age

Inactivation of Yes-Associated Protein Mediates Trophoblast Dysfunction: A New Mechanism of Pregnancy Loss Associated with Anti-Phospholipid Antibodies?

Pregnancy morbidity induced by anti-phospholipid antibodies (aPL+/PM+) is mainly thought to arise from placental abnormalities. We attempted to investigate the effect of aPL on the activity of Yes-associated protein (YAP) in the trophoblast and how YAP regulated human trophoblasts function. Thus, HTR-8 cells were treated with IgG purified from aPL+/PM+ women or normal controls. We found that aPL+/PM+ IgG impacted YAP activity via abrogating YAP expression. Further investigation of the anti-β2GPI-IgG/β2GPI complex showed an inhibition of nuclear YAP level and translocation in a dose-dependent manner, which might be rescued by progesterone in HTR-8 cells. YAP overexpression or knockdown HTR-8 cells were established for the evaluation of cell function and related gene expression in vitro. Loss of YAP arrested cell cycles in the G2/M phase, accelerated cell apoptosis by increasing the ratio of Bax/Bcl2, and disrupted MMP2/9-mediated cell migration and angiogenesis tube formation by VEGF. These findings support a new mechanism of PM associated with aPL through which YAP inactivation induced by aPL perturbs the trophoblast cell cycle, apoptosis, migration, and angiogenesis, finally developing into pregnancy failure

The Peanut (<i>Arachis hypogaea</i> L.) Gene <i>AhLPAT2</i> Increases the Lipid Content of Transgenic Arabidopsis Seeds

<div><p>Lysophosphatidic acid acyltransferase (LPAT), which converts lysophosphatidic acid (LPA) to phosphatidic acid (PA), catalyzes the addition of fatty acyl moieties to the <i>sn</i>-2 position of the LPA glycerol backbone in triacylglycerol (TAG) biosynthesis. We recently reported the cloning and temporal-spatial expression of a peanut (<i>Arachis hypogaea</i>) <i>AhLPAT2</i>gene, showing that an increase in <i>AhLPAT2</i> transcript levels was closely correlated with an increase in seed oil levels. However, the function of the enzyme encoded by the <i>AhLPAT2</i> gene remains unclear. Here, we report that <i>AhLPAT2</i> transcript levels were consistently higher in the seeds of a high-oil cultivar than in those of a low-oil cultivar across different seed developmental stages. Seed-specific overexpression of <i>AhLPAT2</i> in Arabidopsis results in a higher percentage of oil in the seeds and greater-than-average seed weight in the transgenic plants compared with the wild-type plants, leading to a significant increase in total oil yield per plant. The total fatty acid (FA) content and the proportion of unsaturated FAs also increased. In the developing siliques of <i>AhLPAT2</i>-overexpressing plants, the expression levels of genes encoding crucial enzymes involved in <i>de novo</i> FA synthesis, acetyl-CoA subunit (<i>AtBCCP2</i>) and acyl carrier protein 1 (<i>AtACP1</i>) were elevated. <i>AhLPAT2</i> overexpression also promoted the expression of several key genes related to TAG assembly, sucrose metabolism, and glycolysis. These results demonstrate that the expression of <i>AhLPAT2</i> plays an important role in glycerolipid production in peanuts.</p></div

Altered Expression of Genes Involved in the FAs and TAG Biosynthesis Pathway.

<p>Values are means ± SE (<i>n</i> = 3). Total RNA was prepared from developing siliques of transgenic lines. Gene expression levels are shown relative to the expression of <i>AtActin7</i> in each sample. The transcription level of each gene in the wildtype was set as 1.0.Asterisks indicate significant differences between the wild-type and transgenic lines at p < 0.01 (**) and p < 0.05 (*).</p