An Improved Equivalent Squint Range Model and Imaging Approach for Sliding Spotlight SAR Based on Highly Elliptical Orbit

As an emerging orbital system with flexibility and brand application prospects, the highly elliptical orbit synthetic aperture radar (HEO SAR) can achieve both a low orbit detailed survey and continuous earth surface observation in high orbit, which could be applied to marine reconnaissance and surveillance. However, due to its large eccentricity, two challenges have been faced in the signal processing of HEO SAR at present. The first challenge is that the traditional equivalent squint range model (ESRM) fails to accurately describe the entire range for the whole orbit period including the perigee, the apogee, and the squint subduction section. The second one is to exploit an efficient HEO SAR imaging algorithm in the squinted case which solves the problem that traditional imaging algorithm fails to achieve the focused imaging processing of HEO SAR during the entire orbit period. In this paper, a novel imaging algorithm for HEO SAR is presented. Firstly, the signal model based on the geometric configuration of the large elliptical orbit is established and the Doppler parameter characteristics of SAR are analyzed. Secondly, due to the particularity of Doppler parameters variation in the whole period of HEO, the equivalent velocity and equivalent squint angle used in MESRM can no longer be applied, a refined fourth-order equivalent squint range model(R4-ESRM) that is suitable for HEO SAR is developed by introducing fourth-order Doppler parameter into Modified ESRM (MESRM), which accurately reconstructs the range history of HEO SAR. Finally, a novel imaging algorithm combining azimuth resampling and time-frequency domain hybrid correlation based on R4-ESRM is derived. Simulation is performed to demonstrate the feasibility and validity of the presented algorithm and range model, showing that it achieves the precise phase compensation and well focusing

An Improved Equivalent Squint Range Model and Imaging Approach for Sliding Spotlight SAR Based on Highly Elliptical Orbit

As an emerging orbital system with flexibility and brand application prospects, the highly elliptical orbit synthetic aperture radar (HEO SAR) can achieve both a low orbit detailed survey and continuous earth surface observation in high orbit, which could be applied to marine reconnaissance and surveillance. However, due to its large eccentricity, two challenges have been faced in the signal processing of HEO SAR at present. The first challenge is that the traditional equivalent squint range model (ESRM) fails to accurately describe the entire range for the whole orbit period including the perigee, the apogee, and the squint subduction section. The second one is to exploit an efficient HEO SAR imaging algorithm in the squinted case which solves the problem that traditional imaging algorithm fails to achieve the focused imaging processing of HEO SAR during the entire orbit period. In this paper, a novel imaging algorithm for HEO SAR is presented. Firstly, the signal model based on the geometric configuration of the large elliptical orbit is established and the Doppler parameter characteristics of SAR are analyzed. Secondly, due to the particularity of Doppler parameters variation in the whole period of HEO, the equivalent velocity and equivalent squint angle used in MESRM can no longer be applied, a refined fourth-order equivalent squint range model(R4-ESRM) that is suitable for HEO SAR is developed by introducing fourth-order Doppler parameter into Modified ESRM (MESRM), which accurately reconstructs the range history of HEO SAR. Finally, a novel imaging algorithm combining azimuth resampling and time-frequency domain hybrid correlation based on R4-ESRM is derived. Simulation is performed to demonstrate the feasibility and validity of the presented algorithm and range model, showing that it achieves the precise phase compensation and well focusing

Explainable prediction of loan default based on machine learning models

Owing to the convenience of online loans, an increasing number of people are borrowing money on online platforms. With the emergence of machine learning technology, predicting loan defaults has become a popular topic. However, machine learning models have a black-box problem that cannot be disregarded. To make the prediction model rules more understandable and thereby increase the user’s faith in the model, an explanatory model must be used. Logistic regression, decision tree, XGBoost, and LightGBM models are employed to predict a loan default. The prediction results show that LightGBM and XGBoost outperform logistic regression and decision tree models in terms of the predictive ability. The area under curve for LightGBM is 0.7213. The accuracies of LightGBM and XGBoost exceed 0.8. The precisions of LightGBM and XGBoost exceed 0.55. Simultaneously, we employed the local interpretable model-agnostic explanations approach to undertake an explainable analysis of the prediction findings. The results show that factors such as the loan term, loan grade, credit rating, and loan amount affect the predicted outcomes

Factors Related to Bone Metabolism in Kidney Transplant Recipients

This study is aimed at establishing the prevalence of osteoporosis and osteopenia in kidney transplant recipients (KTRs) and determining the risk factors for bone mass loss. We invited KTRs who were under regular follow-up at Jiangxi Provincial People’s Hospital Affiliated with Nanchang University to attend an assessment of osteoporotic risk assessed by questionnaire, biochemical profile, and dual-energy X-ray absorptiometry (DXA) scanning of the lumbar spine, total hip, and femoral neck. Binary logistic regression models were used to investigate the relationship between the different variables and bone mass density (BMD). A total of 216 patients satisfied the inclusion criteria. The group consisted of 156 men (72.22%) and 60 women (27.78%), and the mean age was 41.50±9.98 years. There were 81 patients with normal bone mass (37.50%) and 135 patients with bone mass loss (62.50%). Logistic regression analysis showed that a higher phosphorus value and higher alkaline phosphatase concentration and a longer use of glucocorticoids were risk factors for bone mass loss in KTRs, and maintaining an appropriate weight and exercising an appropriate number of times per week helped to maintain bone mass

Genomic and Transcriptomic Dissection of the Large-Effect Loci Controlling Drought-Responsive Agronomic Traits in Wheat

Drought tolerance is one of the most important targets for wheat breeding. Previous population genetics studies have uncovered 20 large-effect quantitative trait loci (QTLs) that contribute to stress-responsive agronomic traits. Here, we identified 19,035,814 single nucleotide polymorphisms and 719,049 insertion/deletion variations in the genomes of two popular winter wheat cultivars, Lu-Mai 14 and Han-Xuan 10, using a whole-genome re-sequencing assay. There were 4972 loss-of-function mutations carried by protein-coding genes, such as CCA1/LHY, AGO1, ABI3/VP1, EIN3, TPP, and ARFs. We carried out a time-course abscisic acid (ABA)-treatment experiment and profiled 61,251 expressed genes in the roots using a strand-specific RNA sequencing approach. A large number of genes showed time-point specific and/or cultivar-preferential responsive expression patterns. Gene ontology enrichment analysis revealed that ABA-responsive genes were associated with stress-related functions. Among the 20 QTLs, we uncovered 306 expressed genes with high- and/or moderate-effect variations and 472 differentially expressed genes. Detailed analysis and verification of the homozygous genomic variations in the candidate genes encoding sulfotransferase, proteinase, kinase, nitrate transporter, and transcription factors suggested previously unexpected pathways associated with abiotic stress responses in wheat

Genomic and Transcriptomic Dissection of the Large-Effect Loci Controlling Drought-Responsive Agronomic Traits in Wheat

Drought tolerance is one of the most important targets for wheat breeding. Previous population genetics studies have uncovered 20 large-effect quantitative trait loci (QTLs) that contribute to stress-responsive agronomic traits. Here, we identified 19,035,814 single nucleotide polymorphisms and 719,049 insertion/deletion variations in the genomes of two popular winter wheat cultivars, Lu-Mai 14 and Han-Xuan 10, using a whole-genome re-sequencing assay. There were 4972 loss-of-function mutations carried by protein-coding genes, such as CCA1/LHY, AGO1, ABI3/VP1, EIN3, TPP, and ARFs. We carried out a time-course abscisic acid (ABA)-treatment experiment and profiled 61,251 expressed genes in the roots using a strand-specific RNA sequencing approach. A large number of genes showed time-point specific and/or cultivar-preferential responsive expression patterns. Gene ontology enrichment analysis revealed that ABA-responsive genes were associated with stress-related functions. Among the 20 QTLs, we uncovered 306 expressed genes with high- and/or moderate-effect variations and 472 differentially expressed genes. Detailed analysis and verification of the homozygous genomic variations in the candidate genes encoding sulfotransferase, proteinase, kinase, nitrate transporter, and transcription factors suggested previously unexpected pathways associated with abiotic stress responses in wheat

Bioactivity Determination of a Therapeutic Recombinant Human Keratinocyte Growth Factor by a Validated Cell-based Bioassay

The therapeutic recombinant human keratinocyte growth factor 1 (rhKGF-1) was approved by the FDA for oral mucositis resulting from hematopoietic stem cell transplantation for hematological malignancies in 2004. However, no recommended bioassay for rhKGF-1 bioactivity has been recorded in the U.S. Pharmacopoeia. In this study, we developed an rhKGF-1-dependent bioassay for determining rhKGF-1 bioactivity based on HEK293 and HaCat cell lines that stably expressed the luciferase reporter driven by the serum response element (SRE) and human fibroblast growth factor receptor (FGFR2) IIIb. A good responsiveness to rhKGF-1 and rhKGF-2 shared by target HEK293/HaCat cell lines was demonstrated. Our stringent validation was completely focused on specificity, linearity, accuracy, precision, and robustness according to the International Council for Harmonization (ICH) Q2 (R1) guidelines, AAPS/FDA Bioanalytical Workshop and the Chinese Pharmacopoeia. We confirmed the reliability of the method in determining rhKGF bioactivity. The validated method is highly timesaving, sensitive, and simple, and is especially valuable for providing information for quality control during the manufacture, research, and development of therapeutic rhKGF