211 research outputs found

    Two-Dimensional Imaging Algorithm Based on Linear Prognosis for Space Target in Bistatic ISAR System

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    In bistatic inverse synthetic aperture radar (Bi-ISAR) system, its image resolution is lower than monostatic ISAR system. In order to solve this problem, the linear prognosis algorithm is adopted in the imaging process and the imaging algorithm based on linear prognosis is proposed. Space target Bi-ISAR imaging is taken as example in the research. The one-dimensional range profile is created through pulse compression method. Before the azimuth compression, burg entropy maximum algorithm in Levions recursive method is used to estimate the prognosis coefficients and the azimuth echo data. Then Fourier transformation is used to compress the azimuth data in order to get the high resolution azimuth image. This imaging method can obtain the two-dimensional image with the resolution equal to the monostatic ISAR or even higher than it. Simulation experiments have verified the effectiveness and availability of the algorithm

    Bus Travel Time Deviation Analysis Using Automatic Vehicle Location Data and Structural Equation Modeling

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    To investigate the influences of causes of unreliability and bus schedule recovery phenomenon on microscopic segment-level travel time variance, this study adopts Structural Equation Modeling (SEM) to specify, estimate, and measure the theoretical proposed models. The SEM model establishes and verifies hypotheses for interrelationships among travel time deviations, departure delays, segment lengths, dwell times, and number of traffic signals and access connections. The finally accepted model demonstrates excellent fitness. Most of the hypotheses are supported by the sample dataset from bus Automatic Vehicle Location system. The SEM model confirms the bus schedule recovery phenomenon. The departure delays at bus terminals and upstream travel time deviations indeed have negative impacts on travel time fluctuation of buses en route. Meanwhile, the segment length directly and negatively impacts travel time variability and inversely positively contributes to the schedule recovery process; this exogenous variable also indirectly and positively influences travel times through the existence of signalized intersections and access connections. This study offers a rational approach to analyzing travel time deviation feature. The SEM model structure and estimation results facilitate the understanding of bus service performance characteristics and provide several implications for bus service planning, management, and operation

    Molecular cloning, characterization and expression analysis of CpCBF2 gene in harvested papaya fruit under temperature stresses

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    Background: C-repeat binding factors (CBFs) are transcription factors that regulate the expression of a number of genes related to abiotic stresses. Few CBF genes have been cloned from other plants but no report in papaya. In present study, a full-length cDNA, designated as CpCBF2, was cloned from papaya using in silico cloning and 5\u2019- rapid amplification cDNA ends (RACE). Sequence analysis was performed to understand the gene function. The expression pattern of CpCBF2 in papaya under low (7\ubaC) and high temperature (35\ubaC) stresses was examined using real-time quantitative polymerase chain reaction (RT-qPCR). Results: The full-length cDNA of CpCBF2 was 986-bp, with a 762-bp open reading frame (ORF) encoding a 254 amino acid polypeptide. CpCBF2 contained several major highly conserved regions including the CBF-family signature PKRRAGRKKFQETRHP and FADSAW in its amino acid sequence. Phylogenetic tree and three-dimensional structure analysis showed that CpCBF2 had a relatively close relationship with other plant CBFs. Gene expression analysis showed that high temperature stress had little effect on the expression of CpCBF2 but low temperature repressed CpCBF2 expression. Conclusion: The results showed that CpCBF2 may involve in different roles in temperature stress tolerance. This study provided a candidate gene potentially useful for fruit temperature stress tolerance, although its function still needs further confirmation

    The role of fluconazole in the regulation of fatty acid and unsaponifiable matter biosynthesis in Schizochytrium sp. MYA 1381.

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    BACKGROUND(#br)Schizochytrium has been widely used in industry for synthesizing polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid (DHA). However, unclear biosynthesis pathway of PUFAs inhibits further production of the Schizochytrium. Unsaponifiable matter (UM) from mevalonate pathway is crucial to cell growth and intracellular metabolism in all higher eukaryotes and microalgae. Therefore, regulation of UM biosynthesis in Schizochytrium may have important effects on fatty acids synthesis. Moreover, it is well known that UMs, such as squalene and β-carotene, are of great commercial value. Thus, regulating UM biosynthesis may also allow for an increased valuation of Schizochytrium.(#br)RESULTS(#br)To investigate the correlation of UM biosynthesis with fatty acids accumulation in Schizochytrium, fluconazole was used to block the sterols pathway. The addition of 60 mg/L fluconazole at 48 h increased the total lipids (TLs) at 96 h by 16% without affecting cell growth, which was accompanied by remarkable changes in UMs and NADPH. Cholesterol content was reduced by 8%, and the squalene content improved by 45% at 72 h, which demonstrated fluconazole’s role in inhibiting squalene flow to cholesterol. As another typical UM with antioxidant capacity, the β-carotene production was increased by 53% at 96 h. The increase of squalene and β-carotene could boost intracellular oxidation resistance to protect fatty acids from oxidation. The NADPH was found to be 33% higher than that of the control at 96 h, which meant that the cells had more reducing power for fatty acid synthesis. Metabolic analysis further confirmed that regulation of sterols was closely related to glucose absorption, pigment biosynthesis and fatty acid production in Schizochytrium.(#br)CONCLUSION(#br)This work first reported the effect of UM biosynthesis on fatty acid accumulation in Schizochytrium. The UM was found to affect fatty acid biosynthesis by changing cell membrane function, intracellular antioxidation and reducing power. We believe that this work provides valuable insights in improving PUFA and other valuable matters in microalgae

    Nitrogen addition mediates the effect of soil microbial diversity on microbial carbon use efficiency under long-term tillage practices

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    peer reviewedTillage practices can influence soil microbial carbon use efficiency (CUE), which is critical for carbon cycling in terrestrial ecosystems. The effect of tillage practices could also be regulated by nitrogen (N) addition. However, the soil microbial mechanism relating to N fertilizer effect on microbial CUE under no-tillage (zero-tillage) is still unclear. We investigated how N fertilizer regulates the effect of tillage management on microbial CUE through changing microbial properties and further assessed the impact of microbial CUE on particulate (POC) and mineral-associated organic matter carbon (MAOC). For this we used a 16-year field experiment with no-tillage (NT) and conventional tillage (CT), both of which combined with 105 (N1), 180 (N2), and 210 kg N ha−1 (N3) N application. We found that microbial CUE increased with increasing N application rate. NT increased microbial CUE compared with CT in the 0–10 cm. The bacterial and fungal diversities of NT were higher than CT and N application decreased their diversities in 0–10 cm. The partial least squares path model showed that bacterial and fungal diversity had a significant influence on microbial CUE. Furthermore, POC and MAOC under NT were higher than CT and they also increased with increasing N application rate. It suggested that increasing microbial CUE induced by N application had the potential to increase POC and MAOC. Overall, this study highlights that N addition can alter the effect of soil microbial diversity on CUE, which further improves our understanding to explain and predict the fractions of SOC (i.e., POC and MAOC) in tillage systems

    Pan-genome wide association study of Glaesserella parasuis highlights genes associated with virulence and biofilm formation

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    Glaesserella parasuis is a gram-negative bacterium that causes fibrotic polyserositis and arthritis in pig, significantly affecting the pig industry. The pan-genome of G. parasuis is open. As the number of genes increases, the core and accessory genomes may show more pronounced differences. The genes associated with virulence and biofilm formation are also still unclear due to the diversity of G. parasuis. Therefore, we have applied a pan-genome-wide association study (Pan-GWAS) to 121 strains G. parasuis. Our analysis revealed that the core genome consists of 1,133 genes associated with the cytoskeleton, virulence, and basic biological processes. The accessory genome is highly variable and is a major cause of genetic diversity in G. parasuis. Furthermore, two biologically important traits (virulence, biofilm formation) of G. parasuis were studied via pan-GWAS to search for genes associated with the traits. A total of 142 genes were associated with strong virulence traits. By affecting metabolic pathways and capturing the host nutrients, these genes are involved in signal pathways and virulence factors, which are beneficial for bacterial survival and biofilm formation. This research lays the foundation for further studies on virulence and biofilm formation and provides potential new drug and vaccine targets against G. parasuis

    Effects of Perfluorooctanoic Acid on the Associated Genes Expression of Autophagy Signaling Pathway of Carassius auratus Lymphocytes in vitro

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    Perfluorooctanoic acid (PFOA) has been detected in various water bodies and caused harm to aquatic organisms. The aim of this study was to investigate the cytotoxicity and mechanism associated with autophagy and oxidative stress after exposure to PFOA (0, 1, 10, 100 μg/L) for 12 h on lymphocytes, which was isolated from the head kidney of Carassius auratus (C. auratus). Both of autophagy formation, cell activity, and intracellular reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) levels were measured. The relative expression of partial autophagy-related genes autophagy related 5 (Atg 5), autophagy related 7 (Atg 7), and Beclin 1 were also cloned and detected. Homologous relationships analysis showed high identities of genes in C. auratus and other fish by blast. C. auratus lymphocytes growth inhibition rates was increased induced by PFOA. Compared with the control group, the ROS generation and the MDA content were significantly increased in all of the PFOA-treated group. Besides, decreased SOD activity and decrease of GSH activity induced by PFOA further confirmed the occurrence of oxidative stress. The number of autophagosome formations was increased in a dose-dependent manner. Compared with the control group, Atg 7 and Beclin 1 mRNA expression was elevated significantly after PFOA exposed, showing a time-dependent manner, while mRNA expression of Atg 5 was increased remarkably in 100 μg/L PFOA-treated group. Our results indicated that PFOA caused oxidative damage to lymphocytes in C. auratus and caused various autophagy signaling pathway-associated genes imbalances in the lymphocytes. Autophagy signaling pathway-associated genes imbalance could weaken antioxidant capacity and involve in the mechanism of C. auratus lymphocytes oxidative injury caused by PFOA

    Automatic Recognition of Laryngoscopic Images Using a Deep-Learning Technique

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    Objectives/Hypothesis: To develop a deep-learning–based computer-aided diagnosis system for distinguishing laryngeal neoplasms (benign, precancerous lesions, and cancer) and improve the clinician-based accuracy of diagnostic assessments of laryngoscopy findings. Study Design: Retrospective study. Methods: A total of 24,667 laryngoscopy images (normal, vocal nodule, polyps, leukoplakia and malignancy) were collected to develop and test a convolutional neural network (CNN)-based classifier. A comparison between the proposed CNN-based classifier and the clinical visual assessments (CVAs) by 12 otolaryngologists was conducted. Results: In the independent testing dataset, an overall accuracy of 96.24% was achieved; for leukoplakia, benign, malignancy, normal, and vocal nodule, the sensitivity and specificity were 92.8% vs. 98.9%, 97% vs. 99.7%, 89% vs. 99.3%, 99.0% vs. 99.4%, and 97.2% vs. 99.1%, respectively. Furthermore, when compared with CVAs on the randomly selected test dataset, the CNN-based classifier outperformed physicians for most laryngeal conditions, with striking improvements in the ability to distinguish nodules (98% vs. 45%, P <.001), polyps (91% vs. 86%, P <.001), leukoplakia (91% vs. 65%, P <.001), and malignancy (90% vs. 54%, P <.001). Conclusions: The CNN-based classifier can provide a valuable reference for the diagnosis of laryngeal neoplasms during laryngoscopy, especially for distinguishing benign, precancerous, and cancer lesions. Level of Evidence: NA Laryngoscope, 130:E686–E693, 2020
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