Study on THz Imaging System for Concealed Threats Detection.

PhD ThesisMany research groups have conducted studies on Terahertz technology for various applications in the last decades. THz imaging for personnel screening is one prospective application due in part to its superior performance compared with imaging microwave bands. Because of the demand for the accurate detection, it is desirable to devise a high-performance THz imaging system for concealed threats detection. Therefore, this thesis presents my research on the low-cost THz imaging system for security detection. The key contributions of this research lie in investigating the linear sparse periodic array (SPA) THz imaging system for concealed threats detection, improving the traditional reconstruction algorithm of Generalized Synthetic Aperture Focusing Technique (GSAFT) to suppress the ghost images and applying the compressive sensing technique into the proposed SPA-THz imaging system to reduce the sampling data but maintain the image quality. The first part of the work is to investigate the linear sparse periodic array (SPA) and its configuration with large element spacing in simulation, deriving the design guideline for such a SPA THz imaging system. Meanwhile, the improved GSAFT reconstruction algorithm and multi-pass interferometric synthetic aperture imaging technique have been proposed to suppress the ghost image and improve the image quality, respectively. Secondly, the compressive sensing technique has been investigated to reduce the sampling data. Therefore, we have proposed the corresponding discrete CS SPA-THz reconstruction model and verified it in simulation. Finally, we have devised a simplified experimental set-up to assess the practical imaging performance, verifying the proposed SPA-THz imaging system. The set-up only uses 1 Tx and 1 Rx scanning on two separate tracks to effectively realize the proposed imaging system. The reconstructed images by the GSAFT and CS approaches with the measured data have both shown good consistency with the simulated results, respectively. And the multi-pass interferometric synthetic aperture imaging has been experimentally proved effective in improving image SNR and contras

Genetic Diversity and Genetic Structure of Different Types of Natural Populations in Osmanthus fragrans

Osmanthus fragrans Lour., an evergreen small tree, has the rare sexual system of androdioecy (coexistence of males and hermaphrodites), once with wide-spread natural distribution in the areas of the South Yangzi river basin. However, due to excessive human utilization, natural distribution became fragmented and the number and size of natural populations reduced sharply. With four different types of natural populations from the same region as research object, we aim to provide a comparative analysis on the relationships among genetic diversity, sexual system, population structure and size, and geographic isolation by ISSR. In genetic parameters of Ne, He, and I, the LQGC population had the highest value and the LQZGQ population had the lowest value. These indicated that LQGC population showed the highest genetic diversity, followed by QDH and JN population, and LQZGQ population exhibited the lowest genetic diversity. Genetic diversity in populations is closely related to population structure, reproduction mode, and sex ratio. However, there seems to be no obvious correlation between genetic diversity and population size. The results of AMOVA showed that genetic variations mostly occurred within populations. It indicates that no significant genetic differentiation among populations occurs, and geographic isolation has no significant effect on genetic diversity

The mitochondrial gene orfH79 plays a critical role in impairing both male gametophyte development and root growth in CMS-Honglian rice

<p>Abstract</p> <p>Background</p> <p>Cytoplasmic male sterility (CMS) has often been associated with abnormal mitochondrial open reading frames. The mitochondrial gene <it>orfH79 </it>is a candidate gene for causing the CMS trait in CMS-Honglian (CMS-HL) rice. However, whether the <it>orfH79 </it>expression can actually induce CMS in rice remains unclear.</p> <p>Results</p> <p>Western blot analysis revealed that the ORFH79 protein is mainly present in mitochondria of CMS-HL rice and is absent in the fertile line. To investigate the function of ORFH79 protein in mitochondria, this gene was fused to a mitochondrial transit peptide sequence and used to transform wild type rice, where its expression induced the gametophytic male sterile phenotype. In addition, excessive accumulation of reactive oxygen species (ROS) in the microspore, a reduced ATP/ADP ratio, decreased mitochondrial membrane potential and a lower respiration rate in the transgenic plants were found to be similar to those in CMS-HL rice. Moreover, retarded growth of primary and lateral roots accompanied by abnormal accumulation of ROS in the root tip was observed in both transgenic rice and CMS-HL rice (YTA).</p> <p>Conclusion</p> <p>These results suggest that the expression of <it>orfH79 </it>in mitochondria impairs mitochondrial function, which affects the development of both male gametophytes and the roots of CMS-HL rice.</p

Root Morphology and Rhizosphere Characteristics Are Related to Salt Tolerance of Suaeda salsa and Beta vulgaris L.

Halophytes are capable of resisting salinity, and their root system is the part in direct contact with the saline soil environment. The aim of this study was to compare the responses of root morphology and rhizosphere characteristics to salinity between a halophyte, Suaeda salsa (suaeda), and a glycophyte, Beta vulgaris L. (sugar beet). The soil salt content was set to four levels (0.7, 1.2, 1.7, and 2.7%) by NaCl-treated plants. We investigated the soil pH, EC, nutrients and soil, plant ion (Na+, Cl−, K+, and Mg2+) concentration to evaluate the rhizospheric processes, and salt tolerance of suaeda by the root mat method. The highest biomass was in the 1.2% salt level for suaeda and in the 0.7% salt level for sugar beet. The root length and root surface area of suaeda showed similar trends to biomass, but the root diameter decreased by 11.5–17.9% with higher salinity. The Na+, Cl−, and K+ accumulations in the shoot of suaeda displayed higher than that in sugar beet, while the Mg2+ accumulation was lower in suaeda than that in sugar beet. High salinity resulted in increased pH and EC values in the rhizosphere for suaeda, but lower values of these parameters for sugar beet. Under high salinity, the Olsen phosphorus content was 0.50 g·kg−1 and 0.99 g·kg−1 higher in the rhizosphere than in the non-rhizosphere for suaeda and sugar beet. We concluded that the two species [halophyte, Suaeda salsa (suaeda), and a glycophyte, B. vulgaris L. (sugar beet)] showed diverse approaches for nutrient absorption under salinity stress. Suaeda altered its root morphology (smaller root diameter and longer roots) under salt stress to increase the root surface area, while sugar beet activated rhizospheric processes to take up more nutrients

Carotenoid Accumulation and Its Contribution to Flower Coloration of Osmanthus fragrans

Among naturally occurring pigments, carotenoids are importantly involved in the photosynthesis of plants and responsible for the coloration of petals and fruits. Osmanthus fragrans Lour., a famous ornamental plant, has many cultivars with different flower color. Petal coloration in O. fragrans mainly depends on the kinds of carotenoids and their contents. To investigate the mechanism of flower coloration in different cultivars, an analysis of phenotypic classification, phytochemistry, as well as the expression of carotenoid metabolism genes based on different groups was performed in the present study. Two main clusters including the orange-red cluster containing Aurantiacus cultivars and the yellowish-white cluster containing the other three cultivar groups were classified using the CIEL∗a∗b∗ system. No significant differences in flavonoid contents were observed between these two clusters. However, carotenoids, especially α-carotene and β-carotene, were found to have crucial roles in the diversity of floral coloration among the different cultivars. Carotenoid compositions in the petals of cultivars from both clusters consisted of α-carotene, β-carotene, α-cryptoxanthin, β-cryptoxanthin, lutein, and zeaxanthin, but carotenoid accumulation patterns during the flowering process were different. The petals of the yellowish-white cultivars exhibited high contents of β-carotene, lutein and α-carotene, whereas the petals of the orange-red cultivars mainly contained β-carotene and α-carotene. The profound diversity in the total carotenoid concentrations in the two clusters was determined by the transcript levels of OfCCD4. Furthermore, the accumulation of upstream products with orange color in orange-red cultivars was partially due to the low expression of OfCHYB, whereas the relatively higher OfCHYB expression in the petals of the yellowish-white cultivars led to higher proportions of lutein, which is yellow. We also found that downregulation of OfLCYE, which encodes -ring cyclase, indicated that the carotenoid flux of most cultivars mainly resulted in more β, β-branched products. Additionally, carotenoid biosynthesis in green tissues and petals was compared, revealing the tissue specificity of carotenoid accumulation in O. fragrans. Therefore, the effects of multiple genes on carotenoid accumulation give rise to the colorful O. fragrans

Template Synthesis of Carbon Nanofibers Containing Linear Mesocage Arrays

Carbon nanofibers containing linear mesocage arrays were prepared via evaporation induced self-assembly method within AAO template with an average channel diameter of about 25 nm. The TEM results show that the mesocages have an elongated shape in the transversal direction. The results of N2 adsorption–desorption analysis indicate that the sample possesses a cage-like mesoporous structure and the average mesopore size of the sample is about 18 nm

Guinea Pig Model for Evaluating the Potential Public Health Risk of Swine and Avian Influenza Viruses

BACKGROUND: The influenza viruses circulating in animals sporadically transmit to humans and pose pandemic threats. Animal models to evaluate the potential public health risk potential of these viruses are needed. METHODOLOGY/PRINCIPAL FINDINGS: We investigated the guinea pig as a mammalian model for the study of the replication and transmission characteristics of selected swine H1N1, H1N2, H3N2 and avian H9N2 influenza viruses, compared to those of pandemic (H1N1) 2009 and seasonal human H1N1, H3N2 influenza viruses. The swine and avian influenza viruses investigated were restricted to the respiratory system of guinea pigs and shed at high titers in nasal tracts without prior adaptation, similar to human strains. None of the swine and avian influenza viruses showed transmissibility among guinea pigs; in contrast, pandemic (H1N1) 2009 virus transmitted from infected guinea pigs to all animals and seasonal human influenza viruses could also horizontally transmit in guinea pigs. The analysis of the receptor distribution in the guinea pig respiratory tissues by lectin histochemistry indicated that both SAα2,3-Gal and SAα2,6-Gal receptors widely presented in the nasal tract and the trachea, while SAα2,3-Gal receptor was the main receptor in the lung. CONCLUSIONS/SIGNIFICANCE: We propose that the guinea pig could serve as a useful mammalian model to evaluate the potential public health threat of swine and avian influenza viruses

Genome-wide identification and expression analysis of 3-ketoacyl-CoA synthase gene family in rice (Oryza sativa L.) under cadmium stress

3-Ketoacyl-CoA synthase (KCS) is the key rate-limiting enzyme for the synthesis of very long-chain fatty acids (VLCFAs) in plants, which determines the carbon chain length of VLCFAs. However, a comprehensive study of KCSs in Oryza sativa has not been reported yet. In this study, we identified 22 OsKCS genes in rice, which are unevenly distributed on nine chromosomes. The OsKCS gene family is divided into six subclasses. Many cis-acting elements related to plant growth, light, hormone, and stress response were enriched in the promoters of OsKCS genes. Gene duplication played a crucial role in the expansion of the OsKCS gene family and underwent a strong purifying selection. Quantitative Real-time polymerase chain reaction (qRT-PCR) results revealed that most KCS genes are constitutively expressed. We also revealed that KCS genes responded differently to exogenous cadmium stress in japonica and indica background, and the KCS genes with higher expression in leaves and seeds may have functions under cadmium stress. This study provides a basis for further understanding the functions of KCS genes and the biosynthesis of VLCFA in rice