Surface Chemistry of Lead and Lead Free Metal Halide Nanocrystals

In this thesis, the surface chemistry of different metal halide NCs were investigated. Two new synthesis approaches to produce LHP NCs were developed by employing phosphonic acids (either alkyl or oleyl PAs) as the sole surfactants. The NMR analysis of these samples indicated the steric binding state of PA. PA-capped NCs show near unity PLQY with uncommon truncated shape, and high stability against dilution. We also investigated the interaction between neutral ligands and LHP NCs. Among various neutral ligands, it was found out that oleyl PAs are able to strip a large fraction of original surface species. Surprisingly, after such loss of ligands, the PLQY, morphology and phase of CsPbBr3 NCs remain unaltered, empirically confirming the defect tolerance of LHP NCs. We also studied the surface chemistry of Pb-free double perovskite NCs. We optimized the optical properties of Bi-doped Cs2(NaxAg1-x)InCl6 NCs by systematically varying the amine and acid. We found out that both ligands are anchored to the surface of the NCs. Moreover, we observed that even with a high ligands density, the PLQY of the NCs was still low indicating that \u2018normal\u2019 surface passivation is not enough to efficiently passivate these NCs, which suggest that such DP NCs is sensitivity to non-radiative surface traps. We also investigated the optical physical behavior of Sb3+ centers in different coordination environment. The Rb7Sb3Cl16 NCs were composed by isolated [SbCl6]3- octahedra and [Sb2Cl10]4- dimer. The isolated [SbCl6]3- octahedra show dual emission under different excitation, whereas the [Sb2Cl10]4- dimer is non-emissive even in cryogenic temperature. In the final part, we have investigated a special LHP species, so called nanoclusters (NCLs), which was regard as intermediate between molecular precursors and solid LHP NCs. We here firstly revealed their shape and structure by SXAX, WAXS and PDF analysis

Large-time behavior of solutions for the one-dimensional infrarelativistic model of a compressible viscous gas with radiation

AbstractIn this paper, assuming suitable hypotheses on the transport coefficients, we prove the large-time behavior, as time tends to infinity, of solutions in Hi=Hi×H0i×Hi×Hi+1 (i=1,2) for the one-dimensional infrarelativistic model of a compressible viscous gas with radiation

Performance Evaluation of MDO Architectures within a Variable Complexity Problem

Though quite a number of multidisciplinary design optimization (MDO) architectures have been proposed for the optimal design of large-scale multidisciplinary systems, how their performance changes with the complexity of MDO problem varied is not well studied. In order to solve this problem, this paper presents a variable complexity problem which allows people to obtain a MDO problem with arbitrary complexity by specifying its changeable parameters, such as the number of disciplines and the numbers of design variables. Then four investigations are performed to evaluate how the performance of different MDO architectures changes with the number of disciplines, global variables, local variables, and coupling variables varied, respectively. Finally, the results supply guidance for the selection of MDO architectures in solving practical engineering problems with different complexity

Dietary specialization drives multiple independent losses and gains in the bitter taste gene repertoire of Laurasiatherian Mammals

Background: Bitter taste perception is essential for species with selective food intake, enabling them to avoid unpalatable or toxic items. Previous studies noted a marked variation in the number of TAS2R genes among various vertebrate species, but the underlying causes are not well understood. Laurasiatherian mammals have highly diversified dietary niche, showing repeated evolution of specialized feeding preferences in multiple lineages and offering a unique chance to investigate how various feeding niches are associated with copy number variation for bitter taste receptor genes. Results: Here we investigated the evolutionary trajectories of TAS2Rs and their implications on bitter taste perception in whole-genome assemblies of 41 Laurasiatherian species. The number of intact TAS2Rs copies varied considerably, ranging from 0 to 52. As an extreme example of a narrow dietary niche, the Chinese pangolin possessed the lowest number of intact TAS2Rs (n = 2) among studied terrestrial vertebrates. Marine mammals (cetacea and pinnipedia), which swallow prey whole, presented a reduced copy number of TAS2Rs (n = 0-5). In contrast, independent insectivorous lineages, such as the shrew and insectivorous bats possessed a higher TAS2R diversity (n = 52 and n = 20-32, respectively), exceeding that in herbivores (n = 9-22) and omnivores (n = 18-22). Conclusions: Besides herbivores, insectivores in Laurasiatheria tend to have more functional TAS2Rs in comparison to carnivores and omnivores. Furthermore, animals swallowing food whole (cetacean, pinnipedia and pangolin) have lost most functional TAS2Rs. These findings provide the most comprehensive view of the bitter taste gene repertoire in Laurasiatherian mammals to date, casting new light on the relationship between losses and gains of TAS2Rs and dietary specialization in mammals

How much genetic variation is stored in the endangered and fragmented shrub Tetraena mongolica Maxim?

Tetraena mongolica Maxim (Zygophyllaceae) is an endangered species endemic to western Inner Mongolia and China, and is currently threatened by habitat loss and human over-exploitation. We explored the genetic background, its genetic diversity, population structure, and demographic history, based on 12 polymorphic nuclear microsatellite loci. Our results indicated high genetic diversity in extant populations, but no distinguishable gene cluster corresponding with a specific biogeography. Population demography analysis using a MSVAR indicated a strong, recent population decline approximately 5,455 years ago. These results suggest that the Yellow River and Zhuozi Mountain range may not prevent pollination between populations. Finally, we surmised that the population demography of T. mongolica was likely to have been affected by early mankind activities

Framework for Hyperspectral Image Processing and Quantification for Cancer Detection During Animal Tumor Surgery

Hyperspectral imaging (HSI) is an imaging modality that holds strong potential for rapid cancer detection during image-guided surgery. But the data from HSI often needs to be processed appropriately in order to extract the maximum useful information that differentiates cancer from normal tissue. We proposed a framework for hyperspectral image processing and quantification, which includes a set of steps including image preprocessing, glare removal, feature extraction, and ultimately image classification. The framework has been tested on images from mice with head and neck cancer, using spectra from 450- to 900-nm wavelength. The image analysis computed Fourier coefficients, normalized reflectance, mean, and spectral derivatives for improved accuracy. The experimental results demonstrated the feasibility of the hyperspectral image processing and quantification framework for cancer detection during animal tumor surgery, in a challenging setting where sensitivity can be low due to a modest number of features present, but potential for fast image classification can be high. This HSI approach may have potential application in tumor margin assessment during image-guided surgery, where speed of assessment may be the dominant factor

Microbiome Structure and Mucosal Morphology of Jejunum Appendix and Colon of Rats in Health and Dysbiosis

Gut microbiota contributes to human health. Plenty of studies demonstrate that antibiotics can disrupt gut ecosystem leading to dysbiosis. Little is known about the microbial variation of appendix and its up/downstream intestine after antibiotic treatment. This study aimed to investigate the microbiome and mucosal morphology of jejunum, appendix, and colon of rats in health and dysbiosis. A rodent model of antibiotic-induced dysbiosis was employed. Microscopy was used to observe mucosal morphological changes. 16S rRNA sequencing was performed for identifying bacterial taxa and microbiome structure. The appendices of dysbiosis were found enlarged and infated with loose contents. Microscopy revealed the impairment of intestinal epithelial cells. High-throughput sequencing showed the Operational Taxonomic Units changed from 361±33, 634±18, 639±19 in the normal jejunum, appendix, colon to 748±98, 230±11, 253±16 in the disordered segments, respectively. In dysbiosis, Bacteroidetes translocated inversely from the colon and appendix (0.26%, 0.23%) to the jejunum (13.87%±0.11%); the relative abundance of all intestinal Enterococcaceae increased, while Lactobacillaceae decreased. Several bacterial clusters were found correlated to the normal appendix, whereas nonspecifc clusters correlated to the disordered appendix. In conclusion, species richness and evenness reduced in the disordered appendix and colon; similar microbiome patterns were shared between the appendix and colon regardless of dysbiosis; site-specifc bacteria were missing in the disordered appendix. Appendix is likely a transit region involving in upper and lower intestinal microfora modulation. The limitation of this study is all the data were derived from rats. We must be cautious about translating the microbiome results from rats to humans