743 research outputs found
The Last Entrustment: Funeral Concepts and Arrangements of for the Afterlife in the Tang Dynasty
No full textArrangements for the afterlife were important matters to the Tang 唐 (618–907) people. The newly unearthed epitaphs of the Tang Dynasty contain a large number of dialogues and words of the deceased before their death, as well as their instructions concerning the arrangements for funerals and the inheritance of family traditions. These instructions not only reflect Tang funeral concepts and the importance of arrangements for the afterlife, but they also allow us to perceive the characters and personalities of the deceased, which are valuable new materials for the study of ancient Chinese biographical literature
Soil organic carbon and total nitrogen stocks as affected by vegetation types and altitude across the mountainous regions in the Yunnan Province, south-western China
No full textStructure and function of the terpene biosynthesis enzyme, IspH
No full text"The protein IspH, (E)-1-hydroxy-2-methyl-but-2-enyl 4-diphosphate reductase, is an essential enzyme in isoprenoid biosynthesis and an important drug/herbicide target. The main research in this work investigated the structures and functions of IspHs from various organisms.
Using a sequence similarity network we found that some IspHs form ""Rosetta-stone"" fusion proteins with either the ribosomal protein S1 (RPS1), or a UbiA (4-hydroxybenzoate octaprenyltransferase)-like protein. These fusion proteins are all from obligately anaerobic bacteria. A catalytically active IspH-RPS1 was expressed and characterized. The existance of these fusion proteins is indicative of possible secondary roles of the enzyme IspH, perhaps being involved in O2 sensing and regulation.
Using crystallographic and bioinformatics results we show that IspHs can be classified into four major classes, based on the arrangement of the aromatic residues near the 4Fe-4S cluster and the presence of N- and C-terminal extensions, and these structure features are related to the environments in which IspHs are found. These aromatic groups protect the 4Fe-4S clusters from oxidation and are also involved in electron transfer. The results revealed how nature has evolved different structure features for a sensitive protein in different environments.
In addition, another terpene biosyntheis enzyme, MenA, and two other metalloenzymes that are drug targets, DHAD and LOX, were also investigated. Overall, this research is of interest since it revealed the structure and functions of the terpene biosynthesis enzyme IspH from various organisms, as well as other proteins that are possible drug targets."Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-08-01The student, Guodong Rao, accepted the attached license on 2016-06-27 at 21:31.The student, Guodong Rao, submitted this Dissertation for approval on 2016-06-27 at 21:37.This Dissertation was approved for publication on 2016-06-28 at 15:33.DSpace SAF Submission Ingestion Package generated from Vireo submission #9715 on 2016-11-10 at 12:24:45Made available in DSpace on 2016-11-10T18:39:14Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-06-28Embargo set by: Seth Robbins for item 95443
Lift date: 2018-11-10T18:39:22Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 95443
Lift date: 2018-11-10T18:43:22Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 95443 on 2018-11-11T10:15:32Z
Effect of geometric position on the film properties for a complex-shaped substrate in HiPIMS discharge: Experiment and simulation
No full textThe purpose of this paper is to explore the effect of geometric position on the film properties for a complex shaped substrate in high-power impulse magnetron sputtering (HiPIMS) discharge. The substrate is a trapezoidal prism, whose base has four inner corners of 60?degrees, 120 degrees, 75 degrees, and 105 degrees. A negative bias is added to this trapezoidal prism during the high-density discharge to deposit TiAlSiN films. The chemical compositions, microstructures and mechanical properties of the films at different area of the substrate are analyzed using the energy dispersive spectroscopy, X-ray diffraction, scanning electron microscope, nano-indentor and Vickers indentation tester. Systematic investigations demonstrate that the films properties have prominent differences on various planes of the trapezoidal-prism sample, due to the so-called shadowing effect. Compared with the measurements on the plane perpendicular to the target surface, there is a higher average hardness and stronger toughness on the plane facing to the target surface. However, the values of both the hardness and toughness are the lowest on the plane facing away from the target surface. Moreover, even for the same plane, the enhanced mechanical properties as well as a smoother surface and denser microstructure appear in the edge regions, with respect to that in the planar center regions. To understand these interesting phenomena, a two-dimensional particle-in-cell/Monte Carlo collision simulation (2D PIC-MCC) and Transport of Ions in Matter method (TRIM) are employed to explore the ion dynamics at the different sites of the sample. Simulation results suggest that a higher ion flux density and larger re-sputtering rate may contribute to the improved film properties in the edge regions. These results in this paper are important for broadening the industrial applications of high ion fraction plasma sources in irregular structures, especially for cutting tools
Electronic and hyperbolic dielectric properties of ZrS<sub>2</sub>/HfS<sub>2</sub> heterostructures
No full textIn this paper we investigate the electronic and optical dielectric properties of lateral and vertical heterostructures composed of two-dimensional (2D) ZrS2 and HfS2 monolayers based on density functional theory. First, we show that the bulk and monolayer ZrS2 and HfS2 as well as the vertical (ZrS2)m/(HfS2)n heterostructures are in direct band gap semiconductors, while the lateral heterostructures exhibit an indirect to direct bandgap transition. Then we demonstrate that the optical properties of the bulk and monolayer HfS2 and ZrS2are strongly anisotropic, for the bulk HfS2 and ZrS2, the in-plane components of the dielectric function is negative in a certain frequency band, where they can work as naturally hyperbolic metamaterials (HMMs). Interestingly, the vertical heterostructures also possess a hyperbolic region, whose position and width can be tunable with the thickness ratio of constituents. It is also found that the (ZrS2)/(HfS2) vertical heterostructures can enhance spontaneous emission and about 100-fold improvement of the Purcell factor is obtained. These results prove the feasibility of 2D material heterostructures to realize tunable hyperbolic metamaterials, the heterostructures present a promising opportunity for the practical applications in light-generation technologies
Dysfunctional signaling pathway for nitric oxide production in endothelial cells chronically exposed to high glucose or high fatty acids
No full textPh.DDOCTOR OF PHILOSOPH
Sedimentary processes in the Thau Lagoon (France): From seasonal to century time scales
No full textAs a part of the MICROBENT programme, an investigation of the sedimentation framework was carried out at the water-sediment interface in the Thau Lagoon (French Mediterranean coast). Two main sites, C4 in the middle of the lagoon and C5 near oyster farms, were visited six times between December 2001 and May 2003. Interface sediments were studied using classical sedimentology parameters (radiography RX, grain size distribution) and analysis of selected radionuclides (234Th, 7Be, 210Pb, 226Ra). On a century time scale, excess 210Pb (210Pbxs) presents classical profiles with an upper mixed layer, followed by an exponential decrease of activities to undetectable levels below 20 – 30 cm. At the central site, C4, cores seem to register episodic changes in mean grain size, presenting recurrently peaks. The upper 10 cm of 210Pbxs profiles at site C5 exhibit a mixed layer associated with coarser sediments: this could be related to biological activity. Sedimentation rates derived from 210Pbxs varied from 0.15 cm y−1 at the edge of the basin, to 0.25 cm y−1 at the central site. On a seasonal time scale, 234Th and 7Be both show significant variations in activities and in penetration within the sediment. Bioturbation rates derived from both radionuclides agree well and range between 1–10 cm2 y−1 at site C4 and 1–31 cm2 y−1 at site C5. 234Th and 7Be fluxes at the water-sediment interface show too seasonal variations, more pronounced for site C5. This latter site presents especially a higher variability that is well marked with season, probably in relation with its position near oyster farms
Study on the cavity solitons in fiber lasers
No full textSince it was first proposed in 1960s, fiber laser has attracted consistent focus both from industry and scientific research for these decades. In industry, fiber laser is an ideal source of high power CW /pulse beam output for the fine machining. In scientific research, pulse fiber lasers can provide picosecond or femtosecond optical pulses which are needed in physics, chemistry, medical and material research. On the other hand, the pulse propagation in optical fiber is mathematically described by the nonlinear Schrodinger equation (NLSE), and pulse propagation in a fiber laser is mathematically described by the Grinzburg-Laudau Equation (GLE). Both equations are very important in nonlinear science, describing a conservative and dissipative nonlinear system, respectively. Therefore, fiber laser is also an excellent testbed for experimentally studying the nonlinear physics. As a typical nonlinear cavity, fiber laser has nonlinear properties as those externally pumped nonlinear fiber ring cavities. Moreover, without the polarization selective components, fiber laser is a vectorial cavity which has two orthogonal polarization modes. Two orthogonal polarization modes will couple together through either coherent or incoherent interaction. Recently, the temporal cavity solitons in the externally pumped nonlinear fiber ring cavities have received much attention. As a nonlinear cavity, in principle temporal cavity solitons should also can be generated in fiber laser cavity. In this thesis, I'll focus on the study of cavity solitons in fiber laser. First of all, inspired by modulation instability induced by cavity boundary conditions in the externally pumped nonlinear fiber ring cavities, the cavity induced modulation instability (CIMI) is both theoretically and experimentally confirmed existing in a fiber ring laser. ClMI origins from the cavity detuning. It's theoretically shown that when the total cavity phase delay (linear phase delay with nonlinear phase delay) is not 2mn, the non-zero cavity detuning will cause a new type of modulation instability. Compare with the traditional modulation instability appeared in single mode fibers, CIMI can occur both in normal and anomalous dispersion regime, and the modulation frequency is related with the cavity detuning. In experiment, we studied the ClMl lasing state of fiber laser. Stable periodical pulse train emjssion can be achieved, whose repetition rate can be altered by either tuning the cavity or changing the light intensity. The experimental results match well with theoretical conclusions. CIMI makes the fiber laser as a promising pulse source with tunable repetition rate, without any external modulation methods. Under the CIMI induced pulse train emission state, if increasing the light intensity, we experimentally found the pulse train will be finally shaped into dissipative solitons. Through numerical simulate the operation of fiber laser, the gain bandwidth limitation plays a key role in the shaping mechanism. Under sufficient narrow gain bandwidth limitation, the CIMI modulated CW beam can evolve into dissipative solitons. We named this kind of spontaneously generated solitons as the temporal cavity solitons in fiber laser, which distinguish from the previously reported solitons in the mode-locked fiber lasers, nevertheless they are experimentally found having similar properties. The vector temporal cavity solitons are also experimentally observed. In an anomalous dispersive fiber laser, the induced vector solitons under either coherent or incoherent coupling between two polarization modes are observed. The numerical simulation also supports the experimental conclusion. The coherently coupled vector solitons are also observed in the normal dispersive fiber laser. The coherent energy exchange between vector solitons is first time experimentally observed in normal dispersion regime. In the vector fiber laser cavity, the temporal cavity solitons will be coupled with the light on their orthogonal polarization. Under the incoherent coupling, when the cavity birefringence is strong, an interesting phenomenon call "soliton-dark pulse pair" is experimentally observed. It can be interpreted as an extreme case of polarization domain formation, where one polarization mode are bright solitons. On the other hand, under weak birefringence and coherent coupling, a novel state of induced dark solitons is experimentally observed. Through numerical simulation, it finds that the formation of induced dark solitons is due to the coherent coupling between soliton and a dark pulse with phase jump. Without phase jump, a bright soliton will be induced instead In the research of dark solitons, an interesting phenomenon of dark envelope emission of a fiber ring laser is discussed. When a high frequency modulation and a dark-soliton-like dark pulse coexist in a fiber laser, they will be shaped into a high repetition rate dark pulse train and a dark soliton, respectively. Due to the superposition of their optical fields , the narrow dark soliton will form a wide dark envelope embedded in the dark pulse train background. The formed dark envelope makes the narrow dark soliton easily detectable. This finding brings a new understanding on the dark soliton formation in fiber lasers, especially on their experimental detection. Based on this understanding , the formation mechanism of the experimentally observed bright-dark vector solitons also becomes clear. In a weak birefringence cavity fiber laser, as a result of the strong coherent coupling between the two orthogonal polarization components, either the phase locked bright-bright vector cavity solitons or the bright-dark vector cavity solitons will be formed, which type of the vector cavity solitons will be formed depends on the phase relationship between the solitons. The coherent polarization coupling could lead to novel types of vector solitons formation.Doctor of Philosophy (EEE
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