X-ray Absorption Fine Structure and X-ray Excited Optical Luminescence Studies of One-dimensional Nanomaterials

One dimensional nanomaterials have attracted extensive attention in recent years due to their superior electrical, optical, mechanical and chemical properties compared to their bulk counterparts. In this thesis, electronic structure and optical properties of three types of nanomaterials are investigated using synchrotron based X-ray absorption spectroscopy: X-ray absorption fine structure (XAFS) and X-ray excited optical luminescence (XEOL). Si nanowire arrays are synthesized using electroless chemical etching, and coated with platinum and gold nanoparticles. The interaction between metal nanoparticles and the nanowire substrate is investigated using X-ray absorption near-edge structure (XANES). The luminescence properties of thermally oxidized Si nanostructures, such as Si nanowires, porous Si nanowires, and porous Si are comparatively studied. Using XEOL in combination with XANES, luminescence from defect centers in SiO2 and from Si/SiO2 interface can be distinguished. Electronic structure and luminescence of silicon carbide micro- and nanostructures of different crystal structures (polytypes) are investigated. Although hexagonal and cubic SiC have similar electronic structures locally, they exhibit different luminescence properties. It is found that all SiC samples have a same defect emission regardless of crystal size and structure. Additional luminescence bands are observed when oxide is present. Cubic SiC has two luminescence bands, originated from SiC and surface native SiO2, respectively. SiC nanowires also exhibit quantum confined band gap luminescence. As for boron nitride nanotubes, the presence of oxygen atoms in BN lattice alters the luminescence significantly by introducing a new defect center. The presence of oxygen impurities results in an intense signal revealed by XANES which is associated with B-O bonding, but no noticeable difference is seen in XANES at N site

Luminescence from TiO2 Nanotubes and Related Nanostructures Investigated Using Synchrotron X-Ray Absorption Near-Edge Structure and X-Ray Excited Optical Luminescence

Understanding the optical property of nanostructured TiO2 is crucial for their use in a variety of applications such as solar cells, photocatalysis, and light emitting devices. Herein, we introduce the use of synchrotron radiation-based spectroscopic techniques: X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) in analyzing the luminescence properties of anodized TiO2 nanotubes (TiO2 NT) and related materials. A description on the spectroscopic technique is first given, including conventional XANES-XEOL combined analysis and a more recently developed 2D XANES-XEOL probing technique. We then discuss several examples of analyzing the luminescence mechanism of TiO2 NT using XANES and XEOL technique, which are the phase transformation accompanied luminescence, luminescence from TiO2 NT hierarchical structure, and metal particle–coated TiO2 NT

Analysis of complex movements

In most everyday repetitive movements such as walking, sitting, and reaching, humans exhibit large degrees of regularity. However, at the other end of the movement spectrum, in complex movement tasks, such as retrieving an object from a cluttered environment or choosing balance positions for transporting a large, unwieldy object, humans are inventive problem solvers. Therefore, in the quest to understand the human movement system, it would be essential to know if general movements have regularities across subjects as it would provide an essential scaffold in the development of more detailed dynamic movement models. This research mainly aims to learn the principles behind large-scale arbitrary movements, particularly regarding variations between different subjects. For example, given a goal-directed task, do the movements appear similar across subjects, or are movements very individualized? The tasks for the research covers developing an interactive virtual reality environment to capture goal-directed whole-body human movements, getting insights into the regularities underlying those motion capture data (kinematics), and finally analyzing the corresponding energy cost by using a forty-eight degree of freedom dynamic human model (dynamics). The results illustrate that humans chose trajectories that are economical in energetic cost while accomplishing goal-directed tasks.Computer Science

Dynamical and finite-size effects on the signal of first-order phase transition

We study the dynamical behaviors of the criterion identifying the first-order phase transition in the matter generated by the relativistic heavy-ion collisions, by explicitly involving the dynamical effects based on the Fokker-Plank framework. The perspectives we taken into account range from phase transition scenarios, initial temperatures, volume effect, relaxation rates, and evolution trajectories. Our numerical calculations show that the dynamical signal of the first-order phase transition can be reserved in certain conditions. Besides the delaying effects due to a finite relaxation time, a larger initial temperature, a smaller volume, a larger relaxation rate, or bending of the trajectory will lead to reduction of the signal. Our discussions on the criterion offer valuable reference information for the experimental detection of the first-order phase transition signal.Comment: 9 pages, 7 figure

Immunomodulatory activity of carboxymethyl pachymaran on immunosuppressed mice induced by cyclophosphamide

The effects of immunomodulatory activity of two types of carboxymethyl pachymaran (CMP-1 and CMP-2) on cyclophosphamide (CTX)-induced mice were investigated. Both CMP-1 and CMP-2 were found to restore the splenomegaly and alleviate the spleen lesions and the mRNA ex-pressions of TLR4, MyD88, p65 and NF-κB in spleen were also increased. CMP-1 and CMP-2 could enhance the immunity by increasing the levels of TNF-α, IL-2, IL-6, IFN-γ, Ig-A and Ig-G in serum. In addition, CMP-1 could increase the relative abundance of Bacteroidetes and reduce the relative richness of Firmicutes at the phylum level. CMP-1 and CMP-2 could reduce the relative abundance Erysipelatoclostridum at the genus level. CMP-1 and CMP-2 might enhance the immune function of immunosuppression mice by regulating the gene expression in the TLR4/NF-κB signaling pathway and changing the composition and abundance of the intestinal microbiota. The results suggested that CMP-1 and CMP-2 would be as potential immunomodulatory agents in functional foods

Involvement of Mast Cells in the Pathophysiology of Pain

Mast cells (MCs) are immune cells and are widely distributed throughout the body. MCs are not only classically viewed as effector cells of some allergic diseases but also participate in host defense, innate and acquired immunity, homeostatic responses, and immunoregulation. Mounting evidence indicates that activation of MCs releasing numerous vasoactive and inflammatory mediators has effects on the nervous system and has been involved in different pain conditions. Here, we review the latest advances made about the implication of MCs in pain. Possible cellular and molecular mechanisms regarding the crosstalk between MC and the nervous system in the initiation and maintenance of pain are also discussed

The Fas/Fap-1/Cav-1 Complex Regulates IL-1RA Secretion in Mesenchymal Stem Cells to Accelerate Wound Healing

Mesenchymal stem cells (MSCs) are capable of secreting exosomes, extracellular vesicles, and cytokines to regulate cell and tissue homeostasis. However, it is unknown whether MSCs use a specific exocytotic fusion mechanism to secrete exosomes and cytokines. We show that Fas binds with Fas-associated phosphatase–1 (Fap-1) and caveolin-1 (Cav-1) to activate a common soluble N-ethylmaleimide–sensitive factor (NSF) attachment protein receptor (SNARE)–mediated membrane fusion mechanism to release small extracellular vesicles (sEVs) in MSCs. Moreover, we reveal that MSCs produce and secrete interleukin-1 receptor antagonist (IL-1RA) associated with sEVs to maintain rapid wound healing in the gingiva via the Fas/Fap-1/Cav-1 cascade. Tumor necrosis factor–α (TNF-α) serves as an activator to up-regulate Fas and Fap-1 expression via the nuclear factor κB pathway to promote IL-1RA release. This study identifies a previously unknown Fas/Fap-1/Cav-1 axis that regulates SNARE-mediated sEV and IL-1RA secretion in stem cells, which contributes to accelerated wound healing

Advances in Application of Nanomaterials in Life Science

Nanomaterials had attracted much attention since their discovery with their unique structure, peculiar physical,chemical, mechanical properties and potential application prospects. In the past few years, the theoretical andexperimental research on biological nanomaterials has become the focus of attention, especially the biochemistry,biophysics, biomechanics, thermodynamics and electromagnetism of nucleic acid and protein, while its intelligentcomposites have become the forefront of life science and materials science. At present, nano-bio-chip materials,biomimetic materials, nano-motors, nanocomposites, interface biomaterials, nano-sensors and drug delivery systemshave made great progress. In this paper, the characteristics of these materials, research and development of theapplication were reviewed, a brief overview of the nano-materials in the life sciences of the main applications, and toexplore the development prospects of biological nano-materials