Confronting Tracker Field Quintessence with Data

We confront tracker field quintessence with observational data. The potentials considered in this paper include $V(\phi)\propto\phi^{-\alpha}$, $\exp(M_{p}/\phi)$, $\exp(M_{p}/\phi)-1$, $\exp(\beta M_{p}/\phi)$ and $\exp(\gamma M_{p}/\phi)-1$; while the data come from the latest SN Ia, CMB and BAO observations. Stringent parameter constraints are obtained. In comparison with the cosmological constant via information criteria, it is found that models with potentials $\exp(M_{p}/\phi)$, $\exp(M_{p}/\phi)-1$ and $\exp(\gamma M_{p}/\phi)-1$ are not supported by the current data.Comment: 16 pages, 3 figure

\u3cem\u3eIn vitro\u3c/em\u3e surface reaction layer formation and dissolution of calcium phosphate cement – bioactive glass composites

Composites of hydrated calcium phosphate cement (CPC) and bioactive glass (BG) containing Si were immersed in vitro to study the effect of chemical composition on surface reaction layer formation and dissolution/precipitation behavior. The solutions used were 0.05M tris hydroxymethyl aminomethane/HCl (tris buffer), tris buffer supplemented with plasma electrolyte (TE) with pH 7.4 at 37°C, and this solution complemented with 10% newborn bovine serum (TES). The post-immersion solutions were analyzed for changes in Ca, PO4 and Si concentrations. The reacted surfaces were analyzed using Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX). The sample weight variations after immersion were also determined. The results showed that the composition of the bioactive composite CPCs greatly affected their behavior in solution and the formation of apatite bioactive surface reaction layers. After immersion in TE solution, Ca ions were taken up by all samples during the entire immersion duration. Initially, the P ion concentration increased sharply, and then decreased. This reaction pattern reveals the formation of an amorphous calcium phosphate layer on the surface of these composite calcium phosphate cements. FTIR revealed that the layer was, in fact, poorly crystallized Ca-deficient carbonate apatite. The thickness of the layer was 12-14 μm and was composed of rod-like apatite with directional arrangement. For immersion in TES solution, the Ca and Si ion concentrations showed a similar behavior as that in TE, but the release rate of Si ion was higher. FTIR revealed that after TES immersion, not only did the typical, poorly crystallized, Ca-deficient carbonated apatite form, as it did in TE, but that the serum proteins co-adsorbed on the surface and thereby affected the surface reaction layer formation. A thinner apatite layer was formed and was composed of a micro-porous layer comprising rounded particles in a glue-like appearing matrix. The addition of BG to the calcium phosphate cements to create composite calcium phosphate cements obviously is at the basis of this altered behavior of the cements. All data combined are useful for the design and optimization of degradable implant materials for use in bone tissue repair and regeneration procedures

Fabrication of GaN-Based White Light-Emitting Diodes on Yttrium Aluminum Garnet-Polydimethylsiloxane Flexible Substrates

This study concerns the characteristics of white GaN-based light-emitting diode (LED) on flexible substrates. The thin film GaN-based blue LEDs were directly transferred from sapphire onto the flexible polydimethylsiloxane (PDMS) substrates by laser lift-off (LLO) process. The PDMS substrates were incorporated 10–40% cerium doped yttrium aluminum garnet phosphor, YAG:Ce3+, and formed the GaN-based white LEDs. The white LEDs prepared by the GaN-based LEDs on the YAG-PDMS substrates reveal one peak at 470 nm corresponding to the emission of the GaN-based LED and a broadband included five weak peaks caused by YAG:Ce3+ phosphors

The Role of Human Blood-Vessel-Derived Stem Cells in Tissue Repair and Regeneration

Multipotent stem/progenitor cells have been identified in nearly all vascularized organs in the human body. Our research group recently discovered that human blood vessels harbor various stem/progenitor cell populace of mesodermal lineage, exhibiting common multi-lineage differentiation capacity and yet distinct cell lineage markers. Specifically, each of the three structural layers of blood vessels: intima, media, and adventitia, have been found to respectively include one of the three populations of precursor cells: myogenic endothelial cells (MECs), pericytes, and adventitial cells (ACs). Our studies have independently characterized each of “Three Musketeers” and evaluated their myogenic capacity. Nevertheless, the therapeutic potential of pericytes in cardiac repair remains unknown, and whether pericytes natively residing in human heart possess similar stem cell characteristics and multipotency has not been investigated. Moreover, none of our prior studies has directly compared the regenerative efficacy between subpopulations of blood-vessel-derived stem cells (BVSCs), nor did we explore any alternative source, other than fresh tissue biopsies, to isolate BVSCs. My dissertation study aims to understand the role of subpopulations of BVSCs, pericytes in particular, and their relative efficiency in tissue repair/regeneration, with emphases in myocardial infarction and skeletal muscle injury. Specifically, my work has three independent yet related focuses: (I) to investigate the therapeutic efficacy of human pericyte transplantation and associated mechanisms of action in ischemic heart repair; (II) to characterize native human heart pericytes and examine whether tissue specificity exists between pericytes of different tissue origins; (III) to directly compare the myogenic potential between subpopulations of BVSCs and explore alternative source(s) of BVSCs that are more clinically accessible for skeletal muscle repair. The results of my studies showed that transplantation of human skeletal muscle-derived pericytes (SkMPs) repair the infarcted hearts more effectively than control and myoblast groups with their multiple restorative effects under hypoxia, including angiogenesis, anti-fibrosis, and anti-inflammation. Resident human heart pericytes (HPs) shared common similarity with pericytes of other tissues, such as typical pericyte and MSC marker expression, cell growth pattern in culture, and certain mesodermal developmental potential. Nevertheless, HPs differ from SkMPs in the lack of skeletal myogenic potential and differential angiogenic response under hypoxia, tissue-specific phenomena that were not observed previously. Additionally, in terms of skeletal myogenesis, MECs demonstrated superior efficiency to pericytes in vitro and in vivo. Finally, MECs and pericytes purified from long-term cryopreserved primary human muscle culture by cell sorting exhibited similar myogenic potential in vivo to their counterparts isolated from fresh biopsies, indicating cryopreservation of unpurified cells may serve as an alternative source of therapeutic myogenic precursors