Identification and Characterization of a LIF-STAT3/Activin-Smad2/3 Dual Responsive Pluripotent Stem Cell State

The medical and bioindustrial applications of pluripotent stem cells rely on our understanding of their biology. Pluripotent stem cell lines derived from embryos in different stages depend on distinct signalling pathways. Embryonic stem cells (ESCs), derived from the inner cell mass (ICM) of preimplantation embryos, are dependent on LIF/STAT3 signalling, while epiblast stem cells (EpiSCs), established from the postimplantation embryos, require Activin A/Smad2/3 signalling. Recent studies revealed the presence of intermediate pluripotent stem cell populations. Their growth factor responsiveness, gene expression pattern and associated chromatic signatures, are compatible with the state intermediate between ESCs and EpiSCs. However, it remains unknown whether such cell populations represent a stable clonally intermediate cell state. In this thesis, I describe the discovery and characterization of novel stem cell lines displaying gene expression pattern intermediate between ESCs and EpiSCs. These cells respond to LIF/STAT3 as well as Activin/Smad2/3 signalling at single cell level. They can integrate into the ICM and generate chimeric embryos. In keeping with a more advanced differentiation stage than that of ESCs, the LIF/Activin dual responsive stem cells showed accelerated temporal gene expression kinetics during in vitro differentiation in embryo bodies. I found that these properties are shared by some induced pluripotent stem cell (iPSC) lines. The notion of an intermediate state was consolidated by a genome-wide microarray profiling. The hierarchical clustering analysis grouped LIF/Activin dual responsive stem cells together into a cluster intermediate between ESCs and EpiSCs. These findings advanced our understanding of the regulation of pluripotency. A better understanding of distinct differentiation state of pluripotent stem cells and their signalling responsiveness is crucial for developing tailored strategies for lineage/cell type differentiation

Bootstrapping 2D CFTs in the Semiclassical Limit

We study two dimensional conformal field theories in the semiclassical limit. In this limit, the four-point function is dominated by intermediate primaries of particular weights along with their descendants, and the crossing equations simplify drastically. For a four-point function receiving sufficiently small contributions from the light primaries, the structure constants involving heavy primaries follow a universal formula. Applying our results to the four-point function of the $\mathbb Z_2$ twist field in the symmetric product orbifold, we produce the Hellerman bound and the logarithmically corrected Cardy formula that is valid for $h \geq c/12$.Comment: 32 pages, 7 figures. v2, v3: references added, minor clarification

Carving Out the End of the World or (Superconformal Bootstrap in Six Dimensions)

We bootstrap ${\cal N}=(1,0)$ superconformal field theories in six dimensions, by analyzing the four-point function of flavor current multiplets. Assuming $E_8$ flavor group, we present universal bounds on the central charge $C_T$ and the flavor central charge $C_J$. Based on the numerical data, we conjecture that the rank-one E-string theory saturates the universal lower bound on $C_J$, and numerically determine the spectrum of long multiplets in the rank-one E-string theory. We comment on the possibility of solving the higher-rank E-string theories by bootstrap and thereby probing M-theory on AdS${}_7\times{\rm S}^4$/$\mathbb{Z}_2$.Comment: 59 pages, 10 figures, 4 tables; v2-v5: typos corrected, references adde

A PROFESSIONAL COMPETENCE EVALUATION SYSTEM FOR COLLEGE STUDENT

[[conferencetype]]國際[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]青海省西寧市, 中

Exergy Analysis and Exergoeconomic Analysis of An Ethylene Process

[[abstract]]This paper presents the results of exergy analysis and exergoeconomic analysis for an ethylene process and its auxiliary refrigeration system. The exergy analysis results indicate that the exergetic efficiencies of the demethanization and the debutanization sections are the lowest. On the other hand, the exergoeconomic analysis results indicate that the increase of the unit thermoeconomic cost of the compression section and the demethanization section are the highest. This study demonstrates that exergoeconomic analysis can provide extra information than exergy analysis and the results from exergoeconomic analysis provide cost-based information suggesting potential locations for process improvement.[[notice]]補正完畢[[incitationindex]]E

CFD study of heat transfer enhanced membrane distillation using spacer-filled channels

[[abstract]]Membrane distillation (MD) can utilize low level thermal energy and holds high potential to replace conventional energetically intensive separation technologies. Direct contact membrane distillation (DCMD) is suitable for the applications of desalination and concentration of aqueous solutions. Employing spacer-filled channels can enhance the mass flux of the DCMD modules, which can further result in the increase of energy utilization efficiency of the separation. The trans-membrane mass flux is controlled by the boundary layer heat transfer of both fluid channels. The estimation of heat transfer coefficients is critical to the analysis and design of MD modules. This paper presents the results of a comprehensive 3-D computational fluid dynamics (CFD) simulation which covers the entire length of the module and takes into account the trans-membrane heat and mass transfer. The model was verified with experimental data in the literature. The contour maps show that spacers create high velocity regions in the vicinity of the membrane. The trans-membrane heat and mass fluxes both show fluctuating patterns corresponding to the repetitive structure of the spaces and the fluxes are much higher than that of the modules using empty channels. The heat transfer coefficient enhancement factors obtained from CFD simulation are significantly higher than the predictions from literature correlations. The model can serve as an effective tool for developing correlations of heat transfer coefficients and optimal design of spacer-filled MD modules.[[sponsorship]]Masdar Institute of Science and Technology[[incitationindex]]EI[[conferencetype]]國際[[conferencedate]]20150328~20150331[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Abu Dhabi, United Arab Emirate