Evaluation of bubble removing Performance in a TV glass furnace : Part 2. Verification using real furnace data

In part 2, a furnace for melting TV panel glass is studied to examine the effectiveness of the Simulator developed by the authors. Because panel glass is used as a part of a cathodic ray tube where the TV image is projected and its defect is easily recognizable, bubble-free glass quality is defmitely required. If the bubble quality becomes worse, a heap of rejected products is piled up, which leads to tremendous economical loss. In order to avoid such trouble designing and operating a TV glass furnace and inspecting glass quality are conducted with great care, and therefore, lots of field data have been accumulated so far. Accordingly, it is meaningful to utilize a TV glass furnace to verify the effectiveness of such simulating technology. The values and phenomena predicted by the Simulator and the data having been observed in real furnaces were found to be in reasonable agreement. Therefore, it may be concluded that the proposed Simulator is useful as a method of scale-up and trouble-shooting for glass furnaces

Significance of redox reactions in glass refining processes

The role of the redox reactions due to refining agents in the glass refining processes was examined. Α new approximate model for shrinkage (or growth) of gas bubbles in glassmelts in which redox reactions caused by refining agents were taken into account was developed. The proposed model is a modification of the quasi-stationary model by which the redox reactions due to refining agents can not be considered. It was found that the shrinkage (or growth) of gas bubbles in melts with refining agents is quite faster than that in those without refining agents. Numerical results for single-component and multicomponent gas bubbles indicate that the mechanism of the bubble shrinkage (or growth) in the refining process is significantly controlled by the oxidation of refining agents, which decreases (or increases) the oxygen concentration in the glassmelt and as a result causes the rapid oxygen transfer across the bubble/glassmelt Interface and hence the fast shrinkage (or growth) of the gas bubble. The applicability of the proposed model was examined using the computational results and experimental measurements in the literature. It was also found that the proposed model provides better predictions compared with the quasi-stationary model

Evaluation of bubble removing Performance in a TV glass furnace : Part 1. Mathematical formulation

The bubble evolution and dissolution process in a glass furnace is an extremely complicated physico-chemical phenomenon. Most of the huge number of bubbles, generated in molten glass during the decomposition of the glass batch, are removed during the trajectory from the charging end to the forming section, but some remain in fmal products. On the basis of the two mechanisms, flotation and absorption, in the bubble removing process, a numerical Simulator was developed to evaluate the influence of first, glass and batch composition, including refining agents, second, geometrical tank design and third, furnace operating conditions upon the bubble quality in products. In particular, the Simulator enabled the estimation of the effect of refining gases which are caused by decomposition of the refining agents. Furthermore, an index was devised to synthetically assess the numbers of bubbles in final products. In part 1, the principles of the model which composes the Simulator are described in mathematical formulation. The basic equations with boundary conditions and calculation procedures for thermal flow of molten glass, gas concentration in glass melt and gas evolvement from the refining agents are presented. The calculation strategy of the bubble removing process is also described

Modeling of bubble removal from glassmelts at fining temperatures

Α new model based on the quasi-stationary approximation is developed for removal of gas bubbles from glassmelts due to buoyant rise of bubbles. The growth and rising of multicomponent gas bubbles in glassmelts are examined from the view point of interfacial mass transfer. It is shown that the models for rising bubbles in glassmelts available in the literature are based on the quasi-steady approximation which is not very reasonable. The growth of a gas bubble initially consisting of nitrogen only is studied in a glassmelt whose diffusing gases are oxygen, water, carbon dioxide, sulfide and nitrogen. The proposed model based on the unsteady-state mass transfer (the quasi-stationary approximation) is compared with the model based on the steady-state mass transfer (the quasisteady approximation). The former, which provides more rational and better descriptions of bubble behavior in refming processes compared with the latter, predicts rather shorter refming times than the latter

Evaluation of reaction rate of refining agents

To elucidate the thermal decomposition behavior of antimony oxide which is added to promote (re)fming of bubbles in TV glass, an evolved gas analysis (EGA) was conducted using a newly designed device for detecting the gases from the glass batch at increasing temperatures. Furthermore, a mathematical formulation was made to describe the above behavior. From the results of the EGA measurements, three parameters, which govern the reaction rate constant, viz. reaction order, activation energy and frequency factor, were decided. By coupling this mathematical model and the thermal fluid model of glass melts in tank furnaces, it is possible to simulate the conditions of generating refming oxygen in the furnace

Identification of a novel intronic enhancer responsible for the transcriptional regulation of musashi1 in neural stem/progenitor cells

<p>Abstract</p> <p>Background</p> <p>The specific genetic regulation of neural primordial cell determination is of great interest in stem cell biology. The Musashi1 (Msi1) protein, which belongs to an evolutionarily conserved family of RNA-binding proteins, is a marker for neural stem/progenitor cells (NS/PCs) in the embryonic and post-natal central nervous system (CNS). Msi1 regulates the translation of its downstream targets, including <it>m-Numb </it>and <it>p21 </it>mRNAs. <it>In vitro </it>experiments using knockout mice have shown that Msi1 and its isoform Musashi2 (Msi2) keep NS/PCs in an undifferentiated and proliferative state. Msi1 is expressed not only in NS/PCs, but also in other somatic stem cells and in tumours. Based on previous findings, Msi1 is likely to be a key regulator for maintaining the characteristics of self-renewing stem cells. However, the mechanisms regulating <it>Msi1 </it>expression are not yet clear.</p> <p>Results</p> <p>To identify the DNA region affecting <it>Msi1 </it>transcription, we inserted the fusion gene <it>ffLuc</it>, comprised of the fluorescent <it>Venus </it>protein and firefly <it>Luciferase</it>, at the translation initiation site of the mouse <it>Msi1 </it>gene locus contained in a 184-kb bacterial artificial chromosome (BAC). Fluorescence and Luciferase activity, reflecting the <it>Msi1 </it>transcriptional activity, were observed in a stable BAC-carrying embryonic stem cell line when it was induced toward neural lineage differentiation by retinoic acid treatment. When neuronal differentiation was induced in embryoid body (EB)-derived neurosphere cells, reporter signals were detected in Msi1-positive NSCs and GFAP-positive astrocytes, but not in MAP2-positive neurons. By introducing deletions into the BAC reporter gene and conducting further reporter experiments using a minimized enhancer region, we identified a region, "D5E2," that is responsible for <it>Msi1 </it>transcription in NS/PCs.</p> <p>Conclusions</p> <p>A regulatory element for <it>Msi1 </it>transcription in NS/PCs is located in the sixth intron of the <it>Msi1 </it>gene. The 595-bp D5E2 intronic enhancer can transactivate <it>Msi1 </it>gene expression with cell-type specificity markedly similar to the endogenous Msi1 expression patterns.</p

A sperm-activating peptide controls a cGMP-signaling pathway in starfish sperm☆

AbstractPeptides released from eggs of marine invertebrates play a central role in fertilization. About 80 different peptides from various phyla have been isolated, however, with one exception, their respective receptors on the sperm surface have not been unequivocally identified and the pertinent signaling pathways remain ill defined. Using rapid mixing techniques and novel membrane-permeable caged compounds of cyclic nucleotides, we show that the sperm-activating peptide asterosap evokes a fast and transient increase of the cGMP concentration in sperm of the starfish Asterias amurensis, followed by a transient cGMP-stimulated increase in the Ca2+ concentration. In contrast, cAMP levels did not change significantly and the Ca2+ response evoked by photolysis of caged cAMP was significantly smaller than that using caged cGMP. By cloning of cDNA and chemical crosslinking, we identified a receptor-type guanylyl cyclase in the sperm flagellum as the asterosap-binding protein. Sperm respond exquisitely sensitive to picomolar concentrations of asterosap, suggesting that the peptide serves a chemosensory function like resact, a peptide involved in chemotaxis of sperm of the sea urchin Arbacia punctulata. A unifying principle emerges that chemosensory transduction in sperm of marine invertebrates uses cGMP as the primary messenger, although there may be variations in the detail

RNA-Binding Protein Musashi1 Modulates Glioma Cell Growth through the Post-Transcriptional Regulation of Notch and PI3 Kinase/Akt Signaling Pathways

Musashi1 (MSI1) is an RNA-binding protein that plays critical roles in nervous-system development and stem-cell self-renewal. Here, we examined its role in the progression of glioma. Short hairpin RNA (shRNA)-based MSI1-knock down (KD) in glioblastoma and medulloblastoma cells resulted in a significantly lower number of self renewing colony on day 30 (a 65% reduction), compared with non-silencing shRNA-treated control cells, indicative of an inhibitory effect of MSI1-KD on tumor cell growth and survival. Immunocytochemical staining of the MSI1-KD glioblastoma cells indicated that they ectopically expressed metaphase markers. In addition, a 2.2-fold increase in the number of MSI1-KD cells in the G2/M phase was observed. Thus, MSI1-KD caused the prolongation of mitosis and reduced the cell survival, although the expression of activated Caspase-3 was unaltered. We further showed that MSI1-KD glioblastoma cells xenografted into the brains of NOD/SCID mice formed tumors that were 96.6% smaller, as measured by a bioluminescence imaging system (BLI), than non-KD cells, and the host survival was longer (49.3±6.1 days vs. 33.6±3.6 days; P<0.01). These findings and other cell biological analyses suggested that the reduction of MSI1 in glioma cells prolonged the cell cycle by inducing the accumulation of Cyclin B1. Furthermore, MSI1-KD reduced the activities of the Notch and PI3 kinase-Akt signaling pathways, through the up-regulation of Numb and PTEN, respectively. Exposure of glioma cells to chemical inhibitors of these pathways reduced the number of spheres and living cells, as did MSI1-KD. These results suggest that MSI1 increases the growth and/or survival of certain types of glioma cells by promoting the activation of both Notch and PI3 kinase/Akt signaling