Experimental and Theoretical Analysis of Cracking Moment of Concrete Beams Reinforced with Hybrid Fiber Reinforced Polymer and Steel Rebars

This study aims at experimentally and theoretically investigating the cracking moment (Mcrc) of hybrid Fiber Reinforced Polymer (FRP)/steel Reinforced Concrete (RC) beams. Six hybrid Glass FRP (GFRP)/steel and three GFRP RC beams with various GFRP and steel reinforcement ratios are tested in four-point bending scheme. Experimental results indicate that both GFRP and steel rebars affect Mcrc, but the effect of steel reinforcement is more significant. When the steel reinforcement ratio increases to 1.17%, Mcrc goes up to 15.9%, while the same value for GFRP is only 9.7%. An analytical method is proposed based on the plain section assumption and nonlinear behavior of materials for estimating Mcrc. The proposed model shows a good agreement with the experimental data conducted in this study and collected from the literature. The results of the parametric study give evidence of the positive effects of hybrid reinforcement ratios and elastic modulus of FRP on Mcrc of hybrid RC beams

Invariant mRNA and mitotic protein breakdown solves the Russian Doll problem of the cell cycle

It has been proposed that cyclical gene expression occurs at a large number of different times during the cell cycle. The existence of a large number of cycle‐specific variations in mRNA and protein during the eukaryotic cell cycle raises the problem of how cell‐cycle variations are regulated. This is the “infinite regression” or Russian Doll problem where postulating a cell‐cycle specific control element pushes the explanation of cell‐cycle variation back one step to the problem of how that control element varies during the cell cycle. PCR studies on unperturbed cells indicate Cyclin mRNA content is invariant during the cell cycle. Furthermore, calculations reveal that variations in mRNA content do not account for observed protein variations. Continuous and constant gene expression during the cell cycle, continuous protein accumulation, and protein breakdown only within the mitotic window solves the Russian Doll problem or infinite regression problem. These results, and theoretical ideas support an alternative view of the cell cycle where many of the proposed control systems do not exist.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96423/1/j.cellbi.2008.10.004.pd

Cancer-Stem-Cell-Like, Wnt/TCF Responsive Cells Are Activated by Pax8 PPAR? Fusion Protein.

Pax8 PPARγ Fusion Protein (PPFP) occurs in ~35% of follicular thyroid carcinoma cases. Expression of PPFP in the non-transformed rat thyroid cell line PCCL3 conferred on the cells the ability to invade through matrigel and to form colonies in anchorage independent conditions. PPFP also increased the percentage of cells that have activated β-catenin/TCF. We transduced control and PPFP-expressing PCCL3 thyroid cell lines with two different β-catenin/TCF-GFP reporter systems. PPFP expressing cell lines contained more than twice the percent of GFP positive cells compared to control cell lines. A hierarchy existed within the cell lines based on the TCF activation status. A single TCF_GFP+ cell generated a clonal population containing both GFP+ and GFP- cells, whereas clonal populations derived TCF_GFP- cells remained GFP-. Single cells sorted by TCF status demonstrated that very few TCF_GFP- cells can generate any TCF_GFP+ cells. The TCF responsive cells exhibited increased proliferative potential and invasive capacity. GFP+ cells were twice as enriched for anchorage independent colony forming cells than GFP cells. More strikingly, GFP positive clones were 5-10 times more invasive than negative clones, which exhibited the same invasive potential as control cells. The hierarchy and more transformed phenotype of TCF responsive cells indicate that they have the in vitro properties of cancer stem cells. Full agonists of PPARγ further increased the effects of PPFP. The β-catenin/TCF population in PPFP expressing cells increased again while similarly treated empty vector control cells were unaffected. Invasion was also increased by the PPARγ agonists. The effects were blocked by PPARγ antagonists, demonstrating PPARγ specificity. Selective PPARγ agonists which only activate a fraction of the PPARγ effects also increased the effects of PPFP. We could then assume that the adipogenic pathways activated by full agonists but not selective PPARγ agonists did not contribute to PPFP oncogenesis. These data suggested that PPFP acts via its PPARγ domains to expand the Wnt/TCF active cell fraction and that these cells have the properties of cancer stem cells. The pathways by which PPFP effect oncogenesis are activated by both full and partial PPARγ agonists.PHDCellular & Molecular BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/97940/1/vudang_1.pd

Concrete beams using seawater and sea sand reinforced with steel and GFRP rebars exposed to marine environment: An experimental study

Using fresh water and river sand in concrete mix composition makes a lot of negative impacts on resources and the environment while the source of sea sand and sea water is abundant and less harmful to the environment. However, sea sand and seawater in concrete can cause severe corrosion of the reinforcement, reducing the durability and bearing capacity of the structure. This paper illustrates the results of a comparative study on the flexural behavior of six corroded seawater sea-sand concrete (SWSSC) beams. The corrosion process of two concrete beams reinforced with traditional steel bars and four concrete beams reinforced with a combination of glass fiber reinforced polymer (GFRP) and steel bars was coupled by the effect of seawater exposure and sustained load. It was found that after exposure to a marine environment during the period of 60 months the GFRP bar retains surface integrity, meanwhile, the steel bars were significantly corroded with a cross-sectional area loss of approximately 13.93%. The decrease in bending stiffness, yield load, and ultimate load of the RC beams was found due to the deterioration of SWSSC and corrosion of steel bars.

Concrete beams using seawater and sea sand reinforced with steel and GFRP rebars exposed to marine environment: An experimental study

Using fresh water and river sand in concrete mix composition makes a lot of negative impacts on resources and the environment while the source of sea sand and sea water is abundant and less harmful to the environment. However, sea sand and seawater in concrete can cause severe corrosion of the reinforcement, reducing the durability and bearing capacity of the structure. This paper illustrates the results of a comparative study on the flexural behavior of six corroded seawater sea-sand concrete (SWSSC) beams. The corrosion process of two concrete beams reinforced with traditional steel bars and four concrete beams reinforced with a combination of glass fiber reinforced polymer (GFRP) and steel bars was coupled by the effect of seawater exposure and sustained load. It was found that after exposure to a marine environment during the period of 60 months the GFRP bar retains surface integrity, meanwhile, the steel bars were significantly corroded with a cross-sectional area loss of approximately 13.93%. The decrease in bending stiffness, yield load, and ultimate load of the RC beams was found due to the deterioration of SWSSC and corrosion of steel bars.

Experimental study of short concrete columns reinforced with GFRP bars under monotonic loading

The glass fiber reinforced polymer (GFRP) bars are considered as an alternative reinforcement to steel in concrete structures subjected to chloride environment because of their non- corrosive and non-magnetic properties. To examine the applicability of GFRP bars to performance of concrete columns, this work was conducted. The effect of the compressive reinforcement ratio and stirrup spacing on the load carrying capacity of concrete columns reinforced with GFRP bars is experimentally investigated. Nine short concrete columns with dimensions of 150 × 150 × 600 mm were cast and tested until failure under displacement-controlled concentric loading. The experimental results demonstrated that by increasing the reinforcement ratio from 0.37% to 3.24%, the load-bearing capacity of GFRP RC columns was found to increase by an average of 28%. Moreover, the tested results confirmed that the GFRP stirrup spacing had a significant influence on the load-carrying capacity of the columns