Effects of Deicers on Concrete Deterioration

Concrete specimens were exposed to weekly cycles of wetting and drying in distilled water and in solutions of sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), and calcium magnesium acetate (CMA) with either a 6.04 molal ion concentration, equivalent in ion concentration to a 15% solution of NaCl, or a 1.06 molal ion concentration, equivalent in ion concentration to a 3% solution of NaCl, for periods of up to 95 weeks. Specimens were also exposed to air only. The effects of exposure were evaluated based on changes in the dynamic modulus of elasticity and the physical appearance of the specimens at the conclusion of the tests. Concretes exposed to distilled water and air show, respectively, an increase and a decrease in dynamic modulus of elasticity, due principally to changes in moisture content; overall, no negative impact on the properties of these specimens is observed. At lower concentrations, NaCl and CaCl2 have a relatively small negative impact on the properties of concrete. At high concentrations, NaCl has a greater but still relatively small negative effect. At low concentrations, MgCl2 and CMA can cause measurable damage to concrete. At high concentrations, CaCl2, MgCl2, and CMA cause significant changes in concrete that result in loss of material and a reduction in stiffness and strength

Evaluation of Multiple Corrosion Protection Systems and Stainless Steel Clad Reinforcement for Reinforced Concrete

The corrosion performance of multiple corrosion protection systems and stainless steel clad reinforcement is compared and evaluated in this study. Conventional steel and conventional epoxy-coated steel coated with 3M™ Scotchkote™ 413 Fusion Bonded Epoxy are used as “control” systems. The corrosion protection systems, which are compared to the control systems based on macrocell and bench-scale tests, include stainless steel clad reinforcement, conventional epoxycoated reinforcement cast in concrete containing one of three corrosion inhibitors (DCI-S, Rheocrete 222+, or Hycrete), epoxy-coated steel with the epoxy applied over a primer coat that contains microencapsulated calcium nitrite, epoxy-coated steel with the epoxy applied after pretreatment of the steel with zinc chromate to improve adhesion between the epoxy and the steel, epoxy-coated steel using improved adhesion epoxies developed by DuPont and Valspar, and multiple coated steel with a zinc layer underlying the DuPont 8-2739 Flex West Blue epoxy layer. Macrocell tests are conducted on bare bars and bars symmetrically embedded in a mortar cylinder. Bench-scale tests include the Southern Exposure, cracked beam, and ASTM G 109 tests. The results indicate stainless steel clad reinforcement exhibits very good corrosion performance when the cladding is intact. In uncracked mortar or concrete containing corrosion inhibitors, corrosion rates and losses are lower than observed using the same mortar and concrete with no inhibitor. For concrete with cracks above and parallel to the reinforcing steel, the presence of corrosion inhibitors does not provide an advantage in protecting the reinforcing steel. In uncracked concrete, a lower water-cement ratio results in corrosion rates and losses that are lower than observed at the higher water-cement ratio. In cracked concrete, a lower-water cement ratio provides only limited additional corrosion protection when cracks provide a direct path for the chlorides to the steel. iii When adhesion loss between epoxy and steel is not considered, a 230-mm (9 in.) deck reinforced with conventional epoxy-coated steel or one of the three high adhesion epoxy-coated steels is the most cost-effective. When the potential effects of adhesion loss are considered, at a discount rate of 2%, the most cost-effective option is a 216-mm deck containing stainless steel clad reinforcement

Intergenerational mobility in socio-economic status in Ethiopia

Using data from two comprehensive national Labour Force Surveys and monetary and non-monetary outcomes, we examine the extent of intergenerational mobility in Ethiopia. Results from OLS and Quantile regression suggest moderate to high levels of earnings persistence. Generalised Ordered Logit based results suggest significant mobility educationally, which may be linked to the significant widening of educational opportunities over the last two decades; but hardly any evidence of mobility occupationally. Sons are found to be relatively more mobile than daughters in all cases. Public policy may have to foster the equality of opportunities generally and along gender lines to enhance mobility

Marking Embryonic Stem Cells with a 2A Self-Cleaving Peptide: A NKX2-5 Emerald GFP BAC Reporter

Fluorescent reporters are useful for assaying gene expression in living cells and for identifying and isolating pure cell populations from heterogeneous cultures, including embryonic stem (ES) cells. Multiple fluorophores and genetic selection markers exist; however, a system for creating reporter constructs that preserve the regulatory sequences near a gene's native ATG start site has not been widely available.Here, we describe a series of modular marker plasmids containing independent reporter, bacterial selection, and eukaryotic selection components, compatible with both Gateway recombination and lambda prophage bacterial artificial chromosome (BAC) recombineering techniques. A 2A self-cleaving peptide links the reporter to the native open reading frame. We use an emerald GFP marker cassette to create a human BAC reporter and ES cell reporter line for the early cardiac marker NKX2-5. NKX2-5 expression was detected in differentiating mouse ES cells and ES cell-derived mice.Our results describe a NKX2-5 ES cell reporter line for studying early events in cardiomyocyte formation. The results also demonstrate that our modular marker plasmids could be used for generating reporters from unmodified BACs, potentially as part of an ES cell reporter library

When, where and how to perform efficiency estimation

In this paper we compare two flexible estimators of technical efficiency in a cross-sectional setting: the nonparametric kernel SFA estimator of Fan, Li and Weersink (1996) to the nonparametric bias corrected DEA estimator of Kneip, Simar andWilson (2008). We assess the finite sample performance of each estimator via Monte Carlo simulations and empirical examples. We find that the reliability of efficiency scores critically hinges upon the ratio of the variation in efficiency to the variation in noise. These results should be a valuable resource to both academic researchers and practitioners

Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented

Wnt5a Regulates Ventral Midbrain Morphogenesis and the Development of A9–A10 Dopaminergic Cells In Vivo

Wnt5a is a morphogen that activates the Wnt/planar cell polarity (PCP) pathway and serves multiple functions during development. PCP signaling controls the orientation of cells within an epithelial plane as well as convergent extension (CE) movements. Wnt5a was previously reported to promote differentiation of A9–10 dopaminergic (DA) precursors in vitro. However, the signaling mechanism in DA cells and the function of Wnt5a during midbrain development in vivo remains unclear. We hereby report that Wnt5a activated the GTPase Rac1 in DA cells and that Rac1 inhibitors blocked the Wnt5a-induced DA neuron differentiation of ventral midbrain (VM) precursor cultures, linking Wnt5a-induced differentiation with a known effector of Wnt/PCP signaling. In vivo, Wnt5a was expressed throughout the VM at embryonic day (E)9.5, and was restricted to the VM floor and basal plate by E11.5–E13.5. Analysis of Wnt5a−/− mice revealed a transient increase in progenitor proliferation at E11.5, and a precociously induced NR4A2+ (Nurr1) precursor pool at E12.5. The excess NR4A2+ precursors remained undifferentiated until E14.5, when a transient 25% increase in DA neurons was detected. Wnt5a−/− mice also displayed a defect in (mid)brain morphogenesis, including an impairment in midbrain elongation and a rounded ventricular cavity. Interestingly, these alterations affected mostly cells in the DA lineage. The ventral Sonic hedgehog-expressing domain was broadened and flattened, a typical CE phenotype, and the domains occupied by Ngn2+ DA progenitors, NR4A2+ DA precursors and TH+ DA neurons were rostrocaudally reduced and laterally expanded. In summary, we hereby describe a Wnt5a regulation of Wnt/PCP signaling in the DA lineage and provide evidence for multiple functions of Wnt5a in the VM in vivo, including the regulation of VM morphogenesis, DA progenitor cell division, and differentiation of NR4A2+ DA precursors