Behavior of Epoxy-Coated Textured Reinforcing Bars

Cracking in bridge decks is a common but difficult problem to control. Both research and experience show that the use of epoxy-coated reinforcement, which is mandated by most state departments of transportation (DOT’s) for bridge decks, increases cracking. Although the epoxy coating protects the steel from corrosion, bond strength is compromised and the increased cracking exacerbates durability issues in concrete. As a means to improve bond and reduce the formation of cracks, the Illinois Department of Transportation (IDOT) proposed texturizing the surface of epoxy-coated bars. IDOT developed a prototype textured epoxy coating and this report details a preliminary study on the bond strength of reinforcing bars with the new coating. Direct pull-out tests were performed on uncoated, standard epoxy-coated, and textured epoxy-coated No. 5 and No. 8 reinforcing bars to compare the bond characteristics. Standard epoxy-coated bars clearly demonstrated an increased tendency to slip and split the concrete. Initially, bars with the textured epoxy coating showed good force-slip behavior similar to black steel, but a rapid degradation of slip resistance was observed. On average, the peak nominal bond stress developed in the textured epoxy-coated No. 5 bars was approximately 17% lower than the uncoated bars. Pull-out specimens with No. 8 bars were confined using steel and shape memory alloy (SMA) wires to prevent concrete splitting. The confined No.8 bar specimens demonstrated behavior similar to the No. 5 bar specimens. In addition to the direct pull-out tests, three beam specimens were fabricated using No. 5 bars as a preliminary means to compare the bond behavior of the bars flexure. Overall, in both the direct pull-out and flexural testing—the added frictional resistance of the textured epoxy-coating showed promise as an effective way to improve slip resistance and reduce concrete cracking. However, further research is needed to optimize the coating and characterize its behavior.IDOT-R27-SP35Ope

Behavior of NiTiNb SMA wires under recovery stress or prestressing

The recovery stress of martensitic shape-memory alloy [SMA] wires can be used to confine concrete, and the confining effectiveness of the SMA wires was previously proved through experimental tests. However, the behavior of SMA wires under recovery stress has not been seriously investigated. Thus, this study conducted a series of tests of NiTiNb martensitic SMA wires under recovery stress with varying degrees of prestrain on the wires and compared the behavior under recovery stress with that under prestressing of the wires. The remaining stress was reduced by the procedure of additional strain loading and unloading. More additional strains reduced more remaining stresses. When the SMA wires were heated up to the transformation temperature under prestress, the stress on the wires increased due to the state transformation. Furthermore, the stress decreased with a decreasing temperature of the wires down to room temperature. The stress of the NiTiNb wires was higher than the prestress, and the developed stress seemed to depend on the composition of the SMAs. When an additional strain was subsequently loaded and unloaded on the prestressed SMA wires, the remaining stress decreased. Finally, the remaining stress becomes zero when loading and unloading a specific large strain

Analysis of residual acrylamide in field crops

Polyacrylamide (PAM) is a widely used product for a large number of applications. Many of the emerging applications are in the area of agriculture. PAM is blended with pesticides as a thickening agent, added to irrigation water to minimize soil erosion, and used as a medium for hydroponically grown crops. Although PAM is stable and considered to be safe, residual acrylamide (AMD) monomer is a neurotoxin and animal carcinogen. In this work, residual AMD is analyzed in a variety of crops that were grown under PAM treatment to stabilize soil erosion. Corn, potatoes, sugar beets, and beans are analyzed for AMD. A sample of the crop is homogenized with water, and the water layer is filtered and derivatized with bromine to form 2,3-dibromopropionamide. The derivative is then extracted with ethyl acetate and converted to the more stable 2-propenamide prior to gas chromatographic analysis using an electron capture detector. Capillary Carbowax columns were used. All tested crops show < 10 ppb AMD. Furthermore, it seems that AMD is not stable when it comes in contact with the crop tissues. In the presence of plant tissues, AMD will disappear as a function of time. Beans blended with 100 ppb AMD for 10 min yield a recovery of only 22%. For a bean sample that was soaked with 500 ppb AMD solution for 18 h, the recovery is 7%. Other crops show different AMD recoveries

Safety and efficacy of endoscopic submucosal dissection for rectal neoplasia: a multicenter North American experience.

Background and aims  Rectal lesions traditionally represent the first lesions approached during endoscopic submucosal dissection (ESD) training in the West. We evaluated the safety and efficacy of rectal ESD in North America. Methods  This is a multicenter retrospective analysis of rectal ESD between January 2010 and September 2018 in 15 centers. End points included: rates of en bloc resection, R0 resection, adverse events, comparison of pre- and post-ESD histology, and factors associated with failed resection. Results  In total, 171 patients (median age 63 years; 56 % men) underwent rectal ESD (median size 43 mm). En bloc resection was achieved in 141 cases (82.5 %; 95 %CI 76.8-88.2), including 24 of 27 (88.9 %) with prior failed endoscopic mucosal resection (EMR). R0 resection rate was 74.9 % (95 %CI 68.4-81.4). Post-ESD bleeding and perforation occurred in 4 (2.3 %) and 7 (4.1 %), respectively. Covert submucosal invasive cancer (SMIC) was identified in 8.6 % of post-ESD specimens. There was one case (1/120; 0.8 %) of recurrence at a median follow-up of 31 weeks; IQR: 19-76 weeks). Older age and higher body mass index (BMI) were predictors of failed R0 resection, whereas submucosal fibrosis was associated with a higher likelihood of both failed en bloc and R0 resection. Conclusion  Rectal ESD in North America is safe and is associated with high en bloc and R0 resection rates. The presence of submucosal fibrosis was the main predictor of failed en bloc and R0 resection. ESD can be considered for select rectal lesions, and serves not only to establish a definitive tissue diagnosis but also to provide curative resection for lesions with covert advanced disease

Characterization of Notch1 Antibodies That Inhibit Signaling of Both Normal and Mutated Notch1 Receptors

Notch receptors normally play a key role in guiding a variety of cell fate decisions during development and differentiation of metazoan organisms. On the other hand, dysregulation of Notch1 signaling is associated with many different types of cancer as well as tumor angiogenesis, making Notch1 a potential therapeutic target.Here we report the in vitro activities of inhibitory Notch1 monoclonal antibodies derived from cell-based and solid-phase screening of a phage display library. Two classes of antibodies were found, one directed against the EGF-repeat region that encompasses the ligand-binding domain (LBD), and the second directed against the activation switch of the receptor, the Notch negative regulatory region (NRR). The antibodies are selective for Notch1, inhibiting Jag2-dependent signaling by Notch1 but not by Notch 2 and 3 in reporter gene assays, with EC(50) values as low as 5+/-3 nM and 0.13+/-0.09 nM for the LBD and NRR antibodies, respectively, and fail to recognize Notch4. While more potent, NRR antibodies are incomplete antagonists of Notch1 signaling. The antagonistic activity of LBD, but not NRR, antibodies is strongly dependent on the activating ligand. Both LBD and NRR antibodies bind to Notch1 on human tumor cell lines and inhibit the expression of sentinel Notch target genes, including HES1, HES5, and DTX1. NRR antibodies also strongly inhibit ligand-independent signaling in heterologous cells transiently expressing Notch1 receptors with diverse NRR "class I" point mutations, the most common type of mutation found in human T-cell acute lymphoblastic leukemia (T-ALL). In contrast, NRR antibodies failed to antagonize Notch1 receptors bearing rare "class II" or "class III" mutations, in which amino acid insertions generate a duplicated or constitutively sensitive metalloprotease cleavage site. Signaling in T-ALL cell lines bearing class I mutations is partially refractory to inhibitory antibodies as compared to cell-penetrating gamma-secretase inhibitors.Antibodies that compete with Notch1 ligand binding or that bind to the negative regulatory region can act as potent inhibitors of Notch1 signaling. These antibodies may have clinical utility for conditions in which inhibition of signaling by wild-type Notch1 is desired, but are likely to be of limited value for treatment of T-ALLs associated with aberrant Notch1 activation

Estudio de las condiciones de contorno en válvulas de asiento

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