Pullout Resistance of Reinforcement of Lightweight Cellular Concrete Fill

C2169Lightweight Cellular Concrete (LCC) (also called foam or gas concrete) is a special construction material, which is typically composed of portland cement, water, and air voids created by a foaming agent. This material has been increasingly used as a backfill material for geotechnical applications. This report presents a series of laboratory tests conducted to evaluate the material properties of LCC including density, permeability, compressive strength, shear strength, compressibility, elastic modulus, and Poisson\u2019s ratio with different cement to fly ash ratios and at different ages. LCC specimens used in this research project were cast in the field, and the cement to fly ash ratios used for the production of the specimens ranged from 50:50 to 100:0. Large direct shear box tests were conducted on prismatic specimens with a size of 12 inches long, 12 inches wide, and 8 inches high, while small direct shear box tests were conducted on cylindrical specimens with a size of 2.5 inches in diameter and 1 inch high. This report also presents a series of pullout tests conducted in the laboratory to investigate pullout resistance of extensible reinforcement (geogrid) and inextensible reinforcement (steel strip) embedded in LCC. Pullout displacements and pullout forces were monitored using linear variable displacement transducers (LVDT) and a load cell during the pullout process. This research project investigated the effects of age, normal stress, LCC type, cold joint, and re-pullout on pullout resistance and calculated the pullout resistance factors F* for geogrid and steel strip embedded in LCC. The laboratory material test results show that the average wet densities of LCC ranged from 30 to 36 pcf at the age of 28 days and the average dry densities ranged from 21 to 24 pcf at the same age. The permeability values of LCC ranged from 2.1 710-5 to 3.0 710-4 in./s and they increased as the cement to fly ash ratio increased. The measured cohesion values of LCC in large direct shear box tests ranged from 33 to 50 psi, while the measured cohesion values in small direct shear box tests ranged from 19 to 37 psi. This report also compares the material properties of LCC measured in this research project with those reported in the literature and shows overall good agreement. The laboratory pullout test results show that for the geogrid embedded in LCC, the maximum pullout force increased as the normal stress increased. For the steel strip embedded in LCC, the maximum pullout force was independent of the normal stress and increased as the age and the cement to fly ash ratio increased. Pullout test results also show that the presence of a cold joint did not reduce the pullout resistance, while the re-pullout test had lower pullout resistance as compared with the original pullout test for the same specimen. The pullout resistance factors F* for steel strips were greater than those for geogrids and these factors decreased as the normal stress increased

Succession Patterns of Microbial Composition and Activity following the Diesel Spill in an Urban River

Diesel spills in freshwater systems have adverse impacts on the water quality and the shore wetland. Microbial degradation is the major and ultimate natural mechanism that can clean the diesel from the environment. However, which, and how fast, diesel-degrading microorganisms could degrade spilled diesel has not been well-documented in river water. Using a combination of 14C-/3H--based radiotracer assays, analytical chemistry, MiSeq sequencing, and simulation-based microcosm incubation approaches, we demonstrated succession patterns of microbial diesel-degrading activities, and bacterial and fungal community compositions. The biodegradation activities of alkanes and polycyclic aromatic hydrocarbons (PAHs) were induced within 24 h after diesel addition, and reached their maximum after incubation for 7 days. Potential diesel-degrading bacteria Perlucidibaca, Acinetobacter, Pseudomonas, Acidovorax, and Aquabacterium dominated the community initially (day 3 and day 7), but later community structure (day 21) was dominated by bacteria Ralstonia and Planctomyces. The key early fungi responders were Aspergillus, Mortierella, and Phaeoacremonium by day 7, whereas Bullera and Basidiobolus dominated the fungal community at day 21. These results directly characterize the rapid response of microbial community to diesel spills, and suggest that the progression of diesel microbial degradation is performed by the cooperative system of the versatile obligate diesel-degrading and some general heterotrophic microorganisms in river diesel spills

High Color Purity CsPbBr₃ Nanocrystals Prepared by a Heterogeneous Reaction System

All inorganic perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals (NCs) have emerged as new semiconductor materials for light-emitting applications due to their high light absorption coefficient, tunable spectrum, and high photoluminescence quantum yields (PLQYs). However, owing to their burst nucleation and growth, the size distribution of CsPbX3 NCs prepared by the conventional homogeneous reaction system is wide, which affects their high color purity. Here, a heterogeneous reaction system was designed to prepare CsPbBr3 NCs with a narrow size distribution by controlling the nucleation and growth kinetics of CsPbBr3 NCs and eliminating the undesired Ostwald ripening effect. The synthesized CsPbBr3 NCs exhibit nearly a unit PLQY and a narrow size distribution. Benefiting from the tight ligands on the surface of NCs that can both stabilize the inorganic nuclei of CsPbBr3 NCs and passivate the Br vacancy defects of the NC surface, the obtained CsPbBr3 NCs have excellent optical stability. In particular, the PLQY of the CsPbBr3 NC colloidal dispersion can be as high as 86% even after 13 cycles of purification with methyl acetate

Pullout Resistance of Reinforcement of Lightweight Cellular Concrete Fill [Technical Summary]

This report presents a series of laboratory tests to evaluate the material properties of LCC and the pullout resistances of geogrid and steel strip in LCC specimens cast in the field. Based on the test results, the following conclusions can be drawn: The average wet densities of LCC ranged from 30 to 36 pcf at the age of 28 days and the average dry densities ranged from 21 to 24 pcf at the same age. The dry density was approximately 67% of the wet density. The density increased as the cement to fly ash ratio increased. All LCC specimens used in this study are considered ultra-low density cellular concrete. The permeability values for LCC measured using the falling head method ranged from 2.1 710-5 to 3.0 710-4 in./s, respectively. In general, the permeability decreased as the hydraulic gradient and the confining stress increased. For the small shear box tests, the cohesion values of the LCC specimens ranged from 19 to 37 psi, while their frictional angles ranged from 19 to 63 degrees. For the large shear box tests, the cohesion values of the LCC specimens ranged from 33 to 50 psi, while their frictional angles ranged from 23 to 79 degrees. The large shear box tests measured higher shear strengths than the small shear box tests

CXCR6+ Tumor-Associated Macrophages Identify Immunosuppressive Colon Cancer Patients with Poor Prognosis but Favorable Response to Adjuvant Chemotherapy

We explored the infiltration and prognostic value of CXCR6+TAMs in all stages of colon cancer (CC) patients and assessed predictive ability as a biomarker for different ACT regimens among high-risk stage II and stage III patients in both primary and validation cohorts. Two independent cohorts of 360 and 126 consecutive colon cancer patients were enrolled from two medical centers of Zhongshan Hospital. Immunofluorescence and immunohistochemistry were performed to detect the density of CXCR6+TAMs and activated CD8+ T cells. The infiltration of CXCR6+TAMs was higher in tumor tissues and increased with advanced tumor stage. A high density of CXCR6+TAMs predicted worse overall survival (OS) in all CC patients (HR = 2.49, 95% CI = (1.68, 3.70), p < 0.001), and was an independent risk factor verified by Cox regression analysis (HR = 1.68, 95% CI = (1.09, 2.59), p = 0.019). For high-risk stage II and stage III patients with a high density of CXCR6+TAMs, better disease-free survival (DFS) (HR = 0.32, 95% CI = (0.11, 0.89), p = 0.003), and OS (HR = 0.28, 95% CI = (0.07, 1.11), p = 0.014) were observed in the 6-month treatment group. There was a negative relationship between the density of CXCR6+TAMs and CD8+ T cells (R = −0.51, p < 0.001) as well as activated CD8+ T cells (R = −0.54, p < 0.001). Higher levels of IL-6 and lower levels of IL-2R and TNF-α were expressed in high-CXCR6+ TAM-density patients, which indicates that CXCR6+TAMs contribute to an immunosuppressive microenvironment. CXCR6+TAMs predicted prognosis and response to different durations of ACT in CC patients. CXCR6+TAMs were associated with an immunosuppressive microenvironment and suppressed the activation of CD8+ T cells