Monitoring of Concrete Cylinders With and Without Steel Fibers Under Compression Using Piezo-Ceramic Smart Aggregates

An active sensing approach is employed to analyze the damage behavior of concrete cylinders under compression using smart aggregates. The smart aggregate sensor used in this study is developed by embedding a soldered water-proof piezo-ceramic patch inside stiff cement mortar. These smart aggregates are embedded at the desired locations in the concrete cylinders. A pair of smart aggregates is used with one acting as an actuator and other as a sensor. Wavelet packet analysis is used to analyze the recorded signals. Variation of cracking pattern observed at different levels of loading modifies the signal characteristics. Experimental investigations are carried out by testing eight concrete cylinders with and without steel fibers. The experimental result shows that the proposed method of using smart aggregates and evaluating damage index based on wavelet analysis is effective in monitoring the health of the concrete cylinders. Compression tests on steel fiber reinforced concrete cylinders indicate that the addition of fibers improves the ductility and post peak behavior under compression. Damage index variation shows that the steel fibers resist the crack propagation and results in improved performance.     

The Catalytic Efficacy of Co(salen)(AL) in O2 Oxidation Reactions in CO2-Expanded Solvent Media: Axial Ligand Dependence and Substrate Selectivity

This work correlates the basicity of various axial ligands (AL), including triethylamine, methylimidazole, pyridine, acetonitrile or water, with the efficacy of catalytic oxidation of 2,6-di-tert-butylphenol by Co(salen)(AL) in CO₂-expanded methylene chloride. Further, Co(salen)(AL)O₂ abstracts hydrogen atoms from substrates of high to intermediate reactivity (BDECH ≤~90 kcal/mol).     

Chitosan Nanoparticle Penetration into Shrimp Muscle and its Effects on the Microbial Quality

Chitosan (CH) and chitosan-sodium tripolyphosphate (CH-TPP) solutions were produced with and without sonication and ultra-shearing. The CH and CH-TPP particles and solutions were evaluated for physicochemical properties, and fluorescently labeled particle penetration into shrimp muscle tissue through vacuum tumbling was observed. Two solutions were prepared: (1) a 0.5 % CH solution in 1 % acetic acid and (2) a CH-TPP solution, prepared by adding 0.167 % sodium tripolyphosphate to the CH solution, instantly forming CH-TPP nanoparticles through ionotropic gelation. Untreated shrimp meat and shrimp meat vacuum tumbled with CH, CH-TPP, acetic acid, sodium tripolyphosphate, and distilled water solutions were analyzed for aerobic plate counts for 24 days of refrigerated storage at 4 °C. Processing with sonication and ultra-shearing reduced the particle sizes of CH and CH-TPP nanoparticles and the molecular weight of CH. It was observed that after processing, fluorescently labeled CH and CH-TPP nanoparticles could penetrate inside of and attach to shrimp muscle tissues through vacuum tumbling. At 24 days of refrigerated storage, shrimp vacuum tumbled with processed CH solution had the lowest aerobic plate counts of all treatments and it was the only treatment to have unchanged microbial quality throughout the entire storage time. Vacuum tumbling with sonicated and ultra-sheared CH solution enhanced particle penetration into shrimp and inhibited microbial growth during refrigerated storage.     

Thermal and mechanical properties of epoxidized natural rubber modified epoxy matrices

Two sets (A and B) of bisphenol A–diglycidyl ether (DGEBA) based epoxy resin formulations were modified with epoxidized natural rubber (ENR 50) and its liquid version (LENR 50), and cured with amino propoxylate initiator/accelerator at ambient temperatures. The ENR 50 loading range was 1.6–5.9 wt%. Both sets could be loaded up to 12 wt% with LENR 50. Significant improvements in tensile toughness and impact toughness could only be observed for set A formulations. At the maximum LENR 50 loading achieved, the improvement in tensile toughness is 250% in comparison with that of the neat formulation; that for impact toughness is 125%. Differential scanning calorimetry reveals multiple transitions, characteristic of these systems. Scanning electron micrographs of fractured surfaces show uniform rubber dispersions in the submicrometre size range. At the loading levels used, LENR 50 particle dispersions fall within the range of 0.33–0.47 µm in size; those of ENR 50 are 0.48–0.67 µm in average size. Improvements in toughness are similar for both versions of epoxidized natural rubber. For both LENR 50 and ENR 50 modified epoxy systems, the extremes of 0.80 (set A) and 1.95 (set B) in glycidyl ether/reactive hydrogen molar ratios considered show distinct failure mechanisms, that of ductile failure with yielding in the former and brittle failure in the latter, irrespective of reactive diluent content. © 1999 Society of Chemical Industry     

Sex-Specific Alterations in Dopamine Metabolism in the Brain after Methamphetamine Self-Administration

Methamphetamine (METH) use disorder affects both sexes, with sex differences occurring in behavioral, structural, and biochemical consequences. The molecular mechanisms underlying these differences are unclear. Herein, we used a rat model to identify potential sex differences in the effects of METH on brain dopaminergic systems. Rats were trained to self-administer METH for 20 days, and a cue-induced drug-seeking test was performed on withdrawal days 3 and 30. Dopamine and its metabolites were measured in the prefrontal cortex (PFC), nucleus accumbens (NAc), dorsal striatum (dSTR), and hippocampus (HIP). Irrespective of conditions, in comparison to females, male rats showed increased 3,4-dihydroxyphenylalanine (DOPA) in the PFC, dSTR, and HIP; increased cys-dopamine in NAc; and increased 3,4-dihydroxyphenylethanol (DOPET) and 3,4-dihydroxyphenylacetic acid (DOPAC) in dSTR. Males also showed METH-associated decreases in DA levels in the HIP but increases in the NAc. Female rats showed METH-associated decreases in DA, DOPAL, and DOPAC levels in the PFC but increases in DOPET and DOPAC levels in the HIP. Both sexes showed METH-associated decreases in NAc DA metabolites. Together, these data document sex differences in METH SA-induced changes in DA metabolism. These observations provide further support for using sex as an essential variable when discussing therapeutic approaches against METH use disorder in humans.     

Survivability in optical networks

Survivability, the ability of a network to withstand and recover from failures, is one of the most important requirements of networks. Its importance is magnified in fiber optic networks with throughputs on the order of gigabits and terabits per second. This article takes a look at the techniques used to achieve survivability in traditional optical networks, and how those techniques are evolving to make next-generation WDM networks survivable.     

Hot corrosion behaviors of gas tunnel type plasma sprayed La2Zr2O7 thermal barrier coatings

Gas tunnel type plasma sprayed free-standing La₂Zr₂O₇ coating specimens with a thickness of 300-400 μm were prepared under optimized operating conditions and were subjected to hot corrosion test in the presence of corrosive impurities such as V₂O₅, Na₂SO₄, and Na₂SO₄ + V₂O₅ mixtures (60:40 wt%) at two different temperatures for duration of 5 h, i.e. 1000 and 1350 K for V₂O₅ and Na₂SO₄ + V₂O₅ mixtures, 1200 and 1350 K for Na₂SO₄. For temperatures at 1350 K, the reaction mechanism of V₂O₅ and the mixture of Na₂SO₄ + V₂O₅ are similar and LaVO₄ is formed as the corrosive product, which leads to massive phase transformation from pyrochlore to tetragonal and monoclinic phases. Microstructural observations from planar reaction zone (PRZ) and melt infiltrated reaction zone (MIRZ) reveals that the present La₂Zr₂O₇ coating exhibits good hot corrosion resistance in V₂O₅ environment and moderate for the mixture of Na₂SO₄ + V₂O₅, but is worst in Na₂SO₄ environment.     

Cross-sectional TEM investigation of Mg-LaNi5-Soot hybrids for hydrogen storage

Accumulatively roll bonded (ARB) Mg-LaNi₅-Soot hybrid has emerged as a promising hydrogen storage material with enhanced hydrogen storage characteristics, which is amenable to scaled-up production. The key to understanding the hydrogen storage behaviour lies in the nanoscale structure of the hybrid and the associated mechanisms. The focus of the current study is on the use of cross-sectional transmission electron microscopy (TEM) to unravel the underlying mechanisms of hydrogen storage, in the Mg-LaNi₅-Soot hybrid. The role of processing variables (ARB passes and strain) and the concomitant evolution of the microstructure (distribution of second phase particles (LaNi₅ and soot)) are studied, keeping in view the diffusion of hydrogen and the nucleation of the hydride phase. It is established that the interface between Mg and second phase (LaNi₅ and soot) plays a dominant role in the nucleation of the MgH₂ phase. The MgH₂ nucleation mechanism is studied under the ambit of the Johnson-Mehl-Avrami kinetic (JMAK) model. It is concluded that the internal interfaces provides sites for the nucleation of magnesium hydride.     

Amphiphilic Biopolyester‐Carbon Nanotube Anode Enhances Electrochemical Activities of Microbial Fuel Cell

Hydrophobic bacterial polyhydroxyalkanoates were rendered amphiphilic by grafting with poly(ethylene glycol) methacrylate, followed by compositing with carbon nanotubes. The polymer graft composite as an anode material encouraged superior biofilm surface growth; thus enhancing electrochemical activities in microbial fuel cells and resulting in higher current and power densities. The internal resistance of the cell was greatly reduced due to improved electron transfer from the biofilm to the anode.     

Global Mindset and Entry Mode Decisions: Moderating Roles of Managers’ Decision-Making Style and Managerial Experience

From the managerial cognition perspective, we develop a contingency framework that empirically examines the effect of senior managers’ global mindset on their decisions regarding the choice of entry mode for foreign subsidiaries and how their cognitive decision-making style and managerial experience interact with their global mindset and thereby affect their decisions. Data were collected from both headquarters and subsidiary senior managers of 345 Chinese multinational enterprises. The results show that senior managers who exhibit a stronger global mindset tend to choose a lower-level ownership entry mode for their foreign subsidiaries. This tendency is stronger when senior managers possess a ‘thinking’ decision-making style as opposed to a ‘feeling’ decision-making style but weaker when senior managers have more experience in their managerial positions.