Temperature‐Enhanced Solvent Vapor Annealing of a C3 Symmetric Hexa‐peri‐Hexabenzocoronene: Controlling the Self‐Assembly from Nano‐ to Macroscale

Temperature‐enhanced solvent vapor annealing (TESVA) is used to self‐assemble functionalized polycyclic aromatic hydrocarbon molecules into ordered macroscopic layers and crystals on solid surfaces. A novel C₃ symmetric hexa‐peri‐hexabenzocoronene functionalized with alternating hydrophilic and hydrophobic side chains is used as a model system since its multivalent character can be expected to offer unique self‐assembly properties and behavior in different solvents. TESVA promotes the molecule's long‐range mobility, as proven by their diffusion on a Si/SiO_x surface on a scale of hundreds of micrometers. This leads to self‐assembly into large, ordered crystals featuring an edge‐on columnar type of arrangement, which differs from the morphologies obtained using conventional solution‐processing methods such as spin‐coating or drop‐casting. The temperature modulation in the TESVA makes it possible to achieve an additional control over the role of hydrodynamic forces in the self‐assembly at surfaces, leading to a macroscopic self‐healing within the adsorbed film notably improved as compared to conventional solvent vapor annealing. This surface re‐organization can be monitored in real time by optical and atomic force microscopy.     

Experimental analysis on desiccant regeneration in a packed column with structured and random packing

This paper presents the experimental tests on desiccant regeneration carried out in a packed column with the hygroscopic solution H₂O/LiBr. Two different packed columns have been tested: a random column consisting of 1” Pall Ring elements and a structured column Mellapack 250Y. The experimental results are reported in terms of desiccant concentration increase, regeneration effectiveness and air side pressure drop. The experimental tests show that desiccant regeneration requires a temperature level around 50 °C that can be easily obtained by using solar energy or heat recovered from an industrial process or from a thermal engine. The random column shows regeneration performance 20-25% higher than structured column, whereas the structured column shows air side pressure drop from 65% to 75% lower. The experimental results have been compared against a one-dimensional simulation code of a packed column: a fair agreement is found between experiments and simulation.     

Size effect in S–N curves: A fractal approach to finite-life fatigue strength

It has experimentally been observed that the finite-life fatigue strength of metallic materials in the high-cycle regime decreases with increasing the specimen size. In the present paper, such a decrease is explained by considering the fractal nature of the reacting cross-sections of structures. Accordingly, the so-called fractal (or renormalized) fatigue strength is represented by a force amplitude acting on a surface with a fractal dimension lower than 2, where such a dimensional decrement depends on the presence of heterogeneity, cracks, defects, voids, etc. in the material ligament. Moreover, it is shown that this decrement tends to progressively diminish with increasing the structure size. Two scaling laws (monofractal and multifractal, respectively) for the finite-life fatigue strength of metals are proposed, and some experimental results are examined to show how to apply such a theoretical fractal approach.     

Fatigue damage of high performance concrete through a 2D mesoscopic lattice model

Based on high-resolution digital images of High Performance Concrete (HPC) microstructures, a two-dimensional mesoscopic lattice model which accounts for fatigue damage is proposed. Fatigue damage is introduced by considering the coupled effects of loading cycles and tensile strain on stiffness degradation of microstructural lattice elements under fatigue loading. The ultimate tensile strain is defined as the failure threshold value for microstructural lattice elements. Further, the effects of the lattice element properties (i.e. size and finite element type) and fatigue loading parameters (i.e. stress levels) on the damage mechanisms of the HPC microstructure are investigated and discussed. It is found that lattice truss elements 1 mm long are satisfactory, giving also their smaller computational requirements in comparison to beam counterparts, to investigate fatigue damage in the HPC microstructure. The numerical results of the present model are consistent with experimental observations.     

Inspecting the Lightweight Precast Concrete Panels in the Woodrow Wilson Bridge Deck of 1982

This paper presents the results of a detailed inspection of the deck panels of the Woodrow Wilson Bridge installed in 1982. The original cast-in-place concrete deck, constructed in 1962, was replaced with full-depth lightweight precast concrete deck panels that enabled rapid construction with minimal traffic disruption. The inspection of the Woodrow Wilson deck provides valuable information about the performance of the precast concrete panels, joints, and connections after 20 years of very harsh traffic loads and environmental stressors. The deck panels performed well overall, with the only serious problems at expansion and contraction joints. All of these joints exhibited cracking and rusting. The most prevalent type of cracking appeared to be due to restrained shrinkage between the new polymer concrete, the older precast panels, and the rigid steel joints. This location is more vulnerable to cracking and leaking because there is no prestress across the joint. The multilayered corrosion protection methods used for the transverse and longitudinal post-tensioning tendons were very successful.     

Immune parameters in female workers exposed to urban pollutants

Urban outside workers, such as traffic police, are daily exposed to air pollutants and psychosocial stressors: for these workers, the working environment corresponds to the living environment of the general population. Studies in the literature have shown that immune parameters could be affected by chronic exposure to various chemical pollutants. The aim of this study is to evaluate whether occupational exposure to urban pollutants can cause alterations in NK, IL-2, IFN-gamma and C3 plasma levels in female traffic police compared to a control group. After excluding subjects with the principal confounding factors, 86 female traffic police and 87 controls were matched by age, years of police work and habitual alcohol consumption. The distribution of NK values in female traffic police and controls was significantly different (p=0.000); NK values above the upper limit of the normal laboratory range were observed in 23 female traffic police and in 2 controls (p=0.000). IL-2 mean levels were higher in traffic police compared to controls, but the difference was not significant. The mean and the distribution of IFN-gamma values in female traffic police and controls were not different. C3 mean levels were higher in female traffic police versus controls, but the difference was not significant. Considering that the subjects with the principal confounding factors were excluded from the study and that female traffic police and controls were matched by the above-mentioned variables, our results suggest that chronic occupational exposure to low doses of chemical stressors, which may interact with and add to psychosocial ones, can affect both innate and adaptative immunity.     

Cometabolism of trihalomethanes by mixed culture nitrifiers

Three mixed-culture nitrifier sources degraded low concentrations (25-450 microg/L) of four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Individual THM rate constants (k1THM) increased with increasing THM bromine-substitution with TBM>DBCM>BDCM>TCM and were comparable to previous studies with the pure culture nitrifier, Nitrosomonas europaea. A decrease in temperature resulted in a decrease in both ammonia and THM degradation rates with ammonia rates affected to a greater extent than THM degradation rates. The significant effect of temperature indicates that seasonal variations in water temperature should be a consideration for technology implementation. Product toxicity, measured by transformation capacity (T(c)), was similar to that observed with N. europaea. Because both rate constants and product toxicities increase with increasing THM bromine-substitution, a water's THM speciation is an important consideration for process implementation during drinking water treatment. Even though a given water is kinetically favored, the resulting THM product toxicity may not allow stable treatment process performance.