Drying-induced surface roughening of polymeric coating under periodic air blowing

We carried out numerical simulations of drying-induced surface roughening of a moving liquid layer under periodic air blowing conditions. Using spatially non-uniform Biot number profiles along the coating surface, the solutions of coupled diffusion/heat transfer equations reveal a periodic growth and relaxation in concentration gradients in the vicinity of the liquid–gas interface. The resultant interfacial stress variations promote particular asymmetric surface topographies that grow and level in a sequential manner. The unique surface roughness is identified by considering time scales required for the web motion, the stress-induced surface evolution, and the pressure-driven leveling. Predicted drying maps represent the surface roughening behavior as regions in parameter space. © 2009 American Institute of Chemical Engineers AIChE J, 200

Measuring the drying rate of liquid film coatings using heat-flux method

We propose a simple method of determining solvent drying rates from heat flux measurements across thin liquid films. The theory is based on quasi-steady conductive heat transport through coatings, combined with simultaneous heat and mass transfer in the gas phase. The measured evaporation rates well reproduce conventional gravimetric measurements with an uncertainty of less than 5%. Drying experiments also revealed that the proposed method is robust in systems with high levels of fluctuation and thus provides an alternative tool for monitoring drying kinetics in forced air flows

Flow Pattern Transition of Fine Cohesive Powders in a Gas-Solid Fluidized Bed under Mechanical Vibrating Conditions

AbstractIn this study, the fluidization characteristics for fine cohesive powders under mechanical vibrating conditions were experimentally investigated. In a case of handling of fine cohesive powders with fluidized bed, stable gas channels and cracks were easily formed in the bed due to the strong cohesiveness acting among particles. A mechanical vibration is one of the methods to improve the fluidity of fine cohesive powders. In this study, we focused on the transition of the dominant bed flow pattern induced by mechanical bed vibrating conditions. The powders used in this study were different sizes (0.7 – 20μm) and materials (silica, alumina, polymer). All powders belonged to group-C in the Geldart classification. The bed expansion ratio was lower in the relatively smaller vibration strengths regardless of the gas velocity, however, it steeply increased with larger a certain vibration strength. Form the visual observation of the bed, the bubble formation appeared with larger than such a critical vibration strength. This implied that the dominant bed fluidization pattern was transitioned from channeling behavior (group-C) to bubbling behavior (group-A or –AC) by the addition of the mechanical vibration

Drying-induced reduction in electrical resistivity of carbon black-polyamideimide nanocomposite films

We provide evidence that the electrical resistivity of carbon black (CB)/polyamideimide (PAI) composites are tunable by drying below the glass transition temperature of the polymer matrix. Solution casting experiments of N-methyl-2-pyrrolidone (NMP)/CB/PAI systems reveal that with increasing drying temperature, the measured volume resistivity reduces by four orders of magnitude in an intermediate range of particle volume fractions, which is between 12% and 15%. However, no temperature-dependence was observed for particle-free polymeric films and nanocomposites with high particle volume fractions, which is above 23%. The measured values obey a single master curve, independent of the primary size and surface pH of the nanoparticles. This suggests that the desorption of PAI molecules from the nanoparticle surface enhances the evolution of conductive pathway formation in the course of drying

Vibro-Fluidization Characteristics for Size Arranged Agglomerates

Fine cohesive powders (Geldart’s group-C) were fluidized with a vibro-fluidized bed. Diameters of the powder used in this study were 0.2μm. For 0.2μm titanium oxide powder, stable and relatively large agglomerates were observed. In this study, the size distribution of agglomerates was arranged by sieving to examine its effect on the fluidization characteristics, such as the minimum fluidization velocity, the minimum bubbling velocity and the bed expansion ratio. The fluidization characteristics were drastically influenced by the size distribution of agglomerates. It was found that the size arrangement of agglomerates was one of the factors to obtain stable fluidization state for agglomerated cohesive powder

Subphthalocyanine-Stoppered [2]Rotaxanes:Synthesis and Size/Energy Threshold of Slippage

Subphthalocyanine (SubPc)-stoppered [2]rotaxanes were synthesized for the first time. The rotaxane bearing unsubstituted SubPc as a stopper exhibited an equilibrium of slipping-on and slipping-off, whereas a perfluorinated SubPc stopper completely blocked slippage of the ring due to its slightly larger size. Kinetic studies revealed the Gibbs free energy of activation for the slipping-on and slipping-off processes. The optical properties of the rotaxanes, including photoinduced electron transfer, were also revealed.</p

Study on Technical Standards of Reinforced Concrete Structures with Long Service Life when Using Blended Cement and Finishing Materials

It is very important to improve and secure durability of reinforced concrete (RC) building and housing, in order to extend the service life of it. In this study, these were studied experimentally that the contribution ratio of blended cement to the carbonation resistance of concrete when a part of OPC replaced to FA or BFS much more were used for concrete, and the effect of carbonation suppression required for an effective finishing materials when these were applied for concrete surface. As a result, we were able to obtain the knowledge that the contribution ratio to the carbonation resistance of concrete using blended cement with different mixture replacement ratio, and the effect of carbonation suppression required for 4 types of finishing materials and its specifications, from the viewpoint of securing durability and extending the service life of RC structures. Therefore, these were considered to be able to sufficiently contribute to the review of the evaluation method or technical standards concerning about the durability of RC structures prescribed in "Housing Quality Assurance Act" in Japan

Composition-depenjdent stress oscillations in a dilute suspension under shear

This study presents empirical evidence that dilute particle-polymer suspensions exhibit composition-dependent stress oscillations at constant shear rate. In ethanol/toluene co-solvent suspensions, an increase in the ethanol concentration promoted a transition of the particle-polymer suspension from a stable state, through an oscillating state with well-defined periodicity, toward an unstable mode with multiple frequency peaks. This transition corresponded to increases in the gyration radii of the polymer chains in the fluids. Furthermore, the opposite transition from an unstable state to stable states was observed with increasing polymer concentrations. In contrast, the extent of the transition was curtailed in cyclohexane/toluene suspension, in which both the shear stress and gyration radius remained constant with negligible dependence on the fluid composition. These facts indicate that the non-hydrodynamic deletion attractions among particles play a significant role in influencing the stress instability of polymer-particle suspensions

Mutant analyses reveal different functions of fgfr1 in medaka and zebrafish despite conserved ligand–receptor relationships

AbstractMedaka (Oryzias latipes) is a small freshwater teleost that provides an excellent developmental genetic model complementary to zebrafish. Our recent mutagenesis screening using medaka identified headfish (hdf) which is characterized by the absence of trunk and tail structures with nearly normal head including the midbrain–hindbrain boundary (MHB). Positional-candidate cloning revealed that the hdf mutation causes a functionally null form of Fgfr1. The fgfr1hdf is thus the first fgf receptor mutant in fish. Although FGF signaling has been implicated in mesoderm induction, mesoderm is induced normally in the fgfr1hdf mutant, but subsequently, mutant embryos fail to maintain the mesoderm, leading to defects in mesoderm derivatives, especially in trunk and tail. Furthermore, we found that morpholino knockdown of medaka fgf8 resulted in a phenotype identical to the fgfr1hdf mutant, suggesting that like its mouse counterpart, Fgf8 is a major ligand for Fgfr1 in medaka early embryogenesis. Intriguingly, Fgf8 and Fgfr1 in zebrafish are also suggested to form a major ligand–receptor pair, but their function is much diverged, as the zebrafish fgfr1 morphant and zebrafish fgf8 mutant acerebellar (ace) only fail to develop the MHB, but develop nearly unaffected trunk and tail. These results provide evidence that teleost fish have evolved divergent functions of Fgf8–Fgfr1 while maintaining the ligand–receptor relationships. Comparative analysis using different fish is thus invaluable for shedding light on evolutionary diversification of gene function

Intracellular Phospholipase A1 and Acyltransferase, Which Are Involved in Caenorhabditis elegans Stem Cell Divisions, Determine the sn-1 Fatty Acyl Chain of Phosphatidylinositol

Phosphatidylinositol (PI) is unique in the abundance of stearic acid at the sn-1 position. This fatty acid is thought to be incorporated through fatty acid remodeling. Here, we identified a phospholipase and acyltransferases involved in the fatty acid remodeling at the sn-1 position of PI and provide a link between the sn-1 fatty acid of PI and asymmetric cell division