Micromixer as a continuous flow reactor for the synthesis of a pharmaceutical intermediate

A mixing device composed of a micron scale flow channel was applied as a continuous reactor to control exothermic reaction heat and to increase the product yield, in a synthesis of a pharmaceutical intermediate of quinolone antibiotics. The model reaction featured a fast reaction rate, high heat generation, and impurity formation due to a prolonged contact time between reactants and products. Using the micromixer reactor, the reaction heat was efficiently removed so that virtually no impurities were produced during the reaction. A product yield comparable to the theoretical value was achieved in a single micromixer unit. Optimum operating conditions were acquired from a statistical method by using factorial design, which was also verified by a CFD calculation.     

Rational and Facile Construction of 3D Annular Nanostructures with Tunable Layers by Exploiting the Diffraction and Interference of Light

This paper reports a rational and facile approach to fabricating arrays of 3D annular nanostructures with tunable layers by utilizing the diffraction and interference of UV light. Based on discretized Fresnel bright spots and standing waves formed within a photoresist film, the structures with nanoscale features are realized using simple, conventional photolithography. The 3D annular nanostructures are produced in arrays of single‐, double‐, and triple‐layered ring structures with the height of single layer on a 100 nm scale. The structural formation process and features of the nanostructures are analyzed and explained through 3D modeling that integrates the effects of both UV exposure dose and chemical kinetics. The approach to generating 3D annular nanostructures with tunable layers and discrete heights can be adapted for various applications that require the 3D structures fabricated over a large area with high throughput.     

A STUDY OF CARBIDE GROWTH IN MAR-M247 LC ALLOY BY DIRECTIONAL SOLIDIFICATION METHOD

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A study of the dynamic behavior of dispersion-type tubular reactor models

The dynamic behavior of dispersion-type tubular reactors, referred to as finite and truncated models depending on the boundary condition representations at the reactor exit, was investigated through numerical simulations. It was found that the dynamic behavior of the two models can be identical or different depending on how thePéclet number changes.     

High temperature mechanical properities and creep crack initiation of DS CM186LC for nozzle guide vane

The second generation DS alloy, CM186LC is used in the as-cast and double aged condition which has creep-rupture properities equivalent to the first generation single crystal alloys CMSX-2 and CMSX-3. In production, cast vane components have to be subjected to a brazing treatment for joining into pairs. The effect of the brazing treatment and modified brazing treatment (heat treatment) on mechanical properities at high temperature was studied in accordance with microstructure. Brazing treatments gave no effect on tensile properities and creep failure mode of DS CM186LC, although a small decrease in stress-rupture life was observed. Creep failure was related to the solidified microstructure. Creep cracks began at the grain boundary normal to the applied stress, especially at the γ/γ’ eutectic phase on grain boundaries. Most of γ/γ’ eutectics which had solidified at the last stage of casting, had microporosity which became a crack initiation site during creep. MC carbide reaction with the matrix γ was observed in the creep failed specimens.     

Quantitative models on corrosion fatigue crack growth rates in metals: Part II. application of fatigue crack growth rate modeling for nickel-based superalloys at elevated temperatures

Approaches to predict da/dN-àK for environmental situations; including empirical interpolative equations, linear superposition of mechanical fatigue and time-based environmental cracking, and mechanism-based models; are presented. For several material-environment systems, these models were incorporated in fracture mechanics life prediction methods, and successes have been reported in evaluating the corrosion fatigue contribution. Considerable uncertainties are, however, associated with these models. The linear superposition analysis is emphasized; material-environment systems that are severely environment-sensitive should be adequately described by this method. Direct and indirect methods exist to define time-based crack growth rates for use in linear superposition predictions of da/dN. The linear superposition approach is effective, but only for those cases where K_ISCC is high relative to typical flawed component stress intensity levels. Empirical curve-fit models require an extensive environmental crack growth rate data base, which are costly to develop, and are effective for interpolations but not predictions of fatigue crack growth data. Mechanism-based models for broad predictions of cycle-time dependent da/dN versus àK, and other variables such as frequency or hold time, are in an infant state.     

The effect of crystalline morphology of poly (butylene terephthalate) phases on toughening of poly(butylene terephthalate)/epoxy blends

In an effort to investigate the effect of the crystalline morphology of a poly(butylene terephthalate) (PBT) phase on the toughening of PBT/epoxy blends, the blends, having different degrees of perfectness of the PBT crystalline phase, were prepared by blending PBT and epoxy at various temperatures ranging from 200 to 240 °C. As the blending temperature decreases, the degree of perfectness of the PBT crystalline phase increases as a result of the increase of crystal growth rate. For PBT/epoxy blends, the change in crystalline morphology induced by processing may be the most important cause for the dependency of the fracture energy on blending temperatures. It has been found that PBT phases with a well-developed Maltese cross are most effective for epoxy toughening. This dependency reveals the occurrence of a phase transformation toughening mechanism. Also, the higher relative enhancement of fracture energy of a higher molecular weight epoxy system is further indirect evidence for a phase transformation toughening mechanism. Some other toughening mechanisms observed from the fracture surfaces, such as crack bifurcation, crack bridging, and ductile fracture of PBT phases, have been found to also be affected by the blending temperatures.     

Blends of ethylene 1‐octene copolymer synthesized by Ziegler–Natta and metallocene catalysts. II. Rheology and morphological behaviors

The rheological and morphological behaviors of commercially available three binary blends of ethylene 1‐octene copolymer (EOC) regarding the melt index (MI), density and comonomer contents, one component made by the Ziegler–Natta and the other by the metallocene catalysts, were investigated to elucidate miscibility and phase behavior. Miscibility of the EOCs blend in a melt state was related to the value of the MI, density, and comonomer content. If the comonomer contents are similar, then the melt viscosity is weight average value, otherwise it is positively or negatively deviated. The microtomed surface prepared by two different cooling processes—one is fast cooling and the other is slow cooling—indicated that all the blends were not homogenous regardless the density, MI, and comonomer content. The Ziegler–Natta catalyzed EOCs exhibited bigger spherulitic diameter and larger ring space than those of the metallocene EOCs prepared by a cooling process. The blends consisting of similar MI showed banded spherulites with different diameter, whereas the blend consisting of different MI and density takes place of explicit phase separation and phase inversion at 1 : 1 blend composition. The melt rheology appeared to influence the mechanical and film properties in the solid state. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1950–1964, 2000     

Miscibility and processibility in linear low density polyethylene and ethylene-propylene-butene-1 terpolymer binary blends

Blends of linear low density polyethylene (ethylene-octene-1 copolymer) and ethylene-propylene-butene-1 terpolymer (ter-PP) mixed in a twin-screw extruder have been characterized by using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis, scanning electron microscopy (SEM), rheometric mechanical spectrometry, a capillary rheometer, and a universal test machine. Melting and crystallization behaviors by DSC and the α, β, and γ dynamic mechanical relaxations proposed that the blend is immiscible in the amorphous and crystalline phases by observing the characteristic peaks arised solely from those of the constituents. The lack of interfacial interaction between the components was suggested by the SEM study. A strong negative deviation of melt viscosity from the additive rule and the Cole-Cole plot confirmed the immiscibility in melt state. Incorporation of ter-PP induced a reduction in melt viscosity, shear stress, and final load. Flexural modulus and yield stress were linearly increased with ter-PP content, while the tensile strength and elongation at break were more or less changed. Although this blend system is immiscible in the solid and melt states, addition of less than 20 wt % ter-PP in the blend is viable for engineering applications with the advantages of improved processibility and mechanical properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1265–1274, 1997     

Correlation between Oxidative Stress and Transforming Growth Factor-Beta in Cancers

The downregulation of reactive oxygen species (ROS) facilitates precancerous tumor development, even though increasing the level of ROS can promote metastasis. The transforming growth factor-beta (TGF-β) signaling pathway plays an anti-tumorigenic role in the initial stages of cancer development but a pro-tumorigenic role in later stages that fosters cancer metastasis. TGF-β can regulate the production of ROS unambiguously or downregulate antioxidant systems. ROS can influence TGF-β signaling by enhancing its expression and activation. Thus, TGF-β signaling and ROS might significantly coordinate cellular processes that cancer cells employ to expedite their malignancy. In cancer cells, interplay between oxidative stress and TGF-β is critical for tumorigenesis and cancer progression. Thus, both TGF-β and ROS can develop a robust relationship in cancer cells to augment their malignancy. This review focuses on the appropriate interpretation of this crosstalk between TGF-β and oxidative stress in cancer, exposing new potential approaches in cancer biology.