The effect of solidification on the casting window after bubble entrainment

The objective of this work is to investigate the feasibility of extending the velocity boundary during the slot die casting of a polymer film, by studying the dynamics of entrained bubbles as they transition from the fluid to the solid phase. The solution of interest is a relatively high viscosity non-Newtonian solution. A 2D computational fluid dynamics model, using ANSYS FLUENT 13.0 software, was developed to analyze this behavior. The volume of fluid method and enthalpy–porosity technique were used to track the air (i.e., entrained bubbles) and fluid phases and the solidification of the solution, respectively. It has been found that for this class of solution, bubbles that are entrained in the fluid phase will not diffuse out of the fluid due to the stresses formed during solidification. Thus, for relatively high viscosity non-Newtonian solution, the upper boundary of the casting window cannot be extended after a defect has originated in the film during the casting process.     

Development of Isatin-Based Schiff Bases Targeting VEGFR-2 Inhibition: Synthesis,Characterization, Antiproliferative Properties,and QSAR Studies

Three sets of isatin-based Schiff bases were synthesized utilizing the molecular hybridization approach. Some of the synthesized Schiff bases show significant to moderate antiproliferative properties against MCF7 (breast), HCT116 (colon), and PaCa2 (pancreatic) cancer cell lines with potency compared to reference drugs 5-fluorouracil (5-FU) and Sunitinib. Among all, compound 17 f (3-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1-((1-(2-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)-5-methylindolin-2-one) exhibits promising antiproliferative properties against the MCF7 cancer cell line with 2.1-fold more potency than Sunitinib. However, among all the synthesized compounds, three (5-methylisatin derivatives) were the most effective against HCT116 in comparison to 5-FU. Compound 17 f exhibited the highest anti-angiogenic effect on the vasculature as it significantly reduced BV from 43 mm to 2 mm in comparison to 5.7 mm for Sunitinib and flow cytometry supports the arrest of the cell cycle at G1/S phases. In addition, compound 17 f also showed high VEGFR-2 inhibition properties against breast cancer cell lines. Robust 2D-QSAR studies supported the biological data.     

Antibacterial and Antibiofilm Activity of Mercaptophenol Functionalized-Gold Nanorods Against a Clinical Isolate of Methicillin-Resistant Staphylococcus aureus

Journal of Inorganic and Organometallic Polymers and Materials - Gold nanorods (AuNRs) were synthesized by the seed-mediated wet chemical method using a binary surfactant system. AuNRs were...     

Enhanced adsorption of anionic phenol red using cationic polyethylenimine-incorporated chitosan beads

Journal of Porous Materials - In this study, a fast and simple dissolution and coagulation method was adopted to produce polyethylenimine (PEI)-incorporated chitosan beads. The beads were...     

In situ preparation of CdS/PVA nanocomposites using gamma radiation

Films of poly(vinyl alcohol)/cadmium sulphide (PVA/CdS) nanocomposite containing various concentrations of Cd²⁺ ions were prepared using gamma radiation at different doses from 50 up to 200 kGy. The UV/VIS spectra revealed that the CdS/PVA nanocomposites showed blue shift for the absorption peak as compared with bulk CdS. As the irradiation dose increased, a gradual red shift in the wavelength accompanying with broadening of the absorption peak was observed. The estimated optical band gap energies and the calculated CdS particle sizes of (PVA/CdS) showed correlation between their values and the variable parameters (irradiation dose and Cd⁺²:S^?2 molar ratio). Transmission electron microscopy images showed that the CdS/PVA nanocomposites were dispersed as spherical CdS nanoparticles with homogeneity at either lower concentration of CdCl₂ or irradiation dose. The nano‐rod structures of CdS was accompanied with small agglomeration at either higher CdCl₂ concentration or irradiation dose. A cubic phase and mixture of cubic and hexagonal phases of the prepared CdS nanoparticles were formed at lower and higher CdCl₂ concentrations, respectively. Fourier Transform Infrared spectra confirmed the coordination of CdS nanoparticles with the hydroxyl groups of PVA matrix. POLYM. ENG. SCI., 55:2583–2590, 2015. © 2015 Society of Plastics Engineers     

Fabrication of silver nanoparticles dispersed in palm oil using laser ablation

In this study we used a laser ablation technique for preparation of silver nanoparticles. The fabrication process was carried out by ablation of a silver plate immersed in palm oil. A pulsed Nd:YAG laser at a wavelength of 1064 nm was used for ablation of the plate at different times. The palm coconut oil allowed formation of nanoparticles with very small and uniform particle size, which are dispersed very homogeneously within the solution. The obtained particle sizes for 15 and 30 minute ablation times were 2.5 and 2 nm, respectively. Stability study shows that all of the samples remained stable for a reasonable period of time.     

Numerical analysis of the influence of two-phase flow mass and heat transfer on n-heptane autoignition

This paper investigates the influence of liquid fuel presence on the autoignition of n-heptane/air mixtures over a wide range of conditions encountered in internal combustion engines. To this end, evaporating droplet physics and skeletal chemistry mechanisms are simultaneously solved considering a homogeneous constant-pressure reactor. A skeletal mechanism is introduced to account for specific kinetics behavior in the Negative Temperature Coefficient (NTC) region. The impact of mass and heat source terms during evaporation is emphasized by comparing a two-phase flow scenario with a purely gaseous case. The competition between fuel vapor availability and the evaporation-induced gas temperature decrease is specific to two-phase flow autoignition. On the one hand, droplet evaporation delay restricts the gaseous local fuel/air equivalence ratio and consequently the kinetics runaway. On the other hand, temperature reduction due to evaporation may either reduce or enhance chemical reactivity, depending on the local thermodynamic conditions lying either inside or outside the NTC region. By simultaneously accounting for evaporation source terms and skeletal chemistry, we can reproduce the already experimentally observed transformation of the NTC region into a Zero Temperature Coefficient (ZTC) region depending on thermodynamic conditions and droplet size. The ZTC phenomenon appears when combustion heat-release starts before complete droplet evaporation. Since the ZTC behavior can be captured using the point source approach, in which droplets are considered only as zero-dimensional source terms of mass and energy, the present results pave the way for future exploration of NTC chemistry in sprays with a direct numerical simulation of discrete particles considering detailed chemistry and turbulent flows.     

Structure and Dynamic Mechanical Properties of Melt Intercalated Polyamide 6—Montmorillonite Nanocomposites

Summary: Polymer‐layered silicate nanocomposites (PLSN), based on polyamide 6 (PA6) and montmorillonite (MMT) modified with an octadecylammonium salt, were produced via melt compounding in a co‐rotating twin‐screw extruder. Wide angle X‐ray diffraction (WAXD) and TEM revealed a PLSN containing 3.3% by weight (wt.‐%) of MMT to exhibit a mixed exfoliated/intercalated morphology, consisting mainly of individual silicate lamellae together with some intercalated stacks, resulting in a mean value of 1.8 lamellae per particle. In contrast, a PLSN containing a higher level of 7.2 wt.‐% MMT exhibited a more ordered intercalated structure, consisting mainly of a distribution of lamellae stacks with a mean value of 3.8 lamellae per particle. The dispersion of MMT in the PLSN generated very large polymer–filler interfacial areas, resulting in significant increase in the volume of constrained PA6 chain segments. Consequently, significant changes in the ratio of α/γ crystallites and in the thermal behaviour of the matrix PA6 were observed during WAXD, DSC and dynamic‐mechanical thermal analysis (DMTA) studies of the PLSN. In particular, damping data from DMTA showed relaxations between T_g and T_m resulting from amorphous polymer chain segments constrained at the polymer–filler interface, indicating the formation of a continuous phase of constrained polymer. In contrast, a PA6 microcomposite formed using unmodified MMT generated much lower polymer–filler interfacial area, with most of the MMT residing within large, poorly wetted aggregates. Consequently, changes to the thermal behaviour of the matrix PA6 were much less significant than those induced in the PLSN.

Shear storage modulus (G′) versus temperature data for the matrix PA6, the 5T and 10T PLSN and the 5P microcomposite.     

Development of foolproof catheter guide system based on mechatronic design

Minimally invasive surgery (MIS) is a less invasive procedure compared to traditional open surgery. It usually involves laparoscopic devices and remote control manipulation instruments comprising an endoscope for indirect observation of the surgical field. Interventional radiology (IVR) is one of the MIS methodologies. The IVR procedures include diagnosis such as angiograms, and treatment. The IVR procedures use small tubes called catheters, which are inserted through the body cavity or blood vessel to the treatment area. The IVR procedures lead to the risk of X-ray exposure to surgeon since the procedures is using the digital subtraction angiography device to get clear image of the patient blood vessel. Therefore, we have developed a foolproof tele-operated system to guide the catheter. Hence, the reliability in IVR procedure is crucial. The system is based on a mechatronic design methodology characterized by a principle solution specified in CONSENS^® (CONceptual design Specification technique for the ENgineering of complex Systems). This principle solution serves as a basis for the first analysis and verification on the system level. Further, the proposed concept of control system can also be re-used in the other foolproof guidance systems.     

Void formation and morphology in NiAl

Void formation in stoichiometric NiAl was studied through controlled heat treatments and microstructural characterization through transmission electron microscopy. Voids were observed to form at temperatures as low as 400°C, but were noted to dissolve during annealing at 900°C. Two distinct void shapes, cuboidal and rhombic dodecahedral, were observed, often at the same annealing temperature. At higher temperatures (800°C) extensive dislocation climb, rather than void formation, was noted. The relative incidence of void formation and dislocation climb can be related to the mobility of vacancies at each annealing temperature. The shape of void type is described in terms of their relative surface energy and mode of nucleation.