Designing of biodegradable polycaprolactone: Binary and ternary coatings to minimize the defects and cost of solvent(s)

Coatings of polycaprolactone (PCL) in methylene chloride and toluene were prepared using solution casting method. Coatings of two different polymer mass percentages (5% and 10%), and thicknesses (800 and 1600 μm) were prepared. A drying study on PCL-methylene chloride-toluene coatings was carried out. The binary coatings of PCL-methylene chloride and PCL-toluene served as control cases. The results showed that the drying behavior was external mass transfer controlled for the binary coatings but diffusion controlled for the ternary coatings for most of the drying period. The drying rate enhanced but residual solvent increased with the progressive increase in initial concentration of methylene chloride and decrease in initial concentration of toluene. This shows that the drying rate can be enhanced by partially replacing the costly solvent with cheaper one, that is, toluene with methylene chloride. The coatings were characterized by scanning electron microscopy to understand the surface morphology. The scanning electron microscopy results further indicate that replacing toluene with methylene chloride caused disappearance of cracks, wrinkles, and phase-separation. The coatings with high initial content of methylene chloride were smooth and dense, and more residual solvent content does not manifest in coating defects. Hence, replacement of toluene with methylene chloride leads to savings on material and energy costs for drying along with better quality coatings.     

Chemical fixation of carbon dioxide to dimethyl carbonate from propylene carbonate and methanol using ionic liquid catalysts

The synthesis of dimethyl carbonate (DMC) through the transesterification of propylene carbonate (PC) with methanol was investigated by using imidazolium salt ionic liquid catalysts. 1-alkyl-3-methyl imidazolium salts of different alkyl group (C₂, C₄, C₆, C₈) and anions (Cl⁻, Br⁻, BF₄⁻, PF₆⁻) were used for catalysts. The reaction was carried out in an autoclave at 140–180°C under carbon dioxide pressure of 1.48–5.61 MPa. The imidazolium salts of shorter alkyl group, and more nucleophilic counter anion exhibited higher catalytic activity. The conversion of PC increased as CO₂ pressure and reaction temperature increased. Kinetic studies were also performed to better understand the reaction mechanism. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Detection of DDOS Attack using Deep Learning Model in Cloud Storage Application

Wireless Personal Communications - In recent years, distributed denial of service (DDoS) attacks pose a serious threat to network security. How to detect and defend against DDoS attacks is...     

Determination of Putrescine in Tiger Prawn Using an Amperometric Biosensor Based on Immobilization of Diamine Oxidase onto Ceria Nanospheres

An increase of putrescine content in tiger prawn can be related to the deterioration of its quality. Increase in putrescine consumption causes nausea, vomiting, diarrhea, allergy, and flushing in humans. To address this issue, a glassy carbon electrode modified with diamine oxidase on ceria nanoparticles was fabricated for rapid determination of putrescine in tiger prawn. Based on the amperometric response, calibrated models such as linear, Hill, and Michaelis–Menten functions were constructed. The best performing model was based on Hill analysis, yielding relative prediction error of 0.035, percentage recovery of 113.10, and root mean square error of cross validation of 0.083. All the three models were verified with extract of tiger prawn sample. Among the three models, only the amperometric biosensor based on Hill analysis showed acceptable recovery with low relative standard deviation in tiger prawn sample.     

Thermally induced cation ordering in $$\hbox {ZnAl}_{2}\hbox {O}_{4}{:}\hbox {Mg}^{2+}$$ ZnAl 2 O 4 : Mg 2 + , $$\hbox {Fe}^{3+}$$ Fe 3 + for sensing thermal history through photoluminescence

Journal of Materials Science - Applicability of spinel compounds is mainly governed by cation distribution in them. In the presented study, thermally induced cation ordering is found to influence...     

A Dual Band Notched Ultra-Wideband Antenna

Wireless Personal Communications - In this paper, we design a planar monopole UWB antenna among two notched. Two semi-elliptical geometries are introduced at the lower and upper side’s...     

Effect of iron on the solubility of hydrogen in tantalum

Pressure-composition-isotherms for Ta–Fe–H systems have been investigated in the temperature range 673–873 K. Tantalum–iron alloys (Ta–xFe, x = 0, 1.6 and 3.2 atom  % Fe) were prepared by arc melting using high purity elements. The equilibrium solid solubility of hydrogen in the alloys decreases with an increase of iron content. Thermodynamic parameters of the solution process—the Gibb’s free energy, enthalpy, and entropy, for each of the solutions have been calculated. The relative partial molar enthalpy becomes less negative with increase in iron content, whereas the entropy values are nearly constant for these alloys. The solubility changes were explained on the basis of change in lattice strain energy of tantalum due to iron addition.