Thermosensitive nanoparticles prepared from poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) and its blend with poly(lactide‐co‐glycolide) for efficient drug delivery system

Temperature‐responsive polymers have become increasingly attractive as carrier for the injectable drug delivery systems. In the present work, we have studied the preparation of poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) (NIPAAm‐AAm‐VP terpolymer) nanoparticulated terpolymer and its blend with poly(lactide‐co‐glycolide, PLGA; molar ratio of lactide/glycolid 1/3). Thermosensitive terpolymer, poly(NIPAAm‐AAm‐VP) was prepared by free‐radical polymerization in aqueous solution. The nanoparticles of poly(NIPAAm‐AAm‐VP) and its blend with PLGA containing naltrexone were prepared using the evaporation and w/o emulsion‐solvent evaporation methods, respectively. Nanoparticles prepared from terpolymer‐PLGA blend at low polymer concentration (5%) shows larger particle size (>300 nm) and higher drug content%. Various types of nanoparticles showed a burst release of less than 10% after 24 h . The results suggest that by regulating different variables, desired release profiles of naltrexone can be achieved using a blend of PLGA‐poly(NIPAAm‐AAm‐VP) nanoparticulate system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Convective drying of wood-waste in air and superheated steam

The convective batch drying of Western Hemlock hog fuel-sized particles in fixed beds under various operating conditions quantiatively established the effect of factors which govern the drying process. A correlation was obtained for the Nusselt number during the heat transfer controlled period. Under specific conditions, the existence of a unified characteristic drying rate curve was confirmed. Drying behaviour as described by the receding plane model provided a mathematical expression for such a curve. The existence of an inversion point temperature was experimentally confirmed.     

Robust stochastic moment control via genetic-pole placement in communication network parameter setting

In this paper, the problems of stochastic robust approximate covariance assignment and robust covariance feedback stabilization, which are applied to variable parameters of additive increase/multiplicative decrease (AIMD) networks, are considered. The main idea of the developed algorithm is to use the parameter settings of an AIMD network congestion control scheme, where parameters may assign the desired network’s window covariance, with respect to the current network conditions. The aim is to search for the optimal AIMD parameters of a feedback gain matrix such that the objective functions defined via appropriate robustness measures and covariance assignment constraints can be optimized using an adaptive genetic algorithm (AGA). It is shown that the results can be used to develop tools for analyzing the behavior of AIMD communication networks. Quality of service (QoS) and other performance measures of the network have been improved by using the proposed congestion control. The accuracy of the controller is demonstrated by using MATLAB and NS software programs.     

Plasticized poly(vinyl chloride) composites: Influence of different nanofillers as antimigration agents

In this study, plasticized poly(vinyl chloride) (PVC) composites with different nanofillers, including single‐walled carbon nanotubes (SWCNTs), organoclay, TiO₂, and ZnO nanoparticles, were prepared, and their effects on plasticizer migration were investigated. Scanning electron micrographs revealed the dispersion quality of the nanofillers in the polymer matrix. It had a significant influence on the performance of the nanofillers in the process of plasticizer migration. Migration and exudation tests showed that the nanofillers could efficiently hinder plasticizer migration. On the basis of these results, we concluded that carbon nanotubes were the best antimigration agent in the plasticized system. This was ascribed to the high aspect ratio of the SWCNTs and the good interactions between them and the plasticizer. Also, TiO₂ nanoparticles showed a better performance compared to the ZnO nanoparticles. This was due to the more homogeneous dispersion of the TiO₂ in the polymer matrix and the higher surface area of the particles. The differential scanning calorimetry thermograms were in good agreement with the migration tests. The lowest change in the glass‐transition temperature was observed for the composite filled with SWCNTs. This indicated that a lower amount of the plasticizer migrated from PVC. The thermogravimetric analysis curves showed that the incorporation of the nanofillers improved the thermal stability of the PVC. The results could be useful for determining the efficiency of plasticized PVC in applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42559.     

A wide frequency range delay line for fast-locking and low power delay-locked-loops

A voltage controlled delay cell with wide frequency range is presented in this paper. The delay-line which is resulted by connecting five series of delay cells generating a wide range of delay from 1.9 to 13.24 ns. It can be used in an analog delay locked loop. The linear characteristic of the circuit with respect to the conventional delay line structures is improved, and a better performance of noise is obtained using differential structure. This circuit is designed by ADS software and TSMC CMOS 0.18 μm technology, with supply voltage 1.8 V. By changing control voltage from 0.335 to 1.8 V in delay line, a wide range of frequency from 75.52 to 917.43 MHz will be covered. Simulation results show that the proposed delay line has power consumption of maximum 3.77 mW at frequency of 75.52 MHz. It also shows that increasing of frequency will reduce power dissipation which is the one of the main characteristics of this novel circuit. Moreover, the delay locked loop which uses these delay cells has a very high lock speed so that the maximum lock time in just five clock cycles.     

Meso-tetraarylporphyrin catalyzed highly regioselective ring opening of epoxides with acetic acid

Highly regioselective ring opening of styrene oxide with acetic acid in the presence of catalytic amounts of meso-tetra(4-CH₃)phenyl- or meso-tetraphenylporphyrin at room temperature is reported. Under the same reaction conditions, cyclohexene oxide is more reactive than styrene oxide and gives the trans-isomer as the sole product.     

Dendritic macromolecules containing several types of functional groups

Dendritic macromolecules containing several types of functional groups were successfully synthesized through divergent method. Poly(ethylene glycol) was functionalized using cyanuric chloride and it was reacted with p‐toluidine at room temperature and a macromolecule containing chloride and methyl functional groups (PEG‐Cl₂‐Me₂) was obtained. Substitution of chloride functional groups of PEG‐Cl₂‐Me₂ by hydroxyl functional groups led to a macromolecule containing methyl and hydroxyl functional groups (PEG‐Me₂‐OH₄). Hydroxyl functional groups of PEG‐Me₂‐OH₄ were reacted with cyanuric chloride and PEG‐Me₂‐Cl₈ was obtained. Finally, PEG‐Me₂‐Cl₈ was reacted with p‐aminophenol at room temperature and a macromolecule containing methyl, hydroxyl, and chloride functional groups (PEG‐Me₂‐(PhOH)₄‐Cl₄) was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Test methods for characterizing concrete properties at elevated temperature

Fire resistance of structural members is dependent on the thermal and mechanical properties of constituent materials and these properties vary as a function of temperature. Currently, there are limited standardized test procedures for evaluating thermal and mechanical properties of construction materials at elevated temperatures. This paper provides a review and assessment of test methods and procedures for evaluating high temperature thermal and mechanical properties of concrete. The drawbacks and variations in currently available test procedures and methods in standards are discussed. Recommendations on the most suitable methods and procedures for measuring thermal and mechanical properties at elevated temperature is presented. In addition, applicability of the proposed high temperature test methods and procedures is illustrated through a case study on conventional concrete specimens. Further, the need for developing standards by organizations such as American Society for Testing and Materials (ASTM), with standardized specifications and test procedures for measuring high temperature properties of construction materials, is laid out.