Electrospun fibers loaded with ball-milled poly(n-isopropylacrylamide) microgel particles for smart delivery applications

Stimuli-responsive electrospun fibers loaded with therapeutic agents for smart delivery are attractive biomedical applications. However, development of such fibers requires the use of complex chemical processes that can induce toxicity, reduce fiber quality, or prohibit fiber electrospinnablity. To address these challenges, core-shell structured fibers capable of temperature-controlled delivery of nanoparticles were developed. The fiber core contained an aqueous suspension of poly(n-isopropylacrylamide) (PNIPAM) microgel particles and silver nanoparticles (model antibacterial drug). A novel use of ball-milling was applied to produce microgel particles with an average hydrodynamic diameter of 511 ± 100 nm. The ball-milling technique was developed to avoid the current complex chemical processes for syntheses of microgels, and to address the need for high-yield techniques in industrial manufacturing. The results show that the thermoresponsive properties of the PNIPAM hydrogel particles were preserved during the ball-milling process. The fiber shell formed a strong structure matrix, regulated the nanoparticles release pathway (through open pores formed via selective dissolution of porogen), and served as a barrier to prevent direct contact of microgel particles with tissues. This core-shell fiber design allows for the future application of various therapeutic agents, including fragile and bioactive agents, and microgel particles with special properties.     

Removal of Arsenic and Copper from Water Solution Using Magnetic Iron/Bentonite Nanoparticles (Fe3O4/Bentonite)

Silicon - Heavy metal pollution is one problem in the water purification industry, which causes extreme risk aversion. The purpose of this study was to investigate the removal of arsenic (As) and...     

Fire‐retarding properties of nanowollastonite in particleboard

Effects of wollastonite nanofibers on fire‐retarding properties of particleboard were studied here. Nanowollastonite (NW) was applied at 5%, 10%, 15%, and 20% based on the dry weight of wood particles. The size range of wollastonite nanofibers was 30 to 110 nm. Two application methods of NW were used: surface application (SA) in which NW was mixed with a water‐based paint and sprayed on the specimens, and internal application (IA) in which NW was mixed with the urea‐formaldehyde resin. Density was kept constant at 0.68 g/cm³ for all treatments. Specimens of 150 × 130 × 9 mm were prepared, and fire‐retarding properties were measured using 2 apparatuses: slide fire test apparatus and fixed fire test apparatus. The obtained results indicated that most fire‐retarding properties were improved with the increase in NW content up to 15% when applied internally. More than this amount resulted in decreasing of properties that was partly due to the less wood‐chips content and partly due to the absorption of resin by the NW fibers. Surface application showed higher improving effects on the properties. It can be concluded that SA of NW is more effective in improving fire‐retarding properties of particleboard; furthermore, 10% of NW is recommended as an optimum level of consumption.     

Kinetics of (TBAF + CO2) semi-clathrate hydrate formation in the presence and absence of SDS

In this communication, the impacts of adding SDS (sodium dodecyl sulfate), TBAF (tetra-n-butylammonium fluoride) and the mixture of SDS + TBAF on the main kinetic parameters of CO₂ hydrate formation (induction time, the quantity and rate of gas uptake, and storage capacity) were investigated. The tests were performed under stirring conditions at T = 5 ℃ and P = 3.8 MPa in a 169 cm³ batch reactor. The results show that adding SDS with a concentration of 400 ppm, TBAF with a concentration of 1–5 wt%, and the mixture of SDS + TBAF, would increase the storage capacity of CO₂ hydrate and the quantity of gas uptake, and decrease the induction time of hydrate formation process. The addition of 5 wt% of TBAF and 400 ppm of SDS would increase the CO₂ hydrate storage capacity by 86.1% and 81.6%, respectively, compared to pure water. Investigation of the impact of SDS, TBAF and their mixture on the rate of gas uptake indicates that the mixture of SDS + TBAF does not have a significant effect on the rate of gas uptake during hydrate formation process.     

Oxidation and Hot Corrosion Behaviors of Service-Exposed and Heat-Treated Gas Turbine Vanes Made of IN939 Alloy

Oxidation and hot corrosion tests were conducted on service-exposed and heat-treated IN939 alloys at 830, 930 and 1030 °C for testing times up to 800 h. The degradation behaviors were studied using optical and scanning electron microscopes. The oxidation results showed no tangible weight change in the samples at 830 °C. At 930 °C, after initial weight gain, the oxidation samples showed weight loss; whereas a continuous weight loss was observed at the higher temperature of 1030 °C. In the hot corrosion tests, however, a large weight loss occurred in the samples even at 830 °C, indicating an effect of fuel impurities on the high-temperature behavior of the alloy. SEM observations revealed that the main features of oxidation and hot corrosion of the alloy were internal oxidation of aluminum and depletion of chromium in the regions beneath the surface scales.     

Choline chloride/monoethylene glycol deep eutectic solvent as a new asphaltene precipitation inhibitor

In this research work, a family of green solvents named deep eutectic solvents (DES) was used as asphaltene precipitation inhibitor for the first time as per our knowledge, i.e., choline chloride:monoethylene glycol acid (1:1). Ultraviolet–visible (UV–vis) spectrometry was used to estimate the precipitation onset point of asphaltene and to evaluate the impact of the DES to increase their resistance against the precipitant effect. A microscopic method was used to monitor the agglomeration trend during titration. The distribution of asphaltene particles monitored by dynamic light scattering (DLS) showed a value of 1,419 nm for inhibitor-free sample, while for sample with the DES was 1,039 nm under similar conditions.     

Optimum Design of Fractional Order Pid Controller Using Chaotic Firefly Algorithms for a Control CSTR System

A fractional‐order PID controller is a generalization of a standard PID controller using fractional calculus. Compared with the standard PID controller, two adjustable variables, “differential order” and “integral order”, are added to the PID controller. Fractional‐order PID is more flexible, has better responses, and the precise adjustment closed‐loop system stability region is larger than that of a classic PID controller. But the design and stability analysis is more complicated than for the PID controller. Therefore, the optimal setting of parameters is very important. A firefly algorithm in standard mode has only local optimization and accuracy is low. In order to fix this flaw an improved chaotic algorithm firefly is proposed for a design controller FOPID. To evaluate the performance of the proposed controller, it has been used in the control of a CSTR system with a variety of fitness functions. Simulations confirm the optimal performance of the proposed controller.     

Semi‐aromatic polyimide/Ag nanocomposite derived from vanillin

The development of bioprecursor polyimide/Ag nanocomposites (PI/Ag NCs) is reported in this investigation. Semiaromatic bioprecursor PI was successfully synthesized through direct polycondensation reaction between aromatic diamine containing pyridine ring and aliphatic dianhydride. Aromatic diamine as a monomer was synthesized using a renewable resource, vanillin. The main attractive aspects of this PI are the renewable origin of the diamine, presence of pyridine and high aromatic rings content, as well as aliphatic content on the polymer backbone. The structure of synthesized monomer and PI were proven by FTIR, and nuclear magnetic resonance. The PI/Ag NCs containing 3, 5, and 7 wt % of Ag nanoparticles (Ag NPs) were prepared through solution technique and the resulting NCs were characterized by Fourier transform infrared spectra, wide angle X‐ray diffraction, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). TEM results showed that the Ag NPs were dispersed homogeneously in the PI matrix on nanoscale. TGA results indicated improving in thermal properties of PI/Ag NCs compared to the neat PI due to the interaction between the PI matrix and the Ag NPs. Antibacterial activity of PI/Ag NCs was tested by the disk diffusion method using Escherichia coli as model strain of gram‐negative bacteria. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44001.     

Advances in cryopreservation of spermatogonial stem cells and restoration of male fertility

Spermatogenesis is a highly complicated process which initiated by spermatogonial stem cells (SSCs). SSCs are the only cell type that can restore fertility in infertile recipient after SSCs transplantation. SSCs damage during cancer diagnosis and therapy and their depletion may be cause of male infertility in cancer survivors. In this review, used experimental methods regarding SSCs and testis tissue cryopreservation have been reviewed with a special focus on animal models and human which have generated the majority of data about SSCs and the cryopreservation process. Microsc. Res. Tech. 79:122–129, 2016. © 2015 Wiley Periodicals, Inc.