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.     

Advantages of asymmetrical over symmetrical cells for detection of under deposit CO2 corrosion using electrochemical noise

Electrochemical noise (EN) measurements were done on symmetrical and asymmetrical cells after immersion in 3.5% NaCl solutions saturated with CO₂ and containing different concentrations of sodium bicarbonate to get a better interpretation of the under‐deposit corrosion of mild steel. The symmetrical cell was constructed from two sand‐deposited electrodes and the asymmetrical cell was prepared from one sand‐deposited electrode and one bare electrode. The combination of the standard deviation of partial signal (SDPS) plots arising from wavelet analysis and recurrence plots for analyzing the EN signals obtained from symmetrical and asymmetrical cells confirmed the higher detective ability of the asymmetrical cells in comparison with the symmetrical cells for measuring the under‐deposit corrosion of mild steel. Both the SDPS and recurrence plots arising from symmetrical cells showed no significant change in the corrosion severity of the steel alloy with adding sodium bicarbonate. In contrast, the SDPS and recurrence plots of the asymmetrical cells proved that the corrosion severity decreased initially with adding the bicarbonate and thereafter remained constant with increasing the bicarbonate concentration. The optical microscopy images of the sand‐covered electrode surface confirmed the latter result.     

Identification of Acid Mine Drainage Potential Using Sentinel 2a Imagery and Field Data

Mine Water and the Environment - Secondary iron minerals associated with acid mine drainage (AMD) such as copiapite, jarosite, schwertmannite, goethite, ferrihydrite, and hematite can be generated...     

Unraveling the effect of dislocations and deformation-induced boundaries on environmental hydrogen embrittlement behavior of a cold-rolled Al–Zn–Mg–Cu alloy

The effect of dislocation substructure, and deformation-induced boundaries on the hydrogen embrittlement (HE) behavior and the fracture mechanism of a 7xxx series aluminum alloy was investigated using X-ray diffraction line-profile analysis, electron backscatter diffraction, transmission electron microscopy, thermal desorption spectroscopy, and visualization of hydrogen. Hydrogen resides at interstitial lattice sites, statistically-stored dislocations (SSDs), and high-angle boundaries (HABs). SSDs are not the main trap site affecting HE behavior of the alloy. However, the HABs with the high desorption energy act as an almost irreversible trap site, which strongly absorbs hydrogen. It was firstly reported that the higher density of HABs as a strong trap site in a deformed 7xxx series aluminum alloy leads to decreasing the possibility of building up a critical hydrogen concentration required for crack initiation in a typical HAB, resulting in an excellent hydrogen embrittlement resistance.     

Thermodynamic model for prediction of performance and emission characteristics of SI engine fuelled by gasoline and natural gas with experimental verification

In this study, a thermodynamic cycle simulation of a conventional four-stroke SI engine has been carried out to predict the engine performance and emissions. The first law of thermodynamics has been applied to determine in-cylinder temperature and pressure as a function of crank angle. The Newton-Raphson method was used for the numerical solution of the equations. The non-differential form of equations resulted in the simplicity and ease of the solution to predict the engine performance. Two-zone model for the combustion process simulation has been used and the mass burning rate was predicted by simulating spherical propagation of the flame front. Also, temperature dependence of specific heat capacity has been considered. The performance characteristics including power, indicated specific fuel consumption, and emissions concentration of SI engine using gasoline and CNG fuels have been determined by the model. The results of the present work have been evaluated using corresponding available experimental data of an existing SI engine running on both gasoline and CNG. It has been found that the simulated results show reasonable agreement with the experimental data. Finally, parametric studies have been carried out to evaluate the effects of equivalence ratio, compression ratio and spark timing on the engine performance characteristics in order to show the capability of the model to predict of engine operation.     

Microstructure evolution during spark plasma sintering of FJS-1 lunar soil simulant

A spark plasma sintering (SPS) process has been explored to densify FJS-lunar soil simulants for structural applications in space explorations. The effect of SPS conditions, such as temperature and pressure, on the densification behavior, phase transformation, microstructural evolution, and mechanical properties of FJS-1 have been examined by conducting the X-ray diffraction analysis, electron microscopy imaging, and nano/micro indentation testing. Test analysis results were also compared to results from the FJS-1 powder and sintered samples without pressure. The FJS-1 powder was composed of sodian anorthite, augite, pigeonite, and iron titanium oxide. When FJS-lunar soil simulants were sintered without pressure, the main phase evolved from sodian anorthite to the intermediate sodian anorthite, jadeite and glass, and iron titanium oxide at 1000°C, which were further transformed into filiform and feather-shaped augite and schorlomite at 1100°C. Most densification processes in pressureless sintering occurred at 1050°C-1100°C. During the SPS process, the main phases were sodian anorthite, pigeonite, and iron titanium oxide at 900°C. These phases were transformed to sodian anorthite, glass, and feather-shaped augite at 1000°C and 1050°C, with the nucleation of dendritic schorlomite at 1050°C. Significant densification by SPS can be observed as low as 900°C, which indicates that the application of pressure can substantially lower the sintering temperature. The SPSed samples showed higher Vickers microhardness than the pressureless sintered samples. The mechanical properties of the local phases were represented by the contour maps of elastic modulus and nanohardness. Multiscale mechanical test results along with the microstructural characteristics further imply that the SPS can be considered a promising in-situ resource utilization (ISRU) method to densify lunar soils.     

Imparting conductivity and chromic behavior on polyester fibers by means of poly(3‐methylthiophene) nanocoating

Poly(3‐methylthiophene) (P3MT)‐coated polyester fabric is a conductive textile with specific electrical and optical properties; for instance, color change under external stimulus (chromic behavior) was successfully prepared by chemical polymerization with continuous, speed stirring technique. To investigate the striking effect of some variable conditions of polymerization process, the effect of reaction time, temperature, and oxidant concentration on conductivity of the P3MT‐coated fabric was studied. Scanning electron microscopy confirmed that the surface of fabric has entirely been coated with P3MT particles. The further characterizations were investigated using Fourier transform infrared spectroscopy to provide evidence of forming particles onto the fabric, UV–vis absorption spectroscopy, electrical surface resistivity, and pressure dependence visible reflectance spectrophotometer measurements and X‐ray diffraction analysis. The blue shift in wavelength of maximum absorption of about 95 nm to a longer wavelength from that observed in the reflectance spectra of coated polyester fabric; under high‐pressure P3MT‐coated polyester fabric demonstrated piezochromism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012