Development and Validation of an Artificial Mechanical Skin Model for the Study of Interactions between Skin and Microneedles

Microneedles are small needle‐like structures that are almost invisible to the naked eye. They have an immense potential to serve as a valuable tool in many medical applications, such as painless vaccination. Microneedles work by breaking through the stratum corneum, the outermost barrier layer of the skin, and providing a direct path for drug delivery into the skin. A lot of research has been presented over the past two decades on the applications of microneedles, yet the fundamental mechanism of how they interact, pressure, and penetrate the skin in its native state is worth examining further. As such, a major difficulty with understanding the mechanism of microneedle–skin interaction is the lack of an artificial mechanical human skin model to use as a standardized substrate. In this research news, the development of an artificial mechanical skin model based on a thorough mechanical study of fresh human and porcine skin samples is presented. The artificial mechanical skin model can be used to study the mechanical interactions between microneedles and skin, but not diffusion of molecules across skin. This model can assist in improving the performance of microneedles by enhancing the reproducibility of microneedle depth insertions for optimal drug delivery and biosensing.

     

Enhanced calcium–magnesium–aluminosilicate (CMAS) resistance of GdAlO3 (GAP) for composite thermal barrier coatings

The impact of calcium–magnesium–alumino-silicate (CMAS) degradation is a critical factor for development of new thermal and environmental barrier coatings. Several methods of preventing damage have been explored in the literature, with formation of an infiltration inhibiting reaction layer generally given the most attention. Gd₂Zr₂O₇ (GZO) exemplifies this reaction with the rapid precipitation of apatite when in contact with CMAS. The present study compares the CMAS behavior of GZO to an alternative thermal barrier coating (TBC) material, GdAlO₃ (GAP), which possesses high temperature phase stability through its melting point as well as a significantly higher toughness compared with GZO. The UCSB laboratory CMAS (35CaO–10MgO–7Al₂O₃–48SiO₂) was utilized to explore equilibrium behavior with 50:50 mol% TBC:CMAS ratios at 1200, 1300, and 1400°C for various times. In addition, 8 and 35 mg/cm² CMAS surface exposures were performed at 1425°C on dense pellets of each material to evaluate the infiltration and reaction in a more dynamic test. In the equilibrium tests, it was found that GAP appears to dissolve slower than GZO while producing an equivalent or higher amount of pore blocking apatite. In addition, GAP induces the intrinsic crystallization of the CMAS into a gehlenite phase, due in part to the participation of the Al₂O₃ from GAP. In surface exposures, GAP experienced a substantially thinner reaction zone compared with GZO after 10 h (87 ± 10 vs. 138 ± 4 μm) and a lack of strong sensitivity to CMAS loading when tested at 35 mg/cm² after 10 h (85 ± 13 versus 246 ± 10 μm). The smaller reaction zone, loading agnostic behavior, and intrinsic crystallization of the glass suggest this material warrants further evaluation as a potential CMAS barrier and inclusion into composite TBCs.     

Silver monoliths and their applications in catalytic reduction of 4-NP to 4-AP and sensing against As3+

Journal of Porous Materials - Silver monoliths using non-ionic surfactant Triton X-102 as reducing agent with and without additives such as Dextran and Ludox (SiNPs) were synthesized by modified...     

pH‐sensitive crosslinked guar gum‐based superabsorbent hydrogels: Swelling response in simulated environments and water retention behavior in plant growth media

Crosslinked guar gum‐g‐polyacrylate (cl‐GG‐g‐PA) superabsorbent hydrogels were prepared to explore their potential as soil conditioners and carriers. The hydrogels were prepared by in situ grafting polymerization and crosslinking of acrylamide onto a natural GG followed by hydrolysis. Microwave‐initiated synthesis under the chosen experimental conditions did not exhibit any significant improvement over the conventional technique. The optimization studies of various synthesis parameters, namely, monomer concentration, crosslinker concentration, initiator concentration, quantity of water per unit reaction mass, particle size of backbone, and concentration of alkali were performed. The hydrogels were characterized by wide‐angle X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and solid‐state ¹³C‐NMR spectroscopy. Swelling behavior of a candidate hydrogel [GG‐superabsorbent polymer (SAP)] in response to external stimuli, namely, salt solutions, fertilizer solutions, temperature, and pH, was studied. The GG‐SAP exhibited significant swelling in various environments. The effect of GG‐SAP on water absorption and the retention characteristics of sandy loam soil and soil‐less medium were also studied as a function of temperature and moisture tensions. The addition of GG‐SAP significantly improved the moisture characteristics of plant growth media (both soil and soil‐less), showing that it has tremendous potential for diverse applications in moisture stress agriculture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41060.     

Performance enhancement and energy reduction using hybrid cryogenic distillation networks for purification of natural gas with high CO2 content

A novel concept of hybrid cryogenic distillation network has been explored which maximizes the benefits of both desublimation or solid-vapor based separation as well as distillation or vapor-liquid equilibrium based separation during the separation of carbon dioxide from methane or natural gas. Process network synthesis has been performed for four case studies with high carbon dioxide (72 mole%) and medium carbon dioxide (50 mole%) natural gas feed streams. The benefits of optimal locations for cryogenic packed beds were investigated. A conventional cryogenic network consisting of multiple distillation columns with butane as additive for extractive distillation was also studied and presented in this paper. Process modeling of cryogenic distillation network with MESH equations was attempted using an integrated dual loop (C+3) convergence and the results were compared with Aspen Plus simulator for benchmarking. The prediction of solidification region was employed using experimental data from literature to avoid solidification regions in the column. The proposed hybrid cryogenic distillation network showed promising potential for energy and size reduction.     

Significantly high electromagnetic shielding effectiveness in polypyrrole synthesized by eco-friendly and cost-effective technique

A facile and eco-friendly synthesis of polypyrrole from monomer pyrrole using nominal amount of ferric chloride hexahydrate (FeCl₃.6H₂O) oxidant in aqueous solution by chemically oxidative polymerization method has been reported. The use of aqueous solvent and ferric chloride hexahydrate salt in polypyrrole synthesis have an eco-friendly route favorable for the production of polypyrrole in large quantities. The synthesized polypyrrole samples exhibit good electrical conductivity (2 S/cm) and yield of 80% for reaction time of 8 hr at 5°C. Quality and properties of polypyrrole samples have been thoroughly investigated with varying reaction time and temperature while other synthesis parameters like molar ratio of oxidant to monomer, oxidant concentration, and solvent were kept constant. X-ray diffraction analysis of polypyrrole with a shorter reaction time shows the presence of iron oxide (Fe₂O₃) peaks. The complete reaction may not occur at shorter reaction times due to which residual ferric ions converted into Fe₂O₃. X-ray photoelectron spectroscopy measurement of polypyrrole also confirms the formation of Fe₂O₃. Appropriate selection of reaction time and temperature produced pure phase polypyrrole with high yield and good conductivity. Synthesized polypyrrole by our eco-friendly and cost-effective technique exhibits prominent electromagnetic shielding effectiveness value of 30 dB in the X-band (8–12 GHz).     

TRISO fuel volume fraction and homogeneity:a nondestructive characterization

A new nondestructive method to estimate the volume fraction and homogeneity of tristructural isotropic(TRISO)-coated fuel particles in fuel compacts designed for high-temperature reactors has been developed using image analysis of conventional X-radiographs. The method is demonstrated on surrogate fuel compacts containing TRISO-coated particles with kernels made of zirconium dioxide. The methodology incorporates a correction for superimposed images of TRISO particles such that a single X-ray image obtained in any one random orientation is sufficient to characterize the fuel compact in terms of volume fraction and homogeneity. The method is based on the virtual segregation of images of each particle inside the compact with the aid of a calibration standard.     

Bacterial Quorum Sensing and Food Industry

Abstract: Food spoilage and biofilm formation by food‐related bacteria are significant problems in the food industry. Even with the application of modern‐day food preservative techniques, excessive amounts of food are lost due to microbial spoilage. A number of studies have indicated that quorum sensing plays a major role in food spoilage, biofilm formation, and food‐related pathogenesis. Understanding bacterial quorum‐sensing signaling systems can help in controlling the growth of undesirable food‐related bacteria. This review focusses on the various signaling molecules produced by Gram‐negative and Gram‐positive bacteria and the mechanism of their quorum‐sensing systems, types of signaling molecules that have been detected in different food systems using biosensors, the role of signaling molecules in biofilm formation, and significance of biofilms in the food industry. As quorum‐sensing signaling molecules are implicated in food spoilage, based on these molecules potential, quorum‐sensing inhibitors/antagonists can be developed to be used as novel food preservatives for maintaining food integrity and enhancing food safety. Practical Application: Bacteria use signaling molecules for inter‐ and intracellular communication. This phenomenon of bacterial cell‐to‐cell communication is known as quorum sensing. Quorum‐sensing signals are implicated in bacterial pathogenicity and food spoilage. Therefore, blocking the quorum‐sensing signaling molecules in food‐related bacteria may possibly prevent quorum‐sensing‐regulated phenotypes responsible for food spoilage. Quorum‐sensing inhibitors/antagonists could be used as food preservatives to enhance the shelf life and also increase food safety.