CNTs-added PMNT/PDMS flexible piezoelectric nanocomposite for energy harvesting application

The flexible piezoelectric nanocomposites based on lead magnesium niobate titanate [Pb(Mg1/3Nb2/3)0.65Ti0.35O3; PMNT] particles in polydimethylsiloxane (PDMS) matrix were fabricated and characterized. PMNT powders are synthesized using the columbite precursor method. PMNT/PDMS flexible nanocomposites are then prepared by spin casting technique, where a small amount of carbon nanotubes (CNTs) is added into the PMNT/PDMS composite to enhance cross-links between PMNT particles and PDMS matrix. The phase and microstructure of the nanocomposite are investigated by using X-ray diffraction and scanning electron microscope (SEM). The electromechanical behavior is evaluated by using an autonomous pneumatic actuator. The flexible composite, occupying approximately 300 mm2, is capable of generating an open-circuit voltage (Voc) of 2.83 ± 0.24 V and a short-circuit current (Isc) signal of 0.33 ± 0.01 µA across 10 Ω resistor under mechanical load of 300 N. The generated electrical charges are 29026 pC. The relative dielectric constant is measured at 10 kHz and found to be 6.76 ± 1.15. The piezoelectric PMNT/PDMS composite can potentially be used in a variety of applications such as wearable sensors, actuators, and energy harvesting for converting kinetic energy into useful electrical energy

Production of biodiesel over waste seashell-derived active and stable extrudate catalysts in a fixed-bed reactor

In this work, waste seashell (Meretrix meretrix) was used as a renewable calcium source to prepare a series of heterogeneous base catalysts for production of biodiesel, a mixture of fatty acid methyl esters (FAME), via transesterification of palm oil with methanol in a continuous-flow fixed-bed reactor. To avoid a severe pressure drop in the reactor column, the catalysts were prepared via the dissolution–precipitation method in the presence of zinc nitrate and alumina, shaped in an extrudate form, and calcined at different temperatures. The catalytic performance of the resulting extrudates in the transesterification depended on not only the active phase type, but also the cluster size of active phase, which was strongly determined by the calcination temperature. Synchrotron-based X-ray micro-computed tomography (micro-CT) was applied for the first time in the development of shaped catalysts. The pore structure of extrudate catalysts obtained at different temperatures was analyzed by nitrogen physisorption measurement, scanning electron microscopy (SEM), and micro-CT, and then correlated with their mechanical properties and catalytic performance. The micro-CT and low-magnification SEM visualized the macroporosity as air voids in the extrudate catalysts. Increasing the calcination temperature from 300 °C to 800 °C decreased the fraction of air voids, resulting in a severe drop of FAME yield due to mass transport problem. The addition of commercial methyl esters into the reaction improved the mass diffusion effectively, and enhanced the biodiesel production. The extrudate catalyst calcined at 300 °C had calcium hydroxide as a main active phase, and the highest macroporosity, which provided a stable FAME yield (>95 wt%) throughout the operation, and a high structural stability

Improved X‐ray diffraction from Bacillus megaterium penicillin G acylase crystals through long cryosoaking dehydration

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89569/1/S1744309111040462.pd

Increasing the X-ray Diffraction Power of Protein Crystals by Dehydration: The Case of Bovine Serum Albumin and a Survey of Literature Data

Serum albumin is one of the most widely studied proteins. It is the most abundant protein in plasma with a typical concentration of 5 g/100 mL and the principal transporter of fatty acids in plasma. While the crystal structures of human serum albumin (HSA) free and in complex with fatty acids, hemin, and local anesthetics have been characterized, no crystallographic models are available on bovine serum albumin (BSA), presumably because of the poor diffraction power of existing hexagonal BSA crystals. Here, the crystallization and diffraction data of a new BSA crystal form, obtained by the hanging drop method using MPEG 5K as precipitating agent, are presented. The crystals belong to space group C2, with unit-cell parameters a = 216.45 Å, b = 44.72 Å, c = 140.18 Å, β = 114.5°. Dehydration was found to increase the diffraction limit of BSA crystals from ~8 Å to 3.2 Å, probably by improving the packing of protein molecules in the crystal lattice. These results, together with a survey of more than 60 successful cases of protein crystal dehydration, confirm that it can be a useful procedure to be used in initial screening as a method of improving the diffraction limits of existing crystals

Controlled Release of Felodipine from 3D-Printed Tablets with Constant Surface Area: Influence of Surface Geometry

In this study, 3D-printed tablets with a constant surface area were designed and fabricated using polylactic acid (PLA) in the outer compartment and polyvinyl alcohol and felodipine (FDP) in the inner compartment. The influences of different surface geometries of the inner compartment, namely, round, hexagon, square, and triangle, on drug release from 3D-printed tablets were also studied. The morphology and porosity of the inner compartment were determined using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy, respectively. Additionally, drug content and drug release were also evaluated. The results revealed that the round-shaped geometry seemed to have the greatest total surface area of the inner compartment, followed by square-shaped, hexagon-shaped, and triangle-shaped geometries. FDP-loaded 3D-printed tablets with triangle and hexagon surface geometries had the slowest drug release (about 80% within 24 h). In the round-shaped and square-shaped 3D-printed tablets, complete drug release was observed within 12 h. Furthermore, the drug release from triangle-shaped 3D-printed tablets with double the volume of the inner compartment was faster than that of a smaller volume. This was due to the fact that a larger tablet volume increased the surface area contacting the medium, resulting in a faster drug release. The findings indicated that the surface geometry of 3D-printed tablets with a constant surface area affected drug release. This study suggests that 3D printing technology may be used to develop oral solid dosage forms suitable for customized therapeutic treatments

New Insight into the Impact of Effervescence on Gel Layer Microstructure and Drug Release of Effervescent Matrices Using Combined Mechanical and Imaging Characterisation Techniques

Gel layer characteristics play a crucial role in hydrophilic hydroxypropyl methylcellulose (HPMC) matrix development. Effervescent agents have the potential to affect the gel layer microstructures. This study aimed to investigate the influence of effervescence on the microstructure of the gel layer around HPMC matrices using a combination of texture analysis and imaging techniques. The relationship with drug release profile and release mechanisms were also examined. The high amounts of effervescent agents promoted a rapid carbonation reaction, resulting in a high gel layer formation with a low gel strength through texture analysis. This finding was ascribed to the enhanced surface roughness and porosity observed under digital microscopy and microporous structure of the gel layer under scanning electron microscopy. The reconstructed three-dimensional images from synchrotron radiation X-ray tomographic microscopy notably exhibited the interconnected pores of various sizes from the carbonation reaction of effervescent and microporous networks, indicating the gel layer on the tablet surface. Notably, effervescence promoted the increase in interconnected porosities, which directly influenced the strength of the gel layer microstructure, drug release patterns and release mechanism of the effervescent matrix tablet. Therefore, combined mechanical characterisation and imaging techniques can provide new insights into the role of effervescent agents on the gel layer microstructure, and describe the relationship of drug release patterns and release mechanism of matrix tablets

Levofloxacin HCl-Incorporated Zein-Based Solvent Removal Phase Inversion In Situ Forming Gel for Periodontitis Treatment

Zein is composed of nonpolar amino acids and is a water-insoluble protein used as the matrix-forming agent of localized in situ forming gel (ISG). Therefore, this study prepared solvent removal phase inversion zein-based ISG formulations to load levofloxacin HCl (Lv) for periodontitis treatment using dimethyl sulfoxide (DMSO) and glycerol formal (GF) as the solvents. Their physicochemical properties were determined, including viscosity, injectability, gel formation, and drug release. The topography of dried remnants after drug release was revealed using a scanning electron microscope and X-ray computed microtomography (μCT) to investigate their 3D structure and % porosity. The antimicrobial activities were tested against Staphylococcus aureus (ATCC 6538), Escherichia coli ATCC 8739, Candida albicans ATCC 10231, and Porphyromonas gingivalis ATCC 33277 with agar cup diffusion. Increasing zein concentration or using GF as the solvent notably enhanced the apparent viscosity and injection force of the zein ISG. However, its gel formation slowed due to the dense zein matrix barrier’s solvent exchange: the higher loaded zein or utilization of GF as an ISG solvent prolonged Lv release. The SEM and μCT images revealed the scaffold of dried ISG in that their % porosity corresponded with their phase transformation and drug release behavior. In addition, the sustainability of drug diffusion promoted a smaller antimicrobial inhibition clear zone. Drug release from all formulations was attained with minimum inhibitory concentrations against pathogen microbes and exhibited a controlled release over 7 days. Lv-loaded 20% zein ISG using GF as a solvent exhibited appropriate viscosity, Newtonian flow, acceptable gel formation and injectability, and prolonged Lv release over 7 days with efficient antimicrobial activities against various test microbes; thus, it is the potential ISG formulation for periodontitis treatment. Consequently, the Lv-loaded solvent removal zein-based ISGs proposed in this investigation offer promising potential as an efficacious drug delivery system for periodontitis treatment by local injection

Effects of Different Application Times of Silver Diamine Fluoride on Mineral Precipitation in Demineralized Dentin

Silver diamine fluoride (SDF) is a cost-effective method for arresting active dental caries. However, the limited cooperation of patients may lead to an SDF application time that is shorter than the recommended 1–3 min for carious lesions. Therefore, the aim of this study was to assess the effect of different application times of SDF on the degree of mineral precipitation in demineralized dentin. Demineralized dentin specimens from permanent maxillary molars were treated by applying 38% SDF for 30, 60, or 180 s. Water was applied in the control group. The specimens were immersed in simulated body fluid for 2 weeks, and the mineral precipitation in demineralized dentin was then analyzed using FTIR-ATR, SEM-EDX, and synchrotron radiation X-ray tomographic microscopy (SRXTM). The FTIR-ATR results showed a significant increase in mineral precipitation in the 180 s group after 1 week. However, after 2 weeks, the SRXTM images indicated comparable mineral density between the 30, 60, and 180 s groups. The precipitation of silver chloride and calcium phosphate crystals that occluded dentinal tubules was similar in all experimental groups. In conclusion, an application time of either 30, 60, or 180 s promoted a comparable degree of mineral precipitation in demineralized dentin

Combined operando and ex-situ monitoring of the Zn/electrolyte interface in Zn-ion battery systems

Operando optical microscopy enables imaging at the interface between the Zn electrode and the electrolyte of 1 M ZnSO4(aq) in the symmetrical Zn/Zn cells assembled as the pouch cells with the mechanical load of 0.8 MPa. The imaging was executed during cycling of Zn plating and stripping at the different current densities of 0.5, 1.0, 2.0, and 4.0 mA cm−2, and the areal capacity of 2 mAh·cm−2. When the current densities are below 4.0 mA cm−2, no intense Zn dendrites are observed. However, at 4.0 mA cm−2, the severe Zn dendrites can penetrate through the separator and cause short-circuiting. From the electrochemical perspective, the voltage profile of such system drops to almost zero volt. Both operando optical and ex-situ synchrotron X-ray imaging further prove the appearance of the Zn dendrites. By Raman spectroscopy and X-ray diffraction, the cycled Zn electrode surface contains passivation species of Zn4(OH)6SO4, ZnO, and Zn(OH)2 that could limit the active surface area for the Zn plating/stripping, accelerating the localized current density and favoring the growth of Zn dendrites. With the SiO2 additive of 0.5% w/v in 1 M ZnSO4(aq), the severe Zn dendrites disappear, as well as the cycled Zn/electrolyte interface becomes close to the pristine state; low degree of the Zn electrode roughness and the Zn surface passivation is noticed. The appearance of the claimed Zn surface morphology was also confirmed by Scanning Electron Microscopy (SEM). In turn, too low or too high SiO2 content in the electrolyte does not generate desirable effects. A high level of Zn dendrites and short circuiting are still recognized. Hence, both the operando and ex-situ characterizations can mutually validate the phenomena at the Zn/electrolyte interface