Oxytetracycline nanosensor based on poly-ortho-aminophenol/multi-walled carbon nanotubes composite film

Poly-ortho-aminophenol (PoAP) and multi-walled carbon nanotubes (MWCNTs) were deposited on the platinum electrode using cyclic voltammetry technique to form the Pt/PoAP/MWCNTs nanosensor for the electrochemical determination of oxytetracycline as analyte. This electrochemical nanosensor with good uniformity and high surface area was prepared in the presence of an ionic surfactant (sodium dodecyl sulfate) as electrolyte to suspend carbon nanotubes within the PoAP and improve the stability and electroactivity of the composite film. The surface morphology of the prepared nanosensor was characterized by scanning electron microscopy and showed a three-dimensional network structure. The influence of several parameters such as number of potential cycles, scan rate and pH of the solution on the electrochemical response of the resultant electrode was investigated. The prepared electrode functioned as a selective recognition element for oxytetracycline determination. It showed excellent electrochemical response to oxytetracycline at low oxidative potential in buffer solution of pH 2.0, with good stability and sensitivity. Under the optimal experimental conditions, the electrochemical response of the sensor was linear with respect to the concentration of oxytetracycline in a dynamic range of 0.2 μM–0.25 mM. The detection limit of the fabricated nanosensor was calculated as 0.10 μM (signal/noise = 3). This sensor was used successfully for the oxytetracycline determination in real samples with recoveries of 96.9–103.5 %.     

Numerical evaluation of a granular column reinforced by geosynthetics using encasement and laminated disks

Structures built on soft strata may experience substantial settlement, large lateral deformation of the soft layer and global or local instability. Granular columns reinforced by geosynthetic materials reduce settlement and increase the bearing capacity of the composite ground. Reinforcement is more common in the form of geosynthetic encasement, but laminated disks can also be used. This paper compares these two forms of reinforcement by means of unit cell finite element analyses. Numerical results were initially validated using field and experimental data, and parametric studies were subsequently performed. The parametric studies varied the geosynthetic interval and the geosynthetic tensile stiffness of the laminated disks as well as the length of the reinforced column. The analyses showed that in both modes; encasement and laminated disks; the geosynthetic increases the vertical stress mobilized on the reinforced column and reduces settlement on soft soil. It was also observed that in order to achieve the same performance as with encased column, the optimum interval between laminated disks is dependent on the stiffness of the geosynthetics and the column reinforced length.     

Endosomal Escape of Polymer‐Coated Silica Nanoparticles in Endothelial Cells

Current investigations into hazardous nanoparticles (i.e., nanotoxicology) aim to understand the working mechanisms that drive toxicity. This understanding has been used to predict the biological impact of the nanocarriers as a function of their synthesis, material composition, and physicochemical characteristics. It is particularly critical to characterize the events that immediately follow cell stress resulting from nanoparticle internalization. While reactive oxygen species and activation of autophagy are universally recognized as mechanisms of nanotoxicity, the progression of these phenomena during cell recovery has yet to be comprehensively evaluated. Herein, primary human endothelial cells are exposed to controlled concentrations of polymer‐functionalized silica nanoparticles to induce lysosomal damage and achieve cytosolic delivery. In this model, the recovery of cell functions lost following endosomal escape is primarily represented by changes in cell distribution and the subsequent partitioning of particles into dividing cells. Furthermore, multilamellar bodies are found to accumulate around the particles, demonstrating progressive endosomal escape. This work provides a set of biological parameters that can be used to assess cell stress related to nanoparticle exposure and the subsequent recovery of cell processes as a function of endosomal escape.     

Applying simulated annealing for designing cellular manufacturing systems using MDmTSP

The design of cellular manufacturing systems involves many structural and operational issues. One of the important design steps is the formation of part families and machine cells (cell formation). Despite a large number of papers on cell formation published worldwide, only a handful incorporates operation sequence in layout design (intra-cell move calculations). We propose a solution to solve the part-family and machine-cell formation problem considering the within-cell layout problem, simultaneously. In this paper, the cellular manufacturing system is formulated as a multiple departures single destination multiple travelling salesman problem (MDmTSP) and a solution methodology based on simulated annealing is proposed to solve the formulated model. Numerical examples show that the proposed method is efficient and effective in finding optimal solutions. The results also indicate that the proposed approach performs well compared to some well-known cell formation methods.     

Microstructured silicon membrane with soft suspension beams for a high performance MEMS microspeaker

This study presents a novel approach to MEMS microspeakers design aiming to tackle two main drawbacks of conventional microspeakers: their poor sound quality and their weak efficiency. For this purpose, an acoustic emissive surface based on a very light but very stiff structured silicon membrane was designed and microfabricated. This architecture, for which the membrane undesirable vibration modes were reduced to only three within the microspeaker bandwidth, is promising to let the microspeaker produce high sound quality from 300?Hz to 20?kHz. This silicon membrane is suspended by a whole set of silicon springs designed to enable out-of-plane displacements as large as 300?μm. Different geometries of springs were considered and the material maximum stress was analyzed in each case by finite element modeling. The proposed structure promises an efficiency of 10^?4, that is to say ten times higher than that of conventional microspeakers.     

Effect of partial replacement of chitosan with halloysite nanotubes on the properties of polylactic acid hybrid biocomposites

In this study, hybrid chitosan/halloysite nanotubes (Cs/HNTs) reinforced polylactic acid (PLA) were prepared via melt compounding and compression molding techniques. In the fabrication of PLA/Cs/HNTs hybrid biocomposites, the partial replacement of Cs with HNTs was performed at filler loading of 2.5 parts per hundred parts of polymer (php), proceeding from the highest tensile strength of PLA/Cs obtained in our previous study. Cs was partially replaced with different HNTs loadings (0.5, 1, 1.5, 2, and 2.5) php and its effects on the functional group, thermal, tensile, morphological, and water absorption properties were investigated systematically. The results revealed that the combined loading of 1 php Cs and 1.5 php HNTs hybrid fillers into PLA showed the best performance in all properties. Fourier transform infrared spectroscopy (FTIR) analysis indicated that the siloxane (Si O) group of HNTs had chemically interacted with the amine group of Cs. The thermal analysis demonstrated that partial replacement of Cs with 1.5 php HNTs improved the thermal stability of PLA/2.5Cs/0HNTs biocomposite by ~12%. Yet, the percentage of crystallinity (χ_c) reduced with HNTs addition due to the phase adhesion improvement. Moreover, PLA/1Cs/1.5HNTs hybrid biocomposites showed the highest tensile strength and elongation at break of 59 MPa and 2.72%, respectively. This correlated with the uniform dispersion and better interfacial adhesion between Cs/HNTs fillers in the PLA matrix, as confirmed by the field emission scanning electron microscopy (FESEM). In addition, partial replacement of Cs with HNTs exhibited a lower water absorption percentage, which suggested the advantage of hybrid fillers to reduce water uptake, and is beneficial in a wide range of applications.     

Integrative Study of the Structural and Dynamical Properties of a KirBac3.1 Mutant: Functional Implication of a Highly Conserved Tryptophan in the Transmembrane Domain

ATP-sensitive potassium (K-ATP) channels are ubiquitously expressed on the plasma membrane of cells in several organs, including the heart, pancreas, and brain, and they govern a wide range of physiological processes. In pancreatic β-cells, K-ATP channels composed of Kir6.2 and SUR1 play a key role in coupling blood glucose and insulin secretion. A tryptophan residue located at the cytosolic end of the transmembrane helix is highly conserved in eukaryote and prokaryote Kir channels. Any mutation on this amino acid causes a gain of function and neonatal diabetes mellitus. In this study, we have investigated the effect of mutation on this highly conserved residue on a KirBac channel (prokaryotic homolog of mammalian Kir6.2). We provide the crystal structure of the mutant KirBac3.1 W46R (equivalent to W68R in Kir6.2) and its conformational flexibility properties using HDX-MS. In addition, the detailed dynamical view of the mutant during the gating was investigated using the in silico method. Finally, functional assays have been performed. A comparison of important structural determinants for the gating mechanism between the wild type KirBac and the mutant W46R suggests interesting structural and dynamical clues and a mechanism of action of the mutation that leads to the gain of function.     

Simultaneous effect of particle size and solid concentration on the hydrodynamics of slurry bubble column reactors

The simultaneous effect of particle size and concentration on the total gas holdup of slurry bubble column reactors was investigated in this work. The total gas holdup was measured for air–water–glass beads systems. Three solid concentrations and three particle diameters were used. It was found that increasing particle size at high constant concentration decreases gas holdup. Moreover, increasing solid concentration decreases gas holdup and this decreasing effect is higher for larger particles. Also, solid particles have two effects on hydrodynamics, namely, changing the viscosity and density of the liquid phase as well as hindering the bubbles from rising within the column by the collision phenomenon. Therefore, a novel correcting factor was introduced to correct the gas holdup. The hindering factor considers both the collision efficiency affected by the particle size as well as the solid concentration. A novel correlation was developed to predict the experimental data of the three-phase gas holdup.     

Effects of soil‐structure interaction and lateral design load pattern on performance‐based plastic design of steel moment resisting frames

The effects soil‐structure interaction (SSI) and lateral design load‐pattern are investigated on the seismic response of steel moment‐resisting frames (SMRFs) designed with a performance‐based plastic design (PBPD) method through a comprehensive analytical study on a series of 4‐, 8‐, 12‐, 14‐, and 16‐story models. The cone model is adopted to simulate SSI effects. A set of 20 strong earthquake records are used to examine the effects of different design parameters including fundamental period, design load‐pattern, target ductility, and base flexibility. It is shown that the lateral design load pattern can considerably affect the inelastic strength demands of SSI systems. The best design load patterns are then identified for the selected frames. Although SSI effects are usually ignored in the design of conventional structures, the results indicate that SSI can considerably influence the seismic performance of SMRFs. By increasing the base flexibility, the ductility demand in lower story levels decreases and the maximum demand shifts to the higher stories. The strength reduction factor of SMRFs also reduces by increasing the SSI effects, which implies the fixed‐base assumption may lead to underestimated designs for SSI systems. To address this issue, new ductility‐dependent strength reduction factors are proposed for multistory SMRFs with flexible base conditions.