Electrospun nanofibrous alginate sulfate scaffolds promote mesenchymal stem cells differentiation to chondrocytes

Cartilage tissue engineering is one of the interesting approaches used for repairing cartilage injuries. This study reports the fabrication of polyvinyl alcohol/alginate sulfate (PVA/ALG-S) nanofibrous mats as a functional support for chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs). The PVA/ALG-S nanofibers were obtained through electrospinning of PVA solutions containing 10, 20, and 30 wt% of ALG-S. The appearance of a band at 833 cm⁻¹ assigned to the symmetrical C O S vibration associated to a C O SO₃ group confirmed the presence of ALG-S in nanofibrous mat. The SEM images illustrated the bead-free and smooth morphology of PVA/ALG-S nanofibers with a mean diameter of 185 ± 0.06 nm. The MTT assay of the hBM-MSCs seeded on scaffolds indicated the appropriate cytocompatibility of nanofibrous PVA/ALG-S scaffolds. Furthermore, the appropriate attachment and spreading of the hBM-MSCs based on SEM images, and their differentiation to the chondrocyte-like cells accompanied by a decrease in cell growth on MTT analysis and more color absorption in alician blue staining indicated the effective role of alginate sulfate on cell differentiation. Finally, the expression of Type II collagen by RT-PCR and immunocytochemistry analyses revealed the chondrogenic differentiation of hBM-MSCs on alginate sulfate nanofibers.     

Recent Advances in SiO2 Based Composite Electrodes for Supercapacitor Applications

Supercapacitors (SCs) have been widely exploited as a promising energy storage system due to their unique merits, including fast charge/discharge rates, long-term cycling stability and low maintenance cost. Therefore, researchers are focused on designing novel nanostructures with high surface area, optimum pore size and volume, and porous structure are highly desirable. Silicon dioxide (SiO₂) has recently attracted enormous research attention as the electrode materials for SCs due to ease fabrication and integration possibility. However, due to the intrinsically poor electrical conductivity of metal oxides and the short diffusion distance of electrolytes into pseudocapacitor electrodes, only the surface of electroactive materials can effectively contribute to the total capacitance, while the large portion of material underneath the surface could hardly participate in the electrochemical charge storage process, leading to areal specific capacitance (ASC) values lower than expected. The coating of SiO₂ has been recognized as a possible route to reduce the resistance and increase durability. Still, even for coated electrodes, the performance has always been several orders of magnitudes below that of carbon-based SCs. The morphology, structure, and particle size of SiO₂ are related to the synthesis conditions and electrochemical performances. The thin films of SiO₂ nanostructures deposited on conductive substrates and their composites both shows good performance (binder free electrodes). SiO₂ and its composites display a large potential window for asymmetric SCs, delivering high energy density. More importantly, the design and development of composite materials with novel nanostructures are also effective ways to enhance the electrochemical properties of SCs. In this review, the research progress of SiO₂ based composite electrodes for SCs are briefly reviewed. Consequently, the possible developmental direction, challenges, and opportunities for SiO₂ based composite are also discussed.

     

A Comprehensive Review on Effects of Seawater on Engineering Properties of Concrete

Silicon - The concrete and natural seawater have a complex relationship between them, which requires special attention. Therefore, various studies have been conducted to consider the effects of...     

A fast and high frame rate adaptive beamforming using DCT-based RF-line recovery in line-by-line ultrasound imaging

Ultrasound imaging is an important modality used in medical imaging. One of the significant stages in the ultrasound imaging is the beamforming process. This article proposes a new technique for reducing the overall computational time of adaptive linear ultrasound imaging. The method uses the discrete cosine transform-based reconstruction for missing data imputation. The novelty of the paper is that we do not need to beam-form the total scan lines, so the time of image construction can be saved significantly. In other words, a fraction of the total scan lines is selected for beamforming and the others are assumed to have values as Not-a-Number (NaN). The proposed reconstruction technique tries to assign appropriate values to the NaN ones. We applied the proposed method to the simulated and experimental radio frequency (RF) datasets for resolution and contrast evaluation. Results showed that the proposed technique is near to the minimum variance (MV) method in terms of resolution and contrast, and has less computational time for image formation compared to the MV. As some quantitative examples in some experiments we have formed only 50% and 33% of the total lines and reconstructed the rest, then we have been able to increase the frame rate twice and three times, respectively, which can be very useful in many applications, especially in echocardiography imaging. In addition, since the execution time of the reconstruction algorithm is not very significant, we were also able to increase the speed by two and three times while achieving an error of less than 10% compared to the case of using all image lines.     

Robust and hybrid SVD-based image watermarking schemes:

Multimedia Tools and Applications - These days, researchers have used many techniques in e-multimedia data for intellectual property protection. One of these important techniques is watermarking...     

Dynamic model of a novel thermogravity rotary actuator for solar energy harvesting

The direct conversion of thermal energy to mechanical energy is always been a challenging but demanding problem. In this article, we presented a nonconventional direct conversion mechanism of the readily available solar thermal and gravity energy to rotational mechanical energy. The developed rotating assembly affixed concentrically with a plurality of actuating arms harnesses the integrated solar-gravity energy. Each actuating arm shifts the center of gravity of the attached solid mass with concentrated solar heating. The alternate shift in the center of gravity of each actuating arm with exposure to solar radiation produces a continuous revolution of rotating assembly around its axis of rotation. With a particular set of the system parameters with Al/Si₃N₄ bimetallic strip the thermal efficiency of the proposed thermogravity bimetallic strip heat actuator/engine is 12.41% which is 100 times more efficient compared to a gravity-less thermal engine with same set up. The proposed thermogravity system can generate mechanical power ranges from less than 1 W to 40 kW with a particular set of system parameters. This solar-gravity rotary actuator is a novel work in this domain which has a huge impact and contribution in the available rotary actuator or energy harvester knowledge.