Effect of Graphene Addition on Polycaprolactone Scaffolds Fabricated Using Melt-Electrowriting

Melt-electrowriting (MEW) is an emerging method that combines electrospinning and extrusion printing, allowing the fabrication of micron-scale structures suitable for tissue engineering. Compared to other additive fabrication methods, melt-electro written structures can offer more appropriate substrates for cell culture due to filament size and mechanical characteristics of the fabricated scaffolds. In this study, polycaprolactone (PCL)/graphene composites were investigated for fabrication of micron-size scaffolds through MEW. It was demonstrated that the addition of graphene can considerably improve the processability of PCL to fabricate micron-scale scaffolds with enhanced resolution. The tensile strength of the scaffold prepared from PCL/graphene composite (with only 0.5 wt.% graphene) was proved significantly (by more than 270%), better than that of the pristine PCL scaffold. Furthermore, graphene was demonstrated to be a suitable material for tailoring the degradation process to avoid undesirable bulk degradation, rapid mass loss and damage to the internal matrix of the polymer. The findings of this study offer a promising route for the fabrication of high-resolution scaffolds with micron-scale resolution for tissue engineering.

Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

Is Porcine Small Intestinal Submucosal Extracellular Matrix (ECM) a Suitable Material for Right Ventricular Outflow Tract Reconstruction in Association With Pulmonary Valve Replacement?

Pulmonary valve replacement (PVR) with right ventricular outflow tract (RVOT) reconstruction is a common congenital cardiac operation. Porcine submucosal intestinal-derived extracellular matrix (ECM) patches have been used for RVOT reconstruction. We present 2 adult patients with Tetralogy of Fallot who underwent PVR with RVOT reconstruction utilizing ECM. Both cases required reoperation due to patch dehiscence causing a large paravalvular leak. One patient also had a pseudoaneurysm associated with ECM dehiscence. There may be a propensity for ECM dehiscence in this application and, based on these cases, we recommend avoidance of ECM in RVOT reconstruction with PVR. PVR patients repaired with ECM should be monitored for this complication.

Nonlinear Mixing of Two Laser Beams and THz Plasmons Generation in Graphene Coated Optical Fibre

Graphene is a most suitable material for Terahertz (THz) radiation generation. An efficient mechanism of THz surface plasmons (THz SPs) generation in graphene coated optical fibre by nonlinear mixing of two laser beams is proposed. The graphene coated fiber supports THz SPs with plasmon resonance in the THz regime and controllable by thickness of graphene and radius of optical fibre. The laser beams exert a difference frequency ponderomotive force on the electrons of the graphene. This ponderomotive force induces a nonlinear current in graphene which driving the difference frequency THz SPs. The normalized amplitude of THz SPs decreases with frequency as the nonlinear coupling gets weaker. The efficiency of the device is around 0.01% at a laser intensity of 3x1014 W/cm2. This scheme will be useful making the compact THz radiation source and THz plasmon sensor.

Evaluation of a Suitable Material for Soft Actuator Through Experiments and FE Simulations

Soft actuators are generally built to achieve extension, contraction, curling, or bending motions needed for robotic or medical applications. It is prepared with a cylindrical tube, braided with fibers that restrict the radial motion and produce the extension, contraction, or bending. The actuation is achieved through the input of compressed air with a different pressure. The stiffness of the materials controls the magnitude of the actuation. In the present study, Silastic-P1 silicone RTV and multi-wall carbon nanotubes (MWCNT) with reinforced silicone are considered for the evaluation. The dumbbell samples are prepared from both materials as per ASTM D412-06a (ISO 37) standard and their corresponding tensile strength, elongation at break, and tensile modulus are measured. The Ogden nonlinear material constants of respective materials are estimated and used further in the finite element analysis of extension, contraction, and bending soft actuators. It is observed that silicone RTV is better in high strain and fast response, whereas, silicone/MWCNT is better at achieving high actuation.

Replacement of Flexural and Shear Reinforcement of Double-Column Bridge Bent with CFRP under Combined loadings

The bridge bent is the most critical structural component of short span bridge that highly affected by different types of loadings. The bent failure has been observed due to in plane and out of plane loadings. Strengthening techniques are utilized for existing bridges. However, a replacement technique can be used for the new bridges to avoid bent failure. Moreover, the effect of combined loading on bent performance need to be evaluated. Therefore, this study assessed the performance of bridge bent under in plane, out of plane and combined loadings. Furthermore, replace the traditional flexural and shear steel reinforcement of the columns with CFRP bars. The performance of bent is assessed numerically by finite element analysis. For this purpose, six numerical bent models are developed. The first three models with traditional steel bars and the remaining models with CFRP rebars. The results demonstrated that out of plane loadings has more impact on the bent structural performance than other loading cases. Flexural and shear failures are observed in the columns for models with steel rebars. The failure started from lower side of the column for both in plane and out of plane loadings showing low resistance. The steel rebars yielded in early stage of loading indicating limited stiffness. However, the bent performance has been enhanced by replacing rebars with CFRP. The bent stiffness has slightly improved by replacing with less diameter of CFRP rods and stirrups. In addition, the CFRP bars showed considerable resistance and hardly showed plasticity during apply loading indicating that the CFRP is suitable material to replace steel reinforcement.

The Use of Online Authentic Reading Materials In Online Reading Class

Education in Indonesia, as the large-scale power of the has to be compelled the continuity of teaching activities during the COVID-19 pandemic online learning. It inspires teachers to choose a suitable material to fulfill students’ needs and interests in teaching language. The appropriateness and well chosen authentic materials used by teachers in a context of reading have to cover meaningful content in which those are relevant. Thus, this study attempts to investigate those authenticity used as well as teachers’ challenges in implementing online authentic reading materials in online reading class of higher education. The study is a qualitative. The subjects are three EFL teachers of higher education that teach General English and English for Specific Purposes freshmen for two semesters. The data collection techniques are observation and interview. In analyzing the data, this study uses Ary et al. (2010) theory: familiarizing and organizing; coding and reduction; interpreting and representing. The findings revealed that authenticity is considered as the pivotal thing since, in this case, English is taught as foreign language. The authentic materials can be said its prevalence by measuring each authenticity based on three areas including SLA (Second Language Acquisition), language pedagogy and ICT (Information and Communication Technology). It could establish the applied authenticity to the language learning design materials, especially learning English language. Moreover, The challenge was about the materials, students’ interests, classroom activities and classroom interaction occurred among teachers and the students.

Poly(vinyl chloride)-supported triazoles grafted onto calix[4]arene for chromium ions extraction

A new suitable material was synthesized using click reaction between dialkynyl-p-tert-butylcalix[4]arene and poly(vinyl chloride) azide (PVC-N3). This novel dialkynyl-p-tert-butylcalix[4]arene with triazole groups grafted onto PVC polymer (PVC-0.75CX[4]) has an excellent extraction capability for chromium ions from aqueous solutions. It shows a unique ability to extract chromium (VI) ions from aqueous solutions, thanks to the soft cavity, the presence of π-triazole rings and hydrogen bonds. Cr (VI) ion sorption capacity is 95.5% at pH = 3.

Assessment of the Corrosion Behavior of Friction-Stir-Welded Dissimilar Aluminum Alloys

The fuel consumption of high-density automobiles has increased in recent years. Aluminum (Al) alloy is a suitable material for weight reduction in vehicles with high ductility and low weight. To address environmental problems in aircraft and maritime applications, in particular rust development and corrosion, the current study assesses the corrosion behavior during friction stir welding (FSW) of two dissimilar Al alloys (AA6061 and AA8011) in various corrosive conditions using salt spraying and submersion tests. Two acidic solutions and one alkaline solution are used in these tests, which are performed at room temperature. The two specimens (AA6061 and AA8011) and the weld region are suspended in a salt spraying chamber and a 5 wt.% NaCl solution is continually sprayed using the circulation pump for 60 h, with the specimens being weighed every 15 h to determine the corrosion rates. According to the salt spraying data, the weld zone has a higher corrosion resistance than the core components. For twenty-eight days, individual specimens are submerged in 3.5 wt.% HCl + H2O and H2SO4 + H2O solutions and seawater. The weld area specimens exhibit stronger corrosion resistance than the base material specimens, and weight loss in the saltwater medium is lower when compared to the other test solutions, according to the corrosion analysis. The scanning electron microscope (SEM) analysis demonstrates that the base metal AA8011 is considerably corroded on its surface.

Materials for Dentoalveolar Bioprinting: Current State of the Art

Although current treatments can successfully address a wide range of complications in the dentoalveolar region, they often still suffer from drawbacks and limitations, resulting in sub-optimal treatments for specific problems. In recent decades, significant progress has been made in the field of tissue engineering, aiming at restoring damaged tissues via a regenerative approach. Yet, the translation into a clinical product is still challenging. Novel technologies such as bioprinting have been developed to solve some of the shortcomings faced in traditional tissue engineering approaches. Using automated bioprinting techniques allows for precise placement of cells and biological molecules and for geometrical patient-specific design of produced biological scaffolds. Recently, bioprinting has also been introduced into the field of dentoalveolar tissue engineering. However, the choice of a suitable material to encapsulate cells in the development of so-called bioinks for bioprinting dentoalveolar tissues is still a challenge, considering the heterogeneity of these tissues and the range of properties they possess. This review, therefore, aims to provide an overview of the current state of the art by discussing the progress of the research on materials used for dentoalveolar bioprinting, highlighting the advantages and shortcomings of current approaches and considering opportunities for further research.