Axial-flexural coupled vibration and buckling of composite beams using sinusoidal shear deformation theory

A finite element model based on sinusoidal shear deformation theory is developed to study vibration and buckling analysis of composite beams with arbitrary lay-ups. This theory satisfies the zero traction boundary conditions on the top and bottom surfaces of beam without using shear correction factors. Besides, it has strong similarity with Euler–Bernoulli beam theory in some aspects such as governing equations, boundary conditions, and stress resultant expressions. By using Hamilton’s principle, governing equations of motion are derived. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results for cross-ply and angle-ply composite beams are obtained as special cases and are compared with other solutions available in the literature. A variety of parametric studies are conducted to demonstrate the effect of fiber orientation and modulus ratio on the natural frequencies, critical buckling loads, and load-frequency curves as well as corresponding mode shapes of composite beams

Bergmann-Thomson energy-momentum complex for solutions more general than the Kerr-Schild class

In a very well-known paper, Virbhadra's research group proved that the Weinberg, Papapetrou, Landau and Lifshitz, and Einstein energy-momentum complexes ``coincide'' for all metrics of Kerr-Schild class. A few years later, Virbhadra clarified that this ``coincidence'' in fact holds for metrics more general than the Kerr-Schild class. In the present paper, this study is extended for the Bergmann-Thomson complex and it is proved that this complex also ``coincides'' with those complexes for a more general than the Kerr-Schild class metric.Comment: RevTex, 12 page

The effect of solvent and pressure on polycaprolactone solutions for particle and fibre formation

Polycaprolactone (PCL) is a widely used material in many applications to tackle health problems worldwide. Formed micro- or nanosized PCL particles and fibres benefit from a higher surface area to volume ratio and are valuable in those applications, thus there is always a push to achieve smaller diameters. Electrohydrodynamic (EHD) technologies have been at the forefront in the production of polymeric biomaterials, and pressurised gyration (PG) has also enhanced possibilities by its ability to spin comparable fibres at rapid speeds. In this work, PCL microparticles and fibres were separately produced by changing key operating parameters of EHD and PG systems and PCL solution properties. Initially, PCL microparticles were formed by electrospraying with different binary solvent systems, followed by pressurised gyration fibre production with various singular solvents and a pre-optimised binary solvent system. As anticipated, the use of binary systems altered particle morphologies and diameters, while increased pressure and the use of different solvents greatly affected the characteristics of resulting fibres. The morphology of PCL was found to be highly dependent on the solvents and operating parameters of the technology used

Teleparallel Energy-Momentum Distribution of Static Axially Symmetric Spacetimes

This paper is devoted to discuss the energy-momentum for static axially symmetric spacetimes in the framework of teleparallel theory of gravity. For this purpose, we use the teleparallel versions of Einstein, Landau-Lifshitz, Bergmann and M$\ddot{o}$ller prescriptions. A comparison of the results shows that the energy density is different but the momentum turns out to be constant in each prescription. This is exactly similar to the results available in literature using the framework of General Relativity. It is mentioned here that M$\ddot{o}$ller energy-momentum distribution is independent of the coupling constant $\lambda$. Finally, we calculate energy-momentum distribution for the Curzon metric, a special case of the above mentioned spacetime.Comment: 14 pages, accepted for publication in Mod. Phys. Lett.

Severe Acute Respiratory Syndrome Type 2-Causing Coronavirus: Variants and Preventive Strategies

COVID-19 vaccines have constituted a substantial scientific leap in countering severe acute respiratory syndrome type 2-causing coronavirus (SARS-CoV-2), and worldwide implementation of vaccination programs has significantly contributed to the global pandemic effort by saving many lives. However, the continuous evolution of the SARS-CoV-2 viral genome has resulted in different variants with a diverse range of mutations, some with enhanced virulence compared with previous lineages. Such variants are still a great concern as they have the potential to reduce vaccine efficacy and increase the viral transmission rate. This review summarizes the significant variants of SARS-CoV-2 encountered to date (December 2021) and discusses a spectrum of possible preventive strategies, with an emphasis on physical and materials science

Metal-based nanoparticles for combating antibiotic resistance

The resistance to antibiotics in combating bacteria is a serious worldwide problem. The search for new approaches to address antibacterial resistance is therefore of crucial importance and seeking alternatives for the treatment and control of bacterial diseases associated with resistant strains, which is in need of urgent action. There is an ongoing interest in metal-based nanoparticles (MBNPs) and their usage synergy with antibiotics due to their unique properties, such as overcoming bacterial resistance, reducing acute toxicity compared to their sizes, and allowing dosage reduction of active pharmaceutical ingredients. Combining MBNPs and antibiotics not only enhances the antibacterial effect but also allows the inhibition of biofilm production. Furthermore, MBNPs and antibiotics incorporated in polymeric biomaterial matrix have been widely studied to improve their efficiency and devoid the resistance. However, these studies need to be combined in a literature review. Polymeric biomaterials offer high mechanical stability with improved biocompatibility. Moreover, their use makes a single dose of administration of the final product with extended antibiotic half-life possible while slowly releasing their reservoir, which is an advantage in continuously combating resistance. This review focuses on different promising biomedical strategies for enhancing the bactericidal efficacy of antibiotics by the synergistic use of MBNPs, antibiotics, and polymeric biomaterials together to combat the resistance of different bacterial strains. In addition, it is prospected to guide opportunities for new research for future biomedical applications

The Protective Effect of L-carnitine on Ionizing Radiation-induced Free Oxygen Radicals

Ionizing radiation is known to generate reactive oxygen species (ROS) that can be removed by antioxidants.  L-carnitine, a natural component of mammalian tissue, is a necessary factor in the utilization of long-chain  fatty acids to produce energy. Furthermore it has been shown that L-carnitine is an antioxidant which has  a scavenger effect on ROS and a stabilizing effect on damaged cell membranes. The aim of the study was  to evaluate the potential protective effect of L-carnitine on radiation-induced free radicals in hamsters. Lcarnitine  was given by gavage at a dose of 50 mg/kg for 15 consecutive days before irradiation with a single  dose of 8 Gy. 24 h after radiation exposure, the hamsters were sacrificed and samples were taken from  blood and tissues, and the biochemical and histopatological determinations were carried out. In the irradiated  group, there were significant increases in plasma and liver malondialdehyde (MDA) with marked  reduction in glutathione (GSH) levels in the liver, compared with controls. In red blood cells, superoxide  dismutase (SOD) and catalase activities were also reduced. All these effects were reversed by L-carnitine.  In conclusion, L-carnitine with its antioxidant and free radical scavenging properties could play a modulatory  role against the cellular damage produced by free radicals induced by ionizing radiation.