Non-electroactive neurotransmitters such as glutamate, acetylcholine, choline, and adenosine play a critical role in proper activity of living organisms, particularly in the nervous system. While enzyme-based sensing of this type of neurotransmitter has been a research interest for years, non-enzymatic approaches are gaining more attention because of their stability and low cost. Accordingly, this focused review aims to give a summary of the state of the art of non-enzymatic electrochemical sensors used for detection of neurotransmitter that lack an electrochemically active component. In place of using enzymes, transition metal materials such as those based on nickel show an acceptable level of catalytic activity for neurotransmitter sensing. They benefit from fast electron transport properties and high surface energy and their catalytic activity can be much improved if their surface is modified with nanomaterials such as carbon nanotubes and platinum nanoparticles. However, a general comparison reveals that the performance of non-enzymatic biosensors is still lower than those that use enzyme-based methods. Nevertheless, their excellent stability demonstrates that non-enzymatic neurotransmitter sensors warrant additional research in order to advance them toward becoming an acceptable replacement for the more expensive enzyme-based sensors.
The aim of the present study is to investigate the superiority of steady tests simulations relative to the unsteady experiments, especially planar motion mechanism tests (PMM), for computing velocity-based hydrodynamics coefficients. Using CFD analysis, steady maneuvers including towing with drift and attack angles together with rotating arm tests are simulated in order to calculate the linear damping coefficients of a prototype submarine. Comparisons of the obtained results with available unsteady experimental results of the SUBOFF submarine show the reliability of the methods used in this paper. It also demonstrates the accuracy and simplicity of the present simulations due to the steady nature of simulations. In order to compute the linear damping coefficients, the simulations have been performed in small values of the attack and drift angles and angular velocities for the towing and rotating arm tests, respectively.
As part of a design project for a batoid-inspired underwater robot, its dive to a predetermined depth is questioned here. Previously, the vehicle was designed with a streamlined hull shape that resembles a Dasyatis batoid fish, and the fish locomotion was imitated
using undulating fins at each side. We did not, however, provide a buoyancy engine or any fins to turn the vessel in the vertical plane and conduct diving maneuvers. We expect to leave the vessel on the water surface, and it dives to a desired depth and then maintains a constant pitch angle
and a constant forward speed. A new technique is invented here: the thrust forces of the two fins are shifted off the central top-bottom symmetry plane of the hull, therefore producing a pitching moment on the vessel. An initial trim is also introduced by shifting the center of mass forward
the center of buoyancy. Therefore, the vessel is initially bowed down and, by its out-of-plane thrust force, adjusts its pitch attitude. The question is whether a final balance between the thrust force and the hydrodynamic forces will be feasible. The hydrodynamic forces at such forward speeds
and attack angles were numerically derived using the computational fluid dynamics powerful software ANSYS-CFX.
This paper attempted to numerically examine the involvement of serrated fins on natural convection heat transfer between coaxial cylinders. The outer channel of annular cylinders was circular, while the inner channels involved three cross-sections including circular, square and triangular. As two geometric constraints, the area of annular cylinders and the diameter of outer channel were assumed to be identical in each scenario explored in this study. The fins had equal areas placed on the inner surface, so as to compare their effects on thermal properties of annular cylinders under constant temperature boundary within the range of Rayleigh numbers from 10 5 to 10 8. The results indicated that higher a Rayleigh number is directly correlated with higher convection heat transfer coefficient of surfaces. However, the inclusion of fins reduced the rate near the fins, thus mitigating the heat transfer coefficient of inner channel. This trend intensified at higher Rayleigh numbers. Therefore, the involvement of fins at lower Rayleigh numbers brings about greater efficiency in heat transfer. The comparison of fins in terms of efficiency revealed that maximum heat is transferred when the fins have been mounted on a circular channel.
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