The problem of natural convective boundary-layer flow of a nanofluid past a vertical plate is revisited. The model, which includes the effects of Brownian motion and thermophoresis, is revised so ...that the nanofluid particle fraction on the boundary is passively rather than actively controlled. In this respect the model is more realistic physically than that employed by previous authors.
•The problem of natural convective boundary-layer flow of a nanofluid past a vertical plate is revisited.•The model is revised so that the nanofluid particle fraction on the boundary is passively rather than actively controlled.•The model is more realistic physically than that employed by previous authors.
A CMOS-compatible ISFET with a Ta2O5 sensitive surface was developed. The structure was optimized for achieving high sensitivity using a subthreshold operation mode and by reducing the influence of ...the capacitances on the value of subthreshold swing. The developed ISFET was used as a basis for a biosensor for L-carnitine detection. To this end, carnitine acetyltransferase was immobilized on the ISFET sensitive surface. The immobilized enzyme was active (0.082 U/g model plate). The complete microsystem, consisting of a packaged chip, an immobilized enzyme and a microfluidic channel, detected L-carnitine at a range of 0.2–100 μM with a LOD of 0.2 μM. The biosensor response was linear in the range of 0.2–50 μM of L-carnitine with sensitivity 18.0 ± 1.7 mV/μM. An experiment with artificial urine containing 1.3 μM L-carnitine showed that the proposed biosensor could be used on a real sample. Therefore, a new sensor specially optimized for biosensing CMOS-compatible ISFET structures and direct determination of L-carnitine with immobilized carnitine acetyltransferase was developed.
•A novel CMOS-compatible ISFET was developed and specially optimized for use in subthreshold operation mode.•Carnitine acetyltransferase reaction was directly detected using an electrochemical method for the first time.•The fabricated biosensor allowed detection of L-carnitine in artificial urine.
The purpose of this paper is to study the onset of bioconvection in a horizontal layer filled with a nanofluid that also contains gyrotactic microorganisms. The idea is to use microorganisms to ...induce or enhance convection in a nanofluid. A linear instability analysis is used to solve this problem. A Galerkin method is utilized to obtain an analytical solution for the critical Rayleigh number for the non-oscillatory situation. As in the case of a regular nanofluid (without the microorganisms), the presence of nanoparticles can either reduce or increase the value of the critical Rayleigh number, depending on whether the basic nanoparticle distribution is top-heavy or bottom-heavy. In contrast, the effect of gyrotactic microorganisms is always destabilizing.
By assuming that tau protein can be in seven kinetic states, we developed a model of tau protein transport in the axon and in the axon initial segment (AIS). Two separate sets of kinetic constants ...were determined, one in the axon and the other in the AIS. This was done by fitting the model predictions in the axon with experimental results and by fitting the model predictions in the AIS with the assumed linear increase of the total tau concentration in the AIS. The calibrated model was used to make predictions about tau transport in the axon and in the AIS. To the best of our knowledge, this is the first paper that presents a mathematical model of tau transport in the AIS. Our modeling results suggest that binding of free tau to microtubules creates a negative gradient of free tau in the AIS. This leads to diffusion-driven tau transport from the soma into the AIS. The model further suggests that slow axonal transport and diffusion-driven transport of tau work together in the AIS, moving tau anterogradely. Our numerical results predict an interplay between these two mechanisms: as the distance from the soma increases, the diffusion-driven transport decreases, while motor-driven transport becomes larger. Thus, the machinery in the AIS works as a pump, moving tau into the axon.
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•Transport of tau protein in an axon initial segment (AIS) was investigated.•In most of the axon, tau motor-driven fluxes are independent of distance from the soma.•A negative gradient of free tau causes diffusion-driven flux of free tau into the AIS.•Both motor-driven and diffusion-driven transport move tau anterogradely within the AIS.•Deeper into the AIS, tau switches from diffusion-driven to motor-driven transport.
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•A family of models which differ by the modes of axonal cargo transport they account for is studied.•The goal is to study models’ abilities to describe axonal transport against the ...cargo concentration gradient.•The effect of diffusion is limited to a thin diffusion boundary layer near the axon tip.•Anterograde-diffusion model is unable to describe transport against cargo concentration gradient if cargo diffusivity is small.•Our results suggest an explanation for why seemingly inefficient bidirectional transport in axons is utilized.
Even though most axonal cargos are synthesized in the soma, the concentration of many of these cargos is larger at the presynaptic terminal than in the soma. This requires transport of these cargos from the soma to the presynaptic terminal or other active sites in the axon. Axons utilize both bidirectional (for example, slow axonal transport) and unidirectional (for example, fast anterograde axonal transport) modes of cargo transport. Bidirectional transport seems to be less efficient because it requires more time and takes more energy to deliver cargos. In this paper, we studied a family of models which differ by the modes of axonal cargo transport (such as anterograde and retrograde motor-driven transport and passive diffusion) as well as by the presence or absence of pausing states. The models are studied to investigate their ability to describe axonal transport against the cargo concentration gradient. We argue that bidirectional axonal transport is described by a higher-order mathematical model, which allows imposing cargo concentration not only at the axon hillock but also at the axon terminal. The unidirectional transport model allows only for the imposition of cargo concentration at the axon hillock. Due to the great lengths of the axons, anterograde transport mostly relies on molecular motors, such as kinesins, to deliver cargos synthesized in the soma to the terminal and other active sites in the axon. Retrograde transport can be also motor-driven, in which case cargos are transported by dynein motors. If cargo concentration at the axon tip is higher than at the axon hillock, retrograde transport can also occur by cargo diffusion. However, because many axonal cargos are large or they assemble in multiprotein complexes for axonal transport, the diffusivity of such cargos is very small. We investigated the case of a small cargo diffusivity using a perturbation technique and found that for this case the effect of diffusion is limited to a very thin diffusion boundary layer near the axon tip. If cargo diffusivity is decreased in the model, we show that without motor-driven retrograde transport the model is unable to describe a high cargo concentration at the axon tip. To the best of our knowledge, our paper presents the first explanation for the utilization of seemingly inefficient bidirectional transport in neurons.
This paper presents an algorithm for detecting one of the most commonly used types of digital image forgeries - splicing. The algorithm is based on the use of the VGG-16 convolutional neural network. ...The proposed network architecture takes image patches as input and obtains classification results for a patch: original or forgery. On the training stage we select patches from original image regions and on the borders of embedded splicing. The obtained results demonstrate high classification accuracy (97.8% accuracy for fine-tuned model and 96.4% accuracy for the zero-stage trained) for a set of images containing artificial distortions in comparison with existing solutions. Experimental research was conducted using CASIA dataset.
The term 'hidden attractor' relates to a stable periodic, quasiperiodic or chaotic state whose basin of attraction does not overlap with the neighborhood of an unstable equilibrium point. Considering ...a three-dimensional oscillator system that does not allow for the existence of an equilibrium point, this paper describes the formation of several different coexisting sets of hidden attractors, including the simultaneous presence of a pair of coinciding quasiperiodic attractors and of two mutually symmetric chaotic attractors. We follow the dynamics of the system as a function of the basic oscillator frequency, describe the bifurcations through which hidden attractors of different type arise and disappear, and illustrate the form of the basins of attraction.
Slow axonal transport (SAT) moves multiple proteins from the soma, where they are synthesized, to the axon terminal. Due to the great lengths of axons, SAT almost exclusively relies on active ...transport, which is driven by molecular motors. The puzzling feature of slow axonal transport is its bidirectionality. Although the net direction of SAT is anterograde, from the soma to the terminal, experiments show that it also contains a retrograde component. One of the proteins transported by SAT is the microtubule-associated protein tau. To better understand why the retrograde component in tau transport is needed, we used the perturbation technique to analyze how the full tau SAT model can be simplified for the specific case when retrograde motor-driven transport and diffusion-driven transport of tau are negligible and tau is driven only by anterograde (kinesin) motors. The solution of the simplified equations shows that without retrograde transport the tau concentration along the axon length stays almost uniform (decreases very slightly), which is inconsistent with the experimenal tau concentration at the outlet boundary (at the axon tip). Thus kinesin-driven transport alone is not enough to explain the empirically observed distribution of tau, and the retrograde motor-driven component in SAT is needed.
The influence of the surface modification of multi-walled carbon nanotubes (MWCNT) with nitrogen-containing compounds on the performance of 40 wt% Pt/MWCNT catalysts in the oxygen electroreduction ...reaction (ORR) was investigated using a rotating disk electrode (RDE) at 10–35 °C in 0.1 M HClO
4
as electrolyte in electrochemical cell, and in a hydrogen–oxygen polymer electrolyte membrane fuel cell (PEMFC) at 82 °C. The catalysts were characterized by low-temperature nitrogen adsorption, XPS, TEM, gas-phase CO titration, electrooxidation of the adsorbed CO monolayer, and cyclic voltammetry. It was shown that the modification of MWCNT with melamine–formaldehyde resin leads to the surface nitrogen concentration up to 8.3 at.% (CNT-MF sample). The 40 wt% Pt/CNT-MF catalyst with 0.1 mg cm
−2
Pt loading on the cathode showed a good performance in PEMFC (~ 0.61 W cm
−2
) and a high utilization ratio (0.84) of Pt in membrane electrode assembly as compared to Pt/CNT catalyst (~ 0.37 W cm
−2
and utilization of 0.29). The higher power density of nitrogen-modified catalysts was ascribed to a higher utilization of Pt in the electrode layer.
In this paper, a simulation model describing the operation of a PV/wind/diesel hybrid microgrid system with battery bank storage has been proposed. Optimal sizing of the proposed system has been ...presented to minimize the cost of energy (COE) supplied by the system while increasing the reliability and efficiency of the system presented by the loss of power supply probability (LPSP). Novel optimization algorithms of Whale Optimization Algorithm (WOA), Water Cycle Algorithm (WCA), Moth-Flame Optimizer (MFO), and Hybrid particle swarm-gravitational search algorithm (PSOGSA) have been applied for designing the optimized microgrid. Moreover, a comprehensive comparison has been accomplished between the proposed optimization techniques. The optimal sizing of the system components has been carried out using real-time meteorological data of Abu-Monqar village located in the Western Desert of Egypt for the first time for developing this promising remote area. Statistical study for determining the capability of the optimization algorithm in finding the optimal solution has been presented. Simulation results confirmed the promising performance of the hybrid WOA over the other algorithms.
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