Direct methanol fuel cells (DMFCs) within all types of fuel cells are the most viable alternative to lithium-ion batteries in the portable application, and recently attracted much attention. This ...review provides a comprehensive overview of the passive DMFC barriers viz. methanol crossover, slow kinetics, water management, heat management, species management, durability and stability and cost for commercialization. Furthermore, it focuses on different approaches to overcome discussed barriers of passive DMFC. It is shown that the critical challenge regarding to minimize methanol crossover through the membrane using various hybrid membranes and methanol transport barrier so that the cell performance can be maximized. Regarding to reduce the catalyst cost with better kinetics, it is expected for developing non noble catalyst for passive DMFC. The challenges related to the operating temperature of passive DMFC is the selection methanol concentration, current density, ambient temperature, air humidity, cell orientation, membrane thickness, cell design, etc. which affects the cell performance. The several methods related to the water management layer deals with transport of the water produced on the cathode to the anode through the membrane and the cathode with minimum water flooding.
Ca2+ is an important regulatory ion and alteration of mitochondrial Ca2+ homeostasis can lead to cellular dysfunction and apoptosis. Ca2+ is transported into respiring mitochondria via the Ca2+ ...uniporter, which is known to be inhibited by Mg2+. This uniporter-mediated mitochondrial Ca2+ transport is also shown to be influenced by inorganic phosphate (Pi). Despite a large number of experimental studies, the kinetic mechanisms associated with the Mg2+ inhibition and Pi regulation of the uniporter function are not well established. To gain a quantitative understanding of the effects of Mg2+ and Pi on the uniporter function, we developed here a mathematical model based on known kinetic properties of the uniporter and presumed Mg2+ inhibition and Pi regulation mechanisms. The model is extended from our previous model of the uniporter that is based on a multistate catalytic binding and interconversion mechanism and Eyring's free energy barrier theory for interconversion. The model satisfactorily describes a wide variety of experimental data sets on the kinetics of mitochondrial Ca2+ uptake. The model also appropriately depicts the inhibitory effect of Mg2+ on the uniporter function, in which Ca2+ uptake is hyperbolic in the absence of Mg2+ and sigmoid in the presence of Mg2+. The model suggests a mixed-type inhibition mechanism for Mg2+ inhibition of the uniporter function. This model is critical for building mechanistic models of mitochondrial bioenergetics and Ca2+ handling to understand the mechanisms by which Ca2+ mediates signaling pathways and modulates energy metabolism.
Desalinated water, the final product of a solar distillation system, is useful for drinking purpose, community services, industry and agriculture on a small scale. It is expensive and may be ...considered as an industrial product. In the present communication, it has been tried to collect information about the ongoing research activities in the field of solar distillation system with the aim to enhance productivity and efficiency through an effective thermodynamic tool i.e. energy and exergy analysis, especially of the solar stills, similar to its wide application in complex thermal systems such as steam or gas turbine, boiler and cogeneration systems. Thermodynamic models for the energy and exergy analysis have been presented based on the fundamental heat transfer correlations in literatures for the simple basin type solar stills. Energy efficiency and productivity of the conventional solar stills is found to be low in the range of 20–46% and less than 6L/m2/day, respectively, for most cases, even under optimized operating conditions. The exergetic efficiencies are estimated to be between 19% and 26% for a triple effect system, 17–20% for a double effect system, and less than 5% for a single effect system. Productivity increases significantly by the use of integrated solar stills with better efficiency. The overall energy and exergy efficiency of the integrated systems rises up to 62% and 8.5%, respectively, using single effect solar stills. An attempt has also been made to review works on economic and thermo-economic analysis of solar stills. The cost of desalination through solar stills is reported in the range of US$0.014 to 0.237/L. It decreases further with increase in efficiency. It is observed that integrated solar desalination systems and technologies will be better choice than the conventional solar distillation systems for rural as well as urban areas blessed with sufficient sunshine.
Ensuring security in terahertz (THz)-based communications is the prime objective in 6G-based systems. This paper investigates the information-theoretic security of a THz-based communication system ...over fluctuating two-ray (FTR) fading. We analyze the system from a partial secrecy regime and utilize fractional equivocation to obtain closed-form expressions for the generalized secrecy outage probability (GSOP), the average fractional equivocation (AFE), and the average information leakage rate (AILR) metrics. Further, the effect of fading parameters, such as the fading severity index, the average power ratio factor, and the dominant waves similarity index, on the secrecy metrics are also analyzed. Numerical results show that with increasing average power ratio factor, the system's secrecy is compromised from the AFE and AILR perspectives, whereas from the GSOP perspective, increasing the average power ratio factor results in secrecy improvement. Concurrently, degradation in the system's secrecy in terms of the GSOP is observed for increasing similarity index and fractional equivocation values. However, from AFE and AILR metrics perspective, increasing the similarity index results in secrecy improvement. Finally, the confidential information rate effect on the system's secrecy is also analyzed. Increasing the confidential information rate leads to secrecy compromisation, as observed by increasing GSOP and AILR and decreasing AFE.
Diabetes mellitus (DM) is a risk factor for developing active tuberculosis (TB) with a 3-fold increase in susceptibility and a 4-fold higher relapse rate. With increasing DM prevalence in TB endemic ...regions, understanding pathophysiological changes associated with DM-TB comorbidity is imperative. In this study, streptozotocin (STZ)-induced DM C57BL/6 mice were aerosol infected with low dose (100–120 CFU) Mycobacterium tuberculosis H37Rv. At 3 weeks post infection (w.p.i.), multiple tissue mycobacterial load and metabolites were profiled. The liver proteome of DM-TB and controls were analyzed using quantitative proteomics, and multi-omics data were integrated. DM-TB mice showed dysregulated multi-tissue (lungs, liver, brain, kidney and thigh muscle) metabolism. In contrast, the mycobacterial burden in the lung, spleen and liver was similar at 3 w.p.i. in DM-TB and TB groups. Enrichment analysis of deregulated liver metabolites (n = 20; log2DM-TB/TB>±1.0) showed significant perturbation in cysteine-methionine, glycine-serine, BCAA and fatty acid metabolism. 60 out of 1660 identified liver proteins showed deregulation (log2DM-TB/TB>±1.0) and contributed from perturbed cysteine-methionine metabolism corroborating metabolomics data. In addition, amino acid biosynthesis, retinol metabolism and polyol biosynthetic process were also differentially enriched in the livers of DM-TB groups. Global correlation analysis of liver metabolome and proteome data showed a strong association between aspartic acid, pyruvic acid, leucine and isoleucine with CYP450 enzymes involved in retinol metabolism, while iminodiacetic acid, isoleucine and γ-aminobutyric acid (GABA) strong positive correlation involved in cysteine metabolism. Targeting perturbed cysteine metabolism using micro molecules, like DL-Propargylglycine, might help prevent liver damage in DM-TB comorbid conditions.
Water splitting is the process of using energy to break down water molecules into hydrogen and oxygen. The use of an aluminum catalyst in the thermochemical process can help to increase the ...efficiency and rate of the reaction. Furthermore, aluminum is a relatively inexpensive material that can be easily produced, making it an appealing option for use in large-scale water-splitting operations. We investigated the reaction mechanism between aluminum nanotubes and water at various temperatures using reactive molecular dynamic simulations. We found that an aluminum catalyst makes it possible to split water at temperatures higher than
> 600 K. It was also observed that the yield of H
evolution is dependent on the diameter of the Al nanotube and decreases with increasing size. During the process of splitting water, the inner surfaces of the aluminum nanotubes are seen to be severely eroded, as shown by changes in the aspect ratio and solvent-accessible surface area. In order to compare the H
evolution efficiency of water with other solvents, we also split a variety of solvents, including methanol, ethanol, and formic acid. We presume that our study will give researchers enough knowledge to create hydrogen through thermochemical process in the presence of an aluminum catalyst by dissociating water and other solvent molecules.
In this paper, we investigate modulation techniques for end-to-end communication between two nanomachines placed in a fluid medium. The information is encoded as the number of molecules transmitted ...leading to such schemes being aptly named as amplitude modulation schemes. The propagation of molecules obeys the laws of Brownian motion with a positive drift from the transmitter to the receiver nanomachine. The channel is characterized by two parameters of the fluid medium: the drift velocity and the diffusion coefficient. Assuming the molecules degrade over time, the life expectancy of the molecules also plays a significant role in such communication scenarios. We consider an M -ary modulation scheme and also propose an extended scheme, which is a slight variation of a binary modulation scheme. The received symbol is corrupted by interference from the previous symbols as well as other noise sources present in the medium. Considering maximum likelihood detection at the receiver, we derive analytical expressions for the end-to-end symbol error probability and the capacity for these modulation schemes. Numerical results bring out the impact of various parameters on the performance of the system. Our results show that these schemes offer a promising approach to set up molecular communication over diffusion-based channels.
The channel capacity of noncoherent reception of multi-level one-sided amplitude-shift keying (ASK), which is an asymmetric constellation, in Rayleigh fading with receive diversity and energy ...detection is considered. The asymmetries result in capacity achieving input probability distributions, that is, a priori probability distributions, that deviate from uniformity. An analytical expression for the mutual information in terms of a single integral is derived, and from it the set of equations, which can be solved to obtain the optimum or capacity achieving input probabilities, is obtained. High and low signal-to-noise ratio (SNR) approximations of the optimum input probabilities and the capacity are derived next. Furthermore, a logarithmic upper bound on the mutual information is obtained. Numerical results confirm that the uniform distribution of input probabilities is not capacity achieving. For example, with average SNR per symbol per branch of 6 dB, the relative deviation of the mutual information (with uniform input distribution) from the capacity is nearly 20% for 4-level ASK with one transmit diversity branch and two receive diversity branches. Furthermore, the derived high and low SNR approximations to the capacity are shown to be reasonably accurate.
The solar thermal power plant is one of the promising renewable energy options to substitute the increasing demand of conventional energy. The cost per kW of solar power is higher and the overall ...efficiency of the system is lower. In the present communication, a comprehensive literature review on the scenario of solar thermal power plants and its up-to-date technologies all over the world is presented. Results of the technical and economical feasibility studies by researchers are reported in brief for further reference. It is observed that the solar thermal power plants have come out of the experimental stage to commercial applications. Case studies of typical 50MW solar thermal power plants in the Indian climatic conditions at locations such as Jodhpur and Delhi is highlighted with the help of techno-economic model. Different solar concentrator technologies (parabolic trough, parabolic dish and central power tower) for solar thermal power plants are compared economically. It has been found that the parabolic dish concentrating solar Stirling engine power plant generate electricity at a lower unit cost than the other two solar technologies considering 30 years lifespan and 10% interest rate on investment.
This paper develops a tractable framework for exploiting the potential benefits of physical layer security in three-tier wireless sensor networks (WSNs) using stochastic geometry. In such networks, ...the sensing data from the remote sensors are collected by sinks with the help of access points, and the external eavesdroppers intercept the data transmissions. We focus on the secure transmission in two scenarios: 1) the active sensors transmit their sensing data to the access points and 2) the active access points forward the data to the sinks. We derive new compact expressions for the average secrecy rate in these two scenarios. We also derive a new compact expression for the overall average secrecy rate. Numerical results corroborate our analysis and show that multiple antennas at the access points can enhance the security of three-tier WSNs. Our results show that increasing the number of access points decreases the average secrecy rate between the access point and its associated sink. However, we find that increasing the number of access points first increases the overall average secrecy rate, with a critical value beyond which the overall average secrecy rate then decreases. When increasing the number of active sensors, both the average secrecy rate between the sensor and its associated access point, and the overall average secrecy rate decrease. In contrast, increasing the number of sinks improves both the average secrecy rate between the access point and its associated sink, and the overall average secrecy rate.
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