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Open AccessReview
Advances in Methanol Production and Utilization, with Particular Emphasis toward Hydrogen Generation via Membrane Reactor Technology
by , , , , and
Membranes 2018, 8(4), 98; https://doi.org/10.3390/membranes8040098 (registering DOI) -
Abstract
Methanol is currently considered one of the most useful chemical products and is a promising building block for obtaining more complex chemical compounds, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, methylamine, etc. Methanol is the simplest alcohol, appearing as a
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Methanol is currently considered one of the most useful chemical products and is a promising building block for obtaining more complex chemical compounds, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, methylamine, etc. Methanol is the simplest alcohol, appearing as a colorless liquid and with a distinctive smell, and can be produced by converting CO2 and H2, with the further benefit of significantly reducing CO2 emissions in the atmosphere. Indeed, methanol synthesis currently represents the second largest source of hydrogen consumption after ammonia production. Furthermore, a wide range of literature is focused on methanol utilization as a convenient energy carrier for hydrogen production via steam and autothermal reforming, partial oxidation, methanol decomposition, or methanol–water electrolysis reactions. Last but not least, methanol supply for direct methanol fuel cells is a well-established technology for power production. The aim of this work is to propose an overview on the commonly used feedstocks (natural gas, CO2, or char/biomass) and methanol production processes (from BASF—Badische Anilin und Soda Fabrik, to ICI—Imperial Chemical Industries process), as well as on membrane reactor technology utilization for generating high grade hydrogen from the catalytic conversion of methanol, reviewing the most updated state of the art in this field. Full article
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Open AccessReview
Gas Signaling Molecules and Mitochondrial Potassium Channels
by , and
Int. J. Mol. Sci. 2018, 19(10), 3227; https://doi.org/10.3390/ijms19103227 (registering DOI) -
Abstract
Recently, gaseous signaling molecules, such as carbon monoxide (CO), nitric oxide (NO), and hydrogen sulfide (H2S), which were previously considered to be highly toxic, have been of increasing interest due to their beneficial effects at low concentrations. These so-called gasotransmitters affect
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Recently, gaseous signaling molecules, such as carbon monoxide (CO), nitric oxide (NO), and hydrogen sulfide (H2S), which were previously considered to be highly toxic, have been of increasing interest due to their beneficial effects at low concentrations. These so-called gasotransmitters affect many cellular processes, such as apoptosis, proliferation, cytoprotection, oxygen sensing, ATP synthesis, and cellular respiration. It is thought that mitochondria, specifically their respiratory complexes, constitute an important target for these gases. On the other hand, increasing evidence of a cytoprotective role for mitochondrial potassium channels provides motivation for the analysis of the role of gasotransmitters in the regulation of channel function. A number of potassium channels have been shown to exhibit activity within the inner mitochondrial membrane, including ATP-sensitive potassium channels, Ca2+-activated potassium channels, voltage-gated Kv potassium channels, and TWIK-related acid-sensitive K+ channel 3 (TASK-3). The effects of these channels include the regulation of mitochondrial respiration and membrane potential. Additionally, they may modulate the synthesis of reactive oxygen species within mitochondria. The opening of mitochondrial potassium channels is believed to induce cytoprotection, while channel inhibition may facilitate cell death. The molecular mechanisms underlying the action of gasotransmitters are complex. In this review, we focus on the molecular mechanisms underlying the action of H2S, NO, and CO on potassium channels present within mitochondria. Full article
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Open AccessArticle
Underdetermined Blind Source Separation Combining Tensor Decomposition and Nonnegative Matrix Factorization
by , , and
Symmetry 2018, 10(10), 521; https://doi.org/10.3390/sym10100521 (registering DOI) -
Abstract
Underdetermined blind source separation (UBSS) is a hot topic in signal processing, which aims at recovering the source signals from a number of observed mixtures without knowing the mixing system. Recently, expectation-maximization algorithm shows a great potential in the UBSS. However, the final
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Underdetermined blind source separation (UBSS) is a hot topic in signal processing, which aims at recovering the source signals from a number of observed mixtures without knowing the mixing system. Recently, expectation-maximization algorithm shows a great potential in the UBSS. However, the final separation results depend strongly on the parameter initialization, leading to poor separation performance. In this paper, we propose an effective algorithm that combines tensor decomposition and nonnegative matrix factorization (NMF). In the proposed algorithm, we first employ tensor decomposition to estimate the mixing matrix, and NMF source model is used to estimate the source spectrogram factors. Then a series of iterations are derived to update the model parameters. At the same time, the spatial images of source signals are estimated with Wiener filters constructed from the learned parameters. Therefore, time-domain sources can be obtained through inverse short-time Fourier transform. Finally, plenty of experimental results demonstrate the effectiveness and advantages of our proposed algorithm over the compared algorithms. Full article
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Open AccessArticle
Abnormal Anionic Porphyrin Sensing Effect for HER2 Gene Related DNA Detection via Impedance Difference between MWCNTs and Single-Stranded DNA or Double-Stranded DNA
by , , , , , , and
Molecules 2018, 23(10), 2688; https://doi.org/10.3390/molecules23102688 (registering DOI) -
Abstract
Human epidermal growth factor receptor 2 (HER2) is a key tumor marker for several common and deadly cancers. It is of great importance to develop efficient detection methods for its over-expression. In this work, an electrochemical impedance spectroscopy (EIS) method adjustable by anionic
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Human epidermal growth factor receptor 2 (HER2) is a key tumor marker for several common and deadly cancers. It is of great importance to develop efficient detection methods for its over-expression. In this work, an electrochemical impedance spectroscopy (EIS) method adjustable by anionic porphyrin for HER2 gene detection has been proposed, based on the impedance difference between multi-walled carbon nanotubes (MWCNTs) and DNA. The interesting finding herein is that with the addition of anionic porphyrin, i.e., meso-tetra(4-sulfophenyl)-porphyrin (TSPP), the impedance value obtained at a glass carbon electrode (GCE) modified with MWCNTs and a single stranded DNA (ssDNA), the probe DNA that might be assembled tightly onto MWCNTs through π-π stacking interaction, gets a slight decrease; however, the impedance value from a GCE modified with MWCNTs and a double stranded DNA (dsDNA), the hybrid of the probe DNA with a target DNA, which might be assembled loosely onto MWCNTs for the screening effect of phosphate backbones in dsDNA, gets an obvious decrease. The reason may be that on the one hand, being rich in negative sulfonate groups, TSPP will try to push DNA far away from CNTs surface due to its strong electrostatic repulsion towards DNA; on the other hand, rich in planar phenyl or pyrrole rings, TSPP will compete with DNA for the surface of CNTs since it can also be assembled onto CNTs through conjugative interactions. In this way, the “loosely assembled” dsDNA will be repelled by this anionic porphyrin and released off CNTs surface much more than the “tightly assembled” ssDNA, leading to a bigger difference in the impedance value between dsDNA and ssDNA. Thus, through the amplification effect of TSPP on the impedance difference, the perfectly matched target DNA could be easily determined by EIS without any label. Under the optimized experimental conditions, this electrochemical sensor shows an excellent linear response to target DNA in a concentration range of 2.0 × 10−11–2.0 × 10−6 M with a limit of detection (LOD) of 6.34 × 10−11 M (S/N = 3). This abnormally sensitive electrochemical sensing performance resulting from anionic porphyrin for DNA sequences specific to HER2 gene will offer considerable promise for tumor diagnosis and treatment. Full article
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Open AccessFeature PaperArticle
Approximating Nonlinear Relationships for Optimal Operation of Natural Gas Transport Networks
by and
Processes 2018, 6(10), 198; https://doi.org/10.3390/pr6100198 (registering DOI) -
Abstract
The compressor fuel cost minimization problem (FCMP) for natural gas pipelines is a relevant problem because of the substantial energy consumption of compressor stations transporting the large global demand for natural gas. The common method for modeling the FCMP is to assume key
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The compressor fuel cost minimization problem (FCMP) for natural gas pipelines is a relevant problem because of the substantial energy consumption of compressor stations transporting the large global demand for natural gas. The common method for modeling the FCMP is to assume key modeling parameters such as the friction factor, compressibility factor, isentropic exponent, and compressor efficiency to be constants, and their nonlinear relationships to the system operating conditions are ignored. Previous work has avoided the complexity associated with the nonlinear relationships inherent in the FCMP to avoid unreasonably long solution times for practical transportation systems. In this paper, a mixed-integer linear programming (MILP) based method is introduced to generate piecewise-linear functions that approximate the previously ignored nonlinear relationships. The MILP determines the optimal break-points and orientation of the linear segments so that approximation error is minimized. A novel FCMP model that includes the piecewise-linear approximations is applied in a case study on three simple gas networks. The case study shows that the novel FCMP model captures the nonlinear relationships with a high degree of accuracy and only marginally increases solution time compared to the common simplified FCMP model. The common simplified model is found to produce solutions with high error and infeasibility when applied on a rigorous simulation. Full article
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Open AccessArticle
Molecular Disorder of Bicalutamide—Amorphous Solid Dispersions Obtained by Solvent Methods
by , , , , , , , and
Pharmaceutics 2018, 10(4), 194; https://doi.org/10.3390/pharmaceutics10040194 (registering DOI) -
Abstract
The effect of solvent removal techniques on phase transition, physical stability and dissolution of bicalutamide from solid dispersions containing polyvinylpyrrolidone (PVP) as a carrier was investigated. A spray dryer and a rotavapor were applied to obtain binary systems containing either 50% or 66%
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The effect of solvent removal techniques on phase transition, physical stability and dissolution of bicalutamide from solid dispersions containing polyvinylpyrrolidone (PVP) as a carrier was investigated. A spray dryer and a rotavapor were applied to obtain binary systems containing either 50% or 66% of the drug. Applied techniques led to the formation of amorphous solid dispersions as confirmed by X-ray powder diffractometry and differential scanning calorimetry. Moreover, solid–solid transition from polymorphic form I to form II was observed for bicalutamide spray dried without a carrier. The presence of intermolecular interactions between the drug and polymer molecules, which provides the stabilization of molecularly disordered bicalutamide, was analyzed using infrared spectroscopy. Spectral changes within the region characteristic for amide vibrations suggested that the amide form of crystalline bicalutamide was replaced by a less stable imidic one, characteristic of an amorphous drug. Applied processes also resulted in changes of particle geometry and size as confirmed by scanning electron microscopy and laser diffraction measurements, however they did not affect the dissolution significantly as confirmed by intrinsic dissolution study. The enhancement of apparent solubility and dissolution were assigned mostly to the loss of molecular arrangement by drug molecules. Performed statistical analysis indicated that the presence of PVP reduces the mean dissolution time and improve the dissolution efficiency. Although the dissolution was equally affected by both applied methods of solid dispersion manufacturing, spray drying provides better control of particle size and morphology as well as a lower tendency for recrystallization of amorphous solid dispersions. Full article
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Open AccessArticle
Effect of Mixed Meal and Leucine Intake on Plasma Amino Acid Concentrations in Young Men
by , , , , and
Nutrients 2018, 10(10), 1543; https://doi.org/10.3390/nu10101543 (registering DOI) -
Abstract
Dietary protein intake is critical for the maintenance of skeletal muscle mass. Plasma amino acid concentrations increase with protein intake and increases in muscle protein synthesis are dependent on leucine concentrations. We aimed to investigate the effect of a mixed meal and free
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Dietary protein intake is critical for the maintenance of skeletal muscle mass. Plasma amino acid concentrations increase with protein intake and increases in muscle protein synthesis are dependent on leucine concentrations. We aimed to investigate the effect of a mixed meal and free amino acids intake on plasma leucine concentrations. In this randomized crossover study, 10 healthy young men (age 25 ± 1 years, height 1.73 ± 0.02 m, weight 65.8 ± 1.5 kg) underwent tests under different conditions—intake of 2 g of leucine (LEU), intake of a mixed meal (protein 27.5 g, including 2.15 g of leucine, protein: fat: carbohydrate ratio—22:25:53) only (MEAL), intake of 2 g of leucine immediately after a mixed meal (MEAL-LEU) and intake of 2 g of leucine 180 min after a mixed meal (MEAL-LEU180). Blood samples were collected within 420 min (240 min for LEU only) after intake and changes in amino acid concentrations were evaluated. Although the maximum plasma leucine concentration increased to 442 ± 24 µM for LEU, it was lower at 347 ± 16 µM (p < 0.05 vs. LEU) for MEAL-LEU, 205 ± 8 µM (p < 0.05 vs. LEU) for MEAL. The maximum plasma leucine concentration for MEAL-LEU180 increased to 481 ± 27 µM and compared to LEU there was no significant difference (p > 0.1). The observation that rapid elevations in plasma leucine concentrations are suppressed when leucine is ingested at the same time as a meal suggests that the timing of its intake must be considered to maximize the anabolic response. Full article
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