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Sci, Volume 3, Issue 3 (September 2021) – 5 articles

Cover Story (view full-size image): Unlike single joint exercise, whole-body exercise incorporates multiple muscle groups and better imitates real-life sporting competitions (e.g., cycling time trials). It has been extensively reported that fatigue, whether due to peripheral or central factors, is one of the main factors contributing to the cessation of exercise. The impact of transcranial direct current stimulation (tDCS) on exercise performance is one such method that has gained much research interest over the past few years. In addition to physical demands, exercise performance also requires great mental effort. Here, we investigate the effects of tDCS on cycling time trial performance and explore if any changes are associated with prefrontal cortex and muscle oxygenation. View this paper
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Article
Towards Generic Simulation for Demanding Stochastic Processes
Sci 2021, 3(3), 34; https://doi.org/10.3390/sci3030034 - 06 Sep 2021
Viewed by 468
Abstract
We outline and test a new methodology for genuine simulation of stochastic processes with any dependence structure and any marginal distribution. We reproduce time dependence with a generalized, time symmetric or asymmetric, moving-average scheme. This implements linear filtering of non-Gaussian white noise, with [...] Read more.
We outline and test a new methodology for genuine simulation of stochastic processes with any dependence structure and any marginal distribution. We reproduce time dependence with a generalized, time symmetric or asymmetric, moving-average scheme. This implements linear filtering of non-Gaussian white noise, with the weights of the filter determined by analytical equations, in terms of the autocovariance of the process. We approximate the marginal distribution of the process, irrespective of its type, using a number of its cumulants, which in turn determine the cumulants of white noise, in a manner that can readily support the generation of random numbers from that approximation, so that it be applicable for stochastic simulation. The simulation method is genuine as it uses the process of interest directly, without any transformation (e.g., normalization). We illustrate the method in a number of synthetic and real-world applications, with either persistence or antipersistence, and with non-Gaussian marginal distributions that are bounded, thus making the problem more demanding. These include distributions bounded from both sides, such as uniform, and bounded from below, such as exponential and Pareto, possibly having a discontinuity at the origin (intermittence). All examples studied show the satisfactory performance of the method. Full article
(This article belongs to the Special Issue Feature Papers 2021 Editors Collection)
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Article
Progress in Life Cycle Impact Assessment: Water Vapor Emissions and Respiratory Inorganics
Sci 2021, 3(3), 33; https://doi.org/10.3390/sci3030033 - 12 Aug 2021
Viewed by 629
Abstract
Life cycle assessment (LCA) is being included formally in EcoDesign regulations. Especially product carbon footprint will be mandatory in Europe. However, life cycle impact assessment, including global warming potential (GWP) in LCA, is hampered by several challenges. One of these is a lack [...] Read more.
Life cycle assessment (LCA) is being included formally in EcoDesign regulations. Especially product carbon footprint will be mandatory in Europe. However, life cycle impact assessment, including global warming potential (GWP) in LCA, is hampered by several challenges. One of these is a lack of water vapor characterization indexes for GWP. A life cycle inventory profile for air transport fuel, including water vapor emissions, is evaluated with state-of-the-art practice, i.e., Environmental Footprint (EF) Method and International Life Cycle Data (ILCD) 2011 Mid-point+, neglecting water vapor’s high altitude GWP compared to carbon dioxide. Then, the characterization factor in GWP over 100 years (GWP100) for water vapor and alternate normalization for particulates are introduced. The results are compared. The main findings are that the previous EF method and ILCD both generate rather realistic results for Particulate Matter and Respiratory Inorganics mid-point indicators, respectively, but the number of premature deaths should be better allocated to different specific emissions, and that water vapor may dominate the GWP100 result over the usual carbon dioxide. Respiratory inorganics may need one impact category, each starting with particles smaller than 2.5 µm. LCIA mid-points need measurable and understandable bases. The common knowledge of water vapor’s GWP100 should not be neglected in LCIA for air transport and beyond where relevant. Full article
(This article belongs to the Special Issue Feature Papers 2021 Editors Collection)
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Article
Effects of Transcranial Direct Current Stimulation on Cycling Time Trial Performance and Prefrontal Cortex Activation
Sci 2021, 3(3), 32; https://doi.org/10.3390/sci3030032 - 24 Jul 2021
Viewed by 842
Abstract
Background: Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers low levels of a constant current via scalp electrodes to specifically targeted areas of the brain. The effects of tDCS on whole-body exercise performance has been of interest in recent literature. [...] Read more.
Background: Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers low levels of a constant current via scalp electrodes to specifically targeted areas of the brain. The effects of tDCS on whole-body exercise performance has been of interest in recent literature. The purpose of the current investigation was to investigate if tDCS, administered via Halo Sport, influences time trial performance in trained cyclists, and if changes in exercise performance are associated with prefrontal cortex (PFC) activation and/or muscle oxygenation (SmO2). Methods: Twelve recreationally trained cyclists volunteered to participate in a crossover study design involving two 10-kilometer time trials following 20 min of tDCS or a sham condition. Results: t-tests showed there was no significant difference in performance (time to completion) or physiological measures (blood lactate (BL) concentration, heart rate (HR), SmO2, PFC oxygenation) between the Halo and sham conditions. Conclusions: These results indicate that the application of tDCS via Halo Sport does not induce changes in exercise performance or related physiological parameters during a 10-kilometer cycling time trial. Full article
(This article belongs to the Special Issue Feature Papers 2021 Editors Collection)
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Article
Montivipera bornmuelleri Venom: Inhibitory Effect on Staphylococcus epidermidis and Escherichia coli F1F0-ATPases and Cytotoxicity on HCT116 Cancer Cell Lines
Sci 2021, 3(3), 31; https://doi.org/10.3390/sci3030031 - 14 Jul 2021
Viewed by 883
Abstract
In this work, we pursued the biological characterization of the venom of Montivipera bornmuelleri, a viper from the Lebanese mountains. In relation to its antibacterial potential, the inhibitory effect of this venom on the F1F0-ATPase enzymes of Gram-positive [...] Read more.
In this work, we pursued the biological characterization of the venom of Montivipera bornmuelleri, a viper from the Lebanese mountains. In relation to its antibacterial potential, the inhibitory effect of this venom on the F1F0-ATPase enzymes of Gram-positive Staphylocoocus epidermidis and Gram-negative Escherichia coli bacteria was examined. In order to determine the degree of cytotoxicity of the venom on the HCT116 human colon cancer cell lines, the biological MTT proliferation and cell viability test were implemented. After validation of the enzymatic F1F0-ATPase model by the spectrophotometric method, using quercetin as the reference ligand, results revealed that M. bornmuelleri venom is able to inhibit the activity of the enzyme of these two bacteria with a concentration of the order of 100–150 µg/mL. In addition, a venom concentration of 10 µg/mL was sufficient to kill the totality of HCT116 cell lines cultivated in vitro. These data show that M. bornmuelleri venom is a mixture of diverse molecules presenting activities of interest, and is a potential source to explore in order to discover new drug candidates. Full article
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Article
Introducing an Efficient In Vitro Cornea Mimetic Model for Testing Drug Permeability
Sci 2021, 3(3), 30; https://doi.org/10.3390/sci3030030 - 22 Jun 2021
Viewed by 1151
Abstract
There is a growing need for novel in vitro corneal models to replace animal-based ex vivo tests in drug permeability studies. In this study, we demonstrated a corneal mimetic that models the stromal and epithelial compartments of the human cornea. Human corneal epithelial [...] Read more.
There is a growing need for novel in vitro corneal models to replace animal-based ex vivo tests in drug permeability studies. In this study, we demonstrated a corneal mimetic that models the stromal and epithelial compartments of the human cornea. Human corneal epithelial cells (HCE-T) were grown on top of a self-supporting porcine collagen-based hydrogel. Cross-sections of the multi-layers were characterized by histological staining and immunocytochemistry of zonula oc-cludens-1 protein (ZO-1) and occludin. Furthermore, water content and bssic elastic properties of the synthetized collagen type I-based hydrogels were measured. The apparent permeability coefficient (Papp) values of a representative set of ophthalmic drugs were measured and correlated to rabbit cornea Papp values found in the literature. A multilayered structure of HCE-T cells and the expression of ZO-1 and occludin in the full thickness of the multilayer were observed. The hydrogel-based corneal model exhibited an excellent correlation to rabbit corneal permeability (r = 0.96), whereas the insert-grown HCE-T multilayer was more permeable and the correlation to the rabbit corneal permeability was lower (r = 0.89). The hydrogel-based human corneal model predicts the rabbit corneal permeability more reliably in comparison to HCE-T cells grown in inserts. This in vitro human corneal model can be successfully employed for drug permeability tests whilst avoiding ethical issues and reducing costs. Full article
(This article belongs to the Special Issue Biological In Vitro Models)
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