111,922 research outputs found
Robustness in Weighted Networks
No full textIn the last two decades, Network science has become a strategic field of research thanks to both
the increased availability of large datasets, and the strong development of high-performance computing technologies and methodologies. Different types of data will produce different types of complex networks in terms of structure, connectivity, and complexity. Examples range from biology to business and from technology to sociology. A network is said to have a community structure if the nodes are densely connected within groups but sparsely connected between them (1). A number of methods
for community detection have been proposed. However, their implementation leaves unaddressed the
question of the statistical validation of the results. A first method to statistically test the robustness
of undirected and unweighted networks was proposed in (2; 3). The method uses a configuration
model as a null random model to test the hypothesis that the detected communities are due only to
the random position of the edges in the graph.
In this work we propose a Machine Learning approach to perform robustness analysis for weighted
Networks
Biohydrogen and poly-β-hydroxybutyrate production by winery wastewater photofermentation: Effect of substrate concentration and nitrogen source
No full textThe applicability and convenience of biohydrogen and poly-β-hydroxybutyrate production through single-stage photofermentation of winery wastewater is demonstrated in the present study. Experiments are conducted using a purple non-sulfur bacteria mixed consortium, subject to variable nutrient conditions, to analyze the effect of initial chemical oxygen demand and the available nitrogen source on the metabolic response. Results show that winery wastewater is a promising substrate for photofermentation processes, despite the presence of inhibiting compounds such as phenolics. Nonetheless, the initial chemical oxygen demand must be carefully controlled to maximize hydrogen production. Up to 468 mL L−1 of hydrogen and 203 mg L−1 of poly-β-hydroxybutyrate can be produced starting from an initial chemical oxygen demand of 1500 mg L−1. The used nitrogen source may direct substrate transformation through different metabolic pathways. Interestingly, the maximum production of both hydrogen and poly-β-hydroxybutyrate occurred when glutamate was used as the nitrogen source
A comprehensive review of mathematical models of photo fermentation
No full textThis work aims at analyzing and comparing the different modeling approaches used to date to simulate, design and control photo fermentation processes for hydrogen production and/or wastewater treatment. The study is directed to researchers who approach the problem of photo fermentation mathematical modeling. It is a useful tool to address future research in this specific field in order to overcome the difficulty of modeling a complex, not totally elucidate process. We report a preliminary identification of the environmental and biological parameters, included in the models, which affect photo fermentation. Based on model features, we distinguish three different approaches, i.e. kinetic, parametric and non-ideal reactors. We explore the characteristics of each approach, reporting and comparing the obtained results and underlining the differences between models, together with the advantages and the limitations of each of them. The analysis of the approaches indicates that Kinetic models are useful to describe the process from a biochemical point of view, without considering bio-reactor hydrodynamics and the spatial variations that Parametric Models can be utilized to study the influence and the interactions between the operational conditions. They do not take into account the biochemical process mechanism and the influence of reactor hydrodynamics. Quite the opposite, non-ideal reactors models focus on the reactor configuration. Otherwise, the biochemical description of purple non-sulfur bacteria activities is usually simplified. This review indicates that there still is a lack of models that fully describe photo fermentation processes
robin2: accelerating single-cell data clustering evaluation
No full textMotivation: The rapid expansion of single-cell RNA sequencing (scRNA-seq) technologies has increased the need for robust and scalable clustering evaluation methods. To address these challenges, we developed robin2, an optimized version of our R package robin. It introduces enhanced computational efficiency, support for high-dimensional datasets, and harmonious integration with R's base functionalities for robust network analysis. Results: robin2 offers improved functionality for clustering stability validation and enables systematic evaluation of community detection algorithms across various resolutions and pipelines. The application to Tabula Muris and PBMC scRNA-seq datasets confirmed its ability to identify biologically meaningful cell subpopulations with high statistical significance. The new version reduces computational time by 9-fold on large-scale datasets using parallel processing. Availability and implementation: The robin2 package is freely available on CRAN at https://CRAN.R-project.org/package=robin. Comprehensive documentation and a detailed analysis vignette are available on GitHub at https://drighelli.github.io/scrobinv2/index.html
Nitric oxide-induced programmed cell death in human neuroblastoma cells is accompanied by the synthesis of Egr-1, a zinc finger transcription factor.
No full textCarbon catabolite repression occurrence in photo fermentation of ethanol-rich substrates
No full textThe paper investigates the phenomenon of Carbon Catabolite Repression occurring during photo fermentation of ethanol-rich effluents, which usually contain ethanol as main carbon source, and glycerol as secondary one. The study was conducted using mixed phototrophic cultures, adopting, as substrate, the effluent produced by the alcoholic fermentation of sugar cane bagasse. In order to elucidate the phenomenon, experimental tests were carried out using two different ethanol to glycerol ratios. Results were compared with those resulting from pure ethanol and glycerol conversion. According to the obtained data, as a result of Carbon Catabolite Repression occurrence, the presence of glycerol negatively affects hydrogen production. Indeed, part of the ethanol source is converted to biomass and polyhydroxybutyrate rather than to hydrogen. In more details, the presence of glycerol determines a drop of the hydrogen production, which goes from 12 % to 32 %, according to the ethanol/glycerol ratio, compared to the production obtained from fermentation of ethanol alone. Therefore, to promote the hydrogen production, it is advisable to apply strategies to produce low glycerol concentrations in the ethanol production stage
Enhancing photo fermentative hydrogen production using ethanol rich dark fermentation effluents
No full textThe present study demonstrates the feasibility of a two-phase biorefinery process applied to waste substrates producing ethanol rich effluents. The process includes a dark fermentation step followed by photo fermentation and it is able to optimize hydrogen production from waste biomass. The study was conducted using winery wastewater as feedstock. The results indicate that no additional treatments are required when an appropriate dilution of the initial waste is applied. Microbial consortia contained in the winery wastewater promoted a fermentative ethanol pathway. The ethanol rich effluent was converted into hydrogen by phototrophic microorganisms. Despite the presence of inhibiting compounds, the adoption of a mixed phototrophic culture allowed to obtain good results in terms of hydrogen production. Specifically, up to 310 mLH2/gCODconsumed were obtained in the photo fermentative stage. The effectiveness of ethanol rich dark fermentation effluents for hydrogen production enhancement was demonstrated. Noteworthy, polyhydroxybutyrate was also produced during the experiments. The work faces two of the major challenges in the sequential dark fermentation and photo fermentation technology applied to real waste substrates: the minimization of pre-treatments and the enhancement of the hydrogen production yields using ethanol rich DFEs
Community detection of seismic point processes
No full textIn this paper, we combine robin and Local Indicators of Spatio-Temporal Association (LISTA) functions.
robin is an R package to assess the robustness of the community structure of a network found by one or more methods to give indications about their reliability. We use it to propose a classification algorithm of events in a spatio-temporal point pattern, by means of the local second-order characteristics and the community detection procedure in network analysis. We demonstrate the proposed procedure on a real data analysis on seismic data
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