scholarly journals Mathematical Modeling of Biofilm Structures Using COMSTAT Data

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Davide Verotta ◽  
Janus Haagensen ◽  
Alfred M. Spormann ◽  
Katherine Yang
Keyword(s):  
Mathematical Modeling ◽  
Dead Cell ◽  
Mathematical Framework ◽  
Complex Data ◽  
Biofilm Growth ◽  
Statistical Framework ◽  
Cell Accumulation ◽  
Microscopy Data ◽  
Kinetics Of

Mathematical modeling holds great potential for quantitatively describing biofilm growth in presence or absence of chemical agents used to limit or promote biofilm growth. In this paper, we describe a general mathematical/statistical framework that allows for the characterization of complex data in terms of few parameters and the capability to (i) compare different experiments and exposures to different agents, (ii) test different hypotheses regarding biofilm growth and interaction with different agents, and (iii) simulate arbitrary administrations of agents. The mathematical framework is divided to submodels characterizing biofilm, including new models characterizing live biofilm growth and dead cell accumulation; the interaction with agents inhibiting or stimulating growth; the kinetics of the agents. The statistical framework can take into account measurement and interexperiment variation. We demonstrate the application of (some of) the models using confocal microscopy data obtained using the computer program COMSTAT.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

Elaboration and Characterization of the Properties of Refractory Cr Base Alloys

2010 ◽  
Vol 72 ◽  
pp. 46-52 ◽  
Author(s):  
Laurent Royer ◽  
Stéphane Mathieu ◽  
Christophe Liebaut ◽  
Pierre Steinmetz
Keyword(s):  
Mechanical Properties ◽  
Melting Point ◽  
Molten Glass ◽  
Energy Production ◽  
Creep Properties ◽  
Refractory Alloys ◽  
Industrial Use ◽  
Kinetics Of ◽  
Selection Of

For energy production and also for the glass industry, finding new refractory alloys which could permit to increase the process temperatures to 1200°C or more is a permanent challenge. Chromium base alloys can be good candidates, considering the melting point of Cr itself, and also its low corrosion rate in molten glass. Two families of alloys have been studied for this purpose, Cr-Mo-W and Cr-Ta-X alloys (X= Mo, Si..). A finer selection of compositions has been done, to optimize their chemical and mechanical properties. Kinetics of HT oxidation by air, of corrosion by molten glass and also creep properties of several alloys have been measured up to 1250°C. The results obtained with the best alloys (Cr-Ta base) give positive indications as regards the possibility of their industrial use.

scholarly journals New Trimethoprim-Like Molecules: Bacteriological Evaluation and Insights into Their Action

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 709
Author(s):  
Marta Jorba ◽  
Marina Pedrola ◽  
Ouldouz Ghashghaei ◽  
Rocío Herráez ◽  
Lluis Campos-Vicens ◽  
...  
Keyword(s):  
Inhibitory Concentration ◽  
Efflux Pump ◽  
Synergistic Effects ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Detailed Characterization ◽  
Low Concentrations ◽  
Pump Activity ◽  
Bacteriological Evaluation ◽  
Kinetics Of

This work reports a detailed characterization of the antimicrobial profile of two trimethoprim-like molecules (compounds 1a and 1b) identified in previous studies. Both molecules displayed remarkable antimicrobial activity, particularly when combined with sulfamethoxazole. In disk diffusion assays on Petri dishes, compounds 1a and 1b showed synergistic effects with colistin. Specifically, in combinations with low concentrations of colistin, very large increases in the activities of compounds 1a and 1b were determined, as demonstrated by alterations in the kinetics of bacterial growth despite only slight changes in the fractional inhibitory concentration index. The effect of colistin may be to increase the rate of antibiotic entry while reducing efflux pump activity. Compounds 1a and 1b were susceptible to extrusion by efflux pumps, whereas the inhibitor phenylalanine arginyl β-naphthylamide (PAβN) exerted effects similar to those of colistin. The interactions between the target enzyme (dihydrofolate reductase), the coenzyme nicotinamide adenine dinucleotide phosphate (NADPH), and the studied molecules were explored using enzymology tools and computational chemistry. A model based on docking results is reported.

scholarly journals Simultaneous Kinetics of Selenite Oxidation and Sorption on δ-MnO2 in Stirred-Flow Reactors

2021 ◽  
Vol 18 (6) ◽  
pp. 2902
Author(s):  
Zheyong Li ◽  
Yajun Yuan ◽  
Lin Ma ◽  
Yihui Zhang ◽  
Hongwei Jiang ◽  
...  
Keyword(s):  
Rate Constant ◽  
Photoelectron Spectroscopy ◽  
Oxide Surfaces ◽  
Kinetic Rate Constant ◽  
Flow Reactors ◽  
Mn Oxide ◽  
Remediation Strategies ◽  
Process Of Se ◽  
Kinetics Of

Selenium (Se) is an essential and crucial micronutrient for humans and animals, but excessive Se brings negativity and toxicity. The adsorption and oxidation of Se(IV) on Mn-oxide surfaces are important processes for understanding the geochemical fate of Se and developing engineered remediation strategies. In this study, the characterization of simultaneous adsorption, oxidation, and desorption of Se(IV) on δ-MnO2 mineral was carried out using stirred-flow reactors. About 9.5% to 25.3% of Se(IV) was oxidized to Se(VI) in the stirred-flow system in a continuous and slow process, with the kinetic rate constant k of 0.032 h−1, which was significantly higher than the apparent rate constant of 0.0014 h−1 obtained by the quasi-level kinetic fit of the batch method. The oxidation reaction was driven by proton concentration, and its rate also depended on the Se(IV) influent concentration, flow rate, and δ-MnO2 dosage. During the reaction of Se(IV) and δ-MnO2, Mn(II) was produced and adsorbed strongly on Mn oxide surfaces, which was evidenced by the total reflectance Fourier transform infrared (ATR-FTIR) results. The X-ray photoelectron spectroscopy (XPS) data indicated that the reaction of Se(VI) on δ-MnO2 produced Mn(III) as the main product. These results contribute to a deeper understanding of the interface chemical process of Se(IV) with δ-MnO2 in the environment.

scholarly journals Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1686
Author(s):  
Andrey Galukhin ◽  
Roman Nosov ◽  
Ilya Nikolaev ◽  
Elena Melnikova ◽  
Daut Islamov ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Single Step ◽  
Polymerization Kinetics ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Polymerization Product ◽  
The One ◽  
Kinetics Of

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

scholarly journals Material Geometry of Binary Composites

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 892
Author(s):  
Marcelo Epstein
Keyword(s):  
Continuum Mechanics ◽  
Mathematical Framework ◽  
Double Groupoid ◽  
The Individual ◽  
Elastic Composites

The constitutive characterization of the uniformity and homogeneity of binary elastic composites is presented in terms of a combination of the material groupoids of the individual constituents. The incorporation of these two groupoids within a single double groupoid is proposed as a viable mathematical framework for a unified formulation of this and similar kinds of problems in continuum mechanics.

scholarly journals Biosorption and Diffusion Modeling of Pb(II) by Malt Bagasse

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Klaiani B. Fontana ◽  
Giane Gonçalves Lenzi ◽  
Erica R. L. R. Watanabe ◽  
Ervin Kaminski Lenzi ◽  
Juliana A. M. T. Pietrobelli ◽  
...  
Keyword(s):  
Sorption Process ◽  
Isotherm Models ◽  
Diffusion Modeling ◽  
Biosorption Capacity ◽  
Kinetic And Thermodynamic Parameters ◽  
Pseudo Second Order ◽  
Ph Optimization ◽  
Kinetics Of ◽  
And Diffusion

The removal of Pb(II) from water by biosorption processes onto malt bagasse was investigated and the kinetic and thermodynamic parameters were obtained; additionally a diffusion modeling was proposed. The characterization of malt bagasse was performed by FTIR and SEM/EDS. The experiments were conducted in batch system and an experimental design based response surface methodology was applied for agitation speed and pH optimization. The kinetics of biosorption followed pseudo-second-order model and the temperature of the process affected the biosorption capacity. Isotherm models of Langmuir, Freundlich, and Elovich were applied and the Langmuir model showed better fit and the estimated biosorption capacity was 29.1 mg g−1. The negative values obtained for ΔG° and positive values of ΔH° confirm, respectively, the spontaneous and endothermic nature of the process. The diffusion modeling was performed based on experiments in the absence of agitation to investigate the influence of the biosorbent on the sorption process of Pb(II) ions.

scholarly journals High-resolution view of HIV-1 reverse transcriptase initiation complexes and inhibition by NNRTI drugs

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Betty Ha ◽  
Kevin P. Larsen ◽  
Jingji Zhang ◽  
Ziao Fu ◽  
Elizabeth Montabana ◽  
...  
Keyword(s):  
Reverse Transcriptase ◽  
Viral Entry ◽  
Reverse Transcription ◽  
Molecular Mechanisms ◽  
Dissociation Kinetics ◽  
Structural Mechanism ◽  
Medium Resolution ◽  
Kinetics Of ◽  
Hiv 1

AbstractReverse transcription of the HIV-1 viral RNA genome (vRNA) is an integral step in virus replication. Upon viral entry, HIV-1 reverse transcriptase (RT) initiates from a host tRNALys3 primer bound to the vRNA genome and is the target of key antivirals, such as non-nucleoside reverse transcriptase inhibitors (NNRTIs). Initiation proceeds slowly with discrete pausing events along the vRNA template. Despite prior medium-resolution structural characterization of reverse transcriptase initiation complexes (RTICs), higher-resolution structures of the RTIC are needed to understand the molecular mechanisms that underlie initiation. Here we report cryo-EM structures of the core RTIC, RTIC–nevirapine, and RTIC–efavirenz complexes at 2.8, 3.1, and 2.9 Å, respectively. In combination with biochemical studies, these data suggest a basis for rapid dissociation kinetics of RT from the vRNA–tRNALys3 initiation complex and reveal a specific structural mechanism of nucleic acid conformational stabilization during initiation. Finally, our results show that NNRTIs inhibit the RTIC and exacerbate discrete pausing during early reverse transcription.

scholarly journals Biochar Chemistry in a Weathered Tropical Soil: Kinetics of Phosphorus Sorption

Agriculture ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 295
Author(s):  
Marina Moura Morales ◽  
Nicholas Brian Comerford ◽  
Maurel Behling ◽  
Daniel Carneiro de Abreu ◽  
Iraê Amaral Guerrini
Keyword(s):  
Mineral Soil ◽  
Soil Surface ◽  
Kinetic Studies ◽  
Inorganic Phosphorus ◽  
Initial Reaction ◽  
Phosphorus Sorption ◽  
P Sorption ◽  
Published Research ◽  
Kinetics Of

The phosphorus (P) chemistry of biochar (BC)-amended soils is poorly understood. This statement is based on the lack of published research attempting a comprehensive characterization of biochar’s influence on P sorption. Therefore, this study addressed the kinetic limitations of these processes. This was accomplished using a fast pyrolysis biochar made from a mix of waste materials applied to a highly weathered Latossolo Vermelho distrofico (Oxisol) from São Paulo, Brazil. Standard method (batch method) was used. The sorption kinetic studies indicated that P sorption in both cases, soil (S) and soil-biochar (SBC), had a relatively fast initial reaction between 0 to 5 min. This may have happened because adding biochar to the soil decreased P sorption capacity compared to the mineral soil alone. Presumably, this is a result of: (i) Inorganic phosphorus desorbed from biochar was resorbed onto the mineral soil; (ii) charcoal particles physically covered P sorption locations on soil; or (iii) the pH increased when BC was added SBC and the soil surface became more negatively charged, thus increasing anion repulsion and decreasing P sorption.

scholarly journals A Tool for the Analysis and Characterization of School Mathematical Models

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1569
Author(s):  
Jesús Montejo-Gámez ◽  
Elvira Fernández-Ahumada ◽  
Natividad Adamuz-Povedano
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Models ◽  
Educational Research ◽  
Analysis Procedure ◽  
Real System ◽  
The Real ◽  
School Model ◽  
Corresponding Analysis ◽  
Three Components

This paper shows a tool for the analysis of written productions that allows for the characterization of the mathematical models that students develop when solving modeling tasks. For this purpose, different conceptualizations of mathematical models in education are discussed, paying special attention to the evidence that characterizes a school model. The discussion leads to the consideration of three components, which constitute the main categories of the proposed tool: the real system to be modeled, its mathematization and the representations used to express both. These categories and the corresponding analysis procedure are explained and illustrated through two working examples, which expose the value of the tool in establishing the foci of analysis when investigating school models, and thus, suggest modeling skills. The connection of this tool with other approaches to educational research on mathematical modeling is also discussed.

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