scholarly journals Growth and Decay of a Planktonic Microbial Culture

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Alberto Schiraldi
Keyword(s):  
Experimental Data ◽  
Microbial Population ◽  
Intermediate Phase ◽  
A Priori ◽  
Surrounding Medium ◽  
Linear Increase ◽  
Microbial Culture ◽  
Master Plot ◽  
Different Temperatures ◽  
Plate Counts

The paper shows that the phenomenological trends of both growth and decay of a microbial population in a given medium are easily reproducible with simple equations that allow gathering the experimental data (plate counts) related to different microbial species, in different mediums and even at different temperatures, in a single master plot. The guideline of the proposed approach is that microbes and surrounding medium form a system where they affect each other and that the so-called “growth curve” is just the phenomenological appearance of such interaction. The whole system (cells and medium) changes following a definite pathway described as the evolution of a “virtual” microbial population in planktonic conditions. The proposed equations come from the assumption of a duplication mechanism with a variable generation time for the growth and of an exponential-like decline with a linear increase of the rate for the decay. The intermediate phase between growth and decay is a time span during which growth and death counterbalance each other and age differences within the virtual cell population tend to level off. The proposed approach does not provide an a priori description of this phase but allows the fit of the whole evolution trend of a microbial culture whenever the experimental data are available. Deviations of such a trend concern microbes able to form spores, modify their metabolism, or express phenotypic heterogeneity, to counterbalance adverse medium conditions.

Magnetoresistance of Planar Heterostructures Approached on a Theoretical Basis

2012 ◽  
Vol 67 (1-2) ◽  
pp. 50-56 ◽  
Author(s):  
Stanisław Olszewski ◽  
Tomasz Roliński
Keyword(s):  
Experimental Data ◽  
Band Structure ◽  
General Result ◽  
Magnetic Induction ◽  
Theoretical Basis ◽  
Linear Increase ◽  
Average Ratio ◽  
Different Temperatures ◽  
Structure Properties

The change of magnetoresistance in dependence on the strength of the magnetic induction is examined theoretically for several heterostructures taken as examples. Different temperatures of the examined samples, concentrations of the electron or hole carriers, and band structure properties are then involved. A general result is that a linear increase of magnetoresistance as a function of the magnetic induction should be obtained for all samples. This finds its counterpart in the behaviour of the experimental data. The ratios of the theoretical slopes of increase to the experimental ones range between 0.1 and 11, but the average ratio amounts to less than 1.8.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

scholarly journals Extracting real-crack properties from non-linear elastic behaviour of rocks: abundance of cracks with dominating normal compliance and rocks with negative Poisson ratios

2017 ◽  
Vol 24 (3) ◽  
pp. 543-551 ◽  
Author(s):  
Vladimir Y. Zaitsev ◽  
Andrey V. Radostin ◽  
Elena Pasternak ◽  
Arcady Dyskin
Keyword(s):  
Experimental Data ◽  
Poisson Ratio ◽  
A Priori ◽  
Elastic Behaviour ◽  
Crack Model ◽  
Normal Compliance ◽  
S Wave ◽  
Linear Elastic ◽  
Non Linear ◽  
Linear Elastic Behaviour

Abstract. Results of examination of experimental data on non-linear elasticity of rocks using experimentally determined pressure dependences of P- and S-wave velocities from various literature sources are presented. Overall, over 90 rock samples are considered. Interpretation of the data is performed using an effective-medium description in which cracks are considered as compliant defects with explicitly introduced shear and normal compliances without specifying a particular crack model with an a priori given ratio of the compliances. Comparison with the experimental data indicated abundance (∼ 80 %) of cracks with the normal-to-shear compliance ratios that significantly exceed the values typical of conventionally used crack models (such as penny-shaped cuts or thin ellipsoidal cracks). Correspondingly, rocks with such cracks demonstrate a strongly decreased Poisson ratio including a significant (∼ 45 %) portion of rocks exhibiting negative Poisson ratios at lower pressures, for which the concentration of not yet closed cracks is maximal. The obtained results indicate the necessity for further development of crack models to account for the revealed numerous examples of cracks with strong domination of normal compliance. Discovering such a significant number of naturally auxetic rocks is in contrast to the conventional viewpoint that occurrence of a negative Poisson ratio is an exotic fact that is mostly discussed for artificial structures.

scholarly journals A Temperature Variation of Debye-Waller Factor for Alkali and Noble Metals

1983 ◽  
Vol 38 (5) ◽  
pp. 503-508 ◽  
Author(s):  
A. R. Jani ◽  
V. B. Gohel
Keyword(s):  
Experimental Data ◽  
Temperature Variation ◽  
Phenomenological Model ◽  
Noble Metals ◽  
Experimental Information ◽  
Waller Factor ◽  
Critical Examination ◽  
Debye Waller Factor ◽  
Different Temperatures ◽  
Experimental Findings

Debye-Waller factors at different temperatures of four alkali and three noble metals have been computed on the basis of a screened shell phenomenological model. The theoretical values are compared with existing experimental data. Particularly for lithium and potassium, most recent experimental information has been included. A critical examination of the results reveals a satis­factory agreement between the theoretical and experimental findings.

scholarly journals Drying kinetics of baru flours as function of temperature

2018 ◽  
Vol 22 (10) ◽  
pp. 713-719 ◽  
Author(s):  
Douglas R. Reis ◽  
Fabrício B. Brum ◽  
Eduardo J. O. Soares ◽  
Jessiana R. Magalhães ◽  
Fabrício S. Silva ◽  
...  
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Food Industry ◽  
Nutritional Value ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Statistical Parameters ◽  
Noticeable Effect ◽  
Different Temperatures ◽  
Kinetics Of

ABSTRACT Several types of seeds have been initially used in the food industry due to the great potential that vegetable proteins have. Baru is a fruit commonly found in the Cerrado biome, having a high nutritional value. This paper aimed to determine and analyze the drying kinetics of whole and defatted baru almond flours at different temperatures. The flour resulting from almond milling was defatted using petroleum ether. The drying processes were performed at temperatures of 40, 50 and 60 ºC. The mathematical models of Page, Henderson and Pabis, Midilli & Kucuk, Thompson and Approximation of Diffusion were fitted to the experimental data. The results showed a noticeable effect of air temperature on the drying kinetics of whole and defatted baru almond flours. According to the statistical parameters of analysis, the models Midilli & Kucuk and Page were the ones with the best fits to the experimental data. The effective diffusivity values found ranged from 8.02 × 10–10 to 19.90 × 10–10 m2 s-1 and for the activation energy were 22.39 and 39.37 KJ mol-1 for whole and defatted almonds, respectively.

scholarly journals Rethinking the Acquisition of Kinship Terms

1989 ◽  
Vol 12 (4) ◽  
pp. 541-568 ◽  
Author(s):  
Lawrence A. Hirschfeld
Keyword(s):  
Experimental Data ◽  
A Priori ◽  
Semantic Features ◽  
Human Beings ◽  
Alternative Account ◽  
Age Dependent ◽  
Semantic Development

This paper reconsiders the predominant views on the acquisition of kinship terms and challenges the argument that the ontogenesis of these terms reflects global processes of semantic development in which weakly constrained initial representations evolve in discreet stages toward mature representations. Instead, through a re-examination of existing experimental data, an alternative account of kinship acquisition is offered which attributes to the child a significantly greater native conceptual sophistication and argues that age-dependent advances in kinship semantics are constrained by a priori hypotheses the child maintains about human beings in groups rather than through changes in the capacity to handle logical relations or semantic features.

scholarly journals Shubnikov–de Haas Oscillations in Semiconductors at the Microwave-Radiation Absorption

2019 ◽  
Vol 2019 ◽  
pp. 1-5
Author(s):  
G. Gulyamov ◽  
U. I. Erkaboev ◽  
A. G. Gulyamov
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Electromagnetic Field ◽  
Microwave Radiation ◽  
Three Dimensional ◽  
Radiation Absorption ◽  
Narrow Gap ◽  
Proposed Model ◽  
Different Temperatures ◽  
Shubnikov De Haas Oscillations

Mathematical models for the Shubnikov-de Haas oscillations in semiconductors are obtained at the microwave-radiation absorption and its temperature dependence. Three-dimensional image of microwave magnetoabsorption oscillations in narrow-gap semiconductors is established. Using a mathematical model, the oscillations of the microwave magnetoabsorption are considered for different values of the electromagnetic field. The results of calculations are compared with experimental data. The proposed model explains the experimental results in HgSe at different temperatures.

scholarly journals Temperature-Dependence of Rubber Hyperelasticity Based on the Eight-Chain Model

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 932 ◽  
Author(s):  
Xintao Fu ◽  
Zepeng Wang ◽  
Lianxiang Ma ◽  
Zhaoxuan Zou ◽  
Qingling Zhang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Large Temperature ◽  
Chain Model ◽  
Element Analysis ◽  
Filled Rubber ◽  
Different Temperatures

Rubber-based materials are widely used in a variety of industrial applications. In these applications, rubber components withstand various loading conditions over a range of temperatures. It is of great significance to study the mechanical behavior of vulcanized rubber at different temperatures, especially in a range of high temperatures. The temperature dependence of the constitutive behavior of filled rubber is important for the performance of the rubber. However, only a few constitutive models have been reported that investigate the stress–temperature relationship. In this paper, based on an analysis of experimental data, the effects of temperature on the hyperelastic behaviors of both natural rubber and filled rubber, with different mass fractions of carbon black, were studied. The regulation of stress and strain of natural rubber and filled rubber with temperature was revealed. In addition, an eight-chain model that can reasonably characterize the experimental data at different temperatures was proved. An explicit temperature-dependent constitutive model was developed based on the Arruda-Boyce model to describe the stress–strain response of filled rubber in a relatively large temperature range. Meanwhile, it was proved that the model can predict the effect of temperature on the hyperelastic behavior of filled rubber. Finally, the improved Arruda-Boyce model was used to obtain the material parameters and was then successfully applied to finite element analysis (FEA), which showed that the model has high application value. In addition, the model had a simple form and could be conveniently applied in related performance test of actual production or finite element analysis.

A Study of Nanoparticle-Enhanced Heat Transfer

2010 ◽  
Author(s):  
Lawrence M. Jones ◽  
Timothy Sirk ◽  
Eugene Brown
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Molecular Dynamics ◽  
Heat Flux ◽  
Nuclear Power ◽  
Power Plants ◽  
Md Simulations ◽  
Theoretical Description ◽  
Different Temperatures ◽  
Dynamics Simulations

The study of the heat transfer characteristics of nanofluids, i.e. fluids that are suspensions of nanometer size particles, has gained significant attention in the search for new coolants that can effectively service a variety of needs ranging from the increasing heat transfer demands of ever smaller microelectronic devices to mitigating the effects of loss of coolant accidents in nuclear power plants. Experimental data has shown large increases in thermal conductivity and associated increases in the level of critical heat flux in nuclear reactors; however, in some cases the range of the applicability of the experimental results is uncertain and there is a lack of a theory by which this can be resolved. Complicating the theoretical description of heat transfer in nanofluids is the fact that fluids in the vicinity of the nanoparticles are a complex combination of phase transition, interfacial, and transport phenomena. This paper describes a study in which molecular dynamics simulations were used to enhance the understanding of the effect of nanoparticles on heat transfer. The molecular dynamics (MD) simulations presented here model a Lennard-Jones fluid in a channel where the walls are maintained at different temperatures. The heat flux is calculated for a variety of nanoparticle sizes and concentrations. The results are compared to experimental data in order to provide information that will more confidently bound the data and provide information that will guide the development of more comprehensive theories. We also anticipate that this work could contribute to the design of biosensors where suspended molecules are transported through micro- and nano-channels in the presence of heat transfer.

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