Estimation of temperature dependent parameters of a batch alcoholic fermentation process

In this work, a procedure was established to develop a mathematical model considering the effect of temperature on reaction kinetics. Experiments were performed in batch mode in temperatures from 30 to 38 degrees C. The microorganism used was Saccharomyces cerevisiae and the culture media, sugarcane molasses. The objective is to assess the difficulty in updating the kinetic parameters when there are changes in fermentation conditions. We conclude that, although the re-estimation is a time-consuming task, it is possible to accurately describe the process when there are changes in raw material composition if a re-estimation of parameters is performed.     

Hybrid neural network model of an industrial ethanol fermentation process considering the effect of temperature

In this work a procedure for the development of a robust mathematical model for an industrial alcoholic fermentation process was evaluated. The proposed model is a hybrid neural model, which combines mass and energy balance equations with functional link networks to describe the kinetics. These networks have been shown to have a good nonlinear approximation capability, although the estimation of its weights is linear. The proposed model considers the effect of temperature on the kinetics and has the neural network weights reestimated always so that a change in operational conditions occurs. This allow to follow the system behavior when changes in operating conditions occur.     

Electrochemiluminescence Mechanisms Investigated with Smartphone-Based Sensor Data Modeling,Parameter Estimation and Sensitivity Analysis

The present study introduces a unified framework combining a mechanistic model with a genetic algorithm (GA) for the parameter estimation of electrochemiluminescence (ECL) kinetics of the Ru(bpy)₃²⁺/TPrA system occurring in a smartphone-based sensor. The framework allows a straightforward solution for simultaneous estimation of multiple parameters which can be, otherwise, time-consuming and lead to non-convergence. Model parameters are estimated by achieving a high correlation between the model prediction and the measured ECL intensity from the ECL sensor. The developed model is used to perform a sensitivity analysis (SA), which provides quantitative effects of the model parameters on the concentrations of chemical species involved in the system. The results demonstrate that the GA-based parameter estimation and the SA approaches are effective in analyzing the kinetics of the ECL mechanism. Therefore, these approaches can be incorporated as analysis tools in the ECL kinetics study with practical application in the calibration of mechanistic models for any required sensing condition.     

New two- and three-coordinate cadmium(II) dialkylamides

Some adducts of the known two-coordinate cadmium disilylamide, Cd[N(SiMe₃)₂]₂, have been studied by ¹H, ²⁹Si, and ¹¹³Cd nuclear magnetic resonance spectroscopy. The physical and spectral properties of three new Cd(NR₂)₂ species are also described.     

Dry friction in the Frenkel-Kontorova-Tomlinson model: dynamical properties

Wearless friction is investigated in a simple mechanical model called Frenkel-Kontorova-Tomlinson model. We have introduced this model in [Phys. Rev. B, 53, 7539 (1996)] where the static friction has already been considered. Here the model is treated for constant sliding speed. The motion of the internal degrees of freedom is regular for small sliding velocities or weak interaction between the sliding surfaces. The regular motion for large velocities is strongly determined by normal and superharmonic resonance of phonons excited by the so-called “washboard wave”. The kinetic friction has maxima near these resonances. For increasing interaction strength the regular motion becomes unstable due to parametric resonance leading to quasistatic and chaotic motion. For sliding velocities beyond first-order parametric resonance bistability occurs between the strongly chaotic motion (fluid sliding state), where friction is large and a regular motion (solid sliding state), where friction is weak. The fluid sliding state is mainly determined by the density of decay channels of m washboard waves into n phonons. This density describes qualitatively the effectiveness of the energy transfer from the uniform sliding motion into the microscopic, irregular motion of the degrees of freedom at the sliding interface. For a narrow interval of the sliding velocities we also found enhanced friction due to coherent motion. In the regime of coherent motion nondestructive interactions of dark envelope solitons occur.     

Foldamer dynamics expressed via Markov state models. II. State space decomposition

The structural landscape of poly-phenylacetylene (pPA), otherwise known as m-phenylene ethynylene oligomers, has been shown to consist of a very diverse set of conformations, including helices, turns, and knots. Defining a state space decomposition to classify these conformations into easily identifiable states is an important step in understanding the dynamics in relation to Markov state models. We define the state decomposition of pPA oligomers in terms of the sequence of discretized dihedral angles between adjacent phenyl rings along the oligomer backbone. Furthermore, we derive in mathematical detail an approach to further reduce the number of states by grouping symmetrically equivalent states into a single parent state. A more challenging problem requires a formal definition for knotted states in the structural landscape. Assuming that the oligomer chain can only cross the ideal helix path once, we propose a technique to define a knotted state derived from a helical state determined by the position along the helical nucleus where the chain crosses the ideal helix path. Several examples of helical states and knotted states from the pPA 12-mer illustrate the principles outlined in this article.     

Omega theorems for the iterated additive convolution of a nonnegative arithmetic function

Let R_k(n) denote the number of ways of representing the integers not exceeding n as the sum of k members of a given sequence of nonnegative integers. Suppose that $\text{1}\text{2}\text{< β < k}$, $\text{δ =}\text{β}\text{2}\text{?}\text{β}\text{(4}\text{min}\text{(β,}\text{k}\text{2}\text{))}$ and

$\text{ξ=}\text{1/2β if β<k/2,}\text{β?1/2 if β=1/2,}\text{(k ? 2)(k + 1)/2k if k/2<β<k.}$

R. C. Vaughan has shown that the relation R_k(n) = G(n) + o(n^δ log^?ξn) as n → +∞ is impossible when G(n) is a linear combination of powers of n and the dominant term of G(n) is cn^β, c > 0. P. T. Bateman, for the case k = 2, has shown that similar results can be obtained when G(n) is a convex or concave function. In this paper, we combine the ideas of Vaughan and Bateman to extend the theorems stated above to functions whose fractional differences are of one sign for large n. Vaughan's theorem is included in ours, and in the case $\text{β <}\text{k}\text{2}$ we show that a better choice of parameter improves Vaughan's result by enabling us to drop the power of log n from the estimate of the error term.     

Dioxouranium(VI) complexes with potentially dibasic tridentate schiff base ligands. Characterization of the uranyl complexes of salicylaldehyde-2-hydroxyanil and its substituted derivatives

Summary Some 11, 23, and 12 uranyl complexes of salicylaldehyde-2-hydroxyanil (H₂SAP) and its substituted (3-methoxy-, 5-nitro-, 5-chloro- and 3,5-dichloro-) derivatives have been synthesized and characterized. The conductivity, i.r.,¹H n.m.r. and visible spectroscopic data allow discussion of the varying ligating behaviour of the potentially dibasic tridentate Schiff base ligands toward dioxouranium(VI).