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Summary: The control problem of a general class of perturbed linear invariant time‐delay systems within the Sliding Mode Control framework is addressed. We introduce a novel class of sliding manifolds with a structure not previously reported in the literature, which constructively emerges from complete type functionals of the corresponding nominal time‐delay systems and depends on the whole state of the system. A fundamental conclusion derived from this proposal is that every time‐delay system with matched perturbations, whose associated nominal system is exponentially stabilizable, is robustly asymptotically stabilizable. In fact, the introduced sliding manifold enables to construct discontinuous and continuous sliding mode control‐based algorithms that mitigate different classes of perturbations. [ABSTRACT FROM AUTHOR]

We investigated the variability of nitrogen stable isotope ratios 15N/14N (expressed as δ15N) on citrus orchards with different fertilization management practices (organic versus conventional) and its correlation with the δ15N values of the key citrus pest Diaphorina citri Kuwayama (Hemiptera: Liviidae) feeding on such plant material. Tracing the origin of this pest in open field is crucial since the insect is a vector of the incurable and devastating citrus disease known as Huanglongbing. We hypothesized that the origin (natal tree) of the pest may be deduced by correlating the δ15N values obtained from the young citrus leaves and from adults of D. citri raised on them. First, laboratory experiments were performed to understand the acquisition and incorportation of the δ15N values by D. citri. Second, we confirmed the positive correlation between the δ15N values of the young citrus leaves and D. citri. Finally, field sampling was carried out in 21 citrus orchards from Southern California to study the variability on the δ15N values on organic and conventional commercial citrus orchards. Laboratory results suggest that the analyses of the δ15N values can be regarded as a useful method to trace the origin of the pest. However, the high variability in nitrogen resource used in both fertilization management practices (especially in organic orchards) by growers makes the application of this technique unfeasible to pinpoint the origin of D. citri in the citrus agroecosystem.

ABSTRACT Developmental larval stages of the geoduck Panopea globosa (Dali, 1898) are described for the first time. Growth rate, survival, and the length-size relationship were also assessed at 22°C in [...]

We address the stabilisation problem of linear time-invariant systems with pointwise and distributed delays. We first introduce the concept of the smoothed spectral abscissa, a robust stability measure previously studied for pointwise delay systems. We show that the new stability measure for distributed systems is smooth with respect to the system parameters, and robust in the sense that it provides a trade-off between the decay rate of the solution and the H 2 norm of the system. Next, we reformulate the stabilisation problem as an unconstrained minimisation problem considering the smoothed spectral abscissa as the objective function, and show that its properties enable solving the stabilisation problem by using standard gradient-based optimisation techniques. We show the potential of the proposed approach by using it for the stabilisation of a fleet of vehicles, and an oscillator with a class of time-varying delays in the input. [ABSTRACT FROM AUTHOR]

This contribution addresses the problem of calculating the critical parameters of a class of integral delay systems. The starting point of the analysis is a neutral‐type system with distributed delay that results from the application of a differential operator, and whose spectrum contains the spectrum of the integral system. Based on recent results concerning the delay Lyapunov matrix for the class of obtained neutral‐type systems, it is shown that the set of critical frequencies of the integral delay system is contained in the set of critical frequencies of a delay‐free system of matrix equations. [ABSTRACT FROM AUTHOR]

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Summary: We present novel theoretical concepts for linear time‐periodic systems with multiple delays, which are closely related to the spectral properties and Lyapunov matrices. At the basis of the main results is the associated dual system, constructed by transposition of the systems matrices and affine transformations of their arguments. We introduce, for the first time, the concepts of the ℋ2 norm and the dual Lyapunov matrix of periodic systems with delays. We show that the primal and dual system have the same ℋ2 norm, characterized by primal and dual delay Lyapunov equations, which extend the well‐known results for time‐invariant systems with delays, and periodic systems without delays. Having at hand the pair of primal‐dual Lyapunov matrices, along with some energy interpretations, allow us to generalize the concept of position balancing and explore its potential for model reduction. The obtained results are illustrated by several examples, including the delayed Mathieu equation. [ABSTRACT FROM AUTHOR]

We investigated the variability of nitrogen stable isotope ratios 15N/14N (expressed as δ15N) on citrus orchards with different fertilization management practices (organic versus conventional) and its correlation with the δ15N values of the key citrus pest Diaphorina citri Kuwayama (Hemiptera: Liviidae) feeding on such plant material. Tracing the origin of this pest in open field is crucial since the insect is a vector of the incurable and devastating citrus disease known as Huanglongbing. We hypothesized that the origin (natal tree) of the pest may be deduced by correlating the δ15N values obtained from the young citrus leaves and from adults of D. citri raised on them. First, laboratory experiments were performed to understand the acquisition and incorportation of the δ15N values by D. citri. Second, we confirmed the positive correlation between the δ15N values of the young citrus leaves and D. citri. Finally, field sampling was carried out in 21 citrus orchards from Southern California to study the variability on the δ15N values on organic and conventional commercial citrus orchards. Laboratory results suggest that the analyses of the δ15N values can be regarded as a useful method to trace the origin of the pest. However, the high variability in nitrogen resource used in both fertilization management practices (especially in organic orchards) by growers makes the application of this technique unfeasible to pinpoint the origin of D. citri in the citrus agroecosystem. [ABSTRACT FROM AUTHOR]

Summary: We introduce a new robust stability measure for systems with multiple pointwise delays, which is called smoothed spectral abscissa, consistently with the existing measure for delay‐free systems. Its main characteristics are that it is smooth with respect to the system parameters and it provides a trade‐off between the decay rate of the system solution and the H2 norm of a transfer matrix related with the system. The smoothed spectral abscissa is implicitly defined in terms of the H2 norm of an auxiliary system, and its computation is based on the so‐called delay Lyapunov matrix. We show that these features make the smoothed spectral abscissa suitable for the design of robust controllers by using standard gradient‐based optimization techniques and exploiting a novel characterization of the derivatives of the delay Lyapunov matrix with respect to the system parameters. [ABSTRACT FROM AUTHOR]

A novel approach for the design of delayed output-feedback controllers that optimize a quadratic cost function is presented. The proposal is based on the formulation of the optimization of the quadratic performance criterion as a minimization problem whose objective function is given in terms of the so-called delay Lyapunov matrix. The computation of the delay Lyapunov matrix sensitivity with respect to the controller gains allows obtaining the gradient of the objective function and solving the minimization problem within a gradient-based optimization framework. The potential of the approach is shown by some examples of practical relevance. [ABSTRACT FROM AUTHOR]

The article focuses on invasive pest Diaphorina citri Kuwayama which was first detected in Arizona in 2009. Topics discussed include survey aimed at evaluation of T. radiata releases on D. citri populations and assess the impact of the climate conditions on the phenology of D. citri and on the establishment success of T. radiata.

Necessary stability conditions depending on the Lyapunov matrix for neutral-type systems with commensurate delays are presented. In order to obtain them, further results are introduced: the computation of the Lyapunov–Krasovskii functional of complete-type by a new Cauchy formula and the introduction of identities that relate the fundamental and the Lyapunov matrix of the system. The main result is illustrated by some examples. [ABSTRACT FROM AUTHOR]

The aim of this study was to produce polygalacturonase from A. sojae mutant and partially purify the crude extract by chromatographic methods. As a preliminary step for the confirmation of its peptides, matrix-assisted laser-desorptionionization-time-of-flight mass spectrometry (Maldi-TOF MS) analysis was performed on in-gel digested sodiumdodecyl-sulphate-polyacrylamide-gel-electrophoresis (SDS-PAGE) gels. Three different carbon sources were employed in submerged and solid-state fermentations for the production of polygalacturonase. Crude extract was first purified by ion-exchange chromatography (IEXC) and followed further by size exclusion chromatography. Crude extracts obtained from sub-merged [of bitter orange peel, sugar beet molasses and (NH4)2SO4] and solid-state [of wheat bran, sugar beet and HCl] fermentation exhibited high levels of polygalacturonase enzyme activity (95.22 and 50.27 U/mL, respectively). Size exclusion of IEXC pooled fraction (180, 200 and 220 mM salt fractions) revealed the highest yield (36%) and purification fold (2.00). The likely polygalacturonase bands from SDS-PAGE were in-gel digested and analyzed by Maldi-TOF MS in route for peptides confirmation. [ABSTRACT FROM AUTHOR]

Exponential stability necessary conditions for linear periodic time-delay systems are presented. They are obtained with the help of new properties of the Lyapunov matrix in the framework of Lyapunov-Krasvoskii functionals of complete type. An academic example illustrates our results. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Synthesis of PEGylated proteins results in a mixture of protein-polyethylene glycol (PEG) conjugates and the unreacted native protein. From a ribonuclease A (RNase A) PEGylation reaction, mono-PEGylated RNase A (mono-PEG RNase A) has proven therapeutic effects against cancer, reason for which there is an interest in isolating it from the rest of the reaction products. Experimental trapping of PEGylated RNase A inside an electrokinetically driven microfluidic device has been previously demonstrated. Now, from a theoretical point of view, we have studied the electrokinetic phenomena involved in the dielectrophoretic streaming of the native RNase A protein and the trapping of the mono-PEG RNase A inside a microfluidic channel. To accomplish this, we used two 3D computational models, a sphere and an ellipse, adapted to each protein. The effect of temperature on parameters related to trapping was also studied. A temperature increase showed to rise the electric and thermal conductivities of the suspending solution, hindering dielectrophoretic trapping. In contrast, the dynamic viscosity of the suspending solution decreased as the temperature rose, favoring the dielectrophoretic manipulation of the proteins. Also, our models were able to predict the magnitude and direction of the velocity of both proteins indicating trapping for the PEGylated conjugate or no trapping for the native protein. In addition, a parametric sweep study revealed the effect of the protein zeta potential on the electrokinetic response of the protein. We believe this work will serve as a tool to improve the design of electrokinetically driven microfluidic channels for the separation and recovery of PEGylated proteins in one single step. [ABSTRACT FROM AUTHOR]