Deadbeat control of linear discrete-time systems by periodic output-feedback

Two deadbeat control problems for open-loop, time-invariant linear, discrete-time multivariable systems by periodic output-feedbacks are formulated and solved. Sufficient conditions for the existence of solutions to the problems are established. Procedures for finding solutions to the problems are presented and illustrated by numerical examples.     

Stabilization of singular 2-D continuous-discrete systems bystate-feedback controllers

Necessary and sufficient conditions are established for the existence of a solution to the stabilization problem for singular two-dimensional (2-D) continuous-discrete linear systems. A procedure is presented for designing a state-feedback controller such that the closed-loop system is asymptotically stable, and its response is impulse-free     

Minimum Energy Control of Fractional Positive Electrical Circuits with Bounded Inputs

Minimum energy control problem for the fractional positive electrical circuits with bounded inputs is formulated and solved. Sufficient conditions for the existence of solution to the problem are established. A procedure for solving of the problem is proposed and illustrated by example of fractional positive electrical circuit.     

Phenotypic and genotypic antimicrobial susceptibility pattern of Streptococcus spp. isolated from cases of clinical mastitis in dairy cattle in Poland

Mastitis of dairy cattle is one of the most frequently diagnosed diseases worldwide. The main etiological agents of mastitis are bacteria of the genus Streptococcus spp., in which several antibiotic resistance mechanisms have been identified. However, detailed studies addressing this problem have not been conducted in northeastern Poland. Therefore, the aim of our study was to analyze, on phenotypic and genotypic levels, the antibiotic resistance pattern of Streptococcus spp. isolated from clinical cases of mastitis from dairy cattle in this region of Poland. The research was conducted using 135 strains of Streptococcus (Streptococcus uberis, n = 53; Streptococcus dysgalactiae, n = 41; Streptococcus agalactiae, n = 27; other streptococci, n = 14). The investigation of the antimicrobial susceptibility to 8 active substances applied in therapy in the analyzed region, as well as a selected bacteriocin (nisin), was performed using the minimum inhibitory concentration method. The presence of selected resistance genes (n = 14) was determined via PCR. We also investigated the correlation between the presence of resistance genes and the antimicrobial susceptibility of the examined strains in vitro. The highest observed resistance of Streptococcus spp. was toward gentamicin, kanamycin, and tetracycline, whereas the highest susceptibility occurred toward penicillin, enrofloxacin, and marbofloxacin. Additionally, the tested bacteriocin showed high efficacy. The presence of 13 analyzed resistance genes was observed in the examined strains [gene mef(A) was not detected]. In most strains, at least one resistance gene, mainly responsible for resistance to tetracyclines [tet(M), tet(K), tet(L)], was observed. However, a relationship between the presence of a given resistance gene and antimicrobial susceptibility on the phenotypic level was not always observed.     

Sufficient conditions for impulse uncontrollability and impulseunobservability of singular systems

Simple sufficient conditions for impulse uncontrollability and impulse unobservability of completely singular systems are established. It is well know that a singular linear system can be decomposed into a regular subsystem and a completely singular subsystem. From previously published results, it follows that a singular system is impulse uncontrollable (unobservable) if its singular subsystem is impulse uncontrollable (unobservable). It is shown that in a particular case the results can be also applied to the controllability and observability of regular linear systems     

Local controllability and minimum energy control of continuous 2-D linear systems with variable coefficients

Necessary and sufficient conditions for the local controllability of continuous 2-D linear systems with variable coefficients are established. The minimum energy control problem is formulated and solved for the 2-D systems.     

The singular general model of 2D systems and its solution

A general singular model for 2D linear discrete systems with constant coefficients is defined. Necessary and sufficient conditions for the existence of a solution to the model are established. The considerations of the author's previous work (1986) can be extended to singular models of 2D linear systems with variable coefficients     

Local controllability, reachability, and reconstructability of thegeneral singular model of 2D systems

Necessary and sufficient conditions for the local controllability, reachability, and reconstructability of the general singular model of 2D linear systems are established     

Alkyl Xylosides: Physico‐Chemical Properties and Influence on Environmental Bacteria Cells

A group of four selected non‐ionic surfactants based on carbohydrates, namely octyl d ‐xyloside (C₈X), nonyl d ‐xyloside (C₉X), decyl d ‐xyloside (C₁₀X) and dodecyl d ‐xyloside (C₁₂X), have been investigated to accomplish a better understanding of their physico‐chemical properties as well as biological activities. The surface‐active properties, such as critical micelle concentration (CMC), emulsion and foam stability, the impact of the compounds on cell surface hydrophobicity and cell membrane permeability together with their toxicity on the selected bacterial strains have been determined as well. The studied group of surfactants showed high surface‐active properties allowing a decrease in the surface tension to values below 25 mN m^?1 for dodecyl d ‐xyloside at the CMC. The investigated compounds did not have any toxic influence on two Pseudomonas bacterial strains at concentrations below 25 mg L^?1. The studied long‐chain alkyl xylosides influenced both the cell inner membrane permeability and the cell surface hydrophobicity. Furthermore, the alkyl chain length, as well as the surfactant concentration, had a significant impact on the modifications of the cell surface properties. The tested non‐ionic surfactants exhibited strong surface‐active properties accompanied by the significant influence on growth and properties of Pseudomonas bacteria cells.