Electrochemical disinfection of simulated ballast water using Artemia salina as indicator

This work examined the potential of electrochemical disinfection to treat simulated ballast water with Artemia salina (A. salina) as an indicator organism. The effect of contact time (residence time in the electrolytic cell) and current density were investigated. Furthermore, the formation of disinfection by-products (trihalomethanes) was also examined. Under conditions of single pass through the electrolytic cell, a current density of 135 mA/cm² and a residence time of around 1 min were required for 100% mortality of A. salina. Dissolved organic carbon due to cell lysis increased by 1–2 mg/L, while the formation of chlorination by-products, expressed as trihalomethanes was very small (less than 10 μg/L at 135 mA/cm²).     

Experimental validation of the Newton observer for a nonlinear flux-controlled AMB system operated with zero-bias flux

ABSTRACT

The paper presents the results of experimental validation of the Newton observer for estimation of the magnetic flux within the feedback control of a nonlinear active magnetic bearing (AMB) system. In the preliminary work the Newton observer was adapted for the exact discrete-time model of the simplified one-degree-of-freedom AMB system, operated with zero-bias flux and under the voltage switching strategy, and showed good results in case of numerical simulations. The objective of this paper is to confirm these results on the basis of experimentation. The experiments were conducted on the AMB test rig, developed and manufactured at Bialystok University of Technology.     

Bacteriocin production by Enterococcus faecium FAIR-E 198 in view of its application as adjunct starter in Greek Feta cheese making

Bacteriocin production by Enterococcus faecium FAIR-E 198, isolated from Greek Feta cheese, was studied in batch fermentations, under conditions simulating Feta cheese preparation. Maximum enterocin activity and growth rate was obtained in de Man-Rogosa-Sharpe (MRS) broth at 37 degrees C with controlled pH 6.5. The enterocin was produced throughout the growth phase of the microorganism, showing primary metabolite kinetics with a peak activity during the mid-exponential phase. The use of skimmed milk as substrate revealed low enterocin activity. When fermentations were performed in skimmed milk in the presence of rennet, CaCl2, and a mixed starter culture, no enterocin activity was observed, although the examined strain grew well under the above conditions. Finally, when E. faecium FAIR-E 198 was applied as adjunct starter in Feta cheese making, no enterocin activity was detected throughout ripening. Results obtained underline the frequently underestimated finding that in vitro production by novel bacteriocinogenic starter or co-cultures is no guarantee for in situ efficiency. It was concluded that the complex food environment thoroughly interferes with bacteriocin production levels.     

Weak reachability and controllability of discrete-time nonlinear systems: generic approach and singular points

ABSTRACT

The paper finds the singular points from which (to which) the generically accessible system is not weakly reachable (controllable) in k steps. These points are found with the help of the space of vector fields, being the discrete-time analogue of the strong accessibility distribution. Unlike in the continuous-time case, a separate object is needed to find the singular points related to weak reachability.     

Silver halide photonic crystal fibers for the middle infrared

Photonic crystal fibers are normally holey silica fibers, which are opaque in the mid- and far-infrared. We have fabricated novel fibers by multiple extrusions of silver halide crystalline materials, which are highly transparent in the mid-infrared. These fibers are composed of two solid materials; The core consists of pure AgBr, and the cladding includes AgCl fiberoptic elements arranged in two concentric hexagonal rings around the core. Flexible fibers of outer diameter 1 mm and length of approximately 1 m were fabricated, and their optical properties were measured. These fibers exhibited core-clad behavior and would be extremely useful for IR laser power transmission, IR radiometry, and IR spectroscopy.     

Antimicrobial effects of butylated hydroxyanisole alone or in combination with potassium sorbate on quality changes in palm oil co-inoculated with Aspergillus flavus and Bacillus spp

Palm oil was sterilised and subjected to different concentrations (0.2 to 1.0 g litre⁻¹) of butylated hydroxyanisole (BHA) alone or in combination with potassium sorbate (KS) and co- inoculated with Aspergillus flavus and Bacillus species, the most prevalent organisms isolated from the palm oil. A dramatic increase of c3.43, 3.16 or 1.83 log₁₀ cfu ml⁻¹ microbial populations occurred in control samples or those treated with 0.2 or 1.0 g litre⁻¹ of BHA alone respectively. On the contrary, populations lower by approximately 1.0–1.3 log₁₀ cfu ml⁻¹ occurred in samples subjected to the combination treatment. Bi-phasic minima-extended-lag-phases were observed in the samples treated with BHA + KS. Mycelial growth was markedly inhibited in samples preserved with BHA + KS, being more apparent at concentrations of between 0.4 and 0.8 g litre⁻¹ of BHA in combination with potassium sorbate. Similarly, significantly (P = 0.05) lower free fatty acid content was observed in samples subjected to the combination treatment particularly at concentrations ranging from 0.6 litre⁻¹. Changes in pH were minimal suggesting less microbial activity, but significantly lower values occurred in samples treated with BHA alone after 14 days of ambient (30(±3) °C) storage. Better sensory qualities (less ‘separation’ i.e enhanced stability and aroma) were exhibited by samples preserved with the combination of BHA with KS. These various induced changes demonstrate the importance of concentration, residence time and synergism in relation to the effectiveness of antimicrobial agents. The benefits of the application of combination treatments have been shown and could be exploited by palm oil processors and importers. However, samples treated with the low concentrations are more likely to present potential hazards to consumers. © 1999 Society of Chemical Industry     

Control systems on regular time scales and their differential rings

The paper describes an algebraic construction of the inversive differential ring, associated with a nonlinear control system, defined on a nonhomogeneous but regular time scale. The ring of meromorphic functions in system variables is constructed under the assumption that the system is submersive, and equipped with three operators (delta- and nabla-derivatives, and the forward shift operator) whose properties are studied. The formalism developed unifies the existing theories for continuous- and discrete-time nonlinear systems, and accommodates also the case of non-uniformly sampled systems. Compared with the homogeneous case the main difficulties are noncommutativity of delta (nabla) derivative and shift operators and the fact that the additional time variable t appears in the definition of the differential ring. The latter yields that the new variables of the inversive closure, depending on t, have to be chosen to be smooth at each dense point t of the time scale.     

Low-Power Scan Testing: A Scan Chain Partitioning and Scan Hold Based Technique

Power consumption during scan testing operations can be significantly higher than that expected in the normal functional mode of operation in the field. This may affect the reliability of the circuit under test (CUT) and/or invalidate the testing process increasing yield loss. In this paper, a scan chain partitioning technique and a scan hold mechanism are combined for low power scan operation. Substantial power reductions can be achieved, without any impact on the test application time or the fault coverage and without the need to use scan cell reordering or clock and data gating techniques. Furthermore, the proposed design solution for scan power alleviation, permits the efficient exploitation of X-filling techniques for capture power reduction or the use of extreme (power independent) compression techniques for test data volume reduction.     

Regioselective combinatorial-type synthesis, characterization, and physical properties of dendronized cellulose

Novel regioselective, homo-(4-6) and heterogeneous (7-10) dendronized cellulose derivatives have been prepared by the reaction of cellulose in a N,N-dimethylacetamide (DMAc)/LiCl solvent system with diverse dendrons (1-3) possessing an isocyanate focal group. The dendronized cellulose derivatives were characterized using Fourier transform infrared (FTIR), ¹³C NMR, thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). These polyfunctionally coated cellulose-based materials showed diverse solubility characteristics in organic solvents ranging from DMAc to methyl alcohol.     

Any dynamical system is fully accessible through one single actuator and related problems

Whether an autonomous system can be rendered fully accessible through one single actuator is a long‐standing open problem, which got some solutions in special cases when additional constraints are considered. Herein, it is shown that a solution to the general problem is provided as an easy consequence of the straightening theorem. This solution is innovative for linear time‐invariant systems as well and relaxes the well‐known cyclicity condition as it involves nonlinear state transformations. The dual problem of designing one single sensor to render a given system observable obtains a similar almost unconditional solution. Copyright © 2015 John Wiley & Sons, Ltd.