Impact of an Engineered Copper-Titanium Dioxide Nanocomposite and Parent Substrates on the Bacteria Viability,Antioxidant Enzymes and Fatty Acid Profiling

Due to the systematic increase in the production of nanomaterials (NMs) and their applications in many areas of life, issues associated with their toxicity are inevitable. In particular, the performance of heterogeneous NMs, such as nanocomposites (NCs), is unpredictable as they may inherit the properties of their individual components. Therefore, the purpose of this work was to assess the biological activity of newly synthesized Cu/TiO₂-NC and the parent nanoparticle substrates Cu-NPs and TiO₂-NPs on the bacterial viability, antioxidant potential and fatty acid composition of the reference Escherichia coli and Bacillus subtilis strains. Based on the toxicological parameters, it was found that B. subtilis was more sensitive to NMs than E. coli. Furthermore, Cu/TiO₂-NC and Cu-NPs had an opposite effect on both strains, while TiO₂-NPs had a comparable mode of action. Simultaneously, the tested strains exhibited varied responses of the antioxidant enzymes after exposure to the NMs, with Cu-NPs having the strongest impact on their activity. The most considerable alternations in the fatty acid profiles were found after the bacteria were exposed to Cu/TiO₂-NC and Cu-NPs. Microscopic images indicated distinct interactions of the NMs with the bacterial outer layers, especially in regard to B. subtilis. Cu/TiO₂-NC generally proved to have less distinctive antimicrobial properties on B. subtilis than E. coli compared to its parent components. Presumably, the biocidal effects of the tested NMs can be attributed to the induction of oxidative stress, the release of metal ions and specific electrochemical interactions with the bacterial cells.     

Grenzen der Anwendbarkeit der Theorie der analytischen Signale

Zusammenfassung Bei der praktischen Anwendung der analytischen Signale ist es erforderlich, die Ermittlung der Hilbert-Transformation numerisch durchzuführen. Dazu wurden u.a. Verfahren von H.W. Schü?ler, R. Unbehauen und G. Wunsch vorgeschlagen. In der Arbeit werden allgemeine Ergebnisse zur numerischen Umsetzung der Hilbert-Transformation dargestellt. Es wird gezeigt, da? alle praktisch realisierbaren Verfahren für bestimmte Signale divergieren. Damit ist es m?glich, die in der Experimentalphysik schon l?nger bekannten Schwierigkeiten bei der Umsetzung der Hilbert-Transformation zu erkl?ren.     

The Infeasible SIR Region Is Not a Convex Set

The infeasible signal-to-interference ratio (SIR) region is a set of SIRs that are not supportable in a power-controlled wireless network. It was conjectured that this set is convex in networks constrained on total power. We disprove the conjecture and discuss how this result may impact optimal medium-access control policies     

Secrecy results for compound wiretap channels

We derive a lower bound on the secrecy capacity of a compound wiretap channel with channel state information at the transmitter which matches the general upper bound on the secrecy capacity of general compound wiretap channels given by Liang et al. [1], thus establishing a full coding theorem in this case. We achieve this with a stronger secrecy criterion and the maximum error probability criterion, and with a decoder that is robust against the effect of randomization in the encoding. This relieves us from the need of decoding the randomization parameter, which is in general impossible within this model. Moreover, we prove a lower bound on the secrecy capacity of a compound wiretap channel without channel state information and derive a multiletter expression for the capacity in this communication scenario.     

A Superlinearly and Globally Convergent Algorithm for Power Control and Resource Allocation With General Interference Functions

In wireless networks, users are typically coupled by interference. Hence, resource allocation can strongly depend on receive strategies, such as beamforming, CDMA receivers, etc. We study the problem of minimizing the total transmission power while maintaining individual quality-of-service (QoS) values for all users. This problem can be solved by the fixed-point iteration proposed by Yates (1995) as well as by a recently proposed matrix-based iteration (Schubert and Boche, 2007). It was observed by numerical simulations that the matrix-based iteration has interesting numerical properties, and achieves the global optimum in only a few steps. However, an analytical investigation of the convergence behavior has been an open problem so far. In this paper, we show that the matrix-based iteration can be reformulated as a Newton-type iteration of a convex function, which is not guaranteed to be continuously differentiable. Such a behavior can be caused by ambiguous representations of the interference functions, depending on the choice of the receive strategy. Nevertheless, superlinear convergence can be shown by exploiting the special structure of the problem. Namely, the function is convex, locally Lipschitz continuous, and an invertible directional derivative exists for all points of interest.     

Invertierung von Multion-Funktionen in fast linearen Systemen

Übersicht Die Identifikation von linearen Systemen hat in der jüngsten Zeit ein grosses Interesse erzielt. Reale Systeme besitzen stets nichtlineare Teilsysteme. Diese nichtlinearen Teilsysteme erzeugen stets Fehler bei der Systemidentifikation. Wenn die zu analysierenden Systeme nur für die Verarbeitung von Signalen mit relativ kleinen Amplituden vorgesehen sind, so können diese Systeme für den interessierenden Bereich als lineare Systeme modelliert werden. Für die Systemidentifikation ist es somit wichtig, Multiton-Funktioner mit relativ kleinen Spitzenwerten zu finden. In der Arbeit wird das Verhalten von Multiton-Funktionen untersucht. Es wird die Frage nach der Invertierbarkeit von Multiton-Funktionen analysiert. Die Resultate der Arbeit lösen eine von Professor J. Massey vorgeschlagene Problemstellung.

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Inversion of multione-functions in almost linear systems

Identification of linear systems with multitone functions has received a great deal of attention in recent years. Identification errors will be caused by nonlinear distortions. If the object is simply to model the system for only small signal deviations from an operating point, then the nonlinear effects may be minimized and the system regarded as linear. So it is important for practical applications to find multitone functions with small peak values. The behavior of a certain class of multitone functions is investigated in this paper. The question of the inversion of multitone functions is analyzed. The results solve a problem proposed by Professor J. Massey.

     

Neue Untersuchungen zur Approximierbarkeit und Rekonstruierbarkeit bandbegrenzter Signale

New results on the reconstruction and approximation behaviour of sampling series are reported in the paper. At first we investigate the behaviour of the Shannon sampling series for non bandlimited signals. It is shown in the paper, that the sequence of the Shannon sampling series is divergent for some non bandlimited signals. Some new sampling series with better reconstruction and approximation behaviour are proposed in the paper. We also investigate the problem of non equidistant sampling of bandlimited signals.