Modulated dust-acoustic wave packets in a plasma with non-isothermal electrons and ions

Nonlinear self-modulation of the dust acoustic waves is studied, in the presence of non-thermal (non-Maxwellian) ion and electron populations. By employing a multiple scale technique, a nonlinear Schrodinger-type equation (NLSE) is derived for the wave amplitude. The influence of non-thermality, in addition to obliqueness (between the propagation and modulation directions), on the conditions for modulational instability to occur is discussed. Different types of localized solutions (envelope excitations) which may possibly occur are discussed, and the dependence of their characteristics on physical parameters is traced. The ion deviation from a Maxwellian distribution comes out to be more important than the electron analogous deviation alone. Both yield a de-stabilizing effect on (the amplitude of) DAWs propagating in a dusty plasma with negative dust grains. The opposite effect, namely a tendency towards amplitude stabilization, is found for the case of positively charged dust presence in the plasma.Comment: To appear in Journal of Plasma Physics (2004

Oscillation criteria for differential equations with several retarded arguments

Consider the first-order linear differential equation with several retarded arguments $$x^{\prime}(t)+\sum\limits_{i=1}^{m}p_{i}(t)x(\tau_{i}(t))=0,\;\;\;t\geq t_{0},$$ where the functions $p_{i},\tau_{i}\in C([t_{0,}\infty),\mathbb{R}^{+}),$ for every $i=1,2,\ldots,m,$ $\tau_{i}(t)\leq t$ \ for $t\geq t_{0}$ and $\lim_{t\rightarrow \infty}\tau_{i}(t)=\infty$. The state of the art on the oscillation of all solutions to these equations are established especially in the case of non-monotone arguments. Examples illustrating the results are given.Comment: 14 pages, paper to appear in Funkcialaj Ekvacio

Revisiting the merger and acquisition performance of European banks

The study examines the value creation of Merger and Acquisition (M&A) deals in European Banking from 1990-2004. This is performed, first, by examining the stock price reaction of banks to the announcement of M&A deals and, second, by analysing the determinants of this reaction. The findings provide evidence of value creation in European banks as the shareholders of the targets have benefited from positive and (statistically) significant abnormal returns while those of the acquirers earn small negative but non-significant abnormal returns. In the case of the shareholders of the acquirers, domestic M&As and especially those between banks with shares listed on the stock market, seem to be more beneficial compared to cross-border ones or those when the target is unlisted. Shareholders of the targets earn in all cases positive abnormal returns. Finally, although the link between abnormal returns and fundamental characteristics of the banks is rather weak, it appears that the acquisition of smaller, less efficient banks generating more diversified income are more value creating, while acquisition of less efficient, liquid and characterised by higher credit risk banks is not a value creating option.Bank mergers; mergers and acquisitions; abnormal returns;

On search for the M-Theory Lagrangian

We present a starting point for the search for a Lagrangian density for M-Theory using characteristic classes for flat foliations of bundles.Comment: Latex, 5 pages, no figure

Computational Astrocyence: Astrocytes encode inhibitory activity into the frequency and spatial extent of their calcium elevations

Deciphering the complex interactions between neurotransmission and astrocytic $Ca^{2+}$ elevations is a target promising a comprehensive understanding of brain function. While the astrocytic response to excitatory synaptic activity has been extensively studied, how inhibitory activity results to intracellular $Ca^{2+}$ waves remains elusive. In this study, we developed a compartmental astrocytic model that exhibits distinct levels of responsiveness to inhibitory activity. Our model suggested that the astrocytic coverage of inhibitory terminals defines the spatial and temporal scale of their $Ca^{2+}$ elevations. Understanding the interplay between the synaptic pathways and the astrocytic responses will help us identify how astrocytes work independently and cooperatively with neurons, in health and disease.Comment: 4 pages, 3 figures, IEEE-EMBS International Conference on Biomedical and Health Informatics (BHI '19