Dynamics of fronts in optical media with linear gain and nonlinear losses

The dynamics of fronts, or kinks, in dispersive media with gain and losses is considered. It is shown that the front parameters, such as the velocity and width, depend on initial conditions. This result is not typical for dissipative systems. For exponentially decreasing initial conditions, the relations for the front parameters are found. A presence of the global bifurcation, when a soliton solution is replaced by the front solution, is demonstrated. It is also shown that in order to observe fronts, the front velocity should be larger than the characteristic velocity of the modulational instability.Comment: 15 pages, 5 figure

Dynamical models for dissipative localized waves of the complex Ginzburg-Landau equation

Finite-dimensional dynamical models for solitons of the cubic-quintic complex Ginzburg-Landau equation CGLE are derived. The models describe the evolution of the pulse parameters, such as the maximum amplitude, pulse width, and chirp. A clear correspondence between attractors of the finite-dimensional dynamical systems and localized waves of the continuous dissipative system is demonstrated. It is shown that stationary solitons of the CGLE correspond to fixed points, while pulsating solitons are associated with stable limit cycles. The models show that a transformation from a stationary soliton to a pulsating soliton is the result of a Hopf bifurcation in the reduced dynamical system. The appearance of moving fronts kinks in the CGLE is related to the loss of stability of the limit cycles. Bifurcation boundaries and pulse behavior in the regions between the boundaries, for a wide range of system parameters, are found from analysis of the reduced dynamical models. We also provide a comparison between various models and their correspondence to the exact results

A multilevel system of algorithms for detecting and isolating signals in a background of noise

Signal information is processed with the help of algorithms, and then on the basis of such processing, a part of the information is subjected to further processing with the help of more precise algorithms. Such a system of algorithms is studied, a comparative evaluation of a series of lower level algorithms is given, and the corresponding algorithms of higher level are characterized

Steady (robust) conditionally effective estimation of parameters

The concept of conditionally-effective estimation which provides optimum estimates for a given criterion in cases of given limitations is examined. The concept has the best accuracy for given limitation on the suitability of the algorithm concerning the deviation of the law governing error distribution from the proposed law. It is concluded that there must be a greater difference between individual algorithms in terms of difficulty, and that for the linear regression problem algorithms based on excluding lost points should be studied

Stable localized modes in asymmetric waveguides with gain and loss

It is shown that asymmetric waveguides with gain and loss can support a stable propagation of optical beams. This means that the propagation constants of modes of the corresponding complex optical potential are real. A class of such waveguides is found from a relation between two spectral problems. A particular example of an asymmetric waveguide, described by the hyperbolic functions, is analyzed. The existence and stability of linear modes and of continuous families of nonlinear modes are demonstrated.Comment: 10 pages, 4 figures. Accepted in Optics Letters, 201

Impact of Financial Crises on Dynamics of Capital Structure: Evidence from Korean Listed Companies

This study examines the impact of 1997 Asian and 2008 Global financial crises on the capital structure of Korean listed companies. Using a data set covering 1,159 Korean listed non-financial firms from 10 industrial sectors over period 1985-2015, the pattern of firms' capital structure before and after the crises is investigated and the speed of adjustment toward the optimal leverage identified. Different effects of the two crises on both capital structure and its adjustment speed is found. The average debt ratio fell significantly, the distance between optimal and observed debt ratios shrank, while the speed of adjustment increased twofold after the Asian crisis. Unlike the Asian crisis, the Global crisis of 2008 had a positive effect on companies' debt ratio and the speed of their adjustment toward optimal leverage. The empirical analysis revealed that Korean non-financial listed companies on average decreased their debt ratios over the entire study period, with leverage being highest before the Asian crisis and lowest after the Global financial crisis. The results also show that the debt ratio of Korean chaebols is higher than that of non-chaebols. Moreover, the high level of leverage is associated with tangible assets, income variability, size and age of the firm, non-debt tax shield, and uniqueness

Small Open Reading Frames, Non-Coding RNAs and Repetitive Elements in Bradyrhizobium japonicum USDA 110

Small open reading frames (sORFs) and genes for non-coding RNAs are poorly investigated components of most genomes. Our analysis of 1391 ORFs recently annotated in the soybean symbiont Bradyrhizobium japonicum USDA 110 revealed that 78% of them contain less than 80 codons. Twenty-one of these sORFs are conserved in or outside Alphaproteobacteria and most of them are similar to genes found in transposable elements, in line with their broad distribution. Stabilizing selection was demonstrated for sORFs with proteomic evidence and bll1319_ISGA which is conserved at the nucleotide level in 16 alphaproteobacterial species, 79 species from other taxa and 49 other Proteobacteria. Further we used Northern blot hybridization to validate ten small RNAs (BjsR1 to BjsR10) belonging to new RNA families. We found that BjsR1 and BjsR3 have homologs outside the genus Bradyrhizobium, and BjsR5, BjsR6, BjsR7, and BjsR10 have up to four imperfect copies in Bradyrhizobium genomes. BjsR8, BjsR9, and BjsR10 are present exclusively in nodules, while the other sRNAs are also expressed in liquid cultures. We also found that the level of BjsR4 decreases after exposure to tellurite and iron, and this down-regulation contributes to survival under high iron conditions. Analysis of additional small RNAs overlapping with 3’-UTRs revealed two new repetitive elements named Br-REP1 and Br-REP2. These REP elements may play roles in the genomic plasticity and gene regulation and could be useful for strain identification by PCR-fingerprinting. Furthermore, we studied two potential toxin genes in the symbiotic island and confirmed toxicity of the yhaV homolog bll1687 but not of the newly annotated higB homolog blr0229_ISGA in E. coli. Finally, we revealed transcription interference resulting in an antisense RNA complementary to blr1853, a gene induced in symbiosis. The presented results expand our knowledge on sORFs, non-coding RNAs and repetitive elements in B. japonicum and related bacteria

Extract of limonium gmelinii attenuates AB-and H2O2-induced oxidative response in cerebral endothelial cells

Alzheimer's disease (AD) is a chronic neurodegenerative disorder which affects approximately 10% of the population at age 65 and 40% of people over the age 80. Clinically, AD pathology is characterized by an increased deposition of amyloid-(3 peptide (A(3) in the brain, and a progressive impairment of cognition and memory of affected individuals. Blood Brain Barrier (BBB) dysfunction is observed in all of the stages of AD, and may even precede neuron degeneration in AD brains. During the early stages of AD, microvasculature deficiencies and hypertrophy of astrocytes are commonly observed. Numerous in vivo and in vitro studies have demonstrated that the vascular deposition of A(3 induces oxidative stress in cerebral endothelial cells (CECs). A(3-induced oxidative stress in cells, in turn, initiates a cascade of redox reactions leading to apoptosis and neurovascular inflammation. Consequently, antioxidants are considered as therapeutic agents in A(3-induced CECs damage