Hardness of Approximation for H-Free Edge Modification Problems: Towards a Dichotomy

For a fixed graph H, the H-free Edge Deletion/Completion/Editing problem asks to delete/add/edit the minimum possible number of edges in G to get a graph that does not contain an induced subgraph isomorphic to the graph H. In this work, we investigate H-free Edge Deletion/Completion/Editing problems in terms of the hardness of their approximation. We formulate a conjecture according to which all the graphs with at least five vertices can be classified into several groups of graphs with specific structural properties depending on the hardness of approximation for the corresponding H-free Edge Deletion/Completion/Editing problems. Also, we make significant progress in proving that conjecture by showing that it is sufficient to resolve it only for a finite set of graphs

Peptide Inhibitors of Vascular Endothelial Growth Factor A : Current Situation and Perspectives

Vascular endothelial growth factors (VEGFs) are the family of extracellular signaling proteins involved in the processes of angiogenesis. VEGFA overexpression and altered regulation of VEGFA signaling pathways lead to pathological angiogenesis, which contributes to the progression of various diseases, such as age-related macular degeneration and cancer. Monoclonal antibodies and decoy receptors have been extensively used in the anti-angiogenic therapies for the neutralization of VEGFA. However, multiple side effects, solubility and aggregation issues, and the involvement of compensatory VEGFA-independent pro-angiogenic mechanisms limit the use of the existing VEGFA inhibitors. Short chemically synthesized VEGFA binding peptides are a promising alternative to these full-length proteins. In this review, we summarize anti-VEGFA peptides identified so far and discuss the molecular basis of their inhibitory activity to highlight their pharmacological potential as anti-angiogenic drugs.Peer reviewe

Efficiency of Governance Model and Ownership Structure of Ukrainian Seaports

The purpose of this study is to examine the differences and efficiency in governance style of public and private owned seaports in Ukraine. Observation and comparative analysis of models of public and private seaports ownership in the Ukrainian context, considering the experience of other countries, allowed to conclude that private ownership model for seaports is more flexible in conditions of modern political and economic transformations in Ukraine. Private seaports have higher level of investment attraction and better financial results than public seaports. Worldwide experience in port infrastructure privatization demonstrates that seaports governed according to private ownership model are predominantly much more effective than public-owned seaports in particular in style of cooperation with investors and possibility of rapid development due to investments attraction. However, current Ukrainian legislature predominantly considers seaports as the objects for concession in order to save public ownership of seaports. This investigation attempts to contribute to future studies that relate to an important issue such as efficiency of Ukrainian seaports in global economic development

Azimuthal patterns in planetesimal circumstellar disks

Ways of formation of azimuthal resonant patterns in circumstellar planetesimal disks with planets are considered. Our analytical estimates and massive numerical experiments show that the disk particles that initially reside in zones of low-order mean-motion resonances with the planet may eventually concentrate into potentially observable azimuthal patterns. The structuring process is rapid, usually taking ~100 orbital periods of the planet. It is found that the relative number of particles that retain their resonant position increases with decreasing the mass parameter $\mu$ (the ratio of masses of the perturbing planet and the parent star), but a significant fraction of the particle population is always removed from the disk due to accretion of the particles onto the star and planet, as well as due to their transition to highly elongated and hyperbolic orbits. Expected radio images of azimuthally structured disks are constructed. In the considered models, azimuthal patterns associated with the 2:1 and 3:2 resonances are most clearly manifested; observational manifestations of the 1:2 and 2:3 resonances are also possible.Comment: 24 pages, 8 figures. Accepted for publication in Astronomy Letter