Bulgarian Academy of Sciences

About: Bulgarian Academy of Sciences is a government organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Coupling constant & Catalysis. The organization has 17989 authors who have published 36276 publications receiving 642820 citations. The organization is also known as: Bulgarian Academy of Sciences，簡稱：BAS & Balgarska Akademiya na Naukite.

Oxidative stress and chronic inflammation in osteoarthritis: can Nrf2 counteract these partners in crime?

Abstract: Osteoarthritis (OA) is an age-related joint degenerative disease associated with pain, joint deformity, and disability. The disease starts with cartilage damage but then progressively involves subchondral bone, causing an imbalance between osteoclast-driven bone resorption and osteoblast-driven remodeling. Here, we summarize the data for the role of oxidative stress and inflammation in OA pathology and discuss how these two processes are integrated during OA progression, as well as their contribution to abnormalities in cartilage/bone metabolism and integrity. At the cellular level, oxidative stress and inflammation are counteracted by transcription factor nuclear factor erythroid p45-related factor 2 (NRF2), and we describe the regulation of NRF2, highlighting its role in OA pathology. We also discuss the beneficial effect of some phytonutrients, including the therapeutic potential of NRF2 activation, in OA.

Perturbations of quadratic centers

Abstract: We study the bifurcation of limit cycles in general quadratic perturbations of plane quadratic vector fields having a center at the origin. For any of the cases, we determine the essential perturbation and compute the corresponding bifurcation function. As an application, we find the precise location of the subset of centers in Q 3 R surrounded by period annuli of cyclicity at least three. Two specific cases are considered in more detail: the isochronous center S 1 and one of the intersection points ( Q 4 + ) of Q 4 and Q 3 R . We prove that the period annuli around S 1 and Q 4 + have cyclicity two and three respectively. The proof is based on the possibility to derive appropriate Picard-Fuchs equations satisfied by the independent integrals included in the related bifurcation function.

Gold catalysts supported on mesoporous zirconia for low-temperature water–gas shift reaction

Abstract: Mesoporous ZrO2 with high surface area and uniform pore size distribution, synthesized by surfactant templating through a neutral [C13(EO)6–Zr(OC3H7)4] assembly pathway, was used as a support of gold catalysts prepared by deposition–precipitation method. The supports and the catalysts were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, N2 adsorption analysis, temperature programmed reduction and desorption. The catalytic activity of gold supported on mesoporous zirconia was evaluated in water–gas shift (WGS) reaction at wide temperature range (140–300 °C) and at different space velocities and H2O/CO ratios. The catalytic behaviour and the reasons for а reversible deactivation of Au/mesoporous zirconia catalysts were studied. The influence of gold content and particle size on the catalytic performance was investigated. The WGS activity of the new Au/mesoporous zirconia catalyst was compared to the reference Au/TiO2 type A (World Gold Council), revealing significantly higher catalytic activity of Au/mesoporous zirconia catalyst. It is found that the mesoporous zirconia is a very efficient support of gold-based catalyst for the WGS reaction.