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: Catalysis & Coupling constant. 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.

Global Geographic Distribution and Host Range of Fusarium circinatum, the Causal Agent of Pine Pitch Canker

Abstract: Fusarium circinatum, the causal agent of pine pitch canker (PPC), is currently one of the most important threats of Pinus spp. globally. This pathogen is known in many pine-growing regions, including natural and planted forests, and can affect all life stages of trees, from emerging seedlings to mature trees. Despite the importance of PPC, the global distribution of F. circinatum is poorly documented, and this problem is also true of the hosts within countries that are affected. The aim of this study was to review the global distribution of F. circinatum, with a particular focus on Europe. We considered (1) the current and historical pathogen records, both positive and negative, based on confirmed reports from Europe and globally; (2) the genetic diversity and population structure of the pathogen; (3) the current distribution of PPC in Europe, comparing published models of predicted disease distribution; and (4) host susceptibility by reviewing literature and generating a comprehensive list of known hosts for the fungus. These data were collated from 41 countries and used to compile a specially constructed geo-database. A review of 6297 observation records showed that F. circinatum and the symptoms it causes on conifers occurred in 14 countries, including four in Europe, and is absent in 28 countries. Field observations and experimental data from 138 host species revealed 106 susceptible host species including 85 Pinus species, 6 non-pine tree species and 15 grass and herb species. Our data confirm that susceptibility to F. circinatum varies between different host species, tree ages and environmental characteristics. Knowledge on the geographic distribution, host range and the relative susceptibility of different hosts is essential for disease management, mitigation and containment strategies. The findings reported in this review will support countries that are currently free of F. circinatum in implementing effective procedures and restrictions and prevent further spread of the pathogen.

Enhancement of photocatalytic oxidation of oxalic acid by gold modified WO3/TiO2 photocatalysts under UV and visible light irradiation

Abstract: The photooxidation of oxalic acid, catalyzed by nanosized TiO2 or WO3 and composite photocatalysts: Au/TiO2, Au/WO3, WO3/TiO2, Au/WO3/TiO2 was studied under irradiation with UV, visible and combined UV–visible light. The catalysts were characterized by the XRD, XPS, SEM and TEM methods. The photocatalytic mineralization of oxalic acid, catalyzed by WO3/TiO2 or Au/WO3/TiO2, proceeded at a significantly higher rate under UV-A irradiation than that under visible light. This is due to the lower specific surface area of the WO3 and its small amount in the composite catalyst. Doping of the semiconductor materials with gold nanoparticles more than doubles the rates of mineralization of oxalic acid, compared to the un-doped samples, and more significantly in the case of Au/WO3/TiO2. The higher rate constants of oxalic acid decomposition under UV, visible or UV–visible light irradiation with the WO3/TiO2 and Au/WO3/TiO2 catalysts, compared with those measured with the individual oxide photocatalysts, are due to the more efficient separation of the electron–hole charges generated upon irradiation. Especially efficient is the charge separation in the case of the Au/WO3/TiO2 photocatalyst under irradiation with UV or combined UV–visible light, when the rate constants of oxalic acid destruction are approximately 1.7 times higher than that of the process catalyzed by Au/TiO2 and 3 times higher than that catalyzed by pure TiO2.

Search for long-lived neutral particles decaying to quark-antiquark pairs in proton-proton collisions at √s =8TeV

Abstract: A search is performed for long-lived massive neutral particles decaying to quark-antiquark pairs. The experimental signature is a distinctive topology of a pair of jets, originating at a secondary vertex. Events were collected with the CMS detector at the CERN LHC in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data analyzed correspond to an integrated luminosity of 18.5 inverse femtobarns. No significant excess is observed above standard model expectations. Upper limits at 95% confidence level are set on the production cross section of a heavy neutral scalar particle, H, in the mass range of 200 to 1000 GeV, decaying promptly into a pair of long-lived neutral X particles in the mass range of 50 to 350 GeV, each in turn decaying into a quark-antiquark pair. For X with mean proper decay lengths of 0.4 to 200 cm, the upper limits are typically 0.5-200 fb. The results are also interpreted in the context of an R-parity-violating supersymmetric model with long-lived neutralinos decaying into a quark-antiquark pair and a muon. For pair production of squarks that promptly decay to neutralinos with mean proper decay lengths of 2-40 cm, the upper limits on the cross section are typically 0.5-3 fb. The above limits are the most stringent on these channels to date.