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Institution

Bulgarian Academy of Sciences

GovernmentSofia, Bulgaria
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.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors report on follow-up observations to study the multiwavelength emission in the post-outburst phase of 3C 454.3 and ascribe this redder-when-brighter behaviour to the presence of a ''little blue bump'' due to line emission from the broad line region, which is clearly visible in the source spectral energy distribution (SED) during faint states.
Abstract: Context. The quasar-type blazar 3C 454.3 was observed to undergo an unprecedented optical outburst in spring 2005, affecting the source brightness from the near-IR to the X-ray frequencies. This was first followed by a millimetric and then by a radio outburst, which peaked in February 2006. Aims. In this paper we report on follow-up observations to study the multiwavelength emission in the post-outburst phase. Methods. Radio, near-infrared, and optical monitoring was performed by the Whole Earth Blazar Telescope (WEBT) collaboration in the 2006-2007 observing season. XMM-Newton observations on July 2-3 and December 18-19, 2006 added information on the X-ray and UV states of the source. Results. The source was in a faint state. The radio flux at the higher frequencies showed a fast decreasing trend, which represents the tail of the big radio outburst. It was followed by a quiescent state, common at all radio frequencies. In contrast, moderate activity characterized the near-IR and optical light curves, with a progressive increase of the variability amplitude with increasing wavelength. We ascribe this redder-when-brighter behaviour to the presence of a ""little blue bump"" due to line emission from the broad line region, which is clearly visible in the source spectral energy distribution (SED) during faint states. Moreover, the data from the XMM- Newton Optical Monitor reveal a rise of the SED in the ultraviolet, suggesting the existence of a "" big blue bump"" due to thermal emission from the accretion disc. The X-ray spectra are well fitted with a power- law model with photoelectric absorption, possibly larger than the Galactic one. However, the comparison with previous X-ray observations would imply that the amount of absorbing matter is variable. Alternatively, the intrinsic X-ray spectrum presents a curvature, which may depend on the X-ray brightness. In this case, two scenarios are possible. i) There is no extra absorption, and the X-ray spectrum hardens at low energies, the hardening being more evident in bright states; ii) there is a constant amount of extra absorption, likely in the quasar environment, and the X-ray spectrum softens at low energies, at least in faint X-ray states. This softening might be the result of a flux contribution by the high-frequency tail of the big blue bump.

111 citations

Proceedings ArticleDOI
09 Jul 2012
TL;DR: In this paper, the validity of Dempster-Shafer theory to solve practical problems is challenged by using an emblematic example to show that DS rule produces counter-intuitive result.
Abstract: We challenge the validity of Dempster-Shafer Theory by using an emblematic example to show that DS rule produces counter-intuitive result. Further analysis reveals that the result comes from a understanding of evidence pooling which goes against the common expectation of this process. Although DS theory has attracted some interest of the scientific community working in information fusion and artificial intelligence, its validity to solve practical problems is problematic, because it is not applicable to evidences combination in general, but only to a certain type situations which still need to be clearly identified.

111 citations

Journal ArticleDOI
14 Aug 2012
TL;DR: In this paper, a search for high-mass resonances decaying to electron or muon pairs has been performed using pp collision data collected at 7 TeV by the CMS experiment in 2011, and the event yields observed in the signal regions are consistent with predictions of the standard model backgrounds.
Abstract: A search for narrow, high-mass resonances decaying to electron or muon pairs has been performed using pp collision data collected at sqrt(s)=7 TeV by the CMS experiment in 2011. The data sample corresponds to an integrated luminosity of approximately 5 inverse femtobarns. The event yields observed in the signal regions are consistent with predictions of the standard model backgrounds, and upper limits on the cross section times branching fraction for a resonance decaying to dileptons are extracted from a shape analysis of the dilepton invariant mass distribution. The resulting mass limits at 95% confidence level are 2330 GeV for the Z' in the Sequential Standard Model, 2000 GeV for the superstring-inspired Z'(psi) resonance, 890 (540) GeV for the Stueckelberg extension Z'(St) with the mass parameter epsilon=0.06 (0.04), and 2140 (1810) GeV for Kaluza--Klein gravitons with the coupling parameter k/Mbar(Pl) of 0.10 (0.05). These limits are the most stringent to date.

110 citations

Journal ArticleDOI
TL;DR: Two procedures were employed to reproduce the basic physicochemical and sensory characteristics of traditional kefir and the lactobacilli predominated nearly twice over the cocci in kefirs with pure cultures.

110 citations

Journal ArticleDOI
TL;DR: The present review focuses on the main factors which have been found to have an impact on the increase in honey bee colony losses, particularly the ectoparasitic mite Varroa destructor.
Abstract: The Western honey bee (Apis mellifera L., Hymenoptera: Apidae) is a species of crucial economic, agricultural and environmental importance. In the last ten years, some regions of the world have suffered from a significant reduction of honey bee colonies. In fact, honey bee losses are not an unusual phenomenon, but in many countries worldwide there has been a notable decrease in honey bee colonies. The cases in the USA, in many European countries, and in the Middle East have received considerable attention, mostly due to the absence of an easily identifiable cause. It has been difficult to determine the main factors leading to colony losses because of honey bees’ diverse social behavior. Moreover, in their daily routine, they make contact with many agents of the environment and are exposed to a plethora of human activities and their consequences. Nevertheless, various factors have been considered to be contributing to honey bee losses, and recent investigations have established some of the most important ones, in particular, pests and diseases, bee management, including bee keeping practices and breeding, the change in climatic conditions, agricultural practices, and the use of pesticides. The global picture highlights the ectoparasitic mite Varroa destructor as a major factor in colony loss. Last but not least, microsporidian parasites, mainly Nosema ceranae, also contribute to the problem. Thus, it is obvious that there are many factors affecting honey bee colony losses globally. Increased monitoring and scientific research should throw new light on the factors involved in recent honey bee colony losses. The present review focuses on the main factors which have been found to have an impact on the increase in honey bee colony losses.

110 citations


Authors

Showing all 18074 results

NameH-indexPapersCitations
Dimitri Bourilkov134148996884
Eduardo De Moraes Gregores133145492464
Georgi Sultanov132149393318
Plamen Iaydjiev131128587958
Pedro G Mercadante129133186378
Jordan Damgov129119585490
Roumyana Hadjiiska126100373091
Mircho Rodozov12497270519
Cesar Augusto Bernardes12496570889
Viktor Matveev123121273939
Ayda Beddall12081667063
Andrey Marinov11989357183
Mariana Vutova11760656698
Lester Packer11275163116
Patrick Couvreur11167856735
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202345
2022137
20211,321
20201,465
20191,284
20181,248