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.

Implementing and innovating marine monitoring approaches for assessing marine environmental status

Abstract: Marine environmental monitoring has tended to focus on site-specific methods of investigation. These traditional methods have low spatial and temporal resolution and are relatively labor intensive per unit area/time that they cover. To implement the Marine Strategy Framework Directive (MSFD), European Member States are required to improve marine monitoring and design monitoring networks. This can be achieved by developing and testing innovative and cost-effective monitoring systems, as well as indicators of environmental status. Here, we present several recently developed methodologies and technologies to improve marine biodiversity indicators and monitoring methods. The innovative tools are discussed concerning the technologies presently utilized as well as the advantages and disadvantages of their use in routine monitoring. In particular, the present analysis focuses on: (i) molecular approaches, including microarray, Real Time quantitative PCR (qPCR), and metagenetic (metabarcoding) tools; (ii) optical (remote) sensing and acoustic methods; and (iii) in situ monitoring instruments. We also discuss their applications in marine monitoring within the MSFD through the analysis of case studies in order to evaluate their potential utilization in future routine marine monitoring. We show that these recently-developed technologies can present clear advantages in accuracy, efficiency and cost.

Results of WEBT, VLBA and RXTE monitoring of 3C 279 during 2006-2007 ⋆

Abstract: Context. The quasar 3C 279 is among the most extreme blazars in terms of luminosity and variability of flux at all wavebands. Its vari ations in flux and polarization are quite complex and therefore require intensive monitoring observations at multiple wavebands to characterise and interpret the observed changes. Aims. In this paper, we present radio-to-optical data taken by the WEBT, supplemented by our VLBA and RXTE observations, of 3C 279. Our goal is to use this extensive database to draw inferences regarding the physics of the relativistic jet. Methods. We assemble multifrequency light curves with data from 30 ground-based observatories and the space-based instruments SWIFT (UVOT) and RXTE, along with linear polarization vs. time in the optical R band. In addition, we present a sequence of 22 images (with polarization vectors) at 43 GHz at resolution 0.15 milliarcse c, obtained with the VLBA. We analyse the light curves and polarization, as well as the spectral energy distributions at different epochs, corresponding to different brightness states. Results. We find that the IR-optical-UV continuum spectrum of the vari able component corresponds to a power law with a constant slope of−1.6, while in the 2.4‐10 keV X-ray band it varies in slope from−1.1 to−1.6. The steepest X-ray spectrum occurs at a flux minimum. Durin g a decline in flux from maximum in late 2006, the optical and 43 GHz core po larization vectors rotate by∼ 300 ◦ . Conclusions. The continuum spectrum agrees with steady injection of relativistic electrons with a power-law energy distribution of slope−3.2 that is steepened to−4.2 at high energies by radiative losses. The X-ray emission at flux minimum comes most likely from a new component that starts in an upstream section of the jet where inverse Compton scattering of seed photons from outside the jet is important. The rotation of the polarization vector implies that the jet contains a helical magnetic field that extends ∼ 20 pc past the 43 GHz core.

Anisotropy, phonon modes, and free charge carrier parameters in monoclinic β-gallium oxide single crystals

Abstract: There is growing interest in low-symmetry metal oxides because of their potential use in high-power electronics capable to sustain very high voltages. Very little is known about their fundamental physical properties, such as transverse and longitudinal optical phonon modes, dielectric constants, and how free charge carriers couple with lattice vibrations. This lack of information is partially due to the complexity by which these properties intertwine due to the low symmetry crystal systems. Here, the authors describe a general pathway to the analysis of long-wavelength experiments for monoclinic and triclinic crystal systems, and they report for the first time a complete set of phonon modes for the monoclinic phase of gallium oxide. These parameters may arrive just in time to support computational optimization of charge and heat transport for device designs. The concept for analysis of long wavelength properties in monoclinic and triclinic crystal systems can help access a widely uncharted field in condensed matter physics.