Montenegro in the PISA study

Montenegro, a country that has been in transition for the last two decades, is trying intensively to restructure its socioeconomic system and reform the main social systems, such as the education system, health care, the judicial system, the social welfare system, etc. Numerous strategic documents have been adopted in the past decade emphasising the importance of making the country’s abundant natural resources functional, and of making the utilisation of human resources in the country significantly more effective. In order to achieve improvements in one of the key areas of Montenegrin development, human resources, a reform of the entire education system was launched in the first years of 21st century. The processes of joining the European Union, whose fundamental principles are the free movement of people, goods, services and capital, have also significantly increased the need to raise the quality of the education of Montenegro’s citizens and to improve the competitiveness of the Montenegrin workforce in the labour market. However, we believe that the results of PISA testing in 2006 and 2009 suggest that Montenegro is far from the proclaimed goals of reform in the field of education, and that for the coming years and decades considerable attention should be devoted to improvement of the education system. PISA tests should be understood in a much wider context, not only as a reflection of curricular reform and standards of verification and assessment of students’ knowledge, but rather as a set of guidelines that indicate the direction in which to develop and improve the education system, so that society can really ‘invest’ in the education of young people. It is a very problematic fact that from the time of testing in 2009 until April 2011, nobody in Montenegro published any technical or scientific analysis of the success, or rather failure, of Montenegrin students in PISA testing. We believe that the use of this study should be significantly increased; not for comparing academic achievements with those of students from other countries, but primarily for improving educational policy and defining the strategic orientation of the development of the education system in Montenegro. Therefore, the absence of analysis implies an absence of certain professional activities focused on training teachers and improving the quality of students’ knowledge. (DIPF/Orig.

Scattering line polarization in rotating, optically thick disks

To interpret observations of astrophysical disks it is essential to understand the formation process of the emitted light. If the disk is optically thick, scattering dominated and permeated by a Keplerian velocity field, Non-Local Thermodynamic Equilibrium radiative transfer modeling must be done to compute the emergent spectrum from a given disk model. We investigate Non-local thermodynamic equilibrium polarized line formation in different simple disk models and aim to demonstrate the importance of both radiative transfer effects and scattering as well as the effects of velocity fields. We self-consistently solve the coupled equations of radiative transfer and statistical equilibrium for a two level atom model by means of Jacobi iteration. We compute scattering polarization, that is Q/I and U/I line profiles. The degree of scattering polarization is significantly influenced by the inclination of the disk with respect to observer, but also by the optical thickness of the disk and the presence of rotation. Stokes U shows double-lobed profiles with amplitude which increases with the disk rotation. Our results suggest that the line profiles, especially the polarized ones, emerging from gaseous disks differ significantly from the profiles predicted by simple approximations. The profiles are diverse in shape, but typically symmetric in Stokes Q and antisymmetric in Stokes U. A clear indicator of disk rotation is the presence of Stokes U, which might prove to be a useful diagnostic tool. We also demonstrate that, for moderate rotational velocities, an approximate treatment can be used, where non-local thermodynamic equilibrium radiative transfer is done in the velocity field-free approximation and Doppler shift is applied in the process of spatial integration over the whole emitting surface.Comment: 16 pages; 12 figures; Accepted with revision for A&A. This is the version after first round of referee's suggestion

Middle latitude changes in topside electron density through a magnetic storm technical note no. 1, 24.- 28 jun. 1963

Middle latitude changes in topside electron density during magnetic stor

Spectropolarimetric NLTE inversion code SNAPI

Inversion codes are computer programs that fit a model atmosphere to the observed Stokes spectra, thus retrieving the relevant atmospheric parameters. The rising interest in the solar chromosphere, where spectral lines are formed by scattering, requires developing, testing, and comparing new non-local thermal equilibrium (NLTE) inversion codes. We present a new NLTE inversion code that is based on the analytical computation of the response functions. We named the code SNAPI, which is short for spectropolarimetic NLTE analytically powered inversion. SNAPI inverts full Stokes spectrum in order to obtain a depth-dependent stratification of the temperature, velocity, and the magnetic field vector. It is based on the so-called node approach, where atmospheric parameters are free to vary in several fixed points in the atmosphere, and are assumed to behave as splines in between. We describe the inversion approach in general and the specific choices we have made in the implementation. We test the performance on one academic problem and on two interesting NLTE examples, the Ca\,II\,8542 and Na\,I\,D spectral lines. The code is found to have excellent convergence properties and outperforms a finite-difference based code in this specific implementation by at least a factor of three. We invert synthetic observations of Na lines from a small part of a simulated solar atmosphere and conclude that the Na lines reliably retrieve the magnetic field and velocity in the range $-3<\log \tau < -0.5$.Comment: To appear in A&

Using the infrared iron lines to probe solar subsurface convection

Studying the properties of the solar convection using high-resolution spectropolarimetry began in the early 90's with the focus on observations in the visible wavelength regions. Its extension to the infrared (IR) remains largely unexplored. The IR iron lines around 15600\,$\rm{\AA}$, most commonly known for their high magnetic sensitivity, also have a non-zero response to line-of-sight velocity below $\log (\tau)=0.0$. In this paper we aim to tap this potential to explore the possibility of using them to measure sub-surface convective velocities. By assuming a snapshot of a three-dimensional magnetohydrodynamic simulation to represent the quiet Sun, we investigate how well the iron IR lines can reproduce the LOS velocity in the cube and up to what depth. We use the recently developed spectropolarimetric inversion code SNAPI and discuss the optimal node placements for the retrieval of reliable results from these spectral lines. We find that the IR iron lines can measure the convective velocities down to $\log (\tau)=0.5$, below the photosphere, not only at original resolution of the cube but also when degraded with a reasonable spectral and spatial PSF and stray light. Meanwhile, the commonly used Fe~{\sc i} 6300\,\AA{} line pair performs significantly worse. Our investigation reveals that the IR iron lines can probe the subsurface convection in the solar photosphere. This paper is a first step towards exploiting this diagnostic potential.Comment: 11 pages, Accepted for publication in Astronomy and Astrophysic

Inference of magnetic fields in inhomogeneous prominences

Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D slab model. We find that differences between input and the inferred magnetic field vector are non-negligible. Namely, we almost universally find that the inferred field is weaker and more horizontal than the input field. Spatial inhomogeneities and radiative transfer have a strong effect on scattering line polarization in the optically thick lines. In real-life situations, ignoring these effects could lead to a serious misinterpretation of spectropolarimetric observations of chromospheric objects such as prominences.Comment: 11 pages, 9 figure

Role of Random Numbers in Simulations of Economic Processes

Various ways of selecting random numbers used in process simulations will be presented in this paper. Special attention will be given to complex phenomena not known enough to be precisely described. Modes of interaction are unknown; what is known are probabilities of interaction outcome. Such cases are found mostly in social and economic phenomena, such as population growth, economic predictions, decision-making risk analysis, etc.random numbers, simulation, process, distribution, model.