Revisiting the Equipartition Assumption in Star-forming Galaxies

Energy equipartition between cosmic rays and magnetic fields is often assumed to infer magnetic field properties from the synchrotron observations of star-forming galaxies. However, there is no compelling physical reason to expect the same. We aim to explore the validity of the energy equipartition assumption. After describing popular arguments in favour of the assumption, we first discuss observational results which support it at large scales and how certain observations show significant deviations from equipartition at scales smaller than $\approx 1 \, {\rm kpc}$, probably related to the propagation length of the cosmic rays. Then we test the energy equipartition assumption using test-particle and MHD simulations. From the results of the simulations, we find that the energy equipartition assumption is not valid at scales smaller than the driving scale of the ISM turbulence ($\approx 100 \, {\rm pc}$ in spiral galaxies), which can be regarded as the lower limit for the scale beyond which equipartition is valid. We suggest that one must be aware of the dynamical scales in the system before assuming energy equipartition to extract magnetic field information from synchrotron observations. Finally, we present ideas for future observations and simulations to investigate in more detail under which conditions the equipartition assumption is valid or not.Comment: Invited review article for the special issue "New Perspectives on Galactic Magnetism" of the journal "Galaxies", accepted for publicatio

Suzaku Detection of Thermal X-Ray Emission Associated with the Western Radio Lobe of Fornax A

We present the results of X-ray mapping observations of the western radio lobe of the Fornax A galaxy, using the X-ray Imaging Spectrometer (XIS) onboard the Suzaku satellite with a total exposure time of 327 ks. The purpose of this study is to investigate the nature and spatial extent of the diffuse thermal emission around the lobe by exploiting the low and stable background of the XIS. The diffuse thermal emission had been consistently reported in all previous studies of this region, but its physical nature and relation to the radio lobe had not been examined in detail. Using the data set covering the entire western lobe and the central galaxy NGC 1316, as well as comparison sets in the vicinity, we find convincingly the presence of thermal plasma emission with a temperature of ~1 keV in excess of conceivable background and contaminating emission (cosmic X-ray background, Galactic halo, intra-cluster gas of Fornax, interstellar gas of NGC 1316, and the ensemble of point-like sources). Its surface brightness is consistent with having a spherical distribution peaking at the center of the western lobe with a projected radius of ~12 arcmin. If the volume filling factor of the thermal gas is assumed to be unity, its estimated total mass amounts to ~10^{10} M_sun, which would be ~10^{2} times that of the central black hole and comparable to that of the current gas mass of the host galaxy. Its energy density is comparable to or larger than those in the magnetic field and non-thermal electrons responsible for the observed radio and X-ray emission.Comment: 10 pages, 5 figures, accepted for publication in PAS

From pixel to mesh: accurate and straightforward 3D documentation of cultural heritage from the Cres/Lošinj archipelago

Most people like 3D visualizations. Whether it is in movies, holograms or games, 3D (literally) adds an extra dimension to conventional pictures. However, 3D data and their visualizations can also have scientic archaeological benets: they are crucial in removing relief distortions from photographs, facilitate the interpretation of an object or just support the aspiration to document archaeology as exhaustively as possible. Since archaeology is essentially a spatial discipline, the recording of the spatial data component is in most cases of the utmost importance to perform scientic archaeological research. For complex sites and precious artefacts, this can be a di€cult, time-consuming and very expensive operation. In this contribution, it is shown how a straightforward and cost-eective hard- and software combination is used to accurately document and inventory some of the cultural heritage of the Cres/Lošinj archipelago in three or four dimensions. First, standard photographs are acquired from the site or object under study. Secondly, the resulting image collection is processed with some recent advances in computer technology and so-called Structure from Motion (SfM) algorithms, which are known for their ability to reconstruct a sparse point cloud of scenes that were imaged by a series of overlapping photographs. When complemented by multi-view stereo matching algorithms, detailed 3D models can be built from such photo collections in a fully automated way. Moreover, the software packages implementing these tools are available for free or at very low-cost. Using a mixture of archaeological case studies, it will be shown that those computer vision applications produce excellent results from archaeological imagery with little eort needed. Besides serving the purpose of a pleasing 3D visualization for virtual display or publications, the 3D output additionally allows to extract accurate metric information about the archaeology under study (from single artefacts to entire landscapes)

Implicit temperature-correction-based immersed-boundary thermal lattice Boltzmann method for the simulation of natural convection

In the present paper, we apply the implicit-correction method to the immersed-boundary thermal lattice Boltzmann method (IB-TLBM) for the natural convection between two concentric horizontal cylinders and in a square enclosure containing a circular cylinder. The Chapman-Enskog multiscale expansion proves the existence of an extra term in the temperature equation from the source term of the kinetic equation. In order to eliminate the extra term, we redefine the temperature and the source term in the lattice Boltzmann equation. When the relaxation time is less than unity, the new definition of the temperature and source term enhances the accuracy of the thermal lattice Boltzmann method. The implicit-correction method is required in order to calculate the thermal interaction between a fluid and a rigid solid using the redefined temperature. Simulation of the heat conduction between two concentric cylinders indicates that the error at each boundary point of the proposed IB-TLBM is reduced by the increment of the number of Lagrangian points constituting the boundaries. We derive the theoretical relation between a temperature slip at the boundary and the relaxation time and demonstrate that the IB-TLBM requires a small relaxation time in order to avoid temperature distortion around the immersed boundary. The streamline, isotherms, and average Nusselt number calculated by the proposed method agree well with those of previous numerical studies involving natural convection. The proposed IB-TLBM improves the accuracy of the boundary conditions for the temperature and velocity using an adequate discrete area for each of the Lagrangian nodes and reduces the penetration of the streamline on the surface of the body

On Metaphor

メタファー(metaphor)についての研究は,従来の詩的空想の世界における修辞的技法や表現法を離れ,言語学の分野において大きな関心を集めている｡とりわけ,80年代に入ると,認知科学の発展とともに,メタファーは,人間の思考や概念構造といった観点から論じられるようになってきた｡本稿では,アリストテレスの時代に遡る伝統的なメタファー論とLakoff and Johnson(1980)に代表される認知言語学におけるメタファー論を比較検討することによって,メタファーの本質に迫り,最終的に独自のメタファーの定義を提示する｡さらに,メタファーの日英比較を基に,文化とメタファーの関係についても解明の糸口を探る

Edukacja informacyjna w bibliotekach uczelni przyrodniczych

In accordance with the objectives of the Bologna Process students finishing each course of the studies should learn to find, evaluate and use information. Libraries should play a crucial role in teaching information literacy. The aim of the paper is to show how the libraries of the universities of life sciences carry out educational activities. The author describes the forms of education which are offered in this types of libraries

A study to determine differences in the level of perceived preparedness in teaching algebra to eighth graders between teachers in the United States and teachers in Lebanon

Algebra is a branch in mathematics and taking Algebra in middle school is often a gateway to advanced courses in high school. The problem is that the United States and Lebanon had low scores in Algebra in the 2007 Trends in Mathematics and Sciences Study (TIMSS), an international assessment administered to 4th and 8th graders every 4 years. On the 2007 TIMSS, Lebanon\u27s average score in Algebra was 465, a lower score than the United States\u27 average of 501. This paper attempted to determine if there were differences in the level of perceived preparedness between teachers in Lebanon and teachers in the United States, in teaching 8th graders the 4 Algebra content areas in mathematics, identified in the 2007 TIMSS assessment, while controlling for the teachers years of teaching experience. Using data from the 2007 TIMSS, multivariate analyses of covariance (MANCOVA) 4 x 2 was performed to determine if there are differences in the level of perceived preparedness between teachers in Lebanon and teachers in the United States, in teaching 8th graders the 4 Algebra content areas in mathematics. Results of the MANCOVA indicated that there were significant differences in at least 1 of the content areas. Further research is recommended, including having a clear definition of teacher preparedness and teacher sample for teachers who taught the representative sample of students. This study has implications to educational leaders and policy makers in mathematics