904 research outputs found
Constraining the parameters of the putative supermassive binary black hole in PG 1302-102 from its radio structure
We investigate the pc-scale kinematics and kpc-scale radio morphology of the
quasar PG 1302-102, which may harbour a sub-pc separation supermassive binary
black hole system at its centre as inferred from optical variability.
High-resolution radio interferometric measurements obtained with the Very Long
Baseline Array (VLBA) in the Monitoring Of Jets in Active galactic nuclei with
VLBA Experiments (MOJAVE) programme at 15 GHz at 20 epochs spanning 17 years
were analysed to investigate the pc-scale radio structure. Archival
observations with the Very Large Array (VLA) at 1.4 GHz and 5 GHz were obtained
to study the kpc-scale morphology. We find that the pc-scale jet is inclined
within ~2.2 deg to the line of sight and has a half-opening angle of about 0.2
deg. The parameters derived from the pc-scale radio jet are qualitatively
consistent with those obtained from the analysis of the optical light curve of
PG 1302-102. We obtain at least 0.08 for the mass ratio of the two black holes
in the system. We find some indication for a helical jet structure on
kpc-scale, but the directions of the inner and the extended radio jets are
significantly different, obstructing a straightforward connection of the pc-
and kpc-scale jets within the binary scenario.Comment: 9 pages, 4 figures, 1 table, accepted to MNRA
Medium-resolution echelle spectroscopy of pulsating variables and exoplanet host stars with sub-meter telescopes
Here we present two of our interesting results obtained over the last 18
months from spectroscopic monitoring of binary pulsating stars and exoplanet
host stars. Our investigations are very promising by demonstrating that modern
fiber-fed spectrographs open a whole new chapter in the life of small national
and university observatories.Comment: 3 pages, 3 figures. To be published in the proceedings of the
workshop on "Observing techniques, instrumentation and science for
metre-class telescopes", Sep. 2013, Tatranska Lomnica, Slovaki
VLBI observation of the newly discovered z=5.18 quasar SDSS J0131-0321
Few high-redshift, radio-loud quasars are known to date. The extremely
luminous, radio-bright quasar, SDSS J013127.34-032100.1 was recently discovered
at a redshift of . We observed the source with high resolution very
long baseline interferometry (VLBI) at 1.7 GHz with the European VLBI Network
(EVN) and found a single compact radio component. We estimated a lower limit to
the brightness temperature of the detected radio component, T_B~10^{11} K.
Additionaly, when compared to archival radio data, the source showed
significant flux density variation. These two findings are indicative of the
blazar nature of the source.Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter
Discovery of the spectroscopic binary nature of the classical Cepheids FN Aql and V1344 Aql
We present the analysis of photometric and spectroscopic data of two
classical Cepheids, FN Aquilae and V1344 Aquilae. Based on the joint treatment
of the new and earlier radial velocity data, both Galactic Cepheids have been
found to be a member in a spectroscopic binary system.
To match the phases of the earlier radial velocity data correctly with the
new ones, we also determined the temporal behaviour of the pulsation period of
these Cepheids based on all available photometric data. The O-C graph covering
about half century shows slight changes in the pulsation period due to stellar
evolution for both Cepheids.Comment: 7 pages, 6 figures, 7 tables, accepted for publishing in the MNRA
Studies on factors affecting superovulation and embryo transfer in Hungarian Merino ewes
The objectives of this study were (a) to assess the ovulatory response and embryo production of Hungarian Merino ewes after superovulation, (b) to investigate the factors influencing the efficiency of embryo transfer (ET) in Hungarian Merino ewes, (c) to compare the results of two ovarian stimulation protocols (PMSG and PMSG+FSH treatment) in Hungarian Merino ewes, and (d) to study how superovulation, laparoscopic insemination and surgical embryo retrieval (ER) affect the subsequent reproduction of Hungarian Merino donor females after an ET programme. There was no significant difference between the ovarian stimulation protocols in the ratio of donor ewes responding to superovulation nor in the average number of corpora lutea. However, the number of transferable embryos recovered per donor ewe was higher in the PMSG+FSH group. The proportion of transferable embryos, unfertilised oocytes and degenerated embryos did not differ between the treatment protocols. The total pregnancy rate was 53.4% (179/335). Neither the developmental stage of the embryo nor the number of transferred embryos affect the implantation of embryos. However, the increased number of transferred embryos positively influenced the pregnancy rate. No difference was found in the pregnancy rate between synchronised and nonsynchronised groups of recipients. Thirty-six out of 45 donor ewes (80%) became pregnant within one year after the ET programme, indicating that ovarian stimulation and surgical ER did not affect adversely their reproduction
Body-centred cubic packing of spheres-the ultimate thermotropic assembly mode for highly divergent dendrons
We have synthesized sodium tris(alkoxy)benzoates in which one of the three alkyl chains branches further into three C 18 H 37 chains. These AB5 hyperbranched minidendrons melt directly into a body-centred cubic (BCC) mesophase formed by spherical "micelles". In contrast, their non-branched counterparts display various mesophases before they turn into BCC upon heating. This agrees with the predictions from a numerical geometric model that relates the shape of the molecular wedge to the type of mesophase they adopt. The spheres were found to shrink in volume upon heating and expand upon cooling, as molecules, in some cases nearly half of them, are ejected and reintegrated in the spheres. The ejection of dendrons is caused by their lateral thermal expansion. The BCC appears to be the ultimate mesophase for the extremely divergent wedges such as the hyperbranched minidendrons. In dendrons with chains of unequal length, the sphere size is fixed by the shorter chains, the longer ones back-folding or interdigitating to effectively widen the wedge. This new understanding of their assembly will help in designing new dendrons, e.g. for better encapsulation of guest molecules
HRD on the Margins: Exploring Resistance to HRD in Adult Education
This paper examines the debates and critiques surrounding HRD and confronts myths about HRD philosophy and practice. We argue that the HRD field is marginalized in adult education and reflect on both the problems this situation creates and the possibilities of ever bridging these two fields
Vegetation history, recent dynamics and future prospects of a Hungarian sandy forest-steppe reserve: forest-grassland relations, tree species composition and size-class distribution
Pannonian forest-steppes host a high number of endemic species and contribute to landscape-scale heterogeneity. Alterations in the proportion of forests and grasslands due to changes in land-use practice and climatic parameters can have serious nature conservation consequences. Hypotheses about forest-steppe dynamics have rarely been verified by detailed analyses, especially for the sandy forest-steppes. We integrated historical analysis, aerial photo interpretation and field investigation to determine how vegetation of a sandy forest-steppe has changed, how current dynamical processes operate and how native and exotic tree species regenerate under present conditions. The vegetation of the study area before the onset of major anthropogenic environmental transformations in the Carpathian Basin may have been a mosaic of forested and unforested patches. However, there is strong evidence that after heavy deforestation, the region was almost completely treeless between the 15th and the 19th centuries. Forest cover was able to recover by the 1800s but the lack of forested areas in the region for centuries explains why forest patches are still poor in species. Grasslands, which existed continuously, are more diverse, supporting several rare and endemic species. From 1953 till 2013, 72.45% of the area proved to be stable, but 27.55% showed clear dynamical character, changing either from forest to grassland, or vice versa. Thus, cyclic dynamics can occur in sandy forest-steppes. We found that forest patches of different size, differently exposed edges and grasslands provide different habitats for the tree species. Exotic species were present in large numbers, probably due to the small size of the reserve and the lack of a buffer zone
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