178,217 research outputs found
Basic parameters of three star clusters in the Small Magellanic Cloud: Kron 11, Kron 63 and NGC 121
No full textWe present observations for three star clusters, Kron 11, Kron 63 and NGC 121, in the Small Magellanic Cloud. We have studied their structure and derived their fundamental parameters by means of their luminosity functions, their colour magnitude diagrams and the Padova suite of isochrones. NGC 121 is a well-studied object, for which we confirm previous evidence about its old age and low-metal content, and have found that it is an undergoing mass segregation. Kron 11 and Kron 63 are poorly populated clusters which had never been studied so far. Kron 11 is several gigayears younger than NGC 121, while Kron 63 is basically a very young star aggregate. Both clusters are immersed in dense stellar fields which share the same population properties, suggesting that in their cases, cluster ages are consistent with typical ages of field stars.GB acknowledges support from the Chilean Centro de Astrofísica
FONDAP No. 15010003 and CONICET (PIP 5970). EC and RAM
acknowledge support by the Fondo Nacional de Investigación
Científica y Tecnológica (proyecto No. 1050718, Fondecyt) and
the Chilean Centro de Astrofísica FONDAP No. 15010003. CG and
NN acknowledge support by the Instituto de Astrofísica de Canarias
(P3-94) and the Ministry of Education and Research of the Kingdom
of Spain (AYA2004-06343)
Basic parameters of three star clusters in the Small Magellanic Cloud: Kron 11, Kron 63 and NGC 121
No full textWe present observations for three star clusters, Kron 11, Kron 63 and NGC 121, in the Small Magellanic Cloud. We have studied their structure and derived their fundamental parameters by means of their luminosity functions, their colour magnitude diagrams and the Padova suite of isochrones. NGC 121 is a well-studied object, for which we confirm previous evidence about its old age and low-metal content, and have found that it is an undergoing mass segregation. Kron 11 and Kron 63 are poorly populated clusters which had never been studied so far. Kron 11 is several gigayears younger than NGC 121, while Kron 63 is basically a very young star aggregate. Both clusters are immersed in dense stellar fields which share the same population properties, suggesting that in their cases, cluster ages are consistent with typical ages of field stars.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica
Towards Optimal Kron-based Reduction Of Networks (Opti-KRON) for the Electric Power Grid
No full textFor fast timescales or long prediction horizons, the AC optimal power flow
(OPF) problem becomes a computational challenge for large-scale, realistic AC
networks. To overcome this challenge, this paper presents a novel network
reduction methodology that leverages an efficient mixed-integer linear
programming (MILP) formulation of a Kron-based reduction that is optimal in the
sense that it balances the degree of the reduction with resulting modeling
errors in the reduced network. The method takes as inputs the full AC network
and a pre-computed library of AC load flow data and uses the graph Laplacian to
constraint nodal reductions to only be feasible for neighbors of non-reduced
nodes. This results in a highly effective MILP formulation which is embedded
within an iterative scheme to successively improve the Kron-based network
reduction until convergence. The resulting optimal network reduction is, thus,
grounded in the physics of the full network. The accuracy of the network
reduction methodology is then explored for a 100+ node medium-voltage radial
distribution feeder example across a wide range of operating conditions. It is
finally shown that a network reduction of 25-85% can be achieved within seconds
and with worst-case voltage magnitude deviation errors within any super node
cluster of less than 0.01pu. These results illustrate that the proposed
optimization-based approach to Kron reduction of networks is viable for larger
networks and suitable for use within various power system applications
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Galaxy and Mass Assembly: FUV, NUV, ugrizYJHK Petrosian, Kron and Sérsic photometry
No full textIn order to generate credible 0.1–2 μm spectral energy distributions, the Galaxy and Mass Assembly (GAMA) project requires many gigabytes of imaging data from a number of instruments to be reprocessed into a standard format. In this paper, we discuss the software infrastructure we use, and create self-consistent ugrizYJHK photometry for all sources within the GAMA sample. Using UKIDSS and SDSS archive data, we outline the pre-processing necessary to standardize all images to a common zero-point, the steps taken to correct for the seeing bias across the data set and the creation of gigapixel-scale mosaics of the three 4 × 12 deg2 GAMA regions in each filter. From these mosaics, we extract source catalogues for the GAMA regions using elliptical Kron and Petrosian matched apertures. We also calculate Sérsic magnitudes for all galaxies within the GAMA sample using sigma, a galaxy component modelling wrapper for galfit 3. We compare the resultant photometry directly and also calculate the r-band galaxy luminosity function for all photometric data sets to highlight the uncertainty introduced by the photometric method. We find that (1) changing the object detection threshold has a minor effect on the best-fitting Schechter parameters of the overall population (M*± 0.055 mag, α± 0.014, ϕ*± 0.0005 h3 Mpc−3); (2) there is an offset between data sets that use Kron or Petrosian photometry, regardless of the filter; (3) the decision to use circular or elliptical apertures causes an offset in M* of 0.20 mag; (4) the best-fitting Schechter parameters from total-magnitude photometric systems (such as SDSS modelmag or Sérsic magnitudes) have a steeper faint-end slope than photometric systems based upon Kron or Petrosian measurements; and (5) our Universe’s total luminosity density, when calculated using Kron or Petrosian r-band photometry, is underestimated by at least 15 per cent
Galaxy and Mass Assembly: FUV, NUV, ugrizYJHK Petrosian, Kron and Sérsic photometry
No full textIn order to generate credible 0.1-2 μm spectral energy distributions, the Galaxy and Mass Assembly (GAMA) project requires many gigabytes of imaging data from a number of instruments to be reprocessed into a standard format. In this paper, we discuss the software infrastructure we use, and create self-consistent ugrizYJHK photometry for all sources within the GAMA sample. Using UKIDSS and SDSS archive data, we outline the pre-processing necessary to standardize all images to a common zero-point, the steps taken to correct for the seeing bias across the data set and the creation of gigapixel-scale mosaics of the three 4 × 12 deg2 GAMA regions in each filter. From these mosaics, we extract source catalogues for the GAMA regions using elliptical Kron and Petrosian matched apertures. We also calculate Sérsic magnitudes for all galaxies within the GAMA sample using sigma, a galaxy component modelling wrapper for galfit 3. We compare the resultant photometry directly and also calculate the r-band galaxy luminosity function for all photometric data sets to highlight the uncertainty introduced by the photometric method. We find that (1) changing the object detection threshold has a minor effect on the best-fitting Schechter parameters of the overall population (M*± 0.055 mag, α± 0.014, ϕ*± 0.0005 h3 Mpc−3); (2) there is an offset between data sets that use Kron or Petrosian photometry, regardless of the filter; (3) the decision to use circular or elliptical apertures causes an offset in M* of 0.20 mag; (4) the best-fitting Schechter parameters from total-magnitude photometric systems (such as SDSS modelmag or Sérsic magnitudes) have a steeper faint-end slope than photometric systems based upon Kron or Petrosian measurements; and (5) our Universe's total luminosity density, when calculated using Kron or Petrosian r-band photometry, is underestimated by at least 15 per cen
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Expression and function of serotonin 2A and 2B receptors in the mammalian respiratory network.
No full textNeurons of the respiratory network in the lower brainstem express a variety of serotonin receptors (5-HTRs) that act primarily through adenylyl cyclase. However, there is one receptor family including 5-HT(2A), 5-HT(2B), and 5-HT(2C) receptors that are directed towards protein kinase C (PKC). In contrast to 5-HT(2A)Rs, expression and function of 5-HT(2B)Rs within the respiratory network are still unclear. 5-HT(2B)R utilizes a Gq-mediated signaling cascade involving calcium and leading to activation of phospholipase C and IP3/DAG pathways. Based on previous studies, this signal pathway appears to mediate excitatory actions on respiration. In the present study, we analyzed receptor expression in pontine and medullary regions of the respiratory network both at the transcriptional and translational level using quantitative RT-PCR and self-made as well as commercially available antibodies, respectively. In addition we measured effects of selective agonists and antagonists for 5-HT(2A)Rs and 5-HT(2B)Rs given intra-arterially on phrenic nerve discharges in juvenile rats using the perfused brainstem preparation. The drugs caused significant changes in discharge activity. Co-administration of both agonists revealed a dominance of the 5-HT(2B)R. Given the nature of the signaling pathways, we investigated whether intracellular calcium may explain effects observed in the respiratory network. Taken together, the results of this study suggest a significant role of both receptors in respiratory network modulation
Unser Friederichs von Gottes Gnaden Königs in Böheimb/ Pfaltzgraffen bey Rhein/ und Churfürsten/ [et]c. Offen Außschreiben/ Warumb Wir die Kron Böheimb/ und der incorporirten Länder Regierung auff Uns genommen
No full textUNSER FRIEDERICHS VON GOTTES GNADEN KÖNIGS IN BÖHEIMB/ PFALTZGRAFFEN BEY RHEIN/ UND CHURFÜRSTEN/ [ET]C. OFFEN AUSSSCHREIBEN/ WARUMB WIR DIE KRON BÖHEIMB/ UND DER INCORPORIRTEN LÄNDER REGIERUNG AUFF UNS GENOMMEN
Unser Friederichs von Gottes Gnaden Königs in Böheimb/ Pfaltzgraffen bey Rhein/ und Churfürsten/ [et]c. Offen Außschreiben/ Warumb Wir die Kron Böheimb/ und der incorporirten Länder Regierung auff Uns genommen ([1]r)
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