1,727,766 research outputs found
The standard model of low-mass star formation applied to massive stars : a multi-wavelength picture of AFGL 2591
No full textContext. While it is currently unclear from a theoretical standpoint which forces and processes dominate the formation of high-mass stars, and hence determine the mode in which they form, much of the recent observational evidence suggests that massive stars are born in a similar manner to their low-mass counterparts. Aims. This paper aims to investigate the hypothesis that the embedded luminous star AFGL 2591-VLA 3 (2.3 × 105 L⊙ at 3.33 kpc) is forming according to a scaled-up version of a low-mass star formation scenario. Methods. We present multi-configuration Very Large Array (VLA) 3.6 cm and 7 mm, as well as Combined Array for Research in Millimeter Astronomy C18O and 3 mm continuum observations to investigate the morphology and kinematics of the ionized gas, dust, and molecular gas around AFGL 2591. We also compare our results to ancillary Gemini North near-IR images, and model the near-IR to sub-mm spectral energy distribution (SED) and Two Micron All Sky Survey (2MASS) image profiles of AFGL 2591 using a Monte-Carlo dust continuum radiative transfer code. Results. The observed 3.6 cm images uncover for the first time that the central powering source AFGL 2591-VLA 3 has a compact core plus collimated jet morphology, extending 4000 AU eastward from the central source with an opening angle of <10° at this radius. However, at 7 mm VLA 3 does not show a jet morphology, but instead compact (<500 AU) emission, some of which (<0.57 mJy of 2.9 mJy) is estimated to be from dust emission. The spectral index of AFGL 2591-VLA 3 between 3.6 cm and 7 mm was found to be between 0.4 and 0.5, similar to that of an ionized wind. If the 3.6 cm emission is modelled as an ionized jet, the jet has almost enough momentum to drive the larger-scale flow. However, assuming a shock efficiency of 10%, the momentum rate of the jet is not sufficient to ionize itself via only shocks, and thus a significant portion of the emission is instead likely created in a photoionized wind. The C18O emission uncovers dense entrained material in the outflow(s) from these young stars. The main features of the SED and 2MASS images of AFGL 2591-VLA 3 are also reproduced by our model dust geometry of a rotationally flattened envelope with and without a disk. Conclusions. The above results are consistent with a picture of massive star formation similar to that seen for low-mass protostars. However, within its envelope, AFGL 2591-VLA 3 contains at least four other young stars, constituting a small cluster. Therefore it appears that AFGL 2591-VLA 3 may be able to source its accreting material from a shared gas reservoir while still exhibiting the phenomena expected during the formation of low-mass stars.Peer reviewe
Chicago, Burlington & Quincy (CBQ) 2591
No full textA photograph print showing Chicago, Burlington & Quincy (CBQ) 2591, 4-4-2, Class P6a, on passenger train, East St. Louis, IL
IO Islamic 2591. Ḥabîb-alsiyar, General History, Fourth Volume
No full textIO Islamic 2591. Ḥabîb-alsiyar, General History, Fourth Volume</p
Other title: [House Bill 2591]
No full textapplication/pdf; "March 22, 2007."; Testimony before the Kansas Legislature, House Social Services Budget Committee, by Dr. Marcia Nielsen, Executive Director, Kansas Health Policy Authority.Testimony in opposition to HB 2591, which concerns providing affordable access to health care in Kansas
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
NNZ-2591, a novel diketopiperazine, prevented scopolamine-induced acute memory impairment in the adult rat
No full textIn rats, cyclo-L-glycyl-L-2-allylproline (NNZ-2591), a diketopiperazine, is neuroprotective after ischemic brain injury and also improves motor function in a rat model of Parkinson's disease. Given nootropic actions of diketopiperazines, we investigated the effects of and potential role for acetylcholine neurotransmission in NNZ-2591 on spatial memory after scopolamine-induced amnesia in rats. Adult male Wistar rats were assigned to four groups: saline/water; saline/NNZ-2591; scopolamine/water and scopolamine/NNZ-2591. Morris Water Maze (MWM) tasks were used to determine spatial learning and memory. Thirty minutes prior to each of four daily acquisition trials, rats were intraperitoneally injected with either scopolamine (0.5 mg/kg) or saline. Either NNZ-2591 (30 mg/kg) or water was administered orally (gavages) 10 min after the injection. Immediately after completion of the day 4 acquisition trial a spatial probe trial was performed. The brains were then collected for immunohistochemical analysis. Scopolamine impaired spatial learning and memory compared to saline treated group, particularly in the day 1 acquisition trial. NNZ-2591 did not reverse this deficit, however it significantly improved memory retention by showing more time spent in the correct quadrant. NNZ-2591 also counteracted the scopolamine-induced up-regulation of choline-acetyltransferase positive neurons in the striatum and similarly counteracted the increased synaptophysin density in the hippocampus. Furthermore, a scopolamine-independent antagonistic effect on muscarinic M2 acetylcholine receptors was found after NNZ-2591 treatment, supporting its modulation of acetylcholine neurotransmission. The data suggest that NNZ-2591 prevents scopolamine-induced acute impairment in memory and modulation of acetylcholine neurotransmission may be the mode of action underlying the memory improvement
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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
Davis, Benjamin T., 1870-1929 (SC 2591)
No full textFinding aid only for Manuscripts Small Collection 2591. Typescript copy of an address titled “The State Line,” delivered by Senator B.T. Davis, Hickman, Kentucky, before the Kentucky State Bar Association at Bowling Green, Kentucky. The address details information about the borders of Kentucky and the history of the borders and territories in America
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