197,591 research outputs found
Oxyloma Westerlund 1885
No full textGenus Oxyloma Westerlund, 1885 Succinea (Oxyloma) Westerlund, 1885: 1, 7. Type species Succinea dunkeri L. Pfeiffer, 1865, subsequent designated by Westerlund (1885). Gender: Neuter. Remarks Readily distinguished anatomically from other succineid genera by presence of a digiform appendix opening to the proximal apex of the penis.Published as part of Perez, Kathryn E., Martinez Cruz, Marco A., Steury, Brent W. & Barker, Gary M., 2021, A fresh start in ambersnail (Gastropoda: Succineidae) taxonomy: finding a foothold using a widespread species of Oxyloma, pp. 102-126 in European Journal of Taxonomy 757 on pages 111-112, DOI: 10.5852/ejt.2021.757.1419, http://zenodo.org/record/507610
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Westerlund 1 and 2 Open Clusters Survey
No full textContext. With a mass exceeding several 104 M and a rich and dense population of massive stars, supermassive young star clusters represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions among stars.Aims. In this paper we present the "Extended Westerlund 1 and 2 Open Clusters Survey" (EWOCS) project, which aims to investigate the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars. The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically, the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec. Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation were carried out using the ACIS-Extract software.Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a photon flux threshold of approximately 2 × 10−8 photons cm−2 s−1. The X-ray sources exhibit a highly concentrated spatial distribution, with 1075 sources located within the central 1 arcminute. We have successfully detected X-ray emissions from 126 out of the 166 known massive stars of the cluster, and we have collected over 71000 photons from the magnetar CXO J164710.20-455217
Panel cointegration and the neutrality of money
No full textMost econometric methods for testing the proposition of long-run monetary neutrality rely on the assumption that money and real output do not cointegrate, a result that is usually supported by the data. This paper argues that these results can be attributed in part to the low power of univariate tests, and that a violation of the noncointegration assumption is likely to result in a nonrejection of the neutrality proposition. To alleviate this problem, two new and more powerful panel cointegration tests are proposed that can be used under quite general conditions. The empirical results obtained from applying these tests to a panel covering ten countries between 1870 and 1986 suggest money and real output are cointegrated, and hence that the neutrality proposition must be rejected
Is the massive young cluster Westerlund I bound?
No full textContext. Westerlund I is the richest young cluster currently known in our Galaxy, making it one of the most massive clusters for which we can resolve the individual stars even in the crowded centre. This makes it an ideal target to assess whether massive clusters formed currently will remain bound or will disperse and contribute significantly to the stellar field population.
Aims. We measure the radial velocity dispersion of Westerlund I to explore whether the cluster is either currently in virial equilibrium, in the process of collapse, or expanding and dispersing into the field.
Methods. We obtained MIKE/Magellan high resolution optical spectra of 22 post main-sequence stars in Westerlund I for 2 or 3 epochs with a maximum baseline of about one year. Radial velocities variations between these spectra are measured by means of cross-correlation.
Results. We calculate the velocity dispersion from the cross-correlation of five yellow hypergiants and one luminous blue variable, that show little radial velocity variations between epochs and have many spectral features in common. After taking into account the effect of small number statistics and undetected binaries, we estimate the velocity dispersion for the massive stars in Westerlund I to be 2.1-2.1+3.3 km s-1. For several different assumptions concerning possible mass segregation and the elongation of the cluster, we find that Westerlund I is subvirial at the 90% confidence level.
Conclusions. We can rule out that the cluster is significantly supervirial at the 97% confidence level, indicating that Westerlund I is currently bound. This implies that Westerlund I has survived past the point where any gas expulsion has taken place and is expected to survive for billions of years
Panel cointegration test (Westerlund)-Subsample analysis.
No full textPanel cointegration test (Westerlund)-Subsample analysis.</p
Fundamental parameters of four massive eclipsing binaries in Westerlund 1
No full textContext. Only a small number of high mass stars (> 30 M-circle dot) have fundamental parameters (i.e. masses and radii) measured with high enough accuracy from eclipsing binaries to constrain formation and evolutionary models of massive stars. Aims. This work aims to increase this limited sample, by studying the four massive eclipsing binary candidates discovered by Bonanos in the young massive cluster Westerlund 1. Methods. We present new follow-up echelle spectroscopy of these binaries and models of their light and radial velocity curves. Results. We obtain fundamental parameters for the eight component stars, finding masses that span a range of 10-40 M-circle dot, and contributing accurate fundamental parameters for one additional very massive star, the 33 M-circle dot component of W13. WR77o is found to have a similar to 40 M-circle dot companion, which provides a second dynamical constraint on the mass of the progenitor of the magnetar known in the cluster. We also use W13 to estimate the first, direct, eclipsing binary distance to Westerlund 1 and therefore the magnetar and find it to be at 3.7 +/- 0.6 kpc. Conclusions. Our results confirm previous evidence for a high mass for the progenitor of the magnetar. In addition, the availability of eclipsing binaries with accurate parameters opens the way for direct, independent, high precision eclipsing binary distance measurements to Westerlund 1
On the roles of genes in Parkinson's disease
No full textParkinson’s disease is a progressive neurodegenerative disorder which affects 1% of the population over the age of 60. In order to identify candidate genes with a potential role in Parkinson’s disease pathology, we investigated genes which are involved in protein aggregation and the ubiquitin‐proteasome system (α‐synuclein and ubiquitin carboxy‐terminal hydrolase L1, UCH‐L1), oxidative stress (DJ‐1), mitochondrial function (mitochondrial transcription factor A, TFAM), regulation of drug/toxin levels (multi‐drug resistance 1, MDR1 and alcohol and aldehyde dehydrogenases, ADH and ALDHs), as well as a gene with unknown function, but highly implicated in Parkinson’s disease genetics (leucine‐rich repeat kinase 2, LRRK2).(1) Using in situ hybridization, we characterized the cellular localization of candidate genes in both human and rodent tissues and found marked diversity in terms of areas and intensities of transcriptional activity. Some genes exhibited a widespread neuronal expression (UCH‐L1, DJ‐1, SNCA), one showed a particularly high expression in the dopamine target area striatum (LRRK2), some were expressed also in non‐neuronal tissues (LRRK2, DJ‐1, MDR1), and others exclusively so (ADH1, ADH4).(2) We also searched for genetic variability in a Swedish case‐control sample consisting of 310 Parkinson patients and 315 controls, which resulted in identification of several potential risk factors (LRRK2 G2019S; MDR1 1236C/T; SNCA rs2737029 (A/G) and rs356204 (A/G), as well as protective factors (UCH‐L1 S18Y) for disease.(3) Behavior, gene expression and/or brain neurotransmitter levels were studied in different transgenic and drug‐induced rodent models (Adh4‐/‐; α‐synuclein over expressing and α‐synuclein‐/‐; Darpp‐32‐/‐ and Darpp‐32 T34A mutant and MitoPark mice and in 6‐OHDA treated rats). A possible co‐regulation between Lrrk2 and α‐synuclein gene activities was found. Moreover, Adh4‐/‐ mice displayed alterations in substantia nigra dopamine levels, as well as in dopamine‐related behavior.In conclusion, the findings in the present thesis suggest an important role for genetic risk factors in the pathogenesis of Parkinson’s disease. Due to the great complexity of the disease, it seems likely that several molecular pathways and networks involving different genes and downstream effectors can affect the trophic support and/or survival of dopamine neurons, subsequently leading to Parkinson’s disease.List of scientific papersI. Westerlund M, Galter D, Carmine A, Olson L (2005). Tissue- and species-specific expression patterns of class I, III, and IV Adh and Aldh 1 mRNAs in rodent embryos. Cell Tissue Res. 322(2): 227-36. Epub 2005 Nov 3 https://pubmed.ncbi.nlm.nih.gov/16047160II. Westerlund M, Belin AC, Felder MR, Olson L, Galter D (2007). High and complementary expression patterns of alcohol and aldehyde dehydrogenases in the gastrointestinal tract: implications for Parkinsons disease. FEBS J. 274(5): 1212-23. Epub 2007 Jan 25 https://pubmed.ncbi.nlm.nih.gov/17257171III. Carmine Belin A, Westerlund M, Anvret A, Lindqvist E, Pernold K, Ögren S O, Duester G, Galter D (2008). Modeling Parkinsons disease genetics: altered function of the dopamine system in Adh4 knockout mice. [Submitted]IV. Westerlund M, Carmine Belin A, Olson L, Galter D (2008). Cellular localization of multi‐drug resistance 1 (MDR1) in human and rodent nervous system and peripheral organs. [Submitted]V. Westerlund M, Carmine Belin A, Anvret A, Håkansson A, Nissbrandt H, Lind C, Sydow O, Olson L, Galter D (2008). Association of a multi‐drug resistance 1 polymorphism with Parkinsons disease. [Submitted]VI. Westerlund M, Carmine Belin A, Anvret A, Håkansson A, Nissbrandt H, Lind C, Sydow O, Olson L, Galter D (2008). Cerebellar alpha‐synuclein levels are decreased in Parkinsons disease and do not correlate with SNCA polymorphisms associated with disease in a Swedish material. [Submitted]VII. Westerlund M, Belin AC, Anvret A, Bickford P, Olson L, Galter D (2008). Developmental regulation of leucine-rich repeat kinase 1 and 2 expression in the brain and other rodent and human organs: Implications for Parkinsons disease. Neuroscience. 152(2): 429-36. Epub 2008 Jan 10 https://pubmed.ncbi.nlm.nih.gov/18272292VIII. Galter D, Westerlund M, Carmine A, Lindqvist E, Sydow O, Olson L (2006). LRRK2 expression linked to dopamine-innervated areas. Ann Neurol. 59(4): 714-9 https://pubmed.ncbi.nlm.nih.gov/16532471IX. Carmine Belin A, Westerlund M, Sydow O, Lundströmer K, Håkansson A, Nissbrandt H, Olson L, Galter D (2006). Leucine-rich repeat kinase 2 (LRRK2) mutations in a Swedish Parkinson cohort and a healthy nonagenarian. Mov Disord. 21(10): 1731-4 https://pubmed.ncbi.nlm.nih.gov/16817197X. Westerlund M, Ran C, Borgkvist A, Sterky FH, Lindqvist E, Lundströmer K, Pernold K, Brené S, Kallunki P, Fisone G, Greengard P, Larsson N‐G, Olson L, Galter D (2008). Leucine‐rich repeat kinase 2 and other PARK genes in rodent models of Parkinsons disease. [Submitted]XI. Galter D, Westerlund M, Belin AC, Olson L (2007). DJ-1 and UCH-L1 gene activity patterns in the brains of controls, Parkinson and schizophrenia patients and in rodents. Physiol Behav. 92(1-2): 46-53. Epub 2007 May 23 https://pubmed.ncbi.nlm.nih.gov/17599367XII. Carmine Belin A, Westerlund M, Bergman O, Nissbrandt H, Lind C, Sydow O, Galter D (2007). S18Y in ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) associated with decreased risk of Parkinsons disease in Sweden. Parkinsonism Relat Disord. 13(5): 295-8. Epub 2007 Feb 6 https://pubmed.ncbi.nlm.nih.gov/17287139</p
Detection of additional Wolf-Rayet stars in the starburst cluster Westerlund 1 with
No full textContext.The young starburst cluster Westerlund 1 is one of the most massive clusters in the Local Group,
harboring a huge population of massive stars.
Aims.We searched for additional Wolf-Rayet stars in Westerlund 1.
Methods.The targets were selected based on 1 μm narrow-band imaging of
the cluster carried out at OPD/LNA (Brazil), and then confirmed as Wolf-Rayet stars by K-band
spectroscopy performed at the 4.1 m SOAR telescope (Chile).
Results.We report the detection of 3 additional Wolf-Rayet stars in Westerlund 1. Together with previous
works, this increases the population of Wolf-Rayet stars detected in the cluster to 22 members.
Moreover, a K-band spectrum of the Luminous Blue Variable W243,
which apparently implies a higher temperature than that derived from optical spectra taken in
2003, is presented for the first time. The WC9 star WR-F was also observed, showing clear evidence of dust emission in the K-band
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Westerlund 1 and 2 Open Clusters Survey
No full textContext. With a mass exceeding several 104 M_sun and a rich and dense population of massive stars, supermassive young star clusters represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions among stars.
Aims: In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars. The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods: The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically, the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec. Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation were carried out using the ACIS-Extract software.
Results: The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a photon flux threshold of approximately 2 × 10−8 photons cm−2 s−1. The X-ray sources exhibit a highly concentrated spatial distribution, with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217
Massive stars in the hinterland of the young cluster, Westerlund 2
No full textAn unsettled question concerning the formation and distribution of massive stars is whether they must be born in massive clusters and, if found in less dense environments, whether they must have migrated there. With the advent of wide-area digital photometric surveys, it is now possible to identify massive stars away from prominent Galactic clusters without bias. In this study we consider 40 candidate OB stars found in the field around the young massive cluster, Westerlund 2, by Mohr-Smith et al (2017): these are located inside a box of 1.5×1.5 square degrees and are selected on the basis of their extinctions and K magnitudes. We present VLT/X-shooter spectra of two of the hottest O stars, respectively 11 and 22 arcmin from the centre of Westerlund 2. They are confirmed as O4V stars, with stellar masses likely to be in excess of 40 M?. Their radial velocities relative to the non-binary reference object, MSP 182, in Westerlund 2 are -29.4 ±1.7 and -14.4 ±2.2 km s-1, respectively. Using Gaia DR2 proper motions we find that between 8 and 11 early O/WR stars in the studied region (including the two VLT targets, plus WR 20c and WR 20aa) could have been ejected from Westerlund 2 in the last one million years. This represents an efficiency of massive-star ejection of up to ~ 25%. On sky, the positions of these stars and their proper motions show a near N–S alignment. We discuss the possibility that these results are a consequence of prior sub-cluster merging combining with dynamical ejection
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