409 research outputs found
ROTSE observations of the young cluster IC 348
CCD observations of stars in the young cluster IC 348 were obtained from 2004
August to 2005 January with a 0.45 m ROTSEIIId robotic reflecting telescope at
the Turkish National Observatory site, Bakirlitepe, Turkey. The timing analysis
of selected stars whose X-Ray counterpart were detected by Chandra X-Ray
Observatory were studied. The time series of stars were searched for rotational
periodicity by using different period search methods. 35 stars were found to be
periodic with periods ranging from 0.74 to 32.3 days. Eighteen of the 35
periodic stars were new detections. Four of the new detections were CTTSs and
the others were WTTSs and G type (or unknown spectral class) stars. In this
study, we confirmed the stability of rotation periods of TTauri stars. The
periods obtained by Cohen et al. and us were different by 1%. We also confirmed
the 3.24 h pulsation period of H254 which is a delta Scuti type star as noted
by Ripepi et al. but the other periods detected by them were not found. We
examined correlation between X-ray luminosity and rotational period of our
sample of TTSs. There is a decline in the rotational period with X-ray
luminosity for late type TTSs.Comment: 15 pages, 14 figures, accepted for publication in Astronomical
Journa
Design and evaluation of an ontology based information extraction system for radiological reports
Cataloged from PDF version of article.This paper describes an information extraction system that extracts and converts the available information in free text Turkish radiology reports into a structured information model using manually created extraction rules and domain ontology. The ontology provides flexibility in the design of extraction rules, and determines the information model for the extracted semantic information. Although our information extraction system mainly concentrates on abdominal radiology reports, the system can be used in another field of medicine by adapting its ontology and extraction rule set. We achieved very high precision and recall results during the evaluation of the developed system with unseen radiology reports. (C) 2010 Elsevier Ltd. All rights reserved
Optical observations of Be/X-ray transient system KS 1947+300
ROTSE-IIId observations of the Be/X-ray transient system KS 1947+300 obtained between September 2004 and December 2005 make it possible to study the correlation between optical and X-ray activity. The optical outburst of 0.1 mag was accompanied by an increase in X-ray flux in 2004 observations. Strong correlation between the optical and X-ray light curves suggests that neutron star directly accretes from the outflowing material of Be star. The nearly zero time lag between X-ray and optical light curves suggests a heating of the disk of Be star by X-rays. No optical brightening and X-ray enhancement was seen in 2005 observations. There is no indication of the orbital modulation in the optical light curve
Superfluid Friction and Late-time Thermal Evolution of Neutron Stars
The recent temperature measurements of the two older isolated neutron stars
PSR 1929+10 and PSR 0950+08 (ages of and yr,
respectively) indicate that these objects are heated. A promising candidate
heat source is friction between the neutron star crust and the superfluid it is
thought to contain. We study the effects of superfluid friction on the
long-term thermal and rotational evolution of a neutron star. Differential
rotation velocities between the superfluid and the crust (averaged over the
inner crust moment of inertia) of rad s for PSR
1929+10 and rad s for PSR 0950+08 would account for their
observed temperatures. These differential velocities could be sustained by
pinning of superfluid vortices to the inner crust lattice with strengths of
1 MeV per nucleus. Pinned vortices can creep outward through thermal
fluctuations or quantum tunneling. For thermally-activated creep, the coupling
between the superfluid and crust is highly sensitive to temperature. If pinning
maintains large differential rotation ( rad s), a feedback
instability could occur in stars younger than yr causing
oscillations of the temperature and spin-down rate over a period of . For stars older than yr, however, vortex creep occurs
through quantum tunneling, and the creep velocity is too insensitive to
temperature for a thermal-rotational instability to occur. These older stars
could be heated through a steady process of superfluid friction.Comment: 26 pages, 1 figure, submitted to Ap
The influence of post-fixation on visualising vimentin in the retina using immunofluorescence method
Background: Post-fixation of sections is especially required for cryostat sections of fresh frozen tissues. Vimentin is an intermediate filament in both fibrillary and non-fibrillary form, expressed in Müller’s cells and astrocytes of the retina. Our aim was to determine the best post-fixation method for visualising vimentin in archival mouse eyes.
Materials and methods: We used an archival mouse eye, slightly pre-fixed with paraformaldehyde and stored at –80°C for 4 years. We tried three fixatives (paraformaldehyde [PFA], alcohol/acetic acid [AAA] and methanol) for post-fixation of eye sections.
Results: We showed that post-fixation alters the labelling properties of vimentin expressed in the retina. In the sections with no post-fixation, vimentin positivity was observed in and around the nuclei in non-fibrillary form. In PFA post-fixed sections, the vimentin in the retina was not observed as fibrils. Positivity was observed in the nuclei and in perinuclear regions of the cells. In AAA post-fixed sections, positive labelling was observed around the nuclei as fibrils. In methanol post-fixed sections, labelling was observed around the nuclei as fibrils.
Conclusions: We conclude that post-fixation with AAA is more convenient for immunofluorescent labelling of vimentin in the retina for slightly PFA pre-fixed and long-term stored retina. (Folia Morphol 2018; 77, 2: 246–252
Precision Timing of Two Anomalous X-Ray Pulsars
We report on long-term X-ray timing of two anomalous X-ray pulsars, 1RXS
J170849.0-400910 and 1E 2259+586, using the Rossi X-ray Timing Explorer. In
monthly observations made over 1.4 yr and 2.6 yr for the two pulsars,
respectively, we have obtained phase-coherent timing solutions which imply that
these objects have been rotating with great stability throughout the course of
our observations. For 1RXS J170849.0-400910, we find a rotation frequency of
0.0909169331(5) Hz and frequency derivative -15.687(4) x 10^(-14) Hz/s, for
epoch MJD 51215.931. For 1E 2259+586, we find a rotation frequency of
0.1432880613(2)Hz, and frequency derivative -1.0026(7) x 10^(-14) Hz/s, for
epoch MJD 51195.583. RMS phase residuals from these simple models are only
about 0.01 cycles for both sources. We show that the frequency derivative for
1E 2259+586 is inconsistent with that inferred from incoherent frequency
observations made over the last 20 yr. Our observations are consistent with the
magnetar hypothesis and make binary accretion scenarios appear unlikely.Comment: 12 pages including 3 figures. To appear in ApJ Letter
Optical and X-ray Outbursts of Be/X-ray binary system SAX J2103.5+4545
We present the relations between Halpha equivalent width, optical brightness
and X-ray flux of Be/X-ray binary system SAX J2103.5+4545, by analyzing the
optical photometric and spectroscopic observations together with the X-ray
observations.
In the photometric observations PSF photometry were applied using MIDAS and
its DAOPHOT package. The reduction and analysis of spectra were done by using
MIDAS and its suitable packages. The X-ray outburst of the system occurred just
after the optical outburst. The nearly symmetric Halpha emission line profiles
observed during the beginning of optical outburst turn into asymmetric profiles
with increased EW values during the dissipation of Be disc. Halpha lines
changed from emission to absorption during the observation period. The observed
double peaked HeI emission lines might come from the accretion disc of neutron
star which is temporarily formed at the time of X-ray outburst.Comment: to be pubished at Astronomy and Astrophysics on June 200
Bacterial Death Results from Mutations Made in Translocation Peptide of Leucyl-tRNA Synthetase
The family of aminoacyl-tRNA synthetases (aaRSs) ensures the fidelity of translation through providing a pool of correctly aminoacylated tRNA products that become incorporated by the ribosome. Leucyl-tRNA synthetase (LeuRS) has two functionally separate domains, one is the aminoacylation domain and the other is the CP1 editing domain. LeuRS can aminoacylate noncognate amino acids, therefore it relies on the CP1 editing domain to hydrolyze misaminoacylated tRNA products before they are released from the enzyme. The LeuRS enzyme must undergo a structural transition state in its reaction cycle in order to translocate the 3\u27 acceptor stem of tRNA 30 Å from the aminoacylation active site to the CP1 domain hydrolytic active site. The translocation event is difficult to study, but we believe that we have generated mutations within LeuRS that alter the translocation event of tRNA. The mutations that we have generated lead to bacterial death in Escherichia coli (E. coli). Circular dichorism experiments indicate that our mutations do not significantly alter the secondary structure of LeuRS. In vitro biochemical studies demonstrate that these mutations reduce the rates of aminoacylation and hydrolysis, while also displaying misaminoacylation activity. We attribute these biochemical findings to the resulting bacterial death that is caused by these mutation
Bacterial Death Results from Mutations Made in Translocation Peptide of Leucyl-tRNA Synthetase
The family of aminoacyl-tRNA synthetases (aaRSs) ensures the fidelity of translation through providing a pool of correctly aminoacylated tRNA products that become incorporated by the ribosome. Leucyl-tRNA synthetase (LeuRS) has two functionally separate domains, one is the aminoacylation domain and the other is the CP1 editing domain. LeuRS can aminoacylate noncognate amino acids, therefore it relies on the CP1 editing domain to hydrolyze misaminoacylated tRNA products before they are released from the enzyme. The LeuRS enzyme must undergo a structural transition state in its reaction cycle in order to translocate the 3\u27 acceptor stem of tRNA 30 Å from the aminoacylation active site to the CP1 domain hydrolytic active site. The translocation event is difficult to study, but we believe that we have generated mutations within LeuRS that alter the translocation event of tRNA. The mutations that we have generated lead to bacterial death in Escherichia coli (E. coli). Circular dichorism experiments indicate that our mutations do not significantly alter the secondary structure of LeuRS. In vitro biochemical studies demonstrate that these mutations reduce the rates of aminoacylation and hydrolysis, while also displaying misaminoacylation activity. We attribute these biochemical findings to the resulting bacterial death that is caused by these mutation
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