1,538 research outputs found
Two Cases of Primary Ectopic Ovarian Pregnancy
Primary ovarian pregnancy is one of the rarest varieties of ectopic pregnancies. Patients frequently present with abdominal pain and menstrual irregularities. Intrauterine devices have evolved as probable risk factors. Preoperative diagnosis is challenging but transvaginal sonography has often been helpful. A diagnostic delay may lead to rupture, secondary implantation or operative difficulties. Therefore, awareness of this rare condition is important in reducing the associated risks. Here, we report two cases of primary ovarian pregnancies presenting with acute abdominal pain. Transabdominal ultrasonography failed to hint at ovarian pregnancy in one, while transvaginal sonography aided in the correct diagnosis of the other. Both cases were confirmed by histopathological examinations and were successfully managed by surgery
A constraint on the formation timescale of the young open cluster NGC 2264: Lithium abundance of pre-main sequence stars
The timescale of cluster formation is an essential parameter in order to
understand the formation process of star clusters. Pre-main sequence (PMS)
stars in nearby young open clusters reveal a large spread in brightness. If the
spread were considered as a result of a real spread in age, the corresponding
cluster formation timescale would be about 5 -- 20 Myr. Hence it could be
interpreted that star formation in an open cluster is prolonged for up to a few
tens of Myr. However, difficulties in reddening correction, observational
errors, and systematic uncertainties introduced by imperfect evolutionary
models for PMS stars, can result in an artificial age spread. Alternatively, we
can utilize Li abundance as a relative age indicator of PMS star to determine
the cluster formation timescale. The optical spectra of 134 PMS stars in NGC
2264 have been obtained with MMT/Hectochelle. The equivalent widths have been
measured for 86 PMS stars with a detectable Li line (3500 < T_eff [K] <= 6500).
Li abundance under the condition of local thermodynamic equilibrium (LTE) was
derived using the conventional curve of growth method. After correction for
non-LTE effects, we find that the initial Li abundance of NGC 2264 is A(Li) =
3.2 +/- 0.2. From the distribution of the Li abundances, the underlying age
spread of the visible PMS stars is estimated to be about 3 -- 4 Myr and this,
together with the presence of embedded populations in NGC 2264, suggests that
the cluster formed on a timescale shorter than 5 Myr.Comment: 53 pages, 12 figures, 4 tables, Accepted for publication in the
Astrophysical Journa
Sejong Open Cluster Survey (SOS) - IV. The Young Open Clusters NGC 1624 and NGC 1931
Young open clusters located in the outer Galaxy provide us with an
opportunity to study star formation activity in a different environment from
the solar neighborhood. We present a UBVI and H alpha photometric study of the
young open clusters NGC 1624 and NGC 1931 that are situated toward the Galactic
anticenter. Various photometric diagrams are used to select the members of the
clusters and to determine the fundamental parameters. NGC 1624 and NGC 1931
are, on average, reddened by = 0.92 +/- 0.05 and 0.74 +/- 0.17 mag,
respectively. The properties of the reddening toward NGC 1931 indicate an
abnormal reddening law (Rv,cl = 5.2 +/- 0.3). Using the zero-age main sequence
fitting method we confirm that NGC 1624 is 6.0 +/- 0.6 kpc away from the Sun,
whereas NGC 1931 is at a distance of 2.3 +/- 0.2 kpc. The results from
isochrone fitting in the Hertzsprung-Russell diagram indicate the ages of NGC
1624 and NGC 1931 to be less than 4 Myr and 1.5 - 2.0 Myr, respectively. We
derived the initial mass function (IMF) of the clusters. The slope of the IMF
(Gamma_NGC 1624 = -2.0 +/- 0.2 and Gamma_NGC 1931 = -2.0 +/- 0.1) appears to be
steeper than that of the Salpeter/Kroupa IMF. We discuss the implication of the
derived IMF based on simple Monte-Carlo simulations and conclude that the
property of star formation in the clusters seems not to be far different from
that in the solar neighborhood.Comment: 79 pages, 21 pages, 7 tables, Accepted for publication in the
Astronomical Journa
Ground-state structure of the hydrogen double vacancy on Pd(111)
We determine the ground-state structure of a double vacancy in a hydrogen
monolayer on the Pd(111) surface. We represent the double vacancy as a triple
vacancy containing one additional hydrogen atom. The potential-energy surface
for a hydrogen atom moving in the triple vacancy is obtained by
density-functional theory, and the wave function of the fully quantum hydrogen
atom is obtained by solving the Schr\"odinger equation. We find that an H atom
in a divacancy defect experiences significant quantum effects, and that the
ground-state wave function is centered at the hcp site rather than the fcc site
normally occupied by H atoms on Pd(111). Our results agree well with scanning
tunneling microscopy images.Comment: 5 pages, 3 figure
Structure of AlSb(001) and GaSb(001) Surfaces Under Extreme Sb-rich Conditions
We use density-functional theory to study the structure of AlSb(001) and
GaSb(001) surfaces. Based on a variety of reconstruction models, we construct
surface stability diagrams for AlSb and GaSb under different growth conditions.
For AlSb(001), the predictions are in excellent agreement with experimentally
observed reconstructions. For GaSb(001), we show that previously proposed model
accounts for the experimentally observed reconstructions under Ga-rich growth
conditions, but fails to explain the experimental observations under Sb-rich
conditions. We propose a new model that has a substantially lower surface
energy than all (nx5)-like reconstructions proposed previously and that, in
addition, leads to a simulated STM image in better agreement with experiment
than existing models. However, this new model has higher surface energy than
some of (4x3)-like reconstructions, models with periodicity that has not been
observed. Hence we conclude that the experimentally observed (1x5) and (2x5)
structures on GaSb(001) are kinetically limited rather than at the ground
state.Comment: 6 pages, 6 figure
Sejong Open Cluster Survey (SOS). 0. Target Selection and Data Analysis
Star clusters are superb astrophysical laboratories containing cospatial and
coeval samples of stars with similar chemical composition. We have initiated
the Sejong Open cluster Survey (SOS) - a project dedicated to providing
homogeneous photometry of a large number of open clusters in the SAAO
Johnson-Cousins' system. To achieve our main goal, we have paid much
attention to the observation of standard stars in order to reproduce the SAAO
standard system.
Many of our targets are relatively small, sparse clusters that escaped
previous observations. As clusters are considered building blocks of the
Galactic disk, their physical properties such as the initial mass function, the
pattern of mass segregation, etc. give valuable information on the formation
and evolution of the Galactic disk. The spatial distribution of young open
clusters will be used to revise the local spiral arm structure of the Galaxy.
In addition, the homogeneous data can also be used to test stellar evolutionary
theory, especially concerning rare massive stars. In this paper we present the
target selection criteria, the observational strategy for accurate photometry,
and the adopted calibrations for data analysis such as color-color relations,
zero-age main sequence relations, Sp - Mv relations, Sp - Teff relations, Sp -
color relations, and Teff - BC relations. Finally we provide some data analysis
such as the determination of the reddening law, the membership selection
criteria, and distance determination.Comment: 21 pages, 16 figures, accepted for publication in J. of Korean
Astronomical Society (JKAS
Personal and social factors influencing students' attitudes towards peers with special needs
Within inclusive education, it is crucial to consider how students with special needs are valued as members of school community and may fully and actively take part in school-life. The present study aims: 1) to assess students' attitudes towards peers with special needs; 2) to understand how personal factors (age, gender, school achievement and social competence) and social factors (contacting with persons or family member with SN) predict students' attitudes variation. Participants were 200 Portuguese students from 6th to 12th grade. Instruments were administered during class: (i) CATCH (Rosenbaum, Armstrong & King, 1986), comprising a cognitive and an affective-behavior subscale (ii) Social goals Scale (Wentzel, 1993), comprising a social responsibility and a prosocial subscale. We conducted exploratory factor analysis on CATCH and stepwise regression analysis using attitudes as dependent variable. Affective-behavior attitudes were higher in girls and in students with contact with special needs peers and showed moderate correlations with social competence; Cognitive attitudes were higher in older students and were not related with social competence. Prosocial goals were the best predictor of attitudes towards peers with special needs. Results showed that attitudes towards peers with special needs may be influenced by personal and contextual factors. Confirming other findings girls showed more positive attitudes. Also students who have contact with peers with special needs have more positive attitudes, evidencing the potential impact of inclusive settings. The relation found between attitudes and social motivation (mainly prosocial goals) has implications for educational intervention.8C1E-AFB9-6BE1 | Maria Teresa Martins Gon?alvesN/
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