34 research outputs found
Adolescence as a peak period of borderline personality features? : A meta-analytic approach
This meta-analysis of cross-sectional data aimed to shed light on the often assumed peak in mean-level of borderline personality features during middle to late adolescence (i.e. age 17â22). Borderline personality features were operationalized through the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II). Search terms were entered into PsycINFO and Scopus. A total of 168 samples were included in the analyses, comprising 25,053 participants. Mean age ranged from 14.35 to 51.47 years (M = 29.01, SD = 8.52) and mean number of borderline personality features from 0 to 8.10 (M = 4.59, SD = 2.34). The hypothesized peak between age 17 and 22 was not substantiated by the confirmatory ANOVA analysis. However, subsequent exploratory GAM analysis provided evidence for a peak at 29.4 years. Caution is needed in interpreting these findings given that different trends appeared when GAM models were constructed separately for community, patient and borderline personality disorder (BPD) samples. Age differences in community samples indicated a significant linear decline in mean-level of borderline personality features over time. A linear rising trend was found in BPD samples. As a betweenperson mean-level approach was used in the current study, future longitudinal studies are needed to substantiate if betweenperson age difference generalize to within-person changes
An automated archival VLA transients survey
In this paper we present the results of a survey for radio transients using data obtained from the Very Large Array archive. We have reduced, using a pipeline procedure, 5037 observations of the most common pointings - i.e. the calibrator fields. These fields typically contain a relatively bright point source and are used to calibrate 'target' observations: they are therefore rarely imaged themselves. The observations used span a time range Ë1984-2008 and consist of eight different pointings, three different frequencies (8.4, 4.8 and 1.4 GHz) and have a total observing time of 435 h. We have searched for transient and variable radio sources within these observations using components from the prototype LOFAR transient detection system. In this paper we present the methodology for reducing large volumes of Very Large Array data; and we also present a brief overview of the prototype LOFAR transient detection algorithms. No radio transients were detected in this survey, therefore we place an upper limit on the snapshot rate of GHz frequency transients >8.0 mJy to φ0.032 deg-2 that have typical time-scales 4.3 to 45.3 d. We compare and contrast our upper limit with the snapshot rates - derived from either detections or non-detections of transient and variable radio sources - reported in the literature. When compared with the current Log N-Log S distribution formed from previous surveys, we show that our upper limit is consistent with the observed population. Current and future radio transient surveys will hopefully further constrain these statistics, and potentially discover dominant transient source populations. In this paper we also briefly explore the current transient commissioning observations with LOFAR, and the impact they will make on the field
Exotic bulk viscosity and its influence on neutron star r-modes
We investigate the effect of exotic matter in particular, hyperon matter on
neutron star properties such as equation of state (EoS), mass-radius
relationship and bulk viscosity. Here we construct equations of state within
the framework of a relativistic field theoretical model. As hyperons are
produced abundantly in dense matter, hyperon-hyperon interaction becomes
important and is included in this model. Hyperon-hyperon interaction gives rise
to a softer EoS which results in a smaller maximum mass neutron star compared
with the case without the interaction. Next we compute the coefficient of bulk
viscosity and the corresponding damping time scale due to the non-leptonic weak
process including hyperons. Further, we investigate the role of the
bulk viscosity on gravitational radiation driven r-mode instability in a
neutron star of given mass and temperature and find that the instability is
effectively suppressed.Comment: 5 pages, 3 figure, presented in the Conference on Isolated Neutron
Stars: From the Interior to The Surface, London, UK, 24-28 April, 2006;
revised and final version to appear in Astrophys. Space Sc
New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR
We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 minutes and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg2. We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline (TraP). No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 · 10-3 deg-2 for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates