2,024 research outputs found
Variability of Active Galactic Nuclei from the Optical to X-ray Regions
Some progress in understanding AGN variability is reviewed. Reprocessing of
X-ray radiation to produce significant amounts of longer-wavelength continua
seems to be ruled out. In some objects where there has been correlated X-ray
and optical variability, the amplitude of the optical variability has exceeded
the amplitude of X-ray variability. We suggest that accelerated particles
striking material could be linking X-ray and optical variability (as in
activity in the solar chromosphere). Beaming effects could be significant in
all types of AGN. The diversity in optical/X-ray relationships at different
times in the same object, and between different objects, might be explained by
changes in geometry and directions of motion relative to our line of sight.
Linear shot-noise models of the variability are ruled out; instead there must
be large-scale organization of variability. Variability occurs on
light-crossing timescales rather than viscous timescales and this probably
rules out the standard Shakura-Sunyaev accretion disk. Radio-loud and
radio-quiet AGNs have similar continuum shapes and similar variability
properties. This suggests similar continuum origins and variability mechanisms.
Despite their extreme X-ray variability, narrow-line Seyfert 1s (NLS1s) do not
show extreme optical variability.Comment: Invited talk given at Euro Asian Astronomical Society meeting in
Moscow, June 2002. 20 pages, 4 figures. References update
INSURANCE-CONSUMMATION OF THE CONTRACT-DELIVERY OF THE POLICY
An application for life insurance was accepted, and a policy issued, mailed to, and received by the agent of the insurer. The application provided that the policy would not take effect until manual delivery thereof. The agent made several unsuccessful attempts to deliver the policy, but before any physical transmission of the policy, the insured died. The beneficiaries sued to recover the amount of the policy. The trial court gave judgment for the defendant insurance company. On appeal, held, affirmed. Manual delivery was a valid condition precedent. There having been no manual transmission to the insured, and the plaintiffs having failed to sustain the burden of showing that delivery to the agent of the insurer amounted to delivery to the insured, the policy never became effective. Smith v. Rio Grande Nat. Life Ins. Co., (Tex. Civ. App. 1950) 227 S.W. (2d) 579
Setting UBVRI Photometric Zero-Points Using Sloan Digital Sky Survey ugriz Magnitudes
We discuss the use of Sloan Digital Sky Survey (SDSS) ugriz point-spread
function (PSF) photometry for setting the zero points of UBVRI CCD images. From
a comparison with the Landolt (1992) standards and our own photometry we find
that there is a fairly abrupt change in B, V, R, & I zero points around g, r, i
~ 14.5, and in the U zero point at u ~ 16. These changes correspond to where
there is significant interpolation due to saturation in the SDSS PSF fluxes.
There also seems to be another, much smaller systematic effect for stars with
g, r > 19.5. The latter effect is consistent with a small Malmquist bias.
Because of the difficulties with PSF fluxes of brighter stars, we recommend
that comparisons of ugriz and UBVRI photometry should only be made for
unsaturated stars with g, r and i in the range 14.5 - 19.5, and u in the range
16 - 19.5. We give a prescription for setting the UBVRI zero points for CCD
images, and general equations for transforming from ugriz to UBVRI.Comment: 13 pages. 6 figures. Accepted for publication in the Astronomical
Journa
The effectiveness of cognitive analytic therapy for borderline personality disorder : utilizing a withdrawal experimental design to improve sensitivity to abandonment
Objectives
A primary methodological weakness of the single‐case experimental design (SCED) outcome studies conducted of the treatment of personality disorder with cognitive analytic therapy (CAT) is that they have failed to employ a withdrawal phase or cross‐over design and so are deemed quasi‐experimental. This study sought to implement a withdrawal design, in order to improve the internal validity of the study to make it a true SCED, and also in order to enable the patient to explore abandonment dynamics.
Design
The study employed an A1/B1/A2/B2 with extended follow‐up SCED with a female patient treated with CAT meeting diagnostic criteria for borderline personality disorder (BPD). Following the 6‐week baseline period ‘A1’, treatment occurred in two phases (21 sessions ‘B1’ and 24 sessions ‘B2’) sandwiching a 12‐week treatment withdrawal phase (‘A2’) and a 24‐week structured follow‐up phase. Seven idiographic daily measures were collected that created a N = 698 day timeline. Nomothetic outcome measures were collected at baseline and at the end of each phase of the study, and the Session Impact Scale was completed after each treatment session.
Results
There was a significant increase in the task focus of treatment sessions. Ideographically, CAT was an effective treatment for improving the participant’s self‐to‐self relationship, as their self‐hate reduced and their sense‐of‐self increased. There was a broad pattern of deterioration during the second treatment phase (B2) and follow‐up phase across the ideographic measures, and CAT was ineffective for BPD ideographic emotional or self‐to‐other measures. Reliable change occurred on the primary BPD nomothetic outcome measure from baseline to end of first treatment phase.
Conclusions
The study suggests that the CAT intervention was partially successful and that it is possible to integrate good research practice with clinical innovation. The methodological strengths and limitations of the design and the clinical implications of the results are discussed.
Practitioner points
Cognitive analytic therapy was partially effective in the treatment of BPD in a case that had been unresponsive to other psychological interventions.
Therapists need to complete lengthy and structured follow‐up to capture any emerging relapse.
Therapists need to discuss the patient’s thoughts and feelings about termination regularly in a relationally informed manner
On the significance of radiative corrections on measurements of the EMC effect
Analyzing global data on the EMC effect, which denotes differences in parton
distribution functions in nuclei compared to unbound nucleons, reveals
tensions. Precise measurements at Jefferson Lab, studying both x and A
dependence, show systematic discrepancies among experiments, making the
extraction of the A dependence of the EMC effect sensitive to the selection of
datasets. By comparing various methods and assumptions used to calculate
radiative corrections, we have identified differences that, while not large,
significantly impact the EMC ratios and show that using a consistent radiative
correction procedure resolves this discrepancy, leading to a more coherent
global picture, and allowing for a more robust extraction of the EMC effect for
infinite nuclear matter.Comment: 9 pages, 12 figure
The End of the Lines for OX 169: No Binary Broad-Line Region
We show that unusual Balmer emission line profiles of the quasar OX 169,
frequently described as either self-absorbed or double peaked, are actually
neither. The effect is an illusion resulting from two coincidences. First, the
forbidden lines are quite strong and broad. Consequently, the [N II]6583 line
and the associated narrow-line component of H-alpha present the appearance of
twin H-alpha peaks. Second, the redshift of 0.2110 brings H-beta into
coincidence with Na I D at zero redshift, and ISM absorption in Na I D divides
the H-beta emission line. In spectra obtained over the past decade, we see no
substantial change in the character of the line profiles, and no indication of
intrinsic double-peaked structure. The H-gamma, Mg II, and Ly-alpha emission
lines are single peaked, and all of the emission-line redshifts are consistent
once they are correctly attributed to their permitted and forbidden-line
identifications. A systematic shift of up to 700 km/s between broad and narrow
lines is seen, but such differences are common, and could be due to
gravitational and transverse redshift in a low-inclination disk. Stockton &
Farnham (1991) had called attention to an apparent tidal tail in the host
galaxy of OX 169, and speculated that a recent merger had supplied the nucleus
with a coalescing pair of black holes which was now revealing its existence in
the form of two physically distinct broad-line regions. Although there is no
longer any evidence for two broad emission-line regions in OX 169, binary black
holes should form frequently in galaxy mergers, and it is still worthwhile to
monitor the radial velocities of emission lines which could supply evidence of
their existence in certain objects.Comment: 19 pages, 5 figures, accepted for publication in Ap.
Pressure induced structural and dynamical changes in liquid Si. An ab-initio study
The static and dynamic properties of liquid Si at high-pressure have been
studied using the orbital free ab-initio molecular dynamics method. Four
thermodynamic states at pressures 4, 8, 14 and 23 GPa are considered. The
calculated static structure shows qualitative agreement with the available
experimental data. We analize the remarkable structural changes occurring
between 8 and 14 GPa along with its effect on several dynamic properties.Comment: 10 pages, 11 figures. Accepted for publication in Journal of Physics:
Condensed Matte
Historic Farmsteads: Preliminary Character Statement - North East region
This document is one of eight Preliminary Character\ud
Statements, which provide information on the\ud
characteristics of traditional farm buildings in each\ud
Region
- …