2,885 research outputs found
Preliminary Results of the Louisiana Sex Offender Treatment Program
The purpose of this study was to offer preliminary support for the Louisiana Sex Offender Treatment Program (LSOTP) in addressing the needs of juvenile sex offenders. Research objectives were (1) to offer statistical evidence for reductions in anxiety, depression, cognitive distortion and negative attitudes towards women comparing a group of 21 adolescents, 12 of whom received services as usual and nine of whom participated in the LSOTP. A controlled experimental evaluation design was utilized. The juvenile sex offenders were randomly assigned to the experimental group for 12 weeks receiving treatment services and a control group receiving care “as usual” in a residential group care program. Participants in the experimental group experienced statistically significant decreases in cognitive distortions related specifically to rape and molestation.The results of this study offer preliminary support of the LSOTP as a best practices alternative to other treatment modalities
The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
Understanding the relationship between the magnetic field and coronal heating
is one of the central problems of solar physics. However, studies of the
magnetic properties of impulsively heated loops have been rare. We present
results from a study of 34 evolving coronal loops observed in the Fe XVIII line
component of AIA/SDO 94 A filter images from three active regions with
different magnetic conditions. We show that the peak intensity per unit
cross-section of the loops depends on their individual magnetic and geometric
properties. The intensity scales proportionally to the average field strength
along the loop () and inversely with the loop length () for a
combined dependence of . These loop properties are
inferred from magnetic extrapolations of the photospheric HMI/SDO line-of-sight
and vector magnetic field in three approximations: potential and two Non Linear
Force-Free (NLFF) methods. Through hydrodynamic modeling (EBTEL model) we show
that this behavior is compatible with impulsively heated loops with a
volumetric heating rate that scales as .Comment: Astrophysical Journal, in pres
High-resolution 3D weld toe stress analysis and ACPD method for weld toe fatigue crack initiation
Weld toe fatigue crack initiation is highly dependent on the local weld toe stress-concentrating geometry including any inherent flaws. These flaws are responsible for premature fatigue crack initiation (FCI) and must be minimised to maximise the fatigue life of a welded joint. In this work, a data-rich methodology has been developed to capture the true weld toe geometry and resulting local weld toe stress-field and relate this to the FCI life of a steel arc-welded joint. To obtain FCI lives, interrupted fatigue test was performed on the welded joint monitored by a novel multi-probe array of alternating current potential drop (ACPD) probes across the weld toe. This setup enabled the FCI sites to be located and the FCI life to be determined and gave an indication of early fatigue crack propagation rates. To understand fully the local weld toe stress-field, high-resolution (5 mu m) 3D linear-elastic finite element (FE) models were generated from X-ray micro-computed tomography (mu-CT) of each weld toe after fatigue testing. From these models, approximately 202 stress concentration factors (SCFs) were computed for every 1 mm of weld toe. These two novel methodologies successfully link to provide an assessment of the weld quality and this is correlated with the fatigue performance
Transition region and chromospheric signatures of impulsive heating events. II. Modeling
Results from the Solar Maximum Mission showed a close connection between the hard X-ray (HXR) and transition
region (TR) emission in solar flares. Analogously, the modern combination of RHESSI and IRIS data can inform
the details of heating processes in ways that were never before possible. We study a small event that was observed
with RHESSI, IRIS, SDO, and Hinode, allowing us to strongly constrain the heating and hydrodynamical properties
of the flare, with detailed observations presented in a previous paper. Long duration redshifts of TR lines observed
in this event, as well as many other events, are fundamentally incompatible with chromospheric condensation on a
single loop. We combine RHESSI and IRIS data to measure the energy partition among the many magnetic strands
that comprise the flare. Using that observationally determined energy partition, we show that a proper
multithreaded model can reproduce these redshifts in magnitude, duration, and line intensity, while simultaneously
being well constrained by the observed density, temperature, and emission measure. We comment on the
implications for both RHESSI and IRIS observations of flares in general, namely that: (1) a single loop model is
inconsistent with long duration redshifts, among other observables; (2) the average time between energization of
strands is less than 10 s, which implies that for a HXR burst lasting 10 minutes, there were at least 60 strands
within a single IRIS pixel located on the flare ribbon; (3) the majority of these strands were explosively heated with
an energy distribution well described by a power law of slope »-1.6; (4) the multi-stranded model reproduces the
observed line profiles, peak temperatures, differential emission measure distributions, and densities
Nonparametric Tests for Treatment Effect Heterogeneity
A large part of the recent literature on program evaluation has focused on estimation of the average effect of the treatment under assumptions of unconfoundedness or ignorability following the seminal work by Rubin (1974) and Rosenbaum and Rubin (1983). In many cases however, researchers are interested in the effects of programs beyond estimates of the overall average or the average for the subpopulation of treated individuals. It may be of substantive interest to investigate whether there is any subpopulation for which a program or treatment has a nonzero average effect, or whether there is heterogeneity in the effect of the treatment. The hypothesis that the average effect of the treatment is zero for all subpopulations is also important for researchers interested in assessing assumptions concerning the selection mechanism. In this paper we develop two nonparametric tests. The first test is for the null hypothesis that the treatment has a zero average effect for any subpopulation defined by covariates. The second test is for the null hypothesis that the average effect conditional on the covariates is identical for all subpopulations, in other words, that there is no heterogeneity in average treatment effects by covariates. Sacrificing some generality by focusing on these two specific null hypotheses we derive tests that are straightforward to implement.average treatment effects, causality, unconfoundedness, treatment effect heterogeneity
Moving the Goalposts: Addressing Limited Overlap in the Estimation of Average Treatment Effects by Changing the Estimand
Estimation of average treatment effects under unconfoundedness or exogenous treatment assignment is often hampered by lack of overlap in the covariate distributions. This lack of overlap can lead to imprecise estimates and can make commonly used estimators sensitive to the choice of specification. In such cases researchers have often used informal methods for trimming the sample. In this paper we develop a systematic approach to addressing such lack of overlap. We characterize optimal subsamples for which the average treatment effect can be estimated most precisely, as well as optimally weighted average treatment effects. Under some conditions the optimal selection rules depend solely on the propensity score. For a wide range of distributions a good approximation to the optimal rule is provided by the simple selection rule to drop all units with estimated propensity scores outside the range [0.1,0.9].
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