7,942 research outputs found
Spatio-Temporal Low Count Processes with Application to Violent Crime Events
There is significant interest in being able to predict where crimes will
happen, for example to aid in the efficient tasking of police and other
protective measures. We aim to model both the temporal and spatial dependencies
often exhibited by violent crimes in order to make such predictions. The
temporal variation of crimes typically follows patterns familiar in time series
analysis, but the spatial patterns are irregular and do not vary smoothly
across the area. Instead we find that spatially disjoint regions exhibit
correlated crime patterns. It is this indeterminate inter-region correlation
structure along with the low-count, discrete nature of counts of serious crimes
that motivates our proposed forecasting tool. In particular, we propose to
model the crime counts in each region using an integer-valued first order
autoregressive process. We take a Bayesian nonparametric approach to flexibly
discover a clustering of these region-specific time series. We then describe
how to account for covariates within this framework. Both approaches adjust for
seasonality. We demonstrate our approach through an analysis of weekly reported
violent crimes in Washington, D.C. between 2001-2008. Our forecasts outperform
standard methods while additionally providing useful tools such as prediction
intervals
Extragalactic Radio Sources and the WMAP Cold Spot
We detect a dip of 20-45% in the surface brightness and number counts of NVSS
sources smoothed to a few degrees at the location of the WMAP cold spot. The
dip has structure on scales of approximately 1-10 degrees. Together with
independent all-sky wavelet analyses, our results suggest that the dip in
extragalactic brightness and number counts and the WMAP cold spot are
physically related, i.e., that the coincidence is neither a statistical anomaly
nor a WMAP foreground correction problem. If the cold spot does originate from
structures at modest redshifts, as we suggest, then there is no remaining need
for non-Gaussian processes at the last scattering surface of the CMB to explain
the cold spot. The late integrated Sachs-Wolfe effect, already seen
statistically for NVSS source counts, can now be seen to operate on a single
region. To create the magnitude and angular size of the WMAP cold spot requires
a ~140 Mpc radius completely empty void at z<=1 along this line of sight. This
is far outside the current expectations of the concordance cosmology, and adds
to the anomalies seen in the CMB.Comment: revised version, ApJ, in pres
Influence network linkages across implementation strategy conditions in a randomized controlled trial of two strategies for scaling up evidence-based practices in public youth-serving systems.
BackgroundGiven the importance of influence networks in the implementation of evidence-based practices and interventions, it is unclear whether such networks continue to operate as sources of information and advice when they are segmented and disrupted by randomization to different implementation strategy conditions. The present study examines the linkages across implementation strategy conditions of social influence networks of leaders of youth-serving systems in 12 California counties participating in a randomized controlled trial of community development teams (CDTs) to scale up use of an evidence-based practice.MethodsSemi-structured interviews were conducted with 38 directors, assistant directors, and program managers of county probation, mental health, and child welfare departments. A web-based survey collected additional quantitative data on information and advice networks of study participants. A mixed-methods approach to data analysis was used to create a sociometric data set (n = 176) to examine linkages between treatment and standard conditions.ResultsOf those network members who were affiliated with a county (n = 137), only 6 (4.4%) were directly connected to a member of the opposite implementation strategy condition; 19 (13.9%) were connected by two steps or fewer to a member of the opposite implementation strategy condition; 64 (46.7%) were connected by three or fewer steps to a member of the opposite implementation strategy condition. Most of the indirect steps between individuals who were in different implementation strategy conditions were connections involving a third non-county organizational entity that had an important role in the trial in keeping the implementation strategy conditions separate. When these entities were excluded, the CDT network exhibited fewer components and significantly higher betweenness centralization than did the standard condition network.ConclusionAlthough the integrity of the RCT in this instance was not compromised by study participant influence networks, RCT designs should consider how influence networks may extend beyond boundaries established by the randomization process in implementation studies.Trial registrationNCT00880126
Assessment by finite element analysis of the impact of osteoporosis and osteoarthritis on hip resurfacing
Hip resurfacing is proposed as an alternative to total hip replacement (THR) for treatment of osteoarthritis (OA), especially for younger, heavier and more active sufferers. There is however, concern with regards to the incidence of post operative femoral neck fractures. We have investigated, with finite element models, the changes in stress and strain in the femoral neck following hip resurfacing. We have included several different bone material property values representing normal, elderly, osteoarthritic and osteoporotic bone. We have also modelled two different hip implant orientations. We have shown that hip resurfacing may increase the magnitude of stress and strain in the femoral neck, especially in osteoporotic bone. We have also shown that the superolateral offset associated with the valgus orientation, not the valgus orientation itself, may be what reduces the stress and strain in the neck and leads to lower incidence of fracture
Statistical Inference After Model Selection
Conventional statistical inference requires that a model of how the data were generated be known before the data are analyzed. Yet in criminology, and in the social sciences more broadly, a variety of model selection procedures are routinely undertaken followed by statistical tests and confidence intervals computed for a “final” model. In this paper, we examine such practices and show how they are typically misguided. The parameters being estimated are no longer well defined, and post-model-selection sampling distributions are mixtures with properties that are very different from what is conventionally assumed. Confidence intervals and statistical tests do not perform as they should. We examine in some detail the specific mechanisms responsible. We also offer some suggestions for better practice and show though a criminal justice example using real data how proper statistical inference in principle may be obtained
Playful Pigs: Evidence of consistency and change in play depending on litter and developmental stage
Pathogenic, Molecular, and Immunological Properties of a Virus Associated with Sea Turtle Fibropapillomatosis. Phase II : Viral Pathogenesis and Development of Diagnostic Assays
Research conducted under this RWO from July 1, 1997 through June 30, 2000 has
provided important new information about the pathogenesis, virology, and
immunology of marine turtle fibropapillomatosis. In particular, we have provided
strong evidence for the association of a herpesvirus with fibropapillomatosis of the
green turtle,Chelonia mydas, and the loggerhead turtle, Caretta caretta, in Florida. In
addition we have provided new evidence for the absence of papillomaviruses from
sea turtle fibropapillomas. Although unsuccessful, important new attempts were made
to cultivate the FP-associated herpesvirus in vitro in collaboration with the National
Wildlife Health Center. During this period of time, we completed publication of the first
comprehensive description of the comparative pathology and pathogenesis of
experimentally induced and spontaneous fibropapillomas of green turtles (Chelonia
mydas). We initiated innovative studies on the persistence of a Chelonian
herpesviruses in the marine environment demonstrating for the first time that the
environmental survivability of Chelonian herpesviruses makes them real threats to
marine turtle health. Finally, we explored development of a serological assay for FP
using synthetic herpesvirus peptides and developed methodologies for detection of
antibodies to LETV [Iung-eye-trachea virus] a disease-associated herpesvirus of the
green turtle, Chelonia mydas.. This last initiative is ongoing and will further our efforts
to develop specific immunological assays for the FP-associated herpesvirus and FP. (17 page document
SDSS J013655.91+242546.0 - an A-type hyper-velocity star from the outskirts of the Galaxy
Hyper-velocity stars (HVS) are moving so fast that they are unbound to the
Galaxy. Dynamical ejection by a supermassive black hole is favoured to explain
their origin. Locating the place of birth of an individual HVS is of utmost
importance to understanding the ejection mechanism. SDSS J013655.91+242546.0
(J0136+2425 for short) was found amongst three high-velocity stars (drawn from
a sample of more than 10000 blue stars), for which proper motions were
measured. A kinematical as well as a quantitative NLTE spectral analysis was
performed. When combined with the radial velocity (RV) and the spectroscopic
distance, the trajectory of the star in the Galactic potential was
reconstructed. J0136+2425 is found to be an A-type main-sequence star
travelling at 590 \kms, possibly unbound to the Galaxy and originating
in the outer Galactic rim nowhere near the Galactic centre. J0136+2425 is the
second HVS candidate with measured proper motion, besides the massive B star HD
271791, and also the second for which its proper motion excludes a Galactic
centre origin and, hence, the SMBH slingshot mechanism. Most known HVS are late
B-type stars of about 3 M. With a mass of 2.45 M, J0136+2425
resembles a typical HVS far more than HD 271791 does. Hence, this is the first
time that a typical HVS is found not to originate in the Galactic centre. Its
ejection velocity from the disk is so high (550 \kms) that the extreme
supernova binary scenario proposed for HD 271791 is very unlikely.Comment: 4 pages, 5 figures, accepted for publication in A&
Shwartzman reaction after human renal homotransplantation.
In three human recipients, five renal homografts were destroyed within a few minutes to hours after their revascularization in the new host. The kidneys, removed one to 54 days later, had cortical necrosis. The major vessels were patent, but the arterioles and glomeruli were the site of fibrin deposition. There was little or no fixation of host immunoglobulins in the homografts. The findings were characteristic of a generalized Shwartzman reaction. Although the cause (or causes) of the Shwartzman reaction in our patients is not known, they may have been conditioned by the bacterial contamination and hemolysis that often attend hemodialysis, by immunosuppression and by the transplantation itself. Some of the patients have preformed lymphocytotoxic antibodies. Thus, certain patients may be predisposed. High-risk patients should be recognized and treated prophylactically with anticoagulants
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