4,327 research outputs found
Simulation Approach to Assess the Precision of Estimates Derived from Linking Survey and Administrative Records
Probabilistic record linkage implies that there is some level of uncertainty related to the classification of pairs as links or non-links vis-à-vis their true match status. As record linkage is usually performed as a preliminary step to developing statistical estimates, the question then is how does this linkage uncertainty propagate to them? In this paper, we develop an approach to estimate the impact of linkage uncertainty on derived estimates by using a re-sampling approach. For each iteration of the re-sampling, pairs are classified as links or non-links by Monte-Carlo assignment to model estimated true match probabilities. By looking at the range of estimates produced in a series of re-samples, we can estimate the distribution of derived statistics under the prevailing incidence of linkage uncertainty. For this analysis we use the results of linking the 2014 National Hospital Care Survey to the National Death Index performed at the National Center for Health Statistics. We assess the precision of hospital-level death rate estimates
Rotator Cuff Disease
Shoulder pain is a common clinical presentation. Though the spectrum of disorders affecting the shoulder is quite diverse, emphasis is often placed on abnormalities of the rotator cuff and glenohumeral joint instability. The rotator cuff plays an important role in both the function and stability of the shoulder. Moreover, its pathology, with early and accurate diagnosis, is amenable to treatment, which can markedly affect patient outcome. This unit presents an MR imaging protocol for evaluation of the glenohumeral joint. Though specific emphasis is placed on the rotator cuff, it can also be used for global assessment of the shoulder.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145303/1/cpmia2201.pd
MR Arthrography of Shoulder
The glenohumeral joint boasts the greatest range of motion of any peripheral joint in the body, but not without cost; it is also the most frequently dislocated joint in the body. Stability of this articulation is limited for two major reasons. The articulating surface of the glenoid is significantly smaller than that of the humeral head, and the joint capsule is redundant and provides little support. This unit presents a basic MR arthrography protocol for evaluation of glenohumeral joint instability.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145405/1/cpmia2202.pd
Metastatic Malignant Melanoma Presenting as an Appendiceal Mucocele
Melanoma metastatic to the appendix is extremely rare. Here we describe a case of a 31-year-old female from Bolivia with a remote history of metastatic malignant melanoma first diagnosed as a cutaneous malignant melanoma ten years prior to this presentation. The patient was being followed for a mucocele which on resection was found to be metastatic melanoma. “Mucocele” is a generic diagnosis that warrants further characterization and treatment
Analyzing the Bitcoin Ponzi Scheme Ecosystem
This paper analyzes the supply and demand for Bitcoinbased Ponzi schemes. There are a variety of these types of scams: from
long cons such as Bitcoin Savings & Trust to overnight doubling schemes
that do not take off. We investigate what makes some Ponzi schemes successful and others less so. By scouring 11 424 threads on bitcointalk.org,
we identify 1 780 distinct scams. Of these, half lasted a week or less.
Using survival analysis, we identify factors that affect scam persistence.
One approach that appears to elongate the life of the scam is when the
scammer interacts a lot with their victims, such as by posting more than
a quarter of the comments in the related thread. By contrast, we also find
that scams are shorter-lived when the scammers register their account on
the same day that they post about their scam. Surprisingly, more daily
posts by victims is associated with the scam ending sooner
Heat Conduction Process on Community Networks as a Recommendation Model
Using heat conduction mechanism on a social network we develop a systematic
method to predict missing values as recommendations. This method can treat very
large matrices that are typical of internet communities. In particular, with an
innovative, exact formulation that accommodates arbitrary boundary condition,
our method is easy to use in real applications. The performance is assessed by
comparing with traditional recommendation methods using real data.Comment: 4 pages, 2 figure
Bayesian Networks for Max-linear Models
We study Bayesian networks based on max-linear structural equations as
introduced in Gissibl and Kl\"uppelberg [16] and provide a summary of their
independence properties. In particular we emphasize that distributions for such
networks are generally not faithful to the independence model determined by
their associated directed acyclic graph. In addition, we consider some of the
basic issues of estimation and discuss generalized maximum likelihood
estimation of the coefficients, using the concept of a generalized likelihood
ratio for non-dominated families as introduced by Kiefer and Wolfowitz [21].
Finally we argue that the structure of a minimal network asymptotically can be
identified completely from observational data.Comment: 18 page
Method for fabricating a low stress x-ray mask using annealable amorphous refractory compounds
X‐ray masks have been fabricated by depositing a compressively stressed refractory material on a wafer, annealing to a zero stress state, and then forming the membrane. Amorphous TaSiN and TaSi alloys deposited with a magnetron sputter tool have been extensively characterized in terms of resistivity, composition, defectivity, surface roughness, and crystalline state. Optimization in terms of these parameters has resulted in base line selection of absorber films of the following compositions: Ta_(61)Si_(17)N_(21) and Ta_(75)Si_(23). The process is shown to be extendable to an entire class of amorphous annealable refractory materials. Careful studies of deposition and annealing conditions have resulted in a 4× reduction of image placement to the 30 nm maximum vector level. Finally, the importance of stress gradients is experimentally verified
Corrections to the Central Limit Theorem for Heavy-Tailed Probability Densities
Classical Edgeworth expansions provide asymptotic correction terms to the
Central Limit Theorem (CLT) up to an order that depends on the number of
moments available. In this paper, we provide subsequent correction terms beyond
those given by a standard Edgeworth expansion in the general case of regularly
varying distributions with diverging moments (beyond the second). The
subsequent terms can be expressed in a simple closed form in terms of certain
special functions (Dawson's integral and parabolic cylinder functions), and
there are qualitative differences depending on whether the number of moments
available is even, odd or not an integer, and whether the distributions are
symmetric or not. If the increments have an even number of moments, then
additional logarithmic corrections must also be incorporated in the expansion
parameter. An interesting feature of our correction terms for the CLT is that
they become dominant outside the central region and blend naturally with known
large-deviation asymptotics when these are applied formally to the spatial
scales of the CLT
M/M/ queues in semi-Markovian random environment
In this paper we investigate an M/M/ queue whose parameters depend on
an external random environment that we assume to be a semi-Markovian process
with finite state space. For this model we show a recursive formula that allows
to compute all the factorial moments for the number of customers in the system
in steady state. The used technique is based on the calculation of the raw
moments of the measure of a bidimensional random set. Finally the case when the
random environment has only two states is deeper analyzed. We obtain an
explicit formula to compute the above mentioned factorial moments when at least
one of the two states has sojourn time exponentially distributed.Comment: 17 pages, 2 figure
- …