2,575 research outputs found
An Introduction to G Methods
Robins' generalized methods (g methods) provide consistent estimates of contrasts (e.g. differences, ratios) of potential outcomes under a less restrictive set of identification conditions than do standard regression methods (e.g. linear, logistic, Cox regression). Uptake of g methods by epidemiologists has been hampered by limitations in understanding both conceptual and technical details. We present a simple worked example that illustrates basic concepts, while minimizing technical complications
Shapecollage: Occlusion-Aware, Example-Based Shape Interpretation
This paper presents an example-based method to interpret a 3D shape from a single image depicting that shape. A major difficulty in applying an example-based approach to shape interpretation is the combinatorial explosion of shape possibilities that occur at occluding contours. Our key technical contribution is a new shape patch representation and corresponding pairwise compatibility terms that allow for flexible matching of overlapping patches, avoiding the combinatorial explosion by allowing patches to explain only the parts of the image they best fit. We infer the best set of localized shape patches over a graph of keypoints at multiple scales to produce a discontinuous shape representation we term a shape collage. To reconstruct a smooth result, we fit a surface to the collage using the predicted confidence of each shape patch. We demonstrate the method on shapes depicted in line drawing, diffuse and glossy shading, and textured styles.National Science Foundation (U.S.) (Grant 1111415)United States. Office of Naval Research (Grant N00014-09-1-1051)National Institutes of Health (U.S.) (Grant R01-EY019262
Nondestructive SEM for surface and subsurface wafer imaging
The scanning electron microscope (SEM) is considered as a tool for both failure analysis as well as device characterization. A survey is made of various operational SEM modes and their applicability to image processing methods on semiconductor devices
The Simplified Geneva Score and the Utilization of the D-Dimer and Computerized Tomography for Assessing Pulmonary Embolism
Background. Pulmonary embolism (PE) is clinically suspected in many patients who complain of shortness of breath or chest pain due to its nonspecific nature. The prevalence of PE, however, is low in this population. To assist physicians in diagnostic decision making, several clinical decision rules (CDR) have been developed. The appropriate use of these CDRs has been proven to decrease the need for expensive, time consuming, and invasive diagnostic imaging procedures. In this study, the appropriateness of D-dimer and CT usage was investigated to rule out pulmonary emboli based on the simplified Geneva score. Methods. A retrospective review was performed on 74 patients with a CT scan ordered through a pulmonary embolism (PE) protocol. Using clinical data, the patients were stratified into âunlikelyâ and âlikelyâ groups for the presence of PE based on the simplification of the revised Geneva score. Scores of 0-2 were graded as âunlikelyâ and scores of 3 or greater were âlikely.â Results. There were 45/74 (60.8%) patients in the âunlikelyâ group. Of these, 14/45 (31.1%) received a D-dimer; eight were normal and six elevated. Only one patient in the elevated group had evidence of a PE. Of the remaining 31(39.2%) patients in the âunlikelyâ group that did not receive a D-dimer, only one had a PE. The âlikelyâ group consisted of 29 (39.2%) patients of whom six received a D-dimer. Three patients had a normal D-dimer and three had an elevated level. Neither of these two groups had a PE. Of the remaining 23 (60.8%) in the âlikelyâ group who did not receive a D-dimer, six had a PE. Conclusions. Diagnosing pulmonary emboli using D-dimer levels and CT scans may be aided by clinical decision rules such as the simplified Geneva system. This process may lead to more effective use of medical resources
On Star Formation and the Non-Existence of Dark Galaxies
We investigate whether a baryonic dark galaxy or `galaxy without stars' could
persist indefinitely in the local universe, while remaining stable against star
formation. To this end, a simple model has been constructed to determine the
equilibrium distribution and composition of a gaseous protogalactic disk.
Specifically, we determine the amount of gas that will transit to a Toomre
unstable cold phase via the H2 cooling channel in the presence of a UV--X-ray
cosmic background radiation field.
All but one of the models are predicted to become unstable to star formation.
Moreover, we find that all our model objects would be detectable via HI line
emission, even in the case that star formation is potentially avoided. These
results are consistent with the non-detection of isolated extragalactic HI
clouds with no optical counterpart (galaxies without stars) by HIPASS.
Additionally, where star formation is predicted to occur, we determine the
minimum interstellar radiation field required to restore gravothermal
stability, which we then relate to a minimum global star formation rate. This
leads to the prediction of a previously undocumented relation between HI mass
and star formation rate that is observed for a wide variety of dwarf galaxies
in the HI mass range 10^8--10^10 M_sun. The existence of such a relation
strongly supports the notion that the well observed population of dwarf
galaxies represent the minimum rates of self-regulating star formation in the
universe. (Barely abridged)Comment: 19 pages, 8 figures, TeX using emulateapj.cls, v2 accepted for
publication in ApJ (16/8/5) with one figure deleted and a number of minor
clarifying revision
Food Distribution and Consumption in Knoxville: Exploring Food-Related Local Planning Issues
Summary:
City planners have traditionally made an effort to understand the interrelationships between urban activities and various support systems, such as transportation, water and sewer, waste management, communications and energy. Food is also an important urban support system with a complex system of supply, distribution, and consumption. An understanding of the nature of the food supply and distribution system seems important, but in the past has not been an area of concern for the planning profession. It was the intent of this project to develop a basis from which to seek an understanding of the Knoxville food support system and its implications for local planning policy in Knoxville.
The thrust of the study was three-fold. First, food-related problems and issues were identified. Then, further work was undertaken in order to propose remedial measures or public programs that might be initiated by local units of government. Finally, the group considered the possibility of establishing some kind of public oversight of the local food supply and distribution function. The approach has been general and comprehensive. One assumption here is that before public action can be initiated, those with responsibility for maintaining the public interest must understand the system. Thus, an analysis which would describe the system comprehensively, while allowing an opportunity to detect interrelationships among system components, was utilized.
Patterns of consumption, food services and programs, and marketing channels by food types were also explored. The development of information involves consultation with literature, academicians, public officials, and industry representatives
Microgeometry capture using an elastomeric sensor
We describe a system for capturing microscopic surface geometry. The system extends the retrographic sensor [Johnson and Adelson 2009] to the microscopic domain, demonstrating spatial resolution as small as 2 microns. In contrast to existing microgeometry capture techniques, the system is not affected by the optical characteristics of the surface being measured---it captures the same geometry whether the object is matte, glossy, or transparent. In addition, the hardware design allows for a variety of form factors, including a hand-held device that can be used to capture high-resolution surface geometry in the field. We achieve these results with a combination of improved sensor materials, illumination design, and reconstruction algorithm, as compared to the original sensor of Johnson and Adelson [2009].National Science Foundation (U.S.) (Grant 0739255)National Institutes of Health (U.S.) (Contract 1-R01-EY019292-01
Mitochondria in epithelial ovarian carcinoma exhibit abnormal phenotypes and blunted associations with biobehavioral factors
Malignant tumor cells exhibit mitochondrial alterations and are also influenced by biobehavioral processes, but the intersection of biobehavioral factors and mitochondria in malignant tumors remains unexplored. Here we examined multiple biochemical and molecular markers of mitochondrial content and function in benign tissue and in high-grade epithelial ovarian carcinoma (EOC) in parallel with exploratory analyses of biobehavioral factors. First, analysis of a publicly-available database (nâ=â1435) showed that gene expression of specific mitochondrial proteins in EOC is associated with survival. Quantifying multiple biochemical and molecular markers of mitochondrial content and function in tissue from 51 patients with benign ovarian masses and 128 patients with high-grade EOC revealed that compared to benign tissue, EOCs exhibit 3.3â8.4-fold higher mitochondrial content and respiratory chain enzymatic activities (Pâ<â0.001) but similar mitochondrial DNA (mtDNA) levels (ââ3.1%), documenting abnormal mitochondrial phenotypes in EOC. Mitochondrial respiratory chain activity was also associated with interleukin-6 (IL-6) levels in ascites. In benign tissue, negative biobehavioral factors were inversely correlated with mitochondrial content and respiratory chain activities, whereas positive biobehavioral factors tended to be positively correlated with mitochondrial measures, although effect sizes were small to medium (râ=âââ0.43 to 0.47). In contrast, serous EOCs showed less pronounced biobehavioral-mitochondrial correlations. These results document abnormal mitochondrial functional phenotypes in EOC and warrant further research on the link between biobehavioral factors and mitochondria in cancer
Another intermediate mass black hole in a starburst galaxy?: The luminous X-ray source in NGC 3628 reappears
In a 52 ks-long Chandra ACIS-S observation of the nearby starburst galaxy NGC
3628, obtained to study the starburst-driven outflow from this galaxy, we have
detected a very luminous (L_X = 1.1e40 erg/s in the 0.3-8.0 keV energy band)
point source located at least 20 arcsec (~970 pc) from the nucleus of the
galaxy. No radio, optical or near-IR counterpart to this source has been found.
This is most probably the reappearance of the strongly-variable
X-ray-luminous source discovered by Dahlem et al (1995), which faded by a
factor >27 between December 1991 and March 1994 (at which point it had faded
below the detection limit in a ROSAT HRI observation). This source is clearly a
member of an enigmatic class of X-ray sources that are considerably more
luminous than conventional X-ray binaries but less luminous than AGN, and which
are not found at the dynamical center of the host galaxy.
The Chandra spectrum is best-fit by an absorbed power law model with a photon
index of Gamma = 1.8+/-0.2, similar to that seen in Galactic BH binary
candidates in their hard state. Bremsstrahlung models or multi-color disk
models (the favored spectral model for objects in this class based on ASCA
observations) can provide statistically acceptable fits only if the data at
energies E > 5 keV is ignored. This is one of the first X-ray spectra of such
an object that is unambiguously that of the source alone, free from the
spectral contamination by X-ray emission from the rest of the galaxy that
affects previous spectral studies of these objects using ASCA.Comment: Accepted for publication in the Ap
Alinhamento interpessoal, representacional e morfossintĂĄtico na GramĂĄtica Discursivo-Funcional
Este artigo se debruça sobre o mapeamento entre os NĂveis Interpessoal, Representacional e MorfossintĂĄtico da gramĂĄtica, o chamado alinhamento, segundo o arcabouço da GramĂĄtica Discursivo-Funcional (GDF). PropĂ”e uma tipologia das lĂnguas baseada no que a sua organização morfossintĂĄtica codifica: distinçÔes pragmĂĄticas (p.ex. em Tagalo), distinçÔes semĂąnticas (p.ex. em AchĂ©m), ou distinçÔes inerentes Ă morfossintaxe (p.ex. em InglĂȘs, Basco ou a lĂngua Kham). A inclusĂŁo tanto do Sujeito como do Objeto e de lĂnguas tanto acusativas como ergativas no tratamento do alinhamento morfossintĂĄtico permitiu-nos abranger tipos tipologicamente mais variĂĄveis e demonstrar o potencial da GDF para a anĂĄlise contrastiva das lĂnguas.<br>Within the framework of Functional Discourse Grammar (FDG), alignment concerns the relations between the Interpersonal, Representational and Morphosyntactic Levels of grammar. This article proposes a typology of languages based upon what we find to be encoded in their morphosyntactic organization: pragmatic distinctions (as in Tagalog), semantic distinctions (as in Acheh), or distinctions inherent to the morphosyntax (as in English, Basque and Kham). By including both subject and object, and both accusative and ergative languages in our treatment of morphosyntactic alignment, we provide a better coverage of typological variation and show the potential of FDG for cross-linguistic analysis
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