Comparison between multiplanar and rendering modes in the assessment of fetal atrioventricular valve areas by 3D/4D ultrasonography

Objective: To compare the agreement of multiplanar and rendering modes in the assessment fetal atrioventricular valves (mitral and tricuspid) areas by three-dimensional (3D) ultrasonography using the software spatio-temporal image correlation (STIC). Methods: We conducted a prospective cross-sectional study with normal pregnant women, with single fetuses, between 18-33 weeks. To measure the areas, we used the plan of four-chamber view. In the case of multiplanar, the plane was rotated on the axis "Z" form the heart to position at 9h. For rendering, the green line (region of interest - ROI) was placed from the atria of the heart perpendicular to the crux. The agreement was assessed by a Bland-Altman (limits of agreement) using the relative difference between the measures: ((rendering mode) - (multiplanar mode)) / (average). Results: 328 fetuses were evaluated. We have not identified the occurrence of systematic error between methods: the average relative difference was 1.62% (-2.07% to 5.32%, confidence interval 95%) in the mitral and 1.77% (- 1.08% to 4.62%) in the tricuspid valve. The limits of agreement between methods were -65.26% to 68.51% for the mitral and -49.91% to 53.45% for the tricuspid. Conclusions: There was no systematic error between modes and thus the observed values for the area of fetal atrioventricular valves can be used for comparisons needs to be corrected. However, relatively large variations may be observed when repeating the measurement area by different modes.

A palaeobiologist's guide to 'virtual' micro-CT preparation

This paper provides a brief but comprehensive guide to creating, preparing and dissecting a 'virtual' fossil, using a worked example to demonstrate some standard data processing techniques. Computed tomography (CT) is a 3D imaging modality for producing 'virtual' models of an object on a computer. In the last decade, CT technology has greatly improved, allowing bigger and denser objects to be scanned increasingly rapidly. The technique has now reached a stage where systems can facilitate large-scale, non-destructive comparative studies of extinct fossils and their living relatives. Consequently the main limiting factor in CT-based analyses is no longer scanning, but the hurdles of data processing (see disclaimer). The latter comprises the techniques required to convert a 3D CT volume (stack of digital slices) into a virtual image of the fossil that can be prepared (separated) from the matrix and 'dissected' into its anatomical parts. This technique can be applied to specimens or part of specimens embedded in the rock matrix that until now have been otherwise impossible to visualise. This paper presents a suggested workflow explaining the steps required, using as example a fossil tooth of Sphenacanthus hybodoides (Egerton), a shark from the Late Carboniferous of England. The original NHMUK copyrighted CT slice stack can be downloaded for practice of the described techniques, which include segmentation, rendering, movie animation, stereo-anaglyphy, data storage and dissemination. Fragile, rare specimens and type materials in university and museum collections can therefore be virtually processed for a variety of purposes, including virtual loans, website illustrations, publications and digital collections. Micro-CT and other 3D imaging techniques are increasingly utilized to facilitate data sharing among scientists and on education and outreach projects. Hence there is the potential to usher in a new era of global scientific collaboration and public communication using specimens in museum collections.

Insights into the morphology of the Serra da Cangalha impact structure from geophysical modeling

Forward modeling is commonly applied to gravity field data of impact structures to determine the main gravity anomaly sources. In this context, we have developed 2.5-D gravity models of the Serra da Cangalha impact structure for the purpose of investigating geological bodies/structures underneath the crater. Interpretation of the models was supported by ground magnetic data acquired along profiles, as well as by high resolution aeromagnetic data. Ground magnetic data reveal the presence of short-wavelength anomalies probably related to shallow magnetic sources that could have been emplaced during the cratering process. Aeromagnetic data show that the basement underneath the crater occurs at an average depth of about 1.9 km, whereas in the region beneath the central uplift it is raised to 0.51 km below the current surface. These depths are also supported by 2.5-D gravity models showing a gentle relief for the basement beneath the central uplift area. Geophysical data were used to provide further constraints for numeral modeling of crater formation that provided important information on the structural modification that affected the rocks underneath the crater, as well as on shock-induced modifications of target rocks. The results showed that the morphology is consistent with the current observations of the crater and that Serra da Cangalha was formed by a meteorite of approximately 1.4 km diameter striking at 12 km s-1.

Modeling the gluon propagator in Landau gauge: Lattice estimates of pole masses and dimension-two condensates

We present an analytic description of numerical results for the Landau-gauge SU(2) gluon propagator D(p(2)), obtained from lattice simulations (in the scaling region) for the largest lattice sizes to date, in d = 2, 3 and 4 space-time dimensions. Fits to the gluon data in 3d and in 4d show very good agreement with the tree-level prediction of the refined Gribov-Zwanziger (RGZ) framework, supporting a massive behavior for D(p(2)) in the infrared limit. In particular, we investigate the propagator's pole structure and provide estimates of the dynamical mass scales that can be associated with dimension-two condensates in the theory. In the 2d case, fitting the data requires a noninteger power of the momentum p in the numerator of the expression for D(p(2)). In this case, an infinite-volume-limit extrapolation gives D(0) = 0. Our analysis suggests that this result is related to a particular symmetry in the complex-pole structure of the propagator and not to purely imaginary poles, as would be expected in the original Gribov-Zwanziger scenario.

Complex, 3D strain patterns in a synkinematic tonalite batholith from the Aracuai Neoproterozoic orogen (Eastern Brazil): Evidence from combined magnetic and isotopic chronology studies

This work combines structural and geochronological data to improve our understanding of the mechanical behaviour of continental crust involving large amount of magma or partially melted material in an abnormally hot collisional belt. We performed a magnetic and geochronological (U/Pb) study on a huge tonalitic batholith from the Neoproterozoic Aracual belt of East Brazil to determine the strain distribution through space and time. Anisotropy of magnetic susceptibility, combined with rock magnetism investigations, supports that the magnetic fabric is a good proxy of the structural fabric. Field measurements together with the magnetic fabrics highlight the presence in the batholith of four domains characterized by contrasted magmatic flow patterns. The western part is characterized by a gently dipping, orogen-parallel (similar to NS) magmatic foliation that bears down-dip lineations, in agreement with westward thrusting onto the Sao Francisco craton. Eastward, the magmatic foliation progressively turns sub-vertical with a lineation that flips from sub-horizontal to sub-vertical over short distances. This latter domain involves an elongated corridor in which the magmatic foliation is sub-horizontal and bears an orogen-parallel lineation. Finally the fourth, narrow domain displays sub-horizontal lineations on a sub-vertical magmatic foliation oblique (similar to N150 degrees E) to the trend of the belt. U/Pb dating of zircons from the various domains revealed homogeneity in age for all samples. This, together with the lack of solid-state deformation suggests that: 1) the whole batholith emplaced during a magmatic event at similar to 580 Ma, 2) the deformation occurred before complete solidification. and 3) the various fabrics are roughly contemporaneous. The complex structural pattern mapped in the studied tonalitic batholith suggests a 3D deformation of a slowly cooling, large magmatic body and its country rock. We suggest that the development of the observed 3D flow field was promoted by the low viscosity of the middle crust that turned gravitational force as an active tectonic force combining with the East-West convergence between the Sao Francisco and Congo cratons. (C) 2012 Elsevier Ltd. All rights reserved.