Computerized axial tomographic reconstruction of coronary tree cross sections from a small number of cineradiographic views

Three-dimensional reconstruction of the coronary tree from a conventional cineangiographic study is limited, in part, by the small number of available cineangiographic views. The potential utility of a maximum entropy iterative algorithm (MENT) for reconstruction of myocardial planes perpendicular to the axis of cineangiographic rotation from a small number (n = 6-18) of cineangiographic views was tested in vitro. The coronary arteries of postmortem human, canine, and calf hearts were filled with a silicone/thorium oxide mold to simulate in vivo angiographic contrast. Thirty-five-millimeter cineradiographs of each heart were obtained at 10 degrees intervals over 180 degrees about a myocardial central axis of rotation under exposure conditions which simulated the clinical setting. Projection data were derived from cinedensitometric scans across the entire myocardial shadow, perpendicular to the axis of rotation in each view, after 512 X 512 digitization with a vidicon camera/digitizer interfaced to a VAX computer. Comparison of MENT-reconstructed images with corresponding anatomic myocardial cross sections indicate that as few as 6 to 12 views can be used to reconstruct the cross sections of the multiple coronary branches (n = 6-11) within a plane of reconstruction.     

Accelerated gastric epithelial proliferation

Gastric body mucosal proliferation was quantified and localised under conditions of increased gastrin drive using a variety of techniques. Rats were given omeprazole 400 mumol/kg/day by gavage and after 30 days mean serum gastrin rose 11-fold (p < 0.001). Total mucosal polyamines rose 220% from 15.9 to 50.9 nmol/mg protein (p < 0.001). This was associated with a 238% increase in crypt cell production rate from 0.541 to 1.83 crypt cells/h by vincristine metaphase arrest (p < 0.02). Using computer aided counting of proliferating cell nuclear antigen (PCNA) immunostained nuclei to assess epithelial proliferation in hypergastrinaemia rat stomach: mucus neck cell PCNA labelling was increased by 41% (p < 0.001) and gland cell PCNA labelling was increased by 222% (p < 0.001). PCNA/AgNOR (argyrophilic nuclear organiser regions) co-stained sections were used to assess proliferative activity in cycling and non-cycling cell populations. Data from these experiments suggest that, in addition to increasing the number of mucosal cells in cycle, cell life and cell cycle duration may be reduced in hypergastrinaemia.     

OAM: an office analysis methodology

OAM is a functionally oriented office analysis methodology which provides guidance in preparing an office study, collecting information from office staff, and organizing and presenting the results. It is well suited to semi-structured offices and provides the appropriate level of detail for making decisions regarding the design and justification of a computerized office information system. An evaluation of OAM by several using organizations shows it to be an efficient, effective, teachable methodology. OAM was perceived by users to improve significantly the functionality of office information systems implemented after an OAM study by comparison with task oriented study methodologies.     

Phenomenological approach to the role of C3A in the hardening of portland cement pastes

This paper is a contribution to the growing belief that the C₃A acts as a catalyst on the calcium silicates during hydration. This is based on the finding that the rates of reactions of the silicates are linear functions of the C₃A content of the cement.The effect of C₃A on the ultimate strength is also discussed numerically along with evidence that shows that the rate of hardening, per se, affects the ultimate strength through its effect on the structure of the hardening cement paste.     

The type 1 angiotensin-II receptor mediates intracellular calcium mobilization in rat luteal cells

The intracellular cytosolic calcium concentration ([Ca]i) was determined in cultured rat luteal cells using the calcium-chelating dye fura-2 and microspectrofluorimetry. Angiotensin-II (Ang-II) induced a dose-dependent transient increase in [Ca]i (ED50, 9.0 +/- 6.5 nM). After the initial peak in [Ca]i, cytosolic calcium returned to a secondary elevated basal level that was dependent upon the presence of extracellular calcium. Pretreatment of rat luteal cells with Ang-II (100 nM) desensitized a subsequent response to a higher concentration (1 microM), but did not desensitize a prostaglandin F2 alpha (PGF2 alpha)-induced calcium flux. Although the peak increases in [Ca]i induced by Ang-II (1 microM) and PGF2 alpha (10 microM) were not significantly different, the plateau phase stimulated by PGF2 alpha was significantly higher (P < 0.05) than that stimulated by Ang-II (1 microM). Pretreatment of luteal cells with the type 2 Ang-II receptor antagonist PD 123319 (10 microM) did not inhibit calcium mobilization; however, Ang-II (1 microM)-induced calcium mobilization was dose dependently blocked by the type 1 Ang-II receptor antagonist Losartan (DuP 753). The ID50 for Losartan was 5.2 +/- 1.8 nM. Pretreatment of the luteal cells with the endoplasmic reticulum calcium ATPase inhibitor thapsigargin (1 microM) also blocked Ang-II-induced calcium mobilization. These data demonstrate the presence of the type 1 Ang-II receptor in rat luteal cells, through which Ang-II dose dependently mobilizes calcium from an intracellular source, probably the endoplasmic reticulum.     

Computer graphics on a hexagonal grid

Aberrations in digital images can be attenuated by computing the image at higher-than-display resolution, convolving it with a two-dimensional filter kernel and decimating the filtered image back to display resolution for presentation. Traditionally, this has been performed using a rectangular sampling grid, which is parallel to the display scan direction. In this paper, the application of a hexagonal sampling grid is proposed. Rectangular and hexagonal processing are discussed, and it is shown that despite the differences in their mathematical bases, their algorithmic implementations are similar. A series of test patterns are presented and evaluated. It is concluded that hexagonal processing results in a greater reduction in aliasing in regions of vertical/near vertical features of images than is achieved by rectangular processing, without any degradation in other regions, and with negligible additional computational effort.     

Error-dependent step-size control of adaptive normalized least-mean-square filters used for nonlinear acoustic echo cancellation

This paper proposes novel acoustic echo cancellation (AEC) approaches based on linear and Volterra structures. The AECs use modified normalized least-mean-square (NLMS) updates to improve the convergence and to maintain the same steady-state misadjustment. In the first case, starting from a new cost function, the resulting variable step size depends on the instant error value and on an estimated error threshold. Secondly, the need of beforehand steady-state error threshold estimation is removed by an automatic step-size control involving the absolute error envelope evolution. The methods are tested for an acoustic enclosure setup modeled using measured linear and quadratic kernels, and their behavior is compared to that of the traditional NLMS and another technique found in the open literature. Also, they are tested for a change in the echo path and for assorted nonlinearity and local signal powers. The comparison is made in terms of the echo-return loss enhancement for WGN and speech as excitation. The simulations show that the proposed adaptations offer increased convergence rates for the same steady-state error.     

Automated definition and evaluation of anatomical ROI's for bone mineral determination by QCT

The authors discuss reproducibility in determination of vertebral bone mineral density with quantitative X-ray computed tomography (QCT), which is significantly influenced by the operator's subjective selection of the region of interest (ROI). A method for automated ROI definition and evaluation based on contour detection and an anatomical coordinate system is presented and discussed. The method works reliably, offers improved reproducibility, and facilitates the operator's work. It is integrated into a program system that also supports automatic evaluation of different reference phantoms. The system has been used to create a large database of normal patients and is in clinical use at more than 100 sites.     

Infrastructure Aware Scientific Workflows and Infrastructure Aware Workflow Managers in Science Gateways

The workflow interoperability problem was successfully solved by the SHIWA project if the workflows to be integrated were running in the same grid infrastructure. However, in the more generic case when the workflows were running in different infrastructures the problem has not been solved yet. In the current paper we show a solution for this problem by introducing a new type of workflow called infrastructure-aware workflow. These are scientific workflows extended with new node types that enable the on-the-fly creation and destruction of the required infrastructures in the clouds. The paper shows the semantics of these new types of nodes and workflows and also how they can solve the workflow interoperability problem. The paper also describes how these new type of workflows can be implemented by a new service called Occopus, and how this service can be integrated with the existing SHIWA Simulation Platform services like the WS-PGRADE/gUSE portal to provide the required functionalities of solving the workflow interoperability problem.     

Practical verification of decision-making in agent-based autonomous systems

We present a verification methodology for analysing the decision-making component in agent-based hybrid systems. Traditionally hybrid automata have been used to both implement and verify such systems, but hybrid automata based modelling, programming and verification techniques scale poorly as the complexity of discrete decision-making increases making them unattractive in situations where complex logical reasoning is required. In the programming of complex systems it has, therefore, become common to separate out logical decision-making into a separate, discrete, component. However, verification techniques have failed to keep pace with this development. We are exploring agent-based logical components and have developed a model checking technique for such components which can then be composed with a separate analysis of the continuous part of the hybrid system. Among other things this allows program model checkers to be used to verify the actual implementation of the decision-making in hybrid autonomous systems.