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At least 1,045 records · Page 58Linked to original sources
PubMed1977

A method of computational magnetohydrodynamics defining stable Scyllac equilibria.

A computer code has been developed for the numerical calculation of sharp boundary equilibria of a toroidal plasma with diffuse pressure profile. This generalizes earlier work that was done separately on the sharp boundary and diffuse models, and it allows for large amplitude distortions of the plasma in three-dimensional space. By running the code, equilibria that are stable to the so-called m = 1, k = 0 mode have been found for Scyllac, which is a high beta toroidal confinement device of very large aspect ratio.

Journal Article↗
PubMed2006

A novel three-dimensional computer-assisted method for a quantitative study of microvascular networks of the human cerebral cortex.

OBJECTIVE: Detailed information on microvascular network anatomy is a requirement for understanding several aspects of microcirculation, including oxygen transport, distributions of pressure, and wall shear stress in microvessels, regulation of blood flow, and interpretation of hemodynamically based functional imaging methods, but very few quantitative data on the human brain microcirculation are available. The main objective of this study is to propose a new method to analyze this microcirculation. METHODS: From thick sections of india ink-injected human brain, using confocal laser microscopy, the authors developed algorithms adapted to very large data sets to automatically extract and analyze center lines together with diameters of thousands of brain microvessels within a large cortex area. RESULTS: Direct comparison between the original data and the processed vascular skeletons demonstrated the high reliability of this method and its capability to manage a large amount of data, from which morphometry and topology of the cerebral microcirculation could be derived. CONCLUSIONS: Among the many parameters that can be analyzed by this method, the capillary size, the frequency distributions of diameters and lengths, the fractal nature of these networks, and the depth-related density of vessels are all vital features for an adequate model of cerebral microcirculation.

Capillaries↗
PubMed2004

A rapid method for computationally inferring transcriptome coverage and microarray sensitivity.

MOTIVATION: There are many different gene expression technologies, including cDNA and oligo-based microarrays, SAGE and MPSS. For each organism of interest, coverage of the transcriptome and the genome will be different. We address the question of what level of coverage is required to exploit the sensitivity of the different technologies, and what is the sensitivity of the different approaches in the experimental study. RESULTS: We estimate the transcriptome coverage by randomly sampling transcripts from a pre-defined tag-to-gene mapping function. For a given microarray experiment, we locate the thresholds in intensities that define the distribution of transcript abundance. These values are compared against the distribution obtained by applying the same thresholds to the intensities from differentially expressed genes. The ratio of these two distributions meets at the equilibrium defining sensitivity. We conclude that a collection of approximately 340,000 sequences is adequate for microarrays, but not large enough for maximum utilization of tag-based technologies. In the absence of large-scale sequencing, the majority of the tags detected by the latter approaches will remain unidentified until the genome sequence is available.

Algorithms↗
PubMed2005

Identification of plant microRNA homologs.

MicroRNAs (miRNAs) are a recently discovered class of non-coding RNAs that regulate gene and protein expression in plants and animals. MiRNAs have so far been identified mostly by specific cloning of small RNA molecules, complemented by computational methods. We present a computational identification approach that is able to identify candidate miRNA homologs in any set of sequences, given a query miRNA. The approach is based on a sequence similarity search step followed by a set of structural filters.

Algorithms↗
PubMed1991

A dose-attenuation shield for use in glomerular filtration rate computations. A method for combined renal scintiangiography and functional quantification.

Renal perfusion and function can be determined by renography using Tc-99m DTPA. However, the high dose of tracer necessary for scintiangiography may result in inaccurate syringe-count determinations when measured by the gamma camera necessary for calculating the glomerular filtration rate by a camera technique. This report describes a syringe shield, constructed at minimal cost, which allows for suitable count attenuation and use of high doses of tracer for assessment of both renal perfusion and function.

Adult↗
PubMed1978

An improved method for computed tomography of the base of the skull in head scanners that utilize a water bag.

The original EMI Mark I head scanner as well as the Artronix Neuro CAT scanner utilize a water bag surrounding the patient's head. One of the disadvantages of this system is that the patient's head may be displaced out of the scanning beam by the pressure of the water bag, thus making it difficult to obtain good scans of the base of the skull or the posterior fossa. A device that utilizes an adjustable footboard and restraining straps around the legs to hold the patient in position is described. Although designed specifically for the Artronix Neuro CAT scanner, it can readily be adapted to other scanners that utilize a water bag. In our experience it has worked well in restraining caudal movement of patients, thus enabling us to obtain good images of the posterior fossa and base of the skull.

Humans↗