High Performance GPU‐based Proximity Queries using Distance Fields

Proximity queries such as closest point computation and collision detection have many applications in computer graphics, including computer animation, physics‐based modelling, augmented and virtual reality. We present efficient algorithms for proximity queries between a closed rigid object and an arbitrary, possibly deformable, polygonal mesh. Using graphics hardware to densely sample the distance field of the rigid object over the arbitrary mesh, we compute minimal proximity and collision response information on the graphics processing unit (GPU) using blending and depth buffering, as well as parallel reduction techniques, thus minimizing the readback bottleneck. Although limited to image‐space resolution, our algorithm provides high and steady performance when compared with other similar algorithms. Proximity queries between arbitrary meshes with hundreds of thousands of triangles and detailed distance fields of rigid objects are computed in a few milliseconds at high‐sampling resolution, even in situations with large overlap.     

Unifying statistical classification and geodesic active regions for segmentation of cardiac MRI

This paper presents a segmentation method that extends geodesic active region methods by the incorporation of a statistical classifier trained using feature selection. The classifier provides class probability maps based on class representative local features, and the geodesic active region formulation enables the partitioning of the image according to the region information. We demonstrate automatic segmentation results of the myocardium in cardiac late gadolinium-enhanced magnetic resonance imaging (CE-MRI) data using coupled level set curve evolutions, in which the classifier is incorporated both from a region term and from a shape term from particle filtering. The results show potential for clinical studies of scar tissue in late CE-MRI data.     

Simultaneously amplified electrochemical and surface plasmon optical detection of DNA hybridization based on ferrocene-streptavidin conjugates

A sensitive method based on ferrocene-streptavidin (Fc-Stv) conjugates for the simultaneously amplified electrochemical and surface plasmon optical detection of DNA target hybridization to peptide nucleic acid-modified gold surfaces is reported. The attachment of Fc-Stv to the biotinylated complementary target DNA not only amplified the surface plasmon resonance signal but also enhanced the electrochemical signal due to the many Fc markers per Stv. The ferrocene redox peak current increased with the increase of the target DNA concentration. Consequently, the amount of hybridized target DNA can be estimated by cyclic voltammetry and chronocoulometry. The detection limit of this DNA sensor is 10 pM (2 fmol, with signal to noise > 3). This sensor was also shown to have high selectivity (at the single-base mismatch level) and good reproducibility.     

Efficient Image‐Based Proximity Queries with Object‐Space Precision

We present an efficient algorithm for object‐space proximity queries between multiple deformable triangular meshes. Our approach uses the rasterization capabilities of the GPU to produce an image‐space representation of the vertices. Using this image‐space representation, inter‐object vertex‐triangle distances and closest points lying under a user‐defined threshold are computed in parallel by conservative rasterization of bounding primitives and sorted using atomic operations. We additionally introduce a similar technique to detect penetrating vertices. We show how mechanisms of modern GPUs such as mipmapping, Early‐Z and Early‐Stencil culling can optimize the performance of our method. Our algorithm is able to compute dense proximity information for complex scenes made of more than a hundred thousand triangles in real time, outperforming a CPU implementation based on bounding volume hierarchies by more than an order of magnitude.     

Solar activity variations and global temperature

Variations in the activity of the Sun have long been suspected to affect the climate of the Earth, and a number of correlations have been presented that indicate a link. In many cases, the presented correlations have been associated with poor statistical significance. Recent results, however, have indicated strong correlations between climate parameters and solar activity. Upper troposphere and stratosphere temperatures have been found to vary in phase with the 10- to 12-year solar activity cycle. On a longer time scale, the global temperature, particularly the Northern Hemisphere land air temperature, has been found to be nearly perfectly correlated with the long-term variation of solar activity. The solar activity itself cannot be represented by only one parameter. Different representations of solar activity have different and not understood, long-term variations. It has been found that the longterm variation of solar activity represented by the varying length of the approximately 11-year solar cycle is the parameter that is probably best correlated with global temperature, both with respect to the modern instrumental temperature record from 1860 to 1990 and with respect to a reconstructed temperature record extending back to 1750 when sunspot observations are believed to have been reliable.     

Comparison of Blackbodies for Calibration of Infrared Ear Thermometers

The article presents the results of the EURAMET Project No. 927 ??Comparison of blackbodies for calibration of infrared ear thermometers (IRETs)??. The objective of the comparison was to determine the agreement of blackbodies used for the calibration of IRETs among European national laboratories. To verify the accuracy of an IRET, a suitable blackbody (BB) is needed. Such a blackbody related to the EN standard, designed for the calibration of ear thermometers and immersed in a stirred water bath, was provided for the comparison by the pilot laboratory. The pilot provided also the transfer IRET and organized the comparison.     

Communication of medical images, text, and messages in inter-enterprise systems: a case study in Norway.

There is an increasing demand to discuss diagnostic images and reports of difficult cases with experienced staff. A possible solution besides physically transporting patients and material is to use high-speed communication networks to transfer images and reports electronically. With the web application PACSflow we have developed a solution to transfer images, reports, and messages as a single package in a one-step procedure. The PACSflow is an interoperable and standard compliant web-based application, which gives clinicians a user-friendly interface for their work on a daily basis. The solution assumes that the diagnostic images are compatible with the digital imaging and communications in medicine (DICOM) format. The Department of Cardiology at the Rikshospitalet University Hospital in Oslo, Norway, and the Department of Internal Medicine at the S?rlandet Sykehus in Arendal, Norway, are making clinical use of the system. Initial tests indicate that use of PACSflow has reduced the time required to prepare and transfer data by a factor of 3.     

PNA-DNA hybridization study using labeled streptavidin by voltammetry and surface plasmon fluorescence spectroscopy

Using ferrocene-streptavidin conjugates as amplifiers, we recently have demonstrated the simultaneous detection of DNA hybridization to peptide nucleic acid (PNA)-modified gold surfaces at the femtomole level by electrochemical and surface plasmon resonance techniques (Liu, J.; Tian, S.; Tiefenauer, L.; Nielsen, P. E.; Knoll, W. Anal. Chem. 2005, 77, 2756-2761). In this paper, a detailed study of the binding behavior of PNA-DNA is presented by square wave voltammetry and surface plasmon field-enhanced fluorescence spectroscopy (SPFS). The different binding constants for fully matched and single-mismatched DNA were obtained. The effect of the buffer concentration on the PNA-DNA hybrids was investigated using labeled streptavidin by cyclic voltammetry (CV) and SPFS. At high ionic strength, both the CV and SPFS signals were restrained dramatically, which is most probably due to a conformational change of the short-strand PNA-DNA helices on the surface. We conclude that the combination of electrochemical techniques with SPFS is very useful for the study of short DNA structure transformation.