Computed tomographic angiography for the evaluation of carotid artery stenosis

BACKGROUND AND PURPOSE: No previous study has compared the reliability of carotid artery measurement provided by axial images, shaded surface display (SSD), and maximum intensity projection (MIP). METHODS: Helical CT and conventional angiography were performed prospectively in 20 patients with atherosclerotic stenosis of the internal carotid artery. Stenosis measurement was performed in a blinded fashion on angiography and CT by two independent examiners. Calcifications were segmented when they were located far enough from the vascular lumen. SSD and MIP were systematically performed for each carotid bifurcation. We measured stenosis using conventional angiography as standard and the different CT reconstructions (axial images, SSD, and MIP) by comparing the stenosis diameter at its narrowest point to the normal internal carotid artery. The degree of stenosis was classified into six groups: no stenosis, mild stenosis (< 30%), moderate stenosis (30% to 70%), severe stenosis (> 70%), near occlusion, and occlusion (100%). No measurement was made in cases of normal artery, near occlusion, and occlusion. RESULTS: Correlations between angiography and the three types of reconstruction were very good. Axial sections correctly classified the carotid arteries in 95% of cases. In 10 carotid arteries, stenosis was not assessable by SSD and MIP because of calcifications. In the remaining carotid arteries, MIP correctly classified the degree of stenosis in 96% of cases, whereas SSD misclassified 21% of cases. CONCLUSIONS: Our study showed that axial images provide a reliable evaluation of carotid artery stenosis. Calcifications are limiting factors in SSD or MIP. When atherosclerotic plaques are not calcified, MIP reconstructions provide a more reliable measurement of the vascular lumen than SSD.     

Practical implementation of a highly sensitive receiver using an erbium-doped fiber preamplifier

A practical erbium-doped fiber preamplified direct detection receiver is demonstrated with which receiver input sensitivities of -46.5 dBm at 622 Mb/s and -40.7 dBm at 2.3 Gb/s have been achieved. There is no penalty from the transmission fiber Rayleigh backscattering. The bit error ratio measurements with 2/sup 23/-1 NRZ PRBS (pseudorandom bit sequence) show highly stable characteristics with no apparent error floor, owing to the polarization insensitivity of the preamplifier and to an active locking of the receiver optical filter. The tradeoff between preamplifier and avalanche gain is shown, and the influence of optical filter bandwidth and decision threshold setting is measured.<>     

Performance of demodulation-based frequency measurement algorithms used in typical PMUs

This paper presents a method for evaluating the performance of demodulation-based frequency measurement algorithms in the presence of additive interfering sinusoids. Determination of the performance of amplitude measurement schemes under such conditions is straightforward once the frequency responses of the filters involved in the process are known, since the error induced by a single interfering tone is easily computed using the cascade algorithm's frequency response magnitude. This paper presents a similar method for predicting the worst error of frequency measurement schemes with respect to sinusoidal interference. Once acquainted with the proposed error prediction formula, the only difficulty in designing effective frequency measurement algorithms is the appropriate selection of output filters to achieve the specified performance. The method has been used successfully in designing frequency measurement algorithms currently used in Hydro-Que/spl acute/bec's special protection schemes.     

Effect of mixed solvents on PCDTBT:PC70BM based solar cells

We investigated the effect of solvents on the morphology, charge transport and device performance of poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC₇₀BM) based solar cells. To carry out this investigation, chloroform and 1,2-dichlorobenzene were chosen as good solvents of the two compounds. Films prepared with chloroform exhibit larger domains than those prepared with 1,2-dichlorobenzene and their size increases with the amount of PC₇₀BM. Fine tuning of the domain size was realized by using a solvent of mixed chloroform and 1,2-dichlorobenzene. At a mixing ratio of 50%:50%, a power conversion efficiency of 6.1% was achieved on PCDTBT:PC₇₀BM (1:3) devices with an active area of 1 cm², under air mass 1.5 global (AM 1.5 G) irradiation at 100 mW/cm².     

Real-time dynamic substructuring testing of viscous seismic protective devices for bridge structures

This paper presents a real-time dynamic substructuring (RTDS) test program carried out on bridge structures equipped with two innovative viscous seismic protective devices: a seismic damping unit and a shock transmission unit. In the RTDS tests, the seismic protective units were physically tested in the laboratory using a high performance dynamic actuator imposing, in real time, the displacement time histories obtained from numerical simulations being run in parallel. The integration scheme used in the test program was the Rosenbrock-W variant, and the integration was performed using The MathWorks’ Simulink and XPC target computer environment. The numerical counterpart included the bridge columns and the additional energy dissipation properties. The nonlinear response of these components was accounted for in the numerical models. The tests were run under various ground motions, and the influence of modeling assumptions such as damping and initial stiffness was investigated. Finally, the test results are compared to the predictions from nonlinear dynamic time history analyses performed using commercially available computer programs. The results indicate that simple numerical modeling techniques can lead to accurate prediction of the displacement response of bridge structures equipped with the seismic protective systems studied.     

A recombinant virus-like particle system derived from parvovirus as an efficient antigen carrier to elicit a polarized Th1 immune response without adjuvant

Hybrid virus-like particles (VLP) were prepared by self-assembly of the modified porcine parvovirus (PPV) VP2 capsid protein carrying a CD8+ or CD4+ T cell epitope. Immunization of mice with a single dose of these hybrid pseudo-particles, without adjuvant, induced strong cytotoxic T lymphocyte and T helper (Th) responses against the reporter epitope. The Th response was characterized by a Th1 phenotype. We also analyzed in vitro the uptake mechanism of these parvovirus-like particles and the processing requirements associated with presentation by MHC molecules. Although previously shown to be presented by MHC class I molecules, these particles also enter very efficiently the MHC class II endocytic pathway, and behave as conventional exogenous antigens. Indeed, the processing of chimeric PPV:VLP was performed in endosomal/lysosomal acidic vesicles and the presentation of the foreign epitope carried by these particles was sensitive to brefeldin A and cycloheximide, showing that the foreign peptide was loaded on nascent MHC class II molecules. These results give some indication of how PPV:VLP can be presented by MHC class I and class II molecules, and underscore the wide potency of such VLP system to deliver foreign antigens for vaccine design.     

beta-Actin is confined to structures having high capacity of remodelling in developing and adult rat cerebellum

Neurons undergo complex morphological changes during differentiation and in cases of plasticity. A major determinant of cell morphology is the actin cytoskeleton, which in neurons is comprised of two actin isoforms, non-muscle gamma- and beta-actin. To better understand their respective roles during differentiation and plasticity, their cellular and subcellular localization was examined in developing and adult cerebellar cortex. It was observed that gamma-actin is expressed at a constant level throughout development, while the level of beta-actin expression rapidly decreases with age. At the light microscopic level, gamma-actin staining is ubiquitous and the only developmental change observed is a relative reduction of its concentration in cell bodies and white matter. In contrast, beta-actin staining almost completely disappears from the cytoplasm of cell bodies, primary dendrites and axons. In young cerebellar cultures, gamma-actin is found in the cell body, neurites and growth cones, while beta-actin is mainly found in growth cones, as previously reported in other primary neuronal culture systems [Kaech et al. (1997), J. Neuroscience, 17, 9565-9572; Bassell et al., (1998), J. Neuroscience, 18, 251-265]. Electron microscopy of post-embedding immunogold-labelled tissue confirms the widespread distribution of gamma-actin, and also reveals an increased concentration of gamma-actin in dendritic spines in the adult. During development, beta-actin accumulation is observed in actively growing structures, e.g., growth cones, filopodia, cell bodies and axonal tracts. In the adult cerebellar cortex, beta-actin is preferentially found in dendritic spines, structures which are known to retain their capacity for morphological modifications in the adult brain. This differential subcellular localization and developmental regulation of the two actin isoforms point to their different roles in neurons.     

Coronary endarterectomy revisited: mid-term angiographic results

OBJECTIVES: To evaluate the value of concomitant coronary endarterectomy (CE) in the modern era of coronary revascularization. METHODS: Retrospective study. Twenty-eight patients (five women; 23 men) who underwent coronary endarterectomy were angiographically studied 24 +/- 22 months after the procedure. Necessity CE (vessel completely occluded or with lumen less than 1 mm) was performed on the left anterior descending (LAD) artery in 12 patients, the right coronary artery (RCA) in nine, the obtuse marginal artery (OM) in five and a diagonal branch in two patients. Conduits used for revascularization were the internal thoracic artery (ITA) in 11 (all anastomosed to the LAD; combined with saphenous vein patch in four) and a saphenous vein graft in 17 patients. Mean atherosclerotic core length was 3.3 +/- 1.8 cm. An average of 3.1 +/- 0.7 distal anastomoses per patient were constructed, with mean aortic cross-clamp and cardiopulmonary bypass times of 61.2 +/- 20.2 mins and 94.0 +/- 23.5 mins, respectively. RESULTS: Overall, angiographic patency rate was 71% (20 of 28) for the endarterectomized vessels (12 of 12 LAD, six of nine RCA, two of five OM and none of two diagonal arteries) and 93% (57 of 61) for the nonendarterectomized vessels. Among the eight patients with occluded CE vessels, two sustained a perioperative myocardial infarction, five developed angina during follow-up, and one patient remained asymptomatic. CONCLUSION: Necessity CE demonstrates acceptable mid-term patency. In addition, this study showed excellent patency following CE of the LAD revascularized with the ITA, with or without only a saphenous vein patch.     

Metal oxides as combustion catalysts for a stratified,dual bed partial oxidation catalyst

Bimetallic, dual bed catalysts made up of metal oxides were investigated in the millisecond catalytic partial oxidation of methane to synthesis gas. A metal oxide combustion catalyst containing manganese, chromium, or copper was coupled with a nickel reforming catalyst to carry out the partial oxidation of methane. These catalysts produce hydrogen yields that compare to a platinum/nickel dual bed catalyst at a fraction of the cost. The high space velocity of the millisecond reactor improves performance by giving high rates of heat convection from the exothermic, upstream combustion catalyst to the downstream, endothermic reforming catalyst. Additionally, over a 10 h experiment, the catalyst activity did not decrease.