Polyconductivity in polypyrrole: the correlated electron glass

p-toluensulfonate doped polypyrrole ~PPy!, undergoes an electric-field induced reversible transition from an insulating state to a highly conductive one. The spatially average field can be as small as 200 V/cm, when the temperature of the sample is below 20 K. The applied electric field leads to a sharp jump in the value of the current to a value which is nearly five orders of magnitude higher than before. When the applied electric field is reduced to below a critical value, the system switches back to a low conductive state. The effect is reversible, symmetric in voltage, and reproducible for different samples. The switching is, we believe, an electronic glass melting transition and it is due to the disordered, highly charged granular nature of PPy.

Polyconductivity in polypyrrole: The correlated electron gas

p-toluensulfonate doped polypyrrole (PPy), undergoes an electric-field induced reversible transition from an insulating state to a highly conductive one. The spatially average field can be as small as 200 V/cm, when the temperature of the sample is below 20 K. The applied electric field leads to a sharp jump in the value of the current to a value which is nearly five orders of magnitude higher than before. When the applied electric field is reduced to below a critical value, the system switches back to a low conductive state. The effect is reversible, symmetric in voltage, and reproducible for different samples. The switching is, we believe, an electronic glass melting transition and it is due to the disordered, highly charged granular nature of PPy.

Relationship between coronary endothelial function and coronary calcification in early atherosclerosis.

BACKGROUND: The relationship between coronary endothelial function and coronary calcification is not well established. METHODS: Forty-six patients 17 men [37%]; age, 47.4+/-11.4 years prospectively underwent testing for coronary endothelial function and measurement of coronary artery calcification (CAC). RESULTS: Log CAC scores were not significantly different between patients with normal (n=31) and abnormal (n=15) response of epicardial coronary artery diameter to acetylcholine (%CAD(Ach)) (median (25, 75 percentile) 1.1 (0.0, 3.7) vs. 0.3 (0.0, 2.4), P=.32) and with normal (n=28) and abnormal (n=18) response of coronary blood flow to acetylcholine (%CBF(Ach)) (0.5 (0.0, 3.6) vs. 0.5 (0.0, 3.2), P=.76). Log CAC scores did not correlate with %CAD(Ach) (r=0.08, P=.59), %CBF(Ach) (r=0.14, P=.35). CONCLUSIONS: In patients without significant coronary artery disease, coronary endothelial dysfunction showed no apparent association with coronary calcification. Our findings suggest that these 2 markers may represent separate, independent processes in the progression of coronary atherosclerosis.

Immuno-electron microscopic identification of human estrogen receptor-DNA complexes at the estrogen-responsive element and in the first intron of a Xenopus vitellogenin gene.

Using an extract of nuclei from the estrogen-responsive human breast cancer cell line MCF-7, protein-DNA complexes were assembled in vitro at the 5' end of the Xenopus laevis vitellogenin gene B2 that is normally expressed in liver after estrogen induction. The complexes formed were analyzed by electron microscopy after labeling by the indirect colloidal gold immunological method using a monoclonal antibody specific for the human estrogen receptor. As identified by its interaction with protein A-gold, the antibody was found linked to two protein-DNA complexes, the first localized at the estrogen responsive element of the gene and the second in intron I, thus proving a direct participation of the receptor in these two complexes. The procedure used allows the visualization and rapid localization of specific transcription factors bound in vitro to a promoter or any other gene region.

Atomic Force Microscopy Stiffness Tomography on Living Arabidopsis thaliana Cells Reveals the Mechanical Properties of Surface and Deep Cell-Wall Layers during Growth.

Cell-wall mechanical properties play a key role in the growth and the protection of plants. However, little is known about genuine wall mechanical properties and their growth-related dynamics at subcellular resolution and in living cells. Here, we used atomic force microscopy (AFM) stiffness tomography to explore stiffness distribution in the cell wall of suspension-cultured Arabidopsis thaliana as a model of primary, growing cell wall. For the first time that we know of, this new imaging technique was performed on living single cells of a higher plant, permitting monitoring of the stiffness distribution in cell-wall layers as a function of the depth and its evolution during the different growth phases. The mechanical measurements were correlated with changes in the composition of the cell wall, which were revealed by Fourier-transform infrared (FTIR) spectroscopy. In the beginning and end of cell growth, the average stiffness of the cell wall was low and the wall was mechanically homogenous, whereas in the exponential growth phase, the average wall stiffness increased, with increasing heterogeneity. In this phase, the difference between the superficial and deep wall stiffness was highest. FTIR spectra revealed a relative increase in the polysaccharide/lignin content.

Ascending aorta measurements as assessed by ECG-gated multi-detector computed tomography: a pilot study to establish normative values for transcatheter therapies

The aim of this study was to provide an insight into normative values of the ascending aorta in regards to novel endovascular procedures using ECG-gated multi-detector CT angiography. Seventy-seven adult patients without ascending aortic abnormalities were evaluated. Measurements at relevant levels of the aortic root and ascending aorta were obtained. Diameter variations of the ascending aorta during cardiac cycle were also considered. Mean diameters (mm) were as follows: LV outflow tract 20.3 +/- 3.4, coronary sinus 34.2 +/- 4.1, sino-tubular junction 29.7 +/- 3.4 and mid ascending aorta 32.7 +/- 3.8 with coefficients of variation (CV) ranging from 12 to 17%. Mean distances (mm) were: from the plane passing through the proximal insertions of the aortic valve cusps to the right brachio-cephalic artery (BCA) 92.6 +/- 11.8, from the plane passing through the proximal insertions of the aortic valve cusps to the proximal coronary ostium 12.1 +/- 3.7, and between both coronary ostia 7.2 +/- 3.1, minimal arc of the ascending aorta from left coronary ostium to right BCA 52.9 +/- 9.5, and the fibrous continuity between the aortic valve and the anterior leaflet of the mitral valve 14.6 +/- 3.3, CV 13-43%. Mean aortic valve area was 582.0 +/- 131.9 mm(2). The variation of the antero-posterior and transverse diameters of the ascending aorta during the cardiac cycle were 8.4% and 7.3%, respectively. Results showed large inter-individual variations in diameters and distances but with limited intra-individual variations during the cardiac cycle. A personalized approach for planning endovascular devices must be considered.

Distribution of artifactual gas on post-mortem multidetector computed tomography (MDCT)

L'imagerie est de plus en plus utilisée en médecine forensique. Actuellement, les connaissances nécessaires pour interpréter les images post mortem sont faibles et surtout celles concernant les artéfacts post mortem. Le moyen radiologique le plus utilisé en médecine légale est la tomodensitométrie multi-coupes (TDMC). Un de ses avantages est la détection de gaz dans le corps. Cette technique est utile au diagnostic d'embolie gazeuse mais sa très grande sensibilité rend visible du gaz présent même en petite quantité. Les premières expériences montrent que presque tous les corps scannés présentent du gaz surtout dans le système vasculaire. Pour cette raison, le médecin légiste est confronté à un nouveau problème : la distinction entre du gaz d'origine post-mortem et une embolie gazeuse vraie. Pour parvenir à cette distinction, il est essentiel d'étudier la distribution de ces gaz en post mortem. Aucune étude systématique n'a encore été réalisée à ce jour sur ce sujet.¦Nous avons étudié l'incidence et la distribution des gaz présents en post mortem dans les vaisseaux, dans les os, dans les tissus sous-cutanés, dans l'espace sous-dural ainsi que dans les cavités crânienne, thoracique et abdominale (82 sites au total) de manière à identifier les facteurs qui pourraient distinguer le gaz post-mortem artéfactuel d'une embolie gazeuse¦Les données TDMC de 119 cadavres ont été étudiées rétrospectivement. Les critères d'inclusion des sujets sont l'absence de lésion corporelle permettant la contamination avec l'air extérieur, et, la documentation du délai entre le moment du décès et celui du CT-scan (p.ex. rapport de police, protocole de réanimation ou témoin). La présence de gaz a été évaluée semi-quantitativement par deux radiologues et codifiée. La codification est la suivante : grade 0 = pas de gaz, grade 1 = une à quelques bulles d'air, grade 2 = structure partiellement remplie d'air, grade 3 = structure complètement remplie d'air.¦Soixante-quatre des 119 cadavres présentent du gaz (62,2%), et 56 (75,7%) ont montré du gaz dans le coeur. Du gaz a été détecté le plus fréquemment dans le parenchyme hépatique (40%); le coeur droit (ventricule 38%, atrium 35%), la veine cave inférieure (infra-rénale 30%, supra-rénale 26%), les veines sus-hépatiques (gauche 26%, moyenne 29%, droite 22 %), et les espaces du porte (29%). Nous avons constaté qu'une grande quantité de gaz liée à la putréfaction présente dans le coeur droit (grade 3) est associée à des collections de gaz dans le parenchyme hépatique (sensibilité = 100%, spécificité = 89,7%). Pour décrire nos résultats, nous avons construit une séquence d'animation qui illustre le processus de putréfaction et l'apparition des gaz à la TDMC post-mortem.¦Cette étude est la première à montrer que l'apparition post-mortem des gaz suit un modèle de distribution spécifique. L'association entre la présence de gaz intracardiaque et dans le parenchyme hépatique pourrait permettre de distinguer du gaz artéfactuel d'origine post-mortem d'une embolie gazeuse vraie. Cette étude fournit une clé pour le diagnostic de la mort due à une embolie gazeuse cardiaque sur la base d'une TDMC post-mortem.¦Abstract¦Purpose: We investigated the incidence and distribution of post-mortem gas detected with multidetector computed tomography (MDCT) to identify factors that could distinguish artifactual gas from cardiac air embolism.¦Material and Methods: MDCT data of 119 cadavers were retrospectively examined. Gas was semiquantitatively assessed in selected blood vessels, organs and body spaces (82 total sites).¦Results: Seventy-four of the 119 cadavers displayed gas (62.2%; CI 95% 52.8 to 70.9), and 56 (75.7%) displayed gas in the heart. Most gas was detected in the hepatic parenchyma (40%); right heart (38% ventricle, 35% atrium), inferior vena cava (30% infrarenally, 26% suprarenally), hepatic veins (26% left, 29% middle, 22% right), and portal spaces (29%). Male cadavers displayed gas more frequently than female cadavers. Gas was detected 5-84 h after death; therefore, the post-mortem interval could not reliably predict gas distribution (rho=0.719, p<0.0001). We found that a large amount of putrefaction-generated gas in the right heart was associated with aggregated gas bubbles in the hepatic parenchyma (sensitivity = 100%, specificity = 89.7%). In contrast, gas in the left heart (sensitivity = 41.7%, specificity = 100%) or in peri-umbilical subcutaneous tissues (sensitivity = 50%, specificity = 96.3%) could not predict gas due to putrefaction.¦Conclusion: This study is the first to show that the appearance of post-mortem gas follows a specific distribution pattern. An association between intracardiac gas and hepatic parenchymal gas could distinguish between post- mortem-generated gas and vital air embolism. We propose that this finding provides a key for diagnosing death due to cardiac air embolism.

Model-based Segmentation and Image Fusion of 3D Computed Tomography and 3D Ultrasound of the Eye for Radiotherapy Planning

For radiotherapy treatment planning of retinoblastoma inchildhood, Computed Tomography (CT) represents thestandard method for tumor volume delineation, despitesome inherent limitations. CT scan is very useful inproviding information on physical density for dosecalculation and morphological volumetric information butpresents a low sensitivity in assessing the tumorviability. On the other hand, 3D ultrasound (US) allows ahigh accurate definition of the tumor volume thanks toits high spatial resolution but it is not currentlyintegrated in the treatment planning but used only fordiagnosis and follow-up. Our ultimate goal is anautomatic segmentation of gross tumor volume (GTV) in the3D US, the segmentation of the organs at risk (OAR) inthe CT and the registration of both. In this paper, wepresent some preliminary results in this direction. Wepresent 3D active contour-based segmentation of the eyeball and the lens in CT images; the presented approachincorporates the prior knowledge of the anatomy by usinga 3D geometrical eye model. The automated segmentationresults are validated by comparing with manualsegmentations. Then, for the fusion of 3D CT and USimages, we present two approaches: (i) landmark-basedtransformation, and (ii) object-based transformation thatmakes use of eye ball contour information on CT and USimages.

Visualization of aqueous shunt position and patency using anterior segment optical coherence tomography.

PURPOSE: To describe the use of anterior segment optical coherence tomography (AS-OCT) to clarify the position and patency of aqueous shunt devices in the anterior chamber of eyes where corneal edema or tube position does not permit a satisfactory view. DESIGN: Noncomparative observational case series. METHODS: Four cases are reported in which aqueous shunt malposition or obstruction was suspected but the shunt could not be seen on clinical examination. The patients underwent AS-OCT to identify the position and patency of the shunt tip. RESULTS: In each case, AS-OCT provided data regarding tube position and/or patency that could not be obtained by slit-lamp examination or by gonioscopy that influenced management. CONCLUSIONS: AS-OCT can be used to visualize anterior chamber tubes in the presence of corneal edema that precludes an adequate view or in cases where the tube is retracted into the cornea. In such cases, AS-OCT is useful in identifying shunt patency and position, which helps guide clinical decision making.

Value of positron emission tomography in full-thickness chest wall resections for malignancies.

Preoperative imaging for resection of chest wall malignancies is generally performed by computed tomography (CT). We evaluated the role of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in planning full-thickness chest wall resections for malignancies. We retrospectively included 18 consecutive patients operated from 2004 to 2006 at our institution. Tumor extent was measured by CT and PET, using the two largest perpendicular tumor extensions in the chest wall plane to compute the tumor surface assuming an elliptical shape. Imaging measurements were compared to histopathology assessment of tumor borders. CT assessment consistently overestimated the tumor size as compared to PET (+64% vs. +1%, P<0.001). Moreover, PET was significantly better than CT at defining the size of lesions >24 cm(2) corresponding to a mean diameter >5.5 cm or an ellipse of >4 cm x 7.6 cm (positive predictive value 80% vs. 44% and specificity 93% vs. 64%, respectively). Metabolic PET imaging was superior to CT for defining the extent of chest wall tumors, particularly for tumors with a diameter >5.5 cm. PET can complement CT in planning full-thickness chest wall resection for malignancies, but its true value remains to be determined in larger, prospective studies.